FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Lee, CI Johnston, AH AF Lee, CI Johnston, AH TI Comparison of total dose responses on high resolution analog-to-digital converter technologies SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 4th European Conference on Radiation and its Effects on Components and Systems (RADECS 97) CY SEP 15-19, 1997 CL CANNES, FRANCE SP Thomson CSF, Aerospatiale Espace & Def, TEMIC Semiconductors, CEA/DAM, Ministere Culture, Sandia Natl Labs AB Two different 12-bit analog-to-digital converter technologies, CMOS and BiCMOS, from Burr-Brown were compared for total dose responses. The BiCMOS converter appears to be a better candidate for space applications. CMOS devices showed larger degradation with both high dose rate (HDR) and low dose rate (LDR). An external voltage reference can be used for a radiation hardened process 12-bit converter from Analog Devices to maintain accuracy up to 1 Mrad(Si). DATEL's 16-bit hybrid converter showed a low failure level with HDR. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lee, CI (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 10 TC 11 Z9 16 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 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 1444 EP 1449 DI 10.1109/23.685221 PN 3 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU365 UT WOS:000074189800017 ER PT J AU LaBel, KA Marshall, PW Marshall, CJ Barth, J Leidecker, H Reed, R Seidleck, CM AF LaBel, KA Marshall, PW Marshall, CJ Barth, J Leidecker, H Reed, R Seidleck, CM TI Comparison of MIL-STD-1773 fiber optic data bus terminals: Single event proton test irradiation, in-flight space performance, and prediction techniques SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 4th European Conference on Radiation and its Effects on Components and Systems (RADECS 97) CY SEP 15-19, 1997 CL CANNES, FRANCE SP Thomson CSF, Aerospatiale Espace & Def, TEMIC Semiconductors, CEA/DAM, Ministere Culture, Sandia Natl Labs AB We present a comparison of proton single event ground test results for two generations of MIL-STD-1773 fiber optic data bus interface modules. Single event upset rate prediction techniques for fiber optic data systems are also demonstrated and compared with in-flight space performance. C1 NASA, GSFC, Greenbelt, MD 20771 USA. Hughes STX, Greenbelt, MD USA. RP LaBel, KA (reprint author), NASA, GSFC, Greenbelt, MD 20771 USA. NR 8 TC 5 Z9 5 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1998 VL 45 IS 3 BP 1633 EP 1639 DI 10.1109/23.685252 PN 3 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA ZU365 UT WOS:000074189800048 ER PT J AU Waheed, A Rover, DT Hollingsworth, JK AF Waheed, A Rover, DT Hollingsworth, JK TI Modeling and evaluating design alternatives for an on-line instrumentation system: A case study SO IEEE TRANSACTIONS ON SOFTWARE ENGINEERING LA English DT Article DE instrumentation system; resource occupancy model; workload characterization; parallel tools; parallel and distributed system; monitoring; intrusion ID PERFORMANCE-MEASUREMENT; PARALLEL AB This paper demonstrates the use of a model-based evaluation approach for instrumentation systems (ISs). The overall objective of this study is to provide early feedback to tool developers regarding IS overhead and performance; such feedback helps developers make appropriate design decisions about alternative system configurations and task scheduling policies. We consider three types of system architectures: network of workstations (NOW), symmetric multiprocessors (SMP), and massively parallel processing (MPP) systems. We develop a Resource OCCupancy (ROCC) model for an on-line IS for an existing tool and parameterize it for an IBM SP-2 platform. This model is simulated to answer several 'what if' questions regarding two policies to schedule instrumentation data forwarding: collect-and-forward (CF) and batch-and-forward (BF). In addition, this study investigates two alternatives for forwarding the instrumentation data: direct and binary tree forwarding for an MPP system. Simulation results indicate that the BF policy can significantly reduce the overhead and that the tree forwarding configuration exhibits desirable scalability characteristics for MPP systems. Initial measurement-based testing results indicate more than 60 percent reduction in the direct IS overhead when the BF policy was added to Paradyn parallel performance measurement tool. C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. Michigan State Univ, Dept Elect Engn, E Lansing, MI 48824 USA. Univ Maryland, Dept Comp Sci, College Pk, MD 20742 USA. RP Waheed, A (reprint author), NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. EM waheed@nas.nasa.gov; rover@egr.msu.edu; hollings@cs.umd.edu NR 33 TC 1 Z9 1 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0098-5589 J9 IEEE T SOFTWARE ENG JI IEEE Trans. Softw. Eng. PD JUN PY 1998 VL 24 IS 6 BP 451 EP 470 DI 10.1109/32.689402 PG 20 WC Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA ZZ183 UT WOS:000074703900004 ER PT J AU Retallick, WB Brady, MP Humphrey, DL AF Retallick, WB Brady, MP Humphrey, DL TI A phosphoric acid surface treatment for improved oxidation resistance of gamma titanium aluminides SO INTERMETALLICS LA English DT Article DE gamma (gamma) titanium aluminide; oxidation; coatings; surface treatments; phosphates AB A surface treatment for improving the oxidation resistance of gamma titanium aluminides is described. The treatment involves painting phosphoric acid onto the aluminide and then calcining. At 800 degrees C in air, treated Ti-48Al-2Cr-2Nb specimens oxidized at a significantly lower rate than untreated material. Cross-sectional analysis indicated that the reduced oxidation rate was associated with a continuous or near continuous inner alumina layer, as compared to an intermixed alumina/titania scale on the untreated material. (C) 1998 Elsevier Science Limited. All rights reserved. C1 Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. NASA, Lewis Res Ctr, NYMA Inc Grp, Cleveland, OH 44135 USA. RP 1432 Johnnys Way, W Chester, PA 19382 USA. RI Brady, Michael/A-8122-2008 OI Brady, Michael/0000-0003-1338-4747 NR 7 TC 33 Z9 34 U1 2 U2 4 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0966-9795 EI 1879-0216 J9 INTERMETALLICS JI Intermetallics PD JUN PY 1998 VL 6 IS 4 BP 335 EP 337 DI 10.1016/S0966-9795(97)00096-4 PG 3 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA ZU792 UT WOS:000074235400011 ER PT J AU Matsuura, S Chen, P Blake, GA Pearson, JC Pickett, HM AF Matsuura, S Chen, P Blake, GA Pearson, JC Pickett, HM TI Simultaneous amplification of terahertz difference frequencies by an injection-seeded semiconductor laser amplifier at 850 nm SO INTERNATIONAL JOURNAL OF INFRARED AND MILLIMETER WAVES LA English DT Article DE semiconductor laser amplifier; two-frequency injection seeding; difference-frequency generation; submillimeter; terahertz; coherent radiation AB Two-frequency operation of an 850 nm semiconductor optical amplifier was achieved by simultaneously injection seeding it with two diode lasers. The two frequencies could be independently amplified without strong interference when they were separated by more than 10 GHz, and the spectral purity was preserved by the amplification process. At frequency differences below 10 GHz, unbalanced two-frequency output was observed, which can be explained by a two-mode interaction driven by the refractive index modulation at the beat frequency. The laser system is suitable for the difference-frequency generation of coherent terahertz radiation in ultra-fast photoconductors or nonlinear optical media. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Matsuura, S (reprint author), CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RI Chen, Pin/B-1112-2008; Matsuura, Shuji/B-5658-2016 OI Chen, Pin/0000-0003-1195-9666; Matsuura, Shuji/0000-0002-5698-9634 NR 9 TC 10 Z9 10 U1 0 U2 4 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0195-9271 J9 INT J INFRARED MILLI JI Int. J. Infrared Millimeter Waves PD JUN PY 1998 VL 19 IS 6 BP 849 EP 858 DI 10.1023/A:1022676407601 PG 10 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA ZQ944 UT WOS:000073918700006 PM 11542405 ER PT J AU Sinha, MP Langstaff, DP Narayan, DJ Birkinshaw, K AF Sinha, MP Langstaff, DP Narayan, DJ Birkinshaw, K TI Resolving power enhancement of a discrete detector (array) by single event detection SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY LA English DT Article DE detector; array; resolution; mass spectrometry ID SPECTROSCOPY AB Experiments have been performed to demonstrate the high resolving power of a discrete detector array that can be achieved by measuring and processing single ion events (speckle mode). Measurement of the spectrum of Kr+ using a miniature mass spectrometer developed at the jet propulsion laboratory equipped with a focal plane detector developed at Aberystwyth show a large resolving power enhancement in the speckle mode and good agreement with tabulated peak centroids and isotope abundances. The mode of operation of the instrument is under software control and is instantly variable. This clearly demonstrates the versatility and high performance of the miniaturised system. (Int J Mass Spectrom 176 (1998) 99-102) (C) 1998 Elsevier Science B.V. C1 Univ Wales, Dept Phys, Aberystwyth SY23 3BZ, Dyfed, Wales. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Birkinshaw, K (reprint author), Univ Wales, Dept Phys, Aberystwyth SY23 3BZ, Dyfed, Wales. NR 4 TC 11 Z9 12 U1 0 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1387-3806 J9 INT J MASS SPECTROM JI Int. J. Mass Spectrom. PD JUN PY 1998 VL 176 IS 1-2 BP 99 EP 102 DI 10.1016/S1387-3806(98)14002-2 PG 4 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 111YY UT WOS:000075467500008 ER PT J AU Balasubramaniam, R AF Balasubramaniam, R TI Thermocapillary and buoyant bubble motion with variable viscosity SO INTERNATIONAL JOURNAL OF MULTIPHASE FLOW LA English DT Article ID MARANGONI NUMBERS; MIGRATION; GRAVITY C1 NASA, Lewis Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. RP Balasubramaniam, R (reprint author), NASA, Lewis Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. NR 11 TC 7 Z9 9 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0301-9322 J9 INT J MULTIPHAS FLOW JI Int. J. Multiph. Flow PD JUN PY 1998 VL 24 IS 4 BP 679 EP 683 DI 10.1016/S0301-9322(97)00075-X PG 5 WC Mechanics SC Mechanics GA 102WK UT WOS:000074948900010 ER PT J AU Mattikalli, NM Engman, ET Ahuja, LR Jackson, TJ AF Mattikalli, NM Engman, ET Ahuja, LR Jackson, TJ TI Microwave remote sensing of soil moisture for estimation of profile soil property SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID SURFACE SOIL; CONDUCTIVITY; EMISSION AB Multi-temporal microwave remotely-sensed soil moisture has been utilized for the estimation of profile soil property, viz. the soil hydraulic conductivity. Passive microwave remote sensing was employed to collect daily soil moisture data across the Little Washita watershed, Oklahoma, during 10-18 June 1992. The ESTAR (Electronically Steered Thin Array Radiometer) instrument operating at L-band was flown on a NASA C-130 aircraft. Brightness temperature (TB) data collected at a ground resolution of 200m were employed to derive spatial distribution of surface soil moisture. Analysis of spatial and temporal soil moisture information in conjunction with soils data revealed a direct relation between changes in soil moisture and soil texture. A geographical information system (GIS) based analysis suggested that 2-days initial drainage of soil, measured from remote sensing, was related to an important soil hydraulic property viz. the saturated hydraulic conductivity (K(sat)). A hydrologic modelling methodology was developed for estimation of K(sat) of surface and sub-surface soil layers. Specifically, soil hydraulic parameters were optimized to obtain a good match between model estimated and field measured soil moisture profiles. Relations between 2-days soil moisture change and K(sat) of 0-5 cm, 0-30 cm and 0-60 cm depths yielded correlations of 0.78, 0.82 and 0.71, respectively. These results are comparable to the findings of previous studies involving laboratory-controlled experiments and numerical simulations, and support their extension to the field conditions of the Little Washita watershed. These findings have potential applications of microwave remote sensing to obtain 2-days of soil moisture and then to quickly estimate the spatial distribution of K(sat) over large areas. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Greenbelt, MD 20771 USA. USDA ARS, Great Plains Syst Res, Ft Collins, CO 80522 USA. USDA ARS, Hydrol Lab, Beltsville, MD 20705 USA. RP Mattikalli, NM (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. NR 28 TC 31 Z9 33 U1 1 U2 9 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUN PY 1998 VL 19 IS 9 BP 1751 EP 1767 DI 10.1080/014311698215234 PG 17 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA ZX890 UT WOS:000074565700010 ER PT J AU Sun, G Ranson, KJ AF Sun, G Ranson, KJ TI Radar modelling of forest spatial patterns SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID MICROWAVE BACKSCATTER; LACUNARITY; SAR; TEXTURE; GAPS AB The understanding of ecosystem processes and the impacts of natural and anthropogenic induced change upon these processes requires techniques to monitor structure, composition, and function of ecosystems. Radar backscattering is a useful monitoring technique since it is sensitive to vegetation water content, its arrangement within the 3-D canopy structure as leaves, branches, trunks, and the underlying surface characteristics. In this research we used a 3-D radar backscatter model and lacunarity spatial data analysis to study the effects of forest patterns caused by natural processes or forest management practices on spatial properties of radar images. The simulated results were compared with AIRSAR data from an area of managed forests. The findings from this theoretical study will direct our further research on spatial characterization of forests using SAR imagery. C1 Univ Maryland, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. RP Sun, G (reprint author), Univ Maryland, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. RI Ranson, Kenneth/G-2446-2012 OI Ranson, Kenneth/0000-0003-3806-7270 NR 24 TC 17 Z9 20 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 JUN PY 1998 VL 19 IS 9 BP 1769 EP 1791 DI 10.1080/014311698215243 PG 23 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA ZX890 UT WOS:000074565700011 ER PT J AU Ward, RR Kirschman, RK Jhabvala, MD Babu, RS Das, NC Camin, DV Pessina, G AF Ward, RR Kirschman, RK Jhabvala, MD Babu, RS Das, NC Camin, DV Pessina, G TI Development of cryogenic Ge JFETs SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 3rd European Workshop on Low Temperature Electronics (WOLTE 3) CY JUN 24-26, 1998 CL SAN MINIATO, ITALY AB We report on initial development of new Ge JFETs for deep cryogenic (liquid-helium range) operation. Both p- and n-channel Ge JFETs were fabricated. Due to unsatisfactory epitaxial growth, the p-channel JFETs do not exhibit usable characteristics. The n-channel Ge JFETS have good de characteristics at room temperature, 77 K and 4 K, although at 4 K they exhibit a threshold and "steps" as also observed in earlier Ge JFETs made by Texas Instruments. Noise measurements at 4 K with V-ds = 1.2 V and I-d = 0.3 mA give e(n) of approximate to 0.5-1 mu V/Hz(1/2) at 1 Hz and approximate to 20-30 nV/Hz(1/2) at 10 kHz (input referred). This is considerably higher than that of the best Si JFETs operating at higher temperature or the best GaAs MESFETs operating at 4 K. However, we believe that with refinement of the design and fabrication the noise of the Ge JFETs can be reduced to a range suitable for deep cryogenic applications. C1 Germanium Power Devices Corp, Andover, MA 01810 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ball Aerosp & Technol Corp, Boulder, CO USA. Hughes STX, Lanham, MD USA. Univ Milan, Dept Phys, INFN, I-20133 Milan, Italy. RP Ward, RR (reprint author), Germanium Power Devices Corp, 300 Brickstone Sq,York St,Box 3065,Shawsheen Vil, Andover, MA 01810 USA. NR 11 TC 3 Z9 3 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1998 VL 8 IS P3 BP 123 EP 126 DI 10.1051/jp4:1998328 PG 4 WC Physics, Multidisciplinary SC Physics GA ZZ686 UT WOS:000074756500029 ER PT J AU Cunningham, TJ Fitzsimmons, M AF Cunningham, TJ Fitzsimmons, M TI Advances in discrete GaAs JFETs and simple amplifiers for deep cryogenic readouts SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 3rd European Workshop on Low Temperature Electronics (WOLTE 3) CY JUN 24-26, 1998 CL SAN MINIATO, ITALY AB The progress of the Jet Propulsion Laboratory in developing gallium arsenide junction field-effect transistors (GaAs JFETs) for application in infrared readout electronics operating below 10 Kelvin is discussed. Previously we had presented results on GaAs JFETs and shown that by using a highly isotropic HF-based etchant, the typical input leakage current at 4 K can be reduced to less than 1 fA. These same devices had a low frequency noise of just under 1 mu V/Hz(1/2) at 1 Hz at 4 K, while dissipating less than 1 mu W of power. In this paper we report on the fabrication of small-scale integrated circuit multiplexers and amplifiers made using this GaAs JFET technology. Small 8x1 source-follower-per-detector multiplexers and differential pairs have been fabricated and are fully functional at 4 K. The input-referred noise and leakage current is consistent with that for the discrete devices. Differential amplifier pairs were also measured. A systematic study of the device size dependence of the noise has been started, but as yet is inconclusive. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cunningham, TJ (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-315,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 1 Z9 1 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1998 VL 8 IS P3 BP 127 EP 130 DI 10.1051/jp4:1998329 PG 4 WC Physics, Multidisciplinary SC Physics GA ZZ686 UT WOS:000074756500030 ER PT J AU Romanofsky, RR Van Keuls, FW Miranda, FA AF Romanofsky, RR Van Keuls, FW Miranda, FA TI A cryogenic GaAs PHEMT/ferroelectric Ku-band tunable oscillator SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 3rd European Workshop on Low Temperature Electronics (WOLTE 3) CY JUN 24-26, 1998 CL SAN MINIATO, ITALY ID PHASE NOISE; RING AB A Ku-band tunable oscillator operated at and below 77 K is described. The oscillator is based on two separate technologies: a 0.25 mu m GaAs pseudomorphic high electron mobility transistor (PHEMT) circuit optimized for cryogenic operation, and a gold microstrip ring resonator patterned on a thin ferroelectric (SrTiO3) film which was laser ablated onto a LaAlO3 substrate. A tuning range of up to 3% of the center frequency was achieved by applying de bias between the ring resonator and ground plane. To the best of our knowledge, this is the first tunable oscillator based on a thin film ferroelectric structure demonstrated in the microwave frequency range. The design methodology of the oscillator and the performance characteristics of the tunable resonator are described. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Natl Res Council, Lewis Res Ctr, NASA, Cleveland, OH USA. RP Romanofsky, RR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 12 TC 11 Z9 11 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1998 VL 8 IS P3 BP 171 EP 174 DI 10.1051/jp4:1998337 PG 4 WC Physics, Multidisciplinary SC Physics GA ZZ686 UT WOS:000074756500038 ER PT J AU Demroff, HP Babu, S Bye, MR Coleman, KL Das, N DeBra, DB Ehrensberger, PD Farley, RP Gill, DK Goebel, JH Jhabvala, M Kashani, A Romero, E Sullivan, MT AF Demroff, HP Babu, S Bye, MR Coleman, KL Das, N DeBra, DB Ehrensberger, PD Farley, RP Gill, DK Goebel, JH Jhabvala, M Kashani, A Romero, E Sullivan, MT TI The telescope readout electronics for the gravity probe B satellite SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 3rd European Workshop on Low Temperature Electronics (WOLTE 3) CY JUN 24-26, 1998 CL SAN MINIATO, ITALY AB dThe pointing and stability requirements for the Gravity Probe B (GP-B) Relativity Mission pose a number of challenges for the star-tracking electronics. Because the telescope-gyroscope assembly operates at 2.8 K, the detector circuit's Si JFETs at the telescope focal plane must be thermally isolated and heated to at least 50 K through self-heating or with the aid of heating resistors. We have designed a low noise, thermally stable photodetector circuit that meets the GP-B requirements as well as fabricated an isolator to give the required thermal isolation and mechanical stability. Test results of the detector - isolator assembly are presented. C1 Lockheed Martin Missiles & Space GP B, Ctr Adv Technol, Palo Alto, CA 94304 USA. Ball Aerosp & Technol Corp, Boulder, CO USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Hughes STX, Lanham, MD USA. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Sensors & Instrumentat Branch, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Atlas Sci, Sunnyvale, CA 94086 USA. RP Demroff, HP (reprint author), Lockheed Martin Missiles & Space GP B, Ctr Adv Technol, Bldg 251,3251 Hanover St, Palo Alto, CA 94304 USA. NR 3 TC 2 Z9 2 U1 0 U2 2 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1998 VL 8 IS P3 BP 175 EP 179 DI 10.1051/jp4:1998338 PG 5 WC Physics, Multidisciplinary SC Physics GA ZZ686 UT WOS:000074756500039 ER PT J AU Wang, S Gwo, DH Bower, KA Huff, LW Kirschman, RK Lipa, JA Jhabvala, M Babu, S Das, N AF Wang, S Gwo, DH Bower, KA Huff, LW Kirschman, RK Lipa, JA Jhabvala, M Babu, S Das, N TI Testing the GP-B telescope readout electronics on a flight quality telescope SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT 3rd European Workshop on Low Temperature Electronics (WOLTE 3) CY JUN 24-26, 1998 CL SAN MINIATO, ITALY AB Integrated photodiodes and silicon JFET preamps are used for the optical readout of the Gravity Probe B cryogenic star tracking telescope. The heated circuit assembly is mounted on a thermal isolator so that it can be heated to around 80 K while the telescope remains at its operating temperature of 2.8 K. We present test results of the readout with a night quality telescope. C1 Stanford Univ, Hansen Expt Phys Lab, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ball Aerosp & Technol Corp, Boulder, CO USA. Hughes STX, Lanham, MD USA. RP Wang, S (reprint author), Stanford Univ, Hansen Expt Phys Lab, Stanford, CA 94305 USA. NR 2 TC 3 Z9 3 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD JUN PY 1998 VL 8 IS P3 BP 181 EP 184 DI 10.1051/jp4:1998339 PG 4 WC Physics, Multidisciplinary SC Physics GA ZZ686 UT WOS:000074756500040 ER PT J AU Young, DF Minnis, P Doelling, DR Gibson, GG Wong, T AF Young, DF Minnis, P Doelling, DR Gibson, GG Wong, T TI Temporal interpolation methods for the Clouds and the Earth's Radiant Energy system (CERES) experiment SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID RADIATION BUDGET EXPERIMENT; OUTGOING LONGWAVE RADIATION; DIURNAL-VARIATIONS; EXPERIMENT ERBE; VARIABILITY; BALANCE; COVER AB The Clouds and the Earth's Radiant Energy System (CERES) is a NASA multisatellite measurement program for monitoring the radiation environment of the earth-atmosphere system. The CERES instrument was flown on the Tropical Rainfall Measuring Mission satellite in late 1997, and will be flown on the Earth Observing System morning satellite in 1998 and afternoon satellite in 2000. To minimize temporal sampling errors associated with satellite measurements, two methods have been developed for temporally interpolating the CERES earth radiation budget measurements to compute averages of top-of-the-atmosphere shortwave and longwave flux. The first method is based on techniques developed From the Earth Radiation Budget Experiment (ERBE) and provides radiation data that are consistent with the ERBE processing. The second method is a newly developed technique for use in the CERES data processing. This technique incorporates high temporal resolution data from geostationary satellites to improve modeling of diurnal variations of radiation due to changing cloud conditions during the day. The performance of these two temporal interpolation methods is evaluated using a simulated dataset. Simulation studies show that the introduction of geostationary data into the temporal interpolation process significantly improves the accuracy of hourly and daily radiative products. Interpolation errors for instantaneous flux estimates are reduced by up to 68% for longwave flux and 80% for shortwave flux. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Analyt Serv & Mat Inc, Hampton, VA 23666 USA. RP Young, DF (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 420, Hampton, VA 23681 USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 25 TC 72 Z9 72 U1 0 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 JUN PY 1998 VL 37 IS 6 BP 572 EP 590 DI 10.1175/1520-0450(1998)037<0572:TIMFTC>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZV750 UT WOS:000074337400003 ER PT J AU Ozcan, M AF Ozcan, M TI Influence of electric potentials on atom interferometers: Increased rotation sensitivity SO JOURNAL OF APPLIED PHYSICS LA English DT Article AB An atomic interferometer for rotation sensing is proposed. The arms of the interferometer are enclosed in a Faraday cage, and when a potential is applied to the cage, the resultant phase difference in the counterpropagating atom de Broglie waves due to rotation can be much larger than the Sagnac phase shift. This effect, being quantum mechanical in nature, could be used to increase the rotation sensitivity of atomic interferometers. (C) 1998 American Institute of Physics. [S0021-8979(98)01311-5] C1 NASA, Ames Res Ctr, Informat Phys Grp, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, Informat Phys Grp, MS 269-3, Moffett Field, CA 94035 USA. NR 7 TC 4 Z9 4 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0021-8979 EI 1089-7550 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 1998 VL 83 IS 11 BP 6185 EP 6186 PN 1 PG 2 WC Physics, Applied SC Physics GA 108GE UT WOS:000075257100087 ER PT J AU Namkung, M Wincheski, B Bryant, RG Buchman, A AF Namkung, M Wincheski, B Bryant, RG Buchman, A TI Effects of heat treatment on the magnetic properties of polymer-bound iron particle cores SO JOURNAL OF APPLIED PHYSICS LA English DT Article; Proceedings Paper CT 7th Joint Magnetism and Magnetic Materials / International Magnetics Conference CY JAN 06-09, 1998 CL SAN FRANCISCO, CALIFORNIA SP Amer Inst Phys, IEEE Magnet Soc, TMS, Off Naval Res, Amer Soc Testing & Mat, Amer Ceram Soc AB Spherical iron particles of three different size distributions, 6-10 mu in diameter, 100 mesh and 30-80 mesh, were mixed with 2.0 wt % of soluble imide and compression molded at 300 degrees C under 131 MPa. Post-fabrication heat treatments were performed at 960 degrees C for 6 h resulting in a significant enhancement of the permeability in low field region for all the specimens except for the one made of 30-80 mesh particles. The rate of core loss of these specimens at a magnetic induction of 5 kG measured up to 1 kHz shows a noticeable increase after heat treatment which, along with the permeability enhancement, can be explained by the coalescence of particles forming a network of conductivity paths in the specimens. The scanning electron micrographs taken for the 6-10 mu particle specimens show no evidence of heat treatment-induced grain growth. The untreated specimens show a very weak f(2)-dependence of the core loss which clearly indicates a negligible contribution from the eddy current loss. In particular, an almost perfect linearity was found in the frequency dependence of the core loss of the untreated specimen made of 100 mesh iron particles. (C) 1998 American Institute of Physics. [S0021-8979(98)34711-8]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Old Dominion Univ, Norfolk, VA 23529 USA. RP Namkung, M (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. RI Namkung, Min/E-1533-2012 NR 6 TC 2 Z9 2 U1 0 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 1998 VL 83 IS 11 BP 6474 EP 6476 DI 10.1063/1.367923 PN 2 PG 3 WC Physics, Applied SC Physics GA 152UQ UT WOS:000077795500083 ER PT J AU Dooley, J De Graef, M McHenry, ME AF Dooley, J De Graef, M McHenry, ME TI Induction mapping of magnetostrictive materials SO JOURNAL OF APPLIED PHYSICS LA English DT Article; Proceedings Paper CT 7th Joint Magnetism and Magnetic Materials / International Magnetics Conference CY JAN 06-09, 1998 CL SAN FRANCISCO, CALIFORNIA SP Amer Inst Phys, IEEE Magnet Soc, TMS, Off Naval Res, Amer Soc Testing & Mat, Amer Ceram Soc ID ELECTRON-MICROSCOPY; DIFFRACTION; CRYSTAL AB An energy-filtered magnetic induction mapping technique has been implemented on a JEOL 4000EX equipped with a Gatan imaging filter. A study of the magnetic domain structure in Terfenol-D, a magnetostrictive actuator material, is presented as an example application of the technique. The method is equivalent to differential phase contrast microscopy by the reciprocity theorem. Image simulations of all stages of the induction mapping process are shown to support these observations. (C) 1998 American Institue of Physics. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Dept Mat Sci & Engn, Pittsburgh, PA 15213 USA. RP Dooley, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI McHenry, Michael/B-8936-2009; DeGraef, Marc/G-5827-2010 OI DeGraef, Marc/0000-0002-4721-6226 NR 13 TC 4 Z9 4 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 1998 VL 83 IS 11 BP 6837 EP 6839 DI 10.1063/1.367817 PN 2 PG 3 WC Physics, Applied SC Physics GA 152UQ UT WOS:000077795500205 ER PT J AU Samoilov, AV Beach, G Fu, CC Yeh, NC Vasquez, RP AF Samoilov, AV Beach, G Fu, CC Yeh, NC Vasquez, RP TI Giant spontaneous Hall effect and magnetoresistance in La1-xCaxCoO3(0.1 <= x <= 0.5) SO JOURNAL OF APPLIED PHYSICS LA English DT Article; Proceedings Paper CT 7th Joint Magnetism and Magnetic Materials / International Magnetics Conference CY JAN 06-09, 1998 CL SAN FRANCISCO, CALIFORNIA SP Amer Inst Phys, IEEE Magnet Soc, TMS, Off Naval Res, Amer Soc Testing & Mat, Amer Ceram Soc ID LA1-XSRXCOO3 AB Results of resistivity and Hall effect measurements in La1-xCaxCoO3 (0.1 less than or equal to x less than or equal to 0.5) epitaxial films and ceramics an presented. The spontaneous Hall effect in La1-xCaxCoO3 (LCCO) is observed for ferromagnetic samples with x greater than or equal to 0.2. The Hall effect is largest near the magnetic percolation threshold x = 0.2. For x = 0.2, the low-field slope of the Hall resistivity, rho(xy)/(mu(0)H), attains a large value of 2 x 10(-6) m(3)/C below the Curie temperature T-c, which may be applied to sensitive low-held detection. Except near the magnetic percolation threshold, the longitudinal resistivity of LCCO decreases with increasing field at all temperatures. Anomalous temperature-dependent magnetoresistance occurs in the sample with x = 0.2, which may be associated with the spin-state transition in LCCO. (C) 1998 American Institute of Physics. [S0021-8979(98)26211-6]. C1 CALTECH, Dept Phys 114 36, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Samoilov, AV (reprint author), CALTECH, Dept Phys 114 36, Pasadena, CA 91125 USA. EM samoliov@cco.caltech.edu OI Beach, Geoffrey/0000-0001-9158-7430 NR 11 TC 11 Z9 11 U1 0 U2 9 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 1998 VL 83 IS 11 BP 6998 EP 7000 DI 10.1063/1.367623 PN 2 PG 3 WC Physics, Applied SC Physics GA 152UQ UT WOS:000077795500258 ER PT J AU Wei, JYT Yeh, NC Vasquez, RP Gupta, A AF Wei, JYT Yeh, NC Vasquez, RP Gupta, A TI Tunneling evidence of half-metallicity in epitaxial films of ferromagnetic perovskite manganites and ferrimagnetic magnetite SO JOURNAL OF APPLIED PHYSICS LA English DT Article; Proceedings Paper CT 7th Joint Magnetism and Magnetic Materials / International Magnetics Conference CY JAN 06-09, 1998 CL SAN FRANCISCO, CALIFORNIA SP Amer Inst Phys, IEEE Magnet Soc, TMS, Off Naval Res, Amer Soc Testing & Mat, Amer Ceram Soc ID MAGNETORESISTANCE; LA0.7CA0.3MNO3; TRANSPORT AB Direct evidence of half-metallic density of states is observed by scanning tunneling spectroscopy of ferromagnetic La0.7Ca0.3MnO3 and La1-xSrxMnO3 (x=0.3,0.33) epitaxial films which exhibit colossal magnetoresistance (CMR). At 77 K, well below the Curie temperatures, the normalized tunneling conductance (dI/dV)/[I/V] for all samples exhibits similar pronounced peak structures, consistent with the spin-split density of states spectra for the itinerant bands in the ferromagnetic state. The exchange energy splitting between the majority and minority spins, as well as an apparent energy gap near the Fermi level, show variations with the chemical composition and the temperature. For comparison, the tunneling spectrum of a half-metallic ferrimagnet Fe3O4 is also studied. The characteristic spin-split density of states spectrum is observed, and the similarities and differences of Fe3O4 compared with the perovskite manganites are discussed. (C) 1998 American Institute of Physics. [S0021-8979(98)45811-0]. C1 CALTECH, Dept Phys, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. IBM Corp, Thomas J Watson Res Ctr, Yorktown Heights, NY 10598 USA. RP Wei, JYT (reprint author), CALTECH, Dept Phys, Pasadena, CA 91125 USA. EM jytwei@cco.caltech.edu NR 28 TC 39 Z9 39 U1 0 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-8979 J9 J APPL PHYS JI J. Appl. Phys. PD JUN 1 PY 1998 VL 83 IS 11 BP 7366 EP 7368 DI 10.1063/1.367799 PN 2 PG 3 WC Physics, Applied SC Physics GA 152UQ UT WOS:000077795500380 ER PT J AU Ballard, RE Watenpaugh, DE Breit, GA Murthy, G Holley, DC Hargens, AR AF Ballard, RE Watenpaugh, DE Breit, GA Murthy, G Holley, DC Hargens, AR TI Leg intramuscular pressures during locomotion in humans SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE muscle force; soleus; tibialis anterior; walking; running ID FORCE; MUSCLES; EXERCISE; ELECTROMYOGRAPHY; SOLEUS; INVIVO; EMG AB To assess the usefulness of intramuscular pressure (IMP) measurement for studying muscle function during gait, IMP was recorded in the soleus and tibialis anterior muscles of 10 volunteers during treadmill walking and running by using transducer-tipped catheters. Soleus IMP exhibited single peaks during late-stance phase of walking [181 +/- 69 (SE) mmHg] and running (269 +/- 95 mmHg). Tibialis anterior IMP showed a biphasic response, with the largest peak (90 +/- 15 mmHg during walking and 151 +/- 25 mmHg during running) occurring shortly after heel strike. IMP magnitude increased with gait speed in both muscles. Linear regression of soleus IMP against ankle joint torque obtained by a dynamometer produced linear relationships (n = 2, r = 0.97 for both). Application of these relationships to IMP data yielded estimated peak soleus moment contributions of 0.95-1.65 N . m/kg during walking, and 1.43-2.70 N . m/kg during running. Phasic elevations of IMP during exercise are probably generated by local muscle tissue deformations due to muscle force development. Thus profiles of IMP provide a direct, reproducible index of muscle function during locomotion in humans. C1 NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Stanford, CA 94305 USA. San Jose State Univ, Dept Biol Sci, San Jose, CA 95192 USA. RP Hargens, AR (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Stanford, CA 94305 USA. NR 30 TC 45 Z9 46 U1 1 U2 4 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD JUN PY 1998 VL 84 IS 6 BP 1976 EP 1981 PG 6 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA ZR297 UT WOS:000073960000021 PM 9609792 ER PT J AU Evans, GL Morey-Holton, E Turner, RT AF Evans, GL Morey-Holton, E Turner, RT TI Spaceflight has compartment- and gene-specific effects on mRNA levels for bone matrix proteins in rat femur SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE bone histomorphometry; Northern analysis; bone formation; weightlessness; osteoporosis ID MESSENGER-RNA LEVELS; GROWING RATS; TRABECULAR BONE; GROWTH-HORMONE; OSTEONECTIN; EXPRESSION; TISSUE; ACID; WEIGHTLESSNESS; OSTEOCALCIN AB In the present study, we evaluated the possibility that the abnormal bone matrix produced during spaceflight may be associated with reduced expression of bone matrix protein genes. To test this possibility, we investigated the effects of a 14-day spaceflight (SLS-2 experiment) on steady-state mRNA levels for glyceraldehyde-3-phosphate dehydrogenase (GAPDH), osteocalcin, osteonectin, and prepro-alpha(1) subunit of type I collagen in the major bone compartments of rat femur. There were pronounced site-specific differences in the steady-state levels of expression of the mRNAs for the three bone matrix proteins and GAPDH in normal weight-bearing rats, and these relationships were altered after spaceflight. Specifically, spaceflight resulted in decreases in mRNA levels for GAPDH (decreased in proximal metaphysis), osteocalcin (decreased in proximal metaphysis), osteonectin (decreased in proximal and distal metaphysis), and collagen (decreased in proximal and distal metaphysis) compared with ground controls. There were no changes in mRNA levels for matrix proteins or GAPDH in the shaft and distal epiphysis. These results demonstrate that spaceflight leads to site- and gene-specific decreases in mRNA levels for bone matrix proteins. These findings are consistent with the hypothesis that spaceflight-induced decreases in bone formation are caused by concomitant decreases in expression of genes for bone matrix proteins. C1 Mayo Clin & Mayo Fdn, Dept Orthoped, Rochester, MN 55905 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Turner, RT (reprint author), Mayo Clin & Mayo Fdn, Dept Orthoped, Rm 3-69 Med Sci Bldg,200 1st St SW, Rochester, MN 55905 USA. FU NIAMS NIH HHS [AR-35651] NR 48 TC 20 Z9 22 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD JUN PY 1998 VL 84 IS 6 BP 2132 EP 2137 PG 6 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA ZR297 UT WOS:000073960000038 PM 9609809 ER PT J AU Arkoosh, MR Casillas, E Clemons, E Kagley, AN Olson, R Reno, P Stein, JE AF Arkoosh, MR Casillas, E Clemons, E Kagley, AN Olson, R Reno, P Stein, JE TI Effect of pollution on fish diseases: Potential impacts on salmonid populations SO JOURNAL OF AQUATIC ANIMAL HEALTH LA English DT Article; Proceedings Paper CT Symposium on Pathogens and Diseases of Fish in Aquatic Ecosystems - Implications in Fisheries Management CY JUN 03-04, 1997 CL PORTLAND, OREGON SP Pacific NW Fish Hlth Protect Comm, Alaska Fish & Game, Amer Fisheries Soc, Colorado Wyoming Chapter, Amer Fisheries Soc, Fish Hlth Sect, BioProd, Clear Springs Foods Inc, Idaho Aquaculture Assoc, Montana Dept Fish Wildlife & Parks, Moore Clark, Muckelshoot Indian Tribe, Keta Creek Hatchery, Natl Marine Fisheries Serv, Nelson & Sons, Nisqually Indian Tribe, Clear Springs Hatchery, Oregon Dept Fish & Wildlife, Oregon State Univ, Suquamish Indian Tribe, Trout Unlimited, Univ Idaho, US Fish & Wildlife Serv, Washington Dept Fish & Wildlife, Western Chem, Western Fisheries Res Ctr, US Geol Survey, Western Reg Aquaculture Consortium, Whirling Dis Fdn ID JUVENILE CHINOOK SALMON; BACTERIAL KIDNEY-DISEASE; ONCORHYNCHUS-TSHAWYTSCHA; PACIFIC SALMON; EXPOSURE; WASHINGTON; IMMUNITY; URBAN AB Anthropogenic factors have contributed to the precipitous decline of wild Pacific salmon stocks, although the mechanisms and processes at work are largely unknown. Pollution may be one of these factors. Sediments in estuaries are known to act as repositories for contaminants, and estuaries are important habitats for ocean-and river-migrating salmon. We have shown that juvenile salmon Oncorhynchus spp. and their prey bioaccumulate chlorinated hydrocarbons and aromatic hydrocarbons-important classes of toxic xenobiotics. Furthermore, we have shown that exposure to these pollutants can lead to immunosuppression and increased disease susceptibility in juvenile salmon. Whether pollution influences natural disease outbreaks in host populations, including salmon, is currently unknown. It is postulated that the occurrence of disease depends on the interaction of the host, the environment, and the pathogen. Absence of pathogens would reduce the potential for adverse environments to influence disease outbreaks. However, a recent reconnaissance survey of juvenile chinook salmon Oncorhynchus tshawytscha from Oregon coastal rivers revealed that pathogens were an integral component in all systems studied, although the prevalence of the pathogens varied. Furthermore, recent studies of natural fish populations have demonstrated that infectious-disease-induced mortality can significantly reduce the size of the host population. By creating adverse environments (e.g., polluted estuaries) which alter the susceptibility of the host to pathogens that are integral and ubiquitous components of the habitat, pollution increases the probability of disease-related impacts on fish populations. C1 Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, Seattle, WA 98112 USA. Oregon State Univ, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. RP Arkoosh, MR (reprint author), Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, Hatfield Marine Sci Ctr, 2030 S Marine Sci Dr, Newport, OR 97365 USA. NR 32 TC 80 Z9 83 U1 3 U2 23 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0899-7659 J9 J AQUAT ANIM HEALTH JI J. Aquat. Anim. Health PD JUN PY 1998 VL 10 IS 2 BP 182 EP 190 DI 10.1577/1548-8667(1998)010<0182:EOPOFD>2.0.CO;2 PG 9 WC Fisheries; Veterinary Sciences SC Fisheries; Veterinary Sciences GA ZU180 UT WOS:000074170300012 ER PT J AU Durden, SL Haddad, ZS Kitiyakara, A Li, FK AF Durden, SL Haddad, ZS Kitiyakara, A Li, FK TI Effects of nonuniform beam filling on rainfall retrieval for the TRMM precipitation radar SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID DUAL-FREQUENCY ALGORITHMS; SPACEBORNE RADAR; SINGLE-FREQUENCY; MEASURING MISSION; AIRBORNE; TESTS; ATTENUATION; SATELLITE; MODEL; OCEAN AB The Tropical Rainfall Measuring Mission (TRMM) will carry the first spaceborne radar for rainfall observation. Because the TRMM Precipitation Radar (PR) footprint size of 4.3 km is greater than the scale of some convective rainfall events, there is concern that nonuniform filling of the PR antenna beam may bias the retrieved rain-rate profile. The authors investigate this effect theoretically and then observationally using data from the NASA Jet Propulsion Laboratory Airborne Rain Mapping Radar (ARMAR), acquired during Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment in early 1993. The authors' observational approach is to simulate TRMM PR data using the ARMAR data and compare the radar observables and retrieved rain rate from the simulated PR data with those corresponding to the high-resolution radar measurements. The authors find that the path-integrated attenuation and the resulting path-averaged rain rate are underestimated. The reflectivity and rain rate near the top of the rainfall column are overestimated. The near-surface reflectivity can be overestimated or underestimated, with a mean error very close to zero. The near-surface rain rate, however, is usually underestimated, sometimes severely. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Durden, SL (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-227,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM durden@kappa.jpl.nasa.gov NR 23 TC 41 Z9 42 U1 0 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 JUN PY 1998 VL 15 IS 3 BP 635 EP 646 DI 10.1175/1520-0426(1998)015<0635:EONBFO>2.0.CO;2 PG 12 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA ZQ890 UT WOS:000073913300003 ER PT J AU Philipona, R Frohlich, C Dehne, K DeLuisi, J Augustine, J Dutton, E Nelson, D Forgan, B Novotny, P Hickey, J Love, SP Bender, S McArthur, B Ohmura, A Seymour, JH Foot, JS Shiobara, M Valero, FPJ Strawa, AW AF Philipona, R Frohlich, C Dehne, K DeLuisi, J Augustine, J Dutton, E Nelson, D Forgan, B Novotny, P Hickey, J Love, SP Bender, S McArthur, B Ohmura, A Seymour, JH Foot, JS Shiobara, M Valero, FPJ Strawa, AW TI The Baseline Surface Radiation Network pyrgeometer round-robin calibration experiment SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID PERFORMANCE; ACCURACY AB With the aim of improving the consistency of terrestrial and atmospheric longwave radiation measurements within the Baseline Surface Radiation Network, five: Eppley Precision Infrared Radiometer (PIR) pyrgeometers and one modified Mereorological Research Flight (MRF) pyrgeometer were individually calibrated by 11 specialist laboratories. The round-robin experiment was conducted in a "blind" sense in that the participants had no knowledge of the results of others until the wholl: series of calibrations had ended. The responsivities C(mu V/W m(-2)) determined by 6 of the 11 institutes were within about 2% of the median for all five PIR pyrgeometers. Among the six laboratories, the absolute deviation around the median of the deviations of the five instruments is less than 1%. This small scatter suggests that PII: pyrgeometers were stable at least during the two years of the experiment and that the six different calibration devices reproduce the responsivity C of PIR pyrgeometers consistently and within the precision required for climate applications. The results also suggest that the responsivity C can be determined without simultaneous determination of the dome correction factor k, if the temperature difference between pyrgeometer body and dome is negligible during calibration. For field measurements, however, k has to be precisely known. The calibration of the MRF pyrgeometer, although not performed by all institutes, also showed satisfactory results. C1 World Radiat Ctr, Phys Meteorolog Observ, CH-7260 Davos Dorf, Switzerland. Meteorolog Observat Potsdam, Potsdam, Germany. SRRB, Appl Res Lab, NOAA, Boulder, CO USA. CMDL, NOAA, Boulder, CO USA. Bur Meteorol, Melbourne, Vic, Australia. Eppley Lab, Newport, RI USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. Atmospher Environm Serv, Downsview, ON, Canada. ETH Zurich, Inst Geophys, CH-8093 Zurich, Switzerland. Meteorol Res Flight, Farnborough, Hants, England. Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Philipona, R (reprint author), World Radiat Ctr, Phys Meteorolog Observ, Dorfstr 33, CH-7260 Davos Dorf, Switzerland. NR 16 TC 34 Z9 34 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 JUN PY 1998 VL 15 IS 3 BP 687 EP 696 DI 10.1175/1520-0426(1998)015<0687:TBSRNP>2.0.CO;2 PG 10 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA ZQ890 UT WOS:000073913300007 ER PT J AU Kummerow, C Barnes, W Kozu, T Shiue, J Simpson, J AF Kummerow, C Barnes, W Kozu, T Shiue, J Simpson, J TI The Tropical Rainfall Measuring Mission (TRMM) sensor package SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article AB This note is intended to serve primarily as a reference guide to users wishing to make use of the Tropical Rainfall Measuring Mission data. It covers each of the three primary rainfall instruments: the passive microwave radiometer, the precipitation radar. and the Visible and Infrared Radiometer System on board the spacecraft. Radiometric characteristics, scanning geometry, calibration procedures, and data products are described for each of these three sensors. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Commun Res Labs, Tokyo, Japan. RP Kummerow, C (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. EM Kummerow@audry.gsfc.nasa.gov RI PMM, JAXA/K-8537-2016 NR 9 TC 1124 Z9 1222 U1 8 U2 51 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 JUN PY 1998 VL 15 IS 3 BP 809 EP 817 DI 10.1175/1520-0426(1998)015<0809:TTRMMT>2.0.CO;2 PG 9 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA ZQ890 UT WOS:000073913300018 ER PT J AU Southworth, SH LeBrun, T Azuma, Y Dyall, KG AF Southworth, SH LeBrun, T Azuma, Y Dyall, KG TI Argon KM photoelectron satellites SO JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA LA English DT Article DE X-ray photoelectron spectroscopy; satellites; inner shell; shake theory ID SYNCHROTRON RADIATION; NONDIPOLAR ASYMMETRIES; SHELL PHOTOIONIZATION; ANGULAR-DISTRIBUTIONS; HIGH-RESOLUTION; CROSS-SECTION; AR K; THRESHOLD; SPECTRA; EDGE AB Satellite structure in the Ar K-shell photoelectron spectrum due to M-shell excitations was recorded at X-ray energies 122-422 eV above threshold. Relativistic, multiconfiguration shake-theory calculations give a good overall match to the main satellite features, showing that electron correlation in this case is qualitatively well described by the relaxation model. Conjugate satellite intensities appear to be negligible at the X-ray energies used in the experiment. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Argonne Natl Lab, Argonne, IL 60439 USA. Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA. Natl Lab High Energy Phys, Photon Factory, Tsukuba, Ibaraki 305, Japan. NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Southworth, SH (reprint author), Argonne Natl Lab, 9700 S Cass Ave, Argonne, IL 60439 USA. NR 37 TC 4 Z9 4 U1 0 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0368-2048 J9 J ELECTRON SPECTROSC JI J. Electron Spectrosc. Relat. Phenom. PD JUN PY 1998 VL 94 IS 1-2 BP 33 EP 38 DI 10.1016/S0368-2048(98)00149-2 PG 6 WC Spectroscopy SC Spectroscopy GA 100GB UT WOS:000074806800005 ER PT J AU Fejtek, M Souza, K Neff, A Wassersug, R AF Fejtek, M Souza, K Neff, A Wassersug, R TI Swimming kinematics and respiratory behaviour of Xenopus laevis larvae raised in altered gravity SO JOURNAL OF EXPERIMENTAL BIOLOGY LA English DT Article DE Xenopus laevis; tadpole; microgravity; locomotion; swimming; respiration; hypergravity; development ID ONTOGENY; TADPOLES AB We examined the respiratory behaviours and swimming kinematics of Xenopus laevis tadpoles hatched in microgravity (Space Shuttle), simulated microgravity (clinostat) and hypergravity (3g centrifuge), All observations were made in the normal 1 g environment. Previous research has shown that X. laevis raised in microgravity exhibit abnormalities in their lungs and vestibular system upon return to 1 g. The tadpoles raised in true microgravity exhibited a significantly lower tailbeat frequency than onboard 1 g centrifuge controls on the day of landing (day(0)), but this behaviour normalized within 9 days, The two groups did not differ significantly in buccal pumping rates. Altered buoyancy in the space-flight microgravity tadpoles was indicated by an increased swimming angle on the day after landing (day(1)), Tadpoles raised in simulated microgravity differed to a greater extent in swimming behaviours from their 1 g controls. The tadpoles raised in hypergravity showed no substantive effects on the development of swimming or respiratory behaviours, except swimming angle. Together, these results show that microgravity has a transient effect on the development of locomotion in X. laevis tadpoles, most notably on swimming angle, indicative of stunted lung development. On the basis Of the behaviours we studied, there is no indication of neuromuscular retardation in amphibians associated with embryogenesis in microgravity. C1 Dalhousie Univ, Dept Anat & Neurobiol, Halifax, NS B3H 4H7, Canada. NASA, Space Directorate, Ames Res Ctr, Moffett Field, CA 94035 USA. Indiana Univ, Med Sci Program, Bloomington, IN 47405 USA. RP Fejtek, M (reprint author), Dalhousie Univ, Dept Anat & Neurobiol, Sir Charles Tupper Med Bldg, Halifax, NS B3H 4H7, Canada. NR 23 TC 14 Z9 15 U1 0 U2 1 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE, CAMBS, ENGLAND CB4 4DL SN 0022-0949 J9 J EXP BIOL JI J. Exp. Biol. PD JUN PY 1998 VL 201 IS 12 BP 1917 EP 1926 PG 10 WC Biology SC Life Sciences & Biomedicine - Other Topics GA ZY260 UT WOS:000074602300007 PM 9722430 ER PT J AU Folk, CL Remington, R AF Folk, CL Remington, R TI Selectivity in distraction by irrelevant featural singletons: Evidence for two forms of attentional capture SO JOURNAL OF EXPERIMENTAL PSYCHOLOGY-HUMAN PERCEPTION AND PERFORMANCE LA English DT Article ID VISUAL-ATTENTION; PERCEPTUAL SELECTIVITY; CONTROL SETTINGS; APPARENT MOTION; COLOR; CONTINGENT; SEARCH; COST; VOLUNTARY; OBJECTS AB Four experiments addressed the degree of top-down control over attentional capture in visual search for featural singletons. In a modified spatial cuing paradigm, the spatial relationship and featural similarity of target and distracter singletons were systematically varied. Contrary to previous studies, all 4 experiments showed that when searching for a singleton target, an irrelevant featural singleton captures spatial attention only when defined by the same feature value as the target. Experiments 2, 3, and 4 provided a potential explanation for the discrepancy with previous studies by showing that irrelevant singletons can produce distraction effects that are dissociable from shifts of spatial attention. The results suggest the existence of 2 distinct forms of attentional capture. C1 Villanova Univ, Dept Psychol, Villanova, PA 19085 USA. NASA, Ames Res Ctr, Human Factors Res Div, Moffett Field, CA USA. RP Folk, CL (reprint author), Villanova Univ, Dept Psychol, Villanova, PA 19085 USA. RI Martin Arevalo, Elisa/L-4472-2014 OI Martin Arevalo, Elisa/0000-0002-4546-6440 NR 29 TC 392 Z9 401 U1 6 U2 49 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 USA SN 0096-1523 J9 J EXP PSYCHOL HUMAN JI J. Exp. Psychol.-Hum. Percept. Perform. PD JUN PY 1998 VL 24 IS 3 BP 847 EP 858 DI 10.1037/0096-1523.24.3.847 PG 12 WC Psychology; Psychology, Experimental SC Psychology GA ZQ758 UT WOS:000073900100012 PM 9627420 ER PT J AU Farrell, WM Desch, MD Houser, JG AF Farrell, WM Desch, MD Houser, JG TI Modification of the upper atmosphere over power lines: A geological effect SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LOWER IONOSPHERE AB Under certain circumstances, ELF radiation from power lines is able to very mildly heat the electrons in the upper atmosphere via ELF wave/electron interaction. The electron temperature increase for O-mode heating is <1%. However, the significance of the heating is a function of the line construction and also the character of the underlying ground resistivity with the greatest heating effect occurring over a resistive earth. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Farrell, WM (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Farrell, William/I-4865-2013 NR 15 TC 2 Z9 2 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1998 VL 103 IS A6 BP 11573 EP 11578 DI 10.1029/97JA03725 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ564 UT WOS:000073880700001 ER PT J AU Lu, G Baker, DN McPherron, RL Farrugia, CJ Lummerzheim, D Ruohoniemi, JM Rich, FJ Evans, DS Lepping, RP Brittnacher, M Li, X Greenwald, R Sofko, G Villain, J Lester, M Thayer, J Moretto, T Milling, D Troshichev, O Zaitzev, A Odintzov, V Makarov, G Hayashi, K AF Lu, G Baker, DN McPherron, RL Farrugia, CJ Lummerzheim, D Ruohoniemi, JM Rich, FJ Evans, DS Lepping, RP Brittnacher, M Li, X Greenwald, R Sofko, G Villain, J Lester, M Thayer, J Moretto, T Milling, D Troshichev, O Zaitzev, A Odintzov, V Makarov, G Hayashi, K TI Global energy deposition during the January 1997 magnetic cloud event SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID AURORAL ELECTROJET INDEXES; SOLAR-WIND; IONOSPHERIC ELECTRODYNAMICS; GEOMAGNETIC STORM; FIELD; MAGNETOSPHERE; THERMOSPHERE; PARAMETERS; AE AB The passage of an interplanetary magnetic cloud at Earth on January 10-11, 1997, induced significant geomagnetic disturbances, with a maximum AE in excess of 2000 nT and a minimum Dst of about -85 nT. We use a comprehensive set of data collected from space-borne instruments and from ground-based facilities to estimate the energy deposition associated with the three major magnetospheric sinks during the event. It is found that averaged over the 2-day period, the total magnetospheric energy deposition rate is about 400 GW, with 190 GW going into Joule heating rate, 120 GW into ring current injection, and 90 GW into auroral precipitation. By comparison, the average solar wind electromagnetic energy transfer rate as represented by the &EPSILON; parameter is estimated to be 460 GW, and the average available solar wind kinetic power USW is about 11,000 GW. A good linear correlation is found between the AE index and various ionospheric parameters such as the cross-polar-cap potential drop, hemisphere-integrated Joule heating rate, and hemisphere-integrated auroral precipitation. In the northern hemisphere where the data coverage is extensive, the proportionality factor is 0.06 kV/nT between the potential drop and AE, 0.25 GW/nT between Joule heating rate and AE, and 0.13 GW/nT between auroral precipitation and AE. However, different studies have resulted in different proportionality factors. One should therefore be cautious when using empirical formulas to estimate the ionospheric energy deposition. There is an evident saturation of the cross-polar-cap potential drop for large AE(>1000 nT), but further studies are needed to confirm this. C1 Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA. Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Johns Hopkins Univ, Appl Phys Lab, Baltimore, MD 20742 USA. Phillips Lab, Hanscom AFB, MA 01731 USA. NOAA, Space Environm Ctr, Space Environm Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Washington, Dept Geophys, Seattle, WA 98122 USA. Univ Saskatchewan, Dept Phys & Engn Phys, Saskatoon, SK S7N 5E2, Canada. CNRS, Lab Phys & Chim Environm, F-45071 Orleans, France. Univ Leicester, Dept Phys, Leicester LE1 7RH, Leics, England. SRI Int, Menlo Park, CA 94025 USA. Danish Meteorol Inst, Copenhagen, Denmark. York Univ, Dept Phys, York Y01 5DD, N Yorkshire, England. Arctic & Antarctic Res Inst, Dept Geophys, St Petersburg 199226, Russia. IZMIRAN, Troitsk 142092, Moscow Region, Russia. Inst Cosmophys Res & Aeron, Yakutsk, Russia. Univ Tokyo, Dept Earth & Planetary Phys, Tokyo 113, Japan. RP Lu, G (reprint author), Natl Ctr Atmospher Res, High Altitude Observ, POB 3000, Boulder, CO 80307 USA. RI Lu, Gang/A-6669-2011; Moretto, Therese/B-6846-2013 OI Moretto, Therese/0000-0002-2403-5561 NR 30 TC 120 Z9 121 U1 1 U2 11 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1998 VL 103 IS A6 BP 11685 EP 11694 DI 10.1029/98JA00897 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ564 UT WOS:000073880700011 ER PT J AU Yoon, PH Lui, ATY Wong, HK AF Yoon, PH Lui, ATY Wong, HK TI Two-fluid theory of drift-kink instability in a one-dimensional neutral sheet SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FIELD CURRENT INSTABILITY; ION WEIBEL INSTABILITY; GEOMAGNETIC TAIL; STABILITY AB A thin current sheet with thickness comparable to the thermal ion gyroradius possesses free energy capable of driving a number of plasma instabilities for its destabilization. Among these instabilities is the drift-kink instability (DKI) unveiled through previous numerical simulations. To advance our theoretical understanding of DKI, we formulate a two-fluid theory with finite ion and electron temperatures in a one-dimensional (Harris) current sheet to examine the linear properties of DKI. We reduce the stability analysis to solving a nonlocal eigenvalue equation. We find that the eigenvalue equation gives a number of growing modes with both symmetric and antisymmetric magnetic perturbations with respect to the neutral sheet. These solutions have high growth rates, generally of the same order as their real frequencies, which are sizable fractions of the ion gyrofrequencies evaluated outside the current sheet. Near the center of the current sheet, the eigenfunction exhibits fine spatial structures with dimensions much smaller than the ion inertial length. These structures become progressively broadened as the ion to electron mass ratio is arbitrarily reduced. This theoretical result is potentially useful in assessing the impact of adopting unrealistic ion to electron mass ratio in numerical simulations of DKI or thin current sheet stability. C1 Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Yoon, PH (reprint author), Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. EM yoonp@uap.umd.edu; tony.lui@jhuapl.edu; kit.wong@gsfc.nasa.gov RI Yoon, Peter/E-2395-2013 NR 21 TC 31 Z9 31 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1998 VL 103 IS A6 BP 11875 EP 11886 DI 10.1029/98JA00102 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ564 UT WOS:000073880700026 ER PT J AU Connerney, JEP Acuna, MH Ness, NF Satoh, T AF Connerney, JEP Acuna, MH Ness, NF Satoh, T TI New models of Jupiter's magnetic field constrained by the Io flux tube footprint SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HUBBLE-SPACE-TELESCOPE; ULTRAVIOLET AURORA; POLAR AURORA; UV AURORA; MU-M; ULYSSES; H-3(+); IMAGES; H-3+; MAGNETOSPHERE AB Spherical harmonic models of the planetary magnetic field of Jupiter are obtained from in situ magnetic field measurements and remote observations of the position of the foot of the Io flux tube in Jupiter's ionosphere. The Io flux tube (IFT) footprint locates the ionospheric footprint of field lines traced from Io's orbital radial distance in the equator plane (5.9 Jovian radii). The IFT footprint is a valuable constraint on magnetic field models, providing "ground truth" information in a region close to the planet and thus far not sampled by spacecraft. The magnetic field is represented using a spherical harmonic expansion of degree and order 4 for the planetary ("internal") field and an explicit model of the magnetodisc for the field ("external") due to distributed currents. Models fitting Voyager 1 and Pioneer 11 magnetometer observations and the IFT footprint are obtained by partial solution of the underdetermined inverse problem using generalized inverse techniques. Dipole, quadrupole, octupole, and a subset of higher-degree and higher-order spherical harmonic coefficients are determined and compared with earlier models. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Sci Univ Tokyo, Noda, Chiba 278, Japan. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Connerney, JEP (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. EM jec@lepjec.gsfc.nasa.gov; mha@lepmom.gsfc.nasa.gov; nfness@bripv4.bartol.udel.edu; tsatoh@rs.noda.sut.ac.jp RI connerney, john/I-5127-2013; OI connerney, jack/0000-0001-7478-6462 NR 59 TC 219 Z9 219 U1 2 U2 15 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1998 VL 103 IS A6 BP 11929 EP 11939 DI 10.1029/97JA03726 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ564 UT WOS:000073880700030 ER PT J AU Lin, N Kellogg, PJ MacDowall, RJ Scime, EE Balogh, A Forsyth, RJ McComas, DJ Phillips, JL AF Lin, N Kellogg, PJ MacDowall, RJ Scime, EE Balogh, A Forsyth, RJ McComas, DJ Phillips, JL TI Very low frequency waves in the heliosphere: Ulysses observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ELECTRON HEAT-FLUX; SOLAR-WIND; INTERPLANETARY SHOCKS; MAGNETIC-FIELD; ECLIPTIC-PLANE; WHISTLER WAVES; LATITUDES; RADIO AB An overall profile of plasma wave activity in a frequency range of 0.2 to 448 Hz in the solar wind is presented using 6 years of Ulysses data which cover a large range of heliographic latitudes (0 degrees to +/- 80 degrees) at distances from 1 to 5 AU from the Sun. The spacecraft has continuously observed wave activity with peak power below the local electron cyclotron frequency f(ce). Four distinct types of fluctuation phenomena have been observed: (1) enhanced electromagnetic fluctuations associated with the interplanetary shocks and heliospheric current sheet crossings and other solar wind turbulence; (2) enhanced electromagnetic fluctuations associated with compression regions of high-speed stream interfaces, which were observed in periods of increasing solar wind velocity; (3) electric fluctuations associated with the expanding solar wind, which were observed in periods of decreasing solar wind velocity; and (4) enhanced electric fluctuations in the high-latitude fast solar wind plasma. The fourth type of wave activity was observed nearly continuously with the relative power observed peaked near the local f(ce). The first three types of waves were observed in the heliomagnetic streamer belt flows, where the spacecraft frequently encountered enhanced solar mind turbulence, interplanetary shocks, and current sheet crossings. The electromagnetic wave bursts (types 1 and 2) are likely to be whistler mode. The occurrences of apparently electrostatic waves during periods of expanding solar wind are coincident with significant reductions in the electron heat flux intensity. The generation mechanism of these electrostatic waves is still under investigation, but the observations may imply that these waves reduce the intensity of the heat flux through enhanced wave particle scattering associated with a heat flux instability. C1 Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Univ London Imperial Coll Sci Technol & Med, London, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. W Virginia Univ, Dept Phys, Morgantown, WV 26506 USA. RP Lin, N (reprint author), Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. EM lin@waves.space.umn.edu; kellogg@waves.space.umn.edu; xrrjm@leprjm.gsfc.nasa.gov; scime@wvnvaxa.wvnet.edu; a.balogh@ic.ac.uk; r.forsyth@ic.ac.uk; dmccomas@lanl.gov RI MacDowall, Robert/D-2773-2012 NR 38 TC 25 Z9 25 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1998 VL 103 IS A6 BP 12023 EP 12035 DI 10.1029/98JA00764 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ564 UT WOS:000073880700039 ER PT J AU Kahler, SW Cane, HV Hudson, HS Kurt, VG Gotselyuk, YV MacDowall, RJ Bothmer, V AF Kahler, SW Cane, HV Hudson, HS Kurt, VG Gotselyuk, YV MacDowall, RJ Bothmer, V TI The solar energetic particle event of April 14, 1994, as a probe of shock formation and particle acceleration SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CORONAL MASS EJECTIONS; INTERPLANETARY SHOCKS; FILAMENT DISAPPEARANCES; FLARES; ERUPTIONS AB Gradual solar energetic particle (SEP) events observed at 1 AU are associated with coronal mass ejections (CME) that drive shocks which are presumed to accelerate the ions and electrons to suprathermal energies. However, high-energy (> 30 MeV) proton and (> 1 MeV) electron events are nearly always associated with both CMEs and flares, suggesting that the acceleration of those particles, particularly the electrons, could be attributed to the associated flares. Only one dear example of a high-energy SEP event without an active region flare association has been reported previously. We discuss a second such SEP event, on April 14, 1994, associated with a well-observed solar X ray arcade structure spanning similar to 150 degrees of solar longitude. The SEP event, observed by detectors on the IMP 8 and Koronas I spacecraft, began similar to 10 hrs after the beginning of the X ray event and was temporally and spatially associated with the last of three weak interplanetary type III radio bursts observed by the Ulysses low-frequency radio experiment. The delayed onset and rapid rise of the SEP intensities preclude a recent interpretation in which SEPs were presumed to be accelerated by a shock driven by a CME which erupted at the onset of the X ray event. Yohkoh soft X ray subtracted images show a large-scale arcade brightening west of similar to E10 degrees beginning about 8 hours after the initial brightening near the east limb. We suggest that the April 14 SEP event at Earth was produced by a shock driven by a CME associated with the later brightening near central meridian. The initial X ray brightening may also have been associated with an earlier CME. C1 AFRL, VSBS, Hanscom AFB, MA 01731 USA. Univ Kiel, Inst Reine & Angew Kernphys, D-24118 Kiel, Germany. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Moscow MV Lomonosov State Univ, Inst Nucl Phys, Moscow 119899, Russia. Inst Space & Astronaut Sci, Solar Phys Res Corp, Sagamihara, Kanagawa 229, Japan. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Kahler, SW (reprint author), AFRL, VSBS, 29 Randolph Rd, Hanscom AFB, MA 01731 USA. EM kahler@plh.af.mil; cane@ncf.gsfc.nasa.gov; hudson@isass1.solar.isas.ac.jp; vgk@srdlan.npi.msu.su; juvg@srdlan.npi.msu.su; xrrjm@leprjm.gsfc.nasa.gov; bothmer@estec.esa.nl RI MacDowall, Robert/D-2773-2012 NR 40 TC 12 Z9 12 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 JUN 1 PY 1998 VL 103 IS A6 BP 12069 EP 12076 DI 10.1029/98JA00761 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ564 UT WOS:000073880700042 ER PT J AU Jaffe, AB Fogarty, MS Banks, BA AF Jaffe, AB Fogarty, MS Banks, BA TI Evidence from patents and patent citations on the impact of NASA and other federal labs on commercial innovation SO JOURNAL OF INDUSTRIAL ECONOMICS LA English DT Article AB Federal lab commercialization is explored: (1) by analyzing US government patents and (2) in a qualitative analysis of one NASA lab's patents. Tests apply to three distinct sets of patents, 1963-94: NASA, all other US government, and a random sample of all US inventors' patents. The federal patenting rate plummeted in the 1970s. Consistent with increasing commercialization, both NASA's and other federal agencies' rates recovered in the 1980s. The case study finds citations to be a valid but noisy measure of technology spillovers. Excluding 'spurious' cites, two-thirds of cites to patents of NASA-Lewis' Electro-Physics Branch were evaluated as involving spillovers. C1 Brandeis Univ, Grad Sch Int Econ & Finance, Sachar Int Ctr, Waltham, MA 02254 USA. NBER, Cambridge, MA 02138 USA. Case Western Reserve Univ, Ctr Reg Econ Issues, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Electrophys Branch, Cleveland, OH 44135 USA. RP Jaffe, AB (reprint author), Brandeis Univ, Grad Sch Int Econ & Finance, Sachar Int Ctr, Mailstop 021, Waltham, MA 02254 USA. RI Jaffe, Adam/B-7325-2009; OI Jaffe, Adam B/0000-0003-1337-1751 NR 22 TC 102 Z9 105 U1 0 U2 20 PU BLACKWELL PUBL LTD PI OXFORD PA 108 COWLEY RD, OXFORD OX4 1JF, OXON, ENGLAND SN 0022-1821 J9 J IND ECON JI J. Indust. Econ. PD JUN PY 1998 VL 46 IS 2 BP 183 EP 205 PG 23 WC Business, Finance; Economics SC Business & Economics GA ZP568 UT WOS:000073766500004 ER PT J AU Peterson, W AF Peterson, W TI Life cycle strategies of copepods in coastal upwelling zones SO JOURNAL OF MARINE SYSTEMS LA English DT Article; Proceedings Paper CT 6th International Conference on Copepoda CY JUL 29-AUG 03, 1996 CL OLDENBURG, GERMANY DE Copepoda; upwelling zones; advection ID CALANUS-FINMARCHICUS; CALANOIDES-CARINATUS; POPULATION-DYNAMICS; VERTICAL MIGRATION; BENGUELA ECOSYSTEM; MAINTENANCE; CIRCULATION; ZOOPLANKTON; MECHANISMS; MARSHALLAE AB Life cycles of copepods of coastal upwelling zones are of the multigenerational type-as many as 10 or more generations may be produced each year, depending upon water temperature, food concentration and length of the upwelling season. Abundant food resources and moderate temperature convey advantages to those copepods living in coastal upwelling zones, however, there is a clear disadvantage in that coastal upwelling zones are highly advective environments. Typically, water circulation patterns are such that surface waters are carried offshore, deeper waters carried onshore and most of the water column over the continental shelf is moving equatorward. The challenge to copepod species that inhabit upwelling systems is Life cycle closure-how do eggs, nauplii, juveniles and adults avoid being swept out of these ecosystems in the face of persistent transport out of the system? In this review, I first list the species which dominate coastal upwelling ecosystems then discuss three variations on the multigenerational life cycle scheme that are observed in upwelling systems. The latter part of the review is devoted to discussion of how individuals are retained in the productive continental shelf waters within coastal upwelling ecosystems. The suggestion is made that the only copepod species that successfully achieve life cycle closure in such systems are those that are preadapted to upwelling circulation patterns. Our quantitative understanding of the relative importance of physical factors (such as advection) and biological factors (birth, growth, and mortality) on life cycle strategies and population dynamics is quite rudimentary. It would help our understanding if there were more field studies and more computer modeling studies that focused on seasonal cycles of abundance, development times and vertical distribution of life cycle stages, and measurements of water circulation patterns. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Newport, OR 97365 USA. RP Peterson, W (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, 2030 S Marine Sci Dr, Newport, OR 97365 USA. EM bpeterso@sable.nwfsc-hc.noaa.gov NR 44 TC 113 Z9 115 U1 0 U2 17 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 JUN PY 1998 VL 15 IS 1-4 BP 313 EP 326 DI 10.1016/S0924-7963(97)00082-1 PG 14 WC Geosciences, Multidisciplinary; Marine & Freshwater Biology; Oceanography SC Geology; Marine & Freshwater Biology; Oceanography GA 101NY UT WOS:000074876100036 ER PT J AU Bansal, NP Eldridge, JI AF Bansal, NP Eldridge, JI TI Hi-Nicalon fiber-reinforced celsian matrix composites: Influence of interface modification SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB Unidirectional celsian matrix composites having 42-45 vol % of uncoated or BN-SiC coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 +/- 35 MPa and a flat fracture surface. In contrast, composites reinforced with coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 +/- 35 MPa and 0.27 +/- 0.01%, respectively, with ultimate strength as high as 960 MPa. The elastic Young modulus of the uncoated and coated fiber-reinforced composites were 184 +/- 4 GPa and 165 +/- 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of composite with uncoated fibers is due to degradation of the fiber strength from mechanical damage during processing. Because both the coated-and uncoated-fiber-reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SiC dual layer is primarily the protection of fibers from mechanical damage during processing. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bansal, NP (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 23 TC 18 Z9 18 U1 1 U2 1 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUN PY 1998 VL 13 IS 6 BP 1530 EP 1537 DI 10.1557/JMR.1998.0213 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA ZT232 UT WOS:000074063800015 ER PT J AU Liu, CH Barzilai, AM Reynolds, JK Partridge, A Kenny, TW Grade, JD Rockstad, HK AF Liu, CH Barzilai, AM Reynolds, JK Partridge, A Kenny, TW Grade, JD Rockstad, HK TI Characterization of a high-sensitivity micromachined tunneling accelerometer with micro-g resolution SO JOURNAL OF MICROELECTROMECHANICAL SYSTEMS LA English DT Article ID DISPLACEMENT TRANSDUCERS; MINIATURE; SENSORS; NOISE AB A new high-sensitivity bulk-silicon-micromachined tunneling accelerometer with micro-g resolution has been successfully fabricated and tested at Stanford University. This accelerometer is a prototype intended for underwater acoustics applications and is required to feature micro-g resolution at frequencies between 5 Hz and 1 kHz and can be packaged with circuitry in an 8-cm(3) volume with a total mass of 8 g. This paper briefly describes the mechanical design of this tunneling accelerometer and focuses on the experiments carried out in our laboratory to test the tunneling transducer as well as on the experimental determination of accelerometer resolution. The exponential relationship between tunneling gap and tunneling current is verified and results in an effective tunneling barrier height of about 0.2 eV, The goal of this paper is to outline the measurements which are necessary to verify that the sensor is actually tunneling and to confirm that the accelerometer performance is consistent with what should be expected from a tunneling accelerometer. C1 Stanford Univ, Dept Mech Engn, Stanford Microstruct & Sensors Lab, Stanford, CA 94305 USA. Quinta Corp, San Jose, CA 95134 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liu, CH (reprint author), Stanford Univ, Dept Mech Engn, Stanford Microstruct & Sensors Lab, Stanford, CA 94305 USA. OI Liu, Cheng-Hsien/0000-0003-1882-3892 NR 26 TC 64 Z9 72 U1 1 U2 18 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1057-7157 J9 J MICROELECTROMECH S JI J. Microelectromech. Syst. PD JUN PY 1998 VL 7 IS 2 BP 235 EP 244 DI 10.1109/84.679388 PG 10 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Physics, Applied SC Engineering; Science & Technology - Other Topics; Instruments & Instrumentation; Physics GA ZR276 UT WOS:000073957900012 ER PT J AU Mahon, CR Chackerian, C AF Mahon, CR Chackerian, C TI Zeeman tuning rates for Q-branch transitions in the nu(3) band of NO2 SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID SPECTROMETER AB Zeeman tuning rates have been measured for Q-branch transitions, in the nu(3) band of NO2. (similar to 1610 cm(-1)) for magnetic fields of up to 564 Gauss. The average measured tuning rate is 0.1815(53) x 10(-3) cm(-1)/Gauss with no dependence on K-a within the approximate to 3% standard deviation. Despite significant spin-rotation interaction between several of the observed levels the result agrees with the simple linear model for Hunds case (b) molecules (tuning rate 2 mu(o)g(s) = 0.18696 x 10(-3) cm(-1)/G), which neglects the spin-rotation interaction between different J states. The Zeeman effect is analyzed in a full treatment of the Hamiltonian, including spin-rotation interaction, in order to account for the agreement with 2 mu(o)g(s) and to explore the onset of spin-rotation effects in the spectra as the magnetic field is increased. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mahon, CR (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 7 TC 1 Z9 1 U1 0 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD JUN PY 1998 VL 189 IS 2 BP 276 EP 282 DI 10.1006/jmsp.1998.7555 PG 7 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA ZT230 UT WOS:000074063600016 ER PT J AU Borg, LE Clynne, MA AF Borg, LE Clynne, MA TI The petrogenesis of felsic calc-alkaline magmas from the southernmost Cascades, California: Origin by partial melting of basaltic lower crust SO JOURNAL OF PETROLOGY LA English DT Article DE Cascade arc; felsic magma; lower crust; partial melting ID MEDICINE LAKE VOLCANO; MOUNT ST-HELENS; PHASE-EQUILIBRIA; GRANITIC SYSTEMS; SERIES LAVAS; WATER; EVOLUTION; CONSTRAINTS; ELEMENT; LIQUID AB The majority of felsic rocks from composite centers in the southernmost Cascades have geochemical and Sr Nd and Pb isotopic ratios that suggest derivation by partial melting of lower crust that is compositionally similar to calc-alkaline basalts observed in the region. Only a few felsic rocks have delta(18)O and Pb isotopic compositions that indicate interaction with the upper crust. Mineralogical and geochemical differences among the felsic magmas result primarily from melting under variable f(H2O) and temperature conditions. Partial melting under low f(H2O) and high temperature conditions leaves an amphibole-poor residuum, and produces magmas that have orthopyroxene as the most abundant ferromagnesian phenocryst. relatively low silica contents, and straight rare earth element patterns. Partial melting under higher f(H2O) and lower temperature conditions leaves an amphibole-rich residuum, and produces magmas that have amphibole +/- biotite phenocrysts, relatively high silica contents, and pronounced middle rare earth element depletions. These conclusions are consistent with published thermal models that suggest that reasonable volumes of basaltic magma emplaced beneath large composite centers in the southernmost Cascades can serve as the heat source for melting of the lower crust. Melting of the lower crust under variable f(H2O) conditions is likely to result from differences in the H2O contents of these basaltic magmas. C1 Univ Texas, Austin, TX 78712 USA. US Geol Survey, Menlo Park, CA 94025 USA. RP Borg, LE (reprint author), NASA, Lyndon B Johnson Space Ctr, SN2, Houston, TX 77058 USA. NR 46 TC 78 Z9 81 U1 1 U2 10 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0022-3530 J9 J PETROL JI J. Petrol. PD JUN PY 1998 VL 39 IS 6 BP 1197 EP 1222 DI 10.1093/petrology/39.6.1197 PG 26 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZV161 UT WOS:000074276000005 ER PT J AU White, WB Chao, Y Tai, CK AF White, WB Chao, Y Tai, CK TI Coupling of biennial oceanic Rossby waves with the overlying atmosphere in the Pacific basin SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID TROPICAL NORTH PACIFIC; SEA-SURFACE TEMPERATURE; NINO SOUTHERN OSCILLATION; TERM CLIMATIC VARIABILITY; EL-NINO; TOPEX/POSEIDON DATA; BAROCLINIC WAVES; ANOMALIES; GENERATION; FREQUENCY AB Anomalies of TOPEX/Poseidon sea level height (SLH). NCEP sea surface temperature (SST), and ECMWF meridional surface wind (MSW) and derived wind stress curl (WSC) are mapped biweekly over the global ocean from 60 degrees S to 60 degrees N for two years from 1993 to 1994. These anomalies (i.e., differences from the average over the two years) allow one cycle of biennial climate change to be examined, with the paucity of temporal degrees of freedom mitigated by greater numbers of spatial degrees of freedom. Time-longitude diagrams of SLH anomalies reveal biennial Rossby waves in the Pacific ocean with westward phase speeds in the extratropics (Tropics) faster (slower) than expected of free biennial Rossby waves. Complex empirical orthogonal function analysis of SLH, SST, MSW, and WSC anomalies finds the beta-refraction pattern of these biennial Rossby waves in all four variables over most of the eastern-central Pacific Ocean, suggesting that oceanic Rossby waves there are coupled with the overlying atmosphere. The spatial phase relationship between SLH and SST anomaly patterns is consistent with an upper-ocean heat budget where the anomalous meridional heat advection by geostrophic flows associated with biennial Rossby waves is balanced by anomalous heat loss to the atmosphere. The spatial phase relationship between SST and MSW anomaly patterns is consistent with lower-tropospheric heat and vorticity budgets, where MSW anomalies arise from a balance between planetary vorticity advection and SST-induced low-level convergence. Using these basic heat and vorticity balances for upper ocean and lower troposphere, an analytic coupled model is constructed where the subsequent feedback by WSC anomalies upon the Free biennial Rossby waves (via Ekman pumping) is found to be positive, causing wave amplitudes to grow ol be maintained against dissipation, and producing westward phase speeds faster (slower) than expected of the free Rossby wave speeds in the extratropics (Tropics), as observed. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NOAA, Natl Ocean Serv, Silver Spring, MD USA. RP White, WB (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, 95 Gilman Dr, La Jolla, CA 92093 USA. EM wbwhite@ucsd.edu RI Tai, C.K./F-5628-2010 NR 41 TC 39 Z9 41 U1 0 U2 1 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 JUN PY 1998 VL 28 IS 6 BP 1236 EP 1251 DI 10.1175/1520-0485(1998)028<1236:COBORW>2.0.CO;2 PG 16 WC Oceanography SC Oceanography GA ZU133 UT WOS:000074165600012 ER PT J AU Caillat, T Fleurial, JP AF Caillat, T Fleurial, JP TI Thermoelectric properties of the semiconducting Chevrel phase Mo2Re4Se8 SO JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS LA English DT Article DE chalcogenides; semiconductors; transport properties AB We have prepared and measured the electrical resistivity, Seebeck coefficient, and thermal conductivity of the Chevrel material Mo2Re4Se8 in the 300-1000 K temperature range. The results show that Mo:Re,Ses is a semiconductor with a relatively low thermal conductivity. The semiconducting nature of this compound is consistent with theoretical predictions based on the number of valence electrons per [Mo-6] cluster. The crystal structure of Chevrel phases contains several voids of different sizes and shapes which can be filled by a variety of atomic elements. The filling of these interstices may be used as a means to achieve low thermal conductivity values by increasing the phonon scattering. This represents an attractive possibility considering that low thermal conductivity is one of the requirements for a good thermoelectric material. Various approaches to determine the potential of Chevrel phases for thermoelectric applications are presented and discussed. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Caillat, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 16 TC 19 Z9 19 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-3697 J9 J PHYS CHEM SOLIDS JI J. Phys. Chem. Solids PD JUN-JUL PY 1998 VL 59 IS 6-7 BP 1139 EP 1144 DI 10.1016/S0022-3697(97)00183-2 PG 6 WC Chemistry, Multidisciplinary; Physics, Condensed Matter SC Chemistry; Physics GA 102FZ UT WOS:000074914900038 ER PT J AU Toth, RA Brown, LR Plymate, C AF Toth, RA Brown, LR Plymate, C TI Self-broadened widths and frequency shifts of water vapor lines between 590 and 2400 CM-1 SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID TRANSITION FREQUENCIES; NU-2 BAND; STRENGTHS; (H2O)-O-16; COEFFICIENTS; REGION AB This experimental study reports self-broadened linewidths and pressure-induced frequency-shifts of water vapor in the spectral region between 590 and 2400 cm(-1) Over 1900 vibration-rotation transitions have been measured at 0.0054 cm(-1) resolution using the Fourier transform spectrometer at Kitt Peak National Observatory. Self-broadening parameters have been obtained for the (000)-(000), (010)-(010), (010)-(000), (020)-(010), and (100)-(010) vibrational bands of (H2O)-O-16, (H2O)-O-18, and (H2O)-O-17. The observed widths range from 0.52 to 0.1 cm(-1) atm(-1), and the pressure shifts fall between +/-0.05 cm(-1) atm(-1). The present linewidth coefficients are compared with previously measured and computed values given in the available literature. There have been no prior studies of self-broadened frequency-shifts of water vapor lines of this spectral region. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Opt Astron Observ, Natl Solar Observ, Tucson, AZ 85726 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 19 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 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD JUN PY 1998 VL 59 IS 6 BP 529 EP 562 DI 10.1016/S0022-4073(97)00144-1 PG 34 WC Optics; Spectroscopy SC Optics; Spectroscopy GA ZG314 UT WOS:000072988900001 ER PT J AU Chick, KM AF Chick, KM TI A domain decomposition approach for radiation transport in astrophysical dust envelopes SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID ACTIVE GALACTIC NUCLEI; MODEL SCATTERING ENVELOPES; YOUNG STELLAR OBJECTS; H-II REGIONS; INFRARED CONTINUUM; PROTOSTELLAR DISKS; NUMERICAL-SOLUTION; MOLECULAR CLOUDS; STARS; EQUATION AB A spatial domain decomposition method is presented for computing the continuum transfer of radiation associated with luminous astrophysical sources, embedded in extended clouds, in which dust gives rise to a substantial opacity. The method is relevant to the modelling of protostars, evolved stars, galaxies, and active galactic nuclei. Different transport algorithms are used in each subdomain. The algorithms are each specialized to handle conditions of high or low opacity, and internal opacity boundaries. Grid cell spacing can be adjusted to efficiently resolve variation in the radiation field on different length scales. The method is applied to a set of test problems in which a central point source and a luminous accretion disk are enclosed in an envelope A simple two-group wavelength approximation is used, representing optical and thermal radiation. Group opacities drop to zero at the dust vaporization temperature. Domain decomposition computations are first checked against a semi-analytic solution to the diffusion approximation for spherically symmetric problems. The method is then applied to more realistic axisymmetric problems to compute the temperature structure of the envelope and accretion disk surface, and the location of the dust destruction front. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Chick, KM (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. NR 49 TC 1 Z9 1 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 JUN PY 1998 VL 59 IS 6 BP 563 EP 583 DI 10.1016/S0022-4073(97)00146-5 PG 21 WC Optics; Spectroscopy SC Optics; Spectroscopy GA ZG314 UT WOS:000072988900002 ER PT J AU Lynch, R Gamache, RR Neshyba, SP AF Lynch, R Gamache, RR Neshyba, SP TI N-2 and O-2 induced halfwidths and line shifts of water vapor transitions in the (301)<-(000) and (221)<-(000) bands SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID ROTATION-VIBRATION LINES; ASYMMETRIC-TOP MOLECULES; PERTURBER DEPENDENCES; RANGE; H2O; GHZ; COEFFICIENTS; TEMPERATURE; NITROGEN; MOMENTS AB Using a complex version of Robert-Bonamy theory (CRBF), the role of the intermolecular potential in the pressure broadening of water perturbed by nitrogen and oxygen is studied. Investigation focuses on questions surrounding the convergence of calculated line widths, i.e., (i) why certain spectral lines are more sensitive than others to short-range interactions, and (ii) whether converged calculations containing short-range interactions represent an improvement over other treatments. Comparison with a large number of experimentally determined halfwidths and line shifts in the (301)<--(000) and (221)<--(000) bands is provided. It is found that the atom-atom component of the intermolecular potential plays an important role in determining the halfwidth and line shift. To obtain good agreement with measurement, the atom-atom potential needs to be expanded to at least eighth order for all water vapor transitions broadened by oxygen and many broadened by nitrogen. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Lowell, Dept Environm Earth & Atmospher Sci, Lowell, MA 01854 USA. Univ Puget Sound, Dept Chem, Tacoma, WA 98416 USA. Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Gamache, RR (reprint author), Univ Lowell, Dept Environm Earth & Atmospher Sci, 1 Univ Ave, Lowell, MA 01854 USA. NR 50 TC 46 Z9 47 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 JUN PY 1998 VL 59 IS 6 BP 595 EP 613 DI 10.1016/S0022-4073(97)00142-8 PG 19 WC Optics; Spectroscopy SC Optics; Spectroscopy GA ZG314 UT WOS:000072988900004 ER PT J AU Lynch, R Gamache, RR Neshyba, SP AF Lynch, R Gamache, RR Neshyba, SP TI Pressure broadening of H2O in the (301)<-(000) band: Effects of angular momentum and close intermolecular interactions SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID COEFFICIENTS; MOLECULES; WIDTHS; SHIFTS; LINES AB Two spectroscopic lines of water vapor, broadened by N-2, are examined within the Complex Robert-Bonamy formalism in an effort to understand their sensitivity to short-range interactions. The two lines, both of which occur in the (301)<--(000) band, are compared in terms of their dependence on impact parameter, sensitivity to convergence of the short-range potential, and the symmetry terms of the intermolecular potential. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Massachusetts, Dept Environm Earth & Atmospher Sci, Lowell, MA 01854 USA. Columbia Univ, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Puget Sound, Dept Chem, Tacoma, WA 98416 USA. RP Gamache, RR (reprint author), Univ Massachusetts, Dept Environm Earth & Atmospher Sci, 1 Univ Ave, Lowell, MA 01854 USA. NR 25 TC 8 Z9 9 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 JUN PY 1998 VL 59 IS 6 BP 615 EP 626 DI 10.1016/S0022-4073(97)00143-X PG 12 WC Optics; Spectroscopy SC Optics; Spectroscopy GA ZG314 UT WOS:000072988900005 ER PT J AU Pindera, MJ Aboudi, J Arnold, SM AF Pindera, MJ Aboudi, J Arnold, SM TI Thermomechanical analysis of functionally graded thermal barrier coatings with different microstructural scales SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID METAL-MATRIX COMPOSITES; INELASTIC RESPONSE AB The recently developed two-dimensional version of the higher-order theory for functionally graded materials (denoted as HOTFGM-2D in previous communications) has been used to investigate the effects of microstructural architectures in graded thermal barrier coatings (TBCs) on stress distributions in the presence of a through-thickness temperature gradient. In particular, the response of TBCs with different levels of functionally graded microstructural refinement and different arrangements has been investigated, and the results for the through-thickness stress distributions are compared with those based on the standard micromechanical homogenization scheme. The examples presented illustrate the shortcomings of the standard micromechanics-based approach that is applied to the analysis of functionally graded TBCs, particularly if the presence of creep effects is included in the analysis. C1 NASA, Lewis Res Ctr, Struct Fatigue Branch, Cleveland, OH 44315 USA. RP Pindera, MJ (reprint author), Tel Aviv Univ, Dept Solid Mech Mat & Struct, IL-69978 Tel Aviv, Israel. NR 16 TC 17 Z9 17 U1 0 U2 3 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 USA SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD JUN PY 1998 VL 81 IS 6 BP 1525 EP 1536 PG 12 WC Materials Science, Ceramics SC Materials Science GA ZV175 UT WOS:000074277600016 ER PT J AU Fox, DS Cuy, MD Nguyen, QN AF Fox, DS Cuy, MD Nguyen, QN TI Sea-salt corrosion and strength of a sintered alpha-silicon carbide SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article; Proceedings Paper CT 97th Annual Meeting of the American-Ceramic-Society CY MAY 01-03, 1995 CL CINCINNATI, OHIO SP Amer Ceram Soc ID HOT CORROSION AB A commercially available, sintered silicon carbide was exposed to a temperature of 982 degrees C for up to 50 h in a burner rig pressurized to 500 kPa, Synthetic sea salt added to the flame (5 ppm) resulted in the deposition of sodium sulfate and formation of a sodium magnesium silicate corrosion product. A 16% reduction in room-temperature strength occurred after 5 h of exposure; this reduction was due to the formation of surface pits. Exposure for longer times resulted in continued strength reduction, up to 56% at 25 h. Samples exposed for 50 h were so degraded that mechanical tests could not be conducted. The strength after 25 h of exposure to a salt concentration of 2 ppm was similar to the as-received strength, whereas exposures to 10 ppm of salt resulted in strengths similar to that observed with 5 ppm of salt. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NYMA Inc, Brookpark, OH 44142 USA. Cleveland State Univ, Cleveland, OH 44115 USA. RP Fox, DS (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 15 TC 6 Z9 7 U1 1 U2 2 PU AMER CERAMIC SOC PI WESTERVILLE PA 735 CERAMIC PLACE, PO BOX 6136, WESTERVILLE, OH 43081-6136 USA SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD JUN PY 1998 VL 81 IS 6 BP 1565 EP 1570 PG 6 WC Materials Science, Ceramics SC Materials Science GA ZV175 UT WOS:000074277600021 ER PT J AU Qu, WQ Henderson-Sellers, A Pitman, AJ Chen, TH Abramopoulos, F Boone, A Chang, S Chen, F Dai, Y Dickinson, RE Dumenil, L Ek, M Gedney, N Gusev, YM Kim, J Koster, R Kowalczyk, EA Lean, J Lettenmaier, D Liang, X Mahfouf, JF Mengelkamp, HT Mitchell, K Nasonova, ON Noilhan, J Robock, A Rosenzweig, C Schaake, J Schlosser, CA Schulz, JP Shmakin, AB Verseghy, DL Wetzel, P Wood, EF Yang, ZL Zeng, Q AF Qu, WQ Henderson-Sellers, A Pitman, AJ Chen, TH Abramopoulos, F Boone, A Chang, S Chen, F Dai, Y Dickinson, RE Dumenil, L Ek, M Gedney, N Gusev, YM Kim, J Koster, R Kowalczyk, EA Lean, J Lettenmaier, D Liang, X Mahfouf, JF Mengelkamp, HT Mitchell, K Nasonova, ON Noilhan, J Robock, A Rosenzweig, C Schaake, J Schlosser, CA Schulz, JP Shmakin, AB Verseghy, DL Wetzel, P Wood, EF Yang, ZL Zeng, Q TI Sensitivity of latent heat flux from PILPS land-surface schemes to perturbations of surface air temperature SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GENERAL-CIRCULATION MODELS; CLIMATE FEEDBACK PROCESSES; SOIL-MOISTURE; BOUNDARY-LAYER; PARAMETERIZATION; EVAPORATION; HYDROLOGY; BIOSPHERE; GCMS AB In the PILPS Phase 2a experiment, 23 land-surface schemes were compared in an off-line control experiment using observed meteorological data from Cabauw, the Netherlands. Two simple sensitivity experiments were also undertaken in which the observed surface air temperature was artificially increased or decreased by 2 K while all other factors remained as observed. On the annual timescale, all schemes show similar responses to these perturbations in latent, sensible heat flux, and other key variables. For the 2-K increase in temperature, surface temperatures and latent heat fluxes all increase while net radiation, sensible heat fluxes, and soil moistures all decrease. The results are reversed for a 2-K temperature decrease. The changes in sensible heat fluxes and, especially, the changes in the latent heat fluxes are nor linearly related to the change of temperature. Theoretically, the nonlinear relationship between air temperature and the latent heat flux is evident and due to the convex relationship between air temperature and saturation vapor pressure. A simple test shows that, the effect of the change of air temperature on the atmospheric stratification aside, this nonlinear relationship is shown in the form that the increase of the latent heat flux for a 2-K temperature increase is larger than its decrease for a 2-K temperature decrease. However, the results from the Cabauw sensitivity experiments show that the increase of the latent heat flux in the +2-K experiment is smaller than the decrease of the latent heat flux in the -2-K experiment (we refer to this as the asymmetry). The analysis in this paper shows that this inconsistency between the theoretical relationship and the Cabauw sensitivity experiments results (or the asymmetry) is due to (i) the involvement of the beta(g), formulation, which is a function of a series stress factors that limited the evaporation and whose values change in the +/-2-K experiments, leading to strong modifications of the latent heat flux; (ii) the change of the drag coefficient induced by the changes in stratification due to the imposed air temperature changes (+/-2 K) in parameterizations of latent heat flux common in current land-surface schemes. Among all stress factors involved in the beta(g), formulation, the soil moisture stress in the +2-K experiment induced by the increased evaporation is the main factor that contributes to the asymmetry. C1 RMIT Univ, Dept Math, Melbourne, Vic 3001, Australia. Macquarie Univ, Sch Earth Sci, Sydney, NSW 2109, Australia. Sci Syst & Applicat Inc, Sydney, NSW, Australia. NASA, Goddard Space Flight Ctr, Mesoscale Dynam & Precipitat Branch, Greenbelt, MD 20771 USA. Philips Labs, GPAB, PL, Hanscom AFB, MA USA. NOAA, Natl Ctr Environm Predict, Dev Div, Camp Springs, MD USA. Chinese Acad Sci, Inst Atmospher Phys, Beijing, Peoples R China. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. Max Planck Inst Meteorol, Hamburg, Germany. Royal Netherlands Meteorol Inst, NL-3730 AE De Bilt, Netherlands. Univ Reading, Dept Meteorol, Reading, Berks, England. Russian Acad Sci, Inst Water Problems, Moscow, Russia. Lawrence Livermore Natl Lab, Livermore, CA USA. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. CSIRO, Div Atmospher Res, Aspendale, Vic 3195, Australia. Meteorol Off, Hadley Ctr Climate Predict & Res, Bracknell, Berks, England. Univ Washington, Dept Civil Engn, Seattle, WA 98195 USA. Princeton Univ, Dept Civil Engn & Operat Res, Princeton, NJ 08544 USA. ECMWF, Reading, Berks, England. GKSS, Res Ctr, Dept Phys, Geesthacht, Germany. Meteo France, CNRM, Toulouse, France. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NOAA, Natl Weather Serv, Off Hydrol, Silver Spring, MD 20910 USA. Russian Acad Sci, Inst Geog, Moscow, Russia. Atmospher Environm Serv, Climate Res Branch, Downsview, ON, Canada. Australian Oceanog Data Ctr, Sydney, NSW, Australia. RP Qu, WQ (reprint author), RMIT Univ, Dept Math, GPO Box 2476V, Melbourne, Vic 3001, Australia. EM rmawq@gauss.ma.rmit.edu.au RI Yang, Zong-Liang/B-4916-2011; Pitman, Andrew/A-7353-2011; Henderson-Sellers, Ann/H-5323-2011; Koster, Randal/F-5881-2012; Chen, Fei/B-1747-2009; lettenmaier, dennis/F-8780-2011; Nasonova, Olga/B-6093-2014; gusev, yugeniy/G-4711-2014; Robock, Alan/B-6385-2016; Dai, Yongjiu/D-6261-2014 OI Wood, Eric/0000-0001-7037-9675; Pitman, Andrew/0000-0003-0604-3274; Koster, Randal/0000-0001-6418-6383; lettenmaier, dennis/0000-0003-3317-1327; gusev, yugeniy/0000-0003-3886-2143; Dai, Yongjiu/0000-0002-3588-6644 NR 48 TC 32 Z9 36 U1 1 U2 9 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 EI 1520-0469 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUN 1 PY 1998 VL 55 IS 11 BP 1909 EP 1927 DI 10.1175/1520-0469(1998)055<1909:SOLHFF>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZT491 UT WOS:000074093200001 ER PT J AU Begault, DR AF Begault, DR TI Virtual acoustics, aeronautics, and communications SO JOURNAL OF THE AUDIO ENGINEERING SOCIETY LA English DT Article; Proceedings Paper CT 101st Convention of the Audio-Engineering-Society CY NOV 08-11, 1996 CL LOS ANGELES, CALIFORNIA SP Audio Engn Soc ID SPEECH; LOCALIZATION; DISPLAYS AB An optimal approach to auditory display design for commercial aircraft would utilize both spatialized (3-D) audio techniques and active noise cancellation for safer operations. Results from several aircraft simulator studies conducted at NASA Ames Research Center are reviewed, including Traffic alert and Collision Avoidance System (TCAS) warnings, spoken orientation "beacons" for gate identification and collision avoidance on the ground, and hardware for improved speech intelligibility. The implications of hearing loss among pilots is also considered. C1 NASA, Human Factors Res & Technol Div, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Begault, DR (reprint author), NASA, Human Factors Res & Technol Div, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 28 TC 7 Z9 8 U1 0 U2 3 PU AUDIO ENGINEERING SOC PI NEW YORK PA 60 E 42ND ST, NEW YORK, NY 10165-2520 USA SN 0004-7554 J9 J AUDIO ENG SOC JI J. Audio Eng. Soc. PD JUN PY 1998 VL 46 IS 6 BP 520 EP 530 PG 11 WC Acoustics; Engineering, Multidisciplinary SC Acoustics; Engineering GA 101XU UT WOS:000074894100003 PM 11542274 ER PT J AU Krishnakumar, V Lau, KM AF Krishnakumar, V Lau, KM TI Possible role of symmetric instability in the onset and abrupt transition of the Asian monsoon SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID SUMMER MONSOON; GLA GCM; INERTIAL INSTABILITY; HADLEY CIRCULATIONS; EAST-ASIA; ATMOSPHERE; VARIABILITY; STABILITY; PARAMETERIZATION; RAINBANDS AB The physical connections between dry/moist (conditional) symmetric instability (SI/CSI) off equatorial diabatic thermal forcing, and the onset of the Asian monsoon are investigated using the Goddard Laboratory for Atmospheres general circulation model (GLA GCM). The objective of this study is two-fold: to elucidate the causal relationship between SI/CSI and monsoon onset, and to investigate the threshold behavior of asymmetric monsoonal thermal forcing under condition of SI/CSI. This work corroborates the authors' earlier linear instability analysis results, which show, that SI/CSI in the boreal summer monsoon basic states may be a plausible explanation for the abrupt monsoon transition. Monsoon transitions in the model, as depicted by the abrupt meridional movement of the axis of maximum vertical motion from equator to northern latitudes, occur during 16-20 May for the East Asian Monsoon (EAM) and 1-5 June for the South Asian Monsoon (SAM) regions. The necessary stability criterion for dry (moist) SI over the EAM and SAM regions reveals a sudden cross equatorial advection of negative dry potential vorticity (DPV) and moist potential vorticity (MPV) into the summer hemisphere five to ten days preceding the model monsoon transition. This causes dry and moist SI. Maximum shift of the zero line of DPV and MPV (dry and moist symmetrically unstable regions) happens subsequent to monsoon transition. Simplified analysis of the potential vorticity (PV) budget equation reveals that the lower tropospheric negative PV advection into the summer hemisphere is largely governed by the dominance of vertical differential diabatic heating over horizontal differential diabatic heating. The diabatic heating also shows an abrupt increase from 2-3 K day(-1) before the transition, to 12-14 K day(-1) at the time of monsoon transition. The genesis of pre-monsoon weak heat source arises primarily due to unstable SI and CSI of the pre-monsoon basic states, which consequently produce moderately large scale lower (upper) tropospheric convergence (divergence) patterns slightly poleward of the zero line of DPV and MPV. Lower tropospheric conditionally unstable tropical atmosphere, in the presence of off equatorial large scale lower (upper) tropospheric convergence (divergence), is conducive to exciting CISK-like processes, which may eventually release large amounts of latent heat and develop a strong heat source at the time of monsoon transition. We have noted that a fully established model meridional circulation originates only when the diabatic forcing magnitude exceeds some threshold value of around 5 K day(-1) at the time of monsoon transition. The model transition is more pronounced over the EAM region than over the SAM region. The linear steady-state dynamical response of a zonally symmetric atmosphere as a consequence of varying the location and magnitude of an idealized asymmetric thermal forcing reveals that the most intense meridional circulation (maximum efficiency of vertical motion) is accomplished when the thermal forcing is located around 10 degrees N. The interrelationship between the location of zero DPV/MPV contour, lower tropospheric maximum convergence versus maximum vertical velocity of the monsoonal circulation in the summer hemisphere, clearly suggests that SI (CSI) of zonal monsoon flows is a causal mechanism for the onset of monsoon transition. C1 NASA, Goddard Space Flight Ctr, Space Applicat Corp, Atmospheres Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Space Applicat Corp, Atmospheres Lab, Corp 913, Greenbelt, MD 20771 USA. RI Lau, William /E-1510-2012; Kumar, V. Krishna/N-9865-2016 OI Lau, William /0000-0002-3587-3691; Kumar, V. Krishna/0000-0002-4455-0843 NR 45 TC 18 Z9 21 U1 0 U2 3 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 JUN PY 1998 VL 76 IS 3 BP 363 EP 383 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 106YM UT WOS:000075179100002 ER PT J AU Barkai, SM Rand, O Peyran, RJ Carlson, RM AF Barkai, SM Rand, O Peyran, RJ Carlson, RM TI Modeling and analysis of tilt-rotor aeromechanical phenomena SO MATHEMATICAL AND COMPUTER MODELLING LA English DT Article; Proceedings Paper CT 1995 American-Helicopter-Society 2nd International Aeromechanics Specialists Conference CY OCT 11-13, 1995 CL BRIDGEPORT, CONNECTICUT SP Amer Helicopter Soc DE whirl-flutter; stability; aeromechanics; tilt-rotor; wing-rotor coupling AB The paper presents a recent effort to explore tilt-rotor aeromechanical phenomena with an emphasize on aeroelastic stability in forward flight (airplane mode). A general tilt-rotor model has been developed and implemented using a numerical technique that preserves symbolic exactness of the equations of motion. The stability study is based on an eigenvalue analysis about a nonlinear periodic trim solution. The present method enables both high resolution periodic response, and clear tracing of the instability drivers by providing the exact partial derivatives of the involved degrees of freedom in each one of the associated equations of motion. In addition to the common way of identifying trends and sensitivities by parametric study, the present approach supplies information about the effectiveness of possible mechanisms that are not included in the baseline model. The present results demonstrate the ability of the method to provide such unique insight into the aeromechanical phenomena in forward flight. illustrative indications regarding required tilt-rotor design features that will postpone the instability phenomena are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Technion Israel Inst Technol, Fac Aerosp Engn, IL-32000 Haifa, Israel. USA, Aviat & Missile Command, Adv Design Team, Aeroflightdynam Directorate,Ames Res Ctr, Moffett Field, CA 94035 USA. RP Barkai, SM (reprint author), Technion Israel Inst Technol, Fac Aerosp Engn, IL-32000 Haifa, Israel. NR 31 TC 5 Z9 10 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0895-7177 J9 MATH COMPUT MODEL JI Math. Comput. Model. PD JUN PY 1998 VL 27 IS 12 BP 17 EP 43 DI 10.1016/S0895-7177(98)00071-5 PG 27 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA ZT630 UT WOS:000074107100002 ER PT J AU Juretzko, FR Dhindaw, BK Stefanescu, DM Sen, S Curreri, PA AF Juretzko, FR Dhindaw, BK Stefanescu, DM Sen, S Curreri, PA TI Particle engulfment and pushing by solidifying interfaces: Part I. Ground experiments SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID METAL MATRIX COMPOSITES; LIQUID INTERFACE; SOLIDIFICATION; BEHAVIOR; CRYSTALS; ALUMINUM; SILICON; ALLOYS; MELTS AB Directional solidification experiments have been carried out to determine the pushing/engulfment transition for two different metal/particle systems. The systems chosen were aluminum/zirconia particles and zinc/zirconia particles. Pure metals (99.999 pet Al and 99.95 pet Zn) and spherical particles (500 mu m in diameter) were used. The particles were nonreactive with the matrices within the temperature range of interest. The experiments were conducted so as to ensure a planar solid/liquid (SL) interface during solidification. Particle location before and after processing was evaluated by X-ray transmission microscopy (XTM) for the Al/ZrO(2) samples. All samples were characterized by optical metallography after processing. A clear methodology for the experiment evaluation was developed to unambiguously interpret the occurrence of the pushing/engulfment transition (PET). It was found that the critical velocity for engulfment ranges from 1.9 to 2.4 mu m/s for Al/ZrO(2) and from 1.9 to 2.9 mu m/s for Zn/ZrO(2). C1 Univ Alabama, Solidificat Lab, Tuscaloosa, AL 35487 USA. Indian Inst Technol, Kharagpur, W Bengal, India. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35806 USA. RP Juretzko, FR (reprint author), Univ Alabama, Solidificat Lab, Tuscaloosa, AL 35487 USA. RI Stefanescu, Doru/G-8101-2012; OI Dhindaw, Brij Kumar/0000-0001-6991-9793; Stefanescu, Doru M./0000-0001-5544-8396 NR 24 TC 51 Z9 52 U1 1 U2 19 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD JUN PY 1998 VL 29 IS 6 BP 1691 EP 1696 DI 10.1007/s11661-998-0091-4 PG 6 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA ZX470 UT WOS:000074519300017 ER PT J AU Stefanescu, DM Juretzko, FR Dhindaw, BK Catalina, A Sen, S Curreri, PA AF Stefanescu, DM Juretzko, FR Dhindaw, BK Catalina, A Sen, S Curreri, PA TI Particle engulfment and pushing by solidifying interfaces: Part II. Microgravity experiments and theoretical analysis SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID METAL-MATRIX COMPOSITES; SOLID LIQUID INTERFACE; SOLIDIFICATION; BEHAVIOR; MELTS AB Results of the directional solidification (DS) experiments on particle engulfment and pushing by solidifying interfaces (PEP), conducted on the space shuttle Columbia during the Life and Microgravity Science (LMS) Mission, are reported. Two pure aluminum (99.999 pct) 9 mm cylindrical rods, loaded with about 2 vol pet 500-mu m-diameter zirconia particles, were melted and resolidified in the microgravity (mu g) environment of the shuttle. One sample was processed at a stepwise increased solidification velocity and the other at a stepwise decreased velocity. It was found that a pushing/engulfment transition (PET) occurred in the velocity range of 0.5 to 1 mu m/s. This is smaller than the ground PET velocity of 1.9 to 2.4 mu m/s. This demonstrates that natural convection increases the critical velocity. A previously proposed analytical model for PEP was further developed. A major effort to identify and produce data for the surface energy of various interfaces required for calculation was undertaken. The predicted critical velocity for PET was 0.775 mu m/s. C1 Univ Alabama, Solidificat Lab, Tuscaloosa, AL 35487 USA. Indian Inst Technol, Kharagpur, W Bengal, India. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35806 USA. RP Stefanescu, DM (reprint author), Univ Alabama, Solidificat Lab, Tuscaloosa, AL 35487 USA. RI Stefanescu, Doru/G-8101-2012; OI Stefanescu, Doru M./0000-0001-5544-8396; Dhindaw, Brij Kumar/0000-0001-6991-9793 NR 32 TC 93 Z9 101 U1 1 U2 14 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD JUN PY 1998 VL 29 IS 6 BP 1697 EP 1706 DI 10.1007/s11661-998-0092-3 PG 10 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA ZX470 UT WOS:000074519300018 ER PT J AU Alexander, GD Weinman, JA Schols, JL AF Alexander, GD Weinman, JA Schols, JL TI Use of digital warping of microwave integrated water vapor imagery to improve forecasts of marine extratropical cyclones SO MONTHLY WEATHER REVIEW LA English DT Article ID UPPER BOUNDARY-CONDITION; 12-14 MARCH 1993; PRECIPITABLE WATER; SSM/I OBSERVATIONS; MESOSCALE MODEL; ASSIMILATION; SIMULATION; TESTS; PARAMETERIZATION; RETRIEVALS AB A technique is described in which forecasts of the locations of features associated with marine cyclones may be improved through the use of microwave integrated water vapor (IWV) imagery and image warping of forecast mesoscale model fields. Here, image warping is used to optimally match mesoscale model output to observations of IWV measured by microwave sensors. In the mesoscale model simulations presented here (one of the March 1993 "superstorm," one of a rapidly deepening cyclone observed in the North Atlantic in February 1992, and one of the ERICA IOP 4 cyclone), the Pennsylvania State University-National Center for Atmospheric Research MM5 model is initialized from the standard National Meteorological Center (recently renamed the National Centers for Environmental Prediction) operational analysis. The simulations are then run until a time at which a Special Sensor Microwave/Imager (SSM/I) overpass occurs. For each simulation, the forecast pattern of IWV is then compared to the field shown in the SSM/I image. In all three cases, the MM5 moves the cyclones too slowly, and therefore places distinguishing features in the forecast IWV fields significantly upstream of their locations as revealed in the microwave imagery. To rectify these errors, the grid on which the source image (forecast held) is defined is then warped to match the target image (remotely observed IWV field) by choosing pairs of tie points corresponding to similar features in the two images. The values of all model moisture variables at all vertical levels are then carried to the new warped grid points and interpolated back to the original model grid. Model integration then proceeds with the new model fields. The model results at a subsequent time after the warping is applied are then compared with simultaneous model results in simulations in which no warping was applied as well as with model simulations in which a standard nudging technique is applied. Warping results in improved forecasts of cyclone minimum sea level pressure, tracks, and IWV fields over both the control simulations and the nudged simulations. C1 NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD USA. RP Weinman, JA (reprint author), NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Univ Space Res Assoc, Code 975, Greenbelt, MD 20771 USA. NR 33 TC 17 Z9 17 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD JUN PY 1998 VL 126 IS 6 BP 1469 EP 1496 DI 10.1175/1520-0493(1998)126<1469:TUODWO>2.0.CO;2 PG 28 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 100UX UT WOS:000074834700006 ER PT J AU Machado, LAT Rossow, WB Guedes, RL Walker, AW AF Machado, LAT Rossow, WB Guedes, RL Walker, AW TI Life cycle variations of mesoscale convective systems over the Americas SO MONTHLY WEATHER REVIEW LA English DT Article ID TROPICAL SQUALL-LINE; PASSIVE MICROWAVE OBSERVATIONS; MONSOON CLOUD CLUSTERS; ATLANTIC-OCEAN; WESTERN PACIFIC; STRUCTURAL CHARACTERISTICS; LONGWAVE RADIATION; STRATIFORM REGIONS; COPT-81 EXPERIMENT; DIURNAL-VARIATIONS AB Using GOES-7 ISCCP-B3 satellite data for 1987-88, the authors studied the evolution of the morphological and radiative properties of clouds over the life cycles of deep convective systems (CS) over the Americas at both tropical and middle latitudes. A deep convective cloud system is identified by adjacent satellite image pixels with infrared brightness temperatures, T-IR < 245 K (-28 degrees C), that at some time contain embedded convective clusters that are defined by pixel values of T-IR < 218 K (-55 degrees C). The first part of the analysis computes parameters for each convective system that describe the system areal size, number of convective clusters, fractional convective area, average and maximum size of the convective clusters, shape eccentricity and orientation, mean T-IR, variance of T-IR, T-IR gradient, and the mean, variance, and gradient of collocated visible reflectances (when available). The second part of the analysis searches a 5 degrees X 5 degrees region centered on each convective system, but in the subsequent image (3-h time separation), to locate possible candidates representing the same system at the later time. For each possible candidate, the method calculates the fraction of areal overlap with the target system and the implied speed and direction of propagation of the whole convective system and the largest convective cluster within the candidate system. The authors review previous studies of the sensitivity of CS statistics to the temperature thresholds used for identification and quantify the effects on these statistics produced by different ways of tracking convective systems. Comparisons of the results from several tracking methods explains how they work and why most of the life cycle statistics are not sensitive to tracking method used. The authors confirm that simple coincidence (as used in most previous studies) works as long as the time step between satellite images is smaller than the time required for significant evolution of the CS: since smaller systems evolve more rapidly, getting accurate results for CS smaller than about 50-100 km probably requires time resolution better than 3 h. The whole dataset has been analyzed by a tropical meteorologist who choses the best candidate at each time step by comparing listings of all the calculated parameters and visually examining each satellite image pair. The whole dataset has also been analyzed by a simple automated procedure. Eased on about 3200 cases examined by the meteorologist and about 4700 cases obtained by the completely automated method, the statistical behavior of convective systems over the Americas is described: their mean cloud properties as a function of system size and lifetime, the evolution of their cloud properties over their lifetimes, and their motions. The results demonstrate a direct correspondence between the size and lifetime of mesoscale convective systems and exhibit many common features of their growth, maturation, and decay. Some differences between CS over tropical land and tropical ocean are also apparent. C1 NASA, Goddard Inst Space Studies, Sci Syst & Applicat Inc, New York, NY 10025 USA. Aerosp Tech Ctr, Aeronaut & Space Inst, Div Atmospher Sci, Sao Jose Dos Campos, Brazil. RP Rossow, WB (reprint author), NASA, Goddard Inst Space Studies, Sci Syst & Applicat Inc, 2880 Broadway, New York, NY 10025 USA. RI Machado, Luiz/C-4314-2012; Rossow, William/F-3138-2015 OI Machado, Luiz/0000-0002-8243-1706; NR 83 TC 153 Z9 159 U1 1 U2 17 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 JUN PY 1998 VL 126 IS 6 BP 1630 EP 1654 DI 10.1175/1520-0493(1998)126<1630:LCVOMC>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 100UX UT WOS:000074834700013 ER PT J AU Brasunas, J AF Brasunas, J TI Shape memory wire as a drive mechanism for a Fourier transform spectrometer SO OPTICAL ENGINEERING LA English DT Article DE shape memory wire; Fourier transform spectroscopy C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Brasunas, J (reprint author), NASA, Goddard Space Flight Ctr, Code 693, Greenbelt, MD 20771 USA. RI brasunas, john/I-2798-2013 NR 4 TC 0 Z9 0 U1 0 U2 2 PU SPIE - INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING PI BELLINGHAM PA POB 10, BELLINGHAM, WA 98227-0010 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD JUN PY 1998 VL 37 IS 6 BP 1882 EP 1883 DI 10.1117/1.601711 PG 2 WC Optics SC Optics GA ZT109 UT WOS:000074049300035 ER PT J AU Weber, AL AF Weber, AL TI Prebiotic amino acid thioester synthesis: Thiol-dependent amino acid synthesis from formose substrates (formaldehyde and glycolaldehyde) and ammonia SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article ID CONDENSATION-REACTIONS; LIQUID-CHROMATOGRAPHY; AQUEOUS-SOLUTION; PRIMITIVE EARTH; ENERGY; GLYCERALDEHYDE; DERIVATIZATION; ATMOSPHERE; KINETICS; CARBON AB Formaldehyde and glycolaldehyde (substrates of the formose autocatalytic cycle) were shown to react with ammonia yielding alanine and homoserine under mild aqueous conditions in the presence of thiol catalysts. Since similar reactions carried out without ammonia yielded alpha-hydroxy acid thioesters (Weber, 1984a, b), the thiol-dependent synthesis of alanine and homoserine is presumed to occur via amino acid thioesters - intermediates capable of forming peptides (Weber and Orgel 1979). A pH 5.2 solution of 20 mM formaldehyde, 20 mM glycolaldehyde, 20 mM ammonium chloride, 23 mM 3-mercaptopropionic acid, and 23 mM acetic acid that reacted for 35 days at 40 degrees C yielded (based on initial formaldehyde) 1.8% alanine and 0.08% homoserine. In the absence of thiol catalyst, the synthesis of alanine and homoserine was negligible. Alanine synthesis required both formaldehyde and glycolaldehyde, but homoserine synthesis required only glycolaldehyde. At 25 days the efficiency of alanine synthesis calculated from the ratio of alanine synthesized to formaldehyde reacted was 2.1%, and the yield (based on initial formaldehyde) of triose and tetrose intermediates involved in alanine and homoserine synthesis was 0.3 and 2.1%, respectively. Alanine synthesis was also seen in similar reactions containing only 10 mM each of aldehyde substrates, ammonia, and thiol. The prebiotic significance of these reactions that use the formose reaction to generate sugar intermediates that are converted to reactive amino acid thioesters is discussed. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. RP Weber, AL (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 50 TC 44 Z9 46 U1 1 U2 18 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 1998 VL 28 IS 3 BP 259 EP 270 DI 10.1023/A:1006524818404 PG 12 WC Biology SC Life Sciences & Biomedicine - Other Topics GA ZM190 UT WOS:000073513700004 PM 9611766 ER PT J AU Kral, TA Brink, KM Miller, SL McKay, CP AF Kral, TA Brink, KM Miller, SL McKay, CP TI Hydrogen consumptions by methanogens on the early earth SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article ID ECOSYSTEMS; MARS; LIFE; H-2 AB It is possible that the first autotroph used chemical energy rather than light. This could have been the main source of primary production after the initial inventory of abiotic organic material had been depleted. The electron acceptor most readily available for use by this first chemoautotroph would have been CO2. The most abundant electron donor may have been H-2 that would have been outgassing from volcanoes at a rate estimated to be as large as 10(12) moles yr(-1), as well as from photo-oxidation of Fe+2. We report here that certain methanogens will consume H-2 down to partial pressures as low as 4 Pa (4 X 10(-5) atm) with CO2 as the sole carbon source at a rate of 0.7 ng H-2 min(-1) mu g(-1) cell protein. The lower limit of pH(2) for growth of methanogens can be understood on the basis that the pH(2) needs to be high enough for one ATP to be synthesized per CO2 reduced. The pH(2) values needed for growth measured here are consistent with those measured by Stevens and McKinley for growth of methanogens in deep basalt aquifers. H-2-consuming autotrophs are likely to have had a profound effect on the chemistry of the early atmosphere and to have been a dominant sink for H-2 on the early Earth after life began rather than escape from the Earth's atmosphere to space. C1 Univ Arkansas, Dept Biol Sci, Fayetteville, AR 72701 USA. University California San Diego, Dept Chem & Biochem, La Jolla, CA 92093 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Kral, TA (reprint author), Univ Arkansas, Dept Biol Sci, Fayetteville, AR 72701 USA. NR 28 TC 54 Z9 56 U1 2 U2 16 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD JUN PY 1998 VL 28 IS 3 BP 311 EP 319 DI 10.1023/A:1006552412928 PG 9 WC Biology SC Life Sciences & Biomedicine - Other Topics GA ZM190 UT WOS:000073513700007 PM 9611769 ER PT J AU Loewenstein, M AF Loewenstein, M TI Ill-informed comment SO PHOTONICS SPECTRA LA English DT Letter C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Loewenstein, M (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU LAURIN PUBL CO INC PI PITTSFIELD PA BERKSHIRE COMMON PO BOX 1146, PITTSFIELD, MA 01202 USA SN 0731-1230 J9 PHOTON SPECTRA JI Photon. Spect. PD JUN PY 1998 VL 32 IS 6 BP 12 EP 12 PG 1 WC Optics SC Optics GA ZT838 UT WOS:000074132900003 ER PT J AU Bhatia, AK Drachman, RJ AF Bhatia, AK Drachman, RJ TI Another way to calculate the Lamb shift in two-electron systems SO PHYSICAL REVIEW A LA English DT Article ID IONS; LITHIUM; HELIUM; STATE AB We present a calculation of the two-electron Bethe logarithm, the main part of the theoretical expression for the Lamb shift of the atomic ground state. The basic method uses Hylleraas pseudostates to approximate the intermediate states in the slowly convergent sum defining the quantity of interest. Three tricks improve the convergence in our method. First, we choose the nonlinear parameters of the pseudostates by a variational method. Second, we extend the energy sum analytically, beyond the last pseudoenergy. Finally, we extrapolate the result using a physically reasonable parameter as the independent variable; The extrapolation proves to be remarkably linear. Results are given for helium and several two-electron ions and compared with previous calculations. The hydrogen system is also considered. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NR 16 TC 7 Z9 7 U1 1 U2 5 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9926 EI 2469-9934 J9 PHYS REV A JI Phys. Rev. A PD JUN PY 1998 VL 57 IS 6 BP 4301 EP 4305 DI 10.1103/PhysRevA.57.4301 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZU090 UT WOS:000074160600034 ER PT J AU Majer, G Kaess, U Bowman, RC AF Majer, G Kaess, U Bowman, RC TI Nuclear magnetic resonance studies of hydrogen diffusion in LaNi5.0H6.0 and LaNi4.8Sn0.2H5.8 SO PHYSICAL REVIEW B LA English DT Article ID ALPHA-LANI5 HYDRIDE; NEUTRON-SCATTERING; DEGRADATION AB Diffusion measurements of hydrogen in LaNi5.0H6.0 and LaNi4.8Sn0.2H5.8 were carried out between 270 and 365 K using the alternating pulsed field gradient nuclear magnetic resonance technique. The diffusivity of hydrogen in LaNi4.8Sn0.2H5.8 is characterized by a higher mobility and a lower activation enthalpy than observed in LaNi5.0H6.0. The diffusivities at room-temperature, D(300K), are 9.2x10-(12) m(2) s(-1) and 4.6x10(-12) m(2) s(-1) for LaNi4.8Sn0.2H5.8 and LaNi5.0H6.0, respectively. A fit of an Arrhenius expression, D =D(0)exp(-H(a)lk(B)T), to the diffusivities yields an activation enthalpy of H-a = 0.29 eV for LaNi5.0H6.0 and H-a = 0.22 eV for LaNi4.8Sn0.2H5.8. The NMR spin-lattice relaxation rates Gamma(1) and Gamma(1 rho) were measured on the same samples in the temperature range between 100 and 350 K. Tl-le D values and the relaxation data are found to be consistent with respect to the activation enthalpies. For long-range diffusion in both alloys. The hopping rates extracted from the Gamma(1 rho) maxima correspond to long-range diffusion, and both sets of measurements indicate faster motion for the Sn-containing hydride. C1 Max Planck Inst Met Forsch, D-70569 Stuttgart, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Majer, G (reprint author), Max Planck Inst Met Forsch, Heisenbergstr 1, D-70569 Stuttgart, Germany. NR 27 TC 14 Z9 14 U1 0 U2 1 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 JUN 1 PY 1998 VL 57 IS 21 BP 13599 EP 13603 DI 10.1103/PhysRevB.57.13599 PG 5 WC Physics, Condensed Matter SC Physics GA ZT216 UT WOS:000074061700044 ER PT J AU Samoilov, AV Beach, G Fu, CC Yeh, NC Vasquez, RP AF Samoilov, AV Beach, G Fu, CC Yeh, NC Vasquez, RP TI Magnetic percolation and giant spontaneous Hall effect in La1-xCaxCoO3 (0.2 <= x <= 0.5) SO PHYSICAL REVIEW B LA English DT Article ID THIN-FILMS; WEAK-LOCALIZATION; MAGNETORESISTANCE; SUPERLATTICES; EXCHANGE; BEHAVIOR AB We report an unprecedentedly large spontaneous Hall effect in ferromagnetic La1-xCaxCoO3 (0.2 less than or equal to x less than or equal to 0.5) epitaxial films. The effect exceeds existing theoretical predictions for the value of the spontaneous Hall resistivity rho(xy) by several orders of magnitude. The Hall effect is the strongest for x=0.2, which is at a doping level nearest to the ferromagnetic percolation threshold in La1-xCaxCoO3. We suggest that the coexistence of high-and low-spin configurations in the perovskite cobaltites, together with the magnetic percolation behavior, may be responsible for the giant Hall effect. C1 CALTECH, Dept Phys 11436, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91125 USA. RP CALTECH, Dept Phys 11436, Pasadena, CA 91125 USA. NR 34 TC 39 Z9 39 U1 0 U2 9 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9950 EI 2469-9969 J9 PHYS REV B JI Phys. Rev. B PD JUN 1 PY 1998 VL 57 IS 22 BP 14032 EP 14035 PG 4 WC Physics, Condensed Matter SC Physics GA ZU948 UT WOS:000074252500019 ER PT J AU Gambhir, SS Keppenne, CL Banerjee, PK Phelps, ME AF Gambhir, SS Keppenne, CL Banerjee, PK Phelps, ME TI A new method to estimate parameters of linear compartmental models using artificial neural networks SO PHYSICS IN MEDICINE AND BIOLOGY LA English DT Article ID BRAIN TRANSFER CONSTANTS; CEREBRAL BLOOD-FLOW; TIME UPTAKE DATA; GRAPHICAL EVALUATION; EMISSION TOMOGRAPHY; N-13 AMMONIA; QUANTIFICATION; CALIBRATION; REGRESSION; PREDICTION AB At present, the preferred tool for parameter estimation in compartmental analysis is an iterative procedure; weighted nonlinear regression. For a large number of applications, observed data can be fitted to sums of exponentials whose parameters are directly related to the rate constants/coefficients of the compartmental models. Since weighted nonlinear regression often has to be repeated for many different data sets, the process of fitting data from compartmental systems can be very time consuming. Furthermore the minimization routine often converges to a local las opposed to global) minimum. In this paper, we examine the possibility of using artificial neural networks instead of weighted nonlinear regression in order to estimate model parameters. We train simple feedforward neural networks to produce as outputs the parameter values of a given model when kinetic data are fed to the networks' input layer. The artificial neural networks produce unbiased estimates and are orders of magnitude faster than regression algorithms. At noise levels typical of many real applications, the neural networks are found to produce lower variance estimates than weighted nonlinear regression in the estimation of parameters from mono-and biexponential models. These results are primarily due to the inability of weighted nonlinear regression to converge. These results establish that artificial neural networks are powerful tools for estimating parameters for simple compartmental models. C1 Univ Calif Los Angeles, Sch Med, Crump Inst Biol Imaging, Dept Mol & Med Pharmacol, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Sch Med, Dept Biomath, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, NASA, Pasadena, CA 91125 USA. RP Gambhir, SS (reprint author), Univ Calif Los Angeles, Sch Med, Crump Inst Biol Imaging, Dept Mol & Med Pharmacol, A-222B CIBI,700 Westwood Plaza,Box 951770, Los Angeles, CA 90095 USA. EM sgambhir@mednet.ucla.edu NR 31 TC 4 Z9 4 U1 1 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0031-9155 J9 PHYS MED BIOL JI Phys. Med. Biol. PD JUN PY 1998 VL 43 IS 6 BP 1659 EP 1678 DI 10.1088/0031-9155/43/6/021 PG 20 WC Engineering, Biomedical; Radiology, Nuclear Medicine & Medical Imaging SC Engineering; Radiology, Nuclear Medicine & Medical Imaging GA ZU996 UT WOS:000074257600021 PM 9651032 ER PT J AU Kazanas, D Maran, S AF Kazanas, D Maran, S TI Obituary - Andrew Gerasimos Michalitsianos SO PHYSICS TODAY LA English DT Biographical-Item C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kazanas, D (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD JUN PY 1998 VL 51 IS 6 BP 92 EP 92 DI 10.1063/1.882280 PG 1 WC Physics, Multidisciplinary SC Physics GA ZQ938 UT WOS:000073918100022 ER PT J AU Linkin, V Harri, AM Lipatov, A Belostotskaja, K Derbunovich, B Ekonomov, A Khloustova, L Kremnev, R Makarov, V Martinov, B Nenarokov, D Prostov, M Pustovalov, A Shustko, G Jarvinen, I Kivilinna, H Korpela, S Kumpulainen, K Lehto, A Pellinen, R Pirjola, R Riihela, P Salminen, A Schmidt, W Siili, T Blamont, J Carpentier, T Debus, A Hua, CT Karczewski, JF Laplace, H Levacher, P Lognonne, P Malique, C Menvielle, M Mouli, G Pommereau, JP Quotb, K Runavot, J Vienne, D Grunthaner, F Kuhnke, F Musmann, G Rieder, R Wanke, H Economou, T Herring, M Lane, A McKay, CP AF Linkin, V Harri, AM Lipatov, A Belostotskaja, K Derbunovich, B Ekonomov, A Khloustova, L Kremnev, R Makarov, V Martinov, B Nenarokov, D Prostov, M Pustovalov, A Shustko, G Jarvinen, I Kivilinna, H Korpela, S Kumpulainen, K Lehto, A Pellinen, R Pirjola, R Riihela, P Salminen, A Schmidt, W Siili, T Blamont, J Carpentier, T Debus, A Hua, CT Karczewski, JF Laplace, H Levacher, P Lognonne, P Malique, C Menvielle, M Mouli, G Pommereau, JP Quotb, K Runavot, J Vienne, D Grunthaner, F Kuhnke, F Musmann, G Rieder, R Wanke, H Economou, T Herring, M Lane, A McKay, CP TI A sophisticated lander for scientific exploration of Mars: scientific objectives and implementation of the Mars-96 Small Station SO PLANETARY AND SPACE SCIENCE LA English DT Article ID BOUNDARY-LAYER AB A mission to Mars including two Small Stations, two Penetrators and an Orbiter was launched at Baikonur, Kazakhstan: on 16 November 1996. This was called the Mars-96 mission. The Small Stations ere expected to land in September 1997 (L, approximately 178 degrees), nominally to Amazonis-Arcadia region on locations (33 N, 169.4 W) and (37.6 N, 161.9W). The fourth stage of the Mars-96 launcher mal-functioned and hence the mission was lost. However, the state of the art concept of the Small Station can be applied to future Martian lander missions. Also, from the manufacturing and performance point of view, the Mars-96 Small Station could be built as such at low cost, and be fairly easily accommodated on almost any forthcoming Martian mission. This is primarily due to the very simple interface between the Small Station and the spacecraft. The Small Station is a sophisticated piece of equipment. With the total available power of approximately 400 m W the Station successfully supports an ambitious scientific program. The Station accommodates a panoramic camera, an alpha-proton-x-ray spectrometer, a seismometer, a magnetometer, an oxidant instrument, equipment for meteorological observations, and sensors for atmospheric measurement during the descent phase, including images taken by a descent phase camera. The total mass of the Small Station with pay-load on the Martian surface, including the airbags, is only 32 kg. Lander observations.on the surface of Mars combined data from Orbiter instruments will shed on the contemporary Mars and its evolution. As in the Mars-96 mission specific science goals could be exploration of the interior and surface of Mars, investigation of the structure and dynamics of the :atmosphere, the role of water and other materials containing volatiles and in situ studies of the atmospheric boundary layer processes. To achieve the scientific goals of the mission the lander should carry a versatile set of instruments. The Small Station accommodates devices far atmospheric measurements, geophysical I-and geochemical studies of the Martian surface and interior, and cameras for descent phase and panoramic; views. These instruments would be able to contribute remarkably to the process of solving some of the scientific puzzles of Mars. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Finnish Meteorol Inst, Geophys Res Div, FIN-00101 Helsinki, Finland. Russian Space Res Inst, IKI, Moscow 117810, Russia. Babakin Res & Design Ctr, Khimky 141400, Moscow Region, Russia. French Space Agcy, CNES, F-41201 Toulouse, France. French Space Agcy, CNES, F-75039 Paris 1, France. Moscow Power Engn Inst, Special Res Bur, Moscow 111250, Russia. Finnyards Ltd, Tampere 44100, Finland. Space Syst Finland Inc, Espoo 02150, Finland. VTT, Natl Tech Res Ctr, Helsinki 02150, Finland. Serv Aeron, F-91471 Verrieres Le Buisson, Paris, France. Inst Natl Sci Universe, F-92107 St Maur Des Fosses, France. Inst Phys Globe, F-52 Paris, France. Univ Paris 11, Lab Terr & Planetary Phys, F-91205 Orsay, France. Lab Space Astron, F-14476 Marseille 12, France. Max Planck Inst Chem, Abt Kosmochem, D-55128 Mainz, Germany. Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Meteorol, D-4400 Braunschweig, Germany. Univ Chicago, Lab Astrophys & Space Res, Chicago, IL 60637 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Harri, AM (reprint author), Finnish Meteorol Inst, Geophys Res Div, POB 503, FIN-00101 Helsinki, Finland. RI Lognonne, Philippe/F-8846-2010; Harri, Ari-Matti/C-7142-2012 OI Harri, Ari-Matti/0000-0001-8541-2802 NR 37 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 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD JUN-JUL PY 1998 VL 46 IS 6-7 BP 717 EP 737 DI 10.1016/S0032-0633(98)00008-7 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107YZ UT WOS:000075239900008 PM 11541818 ER PT J AU McKay, CP Grunthaner, FJ Lane, AL Herring, M Bartman, RK Ksendzov, A Manning, CM Lamb, JL Williams, RM Ricco, AJ Butler, MA Murray, BC Quinn, RC Zent, AP Klein, HP Levin, GV AF McKay, CP Grunthaner, FJ Lane, AL Herring, M Bartman, RK Ksendzov, A Manning, CM Lamb, JL Williams, RM Ricco, AJ Butler, MA Murray, BC Quinn, RC Zent, AP Klein, HP Levin, GV TI The Mars Oxidant experiment (MOx) for Mars '96 SO PLANETARY AND SPACE SCIENCE LA English DT Article ID VIKING BIOLOGY EXPERIMENTS; LIFE DETECTION EXPERIMENT; MARTIAN SOIL; SURFACE; SEARCH; MODEL; ATMOSPHERE; CHEMISTRY AB The MOx instrument was developed to characterize the reactive nature of the martian soil. The objectives of MOx were: (1) to measure the rate of degradation of organics in the martian environment; (2) to determine if the reactions seen by the Viking biology experiments were caused by a soil oxidant and measure the reactivity of the soil and atmosphere; (3) to monitor the degradation, when exposed to the martian environment, of materials of potential use in future missions; and, finally , (4) to develop technologies and approaches that can be part of future soil analysis instrumentation. The basic approach taken in the MOx instrument was to place a variety of materials composed as thin films in contact with the soil and monitor the physical and chemical changes that result. The optical reflectance of the thin films was the primary sensing-mode. Thin films of organic materials, metals, and semiconductors were prepared. Laboratory simulations demonstrated the response of thin films to active oxidants. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. CALTECH, Pasadena, CA 91125 USA. SETI Inst, Mt View, CA 94043 USA. Biospher Inc, Beltsville, MD 20705 USA. RP McKay, CP (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. EM cmckay@mail.arc.nasa.gov RI Ricco, Antonio/A-5273-2010; OI Ricco, Antonio/0000-0002-2355-4984 FU NIDCR NIH HHS [DE-AC04 94AL85000] NR 35 TC 31 Z9 31 U1 0 U2 8 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 JUN-JUL PY 1998 VL 46 IS 6-7 BP 769 EP 777 DI 10.1016/S0032-0633(98)00011-7 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107YZ UT WOS:000075239900011 PM 11541819 ER PT J AU Zent, AP Quinn, RC Madou, M AF Zent, AP Quinn, RC Madou, M TI A thermo-acoustic gas sensor array for photochemically critical species in the martian atmosphere SO PLANETARY AND SPACE SCIENCE LA English DT Article ID MARS; CHEMISTRY; LIFE; STABILITY AB We describe the development of a thermoacoustic oxidant sensor (TAOS) array to quantify gases that play critical roles in the chemical evolution of the martian surface and atmosphere. The sensor combines a chemiresistor with an acoustic wave-plate device, micro-fabricated on thermally isolated hot-plates; their measurement modes are respectively: conductivity changes of chemically sensitive films, and mass changes of the same coatings. Metal Phthalocyanines (MePcs) and other organic semiconductors such as 1,4-polybutadiene are used as chemical coatings because of their chemical stability and the fact that these compounds have been shown to exhibit selectivity to oxidizing gases. The specific target gases of this experiment are H2O2, H2O, O-3 and CO. Identification and quantification of these gases at the martian surface would contribute to both atmospheric and soil chemistry studies. The species H2O2 and/or O-3, may be responsible for the unique reactive properties of the martin regolith, as discovered in the Viking biology experiments. In addition, each of the target gases are believed to play a role in the photochemical recycling of CO2. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Calif Berkeley, EECS, Berkeley, CA 94720 USA. RP Zent, AP (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RI Madou, Marc/E-5869-2013 OI Madou, Marc/0000-0003-4847-3117 NR 32 TC 6 Z9 6 U1 0 U2 3 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 JUN-JUL PY 1998 VL 46 IS 6-7 BP 795 EP 803 DI 10.1016/S0032-0633(98)00013-0 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107YZ UT WOS:000075239900013 ER PT J AU Sauke, TB Becker, JF AF Sauke, TB Becker, JF TI Stable isotope laser spectrometer for exploration of Mars SO PLANETARY AND SPACE SCIENCE LA English DT Article ID SNC METEORITES; LIFE; NITROGEN; ROCKS; SPECTROSCOPY; HISTORY; CARBON; ESCAPE; SEARCH; CO2 AB On Earth, measurements of the ratios of stable carbon isotopes have provided much information about geological and biological processes. For example, fractionation of carbon occurs in biotic processes and the retention of a distinctive 2-4% contrast in C-13/C-12 between organic carbon and carbonates in rocks as old as 3.8 billion years constitutes some of the firmest evidence for the antiquity of life on the Earth. We have developed a prototype tunable diode Laser spectrometer which demonstrates the feasibility of making accurate in situ isotopic ratio measurements on Mars. This miniaturized instrument, with an optical path length of 10 cm, should be capable of making accurate C-13/C-12 and N-15/N-14 measurements. Gas samples for measurement are to be produced by pyrolysis using soil samples as small as 50 mg. Measurements of C-13/C-12, O-18/O-16 and N-15/N-14 have been made to a precision of better than 0.1% and various other isotopes are feasible. This laser technique, which relies on the extremely narrow emission linewidth of tunable diode lasers (<0.001 cm(-1)) has favorable features in comparison to mass spectrometry, the standard method of accurate isotopic ratio measurement. The miniature instrument could be ready to deploy on the 2003 or other Mars lander missions. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. San Jose State Univ, Dept Phys, San Jose, CA 95192 USA. RP Sauke, TB (reprint author), NASA, Ames Res Ctr, SETI Inst, MS 239-12, Moffett Field, CA 94035 USA. NR 38 TC 9 Z9 9 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD JUN-JUL PY 1998 VL 46 IS 6-7 BP 805 EP 812 DI 10.1016/S0032-0633(98)00014-2 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 107YZ UT WOS:000075239900014 PM 11541820 ER PT J AU Neveu, C Blackmon, T Stark, L AF Neveu, C Blackmon, T Stark, L TI Evaluation of the effects of a head-mounted display on ocular accommodation SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article AB We evaluated a commercially produced head-mounted display (HMD) to determine its short-term effects on human ocular accommodation. Thirteen subjects (seven men and six women, ranging from 13 to 44 years old) were tested for changes in a number of parameters before and after viewing a full-length movie (approximately two hours) on a HMD. As a control, subjects were also tested before and after viewing a movie on a high-quality NTSC color television, and also before and after a one-hour intermission. Accommodation dynamics and range were measured. Data showed well-known trends due to subject age. Only one statistically significant change was found: a slight increase in the latency of relaxation accommodation after HMD viewing. C1 NASA, Ames Res Ctr, Caelum Res Corp, Intelligent Mech Grp, Moffett Field, CA 94035 USA. Univ Calif Berkeley, Neurol & Telerobot Unit, Berkeley, CA 94720 USA. Univ Calif Berkeley, NASA, Ames Res Ctr, Intelligent Mech Grp, Berkeley, CA 94720 USA. RP Neveu, C (reprint author), NASA, Ames Res Ctr, Caelum Res Corp, Intelligent Mech Grp, Moffett Field, CA 94035 USA. NR 21 TC 7 Z9 7 U1 0 U2 0 PU M I T PRESS PI CAMBRIDGE PA FIVE CAMBRIDGE CENTER, CAMBRIDGE, MA 02142 USA SN 1054-7460 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD JUN PY 1998 VL 7 IS 3 BP 278 EP 289 DI 10.1162/105474698565712 PG 12 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA ZU303 UT WOS:000074183200004 ER PT J AU Tait, AB AF Tait, AB TI Estimation of snow water equivalent using passive microwave radiation data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article AB A knowledge of the potential volume of water present in snowpacks is vital for estimates of the global water balance. It is estimated that about three quarters of the world's terrestrial water reserves are locked in snow and ice. The principal objective of this study is to analyze the degree to which passive microwave radiation can be used to interpret snow water equivalent (SWE). The methodology reflects the importance of isolating phenomena other than SWE that may influence the microwave signal. These factors include: snow wetness, depth hoar, complex mountainous terrain, and dense forest cover. Applying these four variables, 16 land-cover categories were identified, and relationships between SWE and brightness temperature were derived for each category. Results show that, for the "simplest" of these categories, a nonforested, nonmountainous terrain, with no depth hoar or melting snow, the SWE can be estimated with 95% confidence within +/-44 mm. The confidence limits increase as the complexity of the snowpack, land form, and land cover increases. (C)Elsevier Science Inc., 1998. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Tait, AB (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Univ Space Res Assoc, Code 974, Greenbelt, MD 20771 USA. NR 11 TC 77 Z9 95 U1 3 U2 16 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 JUN PY 1998 VL 64 IS 3 BP 286 EP 291 DI 10.1016/S0034-4257(98)00005-4 PG 6 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA ZN397 UT WOS:000073641800005 ER PT J AU Sheridan, P McMahan, G Hammerstrom, K Pulich, W AF Sheridan, P McMahan, G Hammerstrom, K Pulich, W TI Factors affecting restoration of Halodule wrightii to Galveston bay, Texas SO RESTORATION ECOLOGY LA English DT Article ID EELGRASS ZOSTERA-MARINA; PLANTED SEAGRASS BEDS; MARITIMA L SL; SUBMERGED VEGETATION; SEASONAL GROWTH; TAMPA-BAY; DYNAMICS; COMPONENTS; SEDIMENTS; BIOMASS AB Experimental restoration of Halodule wrightii (shoalgrass) to its former range on Galveston Island, Texas, began in April 1994. We tested the effects of site, planting density, water depth, and fertilizer addition on survival and growth through June 1996. Temperature, salinity, light transmittance, turbidity, and sediment properties at two restoration sites, Redfish Cove and Snake Island Cove, were similar to those in naturally occurring grassbeds in nearby Christmas Bay. Halodule survival, coverage, and new shoot densities were affected by site (significantly higher at Redfish Cove than at Snake Island Cove, which eventually failed), by planting density (significantly higher when planted on 0.25-m or 0.5-m centers rather than on 1.0-m centers), and by water depth (significantly higher when planted in relatively shallow water). Propagation (spreading from transplant units) was significantly greater from 0.25-m or 0.5-m center plantings but was not consistently affected by site or water depth. Fertilizer enhanced propagation but not survival. After two years, Redfish Cove produced belowground biomass similar to that observed in Christmas Bay, but aboveground biomass remained significantly less. Snake Island Cove plant mortality in September 1995 may have been presaged by low root-rhizome carbohydrate levels observed in October 1994, but causes remain unknown. Further restoration of Halodule to Galveston Bay is possible at selected sites, but structural equivalency will take longer than two growing seasons to achieve. C1 Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Galveston, TX 77551 USA. Texas Pk & Wildlife Dept, Resource Protect Div, Austin, TX 78704 USA. RP Sheridan, P (reprint author), Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, 4700 Ave U, Galveston, TX 77551 USA. NR 38 TC 36 Z9 39 U1 6 U2 16 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 USA SN 1061-2971 J9 RESTOR ECOL JI Restor. Ecol. PD JUN PY 1998 VL 6 IS 2 BP 144 EP 158 DI 10.1046/j.1526-100X.1998.00625.x PG 15 WC Ecology SC Environmental Sciences & Ecology GA ZV113 UT WOS:000074270400004 ER PT J AU Clemmons, JH Herrero, FA AF Clemmons, JH Herrero, FA TI Mass spectroscopy using a rotating electric field SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A mass spectrograph using a rotating electric field and position-sensitive detection is described. Its principles of operation are explained, and a prototype instrument and its test results are presented and discussed. Examination of how the instrument's properties vary under changes of its parameters (e.g., geometry) shows how it can be tailored to specific measurement requirements. The general case utilizing detection in two (polar) dimensions is discussed, and limiting cases employing one-dimensional imaging in each direction, azimuthal and radial, are presented. Applications are suggested and courses for further development are put forth. (C) 1998 American Institute of Physics. [S0034-6748(98)04206-3]. C1 Aerospace Corp, El Segundo, CA 90245 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Clemmons, JH (reprint author), Aerospace Corp, El Segundo, CA 90245 USA. OI Clemmons, James/0000-0002-5298-5222 NR 6 TC 5 Z9 5 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUN PY 1998 VL 69 IS 6 BP 2285 EP 2291 DI 10.1063/1.1148933 PG 7 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 108RK UT WOS:000075279100012 ER PT J AU Beilby, MA Saulson, PR Abramovici, A AF Beilby, MA Saulson, PR Abramovici, A TI Photoelastic measurement of anelasticity and its implications for gravitational wave interferometers SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID PENDULUM AB We have developed a method to determine the internal friction over a wide range of frequencies in transparent materials such as fused silica. We measure the anelastic aftereffect, the relaxation of a sample after a steady stress is removed, by sensing the polarization of a beam of light that traverses the sample. The fractional relaxation of the sample on a given time scale is a direct measure of the anelastic loss angle of the material at the corresponding frequency. To date, we have achieved sensitivity to loss angles as small as 10(-6). We discuss the relevance of these measurements for the design of interferometric detectors of gravitational waves. (C) 1998 American Institute of Physics. [S0034-6748(98)02306-5] C1 Syracuse Univ, Dept Phys, Syracuse, NY 13244 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Beilby, MA (reprint author), Swarthmore Coll, Dept Phys & Astron, 500 Coll Ave, Swarthmore, PA 19081 USA. NR 21 TC 5 Z9 5 U1 0 U2 2 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 JUN PY 1998 VL 69 IS 6 BP 2539 EP 2545 DI 10.1063/1.1148955 PG 7 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 108RK UT WOS:000075279100049 ER PT J AU Sutton, JF AF Sutton, JF TI A low noise synchronous detector SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB A high performance analog switching-type synchronous detector is described. The magnitude of the detected output signal is double that of previous designs, and the signal-to-noise ratio is improved. The square wave caused by dc offsets and 1/f noise components, and the ripple voltage normally produced by synchronous sinusoidal input signals have been eliminated, thus minimizing low pass filter requirements. [S0034-6748(98)02706-3] C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sutton, JF (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUN PY 1998 VL 69 IS 6 BP 2561 EP 2565 DI 10.1063/1.1148958 PG 5 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 108RK UT WOS:000075279100052 ER PT J AU Newton, D Garcia, E Horner, GC AF Newton, D Garcia, E Horner, GC TI A linear piezoelectric motor SO SMART MATERIALS & STRUCTURES LA English DT Article ID ULTRASONIC MOTOR AB The development of a linear hybrid transducer type piezoelectric motor is shown. This design has the advantages of light weight, macro- and micro-positioning, and large force/velocity output. The motor consists of a longitudinal actuator that provides output displacement and force, and two alternating clamping actuators which provide the holding force. The advantages of this design over other types of piezoelectric motor are shown. Significant design considerations for the development of a piezoelectric motor (including material choices, shear loads on piezoelectric materials, and contact surface interaction) are discussed. A simulation, including a finite element analysis of the system, is used to predict the motor response to various input sets. A prototype motor is built and its characteristics are compared to theoretical predictions. C1 Vanderbilt Univ, Dept Mech Engn, Smart Struct Lab, Nashville, TN 37235 USA. NASA, Spacecraft Dynam Branch, Langley Res Ctr, Hampton, VA 23665 USA. NR 13 TC 33 Z9 36 U1 1 U2 6 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0964-1726 J9 SMART MATER STRUCT JI Smart Mater. Struct. PD JUN PY 1998 VL 7 IS 3 BP 295 EP 304 DI 10.1088/0964-1726/7/3/004 PG 10 WC Instruments & Instrumentation; Materials Science, Multidisciplinary SC Instruments & Instrumentation; Materials Science GA ZY200 UT WOS:000074596300004 ER PT J AU Dwivedi, B Mohan, A Thomas, R AF Dwivedi, B Mohan, A Thomas, R TI Spectral diagnostics of an active region observed by the Solar EUV Rocket Telescope and Spectrograph (SERTS) SO SOLAR PHYSICS LA English DT Article ID ELECTRON-IMPACT EXCITATION; EXTREME-ULTRAVIOLET SPECTRUM; LINE DIAGNOSTICS; MG-VIII; NE-VI; IONS; IX AB The EUV spectrum of a solar active region observed by SERTS-89 is used to estimate physical parameters such as electron density, elemental abundance and inhomogeneity in the emitting source. A total of 13 ions, namely, Ne IV-VI, Mg V-IX, Si VII-X and S X, are studied in the SERTS spectral range 170-450 Angstrom, providing plasma diagnostics at temperatures between 10(5)-10(6) K. Attention is called to results derived from ion pairs of different elements that are formed over similar temperature regimes, which allow special checks on the standard assumptions of spectral analyses. Some EUV lines, not originally reported in the SERTS-89 spectrum, are shown to have measureable intensities and are indicated for future observations. C1 Banaras Hindu Univ, Inst Technol, Dept Appl Phys, Varanasi 221005, Uttar Pradesh, India. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Dwivedi, B (reprint author), Banaras Hindu Univ, Inst Technol, Dept Appl Phys, Varanasi 221005, Uttar Pradesh, India. NR 24 TC 8 Z9 8 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUN PY 1998 VL 180 IS 1-2 BP 157 EP 178 DI 10.1023/A:1005077001491 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 103CK UT WOS:000074963700010 ER PT J AU Falconer, DA Jordan, SD Brosius, JW Davila, JM Thomas, RJ Andreatta, V Hara, H AF Falconer, DA Jordan, SD Brosius, JW Davila, JM Thomas, RJ Andreatta, V Hara, H TI Using strong solar coronal emission lines as coronal flux proxies SO SOLAR PHYSICS LA English DT Article AB We investigate the possibility that strong EUV lines observed with the Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) provide good proxies for estimating the total coronal flux over shorter wavelength ranges. We use coordinated SERTS and Yohkoh observations to obtain both polynomial and power-law fits relating the broad-band soft X-ray fluxes to the intensities of Fe XVI 335 Angstrom and 361 Angstrom, Fe XV 284 Angstrom and 417 Angstrom, and Mg IX 368 Angstrom measured with SERTS. We found that the power-law fits best cover the full range of solar conditions from quiet Sun through active region, though not surprisingly the 'cooler' Mg IX 368 Angstrom line proves to be a poor proxy. The quadratic polynomial fits yield fair agreement over a large range for all but the Mg ur line. However, the linear fits fail conspicuously when extrapolated into the quiet-Sun regime. The implications of this work for the He II 304 Angstrom line formation problem are also briefly considered. C1 Univ Alabama, MSFC, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ratheon STX, Lanham, MD 20706 USA. Natl Astron Observ, Mitaka, Tokyo 181, Japan. RP Falconer, DA (reprint author), Univ Alabama, MSFC, Huntsville, AL 35812 USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUN PY 1998 VL 180 IS 1-2 BP 179 EP 191 DI 10.1023/A:1005059816204 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 103CK UT WOS:000074963700011 ER PT J AU Suess, ST Poletto, G Wang, AH Wu, ST Cuseri, I AF Suess, ST Poletto, G Wang, AH Wu, ST Cuseri, I TI The geometric spreading of coronal plumes and coronal holes SO SOLAR PHYSICS LA English DT Article ID WHITE-LIGHT; MASS EJECTIONS; SOLAR CORONA; MODEL; STREAMERS; WIND AB The geometric spreading in plumes and in the interplume region in coronal holes is calculated, using analytic and numerical theoretical models, between 1.0 and 5.0 R-.. We apply a two-scale approximation that permits the rapid local spreading at the base of plumes (fi) to be evaluated separately from the global spreading (f(g)) imposed by coronal hole geometry. We show that fi can be computed from a potential-field model and f(g) can be computed from global magnetohydrodynamic simulations of coronal structure. The approximations are valid when the plasma beta is small with respect to unity and for a plume separation small with respect to a solar radius. C1 NASA, George C Marshall Space Flight Ctr, ES82, Huntsville, AL 35812 USA. Osservatorio Astrofis Arcetri, I-50125 Florence, Italy. Univ Alabama, Dept Mech Engn, Huntsville, AL 35899 USA. Univ Alabama, Ctr Space Plasma & Aeronom Res, Huntsville, AL 35899 USA. Univ Florence, Firenze, Italy. RP Suess, ST (reprint author), NASA, George C Marshall Space Flight Ctr, ES82, Huntsville, AL 35812 USA. NR 27 TC 27 Z9 28 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUN PY 1998 VL 180 IS 1-2 BP 231 EP 246 DI 10.1023/A:1005001618698 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 103CK UT WOS:000074963700014 ER PT J AU Watson, AB AF Watson, AB TI The search for optimal visual stimuli SO VISION RESEARCH LA English DT Letter ID SPATIAL SUMMATION; VISION C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Watson, AB (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 11 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 0042-6989 J9 VISION RES JI Vision Res. PD JUN PY 1998 VL 38 IS 11 BP 1619 EP 1621 PG 3 WC Neurosciences; Ophthalmology SC Neurosciences & Neurology; Ophthalmology GA ZY289 UT WOS:000074605200009 ER PT J AU Alsdorf, D Taylor, P von Frese, R Langel, R Frawley, J AF Alsdorf, D Taylor, P von Frese, R Langel, R Frawley, J TI Arctic and Asia lithospheric satellite magnetic anomalies SO PHYSICS OF THE EARTH AND PLANETARY INTERIORS LA English DT Article DE magnetic anomalies; magnetic field; lithosphere; Arctic Ocean ID IONOSPHERIC FIELD CORRECTION; MAGSAT DATA; GEOMAGNETIC-FIELD; TIEN-SHAN; CRUSTAL STRUCTURE; SOUTHERN URALS; LABRADOR SEA; MAPS; BENEATH; EVOLUTION AB The polar regions present special problems in magnetic studies because they are largely inaccessible and contain the most disturbed magnetic fields on earth (e.g., effects from auroral phenomena). A processing method, previously developed for south polar satellite magnetic data (e.g., Magsat), is applied to north polar data to separate the core and external fields from the lithospheric anomalies. The core field is removed with a least-squares procedure and Fourier correlation coefficient filtering effectively reduces the external field signatures. As demonstrated by improved correlation coefficients and reduced sum-of-squared differences between passes and between dawn and dusk maps, the processing effectively extracts the static geologic signal from the dynamic noise (e.g., external fields). Quantitative comparisons of the resulting lithospheric anomaly map with previous maps suggest that the processing maintains anomaly amplitude while significantly reducing non-lithospheric energy. The map shows a long-wavelength contrast across the Ural mountains, the suture zone between the east European craton (+4 nT) and the west Siberian platform (-4 nT). This contrast night be indicative of significant petrologic differences between these large crustal blocks. If the steepest portion of the magnetic gradient is marking the main Uralian fault, then the fault may extend southward to a latitude coincident with the middle of the Aral sea. The easternmost section of the intraplate Tien Shan is marked by a +3 nT anomaly whereas the remainder of the mountain belt is not associated with a significant anomaly. This pattern agrees with previous interpretations that suggest the eastern Tien Shan is supported by a lithospheric root and the rest of the belt is held up by a positive buoyancy force, i.e., it lacks a root. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Cornell Univ, Dept Geol Sci, Ithaca, NY 14853 USA. Cornell Univ, INSTOC, Ithaca, NY 14853 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. Ohio State Univ, Dept Geol Sci, Columbus, OH 43210 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. Herring Bay Geophys, Dunkirk, MD USA. RP Alsdorf, D (reprint author), Cornell Univ, Dept Geol Sci, Ithaca, NY 14853 USA. NR 57 TC 4 Z9 4 U1 0 U2 1 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 MAY 29 PY 1998 VL 108 IS 1 BP 81 EP 99 DI 10.1016/S0031-9201(97)00081-2 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZW837 UT WOS:000074453300006 ER PT J AU Brown, RH Cruikshank, DP Pendleton, Y Veeder, GJ AF Brown, RH Cruikshank, DP Pendleton, Y Veeder, GJ TI Identification of water ice on the Centaur 1997 CU26 SO SCIENCE LA English DT Article ID SHORT-PERIOD COMETS; OUTER SOLAR-SYSTEM; OPTICAL-CONSTANTS; KUIPER BELT; OBJECTS AB Spectra of the Centaur 1997 CU26 were obtained at the Keck Observatory on 27 October 1997 (universal time). The data show strong absorptions at 1.52 and 2.03 micrometers attributable to water ice on the surface of 1997 CU26. The reflectance spectrum of 1997 CU26 is matched by the spectrum of a mixture of low-temperature particulate water ice and spectrally featureless but otherwise red-colored material. Water ice dominates the Spectrum of 1997 CU26, whereas methane or methane-like hydrocarbons apparently dominate the spectrum of the Kuiper belt object 1993 SC, perhaps indicating different origins, thermal histories, or both for these two objects. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Brown, RH (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NR 21 TC 44 Z9 44 U1 0 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 MAY 29 PY 1998 VL 280 IS 5368 BP 1430 EP 1432 DI 10.1126/science.280.5368.1430 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZQ591 UT WOS:000073883400054 PM 9603731 ER PT J AU Boivin, RF Srivastava, SK AF Boivin, RF Srivastava, SK TI Electron-impact ionization of Mg SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID CROSS-SECTIONS; MULTIPLE IONIZATION; ATOMS; SPECTRUM AB A crossed beam technique is used to measure ionization cross sections of metallic atoms. Relative values of cross sections of single, double and triple ionization of magnesium have been successfully measured over the 0-700 eV range with an estimated accuracy of 11%, 19% and 25%, respectively. Absolute values of cross sections have been obtained by normalization to a theoretical value at high electron energy. The theoretical value is calculated by using the generalized oscillator strength approximation. Results are compared to previously published values and, for single ionization in particular, a comparison with theoretical cross sections is performed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Boivin, RF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 33 TC 23 Z9 24 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD MAY 28 PY 1998 VL 31 IS 10 BP 2381 EP 2394 DI 10.1088/0953-4075/31/10/024 PG 14 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZU423 UT WOS:000074195600024 ER PT J AU Zetner, PW Kanik, I Trajmar, S AF Zetner, PW Kanik, I Trajmar, S TI Electron impact excitation of the a (3)Pi, a ' (3)Sigma(+), d (3)Delta and A (1)Pi states of CO at 10.0, 12.5 and 15.0 eV impact energies SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID SCATTERING CROSS-SECTIONS; CARBON-MONOXIDE AB We have measured the differential and integral cross sections for electron impact excitation of the a(3) Pi, a'(3) Sigma(+), d(3) Delta and A(1) Pi states of CO in the 10-15 eV impact energy region. These measurements fill the gap which existed between the low-energy (threshold to about 12 eV) data of Zobel et al and the intermediate energy (20-50 eV) results of Middleton et ctl. Recent electron time-of-flight measurements are utilized to place the relative cross sections (deduced from energy-loss spectral on the absolute scale. The cross sections are in excellent agreement viith the results obtained by Zobel et al at the overlapping impact energies and always smoothly extrapolate to their low-energy results. Extrapolation to the intermediate energy domain and comparison with the results of Middleton et al is not so clear. Comparison with theoretical differential and integral cross sections of Sun et al and the integral cross sections of Morgan and Tennyson reveals angular and energy dependences which resemble those found for the experimental results but there are serious discrepances concerning the absolute magnitudes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Manitoba, Dept Phys, Winnipeg, MB R3T 2N2, Canada. RP Zetner, PW (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 24 TC 22 Z9 22 U1 0 U2 7 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD MAY 28 PY 1998 VL 31 IS 10 BP 2395 EP 2413 DI 10.1088/0953-4075/31/10/025 PG 19 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZU423 UT WOS:000074195600025 ER PT J AU Ajello, JM James, GK Ciocca, M AF Ajello, JM James, GK Ciocca, M TI High resolution EUV emission spectroscopy of the N-2 c ' (1)Sigma(+)(u) upsilon '=3 and 4 levels by electron impact SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID EXTREME ULTRAVIOLET EMISSION; MOLECULAR NITROGEN; SPECTRUM; STATE; PHOTOABSORPTION; PREDISSOCIATION; 1-SIGMA-U+; ABSORPTION; H-2 AB A high resolution 36 m Angstrom (FWHM), optically thin emission study of the N-2 c' (1) Sigma(u)(+)(4, 3) and (3,2) Rydberg bands excited by electron impact at 100 eV has been completed in the extreme ultraviolet (EUV). A model of the perturbed rotational line intensity distribution of the bands shows the effects of electronic state mixing between the c' (1) Sigma(u)(+) Rydberg state and the b' (1) Sigma(u)(+) valence state. By normalizing the model to the published predissociation yield for J' = 9 the laboratory spectrum can be used to determine the predissociation yields for each rotational level of v' = 3 and 4. Based on a 25% accuracy of the model fit to the measured signal intensities it is found that the predissociation yields of the c', v' = 4 rotational levels increase as the percentage of b' (1) Sigma(u)(+) character increases. On the other hand, the predissociation yields of the cl, v' = 3 rotational levels reach a maximum for 5 < J' < 10. The mean predissociation yields for c', v' = 3 and 4 levels are a function of temperature and are found to be 0.41 and 0.58, respectively at 300 K. The J'-dependent predissociation yields indicate that the emission cross section is a function of temperature. The remainder of the bands forming the v " progressions (v " = 0-5) from v' = 3 and (v " = 0-6) from v' = 4 were studied at 64 m Angstrom (FWHM) resolution. Using this composite spectrum of the two progressions the electron impact emission cross sections of the N-2 c', v' = 3 and 4 levels at 300 K were determined and compared with previous results. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. RP Ajello, JM (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 25 TC 23 Z9 23 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD MAY 28 PY 1998 VL 31 IS 10 BP 2437 EP 2448 DI 10.1088/0953-4075/31/10/028 PG 12 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZU423 UT WOS:000074195600028 ER PT J AU Wilson, RM AF Wilson, RM TI Evidence for solar-cycle forcing and secular variation in the Armagh Observatory temperature record (1844-1992) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SURFACE AIR-TEMPERATURE; SUNSPOT CYCLE; GEOMAGNETIC-ACTIVITY; NORTHERN-HEMISPHERE; CLIMATE-CHANGE; WEATHER; MAXIMUM; SERIES; LEVEL; VARIABILITY AB A prominent feature of previous long-term temperature studies has been the appearance of warming since the 1880s, this often being taken as evidence for anthropogenic-induced global warming. In this investigation, the long-term, annual, mean temperature record (1844-1992) of the Armagh Observatory (Armagh, North Ireland), a set of temperature data based on maximum and minimum thermometers that predates the 1880s and correlates well with northern hemispheric and global standards, is examined for evidence of systematic variation, in particular, as related to solar-cycle forcing and secular variation. Indeed, both appear to be embedded within the Armagh data. Removal of these effects, each contributing about 8% to the overall reduction in variance, yields residuals that are randomly distributed. Application of the 10-year moving average to the residuals, furthermore, strongly suggests that the behavior of the residuals is episodic, inferring that (for extended periods of time) temperatures at Armagh sometimes were warmer or cooler (than expected), while at other times they were stable. Comparison of cyclic averages of annual mean temperatures against the lengths of the associated Hale cycles (i.e., the length of two, sequentially numbered, even-odd sunspot cycle pairs) strongly suggests that the temperatures correlate inversely (r = -0.886 at <2% level of significance) against the length of the associated Hale cycle. Because sunspot cycle 22 ended in 1996, the present Hale cycle probably will be shorter than average, implying that temperatures at Armagh over this Hale cycle will be warmer (about 9.31 +/- 0.23 degrees C at the 90% confidence level) than average (= 9.00 degrees C). C1 NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Wilson, RM (reprint author), NASA, Space Sci Lab, George C Marshall Space Flight Ctr, ES82, Huntsville, AL 35812 USA. EM robert.m.wilson@msfc.nasa.gov NR 79 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1998 VL 103 IS D10 BP 11159 EP 11171 DI 10.1029/98JD00531 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP485 UT WOS:000073758200001 ER PT J AU Descloitres, J Buriez, JC Parol, F Fouquart, Y AF Descloitres, J Buriez, JC Parol, F Fouquart, Y TI POLDER observations of cloud bidirectional reflectances compared to a plane-parallel model using the International Satellite Cloud Climatology Project cloud phase functions SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID RADIATIVE-TRANSFER; SINGLE-SCATTERING; ICE CRYSTALS; ALBEDO AB This study investigates the validity of the plane-parallel cloud model and in addition the suitability of water droplet and ice polycrystal phase functions for stratocumulus and cirrus clouds, respectively. To do that, we take advantage of the multidirectional viewing capability of the Polarization and Directionality of the Earth's Reflectances (POLDER) instrument which allows us to characterize the anisotropy of the reflected radiation field. We focus on the analysis of airborne-POLDER data acquired over stratocumulus and cirrus clouds during two selected flights ton April 17 and April 18, 1994) of the European Cloud and Radiation Experiment (EUCREX'94) campaign. The bidirectional reflectances measured in the 0.86 mu m channel are compared to plane-parallel cloud simulations computed with the microphysical models used by the International Satellite Cloud Climatology Project (ISCCP). Although clouds are not homogeneous plane-parallel layers, the extended cloud layers under study appear to act, on average, as a homogeneous plane-parallel layer. The standard water droplet model (with an effective radius of 10 mu m) used in the ISCCP analysis seems to be suitable for stratocumulus clouds. The relative: root-mean-square difference between the observed bidirectional reflectances and the model is only 2%. For cirrus clouds, the water droplet cloud model is definitely inadequate since the rms difference rises to 9%; when the ice polycrystal model chosen for the reanalysis of ISCCP data is used instead, the rms difference is reduced to 3%. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Sci & Technol Lille, Opt Atmospher Lab, F-59655 Villeneuve Dascq, France. RP Descloitres, J (reprint author), Univ Maryland, Dept Geog, College Pk, MD 20742 USA. EM jack@ltpmail.gsfc.nasa.gov; Jean-Claude.Buriez@univ-lille1.fr; Frederic.Parol@univ-lille1.fr; Yves.Fouquart@univ-lille1.fr NR 22 TC 18 Z9 19 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1998 VL 103 IS D10 BP 11411 EP 11418 DI 10.1029/98JD00592 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP485 UT WOS:000073758200019 ER PT J AU Osborn, MT Kent, GS Trepte, CR AF Osborn, MT Kent, GS Trepte, CR TI Stratospheric aerosol measurements by the Lidar in Space Technology Experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LITE AB The Lidar in Space Technology Experiment (LITE) is a three-wavelength backscatter lidar developed by NASA Langley Research Center to demonstrate and explore the capabilities of space lidar. LITE was flown on space shuttle. Discovery in September 1994. Among the primary experimental objectives of LITE was the measurement of stratospheric aerosols. High-quality stratospheric aerosol measurements at 532 nm and 355 nm were obtained during nighttime, high-gain operation. These LITE data provide a detailed global view of the vertical structure and optical properties of the stratospheric aerosols. The data are also used to study the transport processes influencing the aerosol spatial distribution. LITE data compare well with measurements made by the Stratospheric Aerosol and Gas Experiment (SAGE) II. Individual profile comparisons and comparisons of more global features reinforce and extend the validation of the LITE stratospheric data. LITE demonstrates that a spaceborne lidar, with its high vertical resolution and global coverage, is a powerful tool for tracing atmospheric transport. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA USA. Sci & Technol Corp, Hampton, VA 23666 USA. RP Osborn, MT (reprint author), NASA, Langley Res Ctr, Mail Stop 475, Hampton, VA 23681 USA. EM m.t.osborn@larc.nasa.gov; g.s.kent@larc.nasa.gov; c.r.trepte@larc.nasa.gov NR 20 TC 3 Z9 3 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1998 VL 103 IS D10 BP 11447 EP 11453 DI 10.1029/97JD03429 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP485 UT WOS:000073758200022 ER PT J AU Ho, CH Chou, MD Suarez, M Lau, KM Yan, MMH AF Ho, CH Chou, MD Suarez, M Lau, KM Yan, MMH TI Comparison of model-calculated and ERBE-retrieved clear-sky outgoing longwave radiation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BUDGET EXPERIMENT; EARTH; COMPUTATION; CLIMATE; OCEANS AB In order to validate radiative transfer models and identify sources of errors in the satellite retrieval of radiation budgets, model calculations of clear-sky outgoing longwave radiation (OLR) over oceans are compared with data from the Earth Radiation Budget Experiment (ERBE). The NASA Goddard Earth Observing System (GEOS-1) and the National Centers for Environmental Prediction and National Center for Atmospheric Research reanalyses of temperature and humidity and the Stratospheric Aerosol and Gas Experiment retrieval of the stratospheric humidity are used in the model calculations. Averaged over time (1985-1989) and space (60 degrees S-60 degrees N), the model-calculated clear-sky OLR has a positive bias of 1.9-2.3 W-2 when compared with that of ERBE. Nearly all of the bias can be accounted for by the inclusion of the absorption due to CO2 in the 4.3-mu m band and to the weak CO2 and O-3 molecular lines distant from band centers. The use of the two different reanalyses has only a small effect on the flux calculations (similar to 0.4 W m(-2)). Consistent with suggestions by previous studies, ERBE is found to overestimate (underestimate) the clear-sky OLR over high humid (dry) regions due to incorrect identification of clear scenes in the ERBE retrievals. The importance of the upper tropospheric humidity in affecting the Earth radiation budget is also investigated. Although only similar to 15% of the atmospheric humidity is contained in the region above the 600-hPa level, the upper troposphere is as important as the lower troposphere in contributing to the clear-sky OLR. C1 NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA Univ Maryland Joint Ctr Earth Syst Sci, College Pk, MD USA. Sci Syst & Applicat Inc, Seabrook, MD USA. RP Ho, CH (reprint author), Seoul Natl Univ, Dept Atmospher Sci, Seoul 151742, South Korea. EM hoch@climate.snu.ac.kr; chou@climate.gsfc.nasa.gov; suarez@janus.gsfc.nasa.gov; lau@climate.gsfc.nasa.gov; yan@climate.gsfc.nasa.gov RI Ho, Chang-Hoi/H-8354-2015; Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 26 TC 9 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1998 VL 103 IS D10 BP 11529 EP 11536 DI 10.1029/98JD00085 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP485 UT WOS:000073758200028 ER PT J AU Litvin, FL Wang, AG Handschuh, RF AF Litvin, FL Wang, AG Handschuh, RF TI Computerized generation and simulation of meshing and contact of spiral bevel gears with improved geometry SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article AB The geometry, generation and simulation of meshing and contact of low-noise spiral bevel gears with a localized bearing contact have been developed. The influence of misalignment on the transmission errors and the shift of the bearing contact was investigated. An approach is proposed for detection and avoidance of an edge contact caused by interference of the working part of the surface of one of the gears with the fillet surface of the mating member. The theory that is developed is illustrated with numerical examples and experimental tests. (C) 1998 Elsevier Science S.A. C1 Univ Illinois, Dept Mech Engn, Gear Res Lab, Chicago, IL 60607 USA. NASA, Lewis Res Ctr, USA, Res Lab, Cleveland, OH 44135 USA. RP Litvin, FL (reprint author), Univ Illinois, Dept Mech Engn, Gear Res Lab, Chicago, IL 60607 USA. NR 16 TC 47 Z9 58 U1 2 U2 6 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0045-7825 J9 COMPUT METHOD APPL M JI Comput. Meth. Appl. Mech. Eng. PD MAY 25 PY 1998 VL 158 IS 1-2 BP 35 EP 64 DI 10.1016/S0045-7825(97)00229-6 PG 30 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA ZV275 UT WOS:000074288300003 ER PT J AU Panda, J AF Panda, J TI Shock oscillation in underexpanded screeching jets SO JOURNAL OF FLUID MECHANICS LA English DT Article ID LIGHT-SCATTERING; SUPERSONIC JETS; WAVES; MODEL AB The periodic oscillation of the shock waves in screeching, underexpanded, supersonic jets, issuing from a choked, axisymmetric, nozzle at fully expanded Mach numbers (M-j) of 1.19 and 1.42, is studied experimentally and analytically. The experimental part uses schlieren photography and a new shock detection technique which depends on a recently observed phenomenon of laser light scattering by shock waves. A narrow laser beam is traversed from point to point in the flow field and the appearance of the scattered light is sensed by a photomultiplier tube (PMT). The time-averaged and phase-averaged statistics of the PMT data provide significant insight into the shock motion. It is found that the shocks move the most in the jet core and the least in the shear layer. This is opposite to the intuitive expectation of a larger-amplitude shock motion in the shear layer where organized vortices interact with the shock. The mode of shock motion is the same as that of the emitted screech tone. The instantaneous profiles of the first four shocks over an oscillation cycle were constructed through a detailed phase averaged measurement. Such data show a splitting of each shock (except for the first one) into two weaker ones through a 'moving staircase-like' motion. During a cycle of motion the downstream shock progressively fades away while a new shock appears upstream. Spark schlieren photographs demonstrate that a periodic convection of large organized vortices over the shock train results in the above described behaviour. An analytical formulation is constructed to determine the self-excitation of the jet column by the screech sound. The screech waves, while propagating over the jet column, add a periodic pressure fluctuation to the ambient level, which in turn perturbs the pressure distribution inside the jet. The oscillation amplitude of the first shock predicted from this linear analysis shows reasonable agreement with the measured data. Additional reasons for shock oscillation, such as a periodic perturbation of the shock formation mechanism owing to the passage of the organized structures, are also discussed. C1 Modern Technol Corp, Middleburg Hts, OH 44130 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Panda, J (reprint author), Modern Technol Corp, Middleburg Hts, OH 44130 USA. NR 32 TC 49 Z9 50 U1 2 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 MAY 25 PY 1998 VL 363 BP 173 EP 198 DI 10.1017/S0022112098008842 PG 26 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA ZW735 UT WOS:000074442500008 ER PT J AU McCord, TB Hansen, GB Fanale, FP Carlson, RW Matson, DL Johnson, TV Smythe, WD Crowley, JK Martin, PD Ocampo, A Hibbitts, CA Granahan, JC AF McCord, TB Hansen, GB Fanale, FP Carlson, RW Matson, DL Johnson, TV Smythe, WD Crowley, JK Martin, PD Ocampo, A Hibbitts, CA Granahan, JC CA NIMS Team TI Salts an Europa's surface detected by Galileo's Near Infrared Mapping Spectrometer SO SCIENCE LA English DT Article ID MAGNETOSPHERIC ION-BOMBARDMENT; PLAYA EVAPORITE MINERALS; AMORPHOUS SOLID WATER; MU-M; DEATH-VALLEY; SATELLITES; REFLECTANCE; SPECTRA; ICE; SPECTROSCOPY AB Reflectance spectra in the 1- to 2.5-micrometer wavelength region of the surface of Europa obtained by Galileo's Near Infrared Mapping Spectrometer exhibit distorted water absorption bands that indicate the presence of hydrated minerals, The laboratory spectra of hydrated salt minerals such as magnesium sulfates and sodium carbonates and mixtures of these minerals provide a close match to the Europa spectra. The distorted bands are only observed in the optically darker areas of Europa, including the lineaments, and may represent evaporite deposits formed by water, rich in dissolved salts, reaching the surface from a water-rich layer underlying an ice crust. C1 Univ Hawaii, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Reston, VA 22091 USA. STI Inc, Honolulu, HI 96813 USA. RP Univ Hawaii, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. RI Hibbitts, Charles/B-7787-2016 OI Hibbitts, Charles/0000-0001-9089-4391 NR 60 TC 225 Z9 229 U1 1 U2 24 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 EI 1095-9203 J9 SCIENCE JI Science PD MAY 22 PY 1998 VL 280 IS 5367 BP 1242 EP 1245 DI 10.1126/science.280.5367.1242 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZQ351 UT WOS:000073852500042 PM 9596573 ER PT J AU Kouveliotou, C Dieters, S Strohmayer, T van Paradijs, J Fishman, GJ Meegan, CA Hurley, K Kommers, J Smith, I Frail, D Murakami, T AF Kouveliotou, C Dieters, S Strohmayer, T van Paradijs, J Fishman, GJ Meegan, CA Hurley, K Kommers, J Smith, I Frail, D Murakami, T TI An x-ray pulsar with a superstrong magnetic field in the soft gamma-ray repeater SGR1806-20 SO NATURE LA English DT Article ID NEUTRON-STARS; IDENTIFICATION; SGR-1806-20; EMISSION AB Soft gamma-ray repeaters (SGRs) emit multiple, brief (similar to 0.1-s), intense outbursts of low-energy gamma-rays. They are extremely rare(1)-three(2-4) are known in our Galaxy and one(5) in the Large Magellanic Cloud. Two SGRs are associated(5-7) with young supernova remnants (SNRs), and therefore most probably with neutron stars, but it remains a puzzle why SGRs are so different from 'normal' radio pulsars, Here we report the discovery of pulsations in the persistent X-ray flux of SGR1806 - 20, with a period of 7.47 s and a spindown rate of 2.6 x 10(-3) s yr(-1). We argue that the spindown is due to magnetic dipole emission and fmd that the pulsar age and (dipolar) magnetic field strength are similar to 1,500 years and 8 x 10(14) gauss, respectively. Our observations demonstrate the existence of 'magnetars', neutron stars with magnetic fields about 100 times stronger than those of radio pulsars, and support earlier suggestions(8,9) that SGR bursts are caused by neutron-star 'crust-quakes' produced by magnetic stresses. The 'magnetar' birth rate is about one per millennium-a substantial fraction of that of radio pulsars. Thus our results may explain why some SNRs have no radio pulsars. C1 NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Washington, DC 20002 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Natl Inst Nucl & High Energy Phys, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. MIT, Cambridge, MA 02139 USA. Rice Univ, Houston, TX 77251 USA. Natl Radio Astron Observ, VLA, Socorro, NM 87801 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Kouveliotou, C (reprint author), NASA, Space Sci Lab, George C Marshall Space Flight Ctr, ES-84, Huntsville, AL 35812 USA. EM chryssa.kouveliotou@msfc.nasa.gov NR 28 TC 711 Z9 717 U1 1 U2 13 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD MAY 21 PY 1998 VL 393 IS 6682 BP 235 EP 237 DI 10.1038/30410 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZP513 UT WOS:000073761000042 ER PT J AU Korb, CL Gentry, BM Li, SX Flesia, C AF Korb, CL Gentry, BM Li, SX Flesia, C TI Theory of the double-edge technique for Doppler lidar wind measurement SO APPLIED OPTICS LA English DT Article AB The theory of the double-edge technique is described by a generalized formulation that substantially extends the capabilities of the edge technique. It uses two edges with opposite slopes located about the laser frequency. This doubles the signal change for a given Doppler shift End yields a factor of 1.6 improvement in the measurement accuracy compared with the single-edge technique. Use of two high-resolution edge filters reduces the effects of Rayleigh scattering on the measurement by as much as an order of magnitude and allows the signal-to-noise ratio to be substantially improved in areas of low aerosol backscatter. We describe a method that allows the Rayleigh and aerosol components of the signal to be independently determined. The effects of Rayleigh scattering are then subtracted from the measurement, and we show that the correction process does not significantly increase the measurement noise for Rayleigh-to-aerosol ratios as high as 10. We show that for small Doppler shifts a measurement accuracy of 0.4 m/s can be obtained for 5000 detected photons, 1.2 m/s for 1000 detected photons, and 3.7 m/s for 50 detected photons for a Rayleigh-to-aerosol ratio of 5. Methods for increasing the dynamic range to more than +/-100 m/s are given. (C) 1998 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Sci & Engn Serv Inc, Burtonsville, MD 20866 USA. Univ Geneva, Dept Appl Phys, CH-1211 Geneva, Switzerland. RP Korb, CL (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. NR 11 TC 58 Z9 85 U1 2 U2 9 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1998 VL 37 IS 15 BP 3097 EP 3104 DI 10.1364/AO.37.003097 PG 8 WC Optics SC Optics GA ZM902 UT WOS:000073587800001 PM 18273256 ER PT J AU Wilson, RG AF Wilson, RG TI Ball-lens coupling efficiency for laser-diode to single-mode fiber: comparison of independent studies by distinct methods SO APPLIED OPTICS LA English DT Article AB Results of two recent studies representing distinct approaches to optimizing laser-diode to single-mode fiber ball-lens coupling efficiency are compared and revealed to be in close agreement. One method is based on a conventional optical analysis-design program combining geometrical and diffraction methods, merged with calculated coupling efficiency in terms of balanced spherical aberration. The other is based on exact solution of Maxwell's equations for scattering of a beam from a dielectric sphere. The results suggest that optimum coupling efficiency may depend critically on sufficiently fine discretization of the distances of source and fiber from the lens. The studies compared here are synergistic with several other recently reported studies on coupling efficiency, and those studies are appropriately cross referenced. A graphic relationship is developed, between coupling efficiency and Strehl ratio as an optical tolerance for the coupling system based on balanced spherical aberration. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Wilson, RG (reprint author), NASA, Langley Res Ctr, MS 473, Hampton, VA 23681 USA. NR 14 TC 19 Z9 24 U1 0 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1998 VL 37 IS 15 BP 3201 EP 3205 DI 10.1364/AO.37.003201 PG 5 WC Optics SC Optics GA ZM902 UT WOS:000073587800015 PM 18273270 ER PT J AU Hoge, FE Wright, CW Swift, RN Yungel, JK AF Hoge, FE Wright, CW Swift, RN Yungel, JK TI Airborne laser-induced oceanic chlorophyll fluorescence: solar-induced quenching corrections by use of concurrent downwelling irradiance measurements SO APPLIED OPTICS LA English DT Article ID INHERENT OPTICAL-PROPERTIES; DISSOLVED ORGANIC-MATTER; WARM CORE RING; ABSORPTION-COEFFICIENT; PHYTOPLANKTON; RETRIEVAL; AIRCRAFT; PIGMENTS AB Airborne laser-induced (and water Raman-normalized) spectral fluorescence emissions from oceanic chlorophyll were obtained during variable downwelling irradiance conditions induced by diurnal variability and patchy clouds. Chlorophyll fluorescence profiles along geographically repeated inbound and outbound flight track lines, separated in time by similar to 3-6 h and subject to overlying cloud movement, were found to be identical after corrections made with concurrent downwelling irradiance measurements. The corrections were accomplished by a mathematical model containing an exponential of the ratio of the instantaneous-to-average downwelling irradiance. Concurrent laser-induced phycoerythrin fluorescence and chromophoric dissolved organic matter fluorescence were found to be invariant to downwelling irradiance and thus, along with sea-surface temperature, established the near constancy of the oceanic surface layer during the experiment and validated the need for chlorophyll fluorescence quenching corrections over wide areas of the ocean. C1 NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. EG&G Inc, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Hoge, FE (reprint author), NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. NR 21 TC 5 Z9 6 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1998 VL 37 IS 15 BP 3222 EP 3226 DI 10.1364/AO.37.003222 PG 5 WC Optics SC Optics GA ZM902 UT WOS:000073587800018 PM 18273273 ER PT J AU Cook, AL Hendricks, HD AF Cook, AL Hendricks, HD TI Diode-laser-pumped tunable 896-939.5-nm neodymium-doped fiber laser with 43-mW output power SO APPLIED OPTICS LA English DT Article ID MU-M; ND-3+; FLUORESCENCE; OSCILLATION; GLASS AB A diode-laser-pumped neodymium-doped fiber laser is presented. For a launched pump power of 85 mm, the fiber laser had a cw output power of 43 mW, which is approximately an order of magnitude greater output power than any previously reported diode-pumped neodymium fiber laser operating on the F-4(3/2)-I-4(9/2) transition, which covers the 900-950-nm region. The fiber laser had a threshold power of 10 mW and a slope efficiency of 58% with respect to launched pump power. Tuning with a diffraction grating was obtained from 896 to 937 nm with narrow-band output powers as high as 32 mW. Emission was also obtained at 939.5 nm with use of a fiber Bragg grating as the output reflector. (C) 1998 Optical Society of America. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Cook, AL (reprint author), NASA, Langley Res Ctr, Mailstop 473, Hampton, VA 23681 USA. NR 25 TC 15 Z9 15 U1 0 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1998 VL 37 IS 15 BP 3276 EP 3281 DI 10.1364/AO.37.003276 PG 6 WC Optics SC Optics GA ZM902 UT WOS:000073587800027 PM 18273282 ER PT J AU Olive, JF Barret, D Boirin, L Grindlay, JE Swank, JH Smale, AP AF Olive, JF Barret, D Boirin, L Grindlay, JE Swank, JH Smale, AP TI RXTE observation of the x-ray burster 1E 1724-3045 - I. Timing study of the persistent x-ray emission with the PCA SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : individual : 1E 1724-3045; globular clusters : individual : Terzan 2; X-rays : bursts; X-rays : stars ID QUASI-PERIODIC OSCILLATIONS; APERIODIC VARIABILITY; BINARIES; STARS; STATE AB We report on the Rossi X-ray Timing Explorer Proportional Counter Array (PCA) observation of the X-ray burster 1E1724-3045 located in the globular cluster Terzan 2. The observation lasted for about 100 kiloseconds and spanned from November 4th to 8th, 1996. The PCA source count rate in the 2-20 keV range was about 470 cts/s. No large spectral variations were observed within our observation as inferred from color-color and hardness-intensity diagram analysis. The persistent tent X-ray emission shows a high level of noise variability, the so-called High Frequency Noise (HFN) with a fractional Root Mean Squared (RMS) of similar to 25% in the 2 x 10(-3) - 40 Hz range. The strong HFN together with the hardness of its X-ray spectrum suggest that 1E1724-3045 is an "Atoll" source which was in its "Island" slate during the observation. The Fourier Power Density Spectra (PDS) can be modeled in terms of the sum of two "shot noise" components for which the shots have a single-side exponential shape (i.e. instantaneous rise and exponential decay). The characteristic shot decay timescales inferred from the best fitting of the PDS are similar to 680 and 16 msec respectively. The two components contribute similarly to the total RMS (similar to 15%). The PDS contains also a third component: a broad and asymmetric peaked noise feature centered at 0.8 Hz. This Quasi Periodic Oscillation-like (QPO) feature contributes at the level of similar to 10% to the total RMS. Neither the shot timescales nor the QPO frequency vary with energy. On the other hand, the integrated RMS of all three components shows a positive correlation with energy up to at least 40 keV. Ln addition, in the 2-20 keV energy band where the signal to noise ratio is the highest, we found evidence for a high frequency component which shows up in the PDS above 100 Hz. In terms of the shot noise model, a Lorentzian fit of this last component implies a shot decay timescale of similar to 1.4 ms. We also show that 1E1724-3045 has striking timing similarities with the black hole candidate GROJ0422+32 (Nova Persei 1992). Our observation demonstrates that a low frequency QPO simultaneously with a high level of RMS is not a timing signature unique to black holes. This extends the growing list of similarities between Atoll sources and black hole systems. C1 CNRS, UPS, Ctr Etud Spatiale Rayonnements, F-31028 Toulouse 04, France. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Barret, D (reprint author), CNRS, UPS, Ctr Etud Spatiale Rayonnements, 9 Ave Colonel Roche, F-31028 Toulouse 04, France. RI Swank, Jean/F-2693-2012 NR 38 TC 44 Z9 44 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAY 20 PY 1998 VL 333 IS 3 BP 942 EP 951 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZR231 UT WOS:000073953400024 ER PT J AU Bakes, ELO Tielens, AGGM AF Bakes, ELO Tielens, AGGM TI The effects of polycyclic aromatic hydrocarbons on the chemistry of photodissociation regions SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM, abundances; ISM, general; ISM, molecules ID ATOMIC CARBON; ORION NEBULA; INTERSTELLAR; EMISSION; GRAINS; LINE; BAR; CO AB We have investigated the effects of including polycylic aromatic hydrocarbons (PAHs) on the abundance of neutral atoms and molecules for two typical photodissociation regions (PDRs): a high-density case (the Orion complex) and a low-density case. PAHs provide a large surface area for chemistry between themselves and the gas phase and influence this chemistry directly through their charge state. The PAH charge is dominated by the balance of the photoelectric ejection of electrons and direct PAH-electron recombination. This means that the incident UV Bur and gas density determine the PAH charge balance. We have investigated a wide parameter space for the incident far-ultraviolet flux (measured in units of G(0) = 1.6 x 10(-3) elbos s(-1) cm(-2)) varying as 10 < G(0) < 10(5) and gas density, n(H), where 10(2) cm(-3) < n(H) ( 10(5) cm(-3). Because PAHs are highly efficient charge exchange intermediaries, our results show that their presence in the PDR strongly influences the gas phase abundance of neutral atomic carbon, sulfur, silicon, and metals throughout the PDR by mutual neutralization. We have determined the effects of PAHs on the column density and line intensity of the chemical species in the PDR, and we present these results as functions of depth into the PDR, G(0), and n(H). We discuss the PDR model in detail for the Orion PDR. Typically, the presence of PAHs in a PDR increases the peak C I line intensities by a factor of 2. Our model for the Orion PDR produces a [C I] 610 mu m line intensity of 1.3 x 10(-5) ergs cm(-2) s(-1), which compares well with the observed peak intensity toward this source (10(-5) ergs cm(-2) s(-1)). We conclude that PAHs play a central role in the gas phase chemistry and that they are crucial to our understanding of the structure and evolution of star-forming regions. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. RP Bakes, ELO (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 21 TC 75 Z9 75 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP 258 EP 266 DI 10.1086/305625 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ838 UT WOS:000073908100022 ER PT J AU Tielens, AGGM AF Tielens, AGGM TI Interstellar depletions and the life cycle of interstellar dust SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM, abundances; ISM, clouds ID SIZE DISTRIBUTION; ABUNDANCES; ELEMENTS; CLOUDS; CARBON; GRAINS; EVOLUTION; MANTLES; SHOCKS; STARS AB We have developed a simple model for the evolution of interstellar dust, which relates elemental depletions to the physical processes involved, including stardust injection, accretion in clouds, and dust destruction in interstellar shocks. We compare the results of this model to observed cloud and intercloud depletions of Si, Mg, and Fe and derive dust destruction and accretion rates. The results show that the much lower depletion in the intercloud phase as compared to the cloud phase implies that the dust destruction timescale for Si-bearing dust is comparable to the mixing timescale from the cloud to the intercloud phase and thus much shorter than the stardust injection timescale. The derived average lifetime for Si-bearing dust (6 x 10(7) yr) is considerably less than theoretical calculations for silicates (3 x 10(8) yr) predict. Thus, in agreement with other studies, we conclude that a major fraction of the elemental silicon is locked up in a relatively volatile (binding energy, E(b) similar or equal to 2 eV) dust component. In contrast, the lifetime for Fe-bearing dust (5 x 10(8) yr) is consistent with a refractory (E(b) similar or equal to 5 eV) reservoir. Derived accretion rates for these elements are consistent with expected collision rates in diffuse clouds and imply little chemically driven differentiation upon accretion. The implications of these lifetimes for our understanding of the origin and evolution of interstellar dust are briefly examined. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Tielens, AGGM (reprint author), NASA, Ames Res Ctr, MS245-3, Moffett Field, CA 94035 USA. NR 43 TC 96 Z9 97 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 MAY 20 PY 1998 VL 499 IS 1 BP 267 EP 272 DI 10.1086/305640 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ838 UT WOS:000073908100023 ER PT J AU Titarchuk, L Lapidus, I Muslimov, A AF Titarchuk, L Lapidus, I Muslimov, A TI Mechanisms for high-frequency quasi-periodic oscillations in neutron star and black hole binaries SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion : accretion disks; black hole physics; radiation mechanisms : thermal; stars : neutron; stars : oscillations; x-rays : general ID PROBING ACCRETION DISKS; DIFFERENTIAL ROTATION; RADIATION; COMPTONIZATION; DISKOSEISMOLOGY; STABILITY; VISCOSITY; SPECTRA AB We explain the millisecond variability detected by Rossi X-Ray Timing Explorer (RXTE) in the X-ray emission from a number of low-mass X-ray binary systems (Sco X-1, 4U 1728-34, 4U 1608-522, 4U 1636-536, 4U 0614+091, 4U 1735-44, 4U 1820-30, GX 5-1) in terms of dynamics of the centrifugal barrier, a hot boundary region surrounding a neutron star (NS). We demonstrate that this region may experience the relaxation oscillations and that the displacements of a gas element both in radial and vertical directions occur at the same main frequency, of order of the local Keplerian frequency. We show the importance of the effect of a splitting of the main frequency produced by the Coriolis force in a rotating disk for the interpretation of a spacing between the quasi-periodic oscillation (QPO) peaks. We estimate a magnitude of the splitting effect and present a simple formula for the whole spectrum of the split frequencies. It is interesting that the first three lowest order overtones (corresponding to the azimuthal numbers m = 0, -1, and -2) fall in the range of 200-1200 Hz and match the kHz QPO frequencies observed by RXTE. Similar phenomena should also occur in black hole (BH) systems, but, since the QPO frequency is inversely proportional to the mass of a compact object, the frequency of the centrifugal-barrier oscillations in the BH systems should be a factor of 5-10 lower than that for the NS systems. The X-ray spectrum formed in this region is a result of upscattering of a soft radiation (from a disk and an NS surface) off relatively hot electrons in the boundary layer. The typical size of the emission region should be 1-3 km, which is consistent with the time-lag measurements. We also briefly discuss some alternative QPO models, including the possibility of acoustic oscillations in the boundary layer, the proper stellar rotation, and g-mode disk oscillations. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. George Mason Univ, CSI, Fairfax, VA 22030 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Univ Sussex, Ctr Astron, Brighton BN1 9QJ, E Sussex, England. RP Titarchuk, L (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 60 TC 120 Z9 121 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP 315 EP 328 DI 10.1086/305642 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ838 UT WOS:000073908100029 ER PT J AU King, AR Cannizzo, JK AF King, AR Cannizzo, JK TI Low states in cataclysmic variables SO ASTROPHYSICAL JOURNAL LA English DT Article DE novae, cataclysmic variables; stars, mass-loss; stars, spots ID LONG-TERM BEHAVIOR; SS-CYGNI; MASS-TRANSFER; DWARF NOVAE; SYSTEMS; CYCLE; MODEL; STAR AB Cataclysmic variables are usually classified Into dwarf novae, nova-likes, Z Camelopardalis stars, VY Sculptoris stars, and so on, on the basis of their long-term photometric behavior. We show that some aspects of this behavior may be caused by variations in the mass transfer rate from the secondary star about the current secular mean, and the consequent stability or instability of the accretion disk, if present. The most likely cause of the mass transfer variations on these timescales (years or less) is starspots. Mass transfer variations can cause low states in systems with otherwise steady disks, but they produce only subtle effects on dwarf novae, including variations in the outburst shapes and the standstills of Z Cam systems. C1 Univ Leicester, Astron Grp, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP King, AR (reprint author), Univ Leicester, Astron Grp, Leicester LE1 7RH, Leics, England. NR 26 TC 58 Z9 59 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP 348 EP 354 DI 10.1086/305630 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ838 UT WOS:000073908100032 ER PT J AU Sarna, MJ Antipova, J Muslimov, A AF Sarna, MJ Antipova, J Muslimov, A TI Binary pulsar PSR J1012+53: Evolution, ages, and masses of companions SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, close; pulsars, individual (PSR J1012+53); stars, evolution; stars, neutron; white dwarfs ID CLOSE BINARY; MILLISECOND PULSARS; RADIO PULSARS; SYSTEMS; COMPONENT; NUCLEAR; DWARF; STARS AB We investigate the evolution of the close binary system consisting of the millisecond radio pulsar PSR J1012+53 and its low-mass companion, presumably a helium white dwarf. Within a standard evolutionary scenario, we explore the most plausible range of masses each component would have when the orbital parameters of the system achieve the observed values. We demonstrate that a neutron star of initial mass 1.4 M. can accrete, at most, 0.75 M. during the whole evolution of this binary system and may have increased its gravitational mass to 2.0 M.. Also, our evolutionary calculations reveal that, for all relevant scenarios, the lowest mass the helium white dwarf in this system can reach at the latest stages of binary evolution is 0.15 M.. We present estimates of the age of the neutron star in this system that consistently account for all phases of detached and semidetached binary evolution, including the rather prolonged phase of a white dwarf cooling. For the system PSR J1012+53, we demonstrate the occurrence of thermal hydrogen flashes on a low-mass helium white dwarf at the latest stages of its evolution. We discuss the impact of this system on the issue of the mass limit for a neutron star and on the problem of the structure and evolution of very low mass helium white dwarfs, companions of millisecond pulsars. C1 Polish Acad Sci, Copernicus Astron Ctr, PL-00716 Warsaw, Poland. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Tartu State Univ, Dept Phys, EE-2400 Tartu, Estonia. RP Sarna, MJ (reprint author), Polish Acad Sci, Copernicus Astron Ctr, PL-00716 Warsaw, Poland. NR 44 TC 16 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP 407 EP 413 DI 10.1086/305596 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ838 UT WOS:000073908100039 ER PT J AU Knigge, C Long, KS Wade, RA Baptista, R Horne, K Hubeny, I Rutten, RGM AF Knigge, C Long, KS Wade, RA Baptista, R Horne, K Hubeny, I Rutten, RGM TI Hubble Space Telescope eclipse observations of the nova-like cataclysmic variable UX Ursae Majoris SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries, close; novae, cataclysmic variables; stars, individual (UX Ursae Majoris); ultraviolet, stars ID HOPKINS ULTRAVIOLET TELESCOPE; ACCRETION DISKS; Z-CAMELOPARDALIS; SPECTRA; STARS; MODEL; DISTRIBUTIONS; SPECTROSCOPY; WINDS AB We present and analyze Hubble Space Telescope observations of the eclipsing nova-like cataclysmic variable UX UMa obtained with the Faint Object Spectrograph. Two eclipses each were observed with the G160L grating (covering the ultraviolet waveband) in 1994 August and with the PRISM(covering the near-ultraviolet to near-infrared) in November of the same year. The system was similar to 50% brighter in November than in August, which, if due to a change in the accretion rate, indicates a fairly substantial increase in (M) over dot (acc) by greater than or similar to 50%. The eclipse light curves are qualitatively consistent with the gradual occultation of an accretion disk with a radially decreasing temperature distribution. The light curves also exhibit asymmetries about mideclipse that are likely due to a bright spot at the disk edge. Bright-Spot spectra have been constructed by differencing the mean spectra observed at pre-and posteclipse orbital phases. These difference spectra contain ultraviolet absorption lines and show the Balmer jump in emission. This suggests that part of the bright spot may be optically thin in the continuum and vertically extended enough to veil the inner disk and/or the outflow from UX UMa in some spectral lines. Model disk spectra constructed as ensembles of stellar atmospheres provide poor descriptions of the observed posteclipse spectra, despite the fact that UX UMa's light should be dominated by the disk at this time. Suitably scaled single temperature model stellar atmospheres with T(eff) similar or equal to 12,500-14,500 K actually provide a better match to both the ultraviolet and optical posteclipse spectra. Evidently, great care must be taken in attempts to derive accretion rates from comparisons of disk models to observations. One way to reconcile disk models with the observed posteclipse spectra is to postulate the presence of a significant amount of optically thin material in the system. Such an optically thin component might be associated with the transition region ("chromosphere") between the disk photosphere and the fast wind from the system, whose presence has been suggested by Knigge & Drew. In any event, the wind/chromosphere is likely to be the region in which many, if not most, of the UV Lines are formed. This is clear from the plethora of emission lines that appear in the mideclipse spectra, some of which appear as absorption features in spectra taken at out-of-eclipse orbital phases. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Penn State Univ, Dept Astron & Astrophys, Davey Labs 525, University Pk, PA 16802 USA. Univ Fed Santa Catarina, Dept Fis, BR-88040 Florianopolis, SC, Brazil. Univ St Andrews, Dept Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Isaac Newton Grp, E-38730 Santa Cruz De La Palma, Spain. RP Knigge, C (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 43 TC 23 Z9 23 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP 414 EP 428 DI 10.1086/305617 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ838 UT WOS:000073908100040 ER PT J AU Brandner, W Kohler, R AF Brandner, W Kohler, R TI Star formation environments and the distribution of binary separations SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, visual; open clusters and associations, individual (Scorpius-Centaurus); stars, formation; stars, pre-main sequence ID FORMING REGIONS; MULTIPLICITY AB We have carried out K-band speckle observations of a sample of 114 X-ray-selected weak-line T Tauri stars in the nearby Scorpius-Centaurus OB association. We find that for binary T Tauri stars closely associated with the early-type stars in Upper Scorpius, which is the youngest subgroup of the OB association, the peak in the distribution of binary separations is at 90 AU. For binary T:T Tauri stars located in the direction of an older subgroup but not closely associated with early-type stars, the peak in the distribution is at 215 AU. A Kolmogorov Smirnov test indicates at a significance level of 98% that the two binary populations do not result from the same distribution. Apparently, the same physical conditions that facilitate the formation of massive stars also facilitate the formation of closer binaries among low-mass stars, whereas physical conditions unfavorable for the formation of massive stars lead to the formation of wider binaries among low-mass stars. The outcome of the binary formation process might be related to the internal turbulence and the angular momentum of molecular cloud cores, to the magnetic field, to the initial temperature within a cloud, or-most likely-to a combination of all of these. We conclude that the distribution of binary separations is not a universal quantity and that the broad distribution of binary separations observed among main-sequence stars can be explained by a superposition of more peaked binary distributions resulting from various star-forming environments. The overall binary frequency among pre-main-sequence stars in individual star-forming regions is not necessarily higher than that among main-sequence stars. C1 CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Astrophys Inst Potsdam, D-14482 Potsdam, Germany. Max Planck Inst Astron, D-69117 Heidelberg, Germany. RP Brandner, W (reprint author), CALTECH, Jet Prop Lab, IPAC, Mail Code 100-22, Pasadena, CA 91125 USA. NR 29 TC 52 Z9 52 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP L79 EP L82 DI 10.1086/311338 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ839 UT WOS:000073908200019 ER PT J AU Shrader, C Titarchuk, L AF Shrader, C Titarchuk, L TI The high-energy spectra of accreting black holes: Observational evidence for bulk-motion infall SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms, nonthermal; relativity; stars, individual (GRO J1655-40, GRS 1915+105) ID EMISSION; GALAXY; DISKS; GINGA AB We discuss the emergent spectra from accreting black holes, considering in particular the case where the accretion is characterized by relativistic bulk motion. We suggest that such accretion is likely to occur in a wide variety of black hole environments, where the strong gravitational field is expected to dominate the pressure forces, and that this is likely to lead to a characteristic high-energy spectroscopic signature: an extended power-law tail. It is in the high (soft) state that matter impinging upon the event horizon can be viewed directly, and the intrinsic power law is seen. Certain types of active galactic nuclei (AGNs) may represent the extragalactic analog of the high-soft state accretion, which would further support our ideas, demonstrating the stability of the (alpha similar to 1.8) power law. This stability is a result of the asymptotic independence of the spectral index on the mass accretion rate and its weak dependence on plasma temperatures. We have computed the expected spectral energy distribution for an accreting black hole binary in terms of our three model parameters: the disk color temperature, a geometric factor related to the illumination of the black hole site by the disk, and a spectral index related to the efficiency of the bulk-motion up-scattering. We emphasize that this is a fully self-consistent approach, and it is not to be confused with the more common phenomenological methods employing additive power law and blackbody or multicolor disk. A test of the model is presented using observational data from the Compton Gamma Ray Observatory (CGRO) and the Rossi X-Ray Timing Explorer (RXTE), covering similar or equal to 2-200 keV for two recent galactic black hole X-ray nova outbursts. The resulting model fits are encouraging and, along with some observational trends cited from the literature, they support our bulk-motion hypothesis. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Lanham, MD USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. RP Shrader, C (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 30 TC 47 Z9 47 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1998 VL 499 IS 1 BP L31 EP L35 DI 10.1086/311351 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ839 UT WOS:000073908200008 ER PT J AU McConnell, JR Bales, RC Stewart, RW Thompson, AM Albert, MR Ramos, R AF McConnell, JR Bales, RC Stewart, RW Thompson, AM Albert, MR Ramos, R TI Physically based modelling of atmosphere-to-snow-to-firn transfer of H2O2 at South Pole SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ICE CORES; AIR; DEPOSITION; GREENLAND AB Quantitative interpretation of ice core chemical records requires a detailed understanding of the transfer processes that relate atmospheric concentrations to those in the snow, firn, and ice. A unique, 2 year set of year-round surface snow samples at South Pole and snow pits, with associated accumulation histories, were used to test a physically based model for atmosphere-to-firn transfer of H2O2. The model, which extends our previous transfer modeling at South Pole into the snowpack, is based on the advection-dispersion equation and spherical diffusion within representative snow grains. Required physical characteristics of the snowpack, such as snow temperature and ventilation, were estimated independently using established physical models. The surface snow samples and related model simulations show that there is a repeatable annual cycle in H2O2 in the surface snow at South Pale. It peaks in early spring, and surface snow concentration is primarily determined by atmospheric concentration and temperature, with some dependence on grain size. The snow pits and associated model simulations point out the impor tance of accumulation timing and annual accumulation rate in understanding the deposition and preservation of H2O2 and delta(18)O at South Pole. Long-term snowpack simulations suggest that the firn continues to lose H2O2 to the atmosphere for at least 10-12 years (similar to 3 m) after burial at current South Pole temperatures and accumulation rates. C1 Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Cold Reg Res & Engn Lab, Hanover, NH 03755 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP McConnell, JR (reprint author), Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. EM joe@hwr.arizona.edu RI Thompson, Anne /C-3649-2014 OI Thompson, Anne /0000-0002-7829-0920 NR 31 TC 54 Z9 54 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 20 PY 1998 VL 103 IS D9 BP 10561 EP 10570 DI 10.1029/98JD00460 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZN676 UT WOS:000073670500001 ER PT J AU Shipham, MC Bartlett, KB Crill, PM Harriss, RC Blaha, D AF Shipham, MC Bartlett, KB Crill, PM Harriss, RC Blaha, D TI Atmospheric methane measurements in central New England: An analysis of the long-term trend and the seasonal and diurnal cycles SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC METHANE; GROWTH-RATE; ICE-CORE; EMISSIONS; ACCUMULATION; INCREASE; EXTREMES; LAST AB We have compiled a unique high-resolution ambient-air methane data set consisting of approximately 125,000 independently measured data points for the years 1991-1995 that have been collected at a site in the northeastern United States. The annual median mixing ratio of methane for all measurements was 1808 ppbv in 1992, increasing at a variable rate to 1837 ppbv in 1995. The lower 10-30% of the data from each month were defined as representative of background air and were compared with the global Climate Monitoring and Diagnostics Laboratory (CMDL) data set. The background data exhibit a variable upward trend of 5.5+/-2 ppbv/yr during the 4-year time period, with most of the increase observed during 1993 and 1994. The seasonal cycle for the background data set is similar to what is observed by CMDL stations and varies from 24 to 35 ppbv. The amplitude of the seasonal cycle for the full data set was larger, ranging from 35 to 44 ppbv. Differences between the full and background mixing ratios vary on a seasonal basis and are largest in the winter and smallest in the summer. These differences appear to be controlled by changes in atmospheric stability and changes in emissions from local and regional sources throughout the year. Diurnal cycles exist in the data, with the magnitude and timing of maximum and minimum values being controlled by inputs from local sources and atmospheric stability. Nearby wetlands contribute to an overnight buildup of methane in the late spring and summer. The magnitude of the daily cycle is largest in July and August (similar to 23 ppbv), when inputs from wetlands are large and wind speed is generally low. In April, the daily cycle is smallest (similar to 6 ppbv), when inputs from local sources are low and more vigorous atmospheric mixing limits pollution buildup. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Complex Syst Res Ctr, Durham, NH 03824 USA. NASA Headquarters, Mission Plant Earth, Washington, DC 20546 USA. RP Shipham, MC (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. EM m.c.shipham@larc.nasa.gov; karen@kaos.unh.edu; patrick.crill@unh.edu; harriss@tamu.edu; denise@kaos.sr.unh.edu OI Crill, Patrick/0000-0003-1110-3059 NR 34 TC 11 Z9 12 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 MAY 20 PY 1998 VL 103 IS D9 BP 10621 EP 10630 DI 10.1029/98JD00106 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZN676 UT WOS:000073670500006 ER PT J AU Schoeberl, MR Jackman, CH Rosenfield, JE AF Schoeberl, MR Jackman, CH Rosenfield, JE TI A Lagrangian estimate of aircraft effluent lifetime SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DATA ASSIMILATION SYSTEM; LOWER STRATOSPHERE; MIDDLE ATMOSPHERE; SIMULATION; TRANSPORT; MODEL; CIRCULATION AB The lifetime of aircraft exhaust is estimated using multiyear diabatic trajectory integrations using United Kingdom Meteorological Office and Goddard Space Flight Center (GSFC) Data Assimilation Office winds. Instantaneous January trajectory parcel releases in the midlatitude stratosphere at 19, 16, 14, 13, and 11 km are compared. The first two cases correspond to the proposed flight altitudes of high-speed supersonic aircraft. The last two cases correspond to subsonic flight altitudes. Parcels descending below 250 hPa are eliminated as would occur when aircraft effluent reaches the troposphere. After a transient adjustment period the total number of parcels in most experiments decays exponentially with a decay period (lifetime) of about 1 year. This is the lifetime of the longest-lived eigenmode as discussed by Prather [1996]. Our 1-year ,time is shorter than the 1.5 year GSFC two-dimensional (2-D) model lifetime for same release, but in good agreement with the 1.13 year GSFC 3-D model lifetime. We also find that the effluent lifetime is slightly longer in the southern hemisphere midlatitude stratosphere than in the northern. Both the 13 and 11 km releases are mostly within the stratospheric middle world and rapidly leave the stratosphere. We conclude that there will be a small impact of subsonic aircraft exhaust on the larger stratosphere. Finally, we find that our overall lifetime results are fairly sensitive to the lower stratospheric heating rates. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD 20810 USA. RP Schoeberl, MR (reprint author), NASA, Goddard Space Flight Ctr, Code 910, Greenbelt, MD 20771 USA. EM schom@zephyr.gsfc.nasa.gov RI Jackman, Charles/D-4699-2012 NR 31 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 MAY 20 PY 1998 VL 103 IS D9 BP 10817 EP 10825 DI 10.1029/98JD00363 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZN676 UT WOS:000073670500017 ER PT J AU Gotthelf, EV Vasisht, G AF Gotthelf, EV Vasisht, G TI Discovery of a 7 second anomalous X-ray pulsar in the distant Milky Way SO NEW ASTRONOMY LA English DT Article DE pulsars : general; pulsars : individual : AX J1845-0258; X-rays : general; supernova remnants ID MAGNETIZED NEUTRON-STARS; SOFT GAMMA-REPEATERS; RADIO PULSARS; SUPERNOVA REMNANT; BINARY; ACCRETION; ASCA AB We report the serendipitous discovery of a 7-s X-ray pulsar using data acquired with the Advanced Satellite for Cosmology and Astrophysics (ASCA). The pulsar is detected as an unresolved source located towards a region of the Galactic plane (l,b similar or equal to 29.5,0.08) that coincides with an overdensity of star-formation tracers. The signal suffers tremendous foreground absorption, equivalent to N-H similar or equal to 10(23) cm(-2); the absorption correlates well with a line-of-sight that is tangential to the inner spiral arms and the 4-kpc molecular ring. The pulsar is not associated with any known supernova remnants or other cataloged objects in that direction. The near sinusoidal pulse (period P similar or equal to 6.9712) is modulated at 35% pulsed amplitude, and the steep spectrum is characteristic of hot black-body emission with temperature kT similar to 0.65 keV. We characterize the source as an anomalous X-ray pulsar (AXP). (C) 1998 Elsevier Science B.V. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gotthelf, EV (reprint author), Univ Space Res Assoc, Columbia, MD USA. NR 33 TC 56 Z9 57 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1384-1092 J9 NEW ASTRON JI New Astron. PD MAY 19 PY 1998 VL 3 IS 5 BP 293 EP 300 DI 10.1016/S1384-1076(98)00014-1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP933 UT WOS:000073803000002 ER PT J AU Krainsky, IL Asnin, VM AF Krainsky, IL Asnin, VM TI Negative electron affinity mechanism for diamond surfaces SO APPLIED PHYSICS LETTERS LA English DT Article ID VAPOR-DEPOSITED DIAMOND; FILMS; SPECTROSCOPY; EMISSION AB The energy distribution of the secondary electrons for chemical vacuum deposited diamond films with negative electron affinity (NEA) was investigated. It was found that while for completely hydrogenated diamond surfaces the negative electron affinity peak in the energy spectrum of the secondary electrons is present for any energy of the primary electrons, for partially hydrogenated diamond surfaces there is a critical energy above which the peak is present in the spectrum. This critical energy increases sharply when hydrogen coverage of the diamond surface diminishes. This effect was explained by the change of the NEA from the true type for the completely hydrogenated surface to the effective type for the partially hydrogenated surfaces. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Krainsky, IL (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 14 TC 47 Z9 48 U1 0 U2 9 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 MAY 18 PY 1998 VL 72 IS 20 BP 2574 EP 2576 DI 10.1063/1.121422 PG 3 WC Physics, Applied SC Physics GA ZN118 UT WOS:000073611700026 ER PT J AU Qian, YH Zhou, Y AF Qian, YH Zhou, Y TI Complete Galilean-invariant lattice BGK models for the Navier-Stokes equation SO EUROPHYSICS LETTERS LA English DT Article ID GAS AUTOMATA; SIMULATIONS AB Galilean invariance has been an important issue in lattice-based hydrodynamics models. Previous models concentrated on the nonlinear advection term. In this paper, we take into account the nonlinear response effect in a systematic way. Using the Chapman-Enskog expansion up to second order, complete Galilean invariant lattice BGK models in one dimension (theta = 3) and two dimensions (theta = 1) for the Navier-Stokes equation have been obtained. C1 Columbia Univ, Dept Appl Phys & Appl Math, New York, NY 10027 USA. IBM Corp, Div Res, TJ Watson Res Ctr, Yorktown Heights, NY 10598 USA. NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. RP Qian, YH (reprint author), Columbia Univ, Dept Appl Phys & Appl Math, New York, NY 10027 USA. NR 23 TC 53 Z9 55 U1 5 U2 20 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0295-5075 J9 EUROPHYS LETT JI Europhys. Lett. PD MAY 15 PY 1998 VL 42 IS 4 BP 359 EP 364 DI 10.1209/epl/i1998-00255-3 PG 6 WC Physics, Multidisciplinary SC Physics GA ZP256 UT WOS:000073734100002 ER PT J AU Lanari, R Lundgren, P Sansosti, E AF Lanari, R Lundgren, P Sansosti, E TI Dynamic deformation of Etna volcano observed by satellite radar interferometry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GLOBAL POSITIONING SYSTEM; LANDERS EARTHQUAKE; 1991 ERUPTION; MT ETNA; DEFLATION; HEKLA AB Satellite radar interferometry of Mt. Etna volcano, Sicily, Italy, reveals a sequence of deformation characterized by deflation during the end of the 1993 eruption, inflation from 1993-1995 with an increase in the inflation rate immediately before its resumed eruptive activity in late 1995. This was followed by very low deformation levels during the following year. The source of the deformation changed from a depth of 9 km during deflation to more than 11-14 km during the subsequent inflation, consistent with a model in which deflation at shallower levels is followed by inflation at greater depth as the volcano system recharges from below before its next eruption. This study demonstrates that radar interferometry provides an important contribution towards understanding the dynamic deformation of volcanoes. By revealing large scale changes in their pre-eruption deformation rates, radar interferometry could play an important role in volcano eruption monitoring. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. IRECE, I-80124 Napoli, Italy. RP Lanari, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Sansosti, Eugenio/F-7297-2011 OI Sansosti, Eugenio/0000-0002-5051-4056 NR 20 TC 77 Z9 81 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 15 PY 1998 VL 25 IS 10 BP 1541 EP 1544 DI 10.1029/98GL00642 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900001 ER PT J AU Hannegan, B Olsen, S Prather, M Zhu, X Rind, D Lerner, J AF Hannegan, B Olsen, S Prather, M Zhu, X Rind, D Lerner, J TI The dry stratosphere: A limit on cometary water influx SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TROPOSPHERE; ATMOSPHERE; AIR; CHEMISTRY; TRACERS; BUDGET; N2O; CH4 AB The stratosphere accumulates the bulk of meteoric and cometary material that impacts the Earth and provides a measure of that flux. Recent models and measurements of the effective age of stratospheric air demonstrate our ability to simulate this buildup. Current observations of H2O in the stratosphere and mesosphere are consistent with an extraterrestrial source of H2O, but limit its influx to less than 2 Tg/yr. Such a flux is consistent with standard estimates but is 100 times less than the small-comet hypothesis. C1 Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92697 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Hannegan, B (reprint author), Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92697 USA. NR 33 TC 12 Z9 12 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 MAY 15 PY 1998 VL 25 IS 10 BP 1649 EP 1652 DI 10.1029/98GL01229 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900028 ER PT J AU Miake-Lye, RC Anderson, BE Cofer, WR Wallio, HA Nowicki, GD Ballenthin, JO Hunton, DE Knighton, WB Miller, TM Seeley, JV Viggiano, AA AF Miake-Lye, RC Anderson, BE Cofer, WR Wallio, HA Nowicki, GD Ballenthin, JO Hunton, DE Knighton, WB Miller, TM Seeley, JV Viggiano, AA TI SOx oxidation and volatile aerosol in aircraft exhaust plumes depend on fuel sulfur content SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GAS-PHASE; ION AB Volatile and nonvolatile aerosols were measured in the wake of a B757 airliner in flight, in concert with measurements of gaseous SOx and CO2 emissions, while the airplane was burning fuel with a sulfur content of either 72 parts per million by mass (ppmm) or 676 ppmm. The volatile aerosol number density exceeded that of the nonvolatile for both fuels and, while the nonvolatile (soot) component was largely insensitive to the fuel sulfur content, the volatile component depleted the gas-phase sulfur species with a condensed fraction that increased from 6% (low S) to 31% (high S). The large proportion of SOx in the aerosol phase and its nonlinear dependence on fuel sulfur content cannot be explained by known combustion mechanisms and has the potential for significant environmental effects. C1 Aerodyne Res Inc, Ctr Aerothermodynam, Billerica, MA 01821 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. USAF, Space Vehicles Directorate, VSBP, Hanscom Field, MA USA. RP Miake-Lye, RC (reprint author), Aerodyne Res Inc, Ctr Aerothermodynam, 45 Manning Rd, Billerica, MA 01821 USA. EM rick@aerodyne.com NR 21 TC 37 Z9 37 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 MAY 15 PY 1998 VL 25 IS 10 BP 1677 EP 1680 DI 10.1029/98GL00064 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900035 ER PT J AU Pueschel, RF Verma, S Ferry, GV Howard, SD Vay, S Kinne, SA Goodman, J Strawa, AW AF Pueschel, RF Verma, S Ferry, GV Howard, SD Vay, S Kinne, SA Goodman, J Strawa, AW TI Sulfuric acid and soot particle formation in aircraft exhaust SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Size analyses of Ames wire impactor aircraft exhaust aerosol samples resulted in a continuous particle size distribution between 0.01 mu m and 1.0 mu m particle radius. The two orders of magnitude size range covered by the measurements correspond to 6-7 orders of magnitude particle concentration. The data determined a nucleation mode, composed of aircraft-emitted sulfuric acid aerosol, that contributed between 62% and 85% to the total aerosol surface area and between 31% and 34% to its volume. Soot aerosol contributed 0.3% to the surface area and 0.07% to the volume of sulfuric acid aerosol. Emission indices were: ETH2SO4= 0.09 g/kg(FUEL) and (0.2-0.5) g/kg(FUEL) (for 75 ppmm and 675 ppmm fuel-S, respectively), 1.7E-40.01 = 1.7E14 and (7.7E14 and 5.2E15) particles/kg(FUEL) (for 75 and 675 ppmm fuel-S, respectively). The sulfur (gas) to sulfuric acid (particle) conversion efficiency was between 10% and 37%. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sci Syst & Applicat, Lanham, MD USA. Symtech Corp, Arlington, VA USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. San Jose State Univ, San Jose, CA 95192 USA. RP Pueschel, RF (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 15 TC 22 Z9 22 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 MAY 15 PY 1998 VL 25 IS 10 BP 1685 EP 1688 DI 10.1029/97GL03479 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900037 ER PT J AU Anderson, BE Cofer, WR Bagwell, DR Barrick, JW Hudgins, CH Brunke, KE AF Anderson, BE Cofer, WR Bagwell, DR Barrick, JW Hudgins, CH Brunke, KE TI Airborne observations of aircraft aerosol emissions I: Total nonvolatile particle emission indices SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOWER STRATOSPHERE AB We report airborne measurements of total and nonvolatile (at T < 290 degrees C) fine and ultrafine aerosol emission indices (EI's) generated by a variety of jet aircraft. The data were obtained using an instrumented jet aircraft, flown repeatedly through aircraft wakes. These aircraft were observed to produce 0.5 - 10 x 10(15) nonvolatile particles kg(-1) of fuel burned. Their numbers varied as a function of aircraft type, age, and engine operating parameters, but less with atmospheric conditions. Large numbers of volatile aerosols were measured in all cases. Volatile EI's ranged from 0.1 to 40 x 10(16) kg(-1) fuel burned. The observed soot emissions are estimated to have only a minor impact on atmospheric aerosol loading, but a future fleet producing such high concentrations of implied sulfate aerosols could perturb cloud formation and heterogeneous chemical processes in the upper troposphere/lower stratosphere. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Christopher Newport Coll, Dept Chem, Newport News, VA USA. RP Anderson, BE (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 483, Hampton, VA 23681 USA. EM B.E.Anderson@larc.nasa.gov NR 11 TC 61 Z9 61 U1 0 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 MAY 15 PY 1998 VL 25 IS 10 BP 1689 EP 1692 DI 10.1029/98GL00063 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900038 ER PT J AU Anderson, BE Cofer, WR Barrick, JD Bagwell, DR Hudgins, CH AF Anderson, BE Cofer, WR Barrick, JD Bagwell, DR Hudgins, CH TI Airborne observations of aircraft aerosol emissions II: Factors controlling volatile particle production SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Airborne measurements of fine and ultrafine aircraft aerosol emissions are examined as a Function of environmental conditions, fuel sulfur content, and aircraft type, to determine what factors influence the abundance of volatile particles and what the likely composition of these particles are. The data were obtained from aboard a small jet aircraft flying in near-field (< 20 km aircraft separation) wakes generated by a variety of aircraft, All aircraft produced large numbers of particles relative to background concentrations, a majority of which evaporated at temperatures < 200 degrees C. The volatile particles, except under humid conditions, were typically < 20 nm in diameter, and their numbers varied both as a function of atmospheric conditions and plume age. Their apparent number-density dependence upon fuel sulfur content, and the fact that their inferred mass concentrations are less than the reported shortfall in gas phase sulfur budgets, strongly suggests they were primarily composed of condensed sulfur species. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Anderson, BE (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 483, Hampton, VA 23681 USA. NR 9 TC 28 Z9 28 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 MAY 15 PY 1998 VL 25 IS 10 BP 1693 EP 1696 DI 10.1029/98GL00661 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900039 ER PT J AU Brune, WH Faloona, IC Tan, D Weinheimer, AJ Campos, T Ridley, BA Vay, SA Collins, JE Sachse, GW Jaegle, L Jacob, DJ AF Brune, WH Faloona, IC Tan, D Weinheimer, AJ Campos, T Ridley, BA Vay, SA Collins, JE Sachse, GW Jaegle, L Jacob, DJ TI Airborne in-situ OH and HO2 observations in the cloud-free troposphere and lower stratosphere during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INSTRUMENT AB The hydroxyl (OH) and hydroperoxyl (HO2) radicals were measured for the first time throughout the troposphere and in the lower stratosphere with a new instrument aboard the NASA DC-8 aircraft during the 1996 SUCCESS mission. Typically midday OH was 0.1-0.5 pptv, and HO2 was 3-15 pptv. Comparisons with a steady-state model yield the following conclusions. First, even in the lower stratosphere OH was sensitive to the albedo of low clouds and distant high clouds. Second, although sometimes in agreement with models, observed OH and HO2 were more than 4 times larger at other times. Evidence suggests that for the California upper troposphere on 10 May this discrepancy was due to unmeasured HOX sources from Asia. Third, observed HO2/OH had the expected inverse dependence with NO, but was inexplicably higher than modeled HO2/OH by an average of 30%. Finally, small-scale, midday OH and HO2 features were strongly linked to NO variations. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Brune, WH (reprint author), Penn State Univ, Dept Meteorol, 503 Walker Bldg, University Pk, PA 16802 USA. NR 10 TC 92 Z9 92 U1 0 U2 9 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 MAY 15 PY 1998 VL 25 IS 10 BP 1701 EP 1704 DI 10.1029/97GL03098 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900041 ER PT J AU Jaegle, L Jacob, DJ Wang, Y Weinheimer, AJ Ridley, BA Campos, TL Sachse, GW Hagen, DE AF Jaegle, L Jacob, DJ Wang, Y Weinheimer, AJ Ridley, BA Campos, TL Sachse, GW Hagen, DE TI Sources and chemistry of NOx in the upper troposphere over the United States SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HNO3/NOX RATIO; NITRIC-ACID; OZONE AB The origin of NOx in the upper troposphere over the central United States is examined using aircraft observations obtained during the SUCCESS campaign in April-May of 1996. Correlations between NOy (sum of NOx and its oxidation products) and CO at 8-12 km altitude indicate that NOx originates primarily from convective transport of polluted boundary layer air. Lightning and aircraft emissions appear to be only minor sources of NOx. Chemical steady state model calculations constrained by local observations of NO underestimate the measured NOx/NOy concentration ratio at 8-12 km altitude by a factor of two on average. The magnitude of the underestimate is correlated with concentrations of condensation nuclei, which we take as a proxy for the age of air in the upper troposphere. We conclude that the NOx/O-y ratio is maintained above chemical steady state by frequent convective injections of fresh NOx from the polluted boundary layer and by the long lifetime of NOx in the upper troposphere (5-10 days). In contrast to previous studies, we find no evidence for fast heterogeneous recycling from HNO3 to NOx in the upper troposphere. C1 Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Univ Missouri, Dept Phys, Rolla, MO 65401 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Jaegle, L (reprint author), Harvard Univ, Dept Earth & Planetary Sci, 29 Oxford St,Pierce Hall, Cambridge, MA 02138 USA. RI Wang, Yuhang/B-5578-2014 NR 20 TC 88 Z9 90 U1 1 U2 17 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 MAY 15 PY 1998 VL 25 IS 10 BP 1705 EP 1708 DI 10.1029/97GL03591 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900042 ER PT J AU Jaegle, L Jacob, DJ Brune, WH Tan, D Faloona, IC Weinheimer, AJ Ridley, BA Campos, TL Sachse, GW AF Jaegle, L Jacob, DJ Brune, WH Tan, D Faloona, IC Weinheimer, AJ Ridley, BA Campos, TL Sachse, GW TI Sources of HOx and production of ozone in the upper troposphere over the United States SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TRACE AB The sources of HOx (OH+peroxy radicals) and the associated production of ozone at 8-12 km over the United States are examined by modeling observations of OH, HO2, NO, and other species during the SUCCESS aircraft campaign in April-May 1996, The HOx concentrations measured in SUCCESS are up to a factor of 3 higher than can be calculated from oxidation of water vapor and photolysis of acetone. The highest discrepancy was seen in the outflow of a convective storm. We show that convective injection of peroxides (CH3OOH and H2O2) and formaldehyde (CH2O) from the boundary layer to the upper troposphere could resolve this discrepancy. More generally, the data collected over the central United States during SUCCESS suggest that local convection was a major source of HOx and NOx to the upper troposphere. The OH and HO2 observations together with the observations of NO allow us to directly calculate the ozone production in the upper troposphere and its dependence on NOx. We find an average net ozone production of 2 ppbv day(-1) between 8 and 12 km over the continental United States in the spring. Ozone production was NOx-limited under essentially all the conditions encountered in SUCCESS. The high levels of HOx present in the upper troposphere stimulate ozone production and increase the sensitivity of ozone to NOx emissions from aircraft and other sources. C1 Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Jaegle, L (reprint author), Harvard Univ, Dept Earth & Planetary Sci, 29 Oxford St,Pierce Hall, Cambridge, MA 02138 USA. NR 17 TC 80 Z9 80 U1 1 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 MAY 15 PY 1998 VL 25 IS 10 BP 1709 EP 1712 DI 10.1029/98GL00041 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900043 ER PT J AU Campos, TL Weinheimer, AJ Zheng, J Montzka, DD Walega, JG Grahek, FE Vay, SA Collins, JE Wade, LO Sachse, GW Anderson, BE Brune, WH Tan, D Faloona, I Baughcum, SL Ridley, BA AF Campos, TL Weinheimer, AJ Zheng, J Montzka, DD Walega, JG Grahek, FE Vay, SA Collins, JE Wade, LO Sachse, GW Anderson, BE Brune, WH Tan, D Faloona, I Baughcum, SL Ridley, BA TI Measurement of NO and NOy emission indices during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRCRAFT AB Exhaust measurements in the wake vortex regime of the NASA Boeing 757 aircraft were made during the SUbsonic aircraft: Contrails and Cloud Effects Special Study. Emission indices for NO and NOy were calculated from in situ measurements taken on board the NASA DC-8 for plumes aged 20 - 300 seconds. The average NO emission index is 7.5 g NO2/kg fuel for mean conditions of 37 kft altitude, 0.7 Mach and 0.34 kg/s fuel flow rate. Comparison is made between measured indices and predictions based on ground engine test data and a fuel flow model. Measurements are positively correlated but are on average 22% higher than predictions, with considerable scatter and systematic deviations in measurements made under low thrust conditions. These conditions are lower than typical in commercial cruise operation of the 757, for which the model was optimized. No statistically significant change in nitrogenous emissions is observed for an order of magnitude change in fuel sulfur content. Estimation of the NO2 from photochemical calculations implies a contribution to NOx of 5-19%. Examination of exhaust composition shows that 95% of the NOy is in the form of NOx. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci & Technol Corp, Hampton, VA 23681 USA. Lockheed Engn & Sci Co, Hampton, VA 23666 USA. Penn State Univ, University Pk, PA 16802 USA. Boeing Co, Seattle, WA 98124 USA. RP Campos, TL (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. NR 13 TC 11 Z9 11 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 15 PY 1998 VL 25 IS 10 BP 1713 EP 1716 DI 10.1029/97GL03480 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900044 ER PT J AU Vay, SA Anderson, BE Sachse, GW Collins, JE Podolske, JR Twohy, CH Gandrud, B Chan, KR Baughcum, SL Wallio, HA AF Vay, SA Anderson, BE Sachse, GW Collins, JE Podolske, JR Twohy, CH Gandrud, B Chan, KR Baughcum, SL Wallio, HA TI DC-8-based observations of aircraft CO, CH4, N2O, and H2O(g) emission indices during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EXHAUST; ENGINES AB We report the first measurements of CO, CH4, N2O, CO2, and H2O(g) in the exhaust trails of T-39, B-757, and DC-8 aircraft at cruise conditions. Emission indices (EI) derived from these in-situ measurements are presented. Results are in agreement with ground-based tests indicating aircraft act as a net sink for CH4 and recent airborne in-situ measurements that N2O is not an important exhaust constituent. Condensation of H2O(g) on exhaust particles resulted in EI(H2O(g)) values less than those expected from the combustion of fuel alone. Observed apparent negative EI(H2O(g)) values suggest that aircraft aerosol emissions, under unique atmospheric conditions, seed cloud formation and lead to dehydration of the exhaust-influenced air parcel. Such conditions may induce the formation of cirrus clouds from persistent contrails. Comparisons with the Boeing EMIT Code show measurement-derived CO emission index values consistent with model evaluations. C1 NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Boeing Commercial Airplane Co, Seattle, WA 98124 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aerosp Elect Syst Div, Hampton, VA 23681 USA. RP Vay, SA (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 483, Hampton, VA 23681 USA. EM s.a.vay@larc.nasa.gov NR 15 TC 31 Z9 31 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 MAY 15 PY 1998 VL 25 IS 10 BP 1717 EP 1720 DI 10.1029/98GL00656 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900045 ER PT J AU Tan, D Faloona, I Brune, WH Weinheimer, A Campos, T Ridley, B Vay, S Collins, J Sachse, G AF Tan, D Faloona, I Brune, WH Weinheimer, A Campos, T Ridley, B Vay, S Collins, J Sachse, G TI In situ measurements of HOx in aircraft exhaust plumes and contrails during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LARGE-EDDY SIMULATION; EMISSIONS; SURFACES; OH AB In situ flight measurements of the hydroxyl (OH) and hydroperoxyl (HO2) radicals were performed in the exhaust plume of a Boeing 757 and in the contrail. of a Douglas DC-8 flying under typical cruise conditions in the upper troposphere and lower stratosphere during the SUCCESS mission of April and May 1996. Measurements were made in a range of exhaust plume ages from roughly 10 seconds to 20 minutes. OH mixing ratios were found to be greatly enhanced in the plumes, to 2-5 pptv from a background of 0.3-0.5 pptv in young plumes, and to 0.6 pptv from a background of less than or equal to 0.2pptv in older contrails. HO2 mixing ratios were heavily suppressed in the plumes, to 2-4 pptv from a background of 10-20 pptv, for both young plumes and older contrails. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Tan, D (reprint author), Penn State Univ, Dept Meteorol, 503 Walker Bldg, University Pk, PA 16802 USA. NR 19 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 MAY 15 PY 1998 VL 25 IS 10 BP 1721 EP 1724 DI 10.1029/98GL00117 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900046 ER PT J AU Weinheimer, AJ Campos, TL Walega, JG Grahek, FE Ridley, BA Baumgardner, D Twohy, CH Gandrud, B Jensen, EJ AF Weinheimer, AJ Campos, TL Walega, JG Grahek, FE Ridley, BA Baumgardner, D Twohy, CH Gandrud, B Jensen, EJ TI Uptake of NOy on wave-cloud ice particles SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID REACTIVE NITROGEN; AEROSOL; OZONE AB In a flight through a wave cloud during SUCCESS on 2 May 1996, simultaneous forward- and aft-facing NOy inlets were used to infer the amount of condensed-phase NOy present on ice particles that were up to a few minutes old. Condensed-phase amounts were 25-75 pptv, or 10-20% of gas-phase NOy. Given the rapid HNO3 uptake on ice observed in the laboratory, a model calculation implies that virtually all of the gas-phase HNO3 will be depleted in the first 1-2 minutes after the appearance of ice. Thus the NOy observations are consistent with the laboratory results only if the ambient HNO3/NOy ratio is 10-20%. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Weinheimer, AJ (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. EM wein@ucar.edu NR 14 TC 37 Z9 37 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 MAY 15 PY 1998 VL 25 IS 10 BP 1725 EP 1728 DI 10.1029/97GL02957 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZN248 UT WOS:000073626900047 ER PT J AU Adamec, D AF Adamec, D TI Modulation of the seasonal signal of the Kuroshio Extension during 1994 from satellite data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN; VARIABILITY; PACIFIC; ENERGETICS AB Interannual modulation of the seasonal signal in the Kuroshio Extension region is studied using TOPEX altimeter and advanced very high resolution radiometer (AVHRR) data. Meridional profiles of the surface eddy kinetic energy indicate a significant drop in eddy energy levels beginning early in 1994 and persisting until the summer of 1995. The low eddy energy levels are most apparent during the summer and fall 1994. The contribution of the convergence of Reynolds stresses to the zonal momentum budget, -(<(u'v')over bar>)(y), is much weaker in 1994 than in either 1993 or 1995, especially during summer. The low values of Reynolds stresses lead the low eddy kinetic energy values by about a season, consistent with the characteristic timescale of the eddy energy, which is about 90-110 days in this region. AVHRR-derived estimates of sea surface temperature indicate that the subpolar gyre was cooler during summer 1994 relative;to the summers of 1993 and 1995. Calculations of the baroclinic zonally symmetric. circulation indicate that the Kuroshio Extension was frontolytic during summer 1994, which could account for the observed drop in eddy kinetic energy. In particular, convergence of heat due to eddy flow appears to play a crucial role in the interannual modulation of the seasonal signal of the Kuroshio Extension. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Adamec, D (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Code 971, Greenbelt, MD 20771 USA. NR 25 TC 19 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1998 VL 103 IS C5 BP 10209 EP 10222 DI 10.1029/98JC00456 PG 14 WC Oceanography SC Oceanography GA ZN319 UT WOS:000073634000001 ER PT J AU Sui, CH Li, X Lau, KM AF Sui, CH Li, X Lau, KM TI Selective absorption of solar radiation and upper ocean temperature in the equatorial western Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID ATMOSPHERE RESPONSE EXPERIMENT; WARM POOL AB The solar radiation absorbed by seawater in the upper 0.45 m within the Tropical Ocean-Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) domain is estimated from the observed surface heat fluxes and subsurface temperature during the TOGA COARE Intensive Observation Period. On the average, more than 39% of the net surface solar irradiance is estimated to be absorbed within the first 0.45 m. This value is higher than previous estimates. The observed absorption is applied to modify the parameterized transmittance profile representing the COARE domain, which is bordered by the optical water types IA, IB, and II [Jerlov, 1968]. The original and modified profiles of solar irradiance are prescribed in a one-dimensional ocean model to test their effects on the model responses to the observed surface fluxes. The modified profiles for the three types of water all produce better simulation results than the corresponding original profiles in terms of the diurnal and intraseasonal sea surface temperature amplitudes. The model results support our estimate that the near-surface absorption of solar radiation in the COARE region is stronger than that suggested by the water types IA, IB, and II. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA 22180 USA. RP Sui, CH (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. RI Li, Xiaofan/F-5605-2010; Li, Xiaofan/G-2094-2014; OI SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 19 TC 7 Z9 7 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1998 VL 103 IS C5 BP 10313 EP 10321 DI 10.1029/98JC00453 PG 9 WC Oceanography SC Oceanography GA ZN319 UT WOS:000073634000007 ER PT J AU Anyamba, E Susskind, J AF Anyamba, E Susskind, J TI A comparison of TOVS ocean skin and surface air temperatures with other data sets SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SATELLITE; RADIATION; PACIFIC; WEATHER; MSU AB A data set of geophysical fields has been processed at the Goddard Laboratory for Atmospheres from Tiros operational vertical sounder (TOVS) high-resolution infrared sounder 2 (HIRS2) and microwave sounding unit (MSU) radiance observations. The retrieval system is the physically based Pathfinder Path A methodology. The data set currently covers the period 1985-1995. We compare monthly means of TOVS skin temperature T-s and surface air temperature T-a to the Tropical Ocean Global Atmosphere (TOGA) buoy observations, National Center for Environmental Prediction (NCEP) T-s, and the Comprehensive Ocean Atmosphere Data Set (COADS) T-s and T-a, for the time period 1987-1989. We also compare the T-a data to the European Center for Medium-Range Weather Forecasts (ECMWF) 2 m temperature. The TOVS T-s has a mean cold bias of less than or equal to 0.5 K relative to NCEP T-s, while the T-a has a mean cold bias of less than or equal to 1.0 K in the tropics relative to both ECMWF and GOADS T-a. The bias in the TOVS T-a is largely due to the diurnal sampling of NOAA 10 observations. The bias in the T-s has additional contributions from a possible cool skin effect as well as retrieval errors associated with cloud clearing and accounting for water vapor attenuation and reflected solar radiation. Because of the holistic retrieval of TOVS T-s and T-a, there is a near cancellation of biases due to diurnal Sampling and cloud clearing, so that the derived T-s-T-a have higher accuracy than the individual T-s and T-a, and give a more realistic representation of the evolution of known features of the ocean surface circulation than does the GOADS. These results indicate that TOVS T-s and T-a may be suitable for climate variability studies involving air-sea interactions. The data set is available on a daily, 5-daily, or monthly mean basis with a spatial resolution of 1 degrees by 1 degrees. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Anyamba, E (reprint author), NASA, Goddard Space Flight Ctr, Gen Sci Corp, Code 910-4, Greenbelt, MD 20771 USA. NR 40 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1998 VL 103 IS C5 BP 10489 EP 10511 DI 10.1029/97JC03417 PG 23 WC Oceanography SC Oceanography GA ZN319 UT WOS:000073634000018 ER PT J AU Nalli, NR Smith, WL AF Nalli, NR Smith, WL TI Improved remote sensing of sea surface skin temperature using a physical retrieval method SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TRACK SCANNING RADIOMETER; RESOLUTION INTERFEROMETER SOUNDER; SATELLITE; COEFFICIENTS; ALGORITHMS; EMISSIVITY; VALIDATION; SPACE; WATER AB A new physically based method for retrieving sea surface skin temperature (SST) from satellite measurements of upwelling infrared radiance is developed. The method accounts for atmospheric interference by utilizing multispectral window information to explicitly solve the radiative transfer equation. Two essential elements are required for this SST retrieval: (1) a priori specification of sea surface emissivity and reflectivity spectra and (2) atmospheric transmittances that accurately portray the relative spectral dependence of molecular absorption. The algorithm can be directly applied to any multispectral instrument (e.g., the NOAA advanced very high resolution radiometer and/or the ERS-1 along track scanning radiometer), as well as high resolution spectrometers such as the University of Wisconsin high-resolution interferometer sounder (HIS). Error analyses have shown that SST can theoretically be retrieved to within 0.22 K RMS using high spectral resolution data (or approximately 0.51 K RMS using broadband split-window data) provided that the a priori surface emissivity spectrum does not deviate by more than 0.005 from the true surface emissivity. High spectral resolution has distinct advantages in reducing the effects of atmospheric absorption and instrumental noise errors, as well as providing better guess atmospheric profiles for the transmittance calculations. Application of the method to HIS radiance data acquired from high-altitude aircraft during the 1993 Convection and Moisture Experiment and 1995 Ocean Temperature Interferometric Survey suggests the possibility of physical retrieval of SST from future satellite remote sensing systems (e.g., the EOS advanced infrared sounder) with accuracies limited primarily by detector performance. C1 Univ Wisconsin, Dept Atmospher & Ocean Sci, Madison, WI 53706 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Nalli, NR (reprint author), Univ Wisconsin, Dept Atmospher & Ocean Sci, 1225 W Dayton St, Madison, WI 53706 USA. RI Nalli, Nicholas/F-6731-2010 OI Nalli, Nicholas/0000-0002-6914-5537 NR 54 TC 14 Z9 15 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1998 VL 103 IS C5 BP 10527 EP 10542 DI 10.1029/98JC00196 PG 16 WC Oceanography SC Oceanography GA ZN319 UT WOS:000073634000020 ER PT J AU Yu, JR Singh, UN Barnes, NP Petros, M AF Yu, JR Singh, UN Barnes, NP Petros, M TI 125-mJ diode-pumped injection-seeded Ho : Tm : YLF laser SO OPTICS LETTERS LA English DT Article ID OPERATION AB We describe a diode-pumped, room-temperature Ho:Tm:YLF power oscillator with an optical-to-optical efficiency of 0.03. A Q-switched output energy of as much as 125 mJ at 6 Hz with a pulse width of 170 ns was obtained. Single-frequency, nearly transform-limited operation of the laser was achieved by injection seeding. Laser performance as a function of laser rod temperature and pump intensity was also investigated. The high power and high beam quality of this laser make it well suited for use as a coherent wind lidar transmitter on a space platform. (C) 1998 Optical Society of America. C1 Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Sci & Technol Corp, 101 Res Dr, Hampton, VA 23666 USA. NR 7 TC 84 Z9 87 U1 2 U2 16 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 EI 1539-4794 J9 OPT LETT JI Opt. Lett. PD MAY 15 PY 1998 VL 23 IS 10 BP 780 EP 782 DI 10.1364/OL.23.000780 PG 3 WC Optics SC Optics GA ZM913 UT WOS:000073588900015 PM 18087340 ER PT J AU Alouini, MS Simon, MK AF Alouini, MS Simon, MK TI Generic form for average error probability of binary signals over fading channels SO ELECTRONICS LETTERS LA English DT Article AB The authors present a generic form for the average bit error rate (BER) of coherent, differentially coherent, and noncoherent binary signals over fading channels. This generic form relies on an alternate representation of the incomplete gamma function and, for all the channel fading models under consideration, leads to an expression of the average BER involving a single finite-range integral of tabulated functions which can easily be computed numerically. C1 CALTECH, Dept Elect Engn, Commun Grp, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Alouini, MS (reprint author), CALTECH, Dept Elect Engn, Commun Grp, Mail Code 136-93, Pasadena, CA 91125 USA. NR 7 TC 8 Z9 8 U1 0 U2 0 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD MAY 14 PY 1998 VL 34 IS 10 BP 949 EP 950 DI 10.1049/el:19980709 PG 2 WC Engineering, Electrical & Electronic SC Engineering GA ZR317 UT WOS:000073962000012 ER PT J AU Bandara, SV Gunapala, SD Liu, JK Luong, EM Mumolo, JM Hong, W Sengupta, DK McKelvey, MJ AF Bandara, SV Gunapala, SD Liu, JK Luong, EM Mumolo, JM Hong, W Sengupta, DK McKelvey, MJ TI 10-16 mu m broadband quantum well infrared photodetector SO APPLIED PHYSICS LETTERS LA English DT Article ID PHOTOCONDUCTIVE GAIN; NOISE AB A very long wavelength broadband infrared detector, sensitive over a 10-16 mu m spectral range, based on GaAs/AlxGa1-xAs quantum wells grown by molecular beam epitaxy, has been demonstrated. Wavelength broadening of Delta lambda/lambda(p) similar to 42% is observed to be about a 400% increase compared to a typical bound-to-quasibound quantum well infrared photodetector (QWIP). In this device structure, which is different from typical QWIP device structures, two different gain mechanisms associated with photocurrent electrons and dark current electrons were observed and explained. Even with broader response, D*similar to 1 X 10(10) cm root Hz/W at T=55 K is comparable to regular QWIPs with similar cutoff wavelengths. [S0003-6951(98)01519-8]. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. EM surnith.v.bandara@jpl.nasa.gov NR 12 TC 70 Z9 72 U1 2 U2 10 PU AMER INST PHYSICS PI MELVILLE PA 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA SN 0003-6951 EI 1077-3118 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAY 11 PY 1998 VL 72 IS 19 BP 2427 EP 2429 DI 10.1063/1.121375 PG 3 WC Physics, Applied SC Physics GA ZM442 UT WOS:000073540600025 ER PT J AU Colombi, SP Szapudi, I Szalay, AS AF Colombi, SP Szapudi, I Szalay, AS TI Effects of sampling on statistics of large-scale structure SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE methods, numerical; methods, statistical; galaxies, clusters, general; large-scale structure of Universe ID HIGHER-ORDER STATISTICS; GALAXY REDSHIFT SURVEY; DARK MATTER UNIVERSE; LUMINOSITY FUNCTION; IRAS GALAXIES; COSMOLOGICAL SIMULATIONS; CLUSTER CORRELATIONS; COUNT PROBABILITIES; POWER-SPECTRUM; CFA AB The effects of sampling are investigated on measurements of counts-in-cells in three-dimensional magnitude-limited galaxy surveys, with emphasis on moments of the underlying smooth galaxy density field convolved with a spherical window. A new estimator is proposed for measuring the kth-order moment [rho(k)]: the weighted factorial moment (F) over tilde(k)[omega] Since these statistics are corrected for the effects of the varying selection function, they can extract the moments in one pass without the need to construct a series of volume-limited samples. The cosmic error on the measurement of (F) over tilde(k)[omega] is computed via the formalism of Szapudi & Colombi, which is generalized to include the effects of the selection function. The integral equation for finding the minimum variance weight is solved numerically, and an accurate and intuitive analytical approximation is derived, omega(optimal)(r) proportional to 1/Delta(r), where Delta(r) is the cosmic error as a function of the distance from the observer. The resulting estimator is more accurate than the traditional method of counts-in-cells in volume-limited samples, which discards useful information. As a practical example, it is demonstrated that, unless unforeseen systematics prevent it, the proposed method will extract moments of the galaxy distribution in the future Sloan Digital Sky Survey (hereafter SDSS) with accuracy of order a few per cent for k = 2, 3 and better than 10 per cent for k = 4 in the scale range of 1 less than or equal to l less than or equal to 50 h(-1) Mpc. In the particular case of the SDSS, a homogeneous (spatial) weight omega = 1 is reasonably close to optimal. Optimal sampling strategies for designing magnitude-limited redshift surveys are investigated as well. The arguments of Kaiser are extended to higher order moments, and it is found that the optimal strategy depends greatly on the statistics and scales considered. A sampling rate f similar to 1/3 - 1/10 is appropriate to measure low-order moments with k less than or equal to 4 in the scale range 1 less than or similar to l less than or similar to 50 h(-1) Mpc. However, the optimal sampling rate increases with the order considered, k, and with 1/l. Therefore counts-in-cells statistics in general, such as the shape of the distribution function, high-order moments, cluster selection, etc., require full sampling, especially at small, highly non-linear scales l similar to 1 h(-1) Mpc. Another design issue is the optimal geometry of a catalogue, when it covers only a small fraction of the sky. Similarly to Kaiser, we find that a survey composed of several compact subsamples of angular size Omega(F) spread over the sky on a glass-like structure would do better, with regards to the cosmic error, than the compact or the traditional slice-like configurations, at least at small scales. The required dynamic range of the measurements determines the characteristic size of the subsamples, It is, however, difficult to estimate, since an accurate and cumbersome calculation of edge effects would be required at scales comparable to the size of a subsample. C1 CITA, Toronto, ON M5S 1A7, Canada. CNRS, Inst Astrophys Paris, F-75014 Paris, France. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. RP Colombi, SP (reprint author), CITA, 60 St George St, Toronto, ON M5S 1A7, Canada. NR 82 TC 36 Z9 36 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 MAY 11 PY 1998 VL 296 IS 2 BP 253 EP 274 DI 10.1046/j.1365-8711.1998.01291.x PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP996 UT WOS:000073810600004 ER PT J AU McMillin, LM Goldberg, MD Ding, HJ Susskind, J Barnet, CD AF McMillin, LM Goldberg, MD Ding, HJ Susskind, J Barnet, CD TI Forward calculation for interferometers: method and validation SO APPLIED OPTICS LA English DT Article ID ACCURATE TRANSMITTANCE MODEL; ATMOSPHERIC TRANSMITTANCE; ABSORBING GAS; COMPUTATIONALLY FAST; MIXING RATIOS; OPTRAN AB An approach to approximating the instrument response for an unapodized interferometer is presented. The approach comprises functions that are local enough in frequency space (no more than five wave numbers) that one can use the Planck function at a single frequency to calculate the radiance at a given frequency and atmospheric pressure level, and it is well behaved (transmittances change monotonically from 1.0 to 0.0), so existing transmittance calculation procedures can be used. It is faster than calculating radiances at a high resolution, doing a Fourier transform, and then doing a second transform, and it produces brightness temperatures that agree with exact values to better than the 0.01 K that is due to errors in the approximation. The approach is accurate enough and fast enough to be used for calculating unapodized radiances from an interferometer. It also can be used to calculate transmittances as well as radiances. (C) 1998 Optical Society of America. C1 Natl Environm Satellite Data & Informat Serv, Satellite Res Lab, Off Res & Applicat, Washington, DC 20233 USA. QSS Grp Inc, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Gen Sci Corp, Greenbelt, MD 20771 USA. RP McMillin, LM (reprint author), Natl Environm Satellite Data & Informat Serv, Satellite Res Lab, Off Res & Applicat, Washington, DC 20233 USA. RI Barnet, Christopher/F-5573-2010; Goldberg, Mitch/F-5589-2010 NR 10 TC 3 Z9 3 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD MAY 10 PY 1998 VL 37 IS 14 BP 3059 EP 3068 DI 10.1364/AO.37.003059 PG 10 WC Optics SC Optics GA ZL890 UT WOS:000073483800028 PM 18273253 ER PT J AU Chiar, JE Gerakines, PA Whittet, DCB Pendleton, YJ Tielens, AGGM Adamson, AJ Boogert, ACA AF Chiar, JE Gerakines, PA Whittet, DCB Pendleton, YJ Tielens, AGGM Adamson, AJ Boogert, ACA TI Processing of ICY mantles in protostellar envelopes SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared, ISM, lines and bands; ISM, molecules; stars, evolution; stars, pre-main-sequence ID MAIN-SEQUENCE STARS; TAURUS DARK CLOUDS; INFRARED SPECTRAL PROPERTIES; AUSTRALIS MOLECULAR CLOUD; YOUNG STELLAR OBJECTS; SOLID CARBON-MONOXIDE; ABSORPTION FEATURES; CORONA-AUSTRALIS; MICRON ABSORPTION; GRAIN MANTLES AB We have obtained CO absorption profiles of several young stellar objects (YSOs), spanning a range of mass and luminosity, in order to investigate their ice mantle composition. We present the first detection of CO toward the class I YSO L1489 IRS in the Taurus dark cloud. In general, the CO profiles for YSOs show evidence for both processed and pristine ices in the same line of sight; strong indirect evidence for CO, is suggested in R CrA IRS 7, L1489 IRS, Elias 18, and GL 961E. Toward other sources (R CrA IRS 1, IRS 2, W33A, NGC 7538 IRS 9, Mon R2 IRS 2) CO is present in (nearly) pure form. We propose an evolutionary scenario to explain the chemical diversity of the icy mantles toward these objects. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Rensselaer Polytech Inst, Dept Phys, Troy, NY 12180 USA. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. RP Chiar, JE (reprint author), NASA, Ames Res Ctr, Mail Stop 245-3, Moffett Field, CA 94035 USA. RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 78 TC 98 Z9 98 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1998 VL 498 IS 2 BP 716 EP 727 DI 10.1086/305569 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN664 UT WOS:000073669300018 PM 11542939 ER PT J AU Gopalswamy, N Hanaoka, Y AF Gopalswamy, N Hanaoka, Y TI Coronal dimming associated with a giant prominence eruption SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, corona; Sun, flares; Sun, prominences; Sun, radio radiation; Sun, X-rays, gamma rays ID MASS-EJECTIONS; RADIO; EVENT AB We report the results of our investigation of a giant eruptive prominence (initial mass similar to 6 x 10(16) g) using microwave, X-ray, and white-light observations. The prominence erupted from the northwest limb of the Sun on 1994 April 5. The speed of the prominence was only similar to 70 km s(-1) when it reached a height of similar to 0.5 R. above the solar surface. In X-rays, a large region with reduced X-ray emission was observed enveloping the initial location of the prominence and extending to much larger heights. At the bottom of this depletion and beneath the eruptive prominence, an X-ray arcade formed, progressively spreading from south to north along the limb. This is the first time a direct detailed comparison is made between coronal dimming and a prominence eruption. We were able to confirm that the coronal dimming is indeed a near-surface manifestation of the coronal mass ejection (CME). The orientation of the structures involved did not allow the observations of the coronal cavity, but all the other substructures of the CME could be identified. The mass expelled from the Sun in the form of the eruptive prominence and the coronal dimming are comparable. The estimated total mass is somewhat larger than that reported in other X-ray-dimming events. C1 Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Nobeyama Radio Observ, Nagano 3841305, Japan. RP Gopalswamy, N (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RI Gopalswamy, Nat/D-3659-2012 NR 19 TC 75 Z9 77 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1998 VL 498 IS 2 BP L179 EP + DI 10.1086/311330 PN 2 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN687 UT WOS:000073671600018 ER PT J AU Smale, AP AF Smale, AP TI A type I burst with radius expansion observed from Cygnus X-2 with the Rossi X-Ray Timing Explorer SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, individual (Cygnus X-2); stars, neutron; X-rays, bursts; X-rays, stars ID RAPID BURSTER; GX 17+2; CLASSIFICATION; SPECTRA AB We present the results of a Rossi X-Ray Timing Explorer Proportional Counter Array observation of Cygnus X-2 in its high-intensity state, during which the source passed through the normal and horizontal branches of its Z diagram and mapped out a new, pronounced upturn on its horizontal branch. During this upturn state, a bright X-ray burst was observed, with rise and decay times of similar to 1 and similar to 5 s, respectively, and a peak flux of 1.52 x 10(-8) ergs cm(-2) s(-1). The energy-dependent profile, energetics, and spectral evolution allow us to identify this as a type I X-ray burst, with evidence for photospheric radius expansion in its first 2 s and spectral cooling in its later stages. The detection of these phenomena removes the previous ambiguity about the nature of bursts from Cyg X-2 and, in addition, allows us to make an independent determination of the source distance of 11.6 +/- 0.3 kpc. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Smale, AP (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 660-2, Greenbelt, MD 20771 USA. NR 25 TC 53 Z9 53 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1998 VL 498 IS 2 BP L141 EP L145 DI 10.1086/311319 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN687 UT WOS:000073671600011 ER PT J AU Strohmayer, TE Zhang, W Swank, JH White, NE Lapidus, I AF Strohmayer, TE Zhang, W Swank, JH White, NE Lapidus, I TI On the amplitude of burst oscillations in 4U 1636-54: Evidence for nuclear-powered pulsars SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (4U 1636-54); stars, neutron; stars, rotation; X-rays, bursts ID ACCRETING NEUTRON STAR; PROPAGATION AB We present a study of 581 Hz oscillations observed during a thermonuclear X-ray burst from the low-mass X-ray binary (LMXB) 4U 1636-54 with the Rossi X-Ray Timing Explorer. This is the first X-ray burst to exhibit both millisecond oscillations during the rising phase and photospheric radius expansion. We measure an oscillation amplitude within 0.1 s of the onset of this burst of 75% +/- 17%; that is, almost the entire thermal burst flux is modulated near onset. The spectral evolution during the rising phase of this burst suggests that the X-ray-emitting area on the neutron star was increasing, similar to the behavior of the bursts from 4U 1728-34 with 363 Hz oscillations reported recently. We argue that the combination of large pulsed amplitudes near burst onset and the spectral evidence for localized emission during the rise strongly supports rotational modulation as the mechanism for the oscillations. We discuss how a theoretical interpretation of spin modulation amplitudes, pulse profiles, and pulse-phase spectroscopy can provide constraints on the masses and radii of neutron stars. We also discuss the implications of these findings for the beat-frequency models of kilohertz X-ray variability in LMXBs. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Sussex, Ctr Astron, Phys & Astron Subject Grp, CPES, Brighton BN1 9QH, E Sussex, England. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Mail Code 662, Greenbelt, MD 20771 USA. RI White, Nicholas/B-6428-2012; Swank, Jean/F-2693-2012 OI White, Nicholas/0000-0003-3853-3462; NR 25 TC 92 Z9 92 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 MAY 10 PY 1998 VL 498 IS 2 BP L135 EP L139 DI 10.1086/311322 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN687 UT WOS:000073671600010 ER PT J AU Whittet, DCB Gerakines, PA Tielens, AGGM Adamson, AJ Boogert, ACA Chiar, JE de Graauw, T Ehrenfreund, P Prusti, T Schutte, WA Vandenbussche, B van Dishoeck, EF AF Whittet, DCB Gerakines, PA Tielens, AGGM Adamson, AJ Boogert, ACA Chiar, JE de Graauw, T Ehrenfreund, P Prusti, T Schutte, WA Vandenbussche, B van Dishoeck, EF TI Detection of abundant CO2 ice in the quiescent dark cloud medium toward Elias 16 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared, ISM, lines and bands; ISM, individual (Taurus Dark Cloud); ISM, molecules ID TIME-DEPENDENT CHEMISTRY; DENSE MOLECULAR CLOUDS; SOLID CARBON-MONOXIDE; INFRARED-SPECTROSCOPY; SWS OBSERVATIONS; GRAIN MANTLES; ASTROPHYSICAL ICES; RADIATION-FIELD; INTERSTELLAR; TAURUS AB We report the first detection of solid carbon dioxide (CO2) in quiescent regions of a dark cloud in the solar neighborhood, a result that has important implications for models of ice formation and evolution in the interstellar medium. The K-type field star Elias 16 was previously known to display solid-state absorption features of H2O and CO ices arising in the Taurus Dark Cloud. Our detection of the CO2 feature at 4.27 mu m in this line of sight implies a column density N(CO2) = 4.6(-0.6)(+1.3) x 10(17) cm(-2), equivalent to similar to 18% and 70% of the H2O and CO column densities, respectively. Comparison with laboratory data indicates that (unlike CO) the CO2 resides primarily in a polar (H2O-rich) component of the ices. CO2 is formed easily in the laboratory by the photolysis of ice mixtures containing CO2 but the detection toward Elias 16 indicates that CO2 formation can occur in dark clouds in the absence of a local embedded source of radiation. Possible alternative mechanisms for CO2 production include grain surface reactions and energetic processing driven by the interstellar radiation field or cosmic rays. C1 Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Space Res Org Netherlands, NL-9700 AV Groningen, Netherlands. Leiden Observ, NL-2300 RA Leiden, Netherlands. ESA, Div Astrophys, ISO Sci Operat Ctr, Madrid 28080, Spain. Univ Louvain, Inst Astron, B-3001 Heverlee, Belgium. RP Whittet, DCB (reprint author), Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012; OI Gerakines, Perry/0000-0002-9667-5904; Whittet, Douglas/0000-0001-8539-3891 NR 44 TC 113 Z9 113 U1 1 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1998 VL 498 IS 2 BP L159 EP L163 DI 10.1086/311318 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZN687 UT WOS:000073671600014 ER PT J AU Liu, AK Cavalieri, DJ AF Liu, AK Cavalieri, DJ TI On sea ice drift from the wavelet analysis of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) data SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID MOTION AB Wavelet analysis of DMSP SSM/I 85 GHz radiance data is used to obtain daily sea ice drift information for both the northern and southern polar regions. This technique provides improved spatial coverage over the existing array of Arctic Ocean buoys and better temporal resolution over techniques utilizing data from satellite synthetic aperture radars. Examples of derived ice-drift maps for both hemispheres illustrate large-scale circulation reversals over a period of one month. Comparisons with ice displacements derived from buoys give good quantitative agreement. C1 NASA, Lab Hydropspher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Liu, AK (reprint author), NASA, Lab Hydropspher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 15 TC 39 Z9 39 U1 0 U2 3 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 MAY 10 PY 1998 VL 19 IS 7 BP 1415 EP 1423 DI 10.1080/014311698215522 PG 9 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA ZM780 UT WOS:000073575100011 ER PT J AU Selivanov, VA Ichas, F Holmuhamedov, EL Jouaville, LS Evtodienko, YV Mazat, JP AF Selivanov, VA Ichas, F Holmuhamedov, EL Jouaville, LS Evtodienko, YV Mazat, JP TI A model of mitochondrial Ca2+-induced Ca2+ release simulating the Ca2+ oscillations and spikes generated by mitochondria SO BIOPHYSICAL CHEMISTRY LA English DT Article; Proceedings Paper CT Workshop on Oscillations, Bistability and Waves in Biochemical and Cellular Systems CY JUN 14-20, 1997 CL FONDAT TREILLES, TOURTOUR, FRANCE HO FONDAT TREILLES DE mitochondria; cell calcium signalling; model of calcium oscillations and spikes; mitochondrial calcium-induced-calcium-release; permeability transition pore ID RAT-LIVER MITOCHONDRIA; PERMEABILITY TRANSITION; INOSITOL TRISPHOSPHATE; CALCIUM SPIKING; LAEVIS OOCYTES; POOL MODEL; MEMBRANE; WAVES AB Recent evidence underlines a key role of mitochondrial Ca2+ fluxes in cell Ca2+ signalling. We present here a kinetic model simulating the Ca2+ fluxes generated by mitochondria during mitochondrial Ca2+-induced Ca2+ release (mCICR) resulting from the operation of the permeability transition pore (PTP). Our model connects the Ca2+ fluxes through the ruthenium red-sensitive Ca2+ uniporter, the respiration-dependent and passive HC fluxes, the rate of oxygen consumption, the movements of weak acids across the mitochondrial membrane, the electrical transmembrane potential (Delta Psi), and operation of the PTP. We find that two factors are crucial to account for the various mCICR profiles that can be observed experimentally: (i) the dependence of PTP opening and closure on matrix pH (pH(i)), and (ii) the relative inhibition of the respiratory rate consecutive to PTP opening. The resulting model can simulate irreversible Ca2+ efflux from mitochondria, as well as the genesis of damped or sustained Ca2+ oscillations, and of single Ca2+ spikes. The model also simulates the main features of mCICR, i.e. the threshold-dependence of mCICR triggering, and the all-or-nothing nature of mCICR operation. Our model should appear useful to further mathematically address the consequences of mCICR on the spatiotemporal organisation of Ca2+ signals, as a 'plug-in' module for the existing models of cell Ca2+ signalling. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Victor Segalen, DBM2, GESBI, F-33076 Bordeaux, France. Moscow MV Lomonosov State Univ, Belozersky Inst, Moscow 119899, Russia. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Russian Acad Sci, Inst Theoret & Expt Biophys, Pushchino 142292, Russia. RP Mazat, JP (reprint author), Univ Victor Segalen, DBM2, GESBI, F-33076 Bordeaux, France. RI Holmuhamedov, Ekhson/P-5228-2016; OI Selivanov, Vitaly/0000-0002-7937-9249 NR 28 TC 39 Z9 39 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-4622 J9 BIOPHYS CHEM JI Biophys. Chem. PD MAY 5 PY 1998 VL 72 IS 1-2 BP 111 EP 121 DI 10.1016/S0301-4622(98)00127-6 PG 11 WC Biochemistry & Molecular Biology; Biophysics; Chemistry, Physical SC Biochemistry & Molecular Biology; Biophysics; Chemistry GA ZW122 UT WOS:000074376400011 PM 9652089 ER PT J AU Pavlo, P Vahala, G Vahala, L AF Pavlo, P Vahala, G Vahala, L TI Higher order isotropic velocity grids in lattice methods SO PHYSICAL REVIEW LETTERS LA English DT Article ID SYSTEMS; MODELS AB Kinetic lattice methods are a very attractive representation of nonlinear macroscopic systems because of their inherent parallelizability on multiple processors and their avoidance of the nonlinear convective terms. By uncoupling the velocity lattice from the spatial grid, one can employ higher order (non-space-filling) isotropic lattices-lattices which greatly enhance the stable parameter regions, particularly in thermal problems. In particular, the superiority of the octagonal lattice over previous models used in 2D (hexagonal or square) and 3D (projected face-centered hypercube) is shown. C1 Acad Sci Czech Republ, Inst Plasma Phys, Praha 8, Czech Republic. Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. Old Dominion Univ, Dept Elect & Comp Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23665 USA. RP Pavlo, P (reprint author), Acad Sci Czech Republ, Inst Plasma Phys, Praha 8, Czech Republic. RI Pavlo, Pavol/G-4214-2014 OI Pavlo, Pavol/0000-0003-1400-1074 NR 15 TC 29 Z9 29 U1 0 U2 6 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 MAY 4 PY 1998 VL 80 IS 18 BP 3960 EP 3963 DI 10.1103/PhysRevLett.80.3960 PG 4 WC Physics, Multidisciplinary SC Physics GA ZK808 UT WOS:000073365800018 ER PT J AU Benson, J AF Benson, J TI Conversations with Richard Christiansen SO AEROSPACE AMERICA LA English DT Editorial Material C1 NASA, Aeronaut & Space Transportat Technol Enterprise, Washington, DC 20546 USA. RP Benson, J (reprint author), NASA, Aeronaut & Space Transportat Technol Enterprise, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD MAY PY 1998 VL 36 IS 5 BP 14 EP 16 PG 3 WC Engineering, Aerospace SC Engineering GA ZL240 UT WOS:000073412800006 ER PT J AU Young, SD Jones, DR Bryant, WH Eckhardt, DE AF Young, SD Jones, DR Bryant, WH Eckhardt, DE TI Safely improving airport surface capacity SO AEROSPACE AMERICA LA English DT Article C1 NASA Langley, Hampton, VA 23665 USA. RP Young, SD (reprint author), NASA Langley, Hampton, VA 23665 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD MAY PY 1998 VL 36 IS 5 BP 22 EP + PG 4 WC Engineering, Aerospace SC Engineering GA ZL240 UT WOS:000073412800008 ER PT J AU Mehta, UB AF Mehta, UB TI Credible computational fluid dynamics simulations SO AIAA JOURNAL LA English DT Article AB This summary presents the motivation for the Special Section on the credibility of computational fluid dynamics (CFD) simulations, its objective, its background and context, its content, and its major conclusions. Verification and validation (V&V) are the processes for establishing the credibility of CFD simulations. Validation assesses whether correct things are performed, and verification assesses whether they are performed correctly. Various aspects of V&V are discussed. Progress is made in verification of simulation models. Considerable effort is needed for assessing the validity of simulated reality. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Mehta, UB (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 20 TC 17 Z9 17 U1 0 U2 3 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 MAY PY 1998 VL 36 IS 5 BP 665 EP 667 DI 10.2514/2.431 PG 3 WC Engineering, Aerospace SC Engineering GA ZM078 UT WOS:000073502500001 ER PT J AU Yee, HC Sweby, PK AF Yee, HC Sweby, PK TI Aspects of numerical uncertainties in time marching to steady-state numerical solutions SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 27th Computational Fluid Dynamics Conference CY JUN 17-20, 1996 CL NEW ORLEANS, LA SP Amer Inst Aeronaut & Astronaut ID NONLINEAR DIFFERENTIAL-EQUATIONS; REACTION-CONVECTION EQUATIONS; HYPERBOLIC CONSERVATION-LAWS; GLOBAL ASYMPTOTIC-BEHAVIOR; DYNAMICAL-APPROACH; FLUID-DYNAMICS; SOURCE TERMS; TVD SCHEMES; STABILITY; CHAOS AB Knowledge from recent advances in the understanding of global nonlinear behavior of numerical schemes is employed to isolate some aspects of numerical uncertainties in time-marching approaches to obtain steady state numerical solutions. Strong dependence on initial data and the permissibility of spurious steady-state numerical solutions, stabilization of unstable steady states by implicit time discretizations, and convergence properties and spurious behavior of high-resolution shock capturing schemes are discussed and illustrated with examples. The goal is to illustrate the important role that global nonlinear behavior of numerical schemes can play in minimizing sources of numerical uncertainties in computational fluid dynamics. C1 NASA, Ames Res Ctr, Aeronaut Technol Div, Moffett Field, CA 94035 USA. Univ Reading, Dept Math, Reading RG6 2AX, Berks, England. NASA, Ames Res Ctr, RIACS, Moffett Field, CA USA. RP Yee, HC (reprint author), NASA, Ames Res Ctr, Aeronaut Technol Div, Moffett Field, CA 94035 USA. NR 71 TC 10 Z9 10 U1 0 U2 2 PU AMER INST AERONAUTICS ASTRONAUTICS PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0001-1452 EI 1533-385X J9 AIAA J JI AIAA J. PD MAY PY 1998 VL 36 IS 5 BP 712 EP 724 DI 10.2514/2.459 PG 13 WC Engineering, Aerospace SC Engineering GA ZM078 UT WOS:000073502500007 ER PT J AU Rumsey, CL Gatski, TB Ying, SX Bertelrud, A AF Rumsey, CL Gatski, TB Ying, SX Bertelrud, A TI Prediction of high-lift flows using turbulent closure models SO AIAA JOURNAL LA English DT Article ID NAVIER-STOKES COMPUTATIONS; ALGEBRAIC STRESS MODELS; MULTIELEMENT AIRFOIL AB The flow over two different multielement airfoil configurations is computed using linear eddy-viscosity turbulence models and a nonlinear explicit algebraic stress model. Transition locations that were recently measured using hot film on one of the configurations are presented, and the effect of transition location on the computed solutions is explored. Deficiencies in make profile computations are found to be attributable in large part to poor boundary-layer prediction on the generating element rather than on inadequate turbulence modeling in the wake. Using measured transition locations for the main element improves the prediction of the main-element boundary-layer thickness, skin friction, and wake profile shape. However, using measured transition locations on the slat still yields poor slat-wake predictions. The computation of the slat flowfield remains a major problem in the successful prediction of multielement flows. In general, the nonlinear, explicit algebraic stress turbulence model yields results that are similar to those of the linear eddy-viscosity models. C1 NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. Boeing Co, Flight Performance, Long Beach, CA 90807 USA. Analyt Serv & Mat Inc, Hampton, VA 23681 USA. RP Rumsey, CL (reprint author), NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Mail Stop 128, Hampton, VA 23681 USA. NR 62 TC 27 Z9 30 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 MAY PY 1998 VL 36 IS 5 BP 765 EP 774 DI 10.2514/2.435 PG 10 WC Engineering, Aerospace SC Engineering GA ZM078 UT WOS:000073502500013 ER PT J AU Atkins, HL Shu, CW AF Atkins, HL Shu, CW TI Quadrature-free implementation of discontinuous Galerkin method for hyperbolic equations SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/CEAS 2nd Joint Aeroacoustics Conference CY MAY 06-08, 1996 CL STATE COLL, PENNSYLVANIA SP AIAA, CEAS ID FINITE-ELEMENT METHOD; CONSERVATION-LAWS AB A discontinuous Galerkin formulation that avoids the use of discrete quadrature formulas is described and applied to linear and nonlinear test problems in one and two space dimensions. For many practical problems, this approach requires fewer operations and less storage than conventional implementations but preserves the compactness and robustness that is inherent in the discontinuous Galerkin method. Test problems include the linear and nonlinear one-dimensional scalar advection of both smooth and discontinuous initial value problems, the two-dimensional scalar advection of smooth initial value problems that are discretized by using unstructured grids with varying degrees of smoothness and regularity, and two-dimensional linear Euler solutions on unstructured grids. C1 NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. Brown Univ, Div Appl Math, Providence, RI 02912 USA. RP Atkins, HL (reprint author), NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Hampton, VA 23681 USA. RI Shu, Chi-Wang/A-3216-2013 OI Shu, Chi-Wang/0000-0001-7720-9564 NR 16 TC 94 Z9 97 U1 0 U2 3 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 MAY PY 1998 VL 36 IS 5 BP 775 EP 782 DI 10.2514/2.436 PG 8 WC Engineering, Aerospace SC Engineering GA ZM078 UT WOS:000073502500014 ER PT J AU Taylor, JR Cowley, SWH Yeoman, TK Lester, M Jones, TB Greenwald, RA Sofko, G Villain, JP Lepping, RP Hairston, MR AF Taylor, JR Cowley, SWH Yeoman, TK Lester, M Jones, TB Greenwald, RA Sofko, G Villain, JP Lepping, RP Hairston, MR TI SuperDARN studies of the ionospheric convection response to a northward turning of the interplanetary magnetic field SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Article DE ionosphere (auroral ionosphere); magnetospheric physics (magnetopause, cusp, and boundary layers, magnetosphere-ionosphere interaction) ID LATITUDE DAYSIDE IONOSPHERE; DEPENDENT PLASMA-FLOW; SOLAR-WIND; IMF-BY; BIRKELAND CURRENTS; SOUTH COMPONENT; Y-COMPONENT; MAGNETOSPHERE; POLAR; TIME AB The response of the dayside ionospheric flow to a sharp change in the direction of the interplanetary magnetic field (IMF) measured by the WIND spacecraft from negative B-z and positive B-y, to positive B-z and small B-y, has been studied using SuperDARN radar, DMSP satellite, and ground magnetometer data. In response to the IMF change, the flow underwent a transition from a distorted twin-cell flow involving antisunward flow over the polar cap, to a multi-cell flow involving a region of sunward flow at high latitudes near noon. The radar data have been studied at the highest time resolution available (similar to 2 min) to determine how this transition took place. It is found that the dayside flow responded promptly to the change in the IMF, with changes in radar and magnetic data starting within a few minutes of the estimated time at which the effects could first have reached the dayside ionosphere. The data also indicate that sunward flows appeared promptly at the start of the flow change (within similar to 2 min), localised initially in a small region near noon at the equatorward edge of the radar backscatter band. Subsequently the region occupied by these flows expanded rapidly east-west and poleward, over intervals of similar to 7 and similar to 14 min respectively, to cover a region at least 2 h wide in local time and 5 degrees in latitude, before rapid evolution ceased in the noon sector. In the lower latitude dusk sector the evolution extended for a further similar to 6 min before quasi-steady conditions again prevailed within the field-of-view. Overall, these observations are shown to be in close conformity with expectations based on prior theoretical discussion, except for the very prompt appearance of sunward hows after the onset of the flow change. C1 Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Saskatchewan, Inst Space & Atmospher Studies, Saskatoon, SK S7N 0W0, Canada. CNRS, LPCE, F-45701 Orleans 2, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Texas, WB Hansen Ctr Space Sci, Richardson, TX 75083 USA. RP Cowley, SWH (reprint author), Univ Leicester, Dept Phys & Astron, Univ Rd, Leicester LE1 7RH, Leics, England. RI Yeoman, Timothy/L-9105-2014; OI Yeoman, Timothy/0000-0002-8434-4825; Hairston, Marc/0000-0003-4524-4837; Greenwald, Raymond/0000-0002-7421-5536 NR 43 TC 14 Z9 16 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD MAY PY 1998 VL 16 IS 5 BP 549 EP 565 DI 10.1007/s005850050625 PG 17 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA ZT560 UT WOS:000074100100007 ER PT J AU Ostgaard, N Stadsnes, J Aarsnes, K Soraas, F Maseide, K Smith, M Sharber, J AF Ostgaard, N Stadsnes, J Aarsnes, K Soraas, F Maseide, K Smith, M Sharber, J TI Simultaneous measurements of X-rays and electrons during a pulsating aurora (vol 16, pg 148, 1998) SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Correction C1 Univ Bergen, Dept Phys, N-5007 Bergen, Norway. Univ Oslo, Dept Phys, N-0316 Oslo, Norway. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. SW Res Inst, San Antonio, TX USA. RP Ostgaard, N (reprint author), Univ Bergen, Dept Phys, Allegaten 55, N-5007 Bergen, Norway. NR 1 TC 0 Z9 0 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD MAY PY 1998 VL 16 IS 5 BP 654 EP 656 PG 3 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA ZT560 UT WOS:000074100100018 ER PT J AU Carlson, MN Holtzman, JA Watson, AM Grillmair, CJ Mould, JR Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Westphal, JA AF Carlson, MN Holtzman, JA Watson, AM Grillmair, CJ Mould, JR Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Westphal, JA TI Deep Hubble Space Telescope observations of star clusters in NGC 1275 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, star clusters ID YOUNG GLOBULAR-CLUSTERS; GALAXY MERGERS; NGC-1275; DISCOVERY; CALIBRATION; SPECTROSCOPY; PERFORMANCE; POPULATION; COUNTS; SYSTEM AB We present an analysis of compact star clusters in deep Hubble Space Telescope Wide Field Planetary Camera 2 images of NGC 1275. B- and R-band photometry of roughly 3000 clusters shows a bimodality in the B-R colors, suggesting that distinct old and young cluster populations are present. The small spread in the colors of the blue clusters is consistent with the hypothesis that they are a single-age population, with an inferred age of 0.1 to 1 Gyr. The luminosity function shows increasing numbers of blue clusters to the limit of our photometry, which reaches several magnitudes past the turnover predicted if the cluster population is identical to current Galactic globular clusters seen at a younger age. The blue clusters have a spatial distribution that is more centrally peaked than that of the red clusters. The individual clusters are slightly resolved, with core radii less than or similar to 0.75 pc if they have modified Hubble profiles. We estimate the specific frequencies of the old and young populations and discuss the uncertainties in these estimates. We find that the specific frequency of the young population in NGC 1275 is currently larger than that of the old population and will remain so as the young population evolves, even if the majority of the low-mass clusters are eventually destroyed. If the young population formed during a previous merger, this suggests that mergers can increase the specific frequency of globular clusters in a galaxy. However, the presently observed young population likely contains too few clusters to have a significant impact on the overall specific frequency as it will be observed in the future. C1 New Mexico State Univ, Dept Astron, Dept 4500, Las Cruces, NM 88003 USA. Univ Nacl Autonoma Mexico, Astron Inst, Morelia 58090, Michoacan, Mexico. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. European Space Agcy, Div Astrophys, Dept Space Sci, F-75738 Paris 15, France. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. CALTECH, Dept Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Carlson, MN (reprint author), New Mexico State Univ, Dept Astron, Dept 4500, POB 30001, Las Cruces, NM 88003 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 47 TC 77 Z9 77 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAY PY 1998 VL 115 IS 5 BP 1778 EP 1790 DI 10.1086/300334 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ213 UT WOS:000073834100006 ER PT J AU Holtzman, JA Watson, AM Baum, WA Grillmair, CJ Groth, EJ Light, RM Lynds, R O'Neil, EJ AF Holtzman, JA Watson, AM Baum, WA Grillmair, CJ Groth, EJ Light, RM Lynds, R O'Neil, EJ TI The luminosity function and initial mass function in the Galactic bulge SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, stellar content; stars, luminosity function, mass function ID RADIATIVE OPACITIES; EVOLUTIONARY SEQUENCES; GLOBULAR-CLUSTERS; STELLAR MODELS; STARS; PERFORMANCE; CALIBRATION; WFPC2 AB We present deep photometry obtained with the Hubble Space Telescope in a held in Baade's window in the Galactic bulge, We derive a luminosity function down to I similar to 24.3, or V similar to 27.5, corresponding to M similar to 0.3 M.. The luminosity function from the turnoff down to this level appears remarkably similar to that observed in the solar neighborhood. We derive a mass function using both an empirical local mass-luminosity relation and a mass-luminosity relation from recent stellar model calculations, allowing for the presence of binaries and photometric errors. The mass function has a power-law form with dN/dM proportional to M-2.2 for M greater than or similar to 0.7 M.. However, we find strong evidence for a break in the mass function slope around 0.5-0.7 M., with a significantly shallower slope at lower masses. The value of the slope for the low masses depends on the assumed binary fraction and the accuracy of our completeness correction. This mass function should directly reflect the initial mass function. C1 Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. Univ Washington, Dept Astron, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Princeton Univ, Dept Phys, Joseph Henry Labs, Princeton, NJ 08544 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Kitt Peak Natl Observ, Tucson, AZ 85726 USA. New Mexico State Univ, Dept Astron, Dept 4500, Las Cruces, NM 88003 USA. RP Holtzman, JA (reprint author), New Mexico State Univ, Dept Astron, Dept 4500, POB 30001, Las Cruces, NM 88003 USA. NR 37 TC 116 Z9 116 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAY PY 1998 VL 115 IS 5 BP 1946 EP 1957 DI 10.1086/300336 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ213 UT WOS:000073834100018 ER PT J AU Drake, SA Pravdo, SH Angelini, L Stern, RA AF Drake, SA Pravdo, SH Angelini, L Stern, RA TI Synchronization timescales for three solar-type stars that have Jupiter-mass companions in short-period orbits SO ASTRONOMICAL JOURNAL LA English DT Article DE planetary systems; X-rays ID CLOSE BINARY STARS; MAIN-SEQUENCE; CIRCULARIZATION AB We examine the physical properties of the three currently known star-plus-planet systems that have orbital periods of similar to 3-5 days (51 Peg, nu And, and tau Boo). The observed properties are, in general, more consistent with the Zahn viscous dissipation mechanism than with the Tassoul hydrodynamic spin-down mechanism (at least in the latter's present formulation). However, a comparison of the data for tau Boo with the Zahn theory suggests that the predicted synchronization timescale t(z) might be regarded as an upper limit to the actual time needed to synchronize the outer convective layers, and that the latter may actually be shorter than t(z) by a factor of greater than or equal to 3. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lockheed Martin Solar & Astrophys Lab, Dept H1 12, Palo Alto, CA 94304 USA. RP Drake, SA (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 660-2, Greenbelt, MD 20771 USA. NR 22 TC 13 Z9 13 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAY PY 1998 VL 115 IS 5 BP 2122 EP 2124 DI 10.1086/300346 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ213 UT WOS:000073834100033 ER PT J AU Boogert, ACA Schutte, WA Helmich, FP Tielens, AGGM Wooden, DH AF Boogert, ACA Schutte, WA Helmich, FP Tielens, AGGM Wooden, DH TI Infrared observations and laboratory simulations of interstellar CH4 and SO2 (vol 317, pg 929, 1997) SO ASTRONOMY & ASTROPHYSICS LA English DT Correction C1 Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Leiden Observ, NL-2300 RA Leiden, Netherlands. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Boogert, ACA (reprint author), Kapteyn Astron Inst, POB 800, NL-9700 AV Groningen, Netherlands. NR 1 TC 1 Z9 1 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAY 1 PY 1998 VL 333 IS 1 BP 389 EP 389 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ375 UT WOS:000073854900050 ER PT J AU Shearer, A O'Sullivan, CMM Golden, A Garcia, PVR Redfern, M Danks, A Cullum, M AF Shearer, A O'Sullivan, CMM Golden, A Garcia, PVR Redfern, M Danks, A Cullum, M TI Time-resolved optical observations of PSR 1509-58 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE pulsars : individual : PSR 1509-58 ID X-RAY PULSAR AB Using time resolved 2-dimensional aperture photometry we have established that the optical candidate for PSR 1509-58 does not pulse. Our pulsed upper limits (m(V) = 24.3 and m(B) = 25.7) put severe constraints on this being the optical counterpart. Furthermore the colours of the candidate star are consistent with a main sequence star at a distance of 2-4 kpc. The probability of a chance coincidence with a normal star and the difficulty of explaining the lack of pulsed emission leads us to conclude that this object is an intermediate field star. C1 Natl Univ Ireland Univ Coll Galway, Ctr Informat Technol, Galway, Ireland. Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland. CNRS, UMR 5574, Observ Lyon, CRAL, F-75700 Lyon, France. Univ Porto, Ctr Astrofis, P-4100 Porto, Portugal. Goddard Space Flight Ctr, STX, Greenbank, MD USA. European So Observ, D-8046 Garching, Germany. RP Shearer, A (reprint author), Natl Univ Ireland Univ Coll Galway, Ctr Informat Technol, Galway, Ireland. EM andy.shearer@ucg.ie RI Valente Garcia, Paulo Jorge/B-8933-2009; Shearer, Andy/N-7609-2014 OI Valente Garcia, Paulo Jorge/0000-0002-1678-3535; Shearer, Andy/0000-0001-7903-0074 NR 19 TC 7 Z9 7 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAY 1 PY 1998 VL 333 IS 1 BP L16 EP L18 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZQ375 UT WOS:000073854900005 ER PT J AU Weaver, KA Krolik, JH Pier, EA AF Weaver, KA Krolik, JH Pier, EA TI Detecting Compton reflection and a broad iron line in MCG -5-23-16 with RXTE SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (MCG -5-23-16); galaxies, nuclei; galaxies, Seyfert; X-rays, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY REFLECTION; COLD MATTER; GALAXIES; DISK AB We report the detection with the Rossi X-Ray Timing Explorer (RXTE) of a Compton reflection signature in the Seyfert galaxy MCG -5-23-16. RXTE also resolves the Fe K alpha fluorescence line with FWHM similar to 48,000 km s(-1). This measurement provides the first independent confirmation of ASCA detections in Seyfert galaxies of broad Fe K alpha lines that are thought to be the signature of emission from the inner regions of an accretion disk orbiting a black hole. Under the assumption that reflection arises from an isotropic source located above a neutral accretion disk, and using a theoretical model that accounts for the dependence of the reflected spectrum on inclination angle, we derive a 90% confidence range for the disk inclination of i = 50 degrees-81 degrees. The large inclination is consistent with that expected from the unified model for MCG -5-23-16 based on its Seyfert 1.9 classification. If we assume that the high-energy cutoff in the incident spectrum lies at energies larger than a few hundred keV, then the equivalent width of the Fe K alpha line is much larger than predicted for the amount of reflection. This implies either an enhanced iron abundance, a covering factor of reflecting material c(f) > 0.5, or a cutoff in the incident spectrum at energies between similar to 60 and similar to 200 keV. C1 Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Weaver, KA (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Homewood Campus,3400 N Charles St, Baltimore, MD 21218 USA. NR 19 TC 39 Z9 39 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1998 VL 498 IS 1 BP 213 EP 219 DI 10.1086/305560 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZM044 UT WOS:000073499100019 ER PT J AU Mukai, K AF Mukai, K TI An alternative model of the magnetic cataclysmic variable V1432 aquilae (=RX J1940.1-1025) SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars, individual (V1432 Aql); binaries, eclipsing; novae, cataclysmic variables; X-ray, stars ID INTERMEDIATE POLARS; AM; NGC-6814; VARIABILITY; ACCRETION; SPECTRA; PERIOD; STARS AB V1432 Aql is currently considered to be an asynchronous AM Her type system, with an orbital period of 12,116.3 s and a spin period of 12,150 s. I present an alternative model in which V1432 Aql is an intermediate polar with disk overflow or diskless accretion geometry, with a spin period near 4040 s. I argue that published data are insufficient to distinguish between the two models; instead, I provide a series of predictions of the two models that can be tested against future observations. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD USA. RP Mukai, K (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 26 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1998 VL 498 IS 1 BP 394 EP 399 DI 10.1086/305527 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZM044 UT WOS:000073499100039 ER PT J AU Thejappa, G MacDowall, RJ AF Thejappa, G MacDowall, RJ TI Evidence for strong and weak turbulence processes in the source region of a local type III radio burst SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun, radio radiation; turbulence; waves ID ION-SOUND-WAVES; LANGMUIR-WAVES; SOLAR-WIND; PLASMA EMISSION; FREQUENCY; RADIATION; WHISTLER AB We present the Ulysses Unified Radio and Plasma Wave Experiment (URAP) observations of a local type III radio burst and the associated plasma wave activity generated in the vicinity of the spacecraft. These observations represent the first clear evidence of (1) the occurrence of ion-acoustic waves as well as whistlers in close association with Langmuir waves, (2) the coexistence of strong turbulence processes (modulational instability and soliton formation) and weak turbulence processes (electrostatic decay instability), (3) the frequency ratio of the fundamental (F) and harmonic (H) components as 1:1.67, and (4) a very narrowband F component with relative bandwidth of Delta f/f similar to 6%, in comparison to that of the harmonic (H) component with Delta f/f similar to 38%. Based on energy considerations, it is shown that whistlers are not generated by any nonlinear effects involving Langmuir waves; instead, along with Langmuir waves, they are excited directly by the type III electron beam. On the other hand, ion-acoustic waves are generated by the Langmuir waves through the electrostatic decay process, since (1) the observed frequencies agree with the predicted values, (2) the ion-acoustic occupation numbers are well below those of Langmuir waves, and (3) the normalized peak energy density of Langmuir waves W-L/n(e)T(e) similar to 10(-5) is well above the electrostatic decay threshold similar to 7 x 10(-7). The occurrence of Langmuir waves as intense spikes with spatial scales of 300-3000 Debye lengths with peak energy densities well above the modulational-instability threshold of similar to 2 x 10(-7) suggest that the Langmuir waves are also saturated by strong turbulence processes. The implications of these observations for the emission mechanisms at f(pe) and at 2f(pe) and for beam stabilization processes are discussed. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Thejappa, G (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI MacDowall, Robert/D-2773-2012 NR 42 TC 43 Z9 43 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1998 VL 498 IS 1 BP 465 EP 478 DI 10.1086/305526 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZM044 UT WOS:000073499100046 ER PT J AU Schnaiter, M Mutschke, H Dorschner, J Henning, T Salama, F AF Schnaiter, M Mutschke, H Dorschner, J Henning, T Salama, F TI Matrix-isolated nano-sized carbon grains as an analog for the 217.5 nanometer feature carrier SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; ISM, abundances; line, identification; methods, laboratory; ultraviolet, ISM ID AMORPHOUS-CARBON; OPTICAL-PROPERTIES; ULTRAVIOLET EXTINCTION; PARTICLES; CURVES AB The effect of particle shape or particle clustering on the extinction behavior of nano-sized hydrogenated carbon grains is investigated experimentally. The particles were extracted by a molecular beam technique at different condensation and clustering states and isolated in an argon matrix for UV spectroscopy. The state of clustering in the samples was controlled by transmission electron microscopy analysis. The simple spherical morphology of the matrix-isolated nonagglomerated particles permitted the derivation of reliable optical constants. A clear correlation was found between the measured UV feature width and the degree of particle clustering, in agreement with theoretical investigations based on the derived optical data. Therefore, the results prove unambiguously the expectation that the optical properties of carbonaceous grain material are strongly influenced by the particle shape and the clustering degree. For particles produced in hydrogen-containing atmospheres, the UV extinction peak was shifted blueward to a position close to the 217.5 nm hump. This shift was found to be nearly independent of the amount of hydrogen in the condensation zone. We also discuss the infrared spectra of the hydrogenated carbon materials. The astrophysical implications of the results are discussed with regard to the observational as well as the elemental abundance constraints. C1 Univ Jena, Inst Astrophys, D-07745 Jena, Germany. Univ Jena, Univ Sternwarte, D-07745 Jena, Germany. NASA, Div Space Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Schnaiter, M (reprint author), Univ Jena, Inst Astrophys, Schillergasschen 2-3, D-07745 Jena, Germany. RI Schnaiter, Martin/A-2370-2013; Salama, Farid/A-8787-2009 OI Salama, Farid/0000-0002-6064-4401 NR 44 TC 96 Z9 96 U1 1 U2 8 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1998 VL 498 IS 1 BP 486 EP 496 DI 10.1086/305543 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZM044 UT WOS:000073499100048 ER PT J AU Morey-Holton, ER Globus, RK AF Morey-Holton, ER Globus, RK TI Hindlimb unloading of growing rats: A model for predicting skeletal changes during space flight SO BONE LA English DT Article; Proceedings Paper CT International Workshop on Bone Research in Space CY NOV 11-13, 1996 CL TOKYO, JAPAN SP NASA DE hindlimb unloading; space flight; bone formation; osteoblast; osteoporosis; biomechanics ID TRABECULAR BONE-FORMATION; GROWTH-FACTOR-I; SIMULATED WEIGHTLESSNESS; TAIL SUSPENSION; WEIGHT-BEARING; SPACEFLIGHT; CALCIUM; MUSCLE; DECREASES; PROLIFERATION AB A model that uses hindlimb unloading of rats was developed to study the consequences of skeletal unloading and reloading as occurs during and following space flight. Studies using the model were initiated two decades ago and further developed at National Aeronautics and Space Administration (NASA)Ames Research Center. The model mimics same aspects of exposure to microgravity by removing weightbearing loads from the hindquarters and producing a cephalic fluid shift. Unlike space flight, the forelimbs remain loaded in the model, providing a useful internal control to distinguish between the local and systemic effects of hindlimb unloading. Rats that are hindlimb unloaded by tail traction gain weight at the same rate as pairfed controls, and glucocorticoid levels are not different from controls, suggesting that systemic stress is minimal. Unloaded bones display reductions in cancellous osteoblast number, cancellous mineral apposition rate, trabecular bone volume, cortical periosteal mineralization rate, total bone mass, calcium content, and maturation of bone mineral relative to controls. Subsequent studies reveal that these changes also occur in rats exposed to space flight. In hindlimb unloaded rats, bone formation rates and masses of unloaded bones decline relative to controls, while loaded bones do not change despite a transient reduction in serum 1,25-dihydroxyvitamin D (1,25D) concentrations. Studies using the model to evaluate potential countermeasures show that 1,25D, growth hormone, dietary calcium, alendronate, and muscle stimulation modify, but do not completely correct, the suppression of bone growth caused by unloading, whereas continuous infusion of transforming growth factor-beta 2 or insulin-like growth factor-1 appears to protect against some of the bone changes caused by unloading. These results emphasize the importance of local as opposed to systemic factors in the skeletal response to unloading, and reveal the pivotal role that osteoblasts play in the response to gravitational loading. The hindlimb unloading model provides a unique opportunity to evaluate in detail the physiological and cellular mechanisms of the skeletal response to weightbearing loads, and has proven to be an effective model for space flight. (C) 1998 by Elsevier Science Inc. All rights reserved. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. Univ Calif San Francisco, Dept Med, San Francisco, CA USA. RP Morey-Holton, ER (reprint author), NASA, Ames Res Ctr, Div Life Sci, M-S 239-11, Moffett Field, CA 94035 USA. EM eholton@mail.arc.nasa.gov NR 62 TC 127 Z9 137 U1 1 U2 15 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 8756-3282 J9 BONE JI Bone PD MAY PY 1998 VL 22 IS 5 SU S BP 83S EP 88S DI 10.1016/S8756-3282(98)00019-2 PG 6 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA ZL627 UT WOS:000073453700004 PM 9600759 ER PT J AU LeBlanc, A Shackelford, L Schneider, V AF LeBlanc, A Shackelford, L Schneider, V TI Future human bone research in space SO BONE LA English DT Article; Proceedings Paper CT International Workshop on Bone Research in Space CY NOV 11-13, 1996 CL TOKYO, JAPAN SP NASA ID BED-REST; CALCIUM HOMEOSTASIS; FLIGHT; COUNTERMEASURES AB Skylab crewmembers demonstrated negative calcium (Ca) balance reaching about -300 mg/day by flight day 84, Limited bone density (BMD) measurements documented that bone was not lost equally from all parts of the skeleton. Subsequent BMD studies during long duration Russian flights documented the regional extent of bone loss. These studies demonstrated mean losses in the spine, femur neck, trochanter, and pelvis of about 1%-1.6% with large differences between individuals as well as between bone sites in a given individual. Limited available data indicate postflight bane recovery occurred in some individuals, but may require several years for complete restoration. Long duration bedrest studies showed a similar pattern of bone loss and calcium balance (-180 mg/day) as spaceflight, During long duration bedrest, resorption markers were elevated, formation markers were unchanged, 1,25 vitamin D (VitD) and calcium absorption were decreased, and serum ionized Ca was increased. Although this information is a good beginning, additional spaceflight research is needed to assess architectural and subregional bone changes, elucidate mechanisms, and develop efficient as well as effective countermeasures. Space research poses a number of unique problems not encountered in ground-based laboratory research. Therefore, researchers contemplating human spaceflight research need to consider a number of unique problems related to spaceflight in their experimental design. (C) 1998 by Elsevier Science Inc. All rights reserved. C1 Baylor Coll Med, Houston, TX 77030 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NASA Headquarters, Washington, DC USA. RP LeBlanc, A (reprint author), 6501 Fannin St,Mail Code NB1-004, Houston, TX 77030 USA. NR 19 TC 45 Z9 53 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 8756-3282 J9 BONE JI Bone PD MAY PY 1998 VL 22 IS 5 SU S BP 113S EP 116S DI 10.1016/S8756-3282(98)00013-1 PG 4 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA ZL627 UT WOS:000073453700010 PM 9600765 ER PT J AU Nicholson, SE Tucker, CJ Ba, MB AF Nicholson, SE Tucker, CJ Ba, MB TI Desertification, drought, and surface vegetation: An example from the West African Sahel SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SEMI-ARID REGIONS; JULY CIRCULATION; SATELLITE DATA; UNITED-STATES; NOAA AVHRR; ATMOSPHERE INTERACTION; FEEDBACK MECHANISM; WATER-BALANCE; SOIL-MOISTURE; MINERAL DUST AB Many assumptions have been made about the nature and character of desertification in West Africa. This paper examines the history of this issue, reviews the current state of our knowledge concerning the meteorological aspects of desertification, and presents the results of a select group of analyses related to this question. The common notion of desertification is of an advancing "desert," a generally irreversible anthropogenic process. This process has been Linked to increased surface albedo, increased dust generation, and reduced productivity of the land. This study demonstrates that there has been no progressive change of either the Saharan boundary or vegetation cover in the Sahel during the last 16 years, nor has there been a systematic reduction of "productivity" as assessed by the water-use efficiency of the vegetation cover. While it also showed little change in surface albedo during the years analyzed, this study suggests that a change in albedo of up to 0.10% since the 1950s is conceivable. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Nicholson, SE (reprint author), Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. NR 87 TC 249 Z9 277 U1 10 U2 90 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD MAY PY 1998 VL 79 IS 5 BP 815 EP 829 DI 10.1175/1520-0477(1998)079<0815:DDASVA>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP984 UT WOS:000073809200006 ER PT J AU Ricca, A Bauschlicher, CW AF Ricca, A Bauschlicher, CW TI Accurate D-0 values for SiF and SiF+ SO CHEMICAL PHYSICS LETTERS LA English DT Article ID CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; GAUSSIAN-BASIS SETS; WAVE-FUNCTIONS; ATOMIZATION ENERGIES; ELECTRON CORRELATION; ATOMS; THERMOCHEMISTRY; DISSOCIATION; ABINITIO AB Highly accurate D-0 values are determined for SiF and SiF+ using the CCSD(T) approach in conjunction with basis set extrapolation. The results include the effect of spin-orbit coupling and core-valence correlation. Our best D-0, estimates for SiF and SiF+ are 141.5 and 159.7 kcal/mol, respectively, which we estimate to have an uncertainty of +/-1.0 kcal/mol. For SIF, the value is significantly larger than the older experiments and only slightly larger than the most recent experiment. Our value is slightly larger than previous calculations. For SiF+ our best estimate is in good agreement with previous calculations and slightly smaller than the experimental value. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ricca, A (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 26 TC 8 Z9 10 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD MAY 1 PY 1998 VL 287 IS 3-4 BP 239 EP 242 DI 10.1016/S0009-2614(98)00166-3 PG 4 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZL106 UT WOS:000073399400004 ER PT J AU Southward, RE Boggs, CM Thompson, DW St Clair, AK AF Southward, RE Boggs, CM Thompson, DW St Clair, AK TI Synthesis of surface-metallized polyimide films via in situ reduction of (perfluoroalkanoato)silver(I) complexes in a poly(amic acid) precursor SO CHEMISTRY OF MATERIALS LA English DT Article ID CHEMICAL-VAPOR-DEPOSITION; POLYMER SURFACES; SILVER; INTERFACE; ADHESION; PHOTOEMISSION; PARTICLES; SPECTROSCOPY; CHEMISTRY; COLLOIDS AB Thermal curing of the silver(I)-containing poly(amic acid) formed from 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) and 4,4'-oxydianiline (4,4'-ODA) in dimethylacetamide leads both to polyimide films via cyclodehydration and to reduction of silver(I) giving a metallized surface. The resulting metallized composite films retain mechanical and thermal properties similar to those of the parent polyimide. Variation of the silver(I) additive and concentration and the thermal cure cycle allows the fabrication of silver layers which are both reflective and/or electrically conductive. Silver(I) trifluoroacetate and pentafluoropropanoate give excellent silvered films; however, higher perfluoroalkanoates such as silver(I) heptafluorobutanoate give films which are poorly surface metallized and extensively bubbled. X-ray diffraction shows crystalline face-centered cubic silver in the films after thermal curing. Microscopy data show that the surface particle sizes are in the range of ca. 100-500 nm. Significant silver remains in the bulk of the polyimide film with varying particle sizes generally less than ca. 15 nm. The interior of the metallized films is not electrically conducting. Films were characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. C1 NASA, Div Mat, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. RP Southward, RE (reprint author), NASA, Div Mat, Langley Res Ctr, Hampton, VA 23681 USA. NR 67 TC 27 Z9 30 U1 0 U2 7 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 MAY PY 1998 VL 10 IS 5 BP 1408 EP 1421 DI 10.1021/cm9707770 PG 14 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA ZP381 UT WOS:000073746600030 ER PT J AU Dodelson, S AF Dodelson, S TI The Big Bang SO COMMENTARY LA English DT Letter C1 NASA, Fermilab Astrophys Ctr, Batavia, IL USA. RP Dodelson, S (reprint author), NASA, Fermilab Astrophys Ctr, Batavia, IL USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU AMER JEWISH COMMITTEE PI NEW YORK PA 165 E 56TH ST, NEW YORK, NY 10022 USA SN 0010-2601 J9 COMMENTARY JI Commentary PD MAY PY 1998 VL 105 IS 5 BP 5 EP 6 PG 2 WC Political Science; Social Issues SC Government & Law; Social Issues GA ZJ592 UT WOS:000073232200001 ER PT J AU Baroth, E Wells, G Merrell, J AF Baroth, E Wells, G Merrell, J TI An evaluation of multiplexed analog digitizer boards - Part 2 SO EE-EVALUATION ENGINEERING LA English DT Article C1 CALTECH, Jet Prop Lab, Measurement Technol Ctr, Pasadena, CA 91109 USA. USAF, Res Lab, Edwards AFB, CA USA. RP Baroth, E (reprint author), CALTECH, Jet Prop Lab, Measurement Technol Ctr, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NELSON PUBLISHING PI NOKOMIS PA 2504 NORTH TAMIAMI TRAIL, NOKOMIS, FL 34275-3482 USA SN 0149-0370 J9 EE-EVAL ENG JI EE-Eval. Eng. PD MAY PY 1998 VL 37 IS 5 BP 52 EP + PG 5 WC Engineering, Electrical & Electronic SC Engineering GA ZL826 UT WOS:000073476000010 ER PT J AU Darrach, MR Chutjian, A Plett, GA AF Darrach, MR Chutjian, A Plett, GA TI Trace explosives signatures from World War II unexploded undersea ordnance SO ENVIRONMENTAL SCIENCE & TECHNOLOGY LA English DT Article ID REVERSAL ELECTRON-ATTACHMENT; LIQUID-CHROMATOGRAPHIC DETERMINATION; SOLID-PHASE MICROEXTRACTION; OUT SOLVENT-EXTRACTION; WASTE-WATER; PRECONCENTRATION; NITROORGANICS; MOLECULES; RESIDUES; SOLUTES AB Trace explosives signatures of TNT and DNT have been extracted from multiple sediment samples adjacent to unexploded undersea ordnance at Halifax Harbor, Canada. The ordnance was hurled into the harbor during a massive explosion some 50 years earlier, in 1945 after World War II had ended. Laboratory sediment extractions were made using the solid-phase microextraction (SPME) method in seawater and detection using the Reversal Electron Attachment Detection (READ) technique and, in the case of DNT, a commercial gas chromatograph/mass spectrometer (GC/MS). Results show that, after more than 50 years in the environment, ordnance that appeared to be physically intact gave good explosives signatures at the parts per billion level, whereas ordnance that had been cracked open during the explosion gave no signatures at the 10 parts per trillion sensitivity level. These measurements appear to provide the first reported data of explosives signatures from undersea unexploded ordnance. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chutjian, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 19 TC 80 Z9 80 U1 0 U2 12 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0013-936X J9 ENVIRON SCI TECHNOL JI Environ. Sci. Technol. PD MAY 1 PY 1998 VL 32 IS 9 BP 1354 EP 1358 DI 10.1021/es970992h PG 5 WC Engineering, Environmental; Environmental Sciences SC Engineering; Environmental Sciences & Ecology GA ZL156 UT WOS:000073404400046 ER PT J AU Les, CM Stover, SM Taylor, KT Keyak, JH Willits, NH AF Les, CM Stover, SM Taylor, KT Keyak, JH Willits, NH TI Ex vivo simulation of in vivo strain distributions in the equine metacarpus SO EQUINE VETERINARY JOURNAL LA English DT Article DE horse; metacarpus; bone; mechanical testing ID 3RD METACARPAL; BONE STRAIN; BREAKING STRENGTH; LONG BONES; HORSE; INVIVO; STRESS; AGE; LOCOMOTION; FORCES AB The objective of this study was to examine several simple ex vivo loading conditions for the equine metacarpus, and to evaluate their ability to reproduce the mid-diaphyseal bone surface strain distributions previously reported in vivo at the walk and trot. Distributed axial compressive loads, and 9 different axial compressive point loads at -7.5 kN and -15 kN were applied to metacarpal-distal carpal bone preparations from 6 Thoroughbred horses, aged 1-5 years. The resulting dorsal, medial, palmar, and lateral mid-diaphyseal bone surface axial and shear strains were compared with previously reported in vivo surface strain distributions using a root mean square error (RMSE) protocol. The effects of loading condition and load magnitude on RMSE were assessed with a mixed-model analysis of variance. There were significant differences between loading conditions, and, in most cases, between load magnitudes, in the fit of the ex vivo to the in vivo strain distributions. In vivo mid-diaphyseal bone surface strain distributions at the walk can be well approximated ex vivo by a distributed axial compressive load, or by a point load positioned 0.5 cm mediad to the sagittal midline, at -7.5 kN loads. In vivo mid-diaphyseal bone surface strain distributions at the trot can be wed approximated by the -15 kN loads applied to the same locations. These simplified loading conditions can be used in designing biologically relevant loading protocols for ex vivo mechanical testing studies, as wed as in developing boundary conditions for finite element analysis. As such, these loading conditions may be considered as tools to be used as a means of replicating in vivo loading conditions during the intial design and testing stages in the development of fracture fixation devices, as web as in the theoretical mechanical analysis of the metacarpal structure. C1 Univ Calif Lawrence Livermore Natl Lab, Sch Vet Med, JD Wheat Vet Orthoped Res Lab, Dept Anat Physiol & Cell Biol, Davis, CA 95616 USA. Univ Calif Lawrence Livermore Natl Lab, Div Stat, Davis, CA 95616 USA. Univ Calif Irvine, Dept Orthopaed Surg, Biomech Res Lab, Irvine, CA 92868 USA. RP Les, CM (reprint author), NASA, Ames Res Ctr, Mail Stop 239-11, Moffett Field, CA 94035 USA. FU NIAMS NIH HHS [AR08180] NR 31 TC 6 Z9 7 U1 0 U2 2 PU EQUINE VETERINARY JOURNAL LTD PI NEWMARKET PA GRASEBY HOUSE, ENXING ROAD, NEWMARKET CB8 0AU, SUFFOLK, ENGLAND SN 0425-1644 J9 EQUINE VET J JI Equine Vet. J. PD MAY PY 1998 VL 30 IS 3 BP 260 EP 266 PG 7 WC Veterinary Sciences SC Veterinary Sciences GA ZL369 UT WOS:000073426000015 PM 9622329 ER PT J AU Jovic, S AF Jovic, S TI Recovery of reattached turbulent shear layers SO EXPERIMENTAL THERMAL AND FLUID SCIENCE LA English DT Article DE turbulence; recovering flow; shear layers ID SEPARATION BUBBLE; BOUNDARY-LAYER; REVERSE FLOW AB Turbulence structure of the recovering flow downstream of a backward facing step is investigated for five different flow conditions. Reynolds number Re-h = U(0)h/nu and delta/h (representing a measure of a perturbation strength) appear to be the chief governing parameters of turbulence characteristics. Present measurements reveal that the skin-friction coefficient magnitude decreases everywhere in the flow (including the recirculating region) as the Reynolds number increases. The pressure coefficient distribution <(C)over cap (p)> collapses on a single curve for x < x(r) in the examined parameter range. All <(C)over cap (p)> distributions appear to reach approximately constant values by x approximate to 1.5x(r) (x(r) is a mean reattachment length). The turbulence structure near the wall recovers to that of an equilibrium boundary layer by x = 15h, while the outer region takes much longer distance (order of 100h). The slope of the Prandtl mixing length near the wall does not approach the equilibrium value of 0.41 until x approximate to 40h. The normalized maximum eddy viscosity in the outer layer appears to take more than 100h to approach the equilibrium value of 0.0168. (C) 1998 Elsevier Science Inc. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jovic, S (reprint author), NASA, Ames Res Ctr, MS 247-2, Moffett Field, CA 94035 USA. NR 33 TC 4 Z9 4 U1 1 U2 1 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0894-1777 J9 EXP THERM FLUID SCI JI Exp. Therm. Fluid Sci. PD MAY-JUN PY 1998 VL 17 IS 1-2 BP 57 EP 62 DI 10.1016/S0894-1777(97)10049-8 PG 6 WC Thermodynamics; Engineering, Mechanical; Physics, Fluids & Plasmas SC Thermodynamics; Engineering; Physics GA ZW261 UT WOS:000074391700007 ER PT J AU Stokes, SD Glauser, MN Gatski, TB AF Stokes, SD Glauser, MN Gatski, TB TI An examination of a 3D corner-step experiment SO EXPERIMENTAL THERMAL AND FLUID SCIENCE LA English DT Article DE laser Doppler velocimetry; 3D corner step; 2D channel flow; 2D backstep; step height; turbulence model calibration ID TURBULENT SECONDARY FLOWS; SQUARE DUCT; SIMULATION AB This paper presents results of LDV measurements in a complex three-dimensional (3D) turbulent flow. The experimental configuration studied, shown in Fig. 1, provides a complex 1 parameter (step height) three-dimensional flow with two-dimensional (2D) relaxation limits in the spanwise direction (that is, 2D channel flow and 2D backstep). Note that this flow is more complex than the simple 2D back-step described by Eaten and Johnston, 1981, AIAA Journal, vol. 19, pp. 1093-1100. However, when spanwise limits are taken out from either side of the centerline the flow relaxes to two well studied 2D flows. On the block side, the spanwise limit results in a 2D turbulent channel flow. On the step side, the spanwise limit results in the 2D back-step flow. In the center region of the facility, however the flow is strongly 3D. The data presented here, was taken with a three component laser Velocimetry system, thus all three velocity components can be measured simultaneously. The results presented here clearly indicate that this flow provides a complex 3D flow for turbulence model calibration with the added attraction of the 2D spanwise limits. In the region within two step-heights either side in span of the streamwise step edge, secondary flows are observed. In addition, a spanwise evolving streamwise reattachment length is seen. The prediction of the secondary motions along with the spanwise evolving streamwise reattachment length found here will provide a challenging test for any turbulence model. (C) 1998 Elsevier Science Inc. All rights reserved. C1 Clarkson Univ, Potsdam, NY 13699 USA. NASA, Langley Res Ctr, Hampton, VA 23666 USA. RP Glauser, MN (reprint author), Clarkson Univ, Potsdam, NY 13699 USA. NR 15 TC 0 Z9 0 U1 1 U2 1 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0894-1777 J9 EXP THERM FLUID SCI JI Exp. Therm. Fluid Sci. PD MAY-JUN PY 1998 VL 17 IS 1-2 BP 132 EP 138 DI 10.1016/S0894-1777(97)10058-9 PG 7 WC Thermodynamics; Engineering, Mechanical; Physics, Fluids & Plasmas SC Thermodynamics; Engineering; Physics GA ZW261 UT WOS:000074391700016 ER PT J AU Bogard, DD Garrison, DH AF Bogard, DD Garrison, DH TI Relative abundances of argon, krypton, and xenon in the Martian atmosphere as measured in Martian meteorites SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID NOBLE-GASES; SNC METEORITES; ORTHOPYROXENITE ALH84001; ORIGIN; SHERGOTTITES; EETA-79001; GLASS; FRACTIONATION; NITROGEN; ESCAPE AB We determined the concentrations of trapped Ar, Kr, and Xe in impact-melt glasses from Shergotty, Y793605, and two inclusions of EET79001 not previously analyzed. When combined with literature noble gas data on a single glass inclusion in EET79001 and a glass vein in Zagami, these data give more accurate estimates of the composition of Martian atmospheric gases trapped in these glasses. For the geological recent composition of the Martian atmospheric we infer Xe-129/Xe-132 = 2.60 +/- 0.05, Ar-36/Xe-132 = 900 +/- 100, and Kr-84/Xe-132 = 20.5 +/- 2.5. These elemental ratios differ from those measured by Viking by factors of 2.5 and 1.8, respectively. The Ar-36/Xe-132 and Kr-84/Xe-132 ratios in ALH84001 are considerably less than those in impact glasses and suggest preferential adsorption tin carbonate?) of Xe over Ar and Xe over Kr by factors of similar to 11 and similar to 2.6, respectively. We suggest that noble gases dissolved in water may have largely determined the trapped noble gas abundance pattern in ALH84001. Copyright (C) 1998 Elsevier Science Ltd. C1 NASA, Lockheed Martin Corp, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Bogard, DD (reprint author), NASA, Lockheed Martin Corp, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 36 TC 54 Z9 54 U1 1 U2 2 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 MAY PY 1998 VL 62 IS 10 BP 1829 EP 1835 DI 10.1016/S0016-7037(98)00116-1 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 103LN UT WOS:000075157600014 ER PT J AU Rampino, MR Adler, AC AF Rampino, MR Adler, AC TI Evidence for abrupt latest Permian mass extinction of foraminifera: Results of tests for the Signor-Lipps effect SO GEOLOGY LA English DT Article ID TRIASSIC BOUNDARY; CONFIDENCE-INTERVALS; FUNGAL EVENT; RANGES; RECORD; CRISIS AB We used published biostratigraphic data on ranges of fusulinids and other foraminifera from Permian-Triassic boundary sections in the southern Alps, Italy, to test the effects of sampling and species abundance on the record of the timing of the latest Permian extinction, The number of last occurrences of taxa reaches a maximum close to the local base of the Tesero horizon of the Werfen Formation. Taxa that have less than or equal to 15 % stratigraphic abundance (percent of sample intervals in which a taxon occurs) show last occurrences well before that level, whereas taxa,vith more complete records tend to disappear at or close to that level. These results are in agreement with simulations for abrupt extinctions, as opposed to gradual or steplike extinction scenarios, and support predictions of the Signor-Lipps effect, that errors in the end points of biostratigraphic ranges can produce range truncations and apparent gradual decline preceding a sudden extinction boundary. On the basis of estimated sedimentation rates for the Italian sections, the end-Permian extinctions could have been very sudden (less than or equal to 30 k.y.), and the disappearance of most latest Permian foraminifers was most likely coincident with a world wide ecological stress event, identified by a global negative delta(13)C anomaly that Occurs in Italy near the base or within the time-transgressive Tesero horizon. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NYU, Earth & Environm Sci Program, New York, NY 10003 USA. NYU, Dept Phys, New York, NY 10003 USA. RP Rampino, MR (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NR 28 TC 55 Z9 62 U1 2 U2 14 PU ASSOC ENGINEERING GEOLOGISTS GEOLOGICAL SOCIETY AMER PI COLLEGE STN PA TEXAS A & M UNIV, DEPT GEOLOGY & GEOPHYSICS, COLLEGE STN, TX 77843-3115 USA SN 0091-7613 J9 GEOLOGY JI Geology PD MAY PY 1998 VL 26 IS 5 BP 415 EP 418 DI 10.1130/0091-7613(1998)026<0415:EFALPM>2.3.CO;2 PG 4 WC Geology SC Geology GA ZM147 UT WOS:000073509400008 ER PT J AU Folkins, I Chatfield, R Singh, H Chen, Y Heikes, B AF Folkins, I Chatfield, R Singh, H Chen, Y Heikes, B TI Ozone production efficiencies of acetone and peroxides in the upper troposphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB HOx concentrations in the upper tropical troposphere can be enhanced by the presence of acetone and the convective injection of peroxides. These enhancements in HOx might be expected to increase ozone production by increasing the rate of the HO2 + NO reaction. We show however that the convective enhancements of hydrogen peroxide (H2O2) and methyl hydroperoxide (CH3OOH) above steady state during the PEM West B campaign were largely restricted to air parcels of marine boundary layer origin in which the mean NO concentration was 8 pptv. The ozone production efficiencies of the two peroxides at such low NO concentrations are very small. Their impact on the ozone budget of the upper tropical troposphere during PEM West B was therefore probably modest. Unlike the peroxides, acetone in the upper tropical troposphere during PERI West B exhibited a positive correlation with NO. It also has a much larger ozone production efficiency than either H2O2 or CH3OOH. It therefore has a much greater potential for significantly increasing ozone production rates in the upper tropical troposphere. C1 Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. Dalhousie Univ, Dept Phys, Atmospher Sci Program, Halifax, NS B3H 3J5, Canada. NASA, Div Earth Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Rhode Isl, Grad Sch Oceanog, Ctr Atmospher Chem Studies, Narragansett, RI 02882 USA. RP Folkins, I (reprint author), Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. NR 12 TC 25 Z9 25 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1998 VL 25 IS 9 BP 1305 EP 1308 DI 10.1029/98GL01030 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900005 ER PT J AU Aikin, AC Pesnell, WD AF Aikin, AC Pesnell, WD TI Uptake coefficient of charged aerosols - Implications for atmospheric chemistry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Gas uptake onto liquid particles is influenced by the electrical charge on the particle. This charge rearranges the spatial distribution of the dissolved reactant ions, modifying the solute-solvent reaction at the surface and for some distance into the liquid. This results in a modification of the uptake coefficient. A general expression, applicable to laboratory and atmospheric conditions, is presented. The change in the uptake coefficient is proportional to particle charge and the square of the Debye length within the liquid. It is inversely proportional to the square of the particle radius. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Nomad Res Inc, Bowie, MD 20716 USA. RP Aikin, AC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. RI Pesnell, William/D-1062-2012 OI Pesnell, William/0000-0002-8306-2500 NR 10 TC 2 Z9 2 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1998 VL 25 IS 9 BP 1309 EP 1312 DI 10.1029/98GL00934 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900006 ER PT J AU Goodman, J Pueschel, RF Jensen, EJ Verma, S Ferry, GV Howard, SD Kinne, SA Baumgardner, D AF Goodman, J Pueschel, RF Jensen, EJ Verma, S Ferry, GV Howard, SD Kinne, SA Baumgardner, D TI Shape and size of contrails ice particles SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIATIVE PROPERTIES; CIRRUS CLOUDS; CRYSTALS; CLIMATE AB A NASA DC-8, equipped as an in-situ sampling aircraft, flew in the exhaust wake of a Boeing 757 on May 4, 1996 over Kansas. Ice crystal samples were collected by impaction technique and replicated twice about 8 to 17 km behind the aircraft at an altitude of 11.8 km. The ice crystals in the contrail ( after about 1 minute of growing time) had a unimodal size distribution, with an equivalent volume radius of less than 10 mu m and an effective radius of about 2 mu m. The crystal habits at the observed temperature of -61C were predominantly hexagonal plates (75%), columns (20%) and few triagonal plates (<5%). The habit was already well defined for crystals about 0.5 mu m in radius. C1 San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. TMA Norcal, Richmond, CA 94084 USA. Symtech Corp, Arlington, VA USA. Bay Area Environm Inst, San Francisco, CA USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Goodman, J (reprint author), San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. NR 15 TC 23 Z9 23 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1998 VL 25 IS 9 BP 1327 EP 1330 DI 10.1029/97GL03091 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900011 ER PT J AU Heymsfield, AJ Lawson, RP Sachse, GW AF Heymsfield, AJ Lawson, RP Sachse, GW TI Growth of ice crystals in a precipitating contrail SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB This study examines how jet aircraft contrails develop precipitation trails, using data collected on 12 May, 1996 during SUCCESS. The DC-8 sampled the pre-contrail conditions, produced a contrail largely in clear air at -52 degrees C, and sampled the contrail and developing trails for over an hour. The environment was highly ice-supersaturated, reaching nearly water saturation in some locations. Inside the contrail core, almost all ice particles remained small (similar to 1 to 10 mu m) due to high crystal concentrations (similar to 10(1) to 10(2) cm(-3)) which reduced the vapor density to saturation. Mixing of moist environmental air and vapor-depleted contrail air produced localized regions of supersaturation along the contrail periphery, where crystals grew to several hundred microns at about 0.1 mu m s(-1). These particles could then fall from the contrail into the vapor-rich, undepleted, supersaturated environment below. As heavier crystals left the contrail, others moved into the regions of ice supersaturation. Precipitation trails developed as this process continued over time. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. SPEC Inc, Boulder, CO 80301 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Heymsfield, AJ (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. RI Heymsfield, Andrew/E-7340-2011 NR 14 TC 43 Z9 43 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1998 VL 25 IS 9 BP 1335 EP 1338 DI 10.1029/98GL00189 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900013 ER PT J AU Heymsfield, AJ Miloshevich, LM Twohy, C Sachse, G Oltmans, S AF Heymsfield, AJ Miloshevich, LM Twohy, C Sachse, G Oltmans, S TI Upper-tropospheric relative humidity observations and implications for cirrus ice nucleation SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WAVE CLOUDS; WATER AB Relative humidity (RH) measurements acquired in orographic wave cloud and citrus environments are used to investigate the temperature dependent RH required to nucleate ice crystals in the upper troposphere, RHnuc(T). High ice-supersaturations in clear air - conducive to the maintenance of aircraft contrails yet below RHnuc and therefore insufficient for citrus formation - are not uncommon. Earlier findings are supported that RHnuc in mid-latitude, continental environments decreases from water-saturation at temperatures above -39 degrees C to 75% RH at -55 degrees C. Uncertainty in determining RHnuc below -55 degrees C results in part from size detection limitations of the microphysical instrumentation, but analysis of data from the SUCCESS experiment indicates that RHnuc below -55 degrees C is between 70 and 88%. A small amount of data, acquired off-shore suggests the possibility that RHnuc may also depend on properties of the aerosols. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RP Heymsfield, AJ (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. EM heyms1@ncar.ucar.edu RI Heymsfield, Andrew/E-7340-2011 NR 7 TC 88 Z9 88 U1 2 U2 10 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 MAY 1 PY 1998 VL 25 IS 9 BP 1343 EP 1346 DI 10.1029/98GL01089 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900015 ER PT J AU Demoz, BB Starr, DO Chan, KR Bowen, SW AF Demoz, BB Starr, DO Chan, KR Bowen, SW TI Wavelet analysis of dynamical processes in cirrus SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID VOLCANIC AEROSOLS; CLOUDS; TURBULENCE; MESOSCALE; FIRE AB Vertical air velocity observations obtained from the NASA DC-8 on 21 April 1996 are analyzed using wavelet and spectral analysis methods. Wavelet analysis yielded a very useful characterization of the complex dynamical structures encountered above, below and within the cirrus clouds observed on this flight. Intermittent small groups of apparent gravity waves were found at length scales ranging from 2 km to greater than 40 km. Within the cloud, patches of convective cells were also found. The hierarchy of dynamical structures was well discriminated by the analysis. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Demoz, BB (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 913, Greenbelt, MD 20771 USA. EM demoz@climate.gsfc.nasa.gov; starr@climate.gsfc.nasa.gov; rchan@mail.arc.nasa.gov; bowen@mms.arc.nasa.gov RI Demoz, Belay/N-4130-2014 NR 20 TC 10 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 MAY 1 PY 1998 VL 25 IS 9 BP 1347 EP 1350 DI 10.1029/97GL03226 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900016 ER PT J AU Dean-Day, J Chan, KR Bowen, SW Bui, TP Gary, BL Mahoney, MJ AF Dean-Day, J Chan, KR Bowen, SW Bui, TP Gary, BL Mahoney, MJ TI Dynamics of Rocky Mountain lee waves observed during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB On two days during SUCCESS, the NASA DC-8 flew carefully designed flight tracks to sample wave clouds downstream of the Rocky mountains. Wave morphology was deduced by applying linear perturbation theory to in-situ measurements of the Meteorological Measurement System (MMS) and remotely sensed isentrope profiles of the Micro-wave Temperature Profiler (MTP). Vertical winds from the MMS were consistent with updraft velocities derived from air parcel displacements estimated from the MTP. Derived wave characteristics and cooling rates are useful inputs to cloud microphysics models. C1 San Jose State Univ, San Jose, CA 95192 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Jet Propuls Lab, Pasadena, CA 91109 USA. RP Dean-Day, J (reprint author), San Jose State Univ, San Jose, CA 95192 USA. EM day@mms.arc.nasa.gov; rchan@mail.arc.nasa.gov; bgary@jpl.nasa.gov NR 8 TC 4 Z9 4 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 MAY 1 PY 1998 VL 25 IS 9 BP 1351 EP 1354 DI 10.1029/98GL01004 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900017 ER PT J AU Chan, KR Dean-Day, J Bowen, SW Bui, TP AF Chan, KR Dean-Day, J Bowen, SW Bui, TP TI Turbulence measurements by the DC-8 meteorological measurement system SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRCRAFT; TEMPERATURE; WIND AB The instrumentation of a new MMS on the NASA DC-8 aircraft is briefly described. A method to compute the turbulent dissipation rate, epsilon, is discussed in light of some apparent inconsistencies between high and medium altitude aircraft data and available theory. Examples of turbulence measurements during encounters of a wake vortex, a field of wave clouds, and persistent contrails are illustrated. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. San Jose State Univ, San Jose, CA 95192 USA. RP Chan, KR (reprint author), NASA, Ames Res Ctr, MS 245-5, Moffett Field, CA 94035 USA. NR 11 TC 16 Z9 16 U1 0 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 MAY 1 PY 1998 VL 25 IS 9 BP 1355 EP 1358 DI 10.1029/97GL03590 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900018 ER PT J AU Jensen, EJ Toon, OB Tabazadeh, A Sachse, GW Anderson, BE Chan, KR Twohy, CW Gandrud, B Aulenbach, SM Heymsfield, A Hallett, J Gary, B AF Jensen, EJ Toon, OB Tabazadeh, A Sachse, GW Anderson, BE Chan, KR Twohy, CW Gandrud, B Aulenbach, SM Heymsfield, A Hallett, J Gary, B TI Ice nucleation processes in upper tropospheric wave-clouds observed during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CIRRUS CLOUDS; TEMPERATURE AB We have compared in situ measurements near the leading-edges of wave-clouds observed during the SUCCESS experiment with numerical simulations. Observations of high supersaturations with respect to ice (> 50%) near the leading edge of a very cold wave cloud (T < -60 degrees C) are approximately consistent with recent theoretical and laboratory studies suggesting that large supersaturations are required to homogeneously freeze sulfate aerosols. Also, the peak ice crystal number densities observed in this cloud (about 4 cm(-3)) are consistent with the number densities calculated in our model. In the warmer wave-cloud (T similar or equal to -37 degrees C) relatively large ice number densities were observed (20-40 cm(-3)). Our model calculations suggest that these large number densities are probably caused by activation of sulfate aerosols into liquid droplets followed by subsequent homogeneous freezing. If moderate numbers of effective heterogeneous freezing nuclei (0.5-1 cm(-3)) had been present in either of these clouds, then the number densities of ice crystals and the peak relative humidities should have been lower than the observed values. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, Boulder, CO 80309 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Nevada, Desert Res Inst, Reno, NV 89506 USA. Jet Propuls Lab, Pasadena, CA USA. RP Jensen, EJ (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. RI Heymsfield, Andrew/E-7340-2011; OI Aulenbach, Steve/0000-0002-0172-6538 NR 11 TC 96 Z9 96 U1 0 U2 12 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 MAY 1 PY 1998 VL 25 IS 9 BP 1363 EP 1366 DI 10.1029/98GL00299 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900020 ER PT J AU Jensen, EJ Toon, OB Pueschel, RF Goodman, J Sachse, GW Anderson, BE Chan, KR Baumgardner, D Miake-Lye, RC AF Jensen, EJ Toon, OB Pueschel, RF Goodman, J Sachse, GW Anderson, BE Chan, KR Baumgardner, D Miake-Lye, RC TI Ice crystal nucleation and growth in contrails forming at low ambient temperatures SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRCRAFT AB A model of ice crystal nucleation and growth in a diluting aircraft exhaust plume is used to evaluate the physical processes responsible for the ice number densities and size distributions measured on May 4, 1996. Predicted ice crystal size distributions are compared with observations at about 70 seconds plume age. The simulated crystals grow to about 2 mu m radius within 2-3 seconds, then remain approximately constant in size until 30-60 seconds plume age when crystal sublimations begins. The calculated crystal size distribution has approximately the same volume mode radius as the observed size distribution (1-2 mu m); however, the model does not predict as many crystals larger than 2 mu m radius as indicated by the measurements. Due to the low ambient temperature (-61 degrees C), large ice supersaturations are generated in the plume, and all exhaust soot particles and ambient aerosols entrained into the plume before about 1 second plume age are activated to ice nuclei. The simulations indicate that if the soot particle emission index is on the order of 2 x 10(12) particles (kg fuel)(-1) or lower and freshly nucleated sulfate aerosols are too small to freeze in the young plume, then the majority of the contrail ice crystals may be nucleated on ambient aerosols entrained into the exhaust plume. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, Boulder, CO 80309 USA. San Jose State Univ, San Jose, CA 95192 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Aerodyne Res Inc, Billerica, MA 01821 USA. RP Jensen, EJ (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. NR 9 TC 15 Z9 15 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1998 VL 25 IS 9 BP 1371 EP 1374 DI 10.1029/97GL03592 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900022 ER PT J AU Tabazadeh, A Toon, OB AF Tabazadeh, A Toon, OB TI The role of ammoniated aerosols in cirrus cloud nucleation SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TEMPERATURE AB Recent results obtained during the SUCCESS experiment show that aerosols containing ammonium ion are commonly found in the upper troposphere and therefore it is of great importance to investigate the ice freezing properties of such aerosols. For this purpose we present mathematical expressions, derived from recent model calculations and laboratory data, for calculating the deliquescence relative humidity of (NH4)(2)SO4, NH4HSO4 and NH4NO3 under upper tropospheric conditions. Using these functions we define the temperature and relative humidity requirements for the deliquescence of dry particles in the upper troposphere. Further using a thermodynamic model of the H2SO4/HNO3/NH3/H2O system, we calculate the variation in the supercooled aerosol composition and saturation ratios of various ionic salts in solution as a function of temperature and relative humidity. Using these values we show salt crystallization in the upper troposphere may occur in two distinct type of ammoniated aerosol solutions. First (NH4)(3)H(SO4)(2) (letovicite) may crystallize in acidic solutions of (NH4)(2)SO4. Second double salts of (NH4)(2)SO4 and NH4NO3 may crystallize in nearly neutralized solutions of (NH4)(2)SO4 and NH4NO3. Finally we discuss how the presence of crystalline salt surfaces in aqueous solutions may alter the mode of cirrus cloud formation from homogeneous to heterogeneous freezing nucleation. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, LASP, Boulder, CO 80309 USA. Univ Colorado, Dept Atmospher & Ocean Sci, Boulder, CO 80309 USA. RP Tabazadeh, A (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. NR 14 TC 66 Z9 66 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 1 PY 1998 VL 25 IS 9 BP 1379 EP 1382 DI 10.1029/97GL03585 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900024 ER PT J AU DeMott, PJ Rogers, DC Kreidenweis, SM Chen, YL Twohy, CH Baumgardner, D Heymsfield, AJ Chan, KR AF DeMott, PJ Rogers, DC Kreidenweis, SM Chen, YL Twohy, CH Baumgardner, D Heymsfield, AJ Chan, KR TI The role of heterogeneous freezing nucleation in upper tropospheric clouds: Inferences from SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CIRRUS AB A temperature spectrum of heterogeneous freezing nuclei concentrations in continental air in the upper troposphere was determined based on airborne measurements. Numerical model simulations incorporating ice formation by heterogeneous and homogeneous freezing of deliquesced soluble aerosol particles were performed to investigate the effect of the heterogeneous process on the microphysics of upper tropospheric clouds. Heterogeneous freezing nuclei were predicted to cause lower maximum concentrations of ice particles formed in clouds. These nuclei also initiate the first ice formation and act to broaden ice crystal size distributions in upper tropospheric clouds. Observations of ice formation in an orographic wave cloud supported these predictions. C1 Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP DeMott, PJ (reprint author), Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. RI DeMott, Paul/C-4389-2011; Heymsfield, Andrew/E-7340-2011; Kreidenweis, Sonia/E-5993-2011 OI DeMott, Paul/0000-0002-3719-1889; Kreidenweis, Sonia/0000-0002-2561-2914 NR 12 TC 67 Z9 68 U1 0 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 MAY 1 PY 1998 VL 25 IS 9 BP 1387 EP 1390 DI 10.1029/97GL03779 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900026 ER PT J AU Han, QY Rossow, WB Chou, J Welch, RM AF Han, QY Rossow, WB Chou, J Welch, RM TI Global variation of column droplet concentration in low-level clouds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOCUMULUS CLOUDS; LIQUID WATER; MICROPHYSICS; SATELLITE; CLIMATE; ALBEDO; FIRE; VALIDATION; RADIATION; AEROSOLS AB Cloud droplet concentration is a very important parameter in model studies. However, no global observation is available because it is hard to retrieve by current satellite remote sensing techniques. This study introduces another parameter, column droplet concentration, which can be retrieved by satellite data and used in models. The column droplet concentration (N-c) is the product of cloud geometrical thickness and droplet volume number concentration. This paper presents a method and the results of retrieving column droplet concentration for low-level clouds. The first near-global survey (50 degrees S to 50 degrees N) of N-c reveals more clearly the effect of aerosol concentration variations on clouds. The survey shows the expected increase of column droplet concentrations between ocean and continental clouds and in tropical areas during dry seasons where biomass burning is prevalent. Therefore, column droplet concentration is demonstrated as a good indication of available CCN populations in certain areas. C1 Univ Alabama, Dept Atmospher Sci, Huntsville, AL 35899 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Han, QY (reprint author), Univ Alabama, Dept Atmospher Sci, 977 Explorer Blvd, Huntsville, AL 35899 USA. EM han@atmos.uah.edu RI Rossow, William/F-3138-2015 NR 29 TC 53 Z9 56 U1 3 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 MAY 1 PY 1998 VL 25 IS 9 BP 1419 EP 1422 DI 10.1029/98GL01095 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900034 ER PT J AU Mason, GM Mazur, JE von Rosenvinge, TT AF Mason, GM Mazur, JE von Rosenvinge, TT TI Comment on 'Energetic heavy ions observed upstream of the Earth's bow shock by the STEP/EPACT instrument on WIND' - Reply SO GEOPHYSICAL RESEARCH LETTERS LA English DT Editorial Material ID ELECTRON C1 Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. RP Mason, GM (reprint author), Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NR 3 TC 1 Z9 1 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 MAY 1 PY 1998 VL 25 IS 9 BP 1527 EP 1528 DI 10.1029/98GL00473 PG 2 WC Geosciences, Multidisciplinary SC Geology GA ZL261 UT WOS:000073414900061 ER PT J AU Hapke, B Nelson, R Smythe, W AF Hapke, B Nelson, R Smythe, W TI The opposition effect of the moon: Coherent backscatter and shadow hiding SO ICARUS LA English DT Article ID WEAK LOCALIZATION; LIGHT; SCATTERING; PARTICLES; GRAINS AB The electromagnetic scattering properties of Solar System regoliths are commonly interpreted using the lunar regolith as a prototype. Hence, a thorough understanding of the reflectance of lunar soil is essential to remote sensing planetary studies. We have measured the linearly and circularly polarized reflectances of samples of lunar soil in order to better understand the nature of the lunar opposition effect. Several independent observations show that the zero-phase peak is caused by both shadow hiding and coherent backscatter in roughly equal amounts. Any radiative transfer model for planetary regoliths must take this dual nature into account, The transport mean free path for photons in the lunar regolith is about 1 mu m, which is much smaller than the mean particle size. (C) 1998 Academic Press. C1 Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hapke, B (reprint author), Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. NR 31 TC 88 Z9 90 U1 0 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAY PY 1998 VL 133 IS 1 BP 89 EP 97 DI 10.1006/icar.1998.5907 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU381 UT WOS:000074191400006 ER PT J AU Cabrol, NA Grin, EA Landheim, R Kuzmin, RO Greeley, R AF Cabrol, NA Grin, EA Landheim, R Kuzmin, RO Greeley, R TI Duration of the Ma'adim Vallis/Gusev crater hydrogeologic system, Mars SO ICARUS LA English DT Article DE Mars; surface; geological processes; planets ID LAKE AB Ma'adim Vallis and Gusev crater (Aeolis subquadrangle of Mars) formed a complex hydrogeologic system through time. Crater statistics over five geologic units, coupled with morphologic and geologic observations, show that this system was active over a period ranging from 0.7 to about 2 billion years. These results make the floor of Gusev crater one of the most prominent martian depositional features. The last aqueous sedimentary deposition could have occurred during Early Amazonian. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Ctr Mars Explorat, Div Space Sci, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, SETI Inst, Ctr Mars Explorat, Moffett Field, CA 94035 USA. Russian Acad Sci, Vernadsky Inst, Moscow 117975, Russia. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. RP Cabrol, NA (reprint author), NASA, Ames Res Ctr, Ctr Mars Explorat, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. EM ncabrol@mail.arc.nasa.gov NR 29 TC 58 Z9 58 U1 1 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAY PY 1998 VL 133 IS 1 BP 98 EP 108 DI 10.1006/icar.1998.5914 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZU381 UT WOS:000074191400007 ER PT J AU Simon, MK Alouini, MS AF Simon, Marvin K. Alouini, Mohamed-Slim TI A Simple Single Integral Representation of the Bivariate Rayleigh Distribution SO IEEE COMMUNICATIONS LETTERS LA English DT Article DE Communication channels; digital communications; fading channels AB Using an alternate representation of the Marcum Q-function, an expression for the bivariate Rayleigh cumulative distribution function is found in the form of a single integral with finite limits and an integrand composed of elementary functions. This result has advantage over previous forms of the same CDF which involve the Marcum Q-function itself or are expressed as infinite series of products of integrals. C1 [Simon, Marvin K.] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. [Alouini, Mohamed-Slim] CALTECH, Pasadena, CA 91125 USA. RP Simon, MK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM marvin.k.simon@jpl.nasa.gov; alouini@systems.caltech.edu NR 8 TC 33 Z9 33 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855 USA SN 1089-7798 J9 IEEE COMMUN LETT JI IEEE Commun. Lett. PD MAY PY 1998 VL 2 IS 5 BP 128 EP 130 AR PII S 1089-7798(98)04031-9 DI 10.1109/4234.673656 PG 3 WC Telecommunications SC Telecommunications GA V04WC UT WOS:000207087500005 ER PT J AU Degnan, JJ Coyle, DB Kay, RB AF Degnan, JJ Coyle, DB Kay, RB TI Effects of thermalization on Q-switched laser properties SO IEEE JOURNAL OF QUANTUM ELECTRONICS LA English DT Article ID TERMINAL-LEVEL LIFETIME; ND-YAG; RELAXATION; GARNET AB The conventional rate equations for a Q-switched laser are augmented to explicitly include the effects of time-and level-dependent pumping, thermalization among the sublevels in the upper and lower multiplets, and multiplet relaxation in a homogeneously broadened four-level laser medium. To make the numerical computations more generally valid, we introduce a number of dimensionless variables. We show that the initial set of five coupled differential equations can be reduced to a simple set of two coupled equations for the inversion density and photon flux. Via numerical modeling, we have investigated the manner in which both thermalization and lower multiplet relaxation affect Nd:YAG laser characteristics such as output energy and temporal waveform. Our numerical results confirm earlier predictions that the Q-switched Nd:YAG laser output energy increases monotonically by a factor of 3.33 as one progresses from the assumption of slow to rapid thermalization and by an additional factor of 1.46 if one further assumes a terminal multiplet relaxation which is fast relative to the resonator photon decay time. We also find that the laser pulsewidth is substantially broadened when the resonator photon decay time is comparable to the thermalization, and to a lesser extent, the terminal multiplet relaxation times. Furthermore, when the Q-switched laser is operated near threshold and the photon decay time is significantly less than the thermalization time constant, the laser will produce a damped pulse train resulting from periodic replenishment of the population inversion through thermalization among the Stark sublevels, Our energy and pulsewidth calculations reproduce the measured values of two well-characterized diode-pumped Nd:YAG slab lasers quite well provided one assumes a thermalization time among nondegenerate Stark sublevels of 3-5 ns, This result contrasts with other experimental work which suggests subnanosecond terminal multiplet lifetimes. Possible reasons for the discrepancies are explored. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. American Univ, Dept Phys, Washington, DC 20016 USA. RP Degnan, JJ (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 30 TC 56 Z9 58 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9197 J9 IEEE J QUANTUM ELECT JI IEEE J. Quantum Electron. PD MAY PY 1998 VL 34 IS 5 BP 887 EP 899 DI 10.1109/3.668777 PG 13 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA ZJ412 UT WOS:000073212900019 ER PT J AU Huang, J Pogorzelski, RJ AF Huang, J Pogorzelski, RJ TI A Ka-band microstrip reflectarray with elements having variable rotation angles SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE circular polarization; microstrip element; reflectarray antenna; variable rotation angle ID ANTENNA AB This paper demonstrates a novel means of achieving cophasal far-field radiation for a circularly polarized microstrip reflectarray with elements having variable rotation angles. Two iia-band half-meter microstrip reflectarrays have been fabricated and tested. Both are believed to be the electrically largest reflectarrays ever developed using microstrip patches. One-a conventional design-has identical square patches with variable-length microstrip phase-delay lines attached. The other has identical square patches with identical microstrip phase-delay lines but different element rotation angles. Both antennas demonstrated excellent performance with more than 55% aperture efficiencies, but the one with variable rotation angles resulted in better overall performance. A brief mathematical analysis is presented to validate this "rotational element" approach. With this approach, a means of scanning the main beam of the reflectarray over a nide angular region without any RF beamfomer by using miniature or micromachined motors is viable. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Huang, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 239 Z9 244 U1 2 U2 18 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 MAY PY 1998 VL 46 IS 5 BP 650 EP 656 DI 10.1109/8.668907 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA ZJ759 UT WOS:000073250100008 ER PT J AU Zuffada, C Cwik, T Ditchman, C AF Zuffada, C Cwik, T Ditchman, C TI Synthesis of novel all-dielectric grating filters using genetic algorithms SO IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION LA English DT Article DE filters; genetic algorithms ID DESIGN AB The feasibility of novel all-dielectric waveguide grating filters is demonstrated, using a genetic algorithm (GA) to solve for material dielectric constants and geometric boundaries separating homogeneous regions of the periodic cell. In particular, GA's show that simple geometries (not previously reported) utilizing a small number of layers and/or gratings can be found to yield bandpass or stop-band filters with user defined linewidth. The evaluation of the fitness of a candidate design entails the solution of an integral equation for the electric field in the cell using the method of moments (MOM). Our implementation is made efficient by using only very few design frequency points and accurately approximating a given filter transfer function by a quotient of polynomials as a function of frequency. Additionally, the problem impedance matrices are conveniently represented as the product of a material independent matrix and a vector of dielectric constants, thus allowing us to fill the matrices only once. Our code has been parallelized for the Cray T3D to take advantage of the intrinsic parallelization efficiencies offered by GA's, Solutions are illustrated for a very narrow-band single-grating transmission filter and a relatively broad-band double grating reflection filter. Additionally, a solution for a five homogeneous layers Fabry-Perot filter is also presented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zuffada, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 21 Z9 21 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-926X J9 IEEE T ANTENN PROPAG JI IEEE Trans. Antennas Propag. PD MAY PY 1998 VL 46 IS 5 BP 657 EP 663 DI 10.1109/8.668908 PG 7 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA ZJ759 UT WOS:000073250100009 ER PT J AU Ponchak, GE Downey, AN AF Ponchak, GE Downey, AN TI Characterization of thin film microstrip lines on polyimide SO IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY PART B-ADVANCED PACKAGING LA English DT Article DE microstrip; microwave; multilayer; polyimide; transmission lines AB This paper presents an in depth characterization of thin film microstrip (TFMS) fines fabricated on Dupont PI-2611 polyimide. Measured attenuation and effective dielectric constant is presented for TFMS lines with thicknesses from 2.45-7.4 mu m and line widths from 5-34.4 mu m over the frequency range of 1-110 GHz. The attenuation is separated into conductor and dielectric losses to determine the loss tangent of Dupont PI-2611 polyimide over the microwave frequency range. In addition, the measured characteristics are compared to closed form equations for alpha and epsilon(eff) from the literature. Based on the comparisons, recommendations for the best closed form design equations for TFMS are made. C1 NASA, Lewis Res Ctr, Electron Device Technol Branch, Cleveland, OH 44135 USA. RP NASA, Lewis Res Ctr, Electron Device Technol Branch, Cleveland, OH 44135 USA. NR 25 TC 75 Z9 75 U1 0 U2 6 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1070-9894 J9 IEEE T COMPON PACK B JI IEEE Trans. Compon. Packag. Manuf. Technol. Part B-Adv. Packag. PD MAY PY 1998 VL 21 IS 2 BP 171 EP 176 DI 10.1109/96.673705 PG 6 WC Engineering, Manufacturing; Engineering, Electrical & Electronic; Materials Science, Multidisciplinary SC Engineering; Materials Science GA ZP193 UT WOS:000073726900008 ER PT J AU Freeman, A Durden, SL AF Freeman, A Durden, SL TI A three-component scattering model for polarimetric SAR data SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article ID RADAR POLARIMETRY; FOREST BIOMASS; BACKSCATTER; IMAGERY AB An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations. The mechanisms are canopy scatter from a cloud of randomly oriented dipoles, even-or double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants and Bragg scatter from a moderately rough surface, This composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers. The model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NASA/Jet Propulsion Laboratory's (JPL's) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images, Furthermore, it is shown that the contributions of the three scattering mechanisms to the HH, HV, and VV backscatter can be calculated from the model fit. Finally, this model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Freeman, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 20 TC 765 Z9 879 U1 9 U2 71 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 MAY PY 1998 VL 36 IS 3 BP 963 EP 973 DI 10.1109/36.673687 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 ZM593 UT WOS:000073555700025 ER PT J AU Benedetto, S Divsalar, D Montorsi, G Pollara, F AF Benedetto, S Divsalar, D Montorsi, G Pollara, F TI Serial concatenation of interleaved codes: Performance analysis, design, and iterative decoding SO IEEE TRANSACTIONS ON INFORMATION THEORY LA English DT Article; Proceedings Paper CT 1997 IEEE International Symposium on Information Theory CY JUN 27-JUL 04, 1997 CL ULM, GERMANY SP IEEE DE concatenated codes; iterative decoding; serial concatenation; turbo codes ID CONVOLUTIONAL-CODES; BLOCK-CODES; TRELLIS AB A serially concatenated code with interleaver consists of the cascade of an outer encoder, an interleaver permuting the outer codewords bits, and an inner encoder whose input words are the permuted outer codewords. The construction can be generalized to h cascaded encoders separated by h - 1 interleavers. We obtain upper bounds to the average maximum-likelihood bit error probability of serially concatenated block and convolutional coding schemes, Then, we derive design guidelines for the outer and inner encoders that maximize the interleaver gain and the asymptotic slope of the error probability curves. Finally, we propose a new, low-complexity iterative decoding algorithm. Throughout the paper, extensive comparisons with parallel concatenated convolutional codes known as "turbo codes" are performed, showing that the new scheme can offer superior performance. C1 Politecn Torino, Dipartimento Elettron, Turin, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Benedetto, S (reprint author), Politecn Torino, Dipartimento Elettron, Turin, Italy. RI Montorsi, Guido/D-4867-2012; OI benedetto, sergio/0000-0002-7648-5396 NR 24 TC 683 Z9 707 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 0018-9448 J9 IEEE T INFORM THEORY JI IEEE Trans. Inf. Theory PD MAY PY 1998 VL 44 IS 3 BP 909 EP 926 DI 10.1109/18.669119 PG 18 WC Computer Science, Information Systems; Engineering, Electrical & Electronic SC Computer Science; Engineering GA ZJ299 UT WOS:000073200100001 ER PT J AU Imbriale, WA Otoshi, TY Yeh, C AF Imbriale, WA Otoshi, TY Yeh, C TI Power loss for multimode waveguides and its application to beam-waveguide system SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE beam waveguides; cylindrical waveguide; noise measurement; waveguide theory ID GUIDE AB The conventional way of expressing power loss in decibels/meter for a multimode waveguiding system with finite wall conductivity (such as a beam-waveguide (BWG) system with protective shroud) can be incorrect and misleading. The power loss tin decibels) for a multimode waveguiding system is, in general, not linearly proportional to the length of the waveguide. New power-loss formulas for multimode system are derived in this paper for arbitrarily shaped conducting waveguide tubes. In these formulas, there are factors such as [exp(jx)-1]/(jx), where x = (beta(a) -beta(b))l, with beta(a) and beta(b) being the propagation constants of the different propagating modes and l being the distance from the source plane to the plane of interest along the guide. For a large BWG supporting many propagating modes, beta(a)'s are suite close to beta(b)'s, thus the mode coupling terms remain important for a very long distance from the source plane. The multinode power-loss formula for a large circular conducting tube has been verified by experiments. This formula was also used to calculate the additional noise temperature contribution due to the presence of a protective shroud surrounding a millimeter-wave BWG system. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Imbriale, WA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 6 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1998 VL 46 IS 5 BP 523 EP 529 DI 10.1109/22.668651 PN 1 PG 7 WC Engineering, Electrical & Electronic SC Engineering GA ZL615 UT WOS:000073452200011 ER PT J AU Luy, JF Ponchak, GE AF Luy, JF Ponchak, GE TI Introduction to the Special Issue on Microwave Circuits on Silicon Substrates SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Editorial Material C1 Daimler Benz AG, Microwave Dept, D-89081 Ulm, Germany. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Luy, JF (reprint author), Daimler Benz AG, Microwave Dept, D-89081 Ulm, Germany. NR 0 TC 2 Z9 2 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1998 VL 46 IS 5 BP 569 EP 571 PN 2 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA ZL616 UT WOS:000073452400001 ER PT J AU Rieh, JS Lu, LH Katehi, PB Bhattacharya, P Croke, ET Ponchak, GE Alterovitz, SA AF Rieh, JS Lu, LH Katehi, PB Bhattacharya, P Croke, ET Ponchak, GE Alterovitz, SA TI X- and Ku-band amplifiers based on Si/SiGe HBT's and micromachined lumped components SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE amplifier; HBT; micromachining; MMIC; resonance frequency; SiGe ID HETEROJUNCTION BIPOLAR-TRANSISTORS; SILICON; TECHNOLOGY AB A double mesa-structure Si/SiGe heterojunction bipolar transistor (HBT) and novel micromachined lumped passive components have been developed and successfully applied to the fabrication of X- and Ku-band monolithic amplifiers. The fabricated 5 x 5 mu m(2) emitter-size Si/SiGe HBT exhibited a de-current gain beta of 109, and f(T) and f(max) of 28 and 52 GHz, respectively. Micromachined spiral inductors demonstrated resonance frequency of 20 GHz up to 4 nH, which is higher than that of conventional spiral inductors by a factor of two. Single-, dual-, and three-stage S-band amplifiers have been designed, based on the extracted active-and passive-device model parameters. A single-stage amplifier exhibited a peak gain of 4.0 dB at 10.0 GHz, while dual-and three-stage versions showed peak gains of 5.7 dB at 10.0 GHz and 12.6 dB at 11.1 GHz, respectively, A Ku-band single-stage amplifier has also been designed and fabricated, showing a peak gain of 1.4 dB at 16.6 GHz, Matching circuits for all these amplifiers were implemented by lumped components, leading to a much smaller chip size compared to those employing distributed components as matching elements. C1 Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. Hughes Res Labs, Malibu, CA 90265 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Rieh, JS (reprint author), Univ Michigan, Dept Elect Engn & Comp Sci, Ann Arbor, MI 48109 USA. NR 18 TC 40 Z9 45 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9480 EI 1557-9670 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1998 VL 46 IS 5 BP 685 EP 694 DI 10.1109/22.668683 PN 2 PG 10 WC Engineering, Electrical & Electronic SC Engineering GA ZL616 UT WOS:000073452400015 ER PT J AU Bruce, SPO Rydberg, A Kim, M Beisswanger, FJ Luy, JF Schumacher, H Erben, U Willander, M Karlsteen, M AF Bruce, SPO Rydberg, A Kim, M Beisswanger, FJ Luy, JF Schumacher, H Erben, U Willander, M Karlsteen, M TI Design and realization of a millimeter-wave Si/SiGe HBT frequency multiplier SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article ID TRANSISTORS AB In this paper, the design of an active millimeterwave frequency doubler using an Si/SiGe heterojunction bipolar transistor (HBT) as the active device is studied. Simulations are made using a developed physics-based large-signal model for Si/SiGe HBT's, which includes thermal dependence. Despite the high-output operating frequency of the fabricated doubler being close to f(max) 67 GHz for the Si/SiGe HBT, the conversion efficiency in a not completely optimized circuit is found to be better than -12 dB, The 3-dB bandwidth for the doubler is approximately 7.4%. These results are found to be comparable to a heterojunction field-effect transistor (HFET) doubler operating equally close to its f(max). Simulated results of the doubler performance,vith varied terminating impedances for the HBT are presented as design aids. C1 Uppsala Univ, Signals & Syst Grp, S-75120 Uppsala, Sweden. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. TIMIC Semicond GmbH, D-74025 Heilbronn, Germany. Daimler Benz AG, Res, Microwave Techniques, D-89081 Ulm, Germany. Univ Ulm, Dept Electron Devices & Circuits, D-89069 Ulm, Germany. Gothenburg Univ, Dept Phys, S-41296 Gothenburg, Sweden. Chalmers Univ Technol, S-41296 Gothenburg, Sweden. RP Bruce, SPO (reprint author), Uppsala Univ, Signals & Syst Grp, S-75120 Uppsala, Sweden. RI Karlsteen, Magnus/M-8963-2013 OI Karlsteen, Magnus/0000-0002-2463-0299 NR 12 TC 13 Z9 13 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1998 VL 46 IS 5 BP 695 EP 700 DI 10.1109/22.668684 PN 2 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA ZL616 UT WOS:000073452400016 ER PT J AU Lu, YN Braun, RC Aguirre, A Loh, PC AF Lu, YN Braun, RC Aguirre, A Loh, PC TI Establishment of monk seal cell lines SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Letter C1 Univ Hawaii Manoa, Dept Microbiol, Honolulu, HI 96822 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Loh, PC (reprint author), Univ Hawaii Manoa, Dept Microbiol, Snyder Hall 207,2538 Mall, Honolulu, HI 96822 USA. FU NCRR NIH HHS [G12RR/AI-03061] NR 7 TC 5 Z9 6 U1 0 U2 1 PU SOC IN VITRO BIOLOGY PI LARGO PA 9315 LARGO DR WEST, STE 25, LARGO, MD 20774 USA SN 1071-2690 J9 IN VITRO CELL DEV-AN JI In Vitro Cell. Dev. Biol.-Anim. PD MAY PY 1998 VL 34 IS 5 BP 367 EP 369 PG 3 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA ZQ625 UT WOS:000073886800005 PM 9639098 ER PT J AU Jongen, T Gatski, TB AF Jongen, T Gatski, TB TI General explicit algebraic stress relations and best approximation for three-dimensional flows SO INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE LA English DT Article ID TURBULENT FLOWS; MODELS AB Tensor representation results are reformulated in terms of projections onto tensor bases. A representation identity valid for general three-dimensional cases is obtained in terms of a five-term tensor basis, and three-term expansions, valid for two-dimensional cases, are evaluated as approximations to the full three-dimensional case. The results a.re then used to (1) derive explicit solutions of general algebraic stress relations that can account for any extra turbulence anisotropy effect, such as dissipation rate anisotropies, quadratic effects in the pressure-strain model, or even differential effects. In addition, non-inertial effects are included in a rigorous way; (2) derive explicit expressions for three-dimensional flows based on a five-term tensor basis; (3) evaluate approximations using three-term tensor bases for three-dimensional flows, and show how optimal formulations in the least-squares sense can be derived. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Swiss Fed Inst Technol, Fluid Mech Lab, CH-1015 Lausanne, Switzerland. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Jongen, T (reprint author), Unilever Res Labs Vlaardingen, NL-3130 AC Vlaardingen, Netherlands. EM thibauld.jongen@unilever.com NR 18 TC 42 Z9 44 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7225 J9 INT J ENG SCI JI Int. J. Eng. Sci. PD MAY-JUN PY 1998 VL 36 IS 7-8 BP 739 EP 763 DI 10.1016/S0020-7225(97)00122-5 PG 25 WC Engineering, Multidisciplinary SC Engineering GA ZX905 UT WOS:000074567200004 ER PT J AU Wu, H George, K Yang, TC AF Wu, H George, K Yang, TC TI Estimate of true incomplete exchanges using fluorescence in situ hybridization with telomere probes SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY LA English DT Article ID INSITU HYBRIDIZATION; HUMAN-LYMPHOCYTES; CHROMOSOME; ABERRATIONS; RADIATION; FREQUENCIES; BREAKS AB Purpose: To study the frequency of true incomplete exchanges in radiation-induced chromosome aberrations. Materials and methods: Human lymphocytes were exposed to 2 Gy and 5 Gy of gamma-rays. Chromosome aberrations were studied using the fluorescence in situ hybridization (FISH) technique with whole chromosome-specific probes, together with human telomere probes. Chromosomes 2 and 4 were chosen in the present study. Results: The percentage of incomplete exchanges was 27% when telomere signals were not considered. After excluding false incomplete exchanges identified by the telomere signals, the percentage of incomplete exchanges decreased to 11%. Since telomere signals appear on about 82% of the telomeres, the percentage of true incomplete exchanges should be even lower and was estimated to be 3%. This percentage was similar for chromosomes 2 and 4 and for doses of both 2 Gy and 5 Gy. Conclusions: The percentage of true incomplete exchanges is significantly lower in gamma-irradiated human lymphocytes than the frequencies reported in the literature. C1 NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Houston, TX 77058 USA. Kelsey Seybol Clin, Houston, TX 77058 USA. KRUG Life Sci, Houston, TX 77058 USA. RP Yang, TC (reprint author), NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Mail Code SD2, Houston, TX 77058 USA. NR 19 TC 67 Z9 68 U1 1 U2 2 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0955-3002 J9 INT J RADIAT BIOL JI Int. J. Radiat. Biol. PD MAY PY 1998 VL 73 IS 5 BP 521 EP 527 PG 7 WC Biology; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA ZR534 UT WOS:000073987200008 PM 9652809 ER PT J AU Seraji, H AF Seraji, H TI Nonlinear and adaptive control of force and compliance in manipulators SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article ID MOTION CONTROL; STABILITY AB This paper presents new position-based force and compliance control schemes for robot manipulators using nonlinear and adaptive controllers. The proposed controllers are simple and can easily be implemented in the outer feedback loop that encloses the inner Cartesian position control system supplied by the robot manufacturer In the position-based force control approach, adaptive PID and nonlinear PI controllers are proposed for setpoint tracking in which the controller gains are adjusted on-line as functions of the force error In the position-based compliance control approach, nonlinear and adaptive PD controllers are developed to achieve a desired behavior at contact, where the controller gains are functions of the contact force. Dynamic simulation results for a 7-DOF Robotics Research Corporation (RRC) ann are presented to demonstrate the efficacy of the adaptive compliance control scheme in executing contact tasks. Experimental results are also presented to illustrate nonlinear force control of the RRC arm. The results demonstrate that the proposed nonlinear PI controller where the integral gain is a sigmoidal function of the force error yields superior performance compared to a fixed-gain PI controller by producing a fast force response with a small settling time while preventing oscillations. Finally, the nonlinear PD compliance controller is implemented on the RRC arm and experimental results are presented. These results demonstrate that the nonlinear PD controller where the proportional gain is a hyperbolic function of the contact force, exhibits less sensitivity to the surface stiffness than a fixed-gain PD controller. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Seraji, H (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 27 TC 29 Z9 29 U1 0 U2 1 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 0278-3649 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD MAY PY 1998 VL 17 IS 5 BP 467 EP 484 DI 10.1177/027836499801700501 PG 18 WC Robotics SC Robotics GA 107XV UT WOS:000075237000001 ER PT J AU Greenman, RM Cheung, S Tu, EL AF Greenman, RM Cheung, S Tu, EL TI Coupled Navier-Stokes and optimizer analysis of a transonic wing SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 14th Applied Aerodynamics Conference CY JUN 17-20, 1996 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut AB One of the challenges of wing design is knowing how the geometric parameters affect the aerodynamics in a given flight regime, This study demonstrates the use of a numerical optimization routine to understand the significance of changing different geometric parameters, e.g., wing planform, on the aerodynamic characteristics, such as the lift-to-drag ratio (L/D). A numerical optimization routine is integrated with a grid generator and a computational fluid dynamics Navier-Stokes flow solver. The geometric parameters studied are wing sweep, twist angle at the root, and twist angle at the tip. These geometric parameters are then analyzed to show how each one contributes to the L/D performance of a wing. By using the developed tool to examine the characteristics of a transonic wing, the engineer can develop a better understanding of the related now physics and design a better performing wing. The results of this paper show that proper optimization may require a series of local optimization and angle-of-attack adjustments. Furthermore, it was found that multiple-design variable optimization yielded improved results over a single dominant design variable. C1 NASA, Ames Res Ctr, Appl Computat Aerodynam Branch, Moffett Field, CA 94035 USA. MCAT Inc, Moffett Field, CA 94035 USA. RP Greenman, RM (reprint author), NASA, Ames Res Ctr, Appl Computat Aerodynam Branch, Moffett Field, CA 94035 USA. NR 16 TC 2 Z9 2 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1998 VL 35 IS 3 BP 362 EP 369 DI 10.2514/2.2333 PG 8 WC Engineering, Aerospace SC Engineering GA ZQ723 UT WOS:000073896600003 ER PT J AU Korivi, VM Newman, PA Taylor, AC AF Korivi, VM Newman, PA Taylor, AC TI Aerodynamic optimization using sensitivity derivatives from a three-dimensional supersonic Euler code SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/USAF/NASA/ISSMO 5th Symposium on Multidisciplinary Analysis and Optimization CY SEP 07-09, 1994 CL PANAMA CITY BEACH, FL SP AIAA, USAF, NASA, ISSMO ID STRATEGY AB Initial results from a three-dimensional marching Euler code equipped with an efficient sensitivity analysis capability are presented. The aerodynamic sensitivity derivatives with respect to wing geometry parameters obtained by the incremental iterative method are compared with those obtained by an efficient central finite differencing method and are both accurate and computationally cheaper. Sample cases for a Mach 2.4 high-speed civil transport wing-body configuration are shown that indicate the feasibility of using these sensitivity derivatives in aerodynamic optimization studies. These demonstrations have been given for design variables that determine wing planform and control flap deflections. The filleted wing-body geometry and computational fluid dynamics grid are modified by automated surface geometry and grid generation codes through which sensitivity information is propagated. C1 Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Multidisciplinary Optimizat Branch, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. Old Dominion Univ, Dept Engn Mech, KDH 238, Norfolk, VA 23529 USA. RP Korivi, VM (reprint author), Optimal CAE Inc, Novi, MI 48375 USA. NR 22 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1998 VL 35 IS 3 BP 405 EP 411 DI 10.2514/2.2338 PG 7 WC Engineering, Aerospace SC Engineering GA ZQ723 UT WOS:000073896600008 ER PT J AU Holst, TL AF Holst, TL TI Multizone chimera algorithm for solving the full-potential equation SO JOURNAL OF AIRCRAFT LA English DT Article ID TRANSONIC FLOWS; SCHEMES AB A numerical scheme utilizing a chimera zonal grid approach for solving the three-dimensional full-potential equation is described. Within each grid zone a new approximate factorization scheme based on the approximation factorization scheme 2 algorithm is utilized to advance the solution one iteration. This is followed by the explicit advance of all common zonal grid boundaries using trilinear interpolation of the velocity potential. Two spatial discretization variations are presented; one using a hybrid first-order/second-order-accurate scheme and the second using a fully second-order-accurate scheme. The presentation is highlighted with a grid refinement study and a number of transonic wing flowfield computations. C1 NASA, Ames Res Ctr, Adv Compuat Methods Branch, Moffett Field, CA 94035 USA. RP Holst, TL (reprint author), NASA, Ames Res Ctr, Adv Compuat Methods Branch, Moffett Field, CA 94035 USA. NR 19 TC 3 Z9 3 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1998 VL 35 IS 3 BP 412 EP 421 DI 10.2514/2.2339 PG 10 WC Engineering, Aerospace SC Engineering GA ZQ723 UT WOS:000073896600009 ER PT J AU Lind, R Brenner, M AF Lind, R Brenner, M TI Incorporating flight data into a robust aeroelastic model SO JOURNAL OF AIRCRAFT LA English DT Article AB Stability analysis and control synthesis for high-performance aircraft must account for errors in the aircraft model. This paper introduces a method to update a theoretical model using measured flight data. Variations between the flight data and model are represented as uncertainty operators in a robust stability framework. The structured singular value can directly account for these uncertainty operators to compute stability margins robust to the associated dynamical variations. This procedure is used to formulate an uncertain model of an F/A-18 fighter aircraft and compute stability margins that indicate the worst-case flutter conditions. C1 NASA, Dryden Flight Res Ctr, Edwards, CA 93523 USA. RP Lind, R (reprint author), NASA, Dryden Flight Res Ctr, MS 4840D-RS, Edwards, CA 93523 USA. NR 13 TC 8 Z9 10 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 MAY-JUN PY 1998 VL 35 IS 3 BP 470 EP 477 DI 10.2514/2.2320 PG 8 WC Engineering, Aerospace SC Engineering GA ZQ723 UT WOS:000073896600016 ER PT J AU Jaunky, N Knight, NF Ambur, DR AF Jaunky, N Knight, NF Ambur, DR TI Optimal design of grid-stiffened composite panels using global and local buckling analyses SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 37th Structures, Structural Dynamics, and Materials Conference CY APR 15-17, 1996 CL SALT LAKE CITY, UTAH SP AIAA, ASME, ASCE, AHS, ASC ID ANISOTROPIC PLATES AB A design strategy for optimal design of composite grid-stiffened panels subjected to global and local buckling constraints is developed using a discrete optimizer. An improved smeared stiffener theory is used for the global buckling analysis. Local buckling of skin segments Is assessed using a Rayleigh-Ritz method that accounts for material anisotropy and transverse shear flexibility, The local buckling of stiffener segments is also assessed. Design variables are the axial and transverse stiffener spacing, stiffener height and thickness, skin laminate, and stiffening configuration, where the stiffening configuration is herein defined as a design variable that indicates the combination of axial, transverse, and diagonal stiffeners in the stiffened panel. The design optimization process is adapted to identify the lightest-weight stiffening configuration and stiffener spacing for grid-stiffened composite panels given the overall panel dimensions, in-plane design loads, material properties, and boundary conditions of the grid-stiffened panel. C1 Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. RP Jaunky, N (reprint author), Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. NR 28 TC 18 Z9 31 U1 0 U2 6 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 MAY-JUN PY 1998 VL 35 IS 3 BP 478 EP 486 DI 10.2514/2.2321 PG 9 WC Engineering, Aerospace SC Engineering GA ZQ723 UT WOS:000073896600017 ER PT J AU Mathias, DL Storms, BL Ross, JC AF Mathias, DL Storms, BL Ross, JC TI Lift-enhancing tabs on swept, three-dimensional high-lift systems SO JOURNAL OF AIRCRAFT LA English DT Article C1 Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. Sterling Fed Syst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Low Speed Aerodynam Branch, Moffett Field, CA 94035 USA. RP Mathias, DL (reprint author), Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1998 VL 35 IS 3 BP 494 EP 495 DI 10.2514/2.2325 PG 2 WC Engineering, Aerospace SC Engineering GA ZQ723 UT WOS:000073896600020 ER PT J AU Boeck, WL Vaughan, OH Blakeslee, RJ Vonnegut, B Brook, M AF Boeck, WL Vaughan, OH Blakeslee, RJ Vonnegut, B Brook, M TI The role of the space shuttle videotapes in the discovery of sprites, jets and elves SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID LOWER IONOSPHERE; THUNDERSTORMS; STRATOSPHERE; AIRCRAFT AB The sequence of videotape observations of the upper atmospheric optical flashes called sprites, jets, starters, and ELVES are described in the successive phases of search, discovery, confirmation, and exploration for the years before 1993. Although there were credible eyewitness accounts from ground observers and pilots, these reports did not inspire a systematic search for hard evidence of such phenomena. The science community would instead wait for serendipitous observations to move the leading edge of this science forward. The phenomenon, now known as a sprite, was first accidently documented on ground based videotape recordings on the night of 6 July, 1989. Video observations from the space shuttle acquired from 1989-1991 provided 17 additional examples to confirm the existence of the sprite phenomenon. Successful video observations from a mountain ridge by Lyons, starting an 7 July, 1993, and night-time aircraft video observations by Sentman and Wescott on 8 July, 1993 established the basic science of the sprite phenomena by acquiring and analyzing data based on hundreds of new events. The 1994 Sprites campaign and the video entitled "Red Sprites and Blue Jets" popularized the name sprite and provided a vocabulary of terms to describe the visual attributes. Prior to this video, investigators used a variety of vague descriptive words to describe the individual events. Also, during the 1994 campaign, Wescott and coworkers obtained the first quantitative measurements of jets and provided the name 'blue jets'. A third phenomenon was discovered in video from the STS-41 mission (October 1990) in the lower ionosphere directly above an active thunderstorm. It consisted of a large horizontal brightening several hundred kilometers across at the altitude of the airglow layer. In 1995, Lyons and associates confirmed the existence of this type of very brief brightening which they named Emissions of Light and Very Low Frequency Perturbations From Electromagnetic Pulse Sources (ELVES). Because sprites, jets, and ELVES have appeared for millennia, their discovery was inevitable. The partial history related in this paper outlines the unsophisticated activities using space shuttle videotapes and the dissemination of the results by video presentations during the early phases of sprite research. This paper does not attempt to evaluate the advances in the science based on the measurement campaigns of Lyons, Sentman and many other investigators. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Niagara Univ, Niagara Univ, NY 14109 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. SUNY Albany, Albany, NY 12222 USA. New Mexico Inst Min & Technol, Socorro, NM 87801 USA. RP Boeck, WL (reprint author), Niagara Univ, Niagara Univ, NY 14109 USA. EM boeck@niagara.edu NR 47 TC 32 Z9 32 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD MAY-JUN PY 1998 VL 60 IS 7-9 BP 669 EP 677 DI 10.1016/S1364-6826(98)00025-X PG 9 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 124QP UT WOS:000076193500002 ER PT J AU Boccippio, DJ Wong, C Williams, ER Boldi, R Christian, HJ Goodman, SJ AF Boccippio, DJ Wong, C Williams, ER Boldi, R Christian, HJ Goodman, SJ TI Global validation of single-station Schumann resonance lightning location SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID EARTH-IONOSPHERE CAVITY; ELF; DISTURBANCES; CURRENTS; STROKES; NETWORK; MODE AB Global measurements of large, optically bright lightning events;from the Optical Transient Detector (OTD) satellite are used to validate estimates of lightning location from single-station Schumann resonance (SR) data. Bearing estimates are obtained through conventional magnetic direction-finding techniques, while source range is estimated from the range-dependent impedance spectrum of individual SR transients. An analysis of 40 such transients suggests that single-station techniques can locate lightning globally with an accuracy of 1-2 Mm. This is confirmed by further validation at close ranges from flashes detected by the National Lightning Detection Network (NLDN). Observations with both OTD and SR systems may be useful for globally locating lightning with necessary, if not sufficient, characteristics to trigger mesospheric sprites. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. MIT, Cambridge, MA 02139 USA. MIT, Lincoln Labs, Lexington, MA 01731 USA. RP Boccippio, DJ (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. EM Dennis.Boccippio@msfc.nasa.gov NR 33 TC 28 Z9 29 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD MAY-JUN PY 1998 VL 60 IS 7-9 BP 701 EP 712 DI 10.1016/S1364-6826(98)00035-2 PG 12 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 124QP UT WOS:000076193500006 ER PT J AU Wescott, EM Sentman, DD Heavner, MJ Hampton, DL Vaughan, OH AF Wescott, EM Sentman, DD Heavner, MJ Hampton, DL Vaughan, OH TI Blue Jets: their relationship to lightning and very large hailfall, and their physical mechanisms for their production SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID SPRITES94 AIRCRAFT CAMPAIGN; THUNDERSTORM; DYNAMICS AB Blue jets are narrow cones of blue light that appear to propagate upward from the cloud tops at speeds of about 100 km/s to terminal altitudes of about 40 km (Wescott et al. 1995). In this paper, we present the results of a refined analysis of these optical phenomena and their relationship to cloud-to-ground (CG) and intracloud lightning, and to very large hailfall, their apparent color, and possible mechanisms for their production. In a thunderstorm where more than 50 of these events were observed from aircraft on the night of 1 July 1994, about half of the blue jets occurred in a cluster near Foreman, Arkansas, and the rest in an area near Texarkana, (Texas/Arkansas). Hail 7 cm in diameter fell in those two storm cells at the time of the blue jet occurrences. One other blue jet was observed over an intense multi cell storm in Kansas on the night of 3 July 1994. Comparison to cloud-to-ground (CG) lightning strokes revealed that blue jets were not coincident with either positive or negative CG strokes, but they occurred in the same general area as negative CG strokes and large hail, and that cumulative distributions of the negative CG strokes in +/- 5 s before and after the jet and within a radius of 15 km showed a significant reduction in the flash rate for 2 s following the event. From an analysis of color TV signal levels and calculations of quenching and atmospheric transmission, we conclude that significant ionization is present in the jets. Theoretical work by others suggests that the mechanism for their production is a streamer, but there remain discrepancies between these theories and the observations. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. Ball Aerosp & Technol, Boulder, CO USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Wescott, EM (reprint author), Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. NR 27 TC 44 Z9 44 U1 0 U2 4 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 MAY-JUN PY 1998 VL 60 IS 7-9 BP 713 EP 724 DI 10.1016/S1364-6826(98)00018-2 PG 12 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 124QP UT WOS:000076193500007 ER PT J AU Showen, RL Slingeland, A AF Showen, RL Slingeland, A TI Measuring lightning-induced ionospheric effects with incoherent scatter radar or with cross-modulation SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID ELECTROMAGNETIC PULSES; PLASMA LINES; IONIZATION AB Measurements have been made of the ionosphere during lightning storms using the incoherent scatter radar at Arecibo, Puerto Rico. Attempts were made to detect the expected increases in the D-region electron number densities, and possible changes in the plasma line echoes in the F-region. No D-region density changes were detected, to a limit of under 200/cc. This upper limit on possible lightning-induced ionization is not necessarily in conflict with predictions, which are of the same order as this limit and depend on assumptions of the strength and duration of the lightning. Spectral plasma line measurements of the incoherent scatter in the F-region, which are a sensitive indication of E-field variations also did not show any changes associated with individual lightning strikes. An alternative method of searching for D-region changes due to lightning is a cross-modulation or riometer experiment, which is modeled here. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Trilon Technol, Los Altos, CA USA. Stanford Univ, Stanford, CA 94305 USA. RP Showen, RL (reprint author), NASA Arnes, Mt View, CA USA. NR 16 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 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD MAY-JUN PY 1998 VL 60 IS 7-9 BP 951 EP 956 DI 10.1016/S1364-6826(98)00016-9 PG 6 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 124QP UT WOS:000076193500026 ER PT J AU Globus, RK Doty, SB Lull, JC Holmuhamedov, E Humphries, MJ Damsky, CH AF Globus, RK Doty, SB Lull, JC Holmuhamedov, E Humphries, MJ Damsky, CH TI Fibronectin is a survival factor for differentiated osteoblasts SO JOURNAL OF CELL SCIENCE LA English DT Article DE fibronectin; osteoblast; transforming growth factor-beta 1; apoptosis; differentiation ID NODULES FORMED INVITRO; EXTRACELLULAR-MATRIX; CELL-ADHESION; GENE-EXPRESSION; GROWTH-FACTORS; BONE; APOPTOSIS; PROLIFERATION; SUPPRESSION; INTEGRINS AB The skeletal extracellular matrix produced by osteoblasts contains the glycoprotein fibronectin, which regulates the adhesion, differentiation and function of various adherent cells. Interactions with fibronectin are required for osteoblast differentiation in vitro, since fibronectin antagonists added to cultures of immature fetal calvarial osteoblasts inhibit their progressive differentiation. To determine if fibronectin plays a unique role in fully differentiated osteoblasts, cultures that had already formed mineralized nodules in vitro were treated with fibronectin antagonists. Fibronectin antibodies caused >95% of the cells in the mature cultures to display characteristic features of apoptosis (nuclear condensation, apoptotic body formation, DNA laddering) within 24 hours. Cells appeared to acquire sensitivity to fibronectin antibody-induced apoptosis as a consequence of differentiation, since antibodies failed to kill immature cells and the first cells killed were those associated with mature nodules, Intact plasma fibronectin, as well as fragments corresponding to the amino-terminal, cell-binding, and carboxy-terminal domains of fibronectin, independently induced apoptosis of mature (day-13), but not immature (day-4), osteoblasts. Finally, transforming growth factor-beta 1 partially protected cells from the apoptotic effects of fibronectin antagonists. Thus, in the course of maturation cultured osteoblasts switch from depending on fibronectin for differentiation to depending on fibronectin for survival. These data suggest that fibronectin, together with transforming growth factor-beta 1, may affect bone formation, in part by regulating the survival of osteoblasts. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif San Francisco, Dept Med, San Francisco, CA 94143 USA. Univ Calif San Francisco, Dept Stomatol, San Francisco, CA 94143 USA. Univ Calif San Francisco, Dept Anat, San Francisco, CA 94143 USA. Hosp Special Surg, New York, NY 10021 USA. Univ Manchester, Sch Biol Sci, Manchester, Lancs, England. RP Globus, RK (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Holmuhamedov, Ekhson/P-5228-2016 FU NIDCR NIH HHS [DE-07204, DE-10306]; Wellcome Trust NR 39 TC 194 Z9 205 U1 1 U2 6 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE, CAMBS, ENGLAND CB4 4DL SN 0021-9533 J9 J CELL SCI JI J. Cell Sci. PD MAY PY 1998 VL 111 BP 1385 EP 1393 PN 10 PG 9 WC Cell Biology SC Cell Biology GA ZT526 UT WOS:000074096700007 PM 9570756 ER PT J AU Lau, KM Ho, CH Kang, IS AF Lau, KM Ho, CH Kang, IS TI Anomalous atmospheric hydrologic processes associated with ENSO: Mechanisms of hydrologic cycle-radiation interaction SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; LARGE-SCALE DYNAMICS; WATER-VAPOR; SOUTHERN OSCILLATION; EL-NINO; CLIMATE; CLOUD; CIRCULATION; CONVECTION; SURROGATE AB Using reanalysis data from the Goddard Earth Observing System (GEOS) Data Assimilation System, the authors have documented the basic three-dimensional features of anomalous atmospheric hydrologic processes observed during the El Nino-Southern Oscillation (ENSO). The most dominant anomaly pattern features a pair of subtropical temperature maxima straddling the equator in the upper troposphere coupled to a corresponding pair of temperature minima in the lower stratosphere in the form of a dipole. Over the Tropics and subtropics, the water vapor content is increased in regions of large-scale ascent with maximum response in the middle troposphere, whereas substantial drying is found in the descending branches of the Walker and Hadley circulations. While the temperature and moisture patterns in the lower troposphere are thermodynamically linked to the sea surface temperature anomaly pattern, the distribution of temperature and water vapor in the upper troposphere is largely controlled by dynamics and much less by thermodynamics. The troposphere-stratosphere temperature dipole is fundamentally due to the rising of the tropopause associated with hydrostatic expansion and vertical ascent in regions of enhanced deep convection. The rising motion pushes colder upper-tropospheric air into the lower stratosphere where the climatological temperature gradient reverses. No such dipole anomaly exists in the moisture field. Numerical experiments with the GEOS GCM show that while atmospheric dynamics are principally responsible for the generation of the basic structures of the temperature and moisture anomalies observed during ENSO, the interaction between the hydrologic cycle and radiation plays an important role in enhancing and modifying the response. The role of hydrologic cycle-radiation interaction is most important in rendering the atmosphere more unstable both columnwise and locally, through enhanced longwave heating in the middle and lower troposphere and cooling above. The enhanced instability leads to intensified Hadley and Walker circulations, which are accompanied by stronger latent heating and a more vigorous hydrologic cycle. The intensified hydrologic cycle promotes: further warming and moistening of the middle and lower troposphere, and cooling and drying in the stratosphere. The radiation-dynamics feedback leads to a new equilibrium climate state in which the increased heat transport by convection into the upper troposphere and stratosphere is balanced by increased radiative cooling, which removes the local excessive heat buildup. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Lab Atmospheres, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Associate, Greenbelt, MD 20771 USA. Seoul Natl Univ, Dept Atmospher Sci, Seoul, South Korea. RP Lau, KM (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Lab Atmospheres, Code 913, Greenbelt, MD 20771 USA. EM lau@climate.gsfc.nasa.gov 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 26 TC 13 Z9 14 U1 0 U2 2 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 MAY PY 1998 VL 11 IS 5 BP 800 EP 815 DI 10.1175/1520-0442(1998)011<0800:AAHPAW>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP526 UT WOS:000073762300002 ER PT J AU Rind, D Shindell, D Lonergan, P Balachandran, NK AF Rind, D Shindell, D Lonergan, P Balachandran, NK TI Climate change and the middle atmosphere. Part III: The doubled CO2 climate revisited SO JOURNAL OF CLIMATE LA English DT Article ID TROPOSPHERE-STRATOSPHERE SYSTEM; GENERAL-CIRCULATION MODEL; ANTARCTIC OZONE HOLE; UV VARIABILITY; TRANSPORT; WARMINGS; QBO AB The response of the troposphere-stratosphere system to doubled atmospheric CO2 is investigated in a series of experiments in which sea surface temperatures are allowed to adjust to radiation imbalances. The Goddard Institute for Space Studies (GISS) Global Climate Middle Atmosphere Model (GCMAM) warms by 5.1 degrees C at the surface while the stratosphere cools by up to 10 degrees C. When ozone is allowed to respond photochemically, the stratospheric cooling is reduced by 20%, with little effect in the troposphere. Planetary wave energy increases in the stratosphere, producing dynamical warming at high latitudes, in agreement with previous GCMAM doubled CO2 simulations; the effect is due to increased tropospheric generation and altered refraction, both strongly influenced by the magnitude of warming in the model's tropical upper troposphere. This warming also results in stronger zonal winds in the lower stratosphere, which appears to reduce stratospheric planetary wave 2 energy and stratospheric warming events. The dynamical changes in the lower stratosphere are weakened when O-3 chemistry on polar stratospheric cloud effects are included at current stratospheric chlorine levels. Comparison with the nine-level version of the GISS GCM with a top at 10 mb shows that both the stratospheric and tropospheric dynamical responses are different. The tropospheric effect is mostly a function of the vertical resolution in the troposphere; finer vertical resolution leads to increased latent heat release in the warmer climate, greater zonal available potential energy increase. and greater planetary longwave energy and energy transports. The increase in planetary longwave energy and residual circulation in the stratosphere is reproduced when the model top is lifted from 30 to 50 km, which also affects upper-tropospheric stability, convection and cloud cover, and climate sensitivity. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY USA. Sci Syst & Anal Inc, New York, NY USA. RP Rind, D (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM cddhr@nasagiss.giss.nasa.gov RI Shindell, Drew/D-4636-2012 NR 31 TC 90 Z9 92 U1 0 U2 6 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 MAY PY 1998 VL 11 IS 5 BP 876 EP 894 DI 10.1175/1520-0442(1998)011<0876:CCATMA>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP526 UT WOS:000073762300008 ER PT J AU Shindell, DT Rind, D Lonergan, P AF Shindell, DT Rind, D Lonergan, P TI Climate change and the middle atmosphere. Part IV: Ozone response to doubled CO2 SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; SEA-SURFACE TEMPERATURE; STRATOSPHERIC OZONE; HOLE AB Parameterized stratospheric ozone photochemistry has been included in the Goddard Institute for Space Studies (GISS) GCM to investigate the coupling between chemistry and climate change for the doubled CO2 climate. The chemical ozone response is of opposite sign to temperature changes, so that radiative cooling in the upper stratosphere results in increased ozone, while warming reduces ozone in the lower stratosphere. The increased overhead column reduces the amount of UV reaching the lower stratosphere, resulting in further ozone decreases there. Changes of up to 15% are seen, including both photochemistry and transport. Good agreement is found between the authors' results and those in other models for tropical latitudes where the stratospheric temperature responses are similar. However, in the extratropics, there are large differences between present results and those of the other models due to differences in tropospheric warming and tropospheric forcing of the stratospheric residual circulation. A net decrease in column ozone at midlatitudes is seen in this climate model, in contrast to the other models that showed an increase in column ozone everywhere. These ozone reductions lead to an increase of 10% in UV radiation reaching the surface at northern midlatitudes. The authors find significantly less of an increase in the high-latitude ozone column than in the other models. When parameterized heterogeneous chemistry on polar stratospheric clouds is also included, while maintaining current chlorine loading, it is found that the Antarctic ozone hole becomes significantly larger and of longer duration. In addition, an ozone hole of approximately half the depth in percent of the current Antarctic ozone hole forms in the Arctic due to both chemistry and transport changes resulting from a reduction of sudden warmings seen in the doubled CO2 atmosphere. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY USA. Sci Syst & Applicat, New York, NY USA. RP Shindell, DT (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Shindell, Drew/D-4636-2012 NR 31 TC 43 Z9 45 U1 0 U2 2 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 MAY PY 1998 VL 11 IS 5 BP 895 EP 918 DI 10.1175/1520-0442(1998)011<0895:CCATMA>2.0.CO;2 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP526 UT WOS:000073762300009 ER PT J AU Zhou, JY Lau, KM AF Zhou, JY Lau, KM TI Does a monsoon climate exist over South America? SO JOURNAL OF CLIMATE LA English DT Article ID ASIAN SUMMER MONSOON; TROPOSPHERIC CIRCULATION; TRANSIENT CONVECTION; TROPICAL ATMOSPHERE; MOISTURE BUDGETS; TIBETAN PLATEAU; PRECIPITATION; REGION; CLOUD; HEAT AB The climatology and the basic state of the summertime circulation and rainfall over South America are studied using assimilation products from the data assimilation system of Goddard Earth Observing System-1 (GEOS-1) and satellite-derived rainfall. Results indicate the existence of a regional summer monsoon circulation regime induced by strong diabatic heating over the subtropical South American highland centered at the Altiplano Plateau. Sensitivity of the results to the assimilation scheme is tested by comparing that with the National Centers for Environmental Prediction (NCEP) reanalysis and with satellite rainfall estimates. Results show general agreement between the model produced rainfall anomaly and the satellite estimates, as well as consistency between the basic circulation features in the GEOS-1 and the NCEP reanalyses. A case study of 1989-90 South American summer monsoon (SASM) reveals the following characteristics. 1) In late spring, the onset of SASM is signaled by an abrupt merging of the upper-tropospheric double westerly jets, one in the subtropics and the other in the subpolar region, into a single jet in the midlatitudes. This is followed by the establishment of a vortex to the southeast of Altiplano and occurrence of heavy precipitation over subtropical eastern Brazil. 2) During the mature phase of SASM, the heavy rainfall zone moves over the Altiplano Plateau and the southernmost Brazilian highland. The fully established SASM features are the following: (a) an enhancement of equatorial North Atlantic trade wind, which emanates from the Sahara high and crosses the equator over the South American continent; (b) a buildup of strong northwesterlies along the eastern side of the tropical Andes; and (c) development of the South Atlantic convergence zone in the southernmost position with strong convective activity. Meanwhile, the upper-tropospheric return flow emerges from an anticyclone formed over the Altiplano Plateau, crosses the equator, and sinks over northwestern Africa. 3) The withdrawal of SASM in late summer is signaled by the resplitting of the midlatitude westerly jet. At the same time, the low-level northwest monsoon how diminishes, reducing the moisture supply and leading to the termination of heavy precipitation over the subtropical highland. Results also show that the above-mentioned characteristics of SASM are clearly linked to the tropospheric temperature changes over the central South American highland. Sensible versus latent heating over the highland are bound to play an important role in the evolution of SASM. To provide further support of presence of a monsoon climate over South America, SASM is compared and contrasted to the "classic" east Asian summer monsoon (EASM). Many similar features, including evolution characteristics between the two systems, have been identified. Contrasting aspects of the SASM from the EASM are also discussed. It is pointed out that a number of monsoonal characteristics of the climate of South America, such as the seasonal reversal of the low-level wind, become apparent only when the strong annual mean wind is removed. Based on the characteristic features and their evolution, the authors conclude that a monsoon climate does exist over South America. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Zhou, JY (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 913, Greenbelt, MD 20771 USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 46 TC 357 Z9 372 U1 2 U2 32 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 MAY PY 1998 VL 11 IS 5 BP 1020 EP 1040 DI 10.1175/1520-0442(1998)011<1020:DAMCEO>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZP526 UT WOS:000073762300016 ER PT J AU Johnson, EJ Hyer, PV Culotta, PW Clark, IO AF Johnson, EJ Hyer, PV Culotta, PW Clark, IO TI Evaluation of infrared thermography as a diagnostic tool in CVD applications SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE chemical vapor deposition; infrared thermography; laser velocimetry ID HORIZONTAL MOCVD REACTORS; MASS-TRANSFER; FLOW; DYNAMICS; FLUID; HEAT AB This research is focused on the feasibility of using infrared temperature measurements on the exterior of a chemical vapor deposition (CVD) reactor to ascertain both real-time information on the operating characteristics of a CVD system and provide data which could be post-processed to provide quantitative information for research and development on CVD processes. Infrared thermography techniques were used to measure temperatures on a horizontal CVD reactor of rectangular cross section which were correlated with the internal gas flow held, as measured with the laser velocimetry (LV) techniques. For the reactor tested, thermal profiles were well correlated with the gas how held inside the reactor. Correlations are presented for nitrogen and hydrogen carrier gas flows. The infrared data were available to the operators in real time with sufficient sensitivity to the internal flow field so that small variations such as misalignment of the reactor inlet could be observed. The same data were post-processed to yield temperature measurements at known locations on the reactor surface. For the experiments described herein, temperatures associated with approximately 3.3 mm(2) areas on the reactor surface were obtained with a precision of +/-2 degrees C. These temperature measurements were well suited for monitoring a CVD production reactor, development of improved thermal boundary conditions for use in CFD models of reactors, and for verification of expected thermal conditions. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Langley Res Ctr, Lockheed Martin Engn & Sci, Hampton, VA 23681 USA. RP Johnson, EJ (reprint author), NASA, Langley Res Ctr, Lockheed Martin Engn & Sci, MS 473, Hampton, VA 23681 USA. NR 19 TC 4 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 MAY PY 1998 VL 187 IS 3-4 BP 463 EP 473 DI 10.1016/S0022-0248(97)00818-X PG 11 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA ZP043 UT WOS:000073710800021 ER PT J AU Su, CH Sha, YG AF Su, CH Sha, YG TI Segregation coefficients of impurities in selenium by zone refining SO JOURNAL OF CRYSTAL GROWTH LA English DT Letter DE selenium; zone refining; segregation coefficient AB The purification of Se by zone refining process was studied. The impurity solute levels along the length of a zone-refined Se sample were measured by spark source mass spectrographic analysis. By comparing the experimental concentration levels with theoretical curves the segregation coefficient, defined as the ratio of equilibrium concentration of a given solute in the solid to that in the liquid, k = x(s)/x, for most of the impurities in Se are found to be close to unity, i.e., between 0.85 and 1.15, with the k value for Si, Zn, Fe, Na and Al greater than 1 and that for S, Cl, Ca, P, As, Mn and Cr less than 1. This implies that a large number of passes is needed for the successful implementation of zone refining in the purification of Se. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Su, CH (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NR 10 TC 6 Z9 7 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAY PY 1998 VL 187 IS 3-4 BP 569 EP 572 DI 10.1016/S0022-0248(98)00037-2 PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA ZP043 UT WOS:000073710800032 ER PT J AU Tomasi, P Clark, T Campbell, J AF Tomasi, P Clark, T Campbell, J TI Measurement technique. Very long baseline interferometry SO JOURNAL OF GEODYNAMICS LA English DT Article ID GEODESY; SYSTEM; VLBI AB In the last decade there was a large increase in the number of VLBI antennas around the world, both for radioastronomy and geodesy. This increase is connected to the dramatic improvements in their results, in particular for geodesy. In Europe a network of six antennas, spanning from Sweden to Spain and Italy, one of the world's most densely spaced VLBI networks of fixed antenna, has been operating since 1990. This network was enlarged during 1994 with the Crimea and Ny-Alesund antennas. More are under construction in Russia. The first five years of activity have produced more than 20 purely European experiments of very good quality allowing the measurements of the horizontal velocities of Italian stations with errors at the mm yr(-1) level. The very latest results from Bologna solutions are presented. The future evolution of the technique at the stations and at the correlator is also presented. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 CNR, Ist Radioastron, I-40126 Bologna, Italy. NASA, Goddard Space Flight Ctr, Washington, DC 20546 USA. Univ Bonn, Geodat Inst, D-5300 Bonn, Germany. RP Tomasi, P (reprint author), CNR, Ist Radioastron, I-40126 Bologna, Italy. NR 14 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 0264-3707 J9 J GEODYN JI J. Geodyn. PD MAY-JUL PY 1998 VL 25 IS 3-4 BP 179 EP 193 DI 10.1016/S0264-3707(97)00034-3 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZV270 UT WOS:000074287800003 ER PT J AU Vermaat, E Degnan, JJ Dunn, PJ Noomen, R Sinclair, AT AF Vermaat, E Degnan, JJ Dunn, PJ Noomen, R Sinclair, AT TI Satellite laser ranging, status and impact for WEGENER SO JOURNAL OF GEODYNAMICS LA English DT Article AB The principles of the technique of Satellite Laser Ranging are briefly explained and the current status and outlook for further development are described. Results for the application of this technique in the WEGENER program are reviewed and strategies for continued contributions to this program from stationary and transportable laser ranging systems are presented. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Delft Univ Technol, Fac Aerosp Engn, NL-2629 HS Delft, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Royal Greenwich Observ, London, England. RP Noomen, R (reprint author), Delft Univ Technol, Fac Aerosp Engn, Kluyverweg 1, NL-2629 HS Delft, Netherlands. NR 15 TC 4 Z9 4 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0264-3707 J9 J GEODYN JI J. Geodyn. PD MAY-JUL PY 1998 VL 25 IS 3-4 BP 195 EP 212 DI 10.1016/S0264-3707(97)00036-7 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZV270 UT WOS:000074287800004 ER PT J AU Ambrosius, BAC Beutler, G Blewitt, G Neilan, RE AF Ambrosius, BAC Beutler, G Blewitt, G Neilan, RE TI The role of GPS in the WEGENER project SO JOURNAL OF GEODYNAMICS LA English DT Article AB In recent years, the Global Positioning System (GPS) has become a major tool for high precision geodesy. The precision is now better than 1 ppb. In this paper, the importance of GPS for the WEGENER project is highlighted. First, an overview of the GPS system is presented including a description of the development of its capabilities. One of the most significant developments of the past few years has been the establishment of the International GPS Service for Geodynamics (IGS). Thanks to its standards and products, the state-of-the-art in high precision GPS has been advanced considerably. Therefore, a summary of the goals and principles of IGS is presented next. This is followed by a compilation of the major GPS projects in Europe and its surrounding areas, since 1988. Most of these are not related to the WEGENER project, but it shows how much work has already been done. It also indicates the possible future role of GPS in WEGENER. Since all these projects are usually quite independent, they might benefit from the existence of a consistent, dense, accurate regional reference frame. This is exemplified by the success of IGS, which is based on an expanding global network of continuously operating permanent GPS stations. It provides a stable global reference frame, which makes; it feasible to combine the results from independent field campaigns. In certain regions of the world the coverage is not yet optimal, however, and it is planned to further densify the IG S network. Therefore, it might be interesting to establish a dense regional GPS network in the general research area of WEGENER, which extends from Greenland to mid-Asia. This idea is promoted in Section 5 of the paper, where it is proposed to create such a network under the name of WEGNET, for WEGENER GPS Network. It would seek to establish new sites where none exist yet and to include existing stations that may already have been established for other purposes. Apart from providing a regional densification of IGS and a reference frame for WEGENER, the network may also yield valuable contributions to the monitoring of tectonic motions in the area and for studies concerning ocean and atmospheric loading. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Delft Univ Technol, Fac Aerosp Engn, NL-2629 HS Delft, Netherlands. Univ Bern, Astron Inst, Berne, Switzerland. Univ Newcastle Upon Tyne, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England. NASA, Jet Prop Lab, Pasadena, CA USA. RP Ambrosius, BAC (reprint author), Delft Univ Technol, Fac Aerosp Engn, Kluyverweg 1, NL-2629 HS Delft, Netherlands. NR 23 TC 2 Z9 2 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0264-3707 J9 J GEODYN JI J. Geodyn. PD MAY-JUL PY 1998 VL 25 IS 3-4 BP 213 EP 240 DI 10.1016/S0264-3707(97)00037-9 PG 28 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZV270 UT WOS:000074287800005 ER PT J AU Plag, HP Engen, B Clark, TA Degnan, JJ Richter, B AF Plag, HP Engen, B Clark, TA Degnan, JJ Richter, B TI Post-glacial rebound and present-day three-dimensional deformations SO JOURNAL OF GEODYNAMICS LA English DT Article ID RELATIVE SEA-LEVEL; DEEP MANTLE VISCOSITY; COMPUTING 3-DIMENSIONAL DEFORMATIONS; DEGLACIAL LAND EMERGENCE; PERMANENT GPS NETWORK; CURRENT PLATE MOTIONS; ANTARCTIC ICE-SHEET; ISOSTATIC-ADJUSTMENT; VISCOELASTIC EARTH; SURFACE LOADS AB The WEGENER dagger activities related to the study of post-glacial rebound are presented together with a review of the present state-of-the-art in this study field. Postglacial rebound research is an unique tool for studying the viscoelastic behaviour of the Earth's mantle on time scales of thousands of years. The viscosity structure of the Earth's mantle determined from an inversion of observations of glacially induced deformations is a basic requirement for modelling long-term phenomena such as the convection in the Earth's mantle, and for better understanding unsolved questions sur:h as the nature of the mantle discontinuities or the vertical scale of convection. First, an introduction to the scientific background is given, and the three principal ingredients for post-glacial rebound studies, namely the ice model, the Earth model, and the observations are briefly considered. For the ice model, the uncertainties due to a tradeoff between ice model and Earth theology are outlined. The different approaches used to model the Earth and its deformations in post-glacial rebound studies are discussed emphasising the preliminary nature of the derived theologies and depth dependencies. The observations, in particular the relative sea-level changes and three-dimensional surface deformations, are described with special emphasis on observational gaps. Based on the discussion of the ingredients, an outline of the future developments in post-glacial rebound research is attempted with particular emphasis on the Earth model and the theory of deformations. For several decades extreme efforts have been made to precisely monitor the land uplift in Scandinavia. However, for the height component the existing data still are associated with large uncertainties while reliable data on the horizontal component are practically nil. The ongoing long-term (longer than ten years) spacegeodetic measurements are likely to provide the three-dimensional deformations with the spatial resolution and accuracy required in order to substantially contribute to post-glacial rebound studies. Thus, present-day three-dimensional deformations of the Earth's surface beneath and around the former ice sheets as a constraint for the mantle theology and viscosity structure will increasingly become important as they become known from space-geodetic measurements with high spatial resolution and an accuracy approaching the mm/a-level. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Univ Kiel, Inst Geophys, Kiel, Germany. Statens Kartwerk, Honefoss, Norway. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Angew Geodasie, Frankfurt, Germany. RP Plag, HP (reprint author), Univ Kiel, Inst Geophys, Gutenbergstr 76-78, Kiel, Germany. NR 149 TC 12 Z9 12 U1 2 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0264-3707 J9 J GEODYN JI J. Geodyn. PD MAY-JUL PY 1998 VL 25 IS 3-4 BP 263 EP 301 DI 10.1016/S0264-3707(97)00032-X PG 39 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZV270 UT WOS:000074287800007 ER PT J AU Luhmann, JG Russell, CT Tsyganenko, NA AF Luhmann, JG Russell, CT Tsyganenko, NA TI Disturbances in Mercury's magnetosphere: Are the mariner 10 "substorms" simply driven? SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; ELECTRON AB In addition to providing the first in situ evidence of a magnetosphere at Mercury, the first flyby by Mariner 10 inspired reports of Earth-like substorms. While the small scales at Mercury should make the substorm timescale there much shorter than it is at the Earth, these early interpretations may have too readily assumed that the substorm requirement of an energy storage and release phase occurs. Instead, its size should make Mercury's magnetosphere especially prone to disturbances that are purely "driven" by the changing external boundary conditions on the magnetosphere imposed by the solar wind. These result simply from the magnetosphere's relatively unhindered reconfiguration in response to the varying interplanetary parameters, including the IMF southward component. In this paper we demonstrate that the "disturbed" structure observed outbound from closest approach during the first Mariner 10 flyby can alternately be explained as a consequence of a typical period of rotating IMF. We use an appropriately modified IMF-dependent terrestrial magnetosphere model scaled for Mercury, together with an assumed, reasonable IMF time series, to reproduce the magnetic field signature during the disturbed outbound pass segment. This result suggests that rapid restructuring of the small magnetosphere in response to changing local interplanetary conditions may dominate the magnetospheric dynamics at Mercury. Future Mercury magnetosphere missions should be instrumented to distinguish between this driven magnetospheric dynamism and any internal Earth-like substorm processes. These results also remind us that driven reconfigurations must always be considered in studies of transients in the terrestrial magnetosphere. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20071 USA. RP Luhmann, JG (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Tsyganenko, Nikolai/J-7377-2012; OI Tsyganenko, Nikolai/0000-0002-5938-1579; Russell, Christopher/0000-0003-1639-8298 NR 17 TC 78 Z9 78 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9113 EP 9119 DI 10.1029/97JA03667 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300005 ER PT J AU Berchem, J Raeder, J Ashour-Abdalla, M Frank, LA Paterson, WR Ackerson, KL Kokubun, S Yamamoto, T Lepping, RP AF Berchem, J Raeder, J Ashour-Abdalla, M Frank, LA Paterson, WR Ackerson, KL Kokubun, S Yamamoto, T Lepping, RP TI The distant tail at 200 R-E: Comparison between Geotail observations and the results from a global magnetohydrodynamic simulation SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Review ID INTERPLANETARY MAGNETIC-FIELD; DEEP GEOMAGNETIC TAIL; SOLAR-WIND; EARTHS MAGNETOSPHERE; BOUNDARY-LAYER; NORTHWARD IMF; MAGNETOTAIL CONVECTION; PLASMA OBSERVATIONS; ALIGNED CURRENTS; ELECTRIC-FIELDS AB This paper reports a comparison between Geotail observations of plasmas and magnetic fields at 200 R-E in the Earth's magnetotail with results from a time-dependent, global magnetohydrodynamic (MHD) simulation of the interaction of the solar wind with the magnetosphere. The study focuses on observations from July 7, 1993, during which the Geotail spacecraft crossed the distant tail magnetospheric boundary several times while the interplanetary magnetic field (IMF) was predominantly northward and was marked by slow rotations of its clock angle. Simultaneous IMP 8 observations of solar wind ions and the IMF were used as driving input for the MHD simulation, and the resulting time series were compared directly with those from the Geotail spacecraft. The very good agreement found provided the basis for an investigation of the response of the distant tail associated with the clock angle of the IMF. Results from the simulation show that the stresses imposed by the draping of magnetosheath field lines and the asymmetric removal of magnetic flux tailward of the cusps altered considerably the shape of the distant tail as the solar wind discontinuities convected downstream of Earth. As a result, the cross section of the distant tail was considerably flattened along the direction perpendicular to the IMF clock angle, the direction of the neutral sheet following that of the IMF. The simulation also revealed that the combined action of magnetic reconnection and the slow rotation of the IMF clock angle led to a braiding of the distant tail's magnetic field lines along the axis of the tail, with the plane of the braid lying in the direction of the IMF. C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. RP Berchem, J (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Slichter Hall,405 Hilgard Ave, Los Angeles, CA 90095 USA. EM jberchem@igpp.ucla.edu; jraeder@igpp.ucla.edu; mabdalla@igpp.ucla.edu; frank@iowasp.physics.uiowa.edu; paterson@blanc.physics.uiowa.edu; ackerson@iowasp.physics.uiowa.edu; kokubun@stelab.nagoya-u.ac.jp; yamamoto@gtl.isas.ac.jp; rpl@leprpll.gsfc.nasa.gov RI Paterson, William/F-5684-2012 NR 104 TC 23 Z9 23 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9121 EP 9141 DI 10.1029/97JA02926 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300006 ER PT J AU Birn, J Thomsen, MF Borovsky, JE Reeves, GD McComas, DJ Belian, RD Hesse, M AF Birn, J Thomsen, MF Borovsky, JE Reeves, GD McComas, DJ Belian, RD Hesse, M TI Substorm electron injections: Geosynchronous observations and test particle simulations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID CURRENT DISRUPTION; ION; ACCELERATION; REGION AB We investigate electron acceleration and the flux increases associated with energetic electron injections on the basis of geosynchronous observations and test-electron orbits in the dynamic fields of a three-dimensional MHD simulation of neutral line formation and dipolarization in the magnetotail. This complements an earlier investigation of test protons [Birn et al., 1997b]. In the present paper we consider equatorial orbits only, using the gyrocenter drift approximation. It turns out that this approximation is valid for electrons prior to and during the flux rises observed in the near tail region of the model at all energies considered (similar to 100 eV to 1 MeV). The test particle model reproduces major observed characteristics: a fast flux rise, comparable to that of the ions, and the existence of five categories of dispersionless events, typical for observations at different local times. They consist of dispersionless injections of ions or electrons without accompanying injections of the other species, delayed electron injections and delayed ion injections, and simultaneous two-species injections. As postulated from observations [Birn et al., 1997a], these categories can be attributed to a dawn-dusk displacement of the ion and electron injection boundaries in combination with an earthward motion or expansion. The simulated electron injection region extends farther toward dusk at lower energies (say, below 40 keV) than at higher energies. This explains the existence of observed energetic ion injections that are accompanied by electron flux increases at the lower energies but not by an energetic electron injection at energies above 50 keV. The simulated distributions show that flux increases are limited in energy, as observed. The reason for this limitation and for the differences between the injection regions at different energies is the localization in the dawn-dusk direction of the tail collapse and the associated cross-tail electric field, in combination with a difference in the relative importance of E x B drift and gradient drifts at different energies. The results demonstrate that the collapsing field region earthward of the neutral line appears to be more significant than the neutral line itself for the acceleration of electrons, particularly for the initial rise of the fluxes and the injection boundary. This is similar to the result obtained for test ions [Birn et al., 1997b]. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. RP Birn, J (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87545 USA. EM jbirn@lanl.gov; mthomsen@lanl.gov; jborovsky@lanl.gov; gdreeves@lanl.gov; dmccomas@lanl.gov; rdbelian@lanl.gov; hesse@gsfc.nasa.gov RI Hesse, Michael/D-2031-2012; Reeves, Geoffrey/E-8101-2011 OI Reeves, Geoffrey/0000-0002-7985-8098 NR 22 TC 106 Z9 106 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9235 EP 9248 DI 10.1029/97JA02635 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300014 ER PT J AU Gallagher, DL Craven, PD Comfort, RH AF Gallagher, DL Craven, PD Comfort, RH TI A simple model of magnetospheric trough total density SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ELECTRON-DENSITY; PLASMA; IONOSPHERE; DYNAMICS AB Total electron densities in the magnetospheric trough are used to develop an empirical model of this region. Average trough filling from early morning through to afternoon local times is found to be 0.56+/-0.08 cm(-3)h(-1). Growing trough densities are found to change to falling trough densities at a magnetic local time (Phi(TP)) related to K-p, i.e., Phi(TP)=0.145 K-p(2)-2.63 K-p+21.86. Trough densities are found to fall in the late afternoon and through evening local times with an average rate of -0.83+/-0.15 cm(-3)h(-1). The derived model is smooth and continuous throughout all local times and may be used in a simulation or for defining a static description of typical total electron densities in the magnetospheric trough. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35807 USA. RP Gallagher, DL (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES83, Huntsville, AL 35812 USA. NR 15 TC 18 Z9 18 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9293 EP 9297 DI 10.1029/97JA03665 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300019 ER PT J AU Lanzerotti, LJ Medford, LV Sayres, DS Maclennan, CG Lepping, RP Szabo, A AF Lanzerotti, LJ Medford, LV Sayres, DS Maclennan, CG Lepping, RP Szabo, A TI Space weather: Response of large-scale geopotentials to an interplanetary magnetic cloud SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS MAGNETOSPHERE; STORMS AB The interaction of solar wind disturbances with the Earth's magnetosphere can produce disturbances, and at times complete disruptions, of technological systems on the Earth and in the space around the Earth. This brief report shows the changes induced in the large-scale geopotentials of the Earth (as provided from measurements across transoceanic cables) produced by a well-documented interplanetary magnetic cloud event. The study of such a well-measured event can be used to begin to make empirical space weather phenomena more quantitative. We show that geopotentials at low geomagnetic latitudes can be used to infer the time derivative of the near-equatorial magnetic disturbance index, Dst. At low geomagnetic latitudes, a peak geopotential of about 4 mV/km is found to correspond to a time rate of change of this index of about 50 nT/hr. Further, we show that in this event increases in the near-equatorial geopotential are linearly related to the energy input to the magnetosphere from the solar wind as given by the epsilon parameter [e.g., Akasofu, 1979]. We find that an increase in the geopotential of about 4 mV/km corresponds to an energy input of about 2.8 x 10(11) W for the event analyzed here. C1 AT&T Bell Labs, Lucent Technol, Murray Hill, NJ 07974 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Lanzerotti, LJ (reprint author), AT&T Bell Labs, Lucent Technol, 600 Mt Ave, Murray Hill, NJ 07974 USA. EM ljl@bell-labs.com NR 19 TC 4 Z9 4 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9351 EP 9356 DI 10.1029/97JA03065 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300024 ER PT J AU Kanekal, SG Baker, DN Blake, JB Klecker, B Cummings, JR Mewaldt, RA Mason, GM Mazur, JE AF Kanekal, SG Baker, DN Blake, JB Klecker, B Cummings, JR Mewaldt, RA Mason, GM Mazur, JE TI High-latitude energetic particle boundaries and the polar cap: A statistical study SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR; SUBSTORMS; TELESCOPE; SAMPEX; FIELD; MODEL AB Instruments aboard SAMPEX have been used to monitor high latitude energetic particle boundaries. These boundaries are related to the polar cap areas threaded by open magnetic flux tubes. Variations of the area poleward of the energetic particle boundary and the boundary location itself are examined statistically for possible association with the interplanetary magnetic field (IMF) B-z, VBz, and Kp. We find the average location of the energetic particle boundary under weak IMF coupling conditions (i.e, \B-z\< 2.0 nT) to be approximate to 69 degrees, (approximate to 71 degrees at noon and approximate to 67 degrees at midnight) with the data showing considerable scatter. The boundary varies with IMF \B-z\ for \B-z\> 2 nT and shifts equatorward at a rate of approximate to 0.4 degrees/nT(approximate to 0.1 degrees/nT) for negative (positive) values of B-z. Varying the time offset of the hourly B-z values from 1 to 3 hours prior to the crossing had no significant effect on the correlation. The area poleward of the boundary is well represented by an offset circle fitted to the data. A weak dependence is also seen with VBz for VBz< -1.0 mV/m with the boundary location shifting equatorward at a rate of approximate to 0.9 degrees/(mV/m). The equatorward motion of the boundary with increasing Kp is most pronounced about midnight and least pronounced at noon. In comparison with plasma boundaries the energetic particle boundaries show a lower degree of correlation with B-z, VBz, and Kp. This finding suggests a temporal and spatial decoupling between plasma and energetic particle populations. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Aerosp Corp, Los Angeles, CA 90009 USA. CALTECH, Downs Lab, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX Corp, Greenbelt, MD 20771 USA. Max Planck Inst Astrophys, D-85741 Garching, Germany. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RP Kanekal, SG (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 590, Boulder, CO 80303 USA. EM kanekal@lepsam.gsfc.nasa.gov NR 21 TC 3 Z9 3 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 MAY 1 PY 1998 VL 103 IS A5 BP 9367 EP 9372 DI 10.1029/97JA03669 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300028 ER PT J AU Makela, JS Malkki, A Koskinen, H Boehm, M Holback, B Eliasson, L AF Makela, JS Malkki, A Koskinen, H Boehm, M Holback, B Eliasson, L TI Observations of mesoscale auroral plasma cavity crossings with the Freja satellite SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LOWER-HYBRID WAVES; KILOMETRIC RADIATION; ELECTRON-DENSITY; SOURCE REGION; ACCELERATION; DEPLETIONS; ALTITUDE; ZONE AB We have used data from the Freja satellite, with an apogee of 1700 km over the auroral oval, to make a statistical analysis of mesoscale auroral plasma density cavities. Such cavities are defined to be regions in the auroral zone with size scales between discrete arcs and inverted-V events in which the plasma density abruptly drops to less than 50% of the ambient plasma density. We present occurrence distributions by magnetic activity, local time, and magnetic latitude. It is found that cavity occurrence does not depend on magnetic activity, In contrast to earlier studies, we find cavities at all local times; however, a dawn-dusk asymmetry is found in the distribution. There is likewise a weak dawn-dusk asymmetry in the latitudinal distribution. Since our data cover a full year, seasonal dependence of cavity occurrence can also be investigated. We find a small seasonal trend, with cavities found more commonly during the dark season, but the trend is not quite statistically significant. We also study several plasma depletion processes that could be responsible for cavities at this altitude. The results suggest that more than one process is compatible with tine distributions we find. C1 Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94305 USA. Swedish Inst Space Phys, Kiruna Div, S-98128 Kiruna, Sweden. Swedish Inst Space Phys, Uppsala Div, S-75591 Uppsala, Sweden. Finnish Meteorol Inst, Helsinki 00101, Finland. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Makela, JS (reprint author), Lockheed Martin Palo Alto Res Lab, Palo Alto, CA 94305 USA. RI Koskinen, Hannu/B-4971-2017 OI Koskinen, Hannu/0000-0003-3839-6461 NR 29 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9391 EP 9404 DI 10.1029/98JA00212 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300030 ER PT J AU Ashford, SM Anderson, KA Lin, RP Sommers, R Phillips, JL AF Ashford, SM Anderson, KA Lin, RP Sommers, R Phillips, JL TI Energetic solar particle dropouts detected by Ulysses at 1.63 AU: A possible encounter with the Earth's distant magnetotail SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HEAT-FLUX DROPOUTS; WIND; ELECTRONS; STREAM; TAIL AB Fast solar particles are used to trace the topology of the interplanetary magnetic field during a solar event detected by the heliosphere instrument for spectra composition and anisotropy at low energy (HISCALE) on the Ulysses spacecraft on January 2, 1991. Two sharp-edged dropouts, lasting for 10 and 25 min, were detected in the fluxes of solar ions from similar to 130 keV to >1.8 MeV and halo (heat flux) electrons from 71-461 eV, while simultaneously the flux of high-energy, 38-315 keV solar electrons and 56-78 keV ions remained constant. The halo electrons and 130 keV to >1.8 MeV solar ions are traveling with similar speeds, similar to 4 x 10(6) to 3 x 10(7)m/s, much slower than the energetic solar electrons (>10(8)m/s), and faster than the 56-78 keV ions, suggesting that the dropout field lines were first disconnected from the Sun and then reconnected, with the distance to the reconnection point and time of the reconnection such that >38 keV electrons had already repopulated the dropout field lines. At the time Ulysses was 0.63 AU from the Earth on its way to Jupiter, similar to 2 degrees above the ecliptic with a Sun-Earth-spacecraft angle of similar to 172.8 degrees, approximately where the Earth's magnetotail would be expected to be if it extended to 15,000 Earth radii. We consider the possibility that Ulysses encountered interplanetary field lines connected to the magnetotail. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Stanford Univ, Hansen Expt Phys Lab, Stanford, CA 94305 USA. RP Ashford, SM (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NR 21 TC 1 Z9 1 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9535 EP 9543 DI 10.1029/97JA02864 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300042 ER PT J AU Newbury, JA Russell, CT Phillips, JL Gary, SP AF Newbury, JA Russell, CT Phillips, JL Gary, SP TI Electron temperature in the ambient solar wind: Typical properties and a lower bound at 1 AU SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PLASMA-EXPERIMENT; MAGNETIC-FIELD; HEAT-FLUX; ULYSSES OBSERVATIONS; MACH NUMBER; SHOCK; DISTRIBUTIONS; ISEE-3; SPEED; WAVES AB Our understanding of what controls the solar wind electron temperature is far from complete. Previous studies from the Vela and IMP spacecraft have suggested that twice the proton temperature or an assumed average of similar to 150,000 K are reasonable estimations of total electron temperature at 1 AU. Eighteen months of continuous ISEE 3 solar wind data are analyzed in this paper and are found to have a mean electron temperature of 141,000 +/- 38,000 K, in good agreement with past measurements. No correlation is found between electron temperature and other solar wind parameters, including proton temperature. However, a very distinct lower bound on the electron temperature is found; this bound increases with proton temperature and is observed by both ISEE 3 and Ulysses spacecraft. The bound is also found to vary with bulk solar speed of the solar wind and with distance from the Sun. Solar wind plasma observed following stream interactions are often associated with temperatures near this bound, and enhanced electromagnetic wave activity in the 18-100 Hz range is coincident with intervals where this apparent temperature coupling is observed, suggesting the possible presence of wave-particle interactions. Possible explanations for the existence of this electron temperature bound are explored, but no definitive answer has been found at this time. C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Alamos Natl Lab, Grp NIS 1, Los Alamos, NM 87545 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA. RP Newbury, JA (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, 405 Hilgard Ave, Los Angeles, CA 90095 USA. NR 40 TC 67 Z9 67 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1998 VL 103 IS A5 BP 9553 EP 9566 DI 10.1029/98JA00067 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL412 UT WOS:000073430300044 ER PT J AU Feron, E Brenner, M Paduano, J Turevskiy, A AF Feron, E Brenner, M Paduano, J Turevskiy, A TI Time-frequency analysis for transfer function estimation and application to flutter clearance SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SYSTEM-IDENTIFICATION; ALGORITHMS AB A transfer function estimation procedure that relies on the time-frequency analysis of input and output signals is described. This method was developed in an attempt to better identify the aeroelastic behavior of NASA Dryden's F-18 systems research aircraft and to predict its flutter boundaries using in-flight experimental data. Numerical experiments on field data show that exploiting the time-frequency characteristics of the excitation inputs can bring enhanced accuracy and confidence when identifying multi-input/multi-output transfer functions. In particular, the proposed approach complements many well-established black-box identification procedures by providing an independent way to obtain transfer function estimates. A computational tool implementing this approach is now being evaluated for practical use at NASA Dryden Flight Research Center. C1 MIT, Dept Aeronaut & Astronaut, Cambridge, MA 02139 USA. NASA, Dryden Flight Res Ctr, Edwards, CA 93523 USA. RP Feron, E (reprint author), MIT, Dept Aeronaut & Astronaut, 33-217,77 Massachusetts Ave, Cambridge, MA 02139 USA. EM feron@mit.edu; gonzo@xrd.dfrc.nasa.gov; jdpaduan@mit.edu; arkasha@mit.edu NR 26 TC 17 Z9 21 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 MAY-JUN PY 1998 VL 21 IS 3 BP 375 EP 382 DI 10.2514/2.4269 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZN665 UT WOS:000073669400003 ER PT J AU Azor, R Bar-Itzhack, IY Harman, RR AF Azor, R Bar-Itzhack, IY Harman, RR TI Satellite angular rate estimation from vector measurements SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference and Exhibit CY JUL 29-31, 1996 CL SAN DIEGO, CALIFORNIA SP AIAA AB An algorithm is presented for estimating the angular rate vector of a satellite that is based on the time derivatives of vector measurements expressed in a reference and in body coordinates. The computed derivatives-ate fed into a special Kalman filter, which yields an estimate of the spacecraft angular velocity. This Biter, an extended interlaced Kalman filter (EIKF), is an extension of the interlaced Kalman filter (IKF) presented in the literature. Like the IKF, the EIKF is a suboptimal Kalman filter that, although being linear, estimates the state of a nonlinear dynamic system. It consists of two or three parallel Kalman Biters whose individual estimates are fed to one another and sie considered as known inputs by the other parallel filter(s). The nonlinear dynamics stem from-the nonlinear differential equation that describes the rotation of a three-dimensional body. Tests using simulated as well as real Rossi X-Ray Timing Explore satellite data indicate that the algorithm works satisfactorily. C1 Israel Aircraft Ind Inc, Dept Syst Engn, MBT, Div Elect,Syst & Space Technol, IL-56000 Yehud, Israel. Technion Israel Inst Technol, Fac Aerosp Engn, IL-32000 Haifa, Israel. NASA, Goddard Space Flight Ctr, Flight Mech Branch, Greenbelt, MD 20771 USA. RP Azor, R (reprint author), Israel Aircraft Ind Inc, Dept Syst Engn, MBT, Div Elect,Syst & Space Technol, IL-56000 Yehud, Israel. NR 8 TC 27 Z9 32 U1 0 U2 2 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 MAY-JUN PY 1998 VL 21 IS 3 BP 450 EP 457 DI 10.2514/2.4257 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZN665 UT WOS:000073669400013 ER PT J AU Lim, KB Cox, DE Balas, GJ Juang, JN AF Lim, KB Cox, DE Balas, GJ Juang, JN TI Validation of an experimentally derived uncertainty model SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-10, 1997 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs ID LOOP AB The discrepancies between measurement data and an analytical nominal model for a large gap magnetic suspension testbed is accounted for by an uncertainty model. The results show that uncertainty bounds corresponding to a combination of additive and diagonal input multiplicative uncertainty can be obtained directly by calculating the smallest norm of the difference between the measured and nominal model response. Use of the identified uncertainty model allowed a strong correlation between design predictions and experimental results. In addition, robust controllers based on the experimentally derived uncertainty model show significant stability and performance improvements over controllers designed with assumed ad hoc uncertainty levels. C1 NASA, Langley Res Ctr, Flight Dynam & Control Div, Guidance & Control Branch, Hampton, VA 23681 USA. Univ Minnesota, Dept Aerosp Engn & Mech, Minneapolis, MN 55455 USA. NASA, Langley Res Ctr, Struct Div, Struct Dynam Branch, Hampton, VA 23681 USA. RP Lim, KB (reprint author), NASA, Langley Res Ctr, Flight Dynam & Control Div, Guidance & Control Branch, MS 161, Hampton, VA 23681 USA. EM k.b.lim@larc.nasa.gov; d.e.cox@larc.nasa.gov; balas@jette.aem.umn.edu; j.juang@larc.nasa.gov NR 17 TC 6 Z9 6 U1 0 U2 2 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 MAY-JUN PY 1998 VL 21 IS 3 BP 485 EP 492 DI 10.2514/2.4262 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZN665 UT WOS:000073669400018 ER PT J AU Maghami, PG Sparks, DW Lim, KB AF Maghami, PG Sparks, DW Lim, KB TI Fault accommodation in control of flexible systems SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID ROOT LOCI AB New synthesis techniques for the design of fault accommodating controllers for flexible systems are developed. Three robust control design strategies, static dissipative, dynamic dissipative, and CI-synthesis, are used in the approach. The approach provides techniques for designing controllers that maximize, in some sense, the tolerance of the closed-loop system against faults in actuators and sensors, while guaranteeing performance robustness at a specified performance level, measured in terms of the proximity of the closed-loop poles to the imaginary axis (the degree of stability). For dissipative control designs, nonlinear programming is employed to synthesize the controllers, whereas in mu-synthesis, the traditional D-K iteration is used. To demonstrate the feasibility of the proposed techniques, they are applied to the control design of a structural model of a flexible laboratory test structure. C1 NASA, Langley Res Ctr, Guidance & Control Branch, Hampton, VA 23681 USA. RP Maghami, PG (reprint author), NASA, Langley Res Ctr, Guidance & Control Branch, Hampton, VA 23681 USA. NR 9 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD MAY-JUN PY 1998 VL 21 IS 3 BP 500 EP 507 DI 10.2514/2.4265 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA ZN665 UT WOS:000073669400020 ER PT J AU Molls, T Molls, F AF Molls, T Molls, F TI Space-time conservation method applied to Saint Venant equations SO JOURNAL OF HYDRAULIC ENGINEERING LA English DT Article ID APPROXIMATE RIEMANN SOLVERS; EULER EQUATIONS; FLOW; SCHEMES; SIMULATION AB A new numerical technique by Chang is described and used to solve the one-dimensional (1D) and two-dimensional (2D) Saint Venant equations. This new technique differs from traditional numerical methods (i.e., finite-difference, finite-element, finite-volume, spectral methods, etc.). Chang's method treats space and time on the same footing, so that space and time are unified-a key characteristic that distinguishes the new method from other techniques. This method is explicit, uses a staggered grid, enforces flux conservation in space and time, and does not require upwinding, flux-splitting, flux limiters, evaluation of eigenvalues, or the addition of artificial viscosity. Furthermore, the scheme is simple, easy to implement (see Appendix I), and can be extended to higher dimensions. First, the new technique, as developed by Chang, is introduced, explained, and applied to the 1D Saint Venant equations. To illustrate its effectiveness, an idealized dam-break and a hydraulic jump in a straight rectangular channel are simulated. The numerical results obtained using the new method are compared with results from other, more conventional techniques of similar complexity, experimental data, and an analytical solution. Next, Chang's scheme is extended for solution of the 2D Saint Venant (i.e., shallow water or depth-averaged) equations. The writers do not follow Chang's 2D development but instead employ Strang's method of fractional steps, which transforms the 2D problem into two 1D problems. The new 2D scheme is applied to an oblique hydraulic jump, and the results are compared with an analytical solution. C1 So Illinois Univ, Dept Civil Engn, Carbondale, IL 62901 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Molls, T (reprint author), So Illinois Univ, Dept Civil Engn, Carbondale, IL 62901 USA. NR 31 TC 30 Z9 33 U1 0 U2 2 PU ASCE-AMER SOC CIVIL ENGINEERS PI RESTON PA 1801 ALEXANDER BELL DR, RESTON, VA 20191-4400 USA SN 0733-9429 EI 1943-7900 J9 J HYDRAUL ENG JI J. Hydraul. Eng.-ASCE PD MAY PY 1998 VL 124 IS 5 BP 501 EP 508 DI 10.1061/(ASCE)0733-9429(1998)124:5(501) PG 8 WC Engineering, Civil; Engineering, Mechanical; Water Resources SC Engineering; Water Resources GA ZH949 UT WOS:000073164100007 ER PT J AU Cooper, D Pellis, NR AF Cooper, D Pellis, NR TI Suppressed PHA activation of T lymphocytes in simulated microgravity is restored by direct activation of protein kinase C SO JOURNAL OF LEUKOCYTE BIOLOGY LA English DT Article DE spaceflight; space immunology; gravitational biology; immune suppression ID CELL ANTIGEN RECEPTOR; NECROSIS FACTOR-ALPHA; 12-ORTHO-TETRADECANOYL PHORBOL-13-ACETATE; MONOCLONAL-ANTIBODIES; SIGNAL-TRANSDUCTION; DURATION MISSIONS; SURFACE MOLECULES; IL-2 PRODUCTION; IMMUNE CHANGES; PHORBOL ESTER AB Utilizing clinostatic rotating wall vessel (RWV) bioreactors that simulate aspects of microgravity, we found phytohemagglutinin (PHA) responsiveness to be almost completely diminished. Activation marker expression was significantly reduced in RWV cultures. Furthermore, cytokine secretion profiles suggested that monocytes are not as adversely affected by simulated microgravity as T cells. Reduced cell-cell and cell-substratum interactions may play a role in the loss of PHA responsiveness because placing peripheral blood mononuclear cells (PBMC) within small collagen beads did partially restore PHA responsiveness. However, activation of purified T cells with cross-linked CD2/CD28 and CD3/CD28 antibody pairs was completely suppressed in the RWV, suggesting a defect in signal transduction. Activation of purified T cells with PMA and ionomycin was unaffected by RWV culture. Furthermore, sub-mitogenic doses of PMA alone that not ionomycin alone restored PHA responsiveness of PBMC in RWV culture. Thus our data indicate that during polyclonal activation the signaling pathways upstream of PKC activation are sensitive to stimulated microgravity. C1 Univ Texas, Hlth Sci Ctr, Grad Sch Biomed Sci, Houston, TX USA. Univ Space Res Assoc, Houston, TX USA. NASA, Lyndon B Johnson Space Ctr, Biotechnol Program, Houston, TX USA. RP Pellis, NR (reprint author), NASA, Lyndon B Johnson Space Ctr, Biotechnol Cell Sci Program, 2101 NASA Rd 1-SD3, Houston, TX 77058 USA. NR 66 TC 62 Z9 66 U1 0 U2 1 PU FEDERATION AMER SOC EXP BIOL PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3998 USA SN 0741-5400 J9 J LEUKOCYTE BIOL JI J. Leukoc. Biol. PD MAY PY 1998 VL 63 IS 5 BP 550 EP 562 PG 13 WC Cell Biology; Hematology; Immunology SC Cell Biology; Hematology; Immunology GA ZK602 UT WOS:000073341600004 PM 9581798 ER PT J AU Lee, T Marotzke, J AF Lee, T Marotzke, J TI Seasonal cycles of meridional overturning and heat transport of the Indian Ocean SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID SOMALI CURRENT; DEEP CURRENTS; VARIABILITY; SOUTH; THROUGHFLOW; DYNAMICS; MONSOON; FLUXES AB A general circulation model of the Indian Ocean is fitted to monthly averaged climatological temperatures, salinities, and surface fluxes using the adjoint method. Interannual variability is minimized by penalizing the temporal drift from one seasonal cycle to another during a two-year integration. The resultant meridional overturning and heat transport display large seasonal variations, with maximum amplitudes of 18 and 22 (x 10(6) m(3) s(-1)) for the overturning and 1.8 and 1.4 (x 10(15) W) for heat transport near 10 degrees S and 10 degrees N, respectively. A dynamical decomposition of the overturning and heat transport shows that the rime-varying Ekman flow plus its barotropic compensation can explain a large parr of the seasonal variations in overturning and heat transport. The maximum variations at 10 degrees N and 10 degrees S are associated with monsoon reversal over the northern Indian Ocean and changes of the easterlies over the southern Indian Ocean. An external mode with variable topography has a moderate contribution where the Somali Current and the corresponding gyre reverse direction seasonally. Contribution from vertical shear (thermal wind and ageostrophic shear) is dominant near the southern boundary and large near the Somali Current latitudes. The dominant balance in the zonally integrated heat budget is between heat storage change and heat transport convergence except south of 15 degrees S. Optimization with seasonal forcings improves estimates of sea surface temperatures, but the annual average overturning and heat transport are very similar to previous results with annual mean forcings. The annual average heat transport consists of roughly equal contributions from time-mean and time-varying fields of meridional velocities and temperatures in the northern Indian Ocean, indicating a significant rectification to the hear transport due to the time-varying fields. The time-mean and time-varying contributions are primarily due to the overturning and horizontal gyre, respectively. Inclusion of TOPEX data enhances the seasonal cycles of the estimated overturning and heat transport in the central Indian Ocean significantly and improves the estimated equatorial zonal flows but leads to unrealistic estimates of the velocity structure near the Indonesian Throughflow region, most likely owing to the deficiencies in the lateral boundary conditions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MIT, Ctr Global Change Sci, Cambridge, MA 02139 USA. RP Lee, T (reprint author), CALTECH, Jet Prop Lab, MS 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM tlee@pacific.jpl.nasa.gov NR 34 TC 84 Z9 89 U1 0 U2 6 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 MAY PY 1998 VL 28 IS 5 BP 923 EP 943 DI 10.1175/1520-0485(1998)028<0923:SCOMOA>2.0.CO;2 PG 21 WC Oceanography SC Oceanography GA ZP532 UT WOS:000073762900011 ER PT J AU Dong, P Hong, JK Zhang, J Rogers, P Bynum, J Shah, S AF Dong, P Hong, JK Zhang, J Rogers, P Bynum, J Shah, S TI Effects of repair weld residual stresses on wide-panel specimens loaded in tension SO JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT Pressure Vessels and Piping Conference of the American-Society-of-Mechanical-Engineers CY JUL 27-31, 1997 CL ORLANDO, FLORIDA SP Amer Soc Mech Engineers AB As a part of the welding fabrication procedure development for the next generation space shuttle external talk, aluminum-lithium wide-panel specimens were used to assess the interactions between repair weld residual stresses and external loading conditions. The detailed residual stress development in the wide panel specimens with a repair weld was analyzed using an advanced finite element procedure. External tension loading effects were then incorporated in the residual stress model to study the interactions between the residual stress field and external tensile loading effects were tensile tests were also performed extract photo strain and strain-gage results. A good agreement between the finite element and experimental results was obtained The results demonstrate that the presence of high tensile residual stresses within a repair weld has a drastic impact on the stress/strain distribution in the wide panel specimens subjected to external landing. Its implications on structural integrity are discussed in light of the wide-panel results. The effects of post-welding mechanical treatment such as planishing were also examined. C1 Battelle Mem Inst, Columbus, OH 43201 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Lockheed Martin Manned Space Syst, Huntsville, AL 35812 USA. RP Dong, P (reprint author), Battelle Mem Inst, 505 King Ave, Columbus, OH 43201 USA. NR 17 TC 20 Z9 20 U1 0 U2 1 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0094-9930 J9 J PRESS VESS-T ASME JI J. Press. Vessel Technol.-Trans. ASME PD MAY PY 1998 VL 120 IS 2 BP 122 EP 128 DI 10.1115/1.2842229 PG 7 WC Engineering, Mechanical SC Engineering GA ZP651 UT WOS:000073774800003 ER PT J AU Berry, SA Bouslog, SA Brauckmann, GJ Caram, JM AF Berry, SA Bouslog, SA Brauckmann, GJ Caram, JM TI Shuttle Orbiter experimental boundary-layer transition results with isolated roughness SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The effect of isolated roughness on the windward surface boundary layer of the Shuttle Orbiter has been experimentally examined in the NASA Langley Research Center 20-Inch Mach 6 Tunnel. The size and location of isolated roughness elements (intended to simulate raised or misaligned Shuttle Orbiter Thermal Protection System tiles and protruding gap filler material) were varied to systematically examine the response of the boundary layer. Global heat transfer images of the windward surface of a 0.75 % - scale Orbiter at an angle of attack of 40 deg were obtained over a range of Reynolds numbers using phosphor thermography and were used to infer the status of the boundary layer. Computational predictions were performed to provide both laminar and turbulent heating levels for comparison to the experimental data and to provide flowfield parameters used for investigating boundary-layer transition correlations. A variety of roughness heights and locations along the windward centerline were used. The roughness-transition correlation, using the predicted edge parameters Re-theta/M-e and k/delta, was well behaved. The off-centerline results illustrate the potential for an asymmetric transition pattern to be isolated to one side of the vehicle, thereby causing the increased yawing moments experienced in flight. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. B F Goodrich Aerosp, Chula Vista, CA 91910 USA. NASA, Lyndon B Johnson Space Ctr, Aerosp Flight Mech Div, Houston, TX 77058 USA. RP Berry, SA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gasdynam Div, Hampton, VA 23681 USA. NR 16 TC 19 Z9 19 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 MAY-JUN PY 1998 VL 35 IS 3 BP 241 EP 248 DI 10.2514/2.3327 PG 8 WC Engineering, Aerospace SC Engineering GA ZT729 UT WOS:000074119200001 ER PT J AU Olynick, D AF Olynick, D TI Trajectory-based thermal protection system sizing for an X-33 winged vehicle concept SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A trajectory-based thermal protection system sizing is implemented for an X-33 winged body vehicle concept. The heat pulse is discretized at eight points along the suborbital trajectory. An aerothermal database is generated from both laminar and turbulent flow calculations. With the aerothermal database and one-dimensional thermal protection system stackups, a number of thermal protection system (TPS) sizings are generated. Three major conclusions from the analysis in this study are as follows: 1) The procedure for performing the TPS mapping works well, 2) for the TPS design, a number of traceability issues exist between the X-33 and the full-scale reusable launch vehicle, and 3) for the X-33 TPS material selection, predictions of transition to turbulence and turbulent heating are critical. C1 NASA, Ames Res Ctr, Reacting Flow Environm Branch, Moffett Field, CA 94035 USA. RP Olynick, D (reprint author), NASA, Ames Res Ctr, Reacting Flow Environm Branch, MS 230-2, Moffett Field, CA 94035 USA. NR 27 TC 6 Z9 8 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 MAY-JUN PY 1998 VL 35 IS 3 BP 249 EP 257 DI 10.2514/2.3338 PG 9 WC Engineering, Aerospace SC Engineering GA ZT729 UT WOS:000074119200002 ER PT J AU Lu, P Hanson, JM AF Lu, P Hanson, JM TI Entry guidance for the X-33 vehicle SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The entry Eight of the X-33 Advanced Technology Demonstrated is first examined by using a trajectory optimization approach. For closed-loop guidance the nominal entry trajectory is defined by a piecewise linear drag vs an energy profile. Under a nonlinear tracking control law and an onboard drag-profile updating scheme, the vehicle reaches the designated target point accurately. To further meet the stringent heading requirement at this point, a ground-track design method and the corresponding trajectory control law, which can be applied at a distance before the vehicle reaches the target point, are developed. Simulations with the X-33 vehicle and trajectory data demonstrate good performance of the guidance algorithms. C1 Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. NASA, George C Marshall Space Flight Ctr, Flight Mech Guidance Navigat & Control Syst Branc, Huntsville, AL 35812 USA. RP Lu, P (reprint author), Iowa State Univ, Dept Aerosp Engn & Engn Mech, Ames, IA 50011 USA. EM plu@iastate.edu NR 7 TC 41 Z9 49 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 MAY-JUN PY 1998 VL 35 IS 3 BP 342 EP 349 DI 10.2514/2.3332 PG 8 WC Engineering, Aerospace SC Engineering GA ZT729 UT WOS:000074119200014 ER PT J AU Patel, MR Longuski, JM Sims, JA AF Patel, MR Longuski, JM Sims, JA TI Mars free return trajectories SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID OPTIONS; MISSION; OPPORTUNITY; ORBIT; EARTH; PLUTO AB For human missions to Mars, the top priority is a safe return of the crew to Earth. In the case of an emergency, trajectories that naturally return to the Earth with no intervention are preferred. We use automated design software to compute all possible Mars free return trajectories from 1995 to 2020, given constraints on the total time of Right and on the launch energy. The resulting data file contains all of the previously known types of returns. Because Earth and Mars return to the same inertial positions every 15 years, these results are representative of all Mars free returns. Of particular interest are two families of fast free returns (having times of flight of about 1.4 years) that occur in 2000 and 2002 and repeat in 2015 and 2017. C1 Lockheed Martin Missiles & Space Co, Org K246, Sunnyvale, CA 94089 USA. Purdue Univ, Sch Aeronaut & Astronaut, W Lafayette, IN 47907 USA. CALTECH, Jet Prop Lab, Navigat & Flight Mech Sect, Pasadena, CA 91109 USA. RP Patel, MR (reprint author), Lockheed Martin Missiles & Space Co, Org K246, Bldg 150,1111 Lockheed Martin Way, Sunnyvale, CA 94089 USA. NR 27 TC 17 Z9 17 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 MAY-JUN PY 1998 VL 35 IS 3 BP 350 EP 354 DI 10.2514/2.3333 PG 5 WC Engineering, Aerospace SC Engineering GA ZT729 UT WOS:000074119200015 ER PT J AU Tejwani, GD Bircher, FE Van Dyke, DB Thurman, CC AF Tejwani, GD Bircher, FE Van Dyke, DB Thurman, CC TI Space Shuttle main engine health monitoring with exhaust plume emission spectroscopy SO JOURNAL OF SPACECRAFT AND ROCKETS 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 The spectral data from some recent engine test firings at the A-1 test stand are presented and discussed. On Jan. 25, 1996, test 901-853, a planned 754-s test on block II development engine 0523, was cut by the plume observer at approximately 553 s due to abnormal streaking and flashing in the plume. Also, increased vibration levels and degrading turbine performance were observed. The alternate turbopump high-pressure fuel turbopump experienced major turbine damage during the test. Space Shuttle main engine exhaust plume emission spectral data obtained by various instrumentation are described for test 901-853 and tests 901-851 and 901-852 in which the same four turbopumps were utilized on engine 0523. Spectral data show extreme sensitivity of this technology in detecting abnormal wear of metallic components. The optical multichannel analyzer systems observed emission lines of Ni, Cr, Fe, Co, Al, Mn, Cu, Ag, and Pd during several major plume events during test 901-853. It is the largest number of metallic elements observed at one time in the plume at the Stennis Space Center ever since the exhaust plume emission spectroscopy technology was first implemented at the A-1 test stand in 1989, Most of the emission events in test 901-853 are highly localized in the plume as evidenced by high-speed and low-speed video cameras. This nonuniformity introduces additional complications for the mass quantification algorithms. These algorithms have previously shown to be extremely accurate when the assumption of uniform distribution of plume contaminants holds. These quantification problems, somewhat unique to test 901-853 or other tests involving substantial degradation of one or more major line replaceable units such that the plume events are highly localized, are further discussed. C1 NASA, Lockheed Martin Stennis Operat, Syst Engn & Adv Technol Dept, Stennis Space Ctr, MS 39529 USA. NASA, Prop Test Directorate, Stennis Space Ctr, MS 39529 USA. RP Tejwani, GD (reprint author), NASA, Lockheed Martin Stennis Operat, Syst Engn & Adv Technol Dept, Stennis Space Ctr, MS 39529 USA. NR 20 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1998 VL 35 IS 3 BP 387 EP 394 DI 10.2514/2.3340 PG 8 WC Engineering, Aerospace SC Engineering GA ZT729 UT WOS:000074119200021 ER PT J AU Hwu, SU Panneton, RJ AF Hwu, SU Panneton, RJ TI Truss structure effects on International Space Station Global Positioning System antenna performance SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Lockheed Martin Space Miss Syst & Serv, Commun Syst Anal & Test Sect, Houston, TX 77258 USA. NASA, Johnson Space Ctr, Avion Test & Anal Branch, Houston, TX 77258 USA. RP Hwu, SU (reprint author), Lockheed Martin Space Miss Syst & Serv, Commun Syst Anal & Test Sect, 2400 NASA Rd 1, Houston, TX 77258 USA. NR 4 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1998 VL 35 IS 3 BP 409 EP 411 DI 10.2514/2.3345 PG 3 WC Engineering, Aerospace SC Engineering GA ZT729 UT WOS:000074119200026 ER PT J AU Tesch, PA Ploutz-Snyder, LL Ystrom, L Castro, MJ Dudley, GA AF Tesch, PA Ploutz-Snyder, LL Ystrom, L Castro, MJ Dudley, GA TI Skeletal muscle glycogen loss evoked by resistance exercise SO JOURNAL OF STRENGTH AND CONDITIONING RESEARCH LA English DT Article DE weight training; skeletal muscle fiber types; recruitment ID ECCENTRIC ACTIONS; FIBERS; DEPLETION; STRENGTH; METABOLISM; ACTIVATION; PATTERNS AB Biopsies were taken from the left m. vastus lateralis of 9 young men and analyzed for mixed muscle and for single fiber glycogen to infer recruitment, especially among fast-twitch subtypes, during knee extensions with loads of 30, 45, and 60% of 1-repetition maximum. The relative decline in mixed muscle glycogen was related to relative exercise load, as were the percentage of fast-twitch fibers showing glycogen loss and the relative cross-sectional area (CSA) of m. vastus lateralis occupied by type IIa or by fast-twitch fibers that showed glycogen loss (p less than or equal to 0.0478, r greater than or equal to 0.50). The relative decline in mixed m. vastus lateralis glycogen was related to the percentage of both fast twitch fibers and type IIa fibers, and the relative CSA of m. vastus lateralis occupied by type IIa fibers that showed glycogen loss (p less than or equal to 0.0436, r greater than or equal to 0.51). Type I and IIa fibers were used for all 3 bouts. Type IIab + IIb fibers showed glycogen loss for the heaviest load. The results suggest that mixed muscle glycogen loss is related to load, mainly due to fast fiber usage. It also appears that the general understanding put forth for cycling and running-that fast-twitch fiber type use depends on exercise intensity-holds for resistance exercise. Because type IIab + IIb fibers showed glycogen loss at loads of 60% of maximum, it is suggested that fast-twitch subtypes are used at lower loads than generally appreciated. C1 Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden. Ohio Univ, Dept Biol Sci, Athens, OH 45701 USA. NASA, Kennedy Space Ctr, FL 32899 USA. Univ Georgia, Dept Exercise Sci, Athens, GA 30602 USA. RP Tesch, PA (reprint author), Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden. NR 33 TC 39 Z9 40 U1 2 U2 4 PU HUMAN KINETICS PUBL INC PI CHAMPAIGN PA 1607 N MARKET ST, CHAMPAIGN, IL 61820-2200 USA SN 1064-8011 J9 J STRENGTH COND RES JI J. Strength Cond. Res. PD MAY PY 1998 VL 12 IS 2 BP 67 EP 73 PG 7 WC Sport Sciences SC Sport Sciences GA ZN092 UT WOS:000073608900001 ER PT J AU Seale, MD Smith, BT Prosser, WH AF Seale, MD Smith, BT Prosser, WH TI Lamb wave assessment of fatigue and thermal damage in composites SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID STIFFNESS REDUCTION; TRANSVERSE CRACKING; PREDICTION; PLATES AB Among the various techniques available, ultrasonic Lamb waves offer a convenient method of evaluating composite materials. Since the Lamb wave velocity depends on the elastic properties of a structure, an effective tool exists to monitor damage in composites by measuring the velocity of these waves. Lamb wave measurements can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper describes two studies which monitor fatigue damage and two studies which monitor thermal damage in composites using Lamb waves. In the fatigue studies, the Lamb wave velocity is compared to modulus measurements obtained using strain gage measurements in the first experiment and the velocity is monitored along with the crack density in the second. In the thermal damage studies, one examines samples which were exposed to varying temperatures for a three minute duration and the second includes rapid thermal damage in composites by intense laser beams. In all studies, the Lamb wave velocity is demonstrated to be an excellent method to monitor damage in composites. (C) 1998 Acoustical Society of America. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. Norfolk Acad, Norfolk, VA 23502 USA. RP Seale, MD (reprint author), NASA, Langley Res Ctr, Mail Stop 231, Hampton, VA 23681 USA. NR 39 TC 81 Z9 81 U1 1 U2 3 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 MAY PY 1998 VL 103 IS 5 BP 2416 EP 2424 DI 10.1121/1.422761 PN 1 PG 9 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA ZM942 UT WOS:000073591800019 ER PT J AU Smith, EA Lamm, JE Adler, R Alishouse, J Aonashi, K Barrett, E Bauer, P Berg, W Chang, A Ferraro, R Ferriday, J Goodman, S Grody, N Kidd, C Kniveton, D Kummerow, C Liu, G Marzano, F Mugnai, A Olson, W Petty, G Shibata, A Spencer, R Wentz, F Wilheit, T Zipser, E AF Smith, EA Lamm, JE Adler, R Alishouse, J Aonashi, K Barrett, E Bauer, P Berg, W Chang, A Ferraro, R Ferriday, J Goodman, S Grody, N Kidd, C Kniveton, D Kummerow, C Liu, G Marzano, F Mugnai, A Olson, W Petty, G Shibata, A Spencer, R Wentz, F Wilheit, T Zipser, E TI Results of WetNet PIP-2 project SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Review ID SENSOR MICROWAVE IMAGER; PROBABILITY-DISTRIBUTION FUNCTIONS; PHYSICAL PRECIPITATION RETRIEVAL; VERTICAL STRUCTURE INFORMATION; CLOUD-RADIATION MODEL; OCEAN RAIN RATE; SATELLITE MEASUREMENTS; LIQUID WATER; SNOW COVER; RADIOMETRIC MEASUREMENTS AB The second WetNet Precipitation Intercomparison Project (PIP-2) evaluates the performance of 20 satellite precipitation retrieval algorithms, implemented for application with Special Sensor Microwave/Imager (SSM/I) passive microwave (PMW) measurements and run for a set of rainfall case studies at full resolution-instantaneous space-timescales, The cases are drawn from over the globe during all seasons, for a period of 7 yr, over a 60 degrees N-17 degrees S latitude range. Ground-based data were used for the intercomparisons, principally based on radar measurements but also including rain gauge measurements. The goals of PIP-2 are I) to improve performance and accuracy of different SSM/I algorithms at full resolution-instantaneous scales by seeking a better understanding of the relationship between microphysical signatures in the PMW measurements and physical laws employed in the algorithms; 2) to evaluate the pros and cons of individual algorithms and their subsystems in order to seek optimal "front-end" combined algorithms; and 3) to demonstrate that PMW algorithms generate acceptable instantaneous rain estimates. It is found that the bias uncertainty of many current PMW algorithms is on the order of +/-30%. This level is below that of the radar and rain gauge data specially collected for the study, so that it is nor possible to objectively select a best algorithm based on the ground data validation approach. By decomposing the intercomparisons into effects due to rain detection (screening) and effects due to brightness temperature-rain rate conversion, differences among the algorithms are partitioned by rain area and rain intensity: For ocean, the screening differences mainly affect the light rain rates, which do not contribute significantly to area-averaged rain rates. The major sources of differences in mean rain rates between individual algorithms stem from differences in how intense rain rates are calculated and the maximum rain rate allowed by a given algorithm. The general method of solution is not necessarily the determining factor in creating systematic rain-rate differences among groups of algorithms, as we find that the severity of the screen is the dominant factor in producing systematic group differences among land algorithms, while the input channel selection is the dominant factor in producing systematic group differences among ocean algorithms. The significance of these issues are examined through what is called "fan map" analysis. The paper concludes with a discussion on the role of intercomparison projects in seeking improvements to algorithms, and a suggestion on why moving beyond the "ground truth" validation approach by use of a calibration-quality forward model would be a step forward in seeking objective evaluation of individual algorithm performance and optimal algorithm design. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, NESDIS, Camp Springs, MD USA. Meteorol Res Inst, Tsukuba, Ibaraki 305, Japan. Univ Bristol, Dept Geog, Bristol BS8 1TH, Avon, England. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. Univ Colorado, Dept Aerosp Engn Sci, Boulder, CO 80309 USA. Univ Rome, Dept Elect Engn, Rome, Italy. CNR, Ist Fis Atmosfera, I-00044 Frascati, Italy. Caleum Res Corp, Silver Spring, MD USA. Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN 47907 USA. Remote Sensing Syst, Santa Rosa, CA USA. Texas A&M Univ, Dept Meteorol, College Stn, TX 77843 USA. RP Smith, EA (reprint author), Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. EM esmith@metsat.met.fsu.edu RI Zhang, YIng/F-5751-2011; Liu, Guosheng/D-3479-2011; Petty, Grant/E-3118-2012; Wilheit, Thomas/G-9438-2012; Kidd, Christopher/H-9910-2014; Ferraro, Ralph/F-5587-2010; PMM, JAXA/K-8537-2016 OI Liu, Guosheng/0000-0001-7899-6125; Ferraro, Ralph/0000-0002-8393-7135; NR 124 TC 131 Z9 134 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 MAY 1 PY 1998 VL 55 IS 9 BP 1483 EP 1536 DI 10.1175/1520-0469(1998)055<1483:ROWPP>2.0.CO;2 PG 54 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900002 ER PT J AU Berg, W Olson, W Ferraro, R Goodman, SJ LaFontaine, FJ AF Berg, W Olson, W Ferraro, R Goodman, SJ LaFontaine, FJ TI An assessment of the first- and second-generation navy operational precipitation retrieval algorithms SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SSM/I; GHZ AB Rainfall estimates produced from the Special Sensor Microwave/Imager (SSM/I) data have been utilized operationally by the United States Navy since the launch of the first SSM/I sensor in June of 1987. The navy initially contracted Hughes Aircraft Company to develop a rainfall-retrieval algorithm prior to the launch of SSM/I. This first-generation operational navy rainfall retrieval algorithm, referred to as the D-Matrix algorithm, was used until the development of the second-generation algorithm by the SSM/I Calibration/Validation team, which has subsequently been replaced by a third-generation algorithm developed by the National Oceanic and Atmospheric Administration/National Environmental Satellite, Data and Information System. Results from both the D-Matrix and Cal/Val algorithms have been included in a total of five algorithm intercomparison projects conducted through the Global Precipitation Climatology Project and WetNet. A comprehensive summary of both quantitative and qualitative results from these intercomparisons is given detailing many of the strengths and weaknesses of the algorithms. Based on these results, the D-Matrix algorithm was found to produce excessively large estimates over land and to poorly represent the spatial structure of rainfall systems, especially at higher latitudes. The Cal/Val algorithm produces more realistic structure within storm systems but appears to overestimate the region of precipitation for many systems and significantly underestimates regions of intense rainfall. While the Cal/Val algorithm appears to provide better instantaneous rainfall estimates in the Tropics, the D-Matrix algorithm provides reasonable time-averaged results for monthly or longer periods. C1 Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Caelum Res Corp, Silver Spring, MD USA. NOAA, Satellite Res Lab, Camp Springs, MD USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Hughes STX, Huntsville, AL USA. RP Berg, W (reprint author), Univ Colorado, Cooperat Inst Res Environm Sci, Campus Box 449, Boulder, CO 80309 USA. RI Ferraro, Ralph/F-5587-2010 OI Ferraro, Ralph/0000-0002-8393-7135 NR 23 TC 14 Z9 16 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 MAY 1 PY 1998 VL 55 IS 9 BP 1558 EP 1575 DI 10.1175/1520-0469(1998)055<1558:AAOTFA>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900004 ER PT J AU Kidd, C Kniveton, D Barrett, EC AF Kidd, C Kniveton, D Barrett, EC TI The advantages and disadvantages of statistically derived-empirically calibrated passive microwave algorithms for rainfall estimation SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Review ID PHYSICAL PRECIPITATION RETRIEVAL; CLOUD-RADIATION MODEL; SATELLITE MEASUREMENTS; FOUNDATIONS AB This paper reviews the basis of passive microwave algorithms that derive rainfall rates directly from relationships between brightness temperatures and rainfall rates established by statistical relationships and empirical calibration. The performance of these algorithms and their present and future roles are assessed in comparison with the increasing number of modeling techniques used for passive microwave rainfall retrievals. C1 Univ Bristol, Ctr Remote Sensing, Bristol, Avon, England. RP Kidd, C (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 912-0, Greenbelt, MD 20771 USA. RI Zhang, YIng/F-5751-2011; Kidd, Christopher/H-9910-2014 NR 25 TC 16 Z9 16 U1 1 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 MAY 1 PY 1998 VL 55 IS 9 BP 1576 EP 1582 DI 10.1175/1520-0469(1998)055<1576:TAADOS>2.0.CO;2 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900005 ER PT J AU Ferraro, RR Smith, EA Berg, W Huffman, GJ AF Ferraro, RR Smith, EA Berg, W Huffman, GJ TI A screening methodology for passive microwave precipitation retrieval algorithms SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GLOBAL OCEANIC PRECIPITATION; RAIN-RATE; PHYSICAL RETRIEVALS; SSM/I MEASUREMENTS; SNOW COVER; IMAGER; CLASSIFICATION; IDENTIFICATION; PARAMETERS AB The success of any passive microwave precipitation retrieval algorithm relies on the proper identification of rain areas and the elimination of surface areas that produce a signature similar to that of precipitation. A discussion on the impact of and on methods that identify areas of rain, snow cover, deserts, and semiarid conditions over land, and rain, sea ice, strong surface winds, and clear, calm conditions over ocean, are presented. Additional artifacts caused by coastlines and Special Sensor Microwave/Imager data errors are also discussed, and methods to alleviate their impact are presented. The strengths and weaknesses of the "screening" techniques are examined through application on various case studies used in the WetNet PIP-2. Finally, a methodology to develop a set of screens for use as a common rainfall indicator for the intercomparison of the wide variety of algorithms submitted to PIP-2 is described. C1 NOAA, NESDIS, Off Res & Applicat, Camp Springs, MD 20746 USA. Florida State Univ, Tallahassee, FL 32306 USA. NOAA, CIRES, Boulder, CO USA. NASA, Goddard Space Flight Ctr, SSAI, Greenbelt, MD 20771 USA. RP Ferraro, RR (reprint author), NOAA, NESDIS, Off Res & Applicat, 5200 Auth Rd,Room 601Q, Camp Springs, MD 20746 USA. RI Huffman, George/F-4494-2014; Ferraro, Ralph/F-5587-2010 OI Huffman, George/0000-0003-3858-8308; Ferraro, Ralph/0000-0002-8393-7135 NR 41 TC 116 Z9 119 U1 0 U2 10 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 MAY 1 PY 1998 VL 55 IS 9 BP 1583 EP 1600 DI 10.1175/1520-0469(1998)055<1583:ASMFPM>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900006 ER PT J AU Ritchie, AA Smith, MR Goodman, HM Schudalla, RL Conway, DK LaFontaine, FJ Moss, D Motta, B AF Ritchie, AA Smith, MR Goodman, HM Schudalla, RL Conway, DK LaFontaine, FJ Moss, D Motta, B TI Critical analyses of data differences between FNMOC and AFGWC spawned SSM/I datasets SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MICROWAVE BRIGHTNESS TEMPERATURES AB Antenna temperatures and the corresponding geolocation data from the five sources of the Special Sensor Microwave/Imager data from the Defense Meteorological Satellite Program F11 satellite have been characterized. Data from the Fleet Numerical Meteorology and Oceanography Center (FNMOC) have been compared with data from other sources to define and document the differences resulting from different processing systems. While all sources used similar methods to calculate antenna temperatures, different calibration averaging techniques and other processing methods yielded temperature differences. Analyses of the geolocation data identified perturbations in the FNMOC and National Environmental Satellite, Data and Information Service data. The effects of the temperature differences were examined by generating rain rates using the Goddard Scattering Algorithm. Differences in the geophysical precipitation products are directly attributable to antenna temperature differences. C1 GHCC, Hughes STX, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, GHCC, Huntsville, AL 35806 USA. Univ Alabama, GHCC, Huntsville, AL 35899 USA. RP Ritchie, AA (reprint author), GHCC, Hughes STX, Res Pk W,977 Explorer Blvd, Huntsville, AL 35806 USA. EM adrian.ritchie@msfc.nasa.gov RI Motta, Brian/D-7521-2015 OI Motta, Brian/0000-0002-9048-6432 NR 12 TC 4 Z9 4 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 MAY 1 PY 1998 VL 55 IS 9 BP 1601 EP 1612 DI 10.1175/1520-0469(1998)055<1601:CAODDB>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900007 ER PT J AU Wentz, FJ Spencer, RW AF Wentz, FJ Spencer, RW TI SSM/I rain retrievals within a unified all-weather ocean algorithm SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SATELLITE; RATES; INDEXES AB A new method for the physical retrieval of rain rates from satellite microwave radiometers is presented. The method is part of a unified ocean parameter retrieval algorithm that is based on the fundamental principles of radiative transfer. The algorithm simultaneously finds near-surface wind speed W, columnar water vapor V, columnar cloud liquid water L, rain rate R, and effective radiating temperature T-v for the upwelling radiation. Comparisons with radiosondes demonstrate that the algorithm is able to retrieve water vapor when rain is present: For rain rates from 1 to 15 mm h(-1), the rms difference between the retrieved water vapor and the radiosonde value is 5 mm. A novel feature of the rain retrieval method is a beamfilling correction that is based upon the ratio of the retrieved liquid water absorption coefficients at 37 and 19 GHz. This spectral ratio decreases by about 40% when heavy and light rain coexist within the SSM/I footprint as compared to the case of uniform rain. This correction increases the rain rate when the spectral ratio is small. However, even with this beamfilling correction, tropical rainfall is still unrealistically low when the freezing lever in the Tropics (similar to 5 km) is used to specify the rain layer thickness. Realism is restored by reducing the assumed tropical rain-layer thickness to 3 km. This adjustment is probably compensating for two processes: 1) the existence of warm rain for which the rain layer does not extend to the freezing level and 2) very heavy rain for which the 19-GHz channels saturate. Global rain rates are produced for the 1991-94 period from two SSM/Is. The authors find that approximately 6% of the SSM/I observations detect measurable rain rates (R > 0.2 mm h(-1)). The global rain maps show features that are, in general, similar to those reported in previously published rain climatologies. However, some differences that seem to be related to nonprecipitating cloud water are apparent. C1 Remote Sensing Syst, Santa Rosa, CA 95404 USA. NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. RP Wentz, FJ (reprint author), Remote Sensing Syst, Suite 220,1101 Coll Ave, Santa Rosa, CA 95404 USA. NR 19 TC 196 Z9 201 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 MAY 1 PY 1998 VL 55 IS 9 BP 1613 EP 1627 DI 10.1175/1520-0469(1998)055<1613:SIRRWA>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900008 ER PT J AU Spencer, RW LaFontaine, FJ DeFelice, T Wentz, FJ AF Spencer, RW LaFontaine, FJ DeFelice, T Wentz, FJ TI Tropical oceanic precipitation changes after the 1991 Pinatubo eruption SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID GLOBAL CLIMATE; PACIFIC; MODELS; SCHEME; ICE AB Passive microwave channels like those flown on the Special Sensor Microwave Imager (SSM/I) contain two primary types of information on oceanic precipitation: condensate below the freezing level and precipitation-size condensate above the freezing level. The authors explore the question of whether these two separate pieces of information might contain insight into climate processes during a perturbation in the climate system. In particular, the relative fluctuations of rain and ice signals could be related to precipitation efficiency, an important determinant of the equilibrium climate, and thus a potential feedback mechanism in climate change. As an example of this potential application, SSM/I-derived liquid and frozen precipitation signals are used to infer changes in tropical oceanic precipitation characteristics during the cool period following the 1991 eruption of Mount Pinatubo. The need for an assessment of the temperature sensitivity of precipitation-retrieval algorithms is also discussed. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Hughes STX, Global Hydrol & Climate Ctr, Huntsville, AL USA. Univ Wisconsin, Dept Meteorol, Milwaukee, WI 53201 USA. Remote Sensing Syst, Santa Rosa, CA USA. RP Spencer, RW (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. NR 20 TC 7 Z9 7 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 MAY 1 PY 1998 VL 55 IS 9 BP 1707 EP 1713 DI 10.1175/1520-0469(1998)055<1707:TOPCAT>2.0.CO;2 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZM952 UT WOS:000073592900013 ER PT J AU Worth, DB Kaufman, DS AF Worth, DB Kaufman, DS TI Validation of force-limited vibration testing SO JOURNAL OF THE IEST LA English DT Article; Proceedings Paper CT 17th Aerospace Testing Seminar CY OCT 14-16, 1997 CL MANHATTAN BEACH, CALIFORNIA DE vibration; force limiting; sounding rocket; force gages; telemetry AB A sounding rocket experiment was performed on May 8, 1997, that contributed to the process of validating force-limited random vibration testing. A simple structure was flown and instrumented with accelerometers and force gages. The results of the data acquired during the flight tests are compared with predicted results which were performed prior to the flight tests. The data have helped to validate the force-limited testing approach for random vibration testing. Additionally, the data will be used for others to develop improved analytical techniques for force-limited vibration testing. This flight is the first in a series of at least three that will be performed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Orbital Sci Corp, Greenbelt, MD USA. RP Worth, DB (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 7 TC 2 Z9 2 U1 2 U2 2 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 MAY-JUN PY 1998 VL 41 IS 3 BP 17 EP 23 PG 7 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA ZV265 UT WOS:000074287300001 ER PT J AU Song, QW Wang, XM Birge, RR Downie, JD Timucin, D Gary, C AF Song, QW Wang, XM Birge, RR Downie, JD Timucin, D Gary, C TI Propagation of a Gaussian beam in a bacteriorhodopsin film SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID CHEMICALLY ENHANCED BACTERIORHODOPSIN; REFRACTIVE-INDEX; ABSORPTION AB Gaussian-beam propagation in the bio-optical material bacteriorhodopsin is studied with the consideration of the material's intensity-dependent absorption and refractive-index modulation. The beam-focusing size, focusing position, intensity change in the material, and the dependence of these factors on the incident-beam parameters are simulated. (C) 1998 Optical Society of America [S0740-3224(98)01405-2]. C1 Syracuse Univ, Dept Elect Engn & Comp Sci, Syracuse, NY 13244 USA. Syracuse Univ, WM Keck Ctr Mol Elect, Syracuse, NY 13244 USA. Syracuse Univ, Dept Chem, Syracuse, NY 13244 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Song, QW (reprint author), Syracuse Univ, Dept Elect Engn & Comp Sci, 121 Link Hall, Syracuse, NY 13244 USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD MAY PY 1998 VL 15 IS 5 BP 1602 EP 1609 DI 10.1364/JOSAB.15.001602 PG 8 WC Optics SC Optics GA ZM955 UT WOS:000073593200023 ER PT J AU Minnetyan, L Chamis, CC Gotsis, PK AF Minnetyan, L Chamis, CC Gotsis, PK TI Damage progression in bolted composites SO JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS LA English DT Article DE bolted joints; composites; composite structures; damage; damage tolerance; degradation; durability; fracture; laminates; simulation; structural degradation ID FRACTURE AB Structural durability, damage tolerance, and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions. C1 Clarkson Univ, Dept Civil & Environm Engn, Potsdam, NY 13699 USA. NASA, Lewis Res Ctr, Div Struct, Cleveland, OH 44135 USA. RP Minnetyan, L (reprint author), Clarkson Univ, Dept Civil & Environm Engn, Potsdam, NY 13699 USA. NR 10 TC 3 Z9 3 U1 1 U2 1 PU TECHNOMIC PUBL CO INC PI LANCASTER PA 851 NEW HOLLAND AVE, BOX 3535, LANCASTER, PA 17604 USA SN 0892-7057 J9 J THERMOPLAST COMPOS JI J. Thermoplast. Compos. Mater. PD MAY PY 1998 VL 11 IS 3 BP 231 EP 248 PG 18 WC Materials Science, Composites SC Materials Science GA ZP260 UT WOS:000073734500003 ER PT J AU Yamada, T AF Yamada, T TI Doping scheme of semiconducting atomic chains SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article; Proceedings Paper CT 44th National Symposium of the American-Vacuum-Society CY OCT 20-24, 1997 CL SAN JOSE, CALIFORNIA SP Amer Vacuum Soc ID SCANNING TUNNELING MICROSCOPE; RESISTANCE; ELECTRONS; MOBILITY; SURFACE; STATES; WIRES AB Atomic chains, precise structures of atomic scale created on an atomically regulated Substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are accepters. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or accepters is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br (p-type) and Cs-doped (n type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified. (C) 1998 American Vacuum Society. C1 NASA, Ames Res Ctr, MRJ, Moffett Field, CA 94035 USA. RP Yamada, T (reprint author), NASA, Ames Res Ctr, MRJ, M-S T27A-1, Moffett Field, CA 94035 USA. EM yamada@nas.nasa.gov RI Yamada, Toshishige/E-7834-2012 OI Yamada, Toshishige/0000-0001-7145-9212 NR 33 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 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD MAY-JUN PY 1998 VL 16 IS 3 BP 1403 EP 1408 DI 10.1116/1.581158 PN 2 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA ZT992 UT WOS:000074150500001 ER PT J AU Grunthaner, FJ Bicknell-Tassius, R Deelman, P Grunthaner, PJ Bryson, C Snyder, E Giuliani, JL Apruzese, JP Kepple, P AF Grunthaner, FJ Bicknell-Tassius, R Deelman, P Grunthaner, PJ Bryson, C Snyder, E Giuliani, JL Apruzese, JP Kepple, P TI Ultrahigh vacuum arcjet nitrogen source for selected energy epitaxy of group III nitrides by molecular beam epitaxy SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article; Proceedings Paper CT 44th National Symposium of the American-Vacuum-Society CY OCT 20-24, 1997 CL SAN JOSE, CALIFORNIA SP Amer Vacuum Soc ID PLASMA SOURCE; GROWTH; FILMS; GAN AB The key technical challenge in the molecular beam epitaxial (MBE) growth of group III nitrides is the lack of a suitable source of incorporatable nitrogen. In contrast with the growth of the other III-V compound semiconductors by MBE, direct reaction of N-2 with excess group III metal is not feasible, because of the high bond strength of dinitrogen. An incorporatable MBE nitrogen source must excite N-2 forming a beam of atomic nitrogen, active nitrogen (N-2(*)), or nitrogen ions. rf and electron cyclotron resonance sources use electron impact excitation to obtain atomic nitrogen and in the process generate a wide variety of excited ions and neutrals. Experiments have shown that ionic species in the beam degrade the morphology of the epitaxial layer and generate electrically active defects. Recent theoretical studies have predicted that ground state atomic nitrogen will successfully incorporate into the growing GaN surface, while atomic nitrogen in either of the excited doublet states will lead to etching. In this article, we report on the development of an ultrahigh vacuum-compatible arcjet source which uses an electric are to thermally dissociate N-2. The thermal excitation mechanism offers selective excitation of nitrogen and control of kinetic energy of the active species. This source has been fabricated from refractory materials and uses two stages of differential pumping to minimize the pressure in the growth chamber. The arcjet has been reliably operated at power levels of 10-300 W, with no visible degradation of the thoriated tungsten cathode after 300 h. No metal contaminant lines can be found in the optical emission spectrum. Using an Ar-seeded beam for calibration of the optical spectrum, we find that the arcjet plasma is far from local thermodynamic equilibrium, and show that the fraction of atomic nitrogen in the beam ranges from 0.3% to 9%. This corresponds to a flux of 0.1-4 monolayers per second at the MBE sample location. With an articulated Langmuir probe sampling the beam at the MBE growth position, we find a positive ion flux of less than 4X10(-9) A/cm(2), a maximum ion kinetic energy of 3.5 eV, a median electron energy of 1 eV, and a maximum electron energy of less than 4 eV. With increasing arcjet power, the ion and electron fluxes increase and the ion energy distribution shifts to lower energies. No change in the electron spectrum is observed. Quadrupole mass spectra of the ion flux measured on the arcjet axis show that the N+/N-2(+) ratio has a maximum at an arcjet power of about 35 W. (C) 1998 American Vacuum Society. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Surface Interface Inc, Sunnyvale, CA 94086 USA. USN, Res Lab, Div Plasma Phys, Washington, DC 20375 USA. RP Grunthaner, FJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM Frank.J.Grunthaner@JPL.NASA.gov NR 17 TC 14 Z9 14 U1 1 U2 6 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 MAY-JUN PY 1998 VL 16 IS 3 BP 1615 EP 1620 DI 10.1116/1.581129 PN 2 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA ZT992 UT WOS:000074150500040 ER PT J AU Nicholas, SC Doxey-Gasway, DD Paloski, WH AF Nicholas, SC Doxey-Gasway, DD Paloski, WH TI A link-segment model of upright human posture for analysis of head-trunk coordination SO JOURNAL OF VESTIBULAR RESEARCH-EQUILIBRIUM & ORIENTATION LA English DT Article DE posture control; vestibular; biomechanical model; sensory-motor ID VESTIBULAR DEFICITS; ALTERED SUPPORT; DYNAMICS; BALANCE; POSTUROGRAPHY; ORGANIZATION; ADAPTATION; MOVEMENTS; SYSTEM AB Sensory-motor control of upright human posture may be organized in a top-down fashion such that certain head-trunk coordination strategies are employed to optimize visual and/or vestibular sensory inputs. Previous quantitative models of the biomechanics of human posture control have examined the simple case of ankle sway strategy, in which an inverted pendulum model is used, and the somewhat more complicated case of hip sway strategy, in which multisegment, articulated models are used. While these models can be used to quantify the gross dynamics of posture control, they are not sufficiently detailed to analyze head-trunk coordination strategies that may be crucial to understanding its underlying mechanisms. In this paper, we present a biomechanical model of upright human posture that extends an existing four mass, sagittal plane, link-segment model to a five mass model including an independent head link. The new model was developed to analyze segmental body movements during dynamic posturography experiments in order to study head-trunk coordination strategies and their influence on sensory inputs to balance control. It was designed specifically to analyze data collected on the EquiTest(TM) (NeuroCom International, Clackamas, OR) computerized dynamic posturography system, where the task of maintaining postural equilibrium may be challenged under conditions in which the visual surround, support surface, or both are in motion. The performance of the model was tested by comparing its estimated ground reaction forces to those measured directly by support surface force transducers, We conclude that this model will be a valuable analytical tool in the search for mechanisms of balance control. Published by Elsevier Science Inc. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Krug Life Sci, Neurosci Lab, Houston, TX USA. RP Paloski, WH (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. EM paloski@sdmail.jsc.nasa.gov NR 38 TC 17 Z9 17 U1 3 U2 5 PU IOS PRESS PI AMSTERDAM PA NIEUWE HEMWEG 6B, 1013 BG AMSTERDAM, NETHERLANDS SN 0957-4271 EI 1878-6464 J9 J VESTIBUL RES-EQUIL JI J. Vestib. Res.-Equilib. Orientat. PD MAY-JUN PY 1998 VL 8 IS 3 BP 187 EP 200 PG 14 WC Neurosciences; Otorhinolaryngology SC Neurosciences & Neurology; Otorhinolaryngology GA ZR803 UT WOS:000074015400001 PM 9626646 ER PT J AU Brindley, WJ AF Brindley, WJ TI 1997 Thermal Barrier Coatings Workshop, 19-21 May, 1997, Cincinnati, OH, USA - Preface SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Editorial Material C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Brindley, WJ (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD MAY 1 PY 1998 VL 245 IS 2 BP III EP III PG 1 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZP160 UT WOS:000073723000001 ER PT J AU Siegel, R Spuckler, CM AF Siegel, R Spuckler, CM TI Analysis of thermal radiation effects on temperatures in turbine engine thermal barrier coatings SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT 1997 Thermal Barrier Coatings Workshop CY MAY 19-21, 1997 CL CINCINNATI, OHIO SP USAF, Off Sci Res, USAF, Mat Directorate, US DOE, DARPA, Natl Aeronaut & Space Adm, Natl Inst Stand & Technol, USN, Off Naval Res DE thermal barrier coatings; thermal radiation effects; zirconia ID REFRACTIVE-INDEX; CUBIC ZIRCONIA; CONDUCTIVITY; CERAMICS; YTTRIA AB Thermal barrier coatings on combustor liners and on turbine vanes and rotating blades are important for reducing metal temperatures in current and advanced turbine engines. Some coating materials such as zirconia are partially transparent to thermal radiation, and radiation within a coating will increase as temperatures are raised for higher efficiency engines. Hence, it is necessary to determine if radiation effects in a coating are a design consideration. For this purpose. the engine the mal environment is first summarized with regard to factors affecting radiative heat transfer. Radiative and thermal properties of zirconia are then considered, and methods of radiative analysis are briefly discussed. Typical temperature distributions and heat fluxes are given from the analysis of zirconia thermal barrier coatings on vanes and rotating blades, and on a combustor liner where the coating surface is expected to be covered with soot. The effects of various thermal conditions and heat transfer parameters are examined to indicate when radiation effects might be significant within a coating in a turbine engine. The largest effects were found in the combustor where coatings are subjected to large incident radiation. For coatings on turbine blades away from the combustor, and hence without large incident radiation, effects of radiation were found to be very small. (C) 1998 Elsevier Science S.A. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Siegel, R (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 21 TC 70 Z9 73 U1 2 U2 27 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 MAY 1 PY 1998 VL 245 IS 2 BP 150 EP 159 DI 10.1016/S0921-5093(97)00845-9 PG 10 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZP160 UT WOS:000073723000003 ER PT J AU Freborg, AM Ferguson, BL Brindley, WJ Petrus, GJ AF Freborg, AM Ferguson, BL Brindley, WJ Petrus, GJ TI Modeling oxidation induced stresses in thermal barrier coatings SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT 1997 Thermal Barrier Coatings Workshop CY MAY 19-21, 1997 CL CINCINNATI, OHIO SP USAF, Off Sci Res, USAF, Mat Directorate, US DOE, DARPA, Natl Aeronaut & Space Adm, Natl Inst Stand & Technol, USN, Off Naval Res DE finite element modeling; oxidation induced stress; thermal barrier coating ID BEHAVIOR AB Oxidation of the bond coat of a thermal barrier coating (TBC) is an important contributing factor to spallation of the ceramic top coat during service. However, the mechanisms by which oxidation facilitates TBC failure are poorly understood, It is also unclear how oxidation may interact with other potential degradation mechanisms. A finite element model was developed to evaluate stresses induced by thermal cycling of a typical plasma sprayed TBC system. It was found that oxidation of the bond coat had a strong effect on ceramic layer stresses and that oxidation induced stresses were influenced by other factors, such as bond coat creep. top coat creep and bond coat roughness. (C) 1998 Elsevier Science S.A. All rights reserved. C1 DCT Inc, Cleveland, OH 44130 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Freborg, AM (reprint author), DCT Inc, 7261 Eagle Rd, Cleveland, OH 44130 USA. NR 19 TC 122 Z9 128 U1 4 U2 24 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 MAY 1 PY 1998 VL 245 IS 2 BP 182 EP 190 DI 10.1016/S0921-5093(97)00849-6 PG 9 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZP160 UT WOS:000073723000006 ER PT J AU Zhu, DM Miller, RA AF Zhu, DM Miller, RA TI Investigation of thermal high cycle and low cycle fatigue mechanisms of thick thermal barrier coatings SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT 1997 Thermal Barrier Coatings Workshop CY MAY 19-21, 1997 CL CINCINNATI, OH SP USAF, Off Sci Res, USAF, Mat Directorate, US DOE, DARPA, Natl Aeronaut & Space Adm, Natl Inst Stand & Technol, USN, Off Naval Res DE ceramic sintering; creep; fatigue mechanisms; thermal high cycle fatigue; thermal low cycle fatigue AB Thick thermal barrier coating systems in a diesel engine experience severe thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) during engine operation. In this paper, the mechanisms of fatigue crack initiation and propagation in a ZrO(2)-8wt%Y(2)O(3):,, thermal barrier coating, under simulated engine thermal LCF and HCF conditions, are investigated using a high power CO, laser. Experiments showed that the combined LCF-HCF tests induced more severe coating surface cracking. microspallation and accelerated crack growth, as compared to the pure LCF test. Lateral crack branching and the ceramic;'bond coat interface delaminations were also facilitated by HCF thermal loads, even in the absence of severe interfacial oxidation. Fatigue damage at crack wake surfaces, due to such phenomena as asperity/debris contact induced cracking and splat pull-out bending during cycling, was observed especially for the combined LCF-HCF tests. It is found that the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. The failure associated with HCF process, however, is mainly associated with a surface wedging mechanism. The interaction between the LCF, HCF and ceramic coating creep, and the relative importance of LCF and HCF in crack propagation are also discussed based on the experimental evidence. (C) 1998 Elsevier Science S.A. All rights reserved. C1 NASA, Lewis Res Ctr, Div Mat, Cleveland, OH 44135 USA. RP Zhu, DM (reprint author), NASA, Lewis Res Ctr, Div Mat, Cleveland, OH 44135 USA. NR 19 TC 42 Z9 44 U1 1 U2 17 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 MAY 1 PY 1998 VL 245 IS 2 BP 212 EP 223 DI 10.1016/S0921-5093(97)00852-6 PG 12 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA ZP160 UT WOS:000073723000009 ER PT J AU Gribbon, AP AF Gribbon, AP TI Field test of nonintrusive traffic detection technologies SO MATHEMATICAL AND COMPUTER MODELLING LA English DT Article AB Accurate, low-cost methods of collecting historical traffic information are essential in making well-informed transportation planning decisions. In addition, detection of real-time traffic conditions is a key element in advanced traffic management and traveler information systems. Until the last decade,inductive loop detectors; pneumatic road tubes, and temporary manual counts were the primary methods for collecting both real-time and historical traffic data. However, technological innovations have given rise to design many different types of advanced traffic detectors. Recently developed traffic detectors use sonic, ultrasonic, microwave, or infrared energy. Most of these detectors can be mounted overhead or to the side of traffic lanes. Magnetic sensors are now being built in sizes small enough to be placed in conduits under the roadway. Artificial intelligence algorithms can process videotaped images of road scenes and output many useful traffic parameters. Even though nonintrusive technologies have been available for several years, there are still many uncertainties regarding their use. Traffic engineers lack a comprehensive comparison of the various types of traffic detection technology A study conducted by the Minnesota Department of Transportation (Mn/DOT) and SRF Consulting Group, Inc. (SRF) and sponsored by the Federal Highway Administration (FHWA) seeks to address this need. Mn/DOT and SRF undertook a two-year effort to test a wide variety of nonintrusive traffic detection technologies. The purpose of this evaluation was to collect practical information on the performance, installation requirements, long-term maintenance requirements, and costs of various types of nonintrusive traffic detection technologies. More than a dozen devices representing mag netic, sonic, ultrasonic, microwave, infrared, and video image processing technologies were evaluated during this project. Devices were evaluated for their performance in both freeway and urban intersection monitoring situations. Testing consisted of two phases. During Phase I, which ran from November 1995 to January 1996, all participating devices measured traffic data on three lanes of Interstate 394 in Minneapolis at the Penn Avenue interchange. Phase Ii, which ran from February to November 1996, consisted of an all-season monitoring of the devices' performance and maintenance requirements and involved both freeway and intersection installations. The Minneapolis-St. Paul metropolitan area provided an excellent opportunity to evaluate the devices in many types of weather extremes, including very cold and very hot temperatures, rain, snow, fog, and high winds. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Jet Prop Lab, Washington, DC 20024 USA. RP Gribbon, AP (reprint author), Jet Prop Lab, 525 Sch St SW,Suite 203, Washington, DC 20024 USA. NR 0 TC 4 Z9 4 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0895-7177 J9 MATH COMPUT MODEL JI Math. Comput. Model. PD MAY-JUN PY 1998 VL 27 IS 9-11 BP 349 EP 352 DI 10.1016/S0895-7177(98)00069-7 PG 4 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Mathematics, Applied SC Computer Science; Mathematics GA ZT068 UT WOS:000074045000023 ER PT J AU Asthana, R Tewari, SN Draper, SL AF Asthana, R Tewari, SN Draper, SL TI Strength degradation of sapphire fibers during pressure casting of a sapphire-reinforced Ni-base superalloy SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID COMPOSITES C1 Univ Wisconsin Stout, Dept Technol, Mfg Engn Program, Menomonie, WI 54751 USA. Cleveland State Univ, Dept Chem Engn, Cleveland, OH 44115 USA. NASA, Lewis Res Ctr, Div Mat, Cleveland, OH 44135 USA. RP Asthana, R (reprint author), Univ Wisconsin Stout, Dept Technol, Mfg Engn Program, Menomonie, WI 54751 USA. NR 14 TC 11 Z9 12 U1 0 U2 1 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD MAY PY 1998 VL 29 IS 5 BP 1527 EP 1530 DI 10.1007/s11661-998-0370-0 PG 4 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA ZR054 UT WOS:000073931000020 ER PT J AU Howe, JM Murray, TM Moore, KT Csontos, AA Tsai, MM Garg, A Benson, WE AF Howe, JM Murray, TM Moore, KT Csontos, AA Tsai, MM Garg, A Benson, WE TI Understanding interphase boundary dynamics by in situ high-resolution and energy-filtering transmission electron microscopy and real-time image simulation SO MICROSCOPY AND MICROANALYSIS LA English DT Article DE in situ high-resolution transmission electron microscopy; energy-filtering transmission electron; microscopy; real-time image simulation; interphase boundary dynamics; phase transformations ID MG-0.5 AG ALLOY; HYDRIDE FORMATION; SMALL PARTICLES; OMEGA PHASE; MECHANISM; MIGRATION; GROWTH AB This study discusses the use of in situ high-resolution transmission electron microscropy (HRTEM) techniques to determine the structure, composition, and interphase boundary dynamics during phase transformations at the atomic level. Three main in situ HRTEM techniques are described: (1) in situ HRTEM dynamic studies that are performed on the same precipitate plates from different viewing directions to determine the three-dimensional structure of the interfaces; (2) in situ compositional mapping of precipitate interfaces obtained by energy-filtering TEM experiments at temperature in a HRTEM, and (3) real-time HRTEM image simulations that are being created for comparison with and interpretation of experimental in situ HRTEM dynamic observations. The results from these studies demonstrate that it is possible to understand the mechanisms and kinetics of interphase boundary motion at the atomic level. C1 Univ Virginia, Dept Mat Sci & Engn, Charlottesville, VA 22903 USA. Heraeus Inc, Mat Technol Div, Chandler, AZ 85226 USA. NASA, Lewis Res Ctr, Div Mat, Cleveland, OH 44135 USA. RP Howe, JM (reprint author), Univ Virginia, Dept Mat Sci & Engn, Charlottesville, VA 22903 USA. NR 43 TC 3 Z9 3 U1 1 U2 4 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1431-9276 J9 MICROSC MICROANAL JI Microsc. microanal. PD MAY-JUN PY 1998 VL 4 IS 3 BP 235 EP 247 PG 13 WC Materials Science, Multidisciplinary; Microscopy SC Materials Science; Microscopy GA 125AP UT WOS:000076215500006 ER PT J AU Gnedin, NY Hui, L AF Gnedin, NY Hui, L TI Probing the Universe with the Ly alpha forest - I. Hydrodynamics of the low-density intergalactic medium SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE hydrodynamics; methods, numerical; intergalactic medium; quasars, absorption lines; cosmology, theory ID CLOUDS; MODEL AB We introduce an efficient and accurate alternative to full hydrodynamic simulations, hydro-PM (HPM), for the study of the low column density Ly alpha forest (N-HI less than or similar to 10(14) cm(-2)). It consists of a particle mesh (PM) solver, modified to compute, in addition to the gravitational potential, an effective potential due to the gas pressure. Such an effective potential can be computed from the density field because of a tight correlation between density and pressure in the low-density limit (delta less than or similar to 10), which can be calculated for any photo-re-ionization history by a method outlined by Hui & Gnedin. Such a correlation exists, in part, because of minimal shock heating in the low-density limit. We compare carefully the density and velocity fields as well as absorption spectra, computed using HPM versus hydrodynamic simulations, and find good agreement. We show that HPM is capable of reproducing measurable quantities, such as the column density distribution, computed from full hydrodynamic simulations, to a precision comparable to that of observations. We discuss how, by virtue of its speed and accuracy, HPM can enable us to use the Ly alpha forest as a cosmological probe. We also discuss in detail the smoothing of the gas (or baryon) fluctuation relative to that of the dark matter on small scales due to finite gas pressure. First, it is shown that the conventional wisdom that the linear gas fluctuation is smoothed on the Jeans scale is incorrect for general re-ionization (or reheating) history; the correct linear filtering scale is in general smaller than the Jeans scale after reheating, but larger prior to it. Secondly, it is demonstrated that in the mildly non-linear regime, a PM solver, combined with suitable pre-filtering of the initial conditions, can be used to model the low-density IGM. However, such an approximation is shown to be less accurate than HPM, unless a non-uniform pre-filtering scheme is implemented. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Gnedin, NY (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. NR 38 TC 250 Z9 251 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAY 1 PY 1998 VL 296 IS 1 BP 44 EP 55 DI 10.1046/j.1365-8711.1998.01249.x PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP885 UT WOS:000073798400011 ER PT J AU Rodgers, EB Olson, WS Karyampudi, VM Pierce, HF AF Rodgers, EB Olson, WS Karyampudi, VM Pierce, HF TI Satellite-derived latent heating distribution and environmental influences in Hurricane Opal (1995) SO MONTHLY WEATHER REVIEW LA English DT Article ID SEASON TYPHOON DEVELOPMENT; UPPER TROPOSPHERIC TROUGH; TROPICAL CYCLONE; ANGULAR-MOMENTUM; OUTFLOW LAYER; PRECIPITATION; MODEL; EVOLUTION; PROFILES; CLOUD AB The total (i.e., convective and stratiform) latent hear release (LHR) cycle in the eyewall region of Hurricane Opal (October 1995) has been estimated using observations from the F-10, F-11, and F-13 Defense Meteorological Satellite Program Special Sensor Micromave/Imagers (SSM/Is). This LHR cycle occurred during the hurricane's rapid intensification and decay stages (3-5 October 1995). The satellite observations revealed that there were at least two major episodes in which a period of elevated total LHR (i.e., convective burst) occurred in the eyewall region. During these convective bursts, Opal's minimum pressure decreased by 50 mb and the LHR generated by convective processes increased, as greater amounts of latent heating occurred at middle and upper levels. It is hypothesized that the abundant release of latent heat in Opal's middle- and upper-tropospheric region during these convective burst episodes allowed Opal's eyewall to become more buoyant, enhanced the generation of kinetic energy and, thereby, rapidly intensified the system. The observations also suggest that Opal's intensity became more responsive to the convective burst episodes (i.e., shorter time lag between LHR and intensity and greater maximum wind increase) as Opal became more Intense. Analyses of SSM/I-retrieved parameters, sea surface temperature observations, and the European Centre for Medium-Range Weather Forecasts (ECMWF) data reveal that the connective rainband (CRB) cycles and sea surface and tropopause temperatures, in addition to large-scale environmental forcing, had a profound influence on Opal's episodes of convective burst and its subsequent intensity. High sea surface (29.7 degrees C) and low tropopause (192 K) temperatures apparently created a greater potential for Opal's maximum intensity. Strong horizontal moisture flux convergence within Opal's outer-core regions (i.e., outside 333-km radius from the center) appeared to help initiate and maintain Opal's CRBs. These CRBs, in turn, propagated inward to help generate and dissipate the eyewall convective bursts. The first CRB that propagated into Opal's eyewall region appeared to initiate the first eyewall convective burst. The second CRB propagated to within ill km of Opal's center and appeared to dissipate the first CRB, subjecting it to subsidence and the loss of water vapor flux. The ECMWF upper-tropospheric height and wind analyses suggest that Opal interacted with a diffluent trough that initated an outflow channel, and generated high values of upper-tropospheric eddy relative angular momentum flux convergence. The gradient wind adjustment processes associated with Opal's outflow channel, in turn, may have helped to initiate and maintain the eyewall convective bursts. The ECMWF analyses also suggest that a dry air intrusion within the southwestern quadrant of Opal's outer-core region, together with strong vertical wind shear, subsequently terminated Opal's CRB cycle and caused Opal to weaken prior to landfall. C1 NASA, Atmospheres Lab, Mesoscale Atmospher Proc Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Caelum Res Corp, Silver Spring, MD USA. Sci Syst & Applicat Inc, Lanham, MD USA. RP Rodgers, EB (reprint author), NASA, Atmospheres Lab, Mesoscale Atmospher Proc Branch, Goddard Space Flight Ctr, Code 912, Greenbelt, MD 20771 USA. NR 60 TC 48 Z9 50 U1 0 U2 6 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 MAY PY 1998 VL 126 IS 5 BP 1229 EP 1247 DI 10.1175/1520-0493(1998)126<1229:SDLHDA>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZL980 UT WOS:000073492800010 ER PT J AU Ila, D Williams, EK Sarkisov, S Smith, CC Poker, DB Hensley, DK AF Ila, D Williams, EK Sarkisov, S Smith, CC Poker, DB Hensley, DK TI Formation of metallic nanoclusters in silica by ion implantation SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article; Proceedings Paper CT 9th International Conference on Radiation Effects in Insulators (REI-9) CY SEP 14-19, 1997 CL KNOXVILLE, TENNESSEE SP Ctr Mat Proc at Univ TN, Pacific NW Natl Lab DE ion implantation; metal colloids; nanocrystals; nanoparticles ID OPTICAL-PROPERTIES; GLASS AB We have changed both linear and nonlinear optical properties of suprasil-1 by implanting 2.0 MeV copper, 350 keV tin, 1.5 MeV silver and 3.0 MeV gold. These changes were induced both by over implantation above the threshold fluence for spontaneous cluster formation and by subsequent thermal annealing, and are due to an increase in resonance optical absorption as well as an enhancement of the nonlinear optical properties. Using optical absorption spectrophotometry and Rutherford Backscattering Spectrometry, we have measured the cluster size for each heat treatment temperature. Using Z-scan technique we have determined the third order electric susceptibility for each implanted species to be 1.5 x 10(-6) esu for Sn nanoclusters, 2.7 x 10(-6) esu for Cu nanoclusters, 5 x 10(-)7 esu for Ag nanoclusters, to 6.5 x 10(-7) esu for Au nanoclusters in suprasil-1. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Alabama A&M Univ, Ctr Irradiat Mat, Normal, AL 35762 USA. NASA, MSFC, Marshall Space Flight Ct, AL 35898 USA. Oak Ridge Natl Lab, Div Solid State, Oak Ridge, TN USA. RP Ila, D (reprint author), Alabama A&M Univ, Ctr Irradiat Mat, Normal, AL 35762 USA. EM ila@cim.aamu.edu RI Hensley, Dale/A-6282-2016 OI Hensley, Dale/0000-0001-8763-7765 NR 16 TC 73 Z9 74 U1 1 U2 11 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 MAY PY 1998 VL 141 IS 1-4 BP 289 EP 293 DI 10.1016/S0168-583X(98)00072-X PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 103WA UT WOS:000074979800047 ER PT J AU Collatz, GJ Berry, JA Clark, JS AF Collatz, GJ Berry, JA Clark, JS TI Effects of climate and atmospheric CO2 partial pressure on the global distribution of C-4 grasses: present, past, and future SO OECOLOGIA LA English DT Article DE photosynthesis; C-4; climate change; CO2; grassland ID CARBON ISOTOPE DISCRIMINATION; SURFACE PARAMETERIZATION SIB2; VOSTOK ICE CORE; STOMATAL CONDUCTANCE; C4 GRASSES; WATER-USE; PHOTOSYNTHESIS; PLANTS; MODEL; LEAVES AB C-4 photosynthetic physiologies exhibit fundamentally different responses to temperature and atmospheric CO2 partial pressures (pCO(2)) compared to the evolutionarily more primitive C-3 type. All else being equal, C-4 plants tend to be favored over C-3 plants in warm humid climates and, conversely, C-3 plants tend to be favored over C-4 plants in cool climates. Empirical observations supported by a photosynthesis model predict the existence of a climatological crossover temperature above which C-4 species have a carbon gain advantage and below which C-3 species are favored. Model calculations and analysis of current plant distribution suggest that this pCO(2)-dependent crossover temperature is approximated by a mean temperature of 22 degrees C for the warmest month at the current pCO(2) (35 Pa). In addition to favorable temperatures, C-4 plants require sufficient precipitation during the warm growing season. C-4 plants which are predominantly graminoids of short stature can be competitively excluded by trees (nearly all C-3 plants) - regardless of the photosynthetic superiority of the C-4 pathway - in regions otherwise favorable for C-4. To construct global maps of the distribution of C-4 grasses for current, past and future climate scenarios, we make use of climatological data sets which provide estimates of the mean monthly temperature to classify the globe into areas which should favor C-4 photosynthesis during at least 1 month of the year. This area is further screened by excluding areas where precipitation is <25 mm per month during the warm season and by selecting areas classified as grasslands (i.e., excluding areas dominated by woody vegetation) according to a global vegetation map. Using this approach, grasslands of the world are designated as C-3, C-4, and mixed under current climate and (pCO(2) Published floristic studies were used to test the accuracy of these predictions in many legions of the world, and agreement with observations was generally good. We then make use of this protocol to examine changes in the global abundance of C-4 grasses in the past and the future using plausible estimates for the climates and pCO(2). When pCO(2) is lowered to pre-industrial levels, C-4 grasses expanded their range into large areas now classified as C-3 grasslands, especially in North America and Eurasia. During the last glacial maximum (similar to 18 ka BP) when the climate was cooler and pCO(2) was about 20 Pa, our analysis predicts substantial expansion of C-4 vegetation - particularly in Asia, despite cooler temperatures. Continued use of fossil fuels is expected to result in double the current pCO(2) by sometime in the next century, with some associated climate warming. Our analysis predicts a substantial reduction in the area of C-4 grasses under these conditions. These reductions from the past and into the future are based on greater stimulation of C-3 photosynthetic efficiency by higher pCO(2) than inhibition by higher temperatures. The predictions are testable through large-scale controlled growth studies and analysis of stable isotopes and other data from regions where large changes are predicted to have occurred. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Carnegie Inst Washington, Dept Plant Biol, Stanford, CA 94305 USA. Duke Univ, Dept Biol, Durham, NC 27708 USA. RP Collatz, GJ (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. EM jcollatz@biome.gsfc.nasa.gov RI Berry, Joseph/B-8211-2009; Clark, James/G-6331-2011; collatz, george/D-5381-2012 OI Berry, Joseph/0000-0002-5849-6438; NR 88 TC 275 Z9 286 U1 11 U2 110 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0029-8549 J9 OECOLOGIA JI Oecologia PD MAY PY 1998 VL 114 IS 4 BP 441 EP 454 DI 10.1007/s004420050468 PG 14 WC Ecology SC Environmental Sciences & Ecology GA ZR339 UT WOS:000073964200001 PM 28307893 ER PT J AU Downie, JD Timucin, D Smithey, DT Crew, M AF Downie, JD Timucin, D Smithey, DT Crew, M TI Long holographic lifetimes in bacteriorhodopsin films SO OPTICS LETTERS LA English DT Article AB The D85N genetic variant of bacteriorhodopsin (BR) displays a nearly permanent lifetime of the photochromic P(490) state. We present pump-probe measurements that demonstrate this behavior. However, diffraction efficiency measurements made from holograms recorded in a hydrated D85N film show markedly different decay behavior, suggesting that a molecular diffusion process is occurring in the film. Holograms recorded with different grating frequencies display correspondingly different decay times, thus supporting this hypothesis. A tl-lin D85N film was fabricated that was chemically cross linked, resulting in the elimination of diffusion of BR molecules within the polymer matrix. This film exhibits a grating lifetime of the order of weeks or more, thus permitting the long-term holographic storage of information. (C) 1998 Optical Society of America. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Bend Res Inc, Bend, OR 97701 USA. RP Downie, JD (reprint author), NASA, Ames Res Ctr, M-S 269-3, Moffett Field, CA 94035 USA. NR 3 TC 19 Z9 19 U1 0 U2 2 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 MAY 1 PY 1998 VL 23 IS 9 BP 730 EP 732 DI 10.1364/OL.23.000730 PG 3 WC Optics SC Optics GA ZL010 UT WOS:000073389800026 PM 18087324 ER PT J AU Mehrotra, P Van Rosendale, J Zima, H AF Mehrotra, P Van Rosendale, J Zima, H TI High Performance Fortran: History, status and future SO PARALLEL COMPUTING LA English DT Article DE data parallelism; data distribution; distributed-memory architectures; High Performance Fortran; irregular problems ID SIMULATION AB High Performance Fortran (HPF) is a data-parallel language that was designed to provide the user with a high-level interface for programming scientific applications, while delegating to the compiler the task of generating an explicitly parallel message-passing program. The main objective of this paper is to study the expressivity of the language and related performance issues. After giving an outline of developments that led to HPF and shortly explaining its major features, we discuss in detail a variety of approaches for solving multiblock problems and applications dealing with unstructured meshes. We argue that the efficient solution of these problems does not only need the full range of the HPF Approved Extensions, but also requires additional features such as the explicit control of communication schedules and support for value-based alignment. The final part of the paper points out some classes of problems that are difficult to deal with efficiently within the HPF paradigm. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. Univ Vienna, Inst Software Technol & Parallel Syst, A-1090 Vienna, Austria. RP Mehrotra, P (reprint author), NASA, Langley Res Ctr, ICASE, MS 132C, Hampton, VA 23681 USA. EM pm@icase.edu; jvr@icase.edu; zima@par.univie.ac.at NR 45 TC 17 Z9 18 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8191 J9 PARALLEL COMPUT JI Parallel Comput. PD MAY PY 1998 VL 24 IS 3-4 BP 325 EP 354 DI 10.1016/S0167-8191(98)00016-7 PG 30 WC Computer Science, Theory & Methods SC Computer Science GA ZX437 UT WOS:000074515700002 ER PT J AU Herwitz, SR Slye, RE Turton, SM AF Herwitz, SR Slye, RE Turton, SM TI Co-registered aerial stereopairs from low-flying aircraft for the analysis of long-term tropical rainforest canopy dynamics SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID BROAD-LEAVED FOREST; RAIN-FOREST; TREE POPULATIONS; OREGON TRANSECT; MOIST FORESTS; GROWTH-RATES; MORTALITY; RECRUITMENT; LOWLAND; DIVERSITY AB Ground-based censusing of tagged trees in permanent plots has been the standard research method for monitoring the long-term dynamics of tropical rainforest tree populations. This paper describes a method for quantifying the turnover and crown growth rates of tropical rainforest canopy trees over an 18-year period using a temporal sequence of large-scale aerial stereopairs. The stereopairs were co-registered using an array of control points that consisted of surveyed aerial targets and primary branch bifurcation points (BIPs) having the same persisent geometry and spatial coordinates in the crowns of selected canopy trees. Six crown size classes were distinguished, and critical late stages in the life history of mature canopy trees were identified. The smallest crown size classes (<20 and 20 to 40 m(2)) experienced, more than 75 percent of the canopy tree mortality over the 18-year period; Of the canopy trees that survived, the mid-range 60- to 80-m(2) crown size class was identified as a critical late stage, having both the highest mean crown growth rate (2.42 m(2) yr(-1) among those trees that exhibited positive growth as well as the highest proportion of trees (47 percent) experiencing a reduction in crown size. The results demonstrate that high resolution, aerial stereophotography from low-flying aircraft can serve as a valuable tool for demographic research in tropical rainforest ecosystems. C1 Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA. Clark Univ, Dept Biol, Worcester, MA 01610 USA. NASA, Ames Res Ctr, Ecosyst Sci & Technol Branch, Moffett Field, CA 94035 USA. James Cook Univ N Queensland, Cooperat Res Ctr Trop Rainforest Ecol & Managemen, Sch Trop Environm Studies & Geog, Cairns, Qld 4870, Australia. RP Herwitz, SR (reprint author), Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA. EM sherwitz@clarku.edu RI Turton, Stephen/F-7585-2012 NR 53 TC 12 Z9 13 U1 1 U2 3 PU AMER SOC PHOTOGRAMMETRY PI BETHESDA PA 5410 GROSVENOR LANE SUITE 210, BETHESDA, MD 20814-2160 USA SN 0099-1112 J9 PHOTOGRAMM ENG REM S JI Photogramm. Eng. Remote Sens. PD MAY PY 1998 VL 64 IS 5 BP 397 EP 405 PG 9 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA ZP504 UT WOS:000073760100002 ER PT J AU Cerf, NJ AF Cerf, NJ TI Entropic bounds on coding for noisy quantum channels SO PHYSICAL REVIEW A LA English DT Article ID ERROR-CORRECTING CODES; COMMUNICATION; ENTANGLEMENT; COMPUTATION; THEOREM; STATES AB analogy with its classical counterpart, a noisy quantum channel is characterized by a loss, a quantity that depends on the channel input and the quantum operation performed by the channel. The loss reflects the transmission quality: if the loss is zero, quantum information can be perfectly transmitted at a rate measured by the quantum source entropy. By using block coding based on sequences of II entangled symbols, the average loss (defined as the overall loss of the joint n-symbol channel divided by n, when n-->infinity) can be made lower than the loss for a single use of the channel. In this context, we examine several upper bounds on the rate at which quantum information can be transmitted reliably via a noisy channel, that is, with an asymptotically vanishing average loss while the one-symbol loss of the channel is nonzero. These bounds on the channel capacity rely on the entropic Singleton bound on quantum error-correcting codes [Phys. Rev. A 56, 1721 (1997]. Finally, we analyze the Singleton bounds when the noisy quantum channel is supplemented with a classical auxiliary channel. C1 CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Informat & Comp Technol Res Sect, Pasadena, CA 91109 USA. Free Univ Brussels, Ctr Nonlinear Phenomena & Complex Syst, B-1050 Brussels, Belgium. RP Cerf, NJ (reprint author), CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. NR 42 TC 8 Z9 8 U1 0 U2 2 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 MAY PY 1998 VL 57 IS 5 BP 3330 EP 3347 DI 10.1103/PhysRevA.57.3330 PG 18 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZM869 UT WOS:000073584500027 ER PT J AU Weise, JI Baring, MG Melrose, DB AF Weise, JI Baring, MG Melrose, DB TI Photon splitting in strong magnetic fields: S-matrix calculations SO PHYSICAL REVIEW D LA English DT Article ID SOFT GAMMA-REPEATERS; BOUND PAIR CREATION; QUANTUM ELECTRODYNAMICS; POLAR GAPS; PULSARS; EMISSION AB The S-matrix approach to the treatment of photon splitting in a magnetized vacuum, with the electron propagators expressed in the Landau representation, is discussed critically. Although the analytic results of Mentzel, Berg and Wunner are confirmed, we propose that their available numerical results may be subject to two previously unidentified sources of error associated with the sum over principal quantum number n, leading to spurious contributions to the amplitude, and the extremely slow convergence of the sum for weak fields. It is shown how the sums may be rearranged to avoid the spurious contributions. If the Euler-Maclaurin summation formula is used to evaluate the infinite sums over n, the S-matrix approach then reproduces results derived by the effective Lagrangian and proper-time techniques in the weak-field, low-frequency limit. This method gives reliable results, for B greater than or similar to 0.01 and omega less than or similar to 0.1, that reproduce those obtained by proper-time techniques. The S-matrix approach simplifies in the strong-held limit, B much greater than 1, where the sum over n converges rapidly. Our results show that the branching ratio for the splittings perpendicular to-->perpendicular to perpendicular to and perpendicular to --> parallel to parallel to decreases from its known value similar to 3.4 for B much less than 1 towards zero for B much greater than 1. For weak fields the S-matrix approach is unnecessarily cumbersome, and future numerical work should be based on the alternative approaches. C1 Univ Sydney, Sch Phys, Res Ctr Theoret Astrophys, Sydney, NSW 2006, Australia. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Weise, JI (reprint author), Univ Sydney, Sch Phys, Res Ctr Theoret Astrophys, Sydney, NSW 2006, Australia. RI Melrose, Don/O-8766-2014; Melrose, Donald/G-1564-2016 OI Melrose, Donald/0000-0002-6127-4545 NR 35 TC 10 Z9 10 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD MAY 1 PY 1998 VL 57 IS 9 BP 5526 EP 5538 DI 10.1103/PhysRevD.57.5526 PG 13 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA ZL725 UT WOS:000073464200023 ER PT J AU Yeh, C Bergman, L Morookian, J Monacos, S AF Yeh, C Bergman, L Morookian, J Monacos, S TI Generation of time-aligned picosecond pulses on wavelength-division-multiplexed beams in a nonlinear fiber SO PHYSICAL REVIEW E LA English DT Article ID OPTICAL FIBERS; DISPERSION; WAVEGUIDES AB A fundamentally different way to generate time-aligned data pulses on wavelength-division-multiplexed (WDM) beams in a single-mode fiber is found. A large-amplitude pulse called a shepherd pulse is launched on one of the copropagating beams (shepherd pulse is defined as a pulse that can affect other copropagating pulses in a WDM format while maintaining its own propagation behavior). Initially at the launching plane no other pulse exists on any of the other copropagating wavelength-division-multiplexed beams. Due to the nonlinear cross-phase modulation effect, time-aligned pulses are generated on all other beams after a given fiber length. Both theoretical and experimental results are presented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yeh, C (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 26 TC 6 Z9 6 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 MAY PY 1998 VL 57 IS 5 BP 6135 EP 6139 DI 10.1103/PhysRevE.57.6135 PN B PG 5 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA ZP583 UT WOS:000073768000083 ER PT J AU Mahalov, A Nicolaenko, B Zhou, Y AF Mahalov, A Nicolaenko, B Zhou, Y TI Energy spectra of strongly stratified and rotating turbulence SO PHYSICAL REVIEW E LA English DT Article ID FLUIDS AB Turbulence under strong stratification and rotation is usually characterized as quasi-two-dimensional turbulence. We develop a "quasi-two-dimensional" energy spectrum which changes smoothly between the Kolmogorov - 5/3 law (no stratification), the - 2 scalings of Zhou [Phys. Fluids 7, 2092 (1995)] for the case of strong rotation, as well as the - 2 scalings for the case of strong rotation and stratification. For strongly stratified turbulence, the model may give the - 2 scaling predicted by Herring [Meteorol. Atmos. Phys. 38, 106 1988], and the - 5/3 scaling indicated by some mesoscale observations. C1 Arizona State Univ, Dept Math, Tempe, AZ 85287 USA. IBM Corp, Div Res, TJ Watson Res Ctr, Yorktown Heights, NY 10598 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Mahalov, A (reprint author), Arizona State Univ, Dept Math, Tempe, AZ 85287 USA. NR 19 TC 9 Z9 9 U1 0 U2 1 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 MAY PY 1998 VL 57 IS 5 BP 6187 EP 6190 DI 10.1103/PhysRevE.57.6187 PN B PG 4 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA ZP583 UT WOS:000073768000091 ER PT J AU Wegmann, R Schmidt, HU Lisse, CM Dennerl, K Englhauser, J AF Wegmann, R Schmidt, HU Lisse, CM Dennerl, K Englhauser, J TI X-rays from comets generated by energetic solar wind particles SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ELECTRON-CAPTURE; COMA; IONS AB By means of axisymmetric hydrodynamic models with chemistry we study the X-ray emission of two processes in a comet : Bremsstrahlung of solar wind electrons interacting with the neutral gas coma, and :charge exchange of heavy solar wind ions in high ionization states with the neutral cometary gas. Comparisons of morphology, intensity and spectrum with observations favour heavy ions as the emitting agent (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Max Planck Inst Astrophys, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20742 USA. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. RP Wegmann, R (reprint author), Max Planck Inst Astrophys, D-85748 Garching, Germany. RI Lisse, Carey/B-7772-2016 OI Lisse, Carey/0000-0002-9548-1526 NR 21 TC 83 Z9 84 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 MAY PY 1998 VL 46 IS 5 BP 603 EP 612 DI 10.1016/S0032-0633(97)00196-7 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 100XD UT WOS:000074839900013 ER PT J AU Snipes, JA Granetz, RS Greenwald, M Hubbard, AE Hutchinson, IH Irby, J Kesner, J Migliuolo, S Pedersen, TS Ramos, J Rice, J Stek, PC Takase, Y Wolfe, SM AF Snipes, JA Granetz, RS Greenwald, M Hubbard, AE Hutchinson, IH Irby, J Kesner, J Migliuolo, S Pedersen, TS Ramos, J Rice, J Stek, PC Takase, Y Wolfe, SM TI ELMs and fast edge fluctuations in Alcator C-Mod SO PLASMA PHYSICS AND CONTROLLED FUSION LA English DT Article; Proceedings Paper CT 6th IAEA Technical Committee Meeting on H-Mode Physics CY SEP 22-24, 1997 CL KLOSTER SEEON, GERMANY SP IAEA AB Just above the H-mode threshold power at low density, small amplitude high repetition rate (1-5 kHz) type III edge-localized modes (ELMs) are observed. At higher input power, the H-modes become ELM-free. At high density and high input power ((n) over bar(e) > 2.2 x 10(20) m(-3), P-in > 2 MW), the plasma often enters a new II-mode regime now called the enhanced D-alpha H-mode, which is a steady-state H-mode often without distinct ELMs but with high levels of D-alpha emission. Enhanced D-alpha H-modes are accompanied by persistent high-frequency broadband (50-400 kHz) density and magnetic fluctuations. Above about (n) over bar(e) > 3 x 10(20) m(-3) the enhanced D-alpha H-modes may also exhibit bursting or continuous low m, n coherent magnetic fluctuations with frequencies from 60-90 kHz. In the H-mode, steep edge gradients are observed with a nine-channel electron cyclotron emission (ECE) polychromator and a 38-channel, high-resolution, edge soft-x-ray array. The soft-x-ray pedestal width remains around 3 to 4 mm in the ELM-free H-mode and between type III ELMs. The pedestal collapses within 100 mu s during an ELM. Calculations indicate that the plasma in the H-mode is often near ideal ballooning first stability limits, but no type I ELMs have yet been identified. Edge micro-tearing modes destabilized by a steep temperature gradient are also considered as a possible explanation of the observed fluctuations during the enhanced D-alpha H-mode. C1 MIT, Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA. Jet Propuls Lab, Pasadena, CA USA. Univ Tokyo, Dept Phys, Tokyo 113, Japan. RP Snipes, JA (reprint author), MIT, Plasma Sci & Fus Ctr, 77 Massachusetts Ave, Cambridge, MA 02139 USA. RI Hutchinson, Ian/D-1136-2009; OI Hutchinson, Ian/0000-0003-4276-6576; Greenwald, Martin/0000-0002-4438-729X NR 14 TC 8 Z9 8 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0741-3335 J9 PLASMA PHYS CONTR F JI Plasma Phys. Control. Fusion PD MAY PY 1998 VL 40 IS 5 BP 765 EP 770 DI 10.1088/0741-3335/40/5/039 PG 6 WC Physics, Fluids & Plasmas SC Physics GA ZR833 UT WOS:000074019100039 ER PT J AU Flood, DJ AF Flood, DJ TI Advanced space solar cells SO PROGRESS IN PHOTOVOLTAICS LA English DT Article; Proceedings Paper CT 1997 World Forum on Advanced Solar Cell Materials in Memory of J J Loferski CY MAY 19-20, 1997 CL NATL TSING HUA UNIV, HSINCHU, TAIWAN HO NATL TSING HUA UNIV AB This paper will present a bl ief overview of the status of research and development of advanced space solar cells from a variety of materials. Most of the investigations at present are focused on binary, ternary and quaternary III-V semiconducting compounds suck as InP, GaInAs and GaInP(2). Growth techniques used for producing laboratory cells include liquid-phase epitaxy (LPE), organometallic vapor phase epitaxy (OMVPE), molecular beam epitaxy (MBE) or any of a number of variations of these techniques, suck as atomic layer epitaxy (ALE), etc. Gallium arsenide is at present the only! commercially available III-V compound solar cell. Compound III-V multiple bandgap cells are now under development in a jointly sponsored NASA/Air Force manufacturing technology demonstration program. In general, the decision to use a particular cell technology in space is determined by several factors, emphasis on any particular one depending on the mission environment: some are related to the properties of the photovoltaic material itself, such as efficiency, and resistance to radiation damage, and some are related to details of the cell structure and associated materials, such as survivability under repeated ther mal cycling and resistance to atomic oxygen erosion. The impact of these requirements on cell material selection and structural design is briefly discussed. (C) 1998 John Wiley & Sons, Ltd. This paper is produced under the auspices of the US Government mid it is therefore not subject to copyright in the USA. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Flood, DJ (reprint author), NASA, Lewis Res Ctr, MS 302-1,21000 Brookpark Rd, Cleveland, OH 44135 USA. NR 12 TC 4 Z9 4 U1 0 U2 4 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 1062-7995 J9 PROG PHOTOVOLTAICS JI Prog. Photovoltaics PD MAY-JUN PY 1998 VL 6 IS 3 BP 187 EP 192 DI 10.1002/(SICI)1099-159X(199805/06)6:3<187::AID-PIP227>3.0.CO;2-8 PG 6 WC Energy & Fuels; Materials Science, Multidisciplinary; Physics, Applied SC Energy & Fuels; Materials Science; Physics GA 100KE UT WOS:000074814700006 ER PT J AU Durante, M Furusawa, Y George, K Gialanella, G Greco, O Grossi, G Matsufuji, N Pugliese, M Yang, TC AF Durante, M Furusawa, Y George, K Gialanella, G Greco, O Grossi, G Matsufuji, N Pugliese, M Yang, TC TI Rejoining and misrejoining of radiation-induced chromatin breaks. IV. Charged particles SO RADIATION RESEARCH LA English DT Article ID DOUBLE-STRAND BREAKS; PREMATURE CHROMOSOME CONDENSATION; HUMAN-LYMPHOCYTES; MAMMALIAN-CELLS; IONIZING-RADIATION; HUMAN FIBROBLASTS; ALPHA-PARTICLES; X-RAYS; DAMAGE; INDUCTION AB We have recently reported the kinetics of chromosome rejoining and exchange formation in human lymphocytes exposed to gamma rays using the techniques of fluorescence in situ hybridization (FISH) and premature chromosome condensation (PCC), In this paper, we have extended previous measurements to cells exposed to charged particles. Our goal was to determine differences in chromatin break rejoining and misrejoining after exposure to low-and high-linear energy transfer (LET) radiation. Cells were irradiated with hydrogen, neon, carbon or iron ions in the LET range 0.3-140 keV/pm and were incubated at 37 degrees C for various times after exposure. Little difference was observed in the yield of early prematurely condensed chromosome breaks for the different ions. The kinetics of break rejoining was exponential for all ions and had similar time constants, but the residual level of unrejoined breaks after prolonged incubation was higher for high-LET radiation. The kinetics of exchange formation was also similar for the different ions, but the yield of chromosome interchanges measured soon after exposure was higher for high-LET particles, suggesting that a higher fraction of DNA breaks are misrejoined quickly. On the other hand, the rate of formation of complete exchanges was slightly lower for densely ionizing radiation. The ratios between the yields of different types of aberrations observed at 10 h postirradiation in prematurely condensed chromosome preparations were dependent on LET. We found significant differences between the yields of aberrations measured in interphase (after repair) and metaphase for densely ionizing radiation. This difference might be caused by prolonged mitotic delay and/or interphase death. Overall, the results point out significant differences between low-and high-LET radiation far the formation of chromosome aberrations. (C) 1998 by Radiation Research society. C1 Natl Inst Radiol Sci, Space & Particle Radiat Grp, Inage Ku, Chiba 263, Japan. Univ Naples Federico II, Dipartimento Sci Fis, I-80126 Napoli, Italy. Krug Life Sci, Houston, TX 77058 USA. Natl Inst Radiol Sci, Div Accelerator Phys & Engn, Inage Ku, Chiba 263, Japan. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Durante, M (reprint author), Natl Inst Radiol Sci, Space & Particle Radiat Grp, Inage Ku, 9-1 Anagawa 4 Chome, Chiba 263, Japan. RI Durante, Marco/K-1315-2014; OI Durante, Marco/0000-0002-4615-553X NR 38 TC 91 Z9 96 U1 0 U2 2 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 MAY PY 1998 VL 149 IS 5 BP 446 EP 454 DI 10.2307/3579784 PG 9 WC Biology; Biophysics; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Radiology, Nuclear Medicine & Medical Imaging GA ZK825 UT WOS:000073367500006 PM 9588355 ER PT J AU Mannucci, AJ Wilson, BD Yuan, DN Ho, CH Lindqwister, UJ Runge, TF AF Mannucci, AJ Wilson, BD Yuan, DN Ho, CH Lindqwister, UJ Runge, TF TI A global mapping technique for GPS-derived ionospheric total electron content measurements SO RADIO SCIENCE LA English DT Article ID NETWORK; BIASES AB A worldwide network of receivers tracking the transmissions of Global Positioning System (GPS) satellites represents a new source of ionospheric data that is globally distributed and continuously available. We describe a technique for retrieving the global distribution of vertical total electron content (TEC) from GPS-based measurements. The approach is based on interpolating TEC within triangular tiles that tessellate the ionosphere modeled as a thin spherical shell. The high spatial resolution of pixel-based methods, where widely separated regions can be retrieved independently of each other, is combined with the efficient retrieval of gradients characteristic of polynomial fitting. TEC predictions from climatological models are incorporated as simulated data to bridge significant gaps between measurements. Time sequences of global TEC maps are formed by incrementally updating the most recent retrieval with the newest data as it becomes available. This Kalman filtering approach smooths the maps in time, and provides time-resolved covariance information, useful for mapping the formal error of each global TEC retrieval. Preliminary comparisons with independent vertical TEC data, available from the TOPEX dual-frequency altimeter, suggest that the maps can accurately reproduce spatial and temporal ionospheric variations over latitudes ranging from equatorial to about +/-65 degrees. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ho, CH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 238-600, Pasadena, CA 91109 USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 29 TC 551 Z9 601 U1 1 U2 45 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 MAY-JUN PY 1998 VL 33 IS 3 BP 565 EP 582 DI 10.1029/97RS02707 PG 18 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZR645 UT WOS:000073999500008 ER PT J AU Ellison, W Balana, A Delbos, G Lamkaouchi, K Eymard, L Guillou, C Prigent, C AF Ellison, W Balana, A Delbos, G Lamkaouchi, K Eymard, L Guillou, C Prigent, C TI New permittivity measurements of seawater SO RADIO SCIENCE LA English DT Article; Proceedings Paper CT Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment CY NOV 04-06, 1996 CL BOSTON, MASSACHUSETTS ID COMPLEX PERMITTIVITY; DIELECTRIC-RELAXATION; HIGH-FREQUENCY; WATER; MODEL AB We have measured the permittivity of representative samples of natural seawater, synthetic seawater, and aqueous NaCl solutions over the frequency range 3-20 GHz, in 0.1-GHz steps and over the temperature range -2 degrees-30 degrees C in 1 degrees steps. Additional measurements have been made at spot frequencies (23.8, 36.5, and 89 GHz) and at selected temperatures between -2 degrees and 30 degrees C. The data from these measurements have allowed us to deduce an interpolation function for epsilon(nu, t, S) in the ranges 2 less than or equal to nu less than or equal to 20 GHz, -2 degrees less than or equal to t less than or equal to 30 degrees C, and 20 parts per thousand less than or equal to S less than or equal to 40 parts per thousand with a precision of 1%. If the frequency range is extended up to 40 GHz, the precision of the interpolation function is about 3%. The data have also allowed us to compare the permittivities of natural seawater, synthetic seawater, and aqueous NaCl solution with the same salinities. Natural and synthetic seawater have the same permittivities within a 1% experimental error estimate. An aqueous NaCl solution has a significantly different permittivity (up to about 6% difference, depending upon the frequency and temperature). C1 Univ Bordeaux, Lab Phys Interact Ondes Mat, Talence, France. Fac Sci, Dept Phys, Equipe Spectron, Meknes, Morocco. Ctr Univ, Ctr Etud Environm Terr & Planetaire, F-78140 Velizy, France. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Balana, A (reprint author), Univ Bordeaux 1, ENSCPB, Lab Phys Interact Ondes Mat, 33402 Talence, F-33402 Talence, France. NR 34 TC 121 Z9 135 U1 1 U2 7 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 MAY-JUN PY 1998 VL 33 IS 3 BP 639 EP 648 DI 10.1029/97RS02223 PG 10 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZR645 UT WOS:000073999500017 ER PT J AU Guillou, C Ellison, W Eymard, L Lamkaouchi, K Prigent, C Delbos, G Balana, G Boukabara, SA AF Guillou, C Ellison, W Eymard, L Lamkaouchi, K Prigent, C Delbos, G Balana, G Boukabara, SA TI Impact of new permittivity measurements on sea surface emissivity modeling in microwaves SO RADIO SCIENCE LA English DT Article; Proceedings Paper CT Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment CY NOV 04-06, 1996 CL BOSTON, MASSACHUSETTS ID BRIGHTNESS TEMPERATURES; MILLIMETER WAVELENGTHS; COMPLEX PERMITTIVITY; WATER; FREQUENCIES; SSM/I AB As part of a measuring program dedicated to the analysis of the dielectric properties of seawater in the frequency range 3-89 GHz, a new dielectric permittivity model based on the standard Debye theory has been developed for remote sensing applications over the ocean below 40 GHz, together with polynomial interpolations at the millimeter frequencies 85.5 and 89 GHz. The aim of this paper is to test the relevance of these new dielectric measurements through statistical comparisons of radiative transfer predictions with satellite and airborne radiometric data between 18 and 89 GHz. A radiometric sensitivity analysis to the permittivity measurement errors is proposed, which yields a sea surface brightness temperature accuracy of at least 0.5 K below 20 GHz, 1 K at 24 GHz, and 1.5 K at 37 and 89 GHz. At frequencies less than 40 GHz, superiority of the revised Debye model is pointed out over the most commonly used model of Klein and Swift [1977]. At millimeter frequencies the new permittivity expressions deviate significantly from the standard Debye predictions, especially at low temperature, suggesting the influence of a second "high-frequency" Debye relaxation. Our comparisons with radiometric data at 89 GHz and in the channel 85.5V of the special sensor microwave imager tend to support this hypothesis. The results emphasize the importance of an adequate modeling of the complex permittivity of seawater as input to the surface emissivity models, at any frequency of the microwave spectrum, and augur interesting outputs in both in-flight calibration and interpretation of satellite data. C1 Ctr Univ, Ctr Etud Environm Terrestre & Planetaires, F-78140 Velizy, France. Univ Bordeaux 1, ENSCPB, Lab Phys & Interact Onde Matiere, F-33402 Talence, France. Fac Sci, Dept Phys, Meknes, Morocco. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Guillou, C (reprint author), Ctr Univ, Ctr Etud Environm Terrestre & Planetaires, 10-12 Ave Europe, F-78140 Velizy, France. RI Boukabara, Sid Ahmed/F-5577-2010 OI Boukabara, Sid Ahmed/0000-0002-1857-3806 NR 42 TC 37 Z9 41 U1 1 U2 6 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 MAY-JUN PY 1998 VL 33 IS 3 BP 649 EP 667 DI 10.1029/97RS02744 PG 19 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZR645 UT WOS:000073999500018 ER PT J AU Prigent, C Rossow, WB Matthews, E AF Prigent, C Rossow, WB Matthews, E TI Global maps of microwave land surface emissivities: Potential for land surface characterization SO RADIO SCIENCE LA English DT Article; Proceedings Paper CT Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment CY NOV 04-06, 1996 CL BOSTON, MASSACHUSETTS ID 37 GHZ DATA; SEA ICE; VEGETATION AB Microwave land surface emissivities are derived from special sensor microwave imager (SSM/I) observations. Cloud-free SSM/I observations are first isolated with the help of collocated visible/infrared satellite observations (International Satellite Cloud Climatology Project (ISCCP) data). Then, the cloud-free atmospheric contribution is calculated from an estimate of the local atmospheric temperature-humidity profile (National Centers for Environmental Prediction (NCEP) analyses). Finally, with the surface skin temperature derived from IR observations (ISCCP estimate), the surface emissivity is calculated for all the SSM/I channels. The method is applied to the SSM/I data for the globe for October 1991. Correspondences between geographical patterns of the emissivities and surface characteristics are briefly analyzed to investigate the potential of microwave emissivities to monitor vegetation phenology and surface properties at regional and continental scales. C1 Columbia Univ, NASA, Goddard Inst Space Studies, Ctr Climate Syst Res, New York, NY 10025 USA. RP Prigent, C (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, Ctr Climate Syst Res, New York, NY 10025 USA. RI Rossow, William/F-3138-2015 NR 14 TC 40 Z9 43 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 MAY-JUN PY 1998 VL 33 IS 3 BP 745 EP 751 DI 10.1029/97RS02460 PG 7 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZR645 UT WOS:000073999500025 ER PT J AU Weissman, DE Le Vine, DM AF Weissman, DE Le Vine, DM TI The role of mutual coupling in the performance of synthetic aperture radiometers SO RADIO SCIENCE LA English DT Article; Proceedings Paper CT Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment CY NOV 04-06, 1996 CL BOSTON, MASSACHUSETTS ID MICROWAVE RADIOMETER AB This paper describes research to evaluate the role of mutual coupling between antennas in the performance of synthetic aperture radiometers. Measurements, taken from the aircraft prototype instrument ESTAR (electronically scanned thinned array radiometer), are presented to demonstrate the importance of mutual coupling. Theory for the ESTAR configuration (an array of dipoles) is presented and checked against the measurements. This theory is then used to assess the effects of small displacements in the elementary antennas in the synthesis array of a hypothetical sensor in space. The measurement errors that result from small displacements (as small as a few hundredths of a wavelength) can be important for applications such as the measurement of soil moisture. Therefore the design approach for future systems should include the control of these and should also include the capability to perform onboard calibration to monitor and remedy detrimental effects. A synthetic aperture radiometer is particularly suited to the measurement of mutual coupling because the basic hardware (a correlation radiometer) measures the product for each antenna pair in the array. Hence, in conclusion, this paper proposes a concept for monitoring changes in mutual coupling to correct for such effects in formation of images. C1 Hofstra Univ, Dept Engn, Hempstead, NY 11550 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Weissman, DE (reprint author), Hofstra Univ, Dept Engn, Hempstead, NY 11550 USA. NR 16 TC 7 Z9 8 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 MAY-JUN PY 1998 VL 33 IS 3 BP 767 EP 779 DI 10.1029/98RS00175 PG 13 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA ZR645 UT WOS:000073999500027 ER PT J AU Sandmeier, S Muller, C Hosgood, B Andreoli, G AF Sandmeier, S Muller, C Hosgood, B Andreoli, G TI Sensitivity analysis and quality assessment of laboratory BRDF data SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID REFERENCE REFLECTANCE PANELS; BIDIRECTIONAL REFLECTANCE; DIRECTIONAL REFLECTANCE; CALIBRATION; SCATTERING; LEAVES; CORN AB A derailed quality and sensitivity analysis of hyperspectral BRDF data, acquired under controlled laboratory conditions at the European Goniometric Facility (EGO) of the Joint Research Center, Ispra/Italy, has been performed. In regard to bidirectional reflectance measurements in the field with the FIGOS goniometer, the impact of angular data sampling, the movement of the Sun, and the Lambertian assumption of a Spectralon panel have been analyzed. An erectophile grass lawn canopy and a planophile watercress surface were chosen as main targets. A GER-3700 spectroradiometer providing hyperspectral resolution allowed for analyzing the wavelength dependency of the effects. The results of the sensitivity analysis show; that in a first step a moderate resolution of 15 degrees and 30 degrees in zenith and azimuth, respectively, Is adequate to capture the bidirectional reflectance distribution function (BRDF) of vegetated targets. Only in the hot spot area a higher resolution is desirable. The movement of the light source during data acquisition is found to be critical, and should be kept within +/-1 degrees source zenith angle in order to obtain homologous BRDF data sets. Due to the wavelength dependence of BRDF effects, the impact of the light source may vary significantly between different wavelength ranges. A normalization of the irradiance with the help of frequent reference measurements is recommended, and should be carried out using a panel with known BRDF characteristics. The Spectralon panel examined showed deviations from a Lambertian panel of up to 5% and more, bur obeyed Helmholtz's reciprocity law. Corresponding calibration coefficients are given for correcting the non-Lambertian behavior in field applications. Laboratory specific constraints such as the nonparallelism and heterogeneity of the lamp are assessed and corrected where necessary and feasible. The reproducibility of the BRDF data obtained lies within 1-9% rmse, depending on target type, wavelength range, and measurement duration. (C)Elsevier Science Inc., 1998. C1 Univ Zurich, Dept Geog, RSL, CH-8006 Zurich, Switzerland. Commiss European Communities, Joint Res Ctr, Space Applicat Inst, I-21020 Ispra, Italy. RP Sandmeier, S (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. NR 24 TC 57 Z9 62 U1 3 U2 9 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 MAY PY 1998 VL 64 IS 2 BP 176 EP 191 DI 10.1016/S0034-4257(97)00178-8 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA ZG045 UT WOS:000072960100005 ER PT J AU Dessler, AE Burrage, MD Grooss, JU Holton, JR Lean, JL Massie, ST Schoeberl, MR Douglass, AR Jackman, CH AF Dessler, AE Burrage, MD Grooss, JU Holton, JR Lean, JL Massie, ST Schoeberl, MR Douglass, AR Jackman, CH TI Selected science highlights from the first 5 years of the Upper Atmosphere Research Satellite (UARS) program SO REVIEWS OF GEOPHYSICS LA English DT Review ID RESOLUTION DOPPLER IMAGER; IRRADIANCE COMPARISON EXPERIMENT-1; HALOGEN OCCULTATION EXPERIMENT; VIBRATIONALLY EXCITED OXYGEN; ARRAY ETALON SPECTROMETER; POLAR VORTEX CONDITIONS; ARCTIC OZONE DEPLETION; SOLAR TOTAL IRRADIANCE; LONG-TERM VARIABILITY; ZONAL MEAN WINDS AB We present scientific highlights from the Upper Atmosphere Research Satellite (UARS) program obtained during the first 5 years of the program. The UARS measures the chemical composition and meteorological state of the middle and upper atmosphere as well as the solar irradiance. The comprehensive suite of UARS geophysical parameters, their near-global coverage, and the multiyear time span have yielded new insights into the processes affecting our atmosphere. In this article we select: seven scientific issues, including stratospheric ozone chemistry, the dynamics of the middle and upper atmosphere, and solar irradiance variations, and discuss the significant impact that the UARS observations have had on our understanding of each issue. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Forschungszentrum Julich, ICG1, D-52425 Julich, Germany. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. USN, Res Lab, Washington, DC 20375 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Dessler, AE (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM dessler@atmos.umd.edu; burrage@sprlj.sprl.umich.edu; j.-u.grooss@fz-juelich.de; holton@atmos.washington.edu; lean@demeter.nrl.navy.mil; massie@ncar.ucar.edu; schom@zephyr.gsfc.nasa.gov; douglass@xena.gsfc.nasa.gov; jackman@welkin.span.nasa.gov RI Douglass, Anne/D-4655-2012; GrooSS, Jens-Uwe/A-7315-2013; Jackman, Charles/D-4699-2012; Dessler, Andrew/G-8852-2012; OI GrooSS, Jens-Uwe/0000-0002-9485-866X; Dessler, Andrew/0000-0003-3939-4820; Lean, Judith/0000-0002-0087-9639 NR 137 TC 28 Z9 28 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 8755-1209 J9 REV GEOPHYS JI Rev. Geophys. PD MAY PY 1998 VL 36 IS 2 BP 183 EP 210 DI 10.1029/97RG03549 PG 28 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 126CW UT WOS:000076276200002 ER PT J AU Lee, SH Yi, CS AF Lee, SH Yi, CS TI Statistical representation and computation of tolerance and clearance for assemblability evaluation SO ROBOTICA LA English DT Article DE assemblability evaluation; tolerance and clearance; statistical representation AB The design of tolerances should take the functionality, manufacturability, assemblability and cost effectiveness of a product into consideration. This paper presents a method of analyzing and evaluating the assemblability of a product under given tolerance specifications in order to provide a tool to aide for tolerance design. Introduced is the range of feasible displacement of a part of an assembly as a result of the accumulation of clearances between mating parts along the serial as well as parallel chain of assembly, which can play a role of compensating for the pose error of the corresponding part due to the accumulation of tolerances. Assemblability is determined by the probability that all the parallel as well as serial chains of the assembly can be formed successfully under given statistical properties of tolerances. This requires to numerically compute the probability that a pair of mating parts forming a parallel chain can align themselves within the error margin defined by their mating clearance, accounting for the possible compensation of the ranges of pose errors associated with the mating parts due to tolerance accumulations by the ranges of feasible displacements of the mating parts due to clearance accumulations. Simulation results are shown. C1 Univ So Calif, Dept Comp Sci, Los Angeles, CA 90089 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Univ So Calif, Dept Comp Sci, Los Angeles, CA 90089 USA. NR 22 TC 10 Z9 10 U1 0 U2 2 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0263-5747 EI 1469-8668 J9 ROBOTICA JI Robotica PD MAY-JUN PY 1998 VL 16 BP 251 EP 264 DI 10.1017/S0263574798000344 PN 3 PG 14 WC Robotics SC Robotics GA ZZ452 UT WOS:000074730800003 ER PT J AU Grenoble, RW Messier, BC Marchello, JM Belvin, HL Johnston, NJ AF Grenoble, RW Messier, BC Marchello, JM Belvin, HL Johnston, NJ TI Adhesive bonding of composite ribbon during automated tow placement SO SAMPE JOURNAL LA English DT Article AB Manufacture of thermoplastic composites by automated tow placement (ATP) currently relies on hearing composite ribbons well above the softening temperature of the matrix resin. High temperature causes the ribbon to deform and deconsolidate, which then requires the application of high pressure to re-consolidate and bond the ribbon to the composite substrate. A significant degree of fiber waviness in the composite components results from ribbon distortion. High placement temperatures and pressures require heavy, expensive tooling and slow placement speeds. To lower required placement temperatures, the addition of a thin adhesive layer to the ribbon prior to placement was evaluated. Adhesive coated thermoplastic ribbons were tow placed using gas torch temperatures 400 degrees C below typical settings. Interfacial bond strength of two ply composite laminates made from these ribbons was measured. it was found that current ribbon dimensional variations and placement accuracy limitations require that the matrix resin be softened to permit establishment of full interfacial contact. However, the presence of the adhesive layer was shown to increase interlaminar bond strength at low placement temperatures. With reductions in ribbon dimensional variability, surface roughness, and void and volatile content low temperature placement may become possible. C1 Old Dominion Univ, Norfolk, VA 23508 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Grenoble, RW (reprint author), Old Dominion Univ, Norfolk, VA 23508 USA. NR 16 TC 0 Z9 0 U1 0 U2 0 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 0091-1062 J9 SAMPE J JI Sampe J. PD MAY-JUN PY 1998 VL 34 IS 3 BP 56 EP + PG 5 WC Engineering, Multidisciplinary; Materials Science, Multidisciplinary SC Engineering; Materials Science GA ZP375 UT WOS:000073746000007 ER PT J AU Lucid, SW AF Lucid, SW TI Six months on Mir SO SCIENTIFIC AMERICAN LA English DT Article C1 NASA, Lyndon B Johnson Space Ctr, Shuttle Mir Program, Houston, TX 77058 USA. RP Lucid, SW (reprint author), NASA, Lyndon B Johnson Space Ctr, Shuttle Mir Program, Houston, TX 77058 USA. NR 1 TC 2 Z9 2 U1 0 U2 0 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 USA SN 0036-8733 J9 SCI AM JI Sci.Am. PD MAY PY 1998 VL 278 IS 5 BP 46 EP 55 PG 10 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZJ118 UT WOS:000073181300024 ER PT J AU Ross, HD AF Ross, HD TI Fires in free fall SO SCIENTIFIC AMERICAN LA English DT Editorial Material C1 NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. RP Ross, HD (reprint author), NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 USA SN 0036-8733 J9 SCI AM JI Sci.Am. PD MAY PY 1998 VL 278 IS 5 BP 49 EP 49 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZJ118 UT WOS:000073181300025 ER PT J AU Casper, J Carpenter, MH AF Casper, J Carpenter, MH TI Computational considerations for the simulation of shock-induced sound SO SIAM JOURNAL ON SCIENTIFIC COMPUTING LA English DT Article DE high-order accuracy; shock capturing; ENO; computational aeroacoustics ID HYPERBOLIC-EQUATIONS; NONOSCILLATORY SCHEMES; APPROXIMATIONS; PROPAGATION; RESOLUTION; SMOOTHNESS; REGIONS; ERROR AB The numerical study of aeroacoustic problems places stringent demands on the choice of a computational algorithm because it requires the ability to propagate disturbances of small amplitude and short wavelength. The demands are particularly high when shock waves are involved because the chosen algorithm must also resolve discontinuities in the solution. The extent to which a high-order accurate shock-capturing method can be relied upon for aeroacoustics applications that involve the interaction of shocks with other waves has not been previously quantified. Such a study is initiated in this work. A fourth-order accurate essentially nonoscillatory (ENO) method is used to investigate the solutions of inviscid, compressible flows with shocks. The design order of accuracy is achieved in the smooth regions of a steady-state, quasi-one-dimensional test case. However, in an unsteady test case, only first-order results are obtained downstream of a sound-shock interaction. The difficulty in obtaining a globally high-order accurate solution in such a case with a shock-capturing method is demonstrated through the study of a simplified, linear model problem. Some of the difficult issues and ramifications for aeroacoustic simulations of flows with shocks that are raised by these results are discussed. C1 Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. NASA, Fluid Mech & Acoust Div, Langley Res Ctr, Hampton, VA 23681 USA. RP Casper, J (reprint author), Old Dominion Univ, Dept Aerosp Engn, Norfolk, VA 23529 USA. NR 20 TC 32 Z9 32 U1 0 U2 1 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 1064-8275 J9 SIAM J SCI COMPUT JI SIAM J. Sci. Comput. PD MAY PY 1998 VL 19 IS 3 BP 813 EP 828 DI 10.1137/S1064827595294101 PG 16 WC Mathematics, Applied SC Mathematics GA ZH068 UT WOS:000073068900005 ER PT J AU Saghi, G Reinholtz, K Savory, PA AF Saghi, G Reinholtz, K Savory, PA TI A multithreaded scheduler for a high-speed spacecraft simulator SO SOFTWARE-PRACTICE & EXPERIENCE LA English DT Article DE deadlock; multiprocessing; multithreaded; object-oriented; scheduling policy; simulation AB The Cassini spacecraft is on its journey to Saturn to perform a close-up study of the Saturnian system; its rings, moons, magneto-sphere, and the planet itself. Sequences of commands will be sent to the spacecraft by ground personnel to control every aspect of the mission. To validate and verify these command sequences, a bit-level, High-Speed Simulator (HSS) has been developed. To maximize performance, the HSS is implemented with multiple threads and runs on a multiprocessor system. A key component of the HSS is the scheduler, which controls the execution of the simulator. The general framework of the scheduler can be adapted to solve a wide variety of scheduling problems. The architecture of the scheduler is presented first, followed by a discussion of issues related to performance and multiple threads. Second, the avoidance of deadlocks and race conditions is discussed, and an informal proof for the absence of both in the scheduler is described. Finally, a study of various scheduling policies is provided. (C) 1998 John Wiley & Sons, Ltd. C1 EM US Design Inc, Colorado Springs, CO 80919 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Nebraska, Lincoln, NE 68588 USA. RP Saghi, G (reprint author), EM US Design Inc, 1495 Garden Gods Rd, Colorado Springs, CO 80919 USA. NR 6 TC 0 Z9 0 U1 1 U2 2 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0038-0644 J9 SOFTWARE PRACT EXPER JI Softw.-Pract. Exp. PD MAY PY 1998 VL 28 IS 6 BP 641 EP 656 PG 16 WC Computer Science, Software Engineering SC Computer Science GA ZP126 UT WOS:000073719000004 ER PT J AU Coffa, S Meyyappan, M Nishi, H AF Coffa, S Meyyappan, M Nishi, H TI Materials and technology challenges in semiconductor processing SO SOLID-STATE ELECTRONICS LA English DT Editorial Material C1 CNR, IMETEM, I-95121 Catania, Italy. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Fujitsu Labs Ltd, Nakahara Ku, Kawasaki, Kanagawa 21188, Japan. RP Coffa, S (reprint author), CNR, IMETEM, Str Primosole 50, I-95121 Catania, Italy. NR 1 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 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD MAY PY 1998 VL 42 IS 5 BP A1 EP A4 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA ZT931 UT WOS:000074142500029 ER PT J AU Shaffer, LR AF Shaffer, LR TI International coordination in the era of faster, better, cheaper SO SPACE POLICY LA English DT Article AB Space agencies around the world are seeking innovative approaches to reduce the time and expense of space-based activities, including observation of the Earth and acquisition of environmental data for Earth science research. As government budgets are squeezed, agencies search for innovative approaches to streamline program management, introduce new technology, and share costs with external partners. International cooperation has been a mainstay of Earth observation activity from the beginning of space exploration. It continues to be true that global problems require global solutions, and governments recognize the need to share the investment in understanding and monitoring the planet. Agencies need to carefully consider how changes in their program development and management practices might impact cooperative ventures. Improved communication, enhanced strategic planning, and coordinated rather than comprehensive missions are all tools agencies can use to maintain or improve partnerships. Published by Elsevier Science Ltd. C1 NASA Headquarters, NASA Off External Relat, Mission Planet Earth Div, Washington, DC 20546 USA. RP Shaffer, LR (reprint author), NASA Headquarters, NASA Off External Relat, Mission Planet Earth Div, Washington, DC 20546 USA. NR 0 TC 0 Z9 1 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0265-9646 J9 SPACE POLICY JI Space Policy PD MAY PY 1998 VL 14 IS 2 BP 89 EP 94 DI 10.1016/S0265-9646(98)00003-4 PG 6 WC International Relations; Social Sciences, Interdisciplinary SC International Relations; Social Sciences - Other Topics GA 102CV UT WOS:000074906400004 ER PT J AU Arkoosh, MR Casillas, E Huffman, P Clemons, E Evered, J Stein, JE Varanasi, U AF Arkoosh, MR Casillas, E Huffman, P Clemons, E Evered, J Stein, JE Varanasi, U TI Increased susceptibility of juvenile chinook salmon from a contaminated estuary to Vibrio anguillarum SO TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY LA English DT Article ID HEMATOPOIETIC NECROSIS VIRUS; ONCORHYNCHUS-TSHAWYTSCHA; GAIRDNERI RICHARDSON; RAINBOW-TROUT; POLYCHLORINATED-BIPHENYLS; YERSINIA-RUCKERI; PUGET-SOUND; EXPOSURE; WASHINGTON; INFECTION AB Previous studies have shown that juvenile chinook salmon Oncorhynchus tshawytscha from a contaminated estuary of Puget Sound, Washington, are immunosuppressed. Immunosuppressed fish may be more susceptible to disease and ultimately experience an increase in mortality. To evaluate this possibility, differences in susceptibility to a marine pathogen in outmigrating juvenile chinook salmon from an urban estuary and a nonurban estuary in Puget Sound were assessed. Juvenile chinook salmon were sampled from hatcheries before their release and subsequently from their respective estuaries as the population outmigrated from freshwater to the saltwater environment during the springs of 1993 and 1994. The study was repeated during a 3-month period to assess the duration of the effect after the fish were removed from the source of contaminants and was replicated during a 2-year period to examine interannual variation. Bile, liver, and stomach contents were collected from fish after capture to determine exposure to organic chemical pollutants. Examination of these tissues demonstrated that juvenile salmon from the urban estuary were exposed to higher concentrations of polycyclic aromatic hydrocarbons and polychlorinated biphenyls than juveniles from the nonurban estuary or hatcheries. Juvenile salmon were challenged with serial doses of a marine pathogen, Vibrio anguillarum (serotype 1575), and mortality was measured daily for 7 d. In both years, salmon from the urban estuary challenged with V. anguillarum exhibited a higher cumulative mortality after exposure to the pathogen than salmon from the hatcheries or the nonurban estuary. Our results together with our previous findings support the hypothesis that contaminant-associated immunodysfunction in juvenile chinook salmon may lead to increased susceptibility to infection by a virulent marine bacterium. C1 Natl Ocean & Atmospher Adm, Environm Conservat Div, NW Fisheries Sci Ctr, Natl Marine Fisheries Serv, Newport, OR 97365 USA. NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Environm Conservat Div, Seattle, WA 98112 USA. US Fish & Wildlife Serv, Olympia Fish Hlth Ctr, Olympia, WA 98501 USA. RP Arkoosh, MR (reprint author), Natl Ocean & Atmospher Adm, Environm Conservat Div, NW Fisheries Sci Ctr, Natl Marine Fisheries Serv, 2030 S Marine Sci Dr, Newport, OR 97365 USA. NR 48 TC 57 Z9 62 U1 0 U2 9 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 0002-8487 J9 T AM FISH SOC JI Trans. Am. Fish. Soc. PD MAY PY 1998 VL 127 IS 3 BP 360 EP 374 DI 10.1577/1548-8659(1998)127<0360:ISOJCS>2.0.CO;2 PG 15 WC Fisheries SC Fisheries GA 105GR UT WOS:000075064800002 ER PT J AU Beutter, BR Stone, LS AF Beutter, BR Stone, LS TI Human motion perception and smooth eye movements show similar directional biases for elongated apertures SO VISION RESEARCH LA English DT Article DE pursuit; area MT; barberpole illusion; models; direction perception ID ACCESSORY OPTIC-SYSTEM; VISUAL AREA MT; SUPERIOR TEMPORAL SULCUS; OCULAR-FOLLOWING RESPONSES; LATERAL TERMINAL NUCLEUS; MACAQUE MONKEY; CORTICAL AREAS; HORSERADISH-PEROXIDASE; FUNCTIONAL-PROPERTIES; TRACKING NEURONS AB Although numerous studies have examined the relationship between smooth-pursuit eye movements and motion perception, it remains unresolved whether a common motion-processing system subserves both perception and pursuit. To address this question, we simultaneously recorded perceptual direction judgments and the concomitant smooth eye-movement response to a plaid stimulus that we have previously shown generates systematic perceptual errors. We measured the perceptual direction biases psychophysically and the smooth eye-movement direction biases using two methods (standard averaging and oculometric analysis). We found that the perceptual and oculomotor biases were nearly identical, suggesting that pursuit and perception share a critical motion processing stage, perhaps in area MT or MST of extrastriate visual cortex. Published by Elsevier Science Ltd. C1 NASA, Ames Res Ctr, Human Informat Proc Res Branch, Moffett Field, CA 94035 USA. RP Beutter, BR (reprint author), NASA, Ames Res Ctr, Human Informat Proc Res Branch, MS 262-2, Moffett Field, CA 94035 USA. EM brent@vision.arc.nasa.gov NR 85 TC 60 Z9 60 U1 0 U2 0 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 MAY PY 1998 VL 38 IS 9 BP 1273 EP 1286 DI 10.1016/S0042-6989(97)00276-9 PG 14 WC Neurosciences; Ophthalmology SC Neurosciences & Neurology; Ophthalmology GA ZM343 UT WOS:000073529000009 PM 9666995 ER PT J AU Birkett, CM AF Birkett, CM TI Contribution of the TOPEX NASA radar altimeter to the global monitoring of large rivers and wetlands SO WATER RESOURCES RESEARCH LA English DT Article ID TOPEX/POSEIDON; SURFACES; LAKES AB For certain major rivers and wetlands, hydrological information can often be difficult to obtain due to the inaccessibility of the region, the sparse distribution of gauge stations, or the slow dissemination of data. Satellite radar altimeters have the potential to monitor height variations over inland waters. Here, it is shown that the NASA radar altimeter (NRA), currently operating on board the TOPEX/POSEIDON satellite, can successfully track both large wetlands and rivers of >1 lan width. The coverage, performance, and limitations of the NRA altimeter are discussed with relevance to these regions, and the merits of utilizing the geophysical data records (GDRs) and the sensor data records (SDRs) are explored. Time series of relative water level variations, for the first similar to 3.7 years of the mission, have been obtained for a selection of the world's largest rivers, and for major wetlands of international importance. Validation shows the results can be accurate to similar to 11 cm rms, offering the potential to observe these regions as part of a long-term hydrological monitoring program. C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. UCL, Dept Space & Climate Phys, London, England. RP Birkett, CM (reprint author), NASA, Goddard Space Flight Ctr, USRA, Mail Code 971, Greenbelt, MD 20771 USA. EM cmb@nemo.gsfc.nasa.gov NR 28 TC 173 Z9 181 U1 2 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD MAY PY 1998 VL 34 IS 5 BP 1223 EP 1239 DI 10.1029/98WR00124 PG 17 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA ZL188 UT WOS:000073407600023 ER PT J AU Katul, GG Schieldge, J Hsieh, CI Vidakovic, B AF Katul, GG Schieldge, J Hsieh, CI Vidakovic, B TI Skin temperature perturbations induced by surface layer turbulence above a grass surface SO WATER RESOURCES RESEARCH LA English DT Article ID ORTHONORMAL WAVELET ANALYSIS; SENSIBLE HEAT-FLUX; CANOPY TEMPERATURE; DENSE VEGETATION; BOUNDARY-LAYERS; ENERGY-BALANCE; HIGH REYNOLDS; MASS-TRANSFER; EDDY MOTION; PARAMETERIZATION AB High-frequency (5 Hz) atmospheric surface layer (ASL) turbulent velocity (u') and infrared skin temperature perturbations (T-s') were measured above a grass-covered forest clearing and analyzed for cloud free conditions. These measurements were used to investigate mechanisms responsible for the production of large short-lived T-s' perturbations caused by rapid excursions in u'. To quantify the effects of u' on rapid surface cooling, wavelet spectra of u' and T-s' and cospectra of u' T-s' were computed. The u' wavelet power spectra were then analyzed using Townsend's [1961, 1976] hypothesis. Townsend's hypothesis states that ASL eddy motion can be decomposed into an active component, which is a function of the ground shear stress (u*) and height (z) above the zero plane displacement, and an inactive component, which is produced in the atmospheric boundary layer (ABL) outer region. A -1 power law in the u' power spectrum was used as a signature for inactive eddy motion. Therefore the -1 power law was used to identify wavenumber ranges (about 1.5 decades) associated with inactive eddy motion. The measured T-s', wavelet spectra and u' T-s' cospectra identified with this wavenumber range demonstrate that much of the T-s' energy and [u'T-s'] are due to inactive eddy motion, where the angle brackets indicate time averaging. Hence, in contrast to the laboratory experiments of Owen and Thomson [1963], it is argued that skin temperature perturbations at the canopy-atmosphere interface of a grass-covered surface (small thermal inertia) are strongly dependent on the inactive eddy motion produced in the outer layer of the ABL. C1 Duke Univ, Sch Environm, Durham, NC 27708 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Duke Univ, Inst Stat & Decis Sci, Durham, NC 27708 USA. Duke Univ, Ctr Hydrol Sci, Durham, NC 27708 USA. RP Katul, GG (reprint author), Duke Univ, Sch Environm, Box 90328, Durham, NC 27708 USA. EM gaby@duke.edu; john@lithos.jpl.nasa.gov; hsieh@acpub.duke.edu; brani@stat.duke.edu RI Katul, Gabriel/A-7210-2008 OI Katul, Gabriel/0000-0001-9768-3693 NR 63 TC 40 Z9 40 U1 0 U2 8 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0043-1397 J9 WATER RESOUR RES JI Water Resour. Res. PD MAY PY 1998 VL 34 IS 5 BP 1265 EP 1274 DI 10.1029/98WR00293 PG 10 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA ZL188 UT WOS:000073407600026 ER PT J AU Fischer, CF Rubin, RH AF Fischer, CF Rubin, RH TI Transition rates for some forbidden lines in Fe IV SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID ORION NEBULA AB Results from multiconfiguration Dirac-Fock (MCDF) and multiconfiguration Hartree-Fock (MCHF) with Breit and Breit-Pauli configuration interaction corrections, respectively, are presented for E2 and M1 forbidden transitions between levels of the three lowest quarter terms of Fe rv and the ground state S-6(5/2). The former treats the relativistic effects more accurately whereas for the latter, more correlation can be included. The transition rates in both approximations are compared with values predicted by Garstang in 1958 and more recent semi-empirical values. C1 Vanderbilt Univ, Dept Comp Sci, Nashville, TN 37235 USA. NASA, Ames Res Ctr, Stanford, CA 94305 USA. RP Fischer, CF (reprint author), Vanderbilt Univ, Dept Comp Sci, Box 1679 B, Nashville, TN 37235 USA. NR 23 TC 15 Z9 15 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD APR 28 PY 1998 VL 31 IS 8 BP 1657 EP 1669 DI 10.1088/0953-4075/31/8/016 PG 13 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZM801 UT WOS:000073577200016 ER PT J AU Trajmar, S Kanik, I Khakoo, MA LeClair, LR Bray, I Fursa, D Csanak, G AF Trajmar, S Kanik, I Khakoo, MA LeClair, LR Bray, I Fursa, D Csanak, G TI Elastic electron scattering by laser-excited Ba-138(- 6s6p P-1(1)) atoms SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Letter ID EXCITATION; BA AB The results of a combined experimental and theoretical study of elastic electron scattering by laser-excited Ba-138(...6s6p P-1(1)) atoms are presented. From these studies, we extracted differential scattering cross sections and parameters for elastic scattering both by coherently prepared P-1(1) Pa atoms and by Ba atoms in an isotropic, incoherent state of the P-1(1) level. This is the first time that results of this type have been reported for elastic scattering by excited atoms. Good agreement was found between the limited experimental results and those obtained from our convergent close-coupling (CCC) theoretical calculations. It was demonstrated that elastic scattering can create alignment with significant probability. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Div Chem & Chem Engn, Pasadena, CA 91125 USA. Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92634 USA. Flinders Univ S Australia, Elect Struct Mat Ctr, Adelaide, SA 5001, Australia. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. RP Trajmar, S (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RI Fursa, Dmitry/C-2301-2009; Bray, Igor/B-8586-2009 OI Fursa, Dmitry/0000-0002-3951-9016; Bray, Igor/0000-0001-7554-8044 NR 19 TC 10 Z9 10 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD APR 28 PY 1998 VL 31 IS 8 BP L393 EP L400 DI 10.1088/0953-4075/31/8/010 PG 8 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA ZM801 UT WOS:000073577200010 ER PT J AU Huang, W Shen, Z Huang, NE Fung, YC AF Huang, W Shen, Z Huang, NE Fung, YC TI Engineering analysis of biological variables: An example of blood pressure over 1 day SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article DE Fourier spectrum; Hilbert spectrum; Gumbel extreme-value statistics; pulmonary artery ID ZERO-STRESS STATE; PULMONARY-ARTERIES; VESSELS; RATS AB Almost all variables in biology are nonstationarily stochastic, For these variables, the conventional tools leave us a feeling that some valuable information is thrown away and that a complex phenomenon is presented imprecisely. Here, we apply recent advances initially made in the study of ocean waves to study the blood pressure waves in the lung. We note first that, in a long wave train, the handling of the local mean is of predominant importance. It is shown that a signal can be described by a sum of a series of intrinsic mode functions, each of which has zero local mean at all times. The process of deriding this series is called the "empirical mode decomposition method." Conventionally, Fourier analysis represents the data by sine and cosine functions, but no instantaneous frequency can be defined. In the new way, the data are represented by intrinsic mode functions, to which Hilbert transform can be used. Titchmarsh [Titchmarsh, E, C, (1948) Introduction to the Theory of Fourier Integrals (Oxford Univ. Press, Oxford)] has shown that a signal and i times its Hilbert transform together define a complex variable, From that complex variable, the instantaneous frequency, instantaneous amplitude, Hilbert spectrum, and marginal Hilbert spectrum have been defined, In addition, the Gumbel extreme-value statistics are applied. We present all of these features of the blood pressure records here for the reader to see how they look In the future, me have to learn how these features change with disease or interventions. C1 Univ Calif San Diego, Dept Bioengn, La Jolla, CA 92093 USA. CALTECH, Div Engn Sci, Pasadena, CA 91125 USA. CALTECH, Div Engn & Appl Sci, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD 20771 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 24 TC 114 Z9 132 U1 6 U2 13 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 APR 28 PY 1998 VL 95 IS 9 BP 4816 EP 4821 DI 10.1073/pnas.95.9.4816 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZL269 UT WOS:000073415700008 PM 9560185 ER PT J AU Krotkov, NA Bhartia, PK Herman, JR Fioletov, V Kerr, J AF Krotkov, NA Bhartia, PK Herman, JR Fioletov, V Kerr, J TI Satellite estimation of spectral surface UV irradiance in the presence of tropospheric aerosols - 1. Cloud-free case SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ACTIVE ULTRAVIOLET-RADIATION; TOTAL OZONE; ALBEDO MEASUREMENTS; EARTHS SURFACE; SOLAR; SCATTERING; INDEX; REFLECTIVITY; INSTRUMENT; DEPLETION AB The algorithm for determining spectral UVA (320-300 nm) and UVB (290-320 nm) flux in cloud-free conditions is discussed, including estimates of the various error sources (uncertainties in ground reflectivity, ozone amount, ozone profile shape, surface height, and aerosol attenuation). It is shown that the Brewer-measured spectral dependence of UV flux can be accurately reproduced using just total column ozone amount and the solar flux spectrum. The presence of aerosols tends to reduce the logarithm of the absolute UV flux linearly with aerosol optical depth. Using Brewer measurements of UV flux and aerosol optical depth on clear days at Toronto, the estimated slope falls in the range 0.2 to 0.3 (aerosol single-scattering albedo about 0.95). The Brewer measurements of UV flux can be reproduced using the aerosol model derived within uncertainties of the instrument calibration. We have applied the algorithm to the data collected by the total ozone mapping spectrometer (TOMS) instruments that have been flown by NASA since November 1978. It was demonstrated that in the absence of clouds and UV-absorbing aerosols, TOMS measurements of total column ozone and 380 nm (or 360 nm) radiances can be used in conjunction with a radiative transfer model to provide estimates of surface spectral flux to accuracies comparable to that of typical ground-based instruments. A newly developed technique using TOMS aerosol index data also allows estimation of UV flux transmission by strongly absorbing aerosols. The results indicate that over certain parts of the Earth, aerosols can reduce the UV flux at the surface by more than 50%. Therefore the most important need for reducing errors in TOMS-derived surface UVB spectra is to improve the understanding of UV aerosol attenuation. C1 Raytheon STX Corp, Lanham, MD 20706 USA. Atmospher Environm Serv, Downsview, ON, Canada. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Krotkov, NA (reprint author), Raytheon STX Corp, 4400 Forbes Blvd, Lanham, MD 20706 USA. EM krotkov@hoss.stx.com RI Krotkov, Nickolay/E-1541-2012; Bhartia, Pawan/A-4209-2016; OI Krotkov, Nickolay/0000-0001-6170-6750; Bhartia, Pawan/0000-0001-8307-9137; Herman, Jay/0000-0002-9146-1632; Fioletov, Vitali/0000-0002-2731-5956 NR 71 TC 149 Z9 152 U1 1 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 APR 27 PY 1998 VL 103 IS D8 BP 8779 EP 8793 DI 10.1029/98JD00233 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK155 UT WOS:000073290900013 ER PT J AU Heymsfield, AJ McFarquhar, GM Collins, WD Goldstein, JA Valero, FPJ Spinhirne, J Hart, W Pilewskie, P AF Heymsfield, AJ McFarquhar, GM Collins, WD Goldstein, JA Valero, FPJ Spinhirne, J Hart, W Pilewskie, P TI Cloud properties leading to highly reflective tropical cirrus: Interpretations from CEPEX, TOGA COARE, and Kwajalein, Marshall Islands SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ICE CRYSTALS; CLIMATE; FEEDBACK; PACIFIC; ANVILS AB This study addresses whether high concentrations of small ice crystals in the upper 1 km or so of high, thick tropical cirrus clouds are principally responsible for the highly reflective clouds observed over the equatorial Pacific "warm pool". This region of the tropics has recently been shown to contain extensive shields of cirrus clouds which significantly influence the global climate through their effect on the radiation budget of the tropics. In-situ and remote sensing measurements of cloud microphysical and radiative properties from field programs in the central and western tropical Pacific and radiative transfer calculations are used to derive distributions of cloud microphysical properties with height and their relationship to cloud radiative properties. Clouds associated directly with convection are shown to have sufficiently high optical depths near cloud top to produce localized areas of bright or optically "thick" cirrus, reflecting more than 40% of the incoming solar radiation. However, in general the upper parts of cirrus cannot alone account for the high albedos (fraction of incoming solar energy reflected) but do contribute substantially when high albedos are observed. The lower parts of the. cirrus, in some cases extending down to the melting layer or below when they are called stratiform cloud regions, are usually necessary to produce high albedos. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92037 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Heymsfield, AJ (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. EM heyms1@ncar.ucar.edu RI Heymsfield, Andrew/E-7340-2011; Collins, William/J-3147-2014; OI Collins, William/0000-0002-4463-9848; McFarquhar, Greg/0000-0003-0950-0135 NR 22 TC 21 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 27 PY 1998 VL 103 IS D8 BP 8805 EP 8812 DI 10.1029/97JD03679 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK155 UT WOS:000073290900015 ER PT J AU Wu, DL McLandress, C Read, WG Waters, JW Froidevaux, L AF Wu, DL McLandress, C Read, WG Waters, JW Froidevaux, L TI Equatorial diurnal variations observed in UARS Microwave Limb Sounder temperature during 1991-1994 and simulated by the Canadian Middle Atmosphere Model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LONG-TERM VARIABILITY; GRAVITY-WAVE; TIDE; WIND; COMPONENT AB This paper presents a study of the equatorial diurnal tide at 27-55 km based on temperature data from the Upper Atmosphere Research Satellite (UARS) Microwave Limb Sounder (MLS). The MLS temperature retrieval is significantly improved in the lower stratosphere with the recent (version 4) software and able to provide useful tidal information down to 22 hPa. The diurnal amplitude and phase, derived from MLS ascending-descending temperature differences, show a strong annual variation in the lower stratosphere and a semiannual variation in the upper stratosphere and mesosphere, which are in good agreement with other UARS measurements and simulations from the Canadian Middle Atmosphere Model (CMAM). The largest differences between the observation and the model appear at 22 and 1 hPa, reflecting some shortcomings in current tidal modeling. It is shown in MLS observations that the (1,1) tide suffers severe reduction in amplitude at 1 hPa which could be caused by the interference between the propagating tide and the component generated by stratospheric ozone heating. The data also indicate the possible presence of a short-lived propagating component (i.e., the (1, 2) mode) in the lower stratosphere, which can be excited in the upper troposphere but damped quickly as it propagates upward. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA. RP Wu, DL (reprint author), CALTECH, Jet Prop Lab, MS 183-701,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM dwu@mls.jpl.nasa.gov; charles@atmos.washington.edu RI Wu, Dong/D-5375-2012 NR 25 TC 22 Z9 22 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 APR 27 PY 1998 VL 103 IS D8 BP 8909 EP 8917 DI 10.1029/98JD00530 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK155 UT WOS:000073290900024 ER PT J AU Armengaud, A Koster, RD Jouzel, J Ciais, P AF Armengaud, A Koster, RD Jouzel, J Ciais, P TI Deuterium excess in Greenland snow: Analysis with simple and complex models SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; LAST GLACIAL MAXIMUM; ICE-CORE RECORD; ANTARCTIC PRECIPITATION; CLIMATE; SIMULATIONS; CYCLES; SURFACE; ORIGIN; HDO AB A simple Rayleigh-type isotope model, typical of those used to develop algorithms for extracting climatic information from stable water isotope paleodata, is evaluated against the more complex and presumably more reliable calculations of a general circulation model (GCM) fitted with isotope tracer diagnostics. The evaluation centers on an analysis of how the temperature T-e of an oceanic moisture source affects the deuterium excess d of Greenland precipitation. The annual T-e-d relationship derived from the GCM diagnostics is largely reproduced by the simple isotope model when the latter is properly initialized. This, coupled with the fact that the GCM itself reproduces observed isotope behavior, suggests that the simpler model's atmospheric calculations are indeed adequate for isotope studies. Furthermore, the GCM results support the idea, originally developed with the simpler models, that polar deuterium excess values contain information on meteorological conditions at distant evaporative sources. C1 Univ Grenoble 1, CNRS, Lab Glaciol & Geophys Environm, F-38402 St Martin Dheres, France. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. CEA Saclay, Lab Sci Climat & Environm, DSM, Commissariat Energie Atom, F-91191 Gif Sur Yvette, France. RP Armengaud, A (reprint author), Univ Grenoble 1, CNRS, Lab Glaciol & Geophys Environm, F-38402 St Martin Dheres, France. EM alex@glaciog.ujf-grenoble.fr; randal.koster@gsfc.nasa.gov RI Koster, Randal/F-5881-2012 OI Koster, Randal/0000-0001-6418-6383 NR 36 TC 43 Z9 46 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 APR 27 PY 1998 VL 103 IS D8 BP 8947 EP 8953 DI 10.1029/98JD00274 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK155 UT WOS:000073290900028 ER PT J AU Bhattacharjee, P Shafi, Q Stecker, FW AF Bhattacharjee, P Shafi, Q Stecker, FW TI TeV and superheavy particles from supersymmetric topological defects, the extragalactic gamma-ray background, and the highest energy cosmic rays SO PHYSICAL REVIEW LETTERS LA English DT Article ID SUPERSTRING MODELS; THERMAL INFLATION; STRINGS; SPECTRUM; PHYSICS; CUTOFF; SCALE; WELL AB Cosmic topological defects in a wide class of supersymmetric theories can simultaneously be sources of Higgs bosons of mass similar to supersymmetry breaking scale similar to TeV, as well as superheavy gauge bosons of mass similar to eta much greater than 1 TeV, eta being the gauge symmetry breaking scale. Decay of these Higgs and gauge bosons may contribute significantly to the extragalactic diffuse gamma-ray background (EDGRB) above similar to 10 GeV and explain the highest energy cosmic ray (HECR) flux above similar to 10(11) GeV, respectively. Cosmic strings with eta much above 10(14) GeV overproduce both HECR and EDGRB, and hence are ruled out, if massive particle radiation is their dominant energy loss mechanism. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Bhattacharjee, P (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 45 TC 26 Z9 26 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 APR 27 PY 1998 VL 80 IS 17 BP 3698 EP 3701 DI 10.1103/PhysRevLett.80.3698 PG 4 WC Physics, Multidisciplinary SC Physics GA ZJ826 UT WOS:000073257600007 ER PT J AU Knibbe, WJJ de Haan, JF Hovenier, JW Travis, LD AF Knibbe, WJJ de Haan, JF Hovenier, JW Travis, LD TI Analysis of temporal variations of the polarization of Venus observed by Pioneer Venus Orbiter SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID ATMOSPHERE; SCATTERING; CLOUDS; LIGHT; SO2 AB Time variations of the disk-averaged polarization of Venus at wavelengths of 270, 365, 550, and 935 nm have been analyzed in terms of average haze optical thickness, cloud-top pressure, and cloud absorption optical thickness at 210 nm (presumably due to gaseous SO2 absorption). The polarization data were deduced from observations made by the Pioneer Venus Orbiter between 1978 and 1990. Newton-Raphson iteration was used to derive the atmospheric parameter values from these observations. The required multiple scattering calculations were performed using the adding/doubling method. The atmospheric model consists of a cloud layer and a haze layer. The cloud and haze particles are composed of a concentrated sulfuric acid solution and have an effective radius of 1.05 mu m and 0.25 mu m, respectively. It was found that the disk-averaged haze optical thickness, cloud-top pressure, and cloud absorption optical thickness at 270 nm varied irregularly between 1978 and 1990. No trends were identified for the cloud-top pressure and cloud absorption optical thickness at 270 nm, but we did deduce a decrease in haze optical thickness during this 12 year period. Specific numbers are: (1) a haze optical thickness at 365 nm of about 0.25 in 1978 and less than 0.1 in 1990, (2) a cloud-top pressure that varies between 5 and 20 mbar, and (3) a cloud absorption optical thickness that varies between 0.0 and 4.0. Finally, our analysis revealed that the disk-averaged cloud-top pressure and haze optical thickness behaved anomalously in 1983. C1 Minist Transport Publ Works & Water Management, Transport Res Ctr, AVV, NL-3000 BA Rotterdam, Netherlands. Free Univ Amsterdam, Dept Phys & Astron, NL-1081 HV Amsterdam, Netherlands. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Knibbe, WJJ (reprint author), Minist Transport Publ Works & Water Management, Transport Res Ctr, AVV, POB 1031, NL-3000 BA Rotterdam, Netherlands. EM w.j.j.knibbe@avv.rws.minvenw.pl; johan@nat.vu.nl; hovenier@nat.vu.nl; pdldt@giss.nasa.gov NR 50 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-PLANET JI J. Geophys. Res.-Planets PD APR 25 PY 1998 VL 103 IS E4 BP 8557 EP 8574 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138JV UT WOS:000076969500003 ER PT J AU Bridger, AFC Murphy, JR AF Bridger, AFC Murphy, JR TI Mars' surface pressure tides and their behavior during global dust storms SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARTIAN ATMOSPHERE; THERMAL TIDES; GENERAL-CIRCULATION; MODEL; SIMULATIONS AB Simulations of Mars' atmospheric tides with the NASA-Ames Mars general circulation model are presented and analyzed. In an annual simulation, diurnal and semidiurnal tides in the model's surface pressure field are shown to compare well with tides observed by the Viking landers throughout the Mars year. Focused simulations of global dust storms during the northern winter season show a semidiurnal tide that responds very strongly to the increased dust load during the storms, again matching well with observations. Analysis of the structure and behavior of this tide during global storms verifies that it is dominated by the gravest symmetric Hough mode (H-2(2)),as has been noted previously. However, it is shown here that additional symmetric and asymmetric modes play an important role in accounting for the structure of the tide and its variation during the dust storms. The phase advance observed between the Viking lander sites (earlier semidiurnal phase at the higher-latitude site) is explained by the presence of these higher-order modes. Finally, decomposition of the semidiurnal tide during a global dust storm into its component Hough modes shows that the amplitude of the H-2(2) mode mirrors changes in the observed overhead visible dust opacity, while variations in higher-order modes are indicative of the zonal (and, possibly, longitudinal) distribution of airborne dust. C1 San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. San Jose State Univ, San Jose, CA 95172 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bridger, AFC (reprint author), San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. NR 28 TC 21 Z9 21 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-PLANET JI J. Geophys. Res.-Planets PD APR 25 PY 1998 VL 103 IS E4 BP 8587 EP 8601 DI 10.1029/98JE00242 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138JV UT WOS:000076969500006 ER PT J AU McCord, TB Hansen, GB Clark, RN Martin, PD Hibbitts, CA Fanale, FP Granahan, JC Segura, M Matson, DL Johnson, TV Carlson, RW Smythe, WD Danielson, GE AF McCord, TB Hansen, GB Clark, RN Martin, PD Hibbitts, CA Fanale, FP Granahan, JC Segura, M Matson, DL Johnson, TV Carlson, RW Smythe, WD Danielson, GE CA NIMS Team TI Non-water-ice constituents in the surface material of the icy Galilean satellites from the Galileo near-infrared mapping spectrometer investigation SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID 3.4 MU-M; INTERNAL STRUCTURE; REFLECTANCE SPECTRUM; INTERSTELLAR ICES; OPTICAL-CONSTANTS; EMISSION FEATURE; CARBON-DIOXIDE; CALLISTO; GANYMEDE; SO2 AB We present evidence for several non-ice constituents in the surface material of the icy Galilean satellites, using the reflectance spectra returned by the Galileo near infrared mapping spectrometer (NLMS) experiment. Five new absorption features are described at 3.4, 3.88, 4.05, 4.25, and 4.57 mu m for Callisto and Ganymede, and some seem to exist for Europa as well. The four absorption bands strong enough to be mapped on Callisto and Ganymede are each spatially distributed in different ways, indicating different materials are responsible for each absorption. The spatial distributions are correlated at the local level in complex ways with surface features and in some cases show global patterns. Suggested candidate spectrally active groups, perhaps within larger molecules, producing the five absorptions include C-H, S-H, SO(2), CO(2), and C=N. Organic material like tholins are candidates for the 4.57- and 3.4-mu m features. We suggest, based on spectroscopic evidence, that CO(2) is present as a form which does not allow rotational modes and that SO(2) is present neither as a frost nor a free gas. The CO(2), SO(2), and perhaps cyanogen (4.57 mu m) may be present as very small collections of molecules within the crystal structure, perhaps following models for radiation damage and/or for comet and interstellar grain formation at low temperatures. Some of the dark material on these surfaces may be created by radiation damage of the CO(2) and other carbon-bearing species and the formation of graphite. These spectra suggest a complex chemistry within the surface materials and an important role for non-ice materials in the evolution of the satellite surfaces. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Denver Fed Ctr, Lakewood, CO 80225 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Sci & Technol Int Inc, Honolulu, HI 96813 USA. RP McCord, TB (reprint author), Univ Hawaii, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys & Planetol, 2525 Correa Rd, Honolulu, HI 96822 USA. EM tom@pgd.hawaii.edu; ghansen@pgd.hawaii.edu; rclark@speclab.cr.usgs.gov; martin@pgd.hawaii.edu; hibbitts@pgd.hawaii.edu; fanale@pgd.hawaii.edu; granahan@lava.net; msegura@jpluvs.jpl.nasa.gov; dmatson@jpluvs.jpl.nasa.gov; tjohnson@jpltvj.jpl.nasa.gov; rcarlson@jpluvs.jpl.nasa.gov; wsmythe@jpluvs.jpl.nasa.gov; ged@soll.gps.caltech.edu RI Hibbitts, Charles/B-7787-2016 OI Hibbitts, Charles/0000-0001-9089-4391 NR 77 TC 168 Z9 169 U1 2 U2 18 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 APR 25 PY 1998 VL 103 IS E4 BP 8603 EP 8626 DI 10.1029/98JE00788 PG 24 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 138JV UT WOS:000076969500007 ER PT J AU Bauschilcher, CW Partridge, H AF Bauschilcher, CW Partridge, H TI The sensitivity of B3LYP atomization energies to the basis set and a comparison of basis set requirements for CCSD(T) and B3LYP (vol 240, pg 533, 1995) SO CHEMICAL PHYSICS LETTERS LA English DT Correction C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschilcher, CW (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 1 TC 1 Z9 1 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 APR 24 PY 1998 VL 287 IS 1-2 BP 216 EP 216 DI 10.1016/S0009-2614(98)00139-0 PG 1 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZJ720 UT WOS:000073245700034 ER PT J AU Orta, D Mudgett, PD Ding, L Drybread, M Schultz, JR Sauer, RL AF Orta, D Mudgett, PD Ding, L Drybread, M Schultz, JR Sauer, RL TI Analysis of water from the Space Shuttle and Mir Space Station by ion chromatography and capillary electrophoresis SO JOURNAL OF CHROMATOGRAPHY A LA English DT Article; Proceedings Paper CT 10th Anniversary of the International Ion Chromatography Symposium (IICS 97) CY SEP 14-17, 1997 CL SANTA CLARA, CALIFORNIA DE water analysis; Space Shuttle; Mir Space Station; inorganic cations; inorganic anions; carboxylic acids; amines AB Drinking water and condensate samples collected from the US Space Shuttle and the Russian Mir Space Station are analyzed routinely at the NASA-Johnson Space Center as part of an ongoing effort io verify water quality and monitor the environment of the spacecraft. Water quality monitoring is particularly important for the Mir water supply because approximately half of the water consumed is recovered fr om humidity condensate. Drinking water on Shuttle is derived from the fuel cells. Because there is little equipment on board the spacecraft for monitoring the water quality, samples collected by the crew are transported to Earth on Shuttle or Soyuz vehicles, and analyzed exhaustively. As part of the test battery, anions and cations are measured by ion chromatography, and carboxylates and amines by capillary electrophoresis. Analytical data from Shuttle water samples collected before and after several missions, and Mir condensate and potable recovered water samples representing several recent missions are presented and discussed. Results show that Shuttle water is of distilled quality, and Mir recovered water contains various levels of minerals imparted during the recovery processes as designed. Organic ions are rarely detected in potable water samples, but were present in humidity condensate samples. (C) 1998 Elsevier Science B.V. C1 Krug Life Sci, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Orta, D (reprint author), Krug Life Sci, 1290 Hercules Dr,Suite 120, Houston, TX 77058 USA. NR 17 TC 14 Z9 15 U1 1 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0021-9673 J9 J CHROMATOGR A JI J. Chromatogr. A PD APR 24 PY 1998 VL 804 IS 1-2 BP 295 EP 304 DI 10.1016/S0021-9673(97)01289-2 PG 10 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA ZN363 UT WOS:000073638400037 PM 9615408 ER PT J AU Rose, D Durose, K Palosz, W Szczerbakow, A Grasza, K AF Rose, D Durose, K Palosz, W Szczerbakow, A Grasza, K TI Methods of dislocation distribution analysis and inclusion identification with application to CdTe and (Cd,Zn)Te SO JOURNAL OF PHYSICS D-APPLIED PHYSICS LA English DT Article ID PHYSICAL VAPOR TRANSPORT; CATHODOLUMINESCENCE MICROSCOPY; CRYSTAL-GROWTH; TELLURIDE; DENSITY AB Although the density of dislocations is used as an indicator of the quality of semiconductor wafers, it is also necessary to provide a description of the dislocation distribution for those materials prone to polygonization (namely the formation of sub-grain boundaries). In this work it is shown that visual inspection of etch pit distributions is insufficient and that quantitative comparison with random distributions is more informative. This was achieved in two ways: (i) by comparison with a Poisson distribution and (ii) by using normalized radial dislocation density plots, the former yielding the type of distribution and the latter the characteristic sub-grain tilting angle for the sample. Although these methods are general, examples for melt-and vapour-grown CdTe and (Cd, Zn)Te are given. Also reported upon in this work is the use of etching solutions to reveal inclusions in CdTe and (Cd, Zn)Te and hence permit their chemical identification by SEM/EDAX. C1 Univ Durham, Dept Phys, Durham DH1 3LE, England. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Polish Acad Sci, Inst Phys, PL-02668 Warsaw, Poland. RP Rose, D (reprint author), Univ Durham, Dept Phys, South Rd, Durham DH1 3LE, England. RI Durose, Ken/E-2617-2013 NR 22 TC 14 Z9 14 U1 0 U2 8 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0022-3727 J9 J PHYS D APPL PHYS JI J. Phys. D-Appl. Phys. PD APR 21 PY 1998 VL 31 IS 8 BP 1009 EP 1016 DI 10.1088/0022-3727/31/8/012 PG 8 WC Physics, Applied SC Physics GA ZM480 UT WOS:000073544400012 ER PT J AU Serabyn, E Weisstein, EW Lis, DC Pardo, JR AF Serabyn, E Weisstein, EW Lis, DC Pardo, JR TI Submillimeter Fourier-transform spectrometer measurements of atmospheric opacity above Mauna Kea SO APPLIED OPTICS LA English DT Article ID WATER-VAPOR CONTINUUM; BRIGHTNESS TEMPERATURE; SPECTRAL REGION; MILLIMETER; WAVELENGTHS; CALIBRATION; TRANSMISSION; ATTENUATION; GHZ AB We present accurately calibrated submillimeter atmospheric transmission spectra obtained with a Fourier-transform spectrometer at the Caltech Submillimeter Observatory on Mauna Kea, Hawaii. These measurements cover the 0.9-0.3-mm wavelength range and are the first in a series aimed at defining the terrestrial long-wave atmospheric transmission curve. The 4.1-km altitude of the Mauna Kea site provides access to extremely low zenith water-vapor columns, permitting atmospheric observations at frequencies well above those possible from sea level. We describe the calibration procedures, present our first well-calibrated transmission spectra, and compare our results with those of a singlelayer atmospheric transmission model, AT. With an empirical best-fit continuum opacity term included, this simple single-layer model provides a remarkably good fit to the opacity data for H2O line profiles described by either van Vleck-Weisskopf or kinetic shapes. (C) 1998 Optical Society of America. C1 CALTECH, Dept Phys, Pasadena, CA 91125 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. RP Serabyn, E (reprint author), CALTECH, Dept Phys, MS 320-47, Pasadena, CA 91125 USA. NR 34 TC 32 Z9 33 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD APR 20 PY 1998 VL 37 IS 12 BP 2185 EP 2198 DI 10.1364/AO.37.002185 PG 14 WC Optics SC Optics GA ZH797 UT WOS:000073148600001 PM 18273141 ER PT J AU Dallas, JL Afzal, RS AF Dallas, JL Afzal, RS TI Modeling of a diode-side-pumped Nd : YAG laser SO APPLIED OPTICS LA English DT Article AB We have developed a unique numerical laser model by use of a commercial physical optics software package. The experimentally measured lasing threshold, slope efficiency, power output distribution, and phase front have been derived. This model is particularly powerful for monitoring the effects caused by thermal distortions encountered in power scaling lasers. Extrapolations have been made through parametric studies to predict changes required in the laser design that would optimize the performance of the laser. (C) 1998 Optical Society of America. C1 Sci Syst & Applicat Inc, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dallas, JL (reprint author), Sci Syst & Applicat Inc, Lanham, MD 20706 USA. NR 12 TC 4 Z9 4 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD APR 20 PY 1998 VL 37 IS 12 BP 2365 EP 2370 DI 10.1364/AO.37.002365 PG 6 WC Optics SC Optics GA ZH797 UT WOS:000073148600025 PM 18273165 ER PT J AU de Martino, D Barcaroli, R Matt, G Mouchet, M Belloni, T Beuermann, K Chiappetti, L Done, C Gansicke, BT La Franca, F Mukai, K AF de Martino, D Barcaroli, R Matt, G Mouchet, M Belloni, T Beuermann, K Chiappetti, L Done, C Gansicke, BT La Franca, F Mukai, K TI BeppoSAX observations of the long period polar system V1309 Ori SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : individual : V1309 Ori=RXJ0515.6+0105; cataclysmic variables; X-rays : stars ID RX J0515.6+0105; ACCRETION AB We present BeppoSAX observations of the peculiar long period polar system V1309 Ori (RXJ0515.6+0105). The source was detected simultaneously at soft and, for the first time, at hard X-rays with the LEGS and the MECS detectors. Both, the LEGS and the MECS light curves are irregular with a bursting/flaring type behaviour indicating inhomogeneous accretion onto the white dwarf. This peculiar variability, together with an extreme high soft-to-hard X-ray luminosity ratio, indicates that in V1309 Ori accretion occurs predominantly in highly compressed chunks or "blobs" of matter. From coordinated ESO optical spectroscopy, we find indications that the magnetic field strength of the white dwarf is < 70 MG, not expected either from the 8 hr orbital period synchronism or from the strong soft-to-hard X-ray ratio suggesting alternative solutions for sustaining synchronism in this system. C1 Osservatorio Astron Capodimonte, I-80131 Naples, Italy. Univ Roma Tre, Dipartimento Fis, I-00146 Roma, Italy. Observ Paris, DAEC, Meudon Sect, F-92195 Meudon, France. Univ Denis Diderot, F-75005 Paris, France. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Sternwarte, D-37083 Gottingen, Germany. CNR, Ist Fis Cosm, I-20133 Milan, Italy. Univ Durham, Dept Phys, Durham DH1 3LE, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP de Martino, D (reprint author), Osservatorio Astron Capodimonte, Via Moiariello 16, I-80131 Naples, Italy. RI Gaensicke, Boris/A-9421-2012; La Franca, Fabio/G-9631-2012; done, chris/D-4605-2016; OI Gaensicke, Boris/0000-0002-2761-3005; done, chris/0000-0002-1065-7239; Chiappetti, Lucio/0000-0001-7857-7908; La Franca, Fabio/0000-0002-1239-2721 NR 20 TC 9 Z9 9 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR 20 PY 1998 VL 332 IS 3 BP 904 EP 908 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL736 UT WOS:000073465300020 ER PT J AU Solheim, JE Provencal, JL Bradley, PA Vauclair, G Barstow, MA Kepler, SO Fontaine, G Grauer, AD Winget, DE Marar, TMK Leibowitz, EM Emanuelsen, PI Chevreton, M Dolez, N Kanaan, A Bergeron, P Claver, CF Clemens, JC Kleinman, SJ Hine, BP Seetha, S Ashoka, BN Mazeh, T Sansom, AE Tweedy, RW Meistas, EG Bruvold, A Massacand, CM AF Solheim, JE Provencal, JL Bradley, PA Vauclair, G Barstow, MA Kepler, SO Fontaine, G Grauer, AD Winget, DE Marar, TMK Leibowitz, EM Emanuelsen, PI Chevreton, M Dolez, N Kanaan, A Bergeron, P Claver, CF Clemens, JC Kleinman, SJ Hine, BP Seetha, S Ashoka, BN Mazeh, T Sansom, AE Tweedy, RW Meistas, EG Bruvold, A Massacand, CM TI Whole earth telescope observations of AM Canum Venaticorum - discoseismology at last SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : individual : AM Canum Venaticorum; novae, cataclysmic variables; stars : oscillations; white dwarfs; accretion, accretion disks ID URSAE MAJORIS STARS; ACCRETION DISKS; CLOSE BINARY; CVN; DWARF; SUPEROUTBURST; SUPERHUMPS; SPECTRUM; PERIOD; G61-29 AB We report the results of 143.2 hours of time-series photometry over a 12 day period for AM CVn (= HZ 29) as part of the Whole Earth Telescope (WET) project.(1) This star is believed to be an ultra-short period cataclysmic binary. In the temporal spectrum of the light curve we find a series of 5 harmonically related frequency mo dulations, some with sidebands with a constant frequency spacing of 20.8 mu Hz always on the high-frequency side. The set of harmonics has a fundamental frequency of 951 mu Hz. NO modulation is detected at this frequency in the light curve. In addition, modulations with frequencies 972.5 and 988.9 mu Hz are detected with low amplitudes. The structure of the dominant 1903 mu Hz modulation explains part of the "phase jitter" observed earlier. The amplitude of this peak is modulated with a period of 13.32 +/- 0.05 hrs. The same period is detected in absorption line shape modulations, most likely arising from variable aspects of the outer parts of the disk (Patterson et al. 1993). The observed periodic light modulations can be explained as a combination of aspect variations of disk modifications due to tidally induced shocks as described by Savonie et al. (1994), which leads to a two-armed spiral structure, and the mode coupling model of Lubow (1991), which leads to a three-fold azimuthal symmetry in the outer parts of the disk and a prograde precessing wave. The two-and three-fold aszimuthal structures are stationary in the binary frame and explain the higher harmonics of the orbital period we observe in the light curve. This may be the first example of a successful disco-seismological interpretation. In addition we propose that the variable amplitude modulation at 989 mu Hz may be explained as a g-mode pulsation, which indicates that the central white dwarf may be a DO with a hot envelope. C1 Univ Tromso, Inst Fys, Nordlysobserv, N-9037 Tromso, Norway. Univ Texas, Dept Astron, Austin, TX 78712 USA. Univ Texas, Mcdonald Observ, Austin, TX 78712 USA. Observ Midi Pyrenees, F-31400 Toulouse, France. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. Univ Fed Rio Grande do Sul, Inst Fis, BR-91500970 Porto Alegre, RS, Brazil. Univ Montreal, Dept Phys, Montreal, PQ H3C 3J7, Canada. Univ Arkansas, Dept Phys & Astron, Little Rock, AR 72204 USA. ISRO Satelite Ctr, Tech Phys Div, Bangalore 560017, Karnataka, India. Tel Aviv Univ, Dept Phys & Astron, IL-69978 Tel Aviv, Israel. Observ Paris, F-92195 Meudon, France. Vilnius State Univ, Inst Mat Res & Appl Sci, LT-2009 Vilnius, Lithuania. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Inst Theoret Phys & Astron, Astron Observ, LT-2600 Vilnius, Lithuania. Univ Delaware, Dept Phys, Newark, DE 19716 USA. Los Alamos Natl Lab, XTA, Los Alamos, NM 87545 USA. Kitt Peak Natl Observ, Tucson, AZ 85726 USA. CALTECH, Pasadena, CA 91125 USA. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. RP Solheim, JE (reprint author), Univ Tromso, Inst Fys, Nordlysobserv, N-9037 Tromso, Norway. RI Kepler, S. O. /H-5901-2012 OI Kepler, S. O. /0000-0002-7470-5703 NR 55 TC 28 Z9 28 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 APR 20 PY 1998 VL 332 IS 3 BP 939 EP 957 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL736 UT WOS:000073465300023 ER PT J AU Ayala, S Curiel, SS Raga, AC Noriega-Crespo, A Salas, L AF Ayala, S Curiel, SS Raga, AC Noriega-Crespo, A Salas, L TI Near infrared imaging and spectroscopy of the IRAS 20126+4104 region SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ISM : jets and outflows; infrared : ISM : lines and bands; ISM : individual objects : IRAS 20126+4104 ID HERBIG-HARO OBJECTS; H-2 FLUORESCENCE; OUTFLOWS AB In this paper we present near-infrared images and K'-band spectra (1.95-2.30 mu m) of the nebulae located in the IRAS 20126+4104 region. We find bright cometary shaped objects to the Northwest of the IRAS position and other emission line objects to the Southeast. We have detected 6 low excitation emission lines of molecular hydrogen, and present spatially resolved excitation temperatures, 1-0 S(1)/2-1 S(1) line ratios and ortho-para ratios for the brighter emission line objects near the IRAS source. The integrated flux in the H(2) 1-0 S(1) line of the brighter object located to the Northwest of the IRAS position is 6.85 x 10(-13) erg cm(-2) s(-1), integrated within an aperture of 10.2 arcsec(2). From a spectrophotometric analysis, we conclude that the H(2) emission observed in this nebula is mainly produced by collisional excitation combined with fluorescent H(2) emission. However, it is unclear from our observations whether the UV radiation field that would be responsible for the fluorescent component is produced by the IRAS source itself, or by the stars embedded at the Eastern edges of two of the observed condensations. C1 Univ Nacl Autonoma Mexico, Inst Astron, Mexico City 04510, DF, Mexico. CALTECH, Jet Prop Lab, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Nacl Autonoma Mexico, Inst Astron, Ensenada 22830, Baja California, Mexico. RP Ayala, S (reprint author), Univ Nacl Autonoma Mexico, Inst Astron, Ap 70-264, Mexico City 04510, DF, Mexico. EM sayala@astroscu.unam.mx NR 24 TC 14 Z9 14 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 APR 20 PY 1998 VL 332 IS 3 BP 1055 EP 1063 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL736 UT WOS:000073465300032 ER PT J AU Neukirch, T Martens, PCH AF Neukirch, T Martens, PCH TI An approximate self-consistent theory of the magnetic field of fluted penumbrae SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE sunspots; sun : magnetic fields; MHD; methods : analytical ID SUNSPOTS; VELOCITY AB A self-consistent mathematical description of the magnetic field of fluted sunspot penumbrae is presented. This description is based on an expansion of the nonlinear force-free magnetohydrostatic equations written in cylindrical coordinates. The lowest order solutions are mathematically equivalent to laminated force-free equilibria in Cartesian geometry. The lowest order solutions have no toroidal component of the magnetic field and the magnetic pressure does not vary with azimuth but the solutions allow arbitrary variations of the magnetic field components with azimuth. Explicit solutions are presented which have a realistic radial profile of the magnetic field strength and reproduce the basic features of the observations. C1 Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. NASA, Goddard Space Flight Ctr, ESA, Dept Space Sci, Greenbelt, MD 20771 USA. RP Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. EM thomas@dcs.st-and.ac.uk; pmartens@esa.nascom.nasa.gov RI Neukirch, Thomas/C-1981-2009 OI Neukirch, Thomas/0000-0002-7597-4980 NR 17 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR 20 PY 1998 VL 332 IS 3 BP 1075 EP 1081 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZL736 UT WOS:000073465300035 ER PT J AU Tingay, SJ Murphy, DW Lovell, JEJ Costa, ME McCulloch, P Edwards, PG Jauncey, DL Reynolds, JE Tzioumis, AK King, EA Jones, DL Preston, RA Meier, DL van Ommen, TD Nicolson, GD Quick, JFH AF Tingay, SJ Murphy, DW Lovell, JEJ Costa, ME McCulloch, P Edwards, PG Jauncey, DL Reynolds, JE Tzioumis, AK King, EA Jones, DL Preston, RA Meier, DL van Ommen, TD Nicolson, GD Quick, JFH TI VLBI observations of gamma-ray-quiet active galactic nuclei: Comparing radio-core brightness temperatures SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, jets; gamma-rays, observations; radio continuum; galaxies; techniques, interferometric ID COMPTON LIMIT; QUASARS; BLAZARS; EGRET; JETS AB We present VLBI and Australia Telescope Compact Array images and derive source-frame radio-core brightness temperatures for three prominent, flat-spectrum extragalactic radio sources, notable because they have not been detected as gamma-ray sources with the EGRET instrument. Radio-core brightness temperatures are discussed as an indicator of relativistic beaming. A comparison of source-frame radio-core brightness temperatures for EGRET-identified and gamma-ray-quiet, radio-loud AGNs shows that a wide range in beaming properties is likely to exist, independent of the level of gamma-ray emission. This comparison suggests that, although there is a strong relationship between radio emission and gamma-ray emission in EGRET-identified AGNs, and many EGRET-identified AGNs show evidence for relativistic beaming, there is little evidence for a one-to-one correspondence between the strength of gamma-ray emission and the degree of beaming of the radio emission. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Tasmania, Hobart, Tas 7001, Australia. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Hartebeesthoek Radio Astron Observ, ZA-1740 Krugersdorp, South Africa. RP Tingay, SJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS238-332, Pasadena, CA 91109 USA. EM tingay@hyaa.jpl.nasa.gov; dwm@casa.jpl.nasa.gov; jlovell@vsop.isas.ac.jp; mcosta@kerr.phys.utas.edu; pmcc@physvax.phys.utas.edu; pge@vsop.isas.ac.jp; djauncey@atnf.csiro.au; jreynold@atnf.csiro.au; atzioumi@atnf.csiro.au; eking@atnf.csiro.au; dj@bllac.jpl.nasa.gov; rap@sgra.jpl.nasa.gov; dlm@cena.jpl.nasa.gov; george@bootes.hartrao.ac.za; jon@bootes.hartrao.ac.za RI Tingay, Steven/B-5271-2013; van Ommen, Tas/B-5020-2012; King, Edward/A-1473-2012 OI van Ommen, Tas/0000-0002-2463-1718; King, Edward/0000-0002-6898-2130 NR 37 TC 24 Z9 24 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP 594 EP 600 DI 10.1086/305494 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ199 UT WOS:000073189400011 ER PT J AU Loewenstein, M Hayashida, K Toneri, T Davis, DS AF Loewenstein, M Hayashida, K Toneri, T Davis, DS TI On the nature of the X-ray emission from M32 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, elliptical and lenticular, cD; galaxies, individual (M32); galaxies, nuclei; X-rays, galaxies; X-rays, stars ID EARLY-TYPE GALAXIES; BLACK-HOLE; ASCA; NGC-4472 AB We have obtained the first broadband X-ray spectra of the nearby compact elliptical galaxy M32 by using the ASCA satellite. The extracted spectra and X-ray luminosity are consistent with the properties of the hard spectral component measured in giant elliptical galaxies believed to originate from X-ray binaries. Two ASCA observations were performed two weeks apart; a 25% flux decrease and spectral softening occurred in the interval. We have also analyzed archival ROSAT HRI data, and discovered that the X-ray emission is dominated by a single unresolved source offset from the nucleus of M32. We argue that this offset, combined with the extremely rapid large magnitude variations, and hard X-ray spectrum combine to weakly favor a (single) X-ray binary over an AGN origin for the X-rays from M32. The nuclear black hole in M32 must be fuel-starved and/or accreting from a radiatively inefficient advection-dominated disk: the product of the accretion rate and the radiative efficiency must be less than similar to 10(-10) M. yr(-1) if the X-ray source is indeed an X-ray binary. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Osaka Univ, Dept Earth & Space Sci, Toyonaka, Osaka 560, Japan. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Loewenstein, M (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 28 TC 17 Z9 17 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP 681 EP 688 DI 10.1086/305504 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ199 UT WOS:000073189400017 ER PT J AU Hwang, U Hughes, JP Petre, R AF Hwang, U Hughes, JP Petre, R TI The X-ray iron emission from Tycho's supernova remnant SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (Tycho's supernova); supernova remnants; X-rays, ISM ID WHITE-DWARF MODELS; ABSORPTION-LINES; NOVA REMNANTS; I SUPERNOVAE; SPECTRUM; SN-1006; EJECTA AB We present the results of broadband spectral model fits to the X-ray spectrum of Tycho's supernova remnant obtained by the Solid-State Imaging Spectrometers on the ASCA Observatory. We use single temperature, single ionization age, nonequilibrium ionization models to characterize the ejecta and the blast-shocked interstellar medium. Previous spectral studies have suggested that the Fe ejecta in this Type Ia remnant are stratified interior to the other ejecta. These studies, however, have generally restricted their attention to the Fe K blend at 6.5 keV. ASCA provides data over a broad energy range that allow the placement of important constraints simultaneously from the Fe L emission near 1 keV, as well as the Fe K emission. We find that the simplest models, with emission from the ejecta and blast wave each at a single temperature and ionization age, severely underestimate the flux in the Fe K blend. These models also show that there is little Fe emission associated with the Si and S ejecta shell, which has an average temperature kT similar to 0.86 keV and ionization age n(e)t similar to 10(11) cm(-3) s. The blast-shocked interstellar medium has abundances roughly 0.3 times the solar value, while the ejecta-with the exception of Fe-have relative abundances that are typical of Type Ia supernovae. The addition of another component of Fe emission-which we associate with ejecta-at a temperature at least 2 times higher and an ionization age similar to 100 times lower than the Si ejecta does provide a good fit to the spectrum. This model is consistent with imaging results. Although fluorescent emission from dust in the remnant may contribute to the Fe K flux, we conclude that it is unlikely to be the dominant component. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08855 USA. RP Hwang, U (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 36 TC 43 Z9 44 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP 833 EP 841 DI 10.1086/305501 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ199 UT WOS:000073189400029 ER PT J AU Peng, R Langer, WD Velusamy, T Kuiper, TBH Levin, S AF Peng, R Langer, WD Velusamy, T Kuiper, TBH Levin, S TI Low-mass clumps in TMC-1: Scaling laws in the small-scale regime SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, clouds; ISM, individual (Taurus Molecular Cloud); ISM, molecules; radio lines, ISM; stars, formation ID TAURUS MOLECULAR CLOUD-1; DENSE CORES; DARK CLOUDS; STAR-FORMATION AB We present new observational data on the small-scale structure of the Taurus molecular cloud 1 (TMC-1) in the regime of 0.02-0.04 pc and 0.04-0.6 M.. Our analysis is based on high-resolution, high-S/N, observations of an 8' x 8' area centered on the "cyanopolyyne peak" in the southeastern part of the TMC-1 ridge. The observations were made in the CCS 22 and 45 GHz transitions using NASA's Deep Space Network 70 m and 34 m telescopes at the Goldstone facility. The CCS emission in this region originates in three narrow components centered on LSR velocities of similar to 5.7, 5.9, and 6.1 km s(-1). These components each represent a separate cylindrical feature elongated along the ridge. Among the three velocity components we identified a total of 45 clumps with a typical CCS column density of similar to a few x 10(13) cm(-2), an H-2 density of similar to a few x 10(4) cm(-3), and a mass in the range of 0.04-0.6 M.. The statistical properties of these small-scale clumps are compared with those of the larger "NH3 cores" in cold clouds and "CS cores" in the hotter Orion region. The CCS clumps in TMC-1 are found to conform to Larson's scaling laws (relating observed line width to clump size) derived from the larger cores down to the small-scale regime (0.02 pc and 0.04 M.). These clumps represent a regime in which microturbulence is small, amounting to similar to 10% of the thermal pressure inside a clump. Of the 45 clumps, only five appear to be gravitationally unstable to collapse. All unbound clumps have masses less than 0.2 M., while bound clumps have masses in the range 0.15-0.6 M.. The 6.1 km s(-1) velocity feature contains all the gravitationally unstable clumps and is the most likely site for future star formation. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Langer, WD (reprint author), CALTECH, Jet Prop Lab, MS 169-506, Pasadena, CA 91109 USA. NR 23 TC 49 Z9 49 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP 842 EP 849 DI 10.1086/305483 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ199 UT WOS:000073189400030 ER PT J AU Aschwanden, MJ Dennis, BR Benz, AO AF Aschwanden, MJ Dennis, BR Benz, AO TI Logistic avalanche processes, elementary time structures, and frequency distributions in solar flares SO ASTROPHYSICAL JOURNAL LA English DT Article DE instabilities; methods, statistical; Sun, flares; Sun, radio radiation; Sun, X-rays, gamma rays ID HARD X-RAY; ELECTRON-CYCLOTRON MASER; OF-FLIGHT DISTANCES; III RADIO-BURSTS; RECONNECTION OUTFLOWS; BULK ENERGIZATION; IMPULSIVE PHASE; SPIKES; INSTABILITY; ACCELERATION AB We analyze the elementary time structures (on timescales of approximate to 0.1-3.0 s) and their frequency distributions in solar flares using hard X-ray (HXR) data from the Compton Gamma Ray Observatory (CGRO) and radio data from the radio spectrometers of Eidgenoessische Technische Hochschule (ETH) Zurich. The four analyzed data sets are gathered from over 600 different solar flares and include about (1) 10(4) HXR pulses at greater than or equal to 25 and greater than or equal to 50 keV, (2) 4000 radio type III bursts, (3) 4000 pulses of decimetric quasiperiodic broadband pulsation events, and (4) 10(4) elements of decimetric millisecond spike events. The time profiles of resolved elementary time structures have a near-Gaussian shape and can be modeled with the logistic equation, which provides a quantitative measurement of the exponential growth time tau(G) and the nonlinear saturation energy level W-S of the underlying instability. Assuming a random distribution (Poisson statistics) of saturation times t(S) (with an e-folding constant t(Se)), the resulting frequency distribution of saturation energies W-S or peak energy dissipation rates F-S = (dW/dt)(t=tS) has the form of a power-law function, i.e., N(F-S) proportional to F-S(-alpha), where the power-law index alpha is directly related to the number of e-folding amplifications by the relation alpha = (1 + tau(G)/t(Se)). The same mathematical formalism is used to generate power-law distributions, as in Rosner & Vaiana, but the distribution of energies released in elementary hare instabilities is not related to the global energy storage process. We assume Poissonian noise for the unamplified energy levels in unstable flare cells, implying an exponential frequency distribution of avalanche energies W-S or fluxes F-S in the absence of coherent amplifications. Also, in the case of coherent amplification, the Poissonian noise introduces exponential rollovers of the power law at the low and high ends of the frequency distributions. We fit both power-law and exponential functions to the observed frequency distributions of elementary pulse fluxes N(F) in each flare separately. For HXR pulses, one-half of the flares are better fitted with power-law frequency distributions, demanding coherent amplification of the underlying energy dissipation mechanism, e.g., current exponentiation occurring in the magnetic tearing instability. The majority of type III burst pares are best fitted with power-law distributions, consistent with the interpretation in terms of beam-driven coherent emission. The frequency distributions of decimetric pulsations and decimetric millisecond spikes are found to fit exponential functions, in contrast to the expected power laws for coherent emission mechanisms generally proposed for these radio burst types. A coherent emission mechanism can be reconciled with the observed exponential frequency distributions only if nonlinear saturation occurs at a fixed amplification factor for all elementary pulses or spikes, for example, if it is produced by an oscillatory compact source (in the case of decimetric pulsations) or by a fragmented source with similar spatial cell sizes (in the case of decimetric millisecond spikes). C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. ETH Zurich, Inst Astron, CH-8092 Zurich, Switzerland. RP Aschwanden, MJ (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Dennis, Brian/C-9511-2012 NR 94 TC 73 Z9 75 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP 972 EP 993 DI 10.1086/305484 PN 1 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ199 UT WOS:000073189400044 ER PT J AU Brosius, JW Davila, JM Thomas, RJ AF Brosius, JW Davila, JM Thomas, RJ TI Calibration of the SERTS-95 spectrograph from iron line intensity ratios SO ASTROPHYSICAL JOURNAL LA English DT Article DE instrumentation, spectrographs; sun, activity; sun, corona; sun, UV radiation ID SOLAR-FLARES; ANGSTROMS AB Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph was flown on 1995 May 15 (SERTS-95), carrying a multilayer-coated toroidal diffraction grating which enhanced the instrumental sensitivity within its second-order wave band (170-225 Angstrom). Spectra and spectroheliograms of NOAA Active Region 7870 (N09/W22) were obtained in this wave band with a spectral resolution (instrumental FWHM) similar to 30 m Angstrom. We developed and applied a technique for deriving the relative radiometric calibration independent of laboratory calibration measurements by employing a method proposed by Neupert & Kastner for monitoring variations in the sensitivities of orbiting EUV spectrometers by means of density-and temperature-insensitive Line intensity ratios. Numerous ratios of emission lines from Fe X-XIV are mutually consistent and yield an instrumental response curve that matches the design characteristics of the multilayer coating. This supports the accuracy of the atomic physics parameters and demonstrates the power of the technique. Many of the ratios employed here can be used to carry out a similar calibration exercise on spectra from the Coronal Diagnostic Spectrometer's Grazing Incidence Spectrograph (CDS/GIS) aboard the Solar and Heliospheric Observatory. Because they are relatively free from blending with nearby strong lines, the following density-sensitive ratios are particularly well suited for analysis with the GIS: Fe X lambda 175.265/lambda 174.526, Fe X lambda 175.265/lambda 184.534, Fe XII lambda 186.867\lambda 195.117, Fe XIII X203.820/lambda 202.042, Fe XIII lambda 200.017/lambda 202.042, and Fe XIV lambda 219.121/lambda 211.317. Densities derived from Fe X, XIII, and XIV yield log n(e) similar to 9.3 +/- 0.2. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Brosius, JW (reprint author), Raytheon STX Corp, 4400 Forbes Blvd, Lanham, MD 20706 USA. NR 22 TC 26 Z9 26 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP L113 EP L116 DI 10.1086/311287 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ200 UT WOS:000073189500014 ER PT J AU Harwit, M Neufeld, DA Melnick, GJ Kaufman, MJ AF Harwit, M Neufeld, DA Melnick, GJ Kaufman, MJ TI Thermal water vapor emission from shocked regions in Orion SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared, ISM, lines and bands; ISM, abundances; ISM, individual (Orion); ISM, molecules; molecular processes ID MOLECULAR LINE EMISSION; NEBULA; KL; CO; WAVES; OH AB Using the Long Wavelength Spectrometer on board the Infrared Space Observatory, we have observed thermal water vapor emission from a roughly circular field of view approximately 75 " in diameter centered on the Orion BN-KL region. The Fabry-Perot line strengths, line widths, and spectral line shifts observed in eight transitions between 71 and 125 mu m show good agreement with models of thermal emission arising from a molecular cloud subjected to a magnetohydrodynamic C-type shock. Both the breadth and the relative strengths of the observed lines argue for emission from a shock rather than from warm quiescent gas in the Orion core. Although one of the eight transitions appears anomalously strong and may be subject to the effects of radiative pumping, the other seven indicate an H2O/H-2 abundance ratio on the order of 5 X 10(-4) and a corresponding gas-phase oxygen-to-hydrogen abundance ratio on the order of 4 X 10(-4). Given current estimates of the interstellar, gas-phase, oxygen and carbon abundances in the solar vicinity, this value is consistent with theoretical shock models that predict the conversion into water of all the gas-phase oxygen that is not bound as CO. The overall cooling provided by rotational transitions of H2O in this region appears to be comparable to the cooling through rotational lines of CO but is an order of magnitude lower than cooling through H-2 emission. However, the model that best fits our observations shows cooling by H2O and CO dominant in that portion of the postshock region where temperatures are below similar to 800 K and neither vibrational nor rotational radiative cooling by H-2 is appreciable. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Harwit, M (reprint author), 511 H St SW, Washington, DC 20024 USA. NR 25 TC 86 Z9 86 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP L105 EP L108 DI 10.1086/311291 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ200 UT WOS:000073189500012 ER PT J AU Kaaret, P Yu, WF Ford, EC Zhang, SN AF Kaaret, P Yu, WF Ford, EC Zhang, SN TI Correlation between fast quasi-periodic oscillations and X-ray spectral shape in atoll sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars, individual (4U 0614+091, 4U 1608-52); stars, neutron; X-rays, stars ID EMISSION; ACCRETION AB We present correlations between the frequency of the fast quasi-periodic oscillations (QPOs) and the shape of the X-ray spectrum in the atoll sources 4U 1608-52 and 4U 0614+091. We find that the photon index of a power-law component of the energy spectrum is well correlated with the QPO frequency in both sources. The correlation between the photon index and the QPO frequency most likely represents a common dependence on some physical parameter of the system. C1 Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. Inst High Energy Phys, LCRHEA, Beijing 100039, Peoples R China. Univ Space Res Assoc, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Kaaret, P (reprint author), Columbia Univ, Columbia Astrophys Lab, 550 W 120th St, New York, NY 10027 USA. NR 17 TC 30 Z9 31 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP L93 EP L96 DI 10.1086/311279 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ200 UT WOS:000073189500009 ER PT J AU Tavani, M Kniffen, D Mattox, JR Paredes, JM Foster, RS AF Tavani, M Kniffen, D Mattox, JR Paredes, JM Foster, RS TI The variable gamma-ray source 2CG 135+01 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; gamma rays, theory ID RADIO; LSI+61-DEGREES-303 AB The EGRET instrument on board the Compton Gamma Ray Observatory has detected about 150 sources above 100 MeV. Slightly less than half of these sources have been identified either as active galactic nuclei (AGNs) associated with spectrally flat radio-loud sources of the blazar type or as isolated young/intermediate-age pulsars. Except for rotational modulation, the gamma-ray flux of pulsars does not display significant variation, whereas blazars show variability on timescales as short as similar to 7 hr. We show here that one of the most prominent unidentified gamma-ray sources near the Galactic plane, 2CG 135+01 (first discovered by the COS B satellite), does not fit into either of these two classes. By comparing different EGRET observations, we establish with 98.8% confidence that the gamma-ray flux from 2CG 135+01 is time variable. This is inconsistent with the constant flux observed from isolated gamma-ray pulsars. No potential spectrally flat radio-loud AGN counterpart exists for this source. We show that 2CG 135+01 belongs to a new class of variable gamma-ray emitters in the Galactic plane, a class that also includes the recently discovered nonblazar gamma-ray transient GRO J1838-04. C1 Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. CNR, Inst Fis Cosm, I-20133 Milan, Italy. Hampden Sydney Coll, Hampden Sydney, VA 23943 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD 20771 USA. Boston Univ, Dept Astron, Boston, MA 02215 USA. Univ Barcelona, E-08028 Barcelona, Spain. USN, Res Lab, Washington, DC 20375 USA. RP Columbia Univ, Columbia Astrophys Lab, 538 W 120th St, New York, NY 10027 USA. NR 31 TC 51 Z9 51 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 APR 20 PY 1998 VL 497 IS 2 BP L89 EP L91 DI 10.1086/311281 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ200 UT WOS:000073189500008 ER PT J AU Taylor, JA AF Taylor, JA TI Mass function gradients and the need for dark matter SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; galaxies, evolution; galaxies, halos; galaxies, kinematics and dynamics; galaxies, luminosity function, mass function; Magellanic Clouds ID HUBBLE-SPACE-TELESCOPE; SURFACE PHOTOMETRY; STAR FORMATION; GALACTIC DISK; STELLAR; GALAXY; DENSITY; CLOUD; M82; SUN AB There is both theoretical and empirical evidence that the initial mass function (IMF) may be a function of the local star formation conditions. In particular, the IMF is predicted to flatten with increasing local luminosity density rho(l), with the formation of massive stars being preferentially enhanced in brighter regions. In R136, the bright stellar cluster in 30 Doradus, the IMF gradient is partial derivative Gamma/partial derivative log rho(l) = 0.28 +/- 0.06, where Gamma is the slope of the IMF. If such IMF gradients are indeed general features of galaxies, this implies that several previous astrophysical measurements, such as the surface mass densities of spirals (obtained assuming constant mass-to-light ratios), were plagued by substantial systematic errors. In this Letter, calculations that account for possible IMF gradients are presented for surface densities of spiral galaxies. Compared with previous estimates, the mass surface densities corrected for IMF gradients are higher in the outer regions of the disks. For a model based on the Milky Way but with an IMF scaled according to R136, the rotation curve without the traditional dark halo component falls with Galactocentric radius, although slower than it would without IMF gradients. For a second model of the Milky Way in which the IMF gradient is increased to 0.42, the rotation curve is approximately flat in the outer disk, with a rotational velocity below similar or equal to 220 km s(-1) only before the traditional dark halo component is added. For a third model in which substantial arm/interarm density contrasts are additionally assumed, the solar vicinity mass density drops to 0.10 M-. pc(-3), which is consistent with observations. These results, if generalizable to other galaxies, not only call into question the assertion that dark matter halos are compatible with the flat rotation curves of spiral galaxies but also may clarify our understanding of a wide variety of other astrophysical phenomena such as the G dwarf problem, metallicity gradients, and the Tully-Fisher relation. C1 USN Acad, Dept Phys, Annapolis, MD 21402 USA. RP Taylor, JA (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 35 TC 5 Z9 5 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1998 VL 497 IS 2 BP L81 EP L84 DI 10.1086/311280 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ200 UT WOS:000073189500006 ER PT J AU Chin, M Rood, RB Allen, DJ Andreae, MO Thompson, AM Lin, SJ Atlas, RM Ardizzone, JV AF Chin, M Rood, RB Allen, DJ Andreae, MO Thompson, AM Lin, SJ Atlas, RM Ardizzone, JV TI Processes controlling dimethylsulfide over the ocean: Case studies using a 3-D model driven by assimilated meteorological fields SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BIOGENIC SULFUR EMISSIONS; TROPICAL SOUTH-ATLANTIC; MARINE BOUNDARY-LAYER; ATMOSPHERIC SULFUR; TRANSPORT SCHEMES; AMSTERDAM ISLAND; GAS-EXCHANGE; INDIAN-OCEAN; SULFIDE; AIR AB This study investigates the processes that influence dimethylsulfide (DMS) concentrations over the ocean using a global three-dimensional chemistry and transport model (CTM). The model is driven by assimilated meteorological data from the Goddard Earth Observing System Data Assimilation System (GEOS-1 DAS). Results from the model are compared with DMS measurements from two marine sites, a ship cruise, and an aircraft campaign. When observed seawater DMS concentrations and meteorological conditions are used, the model reproduces the observed daily and diurnal variations of DMS concentrations at a tropical Pacific station. The model also predicts the observed changes of DMS concentrations across the Atlantic, although it overestimates the DMS level by a factor of 2. The calculated vertical DMS concentrations off Tasmania are more than 4 times higher than the measured data. The model simulates day-to-day fluctuations and interannual variations observed at Amsterdam Island but underpredicts the magnitude of the variations. Sensitivities for DMS concentrations to the parameters used in DMS emission, oxidation, boundary layer mixing, and cloud convective transport are tested. The limitations of the current model in interpreting the observations are due to (1) the uncertainties in parameterization of DMS emission from the ocean, (2) the simplistic boundary layer mixing scheme, (3) the inaccurate spatial distribution and intensity of deep convective clouds in the GEOS-1 DAS, and (4) the uncertainties in DMS oxidation rates. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Max Planck Inst Chem, Biogeochem Dept, D-55020 Mainz, Germany. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Georgia Tech Res Inst, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. RP Chin, M (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. EM chin@rondo.gsfc.nasa.gov RI Allen, Dale/F-7168-2010; Atlas, Robert/A-5963-2011; Chin, Mian/J-8354-2012; Rood, Richard/C-5611-2008; Andreae, Meinrat/B-1068-2008; Thompson, Anne /C-3649-2014 OI Allen, Dale/0000-0003-3305-9669; Atlas, Robert/0000-0002-0706-3560; Rood, Richard/0000-0002-2310-4262; Andreae, Meinrat/0000-0003-1968-7925; Thompson, Anne /0000-0002-7829-0920 NR 40 TC 18 Z9 18 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 APR 20 PY 1998 VL 103 IS D7 BP 8341 EP 8353 DI 10.1029/98JD00107 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZJ026 UT WOS:000073172100012 ER PT J AU Mauzerall, DL Logan, JA Jacob, DJ Anderson, BE Blake, DR Bradshaw, JD Heikes, B Sachse, GW Singh, H Talbot, B AF Mauzerall, DL Logan, JA Jacob, DJ Anderson, BE Blake, DR Bradshaw, JD Heikes, B Sachse, GW Singh, H Talbot, B TI Photochemistry in biomass burning plumes and implications for tropospheric ozone over the tropical South Atlantic SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AFRICAN SAVANNA FIRES; TRACE GAS EMISSIONS; BOREAL FOREST FIRES; CARBON-MONOXIDE; AMAZON BASIN; CHEMICAL CHARACTERISTICS; ATMOSPHERIC CHEMISTRY; REACTIVE NITROGEN; FIELD EXPERIMENT; WESTERN AFRICA AB Photochemistry occuring in biomass burning plumes over the tropical south Atlantic is analyzed using data collected during the Transport and Atmospheric Chemistry Near the Equator-Atlantic aircraft expedition conducted during the tropical dry season in September 1992 and a photochemical point model. Enhancement ratios (Delta Y/Delta X, where Delta indicates the enhancement of a compound in the plume above the local background mixing ratio, Y are individual hydrocarbons, CO, O-3, N2O, HNO3, peroxyacetyl nitrate (PAN), CH2O, acetone, H2O2, CH3OOH, HCOOH, CH3COOH or aerosols and X is CO or CO2) are reported as a function of plume age inferred from the progression of Delta non-methane hydrocarbons/Delta CO enhancement ratios. Emission, formation, and loss of species in plumes can be diagnosed from progression of enhancement ratios from fresh to old plumes. O-3 is produced in plumes over at least a 1 week period with mean Delta O-3/Delta CO = 0.7 in old plumes. However, enhancement ratios in plumes can be influenced by changing background mixing ratios and by photochemical loss of CO. We estimate a downward correction of similar to 20% in enhancement ratios in old plumes relative to Delta CO to correct for CO loss. In a case study of a large persistent biomass burning plume at 4 -km we found elevated concentrations of PAN in the fresh plume. The degradation of PAN helped maintain NOx mixing ratios in the plume where, over the course of a week, PAN was converted to HNO3. Ozone production in the plume was limited by the availability of NOx, and because of the short lifetime of O-3 at 4 -km, net ozone production in the plume was negligible. Within the region, the majority of O-3 production takes place in air above median CO concentration, indicating that most O-3 production occurs in plumes. Scaling up from the mean observed Delta O-3/Delta CO in old plumes, we estimate a minimum regional O-3 production of 17 x 10(10) molecules O-3 cm(-2)s(-1). This O-3 production rate is sufficient to fully explain the observed enhancement in tropospheric 03 over the tropical South Atlantic during the dry season. C1 Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Harvard Univ, Div Appl Sci, Cambridge, MA 02138 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Mauzerall, DL (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. EM dlm@ucar.edu RI Mauzerall, Denise/I-5977-2013 OI Mauzerall, Denise/0000-0003-3479-1798 NR 60 TC 147 Z9 148 U1 2 U2 25 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1998 VL 103 IS D7 BP 8401 EP 8423 DI 10.1029/97JD02612 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZJ026 UT WOS:000073172100016 ER PT J AU Matijevic, J AF Matijevic, J TI The Pathfinder mission to Mars - Autonomous navigation and the Sojourner microrover SO SCIENCE LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Matijevic, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM jacob_r_matijevic@jpl.nasa.gov NR 5 TC 12 Z9 12 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 APR 17 PY 1998 VL 280 IS 5362 BP 454 EP 455 DI 10.1126/science.280.5362.454 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZH907 UT WOS:000073159600053 ER PT J AU Velusamy, T Langer, WD AF Velusamy, T Langer, WD TI Outflow-infall interactions as a mechanism for terminating accretion in protostars SO NATURE LA English DT Article ID DARK CLOUD BARNARD-5; MOLECULAR OUTFLOWS; JET; EVOLUTION; DISK AB The formation of stars begins with the collapse of a dense interstellar cloud core to a protostar surrounded by a disk of gas and dust. Material in the envelope of the cloud core falls inwards to feed further growth of the protostar and its accretion disk. At some point during the accretion phase, an outflow of gas begins along the disk's rotation axis. Outflows have been studied in a large number of sources', and recently it has become possible to study infall land outflow) very close to the star(2-8). But the possible interaction between these flows and its effect on the mass of the disk and the young star remain uncertain. Here we present observational evidence for an interaction between infalling and outflowing molecular gas. The opening angle of the outflow cone is largest near the star, indicating a widening of the outflow with time. Outside the lobes of the outflowing gas we see a narrow, disk-like region that is infalling. We suggest that the widening of the outflow may isolate the disk from further infall. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Velusamy, T (reprint author), CALTECH, Jet Prop Lab, MS 169-506, Pasadena, CA 91109 USA. NR 23 TC 74 Z9 75 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 16 PY 1998 VL 392 IS 6677 BP 685 EP 687 DI 10.1038/33624 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZH612 UT WOS:000073129000048 ER PT J AU Rashed, H Cowings, P Toscano, W Abell, T Cardoso, S AF Rashed, H Cowings, P Toscano, W Abell, T Cardoso, S TI Autogenic feedback training as a potential treatment for the symptoms of gastroparesis. SO GASTROENTEROLOGY LA English DT Meeting Abstract C1 Univ Tennessee, Auton Nervous Syst Lab, Dept Med, Memphis, TN 38163 USA. Univ Calif Los Angeles, Dept Psychiat, Los Angeles, CA 90024 USA. NASA, Ames Res Ctr, Moffett Field, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU W B SAUNDERS CO PI PHILADELPHIA PA INDEPENDENCE SQUARE WEST CURTIS CENTER, STE 300, PHILADELPHIA, PA 19106-3399 USA SN 0016-5085 J9 GASTROENTEROLOGY JI Gastroenterology PD APR 15 PY 1998 VL 114 IS 4 SU S MA G3387 BP A825 EP A825 DI 10.1016/S0016-5085(98)83362-3 PN 2 PG 1 WC Gastroenterology & Hepatology SC Gastroenterology & Hepatology GA ZH263 UT WOS:000073089603362 ER PT J AU Minnis, P Smith, WL AF Minnis, P Smith, WL TI Cloud and radiative fields derived from GOES-8 during SUCCESS and the ARM-UAV spring 1996 flight series SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Cloud and radiative properties were derived for the southern Great Plains for April 9 - May 9, 1996 from GOES-8 to provide a large-scale context for SUCCESS and a dataset for mesoscale modeling of cirrus processes. The analyses indicate that cloudiness over the domain was below normal during April 1996. Thin cirrus with optical depths less than 6 was the predominant cloud type over much of the domain, however, providing a considerable number of measurement opportunities for the suite of SUCCESS instruments. Diurnal variation of cloudiness was substantial over the ARM southern Great Plains central facility. Total albedos were below normal because of the diminished thick cloudiness, while surface temperature and total longwave fluxes were relatively high. The data are on a 0.5 degrees grid and are available electronically. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Analyt Serv & Mat Inc, Hampton, VA 23666 USA. RP Minnis, P (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 5 TC 29 Z9 29 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 15 PY 1998 VL 25 IS 8 BP 1113 EP 1116 DI 10.1029/98GL00301 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900002 ER PT J AU Ackerman, SA Moeller, CC Strabala, KI Gerber, HE Gumley, LE Menzel, WP Tsay, SC AF Ackerman, SA Moeller, CC Strabala, KI Gerber, HE Gumley, LE Menzel, WP Tsay, SC TI Retrieval of effective microphysical properties of clouds: A wave cloud case study SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MU-M WINDOW; CIRRUS CLOUDS; RADIATIVE PROPERTIES; ICE CRYSTALS; CONTRAILS; WATER AB One of the important objectives of the SUbsonic aircraft: Contrail and Cloud Effecs Special Study (SUCCESS) field campaign data analysis is to investigate retrieving cloud microphysical properties using remote sensing observations. This paper presents the results of an infrared based retrieval of effective particle radius R-e using brightness temperature observations near 8.5, 11 and 12 mu m. The retrieval method relies on comparing 8.5-11 and 11-12 mu m observed brightness temperature differences to theoretical simulations. During SUCCESS, conducted in April-May 1996 out of Salina KS, the MODIS Airborne Simulator (MAS) on the NASA ER-2 made observations of contrails, cirrus and mountain lee wave clouds. Observations indicate that contrail and cirrus clouds are distinguishable by their radiative properties. Retrieval of R-e for the lee wave cloud case on 2 May agrees with in situ observations from probes mounted on a NASA DC-8 aircraft, validating the infrared retrieval. The addition of the 8.5 mu m information to the R-e retrieval greatly enhances the sensitivity of the retrieval at small particle sizes (< 10 mu m). C1 Univ Wisconsin, Cooperat Inst Meteorol Satellite Studies, Madison, WI 53706 USA. Gerber Sci Inc, Reston, VA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ackerman, SA (reprint author), Univ Wisconsin, Cooperat Inst Meteorol Satellite Studies, Madison, WI 53706 USA. RI Menzel, W. Paul/B-8306-2011; Ackerman, Steven/G-1640-2011; Tsay, Si-Chee/J-1147-2014 OI Menzel, W. Paul/0000-0001-5690-1201; Ackerman, Steven/0000-0002-4476-0269; NR 17 TC 17 Z9 19 U1 1 U2 5 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 15 PY 1998 VL 25 IS 8 BP 1121 EP 1124 DI 10.1029/98GL00042 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900004 ER PT J AU Young, DF Minnis, P Baumgardner, D Gerber, H AF Young, DF Minnis, P Baumgardner, D Gerber, H TI Comparison of in situ and satellite-derived cloud properties during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB The validation of cloud microphysical properties derived from satellite data with in situ observations is generally difficult due to the spatial and temporal variability of observed clouds. Two missions during SUCCESS concentrated on orographic wave clouds that exhibited relative spatial and temporal homogeneity. A comparison has been made of effective ice particle diameters derived from multispectral satellite data with in situ measurements from the MASP and PVM instruments aboard the DC-8 aircraft. For both days, the satellite-derived effective diameters fall well within the bounds of the in situ data. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Gerber Sci Inc, Reston, VA USA. RP Young, DF (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. RI Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 3 TC 16 Z9 16 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 15 PY 1998 VL 25 IS 8 BP 1125 EP 1128 DI 10.1029/98GL00116 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900005 ER PT J AU Mace, GG Sassen, K Kinne, S Ackerman, TP AF Mace, GG Sassen, K Kinne, S Ackerman, TP TI An examination of cirrus cloud characteristics using data from millimeter wave radar and lidar: The 24 April SUCCESS case study SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIATION AB We examine the characteristics of a cirrus system that moved over north central Oklahoma on 24 April 1996 during the Subsonic Aircraft: Contrail and Cloud Effects Speical Study. This system was probed by aircraft and several surface-based active and passive remote sensors located at the Department of Energy's Atmospheric Radiation Measurement facility. Several layers of cirrus were identified and tended to be organized in bands that were maintained by turbulent motions associated with unstable lapse rates. The microphysical properties of two events sampled by a cloud radar were quite different with the earlier event composed, on average, of larger particles and lower concentrations than the later event. C1 Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. NASA, Ames Res Ctr, San Jose, CA USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. RP Mace, GG (reprint author), Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. EM mace@atmos.met.utah.edu; kinee@ice.arc.nasa.gov; ackerman@essc.psu.edu NR 17 TC 14 Z9 14 U1 1 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 15 PY 1998 VL 25 IS 8 BP 1133 EP 1136 DI 10.1029/98GL00232 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900007 ER PT J AU Smith, WL Ackerman, S Revercomb, H Huang, H DeSlover, DH Feltz, W Gumley, L Collard, A AF Smith, WL Ackerman, S Revercomb, H Huang, H DeSlover, DH Feltz, W Gumley, L Collard, A TI Infrared spectral absorption of nearly invisible cirrus clouds SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER-VAPOR AB The SUbsonic aircraft Contrail and Cloud Effects Special Study (SUCCESS) was conducted 8 April - 10 May 1996 to better understand the radiative properties of high level ice crystal clouds produced by anthropogenic (i.e., jet aircraft) and natural (i.e., weather) causes. In this paper multispectral radiance data observed during SUCCESS from the high flying NASA ER-2 aircraft are presented to demonstrate that nearly 'invisible' high level layers of very small ice particles can cause very significant absorption (50% or more) of the upwelling infrared radiation to space. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Wisconsin, Cooperat Inst Meteorol Satellite Studies, Madison, WI 53706 USA. RP Smith, WL (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. RI Ackerman, Steven/G-1640-2011 OI Ackerman, Steven/0000-0002-4476-0269 NR 12 TC 45 Z9 45 U1 2 U2 6 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 15 PY 1998 VL 25 IS 8 BP 1137 EP 1140 DI 10.1029/97GL03491 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900008 ER PT J AU Pilewskie, P Goetz, AFH Beal, DA Bergstrom, RW Mariani, P AF Pilewskie, P Goetz, AFH Beal, DA Bergstrom, RW Mariani, P TI Observations of the spectral distribution of solar irradiance at the ground during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OPTICAL-CONSTANTS; ABSORPTION; CLOUDS; APPROXIMATIONS; RADIATION; PHYSICS AB During SUCCESS two independent and independently calibrated spectrometers were deployed at a surface site to determine the spectrally resolved downwelling solar irradiance. Preliminary evidence shows that for cloud-free conditions there is general agreement between measurements and model derived irradiance, at least to within instrumental and model uncertainties of 5%, with greatest disagreement occurring in the 400 nm - 700 nm band. Cirrus effects are most prominent in the near-infrared bands beyond 1500 nm while the influence of very thin (subvisual) cirrus is evident in the scattered flux at the surface. Further remote sensing applications and the assessment of cloud absorption is contingent upon measurements of the surface spectral albedo. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, CIRES, Ctr Study Earth Space, Boulder, CO 80309 USA. Analyt Spectral Devices Inc, Boulder, CO USA. Bay Area Environm Res Inst, San Francisco, CA USA. RP Pilewskie, P (reprint author), NASA, Ames Res Ctr, M-S 245-4, Moffett Field, CA 94035 USA. NR 22 TC 16 Z9 16 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 15 PY 1998 VL 25 IS 8 BP 1141 EP 1144 DI 10.1029/98GL00238 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900009 ER PT J AU Wang, JR Racette, P Spinhirne, JD Evans, KF Hart, WD AF Wang, JR Racette, P Spinhirne, JD Evans, KF Hart, WD TI Observations of cirrus clouds with airborne MIR, CLS, and MAS during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER-VAPOR; PRECIPITATION AB Observations of cirrus clouds were made with a host of instruments on board the NASA ER-2 aircraft on April 16, 1996. These instruments provide radiometric measurements covering the visible, infrared, and millimeter-wave regions of the electromagnetic wave spectrum, as well as profiles of lidar backscatter at 1.064 mu m. The cirrus clouds are classified into two groups: the modest cirrus clouds with lidar backscatter from the surface and the intense cirrus clouds without lidar surface returns. For the modest clouds, the magnitudes of brightness depressions are typically less than 5 K and are comparable at 150 GHz and 220 GHz. The depressions for the water vapor channels (e.g. 183.3+/-7 GHz) are smaller. We interpret the microwave brightness depressions for the modest cirrus cases as due to reduced skin temperature from the cloud shadow, rather than ice scattering. For the intense cirrus cases, the magnitude of brightness depression at 220 GHz reach 35 K and are far greater than those at 150 GHz. After correcting for the skin temperature effect, a regression between the observed brightness depressions at 150 and 220 GHz frequencies results in a slope of 2.75. Comparison with radiative transfer modeling for solid spherical ice particles, indicates a median equivalent mass diameter of about 350 mu m, and ice water path ranging up to 300 g/m(2). The results illustrate the potential utility of millimeter and sub-millimeter wave radiometry for characterizing microphysical properties of thick cirrus. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. Sci Syst & Applicat Inc, Lanham, MD 20706 USA. RP Wang, JR (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NR 7 TC 17 Z9 18 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 1998 VL 25 IS 8 BP 1145 EP 1148 DI 10.1029/97GL03194 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900010 ER PT J AU Duda, DP Spinhirne, JD Hart, VD AF Duda, DP Spinhirne, JD Hart, VD TI Retrieval of contrail microphysical properties during SUCCESS by the split-window method SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID THIN CIRRUS CLOUDS; MU-M WINDOW; EMISSIVITY DETERMINATION; WATER-VAPOR; TEMPERATURE; REGION; SPECTROMETER; CHANNELS; AEROSOL AB Estimates of cloud particle size and infrared optical depth were inferred from multi-spectral observations of contrails and cirrus during the SUbsonic aircraft: Contrails and Cloud Effects Special Study (SUCCESS) experiment on 20 April 1996. The particles in a newly formed contrail were generally smaller than those in an older contrail, while the microphysics of the older contrail resembled the surrounding cirrus. Split-window retrievals of contrails were sensitive to changes in surface temperature and surface emissivity. C1 Univ Space Res Assoc, Seabrook, MD USA. Sci Syst Applicat Inc, Lanham, MD USA. RP Duda, DP (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 912, Greenbelt, MD 20771 USA. NR 17 TC 13 Z9 13 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 15 PY 1998 VL 25 IS 8 BP 1149 EP 1152 DI 10.1029/97GL03159 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900011 ER PT J AU Spinhirne, JD Hart, WD Duda, DP AF Spinhirne, JD Hart, WD Duda, DP TI Evolution of the morphology and microphysics of contrail cirrus from airborne remote sensing SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLOUDS; WATER; LIDAR AB Contrail cirrus were observed by airborne lidar and multispectral infrared remote sensing. Results of microphysical analysis were obtained for two cases of persistent contrail cirrus which form in the same area but of differing maturity. The cross section area of the older contrail was 18 times greater than the newer case. In both cases the inferred number of particles per distance along the flight track dimension of contrails was nearly similar, close to 26 x 10(11)/m. The average liquid water concentration of the two cases was similar, but the amount of water per distance along the flight line dimension was much greater for the older contrail, 34 g/cm and 680 g/cm. In both cases the amount of liquid water in the contrail was much greater than the amount generated by the aircraft which produced the contrail. These results are consistent with a model of contrail evolution where the effect of the jet exhaust is to generate a dense concentration of small ice particles. Mixing then maintains the total number of particles, and particles grow to the extent of the available vapor in the ambient air. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Syst Applicat Inc, Lanham, MD USA. Univ Space Res Assoc, Seabrook, MD USA. RP Duda, DP (reprint author), NASA, Goddard Space Flight Ctr, MC912, Greenbelt, MD 20771 USA. EM spinhirne@gsfc.nasa.gov; billhart@virl.gsfc.nasa.gov; duda@virl.gsfc.nasa.gov NR 12 TC 17 Z9 17 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 15 PY 1998 VL 25 IS 8 BP 1153 EP 1156 DI 10.1029/97GL03477 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900012 ER PT J AU Minnis, P Young, DF Garber, DP Nguyen, L Smith, WL Palikonda, R AF Minnis, P Young, DF Garber, DP Nguyen, L Smith, WL Palikonda, R TI Transformation of contrails into cirrus during SUCCESS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLOUD AB Three contrail systems were analyzed with geostationary satellite data to document the conversion of the contrails to cirrus clouds. Two unique contrails, a pair of figure eights and a NASA DC-8 oval, were tracked for more than 7 hours. A cluster of contrails from commercial aircraft lasted over 17 hours. The figure eights produced a cirrus cloud having a maximum extent of 12,000 km(2); the commercial cluster reached an area of similar to 35,000 km(2). The contrail-cirrus were thin with optical depths between 0.2 and 0.5. In all cases, cloud particle size increased as the contrails developed into cirrus clouds. The climatic impact of contrails will be greater than would be estimated if only linear contrails, those typically observed in satellite imagery, are considered. Additional research is required to obtain reliable statistics on contrail growth and lifetime. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Analyt Serv & Mat Inc, Hampton, VA 23666 USA. RP Minnis, P (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. RI Garber, Donald/D-7427-2015; Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 5 TC 100 Z9 100 U1 0 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 15 PY 1998 VL 25 IS 8 BP 1157 EP 1160 DI 10.1029/97GL03314 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900013 ER PT J AU Liou, KN Yang, P Takano, Y Sassen, K Charlock, T Arnott, W AF Liou, KN Yang, P Takano, Y Sassen, K Charlock, T Arnott, W TI On the radiative properties of contrail cirrus SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LIGHT-SCATTERING; ICE CRYSTALS; CLOUDS AB Using the observed ice crystal size distribution in contrail cirrus from SUCCESS, we have carried out the scattering and absorption calculations based on a unified theory for light scattering by ice crystals covering all sizes and shapes. We illustrate the effects of ice crystal size and surface roughness on the scattering phase function features for remote sensing applications. The extinction coefficient and single-scattering albedo exhibit a minimum feature at 2.85 mu m, referred to as the Christiansen effect, which is particularly pronounced for clouds consisting of a significant number of small ice crystals. Based on a line-by-line equivalent solar model, we show from spectral curves that cloud reflection increases as ice crystal sizes become smaller, but the cloud absorption increase is only evident for wavelengths longer than about 2.7 mu m. The ice crystal shape has a substantial effect on the cloud reflection and absorption for a given size; more complex ice particles reflect more solar radiation. Finally, we propose a contrail cirrus cloud model consisting of a combination of bullet rosettes (50%), hollow columns (30%), and plates (20%), with sizes ranging from 1 to 90 mu m in association with radiation perturbation studies. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. Univ Utah, Dept Meteorol, Salt Lake City, UT 84112 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. Univ Nevada, Desert Res Inst, Ctr Atmospher Sci, Reno, NV 89506 USA. RP Liou, KN (reprint author), Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. RI Yang, Ping/B-4590-2011 NR 11 TC 24 Z9 24 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 1998 VL 25 IS 8 BP 1161 EP 1164 DI 10.1029/97GL03508 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900014 ER PT J AU Fu, Q Lesins, G Higgins, J Charlock, T Chylek, P Michalsky, J AF Fu, Q Lesins, G Higgins, J Charlock, T Chylek, P Michalsky, J TI Broadband water vapor absorption of solar radiation tested using ARM data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLOUDS; PHYSICS AB A high quality data set collected at the ARM SGP central facility is analyzed to identify the water vapor-related anomalous absorption of solar radiation. We focus on the direct solar broadband surface irradiances under cloud-free conditions in the April 1994 CAGEX and summer 1996 periods. A radiation model without including the H2O continuum in the solar spectrum is compared with observations. This comparison reveals a mean bias of 4.5 W m(-2) that is roughly equivalent to a globally averaged bias of similar to 2 W m(-2). It is therefore unlikely that the excess absorption suggested by recent studies can be attributed to the H2O continuum. We also show that the difference between calculated and observed irradiances has a very weak correlation with water vapor. It is suggested that the discrepancy between model and observations is largely due to the uncertainties associated with aerosol optical properties. C1 Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. NASA, Langley Res Ctr, Hampton, VA 23681 USA. SUNY Albany, Atmospher Sci Res Ctr, Albany, NY 12205 USA. RP Fu, Q (reprint author), Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada. NR 18 TC 17 Z9 17 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 15 PY 1998 VL 25 IS 8 BP 1169 EP 1172 DI 10.1029/98GL00846 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900016 ER PT J AU Schmidt, GA AF Schmidt, GA TI Oxygen-18 variations in a global ocean model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATERS; CYCLE AB The ratio of O-18 to O-16 in water of the world oceans is examined using the GISS ocean general circulation model. This ratio is governed by fractionation during evaporation and sea-ice formation and by the isotopic content of precipitation and runoff entering the oceans. The delta(18)O(w) at any point depends on a balance between local evaporation, precipitation, and regional ocean and sea-ice processes. Surface delta(18)O(w), equilibrates after 30-50 model years to produce a pattern of high values (0.5-1.5 parts per thousand) in the sub-tropics (highest in the Indian and Atlantic oceans) and low values (-0.5--1 parts per thousand) in the mid-to-high latitudes. Arctic values are low especially where runoff enters from Arctic rivers. Comparisons with data show that regional linear relationships between delta(18)O(w) and salinity are reasonably captured by the model. Surface data from the entire ocean show a clear distinction in slope between the tropical oceans and the extra-tropics, however, departures from the linear relationships are significant. Importantly for attempts at calculating paleo-salinities, the seasonal and longer-term temporal gradients (Delta delta(18)O(w)/Delta S at a fixed point) are not generally equal to the spatial gradient (at a fixed time). C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Schmidt, GA (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Schmidt, Gavin/D-4427-2012 OI Schmidt, Gavin/0000-0002-2258-0486 NR 16 TC 30 Z9 30 U1 0 U2 5 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 15 PY 1998 VL 25 IS 8 BP 1201 EP 1204 DI 10.1029/98GL50866 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900024 ER PT J AU Cohen, SC AF Cohen, SC TI On the rapid postseismic uplift along Turnagain Arm, Alaska following the 1964 Prince William Sound earthquake SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB An analysis of leveling data obtained along Turnagain Arm, Alaska in the aftermath of the 1964 Prince William Sound earthquake shows that the postseismic uplift rate was constant during the first year following the earthquake. The maximum 1-yr peak-to-trough uplift was about 15 cm, while the maximum uplift relative to a tide gauge site in Anchorage was about 9 cm. There is some evidence for a modest decrease in the uplift rate between May and October of 1965, although the evidence is weakened by the lack of an appropriate reference point. The longer term temporal evolution of uplift rates, as compiled from leveling, GPS, tide gauge, and VLBI observations by Cohen [1996], can be modeled by an Omori-like or exponential transient decay curve with a time constant of several years. The geodetic data, taken in conjunction with seismological constraints, can be explained by aseismic-slip-at-depth along the tectonic plate interface with an initial slip rate of 35 cm/yr and a slip depth of 25-37 km. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP Cohen, SC (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. EM scohen@carnoustie.gsfc.nasa.gov NR 7 TC 15 Z9 15 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 15 PY 1998 VL 25 IS 8 BP 1213 EP 1215 DI 10.1029/98GL00860 PG 3 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900027 ER PT J AU Maksimovic, M Bougeret, JL Perche, C Steinberg, JT Lazarus, AJ Vinas, AF Fitzenreiter, RJ AF Maksimovic, M Bougeret, JL Perche, C Steinberg, JT Lazarus, AJ Vinas, AF Fitzenreiter, RJ TI Solar wind density intercomparisons on the WIND spacecraft using WAVES and SWE experiments SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERCALIBRATION; INSTRUMENTS AB We present solar wind density comparisons using three different instruments on the WIND spacecraft: The thermal noise receiver (TNR) on the WAVES experiment which yields the total electron density from the detection and the analysis of the electron plasma peak; the SWE Faraday cup detectors which measure ion energy per charge spectra and yield the proton and alpha particle densities in the solar wind; and finally the SWE electron spectrometer which provides 3D electron velocity distribution functions and thus the total electron density. The density comparison between the TNR and the SWE Faraday cups shows a remarkably good agreement, with a systematic offset which is lower than 1% and fluctuations of up to approximate to 5% around this value. Due to the well known spacecraft electrical potential effects, the SWE electron spectrometer densities, uncorrected from the potential, exhibit larger differences when compared with the TNR or the SWE Faraday cups measurements. Using these latter densities as reference, we compute a rough estimation of the spacecraft potential. C1 Observ Paris, Dept Rech Spatiale, CNRS, URA 264, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Maksimovic, M (reprint author), European Space Agcy, Dept Space Sci, Solar Syst Div, POB 299, NL-2200 AG Noordwijk, Netherlands. EM mmaksimo@estec.esa.nl NR 12 TC 17 Z9 17 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 15 PY 1998 VL 25 IS 8 BP 1265 EP 1268 DI 10.1029/98GL00843 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZH464 UT WOS:000073112900040 ER PT J AU Patnaik, SN Gendy, AS Berke, L Hopkins, DA AF Patnaik, SN Gendy, AS Berke, L Hopkins, DA TI Modified Fully Utilized Design (MFUD) method for stress and displacement constraints SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE fully utilized design; force method; optimization techniques ID INTEGRATED FORCE METHOD AB The traditional fully stressed method performs satisfactorily for stress-limited structural design. When this method is extended to include displacement limitations in addition to stress constraints, it is known as the Fully Utilized Design (FUD). Typically, the FUD produces an overdesign, which is the primary limitation of this otherwise elegant method. We have modified FUD in an attempt to alleviate the limitation. This new method, called the Modified Fully Utilized Design (MFUD) method, has been tested successfully on a number of problems that were subjected to multiple loads and had both stress and displacement constraints. The solutions obtained with MFUD compare favourably with the optimum results that can be generated by using non-linear mathematical programming techniques. The MFUD method appears to have alleviated the overdesign condition and offers the simplicity of a direct, fully stressed type of design method that is distinctly different from optimization and optimality criteria formulations. The MFUD method is being developed for practicing engineers who favour traditional design methods rather than methods based on advanced calculus and non-linear mathematical programming techniques. The Integrated Force Method (IFM) was found to be the appropriate analysis tool in the development of the MFUD method. In this paper, the MFUD method and its optimality are examined along with a number of illustrative examples. (C) 1998 John Wiley & Sons, Ltd. C1 Ohio Aerosp Inst, Brook Park, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Patnaik, SN (reprint author), Ohio Aerosp Inst, 22800 Cedar Point Rd, Brook Park, OH 44142 USA. NR 23 TC 21 Z9 21 U1 1 U2 1 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD APR 15 PY 1998 VL 41 IS 7 BP 1171 EP 1194 DI 10.1002/(SICI)1097-0207(19980415)41:7<1171::AID-NME296>3.3.CO;2-F PG 24 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA ZB425 UT WOS:000072471200001 ER PT J AU Hackert, EC Miller, RN Busalacchi, AJ AF Hackert, EC Miller, RN Busalacchi, AJ TI An optimized design for a moored instrument array in the tropical Atlantic Ocean SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-SURFACE TOPOGRAPHY; DATA ASSIMILATION; EQUATORIAL ATLANTIC; CIRCULATION MODEL; KALMAN FILTER; PACIFIC-OCEAN; WIND STRESS; LEVEL; DYNAMICS; VARIABILITY AB This paper presents a series of observing system simulation experiments (OSSEs) which are intended as a design study for a, proposed array of instrumented moorings in the tropical Atlantic Ocean. Fields of TOPEX/Poseidon sea surface height anomalies are subsampled with the goal being reconstruction of the original fields through the use of reduced-space Kalman filter data assimilation at a restricted number of locations. Our approach differs from typical identical and fraternal twin experiments in that real observed data (i.e., TOPEX/Poseidon data) are subsampled and used in place of synthetic data in all phases of the OSSEs. In this way the question of how closely a particular model-generated data set resembles nature is avoided. Several data assimilation runs are performed in order to optimize the location of a limited number of moorings for the proposed Pilot Research Moored Array in the Tropical Atlantic (PIRATA). Results of experiments in which data are assimilated at 2 degrees N, 2 degrees S and the equator and the longitude is systematically varied by 5 degrees show that the greatest impact of the assimilated data occurs when the observations are taken between 15 degrees W and 30 degrees W. Next, a more systematic technique is presented which allows us to determine optimal points in an objective fashion by applying a least squares regression approach to reconstruct the errors on a dense array of points from the data misfits at any three selected points. The forecast error structure from the Kalman filter is used in a novel way to assess the optimality of mooring locations. From a large sample of triads of points, the optimal mooring locations are found to be along the equator at 35 degrees W, 20 degrees W, and 10 degrees W. Additional experiments are performed to demonstrate the efficacy of the initial and final PIRATA configurations and the added value that can be expected from PIRATA observations beyond existing expendable bathythermograph observations. C1 NASA, Goddard Space Flight Ctr, Hughes STX Corp, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. RP Hackert, EC (reprint author), NASA, Goddard Space Flight Ctr, Hughes STX Corp, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RI Hackert, Eric/A-9915-2011 NR 43 TC 30 Z9 31 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1998 VL 103 IS C4 BP 7491 EP 7509 DI 10.1029/97JC03206 PG 19 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800002 ER PT J AU Weingartner, TJ Cavalieri, DJ Aagaard, K Sasaki, Y AF Weingartner, TJ Cavalieri, DJ Aagaard, K Sasaki, Y TI Circulation, dense water formation, and outflow on the northeast Chukchi shelf SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID CENTRAL ARCTIC-OCEAN; CONTINENTAL-SHELF; BERING STRAIT; DEEP-WATER; COASTAL POLYNYAS; BARROW CANYON; SEAS; FLOW; ICE; MODEL AB We investigated circulation and water mass modification processes in the Chukchi Sea using (1) temperature, salinity, and velocity data collected between September 1991 and September 1992 from moorings in Bering Strait and the northeast shelf, and (2) meteorological data and ice concentrations derived from special sensor microwave imager (SSM/I) imagery. In October 1991 and from February to August 1992 the mean monthly circulation was steady and northward. From November to January, strong northeast winds diverted the low-salinity Bering Inflow onto the western shelf, and weakened and reversed flow over the northeast shelf. The winds also opened extensive polynyas, wherein cold hypersaline (salinity > similar to 34) waters formed. The fall/winter circulation enhanced dense water formation by diverting low-salinity waters away from, and prolonging the residence time of water within, the polynyas, Alongshore convergence of the coastal flow swept some of the cold hypersaline water offshore (across isobaths), but the coastal current carried most of it into the Arctic Ocean through Barrow Canyon. The dense outflow mixed little during its descent through the upper canyon, where bottom friction and rotation, but not entrainment, were important in the plume momentum balance. If the outflow is not diluted by mixing in the lower canyon (where theory suggests this will occur), then the densest shelf waters can ventilate layers deeper than the halocline. Salt rejection estimates using SSM/I data and surface heat budget calculations agree, within a factor of 2, with independent estimates from the mooring. Hence remote sensing techniques can monitor winter salt rejection rates in the Chukchi Sea. C1 Univ Alaska, Sch Fisheries & Ocean Sci, Fairbanks, AK 99775 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Japan Marine Sci & Technol Ctr, Yokosuka, Kanagawa 237, Japan. Univ Washington, Appl Phys Lab, Polar Sci Ctr, Seattle, WA 98195 USA. RP Weingartner, TJ (reprint author), Univ Alaska, Sch Fisheries & Ocean Sci, Fairbanks, AK 99775 USA. EM weingart@ims.alaksa.edu NR 51 TC 189 Z9 209 U1 4 U2 21 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 APR 15 PY 1998 VL 103 IS C4 BP 7647 EP 7661 DI 10.1029/98JC00374 PG 15 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800013 ER PT J AU Halpern, D Freilich, MH Weller, RA AF Halpern, D Freilich, MH Weller, RA TI Arabian sea surface winds and ocean transports determined from ERS-1 scatterometer SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTHEAST MONSOON; SATELLITE AB Satellite scatterometer wind velocity measurements are a new source of data for studies of seasonal-to-interannual ocean-atmosphere interactions in the Arabian Sea, where the largest and steadiest wind speeds occur in northern summer. Three satellite wind velocity data products (named CMOD4, FD, and IFR2), all created from radar backscatter measured by the first European Remote Sensing Satellite (ERS-1), were compared to moored-buoy wind measurements recorded in the central Arabian Sea during October 1994 to October 1995. Orthogonal regression analysis of 74 collocations indicated IFR2 winds were more representative of buoy winds compared to CMOD4 and FD. IFR2 winds during 1995 are described, including the time of monsoon onset and the path of the Somali Jet. Monthly mean vertical transport across the bottom of the Ekman layer of the Arabian Sea north of 8 degrees N, meridional Ekman transport along 8.5 degrees N, and Sverdrup transport along 8.5 degrees N were computed with IFR2 data from May 1992 to May 1996. During the 1992-1995 June-September southwest monsoon, upwelling into the Ekman layer of the Arabian Sea occurred at a mean rate of 3.4 Sv (1 Sv = 10(6) m(3) s(-1)), which was one-third smaller than the volume transport exiting within the Ekman layer across the southern boundary of the Arabian Sea, and the southward Sverdrup transport was 15 Sv. During the 1992-1996 December-March northeast monsoon, nearly 5 Sv sank below the bottom of the Ekman layer, 4 Sv entered the Arabian Sea in the Ekman layer, and the Sverdrup transport was negligible. Year-to-year transport variations were small. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. Woods Hole Oceanog Inst, Dept Phys Oceanog, Woods Hole, MA 02543 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. RP Halpern, D (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 16 Z9 17 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1998 VL 103 IS C4 BP 7799 EP 7805 DI 10.1029/97JC02572 PG 7 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800026 ER PT J AU Holt, B Liu, AK Wang, DW Gnanadesikan, A Chen, HS AF Holt, B Liu, AK Wang, DW Gnanadesikan, A Chen, HS TI Tracking storm-generated waves in the northeast Pacific Ocean with ERS-1 synthetic aperture radar imagery and buoys SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SPECTRA; SAR; INVERSION; ALGORITHM; TRANSFORM AB This paper examines the capability of synthetic aperture radar imagery from ERS-1 and buoys to track the wave field emanating from an intense storm over a several-day period. The first part of the study is a validation component that compares SAR-derived wave length and direction with buoy data from two locations over 10 different dates in late 1991 and National Oceanic and Atmospheric Administration (NOAA) wave model (WAM) wave direction results. When the SAR is linear (8 out of 10 cases), mean wavelength is within 5% of the buoy measurements and mean wave direction is within 1 degrees of direction derived from the wave model (albeit with a large standard deviation of 27 degrees), indicating close agreement. The wave field generated from the intense storm in late December 1991 was measured by three separate ERS-1 SAR passes over a 3-day period. A simple kinematic model was used for waves propagating from a storm. Comparing the model results with both SAR and buoy data indicates that SAR-derived peak wavelength and direction measurements can be reliably used to predict arrival times and propagation direction over a several-day period and considerable distances. The measurements can also be used to derive estimated wave generation source regions about the storm as well. Such measurements are useful for comparing with wave model results, which perform less accurately for direction than wave height for example, and for predicting hazardous conditions for ship navigation and coastal regions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Natl Ctr Environm Predict, Washington, DC 20233 USA. Princeton Univ, Program Atmospher & Ocean Sci, Princeton, NJ 08540 USA. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Comp Sci Corp, Appl Technol Div, Stennis Space Ctr, MS 39529 USA. RP Holt, B (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM ben@pacific.jpl.nasa.gov RI Gnanadesikan, Anand/A-2397-2008 OI Gnanadesikan, Anand/0000-0001-5784-1116 NR 43 TC 14 Z9 16 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1998 VL 103 IS C4 BP 7917 EP 7929 DI 10.1029/97JC02567 PG 13 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800034 ER PT J AU Liu, AK Chang, YS Hsu, MK Liang, NK AF Liu, AK Chang, YS Hsu, MK Liang, NK TI Evolution of nonlinear internal waves in the East and South China Seas SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SYNTHETIC-APERTURE RADAR; SULU SEA; MODEL; NORTHEAST; KUROSHIO; TAIWAN; SHELF AB Synthetic Aperture Radar (SAR) images from ERS-1 have been used to study the characteristics of internal waves northeast and south of Taiwan in the East China Sea, and east of Hainan Island in the South China Sea. Rank-ordered packets of internal solitons propagating shoreward from the edge of the continental shelf were observed in the SAR images. On the basis of the assumption of a semidiurnal tidal origin, the wave speed can be estimated and is consistent with the internal wave theory. By using the SAR images and hydrographic data, internal waves of elevation have been identified in shallow water by a thicker mixed layer as compared with the bottom layer on the continental shelf. The generation mechanism includes the influences of the tide and the Kuroshio intrusion across the continental shelf for the formations of elevation internal waves. The effects of water depth on the evolution of solitons and wave packets are modeled by the nonlinear Kortweg-deVries (KdV) type equation and linked to satellite image observations. The numerical calculations of internal wave evolution on the continental shelf have been performed and compared with the SAR observations. For a case of depression waves in deep water, the solitons first disintegrate into dispersive wave trains and then evolve to a packet of elevation waves in the shallow water area after they pass through a "turning point" of approximately equal layer depths that has been observed in the SAR image and simulated by the numerical model. The importance of the dissipation effect in the coastal area is also discussed and demonstrated. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Natl Taiwan Ocean Univ, Dept Oceanog, Keelung, Taiwan. Natl Taiwan Univ, Inst Oceanog, Taipei, Taiwan. RP Liu, AK (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. NR 21 TC 243 Z9 279 U1 6 U2 40 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1998 VL 103 IS C4 BP 7995 EP 8008 DI 10.1029/97JC01918 PG 14 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800037 ER PT J AU Bouzinac, C Vazquez, J Font, J AF Bouzinac, C Vazquez, J Font, J TI Complex empirical orthogonal functions analysis of ERS-1 and TOPEX/POSEIDON combined altimetric data in the region of the Algerian current SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-SURFACE TEMPERATURE; CIRCULATION; WATER AB Maps of sea level anomalies (SLA) relative to the 1993 annual mean sea level combine the data from the two altimetric missions, ERS-1 and TOPEX/POSEIDON, during the overlap period (October 1992 to December 1993). These regular maps in space and time of residual sea level every 10 days on a 0.2 degrees regular grid are used in the region of the Algerian current where the mesoscale eddies are of primary importance to the circulation of all the Mediterranean water masses. They are first compared with ERS-1 along-track scanning radiometer sea surface temperature images to get information on two anticyclonic eddies produced by instabilities of the Algerian current and visible in both infrared and altimetric data sets. Then, an analysis of complex empirical orthogonal functions (CEOFs) is performed on the SLA data set to see the correlation of the different dynamic features of the observed variability. The CEOF analysis is applied to the complex time series formed from the original SLA time series and their Hilbert transforms to separate the variability into spatially coherent modes. The spatially correlated signal in the study area (0-15 degrees E and 35 degrees-40 degrees N) was found to be dominated by the first two CEOFs. These first two modes explain nearly 85% of the variability, with 80% of the total variance for the first one and 5% of the total variance for the second one. The temporal phase of the first mode indicates that a constant frequency of one cycle per year is clearly dominant, corresponding to the seasonal signal. The strongest amplitude is obtained in the southern part of the channel of Sardinia and south of the Strait of Sicily. The temporal amplitude and the temporal phase of the second mode show a periodicity of about 6 months which appears to be associated with the variability of the Algerian current as the phase isolines are parallel to the mean current path along the Algerian coast. The strongest amplitude of the second mode is located near the African coast at similar to 4 degrees E and 8 degrees E. These two points of high variability could correspond to eddy detachments from the main current. C1 CSIC, Inst Ciencias Mar, E-08039 Barcelona, Spain. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CSIC, Inst Ciencias Mar, Paseo Juan de Borbon, E-08039 Barcelona, Spain. EM cath@icm.csic.es; jv@pacific.jpl.nasa.gov; jfont@icm.csic.es RI Font, Jordi/E-5355-2013 OI Font, Jordi/0000-0003-2590-1457 NR 28 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1998 VL 103 IS C4 BP 8059 EP 8071 DI 10.1029/97JC02909 PG 13 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800041 ER PT J AU Kwok, R Schweiger, A Rothrock, DA Pang, S Kottmeier, C AF Kwok, R Schweiger, A Rothrock, DA Pang, S Kottmeier, C TI Sea ice motion from satellite passive microwave imagery assessed with ERS SAR and buoy motions SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID TRACKING AB Observing the motion of sea ice from space is analogous to observing wind stress over the wet oceans; both provide surface forcing for modeling ocean dynamics. Ice motion also directly provides the advective component of the equations governing the mass balance of the sea ice cover. Thus its routine observation from space would be of great value to understanding ice and ocean behavior. To demonstrate the feasibility of creating a global multidecadal ice motion record from satellite passive microwave imagery and to quantitatively assess the errors in the estimated ice motions, we have tracked ice every 3 days in the Arctic Ocean and daily in the Fram Strait and Baffin Bay during the 8 winter months from October 1992 to May 1993 and daily in the Weddell Sea during the 8 winter months from March to October 1992. The method, which has been well used previously, involves finding the spatial offset that maximizes the cross correlation of the brightness temperature fields over 100-km patches in two images separated in time by from 1 to 3 days. The resulting ice motions are compared with contemporaneous buoy- and SAR-derived ice motions, The uncertainties in the displacement vectors, between 5 and 12 km, are better than the spatial resolution of the data. Both 85-GHz data with 12-km spatial resolution and 37-GHz data with 25-km resolution are tracked. These trials with the 37-GHz data are new and show quite surprisingly that the error is only about 1 km larger with these data than with the 12-km 85-GHz data, Errors are typically larger than average in areas of lower ice concentration; in the most dynamic regions, particularly near the ice edge in the Barents and Greenland Seas; and in zones of high shear. These passive microwave ice motions show a large increase in spatial detail over motion fields optimally interpolated from buoy and wind observations, especially where buoy data are virtually absent such as near coasts and in some passages between the Arctic Ocean and its peripheral seas. The feasibility of obtaining ice motion from the 37-GHz data in addition to the 85-GHz data should allow an important record of ice motion to be established for the duration of the scanning multichannel microwave radiometer (SMMR), special sensor microwave/imager (SSM/I), and future microwave sensors, that is, from 1978 into the next millenium. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Karlsruhe, Inst Meteorol & Klimaforsch, D-76128 Karlsruhe, Germany. Univ Washington, Coll Ocean & Fisheries Sci, Appl Phys Lab, Polar Sci Ctr, 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; Kottmeier, Christoph/A-9553-2013 OI Kwok, Ron/0000-0003-4051-5896; NR 13 TC 132 Z9 134 U1 0 U2 20 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1998 VL 103 IS C4 BP 8191 EP 8214 DI 10.1029/97JC03334 PG 24 WC Oceanography SC Oceanography GA ZH476 UT WOS:000073114800050 ER PT J AU Asthana, R AF Asthana, R TI Reinforced cast metals - Part II Evolution of the interface SO JOURNAL OF MATERIALS SCIENCE LA English DT Review ID INTERMETALLIC-MATRIX COMPOSITES; ALUMINUM-ALLOY COMPOSITES; SILICON-CARBIDE COMPACTS; SOLID-LIQUID INTERFACES; OXYGEN PARTIAL-PRESSURE; MOLTEN ALUMINUM; MELT INFILTRATION; CONTACT ANGLES; PARTICULATE COMPOSITES; CERAMIC SYSTEMS AB Interface evolution in metal-matrix composites is a thermodynamic necessity and interface design a kinetics challenge. The synergistic interaction between processing science and surface engineering has led to considerable progress in understanding, modelling and tailoring the fibre-matrix interface at the microstructural, crystallographic and atomic levels. The chemical, morphological, crystallographic and thermoelastic compatibilities between the fibre and the matrix influence the interfacial adhesion strength. This article examines the role of material properties and fabrication conditions in chemical interactions between the fibre and the matrix in metal-matrix composites synthesized using the solidification and casting techniques. (C) 1998 Chapman & Hall. C1 Univ Wisconsin Stout, Dept Technol, Menomonie, WI 54751 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Asthana, R (reprint author), Univ Wisconsin Stout, Dept Technol, Menomonie, WI 54751 USA. EM asthanar@uwstout.edu NR 308 TC 46 Z9 46 U1 0 U2 17 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 15 PY 1998 VL 33 IS 8 BP 1959 EP 1980 DI 10.1023/A:1004334228105 PG 22 WC Materials Science, Multidisciplinary SC Materials Science GA ZH367 UT WOS:000073101400001 ER PT J AU Boggon, TJ Chayen, NE Snell, EH Dong, J Lautenschlager, P Potthast, L Siddons, DP Stojanoff, V Gordon, E Thompson, AW Zagalsky, PF Bi, RC Helliwell, JR AF Boggon, TJ Chayen, NE Snell, EH Dong, J Lautenschlager, P Potthast, L Siddons, DP Stojanoff, V Gordon, E Thompson, AW Zagalsky, PF Bi, RC Helliwell, JR TI Protein crystal movements and fluid flows during microgravity growth SO PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES LA English DT Article; Proceedings Paper CT Meeting on Marangoni and Interfacial Phenomena in Materials Processing CY JUN 04-05, 1997 CL LONDON, ENGLAND SP Royal Soc DE protein crystallization; microgravity; interferometry; CCD video; crystal perfection; g-jitter; Marangoni convection ID CRYSTALLIZATION; FACILITIES AB The growth of protein crystals suitable for X-ray crystal structure analysis is all important topic. The methods of protein crystal growth are under increasing study whereby different methods are being compared via diagnostic monitoring including charge coupled device (CCD) video and interferometry. The quality (perfection) of protein crystals is now being evaluated by mosaicity analysis (rocking curves) and X-rar topographic images as well as the diffraction resolution limit and overall data quality. Choice of a liquid-liquid linear crystal-growth geometry and microgravity can yield a spatial stability of growing crystals and fluid, as seen in protein crystallization experiments on the uncrewed platform EURECA. A similar geometry used within the Advanced Protein Crystallization Facility (APCF) onboard the crewed shuttle missions SpaceHab-01 and IML-2, however, has shown by CCD video some lysozyme crystal movement through the mother liquor. Moreover, spurts and lulls of growth of a stationary lysozyme protein crystal that was probably fixed to the crystal-growth reactor wall suggests g-jitter stimulated movement of fluid on IML-2, thus transporting new protein to the growing crystal faces. In yet another study, use of a hanging drop vapour diffusion geometry on the IML-2 shuttle mission showed, again via CCD video monitoring, growing apocrustacyanin C-1 protein crystals executing near cyclic movement, reminiscent of Marangoni convection flow of fluid, the crystals serving as 'markers' of the fluid flow. These observations demonstrated that the use of vapour diffusion geometry did not yield spatially stable crystal position or fluid conditions for a solely protein diffusive regime to be realized. Indeed mosaicity evaluation of those vapour diffusion-grown apocrustacyanin C-1 crystals showed inconsistent protein crystal quality although the best crystal studied was microgravity grows. Ln general, realizing perfect conditions for protein crystal growth, of absence of movement of crystal or fluid, requires not only the correct choice of geometry but also the avoidance of low-frequency (less than or similar to 5 Hz) g-jitters. A review is given here of existing results and experience over several microgravity missions. Some comment, is given on gel protein crystal growth in attempts to 'mimic' the benefits of microgravity on Earth. Finally, the recent new results from our experiments on the shuttle mission LMS are described. These results include CCD video as well as interferometry during the mission, followed, on return to Earth, by reciprocal space mapping at the NSLS, Brookhaven, and full X-ray data collection on LMS and Earth control lysozyme crystals. Diffraction data recorded from LMS and ground control apocrustacyanin C-1 crystals are also described. C1 Univ Manchester, Dept Chem, Struct Chem Sect, Manchester M13 9PL, Lancs, England. Univ London Imperial Coll Sci Technol & Med, Dept Biophys, Blackett Lab, London SW7 2BZ, England. NASA, Struct Biol Lab, Huntsville, AL 35812 USA. Dornier Syst GmbH, Raumfahrt Infrastrukt, D-88039 Friedrichshafen, Germany. NSLS, Brookhaven Natl Lab, Upton, NY 11973 USA. European Synchrotron Radiat Facil, F-38043 Grenoble, France. Inst Biol Struct, Inst Cristallog Macromol, F-38027 Grenoble, France. EMBL, F-38043 Grenoble, France. Univ London, Royal Holloway & Bedford New Coll, Dept Biochem, Egham TW20 0EX, Surrey, England. Acad Sinica, Inst Biophys, Beijing 100101, Peoples R China. RP Boggon, TJ (reprint author), Univ Manchester, Dept Chem, Struct Chem Sect, Oxford Rd, Manchester M13 9PL, Lancs, England. RI stojanoff, vivian /I-7290-2012; Helliwell, John /C-4587-2014 OI stojanoff, vivian /0000-0002-6650-512X; Helliwell, John /0000-0002-0520-7540 NR 23 TC 26 Z9 26 U1 0 U2 3 PU ROYAL SOC PI LONDON PA 6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLAND SN 1364-503X J9 PHILOS T R SOC A JI Philos. Trans. R. Soc. A-Math. Phys. Eng. Sci. PD APR 15 PY 1998 VL 356 IS 1739 BP 1045 EP 1061 PG 17 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZM298 UT WOS:000073524500031 ER PT J AU Chung, DJH Farrar, GR Kolb, EW AF Chung, DJH Farrar, GR Kolb, EW TI Are ultrahigh energy cosmic rays a signal for supersymmetry? SO PHYSICAL REVIEW D LA English DT Article ID LIGHT-GLUINO; SPECTRUM; RADIATION; CUTOFF; SEARCH; WELL; EYE AB We investigate the possibility that cosmic rays of energy larger than the Greisen-Zatsepin-Kuzmin cutoff are not nucleons, but a new stable, massive, hadron that appears in many extensions of the standard model. We focus primarily on the S-0, a uds-gluino bound state. The range of the S-0 through the cosmic background radiation is significantly longer than the range of nucleons, and therefore S-0's can originate from sources at cosmological distances. C1 Univ Chicago, Dept Phys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08855 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. RP Chung, DJH (reprint author), Univ Chicago, Dept Phys, Chicago, IL 60637 USA. NR 26 TC 88 Z9 89 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD APR 15 PY 1998 VL 57 IS 8 BP 4606 EP 4613 DI 10.1103/PhysRevD.57.4606 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA ZJ378 UT WOS:000073208600009 ER PT J AU Frieman, JA Waga, I AF Frieman, JA Waga, I TI Constraints from high redshift supernovae upon scalar field cosmologies SO PHYSICAL REVIEW D LA English DT Article ID DECAYING LAMBDA-COSMOLOGIES; POWER-LAW INFLATION; LIGHT-CURVE SHAPES; COLD DARK-MATTER; IA SUPERNOVAE; EXPONENTIAL POTENTIALS; CONSTANT; UNIVERSE; SPECTRUM; MODELS AB Recent observations of high-redshift type Ia supernovae have placed stringent constraints on the cosmological constant Lambda. We explore the implications of these SNe observations for cosmological models in which a classically evolving scalar field currently dominates the energy density of the Universe. Such models have been shown to share the advantages of Lambda models: compatibility with the spatial flatness predicted by inflation; a Universe older than the standard Einstein-de Sitter model; and, combined with cold dark matter, predictions for large-scale structure formation in good agreement with data from galaxy surveys. Compared to the cosmological constant, these scalar field models are consistent with the SNe observations for a lower matter density, Omega(m0)similar to 0.2, and a higher age, H(0)t(0) greater than or similar to 1. Combined with the fact that scalar field models imprint a distinctive signature on the cosmic microwave background anisotropy, they remain currently viable and should be testable in the near future. C1 Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Fed Rio de Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil. RP Frieman, JA (reprint author), Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, POB 500, Batavia, IL 60510 USA. RI Waga, Ioav/B-6288-2014 NR 44 TC 71 Z9 71 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 APR 15 PY 1998 VL 57 IS 8 BP 4642 EP 4650 DI 10.1103/PhysRevD.57.4642 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA ZJ378 UT WOS:000073208600013 ER PT J AU He, L Shi, ZQ Jiang, N Han, P Zheng, YD AF He, L Shi, ZQ Jiang, N Han, P Zheng, YD TI Surface morphology study and electrical properties of Si1-xCx on Si grown by low pressure chemical vapor deposition SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT Symposium B on Epitaxial Thin Film Growth and Nanostructures at the ICAM/EMRS Spring Conference CY JUN 16-20, 1997 CL STRASBOURG, FRANCE SP Council Europe, Commiss European Communities DE silicon substrates; chemical vapor deposition; surface morphology ID ALLOYS; GEXSI1-X AB Si1-xCx alloys were grown on silicon substrates by rapid thermal process/very low pressure chemical vapor deposition (RTP/VLP CVD). The growth rate is about 0.4 nm/min within the critical thickness and 1.4 nm/min beyond the critical thickness. Atomic force microscope (AFM) investigation on different samples indicated that the surface roughness is proportional to the growth rate and reverse proportional to the mass flow ratio of SiH4 to C2H2. This result will provide useful information on the material growth condition. The Raman spectrum study indicated the strain in Si1-xCx layer and the substitutional C was confirmed by the observation of the peak at 960 cm(-1). The bandgap of the Si1-xCx layer was studied by making Schottky contacts on the Si1-xCx samples. The barrier height reduction on the strain sample can be attributed to the effect of C incorporation. (C) 1998 Elsevier Science S.A. C1 No Illinois Univ, Dept Elect Engn, De Kalb, IL 60115 USA. Hughes STX, Greenbelt, MD USA. Nanjing Univ, Dept Phys, Nanjing 210008, Peoples R China. RP Shi, ZQ (reprint author), NASA, Goddard Space Flight Ctr, Code 718, Greenbelt, MD 20771 USA. NR 8 TC 0 Z9 0 U1 0 U2 1 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 APR 15 PY 1998 VL 318 IS 1-2 BP 15 EP 17 DI 10.1016/S0040-6090(97)01130-9 PG 3 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA ZV700 UT WOS:000074332300004 ER PT J AU Golub, MA Wydeven, T Johnson, AL AF Golub, MA Wydeven, T Johnson, AL TI Similarity of plasma-polymerized tetrafluoroethylene and fluoropolymer films deposited by rf sputtering of poly(tetrafluoroethylene) SO LANGMUIR LA English DT Article ID FLUOROCARBON FILMS; POLYTETRAFLUOROETHYLENE; SPECTROSCOPY; MECHANISM; ETHYLENE C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Lockheed Martin Engn & Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. Surface Sci Labs, Mt View, CA 94043 USA. RP Golub, MA (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 26 TC 28 Z9 28 U1 0 U2 2 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0743-7463 J9 LANGMUIR JI Langmuir PD APR 14 PY 1998 VL 14 IS 8 BP 2217 EP 2220 DI 10.1021/la971102e PG 4 WC Chemistry, Multidisciplinary; Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA ZK056 UT WOS:000073280500044 ER PT J AU Hansen, J Sato, M Glascoe, J Ruedy, R AF Hansen, J Sato, M Glascoe, J Ruedy, R TI A common-sense climate index: Is climate changing noticeably? SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article DE global warming; greenhouse effect; carbon cycle ID SURFACE AIR-TEMPERATURE; TRENDS; IMPACT; MODEL AB We propose an index of climate change based on practical climate indicators such as heating degree days and the frequency of intense precipitation. We find that in most regions the index is positive, the sense predicted to accompany global warming, In a few regions, especially in Asia and western North America, the index indicates that climate change should be apparent already, but in most places climate trends are too small to stand out above year-to-year variability. The climate index is strongly correlated with global surface temperature, which has increased as rapidly as projected by climate models in the 1980s, We argue that the global area with obvious climate change will increase notably in the nest few years. But we show that the growth rate of greenhouse gas climate forcing has declined in recent years, and thus there is an opportunity to keep climate change in the 21st century less than "business-as-usual" scenarios. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Hansen, J (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 26 TC 49 Z9 51 U1 3 U2 13 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 APR 14 PY 1998 VL 95 IS 8 BP 4113 EP 4120 DI 10.1073/pnas.95.8.4113 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZH535 UT WOS:000073120800011 PM 9539699 ER PT J AU Ning, CZ AF Ning, CZ TI Partial and total alpha parameters in semiconductor optical devices SO APPLIED PHYSICS LETTERS LA English DT Article ID LASERS; GAIN AB alpha parameters due to partial variation of carrier density (alpha(N)) or temperature (alpha(T)) are calculated for a two-dimensional semiconductor. We also introduce and investigate the total alpha parameter (alpha(t)) due to simultaneous variations of the carrier density and temperature. We find that, unlike the usual alpha(N), the partial alpha(T) and total alpha(t) show quite different behavior with changes in underlying variables and could be positive, negative, or singular. (C) 1998 American Institute of Physics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ning, CZ (reprint author), NASA, Ames Res Ctr, Mail Stop T27A-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 9 TC 4 Z9 4 U1 0 U2 0 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 APR 13 PY 1998 VL 72 IS 15 BP 1887 EP 1889 DI 10.1063/1.121216 PG 3 WC Physics, Applied SC Physics GA ZG930 UT WOS:000073054300031 ER PT J AU Bandyopadhyay, R Martini, P Gerard, E Charles, PA Wagner, RM Shrader, C Shahbaz, T Mirabel, IF AF Bandyopadhyay, R Martini, P Gerard, E Charles, PA Wagner, RM Shrader, C Shahbaz, T Mirabel, IF TI Multiwavelength monitoring of GRS 1915+105 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries, close; stars, individual, GRS 1915+105; ISM, jets and outflows; X-rays, stars ID X-RAY TRANSIENT; BINARY-SYSTEMS; GRS-1915+105; A0538-66; EMISSION; OUTBURST AB Since its discovery in 1992, the superluminal X-ray transient GRS 1915 + 105 has been extensively observed in an attempt to understand its behaviour. We present here first results from a multiwavelength campaign undertaken from 1996 July to September. This study includes X-ray data from the RXTE All Sky Monitor and BATSE, two-frequency data from the Nancay radio telescope, and infrared photometry from the 1.8-m Perkins telescope at Lowell Observatory. The first long-term, well-sampled infrared light curve of GRS 1915 + 105 is presented herein; it is consistent with the interpretation of this source as a long-period binary. We compare the various light curves, searching for correlations in the behaviour of the source at differing wavelengths and for possible periodicities. C1 Univ Oxford, Dept Astrophys, Oxford OX1 3RH, England. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Observ Paris, Sect Meudon, Dept ARPEGES, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etud Saclay, Serv Astrophys, CEA, DSM,DAPNIA, F-91191 Gif Sur Yvette, France. Inst Astron & Fis Espacio, Buenos Aires, DF, Argentina. RP Univ Oxford, Dept Astrophys, Nucl Phys Bldg,Keble Rd, Oxford OX1 3RH, England. NR 42 TC 14 Z9 14 U1 0 U2 0 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0035-8711 EI 1365-2966 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD APR 11 PY 1998 VL 295 IS 3 BP 623 EP 631 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ833 UT WOS:000073258300011 ER PT J AU Keenan, FP Aller, LH Bell, KL Espey, BR Feibelman, WA Hyung, S McKenna, FC Ramsbottom, CA AF Keenan, FP Aller, LH Bell, KL Espey, BR Feibelman, WA Hyung, S McKenna, FC Ramsbottom, CA TI Emission lines of [Ne IV] in the optical and ultraviolet spectra of gaseous nebulae SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE atomic data; planetary nebulae, general ID OPACITY CALCULATIONS; PLANETARY-NEBULAE; FORBIDDEN LINES; ATOMIC DATA; DIAGNOSTICS; RATIOS; IONS AB Recent R-matrix calculations of electron impact excitation rates in Ne rv are used to calculate emission line ratio-ratio diagrams involving both the ultraviolet (1602, 2422 and 2424 Angstrom and optical (4714, 4716, 4724 and 4726 ii) [Ne IV] transitions, for a range of electron temperatures (T-e=10 000-30 000K) and electron densities (N-e=10(2)-10(6.5)cm(-3)) appropriate to gaseous nebulae. These diagrams should, in principle, allow the simultaneous determination of T-e and N-e from measurements of the [Ne IV] lines in a spectrum. Plasma parameters deduced for a sample of high-excitation planetary nebulae, using a combination of observational data obtained with the IUE satellite and the Hamilton Echelle Spectrograph (HES) on the 3-m Shane Telescope at the Lick Observatory, are found to show generally excellent internal consistency. In addition, they are in good agreement with the values of T-e and N-e estimated from other high-excitation line ratios in the HES spectra, and by previous authors using infrared and ultraviolet transitions in [O IV] and [Ne V]. These results provide observational support for the accuracy of the theoretical [Ne IV] ratios, and hence the atomic data adopted in their derivation. An inspection of IUE and GHRS/HST spectra of the symbiotic stars Z And and RR Tel reveals asymmetries in the line profile of the [Ne IV] 2s(2)2p(34)S-2s(2)2p(32)P(1/2,3/2) doublet at 1602 Angstrom, hence allowing the measurement of the wavelength separation of the S-4-P-2(1/2) and S-4-P-2(3/2) components. The separation is found to be 0.21 +/- 0.02 Angstrom in good agreement with the theoretical estimate of 0.16 +/- 0.03 Angstrom; this is the first time (to our knowledge) that this quantity has been experimentally determined. 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. Johns Hopkins Univ, Dept Phys & Astron, Ctr Astrophys Sci, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. BohyunSan Observ, Young Cheon 770820, KyungPook, South Korea. RP Keenan, FP (reprint author), Queens Univ Belfast, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland. OI Espey, Brian/0000-0002-2457-1380 NR 24 TC 14 Z9 14 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 APR 11 PY 1998 VL 295 IS 3 BP 683 EP 690 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZJ833 UT WOS:000073258300015 ER PT J AU Downie, JD Timucin, DA AF Downie, JD Timucin, DA TI Modeling the grating-formation process in thick bacteriorhodopsin films SO APPLIED OPTICS LA English DT Article ID WILDTYPE; VARIANTS; MEDIA AB We model the grating-formation process in bacteriorhodopsin films for the interference of two plane waves. We simulate the temporal dependence of grating recording and readout, and we examine the behavior of the diffraction efficiency with respect to exposure, write and read wavelengths, and film parameters such as initial optical density and lifetime of the upper state. Gratings written in thick. bacteriorhodopsin films are generally nonuniform and nonsinusoidal owing to the absorption and saturation properties of the material. The simulations also show that one can often obtain optimization of hologram recording and readout by writing and reading at wavelengths far off the peak of the groundstate absorbance spectrum, especially for films with high values of the peak optical density. (C) 1998 Optical Society of America. C1 NASA, Ames Res Ctr, Computat Sci Div, Moffett Field, CA 94035 USA. RP Downie, JD (reprint author), NASA, Ames Res Ctr, Computat Sci Div, M-S 269-3, Moffett Field, CA 94035 USA. NR 17 TC 18 Z9 19 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD APR 10 PY 1998 VL 37 IS 11 BP 2102 EP 2111 DI 10.1364/AO.37.002102 PG 10 WC Optics SC Optics GA ZG506 UT WOS:000073010500014 PM 18273132 ER PT J AU Wehrle, AE Pian, E Urry, CM Maraschi, L McHardy, IM Lawson, AJ Ghisellini, G Hartman, RC Madejski, GM Makino, F Marscher, AP Wagner, SJ Webb, JR Aldering, GS Aller, MF Aller, HD Backman, DE Balonek, TJ Boltwood, P Bonnell, J Caplinger, J Celotti, A Collmar, W Dalton, J Drucker, A Falomo, R Fichtel, CE Freudling, W Gear, WK Gonzalez-Perez, N Hall, P Inoue, H Johnson, WN Kazanas, D Kidger, MR Kii, T Kollgaard, RI Kondo, Y Kurfess, J Lin, YC McCollum, B McNaron-Brown, K Nagase, F Nair, AD Penton, S Pesce, JE Pohl, M Raiteri, CH Renda, M Robson, EI Sambruna, RM Schirmer, AF Shrader, C Sikora, M Sillanpaa, A Smith, PS Stevens, JA Stocke, J Takalo, LO Terasranta, H Thompson, DJ Thompson, R Tornikoski, M Tosti, G Treves, A Turcotte, P Unwin, SC Valtaoja, E Villata, M Xu, W Yamashita, A Zook, A AF Wehrle, AE Pian, E Urry, CM Maraschi, L McHardy, IM Lawson, AJ Ghisellini, G Hartman, RC Madejski, GM Makino, F Marscher, AP Wagner, SJ Webb, JR Aldering, GS Aller, MF Aller, HD Backman, DE Balonek, TJ Boltwood, P Bonnell, J Caplinger, J Celotti, A Collmar, W Dalton, J Drucker, A Falomo, R Fichtel, CE Freudling, W Gear, WK Gonzalez-Perez, N Hall, P Inoue, H Johnson, WN Kazanas, D Kidger, MR Kii, T Kollgaard, RI Kondo, Y Kurfess, J Lin, YC McCollum, B McNaron-Brown, K Nagase, F Nair, AD Penton, S Pesce, JE Pohl, M Raiteri, CH Renda, M Robson, EI Sambruna, RM Schirmer, AF Shrader, C Sikora, M Sillanpaa, A Smith, PS Stevens, JA Stocke, J Takalo, LO Terasranta, H Thompson, DJ Thompson, R Tornikoski, M Tosti, G Treves, A Turcotte, P Unwin, SC Valtaoja, E Villata, M Xu, W Yamashita, A Zook, A TI Multiwavelength observations of a dramatic high-energy flare in the blazar 3C 279 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, photometry; gamma rays, observations; quasars, individual (3C 279); radiation mechanisms, nonthermal ID ACTIVE GALACTIC NUCLEI; RADIO-SOURCES; RAY-EMISSION; 3C-279; CALIBRATION; VARIABILITY; PHOTOMETRY; RADIATION; SYSTEM; JET AB The blazar 3C 279, one of the brightest identified extragalactic objects in the gamma-ray sky, underwent a large (factor of similar to 10 in amplitude) flare in gamma-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest gamma-ray intensity ever recorded for this object. During the high state, extremely rapid gamma-ray variability was seen, including an increase of a factor of 2.6 in similar to 8 hr, which strengthens the case for relativistic beaming. Coordinated multifrequency observations were carried out with Rossi X-Ray Timing Explorer (RXTE), Advanced Satellite for Cosmology and Astrophysics (ASCA; ol, Astro-D), Roentgen Satellite (ROSAT), and Intel national Ultraviolet Explorer (IUE) and from many ground-based observatories, covering most accessible wavelengths. The well-sampled, simultaneous RXTE light curve shows an outburst of lower amplitude (factor of similar or equal to 3) well correlated with the gamma-ray flare without any lag larger than the temporal resolution of similar to 1 day. The optical-UV light curves, which are not well sampled during the high-energy flare, exhibit more modest variations (factor of similar to 2) and a lower degree of correlation. The flux at millimetric wavelengths was near a historical maximum during the gamma-ray flare peak, and there is a suggestion of a correlated decay. We present simultaneous spectral energy distributions of 3C 279 prior to and near to the flare peak. The gamma-rays vary by more than the square of the observed IR-optical flux change, which poses some problems for specific blazar emission models. The synchrotron self-Compton (SSC) model would require that the largest synchrotron variability occurred in the mostly unobserved submillimeter/far-infrared region. Alternatively, a large variation in the external photon held could occur over a timescale of a few days. This occurs naturally in the "mirror" model, wherein the flaring region in the jet photoionizes nearby broad emission line clouds, which, in turn, provide soft external photons that are Comptonized to gamma-ray energies. C1 Infrared Proc Anal Ctr, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Pasadena, CA 91125 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. CNR, ITESRE, I-40129 Bologna, Italy. Osservatorio Astron Brera, I-20121 Milan, Italy. Univ Southampton, Dept Phys, Southampton SO9 5NH, Hants, England. Osservatorio Astron Brera, I-22055 Merate, Lecco, Italy. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Boston Univ, Dept Astron, Boston, MA 02215 USA. Landessternwarte, Heidelberg Konigsstuhl, D-69117 Heidelberg, Germany. Florida Int Univ, Dept Phys, Miami, FL 33199 USA. NOAO, KPNO, SARA Observ, Tucson, AZ 85726 USA. Univ Minnesota, Dept Astron, Minneapolis, MN 55455 USA. Univ Michigan, Ann Arbor, MI 48109 USA. Franklin & Marshall Coll, Dept Phys & Astron, Lancaster, PA 17604 USA. Colgate Univ, Dept Phys & Astron, Hamilton, NY 13346 USA. SISSA, ISAS, I-34014 Trieste, Italy. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Osservatorio Astron Padova, I-35122 Padua, Italy. Space Telescope European Coordinating Facil, D-85748 Garching, Germany. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. Inst Astrofis Canarias, E-38200 La Laguna, Tenerife, Spain. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. USN, Res Lab, Washington, DC 20375 USA. Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Stanford Univ, WW Hansen Labs Phys, Stanford, CA 94305 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Univ Florida, Dept Astron, Gainesville, FL 32601 USA. Univ Colorado, JILA, Boulder, CO 80309 USA. Penn State Univ, Dept Astron, Davey Lab 525, University Pk, PA 16802 USA. Osservatorio Astron Torino, I-10025 Pino Torinese, Italy. Joint Astron Ctr, Hilo, HI 96720 USA. Polish Acad Sci, Copernicus Astron Ctr, Warsaw, Poland. Tuorla Observ, Tuorla 21500, Piikkio, Finland. Natl Opt Astron Observ, KPNO, Tucson, AZ 85726 USA. Metsahovi Radio Res Stn, Kylmala 02540, Finland. Univ Perugia, Osservatorio Astron, I-06100 Perugia, Italy. Univ Milan, Dept Phys, I-22100 Como, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Pomona Coll, Dept Phys & Astron, Claremont, CA 91711 USA. RP Wehrle, AE (reprint author), Infrared Proc Anal Ctr, Jet Prop Lab, MC 100-22, Pasadena, CA 91125 USA. RI Thompson, David/D-2939-2012; Tosti, Gino/E-9976-2013; Urry, Claudia/G-7381-2011; Johnson, Neil/G-3309-2014; OI Thompson, David/0000-0001-5217-9135; Urry, Claudia/0000-0002-0745-9792; Villata, Massimo/0000-0003-1743-6946; Falomo, Renato/0000-0003-4137-6541; Raiteri, Claudia Maria/0000-0003-1784-2784; Pian, Elena/0000-0001-8646-4858 NR 39 TC 203 Z9 208 U1 1 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1998 VL 497 IS 1 BP 178 EP 187 DI 10.1086/305461 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG883 UT WOS:000073049600016 ER PT J AU Kaufman, MJ Hollenbach, DJ Tielens, AGGM AF Kaufman, MJ Hollenbach, DJ Tielens, AGGM TI High-temperature molecular cores near massive stars and application to the Orion hot core SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM, individual (Orion hot core, IRc2); radiative transfer; stars, formation; stars, pre-main-sequence ID INTERSTELLAR DUST CLOUDS; KLEINMANN-LOW; RADIATION TRANSPORT; INFRARED CLUSTER; KL; EMISSION; NEBULA; MAPS; LINE; AMMONIA AB We calculate the temperature structure of hot, high column density, molecular cores for several assumed density distributions, with either internal or external illumination. We show that large (N[H-2] greater than or similar to 10(23) cm(-2)), warm (T greater than or similar to 100 K) columns of molecular gas are more easily produced when cores are heated from within than when cores are heated externally. We compare our results to the conditions inferred from recent high-resolution observations of the Orion hot core. We find that external heating by the star at the center of the SiO maser disk (radio source "I") may partially heat the nearby core, but heating of the more extended (similar to 10'') hot core likely arises due to a young star (or stars) embedded in the core. We show that high and low-mass cores have physical parameters that lie on a common plane defined by their mass, luminosity and temperature and that we may use such information to determine the physical size of embedded cores even from measurements that do not resolve the structure of a particular core. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Kaufman, MJ (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. NR 40 TC 49 Z9 49 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1998 VL 497 IS 1 BP 276 EP 287 DI 10.1086/305444 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG883 UT WOS:000073049600023 ER PT J AU Toman, J Imamura, JN Pickett, BK Durisen, RH AF Toman, J Imamura, JN Pickett, BK Durisen, RH TI Nonaxisymmetric dynamic instabilities of rotating polytropes. I. The Kelvin modes SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; instabilities; stars, rotation ID PARTICLE HYDRODYNAMICS; PROTOSTARS; STABILITY; STAR; DISKS AB We study the dynamic instabilities of rotating polytropes in the linear regime using an approximate Lagrangian technique and a more precise Eulerian scheme. We consider nonaxisymmetric modes with azimuthal dependence proportional to exp (im phi), where m is an integer and phi is the azimuthal angle, for polytropes with a wide range of compressibilities and angular momentum distributions. We determine stability limits for the m = 2-4 modes and find the eigenvalue and eigenfunction of the most unstable m-mode for given equilibrium models. To the extent that we have explored parameter space, we find that the onset of instability is not very sensitive to the compressibility or angular momentum distribution of the polytrope when the models are parameterized by T/\W\. Here T is the rotational kinetic energy, and W is the gravitational energy of the polytrope. The m = 2, 3, and 4 modes become unstable at T/\W\ approximate to 0.26-0.28, 0.29-0.32, and 0.32-0.35, respectively, limits consistent with those of the Maclaurin spheroids to within +/- 0.015 in T/\W\. The only exception to this occurs for the most compressible polytrope we test and then only for m = 4, where instability sets in at T/\W\ approximate to 0.37-0.39. The eigenfunctions for the fastest growing low in-modes are similar to those of the Maclaurin spheroid eigenfunctions in that they do not show large vertical motions, are only weakly dependent on z, and increase strongly in amplitude as the equatorial radius of the spheroid is approached. The polytrope eigenfunctions are, however, qualitatively different from the Maclaurin eigenfunctions in one respect: they develop strong spiral arms. The spiral arms are stronger for more compressible polytropes and for polytropes whose angular momentum distributions deviate significantly from those of the Maclaurin spheroids. Nevertheless, our approximate Lagrangian method, which explicitly assumes nonspiral Maclaurin-like trial functions, yields reasonable estimates for the pattern periods and e-folding times of unstable m = 2 modes even for highly compressible and strongly differentially rotating polytropes. Comparisons for m = 2 between the linear analyses in this paper and nonlinear hydrodynamic simulations give excellent quantitative agreement in eigenfunctions, pattern speeds, and e-folding times for the dynamically unstable modes. C1 Univ Oregon, Inst Theoret Sci, Eugene, OR 97403 USA. Univ Oregon, Dept Phys, Eugene, OR 97403 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Indiana Univ, Dept Astron, Bloomington, IN 47405 USA. RP Toman, J (reprint author), Univ Oregon, Inst Theoret Sci, Eugene, OR 97403 USA. NR 29 TC 34 Z9 34 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 APR 10 PY 1998 VL 497 IS 1 BP 370 EP 387 DI 10.1086/305466 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG883 UT WOS:000073049600030 ER PT J AU Bhatia, AK Thomas, RJ AF Bhatia, AK Thomas, RJ TI Atomic data and spectral line intensities for Mg VIII SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; sun, corona; sun, UV radiation ID BORON ISOELECTRONIC SEQUENCE; ELECTRON-IMPACT EXCITATION; EUV ROCKET TELESCOPE; COLLISION STRENGTHS; SPECTROGRAPH SERTS; CROSS-SECTIONS; SOLAR; IONS; N=2 AB EUV spectral lines of Mg vm have been observed from the solar corona by Skylab, SERTS, and more recently by SOHO. Atomic data for this astrophysically important ion are presented in this paper. The atomic data include energy levels, oscillator strengths, transition rates, and electron-impact excitation collision strengths. Twenty levels are included by using the configurations 2s(2)2p, 2s2p(2), 2p(3), 2s(2)3s, 2s(2)3p, and 2s(2)3d. Collision strengths are calculated at five incident energies (15.0, 22.5, 30.0, 37.5, and 45.0 Ry) in the distorted wave approximation. The temperature of maximum abundance for this ion is log T-e= 5.9 K. The rate coefficients are calculated at this temperature by averaging the collision strengths over a Maxwellian distribution. Proton rates and solar background radiation have been included in calculating level populations, and intensity ratios are calculated by including proton rates only. The relative intensity ratios are compared with observed ratios obtained from SERTS and SOHO/CDS to infer electron density in different solar features such as an active region, quiet-Sun, and off-limb. With a few exceptions, the predicted intensity ratios match observed values very well over a variety of instrumentation and solar conditions. Since Mg VIII has a number of strong EUV lines, we expect that the spectra of this ion should prove useful for abundance studies and other plasma diagnostics. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Bhatia, AK (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 682, Greenbelt, MD 20771 USA. NR 27 TC 6 Z9 6 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1998 VL 497 IS 1 BP 483 EP 492 DI 10.1086/305441 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG883 UT WOS:000073049600037 ER PT J AU Canuto, VM AF Canuto, VM TI Solar tachocline revisited SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; Sun, interior; Sun, rotation; turbulence ID DIFFERENTIAL ROTATION; DISSIPATION; CONSTRAINTS; CONVECTION; BREAKING AB Using recent helioseismological data, Kosovichev has shown that half of the tachocline lies within the convective zone (CZ). Previous theoretical models suggested that it lies outside the CZ. We propose a new model whereby the tachocline originates within the CZ and/or :in that Dart of the overshooting region where the convective flux is still positive. The key ingredients of the model are shear, vorticity, and buoyancy. We find that (1) shear alone, (2) shear + vorticity, and (3) shear + buoyancy are unable to reproduce the measured Reynolds stresses at the surface of the Sun. The key ingredients are vorticity + buoyancy, both of which are missing in previous models. Without carrying out a detailed numerical calculation, we estimate the thickness of the tachocline to be 0.053 (in units of the solar radius) compared with Kosovichev's value of 0.09 +/- 0.04. The next step is the numerical solution of the equations. C1 Columbia Univ, Dept Appl Phys, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Canuto, VM (reprint author), Columbia Univ, Dept Appl Phys, NASA, Goddard Inst Space Studies, 2800 Broadway, New York, NY 10025 USA. NR 17 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1998 VL 497 IS 1 BP L51 EP L54 DI 10.1086/311275 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG884 UT WOS:000073049700013 ER PT J AU Galama, TJ Groot, PJ van Paradijs, J Kouveliotou, C Strom, RG Wijers, RAMJ Tanvir, N Bloom, J Centurion, M Telting, J Rutten, RGM Smith, P Mackey, C Smartt, S Benn, C Heise, J Zand, J AF Galama, TJ Groot, PJ van Paradijs, J Kouveliotou, C Strom, RG Wijers, RAMJ Tanvir, N Bloom, J Centurion, M Telting, J Rutten, RGM Smith, P Mackey, C Smartt, S Benn, C Heise, J Zand, J TI Optical follow-up of GRB 970508 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts ID SAX AB We report on the results of optical follow-up observations of the counterpart of the gamma-ray burst GRB 970508, starting 7 hr after the event. Multicolor U-, B-, V-, R-c-, and I-c-band observations were obtained during the first three consecutive nights. The counterpart was monitored regularly in R-c, until similar to 4 months after the burst. The light curve after the maximum follows a decline that can be fitted with a power law with exponent alpha = -1.141 +/- 0.014. Deviations from a smooth power-law decay are moderate (rms = 0.15 mag). We find no flattening of the light curve at late times. The optical afterglow fluence is a significant fraction, similar to 5%, of the GRB fluence. The optical energy distribution can be well represented by a power law, the slope of which changed at the time of the maximum (the spectrum became redder). 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. NASA, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Netherlands Fdn Res Astron, NL-7990 AA Dwingeloo, Netherlands. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. CALTECH, Pasadena, CA 91125 USA. Inst Astrofis Canarias, E-38200 Tenerife, Canary Islands, Spain. NFRA, Isaac Newton Grp Telescopes, E-38780 Tenerife, Canary Islands, Spain. Kitt Peak Natl Observ, Tucson, AZ USA. Space Res Org Netherlands, NL-3584 CA Utrecht, Netherlands. RP Galama, TJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X; Wijers, Ralph/0000-0002-3101-1808 NR 42 TC 74 Z9 77 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1998 VL 497 IS 1 BP L13 EP + DI 10.1086/311268 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG884 UT WOS:000073049700004 ER PT J AU Gotthelf, EV Kaspi, VM AF Gotthelf, EV Kaspi, VM TI X-ray emission from the radio pulsar PSR J1105-6107 SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars, individual (PSR J1105-6107); stars, neutron; supernova remnants; X-rays, stars ID SUPERNOVA REMNANT; CRAB-NEBULA; WINDS; STARS AB We have detected significant X-ray emission from the direction of the young radio pulsar PSR J1105-6107 using the ASCA observatory. The 11 sigma detection includes 459 background-subtracted source counts derived using data from all four ASCA detectors. The emission shows no evidence of pulsations; the pulsed fraction is less than 31%, at the 90% confidence level. The X-ray emission can be characterized by a power-law spectrum with photon index alpha = 1.8 +/- 0.4, for a neutral hydrogen column density N(H), = 7 x 10(21) cm(-2). The unabsorbed 2-10 keV flux assuming the power-law model is (6.4 +/- 0.8) x 10(-13) ergs cm(-2) s(-1). The implied efficiency for conversion of spin-down luminosity to ASCA-band emission is (1.6 +/- 0.2)! x 10(-3), assuming a distance of 7 kpc to the source. Within the limited statistics, the source is consistent with being unresolved. We argue that the X-rays are best explained as originating from a pulsar-powered synchrotron nebula. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. EM gotthelf@gsfc.nasa.gov; vicky@space.mit.edu NR 27 TC 2 Z9 2 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 APR 10 PY 1998 VL 497 IS 1 BP L29 EP + DI 10.1086/311266 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG884 UT WOS:000073049700008 ER PT J AU Gharib, M Rambod, E Shariff, K AF Gharib, M Rambod, E Shariff, K TI A universal time scale for vortex ring formation SO JOURNAL OF FLUID MECHANICS LA English DT Article ID CIRCULATION AB The formation of vortex rings generated through impulsively started jets is studied experimentally. Utilizing a piston/cylinder arrangement in a water tank, the velocity and vorticity fields of vortex rings are obtained using digital particle image velocimetry (DPIV) for a wide range of piston stroke to diameter (L/D) ratios. The results indicate that the flow field generated by large L/D consists of a leading vortex ring followed by a trailing jet. The vorticity field of the leading vortex ring formed is disconnected from that of the trailing jet. On the other hand, flow fields generated by small stroke ratios show only a single vortex ring. The transition between these two distinct states is observed to occur at a stroke ratio of approximately 4, which, in this paper, is referred to as the 'formation number'. In all cases, the maximum circulation that a vortex ring can attain during its formation is reached at this non-dimensional time or formation number. The universality of this number was tested by generating vortex rings with different jet exit diameters and boundaries, as well as with various non-impulsive piston velocities. It is shown that the 'formation number' lies in the range of 3.6-4.5 for a broad range of flow conditions. An explanation is provided for the existence of the formation number based on the Kelvin-Benjamin variational principle for steady axis-touching vortex rings. It is shown that based on the measured impulse, circulation and energy of the observed vortex rings, the Kelvin-Benjamin principle correctly predicts the range of observed formation numbers. C1 CALTECH, Grad Aeronaut Labs, Pasadena, CA 91125 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP CALTECH, Grad Aeronaut Labs, Pasadena, CA 91125 USA. OI Shariff, Karim/0000-0002-7256-2497 NR 25 TC 438 Z9 449 U1 6 U2 57 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 APR 10 PY 1998 VL 360 BP 121 EP 140 DI 10.1017/S0022112097008410 PG 20 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA ZM042 UT WOS:000073498900006 ER PT J AU Gipson, JM Ma, C AF Gipson, JM Ma, C TI Site displacement due to variation in Earth rotation SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID BASE-LINE INTERFEROMETRY; POLE TIDE; ATMOSPHERIC-PRESSURE; NORTH-SEA; LONG; ORIENTATION; DEFORMATION; PARAMETERS; GEODESY; MOTIONS AB We study site displacement caused by changes in the rate of rotation of the Earth and in the orientation of the Earth's pole. We include small effects which have been previously neglected, most notably those caused by polar motion induced ocean loading. Using very long baseline interferometry (VLBI) data we estimate the real and imaginary Love numbers associated with vertical and horizontal deformations caused by polar motion. The estimates of the real part of the Love numbers are consistent with theoretical predictions, although the imaginary parts are too large. Including the loading effect improves the agreement of the real part. C1 NVI Inc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Gipson, JM (reprint author), NVI Inc, Goddard Space Flight Ctr, Code 926, Greenbelt, MD 20771 USA. EM jmg@leo.gsfc.nasa.gov; cma@leo.gsfc.nasa.gov RI Ma, Chopo/D-4751-2012 NR 24 TC 7 Z9 7 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 APR 10 PY 1998 VL 103 IS B4 BP 7337 EP 7350 DI 10.1029/98JB00149 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZG619 UT WOS:000073022200019 ER PT J AU Simon, HD Sohn, A Biswas, R AF Simon, HD Sohn, A Biswas, R TI HARP: A dynamic spectral partitioner SO JOURNAL OF PARALLEL AND DISTRIBUTED COMPUTING LA English DT Article ID ALGORITHM; GRAPHS AB Partitioning unstructured graphs is central to the parallel solution of computational science and engineering problems. Spectral partitioners, such as recursive spectral bisection (RSB), have proven effective in generating high-quality partitions of realistically sized meshes. The major problem which hindered their widespread use was their long execution times. This paper presents a new inertial spectral partitioner called HARP. The main objective of the proposed approach is to quickly partition the meshes at runtime for the dynamic load balancing framework JOVE which dynamically balances the computational loads of distributed-memory machines with a global view. The underlying principle of HARP is to find the eigenvectors of the unpartitioned vertices and then project them onto the eigenvectors of the original mesh. Results for various meshes ranging in size from 1000 to 100,000 vertices indicate that HARP can indeed partition meshes rapidly at runtime. Experimental results show that our largest mesh can be partitioned sequentially in only a few seconds on an SP-2, which is several times faster than other spectral partitioners, while maintaining the solution quality of the proven RSB method. These results indicate that graph partitioning can now be truly embedded in dynamically changing real-world applications. (C) 1998 Academic Press. C1 Univ Calif Berkeley, Lawrence Berkeley Lab, NERSC, Berkeley, CA 94720 USA. New Jersey Inst Technol, Dept Comp & Informat Sci, Newark, NJ 07102 USA. NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. RP Simon, HD (reprint author), Univ Calif Berkeley, Lawrence Berkeley Lab, NERSC, MS 50B-4230, Berkeley, CA 94720 USA. EM simon@nersc.gov; sohn@cis.njit.edu; rbiswas@nas.nasa.gov NR 24 TC 9 Z9 9 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0743-7315 J9 J PARALLEL DISTR COM JI J. Parallel Distrib. Comput. PD APR 10 PY 1998 VL 50 IS 1-2 BP 83 EP 103 DI 10.1006/jpdc.1998.1445 PG 21 WC Computer Science, Theory & Methods SC Computer Science GA ZT266 UT WOS:000074067400005 ER PT J AU Salawitch, RJ AF Salawitch, RJ TI Ozone depletion - A greenhouse warming connection SO NATURE LA English DT Editorial Material ID CLIMATE C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Salawitch, RJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Salawitch, Ross/B-4605-2009 OI Salawitch, Ross/0000-0001-8597-5832 NR 14 TC 20 Z9 23 U1 0 U2 4 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 9 PY 1998 VL 392 IS 6676 BP 551 EP 552 DI 10.1038/33287 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZG300 UT WOS:000072987200031 ER PT J AU Shindell, DT Rind, D Lonergan, P AF Shindell, DT Rind, D Lonergan, P TI Increased polar stratospheric ozone losses and delayed eventual recovery owing to increasing greenhouse-gas concentrations SO NATURE LA English DT Article ID 1995-96 ARCTIC WINTER; MIDDLE ATMOSPHERE; VORTEX CONDITIONS; CLIMATE-CHANGE; MODEL; CO2; DEPLETION; HOLE AB The chemical reactions responsible for stratospheric ozone depletion are extremely sensitive to temperature(1). Greenhouse gases warm the Earth's surface but cool the stratosphere radiatively(2-5) and therefore affect ozone depletion. Here we investigate the interplay between projected future emissions of greenhouse gases and levels of ozone-depleting halogen species using a global climate model that incorporates simplified ozone-depletion chemistry. Temperature and wind changes induced by the increasing greenhouse-gas concentrations alter planetary-wave propagation in our model, reducing the frequency of sudden stratospheric warmings in the Northern Hemisphere(4). This results in a more stable Arctic polar vortex, with significantly colder temperatures in the lower stratosphere and concomitantly increased ozone depletion. Increased concentrations of greenhouse gases might therefore be at least partly responsible for the very large Arctic ozone losses observed in recent winters(6-9). Arctic losses reach a maximum in the decade 2010 to 2019 in our model, roughly a decade after the maximum in stratospheric chlorine abundance. The mean losses are about the same as those over the Antarctic during the early 1990s, with geographically localized losses of up to two-thirds of the Arctic ozone column in the worst years. The severity and the duration of the Antarctic ozone hole are also predicted to increase because of greenhouse-gas-induced stratospheric cooling over the coming decades. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. RP Shindell, DT (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Shindell, Drew/D-4636-2012 NR 30 TC 394 Z9 412 U1 5 U2 44 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 9 PY 1998 VL 392 IS 6676 BP 589 EP 592 DI 10.1038/33385 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZG300 UT WOS:000072987200055 ER PT J AU Chertihin, GV Andrews, L Bauschlicher, CW AF Chertihin, GV Andrews, L Bauschlicher, CW TI Reactions of laser-ablated scandium atoms with nitrogen: Matrix infrared spectra and DFT calculations for scandium nitrides and the fixation of nitrogen by two scandium atoms SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID DENSITY-FUNCTIONAL CALCULATIONS; TRANSITION-METAL ATOMS; GAUSSIAN-BASIS SETS; OXYGEN MOLECULES; IRON ATOMS; SPECTROSCOPY; MONONITRIDE; DINITROGEN; COMPLEXES; TITANIUM AB Laser-ablated Sc atoms react with nitrogen to form ScN, Sc(N-2) and (ScN)(2) and their N-2-ligated counterparts. These identifications are based on nitrogen-15 isotopic shifts and agreement with DFT vibrational frequency calculations. It is noteworthy that annealed argon matrix samples containing 2% N-2 give almost the same absorptions as nitrogen matrix samples for the ligated complexes (NN)(x)ScN and(ScN)(2)(NN)(x). The rhombic (ScN)(2) molecule is made by reaction of a second Sc atom with an intermediate ScN2 species and, thus, provides a method of nitrogen fixation with naked metal atoms. C1 Univ Virginia, Dept Chem, Charlottesville, VA 22901 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Andrews, L (reprint author), Univ Virginia, Dept Chem, Charlottesville, VA 22901 USA. NR 41 TC 41 Z9 41 U1 0 U2 7 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0002-7863 J9 J AM CHEM SOC JI J. Am. Chem. Soc. PD APR 8 PY 1998 VL 120 IS 13 BP 3205 EP 3212 DI 10.1021/ja973701d PG 8 WC Chemistry, Multidisciplinary SC Chemistry GA ZH106 UT WOS:000073072700024 ER PT J AU Heinemann, C Koch, W Partridge, H AF Heinemann, C Koch, W Partridge, H TI A study of the low-lying states of CaAr+ and CaKr+ SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; ELECTRON CORRELATION; ATOMS; ENERGIES AB The spectroscopic constants of the ground (2) Sigma(+) states of CaAr+ and CaKr+ are determined using high quality ab initio methods. The computed binding energies are 789 and 1252 cm(-1), respectively, in good agreement with the experimental determination of Pullins, Scurloch, Reddic and Duncan (J. Chem. Phys. 104 (1996) 7518). The much smaller CaKr+ binding energy determined by Buthelezi, Bellert, Lewis and Brucat (Chem. Phys. Lett. 246 (1995) 145) is shown to be due to deficiencies in the method used to approximate the binding energy of the excited state. (C) 1998 Published by Elsevier Science B.V. C1 Tech Univ Berlin, Inst Organ Chem, D-10623 Berlin, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Heinemann, C (reprint author), Hoechst AG, D-65926 Frankfurt, Germany. OI Koch, Wolfram/0000-0002-2399-8358 NR 19 TC 10 Z9 10 U1 0 U2 4 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 APR 3 PY 1998 VL 286 IS 1-2 BP 131 EP 137 DI 10.1016/S0009-2614(97)01379-1 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA ZJ582 UT WOS:000073231200020 ER PT J AU Connolly, HC Love, SG AF Connolly, HC Love, SG TI The formation of chondrules: Petrologic tests of the shock wave model SO SCIENCE LA English DT Article ID PORPHYRITIC PYROXENE CHONDRULES; DYNAMIC CRYSTALLIZATION; FEO-RICH; ORDINARY CHONDRITES; OLIVINE CHONDRULES; SYSTEM; ORIGIN; MELTS AB Chondrules are millimeter-sized rounded igneous rocks within chondritic meteorites, Their textures and fractionated mineral chemistries suggest that they formed by repeated, localized, brief (minutes to hours) melting of cold aggregates of mineral dust in the protoplanetary nebula, Astrophysical models of chondrule formation have been unable to explain the petrologically diverse nature of chondrites. However, a nebular shock wave model for chondrule formation agrees with many of the observed petrologic and geochemical properties of chondrules and shows how particles within the nebula are sorted by size and how rims around chondrules are formed. It also explains the volatile-rich nature of chondrule rims and the chondrite matrix. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Connolly, HC (reprint author), CALTECH, Div Geol & Planetary Sci, Mail Code 100-23, Pasadena, CA 91125 USA. NR 71 TC 96 Z9 96 U1 0 U2 10 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 APR 3 PY 1998 VL 280 IS 5360 BP 62 EP 67 DI 10.1126/science.280.5360.62 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZF314 UT WOS:000072885100035 ER PT J AU Ferrante, RF Moore, MH Nuth, JA AF Ferrante, RF Moore, MH Nuth, JA TI Surface effects and the low temperature crystallization of ices SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 USN Acad, Dept Chem, Annapolis, MD 21402 USA. NASA, Astrochem Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 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 APR 2 PY 1998 VL 215 MA 139-PHYS BP U183 EP U183 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414500616 ER PT J AU Han, J Yang, L Jaffe, RL Yoon, DY AF Han, J Yang, L Jaffe, RL Yoon, DY TI Structures and dynamics at the surfaces of polymethylene and PTFE melts from molecular dynamics simulations. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. IBM Corp, Almaden Res Ctr, San Jose, CA 95120 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 APR 2 PY 1998 VL 215 MA 200-PMSE BP U342 EP U342 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414501097 ER PT J AU Han, J AF Han, J TI Exploring carbon nanotubes for nanoscale devices. 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 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 APR 2 PY 1998 VL 215 MA 170-PHYS BP U192 EP U192 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414500647 ER PT J AU Hockensmith, C AF Hockensmith, C TI Coordination complexes as monomolecular precursors to In2O3-SnO2 and transition metal-doped NOx sensors SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Lewis Res Ctr, Div Mat, Cleveland, OH 44135 USA. Univ Illinois, Dept Chem, Springfield, IL 62794 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 APR 2 PY 1998 VL 215 MA 208-INOR BP U763 EP U763 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414402436 ER PT J AU Jaffe, RL Han, J Yang, L Yoon, DY AF Jaffe, RL Han, J Yang, L Yoon, DY TI Properties of PTFE melts from molecular dynamics simulations. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. IBM Corp, Almaden Res Ctr, San Jose, CA 95120 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 APR 2 PY 1998 VL 215 MA 201-PMSE BP U342 EP U342 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414501098 ER PT J AU Leonard, MJ Smith, JG AF Leonard, MJ Smith, JG TI Synthesis and characterization of low viscosity phenylethynyl-containing imide oligomers from novel tetraamines. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 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 APR 2 PY 1998 VL 215 MA 197-CHED BP U221 EP U222 PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414400714 ER PT J AU Sander, SP Laszlo, B Nickolaisen, SL Friedl, RR Salawitch, RJ Osterman, GB AF Sander, SP Laszlo, B Nickolaisen, SL Friedl, RR Salawitch, RJ Osterman, GB TI Discharge-flow and flash photolysis studies of the HO2+ClO reaction: Implications for ozone trends in the lower stratosphere. 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 APR 2 PY 1998 VL 215 MA 021-ENVR BP U574 EP U574 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414401838 ER PT J AU Short, JW AF Short, JW TI Distinguishing coal from petroleum-derived PAH in environmental samples. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NOAA, Natl Marine Fisheries Serv, Juneau, AK 99801 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 APR 2 PY 1998 VL 215 MA 043-GEOC BP U629 EP U630 PN 1 PG 2 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414402011 ER PT J AU Southward, RE Thompson, DW St Clair, AK AF Southward, RE Thompson, DW St Clair, AK TI beta-diketonate ligand effects on the in situ thermal reduction of Ag(I) complexes constrained in polyimide matrices: Formation of Ag nanocomposite films with migration to give reflective and conductive Ag surfaces SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Coll William & Mary, Williamsburg, VA USA. Natl Acad Sci, NRC, Williamsburg, VA 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 APR 2 PY 1998 VL 215 MA 519-INOR BP U850 EP U850 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414402748 ER PT J AU Southward, RE ST Clair, AK Thompson, DW AF Southward, RE ST Clair, AK Thompson, DW TI Surface conductive and reflective silver-polyimide composite films prepared via thermally induced reduction of (1,1,1-triflouro-2,4-pentaedionato)silver(I) in a curing poly(amic acid) matrix SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23187 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 APR 2 PY 1998 VL 215 MA 211-POLY BP U408 EP U408 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414501322 ER PT J AU Southward, RE St Clair, AK Thompson, DW Sproul, SH Wasyk, JL Scott, JL Broadwater, ST AF Southward, RE St Clair, AK Thompson, DW Sproul, SH Wasyk, JL Scott, JL Broadwater, ST TI The synthesis of reflective surface metallized silver polyimide films via in situ reduction of (4,4,4-trifluoro-1-(thienyl)-1,3-butanedionato)-silver(I) in a polyimide matrix SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23187 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 APR 2 PY 1998 VL 215 MA 118-PMSE BP U316 EP U316 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414501016 ER PT J AU Southward, RE St Clair, AK AF Southward, RE St Clair, AK TI Oxometal-polyimide hybrid materials: Alternatives to silica and titania phases using rare earth metal complexes SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 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 APR 2 PY 1998 VL 215 MA 007-PMSE BP U282 EP U282 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414500908 ER PT J AU Southward, RE St Clair, AK Thompson, DW Sproul, SH Waysk, JL Scott, JL Broadwater, ST Boggs, CM AF Southward, RE St Clair, AK Thompson, DW Sproul, SH Waysk, JL Scott, JL Broadwater, ST Boggs, CM TI Control of surface specular reflectivity and electrical conductivity in silvered polyimide films via in situ thermal reduction of (perfluoroalkanoato)silver(I) complexes SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23187 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 APR 2 PY 1998 VL 215 MA 006-PMSE BP U281 EP U281 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414500907 ER PT J AU Stephens, AB Ticich, TM AF Stephens, AB Ticich, TM TI Optical and microscopy investigations of soot structure alterations by laser-induced incandescence 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, NYMA, Cleveland, OH 44135 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 APR 2 PY 1998 VL 215 MA 451-CHED BP U306 EP U306 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414400964 ER PT J AU Sutter, B Gingl, F Clearfield, A Hossner, LR Ming, DW AF Sutter, B Gingl, F Clearfield, A Hossner, LR Ming, DW TI Structural location of Fe in synthetic hydroxyapatite. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 Texas A&M Univ, Dept Soil & Crop Sci, College Stn, TX 77843 USA. Texas A&M Univ, Dept Chem, College Stn, TX 77843 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 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 APR 2 PY 1998 VL 215 MA 321-INOR BP U793 EP U793 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414402549 ER PT J AU Ticich, TM Stephens, AB VanderWal, RL AF Ticich, TM Stephens, AB VanderWal, RL TI Can soot primary size be determined using laser-induced incandescence? SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Centenary Coll Louisiana, Dept Chem, Shreveport, LA 71134 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 APR 2 PY 1998 VL 215 MA 057-FUEL BP U608 EP U608 PN 1 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA911 UT WOS:000072414401951 ER PT J AU Yoon, DY Han, J Jaffe, RL AF Yoon, DY Han, J Jaffe, RL TI Comparison of chain conformations for polystyrene and model molecules in the gas phase, solvents and melts from MD simulations. SO ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY LA English DT Meeting Abstract C1 IBM Corp, Almaden Res Ctr, San Jose, CA 95120 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 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 APR 2 PY 1998 VL 215 MA 199-PMSE BP U342 EP U342 PN 2 PG 1 WC Chemistry, Multidisciplinary SC Chemistry GA ZA912 UT WOS:000072414501096 ER PT J AU Bartoe, UDF AF Bartoe, UDF TI Arguments in favour of the space station SO NATURE LA English DT Letter C1 NASA, Lyndon B Johnson Space Ctr, Int Space Stn, Houston, TX 77058 USA. RP Bartoe, UDF (reprint author), NASA, Lyndon B Johnson Space Ctr, Int Space Stn, Houston, TX 77058 USA. EM john-david.f.bartoe1@jsc.nasa.gov NR 2 TC 0 Z9 0 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD APR 2 PY 1998 VL 392 IS 6675 BP 432 EP 432 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA ZF215 UT WOS:000072875200020 ER PT J AU Storaasli, OO AF Storaasli, OO TI Preface SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Editorial Material 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 0 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 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD APR-JUL PY 1998 VL 29 IS 3-6 BP 177 EP 177 PG 1 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300001 ER PT J AU Cwik, T Lou, J Katz, DS AF Cwik, T Lou, J Katz, DS TI Scalable, finite element analysis of electromagnetic scattering and radiation. Error estimation and H-adaptivity SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA AB In this paper a method for simulating electromagnetic fields scattered from complex objects is reviewed; namely, an unstructured finite element code that does not use traditional mesh partitioning algorithms. The complete software package is implemented on the Gray T3D massively parallel processor using both Gray Adaptive FORTRAN (CRAFT) compiler constructs to simplify portions of the code that operate on the irregular data, and optimized message passing constructs on portions of the code that operate on regular data and require optimum machine performance. The above finite element solution package is then integrated into an error estimation and adaptive mesh refinement algorithm. An error for the fields over the mesh is estimated and used to drive an adaptive mesh refinement algorithm that refines the mesh where errors are above a given tolerance. This refined mesh is then used once again for a finite element solution of the fields. After estimating the error a second time, the mesh is again refined as needed. This process continues until the error is reduced to an allowable level. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Cwik, T (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. OI Katz, Daniel S./0000-0001-5934-7525 NR 9 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 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD APR-JUL PY 1998 VL 29 IS 3-6 BP 289 EP 296 DI 10.1016/S0965-9978(97)00081-1 PG 8 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300013 ER PT J AU Wang, P AF Wang, P TI Massively parallel finite volume computation of three-dimensional thermal convective flows SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA ID 3-DIMENSIONAL NATURAL-CONVECTION; CAVITY AB A parallel implementation of the finite volume method for three-dimensional, time-dependent, thermal convective flows is presented. The algebraic equations resulting from the finite volume discretization are solved by a parallel multigrid method. A flexible parallel code has been implemented on distributed-memory systems, by using domain decomposition techniques and the MPI communication software. The code uses one-, two- or three-dimensional partition according to different geometries. It currently runs on the Intel Paragon, the Gray T3D, T3E, the IBM SP2 and the Beowulf systems, which can be ported easily to other parallel systems. A comparison of the wallclock time of the code between these systems is made, and code performances with respect to different numbers of processors are presented. Published by Elsevier Science Limited. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wang, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 168-522, Pasadena, CA 91109 USA. NR 15 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 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD APR-JUL PY 1998 VL 29 IS 3-6 BP 307 EP 315 DI 10.1016/S0965-9978(98)00003-9 PG 9 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300015 ER PT J AU Riley, CJ Cheatwood, FM AF Riley, CJ Cheatwood, FM TI Distributed-memory computing with the Langley aerothermodynamic upwind relaxation algorithm (LAURA) SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA ID SCHEMES AB The Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA), a Navier-Stokes solver, has been modified for use in a parallel, distributed-memory environment using the Message-Passing Interface (MPI) standard. A standard domain decomposition strategy is used in which the computational domain is divided into subdomains with each subdomain assigned to a processor. Performance is examined on dedicated parallel machines and a network of desktop workstations. The effect of domain decomposition and frequency of boundary updates on performance and convergence is also examined for several realistic configurations and conditions typical of large-scale computational fluid dynamic analysis. (C) 1998 Published by Elsevier Science Limited. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Riley, CJ (reprint author), NASA, Langley Res Ctr, MS 408A, Hampton, VA 23681 USA. NR 28 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD APR-JUL PY 1998 VL 29 IS 3-6 BP 317 EP 324 DI 10.1016/S0965-9978(97)00074-4 PG 8 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300016 ER PT J AU Vatsa, VN Hammond, DP AF Vatsa, VN Hammond, DP TI Viscous pow computations for complex geometries on parallel computers SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA AB A widely used computational fluid dynamics (CFD) code known as TLNS3D, which was developed for large, shared-memory computers, is ported to a distributed computing environment. An engineering approach is used here to parallelize this code so that minimal deviation from the original (non-parallel) code is incurred. A natural partitioning along grid blocks is adopted in which one or more blocks are distributed to each of the available processors. An automatic, static load-balancing strategy is employed for equitable distribution of computational work to specified processors. The message passing interface (MPI) protocols are incorporated for data communication. Both synchronous and asynchronous communication modes have been incorporated. As the number of processors is increased, the asynchronous communication mode shows much better scalability and clearly outperforms the synchronous mode of communication. (C) 1998 Elsevier Science Limited. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. Comp Sci Corp, Hampton, VA USA. RP Vatsa, VN (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 13 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 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD APR-JUL PY 1998 VL 29 IS 3-6 BP 337 EP 343 DI 10.1016/S0965-9978(97)00076-8 PG 7 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300019 ER PT J AU Hayder, ME Keyes, DE Mehrotra, P AF Hayder, ME Keyes, DE Mehrotra, P TI A comparison of PETSc library and HPF implementations of an archetypal PDS computation SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA DE parallel languages; parallel libraries; parallel scientific computing; nonlinear elliptic boundary value problems AB Two paradigms for distributed-memory parallel computation that free the application programmer from the details of message passing are compared for an archetypal structured scientific computation-a nonlinear, structured-grid partial differential equation boundary value problem-using the same algorithm on the same hardware. Both paradigms, parallel libraries represented by Argonne's PETSc, and parallel languages represented by the Portland Group's HPF, are found to be easy to use for this problem class, and both are reasonably effective in exploiting concurrency after a short learning curve. The level of involvement required by the application programmer under either paradigm includes specification of the data partitioning (corresponding to a geometrically simple decomposition of the domain of the PDE). Programming in SPMD style for the PETSc library requires writing the routines that discretize the PDE and its Jacobian, managing subdomain-to-processor mappings (affine global-to-local index mappings), and interfacing to library solver routines. Programming for HPF requires a complete sequential implementation of the same algorithm, introduction of concurrency through subdomain blocking tan effort similar to the index mapping), and modest experimentation with rewriting loops to elucidate to the compiler the latent concurrency. Correctness and scalability are cross-validated on up to 32 nodes of an IBM. SP2. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Rice Univ, Ctr Res Parallel Computat, Houston, TX 77005 USA. Old Dominion Univ, Dept Comp Sci, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Hayder, ME (reprint author), Rice Univ, Ctr Res Parallel Computat, Houston, TX 77005 USA. NR 19 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 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD APR-JUL PY 1998 VL 29 IS 3-6 BP 415 EP 423 DI 10.1016/S0965-9978(97)00080-X PG 9 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300030 ER PT J AU Fijany, A Cagin, T Jaramillo-Botero, A Goddard, W AF Fijany, A Cagin, T Jaramillo-Botero, A Goddard, W TI Novel algorithms for massively parallel, long-term, simulation of molecular dynamics systems SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA DE molecular dynamics simulation; constrained equations of motion; massively parallel computation ID CELL MULTIPOLE METHOD; MASS OPERATOR METHOD; NONBOND INTERACTIONS; COULOMB; COMPUTATION; PROGRAM AB In this paper, a novel algorithm for solution of the constrained equations of motion with application to simulation of the molecular dynamics systems is presented. The algorithm enables the solution of equations of motion with an internal coordinates model wherein the high-frequency oscillations are frozen by explicit inclusion of hard constraints in the system as well as by clustering of atoms and, thus, allowing a much larger time step in the integration. For a molecular system with N clusters, the algorithm achieves the optimal sequential complexity of O(N). However, the main advantage of this new algorithm is its efficiency for massively parallel computation. In fact, this is the first known algorithm that achieves a both time- and processor-optimal parallel solution for the constrained equations of motion, i.e. an optimal computation time of O(logN) by using an optimal number of O(N) processors. In addition to its theoretical significance, this algorithm is also very efficient for practical implementation on the coarse grain MIMD parallel architectures owing to its highly decoupled computational structure. (C) 1998 Published by Elsevier Science Ltd. AU rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Mat & Proc Simulat Ctr, Pasadena, CA 91125 USA. RP Fijany, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 23 TC 8 Z9 8 U1 0 U2 5 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 APR-JUL PY 1998 VL 29 IS 3-6 BP 441 EP 450 DI 10.1016/S0965-9978(98)00053-2 PG 10 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300033 ER PT J AU Katz, DS Cwik, T Kwan, BH Leu, JZ Springer, PL Sterling, TL Wang, P AF Katz, DS Cwik, T Kwan, BH Leu, JZ Springer, PL Sterling, TL Wang, P TI An assessment of a Beowulf system for a wide class of analysis and design software SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA ID LINEAR ALGEBRA SUBPROGRAMS; SET AB This paper discusses Beowulf systems, focusing on Hyglac, the Beowulf system installed at the Jet Propulsion Laboratory. The purpose of the paper is to assess how a system of this type will perform while running a variety of scientific and engineering analysis and design software. The first part of the assessment contains a measurement of the communication performance of Hyglac, along with a discussion of factors which have the potential to limit system performance. The second part consists of performance measurements of six specific programs (analysis and design software), as well as discussion about these measurements. Finally, the measurements and discussion lead to the conclusion that Hyglac is suitable for running these types of codes tin a research/industrial environment such as at JPL) and that the primary factor for determining how a given code will perform is the code's ratio of communication to computation. Published by Elsevier Science Limited. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Katz, DS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM Daniel.S.Katz@jpl.nasa.gov OI Katz, Daniel S./0000-0001-5934-7525 NR 14 TC 2 Z9 2 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 APR-JUL PY 1998 VL 29 IS 3-6 BP 451 EP 461 DI 10.1016/S0965-9978(97)00083-5 PG 11 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300034 ER PT J AU Patnaik, SN Coroneos, RM Hopkins, DA AF Patnaik, SN Coroneos, RM Hopkins, DA TI Recent advances in the method of forces: integrated force method of structural analysis SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article; Proceedings Paper CT 4th National Symposium on Large-Scale Analysis and Design on High-Performance Computers and Workstations CY OCT 15-17, 1997 CL WILLIAMSBURG, VIRGINIA DE integrated force method; stiffness method; analysis; animation; design ID FINITE-ELEMENT ANALYSIS; COMPATIBILITY CONDITIONS; OPTIMIZATION; CONSTRAINTS; BEHAVIOR; DESIGN; STRESS AB Stress that can be induced in an elastic continuum can be determined directly through the simultaneous application of the equilibrium equations and the compatibility conditions. In the literature, this direct stress formulation is referred to as the integrated force method. This method, which uses forces as the primary unknowns, complements the popular equilibrium-based stiffness method, which considers displacements as the unknowns. The integrated force method produces accurate stress, displacement, and frequency results even for modest finite element models. This version of the force method should be developed as an alternative to the stiffness method because the latter method, which has been researched for the past several decades, may have entered its developmental plateau, Stress plays a primary role in the development of aerospace and other products, and its analysis is difficult. Therefore, it is advisable to use both methods to calculate stress and eliminate errors through comparison. This paper examines the role of the integrated force method in analysis, animation and design. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Ohio Aerosp Inst, Cleveland, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Patnaik, SN (reprint author), Ohio Aerosp Inst, Cleveland, OH 44142 USA. NR 39 TC 4 Z9 4 U1 0 U2 4 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 APR-JUL PY 1998 VL 29 IS 3-6 BP 463 EP 474 DI 10.1016/S0965-9978(97)00070-7 PG 12 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 112LN UT WOS:000075496300035 ER PT J AU Noor, AK Spearing, SM Adams, WW Venneri, SL AF Noor, AK Spearing, SM Adams, WW Venneri, SL TI Frontiers of the material world SO AEROSPACE AMERICA LA English DT Article C1 Univ Virginia, NASA, Ctr Adv Computat Technol, Charlottesville, VA 22903 USA. RP Noor, AK (reprint author), Univ Virginia, NASA, Ctr Adv Computat Technol, Charlottesville, VA 22903 USA. RI Adams, Wade/A-7305-2010 NR 0 TC 3 Z9 3 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD APR PY 1998 VL 36 IS 4 BP 24 EP + PG 6 WC Engineering, Aerospace SC Engineering GA ZE575 UT WOS:000072807800009 ER PT J AU Froggatt, M Bowen, W AF Froggatt, M Bowen, W TI Optical time-domain reflectometry in optical fiber with reflection delay time matched to the period of the optical frequency modulation SO APPLIED OPTICS LA English DT Article AB A method of optical time-domain reflectrometry in optical fiber is described that uses a single distributed feedback diode laser and a reference reflector. When the period of the frequency modulation of the laser matches the time difference between the reference reflection and the reflection of interest an increase in the noise at the detector occurs. The locations of reflections within the fiber are then mapped to frequencies at which the noise at the detector increases. A sinusoidal frequency modulation is analyzed, and an experiment is described in which the system is used to measure the location and the wavelength of two Bragg gratings located 10 cm apart in an optical fiber. Wavelength measurement is accomplished by temperature tuning the diode laser. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Froggatt, M (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 4 TC 4 Z9 4 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD APR 1 PY 1998 VL 37 IS 10 BP 1731 EP 1734 DI 10.1364/AO.37.001731 PG 4 WC Optics SC Optics GA ZD695 UT WOS:000072713700003 PM 18273080 ER PT J AU Froggatt, M Moore, J AF Froggatt, M Moore, J TI High-spatial-resolution distributed strain measurement in optical fiber with Rayleigh scatter SO APPLIED OPTICS LA English DT Article AB A method of measuring strain over 30-cm intervals to an accuracy of 10 microstrain in unaltered low-loss communications-grade single-mode optical fiber is presented. The method uses a tunable external cavity diode laser to measure the reflected intensity of a reflector-fiber system as a function of wavelength. This measurement is performed with no strain applied to the fiber to produce a reference and then again after a strain has been induced. Cross correlation of the Rayleigh scatter spectra from a selected section of fiber in the strained and unstrained states determines the spectral shift resulting from the applied strain. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Froggatt, M (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 10 TC 117 Z9 120 U1 1 U2 23 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD APR 1 PY 1998 VL 37 IS 10 BP 1735 EP 1740 DI 10.1364/AO.37.001735 PG 6 WC Optics SC Optics GA ZD695 UT WOS:000072713700004 PM 18273081 ER PT J AU Froggatt, M Moore, J AF Froggatt, M Moore, J TI Distributed measurement of static strain in an optical fiber with multiple Bragg gratings at nominally equal wavelengths SO APPLIED OPTICS LA English DT Article ID SINGLE-MODE FIBERS; SENSOR AB The Fourier transform relationship between the reflected light from a Bragg grating and the complex spatial modulation of the Bragg grating is used to produce a distributed strain sensing system. A tunable external cavity diode laser along with a reference reflector in an optical fiber are used to produce a measurement of the phase and amplitude of the reflected light from the modulated Bragg grating as a function of wavelength. The system is demonstrated with 22 Bragg gratings in a single fiber on a cantilever beam and compared with foil strain gauge readings. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Froggatt, M (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 14 TC 66 Z9 69 U1 1 U2 9 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD APR 1 PY 1998 VL 37 IS 10 BP 1741 EP 1746 DI 10.1364/AO.37.001741 PG 6 WC Optics SC Optics GA ZD695 UT WOS:000072713700005 PM 18273082 ER PT J AU Perlman, ES Padovani, P Giommi, P Sambruna, R Jones, LR Tzioumis, A Reynolds, J AF Perlman, ES Padovani, P Giommi, P Sambruna, R Jones, LR Tzioumis, A Reynolds, J TI The Deep X-ray Radio Blazar Survey. I. Methods and first results SO ASTRONOMICAL JOURNAL LA English DT Article DE BL Lacertae objects, general; quasars, general; radio continuum; surveys ID BL-LACERTAE OBJECTS; OPTICAL-IDENTIFICATION STATUS; BRIGHT QSO SURVEY; LAC OBJECTS; COMPLETE SAMPLE; COSMOLOGICAL EVOLUTION; PARENT POPULATION; SOURCE CATALOG; HIGH-REDSHIFT; POLARIZATION AB We have undertaken a survey, the Deep X-Ray Radio Blazar Survey (DXRBS), of archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the ROSAT WGACAT database with several publicly available radio catalogs, restricting our candidate list to serendipitous flat radio spectrum sources (alpha(r) less than or equal to 0.70, where S-nu proportional to nu(-alpha r)). We discuss our survey methods, identification procedure, and first results. Our survey is found to be similar to 95% efficient at finding flat-spectrum radio-loud quasars (FSRQs; 59 of our first 85 identifications) and BL Lacertae objects (22 of our first 85 identifications), a figure that is comparable to or greater than that achieved by other radio and X-ray survey techniques. The identifications presented here show that all previous samples of blazars (even when taken together) did not representatively survey the blazar population, missing critical regions of (L-X, L-R) parameter space within which large fractions of the blazar population lie. Particularly important is the identification of a large population of FSRQs (greater than or similar to 25% of DXRBS FSRQs) with ratios of X-ray to radio luminosity greater than or similar to 10(-6) (alpha(rx) less than or similar to 0.78). In addition, as a result of our greater sensitivity, the DXRBS has already more than doubled the number of FSRQs in complete samples with 5 GHz (radio) luminosities between 10(31.5) and 10(33.5) ergs s(-1) Hz(-1), and fills in the region of parameter space between X-ray-selected and radio-selected samples of BL Lac objects. The DXRBS is the very first sample to contain statistically significant numbers of blazars at low luminosities, approaching what should be the lower end of the FSRQ luminosity function. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Roma Tor Vergata, Dipartimento Fis 2, I-00133 Rome, Italy. SAX Sci Data Ctr, Agenzia Spaziale Italiana, I-00198 Rome, Italy. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. CSIRO, Australia Telescope Natl Facil, Epping, NSW 2121, Australia. RP Perlman, ES (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. OI giommi, paolo/0000-0002-2265-5003; Padovani, Paolo/0000-0002-4707-6841; Perlman, Eric/0000-0002-3099-1664 NR 83 TC 179 Z9 180 U1 2 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1998 VL 115 IS 4 BP 1253 EP 1294 DI 10.1086/300283 PG 42 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG635 UT WOS:000073023500004 ER PT J AU Shen, ZQ Wan, TS Moran, JM Jauncey, DL Reynolds, JE Tzioumis, AK Gough, RG Ferris, RH Sinclair, MW Jiang, DR Hong, XY Liang, SG Edwards, PG Costa, ME Tingay, SJ McCulloch, PM Lovell, JEJ King, EA Nicolson, GD Murphy, DW Meier, DL van Ommen, TD White, GL AF Shen, ZQ Wan, TS Moran, JM Jauncey, DL Reynolds, JE Tzioumis, AK Gough, RG Ferris, RH Sinclair, MW Jiang, DR Hong, XY Liang, SG Edwards, PG Costa, ME Tingay, SJ McCulloch, PM Lovell, JEJ King, EA Nicolson, GD Murphy, DW Meier, DL van Ommen, TD White, GL TI A 5 GHz Southern Hemisphere VLBI survey of compact radio sources. II. SO ASTRONOMICAL JOURNAL LA English DT Review DE BL Lacertae objects, general; radio continuum; surveys ID BL-LACERTAE OBJECTS; ACTIVE GALACTIC NUCLEI; BLAZAR PKS 0537-441; GAMMA-RAY EMISSION; MILLIMETER CONTINUUM MEASUREMENTS; FREQUENCY VARIABLE SOURCES; COMPLETE SAMPLE; X-RAY; OPTICAL POLARIZATION; MULTIFREQUENCY OBSERVATIONS AB We report the results of a 5 GHz Southern Hemisphere snapshot VLBI observation of a sample of blazars. The observations were performed with the Southern Hemisphere VLBI Network plus the Shanghai station in 1993 May. Twenty-three hat-spectrum, radio-loud sources were imaged. These are the first VLBI images for 15 of the sources. Eight of the sources are EGRET (>100 MeV) gamma-ray sources. The milliarcsecond morphology shows a core-jet structure for 12 sources and a single compact core for the remaining 11. No compact doubles were seen. Compared with other radio images at different epochs and/or different frequencies, three core-jet blazars show evidence of bent jets, and there is some evidence for superluminal motion in the cases of two blazars. Detailed descriptions for individual blazars are given. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Shanghai Astron Observ, Shanghai 200030, Peoples R China. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Univ Western Australia, Dept Phys, Nedlands, WA 6009, Australia. Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. Hartebeesthoek Radio Astron Observ, ZA-1740 Krugersdorp, South Africa. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Western Sydney Nepean, Dept Phys, Kingswood, NSW 2747, Australia. RP Shen, ZQ (reprint author), Acad Sinica, Inst Astron & Astrophys, POB 1-87, Taipei 115, Taiwan. RI Tingay, Steven/B-5271-2013; van Ommen, Tas/B-5020-2012; King, Edward/A-1473-2012 OI van Ommen, Tas/0000-0002-2463-1718; King, Edward/0000-0002-6898-2130 NR 137 TC 34 Z9 34 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1998 VL 115 IS 4 BP 1357 EP 1370 DI 10.1086/300284 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG635 UT WOS:000073023500010 ER PT J AU Cooray, AR Grego, L Holzapfel, WL Joy, M Carlstrom, JE AF Cooray, AR Grego, L Holzapfel, WL Joy, M Carlstrom, JE TI Radio sources in galaxy clusters at 28.5 GHz SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies, clusters, general; radio continuum; surveys; techniques, interferometric ID ABELL CLUSTERS; SOURCE COUNTS; VLA SURVEY; SYSTEM; MHZ AB We present serendipitous detections of radio sources at 28.5 GHz (1 cm), which resulted from our program to image the thermal Sunyaev-Zeldovich (SZ) effect in 56 galaxy clusters. In a total area of similar to 0.8 deg(2), we find 64 radio sources with fluxes down to similar to 0.4 mJy (greater than 4 sigma) and within 250 " from the pointing centers. The spectral indices (S proportional to nu(-alpha)) of 54 sources with published low-frequency flux densities lie in the range -0.6 less than or similar to alpha less than or similar to 2, with a mean of 0.77 +/- 0.06 and a median of 0.84. Extending low-frequency surveys of radio sources toward the galaxy clusters Cl 0016 + 16, Abell 665, and Abell 2218 to 28.5 GHz and selecting sources with S-1.4 GHz greater than or equal to 7 mJy to form an unbiased sample, we find a mean spectral index of 0.71 +/- 0.08 and a median of 0.71. We find 4 to 7 times more sources than predicted from a low-frequency survey in areas without galaxy clusters. This excess cannot be accounted for by gravitational lensing of a background radio population by cluster potentials, indicating that most of the detected sources are associated with galaxy clusters. The differential source count slope, gamma similar to 1.96 (dN/dS proportional to S-gamma), is flatter than what is expected for a nonevolving Euclidean population (gamma = 2.5). For the cluster Abell 2218, the presence of unsubtracted radio sources with S-28.5 GHz less than or equal to 0.5 mJy (similar to 5 sigma) can reduce the observed SZ temperature decrement by Delta T similar to 10 to 25 mu K. The corresponding overestimation of the Hubble constant derived through a combined analysis of 28.5 GHz SZ images and X-ray emission observations is less than 6%. C1 Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. NASA, Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Cooray, AR (reprint author), Univ Chicago, Dept Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA. RI Holzapfel, William/I-4836-2015 NR 40 TC 61 Z9 61 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1998 VL 115 IS 4 BP 1388 EP 1399 DI 10.1086/300310 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG635 UT WOS:000073023500014 ER PT J AU Cohen, M Witteborn, FC Roush, T Bregman, J Wooden, D AF Cohen, M Witteborn, FC Roush, T Bregman, J Wooden, D TI Spectral irradiance calibration in the infrared. VIII. 5-14 micron spectroscopy of the asteroids Ceres, Vesta, and Pallas SO ASTRONOMICAL JOURNAL LA English DT Article DE infrared radiation; minor planets, asteroids ID THERMAL EMISSION; MU-M; SPECTROMETER; SURFACES; MODEL; RECALIBRATION; SHAPE; MARS AB We describe our efforts to seek "closure" in our infrared absolute calibration scheme by comparing spectra of asteroids, absolutely calibrated through reference stars, with "standard thermal models" and "thermophysical models" for these bodies. Our use of continuous 5-14 mu m airborne spectra provides complete sampling of the rise to, and peak, of the infrared spectral energy distribution and constrains these models. Such models currently support the absolute calibration of the Infrared Space Observatory Imaging Photopolarimeter (ISOPHOT) at far-infrared wavelengths (as far as 300 mu m) and contribute to that of the Mid-Infrared Spectrometer on the Infrared Telescope in Space in the 6-12 mu m region. The best match to our observed spectra of Ceres and Vesta is a standard thermal model using a beaming factor of unity. We also report the presence of three emissivity features in Ceres that may complicate the traditional model extrapolation to the far-infrared from contemporaneous ground-based N-band photometry that is used to support calibration of, for example, ISOPHOT. While identification of specific materials that cause these features is not made, we discuss families of minerals that may be responsible. C1 Univ Calif Berkeley, Radio Astron Lab, Berkeley, CA 94720 USA. Vanguard Res Inc, Scotts Valley, CA 95066 USA. NASA, Ames Res Ctr, Div Space Sci, Planetary Syst Branch, Moffett Field, CA 94035 USA. San Francisco State Univ, Dept Geosci, San Francisco, CA 94132 USA. RP Cohen, M (reprint author), Univ Calif Berkeley, Radio Astron Lab, 601 Campbell Hall, Berkeley, CA 94720 USA. EM mcohen@astro.berkeley.edu; witteborn@aol.com; roush@barsoom.arc.nasa.gov; bregman@ssa1.arc.nasa.gov; wooden@ssa1.arc.nasa.gov NR 52 TC 40 Z9 41 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1998 VL 115 IS 4 BP 1671 EP 1679 DI 10.1086/300271 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG635 UT WOS:000073023500043 ER PT J AU Lieske, JH AF Lieske, JH TI Galilean satellite ephemerides E5 SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE astrometry; celestial mechanics; ephemerides; planets and satellites, Jupiter ID MUTUAL PHENOMENA; PREDICTIONS; JUPITER; OCCULTATIONS; PHOTOMETRY; ASTROMETRY; CONSTANTS; ELEMENTS; ECLIPSES; SYSTEM AB New ephemerides of Jupiter's Galilean satellites are produced from an analysis of CCD astrometric data, Voyager-mission optical navigation images, mutual event observations, photographic plates; and eclipse timing observations. The resulting parameters, for use in the galsat computer software, are in the B1950 frame for use by the Galileo space mission. Results in the J2000 system are also available. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lieske, JH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 301-150, Pasadena, CA 91109 USA. NR 65 TC 44 Z9 47 U1 0 U2 4 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD APR PY 1998 VL 129 IS 2 BP 205 EP 217 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZK127 UT WOS:000073288000001 ER PT J AU Scoccimarro, R Colombi, S Fry, JN Frieman, JA Hivon, E Melott, A AF Scoccimarro, R Colombi, S Fry, JN Frieman, JA Hivon, E Melott, A TI Nonlinear evolution of the bispectrum of cosmological perturbations SO ASTROPHYSICAL JOURNAL LA English DT Article DE large-scale structure of universe; methods, numerical; methods, statistical ID LARGE-SCALE STRUCTURE; POWER-SPECTRUM; GRAVITATIONAL-INSTABILITY; NUMERICAL SIMULATIONS; CORRELATION HIERARCHY; LAGRANGIAN APPROACH; EXPANDING UNIVERSE; REDSHIFT SURVEYS; HIGH-RESOLUTION; COSMIC FIELDS AB The bispectrum B(k(1), k(2), k(3)), the three-point function of density fluctuations in Fourier space, is the lowest order statistic that carries information about the spatial coherence of large-scale structures. For Gaussian initial conditions, when the density fluctuation amplitude is small (delta << 1), tree-level (leading order) perturbation theory predicts a characteristic dependence of the bispectrum on the shape of the triangle formed by the three wave vectors. This configuration dependence provides a signature of gravitational instability, and departures from it in galaxy catalogs can be interpreted as due to bias, that is, nongravitational effects. On the other hand, N-body simulations indicate that the reduced three-point function becomes relatively shape-independent in the strongly nonlinear regime (delta >> 1). In order to understand this nonlinear transition and assess the domain of reliability of shape dependence as a probe of bias, we calculate the one-loop (next-to-leading order) corrections to the bispectrum in perturbation theory. We compare these results with measurements in numerical simulations with scale-free and cold dark matter initial power spectra. We find that the one-loop corrections account very well for the departures from the tree-level results measured in numerical simulations on weakly nonlinear scales (delta less than or similar to 1). In this regime, the reduced bispectrum qualitatively retains its tree-level shape, but the amplitude can change significantly. At smaller scales (delta greater than or similar to 1), the reduced bispectrum in the simulations starts to flatten, an effect that can be partially understood from the one-loop results. In the strong clustering regime, where perturbation theory breaks down entirely, the simulation results confirm that the reduced bispectrum has almost no dependence on triangle shape, in rough agreement with the hierarchical Ansatz. C1 Univ Chicago, Dept Phys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, Fermilab Astrophys Ctr, NASA, Batavia, IL 60510 USA. Mclennan Phys Labs, CITA, Toronto, ON M5S 3H8, Canada. Inst Astrophys, CNRS, F-75014 Paris, France. Univ Florida, Dept Phys, Gainesville, FL 32611 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Theoret Astrophys Ctr, DK-2100 Copenhagen, Denmark. Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA. RP Scoccimarro, R (reprint author), Univ Chicago, Dept Phys, Chicago, IL 60637 USA. OI Hivon, Eric/0000-0003-1880-2733 NR 74 TC 151 Z9 153 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 586 EP 604 DI 10.1086/305399 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100002 ER PT J AU Hill, RJ Ferrarese, L Stetson, PB Saha, A Freedman, WL Graham, JA Hoessel, JG Han, MS Huchra, J Hughes, SM Illingworth, GD Kelson, D Kennicutt, RC Bresolin, F Harding, P Turner, A Madore, BF Sakai, S Silbermann, NA Mould, JR Phelps, R AF Hill, RJ Ferrarese, L Stetson, PB Saha, A Freedman, WL Graham, JA Hoessel, JG Han, MS Huchra, J Hughes, SM Illingworth, GD Kelson, D Kennicutt, RC Bresolin, F Harding, P Turner, A Madore, BF Sakai, S Silbermann, NA Mould, JR Phelps, R TI The extragalactic distance scale key project. V. Photometry of the brightest stars in M100 and the calibration of WFPC2 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; distance scale; galaxies, individual (M100); galaxies, photometry; techniques, photometric ID HUBBLE-SPACE-TELESCOPE; PERFORMANCE; CEPHEIDS; CONSTANT AB We present multiepoch VI observations of the brightest stars in the Virgo spiral galaxy M100 obtained with the WFPC2 aboard the Hubble Space Telescope. Particular attention has been given to the WFPC2 calibration process, and a new calibration is presented hem We find that a calibration based on short exposure (t less than or equal to 60 sec) observations of the galactic globular clusters omega Cen, Pal 4, and NGC 2419 yields results that are in excellent agreement with the calibration of Holtzmann et al. However, a calibration based on longer exposures (t greater than or equal to 1300 s) yields magnitudes that are systematically brighter by 0.05 mag, on average, in both V and I. We have independently employed both the DAOPHOT/ALLFRAME and DoPHOT photometry routines in reducing the M100 data and have found that the two packages yield magnitudes that agree to better than 0.05 mag except for the WFPC2 chip 3 and WFPC2 chip 4 I data. Severe crowding appears to be the problem in the case of the WFPC2 chip 3 data, but we have been unable to determine the source of the discrepancy for the WFPC2 chip 4 I data. We consider the better than 0.05 mag agreement for the other chip/filter combinations to be quite good under the circumstances prevailing in this data set: an undersampled point-spread function (PSF), faint stars, a rapidly varying background, and moderate to severe crowding. A color-magnitude diagram for the brightest stars in M100 is also presented, which shows a plume of bright blue supergiants extending to at least V similar to 23 mag, or M-V similar to 8 mag. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Royal Greenwich Observ, Cambridge CB3 0EZ, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. CALTECH, NASA, IPAC Extragalact Database, Pasadena, CA 91125 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. RP Hill, RJ (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. EM hill@esa.nascom.nasa.gov; lff@astro.caltech.edu; stetson@dao.nrc.ca; saha@stsci.edu; wendy@ociw.edu; graham@jag.ciw.edu; hoessel@uwfpc.astro.wisc.edu; han@adcode.astro.wisc.edu; huchra@cfa.harvard.edu; hughes@mail.ast.cam.ac.uk; gdi@lick.ucolick.org; kelson@lick.ucolick.org; robk@as.arizona.edu; fbresolin@as.arizona.edu; pharding@as.arizona.edu; aturner@as.arizona.edu; barry@ipac.caltech.edu; shoko@ipac.caltech.edu; nancys@ipac.caltech.edu; jrm@merlin.anu.edu.au; phelps@ociw.edu NR 21 TC 52 Z9 52 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 648 EP 660 DI 10.1086/305389 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100007 ER PT J AU Chiang, J Mukherjee, R AF Chiang, J Mukherjee, R TI The luminosity function of the EGRET gamma-ray blazars SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, luminosity function, mass function; gamma rays, observations; quasars, general ID ACTIVE GALACTIC NUCLEI; SAMPLES; QUASARS; RADIATION; EMISSION; GALAXIES AB We examine the properties of the gamma-ray active galactic nuclei (AGNs) detected by EGRET. We calculate the evolution and luminosity function of the gamma-ray-loud AGNs, and we estimate the contribution this source class makes to the diffuse extragalactic gamma-ray background. These calculations are based on a sample of EGRET observations complete through the Compton Gamma-Ray Observatory observing Cycle 4. We use the V-e/V-a test to measure the luminosity evolution and the nonparametric c(-)-method to estimate the de-evolved luminosity function. We also consider inclusion in the 1 Jy radio catalog of Kuhr et al, (1981) as an additional criterion to help guard against selection effects resulting from incomplete redshift determinations for AGNs in our sample. Our results include evidence for a low-luminosity cutoff in the gamma-ray AGN luminosity distribution, a more precise estimate of the contribution of these objects to the diffuse extragalactic gamma-ray background, and constraints on the gamma-ray production mechanism based upon the statistics implied by relativistic beaming of the emission. We discuss the implications of these findings for models of AGN unification and the relationship of gamma-ray to radio emission. C1 USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada. NASA, USRA, Montreal, PQ H3A 2T8, Canada. RP Chiang, J (reprint author), USN, Res Lab, EO Hulburt Ctr Space Res, Code 7653,4555 Overlook Ave, Washington, DC 20375 USA. NR 29 TC 95 Z9 95 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 752 EP 760 DI 10.1086/305403 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100016 ER PT J AU Hamann, F Cohen, RD Shields, JC Burbidge, EM Junkkarinen, V Crenshaw, DM AF Hamann, F Cohen, RD Shields, JC Burbidge, EM Junkkarinen, V Crenshaw, DM TI Broad Ne VIII lambda 774 emission from quasars SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, kinematics and dynamics; quasars, emission lines; quasars, general; ultraviolet, galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-ABSORPTION; STELLAR OBJECTS; LINE REGION; CHEMICAL EVOLUTION; WARM ABSORBERS; DISK WINDS; SPECTRA; QSOS; GALAXIES AB Ne VIII lambda 774 is an important tracer of the high-ionization gas in QSOs. We examine the Ne VIII emission-line properties using new Hubble Space Telescope (HST)-FOS spectra of four sources, mean spectra derived from two QSO samples in the HST archives, and new photoionization calculations. The results support our previous claim that broad Ne vm lines are common in QSOs, with an average flux of similar to 42% of O VI lambda 1034 and velocity widths that are similar to 2 to 5 times larger than O VI, C IV lambda 1549 and other broad lines in the same spectra. The strongest and most reliably measured Ne vm lambda 774 lines (in two sources) have FWHM similar to 14,500 km s(-1). Line profile fits in these cases show that the unusually large widths might be caused by blending with emission from N Iv lambda 765 and O Iv lambda 789. However, standard photoionization calculations indicate that N Iv, O Iv, and all other lines near this wavelength should be too weak, leaving (very broad) Ne VIII as the only viable identification for the similar to 774 Angstrom feature. (This conclusion might be avoided if there are large radial velocity dispersions [greater than or similar to 1000 km s(-)1] in the emitting region, and the resonant absorption of continuum photons enhances the flux in weaker lines.) The calculations also indicate that the Ne vm-emitting regions have ionization parameters in the range 5 less than or similar to U less than or similar to 30, total hydrogen column densities of 10(22) less than or similar to N-H less than or similar to 3 x 10(23) cm(-2), and an average covering factor of greater than or similar to 30% (for solar abundances and a nominal QSO continuum shape). The Ne vm-emitting region is therefore more extensive, more highly ionized, and has much higher velocities than the rest of the broad emission line region (BELR). This highly ionized BELR component would be a strong X-ray "warm" absorber if it lies along our line of sight to the X-ray continuum source. C1 Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. Ohio Univ, Dept Phys & Astron, Athens, OH 45701 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hamann, F (reprint author), Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. NR 69 TC 26 Z9 26 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 761 EP 774 DI 10.1086/305414 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100017 ER PT J AU Colbert, EJM Baum, SA O'Dea, CP Veilleux, S AF Colbert, EJM Baum, SA O'Dea, CP Veilleux, S TI Large-scale outflows in edge-on Seyfert galaxies. III. Kiloparsec-scale soft X-ray emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, active; galaxies, kinematics and dynamics; galaxies, Seyfert; X-rays, galaxies ID SUPERWINDS; CONTINUUM; DYNAMICS; QUASARS; ROSAT AB We present ROSAT PSPC and HRI images of eight galaxies selected from a distance-limited sample of 22 edge-on Seyfert galaxies. Kiloparsec-scale soft X-ray nebulae extend along the galaxy minor axes in three galaxies (NGC 2992, NGC 4388, and NGC 5506). The extended X-ray emission has 0.2-2.4 keV X-ray luminosities of 0.4-3.5 x 10(40) ergs s(-1). The X-ray nebulae are roughly cospatial with the large-scale radio emission, suggesting that both are produced by large-scale galactic outflows. Assuming pressure balance between the radio and X-ray plasmas, the X-ray filling factor is greater than or similar to 10(4) times larger than the radio plasma filling factor, suggesting that large-scale outflows in Seyfert galaxies are predominantly winds of thermal X-ray-emitting gas. We favor an interpretation in which large-scale outflows originate as active galactic nucleus-driven jets that entrain and heat gas on kiloparsec scales as they make their way out of the galaxy. Active galactic nucleus-and starburst-driven winds are also possible explanations in cases where the winds are oriented along the rotation axis of the galaxy disk. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Colbert, EJM (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Mail Code 662, Greenbelt, MD 20771 USA. NR 30 TC 41 Z9 41 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 786 EP 796 DI 10.1086/305417 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100019 ER PT J AU Crenshaw, DM Maran, SP Mushotzky, RF AF Crenshaw, DM Maran, SP Mushotzky, RF TI Resolving the intrinsic C IV absorption in the Seyfert 1 galaxy NGC 3516 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies, individual (NGC 3516); galaxies, Seyfert; line, profiles; ultraviolet, galaxies ID ULTRAVIOLET-SPECTRUM; LINE REGIONS; NGC-3516; TELESCOPE; BROAD AB We observed the Seyfert 1 galaxy NGC 3516 with the Goddard High Resolution Spectrograph on the Hubble Space Telescope, and obtained UV spectra at a resolution of lambda/Delta lambda approximate to 20,000 in the redshifted C IV lambda 1549 region. The intrinsic C rv absorption in the core of the broad emission line is resolved for the first time into four distinct kinematic components, which are all blueshifted, relative to the systemic radial velocity of the host galaxy. Two components are narrow (similar to 20 and similar to 30 km s(-1) FWHM) and at small radial velocities (-90 and -30 km s(-1), respectively), and could arise from the interstellar medium or halo of the host galaxy. The two broad components are centered at radial velocities of -380 and -150 km s(-1), have widths of 130 and 210 km s(-1) FWHM, respectively, and most likely arise in out flowing gas near the active nucleus. At the times of observation, 1995 April 24 and 1995 October 22, there was no evidence for the variable absorption component at a higher outflow velocity that disappeared some time after 1989 October. The cores of the broad C rv absorption components are very close to zero intensity, indicating that the absorption regions are extended enough to occult completely the broad C Iv emitting region (which is similar to 9 light-days in extent). The total column density of the C rv absorption is substantially larger than that measured by Kriss et al. from contemporaneous Hopkins Ultraviolet Telescope (HUT) spectra, but we agree with their conclusion that the UV absorption is too strong to arise primarily from the X-ray warm absorber region. The GHRS observations, separated by six months, reveal no appreciable changes in the equivalent widths or radial velocities of any of the absorption components, although a change in the column density of either broad component at a level less than or equal to 25% cannot be ruled out, because the lines are highly saturated. At present, we know of two Seyfert galaxies, NGC 3516 and NGC 4151, with complex multiple absorption zones, which can remain stable in column density and velocity held over timescales of months to years. C1 Catholic Univ Amer, Goddard Space Flight Ctr, Astron & Solar Phys Lab, NASA, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Space Sci Directorate, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Crenshaw, DM (reprint author), Catholic Univ Amer, Goddard Space Flight Ctr, Astron & Solar Phys Lab, NASA, Code 681, Greenbelt, MD 20771 USA. NR 23 TC 26 Z9 26 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 797 EP 802 DI 10.1086/305428 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100020 ER PT J AU Preece, RD Pendleton, GN Briggs, MS Mallozzi, RS Paciesas, WS Band, DL Matteson, JL Meegan, CA AF Preece, RD Pendleton, GN Briggs, MS Mallozzi, RS Paciesas, WS Band, DL Matteson, JL Meegan, CA TI BATSE observations of gamma-ray burst spectra. IV. Time-resolved high-energy spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma-rays, bursts ID FIREBALLS; EVOLUTION; MODELS AB We report on the temporal behavior of the high-energy power-law continuum component of gamma-ray burst spectra with data obtained by the Burst and Transient Source Experiment. We have selected 126 high-fluence and high-flux bursts from the beginning of the mission up until the present. Much of the data were obtained with the Large Area Detectors, which have nearly all-sky coverage, excellent sensitivity over 2 decades of energy, and moderate energy resolution, ideal for continuum spectra studies of a large sample of bursts at high time resolution. At least eight spectra from each burst were fitted with a spectral form that consisted of a low-energy power law, a spectral break at middle energies, and a high-energy continuum. In most bursts (122), the high-energy continuum was consistent with a power law. The evolution of the fitted high-energy power-law index over the selected spectra for each burst is inconsistent with a constant for 34% of the total sample. The sample distribution of the average value for the index from each burst is fairly narrow, centered on -2.12. A linear trend in time is ruled out for only 20% of the bursts, with hard-to-soft evolution dominating the sample (100 events). The distribution for the total change in the power-law index over the duration of a burst peaks at the value -0.37 and is characterized by a median absolute deviation of 0.39, arguing that a single physical process is involved. We present analyses of the correlation of the power-law index with time, burst intensity, and low-energy time evolution. In general, we confirm the general hard-to-soft spectral evolution observed in the low-energy component of the continuum, while presenting evidence that this evolution is different in nature from that of the rest of the continuum. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci 0424, La Jolla, CA 92093 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Preece, RD (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. OI Preece, Robert/0000-0003-1626-7335 NR 36 TC 102 Z9 106 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 849 EP 862 DI 10.1086/305402 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100026 ER PT J AU Ramanamurthy, PV Thompson, DJ AF Ramanamurthy, PV Thompson, DJ TI Search for short-term variations in the E > 50 MeV gamma-ray emission of the Crab pulsar SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, observations; pulsars, individual (Crab Pulsar); radio continuum, stars ID LONG-TERM AB We present here a search for possible short-term (similar to seconds to hundreds of seconds) variability of emissivity of the Crab pulsar (beyond the 33 ms pulsation) in gamma rays at E > 50 MeV and on possible correlations between giant radio pulses and high-energy gamma rays on timescales of a few to 30 pulsar rotations. We based our analysis on part of the data from the EGRET detector aboard the Compton Gamma Rag, Observatory and on the data of giant radio pulses obtained by Lundgren in 1994 at 1330, 800, and 812.5 MHz by using the Green Bank radio telescope. Finding no evidence for either, we set upper limits to fluctuations of the emissivity of the Crab pulsar in gamma rays at E > 50 MeV. Lack of correlations between giant radio pulses and gamma rays restricts some of the parameters used in the models for the occurrence of giant radio pulses. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ramanamurthy, PV (reprint author), Nagoya Univ, STE Lab, Chikusa Ku, Furo Cho, Nagoya, Aichi 46401, Japan. EM djt@egret.gsfc.nasa.gov RI Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 30 TC 5 Z9 5 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP 863 EP 868 DI 10.1086/305425 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100027 ER PT J AU Lisse, CM A'Hearn, MF Hauser, MG Kelsall, T Lien, DJ Moseley, SH Reach, WT Silverberg, RF AF Lisse, CM A'Hearn, MF Hauser, MG Kelsall, T Lien, DJ Moseley, SH Reach, WT Silverberg, RF TI Infrared observations of comets by COBE SO ASTROPHYSICAL JOURNAL LA English DT Review DE comets, general; infrared, solar system ID HALLEY DUST PARTICLES; NECK-LINE STRUCTURE; ARAKI-ALCOCK 1983D; AUSTIN 1990-V; LEVY 1990C; OPTICAL-PROPERTIES; MASS-DISTRIBUTION; EMISSION FEATURE; IUE OBSERVATIONS; SILICATE GRAINS AB Comets C/Okazaki-Levy-Rudenko 1989 XX (C/OLR), C/Austin 1990 V, (C/Austin) P/Schwassmann-Wachmann 3 1990 VIII (P/SW3), and C/Levy 1990 XX (C/Levy) were detected by the COBE/Diffuse Infrared Background Experiment (DIRBE) with broadband photometry at 1-240 mu m between 1989 November and 1990 September. Extended dust tails were found at 12 and 25 mu m, with detailed structure due to variations in particle properties and mass-loss rate. Spectrophotometry of the central 42' x 42' was found to agree with that of a graybody of temperature 1.1 times the local blackbody temperature for C/OLR and C/Austin, while a nongraybody distribution with a spectral index of emissivity 0.26 +/- 0.15 and temperature 1.25 times the local temperature was found for C/Levy. A model using modified Mie dust particles composed of fractal mixtures of vacuum, silicates, and carbonaceous material was found to fit the observations. Comparison with IUE and ground-based observations indicates that large dark particles of radius greater than 20 mu m predominate by surface area for C/OLR and C/Austin, but 1-10 mu m particles predominate for C/Levy. The detection of P/SW3, an optically faint comet, was surprising, especially since four optically brighter comets were not detected by DIRBE. This may be related to the nuclear breakup observed during its next apparition. The total estimated mass loss from these comets in a perihelion passage is similar to 10 times larger than that expected from optical observations, and the loss rate is similar to that needed to supply the interplanetary dust cloud. No comet trails were detected to a limiting surface brightness of 1 MJy sr(-1), although large, beta < 5 x 10(4) particles, which could evolve into a dust trail, were detected in C/Austin. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Paris 11, Inst Astrophys Spatiale, Orsay, France. RP Lisse, CM (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Moseley, Harvey/D-5069-2012; Lisse, Carey/B-7772-2016; OI Lisse, Carey/0000-0002-9548-1526; Reach, William/0000-0001-8362-4094 NR 122 TC 79 Z9 79 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 APR 1 PY 1998 VL 496 IS 2 BP 971 EP 991 DI 10.1086/305397 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100035 ER PT J AU Brage, T Wahlgren, GM Johansson, SG Leckrone, DS Proffitt, CR AF Brage, T Wahlgren, GM Johansson, SG Leckrone, DS Proffitt, CR TI Theoretical oscillator strengths for Sr II and Y III, with application to abundances in the HgMn-type star chi Lupi SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; stars, abundances; stars, individual (chi Lupi) ID MERCURY-MANGANESE STARS; NORMAL LATE-B; ISOELECTRONIC SEQUENCE; DAO SPECTROGRAMS; MATRIX-ELEMENTS; A-STAR; NA-I; LI; LIFETIMES; ATMOSPHERES AB Oscillator strengths for selected transitions of Sr II and Y III have been determined using ab initio multiconfiguration Hartree-Fock techniques. The importance of including an accurate treatment of the core-valence correlation is emphasized. The results are used to determine the abundances of Sr and Y in the chemically peculiar star chi Lupi from HST/GHRS Echelle spectra. Overabundances of 2.09 dex for Sr and 2.8 dex for Y relative to the solar abundance are derived, and an ionization imbalance of +1.1 dex is evident from abundance determinations using Y III and Y II. C1 NASA, Goddard Space Flight Ctr, Astron Program, Comp Sci Corp, Greenbelt, MD 20771 USA. Lund Univ, Dept Phys, S-22100 Lund, Sweden. Lund Univ, Lund Observ, S-22100 Lund, Sweden. RP Brage, T (reprint author), NASA, Goddard Space Flight Ctr, Astron Program, Comp Sci Corp, Code 680, Greenbelt, MD 20771 USA. EM brage@kurslab.fysik.lu.se; spek_glenn@garbo.lucas.lu.se; spek_sej@garbo.lucas.lu.se; hrsleckrone@hrs.gsfc.nasa.gov; hrsproffitt@figaro.gsfc.nasa.gov NR 50 TC 26 Z9 26 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 APR 1 PY 1998 VL 496 IS 2 BP 1051 EP 1057 DI 10.1086/305401 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG868 UT WOS:000073048100041 ER PT J AU Brainerd, JJ AF Brainerd, JJ TI Physical constraints on GRB 970508 from its radio afterglow SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays, bursts AB Model-independent lower limits on the energy stored in the electrons emitting the radio afterglow from GRB 970508 are derived. These limits arise from the optically thick synchrotron source function and the synchrotron cooling timescale. The primary free parameters for these limits are the dimensionless synchrotron frequency, the bulk Lorentz factor Gamma, and the source diameter theta. When one assumes theta is related to Gamma alone, one finds that the energy stored in electrons is more than 10(51) ergs for a 3 mu as source size and more than 10(19) ergs for a 6 mu as source size. These limits are inconsistent with the energy storage expected for a relativistic shell from a destructive solar mass source. C1 Univ Alabama, Huntsville, AL 35812 USA. RP Brainerd, JJ (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES-84, Huntsville, AL 35812 USA. EM jim.brainerd@msfc.nasa.gov NR 14 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP L67 EP L70 DI 10.1086/311255 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG873 UT WOS:000073048600003 ER PT J AU Koshut, TM Kouveliotou, C van Paradijs, J Woods, PM Fishman, GJ Briggs, MS Lewin, WHG Kommers, JM AF Koshut, TM Kouveliotou, C van Paradijs, J Woods, PM Fishman, GJ Briggs, MS Lewin, WHG Kommers, JM TI Pulse delay observations of GRO J1744-28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries, general; gamma rays, observations; pulsars, individual (GRO J1744-28); X-rays, bursts AB The bursting pulsar GRO J1744-28 exhibits a unique combination of persistent X ray pulsations (with a pulse period P-pulse approximate to 0.467 s) and X-ray bursts. The pulsations are also present (at an enhanced amplitude) during the bursts, but the arrival times of the pulses during the burst are delayed with respect to those of the persistent emission. We present the results of a detailed study of the pulse delays using data obtained with the Burst and Transient Source Experiment on board the Compton Gamma Ray Observatory. We find that the average delay, as measured during a 1.5 s interval at the peak of the burst, is independent of energy in the energy range similar to 25-75 keV and has a magnitude (Delta t) = 74 +/- 13 ms. We also find that the phase delay measured near the peak of the bursts remained approximately constant throughout the first outburst of the source, although the peak flux of the bursts varied by a factor of similar to 3.3. C1 Univ Space Res Assoc, Washington, DC 20036 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. MIT, Dept Phys, Ctr Space Res, Cambridge, MA 02139 USA. RP Koshut, TM (reprint author), Univ Space Res Assoc, Washington, DC 20036 USA. EM Thomas.Koshut@msfc.nasa.gov NR 15 TC 5 Z9 5 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1998 VL 496 IS 2 BP L101 EP L104 DI 10.1086/311254 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZG873 UT WOS:000073048600011 ER PT J AU Conkin, J Foster, PP Powell, MR AF Conkin, J Foster, PP Powell, MR TI Evolved gas, pain, the power law, and probability of hypobaric decompression sickness SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID BUBBLES; SIMULATION; MODEL AB The intensity of a pain-only decompression sickness (DCS) symptom with respect to time at altitude increases, peaks, and then declines in some cases. A similar pattern is also seen in a graph of the probability density function [f(t)] for DCS. The f(t) is the proportion of DCS per unit time with respect to time at altitude. The integration of f(t) with respect to time provides the cumulative probability of DCS [P(DCS)]. We suspect that the perceived intensity of pain with a given stimulus intensity is related to the P(DCS); it may be related to the intensity of the stimulus to a power (alpha). Our stimuli are defined as pressure ratio [PR = (phi P1N(2)/P2) - 1] or pressure difference [Delta P = phi P1N(2) - P2], where phi P1N(2) is the N-2 partial pressure calculated in the 360 min half-time (t1/2) compartment or t1/2 is estimated with other parameters and P2 is ambient pressure after the ascent. Both stimuli represent a potential released volume of gas. We tested the null hypothesis that alpha > 1 was no better than alpha = 1 in PRalpha and Delta P-alpha in a log logistic survival analysis of 1085 exposures in hypobaric chambers. The log likelihood number increased from -1198 for alpha = 0 for the null model to -724 for PRalpha when alpha = 3.52 with a 42 min t1/2 and -714 for Delta P-alpha when alpha = 8.44 with a 91 min t1/2. We conclude that the improvement in our expressions for decompression dose with alpha > 1 is not by random chance and that alpha may link the physics of gas evolution to the biology of pain perception. Because of our empirical approach, we do not exclude other possible interpretations. C1 NASA, Lyndon B Johnson Space Ctr SD3, Life Sci Res Labs, Houston, TX 77058 USA. Univ Space Res Assoc, Div Space Life Sci, Houston, TX USA. RP Conkin, J (reprint author), NASA, Lyndon B Johnson Space Ctr SD3, Life Sci Res Labs, Houston, TX 77058 USA. NR 24 TC 4 Z9 4 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 APR PY 1998 VL 69 IS 4 BP 352 EP 359 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZF402 UT WOS:000072893900004 PM 9561282 ER PT J AU Greenleaf, JE Looft-Wilson, R Wisherd, JL Jackson, CGR Fung, PP Ertl, AC Barnes, PR Jensen, CD Whittam, JH AF Greenleaf, JE Looft-Wilson, R Wisherd, JL Jackson, CGR Fung, PP Ertl, AC Barnes, PR Jensen, CD Whittam, JH TI Hypervolemia in men from fluid ingestion at rest and during exercise SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID PROLONGED EXERCISE; PLASMA-VOLUME; HYPERHYDRATION; TEMPERATURE; STRESS; MECHANISMS; OSMOLALITY AB Background: Plasma osmolality (Osm) is important for controlling and maintaining plasma volume (PV) and body water. The effect of oral rehydration fluids for ameliorating dehydration is well-established; but optimal compostion and Osm of fluids for hyperhydrating normally hy drated subjects is less clear. Methods: Six treatments were used without and with oral fluids of varying ionic and constituent concentrations for hyperhydrating six previously euhydrated men (30 +/- SD 8 yr, 76.84 +/- 16.19 kg, 73 +/- 12 ml.kg(-1) PV, 40 +/- 10 ml.min(-1).kg(-1) peak (V) over dot O-2) sitting at rest for 90 min ((V) over dot O-2 = 0.39 +/- SE 0.02 L.min(-1)) and during subsequent 70 min of submaximal exercise ((V) over dot O-2 = 2.08 +/- SE 0.33 L.min(-1), 70 +/- 7% peak (V) over dot O-2). The hypothesis was that the fluid composition is more important than plasma Osm for increasing PV in euhydrated subjects at rest and maintaining it during exercise. Drink formulation compositions, given at 10 ml.kg(-1) body wt, ((X) over bar = 768 ml), for the sitting period were: Performance 1 (P1; 55 mEq Na+, 365 mOsm.kg H2O-1), P2 (97 mEq Na+, 791 mOsm.kg(-1)), P2G (113 mEq Na+, 4% glycerol, 1382 mOsm.kg(-1)), AstroAde (AA; 164 mEq Na+, 253 mOsm.kg(-1)), and 01 and 02 (no drinking). The exercise drink (10 ml.kg(-1), 768 ml) was P1 for all treatments except 02 (no drinking); thus, drink designations were: P1/P1, P2/P1, P2G/P1, AA/P1, 0/P1, and 0/0. Results: PV at rest increased (p < 0.05) by 4.7% with P1 and by 7.9% with AA. Percent change in PV during exercise was +1% to +3% (NS) with AA/P1; -6% to 0% (NS) with P1/P1, P2/P1, P2G/P1, and 0/P1; and -8% to -5% (p < 0.05) with 0/0. AA, with the lowest Osm of 253 mOsm.kg(-1), increased PV at rest (as did P1) and maintained it during exercise, whereas the other drinks with lower Na+ and higher Osm of 365-1382 mOsm.kg(-1) did not. Conclusion: Drink composition appears to be more important than its Osm for increasing PV at rest and for maintaining it during exercise in previously euhydrated subjects. C1 NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. San Francisco State Univ, Dept Biol Sci, San Francisco, CA 94132 USA. Shaklee Technica, San Francisco, CA USA. RP Greenleaf, JE (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. NR 35 TC 19 Z9 20 U1 0 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 APR PY 1998 VL 69 IS 4 BP 374 EP 386 PG 13 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA ZF402 UT WOS:000072893900007 PM 9561285 ER PT J AU Shafto, MG AF Shafto, MG TI Costs and benefits of statistical significance tests SO BEHAVIORAL AND BRAIN SCIENCES LA English DT Editorial Material AB Chow's book provides a thorough analysis of the confusing array of issues surrounding conventional tests of statistical significance. This book should be required reading for behavioral social scientists. Chow concludes that the null-hypothesis significance-testing procedure (NHSTP) plays a limited, but necessary, role in the experimental sciences. Another possibility is that - owing in part to its metaphorical underpinnings and convoluted logic - the NHSTP is declining in importance in those few sciences in which it ever played a role. C1 NASA, Human Automat Interact Res Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Shafto, MG (reprint author), NASA, Human Automat Interact Res Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 7 TC 0 Z9 0 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0140-525X J9 BEHAV BRAIN SCI JI Behav. Brain Sci. PD APR PY 1998 VL 21 IS 2 BP 218 EP + DI 10.1017/S0140525X98481160 PG 7 WC Psychology, Biological; Behavioral Sciences; Neurosciences SC Psychology; Behavioral Sciences; Neurosciences & Neurology GA 110BM UT WOS:000075359400028 ER PT J AU Ord, GN Gualtieri, JA AF Ord, GN Gualtieri, JA TI Information loss in the continuum limit and Schrodinger's equation in an electromagnetic field SO BIOSYSTEMS LA English DT Article; Proceedings Paper CT 2nd Conference on Foundations of Information Science - From Computers and Quantum Physics to Cells, Nervous Systems, and Societies CY JUN, 1994 CL VIENNA, AUSTRIA SP Univ Carlos III Madrid, Lab Artificial Intelligence, Univ Zaragoza C P S, Dept Elect & Electr Engn DE lattices; diffusion; Schrodinger's equation; random walks ID QUANTUM-MECHANICS; INTERFERENCE; ANALOG; TIME AB Since the time of Einstein's work on Brownian motion it has been known that random walks provide a microscopic model for the diffusion equation. Less well known is the fact that some instances of Schrodinger's equation occur naturally in the description of the statistics of these same walks and thus have classical contexts which are distinct from their usual association with quantum mechanics. An interesting feature of these models is the fact that the information which relates Schrodinger's equation to its classical context is not contained in the partial differential equation itself, but is lost in the continuum limit which gives rise to the equation. In this article we illustrate the above by showing that Schrodinger's equation for a particle in an electromagnetic field in 1 + 1 dimension occurs as a continuum limit of a description of a classical system of point particles on a lattice. The derivation shows that the information lost in the continuum limit is necessary to link the mathematics to the physical context of the equation. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved. C1 Ryerson Polytech Univ, MPCS, Toronto, ON, Canada. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ord, GN (reprint author), Ryerson Polytech Univ, MPCS, 350 Victoria St, Toronto, ON, Canada. NR 21 TC 2 Z9 2 U1 0 U2 2 PU ELSEVIER SCI IRELAND LTD PI CLARE PA CUSTOMER RELATIONS MANAGER, BAY 15, SHANNON INDUSTRIAL ESTATE CO, CLARE, IRELAND SN 0303-2647 J9 BIOSYSTEMS JI Biosystems PD APR PY 1998 VL 46 IS 1-2 BP 21 EP 28 DI 10.1016/S0303-2647(97)00077-4 PG 8 WC Biology; Mathematical & Computational Biology SC Life Sciences & Biomedicine - Other Topics; Mathematical & Computational Biology GA ZR001 UT WOS:000073925200004 PM 9648671 ER PT J AU Rothermel, J Cutten, DR Hardesty, RM Menzies, RT Howell, JN Johnson, SC Tratt, DM Olivier, LD Banta, RM AF Rothermel, J Cutten, DR Hardesty, RM Menzies, RT Howell, JN Johnson, SC Tratt, DM Olivier, LD Banta, RM TI The Multi-center Airborne Coherent Atmospheric Wind Sensor SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID PROSPECTUS DEVELOPMENT TEAM; PLANETARY BOUNDARY-LAYER; WEATHER RESEARCH-PROGRAM; PULSED DOPPLER LIDAR; MARINE LAYER; LASER-RADAR; BACKSCATTER; AEROSOL; CONVECTION; EVOLUTION AB In 1992 the atmospheric Lidar remote sensing groups of the National Aeronautics and Space Administration Marshall Space Flight Center, the National Oceanic and Atmospheric Administration/Environmental Technology Laboratory (NOAA/ETL), and the Jet Propulsion Laboratory began a joint collaboration to develop an airborne high-energy Doppler laser radar (lidar) system for atmospheric research and satellite validation and simulation studies. The result is the Multicenter Airborne Coherent Atmospheric Wind Sensor (MACAWS), which has the capability to remotely sense the distribution of wind and absolute aerosol backscatter in three-dimensional volumes in the troposphere and lower stratosphere. A factor critical to the programmatic feasibility and technical success of this collaboration has been the utilization of existing components and expertise that were developed for previous atmospheric research by the respective institutions. For example, the laser transmitter is that of the mobile ground-based Doppler lidar system developed and used in atmospheric research for more than a decade at NOAA/ETL. The motivation for MACAWS is threefold: 1) to obtain fundamental measurements of subsynoptic-scale processes and features to improve subgrid-scale parameterizations in large-scale models, 2) to obtain datasets in order to improve the understanding of and predictive capabilities for meteorological systems on subsynoptic scales, and 3) to validate (simulate) the performance of existing (planned) satellite-borne sensors. Initial flight tests were made in September 1995; subsequent flights were made in June 1996 following system improvements. This paper describes the MACAWS instrument, principles of operation, examples of measurements over the eastern Pacific Ocean and western United States, and future applications. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Univ Alabama, Huntsville, AL 35899 USA. NOAA, Environm Technol Lab, Boulder, CO 80303 USA. Jet Propuls Lab, Pasadena, CA USA. RP Rothermel, J (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. RI Darby, Lisa/A-8037-2009; Tratt, David/A-7884-2009; Hardesty, Robert/H-9844-2013; Banta, Robert/B-8361-2008 OI Darby, Lisa/0000-0003-1271-0643; Tratt, David/0000-0002-3942-6848; NR 85 TC 27 Z9 27 U1 1 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD APR PY 1998 VL 79 IS 4 BP 581 EP 599 DI 10.1175/1520-0477(1998)079<0581:TMCACA>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK039 UT WOS:000073278800001 ER PT J AU Helser, TE Brodziak, JKT AF Helser, TE Brodziak, JKT TI Impacts of density-dependent growth and maturation on assessment advice to rebuild depleted US silver hake (Merluccius bilinearis) stocks SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID LIFE-HISTORY; FISHERIES; SUCCESS; LARVAE; TIME; SIZE; RISK AB We examined how density-dependent growth and maturation rates would affect scientific advice to rebuild U.S. silver bake (Merluccius bilinearis) stocks to a minimum biomass threshold (SSB50) using an age-structured stochastic projection model. Uncertainty in recruitment and initial stock sizes at age was incorporated to more realistically capture the stochastic nature of the stock's dynamics through time. Performance measures including spawning stock biomass (SSBt)(t) risk (prob(SSBt< SSB50)), and fishery yields were examined under model assumptions of static life history parameters in contrast with density-dependent parameters for various constant fishing mortality rate (F) harvest policies. Model results indicated that unless compensatory mechanisms are accounted for, scientific advice may be too optimistic and lead to unrealistic expectations of F targets to achieve stock rebuilding, requiring longer rebuilding times and entailing more risk and unrealized sustainable yield. For instance, projected median southern stock SSB, exceeded the SSB50 of 104 000 metric tons (t) with 40% risk to the stock by year 20 from harvesting at F = 0.50. However, under the density-dependent assumption, median SSB, did not rebuild as expected, and after 20 years reached only 75 000 t with 85% risk to the stock. Also under this assumption, median yields increased from 9000 to 27 000 t by year 20 but were 30-40% lower than what would have been expected under density independence. C1 Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Populat Dynam Branch, Woods Hole, MA 02543 USA. Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Hatfield Marine Sci Ctr, Newport, OR 97365 USA. RP Helser, TE (reprint author), Fisheries Res Inc, 2528 Gates Circle,Suite 37, Baton Rouge, LA 70809 USA. NR 32 TC 28 Z9 28 U1 0 U2 1 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 APR PY 1998 VL 55 IS 4 BP 882 EP 892 DI 10.1139/cjfas-55-4-882 PG 11 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA ZY881 UT WOS:000074671600012 ER PT J AU Convertino, VA Ludwig, DA Gray, BD Vernikos, J AF Convertino, VA Ludwig, DA Gray, BD Vernikos, J TI Effects of exposure to simulated microgravity on neuronal catecholamine release and blood pressure responses to norepinephrine and angiotensin SO CLINICAL AUTONOMIC RESEARCH LA English DT Article DE autonomic function; cold pressor test; vasoconstriction ID SPACEFLIGHT; PLASMA; HUMANS AB We tested the hypothesis that exposure to microgravity reduces the neuronal release of catecholamines and blood pressure responses to norepinephrine and angiotensin. Eight men underwent 30 days of 6 degrees head-down tilt (HDT) bedrest to simulate exposure to microgravity. Plasma norepinephrine and mean arterial blood pressure (MAP) were measured before and after a cold pressor test (CPT) and graded norepinephrine infusion (8, 16 and 32 ng/kg/min) on day 6 of a baseline control period (C6) and on days 14 and 27 of HDT. MAP and plasma angiotensin II (Ang-II) were measured during graded Ang-II infusion (1, 2 and 4 ng/kg/min) on C8 and days 16 and 29 of HDT. Baseline total circulating norepinephrine was reduced from 1017 ng during the baseline control period to 610 ng at day 14 and 673 ng at day 27 of HDT, confirming a hypoadrenergic state. An elevation of norepinephrine (+178 ng) to the CPT during the baseline control period was eliminated by HDT days 14 and 27. During norepinephrine infusion, similar elevations in plasma norepinephrine (7.7 pg/ml/ng/kg/min) caused similar elevations in MAP (0.12 mmHg/ng/kg/min) across all test days. Ang-II infusion produced higher levels of plasma Ang-II during HDT (47.3 pg/ml) than during baseline control (35.5 pg/ml), while producing similar corresponding elevations in blood pressure. While vascular responsiveness to norepinephrine appears unaffected, impaired neuronal release of norepinephrine and reduced vascular responsiveness to Ang-II might contribute to the lessened capacity to vasoconstrict after spaceflight. The time course of alterations indicates effects that occur within two weeks of exposure. (C) 1998 Lippincott-Raven Publishers. C1 USAF, Res Lab, Flight Mot Effects Branch, Flight Stress Ptotect Div, Brooks AFB, TX USA. Univ N Carolina, Dept Math Sci, Greensborough, NC USA. NASA, Washington, DC 20546 USA. RP Convertino, VA (reprint author), AFRL, HEPM, Physiol Res Branch, Clin Sci Sect, 2504 Gillingham Dr, Brooks AFB, TX 78235 USA. NR 28 TC 16 Z9 16 U1 0 U2 4 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0959-9851 J9 CLIN AUTON RES JI Clin. Auton. Res. PD APR PY 1998 VL 8 IS 2 BP 101 EP 110 DI 10.1007/BF02267820 PG 10 WC Clinical Neurology; Neurosciences SC Neurosciences & Neurology GA ZQ343 UT WOS:000073849800004 PM 9613800 ER PT J AU Alkalai, L Tai, AT AF Alkalai, L Tai, AT TI Long-life deep-space applications SO COMPUTER LA English DT Article AB In "Long-Life Deep-Space Applications," Leon Akkalai and Ann T. Tai describe the design philosophy behind a highly miniaturized, reliable, low-cost, avionics system for long-life deep-space applications. C1 Jet Propuls Lab, Ctr Integrated Space Microsyst, NASA Ctr Excellence, Pasadena, CA 91109 USA. RP Alkalai, L (reprint author), Jet Propuls Lab, Ctr Integrated Space Microsyst, NASA Ctr Excellence, Pasadena, CA 91109 USA. NR 3 TC 9 Z9 9 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0018-9162 J9 COMPUTER JI Computer PD APR PY 1998 VL 31 IS 4 BP 37 EP + PG 3 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA ZE232 UT WOS:000072771400017 ER PT J AU Lowry, MR AF Lowry, MR TI Component-based reconfigurable systems SO COMPUTER LA English DT Article AB In "Component-Based Reconfigurable Systems," Michael R. Lowry describes NASA Ames' Amphion project, a system for building high-assurance reconfigurable software systems from components in a software library. C1 NASA, Ames Res Ctr, Automated Software Engn Grp, Computat Sci Div, Moffett Field, CA 94035 USA. RP Lowry, MR (reprint author), NASA, Ames Res Ctr, Automated Software Engn Grp, Computat Sci Div, Moffett Field, CA 94035 USA. EM lowry@ptolemy.arc.nasa.gov NR 4 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0018-9162 J9 COMPUTER JI Computer PD APR PY 1998 VL 31 IS 4 BP 44 EP + PG 3 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA ZE232 UT WOS:000072771400021 ER PT J AU Ding, HQ Ferraro, RD AF Ding, HQ Ferraro, RD TI An 18 GFLOPS parallel climate data assimilation PSAS package SO COMPUTERS & MATHEMATICS WITH APPLICATIONS LA English DT Article DE climate modeling; PSAS software package; performance; Intel Paragon; Cray C90 AB We have designed and implemented a set of highly efficient and highly scalable algorithms for an unstructured computational package, the PSAS data simulation package, as demonstrated by detailed performance analysis of systematic runs up to 512 nodes of an Intel Paragon. The preconditioned Conjugate Gradient solver achieves a sustained 18 Gflops performance. Consequently, we achieve an unprecedented 100-fold reduction in time to solution on the Intel Paragon over a single head of a Gray C90. This not only exceeds the daily performance requirement of the Data Assimilation Office at NASA's Goddard Space Flight Center, but also makes it possible to explore much larger and challenging data assimilation problems which are unthinkable on a traditional computer platform such as the Gray C90. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ding, HQ (reprint author), Univ Calif Berkeley, Lawrence Berkeley Lab, NERSC, 50A-3111,1 Cyclotron Rd, Berkeley, CA 94720 USA. NR 3 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 0898-1221 J9 COMPUT MATH APPL JI Comput. Math. Appl. PD APR PY 1998 VL 35 IS 7 BP 55 EP 63 DI 10.1016/S0898-1221(98)00032-7 PG 9 WC Mathematics, Applied SC Mathematics GA ZC984 UT WOS:000072639000006 ER PT J AU Deane, AE AF Deane, AE TI Parallel computations of 3-D Rayleigh-Taylor instability SO COMPUTERS & MATHEMATICS WITH APPLICATIONS LA English DT Article DE flux corrected transport; Rayleigh-Taylor instability; compressible flow; Intel Paragon ID FLUIDS AB Results are described of computations of 3-D compressible Rayleigh-Taylor instability. The instability is an important mixing mechanism in a variety of flows such as supernovae and inertial confinement fusion. The code uses Flux Corrected Transport to solve the Euler equations of hydrodynamics. Results of the simulations have been characterized by considering differing resolutions and in terms of growth-rates, Mach number evolution, pattern formation, and (weakly) turbulent structures. C1 Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. NASA, High Performance Comp Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Deane, AE (reprint author), Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. NR 14 TC 3 Z9 3 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0898-1221 J9 COMPUT MATH APPL JI Comput. Math. Appl. PD APR PY 1998 VL 35 IS 7 BP 111 EP 116 DI 10.1016/S0898-1221(98)00038-8 PG 6 WC Mathematics, Applied SC Mathematics GA ZC984 UT WOS:000072639000012 ER PT J AU Freund, MM Duband, L Lange, AE Matsumoto, T Murakami, H Hirao, T Sato, S AF Freund, MM Duband, L Lange, AE Matsumoto, T Murakami, H Hirao, T Sato, S TI Design and flight performance of a space borne He-3 refrigerator for the infrared telescope in space SO CRYOGENICS LA English DT Article DE He-3 refrigerator; flight performance; space-borne ID LOW-TEMPERATURE; IN-SPACE AB We report the design, space-qualification and flight performance of a He-3 refrigerator that has achieved the first sub-Kelvin temperatures in orbit. The refrigerator has been used to cool the bolometric detectors of the Far Infrared Photometer (FIRP) on the Infrared Telescope in Space (IRTS). The refrigerator has no moving parts, and can be re-cycled indefinitely in zero-g with > 95% duty cycle using simple control electronics. It provides 10 mu W Of cooling power at T < 310 mK with less than or equal to 2 mW average power dissipation to a 2.0 K heat sink for about 10 days. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. CALTECH, Pasadena, CA 91125 USA. ISAS, Sagamihara, Kanagawa, Japan. Nagoya Univ, Dept Phys, Chikusa Ku, Nagoya, Aichi, Japan. RP Freund, MM (reprint author), NASA, Ames Res Ctr, MS 239-4, Moffett Field, CA 94035 USA. NR 15 TC 12 Z9 12 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 1998 VL 38 IS 4 BP 435 EP 443 DI 10.1016/S0011-2275(97)00173-2 PG 9 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA ZX988 UT WOS:000074575500012 ER PT J AU Hoetker, G AF Hoetker, G TI Dun and Bradstreet connects with Japan SO DATABASE LA English DT Database Review C1 Dewey Ballantine, New York, NY 10019 USA. NASA, Washington, DC 20546 USA. RP Hoetker, G (reprint author), Univ Michigan, Sch Business, Ann Arbor, MI 48109 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU ONLINE INC PI WILTON PA 462 DANBURY RD, WILTON, CT 06897-2126 USA SN 0162-4105 J9 DATABASE JI Database PD APR-MAY PY 1998 VL 21 IS 2 BP 50 EP + PG 4 WC Computer Science, Information Systems; Information Science & Library Science SC Computer Science; Information Science & Library Science GA ZQ555 UT WOS:000073879800017 ER PT J AU Costanza, R d'Arge, R de Groot, R Farber, S Grasso, M Hannon, B Limburg, K Naeem, S O'Neill, RV Paruelo, J Raskin, RG Sutton, P van den Belt, M AF Costanza, R d'Arge, R de Groot, R Farber, S Grasso, M Hannon, B Limburg, K Naeem, S O'Neill, RV Paruelo, J Raskin, RG Sutton, P van den Belt, M TI The value of the world's ecosystem services and natural capital (Reprinted from Nature, vol 387, pg 253, 1997) SO ECOLOGICAL ECONOMICS LA English DT Reprint DE ecological systems; capital stocks; ecosystem services ID ENVIRONMENTAL FUNCTIONS; VALUATION; MANAGEMENT; ECONOMICS; FISHERIES AB The services of ecological systems and the natural capital stocks that produce them are critical to the functioning of the Earth's life-support system. They contribute to human welfare, both directly and indirectly, and therefore represent part of the total economic value of the planet. We have estimated the current economic value of 17 ecosystem services for 16 biomes, based on published studies and a few original calculations. For the entire biosphere, the value (most of which is outside the market) is estimated to be in the range of US$16-54 trillion (10(12)) per year, with an average of US$33 trillion per year. Because of the nature of the uncertainties, this must be considered a minimum estimate. Global gross national product total is around US$18 trillion per year. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Maryland, Ctr Environm Sci, Dept Zool, Solomons, MD 20688 USA. Univ Maryland, Inst Ecol Econ, Solomons, MD 20688 USA. Univ Wyoming, Dept Econ, Laramie, WY 82070 USA. Agr Univ Wageningen, Ctr Environm & Climate Studies, NL-6700 HB Wageningen, Netherlands. Univ Pittsburgh, Grad Sch Publ & Int Affairs, Pittsburgh, PA 15260 USA. Univ Illinois, Dept Geog, Urbana, IL 61801 USA. Univ Illinois, NCSA, Urbana, IL 61801 USA. Inst Ecosyst Studies, Millbrook, NY USA. Univ Minnesota, Dept Ecol Evolut & Behav, St Paul, MN 55108 USA. Oak Ridge Natl Lab, Div Environm Sci, Oak Ridge, TN 37831 USA. Univ Buenos Aires, Fac Agron, Dept Ecol, RA-1417 Buenos Aires, DF, Argentina. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Geog, Natl Ctr Geog Informat & Anal, Santa Barbara, CA 93106 USA. Ecol Econ Res & Applicat Inc, Solomons, MD 20688 USA. RP Costanza, R (reprint author), Univ Maryland, Ctr Environm Sci, Dept Zool, Box 38, Solomons, MD 20688 USA. RI Costanza, Robert/A-4912-2008; Sutton, Paul/A-6764-2013; Limburg, Karin/M-8380-2013; Ross, Donald/F-7607-2012 OI Costanza, Robert/0000-0001-6348-8734; Sutton, Paul/0000-0001-6972-3256; Ross, Donald/0000-0002-8659-3833 NR 34 TC 133 Z9 193 U1 122 U2 959 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-8009 J9 ECOL ECON JI Ecol. Econ. PD APR PY 1998 VL 25 IS 1 BP 3 EP 15 DI 10.1016/S0921-8009(98)00020-2 PG 13 WC Ecology; Economics; Environmental Sciences; Environmental Studies SC Environmental Sciences & Ecology; Business & Economics GA ZQ724 UT WOS:000073896700002 ER PT J AU Costanza, R d'Arge, R de Groot, R Farber, S Grasso, M Hannon, B Limburg, K Naeem, S O'Neill, RV Paruelo, J Raskin, RG Sutton, P van den Belt, M AF Costanza, R d'Arge, R de Groot, R Farber, S Grasso, M Hannon, B Limburg, K Naeem, S O'Neill, RV Paruelo, J Raskin, RG Sutton, P van den Belt, M TI The value of ecosystem services: putting the issues in perspective SO ECOLOGICAL ECONOMICS LA English DT Article DE ecosystem services; global valuation; GNP C1 Univ Maryland, Dept Zool, Ctr Environm Sci, Solomons, MD 20688 USA. Univ Maryland, Inst Ecol Econ, Solomons, MD 20688 USA. Univ Wyoming, Dept Econ, Laramie, WY 82070 USA. Agr Univ Wageningen, Ctr Environm & Climate Studies, NL-6700 HB Wageningen, Netherlands. Univ Pittsburgh, Grad Sch Publ & Int Affairs, Pittsburgh, PA 15260 USA. Univ Illinois, Dept Geog, Urbana, IL 61801 USA. Univ Illinois, NCSA, Urbana, IL 61801 USA. Inst Ecosyst Studies, Millbrook, NY 12545 USA. Univ Minnesota, Dept Ecol Evolut & Behav, St Paul, MN 55108 USA. Oak Ridge Natl Lab, Div Environm Sci, Oak Ridge, TN 37831 USA. Univ Buenos Aires, Fac Agron, Dept Ecol, RA-1417 Buenos Aires, DF, Argentina. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Geog, Natl Ctr Geog Informat & Anal, Santa Barbara, CA 93106 USA. Ecol Econ Res & Applicat, Solomons, MD 20688 USA. RP Costanza, R (reprint author), Univ Maryland, Dept Zool, Ctr Environm Sci, Box 38, Solomons, MD 20688 USA. RI Costanza, Robert/A-4912-2008; Sutton, Paul/A-6764-2013; Limburg, Karin/M-8380-2013 OI Costanza, Robert/0000-0001-6348-8734; Sutton, Paul/0000-0001-6972-3256; NR 17 TC 86 Z9 100 U1 3 U2 80 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-8009 J9 ECOL ECON JI Ecol. Econ. PD APR PY 1998 VL 25 IS 1 BP 67 EP 72 DI 10.1016/S0921-8009(98)00019-6 PG 6 WC Ecology; Economics; Environmental Sciences; Environmental Studies SC Environmental Sciences & Ecology; Business & Economics GA ZQ724 UT WOS:000073896700015 ER PT J AU Baroth, E Wells, G Merrell, J AF Baroth, E Wells, G Merrell, J TI An evaluation of multiplexed analog digitizer boards - Part 1 SO EE-EVALUATION ENGINEERING LA English DT Article AB How many bits of accuracy does a 16-bit board have on a typical PC? The simple answer is: Sixteen, that's what the manu al says. But the real answer is far more complicated. C1 CALTECH, Jet Prop Lab, Measurement Technol Ctr, Pasadena, CA 91109 USA. USAF, Res Lab, Edwards AFB, CA USA. RP Baroth, E (reprint author), CALTECH, Jet Prop Lab, Measurement Technol Ctr, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU NELSON PUBLISHING PI NOKOMIS PA 2504 NORTH TAMIAMI TRAIL, NOKOMIS, FL 34275-3482 USA SN 0149-0370 J9 EE-EVAL ENG JI EE-Eval. Eng. PD APR PY 1998 VL 37 IS 4 BP 26 EP + PG 6 WC Engineering, Electrical & Electronic SC Engineering GA ZG063 UT WOS:000072961900004 ER PT J AU Huber, E Kortenkamp, D AF Huber, E Kortenkamp, D TI A behavior-based approach to active stereo vision for mobile robots SO ENGINEERING APPLICATIONS OF ARTIFICIAL INTELLIGENCE LA English DT Article DE active vision; stereo vision; mobile robots; intelligent control AB This paper describes an active stereo vision system that uses a behavior-based approach to control gaze. The system concentrates its computational resources on cubic volumes of space called proximity spaces. Each proximity space is controlled by a set of behaviors that combine to determine its location in the next processing frame. Multiple proximity spaces can be chained together using kinematic models to perform complex visual tasks. The vision system is mounted on a mobile robot and integrated into an intelligent control architecture. The intelligent control architecture serves to interpret the vision system output in a task context and produces appropriate robot motion. The resulting robot system can perform tasks such as pursuing other agents, recognizing natural gestures and avoiding obstacles. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Robot & Automat Grp, Metrica Inc, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP NASA, Robot & Automat Grp, Metrica Inc, Lyndon B Johnson Space Ctr, ER2, Houston, TX 77058 USA. EM korten@mickey.jsc.nasa.gov NR 27 TC 6 Z9 6 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0952-1976 EI 1873-6769 J9 ENG APPL ARTIF INTEL JI Eng. Appl. Artif. Intell. PD APR PY 1998 VL 11 IS 2 BP 229 EP 243 DI 10.1016/S0952-1976(97)00078-X PG 15 WC Automation & Control Systems; Computer Science, Artificial Intelligence; Engineering, Multidisciplinary; Engineering, Electrical & Electronic SC Automation & Control Systems; Computer Science; Engineering GA ZX665 UT WOS:000074541700007 ER PT J AU Mindlin, GB Merener, N Boyd, PT AF Mindlin, GB Merener, N Boyd, PT TI Low-dimensional dynamics outside the laboratory: The case of roAp stars SO EUROPHYSICS LETTERS LA English DT Article ID OSCILLATING AP STARS; TOPOLOGICAL ANALYSIS; TIME-SERIES; SYSTEMS; CHAOS AB In this work, we build a nonlinear model to account for the time Variable energy flux of a class of pulsating stars which is simple and robust, and test it against recent observations made with the Hubble Space Telescope. By the construction of a standard global normal form for the model, we not only check that the model has solutions qualitatively similar to the observations; we also fit the parameters of the model from the time series. This allows us to build confidence on a simple model for the phenomenon under study, which should be valid for a class of pulsating stars. C1 Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Fis, RA-1428 Buenos Aires, DF, Argentina. NASA, Goddard Space Flight Ctr, Univ Space Res Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Mindlin, GB (reprint author), Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Fis, Ciudad Univ,Pab I, RA-1428 Buenos Aires, DF, Argentina. RI Boyd, Patricia/D-3274-2012 NR 21 TC 6 Z9 6 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0295-5075 J9 EUROPHYS LETT JI Europhys. Lett. PD APR 1 PY 1998 VL 42 IS 1 BP 31 EP 36 DI 10.1209/epl/i1998-00548-y PG 6 WC Physics, Multidisciplinary SC Physics GA ZE653 UT WOS:000072816100006 ER PT J AU Landingham, JH Sturdevant, MV Brodeur, RD AF Landingham, JH Sturdevant, MV Brodeur, RD TI Feeding habits of juvenile Pacific salmon in marine waters of southeastern Alaska and northern British Columbia SO FISHERY BULLETIN LA English DT Article ID ONCORHYNCHUS-KETA; CHUM SALMON; SIZE; FOOD; KISUTCH; STRAIT; OREGON; COHO; PINK AB First ocean-year feeding habits were determined for juvenile salmon (Oncorhynchus spp.) collected with purse seines in marine waters of southeastern Alaska in 1983 and 1984 and northern British Columbia in 1984. Associated prey assemblages were sampled with neuston and plankton nets in 1984. Salmon diets included at least 30 taxa of prey. Crustaceans (principally hyperiid amphipods), fish, and tunicates were the most important prey of pink (O. gorbuscha), chum (O. Keta), and sockeye (O. nerka) salmon. Fish were the most important prey of coho (O. kisutch) and chinook (O. tshawytscha) salmon and made up the highest percentage of stomach content weight for all salmon species. Diet shifted from crustaceans in 1983 to fish in 1984 for juvenile pink, sockeye, and chum salmon. Diet overlapped significantly ((C) over cap(lambda)>0.60) between pink and sockeye salmon, pink and chum salmon, and chum and sockeye salmon. Coho salmon diet overlap was <0.60 in all paired comparisons. Nearly all (98.6%) of the 2,210 stomachs examined were at least half full. Although, in general, prey consumed were not very similar to prey observed in the environment, the composition of salmon diets was more similar to neuston collections than to zooplankton collections. C1 Natl Marine Fisheries Serv, Auke Bay Lab, Alaska Fisheries Sci Ctr, NOAA, Juneau, AK 99801 USA. NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Seattle, WA 98115 USA. RP Landingham, JH (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, Alaska Fisheries Sci Ctr, NOAA, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 34 TC 26 Z9 27 U1 1 U2 8 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 1998 VL 96 IS 2 BP 285 EP 302 PG 18 WC Fisheries SC Fisheries GA ZG226 UT WOS:000072979800009 ER PT J AU Garrett, ES Jahncke, ML Cole, EA AF Garrett, ES Jahncke, ML Cole, EA TI Effects of Codex and GATT SO FOOD CONTROL LA English DT Article; Proceedings Paper CT 1st International Food Safety / HACCP Conference CY FEB 17-18, 1997 CL NOORDWIJK, NETHERLANDS DE trade; global food safety; technical barriers AB The role of the WHO/FAO Food Standards Programme has become increasingly important since the Uruguay Round of GATT since adherence to Coder Standards offers safe harborage in WTO disputes. This paper reviews some of the Programme's history and successes, discusses Coder's changing role due to GATT and WTO's endorsement of its work products, and discusses HACCP and other topical issues. It also details where the Coder Programme is in relation to streamlining its activities in terms of emphasizing the role of science in its deliberations, accelerating the timeliness of its activities, and recasting its recommendations for national government acceptance of its standards. (C) 1998 Elsevier Science Ltd. AIL rights reserved. C1 Natl Marine Fisheries Serv, Natl Seafood Inspect Lab, Pascagoula, MS USA. Virginia Seafood Res & Extens Ctr, Hampton, VA 23669 USA. RP Garrett, ES (reprint author), Natl Marine Fisheries Serv, Natl Seafood Inspect Lab, 3209 Frederic St, Pascagoula, MS USA. NR 22 TC 7 Z9 7 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0956-7135 J9 FOOD CONTROL JI Food Control PD APR-JUN PY 1998 VL 9 IS 2-3 BP 177 EP 182 DI 10.1016/S0956-7135(98)80004-2 PG 6 WC Food Science & Technology SC Food Science & Technology GA ZY583 UT WOS:000074638200020 ER PT J AU Bogard, DD Garrison, DH AF Bogard, DD Garrison, DH TI Ar-39-Ar-40 ages and thermal history of mesosiderites SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID IRON-METEORITES; COOLING RATES; PARENT BODY; PETROGENESIS AB Determinations of Ar-39-Ar-40 ages for plagioclase separates of three clasts from the Vaca Muerta and Mount Padbury mesosiderites give similar results. Ages increase monotonically by similar to 0.2-0.3 Ga when plotted against increasing Ar-39 release from the samples and give average values of similar to 3.95 Ga. When combined with revised ages for mesosiderite analyses previously reported, nineteen analyses of thirteen mesosiderites give an average Ar-Ar age of 3.94 +/- 0.10 Ga. The average age at 90% Ar-39 release is 4.13 +/-0.14 Ga, and the ages at 10% Ar-39 release range over 3.32-3.97 Ga. It seems unlikely that the Ar-39-Ar-40 ages were produced by direct impact heating, but they probably are independent evidence for slow cooling deep within the mesosiderite parent body. We conclude that the sloped age plateaus and the significant range in Ar-Ar closure temperatures calculated for these mesosiderites (similar to 75-340 degrees C) are due to significant differences in Ar diffusion properties among samples. From the Ar diffusion data, we estimate an approximate mesosiderite cooling rate of similar to 0.2 degrees C/Ma, which is similar to the preferred cooling rate of 0.l-0.5 degrees C/Ma derived by others from Ni diffusion and metal textures. The Ar-39/Ar-49 ages seem incompatible with very slow cooling rates of <0.2 degrees C/Ma, unless the closure temperatures for Ar diffusion and formation of metal cooling textures on the parent body substantially overlap. Any possible role of fragmentation of the mesosiderite parent body in producing the younger Ar Ar ages and the very slow cooling rates is unclear. Copyright (C) 1998 Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Planetary Sci SN2, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Lockheed Martin ESC, Houston, TX 77058 USA. RP Bogard, DD (reprint author), NASA, Lyndon B Johnson Space Ctr, Planetary Sci SN2, Houston, TX 77058 USA. NR 32 TC 21 Z9 21 U1 0 U2 1 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 1998 VL 62 IS 8 BP 1459 EP 1468 DI 10.1016/S0016-7037(98)00077-5 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA ZW044 UT WOS:000074368000012 ER PT J AU Mayr, HG Mengel, JG Chan, KL Porter, HS AF Mayr, HG Mengel, JG Chan, KL Porter, HS TI Seasonal variations of the diurnal tide induced by gravity wave filtering SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PROPAGATING TIDE; MOMENTUM FLUXES; MEAN WINDS; SOLAR; THERMOSPHERE; DISSIPATION; ATMOSPHERE; MIDDLE; ENERGY AB Wind measurements with the UARS spacecraft show that between 90 and 100 km altitude the fundamental diurnal tide is modulated semi-annually with peak amplitudes of almost 100 m/s near equinox, more than a factor of two larger than during solstice. Applying Hines' Doppler-Spread Parameterization (DSP) for small scale gravity waves (GW), we present results from a Numerical Spectral Model (NSM) to describe the seasonal variations in the mean zonal circulation interacting self consistently with the diurnal tide. With the DSP, the GW momentum source increases the amplitude of the tide at altitudes above 70 km, in contrast to the Rayleigh friction parameterization that causes damping. Since the tide absorbs GW momentum, it reduces the wave-generated semi-annual oscillations (SAO) in the mean zonal winds at equatorial latitudes. Outside the tropics, GW momentum is absorbed by the mean zonal winds that peak near the summer and winter solstices. As a result, the GW reach the upper mesosphere with more momentum during equinox periods and thus cause a seasonal modulation of the tide that is predominately semi-annual. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA USA. Hong Kong Univ Sci & Technol, Hong Kong, Peoples R China. Furman Univ, Greenville, SC 29613 USA. RP Mayr, HG (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. OI Chan, Kwing/0000-0002-6428-1812 NR 28 TC 50 Z9 50 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 1998 VL 25 IS 7 BP 943 EP 946 DI 10.1029/98GL00637 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZE646 UT WOS:000072815400002 ER PT J AU Gonzalez, WD de Gonzalez, ALC Dal Lago, A Tsurutani, BT Arballo, JK Lakhina, GK Buti, B Ho, CM Wu, ST AF Gonzalez, WD de Gonzalez, ALC Dal Lago, A Tsurutani, BT Arballo, JK Lakhina, GK Buti, B Ho, CM Wu, ST TI Magnetic cloud field intensities and solar wind velocities SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GEOMAGNETIC-ACTIVITY; STORMS; ORIGIN AB For the sets of magnetic clouds studied in this work we have shown the existence of a relationship between their peak magnetic field strength and peak velocity values, with a clear tendency that clouds which move at higher speeds also possess higher core magnetic field strengths. This result suggests a possible intrinsic property of magnetic clouds and also implies a geophysical consequence. The relatively low field strengths at. low velocities is presumably the cause of the lack of intense storms during low speed ejecta. There is also an indication that this type of behavior is peculiar for magnetic clouds, whereas other types of non cloud-driver gas events do not seem to show a similar relationship, at least for the data studied in this paper. We suggest that a field/speed relationship for magnetic clouds, as that obtained in our present study, could be associated with the cloud release and acceleration mechanism at the sun. Since for magnetic clouds the total field tyically has a substantial southward component, B-s, our results imply that the interplanetary dawn-dusk electric field, given by v x B-s (where v is the cloud's velocity), is enhanced by both factors. Therefore, the consequent magnetospheric energization (that, is governed by this electric field) becomes more efficient for the occurrence of magnetic storms. C1 Inst Nacl Pesquisas Espaciais, BR-12201970 Sao Jose Dos Campos, SP, Brazil. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. Univ Alabama, Dept Mech & Aerosp Engn, Huntsville, AL 35899 USA. RP Gonzalez, WD (reprint author), Inst Nacl Pesquisas Espaciais, CP 515, BR-12201970 Sao Jose Dos Campos, SP, Brazil. RI Lakhina, Gurbax /C-9295-2012 NR 15 TC 54 Z9 54 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 1998 VL 25 IS 7 BP 963 EP 966 DI 10.1029/98GL00703 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZE646 UT WOS:000072815400007 ER PT J AU Webster, CR May, RD Michelsen, HA Scott, DC Wilson, JC Jonsson, HH Brock, CA Dye, JE Baumgardner, D Stimpfle, RM Koplow, JP Margitan, JJ Proffitt, MH Jaegle, L Herman, RL Hu, H Flesch, GJ Loewenstein, M AF Webster, CR May, RD Michelsen, HA Scott, DC Wilson, JC Jonsson, HH Brock, CA Dye, JE Baumgardner, D Stimpfle, RM Koplow, JP Margitan, JJ Proffitt, MH Jaegle, L Herman, RL Hu, H Flesch, GJ Loewenstein, M TI Evolution of HCl concentrations in the lower stratosphere from 1991 to 1996 following the eruption of Mt. Pinatubo SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SULFATE AEROSOLS; MOUNT-PINATUBO; CHLORINE; NO2; SPECTROMETER; AIRCRAFT; HNO3; CLO; CHEMISTRY AB In situ measurements of hydrochloric acid in the lower stratosphere reveal that its mean abundance relative to that of total inorganic chlorine (Cl-y) has evolved upwards from HCl/Cl-gamma=40% in late 1991 to 70% in 1996. This fraction is generally anticorrelated with aerosol surface area concentration, which has been diminishing since the 1991 volcanic eruption of Mt. Pinatubo. Calculations incorporating new laboratory results of faster heterogeneous chemistry show that air parcels with high aerosol loading exposed to temperatures below 205 K can experience enough chlorine activation to drive the HCl/Cl-y below 50%, but overestimate observed ClO/Cl-y. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Univ Denver, Dept Engn, Denver, CO 80208 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Webster, CR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Brock, Charles/G-3406-2011; Herman, Robert/H-9389-2012 OI Brock, Charles/0000-0002-4033-4668; Herman, Robert/0000-0001-7063-6424 NR 31 TC 18 Z9 18 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 1 PY 1998 VL 25 IS 7 BP 995 EP 998 DI 10.1029/98GL00548 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZE646 UT WOS:000072815400016 ER PT J AU Cliver, EW Boriakoff, V Feynman, J AF Cliver, EW Boriakoff, V Feynman, J TI Solar variability and climate change: Geomagnetic aa index and global surface temperature SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MEDIEVAL WARM PERIOD; MAUNDER MINIMUM; CYCLE; MAXIMUM; WIND AB During the past similar to 120 years, Earth's surface temperature is correlated with both decadal averages and solar cycle minimum values of the geomagnetic aa index. The correlation with aa minimum values suggests the existence of a long-term (low-frequency) component of solar irradiance that underlies the 11-year cyclic component. Extrapolating the aa-temperature correlations to Maunder Minimum geomagnetic conditions implies that solar forcing can account for similar to 50% or more of the estimated similar to 0.7-1.5 degrees C increase in global surface temperature since the second half of the 17th century. Our analysis is admittedly crude and ignores known contributors to climate change such as warming by anthropogenic greenhouse-gases or cooling by volcanic aerosols. Nevertheless, the general similarity in the time-variation of Earth's surface temperature and the low-frequency or secular component of the aa index over the last similar to 120 years supports other studies that indicate a more significant role for solar variability in climate change on decadal and century time-scales than has previously been supposed. The most recent aa data for the current solar minimum suggest that the longterm component of solar forcing will level off or decline during the coming solar cycle. C1 AFRL, Space Vehicles Directorate, Hanscom AFB, MA 01731 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Natl Res Council, Washington, DC 20418 USA. RP Cliver, EW (reprint author), AFRL, Space Vehicles Directorate, Hanscom AFB, MA 01731 USA. EM cliver@plh.af.mil; boriakof@amenra.plh.af.mil; jfeynman@jplsp.jpl.nasa.gov NR 25 TC 89 Z9 90 U1 0 U2 5 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 1998 VL 25 IS 7 BP 1035 EP 1038 DI 10.1029/98GL00499 PG 4 WC Geosciences, Multidisciplinary SC Geology GA ZE646 UT WOS:000072815400026 ER PT J AU Baines, KH Yanamandra-Fisher, PA Lebofsky, LA Momary, TW Golisch, W Kaminski, C Wild, WJ AF Baines, KH Yanamandra-Fisher, PA Lebofsky, LA Momary, TW Golisch, W Kaminski, C Wild, WJ TI Near-infrared absolute photometric imaging of the Uranian system SO ICARUS LA English DT Article ID ORGANIC-MATTER; GIANT PLANETS; SOLAR-SYSTEM; WATER ICE; SPECTROPHOTOMETRY; RINGS; SATELLITES; URANUS; METHANE; NEPTUNE AB We report the first multifilter set of absolutely calibrated near-infrared images of Uranus, its rings, and three major satellites-Titania, Ariel, and Miranda. Along with imagery utilizing the canonical K filter bandpass (effective wavelength 2.20 mu m), absolutely calibrated images of the uranian system are presented for the first time for three additional filter bandpasses: J (1.27 mu m), H (1.62 mu m), and in a narrow bandpass (0.1 mu m full-width-at-half-maximum) centered at 1.73 mu m thereafter designated H') particularly diagnostic of C-H stretch vibrational absorptions common in hydrocarbons. Multifilter-derived spectra of the southern ring ansa including the bright apoapse of the dominant epsilon ring show no absorptions due to condensable volatiles, including water, ammonia, and light thigh H:C) hydrocarbons. Plausible near-infrared spherical geometric and single-scattering particle albedos consistent with Voyager-derived phase functions range from 0.069 to 0.102 and from 0.030 to 0.037, respectively. These are approximately 50% greater than visible values, consistent with the optical properties of charcoal, carbonaceous chondrite material, and the darkside of Iapetus, and consistent with the hypothesis that a primary component of the ring particles is high stoichiometric ratio C : if organics produced by charged-particle and/or photochemical weathering of methane clathrate and/or hydrocarbon ice material originating from nearby moonlets. Additional components consistent with the ring spectrum include silicates such as pyroxene, but not olivine. Analytical modeling of the ring structure indicates e-ring near-infrared opacities of 0.37 +/- 0.05 and 1.8 +/- 0.3 at apoapsis and periapsis, respectively. Ariel is more than 25% brighter than Miranda and 15% brighter than Titania at all near-infrared wavelengths. Comparisons with UV-visible spectra by Karkoschka (1997, Icarus 125, 348-363) show consistency with the hypothesis that the water-ice surfaces of Titania and Ariel are contaminated with low-reflectance, near-IR-reddened substances similar to the weathered high C:H material postulated for the uranian ring system, The relatively blue, near-infrared dark surface of Miranda (full-disk near-infrared albedo of similar to 0.22 at 2.4 degrees phase angle) exhibits the greatest water ice absorption band-depth and the largest H- and K-filter brightness surge measured among the uranian satellites, consistent with (1) a markedly heterogeneous surface punctuated with localized outcroppings of relatively pure water ice and (2), as with Titania and Ariel, a surface composition dominated in the near infrared by weathered high C:H material. The uranian disk shows marked latitudinal variability in tropospheric cloud structure, with a "polar cap" of aerosols lying within the planet's southern polar region. This is in sharp contrast with the stratospheric haze structure, which is nearly globally uniform. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. NASA, Infrared Telescope Facil, Honolulu, HI 96822 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. RP Baines, KH (reprint author), CALTECH, Jet Prop Lab, M-S 183-601,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 53 TC 22 Z9 22 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 1998 VL 132 IS 2 BP 266 EP 284 DI 10.1006/icar.1998.5894 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP735 UT WOS:000073783200004 ER PT J AU Cabrol, NA Grin, EA Landheim, R AF Cabrol, NA Grin, EA Landheim, R TI Ma'adim Vallis evolution: Geometry and models of discharge rate SO ICARUS LA English DT Article ID MARS AB Episodes of confined flows in Ma'adim Vallis are reconstructed by surveying the terraces in the valley. Three major levels and their associated tributary systems are identified and mapped. This study points out the evidence of the cessation of the valley activity between the formation of levels 1 and 2, characterized by degraded and large perched valleys, which floor are not adjusted to the following flow episode level. A strong asymmetry in the tributary distribution points toward a groundwater-supplied water origin of the valley. Potential source areas are demonstrated to be in volcano-tectonic regions, implying a hydrothermal origin of the water, that may include melted permafrost. Calculation of hydraulic radii, valley sections, and models of discharge rates associated with the morphologic and geologic survey shows that Ma'adim Vallis was an episodic channel, the lifetime of which spanned between the Noachian and Amazonian. (C) 1998 Academic Press. C1 NASA, SETI Inst, Ames Res Ctr, Space Sci Div,Ctr Mars Explorat, Moffett Field, CA 94035 USA. RP Cabrol, NA (reprint author), NASA, SETI Inst, Ames Res Ctr, Space Sci Div,Ctr Mars Explorat, MS 239-20, Moffett Field, CA 94035 USA. EM ncabrol@mail.arc.nasa.gov NR 20 TC 31 Z9 31 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 1998 VL 132 IS 2 BP 362 EP 377 DI 10.1006/icar.1998.5903 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZP735 UT WOS:000073783200010 ER PT J AU Mehrotra, P Van Rosendale, J Zima, HP AF Mehrotra, P Van Rosendale, J Zima, HP TI Language support for multidisciplinary applications SO IEEE COMPUTATIONAL SCIENCE & ENGINEERING LA English DT Article ID PARALLEL AB The authors survey multidisciplinary-application characteristics and derive a corresponding set of language requirements, focusing on modular system design and multilevel parallelism. After evaluating the MDA compatibility of several languages and paradigms, they present Opus, the language they designed to support MDA requirements. C1 NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. Univ Vienna, Inst Software Technol & Parallel Syst, A-1090 Vienna, Austria. RP Mehrotra, P (reprint author), NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, MS 403, Hampton, VA 23681 USA. EM pm@icase.edu; jvr@icase.edu; zima@par.univie.ac.at NR 11 TC 3 Z9 3 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1070-9924 J9 IEEE COMPUT SCI ENG JI IEEE Comput. Sci. Eng. PD APR-JUN PY 1998 VL 5 IS 2 BP 64 EP 75 DI 10.1109/99.683744 PG 12 WC Computer Science, Theory & Methods; Engineering, Electrical & Electronic; Mathematics, Applied SC Computer Science; Engineering; Mathematics GA ZV451 UT WOS:000074305900009 ER PT J AU Kory, CL Dayton, JA AF Kory, CL Dayton, JA TI Accurate cold-test model of helical TWT slow-wave circuits SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE attenuation; dispersion; helix; impedance; simulation; traveling-wave tube AB Recently, a method has been established to accurately calculate cold-test data ibr helical slow-wave structures using the three-dimensional (3-D) electromagnetic computer code, MAFIA [1], Cold-test parameters have? been calculated for several helical traveling-wave tube (TWT) slow-wave circuits possessing various support rod configurations, and results are presented here showing excellent agreement with experiment, The helical models include tape thickness, dielectric support shapes and material properties consistent with the actual circuits, The cold-test data from this helical model can be used as input into large-signal helical TWT interaction codes making it possible, for the first time, to design a complete TWT via computer simulation. C1 NASA, Lewis Res Ctr, Analex Corp, Cleveland, OH 44135 USA. RP Kory, CL (reprint author), NASA, Lewis Res Ctr, Analex Corp, Cleveland, OH 44135 USA. NR 17 TC 42 Z9 57 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 APR PY 1998 VL 45 IS 4 BP 966 EP 971 DI 10.1109/16.662812 PG 6 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA ZD214 UT WOS:000072662800031 ER PT J AU Kory, CL Dayton, JA AF Kory, CL Dayton, JA TI Effect of helical slow-wave circuit variations on TWT cold-test characteristics SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE dispersion; helix; impedance; manufacturing tolerances; traveling-wave tube AB Recent advances in the state of the art of computer modeling offer the possibility for the first time to evaluate the effect that slow-wave structure parameter variations, such as manufacturing tolerances, have on the cold-test characteristics of helical traveling-wave tubes (TWT's). This will enable manufacturers to determine the cost effectiveness of controlling the dimensions of the component parts of the TWT, which is almost impossible to do experimentally without building a large number of tubes and controlling several parameters simultaneously. The computer code MAFIA is used in this analysis fu determine the effect on dispersion and on-axis interaction impedance of several helical slow-wave circuit parameter variations, including thickness and relative dielectric constant of the support rods, tape width, and height of the metallized films deposited on the dielectric rods, Previous computer analyzes required so many approximations that accurate determinations of the effect of many relevant dimensions on tube performance were practically impossible. C1 NASA, Lewis Res Ctr, Analex Corp, Cleveland, OH 44135 USA. RP Kory, CL (reprint author), NASA, Lewis Res Ctr, Analex Corp, Cleveland, OH 44135 USA. NR 8 TC 25 Z9 33 U1 0 U2 5 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 APR PY 1998 VL 45 IS 4 BP 972 EP 976 DI 10.1109/16.662813 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA ZD214 UT WOS:000072662800032 ER PT J AU Manduchi, R Perona, P Shy, D AF Manduchi, R Perona, P Shy, D TI Efficient deformable filter banks SO IEEE TRANSACTIONS ON SIGNAL PROCESSING LA English DT Letter DE filter banks; multirate filtering; pattern analysis; steerable filters AB This correspondence describes efficient schemes for the computation of a large number of differently scaled/oriented filtered versions of an image. We generalize the well-known steerable/scalable ("deformable") filter bank structure by imposing X-Y separability on the basis filters. The resulting systems, designed by an iterative projections technique, achieve substantial reduction of the computational cost. To reduce the memory requirement, we adopt a multirate implementation. Due to the inner sampling rate alteration, the resulting structure is not shift invariant. We introduce a design criterion for multirate deformable structures that jointly controls the approximation error and the shirt variance. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Padua, Dept Elect & Informat, Padua, Italy. RP Manduchi, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 17 Z9 17 U1 2 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1053-587X J9 IEEE T SIGNAL PROCES JI IEEE Trans. Signal Process. PD APR PY 1998 VL 46 IS 4 BP 1168 EP 1173 DI 10.1109/78.668570 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA ZD453 UT WOS:000072687500032 ER PT J AU Shen, HW Kao, DL AF Shen, HW Kao, DL TI A new line integral convolution algorithm for visualizing time-varying flow fields SO IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS LA English DT Article; Proceedings Paper CT 8th Annual IEEE Conference on Visualization CY OCT 19-24, 1997 CL PHOENIX, AZ SP IEEE Comp Soc, Tech Comm Comp Graph, ACM, SIGGRAPH DE flow visualization; vector field visualization; image convolution; line integral convolution; flow animation; unsteady flows; texture synthesis; parallel algorithm AB New challenges on vector field visualization emerge as time-dependent numerical simulations become ubiquitous in the field of computational fluid dynamics (CFD). To visualize data generated from these simulations, traditional techniques, such as displaying particle traces, can only reveal flow phenomena in preselected local regions and, thus, are unable to track the evolution of global flow features over time. This paper presents a new algorithm, called UFLIC (Unsteady Flow LIC), to visualize Vector data in unsteady flow fields. Our algorithm extends a texture synthesis technique, called Line integral Convolution (LIC), by devising a new convolution algorithm that uses a time-accurate value scattering scheme to model the texture advection. In addition, our algorithm maintains the coherence of the flow animation by successively updating the convolution results over time. Furthermore. we propose a parallel UFLIC algorithm that can achieve high load-balancing for multiprocessor computers with shared memory architecture. We demonstrate the Effectiveness of our new algorithm by presenting image snapshots from several CFD case studies. C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. RP NASA, Ames Res Ctr, MRJ Technol Solut, Mail Stop T27A-2, Moffett Field, CA 94035 USA. EM hwshen@nas.nasa.gov; davidkao@nas.nasa.gov RI Shen, Han-wei/A-4710-2012 NR 13 TC 50 Z9 57 U1 0 U2 4 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1077-2626 EI 1941-0506 J9 IEEE T VIS COMPUT GR JI IEEE Trans. Vis. Comput. Graph. PD APR-JUN PY 1998 VL 4 IS 2 BP 98 EP 108 DI 10.1109/2945.694952 PG 11 WC Computer Science, Software Engineering SC Computer Science GA ZX108 UT WOS:000074480200002 ER PT J AU Lelkes, PI Galvan, DL Hayman, GT Goodwin, TJ Chatman, DY Cherian, S Garcia, RMG Unsworth, BR AF Lelkes, PI Galvan, DL Hayman, GT Goodwin, TJ Chatman, DY Cherian, S Garcia, RMG Unsworth, BR TI Simulated microgravity conditions enhance differentiation of cultured PC12 cells towards the neuroendocrine phenotype SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Article DE PC12 cells; cell culture; PNMT; TH; differentiation; PCR; rotating wall vessel bioreactor; simulated microgravity ID PHENYLETHANOLAMINE N-METHYLTRANSFERASE; NERVE GROWTH-FACTOR; CATECHOLAMINE BIOSYNTHETIC-ENZYMES; ADRENAL PHEOCHROMOCYTOMA CELLS; MEDULLARY ENDOTHELIAL-CELLS; ROTATING-WALL VESSEL; TYROSINE-HYDROXYLASE; CHROMAFFIN CELLS; GENE-EXPRESSION; NEURAL CREST AB We are studying microenvironmental cues which contribute to neuroendocrine organ assembly and tissue-specific differentiation. As our in, vitro model. we cultured rat adrenal medullary PC12 pheochromocytoma cells in a novel cell culture system, the NASA rotating wall vessel (RWV) bioreactors. This "simulated microgravity" environment in RWV bioreactors, characterized by randomizing gravitational vectors and minimizing shear stress, has been shown to favor macroscopic tissue assembly and to induce tissue-specific differentiation. me hypothesized that the unique culture conditions in the RWV bioreactors might enhance the in vitro formation of neuroendocrine organoids. To test our hypothesis, we evaluated the expression of several markers of neuroendocrine differentiation in cultures of PC12 cells maintained for up to 20 d in the slow turning lateral vessel (STLV) type RWW. PC12 cell differentiation was assessed by morphological, immunological, biochemical and molecular techniques. PC12 cells, cultured under "simulated microgravity" conditions, formed macroscopic, tissue-like organoids several millimeters in diameter. Concomitantly, the expression of phenylethanolamine-N-methyl transferase (PNMT), but not of other catecholamine synthesizing enzymes, was enhanced. Increased PNMT expression, as verified on both the gene and protein level, was accompanied by an increase in the specific activity of the enzyme. Furthermore, after 20 d in culture in the STLV we observed altered patterns of protein tyrosine phosphorylation and prolonged activation of c-Sos, a member of the AP-1 nuclear transcription factor complex. We conclude that culture conditions in the RWV appear to selectively activate signal transduction pathways leading to enhanced neuroendocrine differentiation of PC12 cells. C1 Univ Wisconsin, Sch Med, Dept Med, Cell Biol Lab,Sinai Samaritan Med Ctr, Milwaukee, WI 53201 USA. Marquette Univ, Dept Biol, Milwaukee, WI 53233 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Lelkes, PI (reprint author), Univ Wisconsin, Sch Med, Dept Med, Cell Biol Lab,Sinai Samaritan Med Ctr, Winter Res Bldg,Milwaukee Clin Campus, Milwaukee, WI 53201 USA. NR 58 TC 48 Z9 49 U1 0 U2 4 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1071-2690 J9 IN VITRO CELL DEV-AN JI In Vitro Cell. Dev. Biol.-Anim. PD APR PY 1998 VL 34 IS 4 BP 316 EP 325 PG 10 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA ZH779 UT WOS:000073146800008 PM 9590505 ER PT J AU Chien, SA AF Chien, SA TI Static and completion analysis for knowledge acquisition, validation and maintenance of planning knowledge bases SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Article AB A key obstacle hampering the fielding of AI planning applications is the considerable expense of developing, verifying, updating and maintaining the planning knowledge base (KB). Planning systems must be able to compare favorably in terms of software lifecycle costs to other means of automation such as scripts or rule-based expert systems. Consequently, in order to field real systems, planning practitioners must be able to provide (1) tools to allow domain experts to create and debug their own planning knowledge bases; (2) tools for software verification, validation and testing and(3) tools to facilitate updates and maintenance of the planning knowledge base. This paper begins by describing a planning application of automated image processing and our overall approach to knowledge acquisition for this application. This paper then describes two types of tools for planning knowledge-base development: static KB analysis techniques to detect certain classes of syntactic errors in a planning knowledge-base and completion analysis techniques to interactively debug the planning knowledge base. We describe these knowledge development tools and describe empirical results documenting the usefulness of these tools. (C) 1998 Academic Press Limited. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chien, SA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 126-347, Pasadena, CA 91109 USA. NR 22 TC 3 Z9 3 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1071-5819 J9 INT J HUM-COMPUT ST JI Int. J. Hum.-Comput. Stud. PD APR PY 1998 VL 48 IS 4 BP 499 EP 519 DI 10.1006/ijhc.1997.0171 PG 21 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA ZU689 UT WOS:000074223500005 ER PT J AU Oboe, R Fiorini, P AF Oboe, R Fiorini, P TI A design and control environment for Internet-based telerobotics SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article ID TIME-DELAY; DYNAMICAL-SYSTEMS; STATE-DELAY AB This paper describes an environment for the design, simulation, and control of Internet-based force-reflecting telerobotic systems. We define these systems as using a segment of the computer network to connect the master to the slave. Computer networks introduce a time delay that is best described by a time-varying random process. Thus, known techniques for controlling time-delay telerobots are not directly applicable, and an environment for iterative designing and testing is necessary. The underlying software architecture supports tools for modeling the delay of the computer network, designing a stable controller simulating the performance of a telerobotic system, and testing the control algorithms using a force-reflecting input device. Furthermore, this setup provides data about including the Internet into more general telerobotic control architectures. To demonstrate the features of this environment, the complete procedure for the design of a telerobotic controller is discussed. First, the delay parameters of an Internet segment are identified by probing the network. Then, these parameters are used in the design of a controller that includes a quasi-optimal estimator to compensate small data losses. Finally, simulations of the complete telerobotic system and emulations using a planar-force-reflecting master and a virtual slave exemplify a typical design-and-test sequence. C1 Univ Padua, Dipartimento Elettron & Informat, I-35131 Padua, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Oboe, R (reprint author), Univ Padua, Dipartimento Elettron & Informat, I-35131 Padua, Italy. RI Fiorini, Paolo/A-2603-2012; OI Oboe, Roberto/0000-0003-3078-2915 NR 33 TC 101 Z9 106 U1 0 U2 4 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 0278-3649 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD APR PY 1998 VL 17 IS 4 BP 433 EP 449 DI 10.1177/027836499801700408 PG 17 WC Robotics SC Robotics GA ZR126 UT WOS:000073939000008 ER PT J AU Eckstein, MP Whiting, JS AF Eckstein, MP Whiting, JS TI Why do anatomic backgrounds reduce lesion detectability? SO INVESTIGATIVE RADIOLOGY LA English DT Article DE visual detection; medical image perception; anatomic backgrounds; image noise ID VISUAL SIGNAL-DETECTION; CONTRAST GAIN-CONTROL; STRUCTURED NOISE; HUMAN-VISION; DISCRIMINATION; MASKING; CONSPICUITY; MECHANISMS; MODELS AB RATIONALE AND OBJECTIVES. Developing metrics of medical image quality requires an understanding of how anatomic backgrounds reduce human visual detection performance, Visual psychophysics has shown that there are two distinct ways in which a complex background can degrade performance: (1) the presence of a deterministic high-contrast background, (2) variability in the background from location to location, The authors investigated how these two sources of performance degradation reduce human visual performance locating a lesion in anatomic backgrounds, METHODS. Human performance localizing a disk-shaped lesion in one of four locations (four alternative forced choice) was measured for three background conditions, In the first condition the background was a uniform gray, In the second condition (the repeated background condition) an anatomic background was sampled on each trial and used as a background for the four possible lesion locations, In the third condition (the different background condition) four different anatomic backgrounds were sampled on each trial and used for the four possible lesion locations, Test images consisted of computer simulated lesions mathematically projected on digital x-ray coronary angiograms, RESULTS. For five levels of lesion contrast, visual detection performance for two observers decreased significantly from the uniform background condition to the repeated background condition, and decreased even further for the different background condition. CONCLUSIONS. Study results show that both the presence of a deterministic high-contrast background and the background variations contribute to performance degradation of human visual detection of signals in anatomic backgrounds. C1 Univ Calif Los Angeles, Cedars Sinai Med Ctr, Sch Med, Dept Med Phys & Imaging, Los Angeles, CA 90048 USA. NASA, Human & Syst Technol Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Eckstein, MP (reprint author), Univ Calif Los Angeles, Cedars Sinai Med Ctr, Sch Med, Dept Med Phys & Imaging, 8700 Beverly Blvd,D-6065, Los Angeles, CA 90048 USA. FU NHLBI NIH HHS [IRO1HL 53455] NR 33 TC 6 Z9 6 U1 0 U2 2 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0020-9996 J9 INVEST RADIOL JI Invest. Radiol. PD APR PY 1998 VL 33 IS 4 BP 203 EP 208 DI 10.1097/00004424-199804000-00002 PG 6 WC Radiology, Nuclear Medicine & Medical Imaging SC Radiology, Nuclear Medicine & Medical Imaging GA ZE423 UT WOS:000072791100002 PM 9556744 ER PT J AU Kummerow, C AF Kummerow, C TI Beamfilling errors in passive microwave rainfall retrievals SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID TIME STOCHASTIC-MODEL; RADIATIVE-TRANSFER; TROPICAL RAINFALL; SAMPLING ERRORS; CLOUDS; SATELLITES; FIELD AB There are currently large numbers of rainfall retrieval algorithms based upon passive microwave radiances. Most of these algorithms are physically based in that they use explicit physical assumptions to derive relationships between brightness temperatures (Tb's) and rainfall. If these assumptions involve observable quantities, then the physical basis of the algorithms can be extended to determine fundamental uncertainties in the retrieved precipitation fields. In this paper this process begins by examining the largest uncertainty in many of the physical models-the homogenous rainfall assumption. Four months of Tropical Oceans Global Atmosphere Coupled Ocean-Atmosphere Response Experiment shipborne radar data is used to describe the horizontal characteristics of win. The vertical hydrometeor structures needed to simulate the upwelling Tb are taken from a dynamic al cloud model. Radiative transfer computations were performed using a fully three-dimensional Monte Carlo solution in order to test all aspects of the beamfilling problem. Results show that biases as well as random errors depend upon the assumed vertical structure of hydrometeors, the manner in which inhomogeneity is modeled in the retrieval, and the manner in which the radiative transfer problem is handled. Unlike previous works. the goal of this paper is not to determine a mean beamfilling correction or a vertical hydrometeor profile that should be applied to specific retrieval algorithms. Rather, it is to explore the impact of inhomogeneous rainfall upon the predicted brightness temperatures so that these relations may eventually be used to develop a physically based error model for microwave precipitation retrievals. Because the predicted Tb's depend upon assumed cloud vertical structures, the paper offers a procedure to account for the uncertainty introduced by rainfall inhomogeneity rather than a general result. The impact of inhomogeneous rainfall upon specific algorithms must still be investigated within the context of that specific algorithm. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Kummerow, C (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. NR 16 TC 74 Z9 78 U1 1 U2 4 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 APR PY 1998 VL 37 IS 4 BP 356 EP 370 DI 10.1175/1520-0450(1998)037<0356:BEIPMR>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD977 UT WOS:000072744700002 ER PT J AU Wylie, DP Santek, D Starr, DO AF Wylie, DP Santek, D Starr, DO TI Cloud-top heights from GOES-8 and GOES-9 stereoscopic imagery SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID INFRARED RADIANCES; SATELLITES; INFERENCE; FIELDS; ISCCP AB Operational satellite data from GOES-S and GOES-9 were used to make stereoscopic measurements of cloud heights during the National Aeronautics and Space Administration's Subsonic Aircraft: Contrail and Cloud Effects Special Study program. The stereoscopic data were used to differentiate between boundary layer wave clouds and cirrus in the mid-and upper troposphere. This separation was difficult to evaluate from radiometric data alone. Stereographic cloud height analysis provided a definitive result. The technique used for calculating cloud brights is described. GOES-S and -9 data were better suited for stereoscopic measurements than data from previous satellites. C1 Univ Wisconsin, Ctr Space Sci & Engn, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wylie, DP (reprint author), Univ Wisconsin, Ctr Space Sci & Engn, 1225 W Dayton St, Madison, WI 53706 USA. EM donw@ssec.wisc.edu NR 24 TC 12 Z9 14 U1 2 U2 4 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 APR PY 1998 VL 37 IS 4 BP 405 EP 413 DI 10.1175/1520-0450(1998)037<0405:CTHFGA>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZD977 UT WOS:000072744700006 ER PT J AU McCall, GE Allen, DL Linderman, JK Grindeland, RE Roy, RR Mukku, VR Edgerton, VR AF McCall, GE Allen, DL Linderman, JK Grindeland, RE Roy, RR Mukku, VR Edgerton, VR TI Maintenance of myonuclear domain size in rat soleus after overload and growth hormone/IGF-I treatment SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE compensatory hypertrophy; satellite cells; synergist ablation; growth factors; myonuclear number; functional overload ID MULTIPLICATION-STIMULATING ACTIVITY; SATELLITE CELL-PROLIFERATION; SKELETAL-MUSCLE FIBERS; IGF-I; COMPENSATORY HYPERTROPHY; PROTEIN-SYNTHESIS; GENE-EXPRESSION; SUSPENDED RATS; INSULIN; EXERCISE AB The purpose of this study was to determine the effects of functional overload (FO) combined with growth hormone/insulin-like growth factor I (GH/IGF-I) administration on myonuclear number and domain size in rat soleus muscle fibers. Adult female rats underwent bilateral ablation of the plantaris and gastrocnemius muscles and, after 7 days of recovery, were injected three times daily for 14 days with GH/IGF-I (1 mg/kg each; FO + GH/IGF-I group) or saline vehicle (FO group). Intact rats receiving saline vehicle served as controls (Con group). Muscle wet weight was 32% greater in the FO than in the Con group: 162 +/- 8 vs. 123 +/- 16 mg. Muscle weight in the FO + GH/IGF-I group (196 +/- 14 mg) was 59 and 21% larger than in the Con and FO groups, respectively. Mean soleus fiber cross-sectional area of the FO + GH/IGF-I group (2,826 +/- 445 mu m(2)) was increased compared with the Con(2,044 +/- 108 mu m(2)) and FO (2,267 +/- 301 mu m(2)) groups. The difference in fiber size between the FO and Con groups was not significant. Mean myonuclear number increased in FO (187 +/- 15 myonuclei/mm) and FO + GH/IGF-I (217 +/- 23 myonuclei/mm) rats compared with Con (155 +/- 12 myonuclei/mm) rats, although the difference between FO and FO + GH/IGF-I animals was not significant. The mean cytoplasmic volume per myonucleus (myonuclear domain) was similar across groups. These results demonstrate that the larger mean muscle weight and fiber cross-sectional area occurred when FO was combined with GH/IGF-I administration and that myonuclear number increased concomitantly with fiber volume. Thus there appears to be some mechanism(s) that maintains the myonuclear domain when a fiber hypertrophies. C1 Univ Calif Los Angeles, Dept Phys Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Brain Res Inst, Los Angeles, CA 90095 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Genentech Inc, S San Francisco, CA 94080 USA. RP McCall, GE (reprint author), Univ Calif Los Angeles, Dept Phys Sci, 621 Circle Dr S,2301 Life Sci, Los Angeles, CA 90095 USA. FU NIDCR NIH HHS [DE-07212]; NINDS NIH HHS [NS-16333] NR 38 TC 75 Z9 77 U1 1 U2 4 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD APR PY 1998 VL 84 IS 4 BP 1407 EP 1412 PG 6 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA ZD714 UT WOS:000072716100040 PM 9516210 ER PT J AU Gosselink, KL Grindeland, RE Roy, RR Zhong, H Bigbee, AJ Grossman, EJ Edgerton, VR AF Gosselink, KL Grindeland, RE Roy, RR Zhong, H Bigbee, AJ Grossman, EJ Edgerton, VR TI Skeletal muscle afferent regulation of bioassayable growth hormone in the rat pituitary SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE immunoassay; bioassay; proprioception; electrical stimulation; peripheral nerves; low-threshold afferents ID ANTERIOR-PITUITARY; INNERVATION; TRANSPORT; VARIANTS; EXERCISE AB There are forms of growth hormone (GH) in the plasma and pituitary of the rat and in the plasma of humans that are undetected by presently available immunoassays (iGH) but can be measured by bioassay (bGH). Although the regulation of iGH release is well documented, the mechanism(s) of bGH release is unclear. On the basis of changes in bGH and iGH secretion in rats that had been exposed to microgravity conditions, we hypothesized that neural afferents play a role in regulating the release of these hormones. To examine whether bGH secretion can be modulated by afferent input from skeletal muscle, the proximal or distal ends of severed hindlimb fast muscle nerves were stimulated (similar to 2 times threshold) in anesthetized rats. Plasma bGH increased similar to 250%, and pituitary bGH decreased similar to 60% after proximal nerve trunk stimulation. The bGH response was independent of muscle mass or whether the muscles were flexors or extensors. Distal nerve stimulation had little or no effect on plasma or pituitary bGH. Plasma iGH concentrations were unchanged after proximal nerve stimulation. Although there may be multiple regulatory mechanisms of bGH, the present results demonstrate that the activation of low-threshold afferents from fast skeletal muscles can play a regulatory role in the release of bGH, but not iGH, from the pituitary in anesthetized rats. C1 Univ Calif Los Angeles, Dept Physiol Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Brain Res Inst, Los Angeles, CA 90095 USA. NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. RP Edgerton, VR (reprint author), Univ Calif Los Angeles, Dept Physiol Sci, 1804 Life Sci,405 Hilgard Ave, Los Angeles, CA 90095 USA. FU NIDCR NIH HHS [DE-07212] NR 29 TC 35 Z9 37 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 8750-7587 J9 J APPL PHYSIOL JI J. Appl. Physiol. PD APR PY 1998 VL 84 IS 4 BP 1425 EP 1430 PG 6 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA ZD714 UT WOS:000072716100043 PM 9516213 ER PT J AU Schueler, CF Barnes, WL AF Schueler, CF Barnes, WL TI Next-generation MODIS for polar operational environmental satellites SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID IMAGING SPECTROMETER MODIS; WATER-VAPOR; ALGORITHMS; NDVI; EOS AB The Moderate Resolution Imaging Spectroradiometer (MODIS) protoflight model has bran delivered to the NASA Earth Observing System AM-1 platform project to provide highly calibrated, near daily, global atmosphere, land, and ocean observation in 36 spectral channels. MODIS includes extensive in-flight calibration allowing improved environmental data products addressing the visible-infrared imaging Environmental Data Records required by the National Polar-Orbiting Operational Environmental Satellite System. NASA is considering Advanced MODIS concepts to dramatically reduce MODIS mass, power, and volume. Alternatively, next-generation MODIS Light options carl substantially reduce MODIS cost, mass, power, and size bur retain the core MODIS optical bench assembly spectroradiometric sensing subsystem to minimize both performance risk and changes to the data processing algorithms. These MODIS Light options range from in-flight calibration hardware removal to instrument repackaging and scanner redesign. The simplest modification results in a 17% mass reduction. while scanner redesign results in 40% mass and volume reduction. C1 Hughes Santa Barbara Remote Sensing, Goleta, CA 93117 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Schueler, CF (reprint author), Hughes Santa Barbara Remote Sensing, Mail Stop B32-73,75 Coromar Dr, Goleta, CA 93117 USA. NR 23 TC 18 Z9 19 U1 0 U2 1 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 APR PY 1998 VL 15 IS 2 BP 430 EP 439 DI 10.1175/1520-0426(1998)015<0430:NGMFPO>2.0.CO;2 PG 10 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA ZD426 UT WOS:000072684000008 ER PT J AU Grebowsky, JM Goldberg, RA Pesnell, WD AF Grebowsky, JM Goldberg, RA Pesnell, WD TI Do meteor showers significantly perturb the ionosphere? SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID POSITIVE-ION COMPOSITION; MASS-SPECTROMETER; UPPER MESOSPHERE; SODIUM LAYERS; SPORADIC-E; REGION; LATITUDE AB More than 40 rocket flights through the main meteoric ionization layer, which peaks near 95 km, have sampled the meteoric metallic ion concentrations. Five of these flights were conducted during or near the peak times of a meteor shower. In each of the latter studies the observed meteoric ion concentrations were assumed to be a consequence of the shower. These measurements were not complemented by baseline observations made for similar ionospheric conditions immediately before the shower and no rigorous quantitative comparisons were made using average non-shower distributions. In order to further investigate the impact of the shower on the ionosphere, all published ion concentration altitude profiles obtained from sounding rockets in the meteoric ionization regime have been scanned to develop a digital data base of meteoric ion concentrations. These data are used to provide the first empirical altitude profile of the metallic ions. The average observed Mg+ concentrations are lower than those yielded by the most comprehensive model to date (McNeil et al., 1996). This compiled ensemble of data provides supporting evidence that meteor showers do have a significant impact on the average ionosphere composition. Although there is much variability in the observed meteoric layers, the peaks in the total metallic ion concentrations at mid-latitudes, on the dayside, observed during meteor showers had concentrations comparable to, or exceeding, the highest concentrations measured in the same altitude regions during non-shower periods. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Nomad Res Inc, Greenbelt, MD 20771 USA. RP Grebowsky, JM (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. EM u5jmg@lepvax.gsfc.nasa.gov RI Pesnell, William/D-1062-2012; Goldberg, Richard /E-1881-2012; Grebowsky, Joseph/I-7185-2013 OI Pesnell, William/0000-0002-8306-2500; NR 34 TC 30 Z9 30 U1 1 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 1998 VL 60 IS 6 BP 607 EP 615 DI 10.1016/S1364-6826(98)00004-2 PG 9 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 100HG UT WOS:000074810300005 ER PT J AU Raghavarao, R Suhasini, R Hoegy, WR Mayr, HG Wharton, L AF Raghavarao, R Suhasini, R Hoegy, WR Mayr, HG Wharton, L TI Local time variation of equatorial temperature and zonal wind anomaly (ETWA) SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID DYNAMICS EXPLORER-2; THERMOSPHERE; MODEL; SATELLITE AB We describe the average and apparent local (solar) time (LST) variations in the zonal winds (Z) and temperatures (T) as measured with the Wind and Temperature Spectrometer (WATS) on-board the polar orbiting DE-2 satellite in the altitude range of 300-450 km during a near solar maximum period of 1981-1982. During this time period, the variations in the solar flux (F10.7) and magnetic activity (Ap) contribute significantly to the apparent LST variations in T; while those effects on the LST variations in Z are small. The observations are related to the equatorial ionization anomaly (EIA) as seen in the electron density data obtained from the same satellite with the LANG instrument. The latitudinal variations in Z always reveal a maximum at the dip equator where the EIA trough forms and minima (with velocities reduced by a factor of two) are seen on either side of the equator where the EIA crests form. At 20:00 LST, the largest wind velocities are observed, directed eastward, after changing direction at around 17:00 LST where the largest accelerations occur. We delineate the diurnal variations in the strength of the Equatorial Temperature and Wind Anomaly (ETWA) defined by the differences in the wind velocities (DZ) and temperatures (DT) at the crests and troughs of the ionization. The diurnal variations in DZ are similar to those in Z at the trough. The diurnal variations in DT differ from those apparent in T. Excess temperatures, DT, at the crests show up with the development of the EIA as early as 09:30 LST by which time the zonal wind has attained its westward maximum. But DT continues to increase with the EIA crest until 14:00 LST, followed by a dip at around 16:00 LST in phase with the zero crossing of Z. The highest value of DT is only reached at 20:00 LST when both Z and the crest intensification reach their respective maxima. This demonstrates that the development of the equatorial temperature anomaly critically depends both on the development of the EIA crests and the zonal winds, which clearly establishes the primary role of ion drag in generating the ETWA phenomenon. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Phys Res Lab, Ahmedabad 380009, Gujarat, India. RP Raghavarao, R (reprint author), NASA, Goddard Space Flight Ctr, Code 910-4, Greenbelt, MD 20771 USA. NR 27 TC 16 Z9 17 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD APR PY 1998 VL 60 IS 6 BP 631 EP 642 DI 10.1016/S1364-6826(97)00130-2 PG 12 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 100HG UT WOS:000074810300007 ER PT J AU Leroy, SS AF Leroy, SS TI Detecting climate signals: Some Bayesian aspects SO JOURNAL OF CLIMATE LA English DT Article ID NATURAL VARIABILITY; GREENHOUSE AB A Bayesian approach to detecting forced climate signals in a dataset is presented. First, the detection algorithm derived is shown to be capable of uniquely identifying several signals optimally. Other detection techniques are shown to be limiting cases. Second, this approach naturally lends itself to rating models relatively according to their predictions. Both the accuracy of the model prediction and the precision of the prediction are accounted for in rating models. In general, complex models are less probable than simpler models. Finally, this approach to detection is used to detect a signal induced by the solar cycle in the surface temperature record over the past 100 yr. The solar cycle signal-to-noise ratio is found to be similar to 1 but is probably not detected. Estimates of the natural variability noise are taken from model prescriptions, each of which is vastly different. The Geophysical Fluid Dynamics Laboratory models, though, best match the residual temperature fluctuations after the signals are subtracted. The Bayesian viewpoint emphasizes the need for the estimation of uncertainties associated with model predictions. Without estimates of uncertainties it is impossible to determine the predictive capabilities of models. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Leroy, SS (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Mail Stop 183-335,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 20 TC 53 Z9 53 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 1998 VL 11 IS 4 BP 640 EP 651 DI 10.1175/1520-0442(1998)011<0640:DCSSBA>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK575 UT WOS:000073338900010 ER PT J AU Goody, R Haskins, R AF Goody, R Haskins, R TI Calibration of radiances from space SO JOURNAL OF CLIMATE LA English DT Article AB The authors compare the performance of broadband radiometers with spectrally dispersed measurements. Spectrally dispersed radiometers may be more accurately calibrated than is possible with broadband filter instruments. They also have a larger information content than have Alter measurements. Accuracy and information content are two important requirements for climate observations. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goody, R (reprint author), 101 Cumloden Dr, Falmouth, MA 02541 USA. NR 9 TC 19 Z9 19 U1 1 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD APR PY 1998 VL 11 IS 4 BP 754 EP 758 DI 10.1175/1520-0442(1998)011<0754:CORFS>2.0.CO;2 PG 5 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA ZK575 UT WOS:000073338900018 ER PT J AU Neudeck, PG AF Neudeck, PG TI Perimeter governed minority carrier lifetimes in 4H-SiC p(+)n diodes measured by reverse recovery switching transient analysis SO JOURNAL OF ELECTRONIC MATERIALS LA English DT Article; Proceedings Paper CT 39th Electronic Materials Conference (EMC) CY 1997 CL COLORADA STATE UNIV, FT COLLINS, COLORADO HO COLORADA STATE UNIV DE 4H-SiC; minority carrier lifetime; p-n junctions; surface recombination ID SILICON-CARBIDE; RECOMBINATION; SURFACE AB Minority carrier lifetimes in epitaxial 4H-SiC p(+)n junction diodes were measured via an analysis of reverse recovery switching characteristics. Behavior of reverse recovery storage time (t(s)) as a function of initial ON-state forward current (I-F) and OFF-state reverse current (I-R) followed well-documented trends which have been observed for decades in silicon p(+)n rectifiers. Average minority carrier (hole) lifetimes (tau(p)) calculated from plots of t(s) vs I-R/I-F strongly decreased with decreasing device area. Bulk and perimeter components of average hole lifetimes were separated by plotting 1/tau(p) as a function of device perimeter-top area ratio (P/A). This plot reveals that perimeter recombination is dominant in these devices, whose areas are all less than 1 mm(2). The bulk minority carrier (hole) lifetime extracted from the 1/tau(p) vs P/A plot is approximately 0.7 mu s, well above the 60 ns to 300 ns average lifetimes obtained when perimeter recombination effects are ignored in the analysis. Given the fact that there has been little previous investigation of bipolar diode and transistor performance as a function of perimeter-to-area ratio, this work raises the possibility that perimeter recombination may be partly responsible for poor effective minority carrier lifetimes and limited performance obtained in many previous SiC bipolar junction devices. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Neudeck, PG (reprint author), NASA, Lewis Res Ctr, 21000 Brookpk Rd,MS 77-1, Cleveland, OH 44135 USA. NR 21 TC 19 Z9 19 U1 0 U2 1 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 0361-5235 J9 J ELECTRON MATER JI J. Electron. Mater. PD APR PY 1998 VL 27 IS 4 BP 317 EP 323 DI 10.1007/s11664-998-0408-5 PG 7 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA ZJ744 UT WOS:000073248600031 ER PT J AU Smialek, JL AF Smialek, JL TI Oxidation resistance and critical sulfur content of single crystal superalloys SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 41st International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 10-13, 1996 CL BIRMINGHAM, ENGLAND ID OXIDE SCALE ADHERENCE; SEGREGATION; ADHESION; REMOVAL; ADDITIONS; ELEMENTS; ALUMINA; ALLOYS; NICKEL; BASE AB Single crystal superalloys had greatly improved cyclic oxidation resistance when their sulfur content was reduced from impurity levels, typically 5-10 ppmw in past years, down to 1 ppmw or below currently. Excellent alumina scale adhesion has been documented for PWA 1480, PWA 1484, Rene'N5, Rene'N6, and CMSX 4, all without reactive element (Y) additions. Hydrogen annealing was used for effective desulfurization to below 0.1 ppmw, as well as for achieving controlled intermediate levels. This paper summarizes the direct relationship between cyclic oxidation behavior and sulfur content. An adhesion criterion has been proposed based on the concentration of sulfur needed to initiate spallation due to a monolayer of interfacial segregation. This suggests that a level down to similar to 0.2 ppmw would be needed to maximize adhesion for a I mm thick sample, It is in reasonable agreement with the experimental results. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Smialek, JL (reprint author), NASA, Lewis Res Ctr, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 25 TC 11 Z9 11 U1 0 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 1998 VL 120 IS 2 BP 370 EP 374 DI 10.1115/1.2818132 PG 5 WC Engineering, Mechanical SC Engineering GA ZM040 UT WOS:000073498700019 ER PT J AU Sogard, SM Olla, BL AF Sogard, SM Olla, BL TI Behavior of juvenile sablefish, Anoplopoma fimbria (Pallas), in a thermal gradient: Balancing food and temperature requirements SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE diel patterns; vertical distribution; stratification; ontogenetic changes; trade-offs ID CALIFORNIA CURRENT; PREDATION; LARVAL; GROWTH; HUNGER; OREGON; RISK AB The vertical distribution of early juvenile sablefish, Anoplopoma fimbria (Pallas), and their behavioral responses to changing food and temperature conditions were examined in laboratory experiments. Although field collections have suggested that juveniles are obligate residents of the neuston, laboratory experiments on diel movements indicated the potential for downward movement during the day, when activity levels were high and active foraging would be likely. The relationship of downward movement to fish size (small vs. large juveniles), prior feeding success (high vs. low rations) and thermal structure of the water column (isothermal vs. varying intensities of thermal stratification) were tested. Thermal stratification inhibited downward movement, with sablefish displaying clear avoidance of cold water even when the thermal gradient was moderate (12 degrees C top layer and 8 degrees C bottom layer). However, sablefish could be induced to swim downward into cold water if food was introduced beneath the thermocline. Across all temperature treatments, occurrence in cold water significantly increased when food was present. Increasing the sharpness of the thermal gradient (top layer = 12 degrees C, bottom layer = 8, 6, 4 or 2 degrees C) did not affect the percentage of time spent in cold water, but did shorten the maximum time an individual would spend beneath the thermocline. Movement into cold water constituted a potentially lethal risk for juvenile sablefish; dives beneath the thermocline that exceeded 60 s resulted in loss of equilibrium and immediate death for small fish moving from 12 to 2 degrees C water. Thus, sablefish displayed behavioral trade-offs between food acquisition and the physiological risk of cold temperatures, similar to previous studies documenting balancing of foraging behavior and predation risk. Behavioral responses to thermal stratification were modified by fish size and hunger level, with larger juveniles and those held on low rations spending more time in cold water. These behavioral responses correspond with the high feeding requirements necessary to maintain the naturally rapid growth rates of this species and the transitions in habitat associated with different life history stages. (C) 1998 Elsevier Science B.V. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Alaska Fisheries Sci Ctr, Natl Marine Fisheries Serv, Newport, OR 97365 USA. RP Sogard, SM (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Alaska Fisheries Sci Ctr, Natl Marine Fisheries Serv, Newport, OR 97365 USA. NR 25 TC 23 Z9 23 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0981 J9 J EXP MAR BIOL ECOL JI J. Exp. Mar. Biol. Ecol. PD APR 1 PY 1998 VL 222 IS 1-2 BP 43 EP 58 DI 10.1016/S0022-0981(97)00137-8 PG 16 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA ZC792 UT WOS:000072618500004 ER PT J AU Ivry, RB Franz, EA Kingstone, A Johnston, JC AF Ivry, RB Franz, EA Kingstone, A Johnston, JC TI The psychological refractory period effect following callosotomy: Uncoupling of lateralized response codes SO JOURNAL OF EXPERIMENTAL PSYCHOLOGY-HUMAN PERCEPTION AND PERFORMANCE LA English DT Article ID OVERLAPPING-TASK-PERFORMANCE; SPLIT-BRAIN PATIENTS; CEREBRAL HEMISPHERES; BIMANUAL MOVEMENTS; DIVIDED ATTENTION; VISUAL-SEARCH; INTERFERENCE; BOTTLENECKS; SYSTEMS AB A callosotomy patient was tested in 2 dual-task experiments requiring successive speeded responses to lateralized stimuli. The patient showed a robust psychological refractory period (PRP) effect. Three aspects of the data indicate that, unlike for the control participants, the PRP effect for the split-brain patient should not be attributed to a response selection bottleneck. First, the patient did not show an increase in reaction time (RT) when the 2 tasks required responses from a common output system compared with when different output systems were used. Second, inconsistent stimulus-response mappings for the 2 tasks increased RTs for the control participants but had minimal effect on the performance of the split-brain patient. Third, the consistency manipulation was underadditive with stimulus onset asynchrony but was additive or overadditive for the normal participants. These results suggest that the persistent PRP effect following callosotomy should be attributed to a bottleneck associated with response initiation, a strategy adopted to comply with the task demands, or a combination of these factors. C1 Univ Calif Berkeley, Dept Psychol, Berkeley, CA 94720 USA. Univ Alberta, Dept Psychol, Edmonton, AB, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ivry, RB (reprint author), Univ Calif Berkeley, Dept Psychol, 210 Tolman Hall, Berkeley, CA 94720 USA. EM ivry@socrates.berkeley.edu FU NINDS NIH HHS [NS09318, NS30256] NR 40 TC 36 Z9 36 U1 2 U2 2 PU AMER PSYCHOLOGICAL ASSOC PI WASHINGTON PA 750 FIRST ST NE, WASHINGTON, DC 20002-4242 USA SN 0096-1523 J9 J EXP PSYCHOL HUMAN JI J. Exp. Psychol.-Hum. Percept. Perform. PD APR PY 1998 VL 24 IS 2 BP 463 EP 480 DI 10.1037/0096-1523.24.2.463 PG 18 WC Psychology; Psychology, Experimental SC Psychology GA ZF490 UT WOS:000072902700007 PM 9554094 ER PT J AU Dong, D Herring, TA King, RW AF Dong, D Herring, TA King, RW TI Estimating regional deformation from a combination of space and terrestrial geodetic data SO JOURNAL OF GEODESY LA English DT Article DE deformation analysis; estimation; space geodesy ID LANDERS EARTHQUAKE SEQUENCE; CRUSTAL DEFORMATION; SOUTHERN-CALIFORNIA; RADIO INTERFEROMETRY; STRAIN; FAULT AB We discuss an approach for efficiently combining different types of geodetic data to estimate time-dependent motions of stations in a region of active deformation. The primary observations are analyzed separately to produce loosely constrained estimates of station positions and coordinate system parameters which are then combined with appropriate constraints to estimate velocities and coseismic displacements. We define noninteger degrees of freedom to handle the case of finite constraints and stochastic perturbation of parameters and develop statistical tests for determining compatibility between different data sets. With these developments, we show an example of combining space and terrestrial geodetic data to obtain the deformation field in southern California. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. RP Dong, D (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 44 TC 232 Z9 269 U1 2 U2 11 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0949-7714 J9 J GEODESY JI J. Geodesy PD APR PY 1998 VL 72 IS 4 BP 200 EP 214 DI 10.1007/s001900050161 PG 15 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA ZL723 UT WOS:000073464000002 ER PT J AU Gross, RS Eubanks, TM Steppe, JA Freedman, AP Dickey, JO Runge, TF AF Gross, RS Eubanks, TM Steppe, JA Freedman, AP Dickey, JO Runge, TF TI A Kalman-filter-based approach to combining independent Earth-orientation series SO JOURNAL OF GEODESY LA English DT Article DE earth rotation; combination; Kalman filter ID ATMOSPHERIC ANGULAR-MOMENTUM; LONG BASELINE INTERFEROMETRY; POLAR MOTION; UNIVERSAL TIME; MARK-III; ROTATION; SYSTEM; LAGEOS; GEODESY; COMBINATIONS AB An approach, based upon the use of a Kalman filter, that is currently employed at the Jet Propulsion Laboratory (JPL) for combining independent measurements of the Earth's orientation, is presented. Since changes in the Earth's orientation can be described as a randomly excited stochastic process, the uncertainty in our knowledge of the Earth's orientation grows rapidly in the absence of measurements. The Kalman-filter methodology allows for an objective accounting of this uncertainty growth, thereby facilitating the intercomparison of measurements taken at different epochs (not necessarily uniformly spaced in time) and with different precision. As an example of this approach to combining Earth-orientation series, a description is given of a combination, SPACE95, that has been generated recently at JPL. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gross, RS (reprint author), CALTECH, Jet Prop Lab, Mail Stop 238-332,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM rsg@logos.jpl.nasa.gov OI Eubanks, Thomas Marshall/0000-0001-9543-0414 NR 84 TC 43 Z9 51 U1 2 U2 3 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0949-7714 J9 J GEODESY JI J. Geodesy PD APR PY 1998 VL 72 IS 4 BP 215 EP 235 DI 10.1007/s001900050162 PG 21 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA ZL723 UT WOS:000073464000003 ER PT J AU Whang, YC Zhou, J Lepping, RP Szabo, A Fairfield, D Kokubun, S Ogilvie, KW Fitzenreiter, R AF Whang, YC Zhou, J Lepping, RP Szabo, A Fairfield, D Kokubun, S Ogilvie, KW Fitzenreiter, R TI Double discontinuity: A compound structure of slow shock and rotational discontinuity SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID RANKINE-HUGONIOT PROBLEM; MODE SHOCKS; SOLAR-WIND; MAGNETOHYDRODYNAMIC SHOCKS; INTERPLANETARY SPACE; PLASMA; MAGNETOTAIL AB This paper reports the observations of a compound structure in space plasma composed of a slow shock layer and an adjoining rotational discontinuity layer on the postshock side. The compound structure looks like a new kind of MHD discontinuity; it may be called a double discontinuity. Two dual-spacecraft observations of double discontinuities using high-resolution magnetic field data were made in interplanetary space in 1995. The first one observed from Wind and IMP 8 is composed of a reversed slow shock and a rotational discontinuity. The second one observed from Wind and Geotail is composed of a forward slow shock and a rotational discontinuity. A double discontinuity is a stable, large-scale solar wind structure. The thickness of the slow shock layer is of a few ion inertial lengths. The flow in the preshock region has a low beta(i) value and a large shock angle. C1 Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Whang, YC (reprint author), Catholic Univ Amer, Dept Mech Engn, Washington, DC 20064 USA. NR 25 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6513 EP 6520 DI 10.1029/97JA03681 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700004 ER PT J AU Hess, RA MacDowall, RJ Goldstein, B Neugebauer, M Forsyth, RJ AF Hess, RA MacDowall, RJ Goldstein, B Neugebauer, M Forsyth, RJ TI Ion acoustic-like waves observed by Ulysses near interplanetary shock waves in the three-dimensional heliosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS BOW SHOCK; SOLAR-WIND; ECLIPTIC-PLANE; INSTABILITY; UPSTREAM; RADIO AB The Ulysses spacecraft encountered 160 interplanetary shock waves between the time of its launch in October 1990 and the end of 1993 when it reached 48 degrees S heliographic latitude. The onboard radio and plasma wave instrument observed many plasma waves associated with these shocks. Electrostatic waves at frequencies between the ion and electron plasma frequencies are observed intermittently throughout the solar wind but are often strongly enhanced near the shocks. These waves are usually interpreted as ion acoustic waves that have been Doppler shifted to the observed frequencies. They show very diverse characteristics in their amplitude and in their temporal behavior relative to the time of the shock passage at Ulysses. They are most likely to occur within a few minutes bf shock passage, but on average they are enhanced above background levels for several hours before. and after passage of the shock. The temporal behavior of the probability of occurrence of these waves is roughly symmetric relative to the time of shock passage and furthermore is quite similiar for quasi-parallel and quasi-perpendicular shocks and for forward and reverse shocks. These waves are correlated with several of the local plasma parameters measured by the Ulysses plasma instrument, most strongly with T-e/T-p, the ratio of electron temperature to proton temperature, and with the electron heat flux. There is no significant correlation of the waves with the upstream plasma beta or the shock strength. The similiarity of the quasi-parallel and quasi-perpendicular cases implies that the mechanism for wave generation is not sensitive to theta(Bn), the angle between the upstream magnetic field and the shock normal. Examination of the particle distribution function at the shocks indicate that beams in the proton distribution function and enhanced electron heat flux may contribute to driving the waves unstable, particularly when T-e/T-p is small. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Hughes STX Corp, Lanham, MD USA. RP Hess, RA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, MC 690 2, Greenbelt, MD 20771 USA. EM roger.a.hess@gsfc.nasa.gov; robert.j.macdowall@gsfc.nasa.gov; bgoldstein@jplsp2.jpl.nasa.gov; mneugeb@jplsp.jpl.nasa.gov; rforsyth@ic.ac.uk RI MacDowall, Robert/D-2773-2012 NR 39 TC 7 Z9 7 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6531 EP 6541 DI 10.1029/97JA03395 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700006 ER PT J AU Farrugia, CJ Gratton, FT Gnavi, G Ogilvie, KW AF Farrugia, CJ Gratton, FT Gnavi, G Ogilvie, KW TI On the possible excitation of electromagnetic ion cyclotron waves in solar ejecta SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC CLOUDS; ALFVEN WAVES; WIND; INSTABILITIES; PLASMAS; EVENTS; SHOCK; DECAY AB We study the possibility of exciting electromagnetic ion cyclotron waves (EICWs) in solar ejecta (CMEs) by a kinetic instability driven by ion temperature anisotropies. Our approach is to vary key parameters about assumed baseline values. Since T-p,T-parallel to > T-p,T-perpendicular to in most solar ejecta, the polarization of the unstable waves is right-handed. If the average proton beta is low (beta(p) less than or equal to 0.3), the activity is negligible for moderate temperature ratios, T-p,T-parallel to/T-p,T-perpendicular to. Increasing beta(p) increases both the frequency range and the instability growth rate. Increasing the temperature anisotropy brings about qualitatively similar effects as increasing beta(p), with comparable growth rates. Increasing the relative alpha-to-proton density ratio eta has two effects: the active frequency range is shifted toward lower frequencies and the growth rate increases. Between eta = 0 and eta = 0.15, the maximum growth rate increases by a factor of similar to 20, highlighting the importance of the alphas for generating this instability. A case that may represent some magnetic clouds with exceptional parameters, beta(p) = 0.2, T-p,T-parallel to/T-p,T-perpendicular to = 10, and eta = 0.08 - 0.15, is considered. The maximum growth rate is found to be twice the reference CME case, while the active frequency range is 3 times wider. We conclude that EICWs should be present in some ejecta and possibly also in those magnetic clouds with relatively weak magnetic field, high He++ content, and large T-p,T-parallel to/T-p,T-perpendicular to ratios, and whose beta(p) is high, for example, through interaction with a succeeding fast stream. We also suggest that substantial changes with respect to normal conditions should occur in the power spectrum of EICWs in the terrestrial plasma depletion layer when a CME, or a magnetic cloud, with negative anisotropy passes Earth. C1 Univ Buenos Aires, Consejo Nacl Invest Cient & Tecn, Inst Fis Plasma, RA-1428 Buenos Aires, DF, Argentina. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Farrugia, CJ (reprint author), Univ Buenos Aires, Consejo Nacl Invest Cient & Tecn, Inst Fis Plasma, RA-1428 Buenos Aires, DF, Argentina. NR 30 TC 11 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6543 EP 6550 DI 10.1029/97JA03338 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700007 ER PT J AU Wilson, RM Hathaway, DH Reichmann, EJ AF Wilson, RM Hathaway, DH Reichmann, EJ TI An estimate for the size of cycle 23 based on near minimum conditions SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAXIMUM SUNSPOT NUMBER; POLAR CORONAL HOLES; 2-COMPONENT SOLAR-CYCLE; MAGNETIC CLOUDS; PREDICTION; FORECAST; BEHAVIOR; INDEX AB The first occurrence of a high-latitude, new cycle spot group for cycle 23 was in May 1996, in conjunction with a minimum in the smoothed monthly mean sunspot number. Since then, new cycle spot groups have become more predominant, and the smoothed monthly mean sunspot number has slowly risen. Such behavior indicates that new cycle 23 probably had its minimum annual average sunspot number, R(min), equal to 8.7, in 1996. Because this value is larger than the average for R(min), cycle 23 is expected to have a maximum amplitude, R(max), that, likewise, will be larger than average, suggesting further that it probably will be both fast rising (i.e., peaking before May 2000) and of shorter than average length (i.e., ending before May 2007). Another parameter well correlated with R(max) is the minimum amplitude of the qa geomagnetic index, aa(min), which usually occurs either in the year of R(min) occurrence or, more often, in the following year. For 1996 the annual average of aa measured 18.6. Presuming this value to be an(min) for cycle 23, we calculate cycle 23's R(max) to be about 171.0 +/- 17.6 (i.e., the 90% prediction interval), based on the stronger (r = 0.98) bivariate fit of R(max) versus both R(min) and aa(min). Comparison of this estimate with others, using various combinations of parameters, yields an overlap in the prediction intervals for R(max) of about 168 +/- 15, a range that is within the consensus recently reported by Joselyn et al. [1997] (= 160 +/- 30). Thus this study supports the view that cycle 23 will have an R(max) that will be larger than average but smaller than was seen for cycle 19, the largest cycle on record with R(max) = 190.2. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Solar Phys Branch, Huntsville, AL 35812 USA. RP Wilson, RM (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Solar Phys Branch, ES82 96-025, Huntsville, AL 35812 USA. NR 67 TC 46 Z9 46 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6595 EP 6603 DI 10.1029/97JA02777 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700011 ER PT J AU Kozyra, JU Fok, MC Sanchez, ER Evans, DS Hamilton, DC Nagy, AF AF Kozyra, JU Fok, MC Sanchez, ER Evans, DS Hamilton, DC Nagy, AF TI The role of precipitation losses in producing the rapid early recovery phase of the Great Magnetic Storm of February 1986 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID RING CURRENT; GEOMAGNETIC STORM; EQUATORIAL MAGNETOSPHERE; LARGE-SCALE; FIELD; PROTON; MODEL; PLASMASPHERE; PLASMAPAUSE; MIDLATITUDE AB The possible role of precipitation losses in eroding stormtime ring current is subject to debate. To explore this controversy, the recovery phase of the February 6-10, 1986, great magnetic storm is examined, when intense ion precipitation was observed at midlatitudes by NOAA-6 and DMSP satellites, This storm period is particularly interesting because the ring current exhibits distinctive two-phase decay as seen in the Dst index, the early rapid timescale decay corresponding to the intense ion precipitation period described above, Hamilton et al. [1988] concluded, from close agreement between the observed timescale for ring current decay and the theoretical timescale for O+ charge exchange loss, that rapid early recovery phase of this storm resulted from the charge exchange loss of high energy O+; the second and longer decay phase was equated with H+ charge exchange loss. A model of the ring cut-rent evolution during this great magnetic storm [Fok et al., 1995] failed to reproduce the observed ring current decay rates, a puzzling result because charge exchange losses were well represented in the ring current model and initial and boundary conditions were taken from the same data set used in the Hamilton et al. [1988] study. A simple energy balance calculation for the global ring current is carried out using (1) either an energy input predicted from upstream solar wind parameters or one calculated from the drift-loss model output, (2) collisional loss timescales extracted from the drift-loss model, and (3) precipitation losses estimated from NOAA-6 and DMSP observations. The energy balance model replicates the evolution of the ring current energy content derived from Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE) observations when ion precipitation losses are included and model energy input function is reduced to agree with predictions based upon upstream solar wind parameters. The Of charge exchange losses and observed global precipitation losses were of equal magnitude in early recovery of the ring current during this great magnetic storm. Later longer decay timescales in the model resulted from a combination of O+ and H+ charge exchange losses; O+ charge exchange losses remained important throughout the model time interval. The present model produces agreement with the AMPTE/CCE estimates of ring current kinetic energy content versus time. Disagreement between the Dst* inferred from the AMPTE/CCE particle measurements and the observed Dst* is an interesting issue needing further explanation. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. NOAA, Space Environm Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. SRI Int, Menlo Park, CA 94025 USA. RP Kozyra, JU (reprint author), Univ Michigan, Space Phys Res Lab, 2455 Hayward St, Ann Arbor, MI 48109 USA. RI Fok, Mei-Ching/D-1626-2012; OI Hamilton, Douglas/0000-0001-6103-8019 NR 42 TC 66 Z9 65 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6801 EP 6814 DI 10.1029/97JA03330 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700028 ER PT J AU Tsyganenko, NA Karlsson, SBP Kokubun, S Yamamoto, T Lazarus, AJ Ogilvie, KW Russell, CT Slavin, JA AF Tsyganenko, NA Karlsson, SBP Kokubun, S Yamamoto, T Lazarus, AJ Ogilvie, KW Russell, CT Slavin, JA TI Global configuration of the magnetotail current sheet as derived from Geotail, Wind, IMP 8 and ISEE 1/2 data SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERIC MAGNETIC-FIELD; INDEPENDENT PHYSICAL PARAMETERS; GEOMAGNETIC NEUTRAL SHEET; TAIL CURRENT SHEET; PLASMA SHEET; DISTANT MAGNETOTAIL; POSITION; SHAPE; MODEL; AVERAGE AB Based on fine-resolution Geotail magnetometer data, a set of 5-min magnetic field averages was compiled for the period 1993-1997 and merged with 5-min average solar wind parameters, measured by IMP 8 and Wind spacecraft. Using this data set, the shape of the tail current sheet was studied in the interval -100 < X-GSM < -10 R-E as a function of the Earth's dipole tilt angle and of the By component of the IMF. The tilt-related warping of the current sheet and its twisting around the magnetotail axis in response to the IMF were modeled by analytical functions, whose parameters were found by least squares fitting to the data, for several bins of X-GSM A Similar modeling was also done for the near-tail region -20 < X-GSM < -10 R-E, using a set of 5-min ISEE 1/2 data, tagged by corresponding solar wind parameters from IMP 8, for the entire duration of the ISEE magnetometer experiment (1977-1987). The IMF-related twisting steadily increases down the tail and is quite conspicuous even at close geocentric distances (-20 less than or equal to X less than or equal to -10 R-E) A simple and flexible mathematical method is suggested, which allows quantitative modeling on a global scale of the IMF-related deformation of the cross-tail current by means of a "twist transformation" of the tail field. The method allows for a wide variety of possible geometries of the current sheet and keeps the total field confined within the magnetotail boundary. The results of the study are intended to be used in the development of an improved global model of the magnetospheric magnetic field, incorporating the effects of the IMF upon the magnetotail structure. C1 NASA, Goddard Space Flight Ctr, Hughes STX Corp, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Swedish Inst Space Phys, S-75591 Uppsala, Sweden. Nagoya Univ, Solar Terr Environm Lab, Toyokawa 442, Japan. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Space Res Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. RP Tsyganenko, NA (reprint author), NASA, Goddard Space Flight Ctr, Hughes STX Corp, Extraterr Phys Lab, Code 695, Greenbelt, MD 20771 USA. RI Tsyganenko, Nikolai/J-7377-2012; Slavin, James/H-3170-2012; OI Tsyganenko, Nikolai/0000-0002-5938-1579; Slavin, James/0000-0002-9206-724X; Russell, Christopher/0000-0003-1639-8298 NR 38 TC 44 Z9 45 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6827 EP 6841 DI 10.1029/97JA03621 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700030 ER PT J AU Birn, J Hesse, M Schindler, K AF Birn, J Hesse, M Schindler, K TI Formation of thin current sheets in space plasmas SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID NEAR-EARTH MAGNETOTAIL; GROWTH-PHASE; TAIL; CONVECTION; SUBSTORMS; CONFIGURATIONS; FIELDS AB The formation of thin current sheets is investigated on the basis of an adiabatic ideal MHD model. The primary applications are the substorm growth phase in Earth's magnetotail, prior to the dynamic expansion phase, and evolving structures in the solar corona which may similarly lead into an eruption such as a disappearing filament or a flare. A time-dependent MHD code is used to study the evolution under the influence of an external electric field applied at the boundaries of the system. This electric field may be considered as the consequence of the coupling with the solar wind in Earth's case or as a representation of a converging footpoint motion in a bipolar region on the solar photosphere. Thin current sheets are found to form both in the high-beta and low-beta case (where beta is the ratio of plasma pressure over magnetic pressure). They form in the closed field region even though the external electric field and the footpoint displacement are applied predominantly in the surrounding open field region. Within the limits of numerically stable solutions, the current sheet thickness and the maximum current density remain finite, scaling with a high power of the lobe field increase. Larger amplitudes of the current density and a stronger localization of the current sheet in the radial direction are found when the applied electric field decays more rapidly away from Earth or the solar surface. The value of gamma, the polytropic index, has little influence on the evolution and the final current sheet structure. Force-free configurations behave similarly as their equivalent high-beta current sheets. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. Ruhr Univ Bochum, D-44780 Bochum, Germany. RP Birn, J (reprint author), Univ Calif Los Alamos Natl Lab, MS D466, Los Alamos, NM 87545 USA. RI Hesse, Michael/D-2031-2012 NR 25 TC 37 Z9 38 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6843 EP 6852 DI 10.1029/97JA03602 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700031 ER PT J AU Khazanov, GV Liemohn, MW Krivorutsky, EN Moore, TE AF Khazanov, GV Liemohn, MW Krivorutsky, EN Moore, TE TI Generalized kinetic description of a plasma in an arbitrary field-aligned potential energy structure SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PARALLEL ELECTRIC-FIELDS; ION-EXOSPHERE; POLAR WIND; MODEL; DISTRIBUTIONS; MAGNETOSPHERE; ACCELERATION; PARTICLE; REGION AB We present a general solution to the collisionless Boltzmann (Vlasov) equation for a free-flowing plasma along a magnetic field line using Liouville's theorem, allowing for an arbitrary field-aligned potential energy structure including nonmonotonicities. The constraints of the existing collisionless kinetic transport models are explored, and the need for a more general approach to the problem of self-consistent potential energy calculations is described. Then a technique that handles an arbitrary potential energy distribution along the field line is presented and discussed. For precipitation of magnetospherically trapped hot plasma, this model yields moment calculations that vary by up to a factor of 2 for various potential energy structures with the same total potential energy drop. The differences are much greater for the high-latitude outflow scenario, giving order of magnitude variations depending on the shape of the potential energy distribution. Self-consistent calculations for the photoelectron-driven polar wind are compared with previous results, and it is shown that even a photoelectron concentration of 0.03% at the base of the simulation (500 km) will cause the potential energy distribution to violate the constraints of the existing models. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Khazanov, GV (reprint author), Univ Alaska, Dept Phys, Inst Geophys, Fairbanks, AK 99701 USA. RI Moore, Thomas/D-4675-2012; Liemohn, Michael/H-8703-2012; feggans, john/F-5370-2012 OI Moore, Thomas/0000-0002-3150-1137; Liemohn, Michael/0000-0002-7039-2631; NR 35 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6871 EP 6889 DI 10.1029/97JA03436 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700033 ER PT J AU Kamide, Y Yokoyama, N Gonzalez, W Tsurutani, BT Daglis, IA Brekke, A Masuda, S AF Kamide, Y Yokoyama, N Gonzalez, W Tsurutani, BT Daglis, IA Brekke, A Masuda, S TI Two-step development of geomagnetic storms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC STORMS; MAGNETOTAIL; ORIGIN; IONS; DST AB Using the Dst index, more than 1200 geomagnetic storms, from weak to intense, spanning over three solar cycles have been examined statistically. Interplanetary magnetic field(IMF) and solar wind data have also been used in the study. It is found that for more than 50% of intense magnetic storms, the main phase undergoes a two-step growth in the ring current. That is, before the ring current has decayed significantly to the prestorm level, anew major particle injection occurs, leading to a further development of the ring current, and making Dst decrease a second time. Thus intense magnetic storms may often be the result of two closely spaced moderate storms. The corresponding signature in the interplanetary medium is the arrival of double-structured southward IMF at the magnetosphere. C1 Nagoya Univ, Solar Terr Environm Lab, Toyokawa, Aichi 442, Japan. Univ Tromso, Auroral Observ, N-9037 Tromso, Norway. Natl Observ Athens, Inst Ionspher & Space Res, Palea Penteli 15236, Greece. Inst Nacl Pesquisas Espaciais, BR-12200 Sao Jose Dos Campos, SP, Brazil. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kamide, Y (reprint author), Nagoya Univ, Solar Terr Environm Lab, Toyokawa, Aichi 442, Japan. EM kamide@stelab.nagoya-u.ac.jp; nobu@stelab.nagoya-u.ac.jp; gonzalez@magnet.dge.inpe.br; btsurutani@jplsp1.jpl.nasa.gov; daglis@creator.space.noa.gr; asgeir@windows.phys.uit.no; masuda@stelab.nagoya-u.ac.jp RI Daglis, Ioannis/L-6100-2013 OI Daglis, Ioannis/0000-0002-0764-3442 NR 23 TC 141 Z9 144 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD APR 1 PY 1998 VL 103 IS A4 BP 6917 EP 6921 DI 10.1029/97JA03337 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA ZF972 UT WOS:000072951700037 ER PT J AU Lerch, BA Noebe, RD Rao, KBS AF Lerch, BA Noebe, RD Rao, KBS TI The effect of Zr on the low-cycle fatigue behavior of NiAl at 1000 K SO JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE LA English DT Article DE damage; deformation; intermetallic; low cycle fatigue; NiAl ID INTERMETALLIC ALLOYS; DEFORMATION MECHANISMS; TENSILE; ALUMINIDES; ZIRCONIUM; FRACTURE; BRITTLE; NICKEL; IRON AB The effect of a 0.1 at. % alloying addition of Zr on the low-cycle fatigue behavior of polycrystalline NiAl was determined at 1000 It and compared to that of binary NiAl, Samples of binary NiAl and the Zr-doped alloy were processed by either HIP consolidation or extrusion of prealloyed intermetallic powders. The cyclic stress response, cyclic stress-strain behavior, and strain-life relationships were all significantly influenced by the microalloying addition of Zr, regardless of the processing technique. A detailed examination of the post-tested low-cycle fatigue (LCF) samples was conducted by optical and electron microscopy to determine variations in fracture and deformation modes and to characterize any microstructural changes that occurred during LCF testing. Differences in LCF behavior due to the Zr addition are attributed to the strong effect that Zr has on modifying the deformation behavior of the intermetallic. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Lerch, BA (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 37 TC 3 Z9 3 U1 0 U2 4 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9495 J9 J MATER ENG PERFORM JI J. Mater. Eng. Perform. PD APR PY 1998 VL 7 IS 2 BP 205 EP 213 DI 10.1361/105994998770347936 PG 9 WC Materials Science, Multidisciplinary SC Materials Science GA ZF489 UT WOS:000072902600007 ER PT J AU Hunley, JD AF Hunley, JD TI Planet Dora: A memoir of the Holocaust and the birth of the Space Age SO JOURNAL OF MILITARY HISTORY LA English DT Book Review C1 NASA Dryden Flight Res Ctr, Tehachapi, CA USA. RP Hunley, JD (reprint author), NASA Dryden Flight Res Ctr, Tehachapi, CA USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU SOC MILITARY HISTORY PI LEXINGTON PA C/O VIRGINIA MILITARY INST, GEORGE C MARSHALL LIBRARY, LEXINGTON, VA 24450-1600 USA SN 0899-3718 J9 J MILITARY HIST JI J. Mil. Hist. PD APR PY 1998 VL 62 IS 2 BP 427 EP 428 DI 10.2307/120757 PG 2 WC History SC History GA ZF818 UT WOS:000072936300041 ER PT J AU Brown, LR Crisp, JA Crisp, D Naumenko, OV Smirnov, MA Sinitsa, LN Perrin, A AF Brown, LR Crisp, JA Crisp, D Naumenko, OV Smirnov, MA Sinitsa, LN Perrin, A TI The absorption spectrum of H2S between 2150 and 4260 cm(-1): Analysis of the positions and intensities in the first (2 nu(2), nu(1), and nu(3)) and second (3 nu(2), nu(1)+nu(2), and nu(2)+nu(3)) triad regions SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID DEUTERATED HYDROGEN-SULFIDE; FAR-INFRARED SPECTRUM; HIGH-RESOLUTION; ROTATIONAL SPECTRUM; MU-M; FREQUENCY MEASUREMENTS; LASER SPECTROSCOPY; LINE POSITIONS; BAND; WAVE AB The two triad systems of hydrogen sulfide (2 nu(2), nu(1) and nu(3) near 4 mu m and 3 nu(2), nu(1), + nu(2), and nu(2) + nu(3) near 2.7 mu m) were analyzed using 14 spectra recorded at 0.0056 and 0.011 cm(-1) resolution with the McMath Fourier transform spectrometer located at Kitt Peak National Observatory. Experimental upper stare levels of (H2S)-S-32, (H2S)-S-34, and (H2S)-S-33 were obtained from assigned positions (as high as J = 20 and k(d) = 15 for the main isotope). These were fitted to the A-reduced Watson Hamiltonian to determine precise sets of rotational constants through J(10) and up to nine Fermi and Coriolis coupling parameters. Intensities of the two (H2S)-S-32 triads were modeled with rms values of 2.5%, using the transformed transition moment expansion with 19 terms for 568 intensifies of the first triad and 11 terms for the 526 intensities of the second triad. The second derivatives of the dipole moment with respect to normal coordinates were estimated in Debye to be: (22)mu(x), = -0.004873 (90); (12)mu(x) = 0.01372 (30); and (23)mu(z) = 0.01578 (30). This confirmed that for hydrogen sulfide some of the second derivatives are larger than the first derivatives. The calculated line intensities were summed yielding integrated band strengths (in cm(-2)/atm at 296 K) as follows: 0.3315 for 2 nu(2), 0.4522 for nu(1), 0.1201 for nu(3), 0.0303 for 3 nu(2), 1.820 for nu(1) + nu(2), and 2.869 for nu(2) + nu(3). In addition, the hot band transitions were identified in both regions. Finally,a composite database of hydrogen sulfide lint parameters was predicted for the 5- to 2.5-mu m region. (C) 1998 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Russian Acad Sci, Inst Atmospher Opt, Tomsk 634055, Russia. Univ Paris Sud, Photophys Mol Lab, F-91405 Orsay, France. RP Brown, LR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 37 TC 40 Z9 46 U1 1 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 APR PY 1998 VL 188 IS 2 BP 148 EP 174 DI 10.1006/jmsp.1997.7501 PG 27 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA ZJ957 UT WOS:000073270700006 ER PT J AU Smith, DD Sibille, L Cronise, RJ Noever, DA AF Smith, DD Sibille, L Cronise, RJ Noever, DA TI Surface plasmon resonance evaluation of colloidal silver aerogel filters SO JOURNAL OF NON-CRYSTALLINE SOLIDS LA English DT Article; Proceedings Paper CT 5th International Symposium on Aerogels CY SEP 08-10, 1997 CL MONTPELLIER, FRANCE SP Univ Montpellier, CNRS, Reg Languedoc Roussillon, Ctr Etud Commissariat Energie Atom Bruyeres Chatel, Ctr Etud Commissariat Energie Atom Vahrho DE surface plasmon resonance; aerogel; Silver nanoparticles AB Aerogels containing silver nanoparticles were fabricated for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to heterogeneous or porous media. Specifically, we extend the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs modification for aggregated systems. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Smith, DD (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES-76, Huntsville, AL 35812 USA. EM david.d.smith@msfc.nasa.gov NR 10 TC 3 Z9 3 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-3093 J9 J NON-CRYST SOLIDS JI J. Non-Cryst. Solids PD APR PY 1998 VL 225 IS 1-3 BP 330 EP 334 DI 10.1016/S0022-3093(98)00134-3 PG 5 WC Materials Science, Ceramics; Materials Science, Multidisciplinary SC Materials Science GA ZY627 UT WOS:000074642600064 ER EF