FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Thompson, BJ Gurman, JB Neupert, WM Newmark, JS Delaboudiniere, JP St Cyr, OC Stezelberger, S Dere, KP Howard, RA Michels, DJ AF Thompson, BJ Gurman, JB Neupert, WM Newmark, JS Delaboudiniere, JP St Cyr, OC Stezelberger, S Dere, KP Howard, RA Michels, DJ TI SOHO/EIT observations of the 1997 April 7 coronal transient: Possible evidence of coronal Moreton waves SO ASTROPHYSICAL JOURNAL LA English DT Article DE solar wind; Sun : activity; Sun : corona; Sun : flares ID FLARE AB We report observations obtained with the Extreme ultraviolet Imaging Telescope (EIT) on board SOHO of a large-scale coronal transient propagating across the disk of the Sun at a speed of 250 km s(-1), in apparent association with a flare and coronal mass ejection. The observations consist of a series of images taken in the Fe XII 195 A bandpass at an average cadence of 15 minutes. A visible increase in coronal emission propagates away from the erupting region, traveling across most of the solar disk in less than an hour. As the wave propagates through the ambient corona, its path is not homogeneous, and it is less observable near strong magnetic features such as active regions and magnetic neutral lines. The characteristics of this event appear to be representative of several other "EIT waves," which we identify as strong candidates for the coronal manifestation of Moreton waves. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Applicat Corp, Vienna, VA 22180 USA. Inst Astrophys Spatiale, Orsay, France. Computat Phys Inc, Fairfax, VA 22301 USA. USN, Res Lab, Washington, DC 20375 USA. RP Thompson, BJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Thompson, Barbara/C-9429-2012 NR 18 TC 240 Z9 246 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1999 VL 517 IS 2 BP L151 EP L154 DI 10.1086/312030 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VF UT WOS:000081012000020 ER PT J AU Paciesas, WS Meegan, CA Pendleton, GN Briggs, MS Kouveliotou, C Koshut, TM Lestrade, JP McCollough, ML Brainerd, JJ Hakkila, J Henze, W Preece, RD Connaughton, V Kippen, RM Mallozzi, RS Fishman, GJ Richardson, GA Sahi, M AF Paciesas, WS Meegan, CA Pendleton, GN Briggs, MS Kouveliotou, C Koshut, TM Lestrade, JP McCollough, ML Brainerd, JJ Hakkila, J Henze, W Preece, RD Connaughton, V Kippen, RM Mallozzi, RS Fishman, GJ Richardson, GA Sahi, M TI The fourth BATSE gamma-ray burst catalog (revised) SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE catalogs; gamma rays : bursts; gamma rays : observations AB The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) has triggered on 1637 cosmic gamma-ray bursts between 1991 April 19 and 1996 August 29. These events constitute the Fourth BATSE burst catalog. The current version (4Br) has been revised from the version first circulated on CD-ROM in 1997 September (4B) to include improved locations for a subset of bursts that have been reprocessed using additional data. A significant difference from previous BATSE catalogs is the inclusion of bursts from periods when the trigger energy range differed from the nominal 50-300 keV. We present tables of the burst occurrence times, locations, peak fluxes, fluences, and durations. In general, results from previous BATSE catalogs are confirmed here with greater statistical significance. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Alabama, Ctr Space Plasma Aeronom & Astrophys Res, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Mississippi State Univ, Dept Phys, Mississippi State, MS 39762 USA. Minnesota State Univ, Dept Phys & Astron, Mankato, MN 56002 USA. RP Paciesas, WS (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. OI Preece, Robert/0000-0003-1626-7335 NR 23 TC 425 Z9 433 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUN PY 1999 VL 122 IS 2 BP 465 EP 495 DI 10.1086/313224 PG 31 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219PV UT WOS:000081616400004 ER PT J AU Hurley, K Briggs, MS Kippen, RM Kouveliotou, C Meegan, C Fishman, G Cline, T Boer, M AF Hurley, K Briggs, MS Kippen, RM Kouveliotou, C Meegan, C Fishman, G Cline, T Boer, M TI The Ulysses supplement to the BATSE 4Br catalog of cosmic gamma-ray bursts SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE gamma rays : bursts; catalogs AB We present Interplanetary Network localization information for 147 gamma-ray bursts observed by the Burst and Transient Source Experiment between the end of the Third BATSE catalog and the end of the Fourth BATSE catalog, obtained by analyzing the arrival times of these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO) spacecraft. For any given burst observed by these two spacecraft, arrival time analysis (or "triangulation") results in an annulus of possible arrival directions whose half-width varies between 7" and 2 degrees.3, depending on the intensity and time history of the burst, and the distance of the Ulysses spacecraft from Earth. This annulus generally intersects the BATSE error circle, which results in an average reduction of the error box area of a factor of 25. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etude Spatiale Rayonnements, F-31029 Toulouse, France. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. OI Boer, Michel/0000-0001-9157-4349 NR 6 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUN PY 1999 VL 122 IS 2 BP 497 EP 501 DI 10.1086/313220 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219PV UT WOS:000081616400005 ER PT J AU Briggs, MS Pendleton, GN Kippen, RM Brainerd, JJ Hurley, K Connaughton, V Meegan, CA AF Briggs, MS Pendleton, GN Kippen, RM Brainerd, JJ Hurley, K Connaughton, V Meegan, CA TI The error distribution of BATSE gamma-ray burst locations SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE gamma rays : bursts; gamma rays : observations; methods : statistical ID ARRIVAL TIME LOCALIZATIONS; ULYSSES AB Empirical probability models for BATSE gamma-ray burst (GRB) location errors are developed via a Bayesian analysis of the separations between BATSE GRB locations and locations obtained with the Interplanetary Network (IPN). Models are compared and their parameters estimated using 392 GRBs with single IPN annuli and 19 GRBs with intersecting IPN annuli. Most of the analysis is for the 4Br BATSE catalog; earlier catalogs are also analyzed. The simplest model that provides a good representation of the error distribution has 78% of the probability in a "core" term with a systematic error of 1.degrees 85 and the remainder in an extended tail with a systematic error of 5.degrees 1, which implies a 68% confidence radius for bursts with negligible statistical uncertainties of 2.degrees 2. There is evidence for a more complicated model in which the error distribution depends on the BATSE data type that was used to obtain the location. Bright bursts are typically located using the CONT data type, and according to the more complicated model, the 68% confidence radius for CONT-located bursts with negligible statistical uncertainties is 2.degrees 0. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Alabama, Ctr Space Plasma Aeronom & Astrophys Res, Huntsville, AL 35899 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NRC, Huntsville, AL 35812 USA. RP Briggs, MS (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 21 TC 28 Z9 29 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUN PY 1999 VL 122 IS 2 BP 503 EP 518 DI 10.1086/313221 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219PV UT WOS:000081616400006 ER PT J AU Lee, DS Kingdon, RD Pacyna, JM Bouwman, AF Tegen, I AF Lee, DS Kingdon, RD Pacyna, JM Bouwman, AF Tegen, I TI Modelling base cations in Europe - sources, transport and deposition of calcium SO ATMOSPHERIC ENVIRONMENT LA English DT Article DE base cations; calcium; sources; modelling ID URBAN PRECIPITATION CHEMISTRY; UNITED-KINGDOM; WET DEPOSITION; CRITICAL LOADS; ELEMENTAL COMPOSITION; BACKGROUND AEROSOL; SIZE DISTRIBUTION; ACID DEPOSITION; MINERAL DUST; SOILS AB The deposition of the base cations calcium, magnesium and potassium from the atmosphere needs to be quantified in the calculation of the total deposited acidity in the critical loads approach Of these base cations, calcium has been found to be the most important in terms of mass deposited. However, the sources of calcium to the atmosphere are not well understood. Recently, the first spatially disaggregated inventory of industrial calcium emissions for Europe was presented by Lee and Pacyna (1998) who estimated a total European emission of 0.7-0.8 Mt yr(-1). However, it is thought that wind blown dust from soils contributes a substantial fraction to the deposition of calcium. In this work, the source strength of calcium from arid regions within the EMEP modelling domain was estimated using the global mineral dust emission data base of Tegen and Fung (1994) and an estimation of the calcium content of soils. This results in a "natural" calcium emission of 6 hit yr(-1). A long-range transport model, TRACK, was used to calculate the wet and dry deposition of calcium arising from these industrial and natural sources to the UK which resulted in a total deposition of 29-30 kt yr(-1). Of this annual deposition, 0.6-0.7 kt arises from cement manufacturing, 0.02-0.03 kt from iron and steel manufacturing 0.8-0.83 kt from a large point source power generation, and 28 kt from power generation from a small boiler plant. The natural emissions of calcium from arid regions result in a deposition of calcium to the UK of 0.5 kt yr(-1). The measured wet deposition of calcium to the UK is 89 kt yr(-1) and the estimated dry deposition 14 kt yr(-1). The short-fall in the modelled deposition of calcium is thus of the order of 70 kt yr(-1), which is suggested to arise from wind-blown dust from agricultural land in the UK and mainland Europe. The estimated emissions, and thus modelled deposition are rather uncertain, such that estimating deposition of calcium attributable to agricultural soil emissions by differencing has a large uncertainty. However, this is the first such study of its kind for Europe and represents a first step towards understanding the sources of calcium and their contribution to mitigating deposited acidity from acidifying pollutants such as sulphur dioxide, nitrogen oxides and ammonia. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 AEA Technol Environm, Natl Environm Technol Ctr, Culham Lab, Culham OX14 3DB, Oxon, England. Norwegian Inst Air Res, N-2007 Kjeller, Norway. Natl Inst Publ Hlth & Environm, NL-3720 BA Bilthoven, Netherlands. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Lee, DS (reprint author), DERA Pyestock, Prop Dept, Farnborough GU14 0LS, Hants, England. RI Bouwman, Lex/B-7053-2012; Bouwman, Lex/F-1444-2015 OI Bouwman, Lex/0000-0002-2045-1859 NR 65 TC 25 Z9 26 U1 2 U2 15 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD JUN PY 1999 VL 33 IS 14 BP 2241 EP 2256 DI 10.1016/S1352-2310(98)00169-1 PG 16 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 187GL UT WOS:000079778700009 ER PT J AU Kortenkamp, D Schultz, AC AF Kortenkamp, D Schultz, AC TI Integrating robotics research SO AUTONOMOUS ROBOTS LA English DT Editorial Material C1 NASA, Lyndon B Johnson Space Ctr, Metr Inc, TRACLabs, Houston, TX 77058 USA. USN, Res Lab, Navy Ctr Appl Res Artificial Intelligence, Washington, DC 20375 USA. RP Kortenkamp, D (reprint author), NASA, Lyndon B Johnson Space Ctr, Metr Inc, TRACLabs, Mail Code ER2, Houston, TX 77058 USA. NR 0 TC 9 Z9 9 U1 0 U2 3 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0929-5593 J9 AUTON ROBOT JI Auton. Robot. PD JUN PY 1999 VL 6 IS 3 BP 243 EP 245 DI 10.1023/A:1008984727548 PG 3 WC Computer Science, Artificial Intelligence; Robotics SC Computer Science; Robotics GA 204YH UT WOS:000080793200001 ER PT J AU Chang, S AF Chang, S TI Planetary environments and the origin of life SO BIOLOGICAL BULLETIN LA English DT Article; Proceedings Paper CT Workshop on Evolution - A Molecular Point of View CY 1997 CL MARINE BIOL LAB, WOODS HOLE, MA SP NASA, Ctr Adv Studies Space Life Sci, MBL HO MARINE BIOL LAB C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP Chang, S (reprint author), NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. NR 4 TC 5 Z9 5 U1 1 U2 8 PU MARINE BIOLOGICAL LABORATORY PI WOODS HOLE PA 7 MBL ST, WOODS HOLE, MA 02543 USA SN 0006-3185 J9 BIOL BULL-US JI Biol. Bull. PD JUN PY 1999 VL 196 IS 3 BP 308 EP 309 DI 10.2307/1542956 PG 2 WC Biology; Marine & Freshwater Biology SC Life Sciences & Biomedicine - Other Topics; Marine & Freshwater Biology GA 210KR UT WOS:000081104800010 PM 10390827 ER PT J AU Frederickson, AR AF Frederickson, AR TI Progress in high-energy electron and X-irradiation of insulating dielectrics SO BRAZILIAN JOURNAL OF PHYSICS LA English DT Article ID CHARGE DEPOSITION; POLYMER FOILS; SPACECRAFT; ANOMALIES; CURRENTS; DISCHARGES; SURFACES; PROFILE; KAPTON; FIELDS AB The effects of high-energy irradiation on the charging of insulators is reviewed primarily with a viewpoint similar to the seminal work of Professor Bernhard Gross. Recent results relating to insulation breakdown and to insulators in space radiation are more easily explained because of Gross' fundamental studies. A number of important issues remain unsolved, yet the first steps to solutions have been provided by Gross. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, Mail Stop 303-217,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 75 TC 2 Z9 3 U1 0 U2 3 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0103-9733 EI 1678-4448 J9 BRAZ J PHYS JI Braz. J. Phys. PD JUN PY 1999 VL 29 IS 2 BP 241 EP 253 PG 13 WC Physics, Multidisciplinary SC Physics GA 214RL UT WOS:000081341300007 ER PT J AU Karyampudi, VM Palm, SP Reagen, JA Fang, H Grant, WB Hoff, RM Moulin, C Pierce, HF Torres, O Browell, EV Melfi, SH AF Karyampudi, VM Palm, SP Reagen, JA Fang, H Grant, WB Hoff, RM Moulin, C Pierce, HF Torres, O Browell, EV Melfi, SH TI Validation of the Saharan dust plume conceptual model using lidar, Meteosat, and ECMWF data SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SPACE TECHNOLOGY EXPERIMENT; AEROSOL SIZE DISTRIBUTIONS; TROPICAL NORTH-ATLANTIC; ECLATS FIELD EXPERIMENT; RADIATIVE CHARACTERISTICS; TROPOSPHERIC AEROSOLS; WAVE DISTURBANCES; BOUNDARY-LAYER; ISCCP-B2 DATA; MINERAL DUST AB Lidar observations collected during the Lidar In-space Technology Experiment experiment in conjunction with the Meteosat and European Centre for Medium-Range Weather Forecasts data have been used not only to validate the Saharan dust plume conceptual model constructed from the GARP (Global Atmospheric Research Programme) Atlantic Tropical Experiment data, but also to examine the vicissitudes of the Saharan aerosol including their optical depths across the west Africa and east Atlantic regions. Optical depths were evaluated from both the Meteosat and lidar data. Back trajectory calculations were also made along selected lidar orbits to verify the characteristic anticyclonic rotation of the dust plume over the eastern Atlantic as well as to trace the origin of a dust outbreak over West Africa. A detailed synoptic analysis including the satellite-derived optical depths, vertical lidar backscattering cross section profiles, and back trajectories of the 16-19 September 1994 Saharan dust outbreak over the eastern Atlantic and its origin over West Africa during the 12-15 September period have been presented. In addition, lidar-derived backscattering profiles and optical depths were objectively analyzed to investigate the general features of the dust plume and its geographical variations in optical thickness. These analyses validated many of the familiar characteristic features of the Saharan dust plume conceptual model such as (i) the lifting of the aerosol over central Sahara and its subsequent transport to the top of the Saharan air layer (SAL), (ii) the westward rise of the dust layer above the gradually deepening marine mixed layer and the sinking of the dust-layer top, (iii) the anticyclonic gyration of the dust pulse between two consecutive trough axes, (iv) the dome-shaped structure of the dust-layer top and bottom, (v) occurrence of a middle-level jet near the southern boundary of the SAL, (vi) transverse-vertical circulations across the SAL front including their possible role in the initiation of a squall line to the southside of the jet that ultimately developed into a tropical storm, and (vii) existence of satellite-based high optical depths to the north of the middle-level jet in the ridge region of the wave. Furthermore, the combined analyses reveal a complex structure of the dust plume including its origin over North Africa and its subsequent westward migration over the Atlantic Ocean. The dust plume over the west African coastline appears to be composed of two separate but narrow plumes originating over the central Sahara and Lake Chad regions, in contrast to one single large plume shown in the conceptual model. Lidar observations clearly show that the Saharan aerosol over North Africa not only consist of background dust (Harmattan haze) but also wind-blown aerosol from fresh dust outbreaks. They further exhibit maximum dust concentration near the middle-level jet axis with downward extension of heavy dust into the marine boundary layer including a clean dust-free trade wind inversion to the north of the dust layer over the eastern Atlantic region. The lidar-derived optical depths show a rapid decrease of optical depths away from land with maximum optical depths located close to the midlevel jet, in contrast to north of the jet shown by satellite estimates and the conceptual model. To reduce the uncertainties in estimating extinction-to-backscattering ratio for optical depth calculations from lidar data, direct aircraft measurements of optical and physical properties of the Saharan dust layer are needed. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Arizona, Dept Elect & Comp Engn, Tucson, AZ 85721 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. Ctr Atmospher Res Expt, Egbert, ON, Canada. CEA, CNRS, Lab Sci Climat & Environm, F-91198 Gif Sur Yvette, France. Univ Maryland, Baltimore, MD 21201 USA. Sci Syst & Applicat Inc, Lanham, MD USA. Hughes STX Corp, Lanham, MD USA. RP Karyampudi, VM (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RI Hoff, Raymond/C-6747-2012; Grant, William/B-8311-2009; Torres, Omar/G-4929-2013 OI Grant, William/0000-0002-1439-3285; NR 66 TC 205 Z9 206 U1 4 U2 17 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 JUN PY 1999 VL 80 IS 6 BP 1045 EP 1075 DI 10.1175/1520-0477(1999)080<1045:VOTSDP>2.0.CO;2 PG 31 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 214RD UT WOS:000081340600001 ER PT J AU Hollingsworth, JA Hepp, AF Buhro, WE AF Hollingsworth, JA Hepp, AF Buhro, WE TI Spray CVD of copper indium disulfide films: Control of microstructure and crystallographic orientation SO CHEMICAL VAPOR DEPOSITION LA English DT Article ID CUINS2 THIN-FILMS; SINGLE-SOURCE PRECURSORS; PHASE AB Communication: CnInS(2) is a good candidate material for high efficiency absorber layers in thin film solar cells. In this work, spray CVD is used for the first lime to deposit this promising material. Using a single-source precursor, stoichiometric films with little carbon or phosphorus contamination are obtained, and although film microstructure and orientations are quite sensitive to deposition parameters, such as substrate and flow rates, dense columnar growth and faceted crystalline features are produced. C1 Washington Univ, Dept Chem, St Louis, MO 63130 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hollingsworth, JA (reprint author), Washington Univ, Dept Chem, Campus Box 1134, St Louis, MO 63130 USA. RI Buhro, William/A-7682-2009 NR 20 TC 45 Z9 46 U1 0 U2 3 PU WILEY-V C H VERLAG GMBH PI BERLIN PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY SN 0948-1907 J9 CHEM VAPOR DEPOS JI Chem. Vapor Depos. PD JUN PY 1999 VL 5 IS 3 BP 105 EP + DI 10.1002/(SICI)1521-3862(199906)5:3<105::AID-CVDE105>3.3.CO;2-7 PG 5 WC Electrochemistry; Materials Science, Coatings & Films; Physics, Condensed Matter SC Electrochemistry; Materials Science; Physics GA 210FW UT WOS:000081095300003 ER PT J AU Bozzolo, G Ferrante, J Noebe, RD Good, B Honecy, FS Abel, P AF Bozzolo, G Ferrante, J Noebe, RD Good, B Honecy, FS Abel, P TI Surface segregation in multicomponent systems: Modeling of surface alloys and alloy surfaces SO COMPUTATIONAL MATERIALS SCIENCE LA English DT Article DE surface segregation; alloys; surface alloys; Monte Carlo simulations; BFS method; intermetallics ID ENERGY ION-SCATTERING; EMBEDDED-ATOM-METHOD; EQUIVALENT-CRYSTAL THEORY; CU-NI ALLOYS; BINARY-ALLOYS; IMMISCIBLE METALS; INITIAL GROWTH; NICKEL-ALLOYS; DEPTH PROFILE; PROBE FIM AB The study of surface segregation, though of great technological importance, has been largely restricted to experimental work due to limitations associated with theoretical methods. However, recent improvements in both first-principles and semiempirical methods are opening the doors to an array of new possibilities for surface scientists. We apply one of these techniques, the BFS method for alloys, which is particularly suitable for complex systems, to several aspects of the computational modeling of surfaces and segregation, including alloy surface segregation, structure and composition of alloy surfaces, and the formation of surface alloys. We conclude with the study of complex NiAl-based binary, ternary and quaternary thin films (with Ti, Cr and Cu additions to NiAl). Differences and similarities between bulk and surface compositions are discussed, illustrated by the results of Monte Carlo simulations. For some binary and ternary cases, the theoretical predictions are compared to experimental results, highlighting the accuracy and value of this developing theoretical tool. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Ohio Aerospace Inst, Cleveland, OH 44142 USA. Cleveland State Univ, Dept Phys, Cleveland, OH 44115 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bozzolo, G (reprint author), Ohio Aerospace Inst, 22800 Cedar Point Rd, Cleveland, OH 44142 USA. EM guillermo.h.bozzolo@lerc.nasa.gov NR 66 TC 50 Z9 50 U1 3 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-0256 EI 1879-0801 J9 COMP MATER SCI JI Comput. Mater. Sci. PD JUN PY 1999 VL 15 IS 2 BP 169 EP 195 DI 10.1016/S0927-0256(99)00007-5 PG 27 WC Materials Science, Multidisciplinary SC Materials Science GA 209VB UT WOS:000081068800004 ER PT J AU Figueiredo, MA Stakem, PH Flatley, TP Hines, TM AF Figueiredo, MA Stakem, PH Flatley, TP Hines, TM TI Extending NASA's data processing to spacecraft SO COMPUTER LA English DT Article C1 Loyola Coll, Baltimore, MD 21210 USA. NASA, Goddard Space Flight Ctr, Ground Syst Hardware Branch, Greenbelt, MD 20771 USA. NR 0 TC 6 Z9 6 U1 0 U2 2 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 JUN PY 1999 VL 32 IS 6 BP 115 EP 118 PG 4 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA 200YW UT WOS:000080568700026 ER PT J AU Tubiello, FN Lin, G Druitt, JW Marino, BDV AF Tubiello, FN Lin, G Druitt, JW Marino, BDV TI Ecosystem-level evapotranspiration and water-use efficiency in the desert biome of Biosphere 2 SO ECOLOGICAL ENGINEERING LA English DT Article DE Biosphere 2; evapotranspitration; elevated CO2; ecosystems ID CARBON; RESPONSES; CO2 AB We estimate whole-system water and carbon fluxes for the desert biome of Biosphere 2 under two different daily-mean CO2 concentrations: 450 ppmv and 850 ppmv. The desert mesocosm occupies an area of approximately 1500 m(2), has a total atmospheric Volume of about 25000 m(3) and contains a heterogeneous distribution of plants and soils. Atmospheric water content and CO2 concentrations were measured continuously using a variety of sensors, including a Li-cor 6262 for CO2 deployed within the experimental area. Daily carbon and water budgets were calculated in the desert biome, isolated from the rest of Biosphere 2 by deploying isolation curtains for 24-h periods. Data collected for six closure periods suggest that elevated CO2 concentration increased whole-system carbon uptake, while evapotranspiration remained constant. As a result, whole-system water-use efficiency (WUE, defined as net ecosystem carbon uptake per unit water transpired) in the Biosphere 2 desert increased by more than 40%. Our measurements investigate soil-plant processes at a medium scale, ideally bridging the gap between traditional controlled-environment growth chambers and open-field studies. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Biosphere 2 Ctr Res & Educ, Oracle, AZ 85623 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Tubiello, FN (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Lin, Guanghui/I-6850-2013 OI Lin, Guanghui/0000-0001-6108-3215 NR 13 TC 9 Z9 9 U1 2 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-8574 J9 ECOL ENG JI Ecol. Eng. PD JUN PY 1999 VL 13 IS 1-4 BP 263 EP 271 DI 10.1016/S0925-8574(98)00103-7 PG 9 WC Ecology; Engineering, Environmental; Environmental Sciences SC Environmental Sciences & Ecology; Engineering GA 217CK UT WOS:000081482100017 ER PT J AU Tubiello, FN Mahato, T Morton, T Druitt, JW Volk, T Marino, BDV AF Tubiello, FN Mahato, T Morton, T Druitt, JW Volk, T Marino, BDV TI Growing wheat in Biosphere 2 under elevated CO2: Observations and modeling SO ECOLOGICAL ENGINEERING LA English DT Article DE wheat; Biosphere 2; controlled environments; crop models; elevated CO2 ID CROP PRODUCTIVITY; CARBON-DIOXIDE; CLIMATE-CHANGE; WINTER-WHEAT; TEMPERATURE; RESPONSES; GROWTH; EFFICIENCY; ENRICHMENT; RADIATION AB Spring wheat (Triticum aestivum L., cv. Yecora Rojo) was grown in the intensive agricultural biome (IAB) of Biosphere 2 during the 1995-1996 winter/spring season. Environmental conditions were characterized by a day/night temperature regime of 27/17 degrees C, relative humidity (RH) levels around 45%, mean atmospheric CO2 concentration of 450 ppmv, and natural light conditions with mean intensities about half of outside levels. Weekly samples of above-ground plant matter were collected throughout the growing season and phenological events recorded. A computer model, CERES-Wheat, previously tested under both field and controlled conditions, was used to simulate the observed crop growth and to help in data analysis. We found that CERES-Wheat simulated the data collected at Biosphere 2 to within 10% of observed, thus suggesting that wheat growth inside the IAB was comparable to that documented in other environments. The model predicts phenological stages and final dry matter (DM) production within 10% of the observed data. Measured DM production rates, normalized for light absorbed by the crop, suggested photosynthetic efficiencies intermediate between those observed under optimal field conditions and those recorded in NASA-Controlled Ecological Life-Support Systems (CELSS). We suggest that such a difference can be explained primarily in terms of low light levels inside the IAB, with additional effects due to elevated CO2 concentrations and diffuse light fractions. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Biosphere 2 Ctr Res & Educ, Oracle, AZ 85623 USA. Colorado State Univ, Dept Chem & BioEngn, Ft Collins, CO 80523 USA. NYU, Dept Biol, New York, NY 10003 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Tubiello, FN (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 25 TC 6 Z9 7 U1 3 U2 14 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-8574 J9 ECOL ENG JI Ecol. Eng. PD JUN PY 1999 VL 13 IS 1-4 BP 273 EP 286 DI 10.1016/S0925-8574(98)00104-9 PG 14 WC Ecology; Engineering, Environmental; Environmental Sciences SC Environmental Sciences & Ecology; Engineering GA 217CK UT WOS:000081482100018 PM 11542248 ER PT J AU Tubiello, FN Druitt, JW Marino, BDV AF Tubiello, FN Druitt, JW Marino, BDV TI Dynamics of the global water cycle of Biosphere 2 SO ECOLOGICAL ENGINEERING LA English DT Article DE Biosphere 2; water cycle; modeling AB We investigate water usage and movement throughout the major reservoirs of Biosphere 2, Oracle AZ, over a period of 2 months. The data analyzed show reservoir turnover times ranging from hours to several years and the existence of three major water sub-cycles. A 'fast pool', or 60% of the available water used daily in Biosphere 2, is recycled within a month through the air-handler's condensation system, as a consequence of plant and soil evapotranspiration; a 'medium pool', or 30% of available water, moves through the soil profile as drainage and is recycled within a year; while a 'slow pool,' or the remaining 10%, moves through the Biosphere 2 ocean and takes several years to turnover. We develop a simple model of the Biosphere 2 water cycle and discuss its utility in estimating global and single-biome ecosystem processes within this facility. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Columbia Univ, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Biosphere 2 Ctr Res & Educ, Oracle, AZ 85623 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Tubiello, FN (reprint author), Columbia Univ, 2880 Broadway, New York, NY 10025 USA. NR 9 TC 8 Z9 8 U1 4 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0925-8574 J9 ECOL ENG JI Ecol. Eng. PD JUN PY 1999 VL 13 IS 1-4 BP 287 EP 300 DI 10.1016/S0925-8574(98)00105-0 PG 14 WC Ecology; Engineering, Environmental; Environmental Sciences SC Environmental Sciences & Ecology; Engineering GA 217CK UT WOS:000081482100019 ER PT J AU Meise, C Collie, JS Widman, J Howell, P AF Meise, C Collie, JS Widman, J Howell, P TI Growth and mortality of juvenile winter flounder in two New England estuaries SO ESTUARIES LA English DT Article ID LIFE-HISTORY DATA; PSEUDOPLEURONECTES-AMERICANUS; SOUND AB A length-based model for calculating growth and mortality of juvenile winter flounder (Pseudopleuronectes americanus) populations has been developed. This model is based on work by Sullivan et al. (1990) and incorporates the von Bertalanffy growth equation, including stochasticity in growth, and a mortality rate that decreases exponentially with size. The length-based model was fit to observed size-frequency distributions, and model likelihood profiles were generated to produce 95% confidence intervals about parameter estimates. We analyzed size-frequency distributions of 3 to 15 cm juvenile winter flounder, collected with a l-m beam trawl, at monthly intervals from June to October during 1993 and 1994. Growth rates were higher at a contaminated site, New Haven Harbor, than at a clean site, the Connecticut River estuary, however, the parameter estimates had overlapping 95% confidence intervals. Mortality rates were similar at the two sites. C1 Natl Marine Fisheries Serv, JJ Howard Lab, Highlands, NJ 07732 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. Natl Marine Fisheries Serv, Milford Lab, Milford, CT 06460 USA. Marine Headquarters, Old Lyme, CT 06371 USA. RP Meise, C (reprint author), Natl Marine Fisheries Serv, JJ Howard Lab, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 23 TC 8 Z9 8 U1 0 U2 1 PU ESTUARINE RES FEDERATION PI LAWRENCE PA PO BOX 368, LAWRENCE, KS 66044 USA SN 0160-8347 J9 ESTUARIES JI Estuaries PD JUN PY 1999 VL 22 IS 2A BP 297 EP 303 DI 10.2307/1352985 PG 7 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 236BN UT WOS:000082578500012 ER PT J AU Browder, JA Restrepo, VR Rice, JK Robblee, MB Zein-Eldin, Z AF Browder, JA Restrepo, VR Rice, JK Robblee, MB Zein-Eldin, Z TI Environmental influences on potential recruitment of pink shrimp, Farfantepenaeus duorarum, from Florida Bay nursery grounds SO ESTUARIES LA English DT Article ID TORTUGAS GROUNDS; PENAEUS-DUORARUM AB Two modeling approaches were used to explore the basis for variation in recruitment of pink shrimp, Farfantepenaeus duorarum, to the Tortugas fishing grounds. Emphasis was on development and juvenile densities on the nursery grounds. An exploratory simulation modeling exercise demonstrated large year-to-year variations in recruitment contributions to the Tortugas pink shrimp fishery may occur on some nursery grounds, and production may differ considerably among nursery grounds within the same year, simply on the basis of differences in temperature and salinity. We used a growth and survival model to simulate cumulative harvests from a July-centered cohort of early-settlement-stage postlarvae from two parts of Florida Bay (western Florida Bay and northcentral Florida Bay), using historic temperature and salinity data from these areas. Very large year-to-year differences in simulated cumulative harvests were found for recruits from Whipray Basin. Year-to-year differences in simulated harvests of recruits from Johnson Key Basin were much smaller. In a complementary activity, generalized Linear and additive models and intermittent, historic density records were used to develop an uninterrupted multi-year time series of monthly density estimates for juvenile pink shrimp in the Johnson Key Basin. The developed data series was based on relationships of density with environmental variables. The strongest relationship was with sea-surface temperature. Three other environmental variables (rainfall, water level at Everglades National Park Well P35, and mean wind speed) also contributed significantly to explaining variation in juvenile densities. Results of the simulation model and two of the three statistical models yielded similar interannual patterns for Johnson Key Basin. While it is not possible to say that one result validates the other, the concordance of the annual patterns from the two models is supportive of both approaches. C1 NOAA, SE Fisheries Sci Ctr, Natl Marine Fisheries Serv, Miami, FL 33149 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Cooperat Unit Fisheries Educ & Res, Miami, FL 33149 USA. Florida Int Univ, US Geol Survey, Florida Caribbean Sci Ctr, Biol Res Div, Miami, FL 33199 USA. NOAA, SE Fisheries Sci Ctr, Natl Marine Fisheries Serv, Galveston, TX 77550 USA. RP Browder, JA (reprint author), NOAA, SE Fisheries Sci Ctr, Natl Marine Fisheries Serv, 75 Virginia Beach Dr, Miami, FL 33149 USA. EM joan.browder@noaa.gov NR 38 TC 24 Z9 25 U1 1 U2 6 PU ESTUARINE RESEARCH FEDERATION PI PORT REPUBLIC PA 2018 DAFFODIL, PO BOX 510, PORT REPUBLIC, MD 20676 USA SN 0160-8347 J9 ESTUARIES JI Estuaries PD JUN PY 1999 VL 22 IS 2B BP 484 EP 499 DI 10.2307/1353213 PG 16 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 236BP UT WOS:000082578600011 ER PT J AU Lachowicz, JT Yao, C Wlezien, RW AF Lachowicz, JT Yao, C Wlezien, RW TI Flow field characterization of a jet and vortex actuator SO EXPERIMENTS IN FLUIDS LA English DT Article ID SEPARATION CONTROL; GENERATORS AB An actuator, which produces several different flow fields that may be used for active flow control, is characterized in still air using flow visualization and velocity measurements. The primary actuator-induced flow fields are: free jets, wall jets, and vortex flows. The non-dimensional parameters governing these actuator-induced flows are developed. For the vortex-how regime, the operational range of the actuator increases as it's size decreases without a significant decrease in either the actuator induced velocity or vortex core size. The velocity scaling is developed for the vortex flow and suggests that the optimum actuator efficiency occurs at a Stokes number of approximately 7.9 for the range of parameters surveyed. In a turbulent, zero pressure gradient boundary layer, measurements made just downstream of the actuator (when operated in the vortex mode) indicate a vortical disturbance is generated in the boundary layer. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Lachowicz, JT (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 17 TC 14 Z9 14 U1 1 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD JUN PY 1999 VL 27 IS 1 BP 12 EP 20 DI 10.1007/s003480050324 PG 9 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 207DD UT WOS:000080919400003 ER PT J AU Bale, SD Reiner, MJ Bougeret, JL Kaiser, ML Krucker, S Larson, DE Lin, RP AF Bale, SD Reiner, MJ Bougeret, JL Kaiser, ML Krucker, S Larson, DE Lin, RP TI The source region of an interplanetary type II radio burst SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LOCATION; SHOCKS AB We present the first observation of the source region of an interplanetary type II radio burst, using instruments on the Wind spacecraft. Type II radio emission tracks the motion of a CME-driven interplanetary (IP) shock which encounters the spacecraft. Upstream of the IP shock backstreaming electrons are observed, first antiparallel to the interplanetary magnetic field (IMF), and then later parallel as well. Langmuir waves are observed concomitant with the shock-accelerated electrons. The electron energy spectrum and Langmuir wave amplitudes are very similar to those observed in the terrestrial electron foreshock. From the connection times to the shock, we infer the existence and characteristic size of large scale structure on the shock front. The type II radio emission seems to be generated in a small bay upstream of the shock, and this may account for some splitting structure observed in the frequency spectrum of many type II bursts. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Observ Paris, DESPA, F-97005 Meudon, France. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA. Hughes STX, Lanham, MD USA. RP Bale, SD (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Bale, Stuart/E-7533-2011 OI Bale, Stuart/0000-0002-1989-3596 NR 13 TC 128 Z9 128 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 JUN 1 PY 1999 VL 26 IS 11 BP 1573 EP 1576 DI 10.1029/1999GL900293 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 202PG UT WOS:000080660900016 ER PT J AU Marshak, A Oreopoulos, L Davis, AB AF Marshak, A Oreopoulos, L Davis, AB TI Horizontal radiative fluxes in clouds and accuracy of the Independent Pixel Approximation at absorbing wavelengths SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STRATOCUMULUS CLOUDS; OPTICAL DEPTH; ABSORPTION; ALBEDO AB For absorbing wavelengths, we discuss the effect of horizontal solar radiative fluxes in clouds on the accuracy of a conventional plane-parallel radiative transfer calculation for a single pixel, known as the Independent Pixel Approximation (IPA). Vertically integrated horizontal fluxes can be represented as a sum of three components: the IPA accuracies for reflectance, transmittance and absorptance. We show that IPA accuracy for reflectance always improves with more absorption, while the IPA accuracy for transmittance is less sensitive to the changes in absorption: with respect to the non-absorbing case, it may first deteriorate for weak absorption and then improve again for strongly absorbing wavelengths. IPA accuracy for absorptance always deteriorates with more absorption. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21228 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Marshak, A (reprint author), NASA, Goddard Space Flight Ctr, Climate Radiat Branch, MC 913, Greenbelt, MD 20771 USA. RI Oreopoulos, Lazaros/E-5868-2012; Marshak, Alexander/D-5671-2012 OI Oreopoulos, Lazaros/0000-0001-6061-6905; NR 15 TC 12 Z9 12 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 JUN 1 PY 1999 VL 26 IS 11 BP 1585 EP 1588 DI 10.1029/1999GL900306 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 202PG UT WOS:000080660900019 ER PT J AU Ciais, P Friedlingstein, P Schimel, DS Tans, PP AF Ciais, P Friedlingstein, P Schimel, DS Tans, PP TI A global calculation of the delta C-13 of soil respired carbon: Implications for the biospheric uptake of anthropogenic CO2 SO GLOBAL BIOGEOCHEMICAL CYCLES LA English DT Article ID ATMOSPHERIC CO2; SIMULATION; WORLDWIDE; TURNOVER; ISOTOPE AB The continuing emissions of fossil CO2 depleted in C-13 have been causing a gradual decrease in atmospheric delta(13)C by roughly 1.4 parts per thousand since preindustrial times. The progressive penetration of this perturbation into the land biota causes the soil organic matter to be enriched in 13C with respect to recently formed plant material. This effect which we call the "biotic isotope disequilibrium" is important when it comes to deducing the terrestrial carbon fluxes by using delta(13)C in atmospheric CO2. We have estimated the geographical distribution of the isotopic disequilibrium, which is primarily influenced by the turnover of carbon in the various ecosystems, from the output of two biospheric models, (SLAVE and CENTURY). The disequilibrium is estimated to shift up the delta(13)C of atmospheric CO2 by the same amount as a net sink of 0.6 Gt C yr(-1) in the land biota. This "fake" terrestrial sink due to the isotopic disequilibrium is distributed mainly in northern midlatitudes (0.2 Gt C yr(-1)) and tropical forests (0.3 Gt C yr(-1)). C1 CEA, Lab Sci Climat & Environm, F-91191 Gif Sur Yvette, France. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RP Ciais, P (reprint author), CEA, Lab Sci Climat & Environm, F-91191 Gif Sur Yvette, France. RI Friedlingstein, Pierre/H-2700-2014 NR 28 TC 37 Z9 37 U1 1 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0886-6236 J9 GLOBAL BIOGEOCHEM CY JI Glob. Biogeochem. Cycle PD JUN PY 1999 VL 13 IS 2 BP 519 EP 530 DI 10.1029/98GB00072 PG 12 WC Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Geology; Meteorology & Atmospheric Sciences GA 213GQ UT WOS:000081264700016 ER PT J AU Dickey, JO Bentley, CR Bilham, R Carton, JA Eanes, RJ Herring, TA Kaula, WM Lagerloef, GSE Rojstaczer, S Smith, WHF van den Dool, HM Wahr, JM Zuber, MT AF Dickey, JO Bentley, CR Bilham, R Carton, JA Eanes, RJ Herring, TA Kaula, WM Lagerloef, GSE Rojstaczer, S Smith, WHF van den Dool, HM Wahr, JM Zuber, MT TI Gravity and the hydrosphere: new frontier SO HYDROLOGICAL SCIENCES JOURNAL-JOURNAL DES SCIENCES HYDROLOGIQUES LA English DT Article ID ICE-SHEET; OCEAN; MODEL AB Satellite gravity measurements expected in the next few years will provide unprecedented views of the Earth's gravity field and, given sufficient duration, its changes with time. Gravity changes directly reflect changes in the masses of the ocean (thus allowing the separation of steric (heat induced) and non-steric contributions to sea-level rise), the Greenland and Antarctic ice sheets, and the water stored in the continents. Not only can measurements of those changes provide a truly global integrated view of the Earth, they have, at the same time, sufficient spatial resolution to aid in the study Of individual regions of the Earth. These data should yield information on water cycling previously unobtainable and be useful to both fundamental studies of the hydrologic cycle and practical assessments of water availability and distribution. Together with complementary geophysical data, satellite gravity data represent a new frontier in studies of the Earth and its fluid envelope. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Dickey, JO (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI carton, james/C-4807-2009; Smith, Walter/F-5627-2010; OI carton, james/0000-0003-0598-5198; Smith, Walter/0000-0002-8814-015X; Bilham, Roger/0000-0002-5547-4102 NR 14 TC 13 Z9 13 U1 0 U2 2 PU IAHS PRESS, INST HYDROLOGY PI WALLINGFORD PA C/O FRANCES WATKINS, WALLINGFORD OX10 8BB, ENGLAND SN 0262-6667 J9 HYDROLOG SCI J JI Hydrol. Sci. J.-J. Sci. Hydrol. PD JUN PY 1999 VL 44 IS 3 BP 407 EP 415 DI 10.1080/02626669909492236 PG 9 WC Water Resources SC Water Resources GA 203JV UT WOS:000080705300006 ER PT J AU Quirico, E Doute, S Schmitt, B de Bergh, C Cruikshank, DP Owen, TC Geballe, TR Roush, TL AF Quirico, E Doute, S Schmitt, B de Bergh, C Cruikshank, DP Owen, TC Geballe, TR Roush, TL TI Composition, physical state, and distribution of ices at the surface of Triton SO ICARUS LA English DT Article DE Triton; infrared spectroscopy; ices; surfaces; satellites ID INFRARED-SPECTROSCOPY; PLUTO; ATMOSPHERE; N-2; HYDROCARBONS; NITROGEN; NEPTUNE; METHANE AB This paper presents the analysis of near-infrared observations of the icy surface of Triton, recorded on 1995 September 7, with the cooled grating spectrometer CGS4 at the United Kingdom Infrared Telescope (Mauna Kea, HI). This analysis was performed in two steps. The first step consisted of identifying the molecules composing Triton's surface by comparing the observations with laboratory transmission spectra (direct spectral analysis); this also gives information on the physical state of the components. Most of the bands in Triton's spectrum were assigned to specific vibration bands of the CH4,N-2,CO, and CO2 molecules previously discovered. A detailed comparison of the frequencies of the CH4 bands confidently indicated that this molecule exists in a diluted state in solid beta-N-2 Three new bands peaking at 5717, 5943, and 6480 cm(-1) (1.749, 1.683, and 1.543 mu m, respectively) were also observed. Laboratory experiments have shown that C2H6 isolated in solid N-2 fits well the second band, but this would imply the appearance of unobserved bands and thus rules out this assignment. However, C2H6 may exist in another physical state, and more experiments are necessary. No plausible candidate was found for these three bands when comparing with the spectra of nine molecules (C2H2, C2H4, C3H8, NH3, SO2, HC3N, CH3OH, NO, NO2). In view of the results of D. P. Cruikshank et al. (1993, Science 261, 742; in preparation), the work presented here leads to two possible representations of the surface of Triton. First, a two-region surface composed of a N-2 : CH4 : CO terrain, N-2 : CH4 : CO consisting of a solid solution in which N-2 is the dominant molecule, and of a H2O + C-2 terrain, composed of a mixture of pure crystalline H2O and CO2 grains. The second representation is a three-region surface composed of a N-2 : CH4 : CO terrain and two geographically separated H2O and CO2 terrains. The second step of the analysis consisted of using a bidirectionnal reflectance model (S. Doute and B. Schmitt 1998, J. Geophys. Res, Planets 103, 31367). The modeling first confirms the direct spectral analysis in that CH4 is diluted in solid beta-N-2, giving a high degree of confidence to the conclusion that the N-2 : CH4 :CO terrain is in fact a solid solution. It also provides numerical information on this terrain, namely the size of the grains, the geographical abundance, and the CH4 and CO concentrations. The large grain size(around 10 cm) would mean that the texture of this terrain is a compact crystalline solid rather than granular, which is in agreement with calculations from J. Eluszkiewicz (1991, J. Geophys. Res. 96, 19,217). In addition, an accurate modeling of the N-2 band could suggest that the temperature is greater or equal to 35.6 K. Although undistinguishable in the spectra, a maximum of 10% surface area of pure CH4 ice can be present at the surface of Triton, thus explaining the high atmospheric CH4 abundance observed by Voyager 2. Finally, the modeling showed that none of the two- or three-region representations was able to fit simultaneously the K and H regions of the spectrum of Triton. The origin of this misfit is not yet elucidated, but an instrumental effect is suspected. Some questions about the physical state of the H2O and CO2 molecules are thus raised, but unfortunately observational constraints are missing. New near-infrared observations could partly provide these missing constraints, and would be important for detecting new molecules on Triton's surface. Such new data would be especially useful to identify the three bands at 5717, 5943, and 6480 cm(-1) (1.749, 1.683, and 1.543 mu m). (C) 1999 Academic Press. C1 Domaine Univ, CNRS 54, Lab Glaciol & Geophys Environm, F-38402 St Martin Dheres, France. Observ Paris, DESPA 5, F-92195 Meudon, France. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA. Joint Astron Ctr, Hilo, HI 96720 USA. RP Quirico, E (reprint author), Univ Paris 11, Inst Astrophys Spatiale, Batiment 121, F-91405 Orsay, France. RI Schmitt, Bernard/A-1064-2009; quirico, eric/K-9650-2013 OI Schmitt, Bernard/0000-0002-1230-6627; quirico, eric/0000-0003-2768-0694 NR 32 TC 114 Z9 114 U1 0 U2 10 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 JUN PY 1999 VL 139 IS 2 BP 159 EP 178 DI 10.1006/icar.1999.6111 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500001 ER PT J AU Fanale, FP Granahan, JC McCord, TB Hansen, G Hibbitts, CA Carlson, R Matson, D Ocampo, A Kamp, L Smythe, W Leader, F Mehlman, R Greeley, R Sullivan, R Geissler, P Barth, C Hendrix, A Clark, B Helfenstein, P Veverka, J Belton, MJS Becker, K Becker, T AF Fanale, FP Granahan, JC McCord, TB Hansen, G Hibbitts, CA Carlson, R Matson, D Ocampo, A Kamp, L Smythe, W Leader, F Mehlman, R Greeley, R Sullivan, R Geissler, P Barth, C Hendrix, A Clark, B Helfenstein, P Veverka, J Belton, MJS Becker, K Becker, T CA Galileo NIMS Instrument Team SSI Instrument Team UVS Instrument Team TI Galileo's multiinstrument spectral view of Europe's surface composition SO ICARUS LA English DT Article ID INFRARED MAPPING SPECTROMETER; ULTRAVIOLET SPECTROMETER; REFLECTANCE SPECTRA; MU-M; SATELLITES; GANYMEDE; SPECTROSCOPY; MIXTURES; CALLISTO; JUPITER AB We have combined spectral reflectance data from the Solid State Imaging (SSI) experiment, the Near-Infrared Mapping Spectrometer (NIMS), and the Ultraviolet Spectrometer (UVS) in an attempt to determine the composition and implied genesis of non-H2O components in the optical surface of Europa, We have considered four terrains: (1) the "dark terrains" on the trailing hemisphere, (2) the "mottled terrain," (3) the linea on the leading hemisphere, and (4) the linea embedded in the dark terrain on the trailing hemisphere. The darker materials in these terrains exhibit remarkably similar spectra in both the visible and near infrared. In the visible, a downturn toward shorter wavelengths has been attributed to sulfur. The broad concentrations of dark material on the trailing hemisphere was originally thought to be indicative of exogenic sulfur implantation. While an exogenic cause is still probable, more recent observations by the UVS team at higher spatial resolution have led to their suggestions that the role of the bombardment may have primarily been to sputter away overlying ice and to reveal underlying endogenic non-H2O contaminants, If so, this might explain why the spectra in all these terrains are so similar despite the fact that the contaminants in the linea are clearly endogenic and those in the mottled terrain are almost certainly so. In the near infrared, all these terrains exhibit much more asymmetrical bands at 1.4 and 2.0 mu m at shorter wavelengths than spectra from elsewhere on Europa. It has been argued that this is because the water molecules are bound in hydrated salts. However, this interpretation has been challenged and it has also been argued that pure coarse ice can exhibit such asymmetric bands under certain conditions. The nature of this controversy is briefly discussed, as are theoretical and experimental studies bearing on this problem. (C) 1999 Academic Press. C1 Univ Hawaii, Honolulu, HI 96822 USA. Sci & Technol Int, Honolulu, HI 96813 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Inst Geol & Planetary Phys, Los Angeles, CA 90095 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. US Geol Survey, Flagstaff, AZ 86001 USA. RP Fanale, FP (reprint author), Univ Hawaii, 2525 Correa Rd, Honolulu, HI 96822 USA. RI Hibbitts, Charles/B-7787-2016 OI Hibbitts, Charles/0000-0001-9089-4391 NR 42 TC 29 Z9 30 U1 3 U2 5 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 JUN PY 1999 VL 139 IS 2 BP 179 EP 188 DI 10.1006/icar.1999.6117 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500002 ER PT J AU Gibbard, SG Macintosh, B Gavel, D Max, CE de Pater, I Ghez, AM Young, EF McKay, CP AF Gibbard, SG Macintosh, B Gavel, D Max, CE de Pater, I Ghez, AM Young, EF McKay, CP TI Titan: High-resolution speckle images from the Keck Telescope SO ICARUS LA English DT Article DE Titan; infrared observations; surfaces, satellite ID TRIPLE CORRELATION; GEOMETRIC ALBEDO; BINARY STARS; MU-M; ATMOSPHERE; AEROSOLS; SURFACE; MODEL; SATELLITES; RECOVERY AB Saturn's large moon Titan is unique among planetary satellites in that it possesses a thick atmosphere and a haze layer that is opaque to visible light. This haze is believed to be composed of organic compounds produced by the photolysis of methane. It has been suggested that the photochemical products of methane photolysis, primarily ethane, would "rain out" over time and may produce reservoirs of liquid hydrocarbons on Titan's surface. Such material would appear very dark, with an albedo less than or equal to 0.02 (Khare et al. 1990, Bull. Am. Astron, Sec. 22, 1033). Such low-albedo regions have not been previously detected on Titan's surface. Here we report observations of Titan at a resolution of 0.04 arcsec (0.02 arcsec/pixel) using the technique of speckle imaging from the 10-m Keck I Telescope. By observing Titan at specific infrared wavelengths which are windows through its atmosphere, we have made both an albedo map of Titan's surface at 1.6 and 2.1 mu m and an estimate of Titan's haze optical depth at these wavelengths. We clearly distinguish low-albedo features (reflectance <0.05) on Titan's surface. (C) 1999 Academic Press. C1 Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Univ Calif Los Angeles, Dept Phys, Los Angeles, CA 90095 USA. SW Res Inst, Boulder, CO USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Gibbard, SG (reprint author), Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA. EM sgibbard@beowulf.llnl.gov OI Max, Claire/0000-0003-0682-5436 NR 50 TC 63 Z9 63 U1 0 U2 2 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1999 VL 139 IS 2 BP 189 EP 201 DI 10.1006/icar.1999.6095 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500003 ER PT J AU Hillier, JK AF Hillier, JK TI Triton's surface roughness is not unusual SO ICARUS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; PHOTOMETRY; HAZES AB Previous estimates of Triton's macroscopic roughness have been hampered by the presence of atmospheric aerosols in Triton's atmosphere: only a loose constraint on the macroscopic roughness (<20 degrees) could be obtained. This study determines the locations of the clouds on Triton and then examines those areas found to be relatively devoid of cloud cover to yield tighter constraints on the surface macroscopic roughness. The most prominent cloud feature is seen near 50 degrees S, 160 degrees W with smaller features appearing near 60 degrees S, 270 degrees W and 15 degrees S, 280 degrees W. The fact that the cloud cover is not largest toward the south pole argues against a sublimation origin for the clouds, though the results are not conclusive. The surface roughness ranges from similar to 11 degrees to similar to 18 degrees for Triton's various terrains. These are near the upper limit previously determined and, while relatively smooth, are not atypical of icy satellites. Roughness values near zero which would have been suggestive of an unusual surface texture and processes are clearly excluded. These results suggest that Triton's surface structure and the processes which govern its evolution are similar to those present on other icy satellites. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hillier, JK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-501, Pasadena, CA 91109 USA. NR 20 TC 1 Z9 1 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1999 VL 139 IS 2 BP 202 EP 210 DI 10.1006/icar.1999.6100 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500004 ER PT J AU Rages, K Beebe, R Senske, D AF Rages, K Beebe, R Senske, D TI Jovian stratospheric hazes: The high phase angle view from Galileo SO ICARUS LA English DT Article DE Jupiter; atmosphere; atmospheres; structure ID JUPITER; ATMOSPHERE; AEROSOLS; POLARIMETRY; PHOTOMETRY; NEPTUNE; URANUS; ZONE; BELT AB High phase angle Galileo images of Jupiter's limb reveal the presence of stratospheric hazes in the equatorial region (latitude 9 degrees N) and the transition zone at the southern edge of the north polar region (60 degrees N). During orbit E4, images were taken in both violet and near-IR continuum filters, effectively probing Jupiter's stratosphere at two different altitudes. A discrete layer detached from the limb is present at 60 degrees N, 315 degrees W, but not 200 further east at 60 degrees N, 295 degrees W. Bright streaks running roughly north-south are also present on Jupiter's crescent at 60 degrees N. No such discrete features have been seen previously in high phase angle images of the giant planets. Nor are such features seen at 9 degrees N, where the haze appears to be more uniformly distributed in height and longitude. Radial intensity profiles across the limb are inverted to give vertical extinction profiles over similar to 200 km in Jupiter's stratosphere. These show that extinction in the discrete haze layer is enhanced by a factor of similar to 2 over its surroundings in the violet filter, with less pronounced variation in the near-IR filter. Haze distribution models were found for both latitudes in which the near-IR images constrain the haze properties near or above the 100-mbar pressure level, where the mean particle radius is about 0.45 mu m and the haze number density is near 0.15 cm(-3). In these models the violet images constrain the haze properties about 25 km higher in the atmosphere, near or above the 20-mbar pressure level, where the haze particle size is 0.32 +/- 0.01 mu m at 9 degrees N and 0.27 +/- 0.01 mu m at 60 degrees N. At this altitude, the haze number density increases by almost an order of magnitude between the equator and the polar transition region-from 0.1 cm(-3) at 9 degrees N to 0.7 cm(-3) at 60 degrees N. An alternative solution is possible at 60 degrees N, in which the haze is placed near 1 mbar in both filters, with mean particle sizes of 0.6 mu m in the violet and 1.3 mu m in the near IR. (C) 1999 Academic Press. C1 Space Phys Res Inst, Sunnyvale, CA 94087 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. CALTECH, Jet Prop Lab, Sterling Software, Pasadena, CA 91109 USA. RP Rages, K (reprint author), Space Phys Res Inst, Sunnyvale, CA 94087 USA. NR 15 TC 32 Z9 32 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 JUN PY 1999 VL 139 IS 2 BP 211 EP 226 DI 10.1006/icar.1999.6103 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500005 ER PT J AU Cabrol, NA Grin, EA Newsom, HE Landheim, R McKay, CP AF Cabrol, NA Grin, EA Newsom, HE Landheim, R McKay, CP TI Hydrogeologic evolution of Gale crater and its relevance to the exobiological exploration of Mars SO ICARUS LA English DT Article DE Mars; Mars surface; exobiology; impact processes ID GROUND ICE INTERACTIONS; LIFE; ENVIRONMENT; DEPOSITS; VALLEYS; SYSTEM; MODEL; EARTH AB The presence of an Amazonian impact crater lake in the Noachian crater Gale (located in the Aeolis northwest subquadrangle of Mars) is indicated by evidence from young floor deposits, streamlined terraces, layers, and channels observed on the central sedimentary deposit. Evidence for the filling of this lake by two processes is described: (a) the drainage of the aquifer in the Aeolis Mensae region, supported by extended mass-wasting and rim sliding in the crater at the contact with the mensae and (b) the overspilling of the northern rim by an Amazonian south transgression of the Elysium Basin. This last hypothesis is supported by hydrologic features such as channels and channel-like depressions north of the crater and by the crescent-like shape of the central sedimentary deposit. The presence of an impact melt sheet and uplifted central peak may have also generated hydrothermal activity, including an early crater lake, shortly after the formation of the crater in the Noachian period. With time, decreasing heat flux, and changing climates Gale may have experienced transitions in aqueous environments from warm and wet to cold and ice-covered water that could have provided suitable eases for various communities of microorganisms. Preservation of the biological and climatic record may have been favored in this paleolacustrine environment, which probably occured episodically over two billion years. (C) 1999 Academic Press. C1 NASA, Ames Res Ctr, SETI, Ctr Mars Explorat, Moffett Field, CA 94035 USA. Univ New Mexico, Inst Meteorit, Albuquerque, NM 87131 USA. Univ New Mexico, Dept Earth & Planetary Sci, Albuquerque, NM 87131 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Cabrol, NA (reprint author), NASA, Ames Res Ctr, SETI, Ctr Mars Explorat, MS 239-20, Moffett Field, CA 94035 USA. NR 42 TC 61 Z9 62 U1 0 U2 12 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 JUN PY 1999 VL 139 IS 2 BP 235 EP 245 DI 10.1006/icar.1999.6099 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500007 ER PT J AU Mosqueira, I Estrada, PR Brookshaw, L AF Mosqueira, I Estrada, PR Brookshaw, L TI Hydrodynamical simulations of narrow planetary rings. I. Scaling SO ICARUS LA English DT Article DE planetary rings; smoothed particle hydrodynamics; self-gravity model; ring dynamics ID SATELLITE LINDBLAD RESONANCES; SPIRAL DENSITY WAVES; SATURNS RINGS; PARTICLE DISKS; COLLISIONAL SIMULATIONS; NUMERICAL-SIMULATION; LOCAL SIMULATIONS; URANIAN RINGS; DYNAMICS; EVOLUTION AB We investigate the global dynamics of the uranian rings using a modified 2-D smoothed particle hydrodynamic code combined with a 2-D tree code used to compute the particle-to-particle gravitational interactions. This code includes epicyclic fluid motion, nonaxisymmetric Row, local and nonlocal shear viscosity, self-consistent scale height evolution, ring-satellite gravitational interaction and coevolution, and ring self-gravity. To follow the scale height of each SPH particle we solve the vertical momentum equation for the flow using a Runge-Kutta scheme with a second order polynomial fit to the vertical behavior of the fluid pressure (N. Borderies et al., 1985, Icarus 63, 406-420). The behavior of the fluid viscosity is obtained fi-om I. Mosqueira (1996, Ph.D. thesis, Cornell University, Ithaca, NY), who found good agreement between a low optical depth extension of the high optical depth nonlocal viscosity model of Borderies et al. (1985) with the results of a local patch-code ring simulation. Our present viscosity model includes a further correction which accounts for the epicyclic limit to the mean free path (P. Goldreich and S, Tremaine, 1978, Icarus 34, 227-239), This treatment covers both the high and the low ring density regimes so long as the fluid treatment remains valid. All energy source and sink terms in the presence of a nonzero fluid velocity divergence are self-consistently considered, including terms not considered in prior studies of rings. Furthermore, a new method has been tested and used to remove the noise contribution to the viscous momentum Aux which occurs in traditional treatments of the viscosity within the SPN framework. In the present context this correction is needed to assure a physical behavior for the ring. Even within a 2-D framework the uranian rings are so narrow compared to their semimajor axes that radial resolution requires too many particles given our present computer resources. To address this issue we have developed a physical scaling that reduces the semimajor axis of the ring while preserving its width and, we believe, retains the relevant global satellite-ring dynamics. In the case of ring resolution on the order of kilometers, with a value of the scaling parameter that reduces the ring's semi-major axis by a factor of 20, our scaling allows for savings between a factor of 500 in the case of synodic time scales to a factor of 10,000 for viscous time scales. We expect this scaling to figure significantly in numerical studies of the global dynamics of planetary rings in the future. In the present study we use this scaling to follow the evolution of an epsilon-like ring in the presence of an m = 2 mode (but no satellites) with and without self-gravity. In these runs, chosen as an initial demonstration of the usefulness and applicability of our scaling, the ring can be seen to evolve in the presence of shear, (C) 1999 Academic Press. C1 Ames Res Ctr, Div Space Sci, Moffett Field, CA 94305 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Inst Geophys & Planetary Phys, Livermore, CA 94720 USA. RP Mosqueira, I (reprint author), Ames Res Ctr, Div Space Sci, Mail Stop 245-3, Moffett Field, CA 94305 USA. NR 48 TC 4 Z9 4 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 JUN PY 1999 VL 139 IS 2 BP 260 EP 285 DI 10.1006/icar.1999.6114 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500009 ER PT J AU Benner, LAM Hudson, RS Ostro, SJ Rosema, KD Giorgini, JD Yeomans, DK Jurgens, RF Mitchell, DL Winkler, R Rose, R Slade, MA Thomas, ML Pravec, P AF Benner, LAM Hudson, RS Ostro, SJ Rosema, KD Giorgini, JD Yeomans, DK Jurgens, RF Mitchell, DL Winkler, R Rose, R Slade, MA Thomas, ML Pravec, P TI Radar observations of asteroid 2063 Bacchus SO ICARUS LA English DT Article DE asteroids; radar; Bacchus ID NEAR-EARTH ASTEROIDS; BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; ORDINARY CHONDRITE METEORITES; BINARY ASTEROIDS; CATASTROPHIC COLLISIONS; PHOTOMETRIC MODELS; DOUBLET CRATERS; GALILEO SHAPE; TIDAL FORCES; SPIN-STATE AB We report Doppler-only (cw) and delay-Doppler radar observations of Bacchus obtained at Goldstone at a transmitter frequency of 8510 MHz (3.5 cm) on 1996 March 22, 24, and 29. Weighted, optimally filtered sums of cw and delay-Doppler echoes achieve signal-to-noise ratios of similar to 80 and similar to 25, respectively, and cower about 180 degrees of rotation phase (period = 14.90 h; Pravec et al, 1998), Our cw observations place up to four 2-Hz-resolution cells on Bacchus at echo powers greater than two standard deviations of the noise. Delay-Doppler observations typically place about ten 0.5-mu s (75-m)x 1-Hz cells on Bacchus above the same threshold. A weighted sum of all cw spectra gives an OC radar cross section of 0.12(-0.02)(+0.06) km(2) and a circular polarization ratio of 0.21 +/- 0.01. The dispersion of the echoes in time delay indicates a lower bound on Bacchus' maximum pole-on breadth of 0.6 km that is consistent with the echo bandwidth (6+/-2 Hz) and rotation period. Echo spectra on March 22 and delay-Doppler images on all three days show a central deficit of echo power that provides strong evidence for a bifurcation in the shape. Inversion of delay-Doppler images, cw spectra, and optical lightcurves obtained at Ondrejov Observatory yields single-lobe and two-lobe models that define lower and upper bounds on the degree of bifurcation. Both shape models have a prominent central concavity, modestly asymmetric shapes, and similar physical dimensions, spin vectors, and radar and optical geometric albedos, We adopt the more conservative single-lobe shape model as our working model and explore its implications. It has a radar-derived sidereal rotation period P-sid = 15.0 +/- 0.2 h and a north pole within a few tens of degrees of ecliptic longitude lambda = 24 degrees and ecliptic latitude beta = -26 degrees; retrograde rotation is likely, It has dimensions of 1.11 x 0.53 x 0.50 km, an effective diameter (the diameter of a sphere with the same volume as the model) D-eff = 0.63(-0.06)(+0.13) km, and radar and optical geometric albedos <(sigma)over cap> = 0.33(-0.11)(+0.25) and p(v) = 0.56(-0.18)(+0.12), respectively, that are larger than most estimated for other asteroids. Bacchus' low circular polarization ratio and high radar albedo are consistent with nearly regolith-free ordinary chondrite and basaltic achondrite compositions, but its high optical geometric albedo seems inconsistent with an ordinary chondrite composition and may favor a V-class composition. Bacchus has less structural complexity at centimeter-to-decimeter spatial scales and its near-surface is more dense (either more metal, lower porosity, or both) than the average radar-detected near-Earth asteroid. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Washington State Univ, Sch Elect Engn & Comp Sci, Pullman, WA 99164 USA. Acad Sci Czech Republ, Astron Inst, CZ-25165 Ondrejov, Czech Republic. RP Benner, LAM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Pravec, Petr/G-9037-2014 NR 59 TC 23 Z9 24 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1999 VL 139 IS 2 BP 309 EP 327 DI 10.1006/icar.1999.6094 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500012 ER PT J AU Withey, PA Nuth, JA AF Withey, PA Nuth, JA TI Formation of single-magnetic-domain iron particles via vapor-phase nucleation: Implications for the solar nebula SO ICARUS LA English DT Article ID ENHANCED COAGULATION; GRAINS; CHONDRULES AB We report experimental evidence of the production of single-magnetic-domain iron grains via vapor-phase nucleation even in the absence of an ambient magnetic field. These single domain grains are thermodynamically stable as fully saturated magnetic dipoles, The spontaneous formation of fully magnetized single-domain iron grains, and by inference a variety of other single-domain particles such as taenite or magnetite, could greatly increase the coagulation efficiency of submicrometer-sized grains in the primitive solar nebula. An important test of this hypothesis is proposed: an examination of 20- to 50-nm diameter iron grains in the matrix of very primitive chondrites should reveal an interconnected, three-dimensional string or web-like structure within the matrix. C1 W Virginia Wesleyan Coll, Dept Phys & Engn, Buckhannon, WV 26201 USA. NASA, Goddard Space Flight Ctr, Astrochem Branch, Greenbelt, MD 20771 USA. RP Withey, PA (reprint author), W Virginia Wesleyan Coll, Dept Phys & Engn, Buckhannon, WV 26201 USA. RI Nuth, Joseph/E-7085-2012 NR 21 TC 10 Z9 10 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 JUN PY 1999 VL 139 IS 2 BP 367 EP 373 DI 10.1006/icar.1999.6106 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500016 ER PT J AU Brown, RH Cruikshank, DP Pendleton, Y Veeder, GJ AF Brown, RH Cruikshank, DP Pendleton, Y Veeder, GJ TI Water ice on Nereid SO ICARUS LA English DT Article DE Nereid; surface composition; surfaces, icy; spectroscopy ID OUTER SOLAR-SYSTEM; NEAR-INFRARED SPECTROSCOPY; OPTICAL-CONSTANTS; REFLECTANCE; ASTEROIDS; MIXTURES; NEPTUNE; CU26 AB A near-infrared spectrum of Neptune's satellite Nereid was obtained at the Keck Observatory on 1997 May 1. The spectrum shows two absorptions near 1.54 and 2.03 mu m and is well matched by a synthetic spectrum of an intimate mix of low-temperature, particulate water ice and dark, blue-colored material. Comparisons of Nereid's spectrum with those of other objects such as the Centaurs 1997 CU(26), and 5145 Pholus, and Neptune's largest regular satellite Proteus, admit the possibility that Nereid Is a primordial satellite of Neptune (and perhaps its only remaining one) rather than a captured object, but more data are needed to rule out one scenario or the other. (C) 1999 Academic Press. 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. EM rhb@lpl.arizona.edu NR 33 TC 13 Z9 13 U1 0 U2 0 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1999 VL 139 IS 2 BP 374 EP 378 DI 10.1006/icar.1999.6109 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500017 ER PT J AU Owen, TC Cruikshank, DP Ore, CMD Geballe, TR Roush, TL de Bergh, C AF Owen, TC Cruikshank, DP Ore, CMD Geballe, TR Roush, TL de Bergh, C TI Detection of water ice on Saturn's satellite Phoebe SO ICARUS LA English DT Article DE Phoebe; water ice; Kuiper Belt; irregular satellites ID NEAR-INFRARED SPECTROSCOPY; OUTER JOVIAN-SATELLITES; SOLAR-SYSTEM; DARK MATERIAL; ASTEROIDS; PHOTOMETRY; SPECTRA; LAPETUS; BELT AB The near-infrared reflectance spectrum of Saturn's satellite Phoebe shows a broad absorption band at 2.0 mu m and absorption at lambda > 2.2 mu m, both characteristic of H(2)O ice. We have successfully modeled the surface of Phoebe with an intimate (granular) mix of H(2)O ice (3% by weight, grain size 500 mu m) mixed with fine grains of H(2)O ice (0.25%) with amorphous carbon (grain size 900 mu m) as the dominant component. This model reproduces the shape of the measured spectrum and the observed albedo of 0.10 for Phoebe, but it is not unique. The presence of ice establishes Phoebe as an original member of the outer Solar System rather than a renegade asteroid. (C) 1999 Academic Press. C1 Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SETI Inst, Moffett Field, CA 94035 USA. Joint Astron Ctr, Hilo, HI 96720 USA. Observ Paris, F-92195 Meudon, France. RP Owen, TC (reprint author), Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA. EM owen@hubble.ifa.hawaii.edu NR 41 TC 36 Z9 36 U1 1 U2 1 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUN PY 1999 VL 139 IS 2 BP 379 EP 382 DI 10.1006/icar.1999.6116 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 216XJ UT WOS:000081469500018 ER PT J AU Yu, JH Postrekhin, E Ma, KB Chu, WK Wilson, T AF Yu, JH Postrekhin, E Ma, KB Chu, WK Wilson, T TI Vibration isolation for space structures using HTS-magnet interaction SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID LEVITATION-SYSTEM AB We employ the MTS-magnet interaction in the mechanical design of a vibration isolator. One common element of space structures is the coupling between multiple substructures or mechanical parts. Often, such coupling needs to provide a transmission of force between the two systems while blocking out the propagation of the vibration energy from one system to the other. A solution to this is to establish a soft link between the two system. In this paper, we design a passive vibration isolation device employing the characteristics of the MTS-magnet interaction. The configuration of the vibration isolator consists of a ring magnet and a thin disk HTS where the HTS is located in the middle of the magnet and is levitated. Experiments show that the natural frequency of the system is 4 Hz and the frequencies above 10 Hz are successfully isolated. Such a passive device in space applications is superior to similar active devices that often require bulky control circuit boxes and consume considerable energy that is not readily available in the space environment. The concept can also be used as an isolation platform and can combine with the active vibration isolation technology so as to attenuate the vibration of all frequencies. C1 Univ Houston, Texas Ctr Superconduct, Houston, TX 77204 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Yu, JH (reprint author), Univ Houston, Texas Ctr Superconduct, Houston, TX 77204 USA. NR 4 TC 5 Z9 5 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 908 EP 910 DI 10.1109/77.783444 PN 1 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225LY UT WOS:000081964100195 ER PT J AU Lee, E Ma, KB Wilson, TL Chu, WK AF Lee, E Ma, KB Wilson, TL Chu, WK TI Characterization of superconducting bearings for lunar telescopes SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID CERAMICS; FORCES AB The hybrid superconductor magnet bearing system for a lunar telescope has been developed based on passive magnetic levitation and the flux pinning effect of high-temperature superconductivity. The rationale lies in the unique capability of high-temperature superconductor (HTS) to adapt to the low temperature and vacuum environments in space or on the Moon, and to enhance system stability passively without power consumption. Characterization experiments have been conducted to understand its dynamic behavior and to estimate the required motor torque for its driving system design. Characterization experiments show that the hybrid HTS-magnet bearing system has periodical oscillation of drag torque. The bearing also suffers from small periodic oscillation on top of it due to discontinuous distribution of HTS. However, the magnitude of drag torque is velocity independent and very small. It makes the bearing attractive for high speed application. Finally, design guidelines for superconducting bearing systems are suggested based on experimental results. C1 Univ Houston, Texas Ctr Superconduct, Houston, TX 77004 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Lee, E (reprint author), Univ Houston, Texas Ctr Superconduct, Houston, TX 77004 USA. NR 4 TC 11 Z9 11 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 911 EP 915 DI 10.1109/77.783445 PN 1 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225LY UT WOS:000081964100196 ER PT J AU Schoelkopf, RJ Moseley, SH Stahle, CM Wahlgren, P Delsing, P AF Schoelkopf, RJ Moseley, SH Stahle, CM Wahlgren, P Delsing, P TI A concept for a submillimeter-wave single-photon counter SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID ELECTRON TRANSISTOR; BOLOMETERS; DETECTOR; JUNCTION AB We discuss the design for a submillimeter-wave photometer, using a combination of superconducting and single-electron devices, which would have high quantum efficiency, very low noise-equivalent powers, and eventually even submicrosecond timing resolution. The absorption of above-gap photons occurs in a small strip of superconducting Al, whose normal-state resistance can be matched efficiently to an antenna of a higher gap (Nb) superconductor. The quasiparticles produced by photon absorption are then confined via Andreev reflection, and forced to tunnel through a small SIS tunnel junction. The tunneling time is much shorter than the known (> 10 mu s) quasiparticle recombination time, so collection efficiency will be high. The device sensitivity would be limited by the small subgap current in the high-quality Al/AlOx/Al tunnel junction at temperatures (100 mK) well below T-c. Scaling based on the larger junctions used in X-ray detector applications suggests that the total dark current can be < 0.1 pA, or of order 10(5) electrons/second, corresponding to an NEP of less than 10(-19) W/root Hz at 500 microns (600 GHz). The photocurrent will be measured using a fast single-electron transistor (RF-SET), which allows a shot-noise-limited performance even for the very small currents delivered from this low capacitance and high impedance SIS junction. Results of initial fabrication and de characterization of an integrated photodetector are also given. C1 Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. NASA, Goddard Space Flight Ctr, Lab Astron & Astrophys, Greenbelt, MD 20771 USA. Chalmers Univ Technol, Dept Microelect & Nanosci, S-41296 Gothenburg, Sweden. Gothenburg Univ, S-41296 Gothenburg, Sweden. RP Schoelkopf, RJ (reprint author), Yale Univ, Dept Appl Phys, 15 Prospect St, New Haven, CT 06520 USA. RI Delsing, Per/F-7288-2010; Moseley, Harvey/D-5069-2012; Schoelkopf, Robert/J-8178-2012 OI Delsing, Per/0000-0002-1222-3506; NR 26 TC 54 Z9 55 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 2935 EP 2939 DI 10.1109/77.783645 PN 3 PG 5 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500025 ER PT J AU Finkbeiner, FM Chen, TC Aslam, S Figueroa-Feliciano, E Kelley, RL Li, M Mott, DB Stahle, CK Stahle, CM AF Finkbeiner, FM Chen, TC Aslam, S Figueroa-Feliciano, E Kelley, RL Li, M Mott, DB Stahle, CK Stahle, CM TI Fabrication of superconducting bilayer transition edge thermometers and their application for spaceborne X-ray microcalorimetry SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID ELECTROTHERMAL FEEDBACK AB The transition between normal conduction and superconductivity in superconducting materials can be exploited as a highly sensitive thermometer. Transition temperatures can be tailored through the selection of materials, their component material thicknesses, and the comparative ratios in cases of more than one material. Two bilayer configurations, Ag/Al and Au/Mo, are examined, including details of preparation,testing, and encountered difficulties. Proposed designs for spaceflight detector applications are discussed. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Global Sci & Technol Inc, Greenbelt, MD 20770 USA. Raytheon Corp STX, Greenbelt, MD 20770 USA. Orbital Sci Corp, Greenbelt, MD 20771 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. RP Finkbeiner, FM (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Aslam, Shahid/D-1099-2012; Kelley, Richard/K-4474-2012 NR 8 TC 20 Z9 20 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 2940 EP 2942 DI 10.1109/77.783646 PN 3 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500026 ER PT J AU Segall, K Wilson, CM Li, L Davies, AK Lathrop, R Gaidis, MC Prober, DE Szymkowiak, AE Moseley, SH AF Segall, K Wilson, CM Li, L Davies, AK Lathrop, R Gaidis, MC Prober, DE Szymkowiak, AE Moseley, SH TI Single photon imaging X-ray spectrometers SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID SUPERCONDUCTING TUNNEL-JUNCTIONS AB We have developed superconducting, single-photon imaging x-ray detectors with an energy resolution of 26 eV FWHM at 6 keV and a spatial resolution of 0.5 mu m over an effective area of 18 mu m x 100 mu m. The energy resolution is among the best reported for this kind of detector and is within a factor of approximate to 4 of it's theoretical limit. The calculated absorption efficiency of the detector is 28%. Scaling to larger areas and higher quantum efficiency appear possible. We discuss the device design and readout along with possible sources of resolution broadening. C1 Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Segall, K (reprint author), Yale Univ, Dept Appl Phys, New Haven, CT 06520 USA. RI Wilson, Christopher/A-9676-2008; Gaidis, Michael/D-3327-2013 NR 8 TC 9 Z9 9 U1 2 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 3326 EP 3329 DI 10.1109/77.783741 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500121 ER PT J AU Yeager, CJ Finkbeiner, F Shirron, PJ DiPirro, MJ AF Yeager, CJ Finkbeiner, F Shirron, PJ DiPirro, MJ TI High resolution X-ray and infrared detectors using magnetic penetration depth thermometers. SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID ELECTROTHERMAL FEEDBACK; FILM AB We Pre developing a high-resolution a-ray detector using II magnetic penetration depth thermometer (PDT). a PDT uses the strong temperature dependence of the magnetic penetration depth of a superconducting film. PDTs were originally developed for use Pt liquid helium temperatures and achieved resolutions on the order of 2 nK The low intrinsic heat capacity and high sensitivity make it potentially useful for x-ray microcalorimetry. Using a superconducting bilayer film of aluminum and silver, a PDT can be developed to work Pt 100 mK or lower. a detector with a 1 mm pixel would be background limited and have on intrinsic resolution better than 2 eV out of 6 keV. Higher resolutions could be achieved for lower energy sources, making this technique useful as an infrared bolometer. Results of the current work will be presented along with analysis of design issues. C1 Raytheon STX, Lanham, MD 20706 USA. Univ Maryland, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Yeager, CJ (reprint author), Raytheon STX, Lanham, MD 20706 USA. NR 10 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 3334 EP 3337 DI 10.1109/77.783743 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500123 ER PT J AU Miranda, FA Subramanyam, G Van Keuls, FW Romanofsky, RR AF Miranda, FA Subramanyam, G Van Keuls, FW Romanofsky, RR TI A K-band (HTS,gold)/ferroelectric thin film/dielectric diplexer for a discriminator-locked tunable oscillator SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA AB The performance of a K-band conductor/ferroelectric thin film/dielectric tunable diplexer that is being developed as a critical part of a discriminator-locked tunable oscillator will be discussed. This diplexer consists of two K-band (18 to 22 GHz), two-pole YBCO/SrTiO3/LaAlO3 bandpass filters coupled to the microwave signal input port through a 50 Omega power splitter. When tested independently at 77 K and varying bias of +/-400 V, these filters exhibited a passband frequency shift greater than 1.7 GHz, while maintaining a non-deembeded insertion loss near 2.0 dB, Electromagnetic modeling results for the diplexer indicate that varying the dielectric constant of the SrTiO3 from 3000 (similar to 77 K) to 500 (similar to 300 K) will shift the diplexer's "cross-over" frequency from 19 to 21 GHz, with only minor variations in insertion loss. Measurements at 298 K of this diplexer circuit using a gold/SrTiO3/LaAlO3 structure resulted in non-deembeded insertion losses of 3.3 dB and 2.5 dB at the filters' maxima at 20.65 and 22.43 GHz, respectively, with a cross-over frequency at 21.07 GHz, These room temperature results are consistent with modeling. The measured characteristics of YBCO/SrTiO3/LaAlO3 diplexers at cryogenic temperatures will be presented. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Miranda, FA (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 10 TC 7 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 3581 EP 3584 DI 10.1109/77.783804 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500184 ER PT J AU Harnack, O Beuven, S Darula, M Kohlstedt, H Tarasov, M Stephansov, E Ivanov, Z AF Harnack, O Beuven, S Darula, M Kohlstedt, H Tarasov, M Stephansov, E Ivanov, Z TI HTS mixers based on the Josephson effect and on the hot-electron bolometric effect SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CA AB We report on our experimental studies of high-T(C) Josephson mixers and high-T(C) hot-electron bolometric (HEB) effect mixers. Mixers based on high-T(C) bicrystal Josephson junctions have been fabricated, and noise, conversion efficiency, and receiver bandwidth measurements have been performed in the frequency range between 90 and 550 GHz. The dependence of the mixer performance on the operation temperature has been studied. High-T(C) HEB mixers have been fabricated on MgO and sapphire substrates. We successfully sized the dimensions of the effective device volume down and managed to fabricate 50-60 nm long devices. In such short structures phonon diffusion into the normal metal electrodes should significantly improve the mixer performance. C1 Forschungszentrum Julich, Inst Thin Film & Ion Technol, D-52425 Julich, Germany. Chalmers, Inst Phys Appl, S-41296 Gothenburg, Sweden. RP Harnack, O (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 168-314, Pasadena, CA 91109 USA. RI Tarasov, Mikhail/B-2221-2014 OI Tarasov, Mikhail/0000-0002-8330-9163 NR 14 TC 6 Z9 6 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 3765 EP 3768 DI 10.1109/77.783847 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500227 ER PT J AU Kleinsasser, AW Barner, JB Burns, MJ Karasik, BS McGrath, WR AF Kleinsasser, AW Barner, JB Burns, MJ Karasik, BS McGrath, WR TI Fabrication of terahertz YBa2Cu3O7-delta hot-electron bolometer mixers SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID NOISE AB Superconducting hot-electron bolometer (HEB) mixers are promising heterodyne detectors for THz frequencies. HEB mixers operating at 4 K or below offer the possibility of near-quantum limited performance without an upper frequency limit imposed by the superconducting energy gap. High temperature superconductor HEB mixers offer very sensitive, low power heterodyne detectors operating at temperatures ap preaching 90 K for applications requiring closed-cycle refrigeration. We report on recent progress in fabricating and characterizing high-T-c mixers based on ultra-thin (10-20 nm) YBa2Cu3O7-delta films patterned to submicrometer dimensions (0.1-1 mu m) and incorporated into 1-3 THz planar miser circuits. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Kleinsasser, AW (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RI Burns, Michael/D-2939-2011 OI Burns, Michael/0000-0001-9804-405X NR 10 TC 8 Z9 8 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 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 4197 EP 4200 DI 10.1109/77.783950 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500330 ER PT J AU Karasik, BS McGrath, WR Wyss, RA AF Karasik, BS McGrath, WR Wyss, RA TI Optimal choice of material for HEB superconducting mixers SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID ELECTRON-PHONON INTERACTION; ALUMINUM FILMS; NB FILMS; SCATTERING; TRANSITION; NOISE; MICROBOLOMETER; BOLOMETER; THZ AB We demonstrate that a potential distinction in ultimate performance of phonon-cooled and diffusion-cooled HEB mixers is not due to the cooling mechanisms but rather due to the different properties of available superconductors. The only available material for a phonon-cooled mixer with sufficiently large IF bandwidth (similar to 4 GHz) is NbN, whereas a variety of clean materials (e.g., Nb, NbC, Al) are suitable for a diffusion-cooled mixer. For a readily achievable device length of 0.1 mu m for example, the diffusion-cooled IF bandwidth can be greater than or equal to 10 GHz. The requirement of low local oscillator (LO) power can also be more easily met in diffusion-cooled devices by selection of a material with lower critical temperature and low density of electron states. In contrast, the parameters in the NbN-based mixer cannot be widely varied because of the high resistivity and high transition temperature of the material and the necessity of using ultrathin films. Given the limited availability of LO power from compact solid-state sources at frequencies above 1 THz, a diffusion-cooled mixer based on aluminum is a very attractive choice for low-background radioastronomy applications. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Karasik, BS (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RI Karasik, Boris/C-5918-2011 NR 26 TC 11 Z9 11 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 4213 EP 4216 DI 10.1109/77.783954 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500334 ER PT J AU Skalare, A McGrath, WR AF Skalare, A McGrath, WR TI A frequency-domain mixer model for diffusion-cooled hot-electron bolometers SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY LA English DT Article; Proceedings Paper CT 1998 Applied Superconductivity Conference CY SEP 13-18, 1998 CL PALM DESERT, CALIFORNIA ID LOW-NOISE; BANDWIDTH AB A new frequency domain hot-electron bolometer (HEB) mixer model is described, which takes into account the non-uniform temperature distribution found in superconducting diffusion-cooled devices. In this model the bolometer is discretized into a finite number of segments, and the non-linear large signal response to local oscillator and DC heating is found by an iterative algorithm. A frequency-domain coupling matrix is introduced to represent small-signal modulations around the large-signal values of temperatures and heat flows inside the device. The coupling matrix and a Norton representation of the mixer DC and intermediate frequency (IF) circuit allows the mixer conversion to be calculated. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Skalare, A (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. NR 13 TC 3 Z9 3 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1051-8223 J9 IEEE T APPL SUPERCON JI IEEE Trans. Appl. Supercond. PD JUN PY 1999 VL 9 IS 2 BP 4444 EP 4447 DI 10.1109/77.784011 PN 3 PG 4 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 225MC UT WOS:000081964500391 ER PT J AU Ma, KP Chen, M Houshmand, B Qian, YX Itoh, T AF Ma, KP Chen, M Houshmand, B Qian, YX Itoh, T TI Global time-domain full-wave analysis of microwave circuits involving highly nonlinear phenomena and EMC effects SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE crosstalk; electromagnetic compatibility; equivalent-source algorithm; finite-difference time-domain method; housing effect; ring oscillator; self-oscillating mixer ID ACTIVE DEVICES; FDTD AB The global time-domain analysis of microwave circuits involving highly nonlinear phenomena such as injection locking and intermodulation, along with parasitic effects and electromagnetic compatibility (EMC) issues is presented in this paper. Employing the concept of equivalent sources, the device-wave interaction is characterized and incorporated into the finite-difference time-domain method. The investigation of nonlinear phenomena is accomplished by utilizing a large-signal device circuit model. Measured results are also provided for comparisons with simulated results. The applicability of this equivalent-source algorithm for investigating EMC effects is also demonstrated, A correspondence between simulated and measured EMC phenomenon indicates the usefulness of this algorithm in providing an effective tool for real world radio-frequency front-end circuit designs. C1 Apple Comp Inc, Commun Engn, Cupertino, CA 95014 USA. AKM Design Tek, San Diego, CA 92131 USA. CALTECH, Jet Prop Lab, Radar Sci & Engn Sect, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. RP Ma, KP (reprint author), Apple Comp Inc, Commun Engn, Cupertino, CA 95014 USA. NR 12 TC 23 Z9 23 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 JUN PY 1999 VL 47 IS 6 BP 859 EP 866 DI 10.1109/22.769319 PN 2 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 207YB UT WOS:000080962400006 ER PT J AU Su, DL Park, JS Qian, YX Houshmand, B Itoh, T AF Su, DL Park, JS Qian, YX Houshmand, B Itoh, T TI Waveguide bandpass filter analysis and design using multimode parallel FDTD diakoptics SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article ID TIME-DOMAIN DIAKOPTICS; CIRCUITS AB This paper presents an analysis and design method based on finite-difference time-domain diakoptics, A complex structure is di,divided into several smaller subsections. The characteristics of the subsections are analyzed entirely in the time domain using mode-type discrete time-domain Green's functions, A multimode parallel algorithm is proposed to connect the subsections, Several filter analysis and design examples are presented. The effectiveness and accuracy of this method is demonstrated by comparison with other computational methods and measurements. C1 Beijing Univ Aeronaut & Astronaut, Beijing 100083, Peoples R China. Soonchunhyang Univ, Dept Elect, Asan 336745, South Korea. Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Radar Sci & Engn Sect, Pasadena, CA 91101 USA. RP Su, DL (reprint author), Beijing Univ Aeronaut & Astronaut, Beijing 100083, Peoples R China. NR 22 TC 6 Z9 8 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 JUN PY 1999 VL 47 IS 6 BP 867 EP 876 DI 10.1109/22.769320 PN 2 PG 10 WC Engineering, Electrical & Electronic SC Engineering GA 207YB UT WOS:000080962400007 ER PT J AU Li, W He, Z Knoll, GF Wehe, DK Stahle, CM AF Li, W He, Z Knoll, GF Wehe, DK Stahle, CM TI Spatial variation of energy resolution in 3-D position sensitive CZT gamma-ray spectrometers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1998 Nuclear Science Symposium (NSS) CY NOV 08-14, 1998 CL TORONTO, CANADA SP IEEE ID SEMICONDUCTOR AB This paper reports the energy resolutions obtained from two 3-D CZT gamma-ray spectrometers. Each device is a 1 cm(3) cube CZT crystal with an 11x11 pixellated anode. For single-interaction events in the detector, the gamma ray interaction location can be determined in 3-D. With the volume of each detector conceptually divided into 11x11x18 voxels, the spectra of single-interaction events from each of the voxels were collected. The energy resolutions at 662 keV from a single voxel are typically 9.3 keV and 9.9 keV for the two detectors, with electronic noise contributing similar to 7 keV and similar to 6 keV respectively. A spatially-varying energy resolution has been observed for both detectors, which accounts for the degradation of energy resolution of the overall spectrum combined from all the voxels. The causes for the variations have been analyzed, and the impact of a spatially-varying energy resolution on a CZT gamma-ray spectrometer has been investigated. C1 Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48109 USA. NASA, Goddard Space Flight Ctr, Orbital Sci Corp, Greenbelt, MD 20771 USA. RP Li, W (reprint author), Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48109 USA. NR 5 TC 10 Z9 10 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1999 VL 46 IS 3 BP 187 EP 192 DI 10.1109/23.775512 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 216XM UT WOS:000081469800014 ER PT J AU Iwanczyk, JS Tull, CR Segal, JD Kenney, CJ Bradley, J Hedman, B Hodgson, KO AF Iwanczyk, JS Tull, CR Segal, JD Kenney, CJ Bradley, J Hedman, B Hodgson, KO TI Large area silicon drift detectors for X-rays - New results. SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1998 Nuclear Science Symposium (NSS) CY NOV 08-14, 1998 CL TORONTO, CANADA SP IEEE ID HIGH-RESISTIVITY SILICON; SPECTROSCOPY; PREAMPLIFIER; CHAMBER AB Large area silicon drift detectors, consisting of 8 mm and 12 mm diameter hexagons, were fabricated on 0.35 mm thick high resistivity n-type silicon. An external FET and a low-noise charge sensitive preamplifier were used for testing the prototype detectors. The detector performance was measured in the range -75 ts 25 degrees C using Peltier cooling, and from 0.125 to 6 mu s amplifier shaping time. Measured energy resolutions were 159 eV FWHM and 263 eV FWHM for the 0.5 cm(2) and 1 cm(2) detectors, respectively (at 5.9 keV, -75 degrees C, 6 Cls shaping time). The uniformity of the detector response over the entire active area (measured using 560 nm light) was < 0.5 %. C1 Photon Imaging Inc, Northridge, CA 91324 USA. Univ Hawaii, Dept Phys, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Stanford Univ, Stanford Synchrotron Radiat Lab, Stanford, CA 94305 USA. Stanford Univ, Dept Chem, Stanford, CA 94305 USA. RP Iwanczyk, JS (reprint author), Photon Imaging Inc, 19355 Business Ctr Dr,Suite 8, Northridge, CA 91324 USA. NR 15 TC 16 Z9 16 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD JUN PY 1999 VL 46 IS 3 BP 284 EP 288 DI 10.1109/23.775529 PN 1 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 216XM UT WOS:000081469800031 ER PT J AU Fonte, P Peskov, V Ramsey, B AF Fonte, P Peskov, V Ramsey, B TI The fundamental limitations of high-rate gaseous detectors SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 1998 Nuclear Science Symposium (NSS) CY NOV 08-14, 1998 CL TORONTO, CANADA SP IEEE ID MICROSTRIP GAS COUNTERS; BREAKDOWN; MICROMEGAS; RESOLUTION; FEEDBACK; CHAMBERS AB Future high-luminosity experiments make serious demands on detector technologies and have prompted a "chain" of inventions of new high-rate gaseous detectors: Microstrip Gas Counters (MSGC's), Microgap Chambers (MGC's), Compteur A Trou (CAT's), Micromesh Gas Structure (MICROMEGAS), and Gas Electron Multipliers (GEM's). We report results from a systematic study of breakdown mechanisms in these and other gaseous detectors recently chosen or considered as candidates for high-luminosity experiments. It was found that, for all the detectors tested, the maximum achievable gain before breakdown appeared, dropped dramatically with rate, sometimes inversely proportional to it. Further, in the presence of alpha particles, typical of the backgrounds in high-energy experiments, additional gain drops of 1-2 orders of magnitude were observed for some detectors. We discovered that the breakdown in these detectors was through a previously unknown mechanism for which we give a qualitative explanation. We also present possible ways of increasing the value of the maximum achievable detector gain at high rates and have verified these experimentally. C1 Univ Coimbra, LIP, P-3000 Coimbra, Portugal. Univ Coimbra, Inst Super Engn, P-3000 Coimbra, Portugal. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Fonte, P (reprint author), Univ Coimbra, LIP, P-3000 Coimbra, Portugal. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 20 TC 23 Z9 23 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 1999 VL 46 IS 3 BP 321 EP 325 DI 10.1109/23.775537 PN 1 PG 5 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 216XM UT WOS:000081469800039 ER PT J AU Teo, PC Hel-Or, Y AF Teo, PC Hel-Or, Y TI Design of multiparameter steerable functions using cascade basis reduction SO IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE LA English DT Article DE steerable filters; filter design; low-level vision; pattern analysis ID DECOMPOSITION; FILTERS; MOTION; PHASE AB An efficient method of computing the least-squares optimal basis functions to steer any function locally is presented. The method combines the Lie group-theoretic and the singular value decomposition approaches. Its efficiency is demonstrated with the design of basis functions to steer a Gabor function under the four-parameter linear transformation group. C1 Stanford Univ, Dept Comp Sci, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Stanford Univ, Dept Comp Sci, Stanford, CA 94305 USA. EM teo@cs.stanford.edu; toky@hp.technion.ac.il NR 19 TC 15 Z9 15 U1 0 U2 2 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0162-8828 EI 1939-3539 J9 IEEE T PATTERN ANAL JI IEEE Trans. Pattern Anal. Mach. Intell. PD JUN PY 1999 VL 21 IS 6 BP 552 EP 556 DI 10.1109/34.771325 PG 5 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 205KD UT WOS:000080819100006 ER PT J AU Bejczy, AK Tanie, K Coiffet, P AF Bejczy, AK Tanie, K Coiffet, P TI Special section on virtual reality in robotics and automation - Foreword SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MITI, AIST, Mech Engn Lab, Oho, Ibaraki 305, Japan. Lab Robot Paris, F-78140 Velizy, France. RP Bejczy, AK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD JUN PY 1999 VL 15 IS 3 BP 397 EP 399 DI 10.1109/TRA.1999.768173 PG 3 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA 203LK UT WOS:000080709000001 ER PT J AU Kim, WS AF Kim, WS TI Computer vision assisted virtual reality calibration SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article; Proceedings Paper CT IEEE International Conference on Robotics and Automation CY APR 21-27, 1997 CL ALBUQUERQUE, NM SP IEEE DE calibration; computer vision; model matching; simultaneous update; supervisory telerobotics; virtual reality ID ROBOT VISION; SPACE; RECOGNITION; OBJECTS AB A computer vision assisted semi-automatic virtual reality (VR) calibration technology has been developed that can accurately match a virtual environment of graphically simulated three-dimensional (3-D) models to the video images of the real task environment. In conventional model-based computer vision, camera calibration and object localization are performed sequentially. This sequential update cannot compensate for the inaccuracy in initial camera calibrations. We have developed a new 20-variable weighted least-squares algorithm that updates both camera and object models simultaneously for given two camera views of two mating objects. This simultaneous update enables accurate model matching even with rough, approximate initial camera calibrations. The developed semi-automatic VR calibration supports automated intermediate updates, eliminating nearly all operator interaction except for initial coarse matching. In our quasistatic supervisory telerobotic applications, intermediate VR calibrations are performed intermittently at a few robot stopping poses only, as a cost-effective and safer approach compared to real-time visual servoing. Extensive experimental results comparing alignment errors under various viewing conditions are presented in the paper. Using the VR calibration technology developed,we hare successfully demonstrated an orbital replacement unit (ORU) insertion task within the required +/-1/4 in and +/-3 degrees alignment precision. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 30 TC 19 Z9 25 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD JUN PY 1999 VL 15 IS 3 BP 450 EP 464 DI 10.1109/70.768178 PG 15 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA 203LK UT WOS:000080709000006 ER PT J AU Sull, S Sridhar, B AF Sull, S Sridhar, B TI Runway obstacle detection by controlled spatiotemporal image flow disparity SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article DE motion vector estimation; obstacle detection; residual optical flow control; temporal and spatial optical flow disparities AB This paper proposes a method for detecting obstacles on a runway by controlling their expected dow disparities. The runway is modeled as a planar surface. By approximating the runway by a planar surface, the initial model flow field (MFF) corresponding to an obstacle free runway is described by the data from on-board sensors (OBS). The initial residual flow field (RFF) is obtained after warping (or stabilizing) the image using the initial MFF. The error variance of the initial MFF is estimated. The initial RFF and the error variance are first used to identify the pixels corresponding to the obstacle-free runway and then to noniteratively estimate the MFF and RFF, Obstacles are detected by comparing the expected residual how disparities with the RFF, Expected temporal and spatial residual disparities are obtained from the use of the OBS, This allows us to control the residual disparities by increasing the temporal baseline and/or by utilizing the spatial baseline if distant objects cannot be detected for a given temporal baseline. Experimental results for two real flight image sequences are presented. C1 Korea Univ, Sch Elect Engn, Seoul 136701, South Korea. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Sull, S (reprint author), Korea Univ, Sch Elect Engn, Seoul 136701, South Korea. NR 12 TC 4 Z9 5 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD JUN PY 1999 VL 15 IS 3 BP 537 EP 547 DI 10.1109/70.768185 PG 11 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA 203LK UT WOS:000080709000013 ER PT J AU Whittenberger, JD Noebe, RD Joslin, SM Oliver, BF AF Whittenberger, JD Noebe, RD Joslin, SM Oliver, BF TI Elevated temperature compressive slow strain rate properties of several directionally solidified NiAl-(Nb,Mo) alloys SO INTERMETALLICS LA English DT Article DE nickel aluminides, based on NiAl; mechanical properties at high temperatures; crystal growth ID IN-SITU COMPOSITES; MECHANICAL-PROPERTIES; STRENGTH; SYSTEMS; 1200-K; 1300-K AB Three NiAl-based alloys containing 3Nb-10Mo, 5Nb-10Mo or 13.6Nb-18Mo (at%) were directionally solidified to develop three dimensional Mo-based dendrite networks. Examination of the alloys indicated that the desired chemistry was achieved for the 3Nb-10Mo and 5Nb-10Mo versions but the composition of the highly alloyed ingot was NiAl-14.6Nb-13.2Mo. The as-grown structure for all three materials consisted of three major phases: essentially unalloyed B2 crystal structure NiAl, Laves NiAlNb phase alloyed with similar to 8.5 Mo, and a bcc metallic Mo solid solution containing 27Nb-7Ni-7Al. Compressive properties were measured between 1200 to 1400K in air under constant velocity and constant load creep conditions with strain rates ranging from similar to 10(-4) to similar to 10(-8) s(-1). The flow strengths of the two alloys with 10Mo were nearly identical and much weaker than those for NIAl-14.6Nb-13.2Mo under all conditions. Comparison the properties of this latter alloy with other directionally solidified NiAl-based eutectics revealed that it was the strongest material under lower temperature/fast deformation conditions, but this advantage was lost at higher temperatures and/or slower strain rates. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Tennessee, Knoxville, TN 37996 USA. RP Whittenberger, JD (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 14 TC 15 Z9 17 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0966-9795 J9 INTERMETALLICS JI Intermetallics PD JUN PY 1999 VL 7 IS 6 BP 627 EP 633 DI 10.1016/S0966-9795(98)00077-6 PG 7 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 199YG UT WOS:000080511200001 ER PT J AU Barnard, ST Bernardo, LM Simon, HD AF Barnard, ST Bernardo, LM Simon, HD TI An MPI implementation of the SPAI preconditioner on the T3E SO INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS LA English DT Article ID APPROXIMATE AB The authors describe and test spai_1.1, a parallel MPI implementation of the sparse approximate inverse (SPAI) preconditioner. They show that SPAI can be very effective for solving a set of very large and difficult problems on a Gray T3E. The results clearly show the value of SPAI (and approximate inverse methods in general) as the Viable alternative to ILU-type methods when facing very large and difficult problems. The authors strengthen this conclusion by showing that spai_1.1 also has very good scaling behavior. C1 Lawrence Berkeley Lab, Berkeley, CA 94720 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bernardo, LM (reprint author), Lawrence Berkeley Lab, Berkeley, CA 94720 USA. NR 15 TC 20 Z9 20 U1 0 U2 0 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 1094-3420 J9 INT J HIGH PERFORM C JI Int. J. High Perform. Comput. Appl. PD SUM PY 1999 VL 13 IS 2 BP 107 EP 123 DI 10.1177/109434209901300202 PG 17 WC Computer Science, Hardware & Architecture; Computer Science, Interdisciplinary Applications; Computer Science, Theory & Methods SC Computer Science GA 189MN UT WOS:000079909100002 ER PT J AU Olson, WS Kummerow, CD Hong, Y Tao, WK AF Olson, WS Kummerow, CD Hong, Y Tao, WK TI Atmospheric latent heating distributions in the tropics derived from satellite passive microwave radiometer measurements SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID MESOSCALE CONVECTIVE SYSTEMS; FREQUENCY INTRASEASONAL OSCILLATIONS; VERTICAL HYDROMETEOR PROFILES; TOGA COARE; CLOUD CLUSTERS; SQUALL LINE; PRECIPITATION CHARACTERISTICS; RAINFALL; SCALE; MODEL AB A method for the remote sensing of three-dimensional latent heating distributions in precipitating tropical weather systems from satellite passive microwave observations is presented. In this method, cloud model simulated hydrometeor/latent heating vertical profiles that have radiative characteristics consistent with a given set of multispectral microwave radiometric observations are composited to create a best estimate of the observed profile. An estimate of the areal coverage of convective precipitation within the radiometer footprint is used as an additional constraint on the contributing model profiles. This constraint leads to more definitive retrieved profiles of precipitation and latent heating in synthetic data tests. The remote sensing method is applied to Special Sensor Microwave/lmager (SSM/I) observations of tropical systems that occurred during the TOGA COARE Intensive Observing Period, and to observations of Hurricane Andrew (1992). Although instantaneous estimates of rain rates are high-biased with respect to coincident radar rain estimates, precipitation patterns are reasonably correlated with radar patterns, and composite rain rate and latent heating profiles show respectable agreement with estimates from forecast models and heat and moisture budget calculations. Uncertainties in the remote sensing estimates of precipitation/latent heating may be partly attributed to the relatively low spatial resolution of the SSM/I and a lack of microwave sensitivity to tenuous anvil cloud, for which upper-tropospheric latent healing rates may be significant. Estimated latent heating distributions in Hurricane Andrew exhibit an upper-level heating maximum that strengthens as the storm undergoes a period of intensification. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Greenbelt, MD 20771 USA. Univ Maryland, JCET, Baltimore, MD 21201 USA. Caelum Res Corp, Rockville, MD USA. RP Olson, WS (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Code 912, Greenbelt, MD 20771 USA. NR 70 TC 101 Z9 104 U1 1 U2 2 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 1999 VL 38 IS 6 BP 633 EP 664 DI 10.1175/1520-0450(1999)038<0633:ALHDIT>2.0.CO;2 PG 32 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 208TB UT WOS:000081006800001 ER PT J AU Fritsch-Yelle, JM Convertino, VA Schlegel, TT AF Fritsch-Yelle, JM Convertino, VA Schlegel, TT TI Acute manipulations of plasma volume alter arterial pressure responses during Valsalva maneuvers SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE baroreflex; hypovolemia; hypervolemia ID CENTRAL VENOUS-PRESSURE; BAROREFLEX RESPONSES; EXPANSION; PRIMATE; POSTURE; HUMANS AB The effects of changes in blood volume on arterial pressure patterns during the Valsalva maneuver are incompletely understood. In the present study we measured beat-to-beat arterial pressure and heart rate responses to supine Valsalva maneuvers during normovolemia, hypovolemia induced with intravenous furosemide, and hypervolemia induced with ingestion of isotonic saline. Valsalva responses were analyzed according to the four phases as previously described (W. F. Hamilton, R. A. Woodbury, and H. T. Harper, Jr. JAMA 107: 853-856, 1936; W F. Hamilton, R. A. Woodbury, and H. T. Harper, Jr. Am. J. Physiol. 141: 42-50, 1944). Phase I is the initial onset of straining, which elicits a rise in arterial pressure; phase II is the period of straining, during which venous return is impeded and pressure falls (early) and then partially recovers (late); phase III is the initial release of straining; and phase IV consists of a rapid "overshoot" of arterial pressure after the release. During hypervolemia, early phase II arterial pressure decreases were significantly less than those during hypovolemia, thus making the response more "square." Systolic pressure hypervolemic vs. hypovolemic falls were -7.4 +/- 2.1 vs. -30.7 +/- 7 mmHg (P = 0.005). Diastolic pressure hypervolemic vs, hypovolemic falls were -2.4 +/- 1.6 vs. -15.2 +/- 2.6 mmHg (P = 0.05). A significant direct correlation was found between plasma volume and phase II systolic pressure falls, and a significant inverse correlation was found between plasma volume and phase III-TV systolic pressure overshoots. Heart rate responses to systolic pressure falls during phase II were significantly less during hypovolemia than during hypervolemia (0.7 +/- 0.2 vs. 2.82 +/- 0.2 beats.min(-1).mmHg(-1); P = 0.05) but were not different during phase III-TV overshoots. We conclude that acute changes in intravascular volume from hypovolemia to hypervolemia affect cardiovascular responses, particularly arterial pressure changes, to the Valsalva maneuver and should be considered in both clinical and research applications of this maneuver. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. USA, Inst Surg Res, Ft Sam Houston, TX 78234 USA. RP Fritsch-Yelle, JM (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, SD361, Houston, TX 77058 USA. NR 27 TC 25 Z9 26 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 1999 VL 86 IS 6 BP 1852 EP 1857 PG 6 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 204TV UT WOS:000080781400021 PM 10368349 ER PT J AU Baum, BA Trepte, Q AF Baum, BA Trepte, Q TI A grouped threshold approach for scene identification in AVHRR imagery SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID SATELLITE MEASUREMENTS; RADIANCES; SNOW; FIRE; RESOLUTION; AEROSOLS; COVER AB The authors propose a grouped threshold method for scene identification in Advanced Very High Resolution Radiometer imagery that may contain clouds, fire, smoke, or snow. The philosophy of the approach is to build modules that contain groups of spectral threshold tests that are applied concurrently, not sequentially, to each pixel in an image. The purpose of each group of tests is to identify uniquely a specific class in the image, such as smoke. A strength of this approach is that insight into the limits used in the threshold tests may be gained through the use of radiative transfer theory. Methodology and examples are provided for two different scenes, one containing clouds, forest fires, and smoke; and the other containing clouds over snow in the central United States. For both scenes, a limited amount of supporting information is provided by surface observers. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA USA. RP Baum, BA (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 420, Hampton, VA 23681 USA. RI Baum, Bryan/B-7670-2011 OI Baum, Bryan/0000-0002-7193-2767 NR 25 TC 28 Z9 32 U1 0 U2 2 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 1999 VL 16 IS 6 BP 793 EP 800 DI 10.1175/1520-0426(1999)016<0793:AGTAFS>2.0.CO;2 PG 8 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 205BZ UT WOS:000080802600015 ER PT J AU Banerjee, RK Back, LH Back, MR Cho, YI AF Banerjee, RK Back, LH Back, MR Cho, YI TI Catheter obstruction effect on pulsatile flow rate-pressure drop during coronary angioplasty SO JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID ARTERIAL STENOSES; STEADY FLOW; GUIDE-WIRE; HUMANS; GRADIENT; VELOCITY; VESSEL; BLOOD AB The coupling of computational hemodynamics to measured translesional mean pressure gradients with an angioplasty catheter in human coronary stenoses was evaluated. A narrowed flow cross section with the catheter present effectively introduced a tighter stenosis than the enlarged residual stenoses after balloon angioplasty; thus elevating the pressure gradient and reducing blood pow during the measurements. For resting conditions with the catheter present, flow was believed to be about 40 percent of normal basal flow in the absence of the catheter, and for hyperemia, about 20 percent of elevated flow in the patient group. The computations indicated that the velocity field was viscous dominated and quasi-steady with negligible phase lag in the Delta p(t) - (u) over bar(t) relation during the cardiac cycle at the lower hydraulic Reynolds numbers and frequency parameter. Hemodynamic interactions with smaller catheter-based pressure sensors evolving in clinical use require subsequent study since artifactually elevated translesional pressure gradients can occur during measurements with current angioplasty catheters. C1 Fluent Inc, Lebanon, NH 03766 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ S Florida, Coll Med, Div Vasc Surg, Tampa, FL 33606 USA. Drexel Univ, Dept Mech Engn & Mech, Philadelphia, PA 19104 USA. RP Banerjee, RK (reprint author), Fluent Inc, Lebanon, NH 03766 USA. NR 28 TC 17 Z9 18 U1 0 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0148-0731 J9 J BIOMECH ENG-T ASME JI J. Biomech. Eng.-Trans. ASME PD JUN PY 1999 VL 121 IS 3 BP 281 EP 289 DI 10.1115/1.2798321 PG 9 WC Biophysics; Engineering, Biomedical SC Biophysics; Engineering GA 208RW UT WOS:000081006300003 PM 10396693 ER PT J AU Hakkinen, S AF Hakkinen, S TI A simulation of thermohaline effects of a great salinity anomaly SO JOURNAL OF CLIMATE LA English DT Article ID NORTH-ATLANTIC-OCEAN; DEEP-WATER FORMATION; GENERAL-CIRCULATION MODEL; INTERPENTADAL VARIABILITY; FRESH-WATER; SEA-ICE; TEMPERATURE; TRANSPORT; SYSTEM; DRIVEN AB Model simulations of an idealistic "Great Salinity Anomaly" (GSA) demonstrate that variability in the sea ice export from the Arctic when concentrated to short pulses can have a large influence on the meridional heat transport and can lead to an altered overturning state. One single freshwater disturbance resulting from excess ice export, as in 1968, can disrupt the deep mixing process. The critical condition for a large oceanic response is defined by the intensity, duration, and timing of the ice pulse, in particular, as it exits through the Denmark Strait. A recovery from this event takes several years for advection and diffusion to remove the salinity anomaly. Concurrently, the influence of the GSA propagates to the subtropics via the boundary currents and baroclinic adjustment. As a result of this adjustment, there are large (up to 20%) changes in the strength of the overturning cell and in the meridional heat transport in the subtropics and subpolar areas. Simulations show a temperature-salinity shift towards colder and fresher subpolar deep waters after the GSA, which is also found in hydrographic data. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hakkinen, S (reprint author), NASA, Goddard Space Flight Ctr, MC 971, Greenbelt, MD 20771 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 31 TC 79 Z9 79 U1 1 U2 11 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD JUN PY 1999 VL 12 IS 6 BP 1781 EP 1795 DI 10.1175/1520-0442(1999)012<1781:ASOTEO>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 209NZ UT WOS:000081055800016 ER PT J AU Casey, KS Cornillon, P AF Casey, KS Cornillon, P TI A comparison of satellite and in situ-based sea surface temperature climatologies SO JOURNAL OF CLIMATE LA English DT Article AB The purpose of this study is to present a satellite-derived sea surface temperature (SST) climatology based on Pathfinder Advanced Very High Resolution Radiometer (AVHRR) data and to evaluate it and several other climatologies for their usefulness in the determination of SST trends. The method of evaluation uses two longterm observational collections of in situ SST measurements: the 1994 World Ocean Atlas (WOA94) and the Comprehensive Ocean-Atmosphere Data Set (COADS). Each of the SST climatologies being evaluated is subtracted from each raw SST observation in WOA94 and GOADS to produce several separate long-term anomaly datasets. The anomaly dataset with the smallest standard deviation is assumed to identify the climatology best able to represent the spatial and seasonal SST variability and therefore be most capable of reducing the uncertainty in SST trend determinations. The satellite SST climatology was created at a resolution of 9.28 km using both day and night satellite fields generated with the version 4 AVHRR Pathfinder algorithm and cloud-masking procedures, plus an erosion filter that provides additional cloud masking in the vicinity of cloud edges. Using the statistical comparison method, the performance of this "Pathfinder + erosion" climatology is compared with the performances of the WOA94 1 degrees in situ climatology, the Reynolds satellite and in situ blended 1 degrees analysis, version 2.2 of the blended 1 degrees Global Sea-Ice and Sea Surface Temperature (GISST) climatology, and the in situ 50 degrees Global Ocean Surface Temperature Atlas (GOSTA). The standard deviation of the anomalies produced using the raw WOA94 in situ observations and the reference SST climatologies indicate that the 9.28-km Pathfinder + erosion climatology is more representative of spatial and seasonal SST variability than the traditional in situ and blended SST climatologies. For the anomalies created from the raw GOADS observations, the Pathfinder + erosion climatology is also found to minimize variance more than the other climatologies. In both cases, the 5 degrees GOSTA climatology exhibits the largest anomaly standard deviations. Regional characteristics of the climatologies are also examined by binning the anomalies by climatological temperature classes and latitudinal bands. Generally, the Pathfinder + erosion climatology yields lower anomaly variances in the mid- and high latitudes and the Southern Hemisphere, but larger variances than the 1 degrees climatologies in the warm, Northern Hemisphere low-latitude regions. C1 Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. RP Casey, KS (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 971, Greenbelt, MD 20771 USA. RI Casey, Kenneth/D-4065-2013 OI Casey, Kenneth/0000-0002-6052-7117 NR 29 TC 142 Z9 148 U1 1 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD JUN PY 1999 VL 12 IS 6 BP 1848 EP 1863 DI 10.1175/1520-0442(1999)012<1848:ACOSAI>2.0.CO;2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 209NZ UT WOS:000081055800020 ER PT J AU Stoddard, PK Rasnow, B Assad, C AF Stoddard, PK Rasnow, B Assad, C TI Electric organ discharges of the gymnotiform fishes: III. Brachyhypopomus SO JOURNAL OF COMPARATIVE PHYSIOLOGY A-SENSORY NEURAL AND BEHAVIORAL PHYSIOLOGY LA English DT Article DE bioelectricity; communication; electric fish; electrogenesis; electroreception ID APTERONOTUS-LEPTORHYNCHUS; HYPOPOMUS-PINNICAUDATUS; NEURONAL OSCILLATOR; GYMNOTUS-CARAPO; SIGNALS; ELECTRORECEPTORS; OCCIDENTALIS; SENSITIVITY; MODULATION; MECHANISMS AB We measured and mapped the electric fields produced by three species of neotropical electric fish of the genus Brachyhypopomus (Gymnotiformes, Rham phichthyoidea, Hypopomidae), formerly Hypopomus. These species produce biphasic pulsed discharges from myogenic electric organs. Spatio-temporal false-color maps of the electric organ discharges measured on the skin show that the electric field is not a simple dipole in Bvachyhypopomus. Instead, the dipole center moves rostro-caudally during the Ist phase (P1) of the electric organ discharge, and is stationary during the 2nd phase (P2). Except at the head and tip of tail, electric field lines rotate in the lateral and dorso-ventral planes. Rostrocaudal differences in field amplitude, field lines, and spatial stability suggest that different parts of the electric organ have undergone selection for different functions; the rostral portions seem specialized for electrosensory processing, whereas the caudal portions show adaptations for d.c. signal balancing and mate attraction as well. Computer animations of the electric field images described in this paper are available on web sites http:// www.bbb.caltech.edu/ElectricFish or http://www.fiu.edu/similar to stoddard/electricfish.html. C1 Florida Int Univ, Dept Biol Sci, Miami, FL 33199 USA. CALTECH, Div Biol, Pasadena, CA 91125 USA. CALTECH, Div Elect Engn, Pasadena, CA 91125 USA. Amgen, Thousand Oaks, CA 91320 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Stoddard, PK (reprint author), Florida Int Univ, Dept Biol Sci, Miami, FL 33199 USA. FU NIGMS NIH HHS [GM08205] NR 46 TC 27 Z9 30 U1 0 U2 7 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0340-7594 J9 J COMP PHYSIOL A JI J. Comp. Physiol. A-Sens. Neural Behav. Physiol. PD JUN PY 1999 VL 184 IS 6 BP 609 EP 630 DI 10.1007/s003590050359 PG 22 WC Behavioral Sciences; Neurosciences; Physiology; Zoology SC Behavioral Sciences; Neurosciences & Neurology; Physiology; Zoology GA 219PF UT WOS:000081615100005 PM 10418155 ER PT J AU Schweizer, M Croll, A Dold, P Kaiser, T Lichtensteiger, M Benz, KW AF Schweizer, M Croll, A Dold, P Kaiser, T Lichtensteiger, M Benz, KW TI Measurement of temperature fluctuations and microscopic growth rates in a silicon floating zone under microgravity SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE floating-zone silicon growth; Marangoni convection; convective temperature fluctuations; growth rate fluctuations ID THERMOCAPILLARY CONVECTION; CRYSTAL-GROWTH; MAGNETIC-FIELDS; MELT; MICROSEGREGATION; OSCILLATIONS; FLOW AB A silicon crystal growth experiment has been accomplished using the floating-zone technique under microgravity on a sounding rocket (TEXUS 36). Measurements of temperature fluctuations in the silicon melt zone due to time-dependent thermocapillary convection (Marangoni convection) and an observation of the microscopic growth rate were simultaneously performed during the experiment. Temperature fluctuations of about 0.5-0.7 degrees C with a frequency range <0.5 Hz were detectable. The microscopic growth rate fluctuates considerably around the average growth rate of I mm/min: Growth rates up to 3-4 mm/min, close to zero mm/min, as well as negative values (backmelting) were observed. Dopant striations are clearly visible in the Sb-doped crystal. They were characterized by spreading resistance measurements and differential interference contrast microscopy. The frequencies of temperature fluctuations, microscopic growth rates, and the dopant inhomogeneities correspond quite well, with main frequencies between 0.1 sind 0.3 Wt. 3D numerical simulations were performed to predict the optimum position of the temperature sensor, and the characteristic temperature amplitudes and frequencies. At a position 3.4 mm above the interface and 1.4 mm inside the melt, equivalent to the sensor tip position in the experiment, temperature fluctuations up to 1.8 degrees C and frequencies less than or equal to 0.25 Hz were found in the simulations. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Freiburg, Inst Kristallog, D-79104 Freiburg, Germany. Univ Alabama, AMMSA, NASA, MSFC, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Schweizer, M (reprint author), Univ Freiburg, Inst Kristallog, Hebelstr 25, D-79104 Freiburg, Germany. RI Croell, Arne/A-2480-2013 OI Croell, Arne/0000-0002-8673-9994 NR 27 TC 38 Z9 38 U1 0 U2 8 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 JUN PY 1999 VL 203 IS 4 BP 500 EP 510 DI 10.1016/S0022-0248(99)00155-4 PG 11 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 206KH UT WOS:000080877900006 ER PT J AU Musca, CA Dell, JM Faraone, L Bajaj, J Pepper, T Spariosu, K Blackwell, J Bruce, C AF Musca, CA Dell, JM Faraone, L Bajaj, J Pepper, T Spariosu, K Blackwell, J Bruce, C TI Analysis of crosstalk in HgCdTe p-on-n heterojunction photovoltaic infrared sensing arrays SO JOURNAL OF ELECTRONIC MATERIALS LA English DT Article; Proceedings Paper CT 17th US Workshop on the Physics and Chemistry of II-VI Materials CY OCT 20-22, 1998 CL CHARLESTON, SOUTH CAROLINA SP US Army CECOM (NVESD), US Army SMDC, US Army Res Lab, Off Naval Res, AF Res Lab, Minerals Met & Mat Soc DE crosstalk; heterojunctions; HgCdTe; infrared; linear array; photodiodes AB In this paper, an experimental and theoretical study is carried out of crosstalk between nearest-neighbor devices within a backside-illuminated linear HgCdTe photovoltaic infrared sensing array. The dominant form of crosstalk that occurs in high performance photovoltaic arrays is associated with photogenerated minority carriers that diffuse laterally between adjacent devices within the array. To measure crosstalk, a scanning laser microscope is used to obtain a spatial map of spot-scan photoresponse at a temperature of 80K for individual p-on-n photovoltaic devices within the linear array. These experimental results are compared to calculations performed on a commercial two-dimensional device simulation package. The crosstalk measurements and calculations presented in this paper include results on mid-wavelength infrared planar device structures, as well as long-wavelength infrared mesa-isolated devices, which give measured crosstalk values of 6.2 and 8.3%, respectively. The results indicate that the device simulations are in good agreement with experimental results. Further simulations are carried out to determine the sensitivity of crosstalk to various material and device parameters such as epitaxial layer thickness (7 to 25 mu m), illumination wavelength (1.047 to 11.0 mu m), minority carrier diffusion length (8 to 90 mu m), and diode pitch. It is found that the dominant feature influencing the value of crosstalk is the distance between the region of photogeneration and the collecting p-n junction. C1 Univ Western Australia, Dept Elect & Elect Engn, Nedlands, WA 6907, Australia. Rockwell Int Corp, Ctr Sci, Thousand Oaks, CA 91360 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Musca, CA (reprint author), Univ Western Australia, Dept Elect & Elect Engn, Nedlands, WA 6907, Australia. RI Dell, John/B-2389-2013 OI Dell, John/0000-0003-2801-3519 NR 6 TC 15 Z9 17 U1 0 U2 5 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 JUN PY 1999 VL 28 IS 6 BP 617 EP 623 DI 10.1007/s11664-999-0044-8 PG 7 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA 207RJ UT WOS:000080949300007 ER PT J AU Cobb, SD Szofran, FR Jones, KS Lehoczky, SL AF Cobb, SD Szofran, FR Jones, KS Lehoczky, SL TI Microstructural development of directionally solidified Hg1-xZnxSe alloys SO JOURNAL OF ELECTRONIC MATERIALS LA English DT Article; Proceedings Paper CT 17th US Workshop on the Physics and Chemistry of II-VI Materials CY OCT 20-22, 1998 CL CHARLESTON, SOUTH CAROLINA SP US Army CECOM (NVESD), US Army SMDC, US Army Res Lab, Off Naval Res, AF Res Lab, Minerals Met & Mat Soc DE composition; crystal growth; defect density; magnetic field; mercury zinc selenide; thermal stress ID ELECTRICAL-PROPERTIES; INTERFACE SHAPE; MAGNETIC-FIELD; CRYSTAL-GROWTH; BRIDGMAN; SEGREGATION; HGZNTE AB Hg1-xZnxSe alloys have been studied as an alternative to Hg1-xCdxTe for the detection of electromagnetic radiation, because the shorter ZnSe and HgSe bonds have been predicted to improve lattice stability. Several ingots with x = 0.1 were directionally solidified using a modified Bridgman-Stockbarger method; one was grown in an applied magnetic field, which greatly reduced radial compositional variations. A method was developed to reduce wetting. This, combined with the convex liquid-solid interface shape, produced boules that were single crystalline after growing similar to 3.5 cm. Observed surface features indicated ampoule wetting was eliminated using a graphite getter. Microstructural characteristics were greatly improved over HgCdTe alloys. In six boules, a total of only one twin was observed. A method for polishing and producing dislocation etch pits was developed for these alloys, revealing dislocation etch pit densities one to two orders of magnitude less than HgTe-based alloys. A kink in the thermal profile during processing of one boule generated more dislocations than did lattice mismatch due to compositional variations. This alloy has improved microstructural properties and resistance to dislocation formation compared with similar II-VI alloys. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Florida, Gainesville, FL 32611 USA. RP Cobb, SD (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 39 TC 6 Z9 6 U1 0 U2 0 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 JUN PY 1999 VL 28 IS 6 BP 732 EP 739 DI 10.1007/s11664-999-0062-6 PG 8 WC Engineering, Electrical & Electronic; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA 207RJ UT WOS:000080949300025 ER PT J AU Greenman, RM Roth, KR AF Greenman, RM Roth, KR TI High-lift optimization design using neural networks on a multi-element airfoil SO JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID UPWIND DIFFERENCING SCHEME; NAVIER-STOKES EQUATIONS; PREDICTION AB The high-lift performance of a multi-element airfoil was optimized by using neural-net predictions that were trained rising a computational data set. The numerical data was generated using a two-dimensional, incompressible, Navier-Stokes algorithm with the Spalart-Allmaras turbulence model. Because it is difficult to predict maximum lift for high-lift systems, an empirically-based maximum lift criteria was used in this study to determine both the maximum lift and the angle of attack at which it occurs. Multiple input, single output networks were trained using the NASA Ames variation of the Levenberg-Marquardt algorithm for each of the aerodynamic coefficients (lift, drag, and moment). The artificial neural networks were integrated with a gradient-based optimizer Using independent numerical simulations and experimental data for this high-lift configuration, it was shown that this design process successfully optimized flap deflection, gap, overlap, and angle of attack to maximize lift. Once the neural networks were trained and integrated with the optimizer, minimal additional computer resources were required to perform optimization runs with different initial conditions and parameters. Applying the neural networks within the high-lift rigging optimization process reduced the amount of computational time and resources by 83% compared with traditional gradient-based optimization procedures for multiple optimization runs. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Greenman, RM (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 24 TC 8 Z9 9 U1 1 U2 2 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0098-2202 J9 J FLUID ENG-T ASME JI J. Fluids Eng.-Trans. ASME PD JUN PY 1999 VL 121 IS 2 BP 434 EP 440 DI 10.1115/1.2822228 PG 7 WC Engineering, Mechanical SC Engineering GA 210ZT UT WOS:000081136000032 ER PT J AU Valdivia, JA Vassiliadis, D Klimas, A Sharma, AS Papadopoulos, K AF Valdivia, JA Vassiliadis, D Klimas, A Sharma, AS Papadopoulos, K TI Spatiotemporal activity of magnetic storms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETOSPHERE; DYNAMICS; PREDICTION; DIMENSION; MODEL AB We have constructed a data-derived model of the evolution of the spatial structure of the ring current geomagnetic signature during storms. A spatially dependent generalization of the Dessler-Parker-Skopke relation has been derived to explain the spatial structure in the midlatitude magnetic fluctuations (MLMF) as observed by ground magnetometers. Such a relation is used as a basis for constructing solar-wind-driven, data-derived models of the MLMF. The model includes a coupling to the solar wind as the energy driver and also includes a nonlocal coupling as an explanation of the inhomogeneity in the energy density that appears in the ring current during the main phase of a storm. Both linear and nonlinear models for the evolution of the spatial structure of the MLMF are constructed, and the nonlinear spatial model of the ring current produces better predictions than the linear one. This can be taken as an indication that during strong magnetic storms the ring current evolves in a nonlinear fashion. The spatial data used in the generation of the models are rotated to a frame "fixed" with the ring current, and presure effects were accounted through a kinematic relation. The techniques developed in this paper are very general and can be used to study other systems that show spatial structure, such as the high-latitude current system. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Valdivia, JA (reprint author), NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 27 TC 25 Z9 25 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 1999 VL 104 IS A6 BP 12239 EP 12250 DI 10.1029/1999JA900152 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201MY UT WOS:000080600400002 ER PT J AU Brittnacher, M Fillingim, M Parks, G Germany, G Spann, J AF Brittnacher, M Fillingim, M Parks, G Germany, G Spann, J TI Polar cap area and boundary motion during substorms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID AURORAL OVAL BOUNDARIES; ULTRAVIOLET IMAGER; POLEWARD BOUNDARY; MAGNETIC CLOUD; CURRENT SHEET; THETA-AURORA; PLASMA SHEET; GROWTH-PHASE; JANUARY 10; IDENTIFICATION AB The area of the polar cap as a function of local time and substorm phase was measured using images from the Polar Ultraviolet Imager (UVI) for different interplanetary magnetic field (IMF) orientations during three substorms in January 1997. We measured changes in the polar cap area and motion of the poleward and equatorward boundary of the auroral oval. It was found that the polar cap boundary is strongly influenced by thinning of the oval, decrease in polar cap structures, the poleward expansion of the substorm at midnight, and the fading of luminosity below the instrument sensitivity threshold. Generally, these effects dominate over the latitudinal motion of the auroral oval at its equatorward edge. A new feature is that the polar cap region clears of precipitation during the substorm growth phase, which expands the size of the polar cap but is not necessarily related to an expansion of the open flux region. Another finding is that the increase in polar cap area prior to onset can be independent of the strength of the southward IMF component. For one case the polar cap area increased while the southward component of the IMF was 0 +/- 0.5 nT. These observations have strong implications for models that use the polar cap area to estimate the magnitude of energy storage in the lobe magnetic field and loss during substorms. C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Alabama, CSPAR, Huntsville, AL 35807 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Brittnacher, M (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. NR 39 TC 72 Z9 73 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 1999 VL 104 IS A6 BP 12251 EP 12262 DI 10.1029/1998JA900097 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201MY UT WOS:000080600400003 ER PT J AU Rastatter, L Hesse, M Schindler, K AF Rastatter, L Hesse, M Schindler, K TI Hall-MHD modeling of near-Earth magnetotail current sheet thinning and evolution SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GEOMAGNETIC TAIL; GROWTH-PHASE; RECONNECTION; SUBSTORM AB The formation of thin current sheets is a common feature of the late substorm growth phase in the magnetotail of the Earth. The location and the structure of the evolving thin current sheet determine the onset and the dynamic phase of magnetic substorms. To determine the formation and further evolution of thin current sheets in the near-Earth magnetotail, we employ a two-fluid model of electrons and ions, the Hall-MHD. We start from a two-dimensional tail-equilibrium model and apply a plasma inflow from the lobes to simulate the presubstorm loading process of the tail. Our results confirm recent 2.5-dimensional particle and hybrid simulations which have shown thin current sheet formation, with the majority of the new current supported by the electrons. The Hall-MHD simulations are extended to a current sheet thinning model with three-dimensional driving: conditions and different magnetic field boundary conditions. We investigated the changes to the tail magnetic and current structure brought about by the cross-tail magnetic field components generated by Hall electric fields. For all these cases, the additional current is carried by the electrons, with very small effects of magnetic field and driving boundary conditions. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ruhr Univ Bochum, D-44780 Bochum, Germany. RP Rastatter, L (reprint author), NASA, Goddard Space Flight Ctr, Code 696, Greenbelt, MD 20771 USA. RI Hesse, Michael/D-2031-2012; Rastaetter, Lutz/D-4715-2012 OI Rastaetter, Lutz/0000-0002-7343-4147 NR 14 TC 17 Z9 17 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 JUN 1 PY 1999 VL 104 IS A6 BP 12301 EP 12311 DI 10.1029/1999JA900138 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201MY UT WOS:000080600400006 ER PT J AU Lu, G Tsyganenko, NA Lui, ATY Singer, HJ Nagai, T Kokubun, S AF Lu, G Tsyganenko, NA Lui, ATY Singer, HJ Nagai, T Kokubun, S TI Modeling of time-evolving magnetic fields during substorms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TAIL CURRENT SHEET; GROWTH-PHASE; CURRENT DISRUPTION; PLASMA SHEET; SYNCHRONOUS ALTITUDE; CURRENT WEDGE; MAGNETOTAIL; MAGNETOSPHERE; SIGNATURES; EXPANSION AB An attempt has been made to model the dynamics of the magnetospheric magnetic field during substorms by modifying the 1996 version of the data-based model by Tsyganenko [1996]. The modified model incorporates an adjustment to the intensity and thickness of the near-tail current sheet and a contribution from the substorm current wedge. These improvements make it possible to use the model to represent the evolution of the magnetic field during the entire substorm sequence of growth, expansion, and recovery. The modeled magnetic fields have been compared to satellite observations during three isolated substorms. According to the model results, during the substorm growth phase the thickness of the tail current sheet was gradually decreased while the intensity of the tail current was gradually increased; by the end of the growth phase a thin current sheet of 190-1340 km in half thickness was formed in a narrow region around X similar to -7.5 R-E, with a maximum westward current density of 9-23 nA/m(2). During the substorm expansion phase an eastward current associated with the substorm current wedge started to develop around X similar to -12 R-E, resulting in a collapse of the previously stretched field configuration. At the peak of an intense substorm the net tail current flow became eastward between X = -11 and X = -13 R-E, accompanied by a negative (southward) B-z tailward of -13 R-E. C1 Natl Ctr Atmospher Res, Altitude Observ, Boulder, CO 80301 USA. Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi 46401, Japan. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Tokyo Inst Technol, Tokyo 1528551, Japan. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Natl Ctr Atmospher Res, Altitude Observ, 3540 Mitchell Lane, Boulder, CO 80301 USA. EM ganglu@ucar.edu RI Lu, Gang/A-6669-2011; Tsyganenko, Nikolai/J-7377-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579 NR 39 TC 18 Z9 20 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUN 1 PY 1999 VL 104 IS A6 BP 12327 EP 12337 DI 10.1029/1999JA900145 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201MY UT WOS:000080600400008 ER PT J AU St Cyr, OC Burkepile, JT Hundhausen, AJ Lecinski, AR AF St Cyr, OC Burkepile, JT Hundhausen, AJ Lecinski, AR TI A comparison of ground-based and spacecraft observations of coronal mass ejections from 1980-1989 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SMM OBSERVATIONS; WHITE-LIGHT; TRANSIENT; SPEEDS AB We report here an analysis of observations of solar coronal mass ejections (CMEs) acquired in white light by the Mark III (MK3) K coronameter at Mauna Loa Solar Observatory between 1980 and 1989. Statistical properties of the locations, sizes, and speeds of these events are described. These properties are compared to those in the two other white light CME catalogs from the 1980s, the CMEs observed by the Solwind and SMM spaceborne coronagraphs, and relatively good statistical agreement is found between the three data sets taken over the entire period of observation. A detailed examination was performed for the 141 MK3 CMEs that were also observed by SMM. Virtually all (93%) of the CMEs detected low in the corona by the MK3 instrument were observed to travel out of the SMM field of view, into interplanetary space. The average width of CMEs in the MK3 field of view was 120 smaller than that measured in SMM, and we interpret this statistic as an indication of some increase in size as CMEs move outward through the corona. For a subset of 55 of those mass ejections we were able to combine detailed observations from both MK3 and SMM. Using the combined measurements, we were able to detect and to quantify the initial period of acceleration in a much larger fraction (61%) of the features than was possible from either MK3 alone (9%) or SMM alone (21%). The acceleration was positive for 87% of those features, with an average (median) value of +0.264 km s(-2) (+0.044 km s(-2)). A distinction in terms of association with other forms of solar activity was also evident in this analysis: 55% of the CMEs associated with active regions moved with constant speed, but 82% of the features associated with the eruption of solitary prominences moved with constant acceleration. Also, the average speed for CMEs associated with active regions was significantly faster than those with prominence association (955 versus 411 km s(-1)). The detection of positive acceleration demonstrates that the forces propelling the CME continue to dominate these events, at least through the altitudes covered by the MK3 and SMM fields of view. C1 NASA, Goddard Space Flight Ctr, LASCO, SOHO,USN,Res Lab,Computat Phys Inc, Greenbelt, MD 20771 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80301 USA. RP St Cyr, OC (reprint author), NASA, Goddard Space Flight Ctr, LASCO, SOHO,USN,Res Lab,Computat Phys Inc, Code 682-3, Greenbelt, MD 20771 USA. NR 32 TC 133 Z9 134 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 JUN 1 PY 1999 VL 104 IS A6 BP 12493 EP 12506 DI 10.1029/1999JA900045 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201MY UT WOS:000080600400023 ER PT J AU Richardson, IG Cane, HV Wibberenz, G AF Richardson, IG Cane, HV Wibberenz, G TI A 22-year dependence in the size of near-ecliptic corotating cosmic ray depressions during five solar minima SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HELIOSPHERIC CURRENT SHEET; GEOMAGNETIC-ACTIVITY; WIND; LATITUDE; DECREASES; GRADIENTS; PROTONS; CYCLES; EARTH; IMP-8 AB Evidence is presented for a 22-year cycle in the amplitude of recurrent, near-Earth, near-Ecliptic., galactic cosmic ray modulations during the solar minimum periods in the mid-1950s to mid-1990s. These modulations are similar to 50% larger during A > 0 epochs than during A < 0 epochs, where A is the direction of the solar global magnetic field. This difference is evident in all the cosmic ray data examined, including observations by neutron monitors and integral and differential particle data from the IMP 8 spacecraft. A change in the properties of the associated corotating: streams does not appear to be responsible. Rather, the response of the cosmic rays to solar wind speed enhancements appears to be reduced in A < 0 minima. This pattern is inconsistent with a prediction from the drift model of cosmic ray modulation that recurrent modulations should be larger in A < 0 epochs. Other factors may contribute, such as an epoch-dependence of the particle diffusion coefficient which may increase the effect of solar wind convection on the local cosmic ray density near Earth during A > 0 epochs. A change in the latitudinal GCR gradient in successive epochs is unlikely to be the sole reason for the change in depression size since (1) the proportionality constant between the recurrent depressions and. latitudinal gradient depends on A, and (2) the cosmic ray density is not organized by crossings of the heliospheric current sheet. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Kiel, Inst Expt & Angew Phys, D-24118 Kiel, Germany. Univ Kiel, Inst Expt Angew Kernphys, Kiel, Germany. RP Richardson, IG (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. OI Richardson, Ian/0000-0002-3855-3634 NR 30 TC 56 Z9 56 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 JUN 1 PY 1999 VL 104 IS A6 BP 12549 EP 12561 DI 10.1029/1999JA900130 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201MY UT WOS:000080600400028 ER PT J AU Whittenberger, JD Garg, A Hebsur, MG AF Whittenberger, JD Garg, A Hebsur, MG TI Microstructure and 1000-1400 K mechanical properties of cryomilled NiAl-0.7Zr SO JOURNAL OF MATERIALS RESEARCH LA English DT Article AB An attempt has been made to improve the intermediate temperature strength of cryomilled NiAl by utilizing third element solid solution or precipitation strengthening mechanisms. To this end an NiAl-0.7 (at.%) Zr alloy was cryomilled, densified by hot extrusion, and tested between 1000 and 1400 K. Although over 3 wt% nitrogen was introduced via cryomilling, mechanical testing revealed that the cryomilled NiAl-0.7Zr was significantly weaker than the base alloy between 1000 and 1200 K. Chemical and microstructural analyses revealed that, in addition to similar to 16 vol% AIN, all the Zr had been converted into ZrN, A thermodynamic analysis of cryomilling indicated that the formation of ZrN could have been anticipated since it is a more stable nitride than AIN. While Zr was an unsatisfactory addition in NiAl, thermodynamics also suggest several alloying elements that might lead to good intermediate temperature strength after cryomilling. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. AYT Corp, NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NASA, OAI, GRC Grp, Brookpark, OH 44142 USA. RP Whittenberger, JD (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 14 TC 3 Z9 3 U1 0 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 1999 VL 14 IS 6 BP 2418 EP 2429 DI 10.1557/JMR.1999.0325 PG 12 WC Materials Science, Multidisciplinary SC Materials Science GA 235PE UT WOS:000082550600032 ER PT J AU Williamson, R Carbo, J Luna, B Webbon, BW AF Williamson, R Carbo, J Luna, B Webbon, BW TI A thermal physiological comparison of two HAZMAT protective ensembles with and without active convective cooling SO JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL MEDICINE LA English DT Article ID ENERGY-COST; HEAT; RESPIRATORS; RESPONSES; EXERCISE; MEN AB Wearing impermeable garments for hazardous materials (HAZMAT) cleanup can often present a health and safety problem for the wearer. Even short duration cleanup activities can produce heat-stress injuries in HAZMAT workers. It was hypothesized that an internal cooling system might increase worker productivity and decrease the likelihood of heat-stress injuries in typical HAZMAT operations. Two HAZMAT protective ensembles were compared during subjects' treadmill exercise. The different ensembles were created using two different suits: a Trelleborg vapor protective suit representative of current HAZMAT suits and a prototype suit developed by engineers at the National Aeronautics and Space Administration (NASA), The two life-support systems used were a current-technology Interspiro Spirolite breathing apparatus and a liquid air breathing system that also provided convective cooling, Twelve local members of a HAZMAT team served as test subjects. They were fully instrumented to allow a complete physiological comparison of their thermal responses to the different ensembles. Results showed that cooling from the liquid air system significantly decreased thermal stress. The results of the subjective evaluations of new design features in the prototype suit were also highly favorable. Incorporation of these new design features could lead to significant operational advantages in the future. C1 NASA, Ames Res Ctr, Regenerat Life Support Branch, Moffett Field, CA 94035 USA. Lockheed Martin Engn & Sci, Moffett Field, CA USA. Sterling Software Inc, Moffett Field, CA USA. RP Luna, B (reprint author), NASA, Ames Res Ctr, Regenerat Life Support Branch, Mail Stop 239-15, Moffett Field, CA 94035 USA. NR 18 TC 6 Z9 6 U1 0 U2 1 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 1076-2752 J9 J OCCUP ENVIRON MED JI J. Occup. Environ. Med. PD JUN PY 1999 VL 41 IS 6 BP 453 EP 463 DI 10.1097/00043764-199906000-00011 PG 11 WC Public, Environmental & Occupational Health SC Public, Environmental & Occupational Health GA 206MQ UT WOS:000080883500011 PM 10390696 ER PT J AU Ashen, JB Cohen, JD Goff, LJ AF Ashen, JB Cohen, JD Goff, LJ TI GC-SIM-MS detection and quantification of free indole-3-acetic acid in bacterial galls on the marine alga Prionitis lanceolata (Rhodophyta) SO JOURNAL OF PHYCOLOGY LA English DT Article DE bacterial galls; gas chromatography-selective ion-monitoring mass spectrometry; indole-3-acetic acid; Prionitis lanceolata; red algal hormones ID CONJUGATED INDOLEACETIC-ACID; AGROBACTERIUM-TUMEFACIENS; T-DNA; AUXIN; PLANTS; IDENTIFICATION; BIOSYNTHESIS; TOBACCO; IAA; SEAWATER AB Indole-3-acetic acid (IAA), a plant hormone necessary for terrestrial plant growth and development, was detected and quantified in the marine red alga Prionitis lanceolata Harvey (Halymeniaceae, Gigartinales, Rhodophyta) using gas chromatogaphy-selective ion-monitoring mass spectrometry (GC-SIM-MS), This allowed comparison of free IAA levels between the algal thallus and eubacterially induced galls on this alga characterized by abnormal algal growth and cell division and extensive, intercellular microbial proliferation, The levels of free IAA in the P, lanceolata thallus averaged 2.5 (+/-1.1) ng.g(-1) fresh wt. Free IAA levels in galls were more variable, ranging from ca, 4 to 39 (8.3 +/- 10.9) ng.g(-1) fresh wt, but were significantly higher overall (P = 0.0022), The identity of the IAA in this marine florideophycean alga was confirmed by full scan GC-MS analysis of both galls and thalli. The levels of free IAA in P, lanceolata were two to three orders of magnitude higher than those observed previously in the Rhodophyta, The origin of elevated IAA levels in P, lanceolata galls is unknown because it is possible that this compound is produced by either the gall-inducing bacterial symbiont or the host alga. C1 Univ Calif Santa Cruz, Dept Biol, Santa Cruz, CA 95064 USA. USDA ARS, Beltsville Agr Res Ctr, Hort Crops Qual Lab, Agr Res Serv, Beltsville, MD 20705 USA. RP Ashen, JB (reprint author), NASA, Ames Res Ctr, MS 239-20, Moffett Field, CA 94035 USA. OI Cohen, Jerry/0000-0003-2816-8676 NR 39 TC 22 Z9 24 U1 1 U2 11 PU PHYCOLOGICAL SOC AMER INC PI LAWRENCE PA 810 EAST 10TH ST, LAWRENCE, KS 66044 USA SN 0022-3646 J9 J PHYCOL JI J. Phycol. PD JUN PY 1999 VL 35 IS 3 BP 493 EP 500 DI 10.1046/j.1529-8817.1999.3530493.x PG 8 WC Plant Sciences; Marine & Freshwater Biology SC Plant Sciences; Marine & Freshwater Biology GA 212RD UT WOS:000081229300008 ER PT J AU McKenzie, MA Greenleaf, JE Looft-Wilson, R Barnes, PR AF McKenzie, MA Greenleaf, JE Looft-Wilson, R Barnes, PR TI Leucocytosis, thrombocytosis, and plasma osmolality during rest and exercise: An hypothesis SO JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY LA English DT Article DE immune parameters; white blood cells; platelets ID INVITRO PROLIFERATIVE RESPONSES; MONONUCLEAR CELL SUBPOPULATIONS; LYMPHOCYTE SUBPOPULATIONS; STRENUOUS EXERCISE; PHYSICAL EXERCISE; CIRCULATING LEUKOCYTE; MODERATE EXERCISE; MEN; SUBSETS; MOBILIZATION AB The mechanism for inducing leucocytosis (increase in white blood cells) and thrombocytosis (increase in platelets) during exercise is unclear. Because plasma osmolality (Osm) may influence T-cell proliferation, Osm and the number of leucocytes (WBC) and platelets in blood were measured periodically during a 90 min rest period, and were compared with those during upright sitting ergometer exercise in six untrained, healthy men who cycled for 70 min at 71% of their maximal oxygen uptake ((V)over dotO(2max)). There were 6 experiments in which the subjects drank different fluid formulations (10 ml.kg(-1)) of various ionic and osmotic concentrations intermittently during 60 min of the rest period and during the exercise period. Osmolality, and WBC and platelet counts increased significantly (p < 0.05) within the first 10 min of exercise, but the additional 60 min of exercise did not significantly change the leucocytosis or thrombocytosis. There were low but significant correlations between individual values of total WBC and total Osm during exercise (r(0.001(2),284) = 0.39) and during rest plus exercise (r(0.001(2),499) = 0.43). With combined data from the six experiments, mean Osm correlated highly and significantly with both mean WBC (r(0.001(2),6) = 0.95, p < 0.001) and mean platelets (r(0.001(2),6) = 0.94, p < 0.01) during the exercise phase. These data indicate that increases in leucocytes, thrombocytes, and osmolality occur primarily within the first 10 min of high-intensity exercise, but neither hypovolemia nor hyperthermia during exercise contributed to the leucocytosis, thrombocytosis, or hyperosmolality. The high correlations between plasma Osm and WBC or platelet counts suggest changes in osmolality may contribute to the mechanism of leucocytosis and thrombocytosis induced by exercise. C1 NASA, Lab Human Environm Physiol, Gravitat Res Branch 239 11, Ames Res Ctr, Moffett Field, CA 94035 USA. San Francisco State Univ, Dept Biol Sci, San Francisco, CA USA. RP Greenleaf, JE (reprint author), NASA, Lab Human Environm Physiol, Gravitat Res Branch 239 11, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 32 TC 6 Z9 6 U1 0 U2 0 PU POLISH PHYSIOLOGICAL SOC PI GRZEGORZECKA PA JAGIELLONIAN UNIV SCHOOL MED, INST PHYSIOLOGY, 31-531 KRAKOW, 16 GRZEGORZECKA, POLAND SN 0867-5910 J9 J PHYSIOL PHARMACOL JI J. Physiol. Pharmacol. PD JUN PY 1999 VL 50 IS 2 BP 259 EP 273 PG 15 WC Physiology SC Physiology GA 213FH UT WOS:000081261700008 PM 10424721 ER PT J AU Jacobson, NS Morscher, GN Bryant, DR Tressler, RE AF Jacobson, NS Morscher, GN Bryant, DR Tressler, RE TI High-temperature oxidation of boron nitride: II, boron nitride layers in composites SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID SILICON-CARBIDE; MATRIX COMPOSITES; KINETICS; CARBON; INTERFACE; OXYGEN AB The oxidation of BN composite interphases was examined with a series of model materials, Oxidation was examined in both low-water-vapor (similar to 20 ppm H2O/O-2) environments at 900 degrees C and high-water-vapor (1% and 10% H2O/O-2) environments at 700 degrees and 800 degrees C, The low-water-vapor case was explored with layered BN/SiC materials. This case was dominated by borosilicate glass formation, and the 20 ppm water vapor gradually removed the boron from the glass, leaving a larger amount of SiO2 than would be expected from simple SiC oxidation, Layered SiC/BN/SiC materials were also used to study low-water-vapor oxidation effects within the composite. The high-water-vapor case was explored with SiC/BN/SiC minicomposites, and it was dominated by volatilization of BN as HBO2(g), H3BO3(g), and H3B3O6(g), A model for recession of the BN fiber coating was developed based on the gas-phase diffusion of these species out of the annular region around the SiC fiber and concurrent sealing of this annular region by oxidation. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Penn State Univ, University Pk, PA 16802 USA. RP Jacobson, NS (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RI Jacobson, Nathan/A-9411-2009 NR 29 TC 81 Z9 82 U1 1 U2 36 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 1999 VL 82 IS 6 BP 1473 EP 1482 PG 10 WC Materials Science, Ceramics SC Materials Science GA 207QG UT WOS:000080947100019 ER PT J AU Croll, A Dold, P Kaiser, T Szofran, FR Benz, KW AF Croll, A Dold, P Kaiser, T Szofran, FR Benz, KW TI The influence of static and rotating magnetic fields on heat and mass transfer in silicon floating zones SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID SI CRYSTAL-GROWTH; AXIAL FIELDS; FLUID-FLOW; MELT; CONVECTION AB Heat and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio-frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a defined flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to 5 T and in transverse rotating magnetic fields up to 7.5 mT Static fields of a few 100 mT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile toward a more diffusion-limited case, is possible with static fields greater than or equal to 1 T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelectromagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few millitesla. The field shifts time-dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes. (C) 1999 The Electrochemical Society. S0013-4651 (98)03-086-9. All rights reserved. C1 Univ Alabama, Alliance Micrograv Mat Sci & Applicat, NASA, MSFC, Huntsville, AL 35812 USA. Univ Freiburg, Inst Kristallog, D-79104 Freiburg, Germany. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Croll, A (reprint author), Univ Alabama, Alliance Micrograv Mat Sci & Applicat, NASA, MSFC, Huntsville, AL 35812 USA. RI Croell, Arne/A-2480-2013 OI Croell, Arne/0000-0002-8673-9994 NR 28 TC 7 Z9 7 U1 1 U2 4 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD JUN PY 1999 VL 146 IS 6 BP 2270 EP 2275 PG 6 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA 207HC UT WOS:000080930500047 ER PT J AU Heeke, DS White, MP Mele, GD Hanifin, JP Brainard, GC Rollag, MD Winget, CM Holley, DC AF Heeke, DS White, MP Mele, GD Hanifin, JP Brainard, GC Rollag, MD Winget, CM Holley, DC TI Light-emitting diodes and cool white fluorescent light similarly suppress pineal gland melatonin and maintain retinal function and morphology in the rat SO LABORATORY ANIMAL SCIENCE LA English DT Article ID SYRIAN-HAMSTER; CIRCADIAN OSCILLATOR; N-ACETYLTRANSFERASE; DAMAGE; ILLUMINATION; INTENSITY; EXPOSURE; NUCLEUS AB Background and Purpose: A novel light-emitting diode (LED) light source for use in animal-habitat lighting was evaluated. Methods: The LED was evaluated by comparing its effectiveness with that of cool white fluorescent light (CWF) in suppressing pineal gland melatonin content and maintaining normal retinal physiology, as evaluated by use of electroretinography (ERG), and morphology, Results: Pineal melatonin concentration was equally suppressed by LED and CWF light at five light illuminances (100, 40, 10, 1, and 0.1 lux), There were no significant differences in melatonin suppression between LED and CWF light, compared with values for unexposed controls. There were no differences in ERG a-wave implicit times and amplitudes or b-wave implicit times and amplitudes between 100-lux LED exposed rats and 100-lux CWF-exposed rats, Results of retinal histologic examination indicated no differences in retinal thickness, rod outer segment length, and number of rod nuclei between rats exposed to 100-lux LED and 100-lux CWF for 14 days. Furthermore, in all eyes, the retinal pigmented epithelium was intact and not vacuolated, whereas rod outer segments were of normal thickness. Conclusion: LED light does not cause retinal damage and can suppress pineal melatonin content at intensities similar to CWF light intensities. C1 San Jose State Univ, Dept Biol Sci, San Jose, CA 95192 USA. Thomas Jefferson Univ, Jefferson Med Coll, Dept Neurol, Philadelphia, PA 19107 USA. Uniformed Serv Univ Hlth Sci, Dept Anat, Bethesda, MD 20814 USA. NASA, Ames Res Ctr, Sci Payloads Operat Branch, Moffett Field, CA USA. RP Heeke, DS (reprint author), San Jose State Univ, Dept Biol Sci, San Jose, CA 95192 USA. NR 31 TC 5 Z9 6 U1 1 U2 2 PU AMER ASSOC LABORATORY ANIMAL SCIENCE PI MEMPHIS PA 9190 CRESTWYN HILLS DR, MEMPHIS, TN 38125 USA SN 0023-6764 J9 LAB ANIM SCI JI Lab. Anim. Sci. PD JUN PY 1999 VL 49 IS 3 BP 297 EP 304 PG 8 WC Veterinary Sciences; Zoology SC Veterinary Sciences; Zoology GA 207QJ UT WOS:000080947300012 PM 10403445 ER PT J AU Duncan, BW Boyle, S Breininger, DR Schmalzer, PA AF Duncan, BW Boyle, S Breininger, DR Schmalzer, PA TI Coupling past management practice and historic landscape change on John F. Kennedy Space Center, Florida SO LANDSCAPE ECOLOGY LA English DT Article DE historic; landcover; fire suppression; landscape; management; disturbance; scrub; flatwoods; Florida; remote sensing; GIS; GPS ID LAKE WALES RIDGE; VEGETATION; FIRE; PATTERNS; SANDHILL; GEORGIA AB Historic landcover dynamics in a scrubby flatwoods (Tel-4) and scrub landscape (Happy Creek) on John F. Kennedy Space Center were measured using aerial images from 1943, 1951, 1958, 1969, 1979, and 1989. Landcover categories were mapped, digitized, geometrically registered, and overlaid in ARC/INFO. Both study sites have been influenced by various land use histories, including periods of range management, fire suppression, and fire management. Several analyses were performed to help understand the effects of past land management on the amount and spatial distribution of landcover within the study sites. A chi-squared analysis showed a significant difference between the frequency of landcover occurrence and management period. Markov chain models were used to project observed changes over a 100-year period; these showed current management practices being effective at Tel-4 (restoring historic landscape structure) and much less effective at Happy Creek. Documenting impacts of past management regimes on landcover has provided important insight into current landscape composition and will provide the basis for improving land management on Kennedy Space Center and elsewhere. C1 NASA, Biomed Operat Off, Dynam Corp, Kennedy Space Ctr, FL 32899 USA. RP Duncan, BW (reprint author), NASA, Biomed Operat Off, Dynam Corp, Mail Code DYN-2 Kennedy Space Ctr, Kennedy Space Ctr, FL 32899 USA. OI Schmalzer, Paul/0000-0003-2214-0074 NR 48 TC 43 Z9 44 U1 0 U2 7 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0921-2973 J9 LANDSCAPE ECOL JI Landsc. Ecol. PD JUN PY 1999 VL 14 IS 3 BP 291 EP 309 DI 10.1023/A:1008029831187 PG 19 WC Ecology; Geography, Physical; Geosciences, Multidisciplinary SC Environmental Sciences & Ecology; Physical Geography; Geology GA 209HB UT WOS:000081041200007 ER PT J AU Jeganathan, M Lesh, J AF Jeganathan, M Lesh, J TI Laser communications unit prepares for flight test SO LASER FOCUS WORLD LA English DT Article ID OPTICAL COMMUNICATIONS DEMONSTRATOR; EVALUATION STATION; DESIGN C1 CALTECH, Jet Prop Lab, Opt Commun Grp, Pasadena, CA 91109 USA. RP Jeganathan, M (reprint author), CALTECH, Jet Prop Lab, Opt Commun Grp, 4800 Oak Grove Dr,MS 161-135, Pasadena, CA 91109 USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU PENNWELL PUBL CO PI NASHUA PA 98 SPIT BROOK RD, NASHUA, NH 03062-2801 USA SN 0740-2511 J9 LASER FOCUS WORLD JI Laser Focus World PD JUN PY 1999 VL 35 IS 6 BP 103 EP + PG 6 WC Optics SC Optics GA 209GC UT WOS:000081039000032 ER PT J AU Rivera, KS Wohl, KD AF Rivera, KS Wohl, KD TI The FAO seabird initiative - International efforts to reduce seabird bycatch in the longline fisheries: What does that mean at home? An Alaskan perspective SO MARINE TECHNOLOGY SOCIETY JOURNAL LA English DT Editorial Material C1 Natl Marine Fisheries Serv, Protected Resources Div, Juneau, AK 99801 USA. US Fish & Wildlife Serv, Off Migratory Bird Management, Anchorage, AK USA. RP Rivera, KS (reprint author), Natl Marine Fisheries Serv, Protected Resources Div, Juneau, AK 99801 USA. NR 6 TC 1 Z9 1 U1 0 U2 0 PU MARINE TECHNOLOGY SOC INC PI WASHINGTON PA C/O I CLAYION MATTHEWS, 1828 L ST, NW, 9TH FL, WASHINGTON, DC 20036 USA SN 0025-3324 J9 MAR TECHNOL SOC J JI Mar. Technol. Soc. J. PD SUM PY 1999 VL 33 IS 2 BP 85 EP 87 PG 3 WC Engineering, Ocean; Oceanography SC Engineering; Oceanography GA 225FY UT WOS:000081948800013 ER PT J AU Freed, AD AF Freed, AD TI Representing tensor functions with a Cholesky transform SO MATHEMATICS AND MECHANICS OF SOLIDS LA English DT Article ID SCALAR COEFFICIENTS; STRAIN; H(A)=ALPHA-I+BETA-A+GAMMA-A(2); DEFORMATIONS AB The tensor representation theorem provides a powerful tool for evaluating isotropic tenser-valued tensor functions. Efficient computational techniques exist when an analysis is being done in rectangular Cartesian coordinates. Introducing a Cholesky decomposition of the metric tensor permits the tensor polynomial of the tensor representation theorem, when expressed in curvilinear coordinates, to be transformed into a pseudo-Cartesian frame where these efficient algorithms apply. It also leads to accurate descriptions for the physical components of a tensor. C1 NASA, Lewis Res Ctr, Polymers Branch, Div Mat, Cleveland, OH 44135 USA. RP Freed, AD (reprint author), NASA, Lewis Res Ctr, Polymers Branch, Div Mat, MS 49-3,21000 Brookpk Rd, Cleveland, OH 44135 USA. OI Freed, Alan/0000-0002-3492-0628 NR 14 TC 0 Z9 0 U1 0 U2 0 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 1081-2865 J9 MATH MECH SOLIDS JI Math. Mech. Solids PD JUN PY 1999 VL 4 IS 2 BP 169 EP 181 DI 10.1177/108128659900400202 PG 13 WC Materials Science, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Materials Science; Mathematics; Mechanics GA 199JC UT WOS:000080476600002 ER PT J AU Sanders, AJ Alexeev, AD Allison, SW Bronnikov, KA Campbell, JW Cates, MR Corcovilos, TA Earl, DD Gadfort, T Gillies, GT Harris, MJ Kolosnitsyn, NI Konstantinov, MY Melnikov, VN Newby, RJ Schunk, RG Smalley, LL AF Sanders, AJ Alexeev, AD Allison, SW Bronnikov, KA Campbell, JW Cates, MR Corcovilos, TA Earl, DD Gadfort, T Gillies, GT Harris, MJ Kolosnitsyn, NI Konstantinov, MY Melnikov, VN Newby, RJ Schunk, RG Smalley, LL TI Project SEE (Satellite Energy Exchange): proposal for space-based gravitational measurements SO MEASUREMENT SCIENCE AND TECHNOLOGY LA English DT Article; Proceedings Paper CT Conference on the Gravitational Constant - Theory and Experiment 200 Years After Cavendish CY NOV 23-24, 1998 CL INST PHYS, PORTLAND PLACE, ENGLAND HO INST PHYS DE gravity; gravitational constant; Cavendish; equivalence principle; inverse-square law ID INTERACTION PARAMETERS; EARTH SATELLITE; CONSTANT-G AB Project SEE (Satellite Energy Exchange) is an international effort to organize a new space mission for fundamental measurements in gravitation, including tests of the equivalence principle (EP) by composition dependence (CD) and inverse-square-law (ISL) violations, determination of G, and a test for non-zero G-dot. The CD tests will be both at intermediate distances (a few metres) and at long distances (radius of the Earth, R-E). Thus, a SEE mission would obtain accurate information self-consistently on a number of distinct gravitational effects. The EP test by CD at distances of a few metres would provide confirmation of earlier, more precise experiments. All other tests would significantly improve our knowledge of gravity. In particular, the error in G is projected to be less than 1 ppm. Project SEE entails launching a dedicated satellite and making detailed observations of free-floating test bodies within its experimental chamber. C1 Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA. Russian Gravitat Soc, Moscow 117313, Russia. Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35749 USA. Univ Virginia, Beam Phys Lab, Charlottesville, VA 22903 USA. Univ Alabama, Huntsville, AL 35899 USA. RP Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA. EM asanders@utk.edu; w.campbell@msfc.nasa.gov; catesmr@ornl.gov; rgs@com2com.ru RI Corcovilos, Theodore/G-8699-2012; OI Corcovilos, Theodore/0000-0001-5716-1188; Newby, Robert/0000-0003-3571-1067; Allison, Stephen/0000-0002-5887-5403; Bronnikov, Kirill/0000-0001-9392-7558 NR 33 TC 21 Z9 22 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0957-0233 EI 1361-6501 J9 MEAS SCI TECHNOL JI Meas. Sci. Technol. PD JUN PY 1999 VL 10 IS 6 BP 514 EP 524 DI 10.1088/0957-0233/10/6/317 PG 11 WC Engineering, Multidisciplinary; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 205AY UT WOS:000080800200019 ER PT J AU Lesuer, DR Syn, CK Whittenberger, JD Sherby, OD AF Lesuer, DR Syn, CK Whittenberger, JD Sherby, OD TI Microstructure-property relations in As-extruded ultrahigh-carbon steels SO METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE LA English DT Article ID TENSILE PROPERTIES; PEARLITE AB The microstructure and mechanical properties of as-extruded ultrahigh-carbon steels (UHCSs) are described. Extrusion ratios of 16:1 reduction were used at extrusion temperatures of 900 degrees C, 1025 degrees C, and 1150 degrees C. Air cooling followed the extrusion process. The compositions of the four UHCSs investigated ranged from 1.2 to 1.8 pet C and contained either aluminum or silicon and/or chromium as the principal alloying elements. The as-extruded microstructures were predominantly pearlitic. Detailed examination of the microstructures allowed determination of the composition and extrusion temperature at which grain-boundary carbide networks and graphite can be avoided. It is shown that the yield strength of the as-extruded bars, for a given UHCS alloy composition, correlates well with the interlamellar spacing, independent of the extrusion temperature. Ultimate tensile strengths ranged from 1000 to 1690 MPa, and elongations to failure ranged from 3 to 12.5 pet. The present results indicate that single-step mechanical working of UHCSs to achieve fully pearlitic structures, with no postworking heat treatment, can lead to a new class of ultrahigh-strength steels. C1 Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94551 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Stanford Univ, Dept Mat Sci & Engn, Stanford, CA 94305 USA. RP Lesuer, DR (reprint author), Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94551 USA. NR 20 TC 29 Z9 37 U1 0 U2 4 PU MINERALS METALS MATERIALS SOC PI WARRENDALE PA 420 COMMONWEALTH DR, WARRENDALE, PA 15086 USA SN 1073-5623 J9 METALL MATER TRANS A JI Metall. Mater. Trans. A-Phys. Metall. Mater. Sci. PD JUN PY 1999 VL 30 IS 6 BP 1559 EP 1568 DI 10.1007/s11661-999-0093-x PG 10 WC Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Materials Science; Metallurgy & Metallurgical Engineering GA 208XK UT WOS:000081017100010 ER PT J AU Halverson, JB Ferrier, BS Rickenbach, TM Simpson, J Tao, WK AF Halverson, JB Ferrier, BS Rickenbach, TM Simpson, J Tao, WK TI An ensemble of convective systems on 11 February 1993 during TOGA COARE: Morphology, rainfall characteristics, and anvil cloud interactions SO MONTHLY WEATHER REVIEW LA English DT Article ID EQUATORIAL WESTERN PACIFIC; TROPICAL SQUALL-LINE; WARM POOL; CUMULUS CONVECTION; MESOSCALE; SCALE; GATE; ORGANIZATION; MECHANISMS; EVOLUTION AB An active day during the Coupled Ocean-Atmosphere Response Experiment (COARE) Intensive Observation Period (IOP) is examined in which nine convective systems evolved and moved eastward across the region of shipboard radar coverage in the Intensive Flux Array (IFA) within westerly wind burst conditions. The detailed genesis, morphology, and interactions between these cloud systems are documented from a radar and satellite perspective. One of these systems was a large and complex elliptical cluster, among the largest observed during the Tropical Ocean Global Atmosphere COARE. Multiple, parallel deep convective lines spaced 20-30 km apart and embedded within this system were initially oriented from north-northwest to south-southeast, oblique to the storm motion. Furthermore, the lines underwent counterclockwise realignment as the system moved eastward. The influence of strong lower-tropospheric directional and speed shear on these convective system properties is examined in the context of a dynamic, large-scale near-equatorial trough/transequatorial flow regime. A daily analysis of flow conditions during the 119-day IOP revealed that this type of synoptic regime was present in the IFA at least 40% of the time. Radar-derived rainfall statistics are examined throughout the life cycles of each individual convective system. Spatial mapping of accumulated rainfall reveals long, linear swaths produced by the most intense cells embedded within convective lines. The evolution of rainfall properties includes an increase in the stratiform rainfall fraction and areal coverage in later generations of systems, with a peak in total rainfall production after local midnight. These trends can be explained by anvil cloud interactions originating within the sequence of closely spaced disturbances, including the effects of both enhanced midtropospheric moisture and also strong reversing (easterly) shear. The issue of boundary layer recovery between the frequent, intense convective systems on this day is also examined. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Trop Rainfall Measurement Mission Off, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD USA. RP Halverson, JB (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, CODE 912, Greenbelt, MD 20771 USA. NR 53 TC 16 Z9 16 U1 0 U2 3 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 1999 VL 127 IS 6 BP 1208 EP 1228 DI 10.1175/1520-0493(1999)127<1208:AEOCSO>2.0.CO;2 PN 2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 207AU UT WOS:000080913800004 ER PT J AU James, RB Siffert, P Eisen, Y Schlesinger, TE Cuzin, M Franks, LA Trombka, J Campiotti, M Schieber, M AF James, RB Siffert, P Eisen, Y Schlesinger, TE Cuzin, M Franks, LA Trombka, J Campiotti, M Schieber, M TI Proceedings of the Conference on Room Temperature Semiconductor Detectors for Remote, Portable and In-situ Radiation Measurement Systems, Jerusalem, Israel, July 26-29, 1998 - Preface SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Editorial Material C1 Sandia Natl Labs, Livermore, CA 94550 USA. CNRS, Lab PHASE, F-75700 Paris, France. Carnegie Mellon Univ, Pittsburgh, PA 15213 USA. CEA, LETI, Grenoble, France. NASA Goddard, Greenbelt, MD USA. Hebrew Univ Jerusalem, IL-91905 Jerusalem, Israel. RP James, RB (reprint author), Sandia Natl Labs, Livermore, CA 94550 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 1 PY 1999 VL 428 IS 1 BP VII EP VIII PG 2 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 204MF UT WOS:000080767500001 ER PT J AU Franks, LA Brunett, BA Olsen, RW Walsh, DS Vizkelethy, G Trombka, JI Doyle, BL James, RB AF Franks, LA Brunett, BA Olsen, RW Walsh, DS Vizkelethy, G Trombka, JI Doyle, BL James, RB TI Radiation damage measurements in room-temperature semiconductor radiation detectors SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT International Workshop on Room Temperature Semiconductor Detectors for Remote, Portable and In-Situ Radiation Measurement Systems CY JUL 26-29, 1998 CL JERUSALEM, ISRAEL DE cadmium zinc telluride; cadmium telluride; mercuric iodide; radiation damage; neutron damage; charged particle damage; gamma-ray spectrometers ID X-RAY-DETECTORS; RESISTANCE; CDZNTE AB The literature of radiation damage measurements on cadmium zinc telluride (CZT), cadmium telluride (CT), and mercuric iodide (HgI2) is reviewed and in the case of CZT supplemented by new alpha particle data. CZT strip detectors exposed to intermediate energy (1.3 MeV) proton fluences exhibit increased interstrip leakage after 10(10) p/cm(2) and significant bulk leakage after 10(12) p/cm(2). CZT exposed to 200 MeV protons shows a two-fold loss in energy resolution after a fluence of 5 x 10(9) p/cm(2) in thick (3 mm) planar devices but little effect in 2 mm devices. No energy resolution effects were noted from a moderated fission spectrum of neutrons after fluences up to 1010 n/cm(2), although activation was evident. Exposures of CZT to 5 MeV alpha particles at fluences up to 1.5 x 10(10) alpha/cm(2) produced a near linear decrease in peak position with fluence and increases in FWHM beginning at about 7.5 x 10(9) alpha/cm(2), CT detectors show resolution losses after fluences of 3 x 10(9) p/cm(2) at 33 MeV for chlorine-doped detectors. Indium-doped material may be more resistant. Neutron exposures (8 MeV) caused resolution losses after fluences of 2 x 10(10) n/cm(2). Mercuric iodide has been studied with intermediate energy protons (10-33 MeV) at fluences up to 10(12) p/cm(2) and with 1.5 GeV protons at fluences up to 1.2 x 10(8) p/cm(2). Neutron exposures at 8 MeV have been reported at fluences up to 10(15) n/cm(2). No radiation damage was reported under these irradiation conditions. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Sandia Natl Labs, Livermore, CA 94550 USA. Carnegie Mellon Univ, ECE Dept, Pittsburgh, PA 15213 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Idaho State Univ, Pocatello, ID 83209 USA. RP Franks, LA (reprint author), Sandia Natl Labs, Livermore, CA 94550 USA. NR 11 TC 31 Z9 31 U1 1 U2 11 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 1 PY 1999 VL 428 IS 1 BP 95 EP 101 DI 10.1016/S0168-9002(98)01585-X PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 204MF UT WOS:000080767500014 ER PT J AU Marks, DG Barber, HB Barrett, HH Tueller, J Woolfenden, JM AF Marks, DG Barber, HB Barrett, HH Tueller, J Woolfenden, JM TI Improving performance of a CdZnTe imaging array by mapping the detector with gamma rays SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT International Workshop on Room Temperature Semiconductor Detectors for Remote, Portable and In-Situ Radiation Measurement Systems CY JUL 26-29, 1998 CL JERUSALEM, ISRAEL DE gamma-ray imaging; semiconductors AB We can greatly reduce image artifacts in our pixellated CdZnTe arrays by mapping imperfect regions with a narrow collimated beam of gamma rays. Portions of our detectors produce signals that agree well with simulations of gamma-ray interactions, but there are many examples of structures in the material that respond unpredictably to gamma rays. We mapped some of these imperfect regions using 60 and 140 keV gamma-ray beams, recording a 7 x 7 set of pixel signals for each interaction. The pixel pitch was 380 mu m. We used the mapped data to estimate the probability density function (PDF) of the pixel signals for each interaction position. Images were taken on the mapped sections, storing each gamma; ray as a list of pixel signals. Images could be formed by either estimating each gamma-ray interaction position individually or using the entire set of image data in a single iterative computation using the expectation-maximization (EM) algorithm. At 60 keV individual interaction positions were estimated by fitting the data to a Gaussian PDF, correcting the artifacts and giving sub-pixel resolution of less than 150 mu m in some regions. At 140 keV applying the EM algorithm was necessary for improving the images. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. Arizona Hlth Sci Ctr, Div Nucl Med, Tucson, AZ 85724 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Marks, DG (reprint author), Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. RI Tueller, Jack/D-5334-2012 NR 7 TC 16 Z9 16 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 1 PY 1999 VL 428 IS 1 BP 102 EP 112 DI 10.1016/S0168-9002(98)01586-1 PG 11 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 204MF UT WOS:000080767500015 ER PT J AU Schweitzer, JS Trombka, JI AF Schweitzer, JS Trombka, JI TI Room-temperature semiconductors and scintillators for planetary instruments SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT International Workshop on Room Temperature Semiconductor Detectors for Remote, Portable and In-Situ Radiation Measurement Systems CY JUL 26-29, 1998 CL JERUSALEM, ISRAEL DE semiconductors; gamma-ray spectrometers; planetary measurements; spectral quality AB Room temperature semiconductors introduce some exciting potential for use in instruments designed for planetary measurements. It is important, however, to consider carefully the different types of measurement environments. In some cases room temperature semiconductors provide significant advantages over scintillators, while in some cases scintillators still have advantages over room temperature semiconductors. A number of instrumentation applications for detecting X-rays and gamma rays are considered. By focusing on the physical properties of both types of detectors, it is possible to better understand how each type of detector can best be used for measurements from satellites and directly on planetary bodies. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Connecticut, Dept Phys, Storrs, CT 06269 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Schweitzer, JS (reprint author), Univ Connecticut, Dept Phys, U46,2152 Hillside Rd, Storrs, CT 06269 USA. NR 8 TC 1 Z9 2 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 1 PY 1999 VL 428 IS 1 BP 193 EP 198 DI 10.1016/S0168-9002(99)00006-6 PG 6 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 204MF UT WOS:000080767500024 ER PT J AU Trombka, JI Evans, LG Starr, R Clark, PE Floyd, SR AF Trombka, JI Evans, LG Starr, R Clark, PE Floyd, SR TI Future planetary X-ray and gamma-ray remote sensing system and in situ requirements for room temperature solid state detectors SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT International Workshop on Room Temperature Semiconductor Detectors for Remote, Portable and In-Situ Radiation Measurement Systems CY JUL 26-29, 1998 CL JERUSALEM, ISRAEL DE X-ray; gamma-ray; spectroscopy; planetary remote sensing; geochemical mapping AB X-Ray and gamma-ray remote sensing observations find important applications in the study of the development of the planets. Orbital measurements can be carried out on solar-system bodies whose atmospheres and trapped radiation environments do not interfere significantly with the emissions. Elemental compositions can be inferred from observations of these line emissions. Future planetary missions also will involve landing both stationery and roving probes on planetary surfaces. Both X-ray and gamma-ray spectrometers will be used for performing elemental analysis of surface samples. These future planetary missions will impose a number of constraints: the flight instruments must be significantly reduced in weight from those previously flown; for many missions, gravity assist will be required, greatly increasing mission duration, resulting in the passage of several years before the first scientific measurement of a solar system body. The detector systems must operate reliably after years of cosmic-ray irradiation. Both spectroscopy and imaging detection systems are required. Room temperature systems show great promise for application to planetary X-ray and gamma-ray remote systems. A number of laboratory and sub-orbital, orbital, and planetary flight mission investigations have been and will be carried out in order to develop room temperature solid state detector systems for space flight. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Comp Sci Corp, Lanham, MD 20706 USA. Catholic Univ Amer, Washington, DC 20064 USA. RP Trombka, JI (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 28 TC 7 Z9 7 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 1 PY 1999 VL 428 IS 1 BP 199 EP 208 DI 10.1016/S0168-9002(99)00007-8 PG 10 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 204MF UT WOS:000080767500025 ER PT J AU Starr, R Clark, PE Evans, LG Floyd, SR McClanahan, TP Trombka, JI Goldsten, JO Maurer, RH McNutt, RL Roth, DR AF Starr, R Clark, PE Evans, LG Floyd, SR McClanahan, TP Trombka, JI Goldsten, JO Maurer, RH McNutt, RL Roth, DR TI Radiation effects in the Si-PIN detector on the Near Earth Asteroid Rendezvous mission SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT International Workshop on Room Temperature Semiconductor Detectors for Remote, Portable and In-Situ Radiation Measurement Systems CY JUL 26-29, 1998 CL JERUSALEM, ISRAEL DE XRS; GRS; Si-PIN detector; photodiodes; radioactive decay AB A Si-PIN photodiode is being used as a solar X-ray monitor on the X-ray/gamma-ray spectrometer experiment which is flying on the Near Earth Asteroid Rendezvous spacecraft. Since its launch in February 1996 this photodiode has experienced several brief failures. These anomalies and other performance characteristics will be described. Efforts to reproduce these failures in ground tests with flight spare equipment will also be discussed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Washington, DC 20064 USA. Comp Sci Corp, Laurel, MD 20707 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Starr, R (reprint author), NASA, Goddard Space Flight Ctr, Code 690-2, Greenbelt, MD 20771 USA. RI McNutt, Ralph/E-8006-2010 OI McNutt, Ralph/0000-0002-4722-9166 NR 6 TC 8 Z9 9 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 1 PY 1999 VL 428 IS 1 BP 209 EP 215 DI 10.1016/S0168-9002(99)00008-X PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 204MF UT WOS:000080767500026 ER PT J AU Tripathi, RK Cucinotta, FA Wilson, JW AF Tripathi, RK Cucinotta, FA Wilson, JW TI Medium modified nucleon-nucleon cross sections in a nucleus SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article ID MICROSCOPIC CALCULATION AB A simple reliable formalism is presented for obtaining nucleon-nucleon cross sections within a nucleus in nuclear collisions for a given projectile and target nucleus combination at a given energy for use in transport, Monte Carlo and other calculations. The method relies on extraction of these values from experiments and has been tested for absorption experiments to give excellent results. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Hampton Univ, Hampton, VA 23668 USA. Natl Res Council, Washington, DC 20418 USA. Natl Res Council, Hampton, VA USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Tripathi, RK (reprint author), NASA, Langley Res Ctr, Mail Stop 188B, Hampton, VA 23681 USA. NR 16 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-583X J9 NUCL INSTRUM METH B JI Nucl. Instrum. Methods Phys. Res. Sect. B-Beam Interact. Mater. Atoms PD JUN PY 1999 VL 152 IS 4 BP 425 EP 431 DI 10.1016/S0168-583X(99)00181-0 PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 202WA UT WOS:000080674100002 PM 11541772 ER PT J AU Ilchenko, VS Yao, XS Maleki, L AF Ilchenko, VS Yao, XS Maleki, L TI Pigtailing the high-Q microsphere cavity: a simple fiber coupler for optical whispering-gallery modes SO OPTICS LETTERS LA English DT Article ID RESONANCES; RESONATORS AB We demonstrate a simple method for efficient coupling of standard single-mode optical fibers to a high-Q optical microsphere cavity. Phase-matched excitation of whispering-gallery modes is provided by an angle-polished fiber tip in which the core-guided wave undergoes total internal reflection. In the experimental setup, which included a microsphere with both an input and an output coupler, the total fiber-to-fiber transmission at resonance reached 23% (total insertion loss, 6.3 dB), with loaded quality factor Q greater than or equal to 3 x 10(7) and unloaded Q approximate to 1.2 x 10(8) at 1550 nm. A simple pigtailing method for microspheres permits their wider use in fiber optics and photonics devices. (C) 1999 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ilchenko, VS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 152 Z9 157 U1 5 U2 29 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 JUN 1 PY 1999 VL 24 IS 11 BP 723 EP 725 DI 10.1364/OL.24.000723 PG 3 WC Optics SC Optics GA 201GZ UT WOS:000080588200007 PM 18073834 ER PT J AU Brady, MP Verink, ED Smith, JW AF Brady, MP Verink, ED Smith, JW TI Oxidation behavior of two-phase gamma+sigma Nb-Ti-Al alloys SO OXIDATION OF METALS LA English DT Article DE internal oxidation; niobium aluminides; titanium aluminides; sigma phase; gamma phase ID HIGH-TEMPERATURE; SYSTEM; EQUILIBRIA; NITROGEN; ALUMINA AB The oxidation behavior of a series of single- and two-phase Nb-Ti-Al alloys, selected from the same extended gamma + sigma tie-line, was investigated at 1200 degrees C in air. The single-phase sigma alloy suffered from extensive internal oxidation and oxidized at a much higher rate than the single-phase gamma alloy. In a two-phase gamma + sigma microstructure, the gamma phase was preferentially attacked to form "internal" alumina and Ti-rich nitride. This preferential attack of gamma limited the extent to which the sigma phase was internally oxidized, but also interrupted the formation of a continuous alumina scale. The single-phase gamma alloy also did not form a continuous alumina scale. The inability of the gamma phase to form continuous alumina as attributed to a combination of nitride formation and internal oxidation. The oxidation behavior of the two-phase gamma + sigma Nb-Ti-Al alloys is discussed in terms of mechanisms developed for the oxidation of binary two-phase alloys. C1 Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. Univ Florida, Dept Mat Sci & Engn, Gainesville, FL 32611 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Brady, MP (reprint author), Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. RI Brady, Michael/A-8122-2008 OI Brady, Michael/0000-0003-1338-4747 NR 18 TC 11 Z9 11 U1 0 U2 2 PU KLUWER ACADEMIC/PLENUM PUBL PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0030-770X J9 OXID MET JI Oxid. Met. PD JUN PY 1999 VL 51 IS 5-6 BP 539 EP 556 DI 10.1023/A:1018899412977 PG 18 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA 185TQ UT WOS:000079686800011 ER PT J AU Schmidt, GA AF Schmidt, GA TI Error analysis of paleosalinity calculations SO PALEOCEANOGRAPHY LA English DT Article ID OXYGEN ISOTOPIC COMPOSITION; GENERAL-CIRCULATION MODEL; LAST GLACIAL MAXIMUM; PLANKTONIC-FORAMINIFERA; WATER-BALANCE; OCEAN; TEMPERATURE; CARBONATES; DELTA-O-18; SALINITY AB A detailed error analysis is performed for the calculation of open-ocean salinity changes from carbonate oxygen-18 proxy data. Measurement errors are generally negligible, however, errors due to the "goodness of fit" of various regressions used in the calculation are significant. Depending on the method used and on the proxies available, error bars (1 sigma) for the salinity range from 0.6 to 1.8. In particular, expected errors for the midlatitude and tropical salinity differences at the Last Glacial Maximum are around 1.1 to 2.5. The largest errors occur because of the differences between temporal and spatial seawater oxygen-18:salinity relationships and through the use of nonconcurrent temperature measurements. Methods of improving paleosalinity estimates should focus on eliminating these large sources of uncertainty. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, 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 30 TC 93 Z9 95 U1 3 U2 18 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0883-8305 J9 PALEOCEANOGRAPHY JI Paleoceanography PD JUN PY 1999 VL 14 IS 3 BP 422 EP 429 DI 10.1029/1999PA900008 PG 8 WC Geosciences, Multidisciplinary; Oceanography; Paleontology SC Geology; Oceanography; Paleontology GA 198XC UT WOS:000080448700013 ER PT J AU Tait, AB Hall, DK Foster, JL Chang, ATC AF Tait, AB Hall, DK Foster, JL Chang, ATC TI High frequency passive microwave radiometry over a snow-covered surface in Alaska SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article ID WATER-VAPOR; PRECIPITATION AB Millimeter-wave Imaging Radiometer (MIR) data (ranging in frequency from 89 to 325 GHz) were collected from NASA ER-2 flights over Alaska in April 1995. This study determines whether these data can be used to identify clouds, vegetation type, and snow cover. The procedure used is as follows: (1) determine whether a purely MIR-based cloud detection scheme is possible over a snow-covered surface, (2) analyze the influence of changing vegetation type on the brightness temperatures, and (3) compare completely snow-covered scenes with partially snow-covered and snow-free regions for cloudy and clear-sky periods to determine whether varying snow conditions affect the MIR data. Results show that surface features can be identified using the less opaque channels at 89, 150, and 220 GHz, although the 150-GHz (2.0-mm wavelength) and 220-GHz (1.4-mm) channels are more sensitive to atmospheric phenomena compared with 89 GHz (3.4 mm), because the atmospheric contribution to the upwelling radiation is larger for shorter wavelengths. Statistical examination of the MIR data shows that the determination of cloudy pixels over a snow-covered surface is not possible using a simple brightness temperature threshold technique. Furthermore, it is concluded that, while no statistical discrimination between specific vegetation classes can be made, significance is obtained when the vegetation is grouped into two classes only, for example, vegetated and barren. It is also shown that the stale of the snow cover (complete coverage, melting, or patchy) has a distinct effect on these results. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Tait, AB (reprint author), NASA, Goddard Space Flight Ctr, Code 974, Greenbelt, MD 20771 USA. RI Hall, Dorothy/D-5562-2012 NR 13 TC 0 Z9 0 U1 0 U2 0 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 JUN PY 1999 VL 65 IS 6 BP 689 EP 695 PG 7 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 203RK UT WOS:000080720500009 ER PT J AU Abramovici, A AF Abramovici, A TI Pointing stability SO PHOTONICS SPECTRA LA English DT Letter C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Abramovici, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 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 1999 VL 33 IS 6 BP 81 EP 81 PG 1 WC Optics SC Optics GA 204GY UT WOS:000080756900039 ER PT J AU Orient, OJ Chutjian, A AF Orient, OJ Chutjian, A TI Experimental study of dissociative attachment in H-2: Effects of vibrational excitation SO PHYSICAL REVIEW A LA English DT Article ID ION PRODUCTION; HYDROGEN; RECOMBINATION; COLLISIONS; ELECTRONS; MOLECULES; SURFACES; STATES; GAS; D2 AB Dissociative electron attachment (DA) to H-2? has been studied by measuring the outgoing kinetic energies of the H-(1s(2)). with H(nl) in n = I and 2 exit channels. The electron energies E-e, studied no 3-16 eV. Effects of vibration-rotation population in H, are seen, and the DA results herein are modeled in terms of known cross sections for attachment from H-2(upsilon" .J"). Use is made of magnetically confined electron and ion beams with trochoidal deflection to measure outgoing ion energies. [S1050-2947(99)01506-1]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Orient, OJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 30 TC 4 Z9 4 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 JUN PY 1999 VL 59 IS 6 BP 4374 EP 4378 DI 10.1103/PhysRevA.59.4374 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 204RH UT WOS:000080777600034 ER PT J AU Karaganov, V Bray, I Teubner, PJO AF Karaganov, V Bray, I Teubner, PJO TI Electron scattering from optically pumped lithium atoms SO PHYSICAL REVIEW A LA English DT Article ID IMPACT COHERENCE PARAMETERS; DISTORTED-WAVE CALCULATION; LASER-EXCITED BARIUM; SUPERELASTIC-SCATTERING; EXCITATION; SODIUM; POLARIZATION; COLLISIONS; ALIGNMENT; ORIENTATION AB A series of superelastic scattering experiments is described in which electrons are scattered from lithium atoms optically pumped to the 2P excited state. The incident electron energies were 5.2, 12.2, and 20 eV and superelastically scattered electrons with energies of 7, 14, and 21.8 eV were detected over the angular range from 0 degrees to 140 degrees. Both differential cross sections and the orientation and alignment parameters were deduced from the same measurements. A complete set of the four spin-averaged parameters, which fully characterize the electron impact excitation of the 2S-2P transition in lithium, is presented. The experimental results are compared with those predicted from convergent-close-coupling (CCC) calculations and two distorted-wave calculations. Excellent agreement is found with the CCC calculations. [S1050-2947(99)06405-9]. C1 Flinders Univ S Australia, Dept Phys, Elect Struct Mat Ctr, Adelaide, SA 5001, Australia. RP Karaganov, V (reprint author), CALTECH, Jet Prop Lab, MS 183-601, Pasadena, CA 91109 USA. RI Bray, Igor/B-8586-2009 OI Bray, Igor/0000-0001-7554-8044 NR 47 TC 15 Z9 15 U1 0 U2 3 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 JUN PY 1999 VL 59 IS 6 BP 4407 EP 4417 DI 10.1103/PhysRevA.59.4407 PG 11 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 204RH UT WOS:000080777600039 ER PT J AU Cornelius, CM Dowling, JP AF Cornelius, CM Dowling, JP TI Modification of Planck blackbody radiation by photonic band-gap structures SO PHYSICAL REVIEW A LA English DT Article ID INHIBITED SPONTANEOUS EMISSION; APPARATUS-DEPENDENT CONTRIBUTIONS; QUANTUM ELECTRODYNAMICS; DIPOLE ANTENNAS; LEVEL SHIFTS; CONDUCTING PLATES; PARALLEL MIRRORS; 2ND QUANTIZATION; OPTICAL DIODE; SIMPLE ATOMS AB We discuss a simple one-dimensional (1D) model of the modification of Planck blackbody radiation by photonic band-gap materials (PBG's). The model gives qualitative predictions for the thermal power spectrum of 2D and 3D PEG structures, and quantitative results for 1D, distributed Bragg reflecting PBC thin films. C1 USA, Aviat & Missile Command, Sci & Tech Off,Missile Res Dev & Engn Ctr, Weapons Sci Directorate,AMSAM,RD,WS,ST, Redstone Arsenal, AL 35898 USA. CALTECH, Jet Prop Lab, Quantum Algorithms & Technol Grp, Sect 365, Pasadena, CA 91109 USA. RP Cornelius, CM (reprint author), USA, Aviat & Missile Command, Sci & Tech Off,Missile Res Dev & Engn Ctr, Weapons Sci Directorate,AMSAM,RD,WS,ST, Bldg 7804, Redstone Arsenal, AL 35898 USA. RI DOWLING, JONATHAN/L-2749-2013 NR 92 TC 115 Z9 119 U1 3 U2 15 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 JUN PY 1999 VL 59 IS 6 BP 4736 EP 4746 DI 10.1103/PhysRevA.59.4736 PG 11 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 204RH UT WOS:000080777600080 ER PT J AU Dritschel, DG Juarez, MD Ambaum, MHP AF Dritschel, DG Juarez, MD Ambaum, MHP TI The three-dimensional vortical nature of atmospheric and oceanic turbulent flows SO PHYSICS OF FLUIDS LA English DT Article ID 2-DIMENSIONAL VORTEX INTERACTIONS; QUASI-GEOSTROPHIC TURBULENCE; CONTOUR DYNAMICS; FLUID; STRATOSPHERE; INSTABILITY; EQUATIONS; MOTION AB Using a novel numerical method at unprecedented resolution, we demonstrate that structures of small to intermediate scale in rotating, stratified flows are intrinsically three-dimensional. Such flows are characterized by vortices (spinning volumes of fluid), regions of large vorticity gradients, and filamentary structures at all scales. It is found that such structures have predominantly three-dimensional dynamics below a horizontal scale L approximate to 1/2 L-R, where L-R is the so-called Rossby radius of deformation, equal to the characteristic vertical scale of the fluid H divided by the ratio of the rotational and buoyancy frequencies f/N. The breakdown of two-dimensional dynamics at these scales is attributed to the so-called "tall-column instability" [D. G. Dritschel and M. de la Torre Juarez, J. Fluid, Mech. 328, 129 (1996)], which is active on columnar vortices that are tall after scaling by f/N, or, equivalently, that are narrow compared with L-R. Moreover, this instability eventually leads to a simple relationship between typical vertical and horizontal scales: for each vertical wave number (apart from the vertically averaged, barotropic component of the flow) the average horizontal wave number is equal to f/N times the vertical wave number. The practical implication is that three-dimensional modeling is essential to capture the behavior of rotating, stratified fluids, Two-dimensional models are not valid fur scales below L-R. (C) 1999 American Institute of Physics. [S1070-6631(99)02405-8]. C1 Univ St Andrews, Math Inst, St Andrews KY16 9SS, Fife, Scotland. CALTECH, Jet Prop Lab, Dept Earth & Planetary Sci, Pasadena, CA 91109 USA. Univ Reading, Dept Meteorol, Reading RG6 6BB, Berks, England. RP Dritschel, DG (reprint author), Univ St Andrews, Math Inst, St Andrews KY16 9SS, Fife, Scotland. RI Ambaum, Maarten/E-1387-2011; Dritschel, David/D-8131-2013; Dritschel, David/M-8200-2014 OI Ambaum, Maarten/0000-0002-6824-8083; Dritschel, David/0000-0001-6489-3395 NR 40 TC 45 Z9 45 U1 0 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD JUN PY 1999 VL 11 IS 6 BP 1512 EP 1520 DI 10.1063/1.870014 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 197UL UT WOS:000080384000023 ER PT J AU Blandford, R Gehrels, N AF Blandford, R Gehrels, N TI Revisiting the Black Hole SO PHYSICS TODAY LA English DT Article AB A resurgence of theoretical and observational interest in black holes has given new impetus to the study of these intriguing objects. C1 CALTECH, Pasadena, CA 91125 USA. NASA, Goddard Space Flight Ctr, Gamma Ray & Cosm Ray Astrophys Branch, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Blandford, R (reprint author), CALTECH, Pasadena, CA 91125 USA. RI Gehrels, Neil/D-2971-2012 NR 4 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 0031-9228 J9 PHYS TODAY JI Phys. Today PD JUN PY 1999 VL 52 IS 6 BP 40 EP 46 DI 10.1063/1.882697 PG 7 WC Physics, Multidisciplinary SC Physics GA 204ME UT WOS:000080767400013 ER PT J AU Stone, EC AF Stone, EC TI Communications technologies for space exploration SO PROCEEDINGS OF THE IEEE LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Stone, EC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9219 J9 P IEEE JI Proc. IEEE PD JUN PY 1999 VL 87 IS 6 BP 1044 EP 1046 DI 10.1109/5.763318 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 197HH UT WOS:000080359000010 ER PT J AU Launius, RD AF Launius, RD TI NASA history and the challenge of keeping the contemporary past SO PUBLIC HISTORIAN LA English DT Article RP Launius, RD (reprint author), NASA, Washington, DC 20546 USA. NR 72 TC 3 Z9 3 U1 0 U2 0 PU UNIV CALIF PRESS PI BERKELEY PA JOURNALS DEPT 2120 BERKELEY WAY, BERKELEY, CA 94720 USA SN 0272-3433 J9 PUBL HISTORIAN JI Public Hist. PD SUM PY 1999 VL 21 IS 3 BP 63 EP 81 PG 19 WC History SC History GA 225WJ UT WOS:000081988700009 ER PT J AU Plait, P Gull, TR AF Plait, P Gull, TR TI Space Telescope Imaging Spectrograph parallel observations of the planetary nebula M94-20 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID LARGE MAGELLANIC CLOUD; STANDARD CANDLES AB The planetary nebula M94-20 in the Large Magellanic Cloud was serendipitously observed with the Space Telescope imaging Spectrograph on board the Hubble Space Telescope as part of the Hubble Space Telescope Archival Pure Parallel Program. We present spatially resolved imaging and spectral data of the nebula and compare them with ground-based data, including detection of several emission lines from the nebula and the detection of the central star. We find that the total H alpha + [N II] flux is 7.3 x 10(-15) ergs s(-1) cm(-2), and we estimate the magnitude of the central star to be m(v), = 26.0 +/- 0.2. Many other Ha sources have been found in M31, M33, and NGC 205 as well. We discuss the use of the parallel observations as a versatile tool for planetary nebula surveys and for other fields of astronomical research. C1 Adv Comp Concepts Inc, Potomac, MD 20854 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Plait, P (reprint author), Adv Comp Concepts Inc, Potomac, MD 20854 USA. RI Gull, Theodore/D-2753-2012 OI Gull, Theodore/0000-0002-6851-5380 NR 11 TC 1 Z9 1 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD JUN PY 1999 VL 111 IS 760 BP 679 EP 684 DI 10.1086/316377 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 207ZM UT WOS:000080965700003 ER PT J AU Simpson, C Eisenhardt, P AF Simpson, C Eisenhardt, P TI The detection and photometric redshift determination of distant galaxies using SIRTF's Infrared Array Camera SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID HUBBLE DEEP FIELD; TELESCOPE-FACILITY SIRTF; STAR-FORMATION; LOCKMAN HOLE; LYMAN LIMIT; QSO FIELDS; EMISSION; SEARCH AB We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera tb detect distant (z similar to 3) galaxies and measure their photometric redshifts. Our analysis shows that changing the original long-wavelength filter specifications provides significant improvements in performance in this and other areas. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Simpson, C (reprint author), Natl Astron Observ Japan, Subaru Telescope, 650 N Aohoku Pl, Hilo, HI 96720 USA. NR 30 TC 72 Z9 72 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD JUN PY 1999 VL 111 IS 760 BP 691 EP 701 DI 10.1086/316373 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 207ZM UT WOS:000080965700005 ER PT J AU Feibelman, WA AF Feibelman, WA TI Ultraviolet evidence for a binary nucleus of the planetary nebula Sh 2-71 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article AB Archival IUE spectra of the planetary nebula Sh 2-71 show a variable Mg II lambda 2800 emission line superposed on a variable stellar continuum. The Mg II feature is thought to be excited in the chromosphere of the cooler component of a binary nucleus, although other causes are also plausible. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 13 TC 4 Z9 4 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD JUN PY 1999 VL 111 IS 760 BP 719 EP 721 DI 10.1086/316370 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 207ZM UT WOS:000080965700008 ER PT J AU Sauber, J Dmowska, R AF Sauber, J Dmowska, R TI Seismogenic and tsunamigenic processes in shallow subduction zones - Introduction SO PURE AND APPLIED GEOPHYSICS LA English DT Editorial Material C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. Harvard Univ, Div Engn & Appl Sci, Cambridge, MA 02138 USA. RP Sauber, J (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Code 661, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU BIRKHAUSER VERLAG AG PI BASEL PA VIADUKSTRASSE 40-44, PO BOX 133, CH-4010 BASEL, SWITZERLAND SN 0033-4553 J9 PURE APPL GEOPHYS JI Pure Appl. Geophys. PD JUN PY 1999 VL 154 IS 3-4 BP 405 EP 407 DI 10.1007/s000240050236 PG 3 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 216VL UT WOS:000081465100001 ER PT J AU Katz, R Cucinotta, FA AF Katz, R Cucinotta, FA TI Tracks to therapy SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT 19th International Conference on Nuclear Tracks in Solids (ICNTSs) CY AUG 31-SEP 05, 1998 CL BESANCON, FRANCE DE tracks; radiobiology; dosimetry; fractionation; radiation therapy ID HEAVY-ION; INACTIVATION; CELLS AB Studies of the structure of particle tracks have led to models of track effects based on radial dose and radiobiological target theory that have been very successful in describing and predicting track effects in physical, chemical, and biological systems. For describing mammalian cellular inactivation two inactivation modes are required, called gamma-kill and ion-kill, the first due to synergistic effects of delta rays from adjacent ion paths thus resembling the effects from gamma rays, and the second to the effects of single ion transits through a cell nucleus. The ion-kill effect is more severe, where the fraction of cells experiencing ion kill is responsible for a decrease in the oxygen enhancement ratio, and an increase in relative biological effectiveness, but these are accompanied by loss of repair, hence to a reduction in the efficiency of fractionation in high LET therapy, as shown by our calculations for radiobiological effects in the "spread out Bragg Peak". C1 Univ Nebraska, Lincoln, NE 68588 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Katz, R (reprint author), Univ Nebraska, Lincoln, NE 68588 USA. NR 31 TC 16 Z9 17 U1 0 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 31 IS 1-6 SI SI BP 379 EP 388 DI 10.1016/S1350-4487(99)00098-0 PG 10 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 226AG UT WOS:000081997700073 PM 12025838 ER PT J AU Badhwar, GD Benton, EV AF Badhwar, GD Benton, EV TI Impact of Solar Energetic Particle Events for the design of human space missions SO RADIATION MEASUREMENTS LA English DT Editorial Material C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ San Francisco, San Francisco, CA 94117 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 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 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 221 EP 221 PG 1 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000001 ER PT J AU Badhwar, GD Atwell, W AF Badhwar, GD Atwell, W TI Detailed comparison of observed dose-time profile of October 19-20, 1989 SPE on Mir with model calculations SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES DE solar particle event dose; geomagnetic cut-off AB The dose rate dynamics of the October 19-20, 1989 solar energetic particle (SPE) event as observed by the Liulin instrument onboard the Mir orbital station was analyzed in light of new calculations of the geomagnetic cutoff and improved estimates of the > 100 MeV energy spectra from the GOES satellite instrument. The new calculations were performed using the as-flown Mii orbital trajectory and includes time variations of the cutoff rigidity due to changes in the K-p index. Although the agreement of total event integrated calculated dose to the measured dose is good, it results from some measured dose-time profile being higher and some lower than model calculations. They point to the need to include the diurnal variation of the geomagnetic cutoff and modifications of the cutoffs to variations in K-p in model calculations. Understanding of such events in light of the upcoming construction of the International Space Station during the period of maximum solar activity needs to be vigorously pursued. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Boeing N Amer, Houston, TX 77058 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 9 TC 5 Z9 5 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 223 EP 229 DI 10.1016/S1350-4487(99)00051-7 PG 7 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000002 PM 11543128 ER PT J AU Cleghorn, TF Badhwar, GD AF Cleghorn, TF Badhwar, GD TI Comparison of the SPE model with proton and heavy ion data SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID SOLAR AB Proton data from the GOES 6 and 7 satellites and heavy ion data from the IMP-8 satellite have been compared to the expected results of Nymmik's new model for solar particle event fluences. This model calculates the energy spectra of ions for protons through nickel for solar particle events, based upon the observed proton integral fluence above 30 MeV. Based upon 27 observed proton events of solar cycle 22, and three large historical events, with integral fluences above 30 MeV of greater than 10(6) particles/cm(2), a reasonable agreement with model predictions is seen for more than half of the events. However, several events show a marked departure from the model predictions, leading to the conclusion that there may exist more than a single class of event, or that it may be necessary to include additional parameters within the model, such as solar disk position of the source flare, or height of disturbance in the solar corona. Data for heavy ions, (oxygen and iron), were limited to a total of six solar particle events, of which only two occurred in solar cycle 22. The agreement between data and the model predictions appeared to be quite good, however this agreement was sensitively dependent upon the value taken for the proton fluence above 30 MeV. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Cleghorn, TF (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 11 TC 2 Z9 2 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 251 EP 259 DI 10.1016/S1350-4487(99)00053-0 PG 9 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000004 PM 11543130 ER PT J AU Cucinotta, FA AF Cucinotta, FA TI Issues in risk assessment from solar particle events SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES DE dose-rate effects; high LET; apoptosis; space radiation; track structure ID DOUBLE-STRAND BREAKS; LOW-ENERGY PROTONS; IONIZING-RADIATION; MUTATION-INDUCTION; MAMMALIAN-CELLS; ALPHA-PARTICLES; HEAVY-IONS; V79 CELLS; DNA; INACTIVATION AB Uncertainties in risk assessment from solar particle events (SPE) include the role of high linear energy transfer (LET) secondary ions, the assessment of dose-rate effects as they relate to acute injury, the risk of cancer mortality and the modification of health effects due to the stress of spaceflight. We discuss several issues where new knowledge is required for improving estimates of radiation risk from SPE's. Secondary particles such as neutrons and low energy and charge ions (LZE) may dominate radiation risk behind a storm shelter and their biological effects are poorly understood, especially at low dose-rate. Dose-rate modulation of radiation response is also related to genetic pre-disposition an important determinant of radiation sensitivity. Molecular pathways that control cell death and tissue response have been elucidated in recent years and should provide new understanding of dose-rate effects for risk assessment. We consider some of these factors and discuss calculations using radiation transport codes, track structure models of energy deposition, and a molecular kinetics approach to model radiation response. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Cucinotta, FA (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 37 TC 16 Z9 16 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 261 EP 268 DI 10.1016/S1350-4487(99)00054-2 PG 8 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000005 PM 11543131 ER PT J AU Feynman, J Ruzmaikin, A AF Feynman, J Ruzmaikin, A TI Problems in the forecasting of solar particle events for manned missions SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID CORONAL MASS EJECTIONS AB Manned spacecraft will require a much improved ability to forecast solar particle events. The lead time required will depend on the use to which the forecast is put. Here we discuss problems of forecasting with the lead times of hours to weeks. Such forecasts are needed for scheduling and carrying out activities. Our present capabilities with these lead times is extremely limited. To improve our capability we must develop an ability to predict fast coronal mass ejections (CMEs). It is not sufficient to observe that a CME has already taken place since by that time it is already too late to make predictions with these lead times. Both to learn how to predict CMEs and to carry out forecasts on time scares of several days to weeks, observations of the other side of the Sun are required. We describe a low-cost space mission of this type that would further the development of an hours-to-weeks forecast capability. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Feynman, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 11 Z9 11 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 275 EP 280 DI 10.1016/S1350-4487(99)00055-4 PG 6 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000007 PM 11543133 ER PT J AU Reames, D AF Reames, D TI Solar energetic particles: Is there time to hide? SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID EJECTION-DRIVEN SHOCKS; CORONAL MASS EJECTIONS; INTERPLANETARY SHOCKS; CHARGE-STATE; ACCELERATION; EVENTS; SPECTRA; WAVES; IONS AB In the large solar energetic particle (SEP) events that constitute a serious radiation hazard, particles are accelerated at shock waves driven out from the Sun by coronal mass ejections (CMEs). A self-regulating mechanism of wave formation by the streaming particles limits SEP intensities early in the event. Hazardous intensities do not occur until the arrival of the shock itself. This provides an opportunity to warn astronauts to take shelter after the onset of the event at the Sun and before arrival of the shock, a time of similar to 12 h or more. The actual time history of particle intensities depends strongly. on the longitude of the event at the Sun, on the width the CME, and especially on the speed of the shock. Fortunately, hazardous events are relatively rare. Unfortunately, this gives us few events to study, so we are forced to extrapolate knowledge gained at lower energies in the frequent smaller events. It is essential that the spacecraft with our best instrumentation be positioned outside the Earth's magnetosphere where they can observe these rare large events when they do occur. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Reames, D (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 23 TC 31 Z9 31 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 297 EP 308 DI 10.1016/S1350-4487(99)00066-9 PG 12 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000010 PM 11543136 ER PT J AU Wilson, JW Cucinotta, FA Shinn, JL Simonsen, LC Dubey, RR Jordan, WR Jones, TD Chang, CK Kim, MY AF Wilson, JW Cucinotta, FA Shinn, JL Simonsen, LC Dubey, RR Jordan, WR Jones, TD Chang, CK Kim, MY TI Shielding from solar particle event exposures in deep space SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES DE solar particle events; shielding; biological response; mortality; tissue environments ID CELL-KINETICS; CYTOPENIA; PHOTONS; MODELS; DEATH AB The physical composition and intensities of solar particle event exposures of sensitive astronaut tissues are examined under conditions approximating an astronaut in deep space. Response functions for conversion of particle fluence into dose and dose equivalent averaged over organ tissues are used to establish significant fluence levels and the expected dose and dose rates of the most important events from past observations. The BRYNTRN transport code is used to evaluate the local environment experienced by sensitive tissues and used to evaluate bioresponse models developed for use in tactical nuclear warfare. The present results will help to clarify the biophysical aspects of such exposure in the assessment of RBE and dose rate effects and their impact on design of protection systems for the astronauts. The use of polymers as shielding material in place of an equal mass of aluminum would provide a large safety factor without increasing the vehicle mass. This safety factor is sufficient to provide adequate protection if a factor of two larger event than has ever been observed in fact occurs during the mission. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Old Dominion Univ, Norfolk, VA 23508 USA. Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA. Christopher Newport Univ, Newport News, VA 23601 USA. Natl Res Council, Washington, DC 20418 USA. RP Wilson, JW (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 25 TC 63 Z9 64 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 361 EP 382 DI 10.1016/S1350-4487(99)00063-3 PG 22 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000016 PM 11543148 ER PT J AU Yang, TCH AF Yang, TCH TI Proton radiobiology and uncertainties SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID CHARGED-PARTICLES; RHESUS-MONKEYS; HEAVY-IONS; INDUCTION; CATARACTOGENESIS; CELLS AB This paper briefly reviews proton radiobiology. Clinical applications of protons produced by accelerators have led to a significant biological literature that contributes to our goal of estimating the proton shielding requirements for human interplanetary missions. Protons are primarily a low-LET radiation with biological effects much like gamma radiation. There are however data indicating enhanced biological effectiveness for small doses of very low energy (<10 MeV) stopping protons, and some limited data for extremely high energy protons (>0.5 GeV). (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Yang, TCH (reprint author), NASA, Lyndon B Johnson Space Ctr, MailCode SD2,NASA Rd 1, Houston, TX 77058 USA. NR 26 TC 12 Z9 13 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 383 EP 392 DI 10.1016/S1350-4487(99)00209-7 PG 10 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000017 PM 11543142 ER PT J AU Zapp, EN Ramsey, CR Townsend, LW Badhwar, GD AF Zapp, EN Ramsey, CR Townsend, LW Badhwar, GD TI Solar particle event dose and dose-rate distributions: parameterization of dose-time profiles, with subsequent dose-rate analysis SO RADIATION MEASUREMENTS LA English DT Article; Proceedings Paper CT Workshop on Impact of Solar Energetic Particle Events for the Design of Human Space Missions CY SEP 09-11, 1997 CL CTR ADV SPACE STUDIES, HOUSTON, TEXAS HO CTR ADV SPACE STUDIES ID EXPOSURE; AUGUST; RISK AB Calculations of total dose and equivalent dose as functions of time, as well as dose-rate and equivalent dose rate since event start are presented for fifteen of the larger solar particle events that occurred during the period between November 1987 and August 1991. The doses, dose-equivalents, and rates presented are for exposures to the skin; ocular lens, and bone marrow behind a thickness of aluminum shielding which provides protection comparable to that of a thin spacecraft. The calculated dose vs time profiles are parameterized using a Weibull cumulative distribution as the fitting function. Parameters are determined using least-squares techniques. Fitted curves are then differentiated to produce smoothed dose-rate curves for each of the events. These results provide a useful starting point for the development of methods to predict the cumulative doses and times to reach various dose limits from a limited number of dosimeter measurements early in the evolution of a solar particle event. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Tennessee, Dept Nucl Engn, Knoxville, TN 37996 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Townsend, LW (reprint author), Univ Tennessee, Dept Nucl Engn, Knoxville, TN 37996 USA. NR 16 TC 12 Z9 12 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 393 EP 400 DI 10.1016/S1350-4487(99)00064-5 PG 8 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000018 PM 11543143 ER PT J AU Badhwar, GD AF Badhwar, GD TI Radiation dose rates in Space Shuttle as a function of atmospheric density SO RADIATION MEASUREMENTS LA English DT Article DE dose-atmospheric density; phase-lag ID MODULATION AB Current models of the inner trapped belt describe the radiation environment at times of solar minimum and solar maximum, respectively. These two models were constructed using data acquired prior to 1970 during a small solar cycle, and no valid model for the past two high solar cycles exists. There is a clear need to accurately predict the radiation exposure of astronauts at all times between the solar minimum and solar maximum, not only on the short duration Space Shuttle flights, but on the longer term stay onboard the Mir orbital station and the planned International Space Station (ISS). An analysis of the trapped absorbed dose rate, D, at six fixed locations in the habitable volume of the Shuttle shows a power law relationship, D = Ap(-n), where rho is the atmospheric density, rho. The index, n, is weakly dependent on the shielding, decreasing as the average shielding increases. A better representation is provided by D = A tan(-1) [(xi-xi(c))/(xi(c)-xi(m))], where xi = ln(rho), and A, xi(c), and xi(m) are constants. xi(c) is related to the atmospheric density near the altitude of atmospheric cutoff. These relationships hold over nearly four decades of density variation and throughout the solar cycle. This then provides a method of calculating absorbed dose rate at anytime in the solar cycle. These empirically derived relations were used to predict the dose rates for eleven Space Shuttle flights carried out since January 1997. The predictions are in excellent agreement with measured values. This method reduces the uncertainties of a factor of about 2 for the AP-8 MIN/MAX models to less than 30%. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 13 TC 18 Z9 18 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 401 EP 414 DI 10.1016/S1350-4487(99)00067-0 PG 14 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000019 PM 11543144 ER PT J AU Badhwar, GD Kushin, VV Akatov, YA Myltseva, VA AF Badhwar, GD Kushin, VV Akatov, YA Myltseva, VA TI Effects of trapped proton flux anisotropy on dose rates in low Earth orbit SO RADIATION MEASUREMENTS LA English DT Article DE trapped belt anisotropy; proton and neutron dose equivalent ID RADIATION MEASUREMENTS; SHUTTLE; SPACECRAFT; SPECTRA; FLIGHT AB Trapped protons in the South Atlantic Anomaly (SAA) have a rather narrow pitch angle distribution and exhibit east-west anisotropy. In low Earth orbits, the E-W effect results in different amounts of radiation dose received by different sections of the spacecraft. This effect is best studied on missions in which the spacecraft flies in a fixed orientation. The magnitude of the effect depends on the particle energy and altitude through the SAA. In this paper, we describe a clear example of this effect from measurements of radiation dose rates and linear energy transfer spectra made on Space Shuttle flight STS-94 (28.5 degree inclination x 296 km altitude). The ratio of dose rates from the two directions at this location in the mid-deck was 2.7. As expected from model calculations, the spectra from the two directions are different, that is the ratio is energy dependent. The data can be used to distinguish the anisotropy models. The flight carried an active tissue equivalent proportional counter (TEPC), and passive thermoluminscent detectors (TLDs), and two types of nuclear emulsions. Using nuclear emulsions, charged particles and secondary neutron energy spectra were measured. The combined galactic cosmic radiation + trapped charged particle lineal energy spectra measured by the TEPC and the linear energy transfer spectrum measured by nuclear emulsions are in good agreement. The charged particle absorbed dose rates varied from 112 to 175 mu Gy/day, and dose equivalent rates from 264.3 to 413 mu Sv/day. Neutrons in the 1-10 MeV contributed a dose rate of 3.7 mu Gy/day and dose equivalent rate of 30.8 mu Sv/day, respectively. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Moscow Phys Engn Inst, Moscow, Russia. Moscow Biomed Problems Inst, Moscow, Russia. Sci Inst Photochem Ind, Moscow, Russia. RP Badhwar, GD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 17 TC 15 Z9 15 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1350-4487 J9 RADIAT MEAS JI Radiat. Meas. PD JUN PY 1999 VL 30 IS 3 BP 415 EP 426 DI 10.1016/S1350-4487(99)00068-2 PG 12 WC Nuclear Science & Technology SC Nuclear Science & Technology GA 255LU UT WOS:000083671000020 PM 11543145 ER PT J AU Gastellu-Etchegorry, JP Guillevic, P Zagolski, F Demarez, V Trichon, V Deering, D Leroy, M AF Gastellu-Etchegorry, JP Guillevic, P Zagolski, F Demarez, V Trichon, V Deering, D Leroy, M TI Modeling BRF and radiation regime of boreal and tropical forests: I. BRF SO REMOTE SENSING OF ENVIRONMENT LA English DT Article; Proceedings Paper CT 7th International Symposium on Physical Measurements and Signatures in Remote Sensing CY APR 07-11, 1997 CL COURCHEVEL, FRANCE SP Int Soc Photogrammetry & Remote Sensing, Deutsch Forschunganstalt Luft & Raumfahrt, NASA, Nat Environm Res Council, European Space Agcy, INRA, CNRS, Assoc Quebecoise Teledetect, Canadian Remote Sensing Soc, European Assoc Remote Sensing Labs, Remote Sensing Soc, Soc Francaise Photogrammetr & Teledetect ID EARTHS SURFACE; REFLECTANCE; ATMOSPHERE AB Monitoring od forest evolution and functioning with remote sensing depends on canopy BRF (bidirectional reflectance factor) sensitivity to biophysical parameters and to canopy PAR (photosynthetically active radiation) regime. Here, we study the canopy BRF of a tropical (Sumatra) and three boreal (Canada) forest sites, with the DART (discrete anisotropic radiative transfer) model. The behavior of PAR regime of these forests is analysed in a companion article. We assessed the BRF sensitivity to some major experimental parameters (scale of analysis, viewing and illumination directions, sky radiation) and compared it with BRF sensitivity to commonly studied biophysical quantities: Leaf area index (LAI) and leaf optical properties. Simulations show;ed that BRF directional anisotropy is very large for all forests. For example, maximum relative reflectance difference with view zenith angle less than 25 degrees is around 0.5 in the visible, 0.4 in the short wave infrared and 0.25 in the near-infrared for tropical forest. We showed that this BRF variability associated with experimental conditions can hamper the remote detection of forest LAI and tree cover change such as deforestation of tropical forest. DART BRFs of the boreal sites were favourably compared with ground (PARABOLA) and airborne (POLDER) measured BRFs, This work stressed 1) the potential of the DART model, 2) the importance of accurate field data for validation approaches, and 3) the very strong influence of canopy architecture on forest BRF; for example, depending on forest sites, a LAI increase may imply that nadir near-infrared reflectance increases or decreases. (C) Elsevier Science Inc., 1999. C1 Ctr Etud Spatiale Biosphere, CNES, CNRS, UPS, F-31401 Toulouse 4, France. Privateers NV, St Maarten, Neth Antilles. Univ Sherbrooke, CARTEL, Sherbrooke, PQ J1K 2R1, Canada. CNRS, Lab Ecol Terr, UPS, Toulouse, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gastellu-Etchegorry, JP (reprint author), Ctr Etud Spatiale Biosphere, CNES, CNRS, UPS, 18 Av Edouard Belin, F-31401 Toulouse 4, France. EM gastellu@cesbio.cnes.fr NR 24 TC 55 Z9 57 U1 1 U2 6 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0034-4257 J9 REMOTE SENS ENVIRON JI Remote Sens. Environ. PD JUN PY 1999 VL 68 IS 3 BP 281 EP 316 DI 10.1016/S0034-4257(98)00119-9 PG 36 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 209QN UT WOS:000081059900010 ER PT J AU Tabib-Azar, M Pathak, PS Ponchak, G LeClair, S AF Tabib-Azar, M Pathak, PS Ponchak, G LeClair, S TI Nondestructive superresolution imaging of defects and nonuniformities in metals, semiconductors, dielectrics, composites, and plants using evanescent microwaves SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID MICROSCOPE; RESOLUTION; FILMS AB We have imaged and mapped material nonuniformities and defects using microwaves generated at the end of a microstripline resonator with 0.4 mu m lateral spatial resolution at 1 GHz. Here we experimentally examine the effect of microstripline substrate permittivity, the feedline-to-resonator coupling strength, and probe tip geometry on the spatial resolution of the probe. Carbon composites, dielectrics, semiconductors, metals, and botanical samples were scanned for defects, residual stresses, subsurface features, areas of different film thickness, and moisture content. The resulting evanescent microwave probe (EMP) images are discussed. The main objective of this work is to demonstrate the overall capabilities of the EMP imaging technique as well as to discuss various probe parameters that can be used to design EMPs for different applications. (C) 1999 American Institute of Physics. [S0034-6748(99)00406-2]. C1 Case Western Reserve Univ, Dept Elect Engn & Appl Phys, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. USAF, Res Lab, Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA. RP Tabib-Azar, M (reprint author), Case Western Reserve Univ, Dept Elect Engn & Appl Phys, Cleveland, OH 44106 USA. NR 19 TC 84 Z9 84 U1 1 U2 6 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 1999 VL 70 IS 6 BP 2783 EP 2792 DI 10.1063/1.1149795 PG 10 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 201UH UT WOS:000080613500032 ER PT J AU Rhim, WK Ohsaka, K Paradis, PF Spjut, RE AF Rhim, WK Ohsaka, K Paradis, PF Spjut, RE TI Noncontact technique for measuring surface tension and viscosity of molten materials using high temperature electrostatic levitation SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID OSCILLATIONS; NICKEL; DROPS AB A new, noncontact technique is described which entails simultaneous measurements of the surface tension and the dynamic viscosity of molten materials. In this technique, four steps were performed to achieve the results: (1) a small sample of material was levitated and melted in a high vacuum using a high temperature electrostatic levitator, (2) the resonant oscillation of the drop was induced by applying a low level ac electric field pulse at the drop of resonance frequency, (3) the transient signals which followed the pulses were recorded, and (4) both the surface tension and the viscosity were extracted from the signal. The validity of this technique was demonstrated using a molten tin and a zirconium sample. In zirconium, the measurements could be extended to undercooled states by as much as 300 K. This technique may be used for both molten metallic alloys and semiconductors. (C) 1999 American Institute of Physics. [S0034-6748(99)00206-3]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvey Mudd Coll, Dept Engn, Claremont, CA 91740 USA. RP Rhim, WK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 17 TC 120 Z9 122 U1 2 U2 26 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 1999 VL 70 IS 6 BP 2796 EP 2801 DI 10.1063/1.1149797 PG 6 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 201UH UT WOS:000080613500034 ER PT J AU Dunphy, PP Chupp, EL Bertsch, DL Schneid, EJ Gottesman, SR Kanbach, G AF Dunphy, PP Chupp, EL Bertsch, DL Schneid, EJ Gottesman, SR Kanbach, G TI Gamma-rays and neutrons as a probe of flare proton spectra: The solar flare of 11 June 1991 SO SOLAR PHYSICS LA English DT Article ID ACCELERATION; PARTICLES; EGRET; EMISSION; MONITORS; LOOP; GRO AB The large flare of 11 June 1991 (GOES class X12) was detected by the Total Absorption Shower Counter (TASC) segment of the EGRET gamma-ray telescope on board the Compton Gamma Ray Observatory. Significant gamma-ray emission was observed over the entire energy range to which the TASC was sensitive -1 to 140 MeV. Several phases were identified which showed major changes in the intensity and spectral shape of the flare gamma-rays. Furthermore, a 'delayed' phase during which a response consistent with the detection of energetic neutrons and pion-decay gamma-rays was seen, implying a qualitative change in the spectral shape of the accelerated ion spectrum. The similarity of the characteristics of this delayed phase (pion and energetic neutron production) to those in other large flares hint at a common particle acceleration mechanism. C1 Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ New Hampshire, Dept Phys, Durham, NH 03824 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Northrop Grumman Corp, Bethpage, NY 11714 USA. Northrop Grumman Corp, Baltimore, MD 21203 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. RP Dunphy, PP (reprint author), Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. NR 51 TC 24 Z9 24 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 1999 VL 187 IS 1 BP 45 EP 57 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 235GX UT WOS:000082534900005 ER PT J AU Engberg, R Lassiter, J AF Engberg, R Lassiter, J TI Dynamic testing of inflatable spacecraft structures SO SOUND AND VIBRATION LA English DT Article AB Test hardware, procedures and noncontacting measurement techniques are described to determine the modal characteristics of an inflatable solar concentrator under the thermal-vacuum conditions of space. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Engberg, R (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 7 TC 1 Z9 1 U1 0 U2 2 PU ACOUSTICAL PUBL INC PI BAY VILLAGE PA 27101 E OVIATT RD PO BOX 40416, BAY VILLAGE, OH 44140 USA SN 0038-1810 J9 SOUND VIB JI Sound Vib. PD JUN PY 1999 VL 33 IS 6 BP 16 EP 20 PG 5 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 219GV UT WOS:000081600300004 ER PT J AU Xiao, Y Mackenzie, C Orasanu, J Spencer, R Rahman, A Gunawardane, V AF Xiao, Y Mackenzie, C Orasanu, J Spencer, R Rahman, A Gunawardane, V CA Lotus Grp TI Information acquisition from audio-video-data sources: An experimental study on remote diagnosis SO TELEMEDICINE JOURNAL LA English DT Article ID 4 COMMUNICATION MODES; INTERACTIVE COMMUNICATION; TELEMEDICINE; PERFORMANCE; ACCURACY; TEAMS AB Objective: To determine what information sources are used during a remote diagnosis task. Materials and Methods: Experienced trauma care providers viewed segments of videotaped initial trauma patient resuscitation and airway management. Experiment 1 collected responses from anesthesiologists to probing questions during and after the presentation of recorded video materials. Experiment 2 collected the responses from three types of care providers (anesthesiologists, nurses, and surgeons). Written and verbal responses were scored according to detection of critical events in video materials and categorized according to their content. Experiment 3 collected visual scanning data using an eyetracker during the viewing of recorded video materials from the three types of care providers. Eye-gaze data were analyzed in terms of focus on various parts of the videotaped materials. Results: Care providers were found to be unable to detect several critical events. The three groups of subjects studied (anesthesiologists, nurses, and surgeons) focused on different aspects of videotaped materials. Conclusion: When the remote events and activities are multidisciplinary and rapidly changing, experts linked with audio-video-data connections may encounter difficulties in comprehending remote activities, and their information usage may be biased. Special training is needed for the remote decision-maker to appreciate tasks outside his or her speciality and beyond the boundaries of traditional divisions of labor. C1 Univ Maryland, Sch Med, Dept Anesthesiol, Baltimore, MD 21201 USA. NASA Ames, Moffett Field, CA USA. RP Xiao, Y (reprint author), Anesthesiol Res Lab, 10 S Pine St,MSTF 534, Baltimore, MD 21201 USA. RI Xiao, Yan/A-7506-2009 OI Xiao, Yan/0000-0003-2805-0619 NR 23 TC 4 Z9 4 U1 0 U2 1 PU MARY ANN LIEBERT INC PUBL PI LARCHMONT PA 2 MADISON AVENUE, LARCHMONT, NY 10538 USA SN 1078-3024 J9 TELEMED J JI Telemed. J. PD SUM PY 1999 VL 5 IS 2 BP 139 EP 155 DI 10.1089/107830299312104 PG 17 WC Health Care Sciences & Services SC Health Care Sciences & Services GA 239ND UT WOS:000082773500003 PM 10908426 ER PT J AU Sergeev, B Madenci, E Ambur, DR AF Sergeev, B Madenci, E Ambur, DR TI Stress intensity factors for an arbitrarily oriented crack near a hole in longeron web SO THEORETICAL AND APPLIED FRACTURE MECHANICS LA English DT Article ID ELASTIC FIELDS AB Damage-tolerant design of composite components in aerospace structures requires computationally effective stress and failure analysis methods. This study introduces an analytical/numerical method to determine the stress field and the stress intensity factors in a composite longeron web with an arbitrarily oriented straight crack near a hole. Typical of webs in wing longerons with massive belts, the tapered web is loaded in bending and shear. The solution method makes use of the complex potentials in conjunction with the boundary collocation technique. The present results are in close agreement with those obtained by finite element. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23665 USA. RP Madenci, E (reprint author), Univ Arizona, Dept Aerosp & Mech Engn, Tucson, AZ 85721 USA. NR 10 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8442 J9 THEOR APPL FRACT MEC JI Theor. Appl. Fract. Mech. PD JUN PY 1999 VL 31 IS 3 BP 213 EP 222 DI 10.1016/S0167-8442(99)00015-4 PG 10 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 207RB UT WOS:000080948900006 ER PT J AU Famiglietti, JS Devereaux, JA Laymon, CA Tsegaye, T Houser, PR Jackson, TJ Graham, ST Rodell, M van Oevelen, PJ AF Famiglietti, JS Devereaux, JA Laymon, CA Tsegaye, T Houser, PR Jackson, TJ Graham, ST Rodell, M van Oevelen, PJ TI Ground-based investigation of soil moisture variability within remote sensing footprints during the Southern Great Plains 1997 (SGP97) Hydrology Experiment SO WATER RESOURCES RESEARCH LA English DT Article ID WATER CONTENT; TOPOGRAPHIC CONTROL; SURFACE HYDROLOGY; LAND; CATCHMENT AB Surface soil moisture content is highly variable in both space and time. While remote sensing provides an effective methodology for mapping surface moisture content over large areas, it averages within-pixel variability thereby masking the underlying heterogeneity observed at the land surface. This variability must be better understood in order to rigorously evaluate sensor performance and to enhance the utility of the larger-scale remotely sensed averages by quantifying the underlying variability that remote sensing cannot record explicitly. In support of the Southern Great Plains 1997 (SGP97) Hydrology Experiment (a surface soil moisture mapping mission conducted between June 18 and July 17, 1997, in central Oklahoma) an investigation was conducted to characterize soil moisture variability within remote sensing footprints (approximately 0.64 km(2)) with more certainty than would be afforded with conventional gravimetric moisture content sampling. Nearly every day during the experiment period, portable impedance probes were used to intensively monitor volumetric moisture content in the 0- to 6-cm surface soil layer at six footprint-sized fields scattered over the SGP97 study area. A minimum of 49 daily moisture content measurements were made on most fields. Higher-resolution grid and transect data were also collected periodically. In total, more than 11,000 impedance probe measurements of volumetric moisture content were made at the six sites by over 35 SGP97 participants. The wide spatial distribution of the sites, combined with the intensive, near-daily monitoring, provided a unique opportunity (relative to previous smaller-scale and shorter-duration soil moisture studies) to characterize variations in surface moisture content over a range of wetness conditions. In this paper the range and temporal dynamics of the variability in moisture content within each of the six fields are described, as are general relationships between the Variability and footprint-mean moisture content. Results indicate that distinct differences in mean moisture content between the six sites are consistent with variations in soil type, vegetation cover, and rainfall gradients. Within fields the standard deviation, coefficient of variation, skewness, and kurtosis increased with decreasing moisture content; the distribution of surface moisture content evolved from negatively skewed/nonnormal under very wet conditions; to normal in the midrange of mean moisture content, to positively skewed/nonnormal under dry conditions; and agricultural practices of row tilling and terracing were shown to exert a major control on observed moisture content variations. Results presented here can be utilized to better evaluate sensor performance, to extrapolate estimates of subgrid-scale variations in moisture content across the entire SGP97 region, and in the parameterization of soil moisture dynamics in hydrological and land surface models. C1 Univ Texas, Dept Geol Sci, Austin, TX 78712 USA. NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. USDA, Hydrol Lab, Agr Res Serv, Beltsville, MD 20705 USA. Inst Global Change Res & Edu, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Alabama A&M Univ, Dept Plant & Soil Sci, Normal, AL 35762 USA. Wageningen Univ Agr, Dept Water Resources, NL-6700 EK Wageningen, Netherlands. RP Famiglietti, JS (reprint author), Univ Texas, Dept Geol Sci, Austin, TX 78712 USA. RI Rodell, Matthew/E-4946-2012; Houser, Paul/J-9515-2013 OI Rodell, Matthew/0000-0003-0106-7437; Houser, Paul/0000-0002-2991-0441 NR 26 TC 253 Z9 263 U1 2 U2 44 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 JUN PY 1999 VL 35 IS 6 BP 1839 EP 1851 DI 10.1029/1999WR900047 PG 13 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 198ZC UT WOS:000080453800014 ER PT J AU Ferrari, MR Miller, JR Russell, GL AF Ferrari, MR Miller, JR Russell, GL TI Modeling the effect of wetlands, flooding, and irrigation on river flow: Application to the Aral Sea SO WATER RESOURCES RESEARCH LA English DT Article ID CLIMATE; SIMULATION; BASIN AB As the world's population continues to increase, additional stress is placed on water resources. This stress, coupled with future uncertainties regarding climate change, makes arid and semiarid regions particularly vulnerable. One example is the Aral Sea where the freshwater inflow, which is dominated by snowmelt runoff, has decreased significantly since the expansion of intensive irrigation in the 1960s. The purpose of this paper is to use a river routing scheme from a global climate model to examine the flow of the Amu Dar'ya River into the Aral Sea. The river routing scheme is modified to include groundwater flow, flooding, and evaporative losses in the river's wetlands and floodplain and anthropogenic withdrawals for irrigation. A set of scenarios is designed to test the sensitivity of river flow to the inclusion of these modifications into the river routing scheme. When riverine wetlands and floodplains are present, the river flow is reduced significantly and is similar to the observed flow. In addition, the model results show that it is essential to incorporate human diversions to represent accurately the inflow to the Aral Sea, and they also indicate potential management strategies that might be appropriate to maintain a balance between inflow to the sea and upstream diversions for irrigation. C1 Rutgers State Univ, Cook Coll, Dept Environm Sci, New Brunswick, NJ 08903 USA. Rutgers State Univ, Cook Coll, Dept Marine & Coastal Sci, New Brunswick, NJ 08903 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Ferrari, MR (reprint author), Rutgers State Univ, Cook Coll, Dept Environm Sci, New Brunswick, NJ 08903 USA. NR 23 TC 10 Z9 10 U1 0 U2 5 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 JUN PY 1999 VL 35 IS 6 BP 1869 EP 1876 DI 10.1029/1999WR900035 PG 8 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 198ZC UT WOS:000080453800016 ER PT J AU Bower, C Rosen, R Jin, L Han, J Zhou, O AF Bower, C Rosen, R Jin, L Han, J Zhou, O TI Deformation of carbon nanotubes in nanotube-polymer composites SO APPLIED PHYSICS LETTERS LA English DT Article AB Composites of uniaxially oriented multiwalled carbon nanotubes embedded in polymer matrices were fabricated and investigated by transmission electron microscopy. In strained composite films, buckling was ubiquitously observed in bent nanotubes with large curvatures. By analyses of a large number of bent nanotubes, the onset buckling strain and fracture strain were estimated to be approximate to 5% and greater than or equal to 18%, respectively. The buckling wavelengths are proportional to the dimensions of the nanotubes. Examination of the fracture surface showed adherence of the polymer to the nanotubes. (C) 1999 American Institute of Physics. [S0003-6951(99)05222-5]. C1 Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bower, C (reprint author), Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. NR 17 TC 392 Z9 413 U1 2 U2 49 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 31 PY 1999 VL 74 IS 22 BP 3317 EP 3319 DI 10.1063/1.123330 PG 3 WC Physics, Applied SC Physics GA 199HC UT WOS:000080474300025 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI Correlation consistent basis sets for indium SO CHEMICAL PHYSICS LETTERS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; MOLECULAR CALCULATIONS; CONFIGURATION-INTERACTION; ELECTRON CORRELATION; WAVE-FUNCTIONS; ATOMS; APPROXIMATION; ENERGIES; PSEUDOPOTENTIALS AB Correlation consistent basis sets are developed for a 13-electron correlation treatment of indium (In) atom. The basis sets are used in all-electron and effective core potential (ECP) calculations. The atomization energies of InCl and InCl3 are used as a test of the basis set. The atomization energies are extrapolated to the complete basis set (CBS) limit. The all-electron and ECP CCSD(T) CBS atomization energies are in very good mutual agreement when the all-electron values are corrected for scalar relativistic effects, which is 15.1 kcal/mol for InCl3. The best computed atomization energies are in good agreement with experiment. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 29 TC 18 Z9 18 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 MAY 28 PY 1999 VL 305 IS 5-6 BP 446 EP 450 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 202AW UT WOS:000080630800023 ER PT J AU Akapo, SO Dimandja, JMD Kojiro, DR Valentin, JR Carle, GC AF Akapo, SO Dimandja, JMD Kojiro, DR Valentin, JR Carle, GC TI Gas chromatography in space SO JOURNAL OF CHROMATOGRAPHY A LA English DT Review DE reviews; space research; hydrocarbons ID MOLECULAR-WEIGHT HYDROCARBONS; SILOXANE BONDED PHASES; PLOT CAPILLARY COLUMN; TITANS ATMOSPHERE; PERMANENT GASES; LIGHT-HYDROCARBONS; SILICA COLUMNS; NITRILES; SAMPLE; MARS AB Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titan's atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Analyze, Chandler, AZ 85224 USA. Ctr Dis Control & Prevent, Atlanta, GA 30341 USA. NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. RP Akapo, SO (reprint author), Analyze, 318 S Bracken Lane, Chandler, AZ 85224 USA. NR 53 TC 10 Z9 10 U1 0 U2 4 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 MAY 28 PY 1999 VL 843 IS 1-2 BP 147 EP 162 DI 10.1016/S0021-9673(98)00947-9 PG 16 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA 207RM UT WOS:000080949600007 PM 10399853 ER PT J AU Smith, DE Zuber, MT Solomon, SC Phillips, RJ Head, JW Garvin, JB Banerdt, WB Muhleman, DO Pettengill, GH Neumann, GA Lemoine, FG Abshire, JB Aharonson, O Brown, CD Hauck, SA Ivanov, AB McGovern, PJ Zwally, HJ Duxbury, TC AF Smith, DE Zuber, MT Solomon, SC Phillips, RJ Head, JW Garvin, JB Banerdt, WB Muhleman, DO Pettengill, GH Neumann, GA Lemoine, FG Abshire, JB Aharonson, O Brown, CD Hauck, SA Ivanov, AB McGovern, PJ Zwally, HJ Duxbury, TC TI The global topography of Mars and implications for surface evolution SO SCIENCE LA English DT Article ID RADIO OCCULTATION MEASUREMENTS; MARTIAN MANTLE CONVECTION; IMPACT BASINS; HEMISPHERIC DICHOTOMY; PHASE-TRANSITIONS; CRUSTAL DICHOTOMY; GIANT IMPACT; POLAR-REGION; MARINER-9; THARSIS AB Elevations measured by the Mars Orbiter Laser Altimeter have yielded a high-accuracy global map of the topography of Mars. Dominant features include the low northern hemisphere, the Tharsis province, and the Hellas impact basin. The northern hemisphere depression is primarily a long-wavelength effect that has been shaped by an internal mechanism. The topography of Tharsis consists of two broad rises. Material excavated from Hellas contributes to the high elevation of the southern hemisphere and to the scarp along the hemispheric boundary. The present topography has three major drainage centers, with the northern Lowlands being the largest. The two polar cap volumes yield an upper limit of the present surface water inventory of 3.2 to 4.7 million cubic kilometers. C1 NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Smith, DE (reprint author), NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. RI Hauck, Steven/A-7865-2008; Lemoine, Frank/D-1215-2013; Abshire, James/I-2800-2013; Neumann, Gregory/I-5591-2013; Ivanov, Anton/C-8944-2014; OI Hauck, Steven/0000-0001-8245-146X; Neumann, Gregory/0000-0003-0644-9944; Ivanov, Anton/0000-0001-8376-8581; McGovern, Patrick/0000-0001-9647-3096 NR 71 TC 510 Z9 516 U1 4 U2 43 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 28 PY 1999 VL 284 IS 5419 BP 1495 EP 1503 DI 10.1126/science.284.5419.1495 PG 11 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 200PD UT WOS:000080548100029 PM 10348732 ER PT J AU Spencer, JR Tamppari, LK Martin, TZ Travis, LD AF Spencer, JR Tamppari, LK Martin, TZ Travis, LD TI Temperatures on Europa from Galileo photopolarimeter-radiometer: Nighttime thermal anomalies SO SCIENCE LA English DT Article ID SATELLITES; ICE; SURFACE; STATE; PHOTOMETRY; OCEAN; WATER AB Galileo observations of Europa's thermal emission show low-latitude diurnal brightness temperatures in the range of 86 to 132 kelvin. Nighttime temperatures form an unexpected pattern, with high temperatures on the bright ejecta blanket of the crater Pwyll and an equatorial minimum in temperatures after sunset, uncorrelated with surface albedo or geology, The nighttime anomalies may be due to regional thermal inertia variations of an unknown origin, which are equivalent to a two- to threefold variation in thermal conductivity, or to endogenic heat fluxes locally reaching 1 watt per square meter. Endogenic heat flow at this high level, although consistent with some geological evidence, is theoretically unlikely. C1 Lowell Observ, Flagstaff, AZ 86001 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Spencer, JR (reprint author), Lowell Observ, 1400 W Mars Hill Rd, Flagstaff, AZ 86001 USA. NR 34 TC 121 Z9 124 U1 0 U2 6 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 28 PY 1999 VL 284 IS 5419 BP 1514 EP 1516 DI 10.1126/science.284.5419.1514 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 200PD UT WOS:000080548100033 ER PT J AU Leblanc, T McDermid, IS Ortland, DA AF Leblanc, T McDermid, IS Ortland, DA TI Lidar observations of the middle atmospheric thermal tides and comparison with the High Resolution Doppler Imager and Global-Scale Wave Model 1. Methodology and winter observations at Table Mountain (34.4 degrees N) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MESOSPHERIC TEMPERATURE INVERSIONS; DIURNAL TIDE; GRAVITY-WAVE; VARIABILITY; CLIMATOLOGY; LATITUDES; BREAKING AB The tidal signature in the middle atmospheric thermal structure was investigated using more than 140 hours of nighttime lidar measurements at Table Mountain (34.4 degrees N) during January 1997 and February 1998. The lidar profiles (30-85 km) revealed the presence of persistent mesospheric temperature inversions around 65- to 70-km altitude with a clear local solar time (LST) dependence. Daytime temperature profiles (65-105 km) obtained by the High Resolution Doppler Imager (HRDI) on board the Upper Atmosphere Research Satellite (UARS) in January and February from 1994 to 1997 and zonally averaged at the latitude of the Table Mountain Facility (TMF) were considered together with the lidar results. The daytime HRDI and nighttime lidar temperature differences from their respective daytime and nighttime averages were compared to the equivalent differences predicted by the Global Scale Wave Model (GSWM). A remarkable consistency was observed between the lidar and the HRDI upper mesospheric thermal structure, with a continuous downward propagation of warm temperatures from 100 km at 1000 LST to 75 km at 2000 LST and 65-70 km at 0300-0500 LST, surrounded above and below by colder temperatures. This structure was predicted by GSWM but with a 2- to 4-hour delay and a weaker amplitude. On the lower side of this structure (i.e., 65-70 km) a thin layer, characterized by early night cold temperatures and late night warm temperatures, was identified as the result of the downward propagation of the temperature inversions. Using a new analysis technique, which we have named "constrained wave adjustment" for convenience in future reference, and assuming that the observed temperature variability was entirely driven by tides, some estimations of the diurnal and semidiurnal phases and amplitudes were made from the lidar measurements between 40- and 85-km altitude. Although it does not allow a complete and accurate extraction of the tidal components, this new method appeared to work well fur the present TMF study. The estimated diurnal amplitude exhibited a minimum at 63 km with a fast phase transition, characteristic of the transition between the upper stratospheric trapped modes (phase at 1800 LST) and the upward propagating modes. This transition layer was predicted by GSWM to be at 5-km lower altitude. This altitude shift was present throughout the middle mesosphere. Immediately above the transition layer, the very fast growing diurnal amplitude between 65 and 72 km was followed by a substantial decrease and by the emergence of the semidiurnal component, resulting in the formation of the mesospheric temperature inversion layers. However, the amplitude of the inversions remained large compared to the theoretical tidal predictions and a different formation mechanism should possibly be considered. Recent modeling studies have shown that gravity wave breaking can be significantly affected by the tidal background winds and some preferential wave breaking times could emerge that are dependent on the phase of the diurnal tide and the characteristics of the dissipating waves. This "LST filtering" could result in LST-dependent temperature inversion layers similar to those observed by lidar. The new analysis technique presented in this paper was also applied to study the temperature tidal oscillations at Mauna Loa Observatory (19.5 degrees N). The results are presented in a companion paper [Leblanc et al., this issue]. C1 Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. RP Jet Prop Lab, Table Mt Facil, End Table Mt Rd,POB 367, Wrightwood, CA 92397 USA. EM McDermid@tmf.nasa.gov NR 29 TC 27 Z9 27 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 11917 EP 11929 DI 10.1029/1999JD900007 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500004 ER PT J AU Leblanc, T McDermid, IS Ortland, DA AF Leblanc, T McDermid, IS Ortland, DA TI Lidar observations of the middle atmospheric thermal tides and comparison with the High Resolution Doppler Imager and Global Scale Wave Model 2. October observations at Mauna Loa (19.5 degrees N) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIURNAL TIDE; SOLAR TIDES; TEMPERATURE; VARIABILITY; MESOSPHERE; GSWM; MF AB Using more than 145 hours of nighttime lidar measurements obtained during October 3-16, 1996, and October 2-11, 1997, the tidal signature in the middle atmospheric thermal structure (15-95 km) at Mauna Loa, Hawaii (19.5 degrees N), was investigated. The daytime High Resolution Doppler Imager (HRDI) temperatures taken in September and October 1993-1997 and zonally averaged at the same latitude were also used. The daytime HRDI and nighttime lidar temperature differences from their respective daytime and nighttime averages were compared to the equivalent differences predicted by the Global Scale Wave Model (GSWM) at the same latitude. Some consistent local solar time (LST)-related structures were observed in both HRDI and lidar data, suggesting the presence of important migrating tidal components. In particular, a warm period was clearly identified, propagating downward from 105 km at 0800 LST to 65 km at 0000 LST and surrounded by two colder periods above and below. These warm/cold periods were predicted to occur 2 to 3 hours later by GSWM compared to the HRDI observations. Other LST-related structures were observed by lidar between 30- and 80-km altitude, in particular, a colder early night, warmer midnight, and colder late night around similar to 70 km, suggesting a significant semidiurnal component at this altitude. As previously observed, the amplitudes predicted by GSWM were much smaller than those observed by lidar and HRDI. A new analysis "constrained wave adjustment" method described in a companion paper [Leblanc ct nl., this issue] was used to estimate the diurnal and semidiurnal components from the nighttime-only lidar data. The main point of disagreement between the lidar observations and GSWM predictions occurred between 60 and 85 km. A large semidiurnal component was observed by lidar, leading to early and late cold night and warm midnight, while no such large semidiurnal component was predicted by GSWM, leading to an apparent warm early night at 60 km and an apparent cold midnight at 80 km and above. It appears that the tidal structure observed by lidar is more representative of that predicted by GSWM at 24 degrees N, suggesting a latitudinal shift between theory and observation. It is not clear whether this shift is related to an indetermination of the tidal source and/or propagation or if the observed differences are simply due to oscillations related to local/regional local solar time obscuring the global tidal signature. C1 CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. RP CALTECH, Jet Prop Lab, Table Mt Facil, End Table Mt Rd,POB 367, Wrightwood, CA 92397 USA. EM McDermid@tmf.nasa.gov NR 25 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 11931 EP 11938 DI 10.1029/1999JD900008 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500005 ER PT J AU Sherwood, SC AF Sherwood, SC TI On moistening of the tropical troposphere by cirrus clouds SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; WATER-VAPOR; RADIATIVE PROPERTIES; EQUATORIAL PACIFIC; RELATIVE-HUMIDITY; GRAVITY-WAVES; MAINTENANCE; SYSTEMS; CLIMATE; PARAMETERIZATION AB Sublimation of ice crystals in cirrus clouds is often invoked as a moistening mechanism for the free troposphere, particularly in the tropics. An alternative mechanism is investigated here: "pumping" of water vapor into the cloudy atmospheric column from surrounding regions by diabatic transports resulting from the local radiative effects of the cloud. The effectiveness of this mechanism is computed for a variety of cirrus cloud types, using a simple model. For nonprecipitating cirrus clouds it is found that the pumping mechanism can import much more vapor mass into the cloudy column than the clouds contain as ice, especially as the clouds become optically thin. The advected vapor per unit ice mass (or "pumping ratio") also varies with cloud height, is proportional to cloud lifetime, and (for thin clouds) is approximately inversely proportional to effective particle radius. Thin cirrus above 300 hPa can pump vapor rapidly enough to sustain itself against dessication. The overall results are supported by the limited information available from observations and indicate that at sufficient distances from active convection, direct moistening of the environment by the sublimation of ice has significantly less impact on vapor distributions than cloud-radiative-dynamic effects. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Mail Code 916, Greenbelt, MD 20771 USA. EM ssherwood@alum.mit.edu RI Sherwood, Steven/B-5673-2008 OI Sherwood, Steven/0000-0001-7420-8216 NR 35 TC 33 Z9 33 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 11949 EP 11960 DI 10.1029/1999JD900162 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500007 ER PT J AU Herman, JR Krotkov, N Celarier, E Larko, D Labow, G AF Herman, JR Krotkov, N Celarier, E Larko, D Labow, G TI Distribution of UV radiation at the Earth's surface from TOMS-measured UV-backscattered radiances SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ULTRAVIOLET-RADIATION; SATELLITE ESTIMATION; OZONE DEPLETION; IRRADIANCE; ATMOSPHERE; TRENDS; REFLECTIVITY; SCATTERING; AEROSOLS; CLOUDS AB Daily global maps of monthly integrated UV-erythemal irradiance (290-400 nm) at the Earth's surface are estimated using the ozone amount, cloud transmittance, aerosol amounts, and surface reflectivity from the solar UV radiation backscattered from the Earth's atmosphere as measured by the total ozone mapping spectrometer (TOMS) and independently measured values of the extraterrestrial solar irradiance. The daily irradiance values at a given location show that short-term variability (daily to annual) in the amount of UV radiation, 290-400 nm, reaching the Earth's surface is caused by (1) partially reflecting cloud cover, (2) haze and absorbing aerosols (dust and smoke), and (3) ozone, The reductions of UV irradiance estimated from TOMS data can exceed 50 +/- 12% underneath the absorbing aerosol plumes in Africa and South America (desert dust and smoke from biomass burning) and exceeded 70 +/- 12% during the Indonesian fires in September 1997 and again during March 1998. Recent biomass burning in Mexico and Guatemala have caused large smoke plumes extending into Canada with UV reductions of 50% in Mexico and 20% in Florida, Louisiana, and Texas. Where available, ground-based Sun photometer data show similar UV irradiance reductions caused by absorbing aerosol plumes of Just and smoke. Even though terrain height is a major factor in increasing the amount of UV exposure compared to sea level, the presence of prolonged clear-sky conditions can lead to UV exposures at sea level rivaling those at cloudier higher altitudes. In the equatorial regions, +/-20 degrees, the UV exposures during the March equinox are larger than during the September equinox because of increased cloudiness during September, Extended land areas with the largest erythemal exposure are in Australia and South Africa where there is a larger proportion of clear-sky days. The large short-term variations in ozone amount which occur at high latitudes in the range +/-65 degrees cause changes in UV irradiance comparable to clouds and aerosols for wavelengths between 280 nm and 300 nm that are strongly absorbed by ozone. The absolute accuracy of the TOMS monthly erythemal exposure estimates over a TOMS field of view is within +/-6%, except under UV-absorbing aerosol plumes (dust and smoke) where the accuracy is within +/-12%. The error caused by aerosols can be reduced if the height of the aerosol plume is more accurately known. The TOMS estimated irradiances are compared with ground-based Brewer spectroradiometer data obtained at Toronto, Canada. The Brewer irradiances are systematically 20% smaller than TOMS irradiance estimates during the summer months. An accounting of systematic errors brings the Brewer and TOMS irradiances into approximate agreement within the estimated instrumental uncertainties for both instruments. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Software Corp Amer, Beltsville, MD 20705 USA. Raytheon ITSS Corp, Lanham, MD 20706 USA. RP NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 916, Greenbelt, MD 20771 USA. EM herman@tparty.gsfc.nasa.gov RI Krotkov, Nickolay/E-1541-2012; OI Krotkov, Nickolay/0000-0001-6170-6750; Herman, Jay/0000-0002-9146-1632 NR 36 TC 168 Z9 170 U1 2 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 12059 EP 12076 DI 10.1029/1999JD900062 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500014 ER PT J AU Longo, KM Thompson, AM Kirchhoff, VWJH Remer, LA de Freitas, SR Dias, MAFS Artaxo, P Hart, W Spinhirne, JD Yamasoe, MA AF Longo, KM Thompson, AM Kirchhoff, VWJH Remer, LA de Freitas, SR Dias, MAFS Artaxo, P Hart, W Spinhirne, JD Yamasoe, MA TI Correlation between smoke and tropospheric ozone concentration in Cuiaba during Smoke, Clouds, and Radiation-Brazil (SCAR-B) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TRACE-A; BASIN; CONVECTION; MODEL AB Ozone soundings launched from Cuiaba between August 16 and September 10, 1995, during the Smoke, Clouds, and Radiation-Brazil (SCAR-B) experiment show an enrichment of tropospheric ozone when compared with average wet season values and also present a great variability in concentrations depending on the dominant circulation pattern. Smoke tracers, such as aerosol optical thickness, measured from a Sun photometer installed at the Institute Nacional de Pesquisas Espaciais-Cuiaba site, and black carbon ground measurements, also show an enhancement of smoke during the same period. Although there is a connection between the enrichment of the tropospheric ozone around Cuiaba during the dry season and smoke from biomass burning, the correlation between ozone and smoke indicates different behavior in different periods. Trajectory analyses suggest that the strong ozone peak measured in the period between August 26 and 29, 1995, may be associated not only with direct biomass-burning emissions but also with urban/industrial emissions from big cities on the coast of Brazil and recirculation of old smoke. This view is confirmed by measurements made from the Cloud Lidar System instrument aboard the ER-2 aircraft. C1 Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Nacl Pesquisas Espaciais, BR-12201970 Sao Jose Dos Campos, SP, Brazil. Univ Sao Paulo, Dept Ciencias Atmosfer, Inst Astron & Geofis, BR-10165 Sao Paulo, Brazil. RP Univ Sao Paulo, Inst Fis, Rua do Matao,Travessa R,S-N,Edificio Basilio Jafe, BR-05508900 Sao Paulo, Brazil. RI Yamasoe, Marcia/L-3667-2013; Freitas, Saulo/A-2279-2012; Artaxo, Paulo/E-8874-2010; Thompson, Anne /C-3649-2014 OI Yamasoe, Marcia/0000-0003-3066-9146; Freitas, Saulo/0000-0002-9879-646X; Artaxo, Paulo/0000-0001-7754-3036; Thompson, Anne /0000-0002-7829-0920 NR 36 TC 25 Z9 29 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 12113 EP 12129 DI 10.1029/1999JD900044 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500018 ER PT J AU Prigent, C Rossow, WB Matthews, E Marticorena, B AF Prigent, C Rossow, WB Matthews, E Marticorena, B TI Microwave radiometric signatures of different surface types in deserts SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOIL-MOISTURE; EMISSIVITIES; TEMPERATURE; RADAR; ISCCP AB In arid environments, specific microwave signatures have been observed with the Special Sensor Microwave /Imager (SSM/I). For a given diurnal change in surface skill temperature, the corresponding change in the microwave brightness temperature is smaller than expected. With the help of a one-dimensional; time-dependent heat conduction model, this behavior is explained by microwave radiation coming from different depths in the soil: depending on the soil type and on the microwave radiation frequency, Using the 8-times daily estimates of the surface skin temperature by the International Satellite Cloud Climatology Project (ISCCP) and a simple Fresnel model: collocated month-long time series of the SSM/I brightness temperatures and the surface skin temperatures give a consistent estimate of the effective microwave emissivity and penetration depth parameters. Results are presented and analyzed for the Sahara and the Arabian Peninsula, for July and November 1992, The case of the Australian desert is also briefly mentioned. Assuming a reasonable thermal diffusivity for the soil in desert areas, the microwave radiation is estimated to come from soil layers down to depths of at least five wavelengths in some locations. Regions where the microwave radiation comes from deeper soil layers also have large microwave emissivity polarization differences and large risible reflectances, suggesting that these areas correspond to sand dune fields. Two soil classification data sets show good correspondence of sand dunes and the microwave signature of significant penetration, This suggests that this analysis of microwave observations, along with other remote sensing technics, can be used to map the sand dunes in large, poorly surveyed deserts, a map, of the sand dune fields in the Sahara and Saudi Arabia is derived from SSM/I observations. C1 Columbia Univ, Dept Appl Phys, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Ctr Multidisciplinaire Creteil, CNRS, URA 1404, Lab Interuniv Syst Atmospher, F-94010 Creteil, France. RP Columbia Univ, Dept Appl Phys, NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM cpri-gent@giss.nasa.gov RI Rossow, William/F-3138-2015 NR 24 TC 44 Z9 45 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 12147 EP 12158 DI 10.1029/1999JD900153 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500020 ER PT J AU Mehta, A Susskind, J AF Mehta, A Susskind, J TI Outgoing longwave radiation from the TOVS Pathfinder Path A data set SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID BUDGET EXPERIMENT ERBE; INFRARED WINDOW; SOUNDING DATA; CLEAR-SKY; EARTH; ALGORITHMS; SATELLITE; FLUXES; VALIDATION; INVERSION AB A new outgoing longwave radiation (OLR) and clear-sky outgoing longwave radiation (COLR) data set derived from the Goddard TIROS operational vertical sounder (TOVS) Pathfinder Path A retrievals is introduced. Comparisons of OLR and COLR from TOVS Path A and the Earth Radiation Budget Experiment (ERBE) have been carried out for the period February 1985 to May 1989. In the OLR comparison, advanced very high resolution radiometer (AVHRR) OLR has also been included. The mean OLR differences and standard deviations of the differences between TOVS and ERBE are, in general, within 5 W m(-2). The differences AVHRR minus ERBE, and AVHRR minus TOVS OLR are close to -4 and -7 W m(-2), respectively. However, over oceanic subtropical regions, AVHRR OLR differs by -8 to -12 W m(-2) compared with the other two data sets. The differences of TOVS and ERBE COLR over most regions are within +/-4 W m(-2), with standard deviations of differences between 4 and 12 W m(-2). The OLR and COLR data sets have larger discrepancies over snow/ice-covered polar regions. Interannual variability of the OLR and COLR are compared for 1986-1988 in terms of their monthly mean anomalies. The global mean monthly ERBE OLR and COLR anomalies have somewhat larger magnitudes (-3.0 to 1.5 and -2.0 to 1.0 W m(-2) respectively) compared with the other data sets (-1.0 to 1.0 and -0.7 to 0.7 W m(-2) respectively). Both sets of ERBE anomalies appear to be influenced by the change di satellite from NOAA 9 to NOAA 10. The results of this study indicate that TOVS Path A and ERBE OLR and COLR are of comparable accuracy. The TOVS Path A data set covers a substantially longer time period (1985-1998) than ERBE and would be very useful in climate research studies. C1 NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Gen Sci Corp, Code 910-4, Greenbelt, MD 20771 USA. EM f41js@iredell.gsfc.nasa.gov NR 25 TC 20 Z9 21 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X EI 2169-8996 J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD MAY 27 PY 1999 VL 104 IS D10 BP 12193 EP 12212 DI 10.1029/1999JD900059 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 200XX UT WOS:000080566500023 ER PT J AU Bauschlicher, CW Ricca, A AF Bauschlicher, CW Ricca, A TI Accurate heats of formation for BF(n), BF(n)(+), BCl(n), and BCln(+) for n=1-3 SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; EXCITED NEON ATOMS; AB-INITIO; INFRARED-SPECTRA; DISSOCIATION-ENERGIES; ELECTRON CORRELATION; PERTURBATION-THEORY; MATRIX-ISOLATION AB Accurate heats of formation are computed for BF(n), BF(n)(+), BCl(n), and BCl(n)(+), for n = 1-3. The geometries and vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Extrapolation to the basis set limit is discussed. Spin-orbit, scalar relativistic, and core-valence correlation are accounted for. The temperature dependence of the heat of formation, heat capacity, and entropy is computed for the temperature range 300-4000 K and fit to a polynomial. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 45 TC 27 Z9 28 U1 0 U2 0 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD MAY 27 PY 1999 VL 103 IS 21 BP 4313 EP 4318 DI 10.1021/jp9903662 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 202HP UT WOS:000080646500027 ER PT J AU Srivastava, D Brenner, DW Schall, JD Ausman, KD Yu, MF Ruoff, RS AF Srivastava, D Brenner, DW Schall, JD Ausman, KD Yu, MF Ruoff, RS TI Predictions of enhanced chemical reactivity at regions of local conformational strain on carbon nanotubes: Kinky chemistry SO JOURNAL OF PHYSICAL CHEMISTRY B LA English DT Article ID NANOSCALE GRAPHITIC TUBULES; ELECTRONIC-STRUCTURE; DEPOSITION; FULLERENES; SURFACE; C-60 AB Simulations that model the effects of conformational strain on the chemical reactivity of single-walled carbon nanotubes suggest a method for significantly enhancing their reactivity locally by controlled deformations. The chemisorption of hydrogen atoms is predicted to be enhanced by as much as 1.6 eV at regions of high conformational deformation, suggesting that local reactivity will be significantly enhanced. Analysis of the local electronic density of states suggests the introduction of radical p orbital character to the sites that are locally deformed, consistent with the heightened reactivity and large pyramidalization angles at these sites. Preliminary experimental data consistent with this predicted heightened reactivity is also presented. C1 Washington Univ, Dept Phys, St Louis, MO 63130 USA. N Carolina State Univ, Dept Mat Sci & Engn, Raleigh, NC 27695 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Ruoff, RS (reprint author), Washington Univ, Dept Phys, St Louis, MO 63130 USA. RI Ruoff, Rodney/B-7605-2009; Brenner, Donald/D-1741-2009; Yu, Min-Feng/C-2809-2012; Ruoff, Rodney/K-3879-2015 NR 40 TC 151 Z9 153 U1 1 U2 22 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5647 J9 J PHYS CHEM B JI J. Phys. Chem. B PD MAY 27 PY 1999 VL 103 IS 21 BP 4330 EP 4337 DI 10.1021/jp990882s PG 8 WC Chemistry, Physical SC Chemistry GA 202HR UT WOS:000080646700017 ER PT J AU LeBeau, GJ AF LeBeau, GJ TI A parallel implementation of the direct simulation Monte Carlo method SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article AB The underlying assumptions used to formulate the Navier-Stokes equations preclude their use for the analysis of rarefied gas dynamic environments. Alternatively, the Direct Simulation Monte Carlo technique of Bird can be used to numerically investigate such flows. In this methodology, molecules are tracked through representative collisions and boundary interactions. This microscopic view of the flow allows the inclusion of internal energy modes and chemical reactions in a direct and physical manner. This well-established methodology is combined with innovative strategies to improve the performance and overall capabilities of the technique. Beyond basic procedural enhancements, a parallel implementation of the DSMC method is developed using the master/slave programming model. This new tool is applied to several example problems. These are used to compare the performance of the parallel code to a comparable scalar implementation and to investigate the dynamic load balancing capabilities and the overall scalability of the parallel software. High parallel performance is demonstrated using up to 512 processors on a Cray T3E parallel supercomputer. (C) 1999 Elsevier Science S.A. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Aerosci Branch, Houston, TX 77058 USA. RP LeBeau, GJ (reprint author), NASA, Lyndon B Johnson Space Ctr, Aerosci Branch, 2101 NASA Rd 1, Houston, TX 77058 USA. NR 44 TC 59 Z9 65 U1 0 U2 3 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 1999 VL 174 IS 3-4 BP 319 EP 337 DI 10.1016/S0045-7825(98)00302-8 PG 19 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 209VD UT WOS:000081069000005 ER PT J AU McCord, TB Hansen, GB Matson, DL Johnson, TV Crowley, JK Fanale, FP Carlson, RW Smythe, WD Martin, PD Hibbitts, CA Granahan, JC Ocampo, A AF McCord, TB Hansen, GB Matson, DL Johnson, TV Crowley, JK Fanale, FP Carlson, RW Smythe, WD Martin, PD Hibbitts, CA Granahan, JC Ocampo, A TI Hydrated salt minerals on Europa's surface from the Galileo near-infrared mapping spectrometer (NIMS) investigation SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID MAGNETOSPHERIC ION-BOMBARDMENT; PLAYA EVAPORITE MINERALS; AMORPHOUS SOLID WATER; 0.65-2.5 MU-M; SPECTRAL REFLECTANCE; ICY SATELLITES; DEATH-VALLEY; SPECTROSCOPY; GANYMEDE; FROST AB We reported evidence of heavily hydrated salt minerals present over large areas of Europa's surface from analysis of reflectance spectra returned by the Galileo mission near infrared mapping spectrometer (NIMS) [McCord et al., 1997a, b, 1998a, b]. Here we elaborate on this earlier evidence, present spatial distributions of these minerals, examine alternate water-ice interpretations, expand on our hydrated-salts interpretation, consider salt mineral stability on Europa, and discuss the implications. Extensive well-defined areas on Europa show distinct, asymmetric water-related absorption bands in the 1 to 2.5-mu m region. Radiative transfer modeling of water ice involving different particle sizes and layers at Europa temperatures does not reproduce the distinctive Europa water bands. However, ice near its melting temperature, such as in terrestrial environments, does have some characteristics of the Europa spectrum. Alternatively, some classes of heavily hydrated minerals do exhibit such water bands. Among plausible materials, heavily hydrated salt minerals, such as magnesium and sodium sulfates, sodium carbonate and their mixtures, are preferred. All Europa spectral features are present in some salt minerals and a very good match to the Europa spectrum can be achieved by mixing several salt spectra. However, no single or mix of salt mineral spectra from the limited library available has so far been found to perfectly match the Europa spectrum in every detail. The material is concentrated at the lineaments and in chaotic terrain, which are tectonically disrupted areas on the trailing side. Since the spectrum of the material on Europa is nearly the same everywhere so-far studied, the salt or salt-mixture composition may be nearly uniform. This suggests similar sources and processes over at least a near-hemispheric scale. This would suggest that an extensive subsurface ocean containing dissolved salts is the source, and several possible mechanisms for deposit emplacement are considered. The hydrogen bonds associated with hydration of these salts are similar or greater in strength and energy to those in pure water ice. Thus, once on the surface, the salt minerals should be as stable to disruption as water ice at the Europa temperatures, and mechanisms are suggested to enhance the stability of both materials. Spectra obtained of MgSO(4). 6H(2)O at 77 K show only small differences from room temperature spectra. The main difference is the appearance of the individual absorptions composing the broad, composite water features and associated with the several different H(2)O sites in the salt hydrate molecule, This suggests that the Europa absorption bands are also composites. Thus higher spectral resolution may reveal these diagnostic features in Europa's spectrum. The specific salts present and their relative abundances would be indicators of the chemistry and conditions of an ocean environment, and areas of fresh, heavy concentration of these minerals should make ideal lander mission sampling sites. C1 Univ Hawaii, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Reston, VA 22092 USA. Sci & Technol Int Inc, Honolulu, HI 96813 USA. RP McCord, TB (reprint author), Univ Hawaii, Hawaii Inst Geophys & Planetol, 2525 Correa Rd, Honolulu, HI 96822 USA. EM tom@pgd.hawaii.edu; ghansen@pgd.hawaii.edu; dlmatson@maill.jpl.nasa.gov; tjohnson@jpltvj.jpl.nasa.gov; jcrowley@usgs.gov; fanale@pgd.hawaii.edu; rcarlson@issac.jpl.nasa.gov; wsmythe@issac.jpl.nasa.gov; martin@marswatch.tn.comell.edu; hibbitts@pgd.hawaii.edu; granahan@lava.net; aocampo@issac.jpl.nasa.gov RI Hibbitts, Charles/B-7787-2016 OI Hibbitts, Charles/0000-0001-9089-4391 NR 105 TC 161 Z9 163 U1 8 U2 31 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 MAY 25 PY 1999 VL 104 IS E5 BP 11827 EP 11851 DI 10.1029/1999JE900005 PG 25 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 199FV UT WOS:000080470700003 ER PT J AU Margot, JL Campbell, DB Jurgens, RF Slade, MA AF Margot, JL Campbell, DB Jurgens, RF Slade, MA TI The topography of Tycho Crater SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID INTERFEROMETRY AB Three-dimensional mapping of the Moon can be accomplished with an Earth-based radar interferometer. Elevation data and radar imagery obtained with this technique are presented for the Tycho Crater area, with a spatial resolution of 200 m and a height resolution of 30 m. The radar maps are displayed in standard cartographic projections with appropriate corrections for elevation-induced geometric distortions. The digital elevation model allows detailed morphometry of the 85 km diameter crater: the floor of Tycho lies 3970 m below a 1738 km radius sphere, and the crater's central peak rises 2400 m above the floor. The average rim crest elevation is 730 m above the 1738 km datum, giving a mean rim to floor depth of 4700 m. The floor has two distinct units with the western section being higher in elevation by similar to 200 m. This dichotomy is consistent with an asymmetry in the crater shape which reveals that maximum wall slumping occurred in the western and southwestern regions of the crater. Comparison of the radar-derived topography with 87 altimetry points from the Clementine lidar experiment shows rms deviations of similar to 90 m after a 0.11 degrees latitude correction to the location of all the Clementine altimetry points. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Margot, JL (reprint author), Natl Astron & Ionosphere Ctr, Arecibo Observ, HC3 Box 53995, Arecibo, PR 00612 USA. RI Margot, Jean-Luc/A-6154-2012 OI Margot, Jean-Luc/0000-0001-9798-1797 NR 23 TC 16 Z9 23 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD MAY 25 PY 1999 VL 104 IS E5 BP 11875 EP 11882 DI 10.1029/1998JE900047 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 199FV UT WOS:000080470700006 ER PT J AU Kshirsagar, RJ Giver, LP Chackerian, C AF Kshirsagar, RJ Giver, LP Chackerian, C TI Line intensities in the 2 nu(3) band of (12)C(16)O(17)O at 4655.2 cm(-1) SO JOURNAL OF MOLECULAR STRUCTURE LA English DT Article; Proceedings Paper CT 24th European Congress on Molecular Spectroscopy CY AUG 23-28, 1998 CL CZECH TECH UNIV, PRAGUE, CZECH REPUBLIC SP Ioannes Marcus Marci Spectroscopic Soc, Inst Chem Technol, Czech Tech Univ, Charles Univ HO CZECH TECH UNIV DE intensity measurements; (12)C(16)O(17)O; 2 nu(3) band of (12)C(16)O(17)O; carbon dioxide; absorption band ID REGION; CO2 AB The absolute intensities of transitions in the 2v(3) vibrational band of (12)C(16)O(17)O at 4655.2 cm(-1) have been measured in natural isotopic abundance; the spectra being obtained with a resolution of 0.012 cm(-1) using a Bomem DA8 FTS at NASA/Ames and the McMath FTS at Kitt Peak National Observatory, AZ. About 45 transitions were fitted to obtain the rotationless band strength of S(vib)(0) = 8.489 x 10(-25) cm(-1)/(molecule/cm(2)) at 296 K. Although the current HITRAN line positions for this band do not have any defined uncertainties, our measurements average only about 0.0025 cm(-1) smaller. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Kshirsagar, RJ (reprint author), NASA, Ames Res Ctr, N 245-4, Moffett Field, CA 94035 USA. EM rohidas@hertz2.arc.nasa.gov NR 9 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-2860 J9 J MOL STRUCT JI J. Mol. Struct. PD MAY 25 PY 1999 VL 482 SI SI BP 295 EP 300 DI 10.1016/S0022-2860(98)00672-3 PG 6 WC Chemistry, Physical SC Chemistry GA 209FT UT WOS:000081038100055 ER PT J AU Burles, S Nollett, KM Truran, JW Turner, MS AF Burles, S Nollett, KM Truran, JW Turner, MS TI Sharpening the predictions of big-bang nucleosynthesis SO PHYSICAL REVIEW LETTERS LA English DT Article ID PRIMORDIAL ABUNDANCE; HELIUM ABUNDANCE; CROSS-SECTION; LOW ENERGIES; H-2((P)OVER-RIGHT-ARROW,GAMMA)HE-3; HE-3(ALPHA,GAMMA)BE-7 AB We have reexamined the nuclear inputs to big-bang nucleosynthesis using Monte Carlo realization of the cross-section data to directly estimate theoretical uncertainties for the yields of D, He-3, and Li-7. Our results indicate that previous estimates of the uncertainties were too large by a factor of 2. Using the Burles-Tytler deuterium measurement, we infer a baryon density Omega(B)/h(2) = 0.019 +/- 0.0024, predict a primeval He-4 mass fraction Yr = 0.246 +/- 0.0014, and obtain a limit to the equivalent number of neutrino species N-v < 3.20 (all at 95% C.L.). We also identify key reactions and the energies, where improved data would allow further progress. [S0031-9007(99)09188-7]. C1 Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Dept Phys, Chicago, IL 60637 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP Burles, S (reprint author), Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. OI Nollett, Kenneth/0000-0002-0671-320X NR 26 TC 193 Z9 194 U1 1 U2 3 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 24 PY 1999 VL 82 IS 21 BP 4176 EP 4179 DI 10.1103/PhysRevLett.82.4176 PG 4 WC Physics, Multidisciplinary SC Physics GA 198CX UT WOS:000080405500006 ER PT J AU Orient, OJ Chutjian, A AF Orient, OJ Chutjian, A TI Comment on "Detection of new dissociative electron attachment channels in NO" - Orient and Chutjian reply SO PHYSICAL REVIEW LETTERS LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Orient, OJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 2 Z9 2 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 MAY 24 PY 1999 VL 82 IS 21 BP 4365 EP 4365 DI 10.1103/PhysRevLett.82.4365 PG 1 WC Physics, Multidisciplinary SC Physics GA 198CX UT WOS:000080405500054 ER PT J AU Hou, LS Ravindran, SS AF Hou, LS Ravindran, SS TI Numerical approximation of optimal flow control problems by a penalty method: Error estimates and numerical results SO SIAM JOURNAL ON SCIENTIFIC COMPUTING LA English DT Article DE flow control; sequential quadratic programming method; Navier-Stokes equations; finite elements; vorticity; optimization ID NAVIER-STOKES EQUATIONS; FINITE-ELEMENT APPROXIMATION; BACKWARD-FACING STEP; BOUNDARY-CONDITIONS; FLUID AB The purpose of this paper is to present numerically convenient approaches to solve optimal Dirichlet control problems governed by the steady Navier-Stokes equations. We will examine a penalized Neumann control approach for solving Dirichlet control problems from numerical and computational points of view. The control is affected by the suction or injection of fluid through the boundary or by boundary surface movements in the tangential direction. The control objective is to minimize the vorticity in the flow or to drive the velocity field to a desired one. We develop sequential quadratic programming methods to solve these optimal control problems. The effectiveness of the optimal control techniques in flow controls and the feasibility of the proposed penalized Neumann control approaches for flow control problems are demonstrated by numerical experiments for a viscous, incompressible fluid flow in a two-dimensional channel and in a cavity geometry. C1 Iowa State Univ, Dept Math, Ames, IA 50011 USA. York Univ, Dept Math & Stat, N York, ON M3J 1P3, Canada. NASA, Langley Res Ctr, Flow Modeling & Control Branch, Hampton, VA 23681 USA. RP Hou, LS (reprint author), Iowa State Univ, Dept Math, Ames, IA 50011 USA. EM hou@math.iastate.edu; ravi@fmd00.larc.nasa.gov NR 19 TC 39 Z9 39 U1 0 U2 3 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 21 PY 1999 VL 20 IS 5 BP 1753 EP 1777 DI 10.1137/S1064827597325153 PG 25 WC Mathematics, Applied SC Mathematics GA 199TD UT WOS:000080497600010 ER PT J AU Leathers, RA McCormick, NJ AF Leathers, RA McCormick, NJ TI Algorithms for ocean-bottom albedo determination from in-water natural-light measurements SO APPLIED OPTICS LA English DT Article ID DIFFUSE-REFLECTANCE; OPTICAL-PROPERTIES; RADIATIVE-TRANSFER; ATTENUATION; DEPTH AB A method for determining the ocean-bottom optical albedo R-b from in-water upward and downward irradiance measurements at a shallow site is presented, tested, and compared with a more familiar approach that requires additional measurements at a nearby deep-water site. Also presented are two new algorithms for estimating R-b from measurements of the downward irradiance and vertically upward radiance. All methods performed well in numerical situations at depths at which the influence of the bottom on the light field was significant. (C) 1999 Optical Society of America. C1 Univ Washington, Dept Mech Engn, Seattle, WA 98195 USA. RP Leathers, RA (reprint author), NASA, Earth Syst Sci Off, Code SA00, Stennis Space Ctr, MS 39529 USA. EM rleather@ssc.nasa.gov RI McCormick, Norman/K-6411-2013 NR 23 TC 12 Z9 12 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1999 VL 38 IS 15 BP 3199 EP 3205 DI 10.1364/AO.38.003199 PG 7 WC Optics SC Optics GA 197BK UT WOS:000080344600010 PM 18319909 ER PT J AU Whiteman, DN AF Whiteman, DN TI Application of statistical methods to the determination of slope in lidar data SO APPLIED OPTICS LA English DT Article ID RAMAN LIDAR AB Assumptions made in the analysis of both Raman Lidar measurements of aerosol extinction and differential absorption lidar (DIAL) measurements of an absorbing species are tested. Statistical analysis techniques are used to enhance the estimation of aerosol extinction and aerosol extinction error that is usually handled using a linear model. It is determined that the most probable extinction value, can differ from that of the linear assumption by up to 10% and that differences larger than 50% can occur in the calculation of extinction. Ignoring error in the number density alters the calculated extinction by up to 3% and that of extinction error by up to 10%. The preceding results were obtained using the least-squares technique. The least-squares technique assumes that the data being regressed are normally distributed. However, the quantity that is usually regressed in aerosol extinction and DIAL calculations is not normally distributed. A technique is presented that allows the required numerical derivative to be determined by regressing only normally distributed data. The results from this technique are compared with the usual procedure. The same concerns raised here regarding appropriate choice of a model in the context of aerosol extinction calculations should apply to DIAL calculations of absorbing species such as water vapor or ozone as well because the numerical derivative that is required is identical. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Whiteman, DN (reprint author), NASA, Goddard Space Flight Ctr, Code 924, Greenbelt, MD 20771 USA. EM david.whiteman@gsfc.nasa.gov NR 7 TC 38 Z9 39 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1999 VL 38 IS 15 BP 3360 EP 3369 DI 10.1364/AO.38.003360 PG 10 WC Optics SC Optics GA 197BK UT WOS:000080344600034 PM 18319933 ER PT J AU Jarzembski, MA Srivastava, V AF Jarzembski, MA Srivastava, V TI Interference of backscatter from two droplets in a focused continuous-wave CO2 Doppler lidar beam SO APPLIED OPTICS LA English DT Article ID 2 DIELECTRIC SPHERES; ELECTROMAGNETIC SCATTERING; CALIBRATION AB With a focused continuous-wave CO2 Doppler lidar at 9.1-mu m wavelength, the superposition of backscatter from two similar to 14.12-mu m-diameter silicone oil droplets in the lidar beam produced interference that resulted in a single backscatter pulse from the two droplets with a distinct periodic structure. This interference is caused by the phase difference in backscatter from the two droplets while they are traversing the lidar beam at different speeds, and thus the droplet separation is not constant. The complete cycle of interference, with periodicity 2 pi, gives excellent agreement between measurements and lidar theory. (C) 1999 Optical Society of America. C1 Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Huntsville, AL USA. RP Jarzembski, MA (reprint author), Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. EM maurice.jarzembski@msfc.nada.gov; srivastava@msfc.nasa.gov NR 6 TC 0 Z9 0 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1999 VL 38 IS 15 BP 3387 EP 3393 DI 10.1364/AO.38.003387 PG 7 WC Optics SC Optics GA 197BK UT WOS:000080344600037 PM 18319936 ER PT J AU Agrawal, AK Albers, BW Griffin, DW AF Agrawal, AK Albers, BW Griffin, DW TI Abel inversion of deflectometric measurements in dynamic flows SO APPLIED OPTICS LA English DT Article ID RAINBOW SCHLIEREN DEFLECTOMETRY; PROBABILITY DENSITY-FUNCTIONS; OPTICAL TOMOGRAPHY; MOIRE DEFLECTOMETRY; FIELD; RECONSTRUCTION; JET AB We present an Abel-inversion algorithm to reconstruct mean and rms refractive-index profiles from spatially resolved statistical measurements of the beam-deflection angle in time-dependent, axisymmetric flows. An oscillating gas jet diffusion flame was investigated as a test case for applying the algorithm. Experimental data were obtained across the whole field by a rainbow schlieren apparatus. Results show that simultaneous multipoint measurements are necessary to reconstruct the rms refractive index accurately. (C) 1999 Optical Society of America. C1 Univ Oklahoma, Sch Aerosp & Mech Engn, Norman, OK 73019 USA. NASA, Glenn Res Ctr, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. RP Agrawal, AK (reprint author), Univ Oklahoma, Sch Aerosp & Mech Engn, Norman, OK 73019 USA. EM aagrawal@ou.edu RI Agrawal, Ajay/B-5304-2010 NR 17 TC 21 Z9 22 U1 0 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1999 VL 38 IS 15 BP 3394 EP 3398 DI 10.1364/AO.38.003394 PG 5 WC Optics SC Optics GA 197BK UT WOS:000080344600038 PM 18319937 ER PT J AU Adorjan, AJ Lock, JA Taylor, TW Tin, P Meyer, WV Smart, AE AF Adorjan, AJ Lock, JA Taylor, TW Tin, P Meyer, WV Smart, AE TI Particle sizing in strongly turbid suspensions with the one-beam cross-correlation dynamic light-scattering technique SO APPLIED OPTICS LA English DT Article ID SINGLE-MODE FIBERS; MULTIPLE-SCATTERING; CONCENTRATED SUSPENSION; LASER-BEAM; SUPPRESSION; SPECTROSCOPY; DIFFUSION; SPHERES AB The utility of the one-beam cross-correlation dynamic light-scattering system for sizing small particles in suspension was previously limited by its small-intensity signal-to-baseline ratio for strongly turbid suspensions. We describe three improvements in the optical system and sample cell that raise the ratio to a value comparable with that of other cross-correlation dynamic light-scattering systems. These improvements are (i) using a square cross-sectional sample cell to minimize the attenuation of the incident beam and singly scattered light, (ii) placing a 200-mu m-wide slit between the sample cell and the detector fibers to mask off the region of weak single scattering and strong multiple scattering from the detectors' field of view, and (iii) aligning the center of the detectors' field of view with the region of strongest single scattering. We analyze a number of suspensions of polystyrene latex spheres with a diameter between 65 and 562 Ma in water using this improved one-beam instrument and find that the measured radius is determined in a 2-min data collection time to better than +/-10% for volume fractions of the suspended polystyrene latex spheres up to a few percent. (C) 1999 Optical Society of America. C1 Kent State Univ, Dept Phys, Kent, OH 44242 USA. Cleveland State Univ, Dept Phys, Cleveland, OH 44115 USA. NASA, Lewis Res Ctr, Ohio Aerosp Inst, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RP Adorjan, AJ (reprint author), Kent State Univ, Dept Phys, Kent, OH 44242 USA. EM jimandcarlo@stratos.net NR 26 TC 8 Z9 11 U1 4 U2 8 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD MAY 20 PY 1999 VL 38 IS 15 BP 3409 EP 3416 DI 10.1364/AO.38.003409 PG 8 WC Optics SC Optics GA 197BK UT WOS:000080344600040 PM 18319939 ER PT J AU Goldsmith, PF Langer, WD AF Goldsmith, PF Langer, WD TI Population diagram analysis of molecular line emission SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : molecules; radiative transfer ID MASS STAR-FORMATION; CLOUD CORES; COLLISIONAL EXCITATION; TEMPERATURE PROBE; METHYL CYANIDE; ABUNDANCES; MODELS; ORION; HOT; MULTITRANSITION AB We develop the use of the population diagram method to analyze molecular emission in order to derive physical properties of interstellar clouds. We focus particular attention on how the optical depth affects the derived total column density and the temperature. We derive an optical depth correction factor that can be evaluated based on observations and that incorporates the effect of saturation on derived upper level populations. We present analytic results for linear molecules in local thermodynamic equilibrium (LTE). We investigate numerically how subthermal excitation influences the population diagram technique, studying how the determination of kinetic temperature is affected when the local density is insufficient to achieve LTE. We present results for HC3N and CH3OH, representative of linear and nonlinear molecules, respectively. In some cases, alternative interpretations to the standard optically thin and thermalized picture yield significantly different results for column density and kinetic temperature, and we discuss this behavior. The population diagram method can be a very powerful tool for determining physical conditions in dense clouds if proper recognition is given to effects of saturation and subthermal excitation. We argue that the population diagram technique is, in fact, superior to fitting intensities of different transitions directly, and we indicate how it can be effectively employed. C1 Cornell Univ, Dept Astron, Natl Astron & Ionosphere Ctr, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goldsmith, PF (reprint author), Cornell Univ, Dept Astron, Natl Astron & Ionosphere Ctr, Ithaca, NY 14853 USA. RI Goldsmith, Paul/H-3159-2016 NR 24 TC 287 Z9 288 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1999 VL 517 IS 1 BP 209 EP 225 DI 10.1086/307195 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 206RZ UT WOS:000080894200019 ER PT J AU Araya, RA Harding, AK AF Araya, RA Harding, AK TI Cyclotron line features from near-critical magnetic fields: The effect of optical depth and plasma geometry SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic processes; line : formation; magnetic fields; radiation mechanisms : nonthermal; scattering; stars : neutron ID X-RAY PULSAR; RESONANT SCATTERING; NEUTRON STARS; ABSORPTION; SPECTRA; BURSTS; MODELS; ATMOSPHERES; RADIATION; ACCRETION AB A detailed analytical study of the relativistic profile for magnetic Compton scattering is performed and use is made of Monte Carlo methods to construct a numerical scheme for the production of relativistic theoretical cyclotron spectra from internally irradiated scattering atmospheres in the low-density/high-field regime. The cross section includes natural line widths, and the Monte Carlo implementation allows for spatial diffusion of photons in arbitrary geometries while accounting for relativistic angular redistribution. Detailed consideration of "Raman-Landau" scattering permits photon spawning from up to fourth harmonic photons. This scheme is utilized to make specific predictions on the effect of geometry and optical depth on the formation of cyclotron lines in hard incident continua. Even if the injection is isotropic, a strongly anisotropic radiation field ensues at relatively low optical depths. The scattering profiles at large angles and low fields are highly asymmetric and peak at the relativistic energy cutoff, not necessarily at the resonant energy. Higher harmonic features in general bear little resemblance to the fundamental even at high fields (B similar to 10 TG), and slabs yield the deepest features, while cylinders present the widest lines at small angles. Moreover, the fundamental line photons in slab scattering regions tend to redistribute to the line wings from all angles, producing fairly broad emission line wings at small angles. Higher optical depths at those angles hampers such redistribution in cylindrical geometries. C1 Univ Costa Rica, Escuela Fis, Lab Invest Astrofis, San Jose, Costa Rica. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Araya, RA (reprint author), Univ Costa Rica, Escuela Fis, Lab Invest Astrofis, San Jose, Costa Rica. RI Harding, Alice/D-3160-2012 NR 53 TC 62 Z9 63 U1 0 U2 3 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 20 PY 1999 VL 517 IS 1 BP 334 EP 354 DI 10.1086/307157 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 206RZ UT WOS:000080894200029 ER PT J AU Borozdin, K Revnivtsev, M Trudolyubov, S Shrader, C Titarchuk, L AF Borozdin, K Revnivtsev, M Trudolyubov, S Shrader, C Titarchuk, L TI Do the spectra of soft X-ray transients reveal bulk-motion inflow phenomenon? SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; radiation mechanisms : nonthermal; X-rays : stars ID ADVECTION-DOMINATED ACCRETION; HIGH-ENERGY OBSERVATIONS; BLACK-HOLE CANDIDATES; SPHERICAL ACCRETION; NEUTRON-STARS; GRO J1655-40; BINARIES; COMPTONIZATION; DISKS; NOVAE AB We present our analysis of the high-energy radiation from black hole (BH) transients using archival data obtained primarily with RXTE and a comprehensive test of the bulk-motion Comptonization (BMC) model for the high-soft state continuum. The emergent spectra of over 30 separate measurements of the GRO J1655-40, GRS 1915 + 105, GRS 1739-278, 4U 1630-47 XTE J1755-32, and EXO 1846-031 X-ray sources are successfully fitted by the BMC model, which has been derived from basic physical principles in previous work. This in turn provides direct physical insight into the innermost observable regions, where matter impinging on the event horizon can effectively be directly viewed. The BMC model is characterized by three parameters: the disk color temperature, a geometric factor related to the illumination of the BH site by the disk, and a spectral index related to the efficiency of the bulk-motion upscattering. For the case of GRO J1655-40, where there are distance and mass determinations, a self-consistency check of the BMC model has been made, in particular of the assumption regarding the dominance of gravitational forces over the pressure forces within the inner few Schwarzschild radii. We have also examined the time behavior of these parameters, which can provide information on the source structure. Using our inferred model parameters: color temperature, spectral index, and an absolute normalization, we present new, independently derived constraints on the BH mass, mass accretion rate, and the distance for the aforementioned sources. Also notable is the relationship between the color temperature and flux, which for CRO J1655-40 is entirely distinct from a simple T-4 dependence and strikingly consistent with the disk model we have invoked: a standard Shakura-Sunyaev disk with the modification to the electron scattering. This provides insight into the origin of the seed soft photons and allows us to impose an important estimation of the hardening parameter, T-h, which is the ratio of the color temperature to the effective temperature: we find T-h similar or equal to 12.6, higher than previous estimates used in the literature. C1 Univ Calif Los Alamos Natl Lab, NIS 2, Los Alamos, NM 87545 USA. Russian Acad Sci, Space Res Inst, High Energy Astrophys Dept, Moscow 117810, Russia. 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 Borozdin, K (reprint author), Univ Calif Los Alamos Natl Lab, NIS 2, POB 1663, Los Alamos, NM 87545 USA. NR 60 TC 53 Z9 53 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1999 VL 517 IS 1 BP 367 EP 380 DI 10.1086/307186 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 206RZ UT WOS:000080894200031 ER PT J AU Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Wilson, CA Deal, K Harmon, BA Fishman, GJ Lewin, WHG Kommers, J AF Woods, PM Kouveliotou, C van Paradijs, J Briggs, MS Wilson, CA Deal, K Harmon, BA Fishman, GJ Lewin, WHG Kommers, J TI Properties of the second outburst of the bursting pulsar (GRO J1744-28) as observed with BATSE SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (GRO J1744; 28); X-rays : bursts; X-rays : stars ID RAPID BURSTER AB One year after its discovery, the Bursting Pulsar (GRO J1744-28) went into outburst again, displaying the hard X-ray bursts and pulsations that make this source unique. We report on BATSE observations of both the persistent and burst emission for this second outburst and draw comparisons with the first. The second outburst was smaller than the first in both duration and peak luminosity. The persistent flux, burst peak flux, and burst fluence were all reduced in amplitude by a factor of similar to 1.7. Despite these differences, the two outbursts were very similar with respect to the burst occurrence rate, the durations and spectra of bursts, the absence of spectral evolution during bursts, and the evolution of the ratio ct of average persistent to burst luminosity. Although no spectral evolution was found within individual bursts, we find evidence for a small (20%) variation of the spectral temperature during the course of the second outburst. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Greenbelt, MD USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. MIT, Dept Phys, Cambridge, MA 02138 USA. MIT, Ctr Space Res, Cambridge, MA 02138 USA. RP Woods, PM (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 24 TC 16 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1999 VL 517 IS 1 BP 431 EP 435 DI 10.1086/307171 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 206RZ UT WOS:000080894200036 ER PT J AU Nishiuchi, M Koyama, K Maeda, Y Asai, K Dotani, T Inoue, H Mitsuda, K Nagase, F Ueda, Y Kouveliotou, C AF Nishiuchi, M Koyama, K Maeda, Y Asai, K Dotani, T Inoue, H Mitsuda, K Nagase, F Ueda, Y Kouveliotou, C TI ASCA observations of GRO J1744-28 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; pulsars : individual(GRO J1744-28); X-rays : bursts ID GAS IMAGING SPECTROMETER; RAPID BURSTER; BOARD ASCA; II BURSTS; OSCILLATIONS AB We report the ASCA results of the bursting X-ray pulsar GRO J1744-28, which was observed in 1996 February and 1997 March. The source flux in the 2-10 keV band was 2.0 x 10(-8) ergs s(-1) cm(2) in 1996 and 5.0 x 10(-9) ergs s(-1) cm2 in 1997. We detected 12 and 17 type II bursts during type two observations, with mean bursting intervals of about 27 min and 37 min. Each burst is followed by an intensity dip with the depleted flux depending on the burst fluence. The energy spectra are approximated by an absorbed power law with additional structure around 6-7 keV. The constant absorption column, (5-6) x 10(22) cm(-2), independent of the observation dates and emission phases (persistent, burst, and dir) is interpreted as an interstellar absorption. The source may be actually located near the Galactic center, at a distance of 8.5 kpc. The structure in the energy spectrum at 6 7 keV is most probably due to iron and may be reproduced by a disk line model with additional broadening mechanism. C1 Kyoto Univ, Grad Sch Sci, Dept Phys, Sakyo Ku, Kyoto 6068502, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. Univ Space Res Assoc, NASA, MSFC, ES84, Huntsville, AL 35812 USA. RP Nishiuchi, M (reprint author), Kyoto Univ, Grad Sch Sci, Dept Phys, Sakyo Ku, Kyoto 6068502, Japan. RI Mitsuda, Kazuhisa/C-2649-2008 NR 31 TC 19 Z9 19 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1999 VL 517 IS 1 BP 436 EP 448 DI 10.1086/307165 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 206RZ UT WOS:000080894200037 ER PT J AU Finger, MH Bildsten, L Chakrabarty, D Prince, TA Scott, DM Wilson, CA Wilson, RB Zhang, SN AF Finger, MH Bildsten, L Chakrabarty, D Prince, TA Scott, DM Wilson, CA Wilson, RB Zhang, SN TI The outbursts and orbit of the accreting pulsar GS 1843-02=2S 1845-024 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : general; pulsars : individual (GS 1843 02) pulsars : individual (2S 1845 024); stars : emission-line, Be; stars : neutron ID CIRCUMSTELLAR ENVELOPES; RAY-EMISSION; RADIO PULSAR; BINARY; SEQUENCE; GEOMETRY; KICK AB We present observations of a series of 10 outbursts of pulsed hard X-ray flux from the transient 10.6 mHz accreting pulsar GS 1843-02, using the Burst and Transient Source Experiment on the Compton Gamma Ray Observatory. These outbursts occurred regularly every 242 days, coincident with the ephemeris of the periodic transient GRO J1849-03, which has recently been identified with the SAS 3 source 2S 1845-024. Our pulsed detection provides the first clear identification of GS 1843-02 with 2S 1845-024. We present a pulse timing analysis that shows that the 2S 1845-024 outbursts occur near the periastron passage of the neutron star's highly eccentric (e = 0.88 +/- 0.01) 242.18 +/- 0.01 day period binary orbit about a high-mass (M-c > 7 M.) companion. The orbit and transient outburst pattern strongly suggest that the pulsar is in a binary system with a Be star. Our observations show a long-term spin-up trend, with most of the spin-up occurring during the outbursts. From the measured spin-up rates and inferred luminosities we conclude that an accretion disk is present during the outbursts. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Calif Berkeley, Dept Phys & Astron, Berkeley, CA 94720 USA. Univ Space Res Assoc, Huntsville, AL 35806 USA. MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Space Res Ctr, Cambridge, MA 02139 USA. CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Finger, MH (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES 84, Huntsville, AL 35812 USA. NR 33 TC 48 Z9 49 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 20 PY 1999 VL 517 IS 1 BP 449 EP 459 DI 10.1086/307191 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 206RZ UT WOS:000080894200038 ER PT J AU Kravchenko, AG Moin, P Shariff, K AF Kravchenko, AG Moin, P Shariff, K TI B-spline method and zonal grids for simulations of complex turbulent flows SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE zonal grids; turbulence simulations; Galerkin B-spline methods ID LARGE-EDDY SIMULATIONS; CIRCULAR-CYLINDER; REYNOLDS-NUMBERS; NUMERICAL ERRORS; BOUNDARY-LAYER; WAKE; TRANSITION; DRAG AB A numerical technique for computations of turbulent Bows is described. The technique is based on B-splines and allows grid embedding in physically significant Bow regions. Numerical tests, which include solutions of nonlinear advection-diffusion equations and computations of flow over a circular cylinder at Reynolds numbers up to 300, indicate that the method is accurate and efficient. In computations of flow over a cylinder, the lift, drag, and base suction coefficients agree well with existing experimental data and previous numerical simulations. (C) 1999 Academic Press. C1 Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Kravchenko, AG (reprint author), Dupont Co, Expt Stn, Wilmington, DE 19880 USA. OI Shariff, Karim/0000-0002-7256-2497 NR 36 TC 71 Z9 71 U1 3 U2 9 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 J9 J COMPUT PHYS JI J. Comput. Phys. PD MAY 20 PY 1999 VL 151 IS 2 BP 757 EP 789 DI 10.1006/jcph.1999.6217 PG 33 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 198YR UT WOS:000080452600014 ER PT J AU Maran, SP AF Maran, SP TI Deep sky companions: The Messier objects SO NATURE LA English DT Book Review C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Maran, SP (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 600, Greenbelt, MD 20771 USA. NR 1 TC 0 Z9 0 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD MAY 20 PY 1999 VL 399 IS 6733 BP 220 EP 220 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 198MF UT WOS:000080427400044 ER PT J AU Rausch, V AF Rausch, V TI USAF research in danger SO AVIATION WEEK & SPACE TECHNOLOGY LA English DT Letter C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Rausch, V (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU MCGRAW HILL INC PI NEW YORK PA 1221 AVENUE OF THE AMERICAS, NEW YORK, NY 10020 USA SN 0005-2175 J9 AVIAT WEEK SPACE TEC JI Aviat. Week Space Technol. PD MAY 17 PY 1999 VL 150 IS 20 BP 8 EP 8 PG 1 WC Engineering, Aerospace SC Engineering GA 197MN UT WOS:000080368700005 ER PT J AU Lopez, RE Dodelson, S Heckler, A Turner, MS AF Lopez, RE Dodelson, S Heckler, A Turner, MS TI Precision detection of the cosmic neutrino background SO PHYSICAL REVIEW LETTERS LA English DT Article ID EARLY UNIVERSE; ANISOTROPY EXPERIMENTS; MICROWAVE; POLARIZATION; NUCLEOSYNTHESIS AB In the standard big bang cosmology the canonical value fur the ratio of relic neutrinos to cosmic microwave background (CMB) photons is 9/11. Within the framework of the standard model of particle physics there are small corrections, in sum about 1%, due to slight heating of neutrinos by electron-positron annihilations and finite-temperature QED effects. We show that this leads to changes in the predicted CMB anisotropies that will bias determination of the other cosmological parameters if not correctly taken into account. These changes might be detected by future satellite experiments. C1 Univ Chicago, Dept Phys, Chicago, IL 60637 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. RP Lopez, RE (reprint author), Univ Chicago, Dept Phys, Chicago, IL 60637 USA. RI Heckler, Andrew/A-7291-2010 OI Heckler, Andrew/0000-0001-5494-7855 NR 28 TC 67 Z9 67 U1 0 U2 1 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 17 PY 1999 VL 82 IS 20 BP 3952 EP 3955 DI 10.1103/PhysRevLett.82.3952 PG 4 WC Physics, Multidisciplinary SC Physics GA 196QW UT WOS:000080319900007 ER PT J AU Khakoo, MA Larsen, M Paolini, B Guo, X Bray, I Stelbovics, A Kanik, I Trajmar, S AF Khakoo, MA Larsen, M Paolini, B Guo, X Bray, I Stelbovics, A Kanik, I Trajmar, S TI Absolute differential cross sections for the electron impact excitation of the 1(2)S -> 2(2)S+2(2)P levels of atomic hydrogen at 50 and 100 eV SO PHYSICAL REVIEW LETTERS LA English DT Article ID HELIUM; SCATTERING; TRANSITION AB Absolute experimental differential cross sections for the electron impact excitation of the 1(2)S --> 2(2)S + 2(2)P levels of H at 50 and 100 eV incident energy are obtained using an application of the method of mixtures and available accurate He (n = 2) experimental electron impact excitation differential cross sections. The determination of the number density composition of the mixed beam is made from energy loss measurements of the mixed beam at 200 eV and 25 degrees scattering angle using accurate H and He theoretical differential cross sections obtained from the distorted-wave Born approximation [D.H. Madison (private communication)] and convergent close coupling [I. Bray and A. Stelbovics, Phys. Rev. A 46, 6995 (1992); D. V. Fursa and I. Bray, Phys. Rev. A 52, 1279 (1995)]. C1 Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. Flinders Univ S Australia, Adelaide, SA 5001, Australia. Murdoch Univ, Ctr Atom Mol & Surface Phys, Perth, WA 6150, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Khakoo, MA (reprint author), Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. RI Bray, Igor/B-8586-2009 OI Bray, Igor/0000-0001-7554-8044 NR 16 TC 8 Z9 9 U1 1 U2 3 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 17 PY 1999 VL 82 IS 20 BP 3980 EP 3983 DI 10.1103/PhysRevLett.82.3980 PG 4 WC Physics, Multidisciplinary SC Physics GA 196QW UT WOS:000080319900014 ER PT J AU Yuan, JC Shiller, AM AF Yuan, JC Shiller, AM TI Determination of subnanomolar levels of hydrogen peroxide in seawater by reagent-injection chemiluminescence detection SO ANALYTICAL CHEMISTRY LA English DT Article ID CHEMI-LUMINESCENCE; FLOWING STREAMS; SOUTH FLORIDA; LUMINOL; WATERS; SEA; IRON(II); CARBON; H2O2 AB A reagent-injection chemiluminescent method for the determination of hydrogen peroxide (H2O2) has been developed. The method is based on the catalytic (cobalt (IT)) oxidation of luminol by hydrogen peroxide in an alkaline solution. One mixed reagent is used for the analysis using the reagent injection method. The mixed reagent is optimized for pH and concentration of luminol and Co2+. Apart from Fe2+, none of the 14 species tested showed interference at their seawater levels. Because Fe2+ oxidation is rapid compared to the rate of decay of hydrogen peroxide, the Fe2+ interference can be eliminated by storing seawater samples for 1 h. The combination of reagents and the adaptation of reagent injection lead to a subnanomolar detection limit. The accuracy of the method is at least 0.42 nM. The precision of the method is 17 pM (for a 0.57 nM sample). The method has been used aboard ship to determine the concentrations of hydrogen peroxide in seawater samples in the open ocean as well as on the continental shelf. C1 Univ So Mississippi, Stennis Space Ctr, Dept Marine Sci, Mississippi State, MS 39529 USA. RP Yuan, JC (reprint author), Univ So Mississippi, Stennis Space Ctr, Dept Marine Sci, Mississippi State, MS 39529 USA. OI Shiller, Alan/0000-0002-2068-7909 NR 33 TC 108 Z9 121 U1 7 U2 31 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0003-2700 J9 ANAL CHEM JI Anal. Chem. PD MAY 15 PY 1999 VL 71 IS 10 BP 1975 EP 1980 DI 10.1021/ac981357c PG 6 WC Chemistry, Analytical SC Chemistry GA 196JF UT WOS:000080304700010 ER PT J AU Pissinou, N Makki, K Campbell, WJ AF Pissinou, N Makki, K Campbell, WJ TI On the design of a location and query management strategy for mobile and wireless environments SO COMPUTER COMMUNICATIONS LA English DT Article DE common object request broker architecture; mobile support stations; object management group AB The rapid development of wireless digital communication technology led to a new computing environment known as mobile or nomadic computing. Mobile computing no longer requires users to confine to wired network premises, but rather it enables users to access information regardless of their location. Mobility of mobile users poses a new class of problems in the fields of networking, operating systems, and databases. Location management and location dependent query processing are major challenges in mobile computing. Location management addresses the issue of continuously keeping track of the location of each user. This article presents the architecture for the location and query management based on distributed databases and distributed object management standards. The architecture is implemented using the common object request broker architecture (CORBA) and mobile IP standards. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ SW Louisiana, Ctr Telecommun Studies, Lafayette, LA 70504 USA. Univ SW Louisiana, Ctr Adv Comp Studies, Lafayette, LA 70504 USA. NASA, Goddard Space Flight Ctr, Applied Informat Sci Branch, Greenbelt, MD 20771 USA. RP Makki, K (reprint author), Univ SW Louisiana, Ctr Telecommun Studies, Lafayette, LA 70504 USA. NR 12 TC 2 Z9 2 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0140-3664 J9 COMPUT COMMUN JI Comput. Commun. PD MAY 15 PY 1999 VL 22 IS 7 BP 651 EP 666 DI 10.1016/S0140-3664(99)00013-4 PG 16 WC Computer Science, Information Systems; Engineering, Electrical & Electronic; Telecommunications SC Computer Science; Engineering; Telecommunications GA 203FX UT WOS:000080698600008 ER PT J AU Wennberg, PO Salawitch, RJ Donaldson, DJ Hanisco, TF Lanzendorf, EJ Perkins, KK Lloyd, SA Vaida, V Gao, RS Hintsa, EJ Cohen, RC Swartz, WH Kusterer, TL Anderson, DE AF Wennberg, PO Salawitch, RJ Donaldson, DJ Hanisco, TF Lanzendorf, EJ Perkins, KK Lloyd, SA Vaida, V Gao, RS Hintsa, EJ Cohen, RC Swartz, WH Kusterer, TL Anderson, DE TI Twilight observations suggest unknown sources of HOx SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HETEROGENEOUS CHEMISTRY; PEROXYNITRIC ACID; SULFURIC-ACID; ABSORPTION; PHOTOCHEMISTRY; OVERTONES; NITROGEN; HO2NO2 AB Measurements of the concentrations of OH and HO2 (HOx) in the high-latitude lower stratosphere imply the existence of unknown photolytic sources of HOx. The strength of the additional HOx source required to match the observations depends only weakly on solar zenith angle (SZA) for 80 degrees < SZA < 93 degrees. The wavelengths responsible for producing this HOx must be longer than 650 nm because the flux at shorter wavelengths is significantly attenuated at high SZA by scattering and absorption. Provided that the sources involve only a single photon, the strength of the bonds being broken must be <45 kcal mole(-1). We speculate that peroxynitric acid (HNO4) dissociates after excitation to an unknown excited state with an integrated band cross section of 2-3 x 10(-20) cm(2) molecule(-1) nm (650 < lambda < 1250 nm). C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. Univ Toronto, Dept Chem, Toronto, ON M5S 1A1, Canada. Univ Colorado, Dept Chem, Boulder, CO 80309 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NOAA, Aeron Lab, Boulder, CO 80307 USA. Univ Calif Berkeley, Berkeley, CA 94720 USA. RP Wennberg, PO (reprint author), CALTECH, MS 150-21,1200 E Calif Blvd, Pasadena, CA 91125 USA. EM wennberg@gps.caltech.edu RI Salawitch, Ross/B-4605-2009; Cohen, Ronald/A-8842-2011; Wennberg, Paul/A-5460-2012; Swartz, William/A-1965-2010; Gao, Ru-Shan/H-7455-2013; Vaida, Veronica/N-6069-2014; Donaldson, James/G-7120-2012 OI Salawitch, Ross/0000-0001-8597-5832; Cohen, Ronald/0000-0001-6617-7691; Swartz, William/0000-0002-9172-7189; Vaida, Veronica/0000-0001-5863-8056; Donaldson, James/0000-0002-5090-3318 NR 18 TC 69 Z9 69 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 1999 VL 26 IS 10 BP 1373 EP 1376 DI 10.1029/1999GL900255 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 197PR UT WOS:000080374500008 ER PT J AU Marcus, SL Ghil, M Ide, K AF Marcus, SL Ghil, M Ide, K TI Models of solar irradiance variability and the instrumental temperature record SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CLIMATE RESPONSE; GLOBAL CLIMATE; CYCLE LENGTH; BRIGHTNESS; CENTURIES; STARS AB The effects of decade-to-century (Dec-Cen) variations in total solar irradiance on global mean surface temperature T-s during the pre-Pinatubo instrumental era (1854-1991) are studied by using two different proxies for the irradiance and an energy-balance climate model. Irradiance anomalies based on solar-cycle length (CL) and solar-cycle decay rate (CD) proxies can account for most of the warming observed up to 1976, but anthropogenic forcing is needed to explain the subsequent sharp increase in T-s. The time series of CL-solar and anthropogenic radiative forcing resemble each other; this similarity makes it difficult to separate their effects in the instrumental T-s record. The CD-based irradiance values reflect heuristically intensity variations in photospheric turbulence; this proxy allows one to obtain more tightly constrained values of both solar variability and terrestrial climate sensitivity from the instrumental T-s record. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RP Marcus, SL (reprint author), CALTECH, Jet Prop Lab, MS 238-332, Pasadena, CA 91109 USA. RI Ide, Kayo/F-8443-2010; OI Marcus, Steven/0000-0002-5763-6961 NR 36 TC 8 Z9 9 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD MAY 15 PY 1999 VL 26 IS 10 BP 1449 EP 1452 DI 10.1029/1999GL900269 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 197PR UT WOS:000080374500027 ER PT J AU Liu, WT Xie, XS AF Liu, WT Xie, XS TI Spacebased observations of the seasonal changes of South Asian monsoons and oceanic responses SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SEA-SURFACE TEMPERATURE; CHINA SEA AB The seasonal changes of monsoons in the South China Sea and the Arabian Sea are compared, using observations by spaceborne microwave scatterometers and radiometers. The oceanic responses to the forcing of wind stress and latent heat flux resulting from the monsoon changes are identified through surface temperature tendency and sea level changes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liu, WT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-323, Pasadena, CA 91109 USA. NR 14 TC 44 Z9 47 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 15 PY 1999 VL 26 IS 10 BP 1473 EP 1476 DI 10.1029/1999GL900289 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 197PR UT WOS:000080374500033 ER PT J AU Dunn, P Torrence, M Kolenkiewicz, R Smith, D AF Dunn, P Torrence, M Kolenkiewicz, R Smith, D TI Earth scale defined by modern satellite ranging observations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID LAGEOS AB Recent advances in Satellite Laser Ranging (SLR) allow us to determine an improved value of the geocentric gravitational coefficient (GM) of 398600.4419 +/- .0002 km(3)/sec(2) (one sigma). This value is based on recent SLR observations of the LAGEOS I satellite; it is confirmed by observations of LAGEOS II, and is supported by results from Starlette, albeit dt a lower level of precision. The information from these other satellites helps to support our claim of a conservative error estimate for GM, which amounts to about one half of a part per billion (ppb). Our determination of GM with the span of LAGEOS I data originally used to determine the current IERS92 standard (398600.4415 +/- .0008 km(3)/sec(2)) gives approximately the same value at about the same uncertainty quoted by the authors in 1992. The improved value that we suggest falls well within the two-ppb error of the current standard, but differs from it by more than the error of the new estimate. The precision of the estimate of GM from SLR observations has improved by an order of magnitude in each of the last two decades. C1 Raytheon STX, Greenbelt, MD 20770 USA. Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20770 USA. RP Dunn, P (reprint author), Raytheon STX, 7701 Greenbelt Rd, Greenbelt, MD 20770 USA. NR 14 TC 12 Z9 12 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 1999 VL 26 IS 10 BP 1489 EP 1492 DI 10.1029/1999GL900260 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 197PR UT WOS:000080374500037 ER PT J AU Dacles-Mariani, J Kwak, D Zilliac, G AF Dacles-Mariani, J Kwak, D Zilliac, G TI On numerical errors and turbulence modeling in tip vortex flow prediction SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article DE incompressible flow; Navier-Stokes equations; tip vortex flow AB The accuracy of tip vortex flow prediction in the near-field region is investigated numerically by attempting to quantify the shortcomings of the turbulence models and the flow solver. In particular, some turbulence models can produce a 'numerical diffusion' that artificially smears the vortex core. Low-order finite differencing techniques of the convective and pressure terms of the Navier-Stokes equations and inadequate grid density and distribution can also produce the same adverse effect. The flow over a wing and the near-wake with the wind tunnel walls included was simulated using 2.5 million grid points. Two subset problems, one using a steady, three-dimensional analytical vortex, and the other, a vortex obtained from experiment and propagated downstream, were also devised in order to make the study of vortex preservation more tractable. The method of artificial compressibility is used to solve the steady, three-dimensional, incompressible Navier-Stokes equations. Two one-equation turbulence models (Baldwin-Earth and Spalart-Allmaras turbulence models), have been used with the production term modified to account for the stabilizing effect of the nearly solid body rotation in the vortex core. Finally, a comparison between the computed results and experiment is presented. published in 1999 by John Wiley & Sons, Ltd. C1 NASA, Ames Res Ctr, Adv Computat Methods Branch, Moffett Field, CA 94035 USA. Univ Calif Davis, Dept Aeronaut & Mech Engn, Davis, CA 95616 USA. NASA, Fluid Mech Lab, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Dacles-Mariani, J (reprint author), NASA, Ames Res Ctr, Adv Computat Methods Branch, MS T27B-1, Moffett Field, CA 94035 USA. NR 21 TC 14 Z9 17 U1 0 U2 4 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0271-2091 J9 INT J NUMER METH FL JI Int. J. Numer. Methods Fluids PD MAY 15 PY 1999 VL 30 IS 1 BP 65 EP 82 DI 10.1002/(SICI)1097-0363(19990515)30:1<65::AID-FLD839>3.0.CO;2-Y PG 20 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA 191JB UT WOS:000080018400004 ER PT J AU Hakkinen, S AF Hakkinen, S TI Variability of the simulated meridional heat transport in the North Atlantic for the period 1951-1993 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SEA-SURFACE TEMPERATURE; INTERPENTADAL VARIABILITY; OCEAN; CIRCULATION; MODEL; CLIMATE; WINTER; ICE; ANOMALIES; WATERS AB A 43-year ocean model simulation for the period 1951-1993 is analyzed, with a focus on the meridional heat transport (MHT) as a proxy for the strength of meridional overturning cell (MOC) at 25 degrees N. The surface heat flux forcing associated with the North Atlantic Oscillation (NAO) pattern is related to the variability in MHT both on interannual and longer timescales. The manifestation of the interannual and decadal oceanic response to NAO is nonlocal, as evidenced by the concentrated heat content and sea level variability at the Gulf Stream and North Atlantic Current regions and shown by the comparison of the model sea level variability to the altimeter data between low MHT years in mid-1980s and high MHT years in early 1990s. The same area is singled out by empirical orthogonal function analysis in the leading mode of the sea level. MHT and time series of the leading sea level mode are highly correlated, which reflects the importance of the MOC in determining the variability of the heat content of the whole basin. Also, the model suggests that the MHT/MOC has entered a very strong phase since the mid-1980s and this trend has continued up to the end of 1993; this behavior follows the general trend in the NAO index. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hakkinen, S (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 40 TC 95 Z9 95 U1 0 U2 6 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 MAY 15 PY 1999 VL 104 IS C5 BP 10991 EP 11007 DI 10.1029/1999JC900034 PG 17 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200007 ER PT J AU Freilich, MH Dunbar, RS AF Freilich, MH Dunbar, RS TI The accuracy of the NSCAT 1 vector winds: Comparisons with National Data Buoy Center buoys SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SCATTEROMETER WINDS; LINEAR-REGRESSION; MODEL FUNCTIONS; OCEAN; SPEED; CALIBRATION; VALIDATION; ASTRONOMY; SEASAT AB The overall accuracies of vector wind measurements from the NASA scatterometer (NSCAT) are quantified by comparisons with collocated data from operational U.S. National Data Buoy Center ocean buoys. A vector correlation statistic is used to examine the geographical distribution of full-mission NSCAT-buoy differences. The dependences of the vector correlation on collocation radius and scatterometer errors such as wind speed offset and random component errors are quantified. For purposes of NSCAT validation, 30 ocean moored buoys having high full-mission sample correlations are considered. When applied to this set of ocean buoys, a nonlinear analysis shows that the 25-km resolution NSCAT wind speeds have unity gain, an offset of -0.3 m s(-1), an rms error of 1.3 m s(-1), and component standard deviations of similar to 1.3 m s(-1) For wind speeds greater than 6 m s(-1), fewer than 3% of all collocated solutions have significant ambiguity removal errors. The rms directional difference for the remaining vectors is less than 17 degrees. At lower wind speeds the frequency of ambiguity removal errors increases and the directional accuracy Of the "correct" vectors decreases with decreasing wind speed, consistent with the assumptions of the random error model underlying the nonlinear wind speed regression approach. While the primary emphasis of this paper is on determining the quantitative accuracy of the NSCAT wind velocity measurements, the analysis techniques and interpretations have more general application to validation studies involving vector quantities. C1 Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Freilich, MH (reprint author), Oregon State Univ, Coll Ocean & Atmospher Sci, 104 Ocean Adm Bldg, Corvallis, OR 97331 USA. NR 31 TC 147 Z9 150 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-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1999 VL 104 IS C5 BP 11231 EP 11246 DI 10.1029/1998JC900091 PG 16 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200025 ER PT J AU Chen, DK Liu, WT Zebiak, SE Cane, MA Kushnir, Y Witter, D AF Chen, DK Liu, WT Zebiak, SE Cane, MA Kushnir, Y Witter, D TI Sensitivity of the tropical Pacific Ocean simulation to the temporal and spatial resolution of wind forcing SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SATELLITE SCATTEROMETER WINDS; PRIMITIVE EQUATION MODEL; TOGA-COARE; STRESS; CYCLE; TIME AB The effects of temporal and spatial smoothing of wind forcing were evaluated in a model simulation of the tropical Pacific Ocean variability during the onset phase of the 1997/1998 El Nino. A total of 16 experiments were performed using the NASA scatterometer wind data smoothed at time intervals from 1 to 30 days and on spatial scales from 1 degrees to 10 degrees. A major effect of the temporal smoothing of winds is to warm sea surface temperature (SST) by reducing the energy input for vertical turbulent mixing. When the daily wind forcing was replaced by the monthly average, the mean SST increased by 0.5 degrees to 1 degrees over most of the tropical Pacific. The spatial smoothing of winds is not as effective as the temporal smoothing in causing SST warming, but it has a more severe influence on dynamical ocean response for smoothing scales above 5 degrees. The onset of the 1997/1998 Fl Nino can be successfully simulated using the wind forcing averaged to monthly intervals and 2 degrees squares. For climate models the spatial smoothing of wind forcing on scales larger than the width of the equatorial waveguide is a more serious limitation than the temporal smoothing on scales up to 1 month. C1 Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chen, DK (reprint author), Columbia Univ, Lamont Doherty Earth Observ, Route 9W,POB 1000, Palisades, NY 10964 USA. RI Cane, Mark/I-8086-2012; Kushnir, Yochanan/B-4472-2013; Chen, Dake/E-7082-2011 NR 17 TC 21 Z9 21 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-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1999 VL 104 IS C5 BP 11261 EP 11271 DI 10.1029/1998JC900031 PG 11 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200027 ER PT J AU Chu, PC Lu, SH Liu, WT AF Chu, PC Lu, SH Liu, WT TI Uncertainty of South China Sea prediction using NSCAT and National Centers for Environmental Prediction winds during tropical storm Ernie, 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN AB Error propagation from winds to ocean models was numerically investigated using the Princeton Ocean Model (POM) for the South China Sea with 20-km horizontal, resolution and 23 sigma levels conforming to a realistic bottom topography during the lifetime of tropical cyclone Ernie (November 4-18, 1996). Numerical integration was divided into preexperimental and experimental stages. The preexperiment phase generates the initial conditions on November 1 for the sensitivity experiment. During the experimental stage the POM was integrated from November 1 to 30, 1996 under National Centers for Environmental Prediction (NCEP) reanalyzed surface fluxes along with two surface wind data sets, namely, the daily averaged interpolated NASA scatterometer winds and the NCEP winds. The relative root-mean-square differences fluctuate from 0.5 to 1.0 for winds, 0.25 to 0.7 for surface elevations, 0.47 to 1.02 for surface currents, and 0 to 0.23 for surface temperatures. This indicates that the model has less uncertainty overall than the wind fields used to drive it, which in turn suggests that the ocean modeling community may progress without waiting for the atmospheric modelers to build the perfect forecast model. C1 USN, Postgrad Sch, Dept Oceanog, Monterey, CA 93943 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Acad Sinica, Inst Plateau Atmospher Phys, Lanzhou 730000, Peoples R China. RP Chu, PC (reprint author), USN, Postgrad Sch, Dept Oceanog, Monterey, CA 93943 USA. NR 20 TC 18 Z9 19 U1 0 U2 2 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 MAY 15 PY 1999 VL 104 IS C5 BP 11273 EP 11289 DI 10.1029/1998JC900046 PG 17 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200028 ER PT J AU Verschell, MA Bourassa, MA Weissman, DE O'Brien, JJ AF Verschell, MA Bourassa, MA Weissman, DE O'Brien, JJ TI Ocean model validation of the NASA scatterometer winds SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NUMERICAL WEATHER PREDICTION; GENERAL-CIRCULATION MODEL; TROPICAL PACIFIC-OCEAN; RADAR CROSS-SECTION; MOMENTUM FLUX; SEA-LEVEL; STRESS; SURFACE; SENSITIVITY; ATLANTIC AB The suitability of basin-scale, satellite-based scatterometer winds for forcing of numerical ocean models is examined using a reduced gravity, primitive equation model of the tropical Pacific Ocean. Three surface forcing fields are validated in a comparison of upper layer thickness (ULT) from the ocean model with observed sea level data. The forcing fields are the Florida State University observed winds, winds derived from the NASA Scatterometer (NSCAT), and stresses derived directly from NSCAT. The sea level data sets are the World Ocean Circulation Experiment "fast" sea level data set from island measurements and sea level anomalies from TOPEX/POSEIDON. Results of this comparison demonstrate that while the three model results are qualitatively similar, the results are quantitatively better when forcing with the NSCAT derived stresses. This is particularly true in the eastern tropical Pacific and in convergent zones where forcing with the NSCAT stresses can lead to large differences in ULT (> 40 m) compared with results from the other two wind products. C1 Florida State Univ, Ctr Ocean Atmospher Predict Studies, Tallahassee, FL 32306 USA. Hofstra Univ, Dept Engn, Hempstead, NY 11549 USA. RP Verschell, MA (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Code 970, Greenbelt, MD 20771 USA. NR 42 TC 23 Z9 23 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD MAY 15 PY 1999 VL 104 IS C5 BP 11359 EP 11373 DI 10.1029/1998JC900105 PG 15 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200034 ER PT J AU Atlas, R Bloom, SC Hoffman, RN Brin, E Ardizzone, J Terry, J Bungato, D Jusem, JC AF Atlas, R Bloom, SC Hoffman, RN Brin, E Ardizzone, J Terry, J Bungato, D Jusem, JC TI Geophysical validation of NSCAT winds using atmospheric data and analyses SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID A SCATTEROMETER DATA; QE-II STORM; SATELLITE SCATTEROMETER; AMBIGUITY REMOVAL; DATA ASSIMILATION; IMPACT; RESOLUTION; FORECASTS; MODEL; PREDICTION AB A detailed geophysical evaluation of the initial NASA scatterometer (NSCAT) wind data sets was performed in order to determine the error characteristics of these data and their applicability to ocean surface analysis and numerical prediction. The first component of this evaluation consisted of collocations of NSCAT data to ship and buoy wind reports, special sensor microwave imager wind observations, and National Centers for Environmental Prediction and Goddard Earth Observing System (GEOS) model wind analyses. This was followed by data assimilation experiments to determine the impact of NSCAT data on analysis and forecasting. The collocation comparisons showed the NSCAT wind velocity data to be of higher accuracy than operational ERS 2 wind data. The impact experiments showed that NSCAT has the ability to correct major errors in analyses over the oceans and also to improve numerical weather prediction. NSCAT data typically show the precise locations of both synoptic-scale and smaller-scale cyclones and fronts over the oceans. This often results in significant improvements to analyses. Forecast experiments using the GEOS model show approximately a 1-day extension of useful forecast skill in the southern hemisphere, in good agreement with the results of Observing System Simulation Experiments conducted prior to launch. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. Gen Sci Corp, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. RP NASA, Goddard Space Flight Ctr, Data Assimilat Off, Mail Code 910-4, Greenbelt, MD 20771 USA. EM atlas@dao.gsfc.nasa.gov RI Atlas, Robert/A-5963-2011 OI Atlas, Robert/0000-0002-0706-3560 NR 43 TC 40 Z9 42 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 MAY 15 PY 1999 VL 104 IS C5 BP 11405 EP 11424 DI 10.1029/98JC02374 PG 20 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200037 ER PT J AU Quilfen, Y Chapron, B Bentamy, A Gourrion, J Elfouhaily, TM Vandemark, D AF Quilfen, Y Chapron, B Bentamy, A Gourrion, J Elfouhaily, TM Vandemark, D TI Global ERS 1 and 2 and NSCAT observations: Upwind crosswind and upwind downwind measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN SURFACE; WIND VECTOR; MODEL; WAVES; SPECTRUM; SECTION; SCATTERING; SPEED AB This paper presents an analysis of the wind speed dependence of upwind/downwind asymmetry (UDA) and upwind-crosswind anisotropy (UCA) as derived from global C band VV-polarized ERS 1 and 2 and Ku band VV- and HH-polarized NASA scatterometer (NSCAT) data. Interpretation of the results relies on identifying relationships between the differing frequencies and incidence angles that are consistent with Bragg scattering theory from gravity-capillary waves. It is shown that globally derived parameters characterizing UDA and UCA hold information on the wind dependence of short gravity and gravity-capillary wave growth and dissipation. In particular, the UCA behavior is found quadratic for both the C and Ku band, peaking at moderate wind speeds. In addition, the dual-frequency results appear to map out the expected, more rapid adjustment of centimeter-scale (Ku band) waves to the wind direction at light winds. However, as wind increases, the directionality associated with these shorter waves saturates at a lower speed than for the slightly longer waves inferred at C band. It is suggested that this observed phenomenon may be related to increasing wave-drift interactions that can potentially inhibit short-scale surface wave growth along the wind direction. Concerning UDA properties, our present analysis reveals that the NSCAT and ERS 1 and 2 scatterometers give quite different results. Our preliminary interpretation is that C band measurements may be easier to interpret using composite Bragg scattering theory and that upwind/downwind contrasts are mainly supported by short gravity waves. C1 IFREMER, Dept Oceanog Spatiale, F-29280 Plouzane, France. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Lab Hydrospher Proc, Wallops Island, VA 23337 USA. RP Quilfen, Y (reprint author), IFREMER, Dept Oceanog Spatiale, BP 70, F-29280 Plouzane, France. RI Chapron, Bertrand/O-6527-2015; Quilfen, Yves/A-1824-2016 NR 26 TC 27 Z9 27 U1 1 U2 5 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 MAY 15 PY 1999 VL 104 IS C5 BP 11459 EP 11469 DI 10.1029/1998JC900113 PG 11 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200041 ER PT J AU Liu, AK Zhao, YH Wu, SY AF Liu, AK Zhao, YH Wu, SY TI Arctic sea ice drift from wavelet analysis of NSCAT and special sensor microwave imager data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID MOTION; SAR AB Wavelet analysis of NASA scatterometer (NSCAT) backscatter and DMSP special sensor microwave imager (SSM/I) radiance data can be used to obtain daily sea ice drift information for the Arctic region. 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. Comparisons with ice motion derived from ocean buoys give good quantitative agreement. Both comparison results from NSCAT and SSM/I are compatible, and the results from NSCAT can definitely complement that from SSM/I when there are cloud or surface effects. Then, three sea ice drift daily results from NSCAT, SSM/I, and buoy data can be merged as a composite map by some data fusion techniques. The ice flow streamlines are highly correlated with surface air pressure contours. Examples of derived ice drift maps in December 1996 illustrate large-scale circulation reversals over a period of 4 days. These calibrated/validated results indicate that NSCAT, SSM/I merged daily ice motions are suitably accurate to identify and closely locate sea ice processes and to improve our current knowledge of sea ice drift and related processes through the data assimilation of ocean-ice numerical model. C1 NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Greenbelt, MD 20771 USA. Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Liu, AK (reprint author), NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Code 971, Greenbelt, MD 20771 USA. NR 24 TC 23 Z9 23 U1 0 U2 2 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 MAY 15 PY 1999 VL 104 IS C5 BP 11529 EP 11538 DI 10.1029/1998JC900115 PG 10 WC Oceanography SC Oceanography GA 198WX UT WOS:000080448200046 ER PT J AU Hooker, MW AF Hooker, MW TI Correlation of the coercive field and reduced layer thickness in piezoelectric RAINBOW ceramics SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID ACTUATOR AB RAINBOWs are a relatively new type of high-displacement, piezoelectric actuator produced by selectively removing oxygen from one side of a lead-containing ceramic using a high-temperature chemical reduction process. This process yields devices which contain a piezoelectric layer and a metallic layer (i.e., the reduced layer). In this study, piezoelectric RAINBOW actuators with reduced layer-to-total-thickness ratios ranging from 0.05 to 0.8 were produced from five soft-piezoelectric formulations. The ferroelectric hysteresis properties of each specimen were then measured while taking the total thickness of the device to be ferroelectric. Because of this assumption and the metallic nature of the reduced layer, the resulting coercive field measurements were found to correlate strongly with the thickness of the piezoelectric portion of each device. A simple, non-destructive method for estimating the reduced layer thickness in RAINBOW ceramics was devised based on this relationship. (C) 1999 Kluwer Academic Publishers. C1 NASA, Langley Res Ctr, Lockheed Martin Engn & Sci Co, Hampton, VA 23681 USA. RP Hooker, MW (reprint author), NASA, Langley Res Ctr, Lockheed Martin Engn & Sci Co, Hampton, VA 23681 USA. NR 4 TC 0 Z9 2 U1 0 U2 1 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 MAY 15 PY 1999 VL 34 IS 10 BP 2407 EP 2410 DI 10.1023/A:1004558531551 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA 205TF UT WOS:000080836100019 ER PT J AU Choi, SR Gyekenyesi, JP AF Choi, SR Gyekenyesi, JP TI Limitations on the determination of life prediction parameters of a silicon carbide with high resistance to slow crack growth SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Cleveland State Univ, Cleveland, OH 44115 USA. RP Choi, SR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 1 Z9 1 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD MAY 15 PY 1999 VL 18 IS 10 BP 767 EP 769 DI 10.1023/A:1006676714327 PG 3 WC Materials Science, Multidisciplinary SC Materials Science GA 212UZ UT WOS:000081237100006 ER PT J AU Stone, EM Randel, WJ Stanford, JL AF Stone, EM Randel, WJ Stanford, JL TI Transport of passive tracers in baroclinic wave life cycles SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID STRATOSPHERE-TROPOSPHERE EXCHANGE; SOUTHERN-HEMISPHERE SUMMER; TROPOPAUSE MASS-EXCHANGE; COMMUNITY CLIMATE MODEL; POTENTIAL VORTICITY; WATER-VAPOR; SIGMA MODEL; TOTAL OZONE; CCM2; INSTABILITY AB The transport of passive tracers in idealized baroclinic wave life cycles is studied using output from the National Center for Atmospheric Research Community Climate Model (CCM2). Two life cycles, LCn and LCs, are simulated, starting with baroclinically unstable initial conditions similar to those used by Thorncroft ct al. in their study of two life cycle paradigms. The two life cycles LCn and LCs have different initial horizontal wind shear structures that result in distinctive nonlinear development. In terms of potential vorticity-potential temperature (PV-theta) diagnostics, the LCn case is characterized by thinning troughs that are advected anticyclonically and equatorward, while the LCs case has broadening troughs that wrap up cyclonically and poleward. Four idealized passive tracers are included in the model to be advected by the semi-Lagrangian transport scheme of the CCM2, and their evolutions are investigated throughout the life cycles. Tracer budgets are analyzed in terms of the transformed Eulerian mean constituent transport formalism in pressure coordinates and also in isentropic coordinates. Results for both LCn and LCs show transport that is downgradient with respect to the background structure of the tracer field, but with a characteristic spatial structure that maximizes in the middle to high latitudes. For the idealized tropospheric tracers in this study, this represents a net upward and poleward transport that enhances concentrations at high latitudes. These results vary little with the initial distribution of the constituent field. The time tendency of the tracer is influenced most strongly by the eddy Aux term, with the largest transport occurring during the nonlinear growth stage of the life cycle. The authors also study the transport of a lower-stratospheric tracer, to examine stratosphere-troposphere exchange for baroclinic waves. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Iowa State Univ Sci & Technol, Dept Phys & Astron, Ames, IA 50011 USA. RP Stone, EM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stip 183-701, Pasadena, CA 91109 USA. RI Randel, William/K-3267-2016 OI Randel, William/0000-0002-5999-7162 NR 37 TC 17 Z9 18 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 15 PY 1999 VL 56 IS 10 BP 1364 EP 1381 DI 10.1175/1520-0469(1999)056<1364:TOPTIB>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 194YM UT WOS:000080222400007 ER PT J AU Vikram, CS Witherow, WK AF Vikram, CS Witherow, WK TI Chemical silver coating of fiber tips in near-field scanning optical microscopy SO OPTICS LETTERS LA English DT Article ID REPRODUCIBLE FABRICATION; IMAGE-CONTRAST; PROBE; SPECTROSCOPY; SENSORS; OPTIMIZATION; RESOLUTION; REFLECTION; WELL AB We report what is believed to be the first experimental demonstration of silver coating by a wet chemical process on tapered fiber tips used in near-field scanning optical microscopy. The process occurs at room temperature and pressure and takes only a few minutes to complete. Many tips can be coated simultaneously. (C) 1999 Optical Society of America OCIS codes: 170.5810, 060.2310, 350.3950, 310.1860, 110.2350, 120.3930. C1 Univ Alabama, Ctr Appl Opt, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Vikram, CS (reprint author), Univ Alabama, Ctr Appl Opt, Huntsville, AL 35899 USA. NR 40 TC 1 Z9 1 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 15 PY 1999 VL 24 IS 10 BP 682 EP 684 DI 10.1364/OL.24.000682 PG 3 WC Optics SC Optics GA 197DH UT WOS:000080349000016 PM 18073822 ER PT J AU Tinto, M Armstrong, JW AF Tinto, M Armstrong, JW TI Cancellation of laser noise in an unequal-arm interferometer detector of gravitational radiation SO PHYSICAL REVIEW D LA English DT Article ID SPACECRAFT; TRACKING; WAVES AB Equal-arm interferometric detectors of gravitational radiation allow phase measurements many orders of magnitude below the intrinsic phase stability of the laser injecting light into their arms. This is because the noise in the laser light is common to both arms, experiencing exactly the same delay, and thus cancels when it is differenced at the photo detector. In this situation, much lower level secondary noises then set overall performance. If, however, the two arms have different lengths (as will necessarily be the case with space-borne interferometers), the laser noise experiences different delays in the two arms and will hence not directly cancel at the detector. In this paper we present a method for exactly canceling the laser noise in a one-bounce unequal-arm Michelson interferometer. The method requires separate measurements of the phase difference in each arm, made by interfering the returning laser light in each arm with the outgoing light. Let these two time series of phase difference be z(i), i = 1,2. By forming the quantity [z(1)(t-2L(2)/c)-z(1)(t)]-[z(2)(t-2L(1)/c)-z(2)(t)], where L-i are the arm lengths, gravitational wave signals remain while the laser noise is canceled. Unlike other proposed methods, this procedure accurately cancels the laser noise if the arm lengths are known. This method is direct in time and allows for time-varying arm-lengths. In this paper we demonstrate that this method precisely cancels the laser noise, present the transfer function of gravitational waves after forming this linear combination, and discuss system requirements (such as required knowledge of the arm lengths). We verify the technique with numerical simulation of periodic gravitational wave signals embedded in laser and shot noise having spectra expected for a space-borne interferometer, and compare our time-domain approach with approximate correction methods based on Fourier transforms of the z(i) processes. [S0556-2821(99)00710-9]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Tinto, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM Massimo.Tinto@jpl.nasa.gov; John.W.Armstrong@jpl.nasa.gov NR 14 TC 83 Z9 83 U1 0 U2 2 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 15 PY 1999 VL 59 IS 10 AR 102003 DI 10.1103/PhysRevD.59.102003 PG 11 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 198UE UT WOS:000080442000007 ER PT J AU Stothers, RB AF Stothers, RB TI Criterion for the dynamical stability of a non-adiabatic spherical self-gravitating body SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE instabilities; stars : oscillations; stars : variables : other ID LUMINOUS BLUE VARIABLES; ETA-CARINAE; OUTBURSTS; STARS; INSTABILITY AB Why do stars and planets maintain their dynamical stability over cosmically long periods of time? The standard answer is that the first generalized adiabatic exponent of their material, Gamma(1), exceeds the value 4/3. Yet it has never been rigorously demonstrated (except for the simple one-zone model) that non-adiabatic effects do not modify this result at some level. Many authors, in fact, have suggested the probable need for a nan-adiabatic correction to the square of the radial adiabatic eigenfrequency, sigma(2), which ostensibly governs dynamical stability in the more general case where Gamma(1) varies throughout a fully distributed self-gravitating spherical body. Here, a carefully controlled series of numerical experiments based on linear and nonlinear hydrodynamical models of highly non-adiabatic spherically symmetric stellar envelopes (mimicking the envelopes of luminous blue variables) confirms, quite generally, that the purely adiabatic criterion sigma(2) > 0 does in fact determine dynamical stability. An accurate approximation to this criterion is further shown to be that the volumetric pressure-weighted average of Gamma(1) must exceed 4/3. These results, which concern only radial stability, verify the theoretical basis of the more sophisticated models for luminous blue variables that were constructed by the author and C.-w. Chin, but they do not support the objections to these models raised by W. Glatzel and M.. Kiriakidis. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stothers, RB (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 33 TC 17 Z9 17 U1 0 U2 0 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD MAY 11 PY 1999 VL 305 IS 2 BP 365 EP 372 DI 10.1046/j.1365-8711.1999.02444.x PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201BJ UT WOS:000080574500012 ER PT J AU Kouveliotou, C AF Kouveliotou, C TI Magnetars SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Editorial Material ID MAGNETIZED NEUTRON-STARS; SOFT GAMMA-REPEATERS; HIGH-ENERGY TRANSIENT; X-RAY PULSAR; SGR1806-20 AB Recent a-ray observations have shown that a substantial fraction of newly born neutron stars have magnetic fields of several 10(14) G. They reveal themselves as soft gamma repeaters and anomalous x-ray pulsars and may account for the missing radio pulsars in young supernova remnants. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Kouveliotou, C (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, ES-84, Huntsville, AL 35812 USA. NR 23 TC 22 Z9 22 U1 0 U2 1 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 MAY 11 PY 1999 VL 96 IS 10 BP 5351 EP 5352 DI 10.1073/pnas.96.10.5351 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 195JG UT WOS:000080246500007 PM 10318885 ER PT J AU Aller, LH Hung, S Feibelman, WA AF Aller, LH Hung, S Feibelman, WA TI The remarkably high excitation planetary nebula GC 6537 SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID EMISSION-LINES; NGC-6537; NGC-6302; SPECTRA; RADIO; IV AB NGC 6537 is an unusually high excitation point symmetric planetary nebula with a rich spectrum. Its kinematical structures are of special interest. We are here primarily concerned with the high resolution spectrum as revealed by the Hamilton echelle Spectrograph at Lick Observatory (resolution approximate to 0.2 Angstrom) and supplemented by UV and near-UV data. These extensive data permit a determination of interstellar extinction, plasma diagnostics, and ionic concentrations. The photoionization models that have been used successfully for many planetary nebulae are not entirely satisfactory here. The plasma electron temperature of a photoionization model cannot much exceed 20,000 K, but plasma diagnostics show that regions emitting radiation of highly ionized atoms such as [NeIV] and [NeV] are much hotter, showing that shock excitation must be important, as suggested by the remarkable kinematics of this object. Hence, instead of employing a strict photoionization model, we are guided by the nebular diagnostics, which reveal how electron temperature varies with ionization potential and accommodates density effects. The predictions of the photoionization model may be useful in estimating ionization correction factor, In effect, we have estimated the chemical composition by using both photoionization and shock considerations. C1 Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Bohyunsan Opt Observ, Youngcheon 770820, Kyungbuk, South Korea. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Aller, LH (reprint author), Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NR 27 TC 12 Z9 12 U1 0 U2 0 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 MAY 11 PY 1999 VL 96 IS 10 BP 5366 EP 5371 DI 10.1073/pnas.96.10.5366 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 195JG UT WOS:000080246500011 PM 10318889 ER PT J AU Matsuura, S Blake, GA Wyss, RA Pearson, JC Kadow, C Jackson, AW Gossard, AC AF Matsuura, S Blake, GA Wyss, RA Pearson, JC Kadow, C Jackson, AW Gossard, AC TI A traveling-wave THz photomixer based on angle-tuned phase matching SO APPLIED PHYSICS LETTERS LA English DT Article ID TEMPERATURE-GROWN GAAS; TERAHERTZ; GENERATION; DIPOLE; POWER AB A traveling-wave THz photomixer based on a free-space optical-THz phase-matching scheme is proposed. A dc-biased coplanar strip line fabricated on low-temperature-grown GaAs serves as the active area of the device, and is illuminated by two noncollinear laser beams which generate interference fringes that are accompanied by THz waves. The device with the laser-power-handling capability over 300 mW and a 3-dB bandwidth of 1.8 THz was experimentally demonstrated. The results show that traveling-wave photomixers have the potential to surpass small-area designs. (C) 1999 American Institute of Physics. [S0003-6951(99)03719-5]. C1 CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA. RP Matsuura, S (reprint author), CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RI Matsuura, Shuji/B-5658-2016 OI Matsuura, Shuji/0000-0002-5698-9634 NR 11 TC 71 Z9 73 U1 0 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD MAY 10 PY 1999 VL 74 IS 19 BP 2872 EP 2874 DI 10.1063/1.124042 PG 3 WC Physics, Applied SC Physics GA 193TH UT WOS:000080152700046 ER PT J AU Hui, L AF Hui, L TI Recovery of the shape of the mass power spectrum from the Ly alpha forest SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; intergalactic medium; large-scale structure of universe; quasars : absorption lines ID REDSHIFT-SPACE; INTERGALACTIC MEDIUM; FLUCTUATIONS; DISTORTIONS; REAL AB We propose a method for recovering the shape of the mass power spectrum on large scales from the transmission fluctuations of the Ly alpha forest that directly takes into account redshift-space distortions. The procedure, in discretized form, involves the inversion of a triangular matrix that projects the mass power spectrum in three-dimensional real space to the transmission power spectrum in one-dimensional redshift space. We illustrate the method by performing a linear calculation relating the two. A method that does not take into account redshift-space anisotropy tends to underestimate the steepness of the mass power spectrum in the case of linear distortions. The issue of the effective bias factor for the linear distortion kernel is discussed. C1 Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Hui, L (reprint author), Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, POB 500, Batavia, IL 60510 USA. NR 25 TC 35 Z9 35 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 519 EP 526 DI 10.1086/307134 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000002 ER PT J AU Hwang, U Mushotzky, RF Burns, JO Fukazawa, Y White, RA AF Hwang, U Mushotzky, RF Burns, JO Fukazawa, Y White, RA TI Mass and metallicity of five X-ray-bright galaxy groups SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : abundances; galaxies : clusters : general; X-rays : galaxies ID POOR CLUSTERS; EXOSAT OBSERVATIONS; OPTICAL-PROPERTIES; ROSAT OBSERVATIONS; PSPC OBSERVATIONS; RICH CLUSTERS; EMITTING GAS; HOT CORONAE; DARK MATTER; EMISSION AB We present ASCA X-ray observations of a sample of five groups selected from a cross-correlation of the ROSAT All-Sky Survey with the White et al. optical catalog of groups. These X-ray-bright groups significantly increase the number of known systems with temperatures between 2 and 3 keV. They have element abundances of roughly 0.3., which are typical of clusters, but their favored ratio of Si-to-Fe abundance is lower than the cluster value. Combining the ASCA results with ROSAT imaging data, we calculate total masses of a few to several times 10(13) M., gas mass fractions of similar to 10%, and baryonic mass fractions of at least 15%-20% within a radius of 0.5 Mpc. Upper limits for the ratios of gas to galaxy mass and of the iron mass to galaxy luminosity overlap with the range observed in rich clusters and extend to lower values, but not to such low values as seen in much poorer groups. These results support the idea that groups, unlike clusters, are subject to the loss of their primordial and processed gas and show that this transition occurs at the mass scale of the 2-3 keV groups. A discussion of ASCA calibration issues and a comparison of ROSAT and ASCA temperatures are included in an Appendix. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA. Univ Missouri, Res Off, Columbia, MO 65211 USA. Univ Tokyo, Dept Phys, Tokyo 113, Japan. RP NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 67 TC 37 Z9 37 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 1999 VL 516 IS 2 BP 604 EP 618 DI 10.1086/307147 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000010 ER PT J AU Graham, JA Ferrarese, L Freedman, WL Kennicutt, RC Mould, JR Saha, A Stetson, PB Madore, BF Bresolin, F Ford, HC Gibson, BK Han, MS Hoessel, JG Huchra, J Hughes, SM Illingworth, GD Kelson, DD Macri, L Phelps, R Sakai, S Silbermann, NA Turner, A AF Graham, JA Ferrarese, L Freedman, WL Kennicutt, RC Mould, JR Saha, A Stetson, PB Madore, BF Bresolin, F Ford, HC Gibson, BK Han, MS Hoessel, JG Huchra, J Hughes, SM Illingworth, GD Kelson, DD Macri, L Phelps, R Sakai, S Silbermann, NA Turner, A TI The Hubble Space Telescope key project on the Extragalactic Distance Scale. XX. The discovery of cepheids in the Virgo Cluster galaxy NGC 4548 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; distance scale; galaxies : clusters : individual (Virgo); galaxies : individual (NGC 4548) ID PEAK BRIGHTNESS; SPIRAL GALAXIES; CCD PHOTOMETRY; CALIBRATION; PERFORMANCE; VARIABLES; CONSTANT; WFPC2; STARS AB We report on the discovery and properties of Cepheid variable stars in the barred spiral galaxy NGC 4548, which is a member of the Virgo cluster of galaxies. This is one of the galaxies being observed as part of the Hubble: Space Telescope (HST) Key Project on the Extragalactic Distance Scale, which aims to determine the Hubble constant to 10% accuracy. Our analysis is based on observations made with the Wide Field and Planetary Camera 2 during 1996 and 1997. We identify 24 probable Cepheids with periods between 16 and 38 days. They were observed over 13 epochs with the F555W filter and eight epochs with the F814W filter. The HST F555W and F814W data have been transformed to the Johnson V and Cousins I magnitude systems, respectively. Photometry has principally been carried out using the DAOPHOT/ALLFRAME package. A comparison is made with parallel measurements using the DoPHOT package. Apparent period-luminosity relations for V and I have been constructed., Assuming values of mu(0) = 18.50 +/- 0.10 mag and E(B-V) = 0.10 mag for the distance modulus and reddening of the Large Magellanic Cloud, a true distance modulus of 31.01 +/- 0.28 mag is derived corresponding to a distance of 15.9 +/- 2.0 Mpc. HST Cepheid distances of other spiral galaxies in the Virgo Cluster are discussed. Their good agreement with the new NGC 4548 distance strengthens the evidence that this galaxy lies within the Virgo cluster core. C1 Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. CALTECH, Pasadena, CA 91125 USA. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Kitt Peak Natl Observ, Natl Opt Astron Observ, Tucson, AZ 85726 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. CALTECH, NASA, IPAC, Pasadena, CA 91125 USA. European So Observ, D-8046 Garching, Germany. Johns Hopkins Univ, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Colorado, CASA, Boulder, CO 80309 USA. Univ Wisconsin, Madison, WI 53706 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Royal Greenwich Observ, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. RP Graham, JA (reprint author), Carnegie Inst Washington, Dept Terr Magnetism, 5241 Broad Branch Rd NW, Washington, DC 20015 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 55 TC 45 Z9 45 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 626 EP 646 DI 10.1086/307151 PN 1 PG 21 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000012 ER PT J AU Fruchter, AS Pian, E Thorsett, SE Bergeron, LE Gonzalez, RA Metzger, M Goudfrooij, P Sahu, KC Ferguson, H Livio, M Mutchler, M Petro, L Frontera, F Galama, T Groot, P Hook, R Kouveliotou, C Macchetto, D van Paradijs, J Palazzi, E Pedersen, H Sparks, W Tavani, M AF Fruchter, AS Pian, E Thorsett, SE Bergeron, LE Gonzalez, RA Metzger, M Goudfrooij, P Sahu, KC Ferguson, H Livio, M Mutchler, M Petro, L Frontera, F Galama, T Groot, P Hook, R Kouveliotou, C Macchetto, D van Paradijs, J Palazzi, E Pedersen, H Sparks, W Tavani, M TI The fading optical counterpart of GRB 970228, 6 months and 1 year later SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; infrared : galaxies ID GAMMA-RAY BURST; HUBBLE-SPACE-TELESCOPE; HIGH-REDSHIFT GALAXIES; INTERSTELLAR NA I; DEEP FIELD; CA-II; EMISSION; SPECTRA; LINES; STARS AB We report on observations of the fading optical counterpart of the gamma-ray burst GRB 970228, made with the Hubble Space Telescope (HST) and the Keck I telescope. The gamma-ray burst (GRB) was observed approximately 6 months after outburst, on 1997 September 4, using the HST/STIS CCD, and approximately 1 year after outburst, on 1998 February 24, using HST/NICMOS, and on 1998 April 4 using the NIRC on Keck. The unresolved counterpart is detected by STIS at V = 28.0 +/- 0.25, consistent with a continued power-law decline with exponent -1.10 +/- 0.05. The counterpart is located within, but near the edge of, a faint extended source with diameter similar to 0." 8 and integrated magnitude V = 25.8 +/- 0.25. A reanalysis of HST and New Technology Telescope observations performed shortly after the burst shows no evidence of proper motion of the point source or fading of the extended emission. Although the optical transient is not detected in the NICMOS images (H greater than or equal to 25.3), the extended source is visible and has a total magnitude H = 23.3 +/- 0.1. The Keck observations find K = 22.8 +/- 0.3. Comparison with observations obtained shortly after outburst suggests that the nebular luminosity has also been stable in the infrared. We find that several distinct and independent means of deriving the foreground extinction in the direction of GRB 970228 all agree with A(V) = 0.75 +/- 0.2. After adjusting for this Galactic extinction, we find that the size of the observed extended emission is consistent with that of galaxies of comparable magnitude found in the Hubble Deep Field (HDF) and other deep HST images. Only 2% of the sky is covered by galaxies of similar or greater surface brightness. We therefore conclude that the extended source observed about GRB 970228 is almost certainly its host galaxy. Additionally, we find that independent of assumed redshift, the host is significantly bluer than typical nearby blue dwarf irregulars. With the caveat that the presently available infrared observations of the HDF are only fully complete to a limit about one-half magnitude brighter than the host, we find that the extinction-corrected V-H and V-K colors of the host are as blue as any galaxy of comparable or brighter magnitude in the HDF. Taken in concert with recent observations of GRB 970508, GRB 971214, and GRB 980703 our work suggests that all four GRBs with spectroscopic identification or deep multicolor broadband imaging of the host lie in rapidly star-forming galaxies. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. CNR, Ist Tecnol & Studio Radiaz Extraterr, I-40129 Bologna, Italy. Princeton Univ, Joseph Henry Labs, Princeton, NJ 08544 USA. Princeton Univ, Dept Phys, Princeton, NJ 08544 USA. CALTECH, Dept Astron, Pasadena, CA 91125 USA. European Space Agcy, Dept Space Sci, Div Astrophys, F-75738 Paris 15, France. Univ Ferrara, Dipartmento Fis, I-44100 Ferrara, Italy. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Space Telescope European Coordinating Facil, D-85748 Garching, Germany. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Copenhagen Univ Observ, DK-2100 Copenhagen A, Denmark. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. CNR, Ist Fis Cosm & Tecnol Relat, I-20133 Milan, Italy. RP Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. RI Galama, Titus/D-1429-2014; Palazzi, Eliana/N-4746-2015; Groot, Paul/K-4391-2016; OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X; Palazzi, Eliana/0000-0002-8691-7666; Tavani, Marco/0000-0003-2893-1459; Pian, Elena/0000-0001-8646-4858 NR 68 TC 91 Z9 91 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 683 EP 692 DI 10.1086/307136 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000016 ER PT J AU Satyapal, S Watson, DM Forrest, WJ Pipher, JL Fischer, J Greenhouse, MA Smith, HA Woodward, CE AF Satyapal, S Watson, DM Forrest, WJ Pipher, JL Fischer, J Greenhouse, MA Smith, HA Woodward, CE TI Probing the dust-enshrouded regions of the interacting galaxy system ARP 299: A near-infrared study SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (Arp 299); galaxies : nuclei; infrared : galaxies; infrared : ISM : lines and bands ID MICRON EMISSION FEATURE; STARBURST GALAXIES; SUPERNOVA-REMNANTS; STAR-FORMATION; LUMINOSITY FUNCTION; RECOMBINATION-LINE; SPIRAL GALAXIES; STANDARD STARS; RADIO-SOURCES; GAMMA-RATIO AB We present high spectral resolution (lambda/delta lambda congruent to 10(3)) Pa beta(1.28 mu m) and Br gamma(2.17 mu m), 3.29 mu m dust feature, and near-infrared broadband images of the Arp 299 = NGC 3690/IC 694 galaxy system. The emission is found to be concentrated at the positions of three active regions, known as sources A, B, and C. From our Br gamma/Pa beta flux ratio we find the visual extinction toward the ionized gas in A, B, and C is similar to 6, 6, and 2 magnitudes, respectively, assuming case B recombination and a foreground screen geometry for the obscuring material. Our observations can be explained entirely by a starburst model for the Arp 299 system. The putative active galactic nucleus (AGN) in source A does not dominate the properties of this source. We see no evidence of broad recombination lines. In addition, the ratio of the 3.29 mu m dust feature to total luminosity, a tracer of starburst activity, is consistent in each source with that seen in M82 and other starburst galaxies. Also, our imaging observations reveal that the dust feature emission is concentrated in the nucleus of source A, contrary to the extended annular distribution of the feature emission seen surrounding the nucleus of the more distant Seyfert galaxy NGC 7469. In this galaxy, the absence of the feature emission in the nucleus has been attributed to the destruction of the dust carriers in the hard radiation held surrounding the AGN. Our observations suggest that all of the active regions in Arp 299 are characterized by starburst episodes. The observed CO indices and Br gamma equivalent widths imply that source B is older than source A and source C is the youngest star-forming region. Although these regions are probably complex physical systems not necessarily characterized by a single coeval population of stars, we have compared our observations with an instantaneous starburst model with a Salpeter initial mass function. Using this simple model, we find starburst ages of similar to 6 x 10(6), 8 x 10(6), and 4 x 10(6) for sources A, B, and C, respectively. C1 Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Wyoming, Dept Phys & Astron, Laramie, WY 82701 USA. RP NASA, Goddard Space Flight Ctr, Code 685, Greenbelt, MD 20771 USA. EM satyapal@stars.gsfc.nasa.gov NR 54 TC 14 Z9 14 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 704 EP 715 DI 10.1086/307130 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000018 ER PT J AU Crenshaw, DM Kraemer, SB Boggess, A Maran, SP Mushotzky, RF Wu, CC AF Crenshaw, DM Kraemer, SB Boggess, A Maran, SP Mushotzky, RF Wu, CC TI Intrinsic absorption lines in Seyfert 1 galaxies. I. Ultraviolet spectra from the Hubble Space Telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : Seyfert; line : identification; ultraviolet : galaxies ID ACTIVE GALACTIC NUCLEI; QUASI-STELLAR OBJECTS; X-RAY-ABSORPTION; EMISSION-LINES; C-IV; DETAILED OBSERVATIONS; VARIABLE ABSORPTION; IUE OBSERVATIONS; BROAD; NGC-4151 AB We present a study of the intrinsic absorption lines in the ultraviolet spectra of Seyfert 1 galaxies. The study is based on spectra from the Hubble Space Telescope and includes the Seyfert I galaxies observed with the Faint Object Spectrograph and Goddard High-Resolution Spectrograph at spectral resolutions of lambda/Delta lambda approximate to 1000-20,000 with good signal-to-noise ratios. We find that the fraction of Seyfert I galaxies that show intrinsic absorption associated with their active nuclei is more than one-half (10 of 17), which is much higher than previous estimates (3%-10%) based on IUE data. There is a one-to-one correspondence between Seyfert galaxies that show intrinsic UV absorption and X-ray "warm absorbers," indicating that these two phenomena are related. Although our sample is not complete, we conclude that intrinsic absorption represents an important component that needs to be integrated into our overall physical picture of active galaxies. The intrinsic UV absorption is generally characterized by high ionization: C Iv and N v are seen in all 10 Seyfert galaxies with detected absorption tin addition to Ly alpha), whereas Si rv is present in only four of these Seyfert galaxies, and Mg II absorption is detected only in NGC 4151, The absorption lines are blueshifted (or in a few cases at rest) with respect to the narrow emission lines, indicating that the absorbing gas is undergoing net radial outflow. At high resolution, the absorption often splits into distinct kinematic components that show a wide range in widths (20-400 km s(-1) FWHM), indicating macroscopic motions (e.g., radial velocity subcomponents or turbulence) within a component. The strong absorption components have cores that are much deeper than the continuum flux levels, indicating that the regions responsible for these components lie completely outside of the broad emission-line regions. Additional information on the covering factors and column densities can be derived from the absorption profiles in the high-resolution spectra. The covering factor of the absorbing gas in the Line of sight, relative to the total underlying emission, is C-los greater than or equal to 0.86, on average. The global covering factor, which is the fraction of emission intercepted by the absorber averaged over all lines of sight, is C-global greater than or equal to 0.5. Thus, structures covering large solid angles as seen by the central continuum source (e.g., spherical shells, sheets, or cones with large opening angles) are required. The individual absorption components show a wide range in C Iv column densities (0.1-14 x 10(14) cm(-2)), and the ratio of N v to C rv column density varies significantly from one absorption component to the next, even in the same Seyfert galaxy. Thus, the intrinsic absorption in a Seyfert 1 galaxy is typically comprised of distinct kinematic components that are characterized by a range in physical conditions (e.g., ionization parameter and hydrogen column density). Finally, we show evidence for extreme variability in the intrinsic absorption lines of NGC 3783. In addition to our earlier report of the appearance of a C N absorption doublet at -560 km s(-1) (relative to the emission lines) over 11 months, we have detected the appearance of another C rv doublet at - 1420 km s(-1) over 15 months. On the other hand, the C IV absorption lines of NGC 3516 and NGC 4151 were very stable over periods of 6 months and;4 years, respectively. Monitoring observations of individual Seyfert galaxies at higher time resolution are needed to distinguish between different sources of variability (variable ionization, motion of gas across the line of sight) and to determine the densities and radial locations of the absorption components. C1 Catholic Univ Amer, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, 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. Space Telescope Sci Inst, Comp Sci Corp, Baltimore, MD 21218 USA. RP Crenshaw, DM (reprint author), Catholic Univ Amer, Greenbelt, MD 20771 USA. NR 76 TC 279 Z9 280 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 750 EP 768 DI 10.1086/307144 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000022 ER PT J AU Kraemer, KE Deutsch, LK Jackson, JM Hora, JL Fazio, GG Hoffmann, WF Dayal, A AF Kraemer, KE Deutsch, LK Jackson, JM Hora, JL Fazio, GG Hoffmann, WF Dayal, A TI The mid-infrared properties of three star-forming sites in NGC 6334 SO ASTROPHYSICAL JOURNAL LA English DT Article DE HII regions; infrared : ISM : continuum; ISM : individual (NGC 6334); radio continuum : ISM; stars : formation ID H-II REGIONS; PHOTODISSOCIATION REGIONS; NGC-6334 COMPLEX; METHANOL MASERS; MOLECULAR CLOUD; ARRAY CAMERA; WATER-VAPOR; EMISSION; NEBULA; SCATTERING AB To investigate their dust properties, we have imaged three sites of massive star formation in the giant H II region/star-forming cloud NGC 6334 with the MIRAC2 instrument. We obtained high-resolution (1 ") continuum images at 12.5 and 20.6 mu m toward each region, which were compared with observations of the radio and near-infrared (near-IR) continuum emission. Both compact sources and extended emission were found at all three star-forming sites. The detected sources span a wide range of evolutionary states in this highly complex star-forming cloud. The infrared sources near NGC 6334 I were resolved into at least four subsources. One such source is substantially colder, denser, and more optically thick than the other mid-IR sources in the region and may be at the earliest stages of stellar formation. Another may be a torus or disk of dust and gas surrounding an embedded B star. NGC 6334 I was also imaged at additional wavelengths (8.8, 9.8, and 11.7 mu m) to search for silicate absorption. Only at the H II region is there a deep silicate absorption feature from foreground dust. Toward the NGC 6334 IV, warm dust is associated with both the inner portions of the massive molecular torus or disk and with the bipolar continuum lobes. A compact mid-IR source, associated with the near-IR and radio source [HHS87] IRS 20, is cooler and more optically thick than the dust emission associated with the H II region. Toward NGC 6334 V, four embedded sources were found, including one previously unidentified object. This newly identified compact object, associated with a dust temperature peak and a radio source, is probably in a more advanced stage of star formation than the other compact mid-IR sources in NCC 6334. C1 Boston Univ, Dept Astron, Boston, MA 02215 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. RP Kraemer, KE (reprint author), Boston Univ, Dept Astron, 725 Commonwealth Ave, Boston, MA 02215 USA. OI Hora, Joseph/0000-0002-5599-4650; Kraemer, Kathleen/0000-0002-2626-7155 NR 63 TC 30 Z9 30 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 817 EP 833 DI 10.1086/307149 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000028 ER PT J AU Hildebrand, RH Dotson, JL Dowell, CD Schleuning, DA Vaillancourt, JE AF Hildebrand, RH Dotson, JL Dowell, CD Schleuning, DA Vaillancourt, JE TI The far-infrared polarization spectrum: First results and analysis SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared : ISM : continuum; ISM : clouds; polarization; stars : low-mass, brown dwarfs ID GRAIN ALIGNMENT MECHANISMS; INTERSTELLAR GRAINS; MOLECULAR CLOUD; MAGNETIC-FIELDS; SAGITTARIUS B2; STAR-FORMATION; SUBMILLIMETER POLARIZATION; OPTICAL-PROPERTIES; SILICATE GRAINS; DARK CLOUDS AB We present data on the polarization of the thermal emission from Galactic Clouds at 60 mu m, 100 mu m, and 350 mu m. There are examples of rising polarization spectra in dense cloud cores [P(350 mu m/P(100 mu m) approximate to 2], and falling spectra in cloud envelopes CP(350)/P(100 mu m) approximate to 0.6]. We also present data showing that the relationship, P(tau), between polarization and optical depth in cloud cores is different from that in cloud envelopes. We review the principles governing the far-infrared polarization spectrum and discuss applications to the data on P(lambda) and P(tau). We conclude that the cloud envelopes we have observed must contain two populations of grains that differ in their polarization efficiencies and in their emission spectra. We propose a model for cloud envelopes in which the contrasting populations reside in domains of different mean temperatures where the warmer domains contain the aligned grains. C1 Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Dept Phys, Chicago, IL 60637 USA. NASA, Ames Res Ctr, SETI, Moffett Field, CA 94035 USA. CALTECH, Pasadena, CA 91125 USA. RP Hildebrand, RH (reprint author), Univ Chicago, Enrico Fermi Inst, 5640 S Ellis Ave, Chicago, IL 60637 USA. OI Vaillancourt, John/0000-0001-8916-1828 NR 67 TC 92 Z9 93 U1 1 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 834 EP 842 DI 10.1086/307142 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000029 ER PT J AU Robinson, RD Carpenter, KG Percival, JW AF Robinson, RD Carpenter, KG Percival, JW TI A search for microflaring activity on dMe flare stars. II. Observations of YZ Canis Minoris SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : activity; stars : flare; stars : individual (YZ Canis Minoris, CN Leonis); ultraviolet : stars ID SOLAR-FLARES; VARIABILITY; NANOFLARES; CORONA; ULTRAVIOLET; AVALANCHES; FREQUENCY; FIELDS AB We report on time-series photometric observations of the dM4.5e flare star YZ Canis Minoris obtained in 1993 November with the High Speed Photometer on board the Hubble Space Telescope. The data consist of five 30 minute time sequences with a sampling rate of 0.01 a that were taken through the F240W filter (centered at 240 nm with an 80 nm width). At these wavelengths the stellar photospheric background is small, so relatively small flares can be detected. The observations show a stellar background of 120 counts s(-1) on which are superposed 54 flare events ranging in integrated flux from 2.0 x 10(28) to 3.0. 10(30) ergs, as well as longer term variations with an amplitude of up to 50% of the average continuum intensity and timescales ranging from several minutes to hours. A statistical analysis of this background suggests that it may be composed of unresolved microflaring activity that has an energy distribution considerably steeper than that deduced for the larger flare events. This is consistent with previous observations as well as the self-organized criticality and reconnecting current sheet flare theories. These results are compared with data from the dM8e flare star CN Leonis, which was obtained earlier with the same experimental setup. CN Leo has both a smaller stellar background and a lower hare occurrence rate than YZ CMi The fact that CN Leo also has a quiescent X-ray flux that is less than 10% of the YZ CMi emission suggests a Link between chromospheric and coronal heating. C1 Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Wisconsin, Space Astron Lab, Madison, WI 53706 USA. RP Robinson, RD (reprint author), Catholic Univ Amer, Inst Astrophys & Computat Sci, Washington, DC 20064 USA. RI Carpenter, Kenneth/D-4740-2012 NR 24 TC 20 Z9 20 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 916 EP 923 DI 10.1086/307133 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000036 ER PT J AU Straus, T Severino, G Deubner, FL Fleck, B Jefferies, SM Tarbell, T AF Straus, T Severino, G Deubner, FL Fleck, B Jefferies, SM Tarbell, T TI Observational constraints on models of the solar background spectrum SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; Sun : atmosphere; Sun : granulation; Sun : oscillations ID LINE-PROFILES; P-MODE; OSCILLATIONS; DYNAMICS; ASYMMETRIES; ATMOSPHERE; VELOCITY; SPECTROSCOPY; CHROMOSPHERE; REFLECTION AB We discuss the properties of the solar background signal as observed in high-quality, l - v power and phase difference spectra of the continuum (C), velocity (V), and line intensity (I) fluctuations of the Ni I 6768 Angstrom line. These spectra were generated from high-resolution images acquired by the Michelson Doppler Imager on board SOHO. We confirm that the background signal in the velocity power spectra can be reproduced by a composite model with two quasi-stationary components, describing large-scale and small-scale convective motions, and a periodic component. The line and continuum intensity power spectra require additional quasi-stationary and periodic components. The extra quasi-stationary component dominates the intensity and continuum background signals over the spectral region where the I-V phase difference spectra show essentially constant negative phase difference: i.e., below and in between the p-mode ridges (called the plateau-interridge regime by Deubner et al.). Since the I-V phase between the p-mode ridges is not random, the solar background beneath the p-modes must be considered as coherent. We thus speculate that the negative phase regime may be the manifestation of a correlated background. Such a background has been proposed to explain the opposite sense of the asymmetries of the p-mode line profiles in velocity and brightness oscillations. C1 Osservatorio Astron Capodimonte, I-80131 Naples, Italy. Astron Inst, D-97074 Wurzburg, Germany. NASA, Goddard Space Flight Ctr, ESA, Dept Space Sci, Greenbelt, MD 20771 USA. Natl Solar Observ, Tucson, AZ 85726 USA. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. RP Straus, T (reprint author), Osservatorio Astron Capodimonte, Via Moiarello 16, I-80131 Naples, Italy. RI Fleck, Bernhard/C-9520-2012; OI Straus, Thomas/0000-0002-6280-806X NR 26 TC 25 Z9 25 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP 939 EP 945 DI 10.1086/307140 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FQ UT WOS:000080811000039 ER PT J AU Stapelfeldt, KR Watson, AM Krist, JE Burrows, CJ Crisp, D Ballester, GE Clarke, JT Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT AF Stapelfeldt, KR Watson, AM Krist, JE Burrows, CJ Crisp, D Ballester, GE Clarke, JT Evans, RW Gallagher, JS Griffiths, RE Hester, JJ Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT TI A variable asymmetry in the circumstellar disk of HH 30 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; circumstellar matter; stars : individual (HH 30); stars : pre-main-sequence ID HUBBLE-SPACE-TELESCOPE; T-TAURI-STARS; ACCRETION DISKS; WFPC2; PERFORMANCE; CALIBRATION; SCATTERING; OBJECTS; NEBULA AB We report Hubble Space Telescope observations of variability within the reflection nebulosity of HH 30, a compact bipolar nebula that is a nearly edge-on accretion disk system. A dramatic lateral asymmetry appeared in the upper reflection nebula in the spring of 1998, but was largely absent in 1994 and 1995 images. The variability timescale is much shorter than disk dynamical timescales at the projected radius of the asymmetry, which indicates that its origin is a variable illumination pattern projected onto the outer disk by changes in the inner disk or the central star. Orbital motion of coherent clumps or voids in the inner disk at radii of a few AU might produce such an effect. Another possibility recently proposed is accretion hot spots near the star's magnetic poles which produce broad beams of light sweeping across the disk as the star rotates. Simulated images of a disk illuminated by such a central "lighthouse" are a reasonable match to the bright lateral asymmetry in the upper nebula of HH 30, However, a model with identical opposed hot spots is excluded by the absence of a prominent asymmetry in the lower reflection nebula. Further temporal monitoring of the system is needed to better characterize the nebular variability and establish its physical origin. C1 MS 183 900 Jet Prop Lab, Pasadena, CA 91109 USA. Natl Autonomous Univ Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. 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. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. RP Stapelfeldt, KR (reprint author), MS 183 900 Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 21 TC 39 Z9 39 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 10 PY 1999 VL 516 IS 2 BP L95 EP L98 DI 10.1086/312001 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FV UT WOS:000080811400012 ER PT J AU Strohmayer, TE Markwardt, CB AF Strohmayer, TE Markwardt, CB TI On the frequency evolution of X-ray brightness oscillations during thermonuclear X-ray bursts: Evidence of coherent oscillations SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (4U 1702-429, 4U 1728-34); stars : neutron; stars : rotation; X-rays : bursts ID ACCRETING NEUTRON-STAR AB We investigate the time dependence of the frequency of X-ray brightness oscillations during thermonuclear X-ray bursts from several neutron star low-mass X-ray binaries. We find that the oscillation frequency in the cooling tails of X-ray bursts from 4U 1702-429 and 4U 1728-34 is well described by an exponential "chirp" model. With this model, we demonstrate that the pulse trains in the cooling tails of many bursts are highly phase coherent. We measure oscillation quality factors for the bursts from 4U 1728-34 and 4U 1702-429 as high as Q = upsilon(0)/Delta upsilon(FWHM) similar to 4000. we use this model of the frequency evolution to search sensitively for significant power at the harmonics and first subharmonic of the 330 and 363 Hz signal in the bursts from 4U 1702-429 and 4U 1728-23, respectively, but we find no strong evidence of significant power at any harmonic or the subharmonic. We argue that the high coherence of the oscillations favors stellar rotation as the source of the oscillations. The lack of a subharmonic in the bursts from both 4U 1728-34 and 4U 1702-429 suggests that in these sources, the burst oscillation frequency is indeed the stellar spin frequency. We briefly discuss the frequency evolution in terms of the rotational motion of an angular momentum-conserving thermonuclear shell. We discuss how the limits on harmonic content can be used to infer properties of the neutron star. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Strohmayer, TE (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. EM stroh@clarence.gsfc.nasa.gov; craigm@lheamail.gsfc.nasa.gov NR 21 TC 67 Z9 67 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 10 PY 1999 VL 516 IS 2 BP L81 EP L85 DI 10.1086/312009 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 205FV UT WOS:000080811400009 ER PT J AU Resch, R Baur, C Bugacov, A Koel, BE Echternach, PM Madhukar, A Montoya, N Requicha, AAG Will, P AF Resch, R Baur, C Bugacov, A Koel, BE Echternach, PM Madhukar, A Montoya, N Requicha, AAG Will, P TI Linking and manipulation of gold multinanoparticle structures using dithiols and scanning force microscopy SO JOURNAL OF PHYSICAL CHEMISTRY B LA English DT Article ID COULOMB STAIRCASE; METAL-CLUSTERS; NANOPARTICLES; FABRICATION; NANOSTRUCTURES; LITHOGRAPHY; SI AB Rigid nanoscale 2D structures of up to four individual gold nanoparticles were formed by using bifunctional organic molecules (dithiols) in combination with scanning force microscopy manipulation. These structures can be either precisely translated by mechanical pushing across the surface or rotated about a specific axis. Experimental results are presented that show how simple geometric shapes can be manipulated and assembled to form more complicated structures. The nanoparticles were linked either by (i) forming a multiparticle structure and subsequent treatment with dithiols or by (ii) pushing together individual particles, which were treated with dithiols prior to manipulation. C1 Univ So Calif, Lab Mol Robot, Los Angeles, CA 90089 USA. Univ So Calif, Dept Chem, Los Angeles, CA 90089 USA. Univ So Calif, Dept Mat Sci, Los Angeles, CA 90089 USA. Univ So Calif, Dept Comp Sci, Los Angeles, CA 90089 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Resch, R (reprint author), Univ So Calif, Lab Mol Robot, 947 W 37th Pl, Los Angeles, CA 90089 USA. RI Koel, Bruce/H-3857-2013 OI Koel, Bruce/0000-0002-0032-4991 NR 20 TC 38 Z9 39 U1 1 U2 4 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5647 J9 J PHYS CHEM B JI J. Phys. Chem. B PD MAY 6 PY 1999 VL 103 IS 18 BP 3647 EP 3650 DI 10.1021/jp984508o PG 4 WC Chemistry, Physical SC Chemistry GA 196HW UT WOS:000080303800022 ER PT J AU Greenstadt, J AF Greenstadt, J TI Solution of wave propagation problems by the Cell Discretization method SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article AB The Cell Discretization algorithm (CD) is first applied to a fairly complex steady-state wave scattering problem, and the results compared with the same problem solved by the Finite Element Method. (The p.d.e. solved is the elliptic Helmholtz equation for the components of the complex scattered amplitude.) The method is then directly applied to some hyperbolic problems in space-time, using a total discretization (instead of semi discretization). The problem then becomes one of solving a discretized elliptic equation in successive 'time-slabs' as the process progresses through time. The main difficulty is in choosing the right combination of collocation moments (peculiar to the CD method), intracell polynomials and the 'CFL ratio', i.e., the ratio of the cell length in the time direction to its length(s) in the space direction(s). Apart from this (serious) difficulty, there is little problem in solving several problems involving first and second order wave equations in one and two space dimensions, and one solution of a second order wave equation in two space dimensions. Copious figures are supplied, showing surface plots of the solutions and plots of the spectrum, in the complex plane, of the 'propagation matrix' associated with the problem, are supplied. (C) 1999 Elsevier Science S.A. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Greenstadt, J (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 5 TC 7 Z9 7 U1 0 U2 0 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 4 PY 1999 VL 174 IS 1-2 BP 1 EP 21 DI 10.1016/S0045-7825(98)00274-6 PG 21 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 199LW UT WOS:000080484400001 ER PT J AU Hofmeister, WH Bayuzick, RJ Hyers, R Trapaga, G AF Hofmeister, WH Bayuzick, RJ Hyers, R Trapaga, G TI Cavitation-induced nucleation of zirconium in low earth orbit SO APPLIED PHYSICS LETTERS LA English DT Article AB Liquid-to-solid nucleation experiments on pure zirconium were performed onboard Spacelab. No evidence for fluid flow effects on nucleation was found for maximum flows from 5 to 43 cm s(-1). Evidence for fluid flow effects on nucleation was found at flow velocities above 50 cm s(-1). At this flow velocity and above, the dynamic pressure in the drop exceeds the static pressure, a condition that is known to provide a driving force for cavitation in fluids. Under these conditions undercooling was severely limited. (C) 1999 American Institute of Physics. [S0003-6951(99)00318-6]. C1 Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. MIT, Dept Mat Sci & Engn, Cambridge, MA 02139 USA. RP Hofmeister, WH (reprint author), Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. RI Hyers, Robert/G-3755-2010; OI Hofmeister, William/0000-0002-4145-7061; Trapaga-Martinez, L. Gerardo/0000-0002-6780-5917 NR 10 TC 3 Z9 3 U1 2 U2 4 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 3 PY 1999 VL 74 IS 18 BP 2711 EP 2713 DI 10.1063/1.123945 PG 3 WC Physics, Applied SC Physics GA 190PE UT WOS:000079972400049 ER PT J AU Zak, M AF Zak, M TI Physical invariants of biosignatures SO PHYSICS LETTERS A LA English DT Article AB Biosignature is one of the most important evidences of life available to researchers. However, many complex physical and chemical phenomena can mimic prints of life so closely that special methods are required to make the distinction. In addition to that, life, in principle, can be composed of components which are fundamentally different from those known on Earth. That is why identification of biosignatures should be based upon some phenomenological invariants. Such invariants, within the framework of Newtonian formalism, are introduced and discussed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Ultracomp Grp, Pasadena, CA 91105 USA. RP Zak, M (reprint author), CALTECH, Jet Prop Lab, Ultracomp Grp, M-S 126-346, Pasadena, CA 91105 USA. NR 10 TC 6 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0375-9601 J9 PHYS LETT A JI Phys. Lett. A PD MAY 3 PY 1999 VL 255 IS 1-2 BP 110 EP 118 DI 10.1016/S0375-9601(99)00176-0 PG 9 WC Physics, Multidisciplinary SC Physics GA 193ZT UT WOS:000080168200017 ER PT J AU Forsythe, EL Nadarajah, A Pusey, ML AF Forsythe, EL Nadarajah, A Pusey, ML TI Growth of (101) faces of tetragonal lysozyme crystals: measured growth-rate trends SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID HABIT-CONTROLLING FACTOR; ATOMIC-FORCE MICROSCOPY; PROTEIN CRYSTAL; COMBINATORIAL COMPATIBILITY; MONOMER CONCENTRATIONS; CRYSTALLIZATION; KINETICS; TEMPERATURE; SOLUBILITY; INTERFEROMETRY AB Previous extensive measurements of the growth rates of the (110) face of tetragonal lysozyme crystals have shown unexpected dependencies on the supersaturation. In this study, similar growth-rate measurements were performed for the (101) faces of the crystals. The data show a similar dependence on the supersaturation, becoming appreciable only at high supersaturations, reaching a maximum value and then decreasing. The (101) growth rates are larger at low supersaturations than the (110) growth rates under the same conditions and are smaller at high supersaturations. These trends suggest that the growth mechanism of the (101) face is similar to that of the (110) face: both processes involve the addition of multimeric growth units formed in solution, but the average size of the units for the (101) face is likely to be smaller than for the (110) face. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. NASA, George C Marshall Space Flight Ctr, Biophys Branch ES76, Huntsville, AL 35812 USA. RP Forsythe, EL (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. NR 34 TC 31 Z9 31 U1 0 U2 3 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD MAY PY 1999 VL 55 BP 1005 EP 1011 DI 10.1107/S0907444999002899 PN 5 PG 7 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 198AN UT WOS:000080399700007 PM 10216297 ER PT J AU Li, MR Nadarajah, A Pusey, ML AF Li, MR Nadarajah, A Pusey, ML TI Growth of (101) faces of tetragonal lysozyme crystals: determination of the growth mechanism SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID HABIT-CONTROLLING FACTOR; EGG-WHITE LYSOZYME; COMBINATORIAL COMPATIBILITY; CRYSTALLIZATION; MICROSCOPY; CONSTANTS; RATES; FORM AB Measurements of the macroscopic growth rates of the (101) face of tetragonal lysozyme crystals indicate an unusual dependence on the supersaturation [Forsythe et al. (1999), Acta Cryst. D55, 1005-1011] similar to that observed for the (110) face. As performed previously for the (110) face, the surface packing arrangement for the (101) face was constructed in this study based on earlier microscopic observations and theoretical analysis of the internal molecular packing. This allowed the minimum growth unit for this face to be identified as a tetramer corresponding to a single turn of helices centered about the 4(3) axes and the minimum growth step to be identified as of unimolecular height. A macroscopic mathematical model for the growth of the (101) face was developed based on the reversible formation of multimeric growth units in solution and the addition of a unit to the crystal face by dislocation and two-dimensional nucleation mechanisms. The calculations showed that the best fits were obtained for tetramer or octamer growth units in this model, This and other evidence suggests that while growth may proceed by a variety of growth units, the average size of these units is between that of a tetramer and an octamer. C1 Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. NASA, George C Marshall Space Flight Ctr, Biophys Branch ES76, Huntsville, AL 35812 USA. RP Li, MR (reprint author), Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. NR 22 TC 20 Z9 20 U1 0 U2 2 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD MAY PY 1999 VL 55 BP 1012 EP 1022 DI 10.1107/S0907444999002905 PN 5 PG 11 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 198AN UT WOS:000080399700008 PM 10216298 ER PT J AU Li, HY Perozzo, MA Konnert, JH Nadarajah, A Pusey, ML AF Li, HY Perozzo, MA Konnert, JH Nadarajah, A Pusey, ML TI Determining the molecular-packing arrangements on protein crystal faces by atomic force microscopy SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID TETRAGONAL LYSOZYME CRYSTALS; HABIT-CONTROLLING FACTOR; EGG-WHITE LYSOZYME; IN-SITU; COMBINATORIAL COMPATIBILITY; MACROMOLECULAR CRYSTALS; GROWTH MECHANISMS; VIRUS CRYSTALS; CRYSTALLIZATION; VISUALIZATION AB Previous atomic force microscopy (AFM) studies and periodic bond-chain (PBC) analyses of tetragonal lysozyme crystals have suggested that the (110) face consists of chains of molecules related to one another by 4(3) axes parallel to the crystal face. In this study, high-resolution AFM images of the (110) face were obtained and analyzed in order to verify this prediction. A computer program was employed which constructs the theoretical AFM image corresponding to a specific crystallographic molecular-packing arrangement and AFM tip shape. The packing arrangement and tip shape were varied in order to obtain the maximum possible correlation between experimental and theoretical images. The prediction from PBC analysis of an arrangement involving 4(3) helices was confirmed in this manner, while the alternate arrangement, consisting of molecules related to one another by 2(1) axes, was not observed. However, the surface structure was found to differ significantly even from this crystallographic arrangement. The molecules were found to pack slightly closer about what will become the 4(3) axes within the interior of the crystal, suggesting the occurrence of surface reconstruction or rearrangement on the tetragonal lysozyme (110) face. This study represents a new approach for more precise determination of the molecular-packing arrangements on protein crystal faces employing AFM. C1 Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. USN, Res Lab, Lab Struct Matter 6030, Washington, DC 20375 USA. NASA, George C Marshall Space Flight Ctr, Biophys Branch ES76, Huntsville, AL 35812 USA. RP Li, HY (reprint author), Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. NR 37 TC 29 Z9 31 U1 0 U2 1 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD MAY PY 1999 VL 55 BP 1023 EP 1035 DI 10.1107/S090744499900339X PN 5 PG 13 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 198AN UT WOS:000080399700009 PM 10216299 ER PT J AU Li, HY Nadarajah, A Pusey, ML AF Li, HY Nadarajah, A Pusey, ML TI Determining the molecular-growth mechanisms of protein crystal faces by atomic force microscopy SO ACTA CRYSTALLOGRAPHICA SECTION D-BIOLOGICAL CRYSTALLOGRAPHY LA English DT Article ID TETRAGONAL LYSOZYME CRYSTALS; ANGLE NEUTRON-SCATTERING; HABIT-CONTROLLING FACTOR; COMBINATORIAL COMPATIBILITY; MONOMER CONCENTRATIONS; VIRUS CRYSTALS; CRYSTALLIZATION; KINETICS; MORPHOLOGY; PHOTOLYSIS AB A high-resolution atomic force microscopy (AFM) study has shown that the molecular packing on the tetragonal lysozyme (110) face corresponds to only one of two possible packing arrangements, suggesting that growth layers on this face are of bimolecular height [Li et al. (1999). Acta Cryst. D55, 1023-1035]. Theoretical analyses of the packing also indicated that growth of this face should proceed by the addition of growth units of at least tetramer size, corresponding to the 4(3) helices in the crystal. In this study, an AFM linescan technique was used to measure the dimensions of individual growth units on protein crystal faces as they were being incorporated into the lattice. Images of individual growth events on the (110) face of tetragonal lysozyme crystals were observed, shown by jump discontinuities in the growth step in the linescan images. The growth-unit dimension in the scanned direction was obtained from these images. A large number of scans in two directions on the (110) face were performed and the distribution of lysozyme growth-unit sizes were obtained. A variety of unit sizes corresponding to 4(3) helices were shown to participate in the growth process, with the 4(3) tetramer being the minimum observed size. This technique represents a new application for AFM, allowing time-resolved studies of molecular processes to be carried out. C1 Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. NASA, George C Marshall Space Flight Ctr, Biophys Branch ES76, Huntsville, AL 35812 USA. RP Li, HY (reprint author), Univ Toledo, Dept Chem & Environm Engn, Toledo, OH 43606 USA. NR 39 TC 36 Z9 36 U1 0 U2 1 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0907-4449 J9 ACTA CRYSTALLOGR D JI Acta Crystallogr. Sect. D-Biol. Crystallogr. PD MAY PY 1999 VL 55 BP 1036 EP 1045 DI 10.1107/S0907444999003388 PN 5 PG 10 WC Biochemical Research Methods; Biochemistry & Molecular Biology; Biophysics; Crystallography SC Biochemistry & Molecular Biology; Biophysics; Crystallography GA 198AN UT WOS:000080399700010 PM 10216300 ER PT J AU Blosiu, JO AF Blosiu, JO TI Breakthrough technology development on demand SO AEROSPACE AMERICA LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Blosiu, JO (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU 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 1999 VL 37 IS 5 BP 56 EP 58 PG 3 WC Engineering, Aerospace SC Engineering GA 192CV UT WOS:000080061400027 ER PT J AU Roberts, DP Kobayashi, DY Dery, PD Short, NM AF Roberts, DP Kobayashi, DY Dery, PD Short, NM TI An image analysis method for determination of spatial colonization patterns of bacteria in plant rhizosphere SO APPLIED MICROBIOLOGY AND BIOTECHNOLOGY LA English DT Article ID ENTEROBACTER-CLOACAE; BIOCONTROL; BIOLUMINESCENCE; RHIZOBACTERIUM; PATHOGENS; POTATO AB A method that allows the rapid visualization of bacterial spatial colonization patterns on roots for the determination of general colonization trends was developed. This method, which analyzes images of roots, and bioluminescence-enhanced images of bacterial colonization patterns on these roots, was used to study the colonization patterns of seed-applied Enterobacter cloncae strain E6 on 3-day-old cucumber plants. Conventional dilution-plating methods indicated that E6 colonized cucumber tap roots in high populations and that these populations significantly decreased as the distance from the seed increased. In addition to confirming these observations, image analysis indicated that colonization by E6 significantly decreased on lateral roots as the distance increased horizontally away from the tap root, and that this bacterium did not evenly cover the most densely colonized regions of the cucumber root system. Results from these experiments indicate that the majority of E6 populations on cucumber roots after seed application are limited to the upper regions of the tap root and that E6 does not effectively colonize other regions of the root system. C1 USDA ARS, Biocontrol Plant Dis Lab, Beltsville, MD 20705 USA. Rutgers State Univ, Cook Coll, Dept Plant Pathol, New Brunswick, NJ 08901 USA. NASA, Goddard Space Flight Ctr, Informat Sci & Technol Branch, Greenbelt, MD 20771 USA. RP Roberts, DP (reprint author), USDA ARS, Biocontrol Plant Dis Lab, Beltsville, MD 20705 USA. NR 16 TC 13 Z9 20 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0175-7598 J9 APPL MICROBIOL BIOT JI Appl. Microbiol. Biotechnol. PD MAY PY 1999 VL 51 IS 5 BP 653 EP 658 PG 6 WC Biotechnology & Applied Microbiology SC Biotechnology & Applied Microbiology GA 206TK UT WOS:000080895200016 ER PT J AU Vancil, BK Mueller, RA Steele, ER Ohlinger, WL Wintucky, EG AF Vancil, BK Mueller, RA Steele, ER Ohlinger, WL Wintucky, EG TI The metallurgical properties of tungsten-iridium cathodes SO APPLIED SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 2nd International Vacuum Electron Sources Conference 1998 (IVESC 98) CY JUL 07-10, 1998 CL TSUKUBA, JAPAN DE cathode; dispenser cathode; tungsten-iridium; metallurgical properties; mixed metal matrix; micrographs AB The results of an investigation of the effects of fabrication parameters in die-pressing of tungsten-iridium cathode matrix materials up to phi 0.130 in. (3.3 mm) in diameter are reported. Tungsten-iridium matrix cathodes offer important performance advantages over 'M' cathodes, but their performance has often been erratic and unpredictable. This investigation relies on use of metallographic techniques to easily observe and characterize microstructural properties, such as pore size, distribution and density, as well as area and distribution of different phases. Data and micrographs are presented for five cathode matrix variants, along with limited emission testing results. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 FDE Associates, Beaverton, OR 97008 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Vancil, BK (reprint author), FDE Associates, 21070 SW Tile Flat Rd, Beaverton, OR 97008 USA. NR 2 TC 3 Z9 3 U1 1 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-4332 J9 APPL SURF SCI JI Appl. Surf. Sci. PD MAY PY 1999 VL 146 IS 1-4 BP 39 EP 46 DI 10.1016/S0169-4332(99)00063-X PG 8 WC Chemistry, Physical; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Chemistry; Materials Science; Physics GA 203DJ UT WOS:000080692100008 ER PT J AU Mueller, W Dewan, HS Chen, H Mearini, GT Krainsky, IL AF Mueller, W Dewan, HS Chen, H Mearini, GT Krainsky, IL TI Field emission from gated diamond arrays SO APPLIED SURFACE SCIENCE LA English DT Article; Proceedings Paper CT 2nd International Vacuum Electron Sources Conference 1998 (IVESC 98) CY JUL 07-10, 1998 CL TSUKUBA, JAPAN DE gated field emitter; cold cathode; field emission array; diamond ID EMITTERS; TIPS; FABRICATION; CATHODES; CONES AB Diamond field emitter arrays have been developed for use as cold electron sources in fiat panel displays and high-power tubes. Diamond was selectively deposited on patterned silicon wafers, and the common problems of field emission from the gate and the walls have been solved by innovative modifications in the processes involved. This resulted in cathodes where the gate area was completely for of diamond. The leakage currents were less than 8% of the total current. The diamond cathodes were tested in two different diode configurations in a UHV system for voltages ranging from 0-20 V. Field emission has been achieved at ultra-low onset voltages of less than 0.25 V and very high currents were obtained. For a voltage of 3 V applied to the gate, for example, corresponding to an electric field of 1.5 V/mu m, emission currents of up to 1 mA have been observed and tested for several days without deterioration. At 7 V, a current of 3.5 mA was achieved in this configuration. The onset of field emission for measurements to a flat anode was 0.5 V/mu m, and 3.5 mA were reached at 0.8 V/mu m. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Res 2000, Westlake, OH 44145 USA. Gen Vacuum, Highland Hts, OH 44143 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Mueller, W (reprint author), Res 2000, Westlake, OH 44145 USA. NR 25 TC 3 Z9 5 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-4332 J9 APPL SURF SCI JI Appl. Surf. Sci. PD MAY PY 1999 VL 146 IS 1-4 BP 328 EP 333 DI 10.1016/S0169-4332(99)00151-8 PG 6 WC Chemistry, Physical; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Chemistry; Materials Science; Physics GA 203DJ UT WOS:000080692100057 ER PT J AU Witteborn, FC Cohen, M Bregman, JD Wooden, DH Heere, K Shirley, EL AF Witteborn, FC Cohen, M Bregman, JD Wooden, DH Heere, K Shirley, EL TI Spectral irradiance calibration in the infrared. XI. Comparison of alpha Bootis and 1 Ceres with a laboratory standard SO ASTRONOMICAL JOURNAL LA English DT Article DE infrared radiation; minor planets, asteroids; stars : individual (alpha Bootis); techniques : spectroscopic ID SPECTROSCOPY; ASTEROIDS; VESTA AB Infrared spectra of two celestial objects frequently used as flux standards are calibrated against an absolute laboratory flux standard at a spectral resolving power of 100 to 200. The spectrum of the K1.5 III star alpha Boo is measured from 3 to 30 mu m, and that of the C-type asteroid 1 Ceres from 5 to 30 mu m. While these "standard" spectra do not have the apparent precision of those based on calculated models, they do not require the assumptions involved in theoretical models of stars and asteroids. Specifically, they provide a model-independent means of calibrating celestial flux in the spectral range from 12 to 30 mu m, where accurate absolute photometry is not available. The agreement found between the spectral shapes of alpha Boo and Ceres based on laboratory standards and those based on observed ratios to alpha CMa (Sirius) and alpha Lyr (Vega), flux-calibrated by theoretical modeling of these hot stars, strengthens our confidence in the applicability of the stellar models as primary irradiance standards. C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Vanguard Res Inc, Scotts Valley, CA 95066 USA. Univ Calif Berkeley, Radio Astron Lab, Berkeley, CA 94720 USA. Natl Inst Stand & Technol, Opt Technol Div, Gaithersburg, MD 20899 USA. RP Witteborn, FC (reprint author), NASA, Ames Res Ctr, SETI Inst, Mail Stop 245-6, Moffett Field, CA 94035 USA. NR 17 TC 25 Z9 25 U1 1 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD MAY PY 1999 VL 117 IS 5 BP 2552 EP 2560 DI 10.1086/300850 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 201XB UT WOS:000080621200040 ER PT J AU Zand, JJMI Verbunt, F Strohmayer, TE Bazzano, A Cocchi, M Heise, J van Kerkwijk, MH Muller, JM Natalucci, L Smith, MJS Ubertini, P AF Zand, JJMI Verbunt, F Strohmayer, TE Bazzano, A Cocchi, M Heise, J van Kerkwijk, MH Muller, JM Natalucci, L Smith, MJS Ubertini, P TI A new X-ray outburst in the globular cluster NGC 6440: SAX J1748.9-2021 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE X-rays : stars; X-rays : bursts; Galaxy : globular clusters : individual : NGC 6440; stars : neutron; stars : individual : SAX J1748.9-2021; stars : individual : MX 1746-20 ID PROPORTIONAL COUNTER; ASTRONOMY SATELLITE; ON-BOARD; PULSAR; EMISSION; BINARIES; NGC-6652; SPECTRUM; BURSTS; LIGHT AB For the second time in 27 years a bright transient X-ray source has been detected coincident with the globular cluster NGC 6440. It was found to be active in August, 1998, with the Wide Field Camera and the narrow field instruments on the BeppoSAX spacecraft, and with the All-Sky Monitor and the Proportional Counter Array on the RossiXTE spacecraft. Four X-ray bursts were detected, at least one of which shows the characteristics of a thermonuclear flash on a neutron star, in analogy with some similar to 20 optically identified low-mass X-ray binaries. The broad-band spectrum is hard as is common among low-mass X-ray binaries of lower luminosity (less than or similar to 10(37) erg s(-1)) and can be explained by a Comptonized model. During the burst the > 30 keV emission brightened, consistent with part of the burst emission being Compton up scattered within similar to 10(11) cm. C1 Space Res Org Netherlands, NL-3584 TA Utrecht, Netherlands. Astron Inst, NL-3508 TA Utrecht, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CNR, Inst Astrophys Spaziale, Area Ricerca Roma Tor Vergata, I-00133 Rome, Italy. Nuova Telespazio, BeppoSAX Sci Data Ctr, I-00131 Rome, Italy. Nuova Telespazio, BeppoSAX Sci Operat Ctr, I-00131 Rome, Italy. RP Space Res Org Netherlands, Sorbonnelaan 2, NL-3584 TA Utrecht, Netherlands. EM jeanz@sron.nl NR 51 TC 74 Z9 74 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 MAY PY 1999 VL 345 IS 1 BP 100 EP 108 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195UL UT WOS:000080270500017 ER PT J AU Vink, JS Heap, SR Sweigart, AV Lanz, T Hubeny, I AF Vink, JS Heap, SR Sweigart, AV Lanz, T Hubeny, I TI Hot stellar population synthesis from the UV spectrum: the globular cluster M79 (NGC 1904) SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE ultraviolet : stars; ultraviolet : general; stars : evolution; stars : Hertzsprung-Russel (HR) and C-M diagrams; stars : horizontal-branch; galaxy : globular clusters : individual : M79 ID HORIZONTAL-BRANCH; PHOTOGRAPHIC PHOTOMETRY; ELLIPTIC GALAXIES; NGC-1904; STARS; GIANT; MORPHOLOGY; NGC-6752; CORES AB We have analyzed the far UV-spectrum of the globular cluster M79. We show that the nearly Gaussian mass distribution of zero-age horizontal-branch stars, as derived by Dixon et al. (1996), is able to reproduce the far-UV Hopkins Utraviolet Telescope (HUT) spectrum, if there is a luminous UV-bright star of about T-eff = 9,500 K within the HUT entrance slit, or, more likely, if the horizontal branch morphology becomes considerably redder in the core of M79, as observed in some other centrally condensed globular clusters. Agreement between the synthetic and observed far-UV spectra for M79 would also be improved if the surface abundances of the heavy elements in the hot horizontal-branch stars were enhanced by radiative diffusion. Contrary to Dixon et al. (1996) we do not need extremely low gravities to reproduce the width of Ly alpha. C1 Univ Utrecht, Astron Inst, NL-3584 CA Utrecht, Netherlands. Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Vink, JS (reprint author), Univ Utrecht, Astron Inst, Princetonplein 5, NL-3584 CA Utrecht, Netherlands. EM j.s.vink@astro.uu.nl NR 26 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 MAY PY 1999 VL 345 IS 1 BP 109 EP 116 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195UL UT WOS:000080270500018 ER PT J AU Wang, JCL Link, B Van Riper, K Arnaud, KA Miralles, JA AF Wang, JCL Link, B Van Riper, K Arnaud, KA Miralles, JA TI RX J0720.4-3125: Implications for neutron star cooling and the dense matter equation of state SO ASTRONOMY & ASTROPHYSICS LA English DT Review DE stars : neutron; stars : evolution; stars : magnetic; fields; dense matter; X-rays : stars; stars : individual : RX J0720.4-3125 ID MAGNETIC-FIELD DECAY; DIRECT URCA PROCESS; X-RAY; THERMAL EVOLUTION; MODEL ATMOSPHERES; SURFACE-TEMPERATURE; ROSAT OBSERVATIONS; COMPACT STARS; VELA PULSAR; SPIN-DOWN AB The soft X-ray source RX J0720.4-3125 appears to be a clean example of a cooling neutron star. Its X-ray emission is well-fit by a 79 +/- 4 eV blackbody and displays a periodic modulation with period P = 8.391 sec and semi-amplitude similar to 10%. The observational upper limit to the period derivative implies a minimum spindown age of t(0) = 1.7 x 10(5) yr if the star was born rapidly rotating. The absence of a visible supernova remnant independently suggests an age for this source of greater than or similar to 10(5) yr. With the interpretation of this source as a cooling-driven, magnetized, rotating neutron star, we explore the implications for the dense matter equation of state (EOS), the mode of energy loss (modified URCA vs. direct URCA), and the rate of internal heating due to superfluid friction. For the standard (modified URCA) cooling models, we study two types of stars: those born slowly rotating, with relatively small spindown rates and conventional dipole magnetic fields (similar to 10(12) G), and those born rapidly rotating with large spin-down rates and. magnetar-scale dipole fields (similar to 10(14) G). We find that standard cooling with a stiff or moderately stiff EOS is consistent with the observations of RX J0720.4-3125 provided the star's age is less than or similar to 3 t(0) = 5 x 10(5) yr. If the EOS is very stiff, the star must be born with a short rotation period and significant internal heating by superfluid friction is required. More moderate heating suffices only if the star is very massive (similar to 2 M.) and has an age similar to t(0) Stars with M similar to 1.4 M. and a moderately stiff EOS give modulations about a factor of five below that observed. However, the inclusion of atmospheric effects or more complex field geometries could increase the modulation to a level consistent with the observations. Stars with a stiff EOS give modulations close to that observed. As an illustration of the effects of accelerated cooling processes, we consider direct quark URCA cooling. We find that these models cool too fast and are cleanly ruled put for this source. Hence, exotic matter is an insignificant component in the stellar core, or does not participate in accelerated cooling. Direct URCA reactions in nucleonic matter are similarly ruled out. A measure of RX J0720.4-3125's spin-down age would afford crucial tests of our conclusions. C1 Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. White Rock Sci, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Valencia, Dept Astron & Astrofis, Valencia, Spain. RP Link, B (reprint author), Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. EM blink@dante.physics.montana.edu NR 110 TC 6 Z9 6 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 EI 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD MAY PY 1999 VL 345 IS 3 BP 869 EP 883 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 200FC UT WOS:000080528100022 ER PT J AU Kinney, WH Riotto, A AF Kinney, WH Riotto, A TI Dynamical supersymmetric inflation SO ASTROPARTICLE PHYSICS LA English DT Article ID COSMOLOGICAL PERTURBATIONS; DENSITY PERTURBATIONS; UNIVERSE SCENARIO; SCALE; BREAKING; FLATNESS; HORIZON AB We propose a new class of inflationary models in which the scalar field potential governing inflation is generated by the same nonperturbative gauge dynamics that may lead to supersymmetry breaking. Such models satisfy constraints from cosmic microwave background measurements for natural values of the fundamental parameters in the theory. In addition, they have two particularly interesting characteristics: a "blue" spectrum of scalar perturbations, and an upper bound on the total amount of inflation possible. (C) 1999 Elsevier Science B.V. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. EM kinneyw@fnal.gov; riotto@fnas01.fnal.gov NR 25 TC 30 Z9 30 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 EI 1873-2852 J9 ASTROPART PHYS JI Astropart Phys. PD MAY PY 1999 VL 10 IS 4 BP 387 EP 395 DI 10.1016/S0927-6505(98)00057-7 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 194RA UT WOS:000080206300011 ER PT J AU Carr, BJ Sakellariadou, M AF Carr, BJ Sakellariadou, M TI Dynamical constraints on dark matter in compact objects SO ASTROPHYSICAL JOURNAL LA English DT Review DE black hole physics; dark matter; galaxies : star clusters ID MASSIVE BLACK-HOLES; VELOCITY-DISPERSION-RELATION; LIGHT-ELEMENT NUCLEOSYNTHESIS; BIG-BANG NUCLEOSYNTHESIS; LARGE-MAGELLANIC-CLOUD; POPULATION-III STARS; LYMAN-ALPHA FOREST; GALACTIC DISK; GLOBULAR-CLUSTERS; DEUTERIUM ABUNDANCE AB Many of the baryons in the universe are dark and at least some of the dark baryons could be in the form of compact objects. Such objects could be in various locations-galactic disks, galactic halos, clusters of galaxies, or intergalactic space-and each of these is associated with a dark matter problem. For each site we consider the various dynamical constraints that can be placed on the fraction of the dark matter in compact objects of different mass. Small compact objects in the Galaxy are constrained by upper limits on their encounter rate with the Earth and solar system since they would resemble meteors or comets. Larger objects are constrained by the disruptive or disturbing effects they would have on various astronomical systems. For disk objects, time most interesting constraints come from the disruption of binary stars or open star clusters. For halo objects, they come from the disruption of globular clusters, the heating of the Galactic disk, and their accumulation in the Galactic nucleus as a result of dynamical friction. For cluster objects, they come from the tidal distortion and disruption of galaxies. For intergalactic objects, they come from the upper limit on the peculiar motions induced in galaxies. We also apply these limits to the situation in which the compact objects are clusters of smaller objects. C1 Queen Mary Univ London, Astron Unit, London E1 4NS, England. NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Geneva, Dept Phys Theor, CH-1211 Geneva 4, Switzerland. RP Carr, BJ (reprint author), Queen Mary Univ London, Astron Unit, Mile End Rd, London E1 4NS, England. NR 176 TC 38 Z9 38 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP 195 EP 220 DI 10.1086/307071 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NX UT WOS:000080660000017 ER PT J AU Watanabe, K Hartmann, DH Leising, MD The, LS AF Watanabe, K Hartmann, DH Leising, MD The, LS TI The diffuse gamma-ray background from supernovae SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; gamma rays : observations; supernovae : general ID STAR-FORMATION RATE; HUBBLE DEEP FIELD; COSMIC X-RAY; LUMINOSITY FUNCTION; IA SUPERNOVAE; EVOLUTION; EMISSION; UNIVERSE; DENSITY; MODELS AB The diffuse extragalactic gamma-ray background in the MeV region is believed to be due to photons from radioactivity produced in supernovae throughout the history of galaxies in the universe. In particular, gamma-ray line emission from the decay chain Ni-56 --> Co-56 --> Fe-56 provides the dominant photon source (Clayton & Silk). Although iron synthesis occurs in all types of supernovae, the contribution to the background is dominated by Type Ia events due to their higher photon escape probabilities. Estimates of the star formation history in the universe suggest a rapid increase by a factor similar to 10 from the present to a redshift z(p) similar to 1.5, beyond which it either remains constant or decreases slowly. Little is known about the cosmological star formation history for redshift exceeding z similar to 5. We integrate the observed star formation history to determine the cosmic gamma-ray background (CGB) from the corresponding supernova rate history. In addition to gamma-rays from short-lived radioactivity in Type Ia supernovae (SN Ia's) and Type II, Ib, and Ic supernovae (SN II's, SN Ib's, SN Ic's) we also calculate the minor contributions from long-lived radioactivities (Al-26, Ti-44, Co-60, and electron-positron pair annihilation). The time-integrated gamma-ray spectrum of model W10HMM (Pinto & Woosley) was used as a template for Type II supernovae, and for SN Ia's we employ model W7 (Nomoto et al.). Although progenitor evolution for Type Ia supernovae is not yet fully understood, various arguments suggest delays of order 1-2 Gyr between star formation and the production of SN Ia's. The effect of this delay on the CCB is discussed. We emphasize the value of gamma-ray observations of the CGB in the MeV range as an independent tool for studies of the cosmic star formation history. If the delay between star formation and SN Ia activity exceeds 1 Gyr substantially and/or the peak of the cosmic star formation rate occurs at a redshift much larger than unity, the gamma-ray production of SN Ia's would be insufficient to explain the observed CGB and a so far undiscovered source population would be implied. Alternatively, the cosmic star formation rate would have to be higher (by a factor 2-3) than commonly assumed, which is in accord with several upward revisions reported in the recent literature. C1 NASA, Goddard Space Flight Ctr, USRA, LHEA, Greenbelt, MD 20771 USA. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. RP Watanabe, K (reprint author), NASA, Goddard Space Flight Ctr, USRA, LHEA, Code 660-2, Greenbelt, MD 20771 USA. NR 66 TC 55 Z9 55 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP 285 EP 296 DI 10.1086/307110 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NX UT WOS:000080660000025 ER PT J AU Thompson, DJ Bailes, M Bertsch, DL Cordes, J D'Amico, N Esposito, JA Finley, J Hartman, RC Hermsen, W Kanbach, G Kaspi, VM Kniffen, DA Kuiper, L Lin, YC Lyne, A Manchester, R Matz, SM Mayer-Hasselwander, HA Michelson, PF Nolan, PL Ogelman, H Pohl, M Ramanamurthy, PV Sreekumar, P Reimer, O Taylor, JH Ulmer, M AF Thompson, DJ Bailes, M Bertsch, DL Cordes, J D'Amico, N Esposito, JA Finley, J Hartman, RC Hermsen, W Kanbach, G Kaspi, VM Kniffen, DA Kuiper, L Lin, YC Lyne, A Manchester, R Matz, SM Mayer-Hasselwander, HA Michelson, PF Nolan, PL Ogelman, H Pohl, M Ramanamurthy, PV Sreekumar, P Reimer, O Taylor, JH Ulmer, M TI Gamma radiation from PSR B1055-52 SO ASTROPHYSICAL JOURNAL LA English DT Review DE gamma rays : observations; pulsars : individual (PSR B1055-52) ID SPIN-POWERED PULSARS; HIGH-ENERGY EMISSION; X-RAY-EMISSION; CRAB PULSAR; EGRET OBSERVATIONS; VELA PULSAR; ROSAT OBSERVATIONS; GEMINGA PULSAR; GALACTIC PLANE; RADIO PULSARS AB The telescopes on the Compton Gamma Ray Observatory (CGRO) have observed PSR B1055-52 a number of times between 1991 and 1998. From these data a more detailed picture of the gamma radiation from this source has been developed, showing several characteristics that distinguish this pulsar: the light curve is complex; there is no detectable unpulsed emission; the energy spectrum is hat, with no evidence of a sharp high-energy cutoff up to greater than 4 GeV. Comparisons of the gamma-ray data with observations at longer wavelengths show that no two of the known gamma-ray pulsars have quite the same characteristics; this diversity males interpretation in terms of theoretical models difficult. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Swinburne Univ Technol, Hawthorn, Vic 3122, Australia. Cornell Univ, Dept Phys, Ithaca, NY 14853 USA. Osservatorio Astron Bologna, I-40126 Bologna, Italy. Purdue Univ, Dept Phys, Lafayette, IN USA. SRON, NL-3584 CA Utrecht, Netherlands. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. MIT, Dept Phys, Cambridge, MA 02139 USA. Hampden Sydney Coll, Dept Phys, Hampden Sydney, VA 23943 USA. Stanford Univ, WW Hansen Labs Phys, Stanford, CA 94305 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Univ Manchester, Nuffield Radio Astron Labs, Jodrell Bank, Macclesfield SK11 9DL, Cheshire, England. CSIRO, ATNF, Epping, NSW, Australia. Northwestern Univ, Dept Phys, Evanston, IL 60208 USA. Univ Wisconsin, Dept Phys, Madison, WI 53706 USA. Danish Space Res Inst, Copenhagen 2100 O, Denmark. Princeton Univ, Dept Phys, Princeton, NJ 08544 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. EM djt@egret.gsfc.nasa.gov RI Nolan, Patrick/A-5582-2009; D'Amico, Nichi/A-5715-2009; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013 OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385 NR 108 TC 119 Z9 120 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP 297 EP 306 DI 10.1086/307083 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NX UT WOS:000080660000026 ER PT J AU Stothers, RB AF Stothers, RB TI A semiempirical test for dynamical instability in luminous blue variables SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (P Cygni); stars : oscillations; stars : variables : other (luminous blue variables) ID WOLF-RAYET STARS; LARGE MAGELLANIC CLOUD; P-CYGNI; MASSIVE STARS; O-STARS; ABUNDANCES; SPECTRUM; WIND AB By employing as input parameters only observationally determined stellar surface quantities, detailed envelope models for six well-observed luminous blue variables at quiescence are constructed and tested for marginal dynamical instability. The best-observed of these objects, P Cyg, proves to be exactly in a state of marginal dynamical instability, just as predicted. Within the larger observational errors estimated for the five other objects, they too are probably in the same marginally unstable state as P Cyg. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stothers, RB (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 27 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP 366 EP 368 DI 10.1086/307117 PN 1 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NX UT WOS:000080660000033 ER PT J AU Teplitz, VL Stern, SA Anderson, JD Rosenbaum, D Scalise, RJ Wentzler, P AF Teplitz, VL Stern, SA Anderson, JD Rosenbaum, D Scalise, RJ Wentzler, P TI Infrared Kuiper belt constraints SO ASTROPHYSICAL JOURNAL LA English DT Article DE comets : general; interplanetary medium; solar system : general ID SOLAR-SYSTEM; DUST; PARTICLES; ACCRETION; EMISSION; NEPTUNE; GRAINS; COMETS; ORBIT; DISK AB We compute the temperature and IR signal of particles of radius a and albedo a at heliocentric distance R, taking into account the emissivity effect, and give are interpolating formula for the result. We compare with analyses of COBE DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance R, particle radius a, and particle albedo a. We then apply these results to a recently developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40 < R < 50-90 AU) and a more distant sector with a, higher density. We consider the case in which passage through a molecular cloud essentially cleans the solar system of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally, we compare Kuiper belt IR spectra for various parameter values. Results of this work include: (1) numerical limits on Kuiper belt dust as a function of (R, a, alpha) on the basis of four alternative sets of constraints, including those following from recent discovery of the cosmic IR background by Hauser et al.; (2) application to the two-sector Kuiper belt model, finding mass limits and spectrum shape for different values of relevant parameters including dependence on time elapsed since last passage through a molecular cloud cleared the outer solar system of dust; and (3) potential use of spectral information to determine time since last passage of the Sun through a giant molecular cloud. C1 So Methodist Univ, Dept Phys, Dallas, TX 75275 USA. SW Res Inst, Boulder, CO 80302 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Teplitz, VL (reprint author), So Methodist Univ, Dept Phys, Dallas, TX 75275 USA. NR 34 TC 29 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP 425 EP 435 DI 10.1086/307084 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NX UT WOS:000080660000040 ER PT J AU Bhatia, AK Kastner, SO AF Bhatia, AK Kastner, SO TI The optically thick Fe XVII spectrum: X-ray, extreme-ultraviolet and forbidden line ratios SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic processes; Sun : flares; Sun : UV radiation ID NEON ISOELECTRONIC SEQUENCE; ACTIVE-REGION; ATOMIC DATA; ELEMENTAL ABUNDANCES; INTENSITIES; TRANSITIONS; EXCITATION; EMISSION; OPACITY; DENSITY AB Level populations, X-ray line fluxes, and extreme-ultraviolet (EUV) line intensities are calculated for a 37 level model of the Fe XVII ion, as functions of the column density of Fe XVII, in slab geometry and cylindrical geometry. The resonance lines at 15.02 and 15.25 Angstrom are found to exhibit initial increases in fluxes relative to the forbidden line at 17.10 Angstrom and the usual reference resonance line at 16.78 Angstrom as optical thickness increases. Eleven EUV lines and the forbidden 2p(5)3s(P-3(0)-P-3(1)) transition near 1154 Angstrom are also found to be relatively enhanced by opacity. 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, Mail Code 682,Greenbelt Rd, Greenbelt, MD 20771 USA. NR 31 TC 29 Z9 29 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP 482 EP 489 DI 10.1086/307085 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NX UT WOS:000080660000045 ER PT J AU Hudgins, DM Allamandola, LJ AF Hudgins, DM Allamandola, LJ TI Interstellar PAH emission in the 11-14 micron region: New insights from laboratory data and a tracer of ionized PAHs SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : lines and bands; ISM : molecules; molecular data ID POLYCYCLIC AROMATIC-HYDROCARBONS; INFRARED-SPECTROSCOPY; DARK CLOUD; SPECTRA; CATIONS; NAPHTHALENE; MOLECULES; BANDS; TEMPERATURE; HYPOTHESIS AB The Ames infrared spectral database of isolated, neutral and ionized polycyclic aromatic hydrocarbons (PAHs) shows that aromatic CH out-of-plane bending frequencies are significantly shifted upon ionization. For solo- and duet-CH groups, the shift is pronounced and consistently toward higher frequencies. The solo-CH modes are blueshifted by an average of 27 cm(-1) and the duet-CH modes by an average of 17cm(-1). For trio- and quartet CH groups, the ionization shifts of the out-of-plane modes are more erratic and typically more modest. As a result of these ionization shifts, the solo-CH out-of-plane modes move out of the region classically associated with these vibrations in neutral PAHs, falling instead at frequencies well above those normally attributed to out-of-plane bending vibrations of any type. In addition, for the compact PAHs studied, the duet-CH out-of-plane modes are shifted into the frequency range traditionally associated with the solo-CH modes. These results refine our understanding of the origin of the dominant interstellar infrared emission feature near 11.2 mu m, whose envelope has traditionally been attributed only to the out-of-plane bending of solo-CH groups on PAHs, and provide a natural explanation for the puzzling emission feature near 11.0 mu m within the framework of the PAH model. Specifically, the prevalent but variable long-wavelength wing or shoulder that is often observed near 11.4 mu m likely reflects the contributions of duet-CH units in PAH cations. Also, these results indicate that the emission between 926 and 904 cm(-1) (10.8 and 11.1 mu m) observed in many sources can be unambiguously attributed to the out-of-plane wagging of solo-CH units in moderately sized (fewer than 50 carbon atom) PAH cations, making this emission an unequivocal tracer of ionized interstellar PAHs. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hudgins, DM (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. NR 37 TC 93 Z9 93 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD MAY 1 PY 1999 VL 516 IS 1 BP L41 EP L44 DI 10.1086/311989 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202NZ UT WOS:000080660200011 PM 11543063 ER PT J AU Bloom, SD Marscher, AP Moore, EM Gear, W Terasranta, H Valtaoja, E Aller, HD Aller, MF AF Bloom, SD Marscher, AP Moore, EM Gear, W Terasranta, H Valtaoja, E Aller, HD Aller, MF TI Multiwaveband observations of quasars with flat radio spectra and strong millimeter-wave emission SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE quasars : general; radio continuum : galaxies; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRA; COMPACT NONTHERMAL SOURCES; BL-LACERTAE OBJECTS; COMPLETE SAMPLE; RELATIVISTIC JETS; S5 SURVEY; 3C 345; VLBI; BLAZARS AB We present multiwaveband observations of a well-selected sample of 28 quasars and two radio galaxies with flat radio spectra and strong millimeter-wave emission (referred to here as FSRQs). The data are analyzed to determine the radio to infrared and X-ray to gamma-ray properties of FSRQs and the relationships between them. Specifically, the synchrotron. self-Compton (SSC) process is examined as a likely common radiation mechanism. For most sources, the broadband spectra are still incomplete, especially in the far-infrared and ultraviolet range. Therefore, precise analysis, such as model fitting of spectra, is not usually possible. To compensate partially for this, we have taken a statistical approach and examine the relationship between high- and low-energy emission by using the data set for the entire sample. We use very long baseline interferometry (VLBI) at 8.4 and 22 GHz--higher frequencies than those of previous surveys - in conjunction with nearly simultaneous radio to submillimeter-wave observations to determine the parameters of the synchrotron spectrum and to examine the compact angular structure of a subset of sources from our sample. These parameters are used to predict the SSC X-ray flux densities. Seven of 30 sources have predicted self-Compton X-ray flux densities well above the observed flux densities obtained with the ROSAT satellite unless one assumes that the radiating plasma experiences bulk relativistic motion directed toward the observer's line of sight. Three of these seven sources are detected at gamma-ray frequencies. Model spectra show that the X-rays are consistent with the first-order SSC process, with the simultaneous multiwaveband spectrum of the quasar 0836+710 obtained in 1992 March being very well fitted by SSC emission from a uniform, relativistically moving source. The gamma-rays are not produced via second-order self-Compton scattering but rather by either first-order self-Compton scattering or some other process. A comparison of the ROSAT X-ray flux densities and those obtained earlier with the Einstein Observatory show that several FSRQs are X-ray variables on timescales of about a decade. Several sources that were observed more than once with ROSAT also show variability on timescales of 1-2 yr, with the X-ray variability in these cases often associated with millimeter-wave variability and lower VLBI core-to jet flux ratios. Detections at gamma-ray energies also appear to be related to increases in the radio to millimeter-wave flux densities. Statistical analysis shows that the millimeter-wave and X-ray luminosities for the sample are strongly correlated, with a linear regression slope similar to 0.65. The peak in the distribution of X-ray to millimeter spectral indices also indicates a strong connection between millimeter-wave and X-ray emission. Particularly interesting is a correlation between X-ray to millimeter spectral index and fraction of flux density contained in the VLBI core. This tendency toward higher X-ray fluxes from sources with stronger jet emission implies that the knots in the jet are prominent sources of X-rays. C1 Boston Univ, Dept Astron, Boston, MA 02215 USA. Royal Observ, Edinburgh EH9 3HJ, Midlothian, Scotland. Metsahovi Radio Res Stn, FIN-02540 Kylmala, Finland. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. RP CALTECH, Jet Prop Lab, Infrared Proc & Anal Ctr, MS 100-22, Pasadena, CA 91125 USA. NR 71 TC 27 Z9 28 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD MAY PY 1999 VL 122 IS 1 BP 1 EP 27 DI 10.1086/313204 PG 27 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XD UT WOS:000081297800001 ER PT J AU Meixner, M Ueta, T Dayal, A Hora, JL Fazio, G Hrivnak, BJ Skinner, CJ Hoffmann, WF Deutsch, LK AF Meixner, M Ueta, T Dayal, A Hora, JL Fazio, G Hrivnak, BJ Skinner, CJ Hoffmann, WF Deutsch, LK TI A mid-infrared imaging survey of proto-planetary nebula candidates SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE circumstellar matter; infrared : ISM : continuum; ISM : structure; stars : AGB and post-AGB; stars : mass loss ID ASYMPTOTIC GIANT BRANCH; PROTOPLANETARY NEBULAE; IRAS SOURCES; CO OBSERVATIONS; RED RECTANGLE; BIPOLAR; DUST; SPECTRA; STARS; OBJECTS AB We present the data from a mid-infrared (MIR) imaging survey of 66 proto-planetary nebula candidates using two MIR cameras (MIRAC2 and Berkcam) at the NASA Infrared Telescope Facility and the United Kingdom Infrared Telescope. The goal of this survey is to determine the size, flux, and morphology of the MIR emission regions, which sample the inner regions of the circumstellar dust shells of proto-planetary nebulae. We imaged these proto-planetary nebulae with narrowband filters (Delta lambda/lambda similar to 10%) at wavelengths of notable dust features. With our typical angular resolution of 1", we resolve 17 sources, find 48 objects unresolved, and do not detect one source. For several sources we checked optical and infrared associations and positions of the sources. In table format, we list the size and flux measurements for all of the detected objects and show figures of all of the resolved sources. The proto-planetary nebula candidate sample includes, in addition to the predominant proto-planetary nebulae, extreme asymptotic giant branch stars, young planetary nebulae, a supergiant, and a luminous blue variable. We find that dust shells that are cooler (T similar to 150 K) and brighter in the infrared are more easily resolved. Eleven of the seventeen resolved sources are extended and fall into one of two types of MIR morphological classes: core/elliptical or toroidal. Core/elliptical structures show unresolved cores with lower surface brightness elliptical nebulae. Toroidal structures show limb-brightened peaks suggesting equatorial density enhancements. We argue that core/ellipticals have denser dust shells than toroidals. C1 Univ Illinois, Dept Astron, Urbana, IL 61801 USA. CALTECH, JPL, IPAC, Pasadena, CA 91125 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Valparaiso Univ, Dept Phys & Astron, Valparaiso, IN 46383 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Boston Univ, Dept Astron CAS 519, Boston, MA 02215 USA. RP Univ Illinois, Dept Astron, MC-221, Urbana, IL 61801 USA. EM meixner@astro.uiuc.edu; ueta@astro.uiuc.edu; adayal@ipac.caltech.edu; jhora@cfa.harvard.edu; gfazio@cfa.harvard.edu; bhrivnak@exodus.valpo.edu; whoffmann@as.arizona.edu; deutschl@bu.edu OI Hora, Joseph/0000-0002-5599-4650 NR 64 TC 123 Z9 123 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 EI 1538-4365 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD MAY PY 1999 VL 122 IS 1 BP 221 EP 242 DI 10.1086/313215 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XD UT WOS:000081297800009 ER PT J AU Ortiz, RM Wang, TJ Wade, CE AF Ortiz, RM Wang, TJ Wade, CE TI Influence of centrifugation and hindlimb suspension on testosterone and corticosterone excretion in rats SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE microgravity; steroid; stress; tail-suspension; testes ID TESTICULAR FUNCTION; SKELETAL-MUSCLE; LUTEINIZING-HORMONE; ANABOLIC-STEROIDS; CELL STRUCTURE; MICROGRAVITY; PLASMA; SECRETION; MASS AB Background: Alterations in mass loading have been shown to stimulate the pituitary-gonadal and pituitary-adrenal axes resulting in changes in testosterone (T) and corticosterone (B) production which may account for the previously reported Variations in muscle mass under these conditions. Hypothesis: Centrifugation and hindlimb suspension will induce opposing effects on testosterone and corticosterone excretion. Methods: Effects of mass loading (centrifugation at -2Gx) and unloading (hind-limb suspension, HLS) on excreted T and B levels, and testicular mass were examined in Sprague-Dawley rats. For 12 d, 16 (8 controls and 8 centrifuged) rats and 20 (10 unsuspended controls and 10 suspended) rats were studied during the centrifugation and suspension portions of the study, respectively. Following the completion of each study, testicular mass was measured. Results: Absolute testicular mass was not different following 12 d of centrifugation. Excreted T was elevated between days 1 and 6 of centrifugation. Excreted 8 levels were elevated for the first 4 d of centrifugation. Suspension reduced absolute and relative testicular mass. Excreted T levels were reduced from days 3-12 of suspension, while excreted B levels were only elevated on the first day of suspension. Conclusions: Centrifugation stimulated an increase in T excretion despite a lack of a change in absolute testicular mass. Conversely, suspension resulted in a reduction in T excretion which may have been associated with a decrease in absolute testicular mass. The centrifugation-induced increase in T excretion is consistent with previously reported increases in lean body mass following centrifugation, while the HLS-induced reduction in T excretion correlates with previously reported decreases in lean body mass following suspension. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. Lockheed Martin, Moffett Field, CA USA. GB Tech, Moffett Field, CA USA. RP Ortiz, RM (reprint author), NASA, Ames Res Ctr, Div Life Sci, MS 239-11, Moffett Field, CA 94035 USA. NR 31 TC 23 Z9 23 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 MAY PY 1999 VL 70 IS 5 BP 499 EP 504 PG 6 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 190TQ UT WOS:000079981400010 PM 10332947 ER PT J AU Watenpaugh, DE Ballard, RE Breit, GA Hargens, AR AF Watenpaugh, DE Ballard, RE Breit, GA Hargens, AR TI Self-generated lower body negative pressure exercise SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE microgravity; human; deconditioning; force; work; differential pressure ID UPRIGHT EXERCISE; BED REST; RESPONSES AB Background: Exercise during spaceflight helps prevent musculoskeletal and cardiovascular deconditioning to Earth gravity. This report evaluates the aerobic and anaerobic exercise stimulus provided by self-generated lower body negative pressure. Methods: A lower body negative pressure cylinder expands and collapses longitudinally, but not radially. As the legs push footward to expand the cylinder, the air pressure in the cylinder decreases, increasing the force required to continue expanding the cylinder. In addition, valves control air flow into and out of the cylinder, and thus workload, In seven supine subjects, knee bend exercise was performed at 19 cycles per minute for 6 min. Footward force was measured with load cells, cylinder pressure with a transducer, heart rate from EGG, and oxygen consumption with turbine volumetry and gas analysis. Results: Maximum footward force at the peak of the exercise cycle averaged 1120 +/- 88 N (114 +/- 9 kg), and pressure within the cylinder concomitantly decreased 26 +/- 3 mmHg below ambient. Heart rate and oxygen consumption increased 75 +/- 4 bpm and 26.3 +/- 1.4 ml O-2/kg.min(-1) from supine resting values, respectively. Conclusions: With the air inlet valve nearly closed, exercise with this device approximates a resistance-type leg press. With more inflow of air, more rapid, aerobic knee bends can be performed. This exercise device/concept provides simultaneous dynamic musculoskeletal and cardiovascular stresses without an external power source. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. RP Watenpaugh, DE (reprint author), Univ N Texas, Hlth Sci Ctr, Dept Integrat Physiol, 3500 Camp Bowie Blvd, Ft Worth, TX 76107 USA. NR 14 TC 3 Z9 6 U1 0 U2 0 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD MAY PY 1999 VL 70 IS 5 BP 522 EP 526 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 190TQ UT WOS:000079981400014 PM 10332951 ER PT J AU Berejikian, BA Smith, RJF Tezak, EP Schroder, SL Knudsen, CM AF Berejikian, BA Smith, RJF Tezak, EP Schroder, SL Knudsen, CM TI Chemical alarm signals and complex hatchery rearing habitats affect antipredator behavior and survival of chinook salmon (Oncorhynchus tshawytscha) juveniles SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID FATHEAD MINNOWS; COHO SALMON; PIMEPHALES-PROMELAS; NORTHERN PIKE; ESOX-LUCIUS; PREDATOR RECOGNITION; ACQUIRED RECOGNITION; TROUT; MYKISS; STEELHEAD AB The present study examined the effects of chemical antipredator conditioning on antipredator behavior and the relative effects of antipredator conditioning and seminatural rearing environments on postrelease survival of chinook salmon (Onocrhynchus tshawytscha). Hatchery-reared juvenile chinook salmon were exposed to extracts from conspecific tissue or to comparable stimuli from green swordtail (Xiphophorus helleri). These "injured fish" stimuli were paired with water that contained the odour of predatory cutthroat trout (Oncorhynchus clarki). Chinook salmon receiving conspecific stimuli showed higher levels of several antipredator behaviors compared with chinook salmon receiving green swordtail extracts. When the two groups of chinook salmon were tested 2 days later with cutthroat trout stimulus alone, the chinook salmon that had originally received injured conspecific stimuli paired with cutthroat trout odour spent more time motionless than chinook salmon that had received green swordtail stimuli and cutthroat trout odour. In another experiment, complex rearing treatments had a negative effect on instream survival (contrary to previous studies) that was compensated for by the application of the chinook salmon extract and cutthroat trout odour prior to release. Chinook salmon, like rainbow trout (Oncorhynchus mykiss), show antipredator behavior in response to chemical stimuli from injured conspecifics and learn predator recognition when such stimuli are paired with predator odour, improving survival in the wild. C1 Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Manchester Marine Expt Stn, Manchester, WA 98353 USA. Univ Saskatchewan, Dept Biol, Saskatoon, SK S7N 5E2, Canada. Washington Dept Fish & Wildlife, Olympia, WA 98501 USA. RP Berejikian, BA (reprint author), Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Manchester Marine Expt Stn, POB 130, Manchester, WA 98353 USA. NR 30 TC 105 Z9 107 U1 2 U2 22 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 MAY PY 1999 VL 56 IS 5 BP 830 EP 838 DI 10.1139/cjfas-56-5-830 PG 9 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 212UG UT WOS:000081235400011 ER PT J AU Iess, L Giampieri, G Anderson, JD Bertotti, B AF Iess, L Giampieri, G Anderson, JD Bertotti, B TI Doppler measurement of the solar gravitational deflection SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article ID GENERAL-RELATIVITY; SPACECRAFT; TRACKING; GALILEO; GRAVITY; SCINTILLATION; ASTROMETRY; RADIATION; ULYSSES AB Testing alternative metric theories of gravity with an accuracy much better than the present level has recently drawn great attention, in particular in relation to the search for a very weak scalar field, a possible remnant of an early inflationary cosmology. The gravitational deflection of electromagnetic waves is controlled by the dimensionless post-Newtonian parameter gamma, which takes a value of unity in general relativity. In this work we claim that the accuracy in the measurement of gamma can be substantially improved by measuring the Doppler frequency shift of a microwave beam transponded back to the ground by an interplanetary spacecraft near solar conjunction. In this kind of experiment, the dispersion due to the plasma in the solar corona is the crucial difficulty, which, however, can be essentially overcome using skilful combinations of carriers with different frequencies. The spacecraft Cassini; launched in 1997, adopts a sophisticated radio system, including a Ka-band link at 32-34 GHz, which makes this possible. We discuss the noise budget for two experiments to be carried out with Cassini in 2002 and 2003. In particular, we consider the contribution of the solar corona, the non-gravitational accelerations, and thermal noise due to solar radio emission. We estimate that an accuracy in gamma of about 10(-5) is achievable. C1 Univ Rome La Sapienza, Dipartimento Aerosp, I-00184 Rome, Italy. Univ London Queen Mary & Westfield Coll, Astron Unit, London E1 4NS, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Pavia, Dipartimento Fis Nucl & Teor, I-27100 Pavia, Italy. RP Iess, L (reprint author), Univ Rome La Sapienza, Dipartimento Aerosp, Piazzale Aldo Moro 5, I-00184 Rome, Italy. RI IESS, Luciano/F-4902-2011 OI IESS, Luciano/0000-0002-6230-5825 NR 49 TC 45 Z9 45 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD MAY PY 1999 VL 16 IS 5 BP 1487 EP 1502 DI 10.1088/0264-9381/16/5/303 PG 16 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 202NY UT WOS:000080660100003 ER PT J AU Power, S Casey, T Folland, C Colman, A Mehta, V AF Power, S Casey, T Folland, C Colman, A Mehta, V TI Inter-decadal modulation of the impact of ENSO on Australia SO CLIMATE DYNAMICS LA English DT Article ID SOUTHERN OSCILLATION; EL-NINO; VARIABILITY; CLIMATE; TEMPERATURE; RAINFALL; PACIFIC AB The success of an ENSO-based statistical rainfall prediction scheme and the influence of ENSO on Australia are shown to vary in association with a coherent, inter-decadal oscillation in surface temperature over the Pacific Ocean. When this Inter-decadal Pacific Oscillation (IPO) raises temperatures in the tropical Pacific Ocean, there is no robust relationship between year-to-year Australian climate variations and ENSO. When the IPO lowers temperature in the same region, on the other hand, year-to-year ENSO variability is closely associated with year-to-year variability in rainfall, surface temperature, river flow and the domestic wheat crop yield. The contrast in ENSO's influence between the two phases of the IPO is quite remarkable. This highlights exciting new avenues for obtaining improved climate predictions. C1 Bur Meteorol, Res Ctr, Melbourne, Vic 3001, Australia. Monash Univ, Cooperat Res Ctr So Hemisphere Meteorol, Clayton, Vic, Australia. Meteorol Off, Hadley Ctr Climate Predict & Res, Bracknell, Berks, England. Univ Maryland, NASA, Goddard Space Flight Ctr, Joint Ctr Earth Syst Sci, College Pk, MD 20742 USA. RP Power, S (reprint author), Bur Meteorol, Natl Climate Ctr, GPO Box 1289K, Melbourne, Vic 3001, Australia. RI Folland, Chris/I-2524-2013 NR 25 TC 598 Z9 616 U1 7 U2 66 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD MAY PY 1999 VL 15 IS 5 BP 319 EP 324 DI 10.1007/s003820050284 PG 6 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 196KP UT WOS:000080307800001 ER PT J AU Hafez, M Thomas, J AF Hafez, M Thomas, J TI Papers dedicated to Jerry South of NASA Langley Research Center on the occasion of his retirement - Preface SO COMPUTERS & FLUIDS LA English DT Editorial Material C1 Univ Calif Davis, Davis, CA 95616 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Hafez, M (reprint author), Univ Calif Davis, Davis, CA 95616 USA. NR 0 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 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 385 EP 385 PG 1 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000001 ER PT J AU Roberts, TW Swanson, RC Sidilkover, D AF Roberts, TW Swanson, RC Sidilkover, D TI An algorithm for ideal multigrid convergence for the steady Euler equations SO COMPUTERS & FLUIDS LA English DT Article ID NAVIER-STOKES EQUATIONS AB A fast multigrid solver for the steady incompressible Euler equations is presented. Unlike time-marching schemes this approach uses relaxation of the steady equations. Application of this method results in a discretization that correctly distinguishes between the advection and elliptic parts of the operator, allowing efficient smoothers to be constructed. Solvers for both unstructured triangular grids and structured quadrilateral grids have been written. Flows in two-dimensional channels and over airfoils have been computed. Using Gauss-Seidel relaxation with the grid vertices ordered in the flow direction, ideal multigrid convergence rates of nearly one order-of-magnitude residual reduction per multigrid cycle are achieved, independent of the grid spacing. This approach also may be applied to the compressible Euler equations and the incompressible Navier-Stokes equations. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Roberts, TW (reprint author), NASA, Langley Res Ctr, Mail Stop 128, Hampton, VA 23681 USA. NR 17 TC 8 Z9 8 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 427 EP 442 DI 10.1016/S0045-7930(98)00040-1 PG 16 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000004 ER PT J AU Anderson, WK Venkatakrishnan, V AF Anderson, WK Venkatakrishnan, V TI Aerodynamic design optimization on unstructured grids with a continuous adjoint formulation SO COMPUTERS & FLUIDS LA English DT Article ID SENSITIVITY ANALYSIS; FLOWS; ALGORITHM; EQUATIONS AB A continuous adjoint approach for obtaining sensitivity derivatives on unstructured grids is developed and analyzed. The derivation of the costate equations is presented, and a second-order accurate discretization method is described. The relationship between the continuous formulation and a discrete formulation is explored for inviscid, as well as for viscous flow. Several limitations in a strict adherence to the continuous approach are uncovered, and an approach that circumvents these difficulties is presented. The issue of grid sensitivities, which do not arise naturally in the continuous formulation, is investigated and is observed to be of importance when dealing with geometric singularities. A method is described for modifying inviscid and viscous meshes during the design cycle to accommodate changes in the surface shape. The accuracy of the sensitivity derivatives is established by comparing with finite-difference gradients and several design examples are presented. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Anderson, WK (reprint author), NASA, Langley Res Ctr, MS 128, Hampton, VA 23681 USA. NR 42 TC 89 Z9 91 U1 2 U2 8 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 443 EP 480 DI 10.1016/S0045-7930(98)00041-3 PG 38 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000005 ER PT J AU Brandt, A Diskin, B AF Brandt, A Diskin, B TI Multigrid solvers for the non-aligned sonic flow: the constant coefficient case SO COMPUTERS & FLUIDS LA English DT Article AB An approach for the construction of multigrid solvers for non-elliptic equations on a rectangular grid is presented. The results of both the analysis and the numerical experiments demonstrate that such an approach permits a full multigrid efficiency to be achieved, even in the case that the equation characteristics do not align with the grid. To serve as a model problem, the two- and three-dimensional linearized sonic-flow equations with a constant velocity field have been chosen. Efficient FMG solvers for the problems are demonstrated. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Weizmann Inst Sci, Dept Appl Math & Comp Sci, IL-76100 Rehovot, Israel. RP Diskin, B (reprint author), NASA, Langley Res Ctr, ICASE, MS 403,6 N Dryden St, Hampton, VA 23681 USA. NR 11 TC 6 Z9 6 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 511 EP 549 DI 10.1016/S0045-7930(98)00043-7 PG 39 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000007 ER PT J AU Sidilkover, D AF Sidilkover, D TI Some approaches towards constructing optimally efficient multigrid solvers for the inviscid flow equations SO COMPUTERS & FLUIDS LA English DT Article ID CONSERVATION-LAWS AB Some important advances have taken place during the last few years in the development of genuinely multidimensional upwind schemes for the compressible Euler equations. Tn particular, a robust, high-resolution genuinely multidimensional scheme which can be used for any of the flow regimes computations has been constructed. This paper summarizes briefly these developments and outlines the fundamental advantages of this approach (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP Sidilkover, D (reprint author), NASA, Langley Res Ctr, ICASE, Mail Stop 403, Hampton, VA 23681 USA. NR 26 TC 6 Z9 6 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 551 EP 571 DI 10.1016/S0045-7930(98)00044-9 PG 21 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000008 ER PT J AU Vatsa, VN Wedan, BW AF Vatsa, VN Wedan, BW TI Parallelization of a multiblock flow code: an engineering implementation SO COMPUTERS & FLUIDS LA English DT Article AB Current trends in computer hardware are dictating a gradual shift toward the use of clusters of relatively inexpensive but powerful workstations, or massively parallel processing (MPP) machines, for scientific computing. However, most computational fluid dynamics (CFD) codes in use today were developed for large, shared-memory machines and are not readily portable to the distributed computing environment. One major hurdle in porting CFD codes to distributed computing platforms is the difficulty encountered in partitioning the problem so that the computation-to-communication ratio for each compute node (process) is maximized and the idle time during which one node waits for other nodes to transfer data is minimized. In the present work, pertinent issues involved in the parallelization of a widely used multiblock Navier-Stokes code TLNS3D are discussed. An engineering; approach is used here to parallelize this code so that minimal deviation from the original (nonparallel) code is incurred. A natural partitioning along grid blocks is adopted in which one or more blocks are distributed to each of the available nodes. An automatic, static load-balancing strategy is employed for equitable distribution of computational work to specified nodes. Both parallel Virtual machine (PVM) and message passing interface (MPI) protocols are incorporated for data communication to allow maximum portability to a wide range of computer configurations. Results are presented that are comparable with a priori estimates of performance for distributed computing and that are competitive in terms of central processing unit (CPU) time and wall time usage with large, shared-memory supercomputers. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Adv Sci Comp Ltd, Waterloo, ON, Canada. RP Vatsa, VN (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 4 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 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 603 EP 614 DI 10.1016/S0045-7930(98)00046-2 PG 12 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000010 ER PT J AU Newman, JC Newman, PA Taylor, AC Hou, GJW AF Newman, JC Newman, PA Taylor, AC Hou, GJW TI Efficient nonlinear static aeroelastic wing analysis SO COMPUTERS & FLUIDS LA English DT Article ID FLOWS; ALGORITHM AB The objective of this work is to demonstrate a computationally efficient, high-fidelity, integrated static aeroelastic analysis procedure. The aerodynamic analysis consists of solving the nonlinear Euler equations by using an upwind cell-centered finite-Volume scheme on unstructured tetrahedral meshes. The use of unstructured grids enhances the discretization of irregularly shaped domains and the interaction compatibility with the wing structure. The structural analysis utilizes finite elements to model the wing so that accurate structural deflections are obtained and allows the capability for computing detailed stress information for the configuration. Parameters are introduced to control the interaction of the computational fluid dynamics and structural analyses; these control parameters permit extremely efficient static aeroelastic computations. To demonstrate and evaluate this procedure, static aeroelastic analysis results for a flexible wing in low subsonic, high subsonic (subcritical), transonic (supercritical), and supersonic flow conditions are presented. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Multidisciplinary Optimizat Branch, Hampton, VA 23681 USA. Virginia Consortium Engn & Sci, Virginia Polytech Inst & State Univ, Dept Mech Engn, Hampton, VA 23666 USA. Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. RP Newman, JC (reprint author), NASA, Langley Res Ctr, Multidisciplinary Optimizat Branch, Hampton, VA 23681 USA. NR 29 TC 9 Z9 10 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 615 EP 628 DI 10.1016/S0045-7930(98)00047-4 PG 14 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000011 ER PT J AU Garriz, JA Newman, PA Vatsa, VN Haigler, KJ AF Garriz, JA Newman, PA Vatsa, VN Haigler, KJ TI Observations on three-dimensional nonlinear transonic wall-interference assessment and correction using semispan wing data SO COMPUTERS & FLUIDS LA English DT Article ID FLOW AB The current interest in semispan wing testing generally places a greater demand on understanding wall-interference effects than is required in conventional sting-mounted model testing. As part of NASA Langley Research Center's development and evaluation of transonic wind-tunnel wall-interference assessment and correction (WIAC) ideas and methods, a nonlinear, three-dimensional, transonic WIAC code has been applied to four sets of transonic semispan wing data. These data were acquired nearly 20 years ago for the specific purpose of evaluating three-dimensional transonic computational fluid dynamics methodologies and included the measured wall (or near wall) pressure data that are required by the WIAC procedure. Previous papers have focused on the evaluation of nonlinear WIAC and other correction-method results by monitoring the correlations of corrected data and by using a Navier-Stokes code as an independent "free air" check. In the present paper, synoptic observations are made in regard to the transonic WIAC results and the factors that affect these results. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. ViGYAN Incorp, Hampton, VA USA. RP Newman, PA (reprint author), NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Mail Stop 159, Hampton, VA 23681 USA. NR 36 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 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 629 EP 651 DI 10.1016/S0045-7930(98)00048-6 PG 23 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000012 ER PT J AU Iollo, A Salas, MD AF Iollo, A Salas, MD TI Optimum transonic airfoils based on the Euler equations SO COMPUTERS & FLUIDS LA English DT Article ID SHAPE DESIGN; FLOWS AB We solve the problem of determining airfoils that approximate, in a least square sense, a given surface pressure distributions in transonic flight regimes. The flow is modeled by means of the Euler equations and the solution procedure is an adjoint-based minimization algorithm that makes use of the inverse Theodorsen transform in order to parameterize the airfoil. Fast convergence to the optimal solution is obtained by means of the pseudo-time method. Results are obtained using three different pressure distributions for several unperturbed flow conditions. The airfoils obtained have given a trailing edge angle. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Politecn Torino, Dipartmento Ingn Aeronau & Spaziale, I-10129 Turin, Italy. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Iollo, A (reprint author), Politecn Torino, Dipartmento Ingn Aeronau & Spaziale, I-10129 Turin, Italy. NR 30 TC 1 Z9 1 U1 1 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 653 EP 674 DI 10.1016/S0045-7930(98)00049-8 PG 22 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000013 ER PT J AU Reuther, J Alonso, JJ Rimlinger, MJ Jameson, A AF Reuther, J Alonso, JJ Rimlinger, MJ Jameson, A TI Aerodynamic shape optimization of supersonic aircraft configurations via an adjoint formulation on distributed memory parallel computers SO COMPUTERS & FLUIDS LA English DT Article ID SENSITIVITY ANALYSIS; EULER EQUATIONS AB This work describes the application of a control theory-based aerodynamic shape optimization method to the problem of supersonic aircraft design. A high fidelity computational fluid dynamics (CFD) algorithm modelling the Euler equations is used to calculate the aerodynamic properties of complex three-dimensional aircraft configurations. The design process is greatly accelerated through the use of both control theory and parallel computing. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods. The resulting problem is then implemented in parallel using a domain decomposition approach, an optimized communication schedule, and the Message Passing Interface (MPI) Standard for portability and efficiency. In our earlier studies, the serial implementation of this design method, was shown to be effective for the optimization of airfoils, wings, wing-bodies, and complex aircraft configurations using both the potential equation and the Euler equations. In this work, our concern will be to extend the methodologies such that the combined capabilities of these new technologies can be used routinely and efficiently in an industrial design environment. The aerodynamic optimization of a supersonic transport configuration is presented as a demonstration test case of the capability, A particular difficulty of this test case is posed by the close coupling of the propulsion/airframe integration. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, MCAT Inst, Moffett Field, CA 94035 USA. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Simco, Moffett Field, CA 94035 USA. RP Reuther, J (reprint author), NASA, Ames Res Ctr, MCAT Inst, MS 227-6, Moffett Field, CA 94035 USA. NR 51 TC 24 Z9 26 U1 2 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0045-7930 J9 COMPUT FLUIDS JI Comput. Fluids PD MAY-JUN PY 1999 VL 28 IS 4-5 BP 675 EP 700 DI 10.1016/S0045-7930(98)00050-4 PG 26 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 186LV UT WOS:000079732000014 ER PT J AU Wagstaff, J McKay, G Reid, A Reid, G AF Wagstaff, J McKay, G Reid, A Reid, G TI Remote operation of a Cameca SX100 scanning electron microprobe SO COMPUTERS & GEOSCIENCES LA English DT Article DE X-ray; ISDN; analyze; imaging; WAN AB We describe the remote operation of the Cameca SX100 scanning electron microprobe, located in building 31 at Johnson Space Center. A near-real-time graphics communications link was established via Integrated Services Digital Network telephone lines and the Internet between a remote personal computer, located off-site from Johnson Space Center and the Cameca microprobe. With digital communications utilizing only the Internet, it is possible to have full control of all analytical and electron imaging operations at near-real-time imaging rates and demonstrate this from as far away as the University of Houston Central Campus, a distance of approximately 30 miles. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. NASA, SN, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Houston, Dept Geosci, Houston, TX USA. Northrop Grumman, Houston, TX USA. RP Wagstaff, J (reprint author), Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. NR 1 TC 0 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0098-3004 J9 COMPUT GEOSCI JI Comput. Geosci. PD MAY PY 1999 VL 25 IS 4 BP 523 EP 529 DI 10.1016/S0098-3004(98)00157-5 PG 7 WC Computer Science, Interdisciplinary Applications; Geosciences, Multidisciplinary SC Computer Science; Geology GA 200FM UT WOS:000080529000024 ER PT J AU Wang, P Ferraro, RD AF Wang, P Ferraro, RD TI Parallel multigrid finite volume computation of three-dimensional thermal convection SO COMPUTERS & MATHEMATICS WITH APPLICATIONS LA English DT Article DE thermal convection; parallel computation; finite volume; multigrid ID LATERALLY HEATED CAVITY; NUMERICAL-SOLUTIONS; NATURAL-CONVECTION; FLOWS; END 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, including a pressure equation which consumes most of the computation time, are solved by a parallel multigrid method. A flexible parallel code has been implemented on the Intel Paragon, the Gray T3D, and the IBM SP2 by using domain decomposition techniques and the MPI communication software. The code can use 1D, 2D, or 3D partitions as required by different geometries, and is easily ported to other parallel systems. Numerical solutions for air (Prandtl number Pr = 0.733) with various Rayleigh numbers up to 10(7) are discussed. Published by Elsevier Science Ltd. 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 18 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 0898-1221 J9 COMPUT MATH APPL JI Comput. Math. Appl. PD MAY PY 1999 VL 37 IS 9 BP 49 EP 60 DI 10.1016/S0898-1221(99)00113-3 PG 12 WC Mathematics, Applied SC Mathematics GA 191GB UT WOS:000080013200007 ER PT J AU Nakano, A Petrac, D Paine, C Murakami, M AF Nakano, A Petrac, D Paine, C Murakami, M TI Investigation of large dynamic range helium II liquid/vapor phase separator for SIRTF SO CRYOGENICS LA English DT Article DE liquid-vapor phase separator; porous plug; hysteresis; break through ID FLOW AB A large dynamic range superfluid helium, helium II, liquid-vapor phase separator is required for the thermal design of the Space Infrared Telescope Facility (SIRTF). A porous plug type phase separator is adopted for SIRTF mission. A candidate porous plug was tested using two different types of experimental apparatus to obtain the exact flow characteristics. Mass flow rate, pressure and temperature differences across the porous plug were measured in this experiment. The experimental data are compared with the theoretical predictions. The fundamental feature of the flow phenomena through the tested porous plug provides valuable data for the practical design of a phase separator for SIRTF needs. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Minist Int Trade & Ind, Agcy Ind Sci & Technol, Mech Engn Lab, Tsukuba, Ibaraki 3058564, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Tsukuba, Inst Engn Mech & Syst, Tsukuba, Ibaraki 3058573, Japan. RP Nakano, A (reprint author), Minist Int Trade & Ind, Agcy Ind Sci & Technol, Mech Engn Lab, Tsukuba, Ibaraki 3058564, Japan. NR 16 TC 2 Z9 7 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 MAY PY 1999 VL 39 IS 5 BP 471 EP 479 DI 10.1016/S0011-2275(99)00063-6 PG 9 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 235LZ UT WOS:000082544300008 ER PT J AU Mauritzen, C Hakkinen, S AF Mauritzen, C Hakkinen, S TI On the relationship between dense water formation and the "Meridional Overturning Cell" in the North Atlantic Ocean SO DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS LA English DT Article ID GENERAL-CIRCULATION MODEL; SEA-ICE; INTERANNUAL VARIABILITY; THERMOHALINE CIRCULATION; HEAT-TRANSPORT; DEEP-WATER; SIMULATION; SYSTEM AB We analyze the three-dimensional structure of the Meridional Overturning Cell (MOC) in a numerical model of the North Atlantic and Arctic Oceans. The MOC is found to consist of several downward branches: some associated with dense water formation driven by surface buoyancy forcing (Labrador Sea, northern Norwegian Sea and Barents Sea), and some associated with interior mixing processes in the model (most notably entrainment of thermocline waters into the dense overflows at the Greenland-Scotland Ridge). Two experiments with altered surface buoyancy conditions are performed, both resulting in a change in the dense water formation rate in the Labrador Sea. A change of the same sign is observed in the strength of the MOC (and thus in the meridional heat flux); however, the change is less (20-50%) than would be expected from the change in the dense water formation rate. The MOC and the rate of dense water formation at higher latitudes seem not to be tightly linked on the decadal time scale. Instead, significant changes in the volume of water masses may take place. Taking this phenomenon into account may improve the interpretation of the chain of events that constitutes a climate oscillation, whether it be observed in models or in nature. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Mauritzen, C (reprint author), Woods Hole Oceanog Inst, Clark Lab 354, MS 21, Woods Hole, MA 02543 USA. RI Hakkinen, Sirpa/E-1461-2012 NR 31 TC 30 Z9 30 U1 1 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0967-0637 J9 DEEP-SEA RES PT I JI Deep-Sea Res. Part I-Oceanogr. Res. Pap. PD MAY PY 1999 VL 46 IS 5 BP 877 EP 894 DI 10.1016/S0967-0637(98)00094-6 PG 18 WC Oceanography SC Oceanography GA 189FL UT WOS:000079893800007 ER PT J AU Mehta, SK Stevens, DA Mishra, SK Feroze, F Pierson, DL AF Mehta, SK Stevens, DA Mishra, SK Feroze, F Pierson, DL TI Distribution of Candida albicans genotypes among family members SO DIAGNOSTIC MICROBIOLOGY AND INFECTIOUS DISEASE LA English DT Article ID AMPLIFIED POLYMORPHIC DNA; MOLECULAR TYPING METHODS; STRAINS; IDENTIFICATION; VAGINITIS; EPIDEMIOLOGY; OUTBREAKS; SYSTEM AB Thirty-three families (71 subjects) were screened for the presence bf Candida albicans in mouthwash or stool specimens; 12 families (28 subjects) were culture-positive for this yeast. An enrichment procedure provided a twofold increase in the recovery of C. albicans from mouthwash specimens. Nine of the twelve culture-positive families had two positive members each, two families had three positive members each, and one family had four positive members. Genetic profiles were obtained by tl-Il ee methods: pulsed-field gel electrophoresis; restriction endonuclease analysis, and random amplification of polymorphic DNA analysis. DNA fingerprinting of C. albicans isolated from one body site three consecutive times revealed that each of the 12 families carried a distinct genotype. No two families shaved the same strain, and two or more members of a family commonly shared the same strain. Intrafamily genotypic identity (i.e., each member within the family harbored the same strain) was demonstrated in six families. Genotypes of isolates from husband and wife differed from one another in Jive families. All three methods were satisfactory in determining genotypes; however, we concluded that restriction endonuclease analysis provided adequate resolving power. (C) 1999 Elsevier Science Inc. C1 Stanford Univ, Sch Med, Santa Clara Valley Med Ctr, San Jose, CA 95128 USA. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. KRUG Life Sci Inc, Houston, TX USA. Natl Univ Singapore, Singapore 117548, Singapore. RP Stevens, DA (reprint author), Stanford Univ, Sch Med, Santa Clara Valley Med Ctr, 751 S Bascom Ave, San Jose, CA 95128 USA. NR 25 TC 20 Z9 23 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA SN 0732-8893 J9 DIAGN MICR INFEC DIS JI Diagn. Microbiol. Infect. Dis. PD MAY PY 1999 VL 34 IS 1 BP 19 EP 25 DI 10.1016/S0732-8893(98)00100-X PG 7 WC Infectious Diseases; Microbiology SC Infectious Diseases; Microbiology GA 196JK UT WOS:000080305100004 PM 10342103 ER PT J AU Baroth, E Hartsough, C Holst, A Wells, G AF Baroth, E Hartsough, C Holst, A Wells, G TI An evaluation of LabVIEW 5.0 and HP VEE 5.0 - Part 2 SO EE-EVALUATION ENGINEERING LA English DT Article C1 CALTECH, Jet Prop Lab, Measurement Technol Ctr, Pasadena, CA 91109 USA. RP Baroth, E (reprint author), CALTECH, Jet Prop Lab, Measurement Technol Ctr, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 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 1999 VL 38 IS 5 BP 22 EP + PG 5 WC Engineering, Electrical & Electronic SC Engineering GA 193FU UT WOS:000080125900006 ER PT J AU Wood, J Lugg, DJ Hysong, SJ Harm, DL AF Wood, J Lugg, DJ Hysong, SJ Harm, DL TI Psychological changes in hundred-day remote Antarctic field groups SO ENVIRONMENT AND BEHAVIOR LA English DT Article ID ENVIRONMENTS AB Psychological adaptation to extreme environments has been examined from several perspectives. In this study, two Australian teams, each consisting of six male crew members, completed computer-administered questionnaires twice weekly during 100-day traverses around the Lambert Glacier Basin, Antarctica. Only small trends were noted when data were aggregated at the group level, which is consistent with the findings of others. Data were then analyzed using pooled time-series regression. These analyses incorporated personality characteristics, environmental factors, and interpersonal factors as predictors of Group Tensions, Personal Morale, Emotional State, Cognitive Readiness, and the Team's Work Life. Most of the psychological discomfort and problems that occurred appeared to be within the individual or between individuals. They did not affect all members of the group equally. C1 Wyle Life Sci Inc, Psychol & Behav Lab, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Australian Antarctic Div, Kingston, Tas, Australia. Australian Antarctic Div, Kingston, Tas, Australia. Rice Univ, Houston, TX 77251 USA. Lyndon B Johnson Space Ctr, Neurosci Labs, Houston, TX 77058 USA. RP Wood, J (reprint author), Wyle Life Sci Inc, Psychol & Behav Lab, 1290 Hercules 120, Houston, TX 77058 USA. RI Hysong, Sylvia/B-8420-2008 OI Hysong, Sylvia/0000-0002-9063-5207 FU NINR NIH HHS [NRA 93-OLMSA-07] NR 39 TC 28 Z9 31 U1 1 U2 6 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 0013-9165 J9 ENVIRON BEHAV JI Environ. Behav. PD MAY PY 1999 VL 31 IS 3 BP 299 EP 337 DI 10.1177/0013916599313001 PG 39 WC Environmental Studies; Psychology, Multidisciplinary SC Environmental Sciences & Ecology; Psychology GA 194TC UT WOS:000080208800001 PM 11542387 ER PT J AU Taghavi, R Raman, G Bencic, T AF Taghavi, R Raman, G Bencic, T TI Pressure sensitive paint demonstrates relationship between ejector wall pressure and aerodynamic performance SO EXPERIMENTS IN FLUIDS LA English DT Article ID MIXER-EJECTOR; NOZZLE AB This paper provides an example of the application of Pressure Sensitive Paint (PSP) to complex internal suspersonic flows and demonstrates the relationship between ejector wall pressure and aerodynamic performance. Details of such jet mixer-ejector nozzles are relevant to jet noise reduction programs. Several ejector configurations with straight, convergent, and divergent side walls were used in our experiments. The side-wall that was painted with PSP was also instrumented with an array of 156 pressure taps connected to Electronically Scanned Pressure (ESP) modules, enabling simultaneous measurement of "true" reference pressures. The PSP results agreed very well with the "true" reference pressures and also provided a detailed map of the complicated pressure patterns that could not be detected using the pressure taps. Finally, we also demonstrated the direct relationship between ejector side-wall pressure distribution and ejector performance characteristics such as exit mean flow uniformity, pumping, and thrust augmentation. C1 Univ Kansas, Dept Aerosp Engn, Lawrence, KS 66045 USA. NASA, Lewis Res Ctr Grp, Dynacs Inc, Prop Anal Sect, Brookpark, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Taghavi, R (reprint author), Univ Kansas, Dept Aerosp Engn, Lawrence, KS 66045 USA. NR 10 TC 11 Z9 11 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0723-4864 J9 EXP FLUIDS JI Exp. Fluids PD MAY PY 1999 VL 26 IS 6 BP 481 EP 487 DI 10.1007/s003480050314 PG 7 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 196MB UT WOS:000080311200001 ER PT J AU Herzog, GF Xue, S Hall, GS Nyquist, LE Shih, CY Wiesmann, H Brownlee, DE AF Herzog, GF Xue, S Hall, GS Nyquist, LE Shih, CY Wiesmann, H Brownlee, DE TI Isotopic and elemental composition of iron, nickel, and chromium in type I deep-sea spherules: Implications for origin and composition of the parent micrometeoroids SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID POSSIBLE PRECURSOR COMPONENTS; ORDINARY CHONDRITE CHONDRULES; COSMIC SPHERULES; SOLAR NEBULA; METAL; METEORITES; SEDIMENTS; ANOMALIES; SPHERES; BE-10 AB We report elemental and isotopic analyses of Fe, Ni, and Cr in type I deep-sea spherules with masses ranging from 43 to 256 mu g. We measured (1) the isotopic compositions of Fe and Cr by thermal ionization mass spectrometry; and (2) the elemental concentrations of Fe, Ni, and Cr and the isotopic compositions of Ni by inductively-coupled plasma mass spectrometry. Evaporation of Fe, Ni, and Cr during atmospheric entry led to large and similar average degrees of mass-dependent fractionation, Phi, in most spherules. The average value, similar to 16 parts per thousand/AMU, corresponds to mass losses of 80-85%, assuming open-system evaporation of the atoms. We find Phi(Cr) similar to Phi(Fe) in seven spherules. This observation implies similar evaporation rates for Cr and Fe and that the measured Cr/Fe ratios (mass/mass) are close to those of the progenitors. Four spherules have Cr/Fe similar to 0.003; two others with low Cr/Fe, similar to 8 x 10(-4), high Fe/Ni, similar to 2000, and Phi(Cr) similar to Phi(Fe) may belong to a different, possibly terrestrial, population. A seventh spherule with "chondritic" Cr/Fe, similar to 17 x 10(-3) and subaverage Phi(Cr) and Phi(Fe), 8-10 parts per thousand/AMU, may represent still another source of particles. Because the higher vapor pressure of pure Cr should lead to Phi(Cr) > Phi(Fe) we infer either that Cr has a low activity coefficient in liquid Fe or that it forms a relatively involatile species there. A best fit correlation between Phi(Cr) and Phi(Fe) can be expressed in the form Phi(Cr) = 0.31 x Phi(Fe)(1.47), although the data also are adequately fit by a linear regression. Correlated variation of Phi(Ni) and Phi(Fe) can be fit by the empirical relationship Phi(Ni) = 0.016 x Phi(Fe)(2.58). For low Phi(Fe), we find Phi(Ni) < Phi(Fe), which shows that Fe evaporates more rapidly than Ni at first, probably because of the lower vapor pressure of pure Ni and lower activity coefficient of Ni in the melt. For high Phi(Fe), we find Phi(Ni) > Phi(Fe), which probably reflects the increase with temperature of the vapor pressure of pure Ni, changes in activity coefficients of Fe and Ni, and the formation of relatively involatile wustite and magnetite. Differences between Phi(Ni) and Phi(Fe) in many samples mean that measured Fe/Ni ratios may differ appreciably from pre-atmospheric values. After compensating for evaporation by using the Rayleigh law, we estimate an average pre-atmospheric Fe/Ni ratio (by mass) in type I spherules of 19 +/- 4 (sigma(mean)). Similarly, by assuming Ir is involatile, we obtain a preatmospheric ratio of Ir/Ni = 3 x 10(-5), which is about 10 times smaller than the average measured value, but similar to the cosmic (CI) abundance ratio of 4 x 10(-5). Cosmogenic nuclides have been detected in some Type I spherules at levels indicating irradiation as metal in space. Among conventional meteorites, the best matches to both the Cr/Fe and Fe/Ni ratios inferred for type I progenitors are metal from CO, CV, and CR chondrites and from unequilibrated ordinary chondrites. The match with metal from CM chondrites is acceptable but somewhat poorer. Iron meteorites, because of their low Cr/Fe ratios and low flux to Earth, make unlikely progenitors for type I spherules. We propose that most type I spherules derive from metal grains in carbonaceous-chondrite-like objects that were freed by comminution in space, or, less likely, that collisions of large objects formed droplets rich in metal. Copyright (C) 1999 Elsevier Science Ltd. C1 Rutgers State Univ, Dept Chem, Piscataway, NJ 08854 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77258 USA. Univ Washington, Dept Astron, Seattle, WA 98105 USA. RP Herzog, GF (reprint author), Rutgers State Univ, Dept Chem, POB 939, Piscataway, NJ 08854 USA. NR 71 TC 33 Z9 35 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0016-7037 J9 GEOCHIM COSMOCHIM AC JI Geochim. Cosmochim. Acta PD MAY PY 1999 VL 63 IS 9 BP 1443 EP 1457 DI 10.1016/S0016-7037(99)00011-3 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 218PP UT WOS:000081561200014 ER PT J AU Hale, VPS McSween, HY McKay, GA AF Hale, VPS McSween, HY McKay, GA TI Re-evaluation of intercumulus liquid composition and oxidation state for the Shergotty meteorite SO GEOCHIMICA ET COSMOCHIMICA ACTA LA English DT Article ID MICROPROBE ANALYSES; PYROXENES; ZAGAMI; CRYSTALLIZATION; PETROGENESIS; FE-3+; MELTS; MARS AB The Shergotty Martian meteorite contains pigeonite and augite with homogeneous magnesian cores, thought to be cumulus crystals. Using elemental maps of thin sections, we estimate the abundance of cumulus pyroxene cores at 13 vol%. This estimate is roughly half that determined from prior melting experiments (28%), and coincides with the observation of a similar discrepancy between the proportions of cumulus pyroxenes estimated from modal observations and melting experiments in the Zagami shergottite. An intercumulus liquid composition calculated using this new cumulus pyroxene estimate is virtually identical to that calculated for Zagami. Our results suggest the possibility that melting experiments may not have been carried out under conditions appropriate for crystallization of the shergottites. We consider two possible explanations: crystallization of pyroxene cores at depth or under different redox conditions. Prior arguments for polybaric crystallization of shergottites, based on pyroxene intergrowths and kaersutite inclusions, are inconclusive. Using the MELTS program, we have explored crystallization at higher pressure. A greater proportion of pyroxene crystallizes at higher pressures, rather than a smaller amount as necessary in this model. Even in calculations at 1 bar, pigeonite crystallizes before augite, and the temperature interval between the appearance of pigeonite and augite expands with pressure. Both pigeonite and augite appear to be in equilibrium with the same liquid composition and thus are thought to have co-crystallized in Shergotty, so it seems likely that MELTS may not correctly predict pyroxene crystallization behavior in this Fe-rich magma. Fe,Ti-oxide compositions in Shergotty were previously used as evidence that the magma crystallized at redox conditions near QFM. However, Ghosal et al. (1998) recently suggested that the oxides record subsolidus, reducing conditions of QFM-3 at 602 degrees C, and our analyses support that conclusion, if a new solution model for oxides is used. They also proposed that Fe3+ in Shergotty pyroxenes indicates magmatic crystallization at approximately QFM-3, and our estimates of Fe3+ calculated from pyroxene stoichiometry in microprobe analyses match their reported values. However, we doubt that stoichiometric calculations provide accurate Fe3+ determinations. Other indicators suggest that magmatic conditions were oxidizing. The FeO* content of Shergotty maskelynite is greater and the negative Eu anomaly in pyroxene cores is shallower than in another basaltic shergottite, QUE94201, which is thought to have crystallized under reducing conditions near QFM-4. Also, the presence of silica, fayalite, and magnetite in mesostasis indicates oxiding conditions, at least at a late magmatic stage. Thus we argue that Shergotty crystallized under redox conditions near QFM. Copyright (C) 1999 Elsevier Science Ltd. C1 Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP McSween, HY (reprint author), Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. NR 35 TC 50 Z9 50 U1 0 U2 5 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 1999 VL 63 IS 9 BP 1459 EP 1470 DI 10.1016/S0016-7037(99)00095-2 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 218PP UT WOS:000081561200015 ER PT J AU Rowlands, DD Pavlis, DE Lemoine, FG Neumann, GA Luthcke, SB AF Rowlands, DD Pavlis, DE Lemoine, FG Neumann, GA Luthcke, SB TI The use of laser altimetry in the orbit and attitude determination of Mars Global Surveyor SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Altimetry from the Mars Observer Laser Altimeter (MOLA), an instrument on board the Mars Global Surveyor (MGS) spacecraft, has been analyzed for the period of the MGS Science Phasing Orbit-1 (SPO-1) mission phase. Altimeter ranges have been used to improve significantly the orbit and attitude knowledge of the spacecraft by the use of crossover constraint equations derived from short passes of the MOLA data. These constraint equations differ from traditional crossover constraints and exploit the small footprint associated with laser altimetry. The rationale for using this technique with laser altimetry over sloping terrain is laid out and evidence of the resulting benefit is presented. C1 NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. Raytheon ITSS, Greenbelt, MD 20770 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. RP Rowlands, DD (reprint author), NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Code 926, Greenbelt, MD 20771 USA. RI Rowlands, David/D-2751-2012; Luthcke, Scott/D-6283-2012; Lemoine, Frank/D-1215-2013; Neumann, Gregory/I-5591-2013 OI Neumann, Gregory/0000-0003-0644-9944 NR 10 TC 32 Z9 33 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 1999 VL 26 IS 9 BP 1191 EP 1194 DI 10.1029/1999GL900223 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 193EL UT WOS:000080122900002 ER PT J AU Seiff, A Kirk, DB Mihalov, J Knight, TCD AF Seiff, A Kirk, DB Mihalov, J Knight, TCD TI Further evaluation of waves and turbulence encountered by the Galileo Probe during descent in Jupiter's atmosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Data from the Galileo Probe in Jupiter descent indicated descent velocity oscillations as large as +/-5 m/s on a height scale of a few km, which suggested gravity waves in the atmosphere between 4 and 20 bars (Seiff et al., 1998), an important observation for atmospheric stability and dynamics. But we now find these velocity fluctuations to be inconsistent with simultaneous measurements of mean accelerations, which were relatively steady. This conflict is resolved in favor of the accelerometers. The velocity fluctuations can be explained from digital uncertainties in the slow rate of pressure rise. However, the accelerometers did record higher frequency perturbations of up to 0.1g. Attributed to turbulence, these imply turbulent velocities from 0.3 to 5 m/s at scales of 10 to 40 m. However, they were at least partly a result of unsteady parachute aerodynamics. C1 San Jose State Univ Fdn, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Oregon, Dept Phys, Eugene, OR 97403 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Martin Marietta Aerosp Co, Westover, NY USA. RP Seiff, A (reprint author), San Jose State Univ Fdn, Ames Res Ctr, MS 245-1, Moffett Field, CA 94035 USA. NR 7 TC 3 Z9 3 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 1999 VL 26 IS 9 BP 1199 EP 1202 DI 10.1029/1999GL900238 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 193EL UT WOS:000080122900004 ER PT J AU Lohmann, D Lettenmaier, DP Liang, X Wood, EF Boone, A Chang, S Chen, F Dai, YJ Desborough, C Dickinson, RE Duan, QY Ek, M Gusev, YM Habets, F Irannejad, P Koster, R Mitchell, KE Nasonova, ON Noilhan, J Schaake, J Schlosser, A Shao, YP Shmakin, AB Verseghy, D Warrach, K Wetzel, P Xue, YK Yang, ZL Zeng, QC AF Lohmann, D Lettenmaier, DP Liang, X Wood, EF Boone, A Chang, S Chen, F Dai, YJ Desborough, C Dickinson, RE Duan, QY Ek, M Gusev, YM Habets, F Irannejad, P Koster, R Mitchell, KE Nasonova, ON Noilhan, J Schaake, J Schlosser, A Shao, YP Shmakin, AB Verseghy, D Warrach, K Wetzel, P Xue, YK Yang, ZL Zeng, QC TI The project for intercomparison of land-surface parameterization schemes (PILPS) phase 2(c) Red-arkansas river basin experiment 3. Spatial and temporal analysis of water fluxes (vol 19, pg 161, 1998) SO GLOBAL AND PLANETARY CHANGE LA English DT Correction C1 Princeton Univ, Dept Civil Engn & Operat Res, Princeton, NJ 08544 USA. Univ Washington, Dept Civil Engn, Seattle, WA 98195 USA. NASA, Mesoscale Dynam & Precipitat Branch, GSFC, Greenbelt, MD USA. USAF, Res Lab, Hanscom, MA USA. NOAA, NCEP, Environm Modeling Ctr, Camp Springs, MD USA. Chinese Acad Sci, Inst Atmospher Phys, Beijing, Peoples R China. Macquarie Univ, Climat Impacts Ctr, Sydney, NSW, Australia. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. NOAA, NWS, Off Hydrol, Silver Spring, MD USA. Oregon State Univ, Corvallis, OR 97331 USA. Russian Acad Sci, Inst Water Problems, Moscow, Russia. CNRM, MeteoFrance, Toulouse, France. Univ New S Wales, Ctr Adv Numer Computat Engn & Sci, Sydney, NSW 2052, Australia. NASA, Hydrol Sci Branch, GSFC, Greenbelt, MD USA. NOAA, GFDL, Princeton, NJ USA. Inst Geog, Moscow, Russia. RP Lohmann, D (reprint author), Princeton Univ, Dept Civil Engn & Operat Res, Princeton, NJ 08544 USA. RI Yang, Zong-Liang/B-4916-2011; Koster, Randal/F-5881-2012; lettenmaier, dennis/F-8780-2011; Nasonova, Olga/B-6093-2014; Duan, Qingyun/C-7652-2011; gusev, yugeniy/G-4711-2014; Shao, Yaping/G-3606-2013 OI Koster, Randal/0000-0001-6418-6383; lettenmaier, dennis/0000-0003-3317-1327; Duan, Qingyun/0000-0001-9955-1512; gusev, yugeniy/0000-0003-3886-2143; Shao, Yaping/0000-0002-2041-5479 NR 1 TC 0 Z9 0 U1 0 U2 8 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-8181 J9 GLOBAL PLANET CHANGE JI Glob. Planet. Change PD MAY PY 1999 VL 20 IS 4 BP 291 EP 295 PG 5 WC Geography, Physical; Geosciences, Multidisciplinary SC Physical Geography; Geology GA 215BP UT WOS:000081362300007 ER PT J AU Shinn, JL Wilson, JW Singleterry, RC Xapsos, MA AF Shinn, JL Wilson, JW Singleterry, RC Xapsos, MA TI Implication of microdosimetry in estimation of radiation quality in space environment SO HEALTH PHYSICS LA English DT Article DE microdosimetry; lineal energy; quality factor; proportional counters ID ENERGY DEPOSITION; IONIZATION; SITES; DISTRIBUTIONS; FLUCTUATIONS; SPECTRA; MODEL AB Errors introduced using a tissue equivalent proportional counter to estimate radiation quality of an arbitrary ion field as related to space radiations are examined. This is accomplished by using a generalized analytic model to calculate the effect of energy loss straggling, track structure, and pathlength distribution on the microdosimetric distribution, The error can be as large as a factor of two, but no systematic trend could be found. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. USN, Res Lab, Washington, DC 20375 USA. NR 36 TC 3 Z9 3 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 0017-9078 EI 1538-5159 J9 HEALTH PHYS JI Health Phys. PD MAY PY 1999 VL 76 IS 5 BP 510 EP 515 DI 10.1097/00004032-199905000-00007 PG 6 WC Environmental Sciences; Public, Environmental & Occupational Health; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging SC Environmental Sciences & Ecology; Public, Environmental & Occupational Health; Nuclear Science & Technology; Radiology, Nuclear Medicine & Medical Imaging GA 184AZ UT WOS:000079588300006 PM 10201564 ER PT J AU Konopliv, AS Banerdt, WB Sjogren, WL AF Konopliv, AS Banerdt, WB Sjogren, WL TI Venus gravity: 180th degree and order model SO ICARUS LA English DT Article DE Venus; gravity; spherical harmonics; Doppler ID MAGELLAN; TOPOGRAPHY; FIELD; SCINTILLATION; NAVIGATION; TRACKING; CYCLE-5 AB The Magellan Doppler radiometric tracking data provides unprecedented precision for spacecraft-based gravity measurements with the maximum resolution approaching spherical harmonic degree and order 180 in selected equatorial regions. Determining a gravity field to degree 180 with a complete covariance containing the correlations between all the spherical harmonic coefficients (a 4.5-GB binary file for the triangular matrix) would be an extensive computational task even on the JPL/Caltech supercomputer that we used. Instead we determined a gravity field complete to degree and order 180 but in three separate steps. This gravity solution (MGNP180U) was determined first to degree and order 120 with a complete covariance for all the coefficients to degree 120. The second step solved far the coefficients from degree 116 to 155 only and the third step from degree 154 to 180. MGNP180U shows substantial improvement over previous solutions (up to and including MGNP120PSAAP, A. S. Konopliv et al. 1996a, presented at 1996 AGU Fall Meeting, San Francisco, CA) especially in the medium to shorter wavelengths (harmonic degree 80 and greater). The RMS magnitude power in the spectrum has increased as well as the correlations with topography, The amplitudes of various features have increased substantially (up to 33%, e.g., Bell Regio and Maat Mons). This will allow for better investigation of lithospheric modeling for shorter wavelength features such as coronae, volcanoes, and impact basins, (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Konopliv, AS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 42 TC 92 Z9 96 U1 1 U2 7 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 1999 VL 139 IS 1 BP 3 EP 18 DI 10.1006/icar.1999.6086 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202LW UT WOS:000080654800002 ER PT J AU Rappaport, NJ Konopliv, AS Kucinskas, AB Ford, PG AF Rappaport, NJ Konopliv, AS Kucinskas, AB Ford, PG TI An improved 360 degree and order model of Venus topography SO ICARUS LA English DT Article DE Venus surface; Venus interior ID MANTLE DYNAMICS; GRAVITY; HIGHLANDS; REGIO; EARTH AB We present an improved 360 degree and order spherical harmonic solution for Venus' topography, The new model uses the most recent set of Venus altimetry data with spacecraft positions derived from a recent high resolution gravity model. Geometric analysis indicates that the offset between the center of mass and center of figure of Venus is about 10 times smaller than that for the Earth, the Moon, or Mars. Statistical analyses confirm that the RMS topography follows a power law over the central part of the spectrum. Compared to the previous topography model, the new model is more highly correlated with Venus' harmonic gravity field. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. RP Rappaport, NJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 50 Z9 52 U1 1 U2 5 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 1999 VL 139 IS 1 BP 19 EP 31 DI 10.1006/icar.1999.6081 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202LW UT WOS:000080654800003 ER PT J AU Guest, JE Stofan, ER AF Guest, JE Stofan, ER TI A new view of the stratigraphic history of Venus SO ICARUS LA English DT Article DE Venus; geological processes; planetary surfaces; tectonics; volcanism ID IMPACT CRATER DENSITIES; TOPOGRAPHIC RISES; LAVINIA-PLANITIA; GLOBAL SURVEY; VOLCANISM; EVOLUTION; TECTONICS; CORONAE; MAGELLAN; PLAINS AB Studies of Venus using Magellan data have so far generated two views about the way Venus has evolved. On the one hand, Venus has been suggested to have had a history in which there was a series of epochs, each represented by a different volcanic or tectonic process on a global scale (Basilevsky and Head 1995; J, W, Head et al, 1996, Lunar Planet Sci, 27th, 525-526; P. T. Basilevsky et al. 1997, In Venus II, Univ, of Arizona Press, Tucson). This we define as a directional history. On the other hand, there is evidence to suggest that coronae, rifts, wrinkle ridges, small and large edifices, and large flow fields have each formed throughout the portion of Venus' history revealed by presently exposed rack units. We propose that the plains have been built up by lavas erupted in a number of different styles, each occurring throughout the history represented by the exposed stratigraphy of the planet. Dates derived from crater counts accumulated from the combined area of specific types of feature such as coronae (e.g., M. H. Price et al, 1996, J, Geophys, Res. 101, 4657-4672) must be interpreted with care as the method is based upon the assumption that features of like morphology have the same age. Detailed studies from full resolution Magellan data indicate that Venus has had a complex history in which most geologic processes have operated in a nondirectional fashion to a greater or lesser extent throughout the planet's history. (C) 1999 Academic Press. C1 UCL, Dept Phys & Astron, Planetary Image Ctr, London NW7 2QS, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Guest, JE (reprint author), UCL, Dept Phys & Astron, Planetary Image Ctr, 33-35 Daws Lane,Mill Hill, London NW7 2QS, England. EM jeg@star.ucl.ac.uk NR 60 TC 75 Z9 75 U1 4 U2 12 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD MAY PY 1999 VL 139 IS 1 BP 55 EP 66 DI 10.1006/icar.1999.6091 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202LW UT WOS:000080654800007 ER PT J AU Smrekar, SE Stofan, ER AF Smrekar, SE Stofan, ER TI Origin of corona-dominated topographic rises on Venus SO ICARUS LA English DT Article DE Venus; corona; gravity; delamination; hotspots ID LITHOSPHERIC FLEXURE; GLOBAL DISTRIBUTION; MANTLE PLUMES; EVOLUTION; COMPENSATION; CONVECTION; VOLCANISM; FEATURES; SURFACE; SUBDUCTION AB Both large-scale mantle upwellings, comparable to terrestrial hotspots on Earth, and smaller scale mantle upwellings, known as coronae, occur on Venus. Corona-dominated rises have many of the characteristics of large-scale mantle upwellings, or hotspots, such as broad topographic, rises greater than 1000 km in diameter and large positive gravity anomalies. Due to the presence of clusters of three to eight coronae, three large volcanic rises (or hotspots) on Venus have been classified as corona-dominated rises (CDRs): Themis, Eastern Eistla, and Central Eistla Regiones. CDRs have been interpreted to result from the break-up of a large-scale plume. Comparison of the topographic morphology for individual coronae at Themis and Eastern Eistla Region to a model of corona evolution indicate that they are in varying stages of evolution. At Eastern Eistla Regio all the coronae have essentially the same topographic morphology, consistent with a late stage of evolution and the presence of a depleted mantle layer at depth. The complex deformation sequences and stratigraphic relationships both between coronae and with respect to the regional plains observed at all three rises indicate a prolonged origin.:This observation, as well as the varying stages of evolution, rule out the previously proposed interpretation of corona-dominated rises as a manifestation of the break-up of a large-scale mantle upwelling, which requires essentially simultaneous formation of the coronae. Instead we suggest that other large topographic rises are the manifestation of deep mantle plumes, likely to originate at the core-mantle boundary, and that CDRs are clusters of coronae that originate at a shallower interface, perhaps at an upper-lower mantle boundary. Using top- and bottom-loading flexural models to fit the gravity/topography admittance spectrum for each of the three CDRs yields elastic thickness estimates that are 10-15 km greater for bottom-loading at longer wavelengths than top-loading at shorter wavelengths. Estimates of elastic thickness assuming top-loading are 10, 12, and 22 km and 20, 25, and 35 km from bottom-loading for Eastern Eistla, Central Eistla, and Themis Regiones, respectively. Wt: believe that the bottom-loading elastic thickness estimates are more reliable because using a top-loading model when both types of loading are present yields an unrealistically low elastic thickness estimate. As there is no obvious source of surface loading at either Themis or at Eastern Eistla, we interpret the top-loading admittance signature to be a result of delamination of the lower lithosphere depressing the surface, which is consistent with the observed coronae morphologies. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Smrekar, SE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 183-501, Pasadena, CA 91109 USA. NR 49 TC 40 Z9 40 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 1999 VL 139 IS 1 BP 100 EP 115 DI 10.1006/icar.1999.6090 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 202LW UT WOS:000080654800011 ER PT J AU Bernard, D Doyle, R Riedel, E Rouquette, N Wyatt, J Lowry, M Nayak, P AF Bernard, D Doyle, R Riedel, E Rouquette, N Wyatt, J Lowry, M Nayak, P TI Autonomy and software technology on NASA's Deep Space One SO IEEE INTELLIGENT SYSTEMS & THEIR APPLICATIONS LA English DT Article C1 Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Stanford, CA 94305 USA. RP Bernard, D (reprint author), Jet Prop Lab, Pasadena, CA 91109 USA. NR 0 TC 8 Z9 8 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1094-7167 J9 IEEE INTELL SYST APP JI IEEE Intell. Syst. Appl. PD MAY-JUN PY 1999 VL 14 IS 3 BP 10 EP 15 DI 10.1109/5254.769876 PG 6 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 204BB UT WOS:000080742100008 ER PT J AU Shimoda, H Liu, WT Masuko, H Nakjima, T Ogawa, T Saino, TT AF Shimoda, H Liu, WT Masuko, H Nakjima, T Ogawa, T Saino, TT TI Special issue on ADEOS SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Editorial Material C1 NASDA, Earth Observat Res Ctr, Tokyo, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Minist Posts & Telecommun, Commun Res Lab, Global Environm Div, Tokyo, Japan. Univ Tokyo, Ctr Climate Syst Res, Tokyo, Japan. Nagoya Univ, Inst Hydrospher Atmospher Sci, Lab Global Aquat Biol Proc, Nagoya, Aichi, Japan. RP Shimoda, H (reprint author), NASDA, Earth Observat Res Ctr, Tokyo, Japan. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAY PY 1999 VL 37 IS 3 BP 1463 EP 1463 PN 2 PG 1 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 197ER UT WOS:000080352300001 ER PT J AU Shimada, M Oaku, H Oguma, H Green, RO Miyachi, Y Shimoda, H AF Shimada, M Oaku, H Oguma, H Green, RO Miyachi, Y Shimoda, H TI Calibration of advanced visible and near infrared radiometer SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE ADEOS; AVIRIS; AVNIR; calibration AB Calibration results of the advanced visible and near infrared radiometer (AVNIR) on board ADEOS are presented. First, the AVNIR responses to the internal and external calibration sources are evaluated, and their short- and long-term stabilities are summarized. Second, absolute radiometric calibration of AVNIR is conducted by using the NASA JPL's calibrated airborne optical sensor, and the results from several different calibration methods (preflight calibration, and in-flight calibrations using the on-board data, the AVIRIS, and the vicarious method) are compared, Third, the geometric accuracy and the image quality are summarized. C1 Natl Space Dev Agcy Japan, Earth Observat Res Ctr, Tokyo 1060032, Japan. Natl Inst Environm Studies, Tokyo, Japan. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. NASDA, Earth Observat Satellite Dev Div, Tokyo, Japan. RP Shimada, M (reprint author), Natl Space Dev Agcy Japan, Earth Observat Res Ctr, Tokyo 1060032, Japan. NR 16 TC 10 Z9 10 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAY PY 1999 VL 37 IS 3 BP 1472 EP 1483 DI 10.1109/36.763260 PN 2 PG 12 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 197ER UT WOS:000080352300003 ER PT J AU Tsai, W Graf, JE Winn, C Huddleston, JN Dunbar, S Freilich, MH Wentz, FJ Long, DG Jones, WL AF Tsai, W Graf, JE Winn, C Huddleston, JN Dunbar, S Freilich, MH Wentz, FJ Long, DG Jones, WL TI Postlaunch sensor verification and calibration of the NASA Scatterometer SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE calibration; NSCAT; scatterometer; sea; winds ID OCEAN AB Scatterometer instruments are active microwave sensors that transmit a series of microwave pulses and measure the returned echo power to determine the normalized radar backscattering cross section (sigma-0) of the ocean surface from which the speed and direction of near-surface ocean winds are derived, The NASA Scatterometer (NSCAT) was launched on board the ADEOS spacecraft in August 1996 and returned ten months of high-quality data before the failure of the ADEOS spacecraft terminated the data stream in June 1997, The purpose of this paper is to provide an overview of the NSCAT instrument and sigma-0 computation and to describe the process and the results of an intensive postlaunch verification, calibration, and validation effort, This process encompassed the functional and performance verification of the flight instrument, the sigma-0 computation algorithms, the science data processing system, and the analysis of the sigma-0 and wind products, The calibration process included the radiometric calibration of NSCAT using both engineering telemetry and science data and the radiometric beam balance of all eight antenna beams using both open ocean and uniform land targets, Finally, brief summaries of the construction of the NSCAT geophysical model function and the verification and validation of the wind products will be presented. The key results of this paper are as follows: The NSCAT instrument was shown to function properly and all functional parameters were within their predicted ranges. The instrument electronics subsystems were very stable and all of the key parameters, such as transmit power, receiver gain, and bandpass filter responses, were shown to be stable to within 0.1 dB. The science data processing system was thoroughly verified and the sigma-0 computation error was shown to be less than 0.1 dB, All eight antenna beams were radiometrically balanced, using natural targets, to an estimated accuracy of about 0.3 dB. Finally, a new model function, called NSCAT-1, was constructed and used to produce wind products. The wind products were statistically verified using ECMWF wind fields and were validated using NDBC buoy measurements. Overall, we believe that NSCAT generated high-quality wind products with wind speed and direction accuracies that met the science requirements. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. Remote Sensing Syst, Santa Rosa, CA 95404 USA. Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84601 USA. Univ Cent Florida, Dept Elect & Comp Engn, Cent Florida Remote Sensing Lab, Orlando, FL 32816 USA. RP Tsai, W (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 27 TC 20 Z9 21 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAY PY 1999 VL 37 IS 3 BP 1517 EP 1542 DI 10.1109/36.763264 PN 2 PG 26 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 197ER UT WOS:000080352300007 ER PT J AU Krueger, AJ Jaross, G AF Krueger, AJ Jaross, G TI TOMS ADEOS instrument characterization SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE atmospheric measurements; ozone; remote sensing; UV calibration; wavelength calibration ID TOTAL OZONE; VERSION-7 AB Data sets from the total ozone mapping spectrometer (TOMS) on the ADEOS I spacecraft have been processed using initial and time-dependent instrument characterizations. Initial characterizations, performed on the ground, focused on wavelength registration of the six near-UV TOMS channels and on the instrument albedo calibration, Few calibration adjustments were required in the postlaunch phase. Instrument performance, including bandpass wavelengths, were stable throughout the life of the instrument, Indirect evidence exists for small changes in the reflectance of the primary solar diffuser. Characterizations used in data processing assume no change. No ozone retrieval errors are expected due to this assumption. All totaled, estimated calibration uncertainties represent less than 1% in total-column ozone uncertainty. A comparison between two TOMS instruments:is marginally consistent with these estimates. However, a comparison with ground measurements resulted in differences exceeding 1%. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon ITSS, Lanham, MD 20706 USA. RP Krueger, AJ (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 12 TC 9 Z9 11 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 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD MAY PY 1999 VL 37 IS 3 BP 1543 EP 1549 DI 10.1109/36.763265 PN 2 PG 7 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 197ER UT WOS:000080352300008 ER PT J AU Long, DG Drinkwater, MR AF Long, DG Drinkwater, MR TI Cryosphere applications of NSCAT data SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE ice sheets; polar; radar; scatterometer; sea-ice ID GREENLAND ICE-SHEET; ARCTIC SEA-ICE; SCATTEROMETER DATA; ENHANCED RESOLUTION; SURFACE-PROPERTIES; WAVELET ANALYSIS; SOUTHERN-OCEAN; RADAR; ANTARCTICA; SHELF AB Though designed to measure vector winds over the ocean, new imaging techniques facilitate the use of NASA scatterometer data (NSCAT) in cryosphere studies. NSCAT provides data of unprecedented coverage, resolution, and quality which, when coupled with the scatterometer image reconstruction with filtering (SIRF) algorithm, enables images of sigma degrees at resolutions approaching 8 km over stationary targets, Such images are useful in ice mapping and classification, and multidecadal studies are possible by comparison with Seasat Scatterometer (SASS) data. The utility of NSCAT data in polar ice studies is illustrated through a review of two cryosphere applications of NSCAT data: 1) sea-ice mapping and tracking and 2) ice-sheet change in Greenland and Antarctica. The wide swath and frequent revisit, coupled with incidence and azimuth angle diversity makes NSCAT data very effective in mapping the extent of sea-ice. In Greenland, snow and ice "facies" are clearly delineated on the basis of the seasonally dependent radar backscattering cross section, due to sensitivity of radar backscatter to diagenetic changes occurring at and beneath the surface, Comparison of NSCAT and SASS data enables study of change in Greenland between 1978 and 1996. C1 Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84602 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Long, DG (reprint author), Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84602 USA. RI Drinkwater, Mark/C-2478-2011; Long, David/K-4908-2015 OI Drinkwater, Mark/0000-0002-9250-3806; Long, David/0000-0002-1852-3972 NR 73 TC 58 Z9 59 U1 1 U2 8 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 1999 VL 37 IS 3 BP 1671 EP 1684 DI 10.1109/36.763287 PN 2 PG 14 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 197ER UT WOS:000080352300020 ER PT J AU Siegel, PH Smith, RP Gaidis, MC Martin, SC AF Siegel, PH Smith, RP Gaidis, MC Martin, SC TI 2.5-THz GaAs monolithic membrane-diode mixer SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE FIR; GaAs; membrane; micromachined; planar; radiometer; Schottky diode mixer; THz; waveguide AB A novel GaAs monolithic membrane-diode (MOMED) structure has been developed and implemented as a 2.5-THz Schottky diode mixer, The mixer blends conventional machined metallic waveguide with micromachined monolithic GaAs circuitry to form, for the first time, a robust, easily fabricated, and assembled room-temperature planar diode receiver at frequencies above 2 THz, Measurements of receiver performance, in air, yield a T-receiver of 16 500-K double sideband (DSB) at 8.4-GHz intermediate frequency (IF) using a 150-K commercial Miteq amplifier. The receiver conversion loss (diplexer through IF amplifier input) measures 16.9 dB in air, yielding a derived "front-end" noise temperature below 9000-K DSB at 2514 GHz, Using a CO2-pumped methanol far-infrared laser as a local oscillator at 2522 GHz, injected via a Martin-Puplett diplexer, the required power is approximate to 5 mW for optimum pumping and can be reduced to less than 3 mW with a 15% increase in receiver noise, Although demonstrated as a simple submillimeter-wave mixer, the all-GaAs membrane structure that has been developed is suited to a wide variety of low-loss high-frequency radio-frequency circuits. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Siegel, PH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Gaidis, Michael/D-3327-2013 NR 22 TC 111 Z9 111 U1 2 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD MAY PY 1999 VL 47 IS 5 BP 596 EP 604 DI 10.1109/22.763161 PG 9 WC Engineering, Electrical & Electronic SC Engineering GA 194LH UT WOS:000080194600012 ER PT J AU Johnson, AE Hebert, M AF Johnson, AE Hebert, M TI Using spin images for efficient object recognition in cluttered 3D scenes SO IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE LA English DT Article DE 3D object recognition; surface matching; spin image; clutter; occlusion; oriented point; surface mesh; point correspondence ID 3-D OBJECTS; REPRESENTATION; REGISTRATION; APPEARANCE; SURFACES; VISION; PARTS AB We present a 3D shape-based object recognition system for simultaneous recognition of multiple objects in scenes containing clutter and occlusion. Recognition is based on matching surfaces by matching points using the spin image representation. The spin image is a data level shape descriptor that is used to match surfaces represented as surface meshes. We present a compression scheme for spin images that results in efficient multiple object recognition which we verify with results showing the simultaneous recognition of multiple objects from a library of 20 models. Furthermore, we demonstrate the robust performance of recognition in the presence of clutter and occlusion through analysis of recognition trials on 100 scenes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carnegie Mellon Univ, Inst Robot, Pittsburgh, PA 15213 USA. RP CALTECH, Jet Prop Lab, Mail Stop 125-209,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM aej@robotics.jpl.nasa.gov; hebert@ri.cmu.edu NR 27 TC 940 Z9 993 U1 3 U2 61 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0162-8828 EI 1939-3539 J9 IEEE T PATTERN ANAL JI IEEE Trans. Pattern Anal. Mach. Intell. PD MAY PY 1999 VL 21 IS 5 BP 433 EP 449 DI 10.1109/34.765655 PG 17 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 194LK UT WOS:000080194900005 ER PT J AU Bayard, DS AF Bayard, DS TI On the LTI properties of adaptive feedforward systems with tap delay-line regressors SO IEEE TRANSACTIONS ON SIGNAL PROCESSING LA English DT Article ID SINUSOIDAL REGRESSORS; REPRESENTATIONS; FILTER; SOUND AB It is shown that an adaptive system whose regressor is Formed by tap delay-line (TDL) filtering of a multitone sinusoidal signal is representable as a parallel connection of a linear time-invariant (LTI) block and a linear time-varying (LTV) block. A norm-bound (induced 2-norm) is computed explicity on the LTV block and is shown to decrease as N-1, where N is the number of taps. Hence, the adaptive system becomes LTI in the limit as the number of taps goes to infinity. In the more realistic case where the number of taps N is finite, the new "LTI plus norm-bounded perturbation" representation renders, for the first time, the adaptive system analyzable by standard robust control methods. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bayard, DS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 21 TC 4 Z9 4 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1053-587X J9 IEEE T SIGNAL PROCES JI IEEE Trans. Signal Process. PD MAY PY 1999 VL 47 IS 5 BP 1288 EP 1296 DI 10.1109/78.757216 PG 9 WC Engineering, Electrical & Electronic SC Engineering GA 187GK UT WOS:000079778600008 ER PT J AU Druyan, LM Lonergan, P Eichler, T AF Druyan, LM Lonergan, P Eichler, T TI A GCM investigation of global warming impacts relevant to tropical cyclone genesis SO INTERNATIONAL JOURNAL OF CLIMATOLOGY LA English DT Article DE global warming; climate change; tropical storm frequency; GISS GCM ID AFRICAN WAVE DISTURBANCES; 50 YEARS LEAD; CLIMATE-CHANGE; GREATER INTENSITY; HIGHER FREQUENCY; MODEL; HURRICANES; VORTICES AB Two approaches that consider how greenhouse warming might impact the frequency of tropical cyclone (TC) genesis are explored. Results are based on GCM experiments with the q-flux version global climate model of the NASA/Goddard Institute for Space Studies (GISS); one set representing contemporary atmospheric concentrations of CO2, contrasting with the second set representing the global climate in double CO2 equilibrium. July-September means of climate parameters relevant to TC genesis are computed from the simulations and combined to formulate a seasonal genesis parameter (SGP), as suggested in an empirical study by Gray (in Shaw, D.B. (ed.), Meteorology Over the Tropical Oceans, 1979, pp. 155-218). The spatial distribution of the July-September SGP based on the control simulations is compared with the observed distribution and results using other models. The corresponding spatial distribution of the July-September SGP derived from the double CO2 simulations, when compared with the control results, projects a 50% increase in the genesis frequency of TC over the western North Atlantic/Gulf of Mexico basin, but 100-200% increases over the North Pacific Ocean. The increases, most of which are attributable to enhanced ocean temperatures, may be exaggerated, suggesting that the original SGP formulation requires tuning or other revisions. For example, it is noted that SGP computed from the NCEP 1982-1994 re-analysis climatology do not accurately reflect the known spatial distributions of TC genesis frequency. The second approach detects easterly waves over the eastern North Atlantic Ocean by spectral analysis of vorticity and wind component time trends, comparing wave activity in the control and double CO2 simulations. Results indicate a southward shift in future trajectories of easterly waves over West Africa and significant increases in their average amplitude as they cross the African coast and begin to traverse the Eastern Atlantic along 14 degrees N. Copyright (C) 1999 Royal Meteorological Society. C1 Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Sci Syst & Applicat Inc, New York, NY USA. Columbia Univ, Dept Geol Sci, New York, NY 10027 USA. RP Druyan, LM (reprint author), Columbia Univ, Ctr Climate Syst Res, 2880 Broadway, New York, NY 10025 USA. RI Eichler, Timothy/A-5040-2015 OI Eichler, Timothy/0000-0003-0342-9681 NR 22 TC 18 Z9 18 U1 0 U2 4 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0899-8418 J9 INT J CLIMATOL JI Int. J. Climatol. PD MAY PY 1999 VL 19 IS 6 BP 607 EP 617 DI 10.1002/(SICI)1097-0088(199905)19:6<607::AID-JOC383>3.0.CO;2-M PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 199KK UT WOS:000080480200002 ER PT J AU Rashidnia, N Ebiana, AB AF Rashidnia, N Ebiana, AB TI Large scale motions in a manipulated turbulent boundary layer SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article AB Experiments were performed to examine structural changes that exist in a turbulent boundary layer with measured 2-10% net drag reduction obtained using a tandem arranged parallel plate manipulator (hereafter abbreviated TAPPM). Conditionally sampled and space-time correlation measurements support a picture of approximately equal reductions in the streamwise and normal components of the large scale fluctuations, both in the boundary layer and in the irrotational ambient flow in the valleys between the large scale motions (LSMs) at 20 delta(o). However, by 51 delta(o), both the LSMs and the response of the irrotational ambient flow relax to approximately their unmanipulated state. Simple modeling suggests that in the valleys of irrotational fluid the motion would reestablish itself in 5 delta, and it is suggested that the presence of the TAPPM's wake in the outer region inhibits the reformation of these large scale wallward sweeps sustaining the lower values of the local skin friction, C-f. Because of the thick boundary layer in the present experiment, at 20 delta(o) the TAPPM's wake has not entered the wall region, in contrast to many other investigations. At streamwise locations just before the main body of the wake intersects the wall (56 delta(o)), a rapid rise in C-f is observed. Afterwards, a small reduction in C-f (confirmed by three independent methods of measurements) is maintained resulting from the remaining defect in the wake, which lasts until the wake is fully mixed. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. NASA, NCMR Inc, Lewis Res Ctr, Brook Pk, OH 44142 USA. RP Ebiana, AB (reprint author), Cleveland State Univ, Dept Mech Engn, Cleveland, OH 44115 USA. NR 33 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 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD MAY PY 1999 VL 42 IS 9 BP 1645 EP 1664 DI 10.1016/S0017-9310(98)00219-1 PG 20 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 166EU UT WOS:000078563900008 ER PT J AU Bain, A Van Vorst, WD AF Bain, A Van Vorst, WD TI The Hindenburg tragedy revisited: the fatal flaw found SO INTERNATIONAL JOURNAL OF HYDROGEN ENERGY LA English DT Article C1 Univ Calif Los Angeles, Dept Chem Engn, Los Angeles, CA 90095 USA. NASA, Kennedy Space Ctr, Hydrogen Programs, Cape Canaveral, FL USA. RP Van Vorst, WD (reprint author), Univ Calif Los Angeles, Dept Chem Engn, Los Angeles, CA 90095 USA. NR 0 TC 10 Z9 10 U1 3 U2 11 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0360-3199 J9 INT J HYDROGEN ENERG JI Int. J. Hydrog. Energy PD MAY PY 1999 VL 24 IS 5 BP 399 EP 403 DI 10.1016/S0360-3199(98)00176-1 PG 5 WC Chemistry, Physical; Electrochemistry; Energy & Fuels SC Chemistry; Electrochemistry; Energy & Fuels GA 199CX UT WOS:000080462800001 ER PT J AU Wu, H George, K Yang, TC AF Wu, H George, K Yang, TC TI Estimate of the frequency of true incomplete exchanges in human lymphocytes exposed to 1 GeV u Fe ions in vitro SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY LA English DT Article ID IN-SITU HYBRIDIZATION; CHROMOSOME-ABERRATIONS; ALPHA-PARTICLES; RADIATION; TRANSLOCATIONS; LESIONS; PROBES AB Purpose: To study the frequency of true incomplete exchanges induced by high-LET radiation. Materials and methods: Human lymphocytes were exposed to 1 GeV/u Fe ions (LET = 140 keV/mu m). Chromosome aberrations were analysed by a fluorescence in situ hybridization using a combination of whole-chromosome-specific probes and human telomere probes. Chromosomes 1, 3 and 4 were investigated. Results: The percentage of incomplete exchanges was between 23 and 29% if telomere signals were not considered. The percentage decreased to similar to 10% after ruling out False incomplete exchanges containing telomere signals. The final estimation of true incomplete exchanges was <10%. Conclusion: Within a degree of uncertainty, the percentage of true incomplete exchanges in 1 GeV/u Fe ion-irradiated human lymphocytes was similar to that induced by gamma rays. C1 NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Houston, TX 77058 USA. NASA, Kelsey Seybold Clin, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Wyle Labs, Houston, TX 77058 USA. RP Wu, H (reprint author), NASA, Lyndon B Johnson Space Ctr, Radiat Biophys Lab, Mail Code SD2, Houston, TX 77058 USA. NR 24 TC 28 Z9 28 U1 1 U2 1 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 1999 VL 75 IS 5 BP 593 EP 599 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 199YM UT WOS:000080511700008 PM 10374941 ER PT J AU Rohloff, TJ Whitmore, SA Catton, I AF Rohloff, TJ Whitmore, SA Catton, I TI Fault-tolerant neural network algorithm for flush air data sensing SO JOURNAL OF AIRCRAFT LA English DT Article AB A fault-tolerant neural network algorithm was successfully developed for use with hush air data sensing systems. This algorithm is composed of a combination of aerodynamic and neural network models used to translate a discrete pressure distribution from the nose of an aircraft into a set of air data parameters, including static pressure, dynamic pressure, Mach number, angle of attack, and angle of sideslip. Techniques were developed to detect and eliminate the effect of a lost signal from the measured pressure distribution. This system was evaluated with archived data, and its performance was compared with a signal processing system based completely on aerodynamic models. C1 Univ Calif Los Angeles, Dept Mech & Aerosp Engn, Los Angeles, CA 90095 USA. NASA, Ames Dryden Flight Res Ctr, Aerodynam Branch, Edwards AFB, CA 93523 USA. RP Rohloff, TJ (reprint author), Univ Calif Los Angeles, Dept Mech & Aerosp Engn, 405 Hilgard Ave, Los Angeles, CA 90095 USA. NR 12 TC 9 Z9 14 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1999 VL 36 IS 3 BP 541 EP 549 DI 10.2514/2.2489 PG 9 WC Engineering, Aerospace SC Engineering GA 209EZ UT WOS:000081036400008 ER PT J AU Ying, SX Spaid, FW McGinley, CB Rumsey, CL AF Ying, SX Spaid, FW McGinley, CB Rumsey, CL TI Investigation of confluent boundary layers in high-lift flows SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 16th Applied Aerodynamics Conference CY JUN 15-18, 1998 CL ALBUQUERQUE, NEW MEXICO SP Amer Inst Aeronaut & Astronaut ID NAVIER-STOKES COMPUTATIONS AB The confluent boundary layers over a three-clement high-lift airfoil are studied using both numerical and experimental approaches. The results suggest that wake prediction is crucial to the convergence and accuracy of the overall solution. At maximum lift, unsteadiness is observed in the experiment, which is not captured by computations. However, solutions at maximum lift indicate that, although the how is attached over the flap, the separation bubble at the leading edge of the slat upper surface is coupled with inviscid flow reaching the compressibility limit. The thickened slat wake results in a displacement of near-surface flow over the main element and limits the main element from gaining more lift. The trends in the confluent boundary layers development require all aspects of the physics be modeled appropriately, including transition, turbulence, and inviscid-viscous interaction. An eddy viscosity turbulence model is shown to be ill-behaved for predicting some of the physics of wake confluence. Also, the isotropic eddy viscosity assumption is not strictly valid for the confluent boundary layers with large flow turning angles. C1 Boeing Co, Flight Performance, Long Beach, CA 90807 USA. Boeing Co, Expt Fluid Dynam, St Louis, MO 63166 USA. NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. RP Ying, SX (reprint author), Boeing Co, Flight Performance, MC 078-0421, Long Beach, CA 90807 USA. NR 44 TC 18 Z9 19 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 1999 VL 36 IS 3 BP 550 EP 562 DI 10.2514/2.2490 PG 13 WC Engineering, Aerospace SC Engineering GA 209EZ UT WOS:000081036400009 ER PT J AU McGowan, DM Ambur, DR AF McGowan, DM Ambur, DR TI Structural response of composite sandwich panels impacted with and without compression loading SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 39th Structures, Structural Dynamics, and Materials Conference CY APR 20-23, 1998 CL LONG BEACH, CALIFORNIA SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC AB The results of an experimental study of the impact damage characteristics and residual strength of composite sandwich panels impacted with and without a compression lending are presented. Results of impact damage screening tests conducted to identify the impact-energy levels at which damage initiates and barely visible impact damage occurs in the impacted facesheet are discussed. Parametric effects studied in these tests include the impactor diameter and dropped-weight vs airgun-launched impactors. Residual strength results of panels tested in compression after impact are presented and compared with results of panels that are subjected to a compressive preload prior to being impacted. C1 NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. RP McGowan, DM (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. NR 11 TC 6 Z9 7 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD MAY-JUN PY 1999 VL 36 IS 3 BP 596 EP 602 DI 10.2514/2.2476 PG 7 WC Engineering, Aerospace SC Engineering GA 209EZ UT WOS:000081036400015 ER PT J AU Evans, KF Evans, AH Nolt, IG Marshall, BT AF Evans, KF Evans, AH Nolt, IG Marshall, BT TI The prospect for remote sensing of cirrus clouds with a submillimeter-wave spectrometer SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID RADIATIVE-TRANSFER; CLIMATE; ICE; SENSITIVITY; TEMPERATURE; SCATTERING; RADIANCES; MICROWAVE; SATELLITE; CHANNELS AB Given the substantial radiative effects of cirrus clouds and the need to validate cirrus cloud mass in climate models, it is important to measure the global distribution of cirrus properties with satellite remote sensing. Existing cirrus remote sensing techniques, such as solar reflectance methods, measure cirrus ice water path (IWP) rather indirectly and with limited accuracy. Submillimeter-wave radiometry is an independent method of cirrus remote sensing based on ice particles scattering the upwelling radiance emitted by the lower atmosphere. A new aircraft instrument, the Far Infrared Sensor for Cirrus (FIRSC), is described. The FIRSC employs a Fourier Transform Spectrometer (FTS), which measures the upwelling radiance across the whole submillimeter region (0.1-1.0-mm wavelength). This wide spectral coverage gives high sensitivity to most cirrus particle sizes and allows accurate determination of the characteristic particle size. Radiative transfer modeling is performed to analyze the capabilities of the submillimeter FTS technique. A linear inversion analysis is done to show that cirrus IWP, particle size, and upper-tropospheric temperature and water vapor may be accurately measured. A nonlinear statistical algorithm is developed using a database of 20 000 spectra simulated by randomly varying most relevant cirrus and atmospheric parameters. An empirical orthogonal function analysis reduces the 500-point spectrum (20-70 cm(-1)) to 15 "pseudo-channels" that are then input to a neural network to retrieve cirrus IWP and median particle diameter. A Monte Carlo accuracy study is performed with simulated spectra having realistic noise. The retrieval errors are low for IWP (rms less than a factor of 1.5) and for particle sizes (rms less than 30%) for IWP greater than 5 g m(-2) and a wide range of median particle sizes. This detailed modeling indicates that there is good potential to accurately measure cirrus properties with a submillimeter FTS. C1 Univ Colorado, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. GATS Inc, Hampton, VA USA. RP Evans, KF (reprint author), Univ Colorado, Program Atmospher & Ocean Sci, Campus Box 311, Boulder, CO 80309 USA. NR 26 TC 23 Z9 25 U1 0 U2 1 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 MAY PY 1999 VL 38 IS 5 BP 514 EP 525 DI 10.1175/1520-0450(1999)038<0514:TPFRSO>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 196CU UT WOS:000080292100002 ER PT J AU Schumann, RS Taylor, GE Merceret, FJ Wilfong, TL AF Schumann, RS Taylor, GE Merceret, FJ Wilfong, TL TI Performance characteristics of the Kennedy Space Center 50-MHz Doppler radar wind profiler using the median filter/first-guess data reduction algorithm SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID QUALITY AB The performance of an improved signal-processing algorithm implemented on the NASA 50-MHz radar wind profiler at Kennedy Space Center is analyzed. In 1990, NASA began using a 50-MHz Doppler radar wind profiler to demonstrate the applicability of the technology to assessing launch wind conditions at Kennedy Space Center. To produce critical wind profiles in minimal time, NASA replaced the conventional signal-processing system delivered by the manufacturer with a more robust system. The new signal-processing system uses a median filter to remove spurious Doppler spectral data and constrains the search for the atmospheric signal by a first guess. The new system has been in nearly continuous operation since mid-1994. Over this period, the system performance was evaluated in varied weather conditions, and numerous comparisons with wind profiles from radar-tracked jimspheres were accomplished. The system is now integrated into the prelaunch wind evaluation structure. This paper discusses the details of the new signal-processing system and presents the results of the performance analysis. C1 ENSCO Inc, Cocoa Beach, FL 32931 USA. NASA, Kennedy Space Ctr, FL USA. Sci & Technol Corp, Boulder, CO USA. RP Schumann, RS (reprint author), ENSCO Inc, Cocoa Beach, FL 32931 USA. NR 29 TC 8 Z9 8 U1 0 U2 0 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 MAY PY 1999 VL 16 IS 5 BP 532 EP 549 DI 10.1175/1520-0426(1999)016<0532:PCOTKS>2.0.CO;2 PG 18 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 194ZM UT WOS:000080224700004 ER PT J AU Flamant, CN Schwemmer, GK Korb, CL Evans, KD Palm, SP AF Flamant, CN Schwemmer, GK Korb, CL Evans, KD Palm, SP TI Pressure measurements using an airborne differential absorption lidar. Part I: Analysis of the systematic error sources SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID ATMOSPHERIC-TEMPERATURE PROFILES; BOUNDARY-LAYER STRUCTURE; OPTICAL-PROPERTIES; OCEAN SURFACE; WATER-VAPOR; AEROSOL; BACKSCATTER; SCATTERING AB Systematic error sources that require correction when making remote airborne measurements of the atmospheric pressure field in the lower troposphere, using an oxygen differential absorption lidar, are analyzed. A derailed analysis of this measurement technique is provided, which includes corrections for imprecise knowledge of the detector background level, the oxygen absorption line parameters, and variations in the laser output energy. In addition, the authors analyze other possible sources of systematic errors, including spectral effects related to aerosol and molecular scattering, water vapor vertical distribution, interference by rotational Raman scattering, and interference by isotopic oxygen lines. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20711 USA. Univ Maryland, College Pk, MD 20742 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Catonsville, MD USA. Sci Syst & Applicat Inc, Seabrook, MD USA. RP Schwemmer, GK (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20711 USA. NR 27 TC 6 Z9 8 U1 0 U2 9 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 MAY PY 1999 VL 16 IS 5 BP 561 EP 574 DI 10.1175/1520-0426(1999)016<0561:PMUAAD>2.0.CO;2 PG 14 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 194ZM UT WOS:000080224700006 ER PT J AU Raghavarao, R Suhasini, R Mayr, HG Hoegy, WR Wharton, LE AF Raghavarao, R Suhasini, R Mayr, HG Hoegy, WR Wharton, LE TI Equatorial spread-F (ESF) and vertical winds SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID RADAR OBSERVATIONS; ELECTRIC-FIELDS; PLASMA BUBBLES; REGION DYNAMO; ANOMALY ETWA; MAGSAT DATA; IONOSPHERE; ONSET; IRREGULARITIES; THERMOSPHERE AB The Equatorial Spread-F (ESF) phenomenon is recorded in ionograms as a hierarchy of plasma instabilities in the F-layer of the equatorial ionosphere. The ESF is characterized by irregularities in the plasma (electron and ion) density and electric field distributions perpendicular to the Earth's magnetic field. Large scale irregularities are generated by a primary plasma instability that develops in electric fields and plasma densities. Other secondary instabilities then develop and generate irregularities at several scale sizes that often produce a plasma 'hole' or 'bubble' that rises up with high E x B velocities. The ESF/plasma bubble phenomenon has been studied extensively with experimental techniques and modeling, which revealed important features. In the bottom side F-layer, near sunset, when the vertical density gradient steepens as the layer is supported by the horizontal (North-South) Earth's magnetic field lines against the omnipresent Earth's gravitational acceleration (g), the plasma conditions can give rise to Rayleigh-Taylor (RT) type instability. But the observed day to day variability of the ESF occurrence suggested that other agencies may also be involved in generating the instability. Sekar and Raghavarao (1987) with linear theory, and Raghavarao, Sekar and Suhasini (1992), with non-linear numerical modeling, suggested that vertical downward (upward) winds in the ambient gas have the potential to cause (inhibit) the ESF/bubble phenomenon. The presence of downward winds near the equator was reported earlier. In this paper, we show evidence for the presence of downward winds collocated with irregularities in electric fields and plasma densities as revealed by an unique combination of highly accurate measurements with instruments onboard the DE-2 satellite. The observations reported here are also consistent with the notion that the build-up of the equatorial ionization anomaly (EIA) prior to local sunset is important for the ESF instability. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Raghavarao, R (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 910 4, Greenbelt, MD 20771 USA. NR 56 TC 9 Z9 9 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 PY 1999 VL 61 IS 8 BP 607 EP 617 DI 10.1016/S1364-6826(99)00017-6 PG 11 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 227DQ UT WOS:000082063400002 ER PT J AU Forsythe, EL Judge, RA Pusey, ML AF Forsythe, EL Judge, RA Pusey, ML TI Tetragonal chicken egg white lysozyme solubility in sodium chloride solutions SO JOURNAL OF CHEMICAL AND ENGINEERING DATA LA English DT Article ID PROTEIN SOLUBILITIES; GROWTH; MICROGRAVITY; IMPURITIES AB The solubility of chicken egg white lysozyme crystallized in the tetragonal form was measured in sodium chloride solutions from 1.6 to 30.7 degrees C, using a miniature column solubility apparatus. Sodium chloride solution concentrations ranged from 1 to 7% (w/v). The solutions were buffered with 0.1 M sodium acetate buffer, with the solubility being measured at pH values in 0.2 pH unit increments in the pH range 4.0-5.4, with data also included at pH 4.5. Lysozyme solubility was found to increase with increasing in temperature and decreasing salt concentration. Solution pH has a varied and unpredictable effect on solubility. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Alliance Micrograv Mat Sci & Applicat, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Biophys ES76, Huntsville, AL 35812 USA. RP Pusey, ML (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. NR 17 TC 89 Z9 90 U1 1 U2 18 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0021-9568 J9 J CHEM ENG DATA JI J. Chem. Eng. Data PD MAY-JUN PY 1999 VL 44 IS 3 BP 637 EP 640 DI 10.1021/je980316a PG 4 WC Thermodynamics; Chemistry, Multidisciplinary; Engineering, Chemical SC Thermodynamics; Chemistry; Engineering GA 200DV UT WOS:000080525100051 ER PT J AU Leroy, SS AF Leroy, SS TI Optimal detection of global warming using temperature profiles: A methodology SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; CLIMATE-CHANGE; RADIO OCCULTATION; POSITIONING SYSTEM; FINGERPRINT METHOD; EARTHS ATMOSPHERE; GREENHOUSE-GAS; ATTRIBUTION; VARIABILITY; SIGNALS AB Optimal fingerprinting is applied to estimate the amount of time it would take to detect warming by increased concentrations of carbon dioxide in monthly averages of temperature profiles over the Indian Ocean. A simple radiative-convective model is used to define the pattern of the warming signal, and the first 100 yr of the 1000yr control run of the Geophysical Fluid Dynamics Laboratory atmospheric-oceanic global climate model is used to estimate the natural variability of the upper-air temperatures. The signal is assumed to be the difference in two epochs of data, each epoch consisting of 12 consecutive months of monthly average temperature profiles. When the variabilities of monthly averages are assumed independent of each other, the difference in August upper-air temperatures yields the strongest fingerprint, giving a time span for a one-sigma detection of 22 yr. When correlations of natural variability between months are considered, the one-sigma detection time is 10 yr. If only an annual average profile is used, the timescale for one-sigma detection increases to 14 yr. These timescales depend on subjective judgments of the details of the model-predicted pattern of global warming. In general, using upper-air temperatures adds approximately two independent pieces of information in detecting global warming for every surface-air temperature measurement, most likely due to the expected overall pattern of tropospheric warming-stratospheric cooling. Finally, testing climate models with data must be undertaken in order to understand the uncertainties in model-predicted global warming patterns and the predictive capability of models in general. 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, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 30 TC 5 Z9 6 U1 1 U2 5 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD MAY PY 1999 VL 12 IS 5 BP 1185 EP 1198 DI 10.1175/1520-0442(1999)012<1185:ODOGWU>2.0.CO;2 PN 1 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 193PQ UT WOS:000080145600002 ER PT J AU Lau, KM Weng, HY AF Lau, KM Weng, HY TI Interannual, decadal-interdecadal, and global warming signals in sea surface temperature during 1955-97 SO JOURNAL OF CLIMATE LA English DT Article ID OCEAN-ATMOSPHERE MODEL; TROPICAL PACIFIC; NORTH PACIFIC; EL-NINO; CLIMATE VARIABILITY; TIME-SERIES; ENSO; PREDICTABILITY; OSCILLATION; CONVECTION AB Sea surface temperature (SST) data from the NOAA analysis for the period of 1955-97 are used to identify dominant spatial and temporal patterns associated with interannual, decadal-interdecadal variabilities, and global warming. For the global annual mean SST variation, a linear trend plus pronounced decadal-interdecadal and interannual variabilities are found. The linear trend reflects a slow warming of about 0.1 degrees C in the past four decades. Superimposed on the linear trend is a relatively fast warming in the past two decades of approximately 0.2 degrees-0.3 degrees C, which is associated with the advent of the warm phase of a decadal-interdecadal oscillation. Also noted is the more frequent occurrence of warm events and the dearth of cold events on interannual timescales in the early and mid-1990s. For the last four decades, the tropical oceans have been warming at the faster rate while the extratropical North Pacific and the northwestern North Atlantic has been cooling at the slower rate. The exceptional intensity of the 1997 warm event stems from the superposition of the warm phases of a moderate interannual signal, a decadal-interdecadal oscillation, and a steady warming trend since 1955. The first annual empirical orthogonal function (EOF) mode shows an El Nino signal, modified by a warming trend. In this mode. the tropical eastern Pacific and Indian Oceans are warmed relative to the western Pacific, leading to a relaxation of the climatological east-west SST gradient. The second annual EOF mode shows that there is a secondary cooling trend in the equatorial eastern Pacific, centered near the Nino-3 (5 degrees S-5 degrees N, 150 degrees-90 degrees W;) area. This cooling is most pronounced in the boreal fall and summer. It was strongest in the 1980s, but considerably weakened in the 1990s. The cooling is well correlated with the observed surface wind divergence in the equatorial eastern Pacific cold tongue region and with anomalous surface easterly wind in the equatorial central Pacific, signaling an enhancement of the Walker circulation. The net result of the warming and cooling tendencies in the tropical eastern Pacific produces slightly less warming in the Nino-3 area compared with the equatorial central and eastern Pacific, but with little change in large-scale SST gradient across the Pacific. The implications of the present results on the mechanisms and detection of global warming are discussed. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Lau, KM (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 913, Greenbelt, MD 20771 USA. RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 38 TC 81 Z9 93 U1 1 U2 17 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 1999 VL 12 IS 5 BP 1257 EP 1267 DI 10.1175/1520-0442(1999)012<1257:IDIAGW>2.0.CO;2 PN 1 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 193PQ UT WOS:000080145600006 ER PT J AU Fasullo, J Webster, PJ AF Fasullo, J Webster, PJ TI Warm pool SST variability in relation to the surface energy balance SO JOURNAL OF CLIMATE LA English DT Article ID TROPICAL WESTERN PACIFIC; TOGA COARE; TEMPERATURE; OCEAN; THERMOSTAT; CONVECTION; RADIATION; PROJECT; CLOUDS; FLUXES AB The warm tropical oceans underlie the most convective regions on earth and are a critical component of the earth's climate, yet there are differing opinions on the processes that control warm pool SST. The Indo-Pacific warm pool is characterized by large-scale variations in SST approaching 30 degrees C on intraseasonal timescales. In this study, surface heat flux anomalies associated with composite warm episodes over three spatial scales in both the Pacific and Indian Ocean basins are examined. The current study benefits from the recently available National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis dataset that enables the examination of variability in surface evaporation with moderate confidence. Solar Aux estimates from the reanalysis are somewhat less reliable than evaporation estimates, however, and two techniques that infer surface shortwave radiation from satellite retrievals of cloud properties are considered. Error in all measurements is quantified. Both shortwave and evaporative flux variability play significant roles in modifying the temperature of the warm pool, though the relative importance of individual Aux anomalies depends on SST tendency and geographical location. There also exist differences in the relative heating roles of the flux anomalies among episodes within a fixed location, though in instances the resolved differences are less than likely nux estimation error. Differences also exist between the ocean basins. A more pronounced annual cycle exists in the eastern Indian Ocean, and SST there is less sensitive to surface thermal forcing. Finally, the analysis offers evidence that SST is nor regulated by a simple atmospheric thermodynamic response to the surface. Instead, the relationship between warm pool variability and large-scale dynamical features of the Tropics (e.g., intraseasonal oscillation and the seasonal monsoon) is demonstrated. The conclusions are shown to be robust to spacial scale and are consistent with a recent analysis of Tropical Oceans and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment observations. C1 Columbia Univ, NASA, GISS, Program Atmospher & Ocean Sci, New York, NY 10028 USA. RP Fasullo, J (reprint author), Columbia Univ, NASA, GISS, Program Atmospher & Ocean Sci, Room 322,2880 Broadway, New York, NY 10028 USA. OI FASULLO, JOHN/0000-0003-1216-892X NR 33 TC 31 Z9 33 U1 0 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD MAY PY 1999 VL 12 IS 5 BP 1292 EP 1305 DI 10.1175/1520-0442(1999)012<1292:WPSVIR>2.0.CO;2 PN 1 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 193PQ UT WOS:000080145600009 ER PT J AU Haskins, R Goody, R Chen, L AF Haskins, R Goody, R Chen, L TI Radiance covariance and climate models SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; FLUCTUATION DISSIPATION; VARIABILITY; STATISTICS; VALIDATION; VARIANCES AB Spectral empirical orthogonal functions (EOFs) derived from the covariance of satellite radiance spectra may he interpreted in terms of the vertical distribution of the covariance of temperature, water vapor, and clouds. This has been done for four major geographic regions: the tropical oceans, midlatitude oceans, and three important land areas. The purpose of the investigation is to demonstrate the important constraints that resolved spectral radiances can place upon climate models. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goody, R (reprint author), 101 Cumloden Dr, Falmouth, MA 02540 USA. NR 19 TC 23 Z9 23 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 1999 VL 12 IS 5 BP 1409 EP 1422 DI 10.1175/1520-0442(1999)012<1409:RCACM>2.0.CO;2 PN 2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 193PR UT WOS:000080145700005 ER PT J AU Bosilovich, MG Sun, WY AF Bosilovich, MG Sun, WY TI Numerical simulation of the 1993 midwestern flood: Land-atmosphere interactions SO JOURNAL OF CLIMATE LA English DT Article ID NORTH-AMERICAN DROUGHT; LOW-LEVEL JET; UNITED-STATES; SOIL-MOISTURE; GREAT-PLAINS; SURFACE PARAMETERIZATION; DIURNAL-VARIATION; SURROUNDING AREA; CONVECTIVE LAYER; DIFFUSION-MODEL AB During the summer of 1993, persistent and heavy precipitation caused a long-lived, catastrophic flood in the midwestern United States. In this paper, Midwest hydrology, atmospheric circulation of the 1993 summer, and feedback between the surface and precipitating systems were investigated using the Purdue Regional Model (PRM). The 30-day PRM control simulations reproduced the large-scale atmospheric features that characterized the summer of 1993. Specifically, the upper-level jet stream and trough over the northwestern United States are present in control cases, as well as the Great Plains low-level jet, general pattern of moisture transport, and heavy precipitation in the Midwest. The daily precipitation record (area averaged over the heaviest rainfall) indicates that the model also reproduces the evolution and periodicity of precipitation events comparable with the observations and correctly depicts the differences between June and July. The sensitivity of the low-level jet, planetary boundary layer, and heavy precipitation were examined by imposing various soil moisture and surface anomalies in the model simulation. The increased surface heating, caused by a strong dry anomaly, induced a large scale surface pressure perturbation, centered in the southeastern United States, that weakened the low-level jet and moisture convergence within the flood region. Separate cases considering both wet and dry regional anomalies in the southern Great Plains caused less precipitation in the flood region. The uniform soil moisture of both anomalies leads to a reduction of the differential heating, surface pressure gradient, and the low-level jet. C1 Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN 47907 USA. RP Bosilovich, MG (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 910-3, Greenbelt, MD 20771 USA. RI Bosilovich, Michael/F-8175-2012 NR 42 TC 62 Z9 63 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 1999 VL 12 IS 5 BP 1490 EP 1505 DI 10.1175/1520-0442(1999)012<1490:NSOTMF>2.0.CO;2 PN 2 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 193PR UT WOS:000080145700010 ER PT J AU Jackson, AW Pinsukanjana, PR Gossard, AC Coldren, LA AF Jackson, AW Pinsukanjana, PR Gossard, AC Coldren, LA TI Noise, drift, and calibration in optical flux monitoring for MBE SO JOURNAL OF CRYSTAL GROWTH LA English DT Article; Proceedings Paper CT 10th International Conference on Molecular Beam Epitaxy (MBE-X) CY AUG 31-SEP 04, 1998 CL CANNES, FRANCE DE molecular beam epitaxy; optical flux monitoring; atomic absorption ID ATOMIC-ABSORPTION SPECTROSCOPY; MOLECULAR-BEAM EPITAXY; VAPOR-DEPOSITION; GROWTH; LASERS; GA AB dSources of error in optical flux monitoring (OFM) for MBE are identified and measured. The primary challenge in measuring atomic flux by OFM is to reduce the effects of signal drift during the measurement. To reduce long term drift we have (1) used an additional reference beam to measure the transparency of the optical path and (2) chopped the atomic beam at low frequencies (2 Hz) with the effusion cell shutters and performed phase-sensitive detection on the absorption signal. With the chopped beam technique, we have essentially eliminated long term drift from our measurements. We have also measured the errors introduced by changes in the relationship between absorption and growth rate that occur as the effusion cell is depleted. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA. Jet Prop Lab, Pasadena, CA USA. RP Jackson, AW (reprint author), Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA. NR 14 TC 6 Z9 6 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD MAY PY 1999 VL 201 BP 17 EP 21 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 198DB UT WOS:000080406000005 ER PT J AU Assad, C Rasnow, B Stoddard, PK AF Assad, C Rasnow, B Stoddard, PK TI Electric organ discharges and electric images during electrolocation SO JOURNAL OF EXPERIMENTAL BIOLOGY LA English DT Article DE electrolocation; electroreception; electric organ discharge; Gymnotiformes; electric fish ID GYMNOTUS-CARAPO; APTERONOTUS-LEPTORHYNCHUS; GYMNOTIFORM FISHES; EIGENMANNIA; PLASTICITY; GENERATION; OBJECTS; SYSTEM; FIELD AB Weakly electric fish use active electrolocation - the generation and detection of electric currents - to explore their surroundings. Although electrosensory systems include some of the most extensively understood circuits in the vertebrate central nervous system, relatively little is known quantitatively about how fish electrolocate objects. We believe a prerequisite to understanding electrolocation and its underlying neural substrates is to quantify and visualize the peripheral electrosensory information measured by the electroreceptors, We have therefore focused on reconstructing both the electric organ discharges (EODs) and the electric images resulting from nearby objects and the fish's exploratory behaviors. Here, we review results from a combination of techniques, including field measurements, numerical and semi-analytical simulations, and video imaging of behaviors. EOD maps are presented and interpreted for six gymnotiform species. They reveal diverse electric field patterns that have significant implications for both the electrosensory and electromotor systems. Our simulations generated predictions of the electric images from nearby objects as well as sequences of electric images during exploratory behaviors. These methods are leading to the identification of image features and computational algorithms that could reliably encode electrosensory information and may help guide electrophysiological experiments exploring the neural basis of electrolocation, C1 CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. CALTECH, Div Biol, Pasadena, CA 91125 USA. Florida Int Univ, Dept Biol Sci, Miami, FL 33199 USA. RP Assad, C (reprint author), CALTECH, Jet Prop Lab, MC 303-300,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM Chris.Assad@jpl.nasa.gov FU NIGMS NIH HHS [GM08205-11] NR 41 TC 74 Z9 77 U1 1 U2 11 PU COMPANY OF BIOLOGISTS LTD PI CAMBRIDGE PA BIDDER BUILDING CAMBRIDGE COMMERCIAL PARK COWLEY RD, CAMBRIDGE CB4 4DL, CAMBS, ENGLAND SN 0022-0949 J9 J EXP BIOL JI J. Exp. Biol. PD MAY PY 1999 VL 202 IS 10 BP 1185 EP 1193 PG 9 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 202VN UT WOS:000080673000002 PM 10210660 ER PT J AU Biesecker, DA Thompson, BJ Gibson, SE Alexander, D Fludra, A Gopalswamy, N Hoeksema, JT Lecinski, A Strachan, L AF Biesecker, DA Thompson, BJ Gibson, SE Alexander, D Fludra, A Gopalswamy, N Hoeksema, JT Lecinski, A Strachan, L TI Synoptic Sun during the first Whole Sun Month Campaign: August 10 to September 8, 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ULTRAVIOLET CORONAGRAPH SPECTROMETER; SOLAR; SOHO; TELESCOPE; MISSION; HOLE AB A large number of synoptic maps from a variety of instruments are used to show the general morphology of the Sun at the time of the First Whole Sun Month Campaign. The campaign was conducted from August 10 to September 8, 1996. The synoptic maps cover the period from Carrington rotation 1912/253 degrees to Carrington rotation 1913/45 degrees. The synoptic maps encompass both on-disk data and limb data from several heights in the solar atmosphere. The maps are used to illustrate which wavelengths and data sets show particular features, such as active regions and coronal holes. Of particular interest is the equatorial coronal hole known as the "elephant's trunk," which is clearly evident in the synoptic maps of on-disk data. The elephant's trunk is similar in appearance to the Shylab-era, "Boot of Italy," equatorial coronal hole. The general appearance of the limb maps is explained as well. The limb maps also show evidence for equatorial coronal holes. C1 Univ Birmingham, Sch Phys & Astron, Birmingham, W Midlands, England. Catholic Univ Amer, Washington, DC 20064 USA. Lockheed Martin Solar & Astrophys Lab, Palo Alto, CA USA. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Stanford Univ, Hansen Expt Phys Lab, Stanford, CA 94305 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Biesecker, DA (reprint author), NASA, Goddard Space Flight Ctr, Space Applicat Corp, Code 682-3, Greenbelt, MD 20771 USA. RI Gibson, Sarah/A-9189-2011; Gopalswamy, Nat/D-3659-2012; Thompson, Barbara/C-9429-2012 NR 21 TC 12 Z9 12 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 1999 VL 104 IS A5 BP 9679 EP 9689 DI 10.1029/1998JA900056 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600002 ER PT J AU Gibson, SE Fludra, A Bagenal, F Biesecker, D Del Zanna, G Bromage, B AF Gibson, SE Fludra, A Bagenal, F Biesecker, D Del Zanna, G Bromage, B TI Solar minimum streamer densities and temperatures using Whole Sun Month coordinated data sets SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ULTRAVIOLET CORONAGRAPH SPECTROMETER; MAGNETIC-FIELD; HOLE AB We model electron densities of the simplest, most symmetric solar minimum streamer structure observed during the Whole Sun Month (WSM) campaign, using coronal observations of both visible white light and extreme ultraviolet (EUV) emission. Using white light data from the SOHO/LASCO/C2 and HAO/ Mauna Loa Mark 3 coronagraphs, we determine electron densities by way of a Van de Hulst inversion. We compare the white light densities to those determined from the density sensitive EUV line ratios of Si IX 350/342 Angstrom observed by the SOHO/coronal diagnostic spectrometer (CDS). Moreover, from the white light density profiles we calculate hydrostatic temperature profiles and compare to temperatures derived from the Si XII/Mg X line ratio. We find the white light and spectral analysis produce consistent density and temperature information. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Catholic Univ Amer, Washington, DC 20064 USA. Rutherford Appleton Lab, Dept Space Sci, Didcot OX11 0QX, Oxon, England. Univ Colorado, Boulder, CO 80303 USA. Space Applicat Corp, Greenbelt, MD USA. Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England. RP Gibson, SE (reprint author), NASA, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20771 USA. RI Gibson, Sarah/A-9189-2011 NR 30 TC 87 Z9 87 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 1999 VL 104 IS A5 BP 9691 EP 9699 DI 10.1029/98JA02681 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600003 ER PT J AU Gopalswamy, N Shibasaki, K Thompson, BJ Gurman, J DeForest, C AF Gopalswamy, N Shibasaki, K Thompson, BJ Gurman, J DeForest, C TI Microwave enhancement and variability in the elephant's trunk coronal hole: Comparison with SOHO observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ULTRAVIOLET IMAGING TELESCOPE; SOLAR; NETWORK; EIT AB We report on an investigation of the microwave enhancement and its variability in the elephant's trunk coronal hole observed during the Whole Sun Month campaign (August 10 to September 9, 1996). The microwave images from the Nobeyama radioheliograph were compared with magnetograms and EUV images obtained simultaneously by the Michelson Doppler imager and the extreme ultraviolet imaging telescope (EIT) on board the SOHO spacecraft. The combined data set allowed us to understand the detailed structure of the microwave enhancement in the spatial and temporal domains. We find that the radio enhancement is closely associated with the enhanced unipolar magnetic regions underlying the coronal hole. The radio enhancement consists of a smooth component originating from network cell interiors and a compact component associated with network magnetic elements. When a minority polarity is present near a majority polarity element, within the coronal hole, the resulting mixed polarity region is associated with a bright-point-like emission in coronal EUV lines such as the Fe XII 195 Angstrom. These coronal bright points are also observed distinctly in the EIT 304 Angstrom band, but not in microwaves, On the other hand, the lower-temperature line emission (304 Angstrom) and the microwave enhancement are associated with the unipolar magnetic flux elements in the network. We found strong time variability of the radio enhancement over multiple timescales, consistent with the initial results obtained by SOHO instruments. The microwave enhancement is most probably due to temperature enhancement in the chromosphere and may be related to the origin of solar wind. C1 Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Astron Observ, Nobeyama Radio Observ, Minamisa Ku, Nagano 3841305, Japan. Space Applicat Corp, Greenbelt, MD USA. Stanford Univ, Ctr Space Sci & Astrophys, Stanford, CA 94305 USA. RP Gopalswamy, N (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RI Gopalswamy, Nat/D-3659-2012; Thompson, Barbara/C-9429-2012 NR 19 TC 25 Z9 25 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 MAY 1 PY 1999 VL 104 IS A5 BP 9767 EP 9779 DI 10.1029/1998JA900168 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600010 ER PT J AU Guhathakurta, M Fludra, A Gibson, SE Biesecker, D Fisher, R AF Guhathakurta, M Fludra, A Gibson, SE Biesecker, D Fisher, R TI Physical properties of a coronal hole from a coronal diagnostic spectrometer, Mauna Loa Coronagraph, and LASCO observations during the Whole Sun Month SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; TEMPERATURE; DENSITY AB Until recently [Guhathakurta and Fisher, 1998], inference of electron density distribution in the solar corona was limited by the field of view of white-light coronagraphs (typically out to 6 R-s). Now, for the first time we have a series of white-light coronagraphs (SOHO/LASCO) whose combined field of view extends from 1.1-30 R-s. Quantitative information on electron density distribution of coronal hole and coronal plumes/rays are estimated by using white-light, polarized brightness (pB) observations from the SOHO/LASCO/C2, and C3 and HAO/Mauna Loa Mark III coronagraphs from 1.15 to 8.0 R-s. Morphological information on the boundary of the polar coronal hole and streamer interface is determined from the white-light observations in a manner similar to the Skylab polar coronal hole boundary estimate [Guhathakurta and Holzer, 1994], The average coronal hole electron density in the region 1-1.15 R-s is estimated from the density-sensitive EUV line ratios of Si IX 350/342 Angstrom observed by the SOHO/coronal diagnostic spectrometer (CDS), We combine these numbers with the estimate from white-light (WL) observations to obtain a density profile from 1 to 8 R-s for the plumes and the polar coronal hole. We find that white light and spectral analysis produce consistent density information. Extrapolated densities inferred from SOHO observations are compared to Ulysses in situ observations of density. Like the density inferred from the Spartan 201-03 coronagraph, the current SOHO density profiles suggest that the acceleration of the fast solar wind takes place very close to the Sun, within 10-15 R-s. The density information is used to put constraints on solar wind flow velocities and effective temperatures. Finally, these results are compared to the recent analysis of the Spartan 201-03 white-light observations. C1 Catholic Univ Amer, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20770 USA. Rutherford Appleton Lab, Dept Space Sci, Didcot OX11 0QX, Oxon, England. RP Guhathakurta, M (reprint author), Catholic Univ Amer, Washington, DC 20064 USA. RI Gibson, Sarah/A-9189-2011 NR 29 TC 65 Z9 65 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 MAY 1 PY 1999 VL 104 IS A5 BP 9801 EP 9808 DI 10.1029/1998JA900082 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600013 ER PT J AU Linker, JA Mikic, Z Biesecker, DA Forsyth, RJ Gibson, SE Lazarus, AJ Lecinski, A Riley, P Szabo, A Thompson, BJ AF Linker, JA Mikic, Z Biesecker, DA Forsyth, RJ Gibson, SE Lazarus, AJ Lecinski, A Riley, P Szabo, A Thompson, BJ TI Magnetohydrodynamic modeling of the solar corona during Whole Sun Month SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD STRENGTH; MINIMUM CORONA; WIND; DISRUPTION; PREDICTION; EVOLUTION; FLOW AB The Whole Sun Month campaign (August 10 to September 8, 1996) brought together a wide range of space-based and ground-based observations of the Sun and the interplanetary medium during solar minimum. The wealth of data collected provides a unique opportunity for testing coronal models. We develop a three-dimensional magnetohydrodynamic (MHD) model of the solar corona (from 1 to 30 solar radii) applicable to the WSM time period, using measurements of the photospheric magnetic field as boundary conditions for the calculation. We compare results from the computation with daily and synoptic white-light and emission images obtained from ground-based observations and the SOHO spacecraft and with solar wind measurements from the Ulysses and WIND spacecraft. The results from the MHD computation show good overall agreement with coronal and interplanetary structures, including the position and shape of the streamer belt, coronal hole boundaries, and the heliospheric current sheet. From the model, we can infer the source locations of solar wind properties measured in interplanetary space. We find that the slow solar wind typically maps back to near the coronal hole boundary, while the fast solar wind maps to regions deeper within the coronal holes. Quantitative disagreements between the MHD model and observations for individual features observed during Whole Sun Month give insights into possible improvements to the model. C1 Sci Applicat Int Corp, San Diego, CA 92121 USA. Univ Birmingham, Birmingham, W Midlands, England. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. Catholic Univ Amer, Washington, DC 20064 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80301 USA. SciberNet Inc, San Diego, CA USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Linker, JA (reprint author), Sci Applicat Int Corp, 10260 Campus Point Dr,MS E3X, San Diego, CA 92121 USA. RI Gibson, Sarah/A-9189-2011; Thompson, Barbara/C-9429-2012 NR 40 TC 171 Z9 175 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD MAY 1 PY 1999 VL 104 IS A5 BP 9809 EP 9830 DI 10.1029/1998JA900159 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600014 ER PT J AU Breen, AR Mikic, Z Linker, JA Lazarus, AJ Thompson, BJ Biesecker, DA Moran, PJ Varley, CA Williams, PJS Lecinski, A AF Breen, AR Mikic, Z Linker, JA Lazarus, AJ Thompson, BJ Biesecker, DA Moran, PJ Varley, CA Williams, PJS Lecinski, A TI Interplanetary scintillation measurements of the solar wind during Whole Sun Month: Comparisons with coronal and in situ observations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EISCAT MEASUREMENTS; MASS EJECTIONS; SOHO MISSION; EVOLUTION; VELOCITY; ULYSSES; SPEED; SLOW; LATITUDE; REGIONS AB Two-site observations of interplanetary scintillation using the EISCAT facility can provide measurements of solar wind velocity at any point in the heliosphere between 15 and 120 solar radii (R). Ln this paper we discuss a series of observations made as part of the Whole Sun Month campaign (August 10 to September 8, 1996) and compare the results with coronal data and in-situ measurements made during the campaign. The results of the comparison revealed extremely good agreement between solar wind speeds measured by IFS at 16-73 R and in situ measurements at 213 R and beyond, both in the general morphology of the solar wind and in the absolute velocities observed. These results confirm that structures in the solar wind, originating in the corona, preserve their form out to 910 R or more. Observations of fast solar wind were always associated with coronal holes and slow wind with the bright corona. Velocities intermediate between normal fast and slow flow speeds are associated with interaction regions between fast and slow flow and are also found above the boundaries of coronal holes. C1 Max Planck Inst Aeron, Katlenburg Lindau, Germany. Sci Applicat Int Corp, San Diego, CA 92121 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80301 USA. RP Breen, AR (reprint author), Adran Ffiseg, Aberystwyth SY23 3BZ, Dyfed, Wales. RI Thompson, Barbara/C-9429-2012 NR 41 TC 23 Z9 24 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 1999 VL 104 IS A5 BP 9847 EP 9870 DI 10.1029/1998JA900091 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600016 ER PT J AU Riley, P Gosling, JT McComas, DJ Pizzo, VJ Luhmann, JG Biesecker, D Forsyth, RJ Hoeksema, JT Lecinski, A Thompson, BJ AF Riley, P Gosling, JT McComas, DJ Pizzo, VJ Luhmann, JG Biesecker, D Forsyth, RJ Hoeksema, JT Lecinski, A Thompson, BJ TI Relationship between Ulysses plasma observations and solar observations during the Whole Sun Month campaign SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HELIOSPHERIC CURRENT SHEET; WIND VARIABILITY; LATITUDES; MISSION; STREAM; MODELS; BAND AB In this report, we summarize measurements made by the plasma experiment on the Ulysses spacecraft during the period designated as "Whole Sun Month" (WSM, August 10 to September 8; 1996). This interval coincided with the return of solar wind variability at Ulysses. Ulysses was located at similar to 28 degrees N heliographic latitude, at a heliocentric distance of 4.25 AU, and on the opposite side of the Sun from Earth. In particular: we explore the evolution of the solar wind between the Sun and Ulysses for several rotations surrounding WSM. Specifically, we map Ulysses measurements back toward the Sun by applying a two-dimensional inverse MHD algorithm. This approach is compared with the commonly used constant speed (or ballistic) approximation. We find that the MHD mapping technique produces substantially better results when compared with solar observations. Both the Ulysses MHD-mapped results and the solar observations are consistent with a picture of a modestly tilted streamer belt (< 10 degrees) that was deformed northward by an active region at 240 degrees - 270 degrees longitude. C1 ScriberNet Inc, San Diego, CA 92121 USA. Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, Los Alamos, NM 87545 USA. NOAA, Space Environm Lab, Boulder, CO 80303 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Birmingham, Sch Phys & Space Res, Birmingham B15 2TT, W Midlands, England. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England. Stanford Univ, Wilcox Solar Observ, Ctr Astrophys & Space Sci, Hansen Expt Phys Lab, Stanford, CA 94305 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Riley, P (reprint author), Sci Applicat Int Corp, San Diego, CA 92121 USA. RI Thompson, Barbara/C-9429-2012 NR 23 TC 23 Z9 23 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 1999 VL 104 IS A5 BP 9871 EP 9879 DI 10.1029/1998JA900078 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600017 ER PT J AU Posner, A Bothmer, V Thompson, BJ Kunow, H Heber, B Muller-Mellin, R Lazarus, AJ Szabo, A Mikic, Z Linker, JA AF Posner, A Bothmer, V Thompson, BJ Kunow, H Heber, B Muller-Mellin, R Lazarus, AJ Szabo, A Mikic, Z Linker, JA TI In-ecliptic CIR-associated energetic particle events and polar coronal hole structures: SOHO/COSTEP observations for the Whole Sun Month Campaign SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERACTION REGIONS; SHOCK ACCELERATION; ION ENHANCEMENTS; SOHO; ULYSSES; EIT AB The Solar and Heliospheric Observatory (SOHO), in halo orbit around the L1 Lagrangian point of the Sun-Earth system, combines a unique set of instruments for studies of the Sun and the heliosphere. SOHO's Comprehensive Suprathermal and Energetic Particle Analyser measures in situ particles in the energy range 44 keV/particle to above 53 MeV/nucleon. For the time period of the Whole Sun Month Campaign in mid 1996 we have identified recurrent energetic particle intensity increases in association with corotating interaction regions (CIRs) in the energy range <10 MeV. Solar wind measurements of the Wind spacecraft were used to estimate the corresponding magnetic source location in Carrington longitude for comparison of energetic particles with synoptic maps of the lower corona, derived from images of SOHO's Extreme-ultraviolet Imaging Telescope, The comparison reveals a close relationship of latitudinal extensions of polar coronal holes, situated in regions up to 40 degrees away from the ecliptic, with CIR-associated in-ecliptic particle events. C1 Univ Kiel, IEAP, D-24118 Kiel, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CEA, DSM, DAPNIA, Serv Astrophys,CE Saclay, F-91191 Gif Sur Yvette, France. MIT, Cambridge, MA 02139 USA. Sci Applicat Int Corp, San Diego, CA 92121 USA. RP Posner, A (reprint author), Univ Kiel, IEAP, Gutenbergstr 76-78, D-24118 Kiel, Germany. RI Thompson, Barbara/C-9429-2012; OI Posner, Arik/0000-0003-1572-8734 NR 24 TC 9 Z9 9 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 MAY 1 PY 1999 VL 104 IS A5 BP 9881 EP 9890 DI 10.1029/98JA02654 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600018 ER PT J AU Burton, ME Neugebauer, M Crooker, NU von Steiger, R Smith, EJ AF Burton, ME Neugebauer, M Crooker, NU von Steiger, R Smith, EJ TI Identification of trailing edge solar wind stream interfaces: A comparison of Ulysses plasma and composition measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID POLYTROPIC INDEX; 1 AU AB Measurements of the specific entropy argument of the solar wind protons, T/n(gamma-1), reveal that nearly every occurrence of a high-speed stream seen at Ulysses in 1992-1993 is characterized by an abrupt interface at its trailing edge. These observations, made by the solar wind plasma instrument (SWOOPS), at a heliocentric range of 4.5 to 5 AU show that there is a discontinuous drop in specific entropy at the interface from a high value in the high-speed wind to a lower value in the slow interstream wind. This interface is coincident with, but much more abrupt than, compositional changes measured by the Solar Wind Ion Composition Spectrometer (SWICS) [Geiss et al., 1995]. These results suggest that a relatively thin interface can be identified which separates two plasmas of distinctly different origins as determined by the compositional measurements. A superposed epoch analysis performed on seventeen events reveal the interface is characterized by (1) an abrupt drop in entropy by a factor of similar to 1/3 due to an enhancement in density along with gradually declining temperature, (2) a distinct drop in the alpha/proton ratio from a value of similar to 5%, typical of the fast wind, to similar to 4% characteristic of the slow solar wind, and (3) relative changes in Mg10+/O6+ at the interface which are as large as the variations in the total Mg/O ratio and the freezing-in temperature derived from O7+/O6+. The specific entropy argument, a combination of commonly measured solar wind parameters, gives a strong signature of the trailing edge interface which is preserved as far out in the heliosphere as 5 AU and may provide useful information regarding the coronal origin of solar wind streams. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Boston Univ, Boston, MA 02215 USA. Inst Space Sci Inst, Bern, Switzerland. RP Burton, ME (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Von Steiger, Rudolf/F-6822-2011 OI Von Steiger, Rudolf/0000-0002-3350-0023 NR 22 TC 30 Z9 30 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 MAY 1 PY 1999 VL 104 IS A5 BP 9925 EP 9932 DI 10.1029/JA104iA05p09925 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600023 ER PT J AU Casalbuoni, S Del Zanna, L Habbal, SR Velli, M AF Casalbuoni, S Del Zanna, L Habbal, SR Velli, M TI Coronal plumes and the expansion of pressure-balanced structures in the fast solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HELIOSPHERIC MAGNETIC-FIELD; ULYSSES OBSERVATIONS; FLOW PROPERTIES; POLAR PLUMES; HOLE; TEMPERATURE; MODEL; SOHO; ACCELERATION; INSTRUMENT AB The expansion of a coronal hole filled with a discrete number of higher-density filaments (plumes) in overall pressure balance with the ambient medium is described within the thin flux tube approximation. The resulting solar wind model extends the results of Parker [1964] and Velli et al. [1994] to nonisothermal temperature profiles and includes a flux of Alfven waves propagating both inside and outside the structures. Remote sensing and solar wind in situ observations are used to constrain the parameter range of our study. Close to the Sun, the precise plasma parameters are fundamental in determining the relative position of the critical points, which are found by means of an iterative procedure because the flows from the two regions are coupled. At greater distances the filling factor of the higher-density regions may vary largely, and streams which are either faster or slower than the wind arising from the ambient hole may result, depending on the temperature differences and on the flux of Alfven waves assumed in the two regions. Velocity differences of the order of similar to 50 km s(-1) such as those found in microstreams in the high-speed solar wind, might be thus easily explained by reasonable fluctuation amplitudes at the Sun, although the natural candidates for plumes at large heliocentric distances are more likely to be the so-called pressure-balanced structures. C1 Univ Florence, Dipartimento Astron & Sci Spazio, I-50125 Florence, Italy. Int Space Sci Inst, Bern, Switzerland. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Casalbuoni, S (reprint author), Univ Bern, Inst Phys, Bern, Switzerland. RI Del Zanna, Luca/N-5598-2015 OI Del Zanna, Luca/0000-0001-5200-882X NR 52 TC 30 Z9 30 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 1999 VL 104 IS A5 BP 9947 EP 9961 DI 10.1029/1999JA900047 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600025 ER PT J AU Greenwald, RA Ruohoniemi, JRM Baker, KB Bristow, WA Sofko, GJ Villain, JP Lester, M Slavin, J AF Greenwald, RA Ruohoniemi, JRM Baker, KB Bristow, WA Sofko, GJ Villain, JP Lester, M Slavin, J TI Convective response to a transient increase in dayside reconnection SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HIGH-LATITUDE CONVECTION; FLUX-TRANSFER EVENTS; IONOSPHERIC SIGNATURES; EARTHS MAGNETOPAUSE; ENHANCED CONVECTION; HF-RADAR; MAGNETOSPHERE; CUSP; DEFLATION AB Measurements with five of the northern hemisphere Super Dual Auroral Radar Network (SuperDARN) radars have yielded a detailed temporal and spatial view of the evolution of a dayside convection enhancement, which we associate with a transient increase in dayside reconnection. The convection enhancement was located in and immediately poleward of the ionospheric footprint of the cusp. During the enhancement, both the cusp and the region of enhanced flow shifted equatorward by similar to 2 degrees. As the flow enhancement diminished, the cusp footprint moved poleward to its original position. The entire event had a duration of similar to 18 min and was associated with a transient 29 kV increase in the cross polar cap potential. We estimate that similar to 3.2 x 10(7) Wb of magnetic flux was opened at the dayside magnetopause during the most active 12 min of this event. The length of the reconnection line on the dayside magnetopause is estimated to have reached 19,000 km. The characteristics of the dayside ionospheric response are very similar to those predicted by Cowley nod Lockwood [1992] in their expanding and contracting polar cap model. These are the first observations that have provided an extended spatial and temporal view of the responses of dayside convection and the cusp to a transient reconnection event. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Univ Saskatchewan, Dept Phys & Engn Phys, Saskatoon, SK, Canada. CNRS, Lab Phys & Chem Environm, Verrieres Le Buisson, France. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Greenwald, RA (reprint author), Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA. RI Slavin, James/H-3170-2012; OI Slavin, James/0000-0002-9206-724X; Greenwald, Raymond/0000-0002-7421-5536 NR 21 TC 19 Z9 19 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 1999 VL 104 IS A5 BP 10007 EP 10015 DI 10.1029/98JA02723 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600030 ER PT J AU Ostgaard, N Stadsnes, J Bjordal, RR Vondrak, RR Cummer, SA Chenette, DL Parks, GK Brittnacher, MJ McKenzie, DL AF Ostgaard, N Stadsnes, J Bjordal, RR Vondrak, RR Cummer, SA Chenette, DL Parks, GK Brittnacher, MJ McKenzie, DL TI Global-scale electron precipitation features seen in UV and X rays during substorms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PARTICLE INJECTIONS; AURORAL-ZONE; WIND; BREMSSTRAHLUNG; REGIONS; EVENTS; SECTOR; ORBIT AB The Polar Ionospheric X-ray Imaging Experiment (PIXIE) and the ultraviolet imager (WI) onboard the Polar satellite have provided the first simultaneous global-scale views of the patterns of electron precipitation through imaging of the atmospheric X-ray bremsstrahlung and the auroral ultraviolet (UV) emissions. While the UV images respond to the total electron energy flux, which is usually dominated by electron energies below 10 keV, the PIXIE, 9.9-19.7 keV X-ray images used in this study respond only to electrons of energy above 10 keV. Previous studies by ground-based, balloon, and space observations have indicated that the patterns of energetic electron precipitation differ significantly from those found in the visible and the UV auroral oval. Because of the lack of global imaging of the energetic electron precipitation, one has not been able to establish a complete picture. In this study the development of the electron precipitation during the different phases of magnetospheric substorms is examined. Comparisons are made between the precipitation patterns of the high-energy (PIXIE) and low-energy (UVI) electron populations, correlated with ground-based observations and geosynchronous satellite data. We focus on one specific common feature in the energetic precipitation seen in almost every isolated substorm observed by PIXIE during 1996 and which differs significantly from what is seen in the UV images. Delayed relative to substorm onsets, we observe a localized maximum of X-ray emission at 5-9 magnetic local time. By identifying the location of the injection region and determining the substorm onset time it is found that this maximum most probably is caused by electrons injected in the midnight sector drifting (i.e,, gradient and curvature drift) into a region in the dawnside magnetosphere where some mechanism effectively scatters the electrons into the loss cone. C1 Univ Bergen, Dept Phys, N-5007 Bergen, Norway. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. Univ Washington, Geophys Program, Seattle, WA 98195 USA. Aerospace Corp, Los Angeles, CA 90009 USA. RP Ostgaard, N (reprint author), Univ Bergen, Dept Phys, N-5007 Bergen, Norway. RI Cummer, Steven/A-6118-2008 OI Cummer, Steven/0000-0002-0002-0613 NR 44 TC 27 Z9 27 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 MAY 1 PY 1999 VL 104 IS A5 BP 10191 EP 10204 DI 10.1029/1999JA900004 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600045 ER PT J AU Tsyganenko, NA Le, G Russell, CT Iyemori, T AF Tsyganenko, NA Le, G Russell, CT Iyemori, T TI A study of the inner magnetosphere based on data of Polar SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; STEADY-STATE RESPONSE; LOW-LATITUDE STATIONS; SUDDEN IMPULSES; CURRENTS AB A statistical study of the near-Earth equatorial magnetic field depression has been done on the basis of-a set of data from 20 months of Polar magnetic field experiment in 1996-1997, supported by simultaneous information on the solar wind state by Wind and IMP 8 spacecraft. This work addresses the spatial distribution of the magnetic field, produced by magnetospheric currents near the dipole equator at radial distances between 2.0 and 4.5 R-E, and its dependence on the ground Dst field, solar wind pressure, and interplanetary magnetic field (IMF). The observed radial and local time variation of the regression coefficients in the expansion for the disturbance field is interpreted in terms of the relative contribution of the principal magnetospheric currents. The inner field has a significant noon-midnight and dawn-dusk asymmetry, sensitive to Dst and to the solar wind pressure. The results confirm the high quality of the Polar magnetic field experiment (MFE) data in a wide range of altitudes and will be a useful guide for the modeling of the inner magnetosphere. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Kyoto Univ, Fac Sci, Data Anal Ctr Geomagnetism & Space Magnetism, Kyoto 606, Japan. RP Tsyganenko, NA (reprint author), Raytheon ITSS Corp, Extraterr Sci Dept, Lanham, MD 20706 USA. RI Le, Guan/C-9524-2012; Tsyganenko, Nikolai/J-7377-2012 OI Le, Guan/0000-0002-9504-5214; Tsyganenko, Nikolai/0000-0002-5938-1579 NR 14 TC 19 Z9 19 U1 0 U2 2 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 1999 VL 104 IS A5 BP 10275 EP 10283 DI 10.1029/1998JA900160 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600052 ER PT J AU Liemohn, MW Khazanov, GV Craven, PD Kozyra, JU AF Liemohn, MW Khazanov, GV Craven, PD Kozyra, JU TI Nonlinear kinetic modeling of early stage plasmaspheric refilling SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID OUTER PLASMASPHERE; SUPERTHERMAL ELECTRONS; TEMPERATURE ANISOTROPY; THERMAL PROTONS; FIELD LINES; MAGNETOSPHERE; IONS; IONOSPHERE; FLOW; PLASMAPAUSE AB A new time-dependent kinetic model is used to investigate the effects of self-consistency and hot plasma influences on plasmaspheric refilling. The model employs a direct solution of the kinetic equation with a Fokker-Planck Coulomb collision operator to obtain the phase space distribution function of the thermal protons along a field line. Of particular interest is the influence of several processes on the source cone distribution function formation. It is found that a self-consistent ion temperature in the collision term can increase or decrease the equatorial plane density, depending not only on the choice of ion temperature in the static-background calculations but also on the form of the nonlinear representation. The inclusion of a self-consistent polarization electric field increases the early stage equatorial plane density by a factor of 2. Investigations of the effects of anisotropic hot plasma populations on the refilling rates shows that, after a slight initial decrease in equatorial density from clearing out the initial distribution, there is a 10 to 30% increase after 4 hours due to these populations. This increase is due primarily to a slowing of the refilling streams near the equator from the reversed electric field. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Liemohn, MW (reprint author), Univ Michigan, Space Phys Res Lab, 2455 Hayward St, Ann Arbor, MI 48109 USA. RI Liemohn, Michael/H-8703-2012 OI Liemohn, Michael/0000-0002-7039-2631 NR 49 TC 15 Z9 15 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 1999 VL 104 IS A5 BP 10295 EP 10306 DI 10.1029/1999JA900104 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600054 ER PT J AU Green, JL Boardsen, SA AF Green, JL Boardsen, SA TI Confinement of nonthermal continuum radiation to low latitudes SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID AURORAL KILOMETRIC RADIATION; MAGNETOSPHERE; POLARIZATION; EARTH AB Applying a wave intensity map technique to 4 years of plasma wave observations from the VLF electric field instrument on the Hawkeye spacecraft reveals the latitudinal distribution of the Earth's nonthermal continuum radiation. The wave intensity maps at frequencies below (23.7 kHz), near (31.1 kHz), and above (56 kHz) the average magnetopause plasma frequency clearly identified a source region and propagation extent of the nonthermal continuum. The Hawkeye observations show that the nonthermal continuum radiation is primarily observed at relatively low latitudes, is rarely observed over the high-altitude polar cap, and is consistent with previous observations as being beamed outward from the dawn source region. The observed angular distribution of the nonthermal continuum radiation is modeled by ray-tracing calculations which show that the trapped and escaping components of the nonthermal continuum can exist simultaneously at the same frequency but with very different spatial distributions in the magnetosphere. In addition, the observations and the ray-tracing calculations show that the trapped continuum radiation component does not uniformly illuminate the magnetospheric cavity as some have previously believed but is confined to mostly low latitudes. C1 NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Greenbelt, MD 20771 USA. RP Green, JL (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX Corp, Code 630, Greenbelt, MD 20771 USA. NR 27 TC 13 Z9 13 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 1999 VL 104 IS A5 BP 10307 EP 10316 DI 10.1029/1998JA900130 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 192BQ UT WOS:000080058600055 ER PT J AU Oshman, Y Markley, FL AF Oshman, Y Markley, FL TI Sequential attitude and attitude-rate estimation using integrated-rate parameters SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID VECTOR OBSERVATIONS; TARGET TRACKING; ALGORITHM; EQUATION; MODEL AB A sequential nonlinear algorithm is presented for gyroless satellite attitude and attitude-rate estimation using vector observations. Based on a third-order, minimal-parameter method for solving the attitude matrix kinematic equation, the resulting estimator is rendered computationally efficient. Employing tracking theory concepts, the angular acceleration is modeled as an exponentially autocorrelated stochastic process, thereby avoiding the use of the typically uncertain spacecraft dynamic model. The estimator's performance is demonstrated via a numerical example, in which it is compared with the estimator implemented onboard the gyroless Solar, Anomalous, and Magnetospheric Particle Explorer spacecraft. C1 Technion Israel Inst Technol, Dept Aerosp Engn, IL-32000 Haifa, Israel. NASA, Goddard Space Flight Ctr, Guidance Navigat & Control Ctr, Greenbelt, MD 20771 USA. RP Oshman, Y (reprint author), Technion Israel Inst Technol, Dept Aerosp Engn, IL-32000 Haifa, Israel. NR 29 TC 18 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 1999 VL 22 IS 3 BP 385 EP 394 DI 10.2514/2.4404 PG 10 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 196KK UT WOS:000080307400001 ER PT J AU Siegel, R AF Siegel, R TI Transient thermal analysis of a translucent thermal barrier coating on a metal wall SO JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME LA English DT Article DE coatings; heat transfer; radiation; transient ID RADIATION C1 NASA, Lewis Res Ctr, Res & Technol Directorate, Cleveland, OH 44135 USA. RP Siegel, R (reprint author), NASA, Lewis Res Ctr, Res & Technol Directorate, 21000 Brookpark Rd, Cleveland, OH 44135 USA. NR 5 TC 14 Z9 14 U1 0 U2 6 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0022-1481 J9 J HEAT TRANS-T ASME JI J. Heat Transf.-Trans. ASME PD MAY PY 1999 VL 121 IS 2 BP 478 EP 481 DI 10.1115/1.2826004 PG 4 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 207TN UT WOS:000080952000030 ER PT J AU Toth, RA AF Toth, RA TI HDO and D2O low pressure, long path spectra in the 600-3100 cm(-1) region I. HDO line positions and strengths SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID TRANSITION FREQUENCIES; 2-NU-2 BANDS; INTENSITIES; NU(2)-BANDS; (D2O)-O-16; (H2O)-O-16; NU-1 AB High-resolution spectra of gas mixtures of HDO, D2O, and H2O were obtained with a Fourier-transform spectrometer with path lengths up to 433 m. The spectra were analyzed to obtain line positions and strengths of over 6000 transitions of HDO and D2O. For HDO, these included the (000)-(000), (020)-(010), and (100)-(010) bands of (HDO)-O-16 and the (010)-(000) bands of (HDO)-O-16, (HDO)-O-17, and (HDO)-O-18. Several of these assignments are reported for the first time. Of interest was the extended coverage of the A-type transitions of the (010)-(000) band of (HDO)-O-16. This is the only A-type infrared band of any of the water vapor species (HDO, D2O, and H2O) that is not involved in interactions with other bands. By this token, the A-type dipole-moment expansion matrix elements can be tested without involving perturbation theory. The measured linestrengths of the interacting bands, (020)-(010) and (100)-(010), were analyzed using a full perturbation treatment. Strong localized Coriolis interactions affected only a few observed transitions, (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 38 Z9 39 U1 0 U2 5 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 MAY PY 1999 VL 195 IS 1 BP 73 EP 97 DI 10.1006/jmsp.1999.7814 PG 25 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 189UN UT WOS:000079924700007 ER PT J AU Toth, RA AF Toth, RA TI HDO and D2O low pressure, long path spectra in the 600-3100 cm(-1) region II. D2O line positions and strengths SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID (D2O)-O-16 AB Measurements of line positions and absolute strengths of D2O from 700 to 3100 cm(-1) were obtained with a Fourier transform spectrometer. The data were analyzed to obtain energy levels of the (000), (010), (020), (100), and (001) vibrational states of (D2O)-O-16 and, first time assignments of the (010)-(000) band of (D2O)-O-17, including the energy levels of the (000) and (010) states. The measurements included transitions of the (010)-(000) band of (D2O)-O-18; however, observations from a previous study provided adequate information for the energy levels. The measured linestrengths of the (010)-(000) bands of (D2O)-O-16, (D2O)-O-17, and (D2O)-O-18 were fitted to the model, which included up to 19 dipole-moment expansion coefficients. The observed linestrengths of the (D2O)-O-16 interacting bands, (020)-(010), (100)-(010), and (001)-(010), were analyzed using a full perturbation treatment. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Toth, RA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 28 Z9 28 U1 0 U2 4 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 MAY PY 1999 VL 195 IS 1 BP 98 EP 122 DI 10.1006/jmsp.1999.7815 PG 25 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 189UN UT WOS:000079924700008 ER PT J AU Minnetyan, L Chamis, CC AF Minnetyan, L Chamis, CC TI Damage tolerance of large shell structures SO JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME LA English DT Article ID SIMULATION AB Progressive damage and fracture of large shell structures is investigated. A computer model is used for the assessment of structural response, progressive fracture resistance, and defect/damage tolerance characteristics. Critical locations of a stiffened conical shell segment are identified Defective and defect-free computer models are simulated to evaluate structural damage/defect tolerance. Safe pressurization levels are assessed for the retention of structural integrity at the presence of damage/defects. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Damage propagation and burst pressures for defective and defect-free shells are compared to evaluate damage tolerance. Design implications with regard to defect and damage tolerance of a large steel pressure vessel are examined. C1 Clarkson Univ, Dept Civil & Environm Engn, Potsdam, NY 13699 USA. NASA, Lewis Res Ctr, Struct Div, Cleveland, OH 44135 USA. RP Minnetyan, L (reprint author), Clarkson Univ, Dept Civil & Environm Engn, POB 5710, Potsdam, NY 13699 USA. NR 3 TC 1 Z9 1 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0094-9930 J9 J PRESS VESS-T ASME JI J. Press. Vessel Technol.-Trans. ASME PD MAY PY 1999 VL 121 IS 2 BP 188 EP 195 DI 10.1115/1.2883685 PG 8 WC Engineering, Mechanical SC Engineering GA 198NG UT WOS:000080429900011 ER PT J AU Smart, MK AF Smart, MK TI Design of three-dimensional hypersonic inlets with rectangular-to-elliptical shape transition SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA 35th Aerospace Science Meeting / Nonlinear Dynamical Systems Symposium CY JAN 06-10, 1997 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut, USAF, Off Sci Res, Sandia Natl Labs AB A methodology has been devised for the design of three-dimensional hypersonic Inlets, This methodology makes extensive use of inviscid stream-tracing techniques to generate an inlet with smooth shape transition from a rectangular-like capture to an elliptical throat. Highly swept leading edges and a significantly notched cowl enable use of these inlets in fixed geometry configurations. The design procedure includes a three-dimensional viscous correction and uses established correlations to check for boundary-layer separation caused by shock wave interactions. Complete details of the design procedure are presented and the characteristics of a modular inlet with a design point of Mach 6.0 are examined. Comparison with a classical two-dimensional inlet optimized for maximum total pressure recovery indicates that these three-dimensional inlets demonstrate good inviscid performance even when operating well below the design point. An estimate of the on-design viscous performance corresponds with that of an efficient inlet for scramjet applications. C1 NASA, Langley Res Ctr, Natl Res Council, Hyperson Airbreathing Propuls Branch, Hampton, VA 23681 USA. RP Smart, MK (reprint author), NASA, Langley Res Ctr, Natl Res Council, Hyperson Airbreathing Propuls Branch, M-S 168, Hampton, VA 23681 USA. RI Smart, Michael/C-8823-2013 NR 16 TC 35 Z9 54 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAY-JUN PY 1999 VL 15 IS 3 BP 408 EP 416 DI 10.2514/2.5459 PG 9 WC Engineering, Aerospace SC Engineering GA 208VU UT WOS:000081013200006 ER PT J AU Srivastava, R Reddy, TSR AF Srivastava, R Reddy, TSR TI Comparative study of coupled-mode flutter-analysis methods for fan configurations SO JOURNAL OF PROPULSION AND POWER LA English DT Article ID UNSTEADY FLOWS; PROPELLERS; CASCADE; BLADES AB A comparative computational study of current flutter-analysis methods, for fan geometry in subsonic flow, is carried out to evaluate the relative advantage of the methods. The flutter characteristics are computed using the following three methods: time domain, work per cycle, and the eigenvalue analysis. The eigenvalue analysis is based on a pulse method in combination with the influence coefficient method. The aeroelastic analyses are performed using a time-accurate solver based on Euler equations. The aeroelastic characteristics of the fan are obtained by coupling the unsteady Euler equation solution with a normal-mode analysis of elastic blades. For the coupled-mode flutter analyzed, the time-domain method indicated stability or instability faster than the eigenvalue method, whereas the work-per-cycle method failed to predict the flutter. The eigenvalue method provided the results in the form of aerodynamic damping and flutter frequency for each interblade phase angle analyzed. However, it was more expensive than the time-domain method, and it was better suited for analysis with a fewer number of modes. C1 Univ Toledo, Toledo, OH 43606 USA. RP Srivastava, R (reprint author), John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. NR 25 TC 8 Z9 8 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAY-JUN PY 1999 VL 15 IS 3 BP 447 EP 453 DI 10.2514/2.5447 PG 7 WC Engineering, Aerospace SC Engineering GA 208VU UT WOS:000081013200011 ER PT J AU Paxson, DE Nalim, MR AF Paxson, DE Nalim, MR TI Modified through-flow wave-rotor cycle with combustor-bypass ducts SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/ASME/SAE/ASEE 33rd Joint Propulsion Conference CY JUL 06-09, 1997 CL SEATTLE, WASHINGTON SP Amer Inst Aeronaut & Astronaut, ASME, SAE, ASEE AB A wave rotor cycle is described that avoids the inherent problem of combustor exhaust gas recirculation (EGR) found in four port, through-flow (uniflow) pressure-gain wave rotor cycles currently under consideration for top ping gas-turbine engines. The recirculated hot gas is eliminated by the judicious placement of a bypass duct that transfers gas from one end of the rotor to the other, The resulting cycle, when analyzed numerically, yields a mean absolute temperature for the rotor that is 18% below the already impressive value (approximately the turbine inlet temperature) predicted for the conventional four-port cycle. The absolute temperature of the gas leading to the combustor is also reduced from the conventional design by 17%. The overall design-point pressure ratio of this new bypass cycle is approximately the same as the conventional cycle. This paper will describe the EGR problem and the bypass-cycle solution, including relevant wave diagrams. Performance estimates of design and off-design operation of a specific wave rotor will be presented, The results were obtained using a one-dimensional numerical simulation and design code. C1 NASA, John H Glenn Res Ctr Lewis Field, Controls & Dynam Technol Branch, Cleveland, OH 44135 USA. Indiana Univ Purdue Univ, Purdue Sch Engn & Technol, Indianapolis, IN 46202 USA. RP Paxson, DE (reprint author), NASA, John H Glenn Res Ctr Lewis Field, Controls & Dynam Technol Branch, M-S 77-1, Cleveland, OH 44135 USA. NR 17 TC 7 Z9 7 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD MAY-JUN PY 1999 VL 15 IS 3 BP 462 EP 467 DI 10.2514/2.5449 PG 6 WC Engineering, Aerospace SC Engineering GA 208VU UT WOS:000081013200013 ER PT J AU Kato, S Ackerman, TP Mather, JH Clothiaux, EE AF Kato, S Ackerman, TP Mather, JH Clothiaux, EE TI The k-distribution method and correlated-k approximation for a shortwave radiative transfer model SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID INHOMOGENEOUS ATMOSPHERES; MULTIPLE-SCATTERING; CLIMATE; ABSORPTION; RATES AB Absorption cross sections are tabulated for water vapor, including continuum absorption, ozone, oxygen and carbon dioxide in the solar spectral region by adopting the k-distribution method. These tables are generated based on line-by-line code results for ranges of total pressure, temperature and water vapor concentration typical of values throughout the troposphere. These tables are incorporated into a shortwave radiative transfer code, which has 32 wavelength intervals across the solar spectrum, by using the correlated-k approximation in order to evaluate the accuracy in the broad band direct normal irradiance computation. A comparison of the direct normal irradiance with MODTRAN3 demonstrates that these tables can be used for shortwave broad band irradiance computations; the difference in the transmissivity is within 0.01 throughout most of the solar spectral region. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. RP Kato, S (reprint author), NASA, Langley Res Ctr, Mail Stop 420, Hampton, VA 23681 USA. NR 26 TC 121 Z9 124 U1 0 U2 9 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 MAY PY 1999 VL 62 IS 1 BP 109 EP 121 DI 10.1016/S0022-4073(98)00075-2 PG 13 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 178WG UT WOS:000079291700009 ER PT J AU Jacquinet-Husson, N Arie, E Ballard, J Barbe, A Bjoraker, G Bonnet, B Brown, LR Camy-Peyret, C Champion, JP Chedin, A Chursin, A Clerbaux, C Duxbury, G Flaud, JM Fourrie, N Fayt, A Graner, G Gamache, R Goldman, A Golovko, V Guelachvili, G Hartmann, JM Hilico, JC Hillman, J Lefevre, G Lellouch, E Mikhailenko, SN Naumenko, OV Nemtchinov, V Newnham, DA Nikitin, A Orphal, J Perrin, A Reuter, DC Rinsland, CP Rosenmann, L Rothman, LS Scott, NA Selby, J Sinitsa, LN Sirota, JM Smith, AM Smith, KM Tyuterev, VG Tipping, RH Urban, S Varanasi, P Weber, M AF Jacquinet-Husson, N Arie, E Ballard, J Barbe, A Bjoraker, G Bonnet, B Brown, LR Camy-Peyret, C Champion, JP Chedin, A Chursin, A Clerbaux, C Duxbury, G Flaud, JM Fourrie, N Fayt, A Graner, G Gamache, R Goldman, A Golovko, V Guelachvili, G Hartmann, JM Hilico, JC Hillman, J Lefevre, G Lellouch, E Mikhailenko, SN Naumenko, OV Nemtchinov, V Newnham, DA Nikitin, A Orphal, J Perrin, A Reuter, DC Rinsland, CP Rosenmann, L Rothman, LS Scott, NA Selby, J Sinitsa, LN Sirota, JM Smith, AM Smith, KM Tyuterev, VG Tipping, RH Urban, S Varanasi, P Weber, M TI The 1997 spectroscopic GEISA databank SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Review ID HETERODYNE FREQUENCY MEASUREMENTS; ABSORPTION CROSS-SECTIONS; FOURIER-TRANSFORM SPECTROSCOPY; CARBONYL SULFIDE TRANSITIONS; HIGH-RESOLUTION MEASUREMENTS; DIODE-LASER SPECTROMETER; FAR-INFRARED-SPECTRUM; 5 MU-M; LINE POSITIONS; NITRIC-OXIDE AB The current version GEISA-97 of the computer-accessible database system GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information) is described. This catalogue contains 1,346,266 entries. These are spectroscopic parameters required to describe adequately the individual spectral lines belonging to 42 molecules (96 isotopic species) and located between 0 and 22,656 cm(-1). The featured molecules are of interest in studies of the terrestrial as well as the other planetary atmospheres, especially those of the Giant Planets. GEISA-97 contains also a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra. The modifications and improvements made to the earlier edition (GEISA-92) and the data management software are described. GEISA-97 and the associated management software are accessible from the ARA/LMD (Laboratoire de Meteorologie Dynamique du CNRS, France) web site: http://ara01.polytechnique.fr/registration. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Ecole Polytech, CNRS, Meteorol Dynam Lab, F-91128 Palaiseau, France. Univ Paris Sud, CNRS, Lab Phys Mol & Applicat, Orsay, France. Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Fac Sci, CNRS, Grp Spectrometrie Mol & Atmospher, Reims, France. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Paris 06, CNRS, Lab Phys Mol & Applicat, Paris, France. Univ Bourgogne, CNRS, Phys Lab, Dijon, France. Inst Atmospher Opt, Tomsk, Russia. Free Univ Brussels, Lab Chim Phys Mol, Brussels, Belgium. Univ Strathclyde, Dept Phys & Appl Phys, Glasgow G4 0NG, Lanark, Scotland. Univ Paris Sud, CNRS, Photophys Mol Lab, Orsay, France. Catholic Univ Louvain, Lab Spect Mol, Louvain, Belgium. Univ Lowell, Dept Environm Earth & Atmospher Sci, Lowell, MA 01854 USA. Univ Denver, Dept Phys, Denver, CO 80208 USA. Observ Paris, DESPA, Meudon Sect, F-92195 Meudon, France. SUNY Stony Brook, Marine Sci Res Ctr, Inst Terr & Planetary Atmospheres, Stony Brook, NY 11794 USA. Univ Bremen, Inst Remote Sensing, Inst Environm Phys, D-28334 Bremen, Germany. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. CNRS, Lab Energet Mol & Macroscop Combust, Chatenay Malabry, France. Ecole Cent Paris, Chatenay Malabry, France. AF Geophys Direcorate, Hanscom AFB, MA 01731 USA. Northrop Grumman, Bethpage, NY 11714 USA. Tech Univ Munich, Inst Phys & Theoret Chem, D-8046 Garching, Germany. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. J Heyrovsky Inst Phys Chem & Electrochem, Prague, Czech Republic. RP Jacquinet-Husson, N (reprint author), Ecole Polytech, CNRS, Meteorol Dynam Lab, F-91128 Palaiseau, France. EM husson@ara01.polytechnique.fr RI Champion, Jean-Paul/C-3963-2009; Weber, Mark/F-1409-2011; Bjoraker, Gordon/D-5032-2012; Orphal, Johannes/A-8667-2012; Nikitin, Andrei/K-2624-2013; clerbaux, cathy/I-5478-2013; OI Weber, Mark/0000-0001-8217-5450; Orphal, Johannes/0000-0002-1943-4496; Nikitin, Andrei/0000-0002-4280-4096; Rothman, Laurence/0000-0002-3837-4847 NR 127 TC 234 Z9 235 U1 1 U2 15 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 MAY PY 1999 VL 62 IS 2 BP 205 EP 254 DI 10.1016/S0022-4073(98)00111-3 PG 50 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 182AH UT WOS:000079476000006 ER PT J AU Braun, RD AF Braun, RD TI Aeroassist systems: An important element in NASA's new era of planetary exploration SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Editorial Material C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Braun, RD (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 0 TC 5 Z9 5 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 1999 VL 36 IS 3 BP 297 EP 297 DI 10.2514/2.3454 PG 1 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500001 ER PT J AU Milos, FS Chen, YK Squire, TH Brewer, RA AF Milos, FS Chen, YK Squire, TH Brewer, RA TI Analysis of Galileo Probe heatshield ablation and temperature data SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 32nd Thermophysics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut ID JUPITER ATMOSPHERE AB The Galileo Probe deceleration module contained instrumentation to measure heatshield ablation and temperatures during its hypersonic entry into the atmosphere of Jupiter. The ablation data reduction and analysis were reported previously; therefore, only a brief review is provided. One-dimensional transient analyses of the heatshield ablation, pyrolysis, and heat conduction were performed at the thermometer locations. These calculations were coupled with an axisymmetric heat conduction model to predict the thermometer temperature response. Near the end of the frustum, the temperature and recession data are very consistent. The measured recession is 3.63 +/- 0.15 cm, and the estimated peak heat flux and heat load are 13.4 +/- 0.5 kW/cm(2) and 161 +/- 6 kJ/cm(2), respectively. At the aft cover, the material response analyses do not match the low magnitude and slope of the temperature data, which seem to indicate that heat conduction into the heatshield was lower than expected. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Eloret Thermosci Inst, Moffett Field, CA 94035 USA. Lockheed Martin Missiles & Space Co, Aerothermophys Unit, King Of Prussia, PA 19406 USA. RP Milos, FS (reprint author), NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. NR 34 TC 17 Z9 18 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 298 EP 306 DI 10.2514/2.3465 PG 9 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500002 ER PT J AU Lyons, DT Beerer, JG Esposito, P Johnston, MD Willcockson, WH AF Lyons, DT Beerer, JG Esposito, P Johnston, MD Willcockson, WH TI Mars Global Surveyor: Aerobraking mission overview SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The Mars Global Surveyor spacecraft was launched on Nov. 6, 1996, and was captured into a highly elliptical, 45-h orbit around Mars with a 973 m/s propulsive maneuver on Sept, 12, 1997. A four-month aerobraking phase was supposed to remove another 1200 mis to circularize the orbit. Unfortunately, one of the two solar wings was damaged during deployment just after launch when the deployment damper failed. What has happened so far to achieve the original mission objectives is described, and the plans for the future of the Mars Global Surveyor Spacecraft are discussed. C1 CALTECH, Jet Prop Lab, Inner Planets Mission Analy, Nav & Flight Mech Sect, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Mars Surveyor Operat Project, Pasadena, CA 91109 USA. Lockheed Martin Astronaut, Reentry Syst, Denver, CO 80127 USA. RP Lyons, DT (reprint author), CALTECH, Jet Prop Lab, Inner Planets Mission Analy, Nav & Flight Mech Sect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 48 Z9 54 U1 2 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 307 EP 313 DI 10.2514/2.3472 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500003 ER PT J AU Wilmoth, RG Rault, DF Cheatwood, FM Engelund, WC Shane, RW AF Wilmoth, RG Rault, DF Cheatwood, FM Engelund, WC Shane, RW TI Rarefied aerothermodynamic predictions for Mars Global Surveyor SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Direct simulation Monte Carlo and free-molecular methods are used to provide aerothermodynamic characteristics for the Mars Global Surveyor spacecraft. These characteristics have been used for spacecraft design, mission planning, flight operations, and atmospheric reconstruction. Rarefied transitional Row effects on both heating and aerodynamic drag are shown to be significant. The spacecraft is shown to be aerodynemically stable in both pitch and yaw. The effects of a partially deployed, unlatched solar panel are also studied to provide the aerothermodynamic characteristics of a revised aerobraking configuration. The predictions show that the heating and aerodynamics of this revised configuration are not significantly different from those of the originally planned configuration. Attitude excursions observed in the early aerobraking passes are shown to be explained by significant deflections of the partially deployed panel. The predicted attitudes and panel deflections are in good agreement with flight measurements. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aerosol Res Branch, Atmospher Sci Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. George Washington Univ, Joint Inst Adv Flight Sci, Hampton, VA 23681 USA. RP Wilmoth, RG (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 17 TC 17 Z9 19 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 1999 VL 36 IS 3 BP 314 EP 322 DI 10.2514/2.3473 PG 9 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500004 ER PT J AU Tolson, RH Keating, GM Cancro, GJ Parker, JS Noll, SN Wilkerson, BL AF Tolson, RH Keating, GM Cancro, GJ Parker, JS Noll, SN Wilkerson, BL TI Application of accelerometer data to Mars Global Surveyor aerobraking operations SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Aerobraking was selected for the Mars Global Surveyor mission as a primary and enabling operation. The application of accelerometer data for determining atmospheric density during operations for the first phase of aerobraking is reported. Acceleration was measured along the body z axis, which is the axis nominally into the flow. For a 1-s count time, the data have a resolution of 0.332 mm/s, permitting the recovery of density to 3% at nominal aerobraking altitudes near 115 km and on many orbits, permitting the recovery of density to altitudes as high as 180 km. Accelerometer data were analyzed in near real time to provide estimates of density at periapsis, maximum density, density scale height, latitudinal gradient information, and longitudinal wave variations. Summaries are given of the aerobraking phase of the mission, the accelerometer data analysis methods and operational procedures, some applications to determining thermospheric properties, and some remaining issues on interpretation of the data. Preflight estimates of 70% 2 sigma natural variability are shown to be realistic, and predictions that dust storms could produce rapid and large increases in thermospheric density have been verified. C1 George Washington Univ, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 12 TC 34 Z9 34 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 323 EP 329 DI 10.2514/2.3474 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500005 ER PT J AU Moss, JN Blanchard, RC Wilmoth, RG Braun, RD AF Moss, JN Blanchard, RC Wilmoth, RG Braun, RD TI Mars Pathfinder rarefied aerodynamics: Computations and measurements SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB On July 4, 1997, after traveling close to 5 x 10(8) km, the Pathfinder spacecraft successfully completed entry, descent, and landing at Mars. The hypersonic rarefied portion of Pathfinder's atmospheric entry, where flight measurements, aerodynamic calculations, and atmospheric modeling tools are used to extract Pathfinder's attitude and the freestream density, is focused on. Accuracy of the capsule aerodynamics directly impacts the inferred atmospheric properties extracted from deceleration measurements made by onboard accelerometers, The range of rarefaction considered extends from free-molecular to continuum conditions; angles of attack vary from 0 to 30 deg. The aerodynamic computations are made with free-molecular and direct simulation Monte Carlo codes. The calculations show that Pathfinder is statistically unstable for much of the transitional rarefied regime. Because of the relatively modest forces and the gyroscopic motion of the spacecraft, the angle of attack excursions were less than 5 deg, as inferred from force measurements for the rarefied portion of entry, and approached a nominal 0-deg trim angle near hypersonic continuum conditions. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. RP Moss, JN (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 21 TC 18 Z9 18 U1 2 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 1999 VL 36 IS 3 BP 330 EP 339 DI 10.2514/2.3475 PG 10 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500006 ER PT J AU Vaughan, RM Kallemeyn, PH Spencer, DA Braun, RD AF Vaughan, RM Kallemeyn, PH Spencer, DA Braun, RD TI Navigation flight operations for Mars Pathfinder SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A detailed description of the techniques used and results obtained for the interplanetary navigation of the Mars Pathfinder spacecraft is presented. Mars Pathfinder was launched on Dec. 4, 1996, and landed on Mars on July 4, 1997. To ensure a successful landing, the navigation team was required to guide the vehicle such that the flight-path angle error was less than 1.0 deg at atmospheric entry. This relatively tight requirement was achieved through the use of a ground-based orbit determination system ming Doppler and range measurements obtained from Earth stations. The resulting orbit solutions were used to design and execute four trajectory correction maneuvers needed to ensure the vehicle would make a correct atmospheric entry. More frequent orbit solutions were performed during the final two days to predict the exact time of entry and preset the onboard entry, descent, and landing sequence to deploy the parachute at the correct moment. The overall result was a successful landing less than 30 km from the intended target, well within the 100 x 200 km requirement ellipse. C1 CALTECH, Jet Prop Lab, Nav & Flight Mech Sect, Pasadena, CA 91109 USA. CALTECH, Jet Prop Lab, Mars Surveyor 01 Project, Pasadena, CA 91109 USA. NASA, Langley Res Ctr, Space Syst & Concepts Div, Hampton, VA 23665 USA. RP Vaughan, RM (reprint author), CALTECH, Jet Prop Lab, Nav & Flight Mech Sect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 8 Z9 8 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 340 EP 347 DI 10.2514/2.3476 PG 8 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500007 ER PT J AU Braun, RD Spencer, DA Kallemeyn, PH Vaughan, RM AF Braun, RD Spencer, DA Kallemeyn, PH Vaughan, RM TI Mars Pathfinder atmospheric entry navigation operations SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA Atmospheric Flight Mechanics Conference CY AUG 11-13, 1997 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut ID LANDING SITE AB On July 4, 1997, the Pathfinder spacecraft ushered in a new era of planetary exploration by successfully landing on the surface of Mars. The atmospheric entry and approach navigation activities required in support of this mission are discussed. In particular, the flight software parameter update and landing site prediction analyses performed by the Pathfinder operations navigation team are described. A suite of atmospheric entry simulation tools, developed during Pathfinder's design cycle and utilized during flight operations, is also presented. Data regarding the accuracy of the primary parachute deployment algorithm are extracted from the Pathfinder flight data, demonstrating that this algorithm performed as predicted. The increased probability of mission success through the software parameter update process is discussed. The importance of modeling atmospheric flight uncertainties in the estimation of an accurate landing site is also demonstrated. With these atmospheric effects included, the center of the final pre-entry landed ellipse prediction differs from the postflight determined landing site by less than 0.5 km in downrange and 5.0 km in crossrange. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. CALTECH, Jet Prop Lab, Pathfinder Operat Nav Team, Pasadena, CA 91109 USA. RP Braun, RD (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 20 TC 10 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 348 EP 356 DI 10.2514/2.3477 PG 9 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500008 ER PT J AU Spencer, DA Blanchard, RC Braun, RD Kallemeyn, PH Thurman, SW AF Spencer, DA Blanchard, RC Braun, RD Kallemeyn, PH Thurman, SW TI Mars Pathfinder entry, descent, and landing reconstruction SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The primary objective of the Mars Pathfinder mission was to demonstrate an innovative, low-cost, reliable method for piecing a science payload on the surface of Mars. The spacecraft performance during entry, descent, and landing is assessed. Analysis of the accelerometer and altimeter flight data obtained by the Pathfinder spacecraft during atmospheric flight is provided. Results of an effort to reconstruct the spacecraft trajectory and attitude history are presented. An estimate of the Mars atmosphere profile encountered during atmospheric flight is given. C1 CALTECH, Jet Prop Lab, Mars Surveyor 2001 Project, Pasadena, CA 91109 USA. NASA, Langley Res Ctr, Space Syst & Concepts Grp, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aero & Gas Dynam Grp, Hampton, VA 23681 USA. CALTECH, Jet Prop Lab, Mars Surveyor Operat Project, Pasadena, CA 91109 USA. RP Spencer, DA (reprint author), CALTECH, Jet Prop Lab, Mars Surveyor 2001 Project, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 59 Z9 65 U1 4 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 357 EP 366 DI 10.2514/2.3478 PG 10 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500009 ER PT J AU Gnoffo, PA Braun, RD Weilmuenster, KJ Mitcheltree, RA Engelund, WC Powell, RW AF Gnoffo, PA Braun, RD Weilmuenster, KJ Mitcheltree, RA Engelund, WC Powell, RW TI Prediction and validation of Mars Pathfinder hypersonic aerodynamic database SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA/ASME 7th Joint Thermophysics and Heat Transfer Conference CY JUN 15-18, 1998 CL ALBUQUERQUE, NEW MEXICO SP AIAA, ASME ID ENTRY AB Postflight analysis of the Mars Pathfinder hypersonic, continuum aerodynamic database is presented. Measured data include accelerations along the body axis and axis normal directions. Comparisons of preflight simulation and measurements show good agreement. The prediction of two static instabilities associated with movement of the sonic line from the shoulder to the nose and back was confirmed by measured normal accelerations. Reconstruction of atmospheric density during entry has an uncertainty directly proportional to the uncertainty in the predicted axial coefficient. The sensitivity of the moment coefficient to freestream density, kinetic models, and center-of-gravity location are? examined to provide additional consistency checks of the simulation with flight data. The atmospheric density as derived from axial coefficient and measured axial accelerations falls within the range required for sonic line shift and static stability transition as independently determined from normal accelerations. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Vehicle Anal & Planetary Explorat Branch, Hampton, VA 23681 USA. RP Gnoffo, PA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 11 TC 22 Z9 27 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 367 EP 373 DI 10.2514/2.3455 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500010 ER PT J AU Milos, FS Chen, YK Congdon, WM Thornton, JM AF Milos, FS Chen, YK Congdon, WM Thornton, JM TI Mars Pathfinder entry temperature data, aerothermal heating, and heatshield material response SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA/ASME 7th Joint Thermophysics and Heat Transfer Conference CY JUN 15-18, 1998 CL ALBUQUERQUE, NEW MEXICO SP AIAA, ASME ID FLOW AB The Mars Pathfinder probe contained instrumentation that measured heatshield temperatures during entry. A description of the experiment, the data, and an analysis of the entry environment and material response are presented, Navier-Stokes forebody heating calculations show a peak unblown radiative-equilibrium heat Bur of 118 W/cm(2) at the stagnation point and 120 W/cm(2) on the shoulder for turbulent flow. The heat load is 3.8 W/cm(2) on the nose, decreases along the frustum, then increases to 2.7-3.1 kJ/cm(2) on the shoulder depending on the onset time for turbulence. One-dimensional charring material response is calculated using three different models. Stagnation point temperature data are consistent with about 85% of fully catalytic laminar heating. Shoulder temperature data are inconclusive, but are consistent with fully catalytic laminar heating or with 85% of fully catalytic heating with early onset of turbulence, Aft temperature data indicate a peak heat flux and heat load of about 1.3 W/cm(2) and 70 J/cm(2), respectively. The aft heating profile is about 20 s longer than the forebody heating profile, Bondline temperature data, although not useful for quantitative analysis of aerothermal heating, clearly show the heatshield had adequate thickness margins for the actual entry. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. Appl Res Associates Inc, Littleton, CO 80123 USA. Lockheed Martin Astronaut, Denver, CO 80201 USA. RP Milos, FS (reprint author), NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. NR 31 TC 32 Z9 33 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 380 EP 391 DI 10.2514/2.3457 PG 12 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500012 ER PT J AU Mitcheltree, RA Moss, JN Cheatwood, FM Greene, FA Braun, RD AF Mitcheltree, RA Moss, JN Cheatwood, FM Greene, FA Braun, RD TI Aerodynamics of the Mars Microprobe entry vehicles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA Atmospheric Flight Mechanics Conference CY AUG 11-13, 1997 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut ID PROBE AB The selection of the unique aeroshell shape for the Mars Microprobes is discussed. A description of its aerodynamics in hypersonic rarefied, hypersonic continuum, supersonic, and transonic flow regimes is then presented. This description is based on direct simulation Monte Carlo analyses in the rarefied flow regime, thermochemical nonequilibrium computational fluid dynamics in the hypersonic regime, existing wind-tunnel data in the supersonic and transonic regime, additional computational work in the transonic regime, and, finally, ballistic-range data. The aeroshell is shown to possess the correct combination of aerodynamic stability and drag to convert the probe's initial tumbling attitude and high velocity at atmospheric interface into the desired surface-impact orientation and velocity. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. RP Mitcheltree, RA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 19 TC 11 Z9 12 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 1999 VL 36 IS 3 BP 392 EP 398 DI 10.2514/2.3458 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500013 ER PT J AU Moss, JN Wilmoth, RG Price, JM AF Moss, JN Wilmoth, RG Price, JM TI Direct simulation Monte Carlo calculations of aerothermodynamics for Mars Microprobe capsules SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The hypersonic transitional flow aerodynamics of the Mars Microprobe capsules are simulated with the direct simulation Monte Carlo method. Calculations of axial, normal, and static pitching coefficients were obtained over an angle of attack range comparable to actual Eight requirements. Comparisons are made with modified Newtonian and free-molecular flow calculations. Aerothermal results were also obtained for zero incidence entry conditions. The current aerodynamic results are shown to be in excellent agreement with Navier-Stokes results for small Knudsen number conditions. Peak heating conditions occur under rarefied conditions where the heating becomes a strong function of assumptions concerning surface catalytic activity. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. RP Moss, JN (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 19 TC 9 Z9 9 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 1999 VL 36 IS 3 BP 399 EP 404 DI 10.2514/2.3459 PG 6 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500014 ER PT J AU Mitcheltree, RA DiFulvio, M Horvath, TJ Braun, RD AF Mitcheltree, RA DiFulvio, M Horvath, TJ Braun, RD TI Aerothermal heating predictions for Mars Microprobe SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID ENTRY AB A combination of computational predictions and experimental measurements of the aerothermal heating expected on the two Mars Microprobes during their entry to Mars is presented. The maximum,nonablating heating rate at the vehicle's stagnation point (at zero angle of attack) is predicted for an undershoot trajectory to be 194 W/cm(2) with associated stagnation-point pressure of 0.064 atm. Maximum stagnation-point pressure occurs later during the undershoot trajectory and is 0.094 atm. From computations at seven overshoot-trajectory points, the maximum heat load expected at the stagnation point is near 8800 J/cm(2). Heat rates and heat loads on the vehicle's afterbody are much lower than on the forebody. At 0-deg angle of attack, heating over much of the hemispherical afterbody is predicted to be less than 2% of the stagnation-point value. Good qualitative agreement is demonstrated for forebody and afterbody heating between computational fluid dynamics calculations at Mars entry conditions and experimental thermographic phosphor measurements from the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. A novel approach that incorporates six-degree-of-freedom trajectory simulations to perform a statistical estimate of the effect of angle of attack and other off-nominal conditions on heating is included. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. RP Mitcheltree, RA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 19 TC 12 Z9 12 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 1999 VL 36 IS 3 BP 405 EP 411 DI 10.2514/2.3460 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500015 ER PT J AU Braun, RD Mitcheltree, RA Cheatwood, FM AF Braun, RD Mitcheltree, RA Cheatwood, FM TI Mars Microprobe entry-to-impact analysis SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID PATHFINDER AB The Mars Microprobe mission will provide the first opportunity for subsurface measurements, including water detection, near the Mars south pole. Performance of the Microprobe aeroshell design is evaluated through development and application of a six-degree-of-freedom flight dynamics simulation. Numerous mission uncertainties are quantified, and a Monte Carlo analysis is performed to statistically assess mission performance. Results from this Monte Carlo flight dynamics simulation demonstrate that the 3-sigma Microprobe impact footprint extends 180 x 20 km, and the aerothermodynamic and deceleration environments are well within design specifications. The probability of a successful impact event is assessed based on penetration data obtained through a ground-test program. The surface elevation, ground slope, and soil hardness of the Microprobe impact site are shown to be primary drivers on mission success. C1 NASA, Langley Res Ctr, Space Syst & Concepts Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aero & Gas Dynam Div, Hampton, VA 23681 USA. RP Braun, RD (reprint author), NASA, Langley Res Ctr, Space Syst & Concepts Div, Mail Stop 359, Hampton, VA 23681 USA. NR 29 TC 11 Z9 11 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 1999 VL 36 IS 3 BP 412 EP 420 DI 10.2514/2.3461 PG 9 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500016 ER PT J AU Queen, EM Cheatwood, EM Powell, RW Braun, RD Edquist, CT AF Queen, EM Cheatwood, EM Powell, RW Braun, RD Edquist, CT TI Mass Polar Lander aerothermodynamic and entry dispersion analysis SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID MARS AB An analysis of the aerothermodynamics and trajectory dispersions experienced by the Mars Polar Lander entry system was performed and is documented herein. Because the Mars Polar Lander aeroshell (forebody) is based on the Mars Pathfinder aeroshell, the Pathfinder aerodynamic database was used by Lockheed Martin Astronautics for their trajectory analyses. However, the afterbodies of the two vehicles are different. The effects of the different geometry and different trajectory were isolated, and the Pathfinder aerodynamic database was found to be appropriate for the Mars Polar Lander entry work with minor modifications. Independent heating calculations were conducted, which agree with the heating analyses done at Lockheed Martin Astronautics. Also, it was determined that, at the expected parachute-deploy conditions, the area of recirculated how extends less than two body lengths behind the vehicle. The extent of this recirculation region can impact successful parachute deployment. A six-degree-of-freedom simulation of the entry phase was developed, including much of the actual flight code for the attitude control autopilot. This simulation was exercised to evaluate the autopilot and overall system performance during entry and to evaluate response to dispersions that might affect the entry trajectory. It was determined that the autopilot keeps the vehicle oriented correctly for the disturbances modeled. Also, the six-degree-af-freedom simulation was used in a Monte Carlo analysis to determine the expected footprint and altitude at parachute deploy. C1 NASA, Langley Res Ctr, Vehicle Anal Branch, Hampton, VA 23681 USA. Lockheed Martin Astronaut, Aerophys Flight Syst, Denver, CO 80127 USA. RP Queen, EM (reprint author), NASA, Langley Res Ctr, Vehicle Anal Branch, Hampton, VA 23681 USA. NR 10 TC 10 Z9 10 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 1999 VL 36 IS 3 BP 421 EP 428 DI 10.2514/2.3462 PG 8 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500017 ER PT J AU Mitcheltree, RA Wilmoth, RG Cheatwood, FM Brauckmann, GJ Greene, FA AF Mitcheltree, RA Wilmoth, RG Cheatwood, FM Brauckmann, GJ Greene, FA TI Aerodynamics of Stardust Sample Return Capsule SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 15th Applied Aerodynamics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut AB Successful return of interstellar dust and cometary material by the Stardust Sample Return Capsule requires an accurate description of the Earth entry vehicle's aerodynamics. This description must span the hypersonic-rarefied, hypersonic-continuum, supersonic, transonic, and subsonic flow regimes. Data from numerous sources are compiled to accomplish this objective. These include direct simulation Monte Carlo analyses, thermochemical nonequilibrium computational fluid dynamics, transonic computational fluid dynamics, existing wind-tunnel data, and new wind-tunnel data. Four observations are highlighted: 1) a static instability is revealed in the free-molecular and early transitional flow regimes due to aft location of the vehicle's center of gravity, 2) the aerodynamics across the hypersonic regime are compared with the Newtonian how approximation and a correlation between the accuracy of the Newtonian flow assumption and the sonic line position is noted, 3) the primary effect of shape change due to ablation is shown to be a reduction in drag, and 4) a subsonic dynamic instability is revealed that necessitated the addition of a stabilizing drogue parachute. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. RP Mitcheltree, RA (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 19 TC 13 Z9 14 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 429 EP 435 DI 10.2514/2.3463 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500018 ER PT J AU Wilmoth, RG Mitcheltree, RA Moss, JN AF Wilmoth, RG Mitcheltree, RA Moss, JN TI Low-density aerodynamics of the Stardust Sample Return Capsule SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 32nd Thermophysics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut AB The aerodynamics of the Stardust Sample Return Capsule are analyzed in the low density, transitional how regime using free-molecular, direct simulation Monte Carlo, Navier-Stokes, and Newtonian methods to provide inputs for constructing a transitional flow bridging relation. The accuracy of this bridging relation in reconstructing the aerodynamic coefficients given by the more exact methods is presented for a range of flight conditions and vehicle attitudes. There is good agreement between the various prediction methods, and a simple sine-squared bridging relation is shown to provide a reasonably good description of the axial force, normal force, and pitching moment over a range of Knudsen numbers from 0.001 to 10. The predictions show a static instability of the Stardust capsule in the free molecular regime that persists well into the transitional flow. The addition of a thin disk to the base of the capsule is shown to remove this static instability. However, the extremely high entry velocity of 12.6 km/s for the proposed trajectory introduces difficult design issues for incorporating this disk caused by the high aerothermal loads that occur even under relatively rarefied conditions. C1 NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. RP Wilmoth, RG (reprint author), NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. NR 13 TC 19 Z9 19 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 436 EP 441 DI 10.2514/2.3464 PG 6 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500019 ER PT J AU Olynick, D Chen, YK Tauber, ME AF Olynick, D Chen, YK Tauber, ME TI Aerothermodynamics of the Stardust sample return capsule SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 32nd Thermophysics Conference CY JUN 23-25, 1997 CL ATLANTA, GEORGIA SP Amer Inst Aeronaut & Astronaut ID MARS; FLOW AB The development of a new high-fidelity methodology for predicting entry flows with coupled radiation and ablation is described. The prediction methodology consists of an axisymmetric, nonequilibrium, Navier-Stokes Bow solver loosely coupled to a radiation prediction code and a material thermal response code. The methodology is used to simulate the 12.6-km/s Earth atmospheric entry of the Stardust sample return capsule using ablating and nonablating boundary conditions. These flow simulations are used to size and design the Stardust forebody and afterbody heatshields and develop arcjet test conditions and models. The Bow simulations indicate that the afterbody heating and pressure profiles in time are significantly different than the forebody heating and pressure profiles. This result is explained in terms of the pertinent aerothermodynamics of the flowfield and the vehicle's geometry. When applied to the afterbody thermal protection system, these results show that the traditional afterbody heatshield design approach is nonconservative for the Stardust sample return capsule shape and entry conditions. C1 NASA, Ames Res Ctr, Reacting Flow Environm Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Thermal Protect & Mat Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Thermosci Inst, 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 56 TC 64 Z9 68 U1 0 U2 5 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 442 EP 462 DI 10.2514/2.3466 PG 21 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500020 ER PT J AU Desai, PN Mitcheltree, RA Cheatwood, FM AF Desai, PN Mitcheltree, RA Cheatwood, FM TI Entry dispersion analysis for the Stardust Comet Sample Return Capsule SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA Atmospheric Flight Mechanics Conference CY AUG 11-13, 1997 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut ID 6-DEGREE-OF-FREEDOM AB Stardust will be the first mission to return samples from a comet. The sample return capsule, which is passively controlled during the fastest Earth entry ever, will land by parachute in Utah. The present study analyzes the entry, descent, and landing of the returning sample capsule. The effects of two aerodynamic instabilities are revealed (one in the high-altitude free-molecular regime and the other in the transonic/subsonic flow regime), These instabilities could lead to unacceptably large excursions in the angle of attack near peak heating and main parachute deployment, respectively, To reduce the excursions resulting from the high-altitude instability, the entry spin rate of the capsule is increased from 5 to 16 rpm. To stabilize the excursions from the transonic/subsonic instability, a drogue chute with deployment triggered by a g-switch and timer is added prior to main parachute deployment. A Monte Carlo dispersion analysis of the modified entry (from which the impact of off-nominal conditions during the entry is ascertained) predicts that the capsule attitude excursions near peak heating and drogue chute deployment are within Stardust program limits. Additionally, the size of the resulting 3-sigma landing ellipse is 83.5 km in downrange by 29.2 km in crossrange, which is within the Utah Test and Training Range boundaries. C1 NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Aerothermodynam Branch, Aero & Gas Dynam Div, Hampton, VA 23681 USA. RP Desai, PN (reprint author), NASA, Langley Res Ctr, Vehicle Anal Branch, Space Syst & Concepts Div, Hampton, VA 23681 USA. NR 13 TC 17 Z9 17 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD MAY-JUN PY 1999 VL 36 IS 3 BP 463 EP 469 DI 10.2514/2.3467 PG 7 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500021 ER PT J AU Chen, YK Milos, FS AF Chen, YK Milos, FS TI Ablation and thermal response program for spacecraft heatshield analysis SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA 36th Aerospace Sciences Meeting CY JAN 12-15, 1998 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB An implicit ablation and thermal response program is presented for simulation of one-dimensional transient thermal energy transport in a multilayer stack of isotropic materials and structure that can ablate from a front surface and decompose in depth. The governing equations and numerical procedures for solution are summarized. Solutions are compared with those of an existing code, CMA, and also with arcjet data. Numerical experiments show that the new code is numerically more stable and solves a much wider range of problems compared with the older code. To demonstrate its capability, applications for thermal analysis and sizing of aeroshell heatshields for planetary missions of Stardust, Mars Microprobe (Deep Space II), Saturn Entry Probe, and Mars 2001, using advanced lightweight ceramic ablators developed at NASA Ames Research Center, are presented and discussed. C1 NASA, Ames Res Ctr, Thermal Project Mat & Syst Branch, Moffett Field, CA 94035 USA. RP Chen, YK (reprint author), NASA, Ames Res Ctr, Thermal Project Mat & Syst Branch, MS 234-1, Moffett Field, CA 94035 USA. NR 18 TC 79 Z9 85 U1 1 U2 14 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 1999 VL 36 IS 3 BP 475 EP 483 DI 10.2514/2.3469 PG 9 WC Engineering, Aerospace SC Engineering GA 207JV UT WOS:000080934500023 ER PT J AU Becker, JC Nitzberg, B Van der Wijngaart, RF Yarrow, M AF Becker, JC Nitzberg, B Van der Wijngaart, RF Yarrow, M TI Predicting price performance trade-offs for Whitney: A commodity computing cluster SO JOURNAL OF SUPERCOMPUTING LA English DT Article DE performance modeling; benchmarking; PC clusters; supercomputing AB We couple simple performance models with pricing to optimize the design of clusters built from commodity components for scientific computing. We apply this technique using the NAS Parallel Benchmarks as a representative workload. We develop models of the BT, LU, and SP benchmarks. The models consist of closed form expressions based on problem size, number of processors, and three measured quantities (single processor performance, network latency, and network bandwidth). These models predict benchmark performance to within 30%. This technique was used in the design of Whitney, a commodity computing cluster at NASA Ames Research Center. In particular, for systems costing less than $1,000,000, the performance characteristics of Intel Pentium processors are better matched to the slower (and less expensive) Fast Ethernet, than to the faster (and more expensive) Myricom Myrinet. C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. RP Becker, JC (reprint author), NASA, Ames Res Ctr, MRJ Technol Solut, M-S 258-6, Moffett Field, CA 94035 USA. NR 7 TC 2 Z9 2 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0920-8542 J9 J SUPERCOMPUT JI J. Supercomput. PD MAY PY 1999 VL 13 IS 3 BP 303 EP 319 DI 10.1023/A:1008061120801 PG 17 WC Computer Science, Hardware & Architecture; Computer Science, Theory & Methods; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 204EC UT WOS:000080749600005 ER PT J AU Rothe, J Kneedler, EM Pecher, K Tonner, BP Nealson, KH Grundl, T Meyer-Ilse, W Warwick, T AF Rothe, J Kneedler, EM Pecher, K Tonner, BP Nealson, KH Grundl, T Meyer-Ilse, W Warwick, T TI Spectromicroscopy of Mn distributions in micronodules produced by biomineralization SO JOURNAL OF SYNCHROTRON RADIATION LA English DT Article; Proceedings Paper CT 10th International Conference on XAFS (XAFS X) CY AUG 10-14, 1998 CL ILLINOIS INST TECHNOL, CHICAGO, ILLINOIS HO ILLINOIS INST TECHNOL DE soft x-ray spectromicroscopy; bacterial metabolism; Mn micronodules ID TRANSITION-METAL COMPOUNDS; OXIDATION-STATE; MANGANESE; ABSORPTION AB The interaction of single cell microorganisms with inorganic substrates is a central issue in soil and aquatic environmental chemistry. The biochemical pathways of the bacterial metabolism based on redox reactions of transition metal compounds involve the processes of microbial attachment to and subsequent modification of inorganic surfaces (biocorrosion), as well as the precipitation of inorganic compounds (biomineralization). Soft x-ray spectromicroscopy has been used to investigate Mn micronodules collected from freshwater sediments in order to attempt the direct mapping of the distribution of Mn valence states in biologically produced minerals. C1 Univ Wisconsin, Dept Phys, Milwaukee, WI 53201 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wisconsin, Dept Geosci, Milwaukee, WI 53201 USA. EO Lawrence Berkeley Natl Lab, Ctr Xray Opt, Berkeley, CA 94720 USA. RP Rothe, J (reprint author), Univ Wisconsin, Dept Phys, POB 413, Milwaukee, WI 53201 USA. NR 10 TC 14 Z9 14 U1 0 U2 3 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0909-0495 J9 J SYNCHROTRON RADIAT JI J. Synchrot. Radiat. PD MAY 1 PY 1999 VL 6 BP 359 EP 361 DI 10.1107/S0909049599001715 PN 3 PG 3 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 212NA UT WOS:000081221700085 PM 15263307 ER PT J AU Bridges, F Cao, DL Anderson, M Booth, CH Neumeier, JJ Snyder, J AF Bridges, F Cao, DL Anderson, M Booth, CH Neumeier, JJ Snyder, J TI Temperature/magnetization-induced distortions in the local structure of substituted LaMnO3 SO JOURNAL OF SYNCHROTRON RADIATION LA English DT Article; Proceedings Paper CT 10th International Conference on XAFS (XAFS X) CY AUG 10-14, 1998 CL ILLINOIS INST TECHNOL, CHICAGO, ILLINOIS HO ILLINOIS INST TECHNOL DE CMR; XAFS; polarons ID LA1-XCAXMNO3; MANGANITES; MN; LA1-XSRXMNO3; SPECTROSCOPY; RESISTIVITY; DIFFRACTION; MAGNETISM; CHARGE AB Much of the work carried out on the Colossal Magnetoresistive (CMR) materials has been interpreted using the double exchange (DE) model which assumes Mn+3 and Mn+4 sites exist. In addition, to explain the large MR in films, it has recently been suggested that local distortions in the form of polarons, must also be present above the ferromagnetic transition temperature T-c; such distortions have now been observed. We present XAFS data which illustrate the magnitude of these distortions and show that the change in the Mn-O distortions correlates well with the magnetization. However the absorption edge is sharp and shows no structure indicative of two valence states, Mn+3 and Mn+4, in either the polaron regime or in the charge-ordered material. C1 Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA. Jet Prop Lab, Pasadena, CA 91109 USA. RP Bridges, F (reprint author), Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. RI Booth, Corwin/A-7877-2008 NR 15 TC 0 Z9 0 U1 1 U2 1 PU MUNKSGAARD INT PUBL LTD PI COPENHAGEN PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK SN 0909-0495 J9 J SYNCHROTRON RADIAT JI J. Synchrot. Radiat. PD MAY 1 PY 1999 VL 6 BP 543 EP 545 DI 10.1107/S0909049598016008 PN 3 PG 3 WC Instruments & Instrumentation; Optics; Physics, Applied SC Instruments & Instrumentation; Optics; Physics GA 212NA UT WOS:000081221700152 PM 15263374 ER PT J AU Presser, WH Seale, MD Smith, BT AF Presser, WH Seale, MD Smith, BT TI Time-frequency analysis of the dispersion of Lamb modes SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID PLATES; WAVES; VELOCITIES AB Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo-Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. in addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the A(0), A(1), S-0, and S-2 Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results. (C) 1999 Acoustical Society of America. [S0001-4966(99)02705-8]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Norfolk Acad, Norfolk, VA 23502 USA. RP Presser, WH (reprint author), NASA, Langley Res Ctr, MS 231, Hampton, VA 23681 USA. RI CHEN, Jiangang/A-1549-2011 NR 31 TC 123 Z9 130 U1 3 U2 12 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 1999 VL 105 IS 5 BP 2669 EP 2676 DI 10.1121/1.426883 PG 8 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 196LQ UT WOS:000080310200014 PM 10335617 ER PT J AU Hwang, HH Govindan, TR Meyyappan, M AF Hwang, HH Govindan, TR Meyyappan, M TI Feature profile evolution simulation using a level set method SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID RECTANGULAR TRENCHES; STEP COVERAGE; LOW-PRESSURE; DEPOSITION; MODEL; SILICON; VIAS; CL+ AB A level set formulation is used to simulate profile evolution in etching and deposition processes. This approach, an alternative to string algorithms to track a moving front, is coupled to a model that computes etch rates based on first principles. Results are presented for silicon etching in a chlorine plasma. Etch profiles for various ratios of neutral to ion flux, ion anisotropy parameters, trench widths, and mask thickness are presented. Simulations capture the reactive ion etching lag effect and shadowing effects due to mask thickness. (C) 1999 The Electrochemical Society. S0013-4651(98)06-088-1. All rights reserved. C1 Thermosci Inst, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Hwang, HH (reprint author), Thermosci Inst, Moffett Field, CA 94035 USA. NR 17 TC 10 Z9 10 U1 2 U2 5 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD MAY PY 1999 VL 146 IS 5 BP 1889 EP 1894 DI 10.1149/1.1391861 PG 6 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA 197AW UT WOS:000080343300047 ER PT J AU Jackson, DJ AF Jackson, DJ TI Technique for recovering images from tightly confined spaces SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID PHASE CONJUGATION; TRANSMISSION; FIBERS AB An approach is described for the recovery of images from tightly confined spaces by use of multimode fibers, and an analytical demonstration shows that the concept is sound. The proof of concept draws on earlier studies that concentrated on image recovery after two-way and one-way transmissions through a multimode fiber; both types of transmission used four-wave-mixing techniques. The approach described also uses four-wave mixing but utilizes two fibers to capture the image at some intermediate point that is accessible to the fibers but that is visually inaccessible to the casual viewer. (C) 1999 Optical Society of America [S0740-3232(99)01505-7]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Jackson, DJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 1 Z9 1 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3232 J9 J OPT SOC AM A JI J. Opt. Soc. Am. A-Opt. Image Sci. Vis. PD MAY PY 1999 VL 16 IS 5 BP 1072 EP 1075 DI 10.1364/JOSAA.16.001072 PG 4 WC Optics SC Optics GA 190GJ UT WOS:000079954200013 ER PT J AU Sacks, RN Qin, L Jazwiecki, M Ringel, SA Clevenger, MB Wilt, D Goorsky, MS AF Sacks, RN Qin, L Jazwiecki, M Ringel, SA Clevenger, MB Wilt, D Goorsky, MS TI Growth and characterization of epitaxial FexAl1-x/(In,Al)As/InP and III-V/FexAl1-x/(In,Al)As/InP structures SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B LA English DT Article; Proceedings Paper CT 17th North American Conference on Molecular Beam Epitaxy (NAMBE-17) CY OCT 04-07, 1998 CL STATE COLL, PENNSYLVANIA ID HETEROSTRUCTURES AB We report on the growth of high quality epitaxial FexAl1-x on (In,A1)As/InP with x = 0.45-0.80 and thicknesses up to 1000 Angstrom, and on overgrowth of III-V semiconductor on the metal. Buffer layers of (In,A1)As were grown on InP substrates in a III-V growth chamber, then transferred to an attached ultrahigh vacuum chamber with dual e-beam evaporators, where FexAl1-x layers were grown by co-evaporation. Despite a large lattice mismatch of similar to 1%-2% between the metal and the semiconductor, high quality layers of FexAl1-x with thicknesses of up to 1000 Angstrom were grown. The metal layers showed bright, streaky reflection high-energy electron diffraction patterns, were specular under Nomarski microscopy, and had roughnesses of similar to 1-2 monolayers as measured by atomic force microscopy. High resolution x-ray diffraction showed that even at 1000 Angstrom, the layers were fully strained, and Pendellosung oscillations were observed, indicating high crystalline quality. Metal layers over similar to 200 Angstrom thick had resistivities in the range of those expected of bulk layers (50-100 mu Omega cm). Reflectivities greater than 90% for lambda = 4-20 mu m were observed for metal layers 1000 A thick. Overgrowth of (In,Ga)As and (In,A1)As on the metal layers shows a marked sensitivity to As overpressure, possibly due to an In surface-riding layer on top of the metal. (C) 1999 American Vacuum Society. [S0734-211X(99)07203-0]. C1 Ohio State Univ, Dept Elect Engn, Columbus, OH 43210 USA. Battis Atom Power Lab, W Mifflin, PA 15122 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Calif Los Angeles, Dept Mat Sci & Engn, Los Angeles, CA 90024 USA. RP Sacks, RN (reprint author), Ohio State Univ, Dept Elect Engn, Columbus, OH 43210 USA. NR 11 TC 2 Z9 2 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1071-1023 J9 J VAC SCI TECHNOL B JI J. Vac. Sci. Technol. B PD MAY-JUN PY 1999 VL 17 IS 3 BP 1289 EP 1293 DI 10.1116/1.590742 PG 5 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 206AD UT WOS:000080853100082 ER PT J AU Park, Y Hanson, B AF Park, Y Hanson, B TI Experimental investigation of Ostwald-ripening rates of forsterite in the haplobasaltic system SO JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH LA English DT Article DE ripening; crystal size distribution; forsterite; basalt ID SIZE DISTRIBUTION CSD; KINETICS; CRYSTALLIZATION; DYNAMICS; GROWTH; ROCKS AB The rate of Ostwald ripening of forsterite is experimentally measured in a haplobasaltic melt (SiO2-Al2O3-CaO-MgO). The goal of the experiments is to determine if the rate of Ostwald ripening is sufficient to affect textural development in crystallizing magmas of a basaltic composition. With preequilibrated charges, experiments were run isothermally so that all textural changes could be ascribed to Ostwald ripening. An increase of crystal size from 3.5 mu m to 14 mu m (in average) has been observed during 10 days. Glass compositions were identical in all charges, indicating that the observed increase in average crystal size is not the results of chemical disequilibrium but the results of Ostwald ripening. Due to the constraints on experimental duration, the rate-limiting process (i.e., diffusion control or reaction control) could not be determined. Our experimental results, however, demonstrate that the rate of Ostwald ripening in basaltic rocks is sufficient to be of fundamental importance in the development of textures in igneous rocks. These results strongly suggest that Ostwald ripening, as well as nucleation and crystal growth, should be considered in analyses of textures in igneous rocks. (C) 1999 Elsevier Science B.V. All rights resented. C1 Korea Univ, Dept Earth & Environm Sci, Seoul 136701, South Korea. NASA, Planetary Mat Branch SN4, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Park, Y (reprint author), Korea Univ, Dept Earth & Environm Sci, Seoul 136701, South Korea. NR 22 TC 23 Z9 23 U1 1 U2 11 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0377-0273 J9 J VOLCANOL GEOTH RES JI J. Volcanol. Geotherm. Res. PD MAY PY 1999 VL 90 IS 1-2 BP 103 EP 113 DI 10.1016/S0377-0273(99)00023-2 PG 11 WC Geosciences, Multidisciplinary SC Geology GA 207HM UT WOS:000080931400006 ER PT J AU Lesh, J AF Lesh, J TI Laser communication in space faces emotional roadblocks SO LASER FOCUS WORLD LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Opt Commun Grp, Pasadena, CA 91109 USA. RP Lesh, J (reprint author), CALTECH, Jet Prop Lab, Opt Commun Grp, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PENNWELL PUBL CO PI NASHUA PA 98 SPIT BROOK RD, NASHUA, NH 03062-2801 USA SN 0740-2511 J9 LASER FOCUS WORLD JI Laser Focus World PD MAY PY 1999 VL 35 IS 5 BP 121 EP 122 PG 2 WC Optics SC Optics GA 195JB UT WOS:000080245900038 ER PT J AU Hoehler, TM Albert, DB Alperin, MJ Martens, CS AF Hoehler, TM Albert, DB Alperin, MJ Martens, CS TI Acetogenesis from CO2 in an anoxic marine sediment SO LIMNOLOGY AND OCEANOGRAPHY LA English DT Article ID RICH COASTAL SEDIMENT; METHANOGENIC BACTERIA; ISOTOPIC EXCHANGE; HYDROGEN TRANSFER; ACETATE; SULFATE; CARBON; WATER; METHANE; LAKE AB A combination of radiotracer and pore-water concentration measurements provide evidence for the occurrence of acetogenesis from CO2 in anoxic marine sediments that are ordinarily dominated by sulfate reduction and methanogenesis. In a month-long incubation experiment using sediments from Cape Lookout Eight, North Carolina, we measured H-2 and acetate concentrations and monitored the incorporation of (CO2)-C-14 into (CH4)-C-14 and C-14-acetate. Depletion of pore water sulfate resulted in a period of elevated H-2 concentrations that made acetogenic CO2 reduction thermodynamically favorable. During this period, C-14-acetate was produced from (CO2)-C-14 at rates comparable to these of methanogenesis or sulfate reduction during their respective periods of dominance in the incubation. Maintenance of elevated but constant H-2 concentrations immediately following sulfate depletion likely reflects control by acetogenic bacteria, suggesting they were the dominant consumers of H-2 during this period. C1 Univ N Carolina, Dept Marine Sci, Chapel Hill, NC 27599 USA. RP Hoehler, TM (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94035 USA. NR 32 TC 49 Z9 49 U1 0 U2 7 PU AMER SOC LIMNOLOGY OCEANOGRAPHY PI WACO PA 5400 BOSQUE BLVD, STE 680, WACO, TX 76710-4446 USA SN 0024-3590 J9 LIMNOL OCEANOGR JI Limnol. Oceanogr. PD MAY PY 1999 VL 44 IS 3 BP 662 EP 667 PG 6 WC Limnology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 196UQ UT WOS:000080326300017 ER PT J AU Mittlefehldt, DW Lindstrom, DJ Lindstrom, MM Martinez, RR AF Mittlefehldt, DW Lindstrom, DJ Lindstrom, MM Martinez, RR TI An impact-melt origin for lithology A of martian meteorite Elephant Moraine A79001 SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID SNC METEORITES; ALH84001; ORTHOPYROXENITE; PETROGENESIS; SHERGOTTITE; ACHONDRITE; ALHA77005; LEW88516; HISTORY; AGE AB Mixing models using major and trace elements show that the bulk composition of lithology A (xenocryst-bearing magnesian basalt) of Elephant Moraine A79001 (EETA79001) can be reasonably approximated as a simple mixture of similar to 44% EETA79001 lithology B (ferroan basalt) and similar to 56% of Allan Hills A77005 (ALHA7705) light lithology (incompatible element-poor Iherzolite). Micro-instrumental neutron activation analysis ((INAA) data on xenocryst-free groundmass samples of lithology A show that about 20-25% of the melt phase could be dissolved Iherzolite. The bulk and groundmass samples of lithology A have excesses in Au, which indicates either meteoritic contamination or addition by some unknown martian geochemical process. Previous workers have suggested that lithology A was formed by either assimilation of cumulates (like ALHA77005), by a basalt (like lithology B), or by mixing of basaltic and Iherzolitic magmas. The former scenario is energetically improbable and unlikely to explain the normal Fe/Mg zonation in lithology A groundmass pyroxenes, whereas the latter scenario is unlikely to satisfy the constraints of the mixing model indicating the ultramafic component is poor in incompatible elements. We suggest rather that EETA79001 lithology A is an impact melt composed dominantly of basalt like lithology B and Iherzolitic cumulates like the trace-element-poor fraction of ALHA77005 or Y-793605. This model can satisfy the energetic, petrologic, and geochemical constraints imposed by the samples. If EETA79001 lithology A is an impact melt, this would have considerable consequences for current models of martian petrologic evolution. It would call into question the generally accepted age of magmatism of martian basalts and preclude the use of lithology A groundmass as a primary martian basalt composition in experimental studies. Regardless, the latter is required because lithology A groundmass is a hybrid composition. C1 Lockheed Martin SO, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Lockheed Martin SO, C23,2400 Nasa Rd 1, Houston, TX 77058 USA. EM david.w.mittlefehldt1.@jsc.nasa.gov NR 51 TC 31 Z9 31 U1 0 U2 3 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 EI 1945-5100 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAY PY 1999 VL 34 IS 3 BP 357 EP 367 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 201AL UT WOS:000080572400009 ER PT J AU Bogard, DD Garrison, DLH AF Bogard, DD Garrison, DLH TI Argon-39-argon-40 "ages" and trapped argon in Martian shergottites, Chassigny, and Allan Hills 84001 SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID NOBLE-GASES; AR-39-AR-40 AGE; SNC METEORITES; ATMOSPHERE; MARS; ORIGIN; EVOLUTION; HISTORY; PLANET; ALLAN-HILLS-84001 AB Argon-isotopic abundances were measured in neutron-irradiated samples of Martian meteorites Chassigny, Allan Hills (ALH) 84001, ALH 77005, Elephant Moraine (EET) 79001, Yamato (Y) 793605, Shergotty, Zagami, and Queen Alexandra Range (QUE) 94201, and in unirradiated samples of ALH 77005. Chassigny gives a Ar-39-Ar-40 age of 1.32 +/- 0.07 Ga, which is similar to radiometric ages of the nakhlites. Argon-39-Argon-40 data for ALH 84001 indicate ages between 3.9 and 4.3 Ga. A more precise definition of this age requires detailed characterization of the multiple trapped Ar components in ALH 84001 and of Ar-39 recoil distribution. All six shergottite samples show apparent Ar-39-Ar-40 ages substantially older than the similar to 165-200 Ma range in ages given by other isotope dating techniques. Shergottites appear to contain ubiquitous Ar components acquired from the Martian atmosphere, the Martian mantle, and commonly terrestrial atmospheric contamination. Zagami feldspar also suggests inherited radiogenic Ar-40. These data analyses indicate that the recent Martian atmospheric component trapped in shergottites has a Ar-40/Ar-36 ratio, possibly as low as similar to 1750 and no greater than similar to 1900. These ratios are less than the value of 3000 +/- 500 reported by Viking. The Ar-40/Ar-36 ratio for the Martian mantle component is probably <500 but is poorly constrained. The correlation between trapped Ar-40/Ar-36 and Xe-129/Xe-132 in shergottite impact glasses and unirradiated samples of ALH 77005 shows considerable scatter and suggests that the Ar-36/Xe-132 ratio in the Martian components may vary. Resolution of Martian atmospheric 40Ar/36Ar ratio at different time periods (i.e., at similar to 4.0 and 0.2 Ga) is also difficult without an understanding of the composition of various trapped components. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Corp, Houston, TX 77058 USA. RP NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. EM donald.d.bogard1@jsc.nasa.gov NR 50 TC 79 Z9 79 U1 0 U2 5 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 EI 1945-5100 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAY PY 1999 VL 34 IS 3 BP 451 EP 473 PG 23 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 201AL UT WOS:000080572400017 ER PT J AU Wilson, L Keil, K Love, SJ AF Wilson, L Keil, K Love, SJ TI The internal structures and densities of asteroids SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID ORDINARY CHONDRITES; PHOBOS; METEORITES; FRAGMENTATION; 253-MATHILDE; DISRUPTION; EVOLUTION; POROSITY; 243-IDA; DEIMOS AB Four asteroidal bodies (the Martian satellites Phobos and Deimos and the main-belt asteroids 243 Ida and 253 Mathilde) have now been the subjects of sufficiently close encounters by spacecraft that the masses and sizes and, hence, the densities of these bodies can be estimated to similar to 10%. All of these asteroids are significantly less dense than most members of the classes of meteorites identified as being compositionally most nearly similar to them on the basis of spectral characteristics. We show that two processes can act, independently or in concert, during the evolutionary histories of asteroids to produce a low bulk density. One of these processes is the result of one or more impact events and can affect any asteroid type, whereas the other can occur only for certain types of small asteroids that have undergone aqueous alteration. C1 Univ Lancaster, Inst Environm & Nat Sci, Dept Environm Sci, Lancaster LA1 4YQ, England. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Hawaii Manoa, Hawaii Ctr Volcanol, Honolulu, HI 96822 USA. RP Keil, K (reprint author), Univ Hawaii Manoa, Hawaii Inst Geophys & Planetol, Honolulu, HI 96822 USA. NR 35 TC 32 Z9 32 U1 2 U2 5 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD MAY PY 1999 VL 34 IS 3 BP 479 EP 483 PG 5 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 201AL UT WOS:000080572400019 ER PT J AU Pietrzyk, RA Feiveson, AH Whitson, PA AF Pietrzyk, RA Feiveson, AH Whitson, PA TI Mathematical model to estimate risk of calcium-containing renal stones SO MINERAL AND ELECTROLYTE METABOLISM LA English DT Article DE renal stones; spaceflight; aerospace medicine; astronauts AB Background/Aims: Astronauts exposed to microgravity during the course of spaceflight undergo physiologic changes that alter the urinary environment so as to increase the risk of renal stone formation. This study was undertaken to identify a simple method with which to evaluate the potential risk of renal stone development during spaceflight. Method: We used a large data base of urinary risk factors obtained from 323 astronauts before and after spaceflight to generate a mathematical model with which to predict the urinary supersaturation of calcium stone forming salts. Result: This model, which involves the fewest possible analytical variables (urinary calcium, citrate, oxalate, phosphorus, and total volume), reliably and accurately predicted the urinary supersaturation of the calcium stone forming salts when compared to results obtained from a group of 6 astronauts who collected urine during flight. Conclusions:The use of this model will simplify both routine medical monitoring during spaceflight as well as the evaluation of countermeasures designed to minimize renal stone development, This model also can be used for Earth-based applications in which access to analytical resources is limited. C1 NASA, Lyndon B Johnson Space Ctr, Astronaut Off, Houston, TX 77058 USA. Wyle Life Sci, Houston, TX USA. NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Houston, TX 77058 USA. RP Whitson, PA (reprint author), NASA, Lyndon B Johnson Space Ctr, Astronaut Off, Mail Code CB, Houston, TX 77058 USA. NR 7 TC 4 Z9 4 U1 0 U2 0 PU KARGER PI BASEL PA ALLSCHWILERSTRASSE 10, CH-4009 BASEL, SWITZERLAND SN 0378-0392 J9 MINER ELECTROL METAB JI Miner. Electrolyte Metab. PD MAY-JUN PY 1999 VL 25 IS 3 BP 199 EP 203 DI 10.1159/000057445 PG 5 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 222AR UT WOS:000081760500010 PM 10436406 ER PT J AU Hu, DM Chao, Y AF Hu, DM Chao, Y TI A global isopycnal OGCM: Validations using observed upper-ocean variabilities during 1992-93 SO MONTHLY WEATHER REVIEW LA English DT Article ID GENERAL-CIRCULATION MODELS; SCALE WATER MASSES; REDUCED-GRAVITY; PRIMITIVE EQUATION; TRACER TRANSPORTS; COORDINATE MODEL; WORLD OCEAN; ATLANTIC; PARAMETERIZATION; SIMULATIONS AB In this study, a global isopycnal ocean model (GIM) is described and used for a simulation of variabilities of the global upper ocean during 1992-93. The GIM simulations are compared and validated with both the available observations and simulations with the Geophysical Fluid Dynamics Laboratory Modular Ocean Model (MOM). The observations include sea surface height from TOPEX/Poseidon (TIP), sea surface temperature (SST) from weekly National Centers for Environmental Prediction analysis, and vertical temperature profiles from gridded expandable bathythermographs (XBTs) data. The major differences between the GIM and MOM used in this study are the vertical coordinates, a Kraus-Turner mixed layer, and a tracer-transport velocity associated with an isopycnal-depth diffusion. Otherwise, the two models are formulated in the same parameter space, model configuration, and boundary conditions. The effects of these differences in model formulation on the model simulations are investigated. Due to the difference in the orientation of interior flow and mixing, SST and the thermocline stratification in the eastern equatorial Pacific in GIM are more sensitive to the wind-driven upwelling than they are in MOM. In GIM there is no effective means to transfer hear between the upwelling cold water and the surrounding warm water since subsurface flow and mixing predominantly occur along isopycnic layers. As a result, the SST tends to be cold and the front tends to be sharp compared with the observations in the wind-driven upwelling region. The sharp front could potentially cause numerical instability in GIM. Thus, a large isopycnal-depth diffusivity has to be used to maintain the model stability since the isopycnal-depth diffusion is the most effective way to reduce the steep slope of isopycnals and the strength of the front associated with the cold upwelling in GIM. But the large isopycnal-depth diffusion results in excessive smoothing in the meridional isotherm doming in the equatorial and tropical thermocline. The trade-off between the numerical instability and the excessive isopycnal smoothing points to the necessity of improvement in the isopycnal-depth diffusion. Sea level variabilities during 1992-93 simulated with both GIM and MOM are in good agreement with T/P observations. However, MOM poorly simulates the vertical distribution of the seasonal temperature anomalies in the upper ocean (the baroclinic component of the sea level variability) during 1992-93. Due to the lack of a realistic surface mixed layer, the MOM-simulated temperature profiles have a sharp subsurface gradient, which is not evident in both the GIM simulation and the XBT observation. As a result, the region below the subsurface gradient is almost insulated from the influence of the seasonal temperature variation. The Kraus-Turner mixed layer used in GIM helps Co improve the model-simulated seasonal variations of the upper-ocean temperature and the background sea level variability. Implications of deficiencies in both GIM and MOM on the altimetric sea level data assimilation and transient tracer simulations are discussed. C1 Univ Washington, JISAO, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Hu, DM (reprint author), Univ Washington, JISAO, Box 354235, Seattle, WA 98195 USA. NR 48 TC 3 Z9 3 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 MAY PY 1999 VL 127 IS 5 BP 706 EP 725 DI 10.1175/1520-0493(1999)127<0706:AGIOVU>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 194RW UT WOS:000080208200008 ER PT J AU Huck, FO Fales, CL Alter-Gartenberg, R Park, SK Rahman, Z AF Huck, FO Fales, CL Alter-Gartenberg, R Park, SK Rahman, Z TI Information-theoretic assessment of sampled imaging systems SO OPTICAL ENGINEERING LA English DT Article DE sampled imaging system; image coding; image restoration; image display; information; entropy; fidelity ID STATISTICS; DESIGN; IMAGES AB By rigorously extending modern communication theory to the assessment of sampled imaging systems, we develop the formulations that are required to optimize the performance of these systems within the critical constraints of image gathering, data transmission, and image display. The goal of this optimization is to produce images with the best possible visual quality for the wide range of statistical properties of the radiance field of natural scenes that one normally encounters. Extensive computational results are presented to assess the performance of sampled imaging systems in terms of information rate, theoretical minimum data rate, and fidelity. Comparisons of this assessment with perceptual and measurable performance demonstrate that (1) the information rate that a sampled imaging system conveys from the captured radiance field to the observer is closely correlated with the fidelity, sharpness and clarity with which the observed images can be restored and (2) the associated theoretical minimum data rate is closely correlated with the lowest data rate with which the acquired signal can be encoded for efficient transmission. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)01305-7]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Comp Sci Corp, Hampton, VA 23666 USA. Coll William & Mary, Williamsburg, VA 23187 USA. RP Huck, FO (reprint author), NASA, Langley Res Ctr, Mail Stop 473, Hampton, VA 23681 USA. NR 17 TC 39 Z9 46 U1 1 U2 5 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD MAY PY 1999 VL 38 IS 5 BP 742 EP 762 DI 10.1117/1.602264 PG 21 WC Optics SC Optics GA 194VU UT WOS:000080215900003 ER PT J AU Schmidt, MH Reichert, KW Ozker, K Meyer, GA Donohoe, DL Bajic, DM Whelan, NT Whelan, HT AF Schmidt, MH Reichert, KW Ozker, K Meyer, GA Donohoe, DL Bajic, DM Whelan, NT Whelan, HT TI Preclinical evaluation of benzoporphyrin derivative combined with a light-emitting diode array for photodynamic therapy of brain tumors SO PEDIATRIC NEUROSURGERY LA English DT Article DE photodynamic therapy; brain tumor; glioma; light-emitting diodes; benzoporphyrin derivative; posterior fossa ID PHOTORADIATION THERAPY; CEREBRAL GLIOMA; GROWTH-FACTORS; CELL-LINE; TISSUE; PENETRATION; NM AB Objective: The aim of this study was to investigate the second-generation photosensitizer benzoporphyrin derivative (BPD) and a novel light source applicator based on light-emitting diode (LED) technology for photodynamic therapy (PDT) of brain tumors. Methods: We used a canine model to investigate normal brain stem toxicity, Twenty-one canines underwent posterior fossa craniectomies followed by PDT with BPD, These animals were compared to light only and BPD control. In addition, we investigated the ability of BPD and LED to cause inhibition of cell growth in canine glioma and human glioma cell lines, in vitro, The biodistribution of BPD labeled with (111)ln-BPD in mice with subcutaneous and intracerebral gliomas and canines with brain tumors was studied. Results: The in vivo canine study resulted in a maximal tolerated dose of 0.75 mg/kg of BPD and 100 J/cm(2) of LED light for normal brain tissue. The in vitro study demonstrated 50% growth inhibition for canine and human glioma cell lines of 10 and 4 ng/ml, respectively. The mucine study using (111)ln-BPD showed a tumor to normal tissue ratio of 12:1 for intracerebral tumors and 3.3:1 for subcutaneous tumors. Nuclear scans of canines with brain tumors showed uptake into tumors to be maximal from 3 to 5 h. Conclusion: Our study supports that BPD and LED light sources when used at appropriate drug and light doses limit normal brain tissue toxicity at doses that can cause significant glioma cell toxicity in vitro. In addition, there is higher BPD uptake in brain tumors as compared to normal brain in a mouse glioma model. These findings make BPD a potential new-generation photosensitizer for the treatment of childhood posterior fossa tumors as well as other malignant cerebral pathology. C1 Med Coll Wisconsin, MACC Fund Res Ctr, Dept Neurol, Milwaukee, WI 53226 USA. Med Coll Wisconsin, Dept Neurosurg, Milwaukee, WI 53226 USA. Med Coll Wisconsin, Dept Nucl Med, Milwaukee, WI 53226 USA. Med Coll Wisconsin, Dept Pediat, Milwaukee, WI 53226 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Whelan, HT (reprint author), Med Coll Wisconsin, MACC Fund Res Ctr, Dept Neurol, 3017,8701 Watertown Plank Rd, Milwaukee, WI 53226 USA. NR 35 TC 19 Z9 22 U1 0 U2 2 PU KARGER PI BASEL PA ALLSCHWILERSTRASSE 10, CH-4009 BASEL, SWITZERLAND SN 1016-2291 J9 PEDIATR NEUROSURG JI Pediatr. Neurosurg. PD MAY PY 1999 VL 30 IS 5 BP 225 EP 231 DI 10.1159/000028802 PG 7 WC Clinical Neurology; Pediatrics; Surgery SC Neurosciences & Neurology; Pediatrics; Surgery GA 227RF UT WOS:000082092900001 PM 10461068 ER PT J AU Folk, CL Remington, R AF Folk, CL Remington, R TI Can new objects override attentional control settings? SO PERCEPTION & PSYCHOPHYSICS LA English DT Article ID ABRUPT VISUAL ONSETS; SELECTIVE ATTENTION; APPARENT MOTION; CAPTURE; CONTINGENT; SEARCH; COLOR; SET AB Previous research suggests that attentional capture by abrupt onsets is contingent on top-down attentional control settings. Four experiments addressed whether similar contingencies hold for capture elicited by the appearance of new perceptual objects. In a modified spatial cuing task, targets defined by abrupt onset or color were paired with distracters consisting of an abrupt brightening of an existing object or the abrupt appearance of anew object. In Experiments 1 and 2, when subjects searched for an onset target, both distracter types produced evidence of capture. When subjects searched for a color target, however, distracters produced no evidence of attentional capture, regardless of whether they consisted of a new perceptual object or not. Experiments 3-5 showed that the lack of distracter effects in the color-target condition cannot be accounted for by rapid recovery from capture. It was concluded that attentional capture by new objects is subject to top-down modulation by attentional control settings. C1 Villanova Univ, Dept Psychol, Villanova, PA 19085 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 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 23 TC 79 Z9 80 U1 1 U2 2 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 USA SN 0031-5117 J9 PERCEPT PSYCHOPHYS JI Percept. Psychophys. PD MAY PY 1999 VL 61 IS 4 BP 727 EP 739 DI 10.3758/BF03205541 PG 13 WC Psychology; Psychology, Experimental SC Psychology GA 202YR UT WOS:000080680300011 PM 10370339 ER PT J AU Tai, AT Alkalai, L Chau, SN AF Tai, AT Alkalai, L Chau, SN TI On-board preventive maintenance: a design-oriented analytic study for long-life applications SO PERFORMANCE EVALUATION LA English DT Article DE on-board preventive maintenance; hardware and software rejuvenation; phased-mission analysis; mission reliability gain ID COMPUTER AB With respect to the long-life missions associated with NASA's X2000 Advanced Deep-Space System Development Program, reliability implies a system's continuous operation for many years in an unsurveyed radiation-intense environment. Further, the stringent constraints on the mass of a spacecraft and the power on-board create unprecedented challenges on the means for achieving the ultra-high mission reliability. In this paper, we present an approach to on-board preventive maintenance which rejuvenates a system by letting system components rotate between on-duty and off-duty shifts, slowing down a system's aging process and thus enhancing mission reliability. By exploiting nondedicated system redundancy, hardware and software rejuvenation are realized simultaneously without significant performance penalty. Our design-oriented analysis confirms a potential for significant gains in mission reliability from on-board preventive maintenance and provides to us useful insights about the collective effect of age-dependent failure behavior, residual mission life, risk of unsuccessful maintenance and maintenance frequency on mission reliability. (C) 1999 Elsevier Science B.V. All rights reserved. C1 IA Tech Inc, Los Angeles, CA 90024 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP IA Tech Inc, Kinnard Ave, Los Angeles, CA 90024 USA. EM a.t.tai@ieee.org NR 25 TC 26 Z9 26 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-5316 EI 1872-745X J9 PERFORM EVALUATION JI Perform. Eval. PD MAY PY 1999 VL 35 IS 3-4 BP 215 EP 232 DI 10.1016/S0166-5316(99)00006-1 PG 18 WC Computer Science, Hardware & Architecture; Computer Science, Theory & Methods SC Computer Science GA 209FQ UT WOS:000081037900007 ER PT J AU Howard, RT Bryan, TC Book, ML Rogers, L AF Howard, RT Bryan, TC Book, ML Rogers, L TI Photonics makes connections in space SO PHOTONICS SPECTRA LA English DT Article C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Opto Power Corp, Tucson, AZ USA. RP Howard, RT (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 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 MAY PY 1999 VL 33 IS 5 BP 191 EP 194 PG 4 WC Optics SC Optics GA 194TZ UT WOS:000080210800042 ER PT J AU Civitarese, O Ray, A AF Civitarese, O Ray, A TI Centroids of Gamow-Teller transitions at finite temperature in fp-shell neutron-rich nuclei SO PHYSICA SCRIPTA LA English DT Article ID BETA-DECAY; RATES AB The temperature dependences of the energy centroids and strength distributions for Gamow-Teller (GT) 1(+) excitations in several fp-shell nuclei are studied. The quasiparticle random phase approximations (QRPA) are extended to describe GT states at finite temperature. A shift to lower energies of the GT(+) strength is found, as compared to values obtained at zero temperature. C1 Natl Univ La Plata, Dept Phys, RA-1900 La Plata, Argentina. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Civitarese, O (reprint author), Natl Univ La Plata, Dept Phys, CC 67, RA-1900 La Plata, Argentina. NR 19 TC 4 Z9 4 U1 0 U2 0 PU ROYAL SWEDISH ACAD SCIENCES PI STOCKHOLM PA PUBL DEPT BOX 50005, S-104 05 STOCKHOLM, SWEDEN SN 0281-1847 J9 PHYS SCRIPTA JI Phys. Scr. PD MAY PY 1999 VL 59 IS 5 BP 352 EP 354 DI 10.1238/Physica.Regular.059a00352 PG 3 WC Physics, Multidisciplinary SC Physics GA 197ZT UT WOS:000080397800004 ER PT J AU Dobson, CC Sung, CC AF Dobson, CC Sung, CC TI Laser-induced optical pumping measurements of cross sections for fine- and hyperfine-structure transitions in sodium induced by collisions with helium and argon atoms SO PHYSICAL REVIEW A LA English DT Article ID RESONANCE AB Optical pumping of the ground states of sodium can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc.. which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections for Delta F transitions of the P-3/2, state induced by collisions with helium and argon atoms, for a range of values assumed for the P-1/2, Delta F cross sections. The hyperfine cross sections measured using this method, which to our knowledge is novel, are compared with cross sections for transitions involving polarized magnetic substates m(F) measured previously using polarization sensitive absorption. Also, fine-structure transition (Delta J) cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping. [S1050-2917(99)04605-3]. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. USA, Aviat & Missile Command, Ctr Res Dev & Engn, AMSAM,RD,WS,CM, Redstone Arsenal, AL 35898 USA. RP Dobson, CC (reprint author), NASA, George C Marshall Space Flight Ctr, EP63, Huntsville, AL 35812 USA. NR 15 TC 1 Z9 1 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 1999 VL 59 IS 5 BP 3402 EP 3407 DI 10.1103/PhysRevA.59.3402 PG 6 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 197UB UT WOS:000080383100038 ER PT J AU Bataille, F Zhou, Y AF Bataille, F Zhou, Y TI Nature of the energy transfer process in compressible turbulence SO PHYSICAL REVIEW E LA English DT Article ID ISOTROPIC TURBULENCE; FORCED TURBULENCE; FLOWS; SIMULATION AB Using a two-point closure theory, the eddy-damped-quasinormal-Markovian approximation, we have investigated the energy transfer process and triadic interactions of compressible turbulence. In order to analyze the compressible mode directly, the Helmholtz decomposition is used. The following issues were addressed: (1) What is the mechanism of energy exchange between the solenoidal and compressible modes, and (2) is there an energy cascade in the compressible energy transfer process? It is concluded that the compressible energy is transferred locally from the solenoidal part to the compressible part. It is also found that there is an energy cascade of the compressible mode for high turbulent Mach number. Since we assume that the compressibility is weak, the magnitude of the compressible (radiative or cascade) transfer is much smaller than that of the solenoidal cascade. These results are further confirmed by studying the triadic energy transfer function, the most fundamental building block of the energy transfer. [S1063-651X(99) 10304-0]. C1 UMR CNRS 5509, Lab Mecan Fluides & Acoust, F-69130 Ecully, France. NASA, Langley Res Ctr, Inst Comp Appl Sci & Engn, Hampton, VA 23681 USA. IBM Corp, Thomas J Watson Res Ctr, Div Res, Yorktown Heights, NY 10598 USA. RP Bataille, F (reprint author), Ctr Therm Lyon, Upres A CNRS 5008, 20 Ave A Einstein, F-69620 Villeurbanne, France. NR 23 TC 7 Z9 7 U1 1 U2 4 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1539-3755 J9 PHYS REV E JI Phys. Rev. E PD MAY PY 1999 VL 59 IS 5 BP 5417 EP 5426 DI 10.1103/PhysRevE.59.5417 PN B PG 10 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 197TZ UT WOS:000080382900003 PM 11969521 ER PT J AU Zimmerli, GA Wilkinson, RA Ferrell, RA Moldover, MR AF Zimmerli, GA Wilkinson, RA Ferrell, RA Moldover, MR TI Electrostriction of a near-critical fluid in microgravity SO PHYSICAL REVIEW E LA English DT Article ID LIQUID CRITICAL-POINT; DIELECTRIC-CONSTANT; GRAVITY AB We used interferometry to measure the electric-field-induced (i.e., electrostrictive) increase of the density of sulfur hexafluoride(SF6) near its critical point. The results at three temperatures (T-c + 5.0mK, T-c + 10.0 mK, T-c + 30.0mK with T-c = 319 K) agree with a calculation based on the Clausius-Mossotti relation and the restricted cubic model equation of state. To measure electrostriction, an inhomogeneous electric field (less than or equal to 26 kV/cm) was applied to the SF6 sample by charging a fine wire that passed through it. These measurements were performed in microgravity so that the small electrostrictive density changes (less than or equal to 3.5% in this paper) would not be complicated by stratification of the fluid's density induced by the Earth's gravity. The predicted shifts of the critical temperature and density resulting fi-om the electric field were too small to detect. [S1063-651X(99)13405-6]. C1 Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NIST, Phys & Chem Properties Div, Gaithersburg, MD 20899 USA. RP Zimmerli, GA (reprint author), Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RI Moldover, Michael/E-6384-2013 NR 24 TC 11 Z9 11 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 1999 VL 59 IS 5 BP 5862 EP 5869 DI 10.1103/PhysRevE.59.5862 PN B PG 8 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 197TZ UT WOS:000080382900049 PM 11969567 ER PT J AU Hesse, M Schindler, K Birn, J Kuznetsova, M AF Hesse, M Schindler, K Birn, J Kuznetsova, M TI The diffusion region in collisionless magnetic reconnection SO PHYSICS OF PLASMAS LA English DT Article; Proceedings Paper CT 40th Annual Meeting of the Division of Plasma Physics of the American-Physical-Society CY NOV 16-20, 1998 CL NEW ORLEANS, LOUISIANA SP Amer Phys Soc, Div Plasma Phys ID PARTICLE SIMULATION; ELECTRON DISSIPATION; EARTHS MAGNETOPAUSE; CURRENT SHEETS; PLASMA; FIELD; DYNAMICS; LINE; LAW AB The structure of the dissipation region in collisionless magnetic reconnection is investigated by means of kinetic particle-in-cell simulations and analytical theory. Analyses of simulations of reconnecting current sheets without guide magnetic field, which keep all parameters fixed with the exception of the electron mass, exhibit very similar large scale evolutions and time scales. A detailed comparison of two runs with different electron masses reveals very similar large scale parameters, such as ion flow velocities and magnetic field structures. The electron-scale phenomena in the reconnection region proper, however, appear to be quite different. The scale lengths of these processes are best organized by the trapping length of bouncing electrons in a field reversal region. The dissipation is explained by the electric field generated by nongyrotropic electron pressure tensor effects. In the reconnection region, the relevant electron pressure tensor components exhibit gradients which are independent of the electron mass. The similarities of the gradients as well as the behavior of the electron flow velocity can be derived from the electron trapping scale and the electron mass independence of the reconnection electric field. A further model which includes a significant guide magnetic field exhibits almost identical behavior. The explanation of this result lies in a Hall-type electric field which locally eliminates the magnetizing effect on the electrons of the guide magnetic field. The resulting electron dynamics is nearly identical to the one found in the model without guide magnetic field. This result strongly supports the hypothesis that the local physics in the dissipation region adjusts itself to the demands of the large-scale evolution. A further verification of this notion is provided by Hall-magnetohydrodynamic simulations which employ simple resistive dissipation models in otherwise similar large-scale models. These results also pertain to the inclusion of local reconnection physics in larger scale simulation models. (C) 1999 American Institute of Physics. [S1070-664X(99)97405-0]. C1 NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. Ruhr Univ Bochum, D-44780 Bochum, Germany. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. RP Hesse, M (reprint author), NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. RI Hesse, Michael/D-2031-2012; Kuznetsova, Maria/F-6840-2012 NR 46 TC 250 Z9 254 U1 0 U2 14 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD MAY PY 1999 VL 6 IS 5 BP 1781 EP 1795 DI 10.1063/1.873436 PN 2 PG 15 WC Physics, Fluids & Plasmas SC Physics GA 190ND UT WOS:000079969500013 ER PT J AU Espresate, J Lissauer, JJ AF Espresate, J Lissauer, JJ TI The effect of collisions on the resonant satellite torque distribution SO PLANETARY AND SPACE SCIENCE LA English DT Article ID LINDBLAD; RINGS AB We present numerical results of the behavior of the torque exerted by a satellite over a particulate annulus centered at a first order resonance. Results for both collisionless and collisonal annuli are presented and compared. Our results show that in the absence of particle interactions, the time required for this problem to become nonlinear scales with the satellite to planet mass ratio as (M-s/M-p)(-2/3). In the absence of collisions, the total initial (transient) torque over the annulus is a strong function of the width of the annulus, W', around the resonance (located at r(L)), so that if W' less than or equal to r(L)(M-s/M-p)(2/3), then the torque value always remains significantly below the linear standard torque. On the other hand, if W' > r(L)(M-s/M-p)(2/3) the annulus reaches greater than or equal to 95% of the linear standard torque before the problem becomes nonlinear. These simulations show that when collisions are present, the critical width to obtain 95% of the linear standard torque is substantially increased, even for very low optical depth annuli. The torque value for a fixed width also depends on the time; it asymptotically approaches the linear standard torque as long as nonlinearities remain small. When collisions are introduced, initially the torque value grows up to the value it would have in the absence of collisions at time t = t(coll) (for the given width), where t(coll) is the mean time between collisions; for t > t(coll) the torque becomes independent of the time (although not independent of the width) for the duration of the simulations. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Inst Astron, Mexico City 04510, DF, Mexico. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Espresate, J (reprint author), Inst Astron, Ciudad Univ, Mexico City 04510, DF, Mexico. NR 8 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 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD MAY PY 1999 VL 47 IS 5 BP 629 EP 641 DI 10.1016/S0032-0633(98)00132-9 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 191XN UT WOS:000080047300004 ER PT J AU Young, JA Farmer, BL Hinkley, JA AF Young, JA Farmer, BL Hinkley, JA TI Molecular modeling of the poling of piezoelectric polyimides SO POLYMER LA English DT Article DE dielectric relaxation strength; amorphous polymer; piezoelectric polymers ID VINYLIDENE CYANIDE; PYROELECTRICITY; SIMULATIONS AB The computational method described in this paper allows the calculation of the dielectric relaxation strength of an amorphous polymer based solely upon its chemical structure. The 4,4' oxydiphthalic anhydride (ODPA) dianhydride and bis-aminophenoxybenzene (APB) diamine based polyimides, (beta-CN) APB-ODPA and APB-ODPA were studied. Amorphous cells were constructed and then poled using molecular dynamics. Dielectric relaxation strengths of Delta epsilon = 17.8 for (P-CN) APB-ODPA and Delta epsilon = 7.7 for APB-ODPA were predicted. These values are in excellent agreement with the experimental values. It was found that both the pendant nitrile dipole and the backbone anhydride residue dipole make significant contributions to the polyimides' dielectric response. Specifically, it was shown that the difference in the magnitude of the dielectric relaxations is directly attributable to the nitrile dipole. The size of the relaxations indicate an absence of cooperative dipolar motions. The model was used to explain these results in terms of the average orientation of the nitrile and anhydride dipoles to within 51 degrees and 63 degrees, respectively, of the applied electric field. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Virginia, Dept Mat Sci & Engn, Charlottesville, VA 22903 USA. NASA, Langley Res Ctr, Div Mat, Hampton, VA 23681 USA. RP Young, JA (reprint author), Univ Virginia, Dept Mat Sci & Engn, Charlottesville, VA 22903 USA. NR 29 TC 29 Z9 30 U1 2 U2 7 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0032-3861 J9 POLYMER JI Polymer PD MAY PY 1999 VL 40 IS 10 BP 2787 EP 2795 DI 10.1016/S0032-3861(98)00474-1 PG 9 WC Polymer Science SC Polymer Science GA 161LP UT WOS:000078290700035 ER PT J AU Lawrence, CR Scott, D White, M AF Lawrence, CR Scott, D White, M TI What have we already learned from the cosmic microwave background? SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Review ID GRAVITATIONAL-WAVES; PHASE-TRANSITIONS; CMB ANISOTROPIES; GALAXY FORMATION; EARLY UNIVERSE; SKY MAPS; INFLATION; PERTURBATIONS; FLUCTUATIONS; EXPLOSIONS AB The Cosmic Background Explorer (COBE) satellite, and the Differential Microwave Radiometer (DMR) experiment in particular, was extraordinarily successful. However, the DMR results were announced about 7 years ago, during which time a great deal more has been learned about anisotropies in the cosmic microwave background (CMB). We assess the current state of knowledge and discuss where we might be going. The CMB experiments currently being designed and built, including long-duration balloons, interferometers, and two space missions, promise to address several fundamental cosmological issues. We present our evaluation of what we already know, what we are beginning to learn now, and what the future may bring. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ British Columbia, Dept Phys & Astron, Vancouver, BC V6T 1Z4, Canada. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Univ Illinois, Dept Phys, Urbana, IL 61801 USA. RP Lawrence, CR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,169-506, Pasadena, CA 91109 USA. EM dscott@astro.ubc.ca RI White, Martin/I-3880-2015 OI White, Martin/0000-0001-9912-5070 NR 73 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD MAY PY 1999 VL 111 IS 759 BP 525 EP 531 DI 10.1086/316364 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 197JQ UT WOS:000080362000001 ER PT J AU Riggs, GA Hall, DK Ackerman, SA AF Riggs, GA Hall, DK Ackerman, SA TI Sea ice extent and classification mapping with the Moderate Resolution Imaging Spectroradiometer Airborne Simulator SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID SURFACE-TEMPERATURE; SNOW COVER; RADIOMETER; THICKNESS; MODIS AB An algorithm for mapping sea ice extent and generalized classification of sea ice by reflective and temperature characteristics with Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) data is presented. The algorithm was tested using a MAS scene over the Bering Sea near St. Lawrence Island, Alaska, USA, acquired 8 April 1995. Clouds were masked with the University of Wisconsin cloud masking algorithm. Ice surface temperature was estimated with a split-window technique. Sea ice extent and generalized type of sea ice were identified based on reflective characteristics and estimated ice surface temperature using a grouped criteria technique. Resulting maps were consistent with visual interpretation and with sea ice extent and type information reported in prior studies of the region. Published by Elsevier Science Inc. C1 Res & Data Syst Corp, Greenbelt, MD USA. Univ Wisconsin, Ctr Space Sci & Engn, Cooperat Inst Meteorol Satellite Studies, Madison, WI 53706 USA. RP Riggs, GA (reprint author), NASA, Goddard Space Flight Ctr, RDC, Code 974, Greenbelt, MD 20771 USA. RI Ackerman, Steven/G-1640-2011; Hall, Dorothy/D-5562-2012 OI Ackerman, Steven/0000-0002-4476-0269; NR 26 TC 38 Z9 42 U1 3 U2 14 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 1999 VL 68 IS 2 BP 152 EP 163 DI 10.1016/S0034-4257(98)00107-2 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 192MW UT WOS:000080083800005 ER PT J AU Mesarch, MA Walter-Shea, EA Asner, GP Middleton, EM Chan, SS AF Mesarch, MA Walter-Shea, EA Asner, GP Middleton, EM Chan, SS TI A revised measurement methodology for conifer needles spectral optical properties: Evaluating the influence of gaps between elements SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID REFLECTANCE; SPRUCE; CANOPY AB Gaps are unavoidable when compositing small or narrow plant parts (e.g., conifer needles, twigs, narrow leaves, and leaflets) on sample holders in preparation for measuring spectral optical properties. The Daughtry et al. (1989) (A new technique to measure the spectral properties of conifer needles. Remote Sens. Environ. 27:81-91.) method of measuring conifer needle optical properties utilizes a relatively large gap fraction (approximately 0.3-0.6) and needles painted black on one surface of the sample from which the gap fraction of the sample is indirectly determined. Following this protocol typically results in distortions in optical properties, including underestimates in transmittance (sometimes negative values), and only one surface of the sample can be measured. The objectives of this article are to: 1) evaluate the influence of gaps between sample elements (conifer needles, twigs, narrow leaves and leaflets) on optical properties calculated with the published equations from Daughtry et al. (1989) and 2) revise the original Daughtry et al. method for optical property measurements by using an image-analysis to directly measure the gap fraction and use both surfaces of the sample. We achieve these objectives by reviewing the theory and investigating the effects of gaps by measurements of an inert photographic film material, fir needles, and mesquite leaflets. Tests to estimate the transmittance of film samples (film) and foliage (fir needles, mesquite leaflets) indicate that a relatively small gap fraction (less than 0.20) reduces the occurrence of computed negative transmittance values, reduces the variation in computed values, and yields values expected for the "true" or "nongap" transmittance. Employing the image analysis along with reduced gap fractions decreased the variance of measurements and permitted measurements of both surfaces per sample, thus reducing the time required by making half as many samples as originally required by Daughtry et al. Published by Elsevier Science, Inc. C1 Univ Nebraska, Sch Nat Resource Sci, Lincoln, NE 68583 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO USA. NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Mesarch, MA (reprint author), Univ Nebraska, Sch Nat Resource Sci, 14 LW Chase Hall, Lincoln, NE 68583 USA. RI Asner, Gregory/G-9268-2013 OI Asner, Gregory/0000-0001-7893-6421 NR 12 TC 33 Z9 33 U1 2 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 1999 VL 68 IS 2 BP 177 EP 192 DI 10.1016/S0034-4257(98)00124-2 PG 16 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 192MW UT WOS:000080083800007 ER PT J AU Golden, DC Ming, DW AF Golden, DC Ming, DW TI Nutrient-substituted hydroxyapatites: Synthesis and characterization SO SOIL SCIENCE SOCIETY OF AMERICA JOURNAL LA English DT Article ID PHOSPHATE-ROCK AB Incorporation of Mg, S, and plant-essential micronutrients into the structure of synthetic hydroxyapatite (HA) may be advantageous for closed-loop systems, such as will be required on Lunar and Martian outposts, because these apatites can be used as slow-release fertilizers. Our objective was to synthesize HA with Ca, P, Mg, S, Fe, Cu, Mn, Zn, Mo, B, and Cl incorporated into the structure, i.e., nutrient-substituted apatites. Hydroxyapatite, carbonate hydroxyapatite (CHA), nutrient-substituted hydroxyapatite (NHA), and nutrient-substituted carbonate hydroxyapatite (NCHA) were synthesized by precipitating from solution. Chemical and mineralogical analysis of precipitated samples indicated a considerable fraction of the added cations were incorporated into BA, without mineral impurities. Particle size of the HA was in the 1 to 40 nm range, and decreased with increased substitution of nutrient elements. The particle shape of HA was elongated in the c-direction in unsubstituted HA and NHA but more spherical in CHA and NCHA. The substitution of cations and anions in the HA structure was confirmed by the decrease of the d[002] spacing of HA with substitution of ions with an ionic radius less than that of Ca or P. The DTPA-extractable Cu ranged from 8 to 8429 mg kg(-1), Zn ranged from 57 to 1279 mg kg(-1), Fe from 211 to 2573 mg kg(-1), and Mn from 190 to 1719 mg kg(-1), depending on the substitution level of each element in HA. Nutrient-substituted HA has the potential to be used as a slow-release fertilizer to supply micronutrients, S, and Mg in addition to Ca and P. C1 Lockheed Martin Corp, Houston, TX 77258 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Golden, DC (reprint author), Lockheed Martin Corp, C-23,POB 58561, Houston, TX 77258 USA. NR 24 TC 20 Z9 20 U1 0 U2 16 PU SOIL SCI SOC AMER PI MADISON PA 677 SOUTH SEGOE ROAD, MADISON, WI 53711 USA SN 0361-5995 J9 SOIL SCI SOC AM J JI Soil Sci. Soc. Am. J. PD MAY-JUN PY 1999 VL 63 IS 3 BP 657 EP 664 PG 8 WC Soil Science SC Agriculture GA 217GB UT WOS:000081490700032 PM 11543409 ER PT J AU Gary, GA Alexander, D AF Gary, GA Alexander, D TI Constructing the coronal magnetic field by correlating parameterized magnetic field lines with observed coronal plasma structures SO SOLAR PHYSICS LA English DT Article ID SOLAR CORONA; DYNAMICS AB A method is presented for constructing the coronal magnetic field from photospheric magnetograms and observed coronal loops. A set of magnetic field lines generated from magnetogram data is parameterized and then deformed by varying the parameterized values. The coronal flux tubes associated with this field are adjusted until the correlation between the field lines and the observed coronal loops is maximized. A mathematical formulation is described which ensures that (i) the normal component of the photospheric field remains unchanged, (ii) the field is given in the entire corona over an active region, (iii) the field remains divergence-free, and (iv) electric currents are introduced into the field. It is demonstrated that a parameterization of a potential field, comprising a radial stretching of the field, can provide a match for a simple bipolar active region, AR 7999, which crossed the central meridian on 1996 November 26. The result is a non-force-free magnetic field with the Lorentz force being of the order of 10(-5.5) g cm s(-2) resulting from an electric current density of 0.079 mu A m(-2). Calculations show that the plasma beta becomes larger than unity at a relatively low height of similar to 0.25 r. supporting the non-force-free conclusion. The presence of such strong non-radial currents requires large transverse pressure gradients to maintain a magnetostatic atmosphere, required by the relatively persistent nature of the coronal structures observed in AR 7999. This scheme is an important tool in generating a magnetic field solution consistent with the coronal flux tube observations and the observed photospheric magnetic field. C1 NASA, Space Sci Lab ES82, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Lockheed Martin Solar & Astrophys Lab, Palo Alto, CA 94304 USA. RP NASA, Space Sci Lab ES82, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. EM allen.gary@msfc.nasa.gov; alexander@lmsal.com NR 34 TC 33 Z9 33 U1 0 U2 0 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0038-0938 EI 1573-093X J9 SOL PHYS JI Sol. Phys. PD MAY PY 1999 VL 186 IS 1-2 BP 123 EP 139 DI 10.1023/A:1005147921110 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 209ZV UT WOS:000081081300008 ER PT J AU Kucera, TA Aulanier, G Schmieder, B Mein, N Vial, JC AF Kucera, TA Aulanier, G Schmieder, B Mein, N Vial, JC TI Filament channel structures in a SiIV line related to a 3D magnetic model SO SOLAR PHYSICS LA English DT Article ID CONFIGURATIONS SUPPORTING PROMINENCES; QUASI-SEPARATRIX LAYERS; CURRENT-SHEET FORMATION; SOLAR-FLARES; TRANSITION REGION; SUMER TELESCOPE; GRADUAL PHASE; LATERAL FEET; H-ALPHA; FIELDS AB A recent 3D magnetic model of filament support (Aulanier and Demoulin, 1998) has shown that specific morphologies derived from the model, based on SOHO/MDI magnetograms, match quite well with the observations of a filament observed in H alpha and Ca II lines with the German telescope VTT in Tenerife on 25 September 1996 (Aulanier et al., 1998, 1999a). Some predictions of this model concern the filament channel. To continue the comparison of model and data, we have investigated the same filament region observed in ultraviolet by the SOHO spectrometers SUMER and CDS. The elongated EUV fine structures in the filament channel observed in the Si iv 1393.76 Angstrom line by SUMER have similar orientations and locations to features predicted by the model of Aulanier et al. (1999a). These regions are near the bases of field lines which tangentially join to the photosphere in so called 'bald patches' and are parts of large arcades above the filament channel. In addition, we consider the Si IV Doppler shifts in these structures and compare them to what might be expected from the model field structure. Our study also suggests that the filament has a very low opacity in Si IV, lower than that of the O V line observed by CDS. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Observ Paris, Sect Meudon, DASOP, CNRS,URA 2080, F-92195 Meudon, France. Univ Paris 11, Inst Astrophys Spatiale, CNRS, Unite Mixte, F-91405 Orsay, France. RI Kucera, Therese/C-9558-2012; OI Kucera, Therese/0000-0001-9632-447X NR 57 TC 13 Z9 13 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 MAY PY 1999 VL 186 IS 1-2 BP 259 EP 280 DI 10.1023/A:1005163226096 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 209ZV UT WOS:000081081300014 ER PT J AU Innes, DE Inhester, B Srivastava, N Brekke, P Harrison, RA Matthews, SA Noens, JC Schmieder, B Thompson, BJ AF Innes, DE Inhester, B Srivastava, N Brekke, P Harrison, RA Matthews, SA Noens, JC Schmieder, B Thompson, BJ TI Multi-wavelength observations of the onset phase of a coronal mass ejection SO SOLAR PHYSICS LA English DT Article ID X-RAY TELESCOPE; H-ALPHA-SURGES; EMERGING MAGNETIC-FLUX; SOLAR CORONA; PROMINENCE ERUPTION; SMM OBSERVATIONS; JETS; RECONNECTION; YOHKOH; FLARES AB The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the emergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the time of the flare. Yohkoh images, taken about 15 min later, show that this cavity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an H alpha surge or small filament eruption occurs about 50 arc sec northwards along the limb from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected by hot loops near their bases. Both jets disappear within a few minutes of one another. Clear evidence of the CME first appeared in the Large Angle Spectrometric Coronagraph (LASCO) and EIT images 40 min after the flare and onset of the filament ejection. It seems to come from a region between the two X-ray jets. This leads to the speculation that magnetic field reconnection near one footpoint of a loop system triggers reconnection near its other footpoint. The loop system is destabilized and ultimately gives rise to the CME. This possibility is supported by magnetic field and H alpha images taken when the active region was at disk center which show that the active region had a double bipole structure with dark H alpha filaments between the bipoles. C1 Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway. Rutherford Appleton Lab, Dept Space Sci, Didcot OX11 0QX, Oxon, England. UCL, Mullard Space Sci Lab, Surrey RH5 6NT, England. Observ Midi Pyrenees, F-65200 Bagneres De Bigorre, France. Observ Paris, Sect Meudon, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Innes, DE (reprint author), Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. RI Matthews, Sarah/C-4292-2008; Thompson, Barbara/C-9429-2012; OI Matthews, Sarah/0000-0001-9346-8179 NR 57 TC 18 Z9 19 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 MAY PY 1999 VL 186 IS 1-2 BP 337 EP 361 DI 10.1023/A:1005109600020 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 209ZV UT WOS:000081081300020 ER PT J AU Khanna, RK Moore, MH AF Khanna, RK Moore, MH TI Carbamic acid: molecular structure and IR spectra SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY LA English DT Article DE carbamic acid; IR spectra; hydrogen bonding ID PROTON IRRADIATED H2O+CO2; CARBONIC-ACID; ICES AB Infrared absorption spectra of mixed H2O, NH3 and (CO2)-C-12/(CO2)-C-13 ices subjected to 1 MeV proton irradiation were investigated. The results of analyses of the spectra suggest formation of carbamic acid at low temperatures. The stability of this compound in the solid phase is attributed to intermolecular hydrogen bonding of the zwitter-ion (NH3+COO-) structure. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Khanna, RK (reprint author), Univ Maryland, Dept Chem & Biochem, College Pk, MD 20742 USA. RI Young, Nigel/B-5472-2010 NR 13 TC 67 Z9 67 U1 2 U2 12 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1386-1425 J9 SPECTROCHIM ACTA A JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr. PD MAY PY 1999 VL 55 IS 5 BP 961 EP 967 DI 10.1016/S1386-1425(98)00228-5 PG 7 WC Spectroscopy SC Spectroscopy GA 191GQ UT WOS:000080014700006 PM 10347902 ER PT J AU Bauschlicher, CW AF Bauschlicher, CW TI The scalar relativistic contribution to gallium halide bond energies SO THEORETICAL CHEMISTRY ACCOUNTS LA English DT Article DE bond energies; relativistic effects; scalar relativistic effects; complete basis set limit ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; ATOMIZATION ENERGIES; ELECTRON CORRELATION; WAVE-FUNCTIONS; HARTREE-FOCK; CHEMISTRY; OPERATORS; 1ST-ROW AB The one-electron Douglas-Kroll (DK) and perturbation theory (+ R) approaches are used to compute the scalar relativistic contribution to the atomization energies of GaFn. These results are compared with previous GaCln results. While the +R and DK results agree well for the GaCln, atomization energies, they differ for GaFn. The present work suggests that the DK approach is more accurate than the +R approach. In addition, the DK approach is less sensitive to the choice of basis set. The computed atomization energies of GaF2 and GaF3 are smaller than the atomization energies from the somewhat uncertain experiments. It is suggested that additional calibration calculations for the scalar relativistic effects in GaF2 and GaF3 would be valuable. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 30 TC 14 Z9 14 U1 0 U2 2 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 1432-881X J9 THEOR CHEM ACC JI Theor. Chem. Acc. PD MAY PY 1999 VL 101 IS 6 BP 421 EP 425 DI 10.1007/s002140050459 PG 5 WC Chemistry, Physical SC Chemistry GA 210UF UT WOS:000081122500006 ER PT J AU Jones, JA Johnston, S Campbell, M Miles, B Billica, R AF Jones, JA Johnston, S Campbell, M Miles, B Billica, R TI Endoscopic surgery and telemedicine in microgravity: Developing contingency procedures for exploratory class spaceflight SO UROLOGY LA English DT Article ID FLIGHTS AB Objectives, The risk of a urinary calculus during an extended duration mission into the reduced gravity environment of space is significant. For medical operations to develop a comprehensive strategy for the spaceflight stone risk, both preventive countermeasures and contingency management (CM) plans must be included. Methods, A feasibility study was conducted to demonstrate the potential CM technique of endoscopic ureteral stenting with ultrasound guidance for the possible in-flight urinary calculus contingency. The procedure employed the International Space Station/Human Research Facility ultrasound unit for guide wire and stent localization, a flexible cystoscope for visual guidance, and banded, biocompatible soft ureteral stents to successfully stent porcine ureters bilaterally in zero gravity (0g). Results. The study demonstrated that downlinked endoscopic surgical and ultrasound images obtained in 0g are comparable in quality to 1g images, and therefore are useful for diagnostic clinical utility via telemedicine transmission. Conclusions. In order to be successful, surgical procedures in 0g require excellent positional stability of the operating surgeon, assistant, and patient, relative to one another, The technological development of medical procedures for long-duration spaceflight contingencies may lead to improved terrestrial patient care methodology and subsequently reduced morbidity. UROLOGY 53: 892-897, 1999, (C) 1999, Elsevier Science Inc, All rights reserved. C1 NASA, JSC SD26, Space & Life Sci Directorate, Med Sci Div,Med Operat Branch, Houston, TX 77058 USA. Univ Texas, Med Branch, Aerosp Med Program, Galveston, TX USA. Wylie Life Sci, Houston Div, Houston, TX USA. Baylor Coll Med, Dept Urol, Houston, TX 77030 USA. RP Jones, JA (reprint author), NASA, JSC SD26, Space & Life Sci Directorate, Med Sci Div,Med Operat Branch, 2101 NASA Rd 1, Houston, TX 77058 USA. NR 11 TC 23 Z9 23 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0090-4295 J9 UROLOGY JI UROLOGY PD MAY PY 1999 VL 53 IS 5 BP 892 EP 897 DI 10.1016/S0090-4295(99)00024-2 PG 6 WC Urology & Nephrology SC Urology & Nephrology GA 189HD UT WOS:000079898200005 PM 10223479 ER PT J AU Macy, NB Les, CM Stover, SM Kass, PH AF Macy, NB Les, CM Stover, SM Kass, PH TI Effect of disk fenestration on sagittal kinematics of the canine C5-C6 intervertebral space SO VETERINARY SURGERY LA English DT Article; Proceedings Paper CT Meeting of the Veterinary-Orthopedic-Society CY FEB 21-28, 1998 CL SNOWMASS, COLORADO SP Vet Orthoped Soc ID CAUDAL CERVICAL SPONDYLOMYELOPATHY; STABILIZING SYSTEM; WOBBLER SYNDROME; SPINE; METHACRYLATE; MOTION; DOGS AB Objective-To determine the effect that ventral intervertebral disk fenestration has on the sagittal range of motion about the C5-C6 intervertebral space. Study Design-A repeated measures in vitro mechanical study of spinal range of motion under controlled loading conditions before and after fenestration. Sample Population-A total of 10 canine cervical vertebral specimens (C4-C7) collected from clinically normal animals within 12 hours of euthanasia. Methods-Specimens were loaded as cantilever beams fixed at C7. Weights (1 to 5 kg) were progressively applied to C4 to produce flexion or extension in the sagittal plane. Radiographs were taken at each load, 3 times before and 3 times after fenestration of the C5-C6 disk. The positions of radiodense markers embedded in the vertebrae were used to calculate flexion and extension angles and range of motion. Results-Range of motion (difference between flexion and extension) and flexion and extension angles (individually) significantly increased after fenestration (P < .0001). Conclusion-Ventral fenestration produces sagittal instability of the C5-C6 disk space. Clinical Relevance-In surgical fusion of caudal cervical intervertebral spaces in dogs, radiographically normal disks adjacent to the affected space are often fenestrated to facilitate distraction before surgical stabilization. This study shows that ventral fenestration produces instability of a caudal cervical intervertebral space in the model used. Such instability may contribute to the development of the secondary instability ("domino lesions") seen in some surgically treated dogs. (C) Copyright 1999 by The American College of Veterinary Surgeons. C1 Univ Calif Davis, Sch Vet Med, Dept Anat Physiol & Cell Biol, Vet Orthoped Res Lab, Davis, CA 95616 USA. NASA, Ames Res Ctr, Space Life Sci Res Branch, Musculoskeletal Biomech Lab, Moffett Field, CA 94035 USA. Univ Calif Davis, Sch Vet Med, Dept Populat Hlth & Reprod, Davis, CA 95616 USA. RP Macy, NB (reprint author), Santa Cruz Vet Hosp, 2585 Soquel Dr, Santa Cruz, CA 95062 USA. NR 19 TC 20 Z9 20 U1 0 U2 4 PU W B SAUNDERS CO PI PHILADELPHIA PA INDEPENDENCE SQUARE WEST CURTIS CENTER, STE 300, PHILADELPHIA, PA 19106-3399 USA SN 0161-3499 J9 VET SURG JI Vet. Surg. PD MAY-JUN PY 1999 VL 28 IS 3 BP 171 EP 179 PG 9 WC Veterinary Sciences SC Veterinary Sciences GA 193GG UT WOS:000080127100006 PM 10338162 ER PT J AU Anderson, SW Stofan, ER Smrekar, SE Guest, JE Wood, B AF Anderson, SW Stofan, ER Smrekar, SE Guest, JE Wood, B TI Pulsed inflation of pahoehoe lava flows: implications for flood basalt emplacement SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE pahoehoe; lava flows; flood basalts; Hawaii ID CRETACEOUS TERTIARY BOUNDARY; COLUMNAR JOINTS; HAWAII; VOLCANISM; GROWTH; CRYSTALLIZATION; CONSTRAINTS; ERUPTIONS; EVOLUTION; RHEOLOGY AB Dilated fractures in Hawaiian pahoehoe lava flows contain three zones that show the kinematics of inflation. The upper columnar zone forms through thermal contraction prior to inflation, the middle planar zone reflects inflation-induced tension, and the lower banded zone contains evidence of brittle and ductile deformation. The formation of the lower banded zone requires varying strain rates during fracture propagation and is best explained by a model where small pulses of lava inject beneath the cooled flow crust through a network of preferred pathways. We demonstrate via simple models of pipe flow that this inflation mechanism is incapable of producing areally extensive continental flood basalts on Earth, although it may explain related features on large Martian volcanoes. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Black Hills State Univ, Dept Sci, Spearfish, SD 57799 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ London Observ, London NW7 2QS, England. RP Anderson, SW (reprint author), Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. NR 49 TC 56 Z9 56 U1 2 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD APR 30 PY 1999 VL 168 IS 1-2 BP 7 EP 18 DI 10.1016/S0012-821X(99)00044-8 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188TQ UT WOS:000079864900002 ER PT J AU Isidori, A Joshi, SM Kelkar, AG AF Isidori, A Joshi, SM Kelkar, AG TI Asymptotic stability of interconnected passive non-linear systems SO INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL LA English DT Article ID PHASE NONLINEAR-SYSTEMS; STABILIZATION AB This paper addresses the problem of stabilization of a class of internally passive non-linear time-invariant dynamic systems. A class of non-linear marginally strictly passive (MSP) systems is defined, which is less restrictive than input-strictly passive systems. It is shown that the interconnection of a non-linear passive system and a non-linear MSP system is globally asymptotically stable. The result generalizes and weakens the conditions of the passivity:theorem, which requires one of the systems to be input-strictly passive. In the case of linear time-invariant systems, it is shown that the MSP property is equivalent to the marginally. strictly positive real (MSPR) property, which is much simpler to check. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 Univ Rome La Sapienza, Dipartimento Informat & Sistemist, I-00184 Rome, Italy. NASA, Langley Res Ctr, Hampton, VA 23666 USA. Kansas State Univ, Manhattan, KS 66506 USA. RP Isidori, A (reprint author), Univ Rome La Sapienza, Dipartimento Informat & Sistemist, I-00184 Rome, Italy. RI Isidori, Alberto/F-5825-2011 NR 26 TC 7 Z9 7 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 1049-8923 J9 INT J ROBUST NONLIN JI Int. J. Robust Nonlinear Control PD APR 30 PY 1999 VL 9 IS 5 BP 261 EP 273 DI 10.1002/(SICI)1099-1239(19990430)9:5<261::AID-RNC403>3.0.CO;2-V PG 13 WC Automation & Control Systems; Engineering, Electrical & Electronic; Mathematics, Applied SC Automation & Control Systems; Engineering; Mathematics GA 192EH UT WOS:000080065100001 ER PT J AU Acuna, MH Connerney, JEP Ness, NF Lin, RP Mitchell, D Carlson, CW McFadden, J Anderson, KA Reme, H Mazelle, C Vignes, D Wasilewski, P Cloutier, P AF Acuna, MH Connerney, JEP Ness, NF Lin, RP Mitchell, D Carlson, CW McFadden, J Anderson, KA Reme, H Mazelle, C Vignes, D Wasilewski, P Cloutier, P TI Global distribution of crustal magnetization discovered by the Mars Global Surveyor MAG/ER experiment SO SCIENCE LA English DT Article ID FIELD AB Vector magnetic field observations of the martian crust were acquired by the Mars Global Surveyor (MCS) magnetic field experiment/electron reflectometer (MAG/ER) during the aerobraking and science phasing orbits, at altitudes between similar to 100 and 200 kilometers. Magnetic field sources of multiple scales, strength, and geometry were observed. There is a correlation between the location of the sources and the ancient cratered terrain of the martian highlands. The absence of crustal magnetism near large impact basins such as Hellas and Argyre implies cessation of internal dynamo action during the early Naochian epoch (similar to 4 billion years ago). Sources with equivalent magnetic moments as Large as 1.3 x 10(17) ampere-meter(2) in the Terra Sirenum region contribute to the development of an asymmetrical, time-variable obstacle to solar wind flow around Mars. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Ctr Etud Spatiale Rayonnements, F-31028 Toulouse 4, France. Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. RP Acuna, MH (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI connerney, john/I-5127-2013 NR 16 TC 551 Z9 561 U1 10 U2 35 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 30 PY 1999 VL 284 IS 5415 BP 790 EP 793 DI 10.1126/science.284.5415.790 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 192AW UT WOS:000080056200042 ER PT J AU Connerney, JEP Acuna, MH Wasilewski, PJ Ness, NF Reme, H Mazelle, C Vignes, D Lin, RP Mitchell, DL Cloutier, PA AF Connerney, JEP Acuna, MH Wasilewski, PJ Ness, NF Reme, H Mazelle, C Vignes, D Lin, RP Mitchell, DL Cloutier, PA TI Magnetic lineations in the ancient crust of Mars SO SCIENCE LA English DT Article ID GLOBAL SURVEYOR MISSION; ANOMALY MAP; MAGSAT; FIELD AB The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit, obtained vector magnetic field measurements above the surface of Mars (altitudes >100 kilometers). Crustal magnetization, mainly confined to the most ancient, heavily cratered martian highlands, is frequently organized in east-west-trending linear features, the Longest extending over 2000 kilometers. Crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity were found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much Larger spatial scale. They may be a relic of an era of plate tectonics on Mars. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. Ctr Etud Spatiale Rayonnements, F-31028 Toulouse, France. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. RP Connerney, JEP (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI connerney, john/I-5127-2013; OI connerney, jack/0000-0001-7478-6462 NR 26 TC 299 Z9 305 U1 3 U2 24 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 30 PY 1999 VL 284 IS 5415 BP 794 EP 798 DI 10.1126/science.284.5415.794 PG 5 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 192AW UT WOS:000080056200043 ER PT J AU Milligan, DB Wilson, PF McEwan, MJ Anicich, VG AF Milligan, DB Wilson, PF McEwan, MJ Anicich, VG TI Ion-molecule association in acrylonitrile SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY LA English DT Article DE acrylonitrile; ICR; SIFT; ion-association reactions; double-well potential model ID LOW-PRESSURE; ELECTRON-ATTACHMENT; CH3+/CH3CN SYSTEM; ENERGY-TRANSFER; RATE-CONSTANT; CHEMISTRY; MECHANISM; NITRILES; DRIFT; C2N2 AB The association reactions of the acrylonitrile ion, CH(2)CHCN(+), and the protonated ion derived from acrylonitrile, CH(2)CHCNH(+). with acrylonitrile (CH(2)CHCN) have been examined using ion cyclotron resonance (ICR) and flowing afterglow selected ion flow drift tube (FA/SIFDT) techniques at room temperature. These techniques yield different results for these two systems that can be rationalized by considerations of the lifetime of the collision complex. In the CH(2)CHCN(+)/CH(2)CHCN system, the measured reaction rate coefficients are: k(ICR) = 2.5 x 10(-9) cm(3) s(-1) with a single product channel (CH(2)CHCNH(+) + C(3)H(2)N) and k(SIFT) = 3.1 x 10(-9) cm(3) s(-1) (with a 30% product channel to the adduct C(6)H(6)N(6)(+)) The rate coefficient and product distributions in the FA/SIFDT instrument are invariant with pressure in the range 0.25-0.75 Torr. In the CH(2)CHCNH(+)/CH(2)CHCN system, the measured rate coefficients are: k(ICR) = 9.2 x 10(-11) cm(3) s(-1) at a CH(2)CHCN pressure of 3.0 x 10(-4) Torr and k(SIFT) = 1.6 x 10(-9) cm(3) s(-1), where association is the only product channel observed by each technique. The termolecular process corresponding to this latter association has a measured reaction rate coefficient of k(3) = 1.2 x 10(-23) cm(6) s(-1) (for M = CH(2)CHCN) and k(3) = 8.1 x 10(-25) cm(6) s(-1) (for M = He). Both systems were modelled: A double well potential model involving the formation of loosely bound and tightly bound complexes was required to account for the kinetic behaviour of the CH(2)CHCN(+)/CH(2)CHCN system whereas a single-well potential model satisfactorily accounted for the behaviour of the CH(2)CHCNH(+)/CH(2)CHCN system. (Int J Mass Spectrom 185/186/187 (1999) 663-672) (C) 1999 Elsevier Science B.V. C1 Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Milligan, DB (reprint author), Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. NR 31 TC 6 Z9 6 U1 0 U2 2 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 APR 29 PY 1999 VL 185 SI SI BP 663 EP 672 DI 10.1016/S1387-3806(98)14191-X PG 10 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 188PV UT WOS:000079857900061 ER PT J AU Rind, D Lerner, J Shah, K Suozzo, R AF Rind, D Lerner, J Shah, K Suozzo, R TI Use of on-line tracers as a diagnostic tool in general circulation model development 2. Transport between the troposphere and stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DOWNWARD CONTROL; SENSITIVITY; RESOLUTION; CLIMATE; SIMULATION; EXCHANGE; SURFACE; SF6 AB The effect of altering the vertical resolution of a general circulation model and processes associated with it are used to investigate mixing between the troposphere and stratosphere. Four on-line tracers are employed: chlorofluorocarbon-11 and SF6 for mixing from the troposphere into the stratosphere, Rn-222 for vertical mixing within the troposphere, and C-14 for mixing from the stratosphere into the troposphere. Four standard models are tested, with varying vertical resolution, gravity wave drag, and location of the model top, and additional subsidiary models are employed to examine specific features. The results show that proper vertical transport between the troposphere and stratosphere in the Goddard Institute for Space Studies models requires lifting the top of the model considerably out of the stratosphere and including gravity wave drag in the lower stratosphere. Increased vertical resolution without these aspects does not improve tropospheric-stratospheric exchange. The transport appears to be driven largely by the residual circulation within the stratosphere; associated Eliassen-Palm flux convergences require both realistic upward propagating energy from the troposphere and realistic pass-through possibilities. A 23-layer version with a top at the mesopause and incorporating gravity wave drag appears to have reasonable stratospheric-tropospheric exchange in terms of both the resulting tracer distributions and atmospheric mass fluxes. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. Sci Syst & Applicat, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. RP Rind, D (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. EM drind@giss.nasa.gov NR 38 TC 53 Z9 54 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 27 PY 1999 VL 104 IS D8 BP 9151 EP 9167 DI 10.1029/1999JD900006 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189UY UT WOS:000079925600005 ER PT J AU Bhatt, PP Remsberg, EE Gordley, LL McInerney, JM Brackett, VG Russell, JM AF Bhatt, PP Remsberg, EE Gordley, LL McInerney, JM Brackett, VG Russell, JM TI An evaluation of the quality of Halogen Occultation Experiment ozone profiles in the lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AEROSOL AB The archived ozone profiles from the Halogen Occultation Experiment (HALOE) have already been corrected for the effects of the spectrally varying, interfering absorption due to aerosols composed of aqueous sulfuric acid, and agreement with correlative measurements in the stratosphere is generally excellent. However, comparisons of sets of coincident HALOE and ozonesonde profiles indicate occasional large differences at the lowest levels of the stratosphere. Most of those instances occur at altitudes just below a well-defined minimum in the 5.26 mu m channel aerosol extinction profile, whose wavelength dependence is not represented by a sulfuric acid aerosol model. Further, when the aerosol extinction exceeds about 10(-3) km(-1), the aerosol correction to the ozone channel transmittances is both large and uncertain. After screening out the HALOE ozone profile segments whose corresponding aerosol/cirrus corrections are likely uncertain and after averaging the ozonesonde profiles into 2.5 km thick layers, we find that the HALOE ozone agrees, on average, to within 10% of their coincident ozonesonde measurements down to 100 hPa at tropical/subtropical latitudes and to 200 hPa at extratropical latitudes. A tightening of the coincidence criteria for the comparisons does not improve the mean differences for the sets nearly as much. Part of the variance of the paired differences was also accounted for when the ozonesonde profile values were integrated into those 2.5 km layers, prior to taking differences. This improvement is due mainly to the vertical averaging of the local, higher-resolution ozonesonde data, matching the lower resolution for HALOE ozone in the lower stratosphere. It is concluded that HALOE is providing accurate ozone profiles throughout the lower stratosphere, when its correction for interfering aerosols has been well characterized and when cirrus layers are not indicated. C1 Sci Applicat Int Corp, Hampton, VA 23666 USA. GATS Inc, Newport News, VA 23606 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Hampton Univ, Ctr Atmospher Sci, Hampton, VA 23668 USA. RP Bhatt, PP (reprint author), Sci Applicat Int Corp, Hampton, VA 23666 USA. EM p.p.bhatt@larc.nasa.gov; e.e.remsberg@larc.nasa.gov; larry@gats-inc.com; joseph.m.mcinerney@larc.nasa.gov; v.g.brackett@larc.nasa.gov; jmr@hamptonu.edu NR 14 TC 43 Z9 45 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 1999 VL 104 IS D8 BP 9261 EP 9275 DI 10.1029/1999JD900058 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189UY UT WOS:000079925600011 ER PT J AU Chiapello, I Prospero, JM Herman, JR Hsu, NC AF Chiapello, I Prospero, JM Herman, JR Hsu, NC TI Detection of mineral dust over the North Atlantic Ocean and Africa with the Nimbus 7 TOMS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID METEOSAT ISCCP-B2 DATA; SAHARAN DUST; AEROSOLS; SATELLITE; LAYER; ULTRAVIOLET; UNCERTAINTY; TRANSPORT; CLOUDS; LOAD AB It has recently been found that the ultraviolet measurements obtained with the Nimbus 7 total ozone mapping spectrometer (TOMS) instrument can be used to retrieve information on the distribution of aerosols over oceanic and continental surfaces. Here we examine the use of the derived TOMS aerosol index (AI) for the detection of absorbing aerosol in terms of mineral dust aerosol over the North Atlantic Ocean and North Africa. Specifically, we compare the TOMS AI with the time series of daily aerosol measurements made in the boundary layer at Sal Island (Cape Verde), Barbados, and Miami and in the free troposphere on Tenerife (Canary Islands); these sites are frequently impacted by African dust events. At Tenerife, over the time period 1988-1992, TOMS detected 80% of the African dust events that yielded daily average dust concentrations greater than 20 mu g m(-3); at Barbados and Miami, TOMS detected 65% and 44% respectively of the events over the period 1979-1992. If we exclude events during which some of the TOMS data are missing and also short (1-day) dust events, TOMS detected 99% of the events at Tenerife, 97% at Barbados, and 81% at Miami. TOMS was also successful in detecting the "low altitude" African dust events recorded at Sal during the winter season. Over Africa we compare the TOMS AI data with ground-based measurements of aerosol optical thickness (AOT) obtained during field experiments in Senegal and Niger; these yield a nearly linear relationship between the TOMS AI and the AOT. Discrepancies between ground-based measurements (in terms of dust concentrations or AOT) and TOMS AI can be attributed to a number of factors: variations in the physical properties of the aerosol; the sensitivity of the TOMS response to the altitude of the aerosol layer; or the coarse spatial resolution of the TOMS pixel. Nonetheless, our results clearly show that the TOMS AI provides a remarkably accurate picture of mineral dust distributions in the atmosphere over both continental and oceanic regions. C1 Univ Sci & Tech Lille Flandres Artois, Opt Atmospher Lab, CNRS, URA 713, F-59655 Villeneuve Dascq, France. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Div Marine & Atmospher Chem, Miami, FL 33149 USA. Hughes STX Corp, Greenbelt, MD USA. RP Chiapello, I (reprint author), Univ Sci & Tech Lille Flandres Artois, Opt Atmospher Lab, CNRS, URA 713, Bat P5, F-59655 Villeneuve Dascq, France. EM chiapello@loa.univ-lille1.fr; jprospero@rsmas.miami.edu; herman@tparty.gsfc.nasa.gov; hsu@hoss.stx.com RI Hsu, N. Christina/H-3420-2013; OI Herman, Jay/0000-0002-9146-1632; Prospero, Joseph/0000-0003-3608-6160 NR 39 TC 117 Z9 119 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 27 PY 1999 VL 104 IS D8 BP 9277 EP 9291 DI 10.1029/1998JD200083 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189UY UT WOS:000079925600012 ER PT J AU Sandmeier, SR Middleton, EM Deering, DW Qin, WH AF Sandmeier, SR Middleton, EM Deering, DW Qin, WH TI The potential of hyperspectral bidirectional reflectance distribution function data for grass canopy characterization SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PHOTOSYNTHETICALLY ACTIVE RADIATION; LEAF-AREA INDEX; VEGETATION CANOPIES; BRDF DATA; MODEL; FIFE AB Hyperspectral bidirectional reflectance distribution function (BRDF) data of Konza prairie grassland acquired in the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) on the ground with two SE-590 instruments and remotely with the airborne advanced solid-state array spectroradiometer (ASAS) are analyzed and compared to BRDF data of dense ryegrass obtained in the laboratory and field with the European goniometric facility (EGO) and the Swiss field-goniometer system (FIGOS). The soil underlying the relatively sparse Konza prairie grass disturbed the spectral BRDF effects of the vegetation components. After a correction of the soil influence based on the bidirectional canopy gap probability, the Konza data from SE-590 and ASAS sensors showed a consistently strong dependence of spectral BRDF effects from nadir reflectance as was observed in the EGO and FIGOS data. BRDF effects were inversely related to reflectance intensities, low reflectances being associated with pronounced BRDF effects and high reflectances with low BRDF effects. This relationship is due to multiple scattering effects and is influenced by the canopy optical properties and architecture parameters such as leaf area index (LAI), leaf angle distribution (LAD), and the gap fraction. The BRDF data of the Konza prairie grass from both ground and aircraft measurements showed a strong relationship between LAI. and spectral BRDF variability. Reflectance data with high spectral resolution in the red edge range from 675 to about 900 nm wavelength, acquired from the two viewing directions with maximum and minimum reflectance intensities proved to be useful for deriving vegetation canopy architecture characteristics from hyperspectral BRDF data. BRDF data with high spectral resolution from the airborne ASAS sensor and from planned commercial remote sensing satellites are therefore an ideal testbed for a further exploration of this promising approach. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Sandmeier, SR (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. EM ssandmei@pop900.gsfc.nasa.gov NR 37 TC 29 Z9 29 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 APR 27 PY 1999 VL 104 IS D8 BP 9547 EP 9560 DI 10.1029/1999JD900094 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189UY UT WOS:000079925600029 ER PT J AU Wang, PH Kent, GS Veiga, RE Yue, GK Poole, LR Fishman, J McCormick, MP AF Wang, PH Kent, GS Veiga, RE Yue, GK Poole, LR Fishman, J McCormick, MP TI A model for identifying the aerosol-only mode of SAGE II 1.02-mu m extinction coefficient data at altitudes below 6.5 km SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC AEROSOL; TRACE-A; CLOUD; OZONE; DISTRIBUTIONS AB A model is proposed for identifying the aerosol mode of the second Stratospheric Aerosol and Gas Experiment (SAGE II) 1.02-mu m extinction coefficient measurements at altitudes below 6.5 km, which also contain cloud samples. This development allows one to extend the SAGE II satellite data analysis from the lower limit at 6.5 km of the SAGE II two-wavelength method into the lower troposphere. Thus the proposed model provides opportunities for fully utilizing the SAGE II tropospheric measurements important to the understanding of the global behavior of tropospheric aerosols, clouds, and ozone and related transports. The effectiveness of this model is examined by using the SAGE II two-wavelength technique at 6.5 km. Sample applications of the proposed model reveal encouraging results. To assess the quality of the aerosol 1.02-mu m data, it is recommended that a comprehensive data comparison analysis be conducted by using tropospheric measurements from different instruments. C1 Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. Hampton Univ, Hampton, VA 23668 USA. RP Wang, PH (reprint author), Sci & Technol Corp, 10 Basil Sawyer Dr, Hampton, VA 23666 USA. EM p.wang@larc.nasa.gov NR 27 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 27 PY 1999 VL 104 IS D8 BP 9609 EP 9615 DI 10.1029/1999JD900017 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189UY UT WOS:000079925600034 ER PT J AU Koshak, WJ Krider, EP Murphy, MJ AF Koshak, WJ Krider, EP Murphy, MJ TI A multipole expansion method for analyzing lightning field changes SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID FLORIDA AB Changes in the surface electric field are frequently used to infer the locations and magnitudes of lightning-caused changes in thundercloud charge distributions. The traditional procedure is to assume that the charges that me effectively deposited by the flash can be modeled either as a single point charge (the Q model) or a point dipole (the P model). The Q model has four unknown parameters and provides a good description of many cloud-to-ground (CG) flashes. The P model has six unknown parameters and describes many intracloud (IC) discharges. In this paper we introduce a new analysis method that assumes that the change in the cloud charge can be described by a truncated multipole expansion, i.e., there are both monopole and dipole terms in the unknown source distribution, and both terms are applied simultaneously. This method can be used to analyze CG flashes that are accompanied by large changes in the cloud dipole moment and complex IC discharges. If there is; enough information content in the measurements, the model can also be generalized to include quadrupole and higher order terms. The parameters of the charge moments are determined using a three-dimensional grid search in combination with a linear inversion, and because of this, local minima in the error function and the associated solution ambiguities are avoided. The multipole method has been tested on computer-simulated sources and on natural lightning at the NASA Kennedy Space Center and U.S. Air Force Eastern Range. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35812 USA. Univ Arizona, Inst Atmospher Phys, Tucson, AZ 85721 USA. RP Koshak, WJ (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, MSFC-ES41, Huntsville, AL 35812 USA. EM william.koshak@msfc.nasa.gov; krider@atmo.arizona.edu NR 16 TC 8 Z9 8 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 27 PY 1999 VL 104 IS D8 BP 9617 EP 9633 DI 10.1029/1999JD900027 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189UY UT WOS:000079925600035 ER PT J AU Wade, ML Agresti, DG Wdowiak, TJ Armendarez, LP Farmer, JD AF Wade, ML Agresti, DG Wdowiak, TJ Armendarez, LP Farmer, JD TI A Mossbauer investigation of iron-rich terrestrial hydrothermal vent systems: Lessons for Mars exploration SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SUPERPARAMAGNETIC COMPONENT; ORGUEIL METEORITE; HOT-SPRINGS; PAST LIFE; SPECTROSCOPY; EVOLUTION; HEMATITE; SPECTRA; SEARCH; REFLECTANCE AB Hydrothermal spring systems may well have been present on early Mars and could have served as a habitat for primitive life. The integrated instrument suite of the Athena Rover has, as a component on the robotic arm, a Mossbauer spectrometer. In the context of future Mars exploration we present results of Mossbauer analysis of a suite of samples from an iron-rich thermal spring in the Chocolate Pots area of Yellowstone National Park (YNP) and from Obsidian Pool (YNP) and Manitou Springs, Colorado. We have found that Mossbauer spectroscopy can discriminate among the iron-bearing minerals in our samples. Those near the vent and on the surface are identified as ferrihydrite, an amorphous ferric mineraloid. Subsurface samples, collected from cores, which are likely to have undergone inorganic and/or biologically mediated alteration (diagenesis), exhibit spectral signatures that include nontronite (a smectite clay), hematite (alpha-Fe2O3), small-particle/nanophase goethite (alpha-FeOOH), and siderite (FeCO3). We find for iron minerals that Mossbauer spectroscopy is at least as efficient in identification as X-ray diffraction, This observation is important from an exploration standpoint. As a planetary surface instrument, Mossbauer spectroscopy can yield high-quality spectral data without sample preparation (backscatter mode). We have also used field emission scanning electron microscopy (FESEM), in conjunction with energy-dispersive X ray (EDX) fluorescence spectroscopy, to characterize the microbiological component of surface sinters and the relation between the microbiological and the mineralogical framework. Evidence is presented that the minerals found in these deposits can have multibillion-year residence times and thus may have survived their possible production in a putative early Martian hot spring up to the present day. Examples include the nanophase property and the Mossbauer signature for siderite, which has been identified in a 2.09-billion-year old hematite-rich chert stromatolite. Our research demonstrates that in situ Mossbauer spectroscopy can help determine whether hydrothermal mineral deposits exist on Mars, which is significant for exobiology because of the issue of whether that world ever had conditions conducive to the origin of life. As a useful tool for selection of samples suitable for transport to Earth, Mossbauer spectroscopy will not only serve geological interests but will also have potential for exopaleontology. C1 Univ Alabama, Dept Phys, Astro & Solar Syst Phys Program, Birmingham, AL 35294 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Alabama Sch Fine Arts, Russell Math & Sci Ctr, Birmingham, AL USA. RP Wade, ML (reprint author), Univ Alabama, Dept Phys, Astro & Solar Syst Phys Program, Birmingham, AL 35294 USA. NR 82 TC 41 Z9 42 U1 0 U2 10 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 1999 VL 104 IS E4 BP 8489 EP 8507 DI 10.1029/1998JE900049 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900004 PM 11542933 ER PT J AU Golombek, M AF Golombek, M TI Introduction to the special section: Mars Pathfinder SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Mars Pathfinder Project, Pasadena, CA 91109 USA. RP Golombek, M (reprint author), CALTECH, Jet Prop Lab, Mars Pathfinder Project, Mail Stop 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 6 Z9 6 U1 0 U2 2 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 1999 VL 104 IS E4 BP 8521 EP 8522 DI 10.1029/1998JE900032 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900006 ER PT J AU Golombek, MP Anderson, RC Barnes, JR Bell, JF Bridges, NT Britt, DT Bruckner, J Cook, RA Crisp, D Crisp, JA Economou, T Folkner, WM Greeley, R Haberle, RM Hargraves, RB Harris, JA Haldemann, AFC Herkenhoff, KE Hviid, SF Jaumann, R Johnson, JR Kallemeyn, PH Keller, HU Kirk, RL Knudsen, JM Larsen, S Lemmon, MT Madsen, MB Magalhaes, JA Maki, JN Malin, MC Manning, RM Matijevic, J McSween, HY Moore, HJ Murchie, SL Murphy, JR Parker, TJ Rieder, R Rivellini, TP Schofield, JT Seiff, A Singer, RB Smith, PH Soderblom, LA Spencer, DA Stoker, CR Sullivan, R Thomas, N Thurman, SW Tomasko, MG Vaughan, RM Wanke, H Ward, AW Wilson, GR AF Golombek, MP Anderson, RC Barnes, JR Bell, JF Bridges, NT Britt, DT Bruckner, J Cook, RA Crisp, D Crisp, JA Economou, T Folkner, WM Greeley, R Haberle, RM Hargraves, RB Harris, JA Haldemann, AFC Herkenhoff, KE Hviid, SF Jaumann, R Johnson, JR Kallemeyn, PH Keller, HU Kirk, RL Knudsen, JM Larsen, S Lemmon, MT Madsen, MB Magalhaes, JA Maki, JN Malin, MC Manning, RM Matijevic, J McSween, HY Moore, HJ Murchie, SL Murphy, JR Parker, TJ Rieder, R Rivellini, TP Schofield, JT Seiff, A Singer, RB Smith, PH Soderblom, LA Spencer, DA Stoker, CR Sullivan, R Thomas, N Thurman, SW Tomasko, MG Vaughan, RM Wanke, H Ward, AW Wilson, GR TI Overview of the Mars Pathfinder Mission: Launch through landing, surface operations, data sets, and science results SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID X-RAY SPECTROMETER; CHEMICAL-COMPOSITION; MARTIAN SOIL; LANDER; TRACKING; CAMERA; ROCKS; SITE AB Mars Pathfinder successfully landed at Ares Vallis on July 4, 1997, deployed and navigated a small rover about 100 m clockwise around the lander, and collected data from three science instruments and ten technology experiments. The mission operated for three months and returned 2.3 Gbits of data, including over 16,500 lander and 550 rover images, 16 chemical analyses of rocks and soil, and 8.5 million individual temperature, pressure and wind measurements. Pathfinder is the best known location on Mars, having been clearly identified with respect to other features on the surface by correlating five prominent horizon features and two small craters in lander images with those in high-resolution orbiter images and in inertial space from two-way ranging and Doppler tracking. Tracking of the lander has fixed the spin pole of Mars, determined the precession rate since Viking 20 years ago, and indicates a polar moment of inertia, which constrains a central metallic core to be between 1300 and similar to 2000 km in radius. Dark rocks appear to be high in silica and geochemically similar to anorogenic andesites; lighter rocks are richer in sulfur and lower in silica, consistent with being coated with various amounts of dust. Rover and lander images show rocks with a variety of morphologies, fabrics and textures, suggesting a variety of rock types are present. Rounded pebbles and cobbles on the surface as well as rounded bumps and pits on some rocks indicate these rocks may be conglomerates (although other explanations are also possible), which almost definitely require liquid water to form and a warmer and wetter past. Airborne dust is composed of composite silicate particles with a small fraction of a highly magnetic mineral, interpreted to be most likely maghemite; explanations suggest iron was dissolved from crustal materials during an active hydrologic cycle with maghemite freeze dried onto silicate dust grains. Remote sensing data at a scale of a kilometer or greater and an Earth analog correctly predicted a rocky plain safe for landing and roving with a variety of rocks deposited by catstrophic floods, which are relatively dust free. The surface appears to have changed little since it formed billions of years ago, with the exception that eolian activity may have deflated the surface by similar to 3-7 cm, sculpted wind tails, collected sand into dunes, and eroded ventifacts (fluted and grooved rocks). Pathfinder found a dusty lower atmosphere, early morning water ice clouds, and morning near-surface air temperatures that changed abruptly with time and height. Small scale vortices, interpreted to be dust devils, were observed repeatedly in the afternoon by the meteorology instruments and have been imaged. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Max Planck Inst Chem, D-55122 Mainz, Germany. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA. Univ Copenhagen, Niels Bohr Inst, Orsted Lab, DK-2100 Copenhagen O, Denmark. DLR, German Aerosp Ctr, Inst Planetary Explorat, D-12489 Berlin, Germany. US Geol Survey, Flagstaff, AZ 86001 USA. Max Planck Inst Aeron, D-3411 Katlenburg Lindau, Germany. Riso Natl Lab, DK-4000 Roskilde, Denmark. Malin Space Sci Syst, San Diego, CA 92191 USA. Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. US Geol Survey, Menlo Park, CA 94025 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Golombek, MP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lemmon, Mark/E-9983-2010; Madsen, Morten/D-2082-2011; Murchie, Scott/E-8030-2015; Johnson, Jeffrey/F-3972-2015; Bridges, Nathan/D-6341-2016; Crisp, Joy/H-8287-2016 OI Lemmon, Mark/0000-0002-4504-5136; Madsen, Morten/0000-0001-8909-5111; Murchie, Scott/0000-0002-1616-8751; Crisp, Joy/0000-0002-3202-4416 NR 21 TC 72 Z9 72 U1 1 U2 17 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 1999 VL 104 IS E4 BP 8523 EP 8553 DI 10.1029/98JE02554 PG 31 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900007 ER PT J AU Ward, AW Gaddis, LR Kirk, RL Soderblom, LA Tanaka, KL Golombek, MP Parker, TJ Greeley, R Kuzmin, RO AF Ward, AW Gaddis, LR Kirk, RL Soderblom, LA Tanaka, KL Golombek, MP Parker, TJ Greeley, R Kuzmin, RO TI General geology and geomorphology of the Mars Pathfinder landing site SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID X-RAY SPECTROMETER; CHEMICAL-COMPOSITION; CHRYSE-PLANITIA; MARTIAN SOIL; MISSION; SHAPES; EARTH; ROCKS AB The Mars Pathfinder (MPF) spacecraft landed on relatively young (late Hesperianearly Amazonian; 3.1-0.7 Ga) plains in Chryse Planitia near the mouth of Ares Vallis. Images returned from the spacecraft reveal a complex landscape of ridges and troughs, large hills and crater rims, rocks and boulders of various sizes and shapes, and surficial deposits, indicating a complex, multistage geologic history of the landing site. After the deposition of one or more bedrock units, depositional and erosional fluvial processes shaped much of the present landscape. Multiple erosional events are inferred on the basis of observations of numerous channels, different orientations of many streamlined tails from their associated knobs and hills, and superposition of lineations and streamlines. Medium- and small-scale features, interpreted to be related to late-stage drainage of floodwaters, are recognized in several areas at the landing site. Streamlined knobs and hills seen in Viking orbiter images support this inference, as they seem to be complex forms, partly erosional and partly depositional, and may also indicate a series of scouring and depositional events that, in some cases, further eroded or partially buried these landforms. Although features such as these are cited as evidence for catastrophic flooding at Ares Vallis, some of these features may also be ascribed to alternative primary or secondary depositional processes, such as glacial or mass-wasting processes. Close inspection of the landing site reveals rocks that are interpreted to be volcanic in origin and others that may be conglomeratic. If such sedimentary rocks are confirmed, fluvial processes have had a greater significance on Mars than previously thought. For the last several hundred million to few billion years, eolian processes have been dominant. Dunes and dune-like features, ventifacts, and deflation and exhumation features around several rocks probably are the most recent landforms. The relatively pristine nature of the overall landscape at the MPF site suggests weathering and erosion processes on Mars are exceptionally slow. C1 US Geol Survey, Astrogeol Program, Flagstaff, AZ 86001 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Russian Acad Sci, Verdansky Inst, Moscow 117975, Russia. RP Ward, AW (reprint author), US Geol Survey, Astrogeol Program, 2255 N Gemini Dr, Flagstaff, AZ 86001 USA. NR 31 TC 27 Z9 27 U1 0 U2 6 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 1999 VL 104 IS E4 BP 8555 EP 8571 DI 10.1029/1998JE900021 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900008 ER PT J AU Greeley, R Kraft, M Sullivan, R Wilson, G Bridges, N Herkenhoff, K Kuzmin, RO Malin, M Ward, W AF Greeley, R Kraft, M Sullivan, R Wilson, G Bridges, N Herkenhoff, K Kuzmin, RO Malin, M Ward, W TI Aeolian features and processes at the Mars Pathfinder landing site SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID ROCKS; SOIL AB The Mars Pathfinder landing site contains abundant features attributed to aeolian, or wind, processes. These include wind tails, drift deposits, duneforms of various types, ripplelike features, and ventifacts (the first clearly seen on Mars). Many of these features are consistant with formation involving sand-size particles. Although some features, such as dunes, could develop from saltating sand-size aggregates of finer grains, the discovery of ventifact flutes cut in rocks strongly suggests that at least some of the grains are crystalline, rather than aggregates. Excluding the ventifacts, the orientations of the wind-related features correlate well with the orientations of bright wind steaks seen on Viking Orbiter images in the general area. They also correlate with wind direction predictions from the NASA-Ames General Circulation Model (GCM) which show that the strongest winds in the area occur in the northern hemisphere winter and are directed toward 209 degrees. C1 Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Russian Acad Sci, Vernadsky Inst, Moscow 117975, Russia. Malin Space Sci Syst, San Diego, CA 92121 USA. US Geol Survey, Flagstaff, AZ 86001 USA. RP Greeley, R (reprint author), Arizona State Univ, Dept Geol, Box 871404, Tempe, AZ 85287 USA. NR 35 TC 66 Z9 66 U1 0 U2 4 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 1999 VL 104 IS E4 BP 8573 EP 8584 DI 10.1029/98JE02553 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900009 ER PT J AU Golombek, MP Moore, HJ Haldemann, AFC Parker, TJ Schofield, JT AF Golombek, MP Moore, HJ Haldemann, AFC Parker, TJ Schofield, JT TI Assessment of Mars Pathfinder landing site predictions SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID THERMAL INERTIA; PARTICULATE MATERIALS; PHYSICAL-PROPERTIES; ROCKS; GEOMORPHOLOGY; CONDUCTIVITY; REGION; RADAR AB Remote sensing data at scales of kilometers and an Earth analog were used to accurately predict the characteristics of the Mars Pathfinder landing site at a scale of meters. The surface surrounding the Mars Pathfinder lander in Ares Vallis appears consistent with orbital interpretations, namely, that it would be a rocky plain composed of materials deposited by catastrophic floods. The surface and observed maximum clast size appears similar to predictions based on an analogous surface of the Ephrata Fan in the Channeled Scabland of Washington state. The elevation of the site measured by relatively small footprint delay-Doppler radar is within 100 m of that determined by two-way ranging and Doppler tracking of the spacecraft. The nearly equal elevations of the Mars Pathfinder and Viking Lander 1 sites allowed a prediction of the atmospheric conditions with altitude (pressure, temperature, and winds) that were well within the entry, descent; and landing design margins. High-resolution (similar to 38 m/pixel) Viking Orbiter 1 images showed a sparsely cratered surface with small knobs with relatively low slopes, consistent with observations of these features from the lander. Measured rock abundance is within 10% of that expected from Viking orbiter thermal observations and models. The fractional area covered by large, potentially hazardous rocks observed is similar to that estimated from model rock distributions based on data from the Viking landing sites, Earth analog sites, and total rock abundance. The bulk and fine-component thermal inertias measured from orbit are similar to those calculated from the observed rock size-frequency distribution. A simple radar echo model based on the reflectivity of the soil (estimated from its bulk density), and the measured fraction of area covered by rocks was used to approximate the quasi-specular and diffuse components of the Earth-based radar echos. Color and albedo orbiter data were used to predict the relatively dust free or unweathered surface around the Pathfinder lander compared to the Viking landing sites. Comparisons with the experiences of selecting the Viking landing sites demonstrate the enormous benefit the Viking data and its analyses and models had on the successful predictions of the Pathfinder site. The Pathfinder experience demonstrates that, in certain locations, geologic processes observed in orbiter data can he used to infer surface characteristics where those processes dominate over other processes affecting the Martian surface layer. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Astrogeol Team, Menlo Park, CA 94025 USA. RP Golombek, MP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 49 TC 36 Z9 36 U1 1 U2 9 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 1999 VL 104 IS E4 BP 8585 EP 8594 DI 10.1029/1998JE900015 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900010 ER PT J AU Bridges, NT Greeley, R Haldemann, AFC Herkenhoff, KE Kraft, M Parker, TJ Ward, AW AF Bridges, NT Greeley, R Haldemann, AFC Herkenhoff, KE Kraft, M Parker, TJ Ward, AW TI Ventifacts at the Pathfinder landing site SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARS; GEOMORPHOLOGY; CIRCULATION; TRANSPORT AB About half of the rocks at the Mars Pathfinder Ares Vallis landing site appear to be ventifacts, rocks abraded by windborne particles. Comparable resolution images taken by the Imager for Mars Pathfinder (IMP) camera and the Viking landers show that ventifacts are more abundant at the Pathfinder site, The ventifacts occur in several forms, including rocks with faceted edges, finger-like projections, elongated pits, flutes, grooves, and possible riils. The trends of elongated pits, flutes, grooves, and rills cluster at similar to 280-330 degrees clockwise from north and generally dip 10-30 degrees away from their trend direction. These orientations are indicative of southeast to northwest winds and differ from the trend of wind tails at the landing site, the direction of local wind streaks, and predictions of the Global Circulation Model, all of which indicate northeast to southwest winds. The disparity between these data sets strongly suggests that local circulation patterns have changed since the abrasion of the ventifacted rocks. The greater number of ventifacts at the Pathfinder site compared to either of the Viking sites is most easily explained as being due to a larger supply of abrading particles, composed of either sand-sized grains or indurated dust aggregates, and higher surface roughness, which should increase the momentum of saltating grains. The Pathfinder ventifacts may have formed shortly after the deposition of outflow channel sediments nearly 2 Gry ago, when a large local supply of abrading particles should have been abundant and atmospheric conditions may have been more conducive to rock abrasion from saltating grains. Based on how ventifacts form on Earth, the several ventifact forms seen at the Pathfinder site and their presence on some rocks but not on others are probably due to local airflow conditions, original rock shape, exposure duration, rock movement, and to a lesser extent, rock lithology. The abundance of ventifacts at the Pathfinder site, together with other evidence of weathering, indicates that unaltered rock surfaces are rare on Mars. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. US Geol Survey, Flagstaff, AZ 86001 USA. RP Bridges, NT (reprint author), CALTECH, Jet Prop Lab, MS 183-501,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Bridges, Nathan/D-6341-2016 NR 46 TC 59 Z9 60 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 1999 VL 104 IS E4 BP 8595 EP 8615 DI 10.1029/98JE02550 PG 21 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900011 ER PT J AU McSween, HY Murchie, SL Crisp, JA Bridges, NT Anderson, RC Bell, JF Britt, DT Bruckner, J Dreibus, G Economou, T Ghosh, A Golombek, MP Greenwood, JP Johnson, JR Moore, HJ Morris, RV Parker, TJ Rieder, R Singer, R Wanke, H AF McSween, HY Murchie, SL Crisp, JA Bridges, NT Anderson, RC Bell, JF Britt, DT Bruckner, J Dreibus, G Economou, T Ghosh, A Golombek, MP Greenwood, JP Johnson, JR Moore, HJ Morris, RV Parker, TJ Rieder, R Singer, R Wanke, H TI Chemical, multispectral, and textural constraints on the composition and origin of rocks at the Mars Pathfinder landing site SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID CALC-ALKALINE DIFFERENTIATION; HAWAIIAN PALAGONITIC SOIL; X-RAY SPECTROMETER; REFLECTANCE SPECTRA; SNC METEORITES; MAGNETIC-PROPERTIES; IRON-OXIDES; LAVA FLOWS; MARTIAN METEORITE; VOLCANIC-ROCKS AB Rocks at the Mars Pathfinder site are probably locally derived. Textures on rock surfaces may indicate volcanic, sedimentary, or impact-generated rocks, but aeolian abration and dust coatings prevent unambiguous interpretation. Multispectral imaging has resolved four spectral classes of rocks: gray and red, which occur on different surfaces of the same rocks; pink, which is probably soil crusts; and maroon, which occurs as large boulders, mostly in the far field. Rocks are assigned to two spectral trends based on the position of peak reflectance: the primary spectral trend contains gray, red, and pink rocks; maroon rocks constitute the secondary spectral trend. The spatial pattern of spectral variations observed is oriented along the prevailing wind direction The primary spectral trend arises from thin ferric coatings of aeolian dust on darker rocks. The secondary spectral trend is apparently due to coating by a different mineral, probably maghemite or ferrihydrite. A chronology based on rock spectra suggests that rounded maroon boulders constitute the oldest petrologic unit (a flood deposit), succeeded by smaller cobbles possibly deposited by impact, and followed by aeolian erosion and deposition. Nearly linear chemical trends in alpha proton X-ray spectrometer rock compositions are interpreted as mixing lines between rock and adhering dust, a conclusion supported by a correlation between sulfur abundance and red/blue spectral ratio. Extrapolations of regression lines to zero sulfur give the composition of a presumed igneous rock. The chemistry and normative mineralogy of the sulfur-free rock resemble common terrestrial volcanic rocks, and its classification corresponds to andesite. Igneous rocks of this composition may occur with elastic sedimentary rocks or impact melts and breccias. However, the spectral mottling expected on conglomerates or breccias is not observed in any APXS-analyzed rocks. Interpretation of the rocks as andesites is complicated by absence of a "1 mu m" pyroxene absorption band. Plausible explanations include impact glass, band masking by magnetite, or presence of calcium- and iron-rich pyroxenes and olivine which push the absorption band minimum past the imager's spectral range. The inferred andesitic composition is most similar to terrestrial anorogenic icelandites, formed by fractionation of tholeiitic basaltic magmas. Early melting of a relatively primitive Martian mantle could produce an appropriate parent magma, supporting the ancient age of Pathfinder rocks inferred from their incorporation in Hesperian flood deposits. Although rocks of andesitic composition at the Pathfinder site may represent samples of ancient Martian crust, inferences drawn about a necessary role for water or plate tectonics in their petrogenesis are probably unwarranted. C1 Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Max Planck Inst Chem, D-55122 Mainz, Germany. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. US Geol Survey, Flagstaff, AZ 86001 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Catalina Technol, Tucson, AZ 85718 USA. RP McSween, HY (reprint author), Univ Tennessee, Dept Geol Sci, Knoxville, TN 37996 USA. RI Murchie, Scott/E-8030-2015; Johnson, Jeffrey/F-3972-2015; Bridges, Nathan/D-6341-2016; Crisp, Joy/H-8287-2016 OI Murchie, Scott/0000-0002-1616-8751; Crisp, Joy/0000-0002-3202-4416 NR 133 TC 173 Z9 172 U1 6 U2 39 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 1999 VL 104 IS E4 BP 8679 EP 8715 DI 10.1029/98JE02551 PG 37 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900016 ER PT J AU Moore, HJ Bickler, DB Crisp, JA Eisen, HJ Gensler, JA Haldemann, AFC Matijevic, JR Reid, LK Pavlics, F AF Moore, HJ Bickler, DB Crisp, JA Eisen, HJ Gensler, JA Haldemann, AFC Matijevic, JR Reid, LK Pavlics, F TI Soil-like deposits observed by Sojourner, the Pathfinder rover SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID PHYSICAL-PROPERTIES; THERMAL INERTIA; LANDING SITE; MARTIAN SURFACE; MARS; MISSION; FINES; RADAR AB Most of the soil-like materials at the Pathfinder landing site behave like moderately dense soils on Earth with friction angles near 34 degrees-39 degrees and are called cloddy deposits. Cloddy deposits appear to be poorly sorted with dust-sized to granule-sized mineral or rock grains; they may contain pebbles, small rock fragments, and clods. Thin deposits of porous, compressible drifts with friction angles near 26 degrees-28 degrees are also present. Drifts are fine grained. Cohesions of both types of deposits are small. There may be indurated soil-like deposits and/or coated or crusted rocks. Cloddy deposits may be fluvial sediments of the Ares-Tiu floods, but other origins, such as ejecta from nearby impact craters, should be considered. Drifts are probably dusts that settled from the Martian atmosphere. Remote-sensing signatures of the deposits inferred from rover observations are consistent with those observed from orbit and Earth. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. US Geol Survey, Menlo Park, CA 94025 USA. Pavl Engn, Santa Barbara, CA 93109 USA. RP Moore, HJ (reprint author), CALTECH, Jet Prop Lab, MS 238-420,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Crisp, Joy/H-8287-2016 OI Crisp, Joy/0000-0002-3202-4416 NR 42 TC 85 Z9 88 U1 1 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD APR 25 PY 1999 VL 104 IS E4 BP 8729 EP 8746 DI 10.1029/1998JE900005 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900018 ER PT J AU Ferguson, DC Kolecki, JC Siebert, MW Wilt, DM Matijevic, JR AF Ferguson, DC Kolecki, JC Siebert, MW Wilt, DM Matijevic, JR TI Evidence for Martian electrostatic charging and abrasive wheel wear from the Wheel Abrasion Experiment on the Pathfinder Sojourner rover SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article AB The Wheel Abrasion Experiment (WAE) on the Mars Pathfinder rover was designed to find out how abrasive the Martian dust would be on strips of pure metals attached to one of the wheels. A specially modified wheel, with 15 thin film samples (five each of three different metals), specularly reflected sunlight to a photovoltaic sensor. When the wheel was rotated to present the different sample surfaces to the sensor, the resulting signal was interpreted in terms of dust adhesion and abrasive wear. Many data sequences were obtained. Ground tests of similar wheels in a simulated Martian environment showed that static charging levels of 100-300 V could be expected. To prevent the possibility of Paschen discharge in the low-pressure Martian atmosphere, charge dissipation points were added to the Sojourner rover and were shown in ground tests to keep charging levels at 80 V or less. Nevertheless, significant dust accumulations on Sojourner's wheels may be interpreted as evidence for electrostatic charging. Simple considerations of the expected maximum level of charging and electrostatic dust adhesion lead to an estimate for the size of the adhering dust grains. From the WAE data, it is hypothesized that the photoelectric effect is the most important mechanism for slow discharge in Martian daylight. Sensor signals obtained late in the Pathfinder mission show that significant wheel wear was seen on the metal wheel strips, with the most wear on the thinnest aluminum samples and the least on the thickest nickel and platinum samples. An estimate is made of the reflectance of the adhering Martian dust. The depth of dig of the WAE wheel shows that the dust is in some places very loose and in others tightly packed. Finally, comparison of the WAE results with ground test results makes possible a comparison of the Martian soil with mineral grain types and sizes found on Earth and show that the Martian dust is fine-grained and of limited hardness. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ferguson, DC (reprint author), NASA, Lewis Res Ctr, MS 302-1, Cleveland, OH 44135 USA. NR 14 TC 26 Z9 26 U1 1 U2 5 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 1999 VL 104 IS E4 BP 8747 EP 8759 DI 10.1029/98JE02249 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900019 ER PT J AU Maki, JN Lorre, JJ Smith, PH Brandt, RD Steinwand, DJ AF Maki, JN Lorre, JJ Smith, PH Brandt, RD Steinwand, DJ TI The color of Mars: Spectrophotometric measurements at the Pathfinder landing site SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article AB We calculate the color of the Martian sky and surface directly using the absolute calibration of the Mars Pathfinder (MPF) lander camera, which was observed to be stable during the mission. The measured colors of the Martian sky and surface at the Pathfinder site are identical to the Viking sites, i.e., a predominantly yellowish brown color with only subtle variations. These colors are distributed continuously and fall into five overlapping groups with distinct average colors and unique spatial characteristics: shadowed soil, soil, soil/rock mixtures, rock, and sky. We report that the primary difference between the sky color and the color of the rocks is due to a difference in brightness. Measurements of the sky color show that the sky reddens away from the Sun and toward the horizon and that the sky color varies with time of day and is reddest at local noon. We present a true color picture of the Martian surface and color enhancement techniques that increase image saturation, maximize color discriminability while preserving hue, and eliminate brightness variations while preserving the chromaticity of the scene. Although Mars has long been called the "red" planet, quantitative measurements of the surface color from telescopic and surface observations indicate a light to moderate yellowish brown color. The Pathfinder camera measurements presented here support the claim that the red planet is not red but indeed yellowish brown. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Maki, JN (reprint author), CALTECH, Jet Prop Lab, MS 168-414,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 15 Z9 15 U1 0 U2 2 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 1999 VL 104 IS E4 BP 8781 EP 8794 DI 10.1029/98JE01767 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900021 ER PT J AU Johnson, JR Kirk, R Soderblom, LA Gaddis, L Reid, RJ Britt, DT Smith, P Lemmon, M Thomas, N Bell, JF Bridges, NT Anderson, R Herkenhoff, KE Maki, J Murchie, S Dummel, A Jaumann, R Trauthan, F Arnold, G AF Johnson, JR Kirk, R Soderblom, LA Gaddis, L Reid, RJ Britt, DT Smith, P Lemmon, M Thomas, N Bell, JF Bridges, NT Anderson, R Herkenhoff, KE Maki, J Murchie, S Dummel, A Jaumann, R Trauthan, F Arnold, G TI Preliminary results on photometric properties of materials at the Sagan Memorial Station, Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; OPPOSITION SURGE; SCATTERING PROPERTIES; SURFACE MATERIALS; ATMOSPHERIC DUST; IRON-OXIDES; VIKING; SOIL; PARTICLES; LANDER AB Reflectance measurements of selected rocks and soils over a wide range of illumination geometries obtained by the Imager for Mars Pathfinder (IMP) camera provide constraints on interpretations of the physical and mineralogical nature of geologic materials at the landing site. The data sets consist of (1) three small "photometric spot" subframed scenes, covering phase angles from 20 degrees to 150 degrees; (2) two image strips composed of three subframed images each, located along the antisunrise and antisunset lines (photometric equator), covering phase angles from similar to 0 degrees to 155 degrees; and (3) full-image scenes of the rock "Yogi," covering phase angles from 48 degrees to 100 degrees. Phase functions extracted from calibrated data exhibit a dominantly backscattering photometric function, consistent with the results from the Viking lander cameras. However, forward scattering behavior does appear at phase angles >140 degrees, particularly for the darker gray rock surfaces, Preliminary efforts using a Hapke scattering model are useful in comparing surface properties of different rock and soil types but are not well constrained, possibly due to the incomplete phase angle availability, uncertainties related to the photometric function of the calibration targets, and/or the competing effects of diffuse and direct lighting. Preliminary interpretations of the derived Hapke parameters suggest that (1) red rocks can be modeled as a mixture of gray rocks with a coating of bright and dark soil or dust, and (2) gray rocks have macroscopically smoother surfaces composed of microscopically homogeneous, clear materials with little internal scattering, which may imply a glass-like or varnished surface. C1 US Geol Survey, Branch Astrogeol, Flagstaff, AZ 86001 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Max Planck Inst Aeron, D-3411 Katlenburg Lindau, Germany. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Jet Prop Lab, Pasadena, CA 91103 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. DLR, Inst Planetary Explorat, D-12489 Berlin, Germany. RP Johnson, JR (reprint author), US Geol Survey, Branch Astrogeol, 2255 N Gemini Dr, Flagstaff, AZ 86001 USA. RI Lemmon, Mark/E-9983-2010; Murchie, Scott/E-8030-2015; Johnson, Jeffrey/F-3972-2015; Bridges, Nathan/D-6341-2016 OI Lemmon, Mark/0000-0002-4504-5136; Murchie, Scott/0000-0002-1616-8751; NR 72 TC 48 Z9 47 U1 2 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 1999 VL 104 IS E4 BP 8809 EP 8830 DI 10.1029/98JE02247 PG 22 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900023 ER PT J AU Lavoie, SK Green, WB Runkle, AJ Alexander, DA Andres, PM DeJong, EM Duxbury, ED Freda, DJ Gorjian, Z Hall, JR Hartman, FR Levoe, SR Lorre, JJ McAuley, JM Suzuki, S Woncik, PJ Wright, JR AF Lavoie, SK Green, WB Runkle, AJ Alexander, DA Andres, PM DeJong, EM Duxbury, ED Freda, DJ Gorjian, Z Hall, JR Hartman, FR Levoe, SR Lorre, JJ McAuley, JM Suzuki, S Woncik, PJ Wright, JR TI Processing and analysis of Mars Pathfinder science data at the Jet Propulsion Laboratory's Science Data Processing Systems Section SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article AB The Mars Pathfinder mission required new capabilities and adaptation of existing capabilities in order to support science analysis and flight operations requirements imposed by the in situ nature of the mission. The Science Data Processing Systems Section of the Jet Propulsion Laboratory was responsible for the design, development, and application of the system required to perform telemetry processing, distribution, and archiving of data from the four primary science instruments, and support of flight operations through production of automatically generated stereo and color mosaics, terrain visualizations, and animations. The system developed for Mars Pathfinder incorporated new capabilities in producing computer-generated color mosaics, for cataloging and distribution of science data, and utilized new display technology to support science analysis and flight operations requirements. This paper describes the data processing performed to support the science and operations payload on the Pathfinder lander and Sojourner rover. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lavoie, SK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 4 Z9 4 U1 0 U2 2 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 1999 VL 104 IS E4 BP 8831 EP 8852 DI 10.1029/1998JE900014 PG 22 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900024 ER PT J AU Stoker, CR Zbinden, E Blackmon, TT Kanefsky, B Hagen, J Neveu, C Rasmussen, D Schwehr, K Sims, M AF Stoker, CR Zbinden, E Blackmon, TT Kanefsky, B Hagen, J Neveu, C Rasmussen, D Schwehr, K Sims, M TI Analyzing Pathfinder data using virtual reality and superresolved imaging SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID DIGITAL MAPS; MARS; VISUALIZATION; EXPLORATION AB The Mars Pathfinder mission used a unique capability to rapidly generate and interactively display three-dimensional (3-D) photorealistic virtual reality (VR) models of the Martian surface. An interactive terrain visualization system creates and renders digital terrain models produced from stereo images taken by the Imager for Mars Pathfinder (IMP) camera. The stereo pipeline, an automated machine vision algorithm, correlates features between the left and right images to determine their disparity and computes the corresponding positions using the known camera geometry. These positions are connected to form a polygonal mesh upon which IMP images are overlaid as textures. During the Pathfinder mission, VR models were produced and displayed almost as fast as images were received. The VR models were viewed using MarsMap, an interface that allows the model to be viewed from any perspective driven by a standard three-button computer mouse. MarsMap incorporates graphical representations of the lander and rover and the sequence and spatial locations at which rover data were taken. Graphical models of the rover were placed in the model to indicate the rover position at the end of each day of the mission. Images taken by Sojourner cameras are projected into the model as 2-D "billboards" to show their proper perspective. Distance and angle measurements can be made on features viewed in the model using a mouse-driven 3-D cursor and a point-and-click interface. MarsMap was used to assist with archiving and planning Sojourner activities and to make detailed measurements of surface features such as wind streaks and rock size and orientation that are difficult to perform using 2-D images. Superresolution image processing is a computational method for improving image resolution by a factor of 1/2 by combining n independent images. This technique was used on Pathfinder to obtain better resolved images of Martian surface features. We show results from superresolving IMP camera images of six targets including near- and far-field objects and discuss how the resolution improvement aids interpretation. Similar flood deposits can be seen on both of the Twin Peaks that cannot be resolved in raw images. Millimeter-sized pits are resolved on the rocks Wedge and Halfdome. Other rocks at the Pathfinder site exhibit fine-scale layering that is otherwise invisible. Use of the method resulted in the probable discovery of an artifact of intelligent life on Mars: a part of the Pathfinder spacecraft. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Stoker, CR (reprint author), NASA, Ames Res Ctr, M5 245-3, Moffett Field, CA 94035 USA. EM cstokes@mail.arc.nasa.gov NR 47 TC 19 Z9 19 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD APR 25 PY 1999 VL 104 IS E4 BP 8889 EP 8906 DI 10.1029/1998JE900019 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900027 ER PT J AU Reid, RJ Smith, PH Lemmon, M Tanner, R Burkland, M Wegryn, E Weinberg, J Marcialis, R Britt, DT Thomas, N Kramm, R Dummel, A Crowe, D Bos, BJ Bell, JF Rueffer, P Gliem, F Johnson, JR Maki, JN Herkenhoff, KE Singer, RB AF Reid, RJ Smith, PH Lemmon, M Tanner, R Burkland, M Wegryn, E Weinberg, J Marcialis, R Britt, DT Thomas, N Kramm, R Dummel, A Crowe, D Bos, BJ Bell, JF Rueffer, P Gliem, F Johnson, JR Maki, JN Herkenhoff, KE Singer, RB TI Imager for Mars Pathfinder (IMP) image calibration SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article AB The Imager for Mars Pathfinder returned over 16,000 high-quality images from the surface of Mars. The camera was well-calibrated in the laboratory, with <5% radiometric uncertainty. The photometric properties of two radiometric targets were also measured with 3% uncertainty. Several data sets acquired during the cruise and on Mars confirm that the system operated nominally throughout the course of the mission. Image calibration algorithms were developed for landed operations to correct instrumental sources of noise and to calibrate images relative to observations of the radiometric targets. The uncertainties associated with these algorithms as well as current improvements to image calibration are discussed. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Max Planck Inst Aeron, Kathenburg Lindau, Germany. DLR, Inst Planetary Explorat, Berlin, Germany. Univ Arizona, Ctr Opt Sci, Tucson, AZ 85721 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Tech Univ Braunschweig, D-3300 Braunschweig, Germany. US Geol Survey, Flagstaff, AZ 86001 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Dept Min & Geol Engn, Tucson, AZ 85721 USA. RP Reid, RJ (reprint author), Univ Arizona, Lunar & Planetary Lab, POB 210092,1629 E Univ Blvd, Tucson, AZ 85721 USA. RI Lemmon, Mark/E-9983-2010; Johnson, Jeffrey/F-3972-2015 OI Lemmon, Mark/0000-0002-4504-5136; NR 18 TC 43 Z9 44 U1 0 U2 2 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 1999 VL 104 IS E4 BP 8907 EP 8925 DI 10.1029/1998JE900011 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900028 ER PT J AU Oberst, J Jaumann, R Zeitler, W Hauber, E Kuschel, M Parker, T Golombek, M Malin, M Soderblom, L AF Oberst, J Jaumann, R Zeitler, W Hauber, E Kuschel, M Parker, T Golombek, M Malin, M Soderblom, L TI Photogrammetric analysis of horizon panoramas: The Pathfinder landing site in Viking orbiter images SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARS PATHFINDER AB Tiepoint measurements, block adjustment techniques, and sunrise/sunset pictures were used to obtain precise pointing data with respect to north for a set of 33 IMP horizon images. Azimuth angles for five prominent topographic features seen at the horizon were measured and correlated with locations of these features in Viking orbiter images. Based on this analysis, the Pathfinder line/sample coordinates in two raw Viking images were determined with approximate errors of 1 pixel, or 40 m. Identification of the Pathfinder location in orbit imagery yields geological context for surface studies of the landing site. Furthermore, the precise determination of coordinates in images together with the known planet-fixed coordinates of the lander make the Pathfinder landing site the most important anchor point in current control point networks of Mars. C1 DLR, Inst Planetary Explorat, D-12489 Berlin, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Malin Space Sci Syst, San Diego, CA 92121 USA. US Geol Survey, Flagstaff, AZ 86001 USA. RP Oberst, J (reprint author), DLR, Inst Planetary Explorat, Rudower Chaussee 5, D-12489 Berlin, Germany. NR 6 TC 9 Z9 9 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 1999 VL 104 IS E4 BP 8927 EP 8933 DI 10.1029/98JE01429 PG 7 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900029 ER PT J AU Magalhaes, JA Schofield, JT Seiff, A AF Magalhaes, JA Schofield, JT Seiff, A TI Results of the Mars Pathfinder atmospheric structure investigation SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GENERAL-CIRCULATION MODEL; MARTIAN ATMOSPHERE; VERTICAL STRUCTURE; DUST; CLOUDS; LANDER; PREDICTIONS; SIMULATION; DYNAMICS AB We report on a thorough analysis of the Mars Pathfinder atmospheric structure investigation (ASI) accelerometer data spanning the altitude range 161-8.9 km. Entry, descent, and landing occurred within 850 km of the Viking 1 lander and somewhat later in northern summer. The early morning entry (0300 hours) provided the first opportunity to study Mars' nighttime atmospheric structure; the close proximity to the Viking 1 site has permitted a search for changes in atmospheric structure during the 21 years between the landings. Our results confirm and refine the major features of the atmospheric structure discovered in the initial analysis of the ASI results reported by Schofield et al. [1997]. The current analysis has yielded a much better definition of the temperature structure above 90 km altitude. Pathfinder measured a thermospheric peak temperature of 153 degrees K at 134 km, which is 30 degrees K colder than the value found by Viking 1. Between 110 and 88 km, Pathfinder found a broad, nearly isothermal plateau at 127 degrees K, which correlates very well with a similar structure evident in Viking 1 data at the same pressures, although the Pathfinder layer is 25 degrees K colder. At levels above 88 km, wavelike oscillations with a wavelength similar to 5 km and amplitudes of 2-3 degrees K are evident, possibly reflecting gravity or planetary wave activity. Between 90 and 60 km the average temperature is 20-30 degrees K cooler than Viking 1 values. Large-amplitude (10-20 degrees K) long-wavelength (20-40 km) oscillations, which show a remarkable correspondence to equivalent structures found in the Viking 1 profile at the same pressures, occur in this region and are likely due to a diurnal tidal mode. Between 85 and 77 km a minimum of one oscillation results in temperatures up to 7 degrees K below the saturation temperature of CO2, well outside the uncertainties in the measurements and the vapor pressure curve and comparable to observed supersaturations of water in Earth's mesosphere. Between 55 and 16 km, temperatures are close to or warmer than Viking 1 values; superposed long-wavelength oscillations correspond well with similar structures observed by Viking 1. Between 16 and 9.9 km the temperature profile shows; an unexpected strong thermal inversion, which may reflect radiative cooling due to a water cloud. At the base of the inversion, temperatures begin to increase abruptly until the last measurement at 8.9 km. The Viking-like temperatures in the lower atmosphere are consistent with the Viking-like dust optical depths observed by the Mars Pathfinder imager. The cool temperatures in the middle and upper atmosphere may be indicative of significant nighttime cooling at these levels, although other interpretations are possible. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. San Jose State Univ Fdn, San Jose, CA USA. RP Magalhaes, JA (reprint author), NASA, Ames Res Ctr, Div Space Sci, Mail Stop 245-3, Moffett Field, CA 94035 USA. NR 54 TC 88 Z9 88 U1 0 U2 16 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 1999 VL 104 IS E4 BP 8943 EP 8955 DI 10.1029/1998JE900041 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900031 ER PT J AU Haberle, RM Joshi, MM Murphy, JR Barnes, JR Schofield, JT Wilson, G Lopez-Valverde, M Hollingsworth, JL Bridger, AFC Schaeffer, J AF Haberle, RM Joshi, MM Murphy, JR Barnes, JR Schofield, JT Wilson, G Lopez-Valverde, M Hollingsworth, JL Bridger, AFC Schaeffer, J TI General circulation model simulations of the Mars Pathfinder atmospheric structure investigation/meteorology data SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID GLOBAL DUST STORMS; MARTIAN ATMOSPHERE; SURFACE PRESSURE; THERMAL INERTIA; LANDER; TIDES; SITE; BUDGET AB The NASA Ames Mars General Circulation Model is used to interpret selected results from the Mars Pathfinder atmospheric structure instrument/meteorology (ASI/MET) experiment. The present version of the model has an improved soil thermal model, a new boundary layer scheme, and a correction for non-local thermodynamic equilibrium effects at solar wavelengths. We find good agreement with the ASI/MET entry data if the dust observed at the Pathfinder site is assumed to be distributed throughout the lowest five to six scale heights. This implies that the dust is globally distributed as well. In the lower atmosphere the inversion between 10 and 16 km in Pathfinder's entry profile is likely due to thermal emission from a water ice cloud in that region. In the upper atmosphere (above 50 km), dynamical processes, tides in particular, appear to have a cooling effect and may play an important role in driving temperatures toward the CO2 condensation temperature near 80 km. Near-surface air temperatures and wind directions are well simulated by the model by assuming a low surface albedo (0.16) and moderately high soil thermal inertia (336 SI). However, modeled tidal surface pressure amplitudes are about a factor of 2 smaller than observed. This may indicate that the model is not properly simulating interference effects between eastward and westward modes. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. San Jose State Univ, Dept Meteorol, San Jose, CA 95192 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Inst Astrofis Andalucia, E-18080 Granada, Spain. San Jose State Univ Fdn, San Jose, CA 95192 USA. Sterling Software, Palo Alto, CA USA. RP Haberle, RM (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. RI Joshi, Manoj/C-1795-2008; OI Joshi, Manoj/0000-0002-2948-2811; Lopez-Valverde, M. A./0000-0002-7989-4267 NR 38 TC 146 Z9 147 U1 0 U2 8 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 1999 VL 104 IS E4 BP 8957 EP 8974 DI 10.1029/1998JE900040 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900032 ER PT J AU Colaprete, A Toon, OB Magalhaes, JA AF Colaprete, A Toon, OB Magalhaes, JA TI Cloud formation under Mars Pathfinder conditions SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID WATER-VAPOR; ICE CLOUDS; ATMOSPHERE; CYCLE; ABSORPTION; DUST AB Temperature data taken during the Mars Pathfinder entry are applied to a time dependent microphysical model of cloud formation. Our goal is to reproduce the characteristics of clouds observed at the Pathfinder site. We assume that the total water column abundance is 11 percipitable microns. We also assume that the atmospheric dust initially has a lognormal size distribution with a modal radius of 0.6 mu m, r(eff) = 15 mu m, and an optical depth of tau = 0.5. Three temperature profiles are used in the model calculations. The first is the Pathfinder entry observation. The second is this same profile but with the inversion at 10 km removed. The third simulation uses the temperature profiles calculated by the Ames Mars general circulation model for Mars Pathfinder conditions. In all cases clouds form at altitudes of 35-45 km. In addition lower thicker clouds form within the 10 km inversion Of the unaltered profile, while peak cloud formation occurred near local noon at 20 km for the GCM calculated profiles. Given a combination of all three temperature scenarios, cloud optical depths, particle sizes, and colors are consistent with IMP observations. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Colaprete, A (reprint author), Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA. NR 19 TC 33 Z9 33 U1 0 U2 5 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 1999 VL 104 IS E4 BP 9043 EP 9053 DI 10.1029/1998JE900018 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900038 ER PT J AU Thomas, N Britt, DT Herkenhoff, KE Murchie, SL Semenov, B Keller, HU Smith, PH AF Thomas, N Britt, DT Herkenhoff, KE Murchie, SL Semenov, B Keller, HU Smith, PH TI Observations of Phobos, Deimos, and bright stars with the Imager for Mars Pathfinder SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARTIAN ATMOSPHERE; SURFACE; HETEROGENEITY; ASTEROIDS; HAZES AB The Imager for Mars Pathfinder (IMP) was used to observe several objects during the Martian night. The satellites, Phobos and Deimos, were observed on two occasions each, through the IMP geological filters covering the wavelength range 440 nm to 1 mu m. The observations were converted to geometric albedo using triaxial ellipsoid models of the satellites and phase functions derived from Viking Orbiter images. The spectral slopes over the full wavelength range were 7.9(+/-0.5)% (100 nm)(-1) and 9.6(+/-0.6)% (100 nm)(-1), respectively referenced to 600 nm. In the Deimos spectra, some evidence for decreased reddening toward the trailing hemisphere was found. The geometric albedoes of Phobos and Deimos were found to be 0.065 (+/-0.010) and 0.068 (+/-0.009), respectively, averaged over 440 and 600 nm, in good agreement with previous measurements. The nighttime optical depth was investigated using observations of stars. A mean value of 0.56 (+/-0.09) was determined from measurements at different airmass. A possible maximum in the optical depth near 0200 local time was found, which may result from condensation during the night. A measurement of the egress of Phobos from eclipse was made. Modeling of the light curve gave a scale height for the scatterers of 10-15 km. The exact time of the eclipse reappearance over the limb could be reconstructed from the measurements and was in reasonable accord with predictions, although a small modification to the predicted position of Phobos of 6.8 (+/-6.0) km would have produced better agreement. C1 Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Jet Prop Lab, Pasadena, CA 91103 USA. Johns Hopkins Univ, Appl Phys Lab, Baltimore, MD 21218 USA. RP Thomas, N (reprint author), Max Planck Inst Aeron, Max Planck Str 2, D-37191 Katlenburg Lindau, Germany. RI Murchie, Scott/E-8030-2015 OI Murchie, Scott/0000-0002-1616-8751 NR 30 TC 16 Z9 16 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 1999 VL 104 IS E4 BP 9055 EP 9068 DI 10.1029/98JE02555 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900039 ER PT J AU Murchie, S Thomas, N Britt, D Herkenhoff, K Bell, JF AF Murchie, S Thomas, N Britt, D Herkenhoff, K Bell, JF TI Mars Pathfinder spectral measurements of Phobos and Deimos: Comparison with previous data SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SOLAR-SYSTEM; SURFACE; PHOTOMETRY; IMAGES; HETEROGENEITY; 253-MATHILDE; BODIES AB The Imager for Mars Pathfinder (IMP) acquired four spectra of parts of the sub-Mars hemispheres of Phobos and Deimos. The measured region of Phobos is expected to be a mixture of the two spectral units identified on that satellite from Phobos 2 data, and the IMP spectra of Phobos are intermediate to the two units as expected. The derived geometric albedo is consistent with the value for that part of Phobos determined from Viking imagery. The IMP spectrum of Deimos is generally consistent with previous measurements acquired from the ground and from the Hubble Space Telescope (HST), but the signal-to-noise ratio is lower than that of the Phobos data. The spectral contrast between the two moons is similar to that seen in HST and Phobos 2 data. Mars Pathfinder measurements therefore substantiate recent results which indicate that Phobos and Deimos are not, as previously believed, analogous to C-type asteroids. They also provide some indications for an absorption near 700 nn, perhaps like that seen in other low-albedo asteroids. Both Martian moons are redder than most asteroids, and most closely resemble two analog materials believed to have undergone very dissimilar histories: primitive D-like asteroids, and highly space-weathered, mafic-rich assemblages, such as are present in lunar mare soils. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. RP Murchie, S (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI Murchie, Scott/E-8030-2015 OI Murchie, Scott/0000-0002-1616-8751 NR 31 TC 22 Z9 22 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 1999 VL 104 IS E4 BP 9069 EP 9079 DI 10.1029/98JE02248 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900040 ER PT J AU Bills, BG James, TS AF Bills, BG James, TS TI Moments of inertia and rotational stability of Mars: Lithospheric support of subhydrostatic rotational flattening SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID VISCOELASTIC EARTH; INTERIOR STRUCTURE; CHAOTIC OBLIQUITY; GROUND ICE; CORE; THARSIS; PRECESSION; THICKNESS; MANTLE; MOTION AB A revised estimate of the spin axis precession rate of Mars has recently been obtained via analysis of range and range-rate data from the Viking and Pathfinder landers. When combined with existing estimates of the degree 2 spherical harmonic coefficients of the gravitational field, this yields a complete determination of the inertia tensor of Mars. Despite this progress, there are still numerous unresolved issues related to the internal structure and rotational dynamics of Mars. We compare results of two different approaches to this problem. In one approach, the observed gravitational field is conceptually partitioned into hydrostatic and nonhydrostatic contributions. In the other approach, the input to the system is partitioned into rotational and load components, and the internal structure (density and elastic rigidity) determines the response. We demonstrate that there is an important, and still unresolved trade-off between lithospheric thickness and the shape of the load component of the gravity field. As the lithospheric thickness is increased, the required load departs more from axial symmetry. The load corresponding to zero lithospheric thickness is nearly symmetric about an equatorial axis, but if the lithospheric thickness is closer to 100 km, the required load is a fully triaxial ellipsoid, with the intermediate moment of inertia halfway between the least and greatest moments. The symmetry of the load has considerable influence on the long-term rotational stability of Mars. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. Univ Calif San Diego, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. Geol Survey Canada, Pacific Geosci Ctr, Sidney, BC V8L 4B2, Canada. RP Bills, BG (reprint author), Scripps Inst Oceanog, Inst Geophys & Planetary Phys, La Jolla, CA 92093 USA. RI Bills, Bruce/C-1156-2008; James, Thomas/D-9301-2013 OI James, Thomas/0000-0001-7321-047X NR 67 TC 16 Z9 16 U1 1 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 1999 VL 104 IS E4 BP 9081 EP 9096 DI 10.1029/1998JE900003 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 188FV UT WOS:000079836900041 ER PT J AU Nesbitt, FL Gleason, JF Stief, LJ AF Nesbitt, FL Gleason, JF Stief, LJ TI Temperature dependence of the rate constant for the reaction HCO+O-2 -> HO2+CO at T = 200-398 K SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAS-PHASE REACTION; LASER PHOTOLYSIS; AB-INITIO; CL ATOMS; KINETICS; FORMYL; O-2; HCO; RADICALS; CHLORINE AB The absolute rate constant for the reaction HCO + O-2 has been measured dyer the temperature range T = 200-398 K in a discharge flow system at a pressure of 1 Torr (He); This study represents the first measurement of:this rate constant at temperatures below T = 298 K. The decay of the HCO radical in the presence of excess Oz was followed by collision-free sampling photoionization mass spectrometry. The results were as follows: k(1)(200 K) = 5.3 +/- 0.8, k(1)(222 K) = 4.8 +/- 0.7, k(1)(250 K) = 4.4 +/- 0.6, k(1)(298 K) = 4.0 +/- 0.6, k(1)(398 K) = 4.5 +/- 0.7 in units 10(-12) cm(3) molecule(-1) s(-1). Over the range T = 200-298 K, the data suggest a slight negative temperature dependence and may be represented by the Arrhenius expression k(1) = (2.2 +/- 0.2) x 10(-12) exp[(170 +/- 22)/T] cm(3) molecule(-1) s(-1). For the related reaction HCO + NO at T = 298 K we measure k(2) = (1.3 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1). The results are compared with previous direct measurements of k(1) and k(2) and with recent theoretical calculations. For the HCO + O-2 reaction there are larger than expected differences between the measured values for what appears to be a relatively simple and well studied reaction. A recent theoretical expression for k(1), recommended for the region T = 300-3000 K, can be made to be in reasonable agreement with most of the results from direct, temperature-dependent studies between T = 200-713 K by an extrapolation to T = 200 K and by multiplying the theoretical expression by a minor uniform scaling factor of 0.80. Our result for HCO + NO at T = 298 K is in excellent agreement with all except one of the previous measurements of this rate constant. C1 Coppin State Coll, Dept Nat Sci, Baltimore, MD 21216 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Stief, LJ (reprint author), Coppin State Coll, Dept Nat Sci, Baltimore, MD 21216 USA. RI Gleason, James/E-1421-2012 NR 33 TC 31 Z9 32 U1 0 U2 16 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD APR 22 PY 1999 VL 103 IS 16 BP 3038 EP 3043 DI 10.1021/jp984781q PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 189YK UT WOS:000079933700019 ER PT J AU Iollo, A Salas, MD AF Iollo, A Salas, MD TI On the propagation of small perturbations in two simple aeroelastic systems SO JOURNAL OF SOUND AND VIBRATION LA English DT Letter C1 NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. RP Iollo, A (reprint author), NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. NR 5 TC 0 Z9 0 U1 1 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD APR 22 PY 1999 VL 222 IS 1 BP 152 EP 162 DI 10.1006/jsvi.1998.2824 PG 11 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 188RN UT WOS:000079862400009 ER PT J AU Lissauer, JJ AF Lissauer, JJ TI Three planets for upsilon Andromedae SO NATURE LA English DT Editorial Material C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Lissauer, JJ (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. NR 6 TC 25 Z9 25 U1 0 U2 0 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 22 PY 1999 VL 398 IS 6729 BP 659 EP 660 DI 10.1038/19409 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 189RP UT WOS:000079920100021 ER PT J AU Barlow, S Bunting, HE Ringham, C Green, JC Bublitz, GU Boxer, SG Perry, JW Marder, SR AF Barlow, S Bunting, HE Ringham, C Green, JC Bublitz, GU Boxer, SG Perry, JW Marder, SR TI Studies of the electronic structure of metallocene-based second-order nonlinear optical dyes SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID CYCLIC VOLTAMMETRY; QUADRATIC HYPERPOLARIZABILITIES; HETEROCYCLIC ACCEPTORS; PHOTOELECTRON-SPECTRA; CONJUGATED FERROCENE; CRYSTAL-STRUCTURE; CHROMOPHORES; DERIVATIVES; COMPLEXES; DONOR AB This paper describes a simple orbital picture for understanding the optical transitions and the second-order nonlinear optical response of metallocene-based chromophores of the form metallocene-(pi-bridge)-acceptor, and experimental studies to test this model. From a combination of UV photoelectron spectroscopy, cyclic voltammetry, and density functional calculations, it is deduced that the three highest occupied orbitals are little perturbed from the parent metallocenes, that the HOMO-3 is a pi-orbital delocalized between the metallocene cyclopentadienyl ring and the unsaturated bridge, and that the LUMO is acceptor based. The lowest energy transition in the UV/visible/near-IR spectra of these compounds is assigned to a metal-to-acceptor transition, while the higher energy transition is attributed to a transition to the acceptor-based LUMO from the delocalized HOMO-3 orbital. The variations in oscillator strength can be rationalized by considering the low-energy transition as borrowing intensity from the high-energy transition. Stark spectroscopy confirms that large dipole moment changes are associated with both transitions, as expected from our assignment. These dipole moment changes indicate that, according to the perturbation theory-derived expression for the first hyperpolarizability, beta, both transitions contribute significantly to the observed optical nonlinearity. C1 CALTECH, Beckman Inst 139 74, Pasadena, CA 91125 USA. Univ Oxford, Inorgan Chem Lab, Oxford OX1 3QR, England. Stanford Univ, Dept Chem, Stanford, CA 94305 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. RP Marder, SR (reprint author), CALTECH, Beckman Inst 139 74, Pasadena, CA 91125 USA. RI Perry, Joseph/B-7191-2011; Barlow, Stephen/E-9754-2010 OI Perry, Joseph/0000-0003-1101-7337; NR 46 TC 236 Z9 242 U1 4 U2 44 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 21 PY 1999 VL 121 IS 15 BP 3715 EP 3723 DI 10.1021/ja9830896 PG 9 WC Chemistry, Multidisciplinary SC Chemistry GA 189YV UT WOS:000079934900017 ER PT J AU Gould, RW Arnone, RA Martinolich, PM AF Gould, RW Arnone, RA Martinolich, PM TI Spectral dependence of the scattering coefficient in case 1 and case 2 waters SO APPLIED OPTICS LA English DT Article ID REMOTE-SENSING REFLECTANCE; OPTICAL-EFFICIENCY FACTORS; OCEANIC WATERS; ABSORPTION-COEFFICIENT; NATURAL-WATERS; PARTICULATE; MATTER; LIGHT; COLOR; NM AB An approximate linear relationship between the scattering coefficient and the wavelength of light in the visible is found in case 1 and case 2 waters. From this relationship, we estimate scattering at an unknown wavelength from scattering at a single measured wavelength. This approximation is based on measurements in a 1.5-m-thick surface layer collected with an AC9 instrument at 63 stations in the Arabian Sea, northern Gulf of Mexico, and coastal North Carolina. The light-scattering coefficient at 412 nm ranged from 0.2 to 15.1 m(-1) in these waters, and the absorption coefficient at 412 nm ranged from 0.2 to 4.0 m(-1). A separate data set for 100 stations from Oceanside, California, and Chesapeake Bay, Virginia, was used to validate the relationship. Although the Oceanside waters were considerably different from the developmental data set (based on absorption-to-scattering ratios and single-scattering albedos), the average error between modeled and measured scattering values was 6.0% for the entire test data set over all wavelengths (without regard to sign). The slope of the spectral scattering relationship decreases progressively from high-scattering, turbid waters dominated by suspended sediments to lower-scattering, clear waters dominated by phytoplankton. (C) 1999 Optical Society of America. C1 Stennis Space Ctr, Naval Res Lab, Remote Sensing Applicat Branch, Mississippi State, MS 39529 USA. Neptune Sci Incorp, Slidell, LA 70458 USA. RP Gould, RW (reprint author), Stennis Space Ctr, Naval Res Lab, Remote Sensing Applicat Branch, Code 7343, Mississippi State, MS 39529 USA. EM gould@csips.nrlssc.navy.mil NR 28 TC 81 Z9 89 U1 0 U2 8 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 20 PY 1999 VL 38 IS 12 BP 2377 EP 2383 DI 10.1364/AO.38.002377 PG 7 WC Optics SC Optics GA 186JJ UT WOS:000079725400007 PM 18319803 ER PT J AU D'Sa, EJ Lohrenz, SE AF D'Sa, EJ Lohrenz, SE TI Theoretical treatment of fluorescence detection by a dual-fiber-optic sensor with consideration of sampling variability and package effects associated with particles SO APPLIED OPTICS LA English DT Article ID CHLOROPHYLL-A FLUORESCENCE; ABSORPTION-SPECTRA; LIGHT-ABSORPTION; PHYTOPLANKTON; PHOTOSYNTHESIS; BOUNDARY; OCEAN AB The characteristics of a dual-fiber-optic sensor for measurements of chlorophyll fluorescence in aquatic environments were evaluated with a theoretical model. Consideration was given to sampling variability and package effects associated with particles (e.g., phytoplankton cells). A numerical simulation was developed to approximate the optical geometry of the dual fiber-optic sensor that permitted a visual representation of the fluorescence distribution within the sensor sampling volume. A Monte Carlo simulation was used to evaluate sampling variability associated with the number and distribution of particles within the sampling volume. Relatively high coefficients of variation were associated with low particle concentrations, although with sufficient signal averaging the coefficient of variation was reduced to less than 20%. The influence of package effects and intracellular absorption of fluorescence was evaluated with a simplified form of the model that treated fluorescence as a linear function of particle density and assumed uniform particle composition, constant fluorescence cross-sectional yield, and sufficient averaging of the fluorescence signal. The model predicted decreasing fluorescence per unit of chlorophyll with increasing values of the product of particle diameter and intraparticle chlorophyll concentration. Experimental trends in size dependence of chlorophyll-fluorescence relationships were compared with predictions of the model. (C) 1999 Optical Society of America. C1 Univ So Mississippi, Stennis Space Ctr, Dept Marine Sci, Mississippi State, MS 39529 USA. RP D'Sa, EJ (reprint author), Natl Ocean & Atmospher Adm, Natl Environm Satellite Data & Informat Serv, Off Res & Applicat, E-RA3,Rm 711,5200 Auth Rd, Camp Springs, MD 20746 USA. EM edsa@nesdis.noaa.gov; steven.lohrenz@usm.edu OI Lohrenz, Steven/0000-0003-3811-2975 NR 30 TC 8 Z9 9 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 20 PY 1999 VL 38 IS 12 BP 2524 EP 2535 DI 10.1364/AO.38.002524 PG 12 WC Optics SC Optics GA 186JJ UT WOS:000079725400026 PM 18319822 ER PT J AU Field, CT Millar, PS AF Field, CT Millar, PS TI Laser remote-sensing system analysis for search and rescue SO APPLIED OPTICS LA English DT Article ID STATE DYE-LASER; HOST; ELEMENTS AB We develop a general model of a laser remote-sensing system for search and rescue using targets marked with fluorescent dye. The dye fluoresces at a longer peak wavelength than the incident radiation, enabling a dye-covered target to be distinguished from the unshifted ground echo by the search system. The principal result is a simple expression derived for the average laser power required to search at a particular rate given a required ground energy density. A similar expression is applicable to imaging lidar systems. The example system shown indicates that active probing for lost planes may be practical. C1 USN Acad, Dept Elect Engn, Annapolis, MD 21402 USA. NASA, Goddard Space Flight Ctr, Laser Remote Sensing Branch, Greenbelt, MD 20771 USA. RP Field, CT (reprint author), USN Acad, Dept Elect Engn, Annapolis, MD 21402 USA. EM Pamela.S.Millar.l@gsfc.nasa.gov RI Millar, Pamela/B-4426-2013 NR 22 TC 2 Z9 2 U1 1 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 20 PY 1999 VL 38 IS 12 BP 2586 EP 2593 DI 10.1364/AO.38.002586 PG 8 WC Optics SC Optics GA 186JJ UT WOS:000079725400035 PM 18319831 ER PT J AU Whiteman, DN Walrafen, GE Yang, WH Melfi, SH AF Whiteman, DN Walrafen, GE Yang, WH Melfi, SH TI Measurement of an isosbestic point in the Raman spectrum of liquid water by use of a backscattering geometry SO APPLIED OPTICS LA English DT Article ID MICROPARTICLES; SCATTERING; ATMOSPHERE AB Measurements presented here confirm that a temperature-insensitive point occurs in the backscattered Raman spectrum from liquid water. This result, coupled with existing laboratory measurements of Raman scattering from liquid droplets, indicates that a Raman lidar measurement of cloud liquid water is feasible. (C) 1999 Optical Society of America. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Howard Univ, Dept Chem, Washington, DC 20059 USA. Univ Maryland Baltimore Cty, Dept Phys, Baltimore, MD 21250 USA. RP Whiteman, DN (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM david.whiteman@gsfc.nasa.gov NR 8 TC 17 Z9 17 U1 3 U2 7 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 20 PY 1999 VL 38 IS 12 BP 2614 EP 2615 DI 10.1364/AO.38.002614 PG 2 WC Optics SC Optics GA 186JJ UT WOS:000079725400038 PM 18319834 ER PT J AU Hurley, K Hartmann, DH Kouveliotou, C Kippen, RM Laros, J Cline, T Boer, M AF Hurley, K Hartmann, DH Kouveliotou, C Kippen, RM Laros, J Cline, T Boer, M TI No evidence for gamma-ray burst Abell cluster or gamma-ray burst/radio-quiet quasar correlations SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : clusters : general; gamma rays : bursts; quasars : general ID GALAXIES; REDSHIFT; ULYSSES AB We examine the recent claims that cosmic gamma-ray bursts are associated with either radio-quiet quasars or Abell clusters. These associations were based on positional coincidences between cataloged quasars or Abell clusters and selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger sample of gamma-ray bursts with more accurate positions, obtained by the Third Interplanetary Network, to reevaluate these possible associations. We find no evidence for either. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. Univ Space Res Assoc, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CESR, F-31029 Toulouse, France. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. OI Boer, Michel/0000-0001-9157-4349 NR 20 TC 1 Z9 1 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1999 VL 515 IS 2 BP 497 EP 499 DI 10.1086/307045 PN 1 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 200EW UT WOS:000080527500005 ER PT J AU Storzer, H Hollenbach, D AF Storzer, H Hollenbach, D TI Photodissociation region models of photoevaporating circumstellar disks and application to the proplyds in Orion SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; ISM : clouds; ISM : individual (Orion Nebula); line : formation; stars : formation ID TRAPEZIUM CLUSTER; LINE EMISSION; NEBULA; DISSOCIATION; OBJECTS; SHOCKS; IMAGES; GAS AB We have modeled the neutral flows emerging from circumstellar disks or small clumps of size r(0) illuminated by an external source of ultraviolet radiation. The models are applied to the disks (proplyds) in the Orion Nebula, most of which are illuminated by theta(1)C Ori. Our models improve upon the simpler models of Johnstone, Hollenbach, & Ballyby including the results of both equilibrium and nonequilibrium photodissociation region (PDR) codes, and by treating the flow speed off the disk surface in a more consistent manner. We present a study that delineates the parameter space (G(0), r(0), and sigma(ext)) in which far-ultraviolet (FUV)-dominated, as opposed to extreme-ultraviolet (EUV)-dominated, flows exist. G(0) is the FUV (6 eV < hv < 13.6 eV) flux (in units of the local average interstellar flux) incident on the neutral how at the ionization front (IF), and sigma(ext) is the dust FUV extinction cross section per H nucleus in the flow region. FUV-dominated flows are extended with sizes of the IF r(IF) greater than or similar to 2r(0), have a shock between the disk surface and IF, and the mass-loss rates are determined by FUV photons. For sigma(ext) = 8 x 10(-22) cm(2) and a UV source similar to theta(1) C Ori, the FUV-dominated region extends from G(0) approximate to 5 x 10(4) to G(0) approximate to 2 x 10(7) (or distances from theta(1) C Ori of 0.3-0.01 pc), for disk or clump size of r(0) approximate to 10(14)-10(15) cm. Outside this parameter space, hydrogen-ionizing EUV photons dominate the photoevaporation, and the IF is close to the disk surface (r(IF) less than or equal to 2r(0)). We show that FUV-dominated flows can explain the observed sizes of the ionization fronts around many of the photoevaporating disks in Orion. The size of the neutral flow region, I-IF, depends mainly on r(0), G(0), and sigma(ext) inside the flow region. Using ten objects in Orion for which both r(0) and r(IF) are directly observed, and for which G(0) can be estimated from the observed projected distance of the proplyd from theta(1)C Ori, we find that sigma(ext) approximate to 8 x 10(-22) cm(2) best fits the observations. In these models, the disk mass-loss rates are roughly 10(-7) M. yr(-1). We have determined the disk masses for circular and radial proplyd orbits. For circular orbits around theta(1)C Ori, the disk masses range between 0.005 and 0.04(t(i)/10(5) yr) M., where t(i) is the illumination timescale. Comparison with millimeter observations of the disk masses (less than or similar to 0.02 M.) indicate t(i) approximate to 10(5) yr, suggesting that theta(1)C Ori is a young (less than or similar to 10(5) yr old) O star in this scenario. The timescale for the disks to significantly lose mass and shrink is similar to 10(5) yr. If the disks cross the Trapezium cluster on radial orbits, the proplyd masses range between 0.002 and 0.01 M.. For radial orbits, the lifetime of the proplyds can be as large as the age of the Orion Cluster (similar to 1 Myr), and theta(1)C Ori can be significantly older than 10(5) yr. We have calculated the thermal and chemical structure of the flow region in the observationally best studied object HST 182-413 (HST 10) and the representative object HST 155-338. A region of atomic hydrogen extends from the IF toward the disk surface, but dose to the surface hydrogen becomes molecular. The temperatures inside the atomic layer are several thousand K. We have calculated the H-2 1-0 S(1) and the H-2 2-1 S(1) vibrational line intensities, the [C II] 158 mu m and [O I] 63 mu m fine-structure line intensities, and the [O I] 6300 Angstrom line intensity. We find good agreement between the observed H-2 1-0 S(1) line intensity and the theoretically predicted one. The models can also reproduce the [O I] 6300 Angstrom line emission observed dose to the disk surface in HST 182-413, HST 155-338, and the other proplyds where the disks can be resolved in the [O I] line. The other lines are not yet observed; we present them here as predictions for future observations. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Cologne, Inst Phys 1, D-50937 Cologne, Germany. RP Storzer, H (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 41 TC 131 Z9 131 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1999 VL 515 IS 2 BP 669 EP 684 DI 10.1086/307055 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 200EW UT WOS:000080527500022 ER PT J AU O'Linger, J Wolf-Chase, G Barsony, M Ward-Thompson, D AF O'Linger, J Wolf-Chase, G Barsony, M Ward-Thompson, D TI L1448 IRS 2: A HIRES-identified class 0 protostar SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; infrared : stars; stars : imaging; stars : individual (L1448 IRS 2); stars : pre-main-sequence ID YOUNG STELLAR OBJECTS; OPHIUCHI CLOUD CORE; MOLECULAR OUTFLOW; MILLIMETER OBSERVATIONS; CONTINUUM OBSERVATIONS; SPECTROSCOPIC EVIDENCE; IMAGE CONSTRUCTION; BIPOLAR OUTFLOW; LINE FORMATION; INFALL AB We present far-infrared and submillimeter images and millimeter-continuum photometry for L1448 IRS 2, a low-luminosity (5.2 L.), embedded young stellar object discovered by IRAS. New far-infrared maps were produced from the archival IRAS data via high-resolution (HIRES) processing, the name given to the implementation of the maximum correlation method for image construction from the IRAS data streams. The HIRES-processed images of L1448 IRS 2 presented here have effective resolutions of similar to 35 " x 28 ", similar to 35 " x 37 ", and similar to 45 " x 40 " at 25, 60, and 100 mu m, respectively, which represent an order of magnitude improvement over previously available far-infrared maps. L1448 IRS 2 was mapped at 450 and 850 mu m, and we acquired continuum photometry at 1.3 mm. With these new data, we plot the most complete spectral energy distribution for L1448 IRS 2 to date. We also present sensitive (CO)-C-12 J = 1 --> 0 emission-line maps of a 47' x 7' area of the L1448 dark cloud, centered on L1448 IRS 2, obtained with the on-the-fly imaging capability of the NRAO 12 m telescope. As a direct consequence of this mapping, we have discovered a parsec-scale molecular outflow associated with L1448 IRS 2. The combined continuum and molecular line data confirm the classification of L1448 IRS 2 as a new member of the rare, short-lived (a few x 10(4) yr), Class 0 phase of protostellar evolution. The use of HIRES imaging of IRAS data as a promising tool for identifying protostellar candidates is demonstrated by the example of L1448 IRS 2. C1 Univ Calif Riverside, Dept Phys, Riverside, CA 92521 USA. Univ Wales, Dept Phys & Astron, Cardiff CF2 3YB, S Glam, Wales. RP O'Linger, J (reprint author), CALTECH, Jet Prop Lab, IPAC MS 100-22,770 S Wilson, Pasadena, CA 91125 USA. NR 62 TC 28 Z9 28 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1999 VL 515 IS 2 BP 696 EP 705 DI 10.1086/307054 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 200EW UT WOS:000080527500024 ER PT J AU Aschwanden, MJ Newmark, JS Delaboudiniere, JP Neupert, WM Klimchuk, JA Gary, GA Portier-Fozzani, F Zucker, A AF Aschwanden, MJ Newmark, JS Delaboudiniere, JP Neupert, WM Klimchuk, JA Gary, GA Portier-Fozzani, F Zucker, A TI Three-dimensional stereoscopic analysis of solar active region loops. I. SOHO EIT observations at temperatures of (1.0-1.5) x 10(6) K SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun : activity; sun : corona; sun : UV radiation; techniques : image processing ID STRUCTURES OBSERVING CAMPAIGN; CORONAL DIAGNOSTIC SPECTROMETER; HIGH-RESOLUTION PHOTOGRAPHY; MAGNETIC-FIELDS; EXTREME-ULTRAVIOLET; TEMPORAL VARIATIONS; VLA STEREOSCOPY; SCALING LAW; RAY CORONA; PLASMA AB The three-dimensional structure of solar active region NOAA 7986 observed on 1996 August 30 with the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) is analyzed. We develop a new method of dynamic stereoscopy to reconstruct the three-dimensional geometry of dynamically changing loops, which allows us to determine the orientation of the mean loop plane with respect to the line of sight, a prerequisite to correct properly for projection effects in three-dimensional loop models. With this method and the filter-ratio technique applied to EIT 171 and 195 Angstrom images we determine the three-dimensional coordinates [x(s), y(s), z(s)], the loop width w(s), the electron density n(e)(s), and the electron temperature T-e(s) as a function of the loop length s for 30 loop segments. Fitting the loop densities with an exponential density model n(e)(h) we iind that the mean of inferred scale height temperatures, T-e(lambda) = 1.22 +/- 0.23 MK, matches closely that of EIT filter-ratio temperatures, T-e(EIT) = 1.21 +/- 0.06 MK. We conclude that these cool and rather large-scale loops (with heights of h approximate to 30-225 Mm) are in hydrostatic equilibrium. Most of the loops show no significant thickness variation w(s), but we measure for most of them a positive temperature gradient (dT/ds > 0) across the first scale height above the footpoint. Based on these temperature gradients we find that the conductive loss rate is about 2 orders of magnitude smaller than the radiative loss rate, which is in strong contrast to hot active region loops seen in soft X-rays. We infer a mean radiative loss time of tau(rad) approximate to 40 minutes at the loop base. Because thermal conduction is negligible in these cool EUV loops, they are nor in steady state, and radiative loss has entirely to be balanced by the heating function. A statistical heating model with recurrent heating events distributed along the entire loop can explain the observed temperature gradients if the mean recurrence time is less than or similar to 10 minutes. We computed also a potential field model (from SOHO/MDI magnetograms) and found a reasonable match with the traced EIT loops. With the magnetic field model we determined also the height dependence of the magnetic field B(h), the plasma parameter beta(h), and the Alfven velocity v(A)(h). No correlation was found between the heating rate requirement E-HO and the magnetic field B-foot at the loop footpoints. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Space Applicat Corp, Vienna, VA 22180 USA. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. Hughes STX Corp, Lanham, MD 20706 USA. USN, Res Lab, Div Space Sci, Washington, DC 20375 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Solar Phys Branch ES82, Huntsville, AL 35812 USA. CNRS, Astron Spatiale Lab, F-13376 Marseille 12, France. Swiss Fed Inst Technol, Inst Astron, CH-8092 Zurich, Switzerland. RP Lockheed Martin ATC, Solar & Astrophys Lab, Dept H1 12, Bldg 252,3251 Hanover St, Palo Alto, CA 94304 USA. EM markus@astro.umd.edu RI Klimchuk, James/D-1041-2012 OI Klimchuk, James/0000-0003-2255-0305 NR 77 TC 214 Z9 216 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1999 VL 515 IS 2 BP 842 EP 867 DI 10.1086/307036 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 200EW UT WOS:000080527500038 ER PT J AU Bezard, B Romani, PN Feuchtgruber, H Encrenaz, T AF Bezard, B Romani, PN Feuchtgruber, H Encrenaz, T TI Detection of the methyl radical on Neptune SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : solar system; planets and satellites : individual (Neptune) ID KINETIC DATA; TEMPERATURE; METHANE; RECOMBINATION; SPECTROMETER; OCCULTATION; DEPENDENCE; PRESSURE; CH3; NM AB We report the first detection of the methyl radical (CH3) in the upper atmosphere of Neptune. Observations with the Short-Wavelength Spectrometer of the Infrared Space Observatory (ISO) satellite at a resolving power of 2200 revealed several emission features from the v(2) Q-branch of CH3 around 16.50 mu m. The column density of methyl radicals above the 0.2 mbar level is 1.6(-0.9)(+1.2) x 10(13) molecules cm(-2) Results are compared with predictions of photochemical models. The CH3 abundance is mostly sensitive to the eddy mixing profile and to the poorly known methyl recombination rate at low pressure. Using Slagle et al.'s expression for this rate, the present observations imply an eddy mixing coefficient at the methane homopause in the range of 2-9 x 10(6) cm(2) s(-1) Recombination rates higher than used in current photochemical models would lead to larger eddy mixing coefficients. C1 Observ Paris, DESPA, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Bezard, B (reprint author), Observ Paris, DESPA, F-92195 Meudon, France. RI Romani, Paul/D-2729-2012 NR 22 TC 62 Z9 62 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 20 PY 1999 VL 515 IS 2 BP 868 EP 872 DI 10.1086/307070 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 200EW UT WOS:000080527500039 ER PT J AU Ibrahim, AH Tiwari, SN Smith, RE AF Ibrahim, AH Tiwari, SN Smith, RE TI Stability analysis and aerodynamic design optimization of Euler equations using variational methods SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE aerodynamics; design optimization; computational fluid dynamics; sensitivity analysis; stability analysis; variational methods ID DISTRIBUTED-PARAMETER-SYSTEMS; FLOW AB The one- and two-dimensional inviscid Euler equations ate formulated in an integro-differential form for shape design sensitivity analysis and optimization. The principal tool employed to derive the performance derivative sensitivity equations is the variational method, which is a continuous alternative to the discrete sensitivity analysis. Along with the sensitivity equations, the co-state equations and their boundary conditions are derived. Thereafter, based on the modal analysis of Von Neumann theory, the stability limits of the co-state equations are investigated. The stability characteristics of the co-state equations are compared with those of the Euler equations. Finally, using the criteria from the stability analysis of the state and co-state equations, some results of shape design optimization and sensitivity analysis for both quasi one- and two-dimensional Euler equations are presented. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 Old Dominion Univ, Dept Mech Engn, Norfolk, VA 23529 USA. Norfolk State Univ, Dept Phys & Elect Engn, Norfolk, VA USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Tiwari, SN (reprint author), Old Dominion Univ, Dept Mech Engn, 238 Kaufman Hall, Norfolk, VA 23529 USA. NR 28 TC 1 Z9 1 U1 0 U2 0 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 20 PY 1999 VL 44 IS 11 BP 1709 EP 1726 PG 18 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 179VE UT WOS:000079349500007 ER PT J AU Hintsa, EJ Weinstock, EM Anderson, JG May, RD Hurst, DF AF Hintsa, EJ Weinstock, EM Anderson, JG May, RD Hurst, DF TI On the accuracy of in situ water vapor measurements in the troposphere and lower stratosphere with the Harvard Lyman-alpha hygrometer SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID DIODE-LASER SPECTROMETER; HYDROGEN BUDGET; H2O; AIRCRAFT; DEHYDRATION; NIMBUS-7; ER-2; CH4 AB In an effort to better constrain atmospheric water vapor mixing ratios and to understand the discrepancies between different measurements of water vapor in the stratosphere and troposphere, we have carefully examined data from the Harvard Lyman-alpha photofragment fluorescence hygrometer, which has flown on the NASA ER-2 aircraft from 1992 through 1998. The instrument is calibrated in the laboratory before and after each deployment, and the calibration is checked by direct absorption measurements in the troposphere. On certain flights, the ER-2 flew level tracks during which water vapor varied by up to 80 ppmv, under nearly constant atmospheric conditions. These flights provide a stringent test of our calibration via direct absorption and indicate agreement to within 3%, During the 1997 Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) mission, our Lyman-alpha instrument was compared with a new diode laser hygrometer from the Jet Propulsion Laboratory. Overall agreement was 5% during the June/July deployment and 1% for potential temperatures of 490 to 540 K. The accuracy of our instrument is shown to be +/-5%, with an additional offset of at most 0.1 ppmv. Data from this instrument, combined with simultaneous measurements of CH4 and H-2, are therefore ideal for studies of the hydrogen budget of the lower stratosphere. C1 Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RP Hintsa, EJ (reprint author), Woods Hole Oceanog Inst, Dept Marine Chem & Geochem, Woods Hole, MA 02543 USA. RI Hurst, Dale/D-1554-2016 OI Hurst, Dale/0000-0002-6315-2322 NR 27 TC 51 Z9 51 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 20 PY 1999 VL 104 IS D7 BP 8183 EP 8189 DI 10.1029/1998JD100110 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 187NV UT WOS:000079793600012 ER PT J AU Hurst, DF Dutton, GS Romashkin, PA Wamsley, PR Moore, FL Elkins, JW Hintsa, EJ Weinstock, EM Herman, RL Moyer, EJ Scott, DC May, RD Webster, CR AF Hurst, DF Dutton, GS Romashkin, PA Wamsley, PR Moore, FL Elkins, JW Hintsa, EJ Weinstock, EM Herman, RL Moyer, EJ Scott, DC May, RD Webster, CR TI Closure of the total hydrogen budget of the northern extratropical lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID IN-SITU MEASUREMENTS; WATER-VAPOR; SEASONAL-VARIATIONS; H2O; WINTER; CH4; SPECTROMETER; TROPOSPHERE; DEHYDRATION; FOUNTAIN AB Methane (CH4), molecular hydrogen (H-2), and water vapor (H2O) were measured concurrently on board the NASA ER-2 aircraft during the 1995-1996 Stratospheric Tracers of Atmospheric Transport (STRAT) and 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaigns. Correlations between these three main hydrogen reservoirs in the northern extratropical lower stratosphere are examined to evaluate H2O production from CH4 and H-2 oxidation. The expected ratio of stratospheric H2O production (P-H2O) to CH4 destruction (L-CH4) = -1.973 +/- 0.003 is calculated from an evaluation of CH4 and H-2 oxidation reactions and the relationship between H-2 and CH4 mixing ratios measured during STRAT. Correlations between H2O and CH4 were tight and linear only for air masses with mean ages greater than or equal to 3.8 years, restricting this analysis predominantly to latitudes between 40 degrees and 90 degrees N and potential temperatures between 470 and 540 K. The mean observed Delta H2O/Delta CH4 (-2.15 +/- 0.18) is in statistical agreement with the expected P-H2O/L-CH4. The annual mean stratospheric entry mixing ratio for H2O calculated from this slope is 4.0 +/- 0.3 ppm. The quantity H2O + 2 . CH4 is quasi-conserved at 7.4 +/- 0.5 ppm in older air masses in the northern extratropical lower stratosphere. Significant departure of H2O + 2 . CH4 from the mean value is a sensitive indicator of processes which influence H2O without affecting CH4, such as dehydration in a polar vortex or near the tropical tropopause. No significant trend is observed in ER-2 aircraft data for H2O + 2 . CH4 in the lower stratosphere from 1993 through 1997. C1 NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. RP Hurst, DF (reprint author), NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. RI Herman, Robert/H-9389-2012; Hurst, Dale/D-1554-2016 OI Herman, Robert/0000-0001-7063-6424; Hurst, Dale/0000-0002-6315-2322 NR 32 TC 34 Z9 34 U1 0 U2 7 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 1999 VL 104 IS D7 BP 8191 EP 8200 DI 10.1029/1998JD100092 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 187NV UT WOS:000079793600013 ER PT J AU Santee, ML Manney, GL Froidevaux, L Read, WG Water, JW AF Santee, ML Manney, GL Froidevaux, L Read, WG Water, JW TI Six years of UARS Microwave Limb Sounder HNO3 observations: Seasonal, interhemispheric, and interannual variations in the lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID WAVE SPECTROSCOPIC MEASUREMENTS; ATMOSPHERE RESEARCH SATELLITE; ARCTIC WINTER STRATOSPHERE; NITRIC-ACID CHEMISTRY; POLAR VORTEX; OZONE DEPLETION; AIRBORNE MEASUREMENTS; SOUTH-POLE; LATITUDINAL VARIATION; PINATUBO AEROSOLS AB We present an overview of the seasonal, interhemispheric, and interannual variations in the distribution of HNO3 in the lower stratosphere based on measurements of gas-phase HNO3 made by the UARS Microwave Limb Sounder (MLS) through six complete annual cycles in both hemispheres, Outside of the winter polar regions, zonal-mean HNO3 mixing ratios on the 465-K potential temperature surface are comparable in the two hemispheres in all latitude bands and in all years examined. Except at high latitudes, interannual variability is minimal, and there is no significant hemispheric asymmetry in the overall HNO3 distribution or its seasonal cycle. Although the Antarctic experiences widespread severe denitrification, the MLS data indicate that the denitrification is not complete; that is, not all polar stratospheric cloud (PSC) particles sediment out of the lower stratosphere. Replenishment of HNO3 at 465 K during the mid- to late-winter period (when temperatures, though still low, are generally rising) is most likely achieved through a combination of PSC evaporation and continuing weak diabatic descent. Despite large interhemispheric and interannual differences in the extent and duration of PSC activity and denitrification, HNO3 recovers to similar values at the end of every winter in both the Arctic and the Antarctic. Zonal-mean HNO3 values for the two hemispheres are virtually indistinguishable for the latitudes equatorward of 65 degrees, even during the winter months, Thus the effects of severe denitrification are confined in both space and time to the regions poleward of 65 degrees S during the winter and early spring. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Santee, ML (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 86 TC 55 Z9 55 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1999 VL 104 IS D7 BP 8225 EP 8246 DI 10.1029/1998JD100089 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 187NV UT WOS:000079793600016 ER PT J AU Danilin, MY Rodriguez, JM Hu, WJ Ko, MKW Weisenstein, DK Kumer, JB Mergenthaler, JL Russell, JM Koike, M Yue, GK Jones, NB Johnston, PV AF Danilin, MY Rodriguez, JM Hu, WJ Ko, MKW Weisenstein, DK Kumer, JB Mergenthaler, JL Russell, JM Koike, M Yue, GK Jones, NB Johnston, PV TI Nitrogen species in the post-Pinatubo stratosphere: Model analysis utilizing UARS measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; LIMB INFRARED MONITOR; MT-PINATUBO; OZONE DEPLETION; NITRIC-ACID; HETEROGENEOUS CONVERSION; VERTICAL-DISTRIBUTION; BALLOON MEASUREMENTS; VOLCANIC AEROSOLS; SULFATE AEROSOLS AB We present an analysis of the impact of heterogeneous chemistry on the partitioning of nitrogen species measured by the Upper Atmosphere Research Satellite (UARS) instruments. The UARS measurements utilized include N2O, HNO3, and ClONO2 from the cryogenic limb array etalon spectrometer (CLAES), version 7 (v.7), and temperature, methane, ozone, H2O, HCl, NO and NO2 from the halogen occultation experiment (HALOE), version 18. The analysis is carried out for the UARS data obtained between January 1992 and September 1994 in the 100- to 1-mbar (similar to 17-47 km) altitude range and over 10 degrees latitude bins from 70 degrees S to 70 degrees N. The spatiotemporal evolution of aerosol surface area density (SAD) is adopted from analysis of the Stratospheric Aerosol and Gas Experiment (SAGE) II data. A diurnal steady state photochemical box model, constrained by the temperature, ozone, H2O, CH4, aerosol SAD, and columns of O-2 and O-3 above the paint of interest, has been used as the main tool to analyze these data. Total inorganic nitrogen (NOy) is obtained by three different methods: (1) as a sum of the UARS-measured NO, NO2, HNO3, and ClONO2; (2) from the N2O-NOy correlation, and (3) from the CH4-NOy correlation. To validate our current understanding of stratospheric heterogeneous chemistry for post-Pinatubo conditions, the model-calculated monthly averaged NOx/NOy ratios and the NO, NO2, and HNO3 profiles are compared with the UARS-derived data. In general, the UARS-constrained box model captures the main features of nitrogen species partitioning in the post-Pinatubo years, such as recovery of NOx after the eruption, their seasonal variability and vertical profiles. However, the model underestimates the NO2 content, particularly in the 30- to 7-mbar (similar to 23-32 km) range. Comparisons of the calculated temporal behavior of the partial columns of NO2 and HNO3 and ground-based measurements at 45 degrees S and 45 degrees N are also presented. Our analysis indicates that ground-based and HALOE v.18 measurements of the NO2 vertical columns are consistent within the range of their uncertainties and are systematically higher (up to 50%) than the model results at midlatitudes in both hemispheres. Reasonable agreement is obtained for HNO3 columns at 45 degrees S, suggesting some problems with nitrogen species partitioning in the model. Outstanding uncertainties are discussed. C1 Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. Lockheed Martin Advance Technol Ctr, Palo Alto, CA 94304 USA. Hampton Univ, Dept Phys, Hampton, VA 23668 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 4428507, Japan. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Inst Water & Atmospher Res, Lauder, New Zealand. RP Danilin, MY (reprint author), Atmospher & Environm Res Inc, 840 Mem Dr, Cambridge, MA 02139 USA. EM danilin@aer.com RI Koike, Makoto/F-4366-2011; Rodriguez, Jose/G-3751-2013; Ko, Malcolm/D-5898-2015; Jones, Nicholas/G-5575-2011 OI Rodriguez, Jose/0000-0002-1902-4649; Jones, Nicholas/0000-0002-0111-2368 NR 77 TC 20 Z9 20 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD APR 20 PY 1999 VL 104 IS D7 BP 8247 EP 8262 DI 10.1029/1999JD900024 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 187NV UT WOS:000079793600017 ER PT J AU Leon, R Okuno, JO Lawton, RA Stevens-Kalceff, M Phillips, MR Zou, J Cockayne, DJH Lobo, C AF Leon, R Okuno, JO Lawton, RA Stevens-Kalceff, M Phillips, MR Zou, J Cockayne, DJH Lobo, C TI Dislocation-induced changes in quantum dots: Step alignment and radiative emission SO APPLIED PHYSICS LETTERS LA English DT Article ID MISFIT DISLOCATIONS; ISLANDS; TRANSITIONS; MULTILAYERS; NUCLEATION; SURFACE; SYSTEMS; ARRAYS; GROWTH; GAAS AB A transition between two types of step alignment was observed in a multilayered InGaAs/GaAs quantum-dot (QD) structure. A change to larger QD sizes in smaller concentrations occurred after formation of a dislocation array. Cathodoluminescence (CL) spectra show a bimodal peak with lower energy peak enhancement when probing at lower e-beam energies. The two peaks separate as a result of QD interdiffusion. CL imaging and cross-sectional transmission electron microscopy showed contrast from a dislocation array formed at the interface between GaAs and the first InGaAs QD layer. Strong QD emission in the near infrared (800-1100 nm) was obtained despite the presence of dislocations. (C) 1999 American Institute of Physics. [S0003-6951(99)01816-1]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Technol Sydney, Microstruct Anal Unit, Sydney, NSW 2007, Australia. Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. Australian Natl Univ, EME, RS Phys SE, Canberra, ACT 0200, Australia. RP Leon, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Zou, Jin/B-3183-2009; Lobo, Charlene/B-3977-2013; Lobo, Charlene/G-5003-2011; OI Zou, Jin/0000-0001-9435-8043; Lobo, Charlene/0000-0002-2746-1363; Lobo, Charlene/0000-0002-2746-1363; Phillips, matthew/0000-0003-1522-9281 NR 20 TC 16 Z9 17 U1 0 U2 4 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 19 PY 1999 VL 74 IS 16 BP 2301 EP 2303 DI 10.1063/1.123831 PG 3 WC Physics, Applied SC Physics GA 186NU UT WOS:000079736500017 ER PT J AU Woodward, WS May, RD AF Woodward, WS May, RD TI Flash-ROM-based multichannel arbitrary-waveform generator SO ELECTRONIC DESIGN LA English DT Article C1 Univ N Carolina, Chapel Hill, NC 27599 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Woodward, WS (reprint author), Univ N Carolina, Venable Hall,CB3290, Chapel Hill, NC 27599 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU PENTON MEDIA, INC PI CLEVELAND PA 1100 SUPERIOR AVE, CLEVELAND, OH 44114-2543 USA SN 0013-4872 J9 ELECTRON DES JI Electron. Des. PD APR 19 PY 1999 VL 47 IS 8 BP 86 EP + PG 2 WC Engineering, Electrical & Electronic SC Engineering GA 189ET UT WOS:000079892000014 ER PT J AU Smelyanskiy, VN Dykman, MI Golding, B AF Smelyanskiy, VN Dykman, MI Golding, B TI Time oscillations of escape rates in periodically driven systems SO PHYSICAL REVIEW LETTERS LA English DT Article ID STOCHASTIC RESONANCE; FLUCTUATIONS; STATE AB We provide an explicit solution of the: problem of activation escape from a metastable state of a periodically driven Brownian particle, including both the exponent and the prefactor. We find the instantaneous and time-average escape rates, and a crossover in their field dependence, from weak to exponentially strong, with amplitude and period of the driving field. The results apply for an arbitrary ratio between the field amplitude and the noise intensity, and between the field period and the relaxation time of the system. [S0031-9007(99)08926-7]. C1 Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. Caelum Res Co, NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Smelyanskiy, VN (reprint author), Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. NR 18 TC 88 Z9 88 U1 1 U2 3 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 19 PY 1999 VL 82 IS 16 BP 3193 EP 3197 DI 10.1103/PhysRevLett.82.3193 PG 5 WC Physics, Multidisciplinary SC Physics GA 186PK UT WOS:000079738000001 ER PT J AU Sud, YC Walker, GK Lau, KM AF Sud, YC Walker, GK Lau, KM TI Mechanisms regulating sea-surface temperatures and deep convection in the tropics SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SCHUBERT CUMULUS PARAMETERIZATION; CIRRUS-CLOUD THERMOSTAT; TOGA COARE; WARM-POOL; FLUXES AB Scientific basis for the emergence of deep convection in the tropics at or above 28 degrees C sea-surface temperature (SST), and its proximity to the highest observed SST of about 30 degrees C, is explained from first principles of moist convection and TOGA-COARE data. Our calculations show that SST of 28-29 degrees C is needed for charging the cloud-base airmass with the required moist static energy for clouds to reach the upper troposphere (i.e., 200 hPa). Besides reducing solar irradiation by cloud-cover, moist convection also produces cool and dry downdrafts, which promote oceanic cooling by increased sensible and latent heat fluxes at the surface. Consequently, the tropical ocean seesaws between the states of net energy absorber before, and net energy supplier after, the deep moist convection, which causes the SST to vacillate between 28 degrees and 30 degrees C. While dynamics of the large-scale circulation embodying the easterly waves and Madden-Julian Oscillations (MJOs) modulate moist convection, we show that the quasi-stationary vertical profile of moist static energy of the tropics is the ultimate cause of the upper limit on tropical SSTs. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Sud, YC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NR 23 TC 39 Z9 39 U1 2 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 1999 VL 26 IS 8 BP 1019 EP 1022 DI 10.1029/1999GL900197 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700004 ER PT J AU Birkett, C Murtugudde, R Allan, T AF Birkett, C Murtugudde, R Allan, T TI Indian Ocean climate event brings floods to East Africa's lakes and the Sudd marsh SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NINO SOUTHERN OSCILLATION; PRECIPITATION; VICTORIA AB During an El Nino, the expected rainfall increase over most of the Lake Victoria catchment area is similar to 15-25%. However, due to anomalous warming of the western equatorial Indian Ocean during 1997, strong convection developed over parts of the Horn and eastern Africa. This resulted in a much larger 20-160% precipitation excess during the "short rainy" season. Satellite radar altimetry data reveals that not only did Lake Victoria rise by similar to 1.7 m, but that the rainfall event similarly affected lakes Tanganyika, Malawi and Turkana. In addition, the seasonal level minima of the Sudd marshes and Lakes T'ana and Nasser continue to increase. Such a rainfall event will have severe, longterm consequences for the natural surface flows and storages along the White Nile. Based on the hydrological impacts of the historic 1961 East Africa event, we can expect the current high levels of Lake Victoria to be maintained for the remainder of this decade. In addition, we anticipate a major expansion of the permanent swamp regions of the Sudd marshes over the forthcoming seasons. Blue Nile flows, further enhanced by the above-average 1998 rainfall season, can also be expected to remain high, at least until early 1999. C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. Univ Maryland, ESSIC, College Pk, MD 20742 USA. Univ London Sch Oriental & African Studies, London WC1H 0XG, England. RP Birkett, C (reprint author), NASA, Goddard Space Flight Ctr, USRA, Mailcode 971, Greenbelt, MD 20771 USA. NR 22 TC 97 Z9 102 U1 4 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 APR 15 PY 1999 VL 26 IS 8 BP 1031 EP 1034 DI 10.1029/1999GL900165 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700007 ER PT J AU Desai, SD Wahr, JM AF Desai, SD Wahr, JM TI Monthly and fortnightly tidal variations of the Earth's rotation rate predicted by a TOPEX/POSEIDON empirical ocean tide model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ALTIMETRY AB Empirical models of the two largest constituents of the long-period ocean tides, the monthly and the fortnightly constituents, are estimated from repeat cycles 10 to 210 of the TOPEX/POSEIDON (T/P) mission. These models are first validated with tide gauge observations which show residual variances with the T/P-derived models that are of the order of 2-3 mm(2) for both the monthly and fortnightly constituents, and which are smaller than residual variances from respective equilibrium models of these long-period ocean tides. These empirical models are used to predict the contribution that they each have on tidal variations of the Earth's rotation rate. For tidal variations in UT1 these contributions are predicted to be of the order of 0.1 ms with a scatter of the order of 8 and 3 mu s for the monthly and fortnightly ocean tides, respectively. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91101 USA. Univ Colorado, Dept Phys, Boulder, CO 80309 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 238-600, Pasadena, CA 91101 USA. EM shailen.desai@jpl.nasa.gov; wahr@lemond.colorado.edu NR 14 TC 5 Z9 5 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 EI 1944-8007 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD APR 15 PY 1999 VL 26 IS 8 BP 1035 EP 1038 DI 10.1029/1999GL900182 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700008 ER PT J AU Leblanc, Y Dulk, GA Kaiser, ML Bougeret, JL AF Leblanc, Y Dulk, GA Kaiser, ML Bougeret, JL TI Type U burst and CME in the solar wind SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID RADIO AB A type U burst was observed on 22 June 1998 with the WAVES radio receivers on the Wind spacecraft. It descended in frequency from 5 MHz to the turning frequency of about 1 MHz. It is extremely rare that a U burst is observed at such a low frequency, well out in the solar wind. Using a density model to convert frequency to radial distance we find that the radio emission started at 3 R-o, and that the electron stream turned back toward the Sun at about 8 R-o. The probable origin of the energetic electrons was in a B 6.8 X-ray flare that was coincident with the onset time of the U burst. A series of images by the LASCO coronagraph show a slow (214 km/s) CME in progress on the west limb whose front was at 9 R-o at the time of the U burst. As no stable magnetic loops exist at radial distances such as 8-9 R-o, we attribute the U burst to a stream of energetic electrons accelerated in an active region at the footpoint of one leg of the expanding arch of the CME. C1 Observ Paris, DESPA, Dept Rech Spatiale, CNRS,URA 264, F-92195 Meudon, France. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Leblanc, Y (reprint author), Observ Paris, DESPA, Dept Rech Spatiale, CNRS,URA 264, F-92195 Meudon, France. NR 13 TC 5 Z9 5 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 APR 15 PY 1999 VL 26 IS 8 BP 1089 EP 1092 DI 10.1029/1999GL900194 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700022 ER PT J AU Zhou, XY Tsurutani, BT AF Zhou, XY Tsurutani, BT TI Rapid intensification and propagation of the dayside aurora: Large scale interplanetary pressure pulses (fast shocks) SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETIC STORMS AB We present two cases of abrupt dayside auroral brightenings and very fast auroral propagation using the POLAR UV imaging data. The brightenings occur first at noon and then propagate along the auroral oval towards dawn and dusk. Ionospheric speeds of 6 to 11 km/s are determined. The auroral brightenings and motion are associated with the arrival and propagation of interplanetary shocks/pressure waves. The brightening at noon occurs within minutes of the shock compression of the noon-time magnetopause. The speed of the auroral propagation in the ionosphere towards dawn and dusk corresponds extremely well to the solar wind downstream flow. Our model assumes that shocks/pressure waves compress the outer dayside magnetosphere, and plasma contained therein. This plasma compression leads to the loss cone instability, wave-particle interactions, and concomitant particle loss into the ionosphere. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zhou, XY (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 123 Z9 127 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 APR 15 PY 1999 VL 26 IS 8 BP 1097 EP 1100 DI 10.1029/1999GL900173 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700024 ER PT J AU Leu, MT Zhang, RY AF Leu, MT Zhang, RY TI Solubilities of CH3C(O)O2NO2 and HO2NO2 in water and liquid H2SO4 SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PEROXYACETYL NITRATE; PEROXYNITRIC ACID; SULFURIC-ACID; HENRYS LAW; DECOMPOSITION; HYDROLYSIS; RADICALS; KINETICS; DECAY AB In this paper we analyze literature values of the Henry's law constants of peroxyacetyl nitrate (CH3C(O)O2NO2, PAN) and peroxynitric acid (HO2NO2) in water and liquid sulfuric acid, and derive correlative expressions to predict the solubilities of PAN and HO2NO2 in liquid H2SO4 over a wide range of temperature and acidic composition. To a first-order approximation, the results indicate that the Henry's law constants (in units of mol kg(-1) atm(-1)) are ln(H) = 1.07 - mH(2)SO(4) x (0.69 - 152/T) - 5810 x (1/T-0 - 1/T) for PAN and ln(H) = 3.69 - mH(2)SO(4) x (- 0.25 + 65/T) - 8400 x (1/T-0 - 1/T) for HO2NO2 where mH(2)SO(4) is the molality of sulfuric acid, T is the temperature of solutions, and T-0 = 298.15 K. The activity coefficients of PAN and HO2NO2 in aqueous H2SO4 are found to have a simple relationship with the molality of H2SO4. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. Texas A&M Univ, Dept Meteorol, College Stn, TX 77843 USA. RP Leu, MT (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. EM Ming-Taun.Leu@jpl.nasa.gov RI Zhang, Renyi/A-2942-2011 NR 16 TC 6 Z9 6 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 1999 VL 26 IS 8 BP 1129 EP 1132 DI 10.1029/1999GL900158 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700032 ER PT J AU Gao, RS Fahey, DW Del Negro, LA Donnelly, SG Keim, ER Neuman, JA Teverovskaia, E Wennberg, PO Hanisco, TF Lanzendorf, EJ Proffitt, MH Margitan, JJ Wilson, JC Elkins, JW Stimpfle, RM Cohen, RC McElroy, CT Bui, TP Salawitch, RJ Brown, SS Ravishankara, AR Portmann, RW Ko, MKW Weisenstein, DK Newman, PA AF Gao, RS Fahey, DW Del Negro, LA Donnelly, SG Keim, ER Neuman, JA Teverovskaia, E Wennberg, PO Hanisco, TF Lanzendorf, EJ Proffitt, MH Margitan, JJ Wilson, JC Elkins, JW Stimpfle, RM Cohen, RC McElroy, CT Bui, TP Salawitch, RJ Brown, SS Ravishankara, AR Portmann, RW Ko, MKW Weisenstein, DK Newman, PA TI A comparison of observations and model simulations of NOx/NOy in the lower stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OZONE; RADICALS; SUMMER; NO2 AB Extensive airborne measurements of the reactive nitrogen reservoir (NOy) and its component nitric oxide (NO) have been made in the lower stratosphere. Box model simulations that are constrained by observations of radical and long-lived species and which include heterogeneous chemistry systematically underpredict the NOx (= NO + NO2) to NOy ratio. The model agreement is substantially improved if newly measured rate coefficients for the OH + NO2 and OH + HNO3 reactions are used. When included in 2-D models, the new rate coefficients significantly increase the calculated ozone loss due to NOx and modestly change the calculated ozone abundances in the lower stratosphere. Ozone changes associated with the emissions of a fleet of supersonic aircraft are also altered. C1 NOAA, Aeron Lab, Boulder, CO 80303 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Univ Colorado, Dept Chem & Biochem, Boulder, CO 80309 USA. Aerospace Corp, Los Angeles, CA 90009 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Denver, Dept Engn, Denver, CO 80208 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Atmospher Environm Serv, Downsview, ON, Canada. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gao, RS (reprint author), NOAA, Aeron Lab, 325 Broadway, Boulder, CO 80303 USA. RI Neuman, Andy/A-1393-2009; Salawitch, Ross/B-4605-2009; Portmann, Robert/C-4903-2009; Cohen, Ronald/A-8842-2011; Wennberg, Paul/A-5460-2012; Newman, Paul/D-6208-2012; Gao, Ru-Shan/H-7455-2013; Brown, Steven/I-1762-2013; Ravishankara, Akkihebbal/A-2914-2011; Ko, Malcolm/D-5898-2015; Fahey, David/G-4499-2013 OI Neuman, Andy/0000-0002-3986-1727; Salawitch, Ross/0000-0001-8597-5832; Portmann, Robert/0000-0002-0279-6087; Cohen, Ronald/0000-0001-6617-7691; Newman, Paul/0000-0003-1139-2508; Fahey, David/0000-0003-1720-0634 NR 18 TC 56 Z9 56 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 1999 VL 26 IS 8 BP 1153 EP 1156 DI 10.1029/1999GL900162 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700038 ER PT J AU Osterman, GB Sen, B Toon, GC Salawitch, RJ Margitan, JJ Blavier, JF Fahey, DW Gao, RS AF Osterman, GB Sen, B Toon, GC Salawitch, RJ Margitan, JJ Blavier, JF Fahey, DW Gao, RS TI Partitioning of NOy species in the summer Arctic stratosphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID NITROGEN; OH AB Volume mixing ratio profiles of the quantitatively significant NOy species NO, NO2, HNO3, HNO4, ClNO3 and N2O5 were measured remotely from 8 to 38 km by the JPL MkIV FTIR solar absorption spectrometer during balloon flights from Fairbanks, Alaska (64.8 degrees N, 147.6 degrees W) on May 8 and July 8, 1997. The observed ratio of NO, (NO+NO2) to NOy (total reactive nitrogen) is 10 to 30% greater than calculated by a steady state model using standard photochemistry constrained by MkIV measurements of long lived precursors (e.g., H2O, CH4, CO and N2O) and SAGE II aerosol surface area. The persistence of this discrepancy to 38 km altitude suggests that processes involving aerosols, such as the reduction of HNO3 on the surface of soot particles, cannot be the sole explanation. The most likely resolution to this discrepancy is that the rate of NO2+OH +M-->HNO3+M (the dominant sink of NOx in the Arctic stratosphere during times of near continuous solar illumination) is significantly slower than the currently recommended rate. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Osterman, GB (reprint author), CALTECH, Jet Prop Lab, MS 183-601,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Salawitch, Ross/B-4605-2009; Gao, Ru-Shan/H-7455-2013; Fahey, David/G-4499-2013 OI Salawitch, Ross/0000-0001-8597-5832; Fahey, David/0000-0003-1720-0634 NR 18 TC 42 Z9 42 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 1999 VL 26 IS 8 BP 1157 EP 1160 DI 10.1029/1999GL900166 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700039 ER PT J AU Hsu, NC Herman, JR Gleason, JF Torres, O Seftor, CJ AF Hsu, NC Herman, JR Gleason, JF Torres, O Seftor, CJ TI Satellite detection of smoke aerosols over a snow/ice surface by TOMS SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ATMOSPHERE AB A recently developed technique of using satellite UV radiance measurements to detect absorbing tropospheric aerosols is found to be effective over snow/ice surfaces. This method takes advantage of the wavelength dependent reduction in the backscattered radiance due to the presence of absorbing aerosols over snow/ice surfaces. An example of the aerosol distribution derived from Total Ozone Mapping Spectrometer (TOMS) data is shown for an August 1998 event in which smoke generated by Canadian forest fires drifts over and across Greenland. During this event, the TOMS observed 360 nm reflectivity over the snow/ice surface dropped drastically from 90-100% down to 30-40%. We investigated the history of smoke events over snow/ice and found that there is a large interannual variability in the amount of smoke aerosols observed over Greenland. C1 Raytheon ITSS, Lanham, MD 20706 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. UMBC, JCET, Greenbelt, MD USA. RP Hsu, NC (reprint author), Raytheon ITSS, 4500 Forbes Blvd,Suite 400, Lanham, MD 20706 USA. RI Gleason, James/E-1421-2012; Hsu, N. Christina/H-3420-2013; Torres, Omar/G-4929-2013; OI Herman, Jay/0000-0002-9146-1632 NR 9 TC 64 Z9 64 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 1999 VL 26 IS 8 BP 1165 EP 1168 DI 10.1029/1999GL900155 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 187NW UT WOS:000079793700041 ER PT J AU Wei, JYT Yeh, NC Fu, CC Vasquez, RP AF Wei, JYT Yeh, NC Fu, CC Vasquez, RP TI Tunneling spectroscopy study of spin-polarized quasiparticle injection effects in cuprate/manganite heterostructures SO JOURNAL OF APPLIED PHYSICS LA English DT Article; Proceedings Paper CT 43rd Annual Conference on Magnetism and Magnetic Materials CY NOV 09-12, 1998 CL MIAMI, FLORIDA SP Amer Inst Phys, IEEE Magnet Soc, Minerals Met Mat Soc, Amer Soc Testing & Mat, Amer Ceramic Soc, Amer Phys Soc, EMTEC Magnet GmbH, Fuji Photo Film Co Ltd, IBM, Imation, Sony corp, TDK Corp, Toda Kogyo Corp, ADE Technol Inc, digital Measurement Syst Div, Komag, MMC Technol Inc ID SURFACE-STATES; TIME-REVERSAL; SUPERCONDUCTORS; YBA2CU3O7-DELTA; FERROMAGNET; SYMMETRY; FILMS AB Scanning tunneling spectroscopy was performed at 4.2 K on epitaxial thin-film heterostructures comprising YBa2Cu3O7-delta and La0.7Ca0.3MnO3, to study the microscopic effects of spin-polarized quasiparticle injection from the half-metallic ferromagnetic manganite on the high Tc cuprate superconductor. The quasiparticle tunneling characteristics observed were consistent with d-wave pairing symmetry, with a gap-maximum Delta(0) approximate to 22 meV, up to at least 35 mA (7 x 10(3) A/cm(2)) injection. Spectral smearing observed at higher injections could be fitted to elevated effective quasiparticle temperatures, even though negligible sample heating was detected by in situ thermometry. The overall spectral evolution with the injection current also appears to be nonthermal in character, showing a nonmonotonic change in both the zero-bias tunneling conductance and the area under the conductance spectrum. We discuss general implications of these results for the scenario of dynamic pair breaking by a nonequilibrium distribution of spin-polarized quasiparticles. (C) 1999 American Institute of Physics. [S0021-8979(99)54208-4]. C1 CALTECH, Dept Phys, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Wei, JYT (reprint author), CALTECH, Dept Phys, Pasadena, CA 91125 USA. NR 19 TC 20 Z9 20 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 APR 15 PY 1999 VL 85 IS 8 BP 5350 EP 5352 DI 10.1063/1.370249 PN 2B PG 3 WC Physics, Applied SC Physics GA 188NF UT WOS:000079853500025 ER PT J AU Dooley, JA Lindensmith, CA Chave, RG Good, N Graetz, J Fultz, B AF Dooley, JA Lindensmith, CA Chave, RG Good, N Graetz, J Fultz, B TI Magnetostriction of single crystal and polycrystalline Tb0.60Dy0.40 at cryogenic temperatures SO JOURNAL OF APPLIED PHYSICS LA English DT Article; Proceedings Paper CT 43rd Annual Conference on Magnetism and Magnetic Materials CY NOV 09-12, 1998 CL MIAMI, FLORIDA SP Amer Inst Phys, IEEE Magnet Soc, Minerals Met Mat Soc, Amer Soc Testing & Mat, Amer Ceramic Soc, Amer Phys Soc, EMTEC Magnet GmbH, Fuji Photo Film Co Ltd, IBM, Imation, Sony corp, TDK Corp, Toda Kogyo Corp, ADE Technol Inc, digital Measurement Syst Div, Komag, MMC Technol Inc AB At cryogenic temperatures, single crystals of TbDy alloys exhibit giant magnetostrictions of nearly 9000 ppm, making these materials promising for engineering service in cryogenic actuators, valves, and positioners. The preparation of single crystals is difficult and costly. Preliminary results on the magnetostriction of textured polycrystalline materials are presented here. For instance, polycrystalline Tb0.60Dy0.40, plane-rolled (one direction of applied stress) to induce crystallographic texture, has shown magnetostrictions at 77 K of 3000 ppm for an applied field of 4.5 kOe and an applied load of 23 MPa, or 48% that of a single crystal under similar conditions. Comparisons are presented between the magnetostrictive response of plane- and form-rolled (two orthogonal directions of applied stress) polycrystalline Tb0.60Dy0.40 at 10 and 77 K. It is reported that at 10 K plane-rolled Tb0.60Dy0.40 exhibits 1600 ppm magnetostriction at an applied field of 4.4 kOe with a minimal applied load of 0.28 MPa. An observed restoration of the initial unstrained state may be a useful feature of polycrystalline materials for engineering service. Finally it is reported that thermal expansion measurements provide a measure of crystallographic texture for comparison with the magnetostriction. (C) 1999 American Institute of Physics. [S0021-8979(99)44008-3]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Dooley, JA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 7 Z9 9 U1 1 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 APR 15 PY 1999 VL 85 IS 8 BP 6256 EP 6258 DI 10.1063/1.370128 PN 2B PG 3 WC Physics, Applied SC Physics GA 188NF UT WOS:000079853500319 ER PT J AU Joblin, C Salama, F Allamandola, L AF Joblin, C Salama, F Allamandola, L TI Absorption and emission spectroscopy of perylene (C20H12) isolated in Ne, Ar, and N-2 matrices SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID DIFFUSE INTERSTELLAR BANDS; POLYCYCLIC AROMATIC-HYDROCARBONS; JET-COOLED PERYLENE; VIBRATIONAL REDISTRIBUTION; FLUORESCENCE; FEATURES; CATIONS; RELAXATION; COMPLEXES; MOLECULES AB The electronic absorption and emission spectra of perylene (C20H12) isolated in rare gas (Ne, Ar) and N-2 matrices are presented. While the electronic band systems show, in all matrices, the same fundamental frequencies as those observed in gas-phase jet experiments, the spectra in Ar and N-2 matrices exhibit much more spectral structure. The observed structure points to strong host-guest interactions and provides new insight into the low frequency modes of perylene. In particular, the spacing observed at 11 and 16 cm(-1) in the S-0 and S-1 states, respectively, might be attributed to the gerade accordion mode of perylene. This mode, which has never been observed directly in jet experiments, could be induced into activity in solid matrices. (C) 1999 American Institute of Physics. [S0021-9606(99)00915-0]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Joblin, C (reprint author), CESR CNRS, 9 Av Colonel Roche, F-31028 Toulouse 04, France. RI Salama, Farid/A-8787-2009 OI Salama, Farid/0000-0002-6064-4401 NR 44 TC 38 Z9 38 U1 4 U2 11 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD APR 15 PY 1999 VL 110 IS 15 BP 7287 EP 7297 DI 10.1063/1.478631 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 184QZ UT WOS:000079625600022 ER PT J AU Elfouhaily, T Thompson, D Vandemark, D Chapron, B AF Elfouhaily, T Thompson, D Vandemark, D Chapron, B TI Weakly nonlinear theory and sea state bias estimations SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SATELLITE ALTIMETRY; OCEANS SURFACE; GRAVITY-WAVES; SPECTRUM AB The theory of "weakly" nonlinear (WNL) waves is commonly used in generating higher statistical moments of a random surface wave field. These moments can be used, for example, to estimate the sea state bias (SSB) in radar altimetry under a geometric optical assumption. The present investigation suggests that several previous SSB studies appear to have misapplied this WNL theory by violating its condition of validity. As a result, a pronounced inconsistency appears even for lower-order moments. This inconsistency appears as a difference between the statistical moments of the nonlinear surface generated by the application of the WNL theory and those of the linear input (or bare) spectrum. If measured spectra, which yield measured moments (such as rms elevation and slope), are chosen as an input to WNL theory, then the corresponding moments of resulting output spectra may be severely overestimated. To strictly avoid the inconsistency, WNL theory must only be applied to long gravity waves where the wave-wave interactions are weak, hence the WNL epithet. To further illustrate this problem, we present an inversion scheme that determines the proper input spectrum by forcing the low-order moments of the output spectrum to equal the measured moments. Analytical solutions are given for this inversion based on an explicit formulation of the low-order nonlinear moments and a simplified one-dimensional power law spectrum. The solutions show that the high-frequency portion (wave components shorter than about 10 m) of the input (or bare) spectrum must be significantly less energetic than that of the output spectrum. Our results emphasize the importance of the shorter-scale waves in the SSB mechanism. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. IFREMER, Ctr Brest, F-29280 Plouzane, France. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. RP Elfouhaily, T (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. EM elfoutm1@nansen.jhuapl.edu; dug@osb.wff.nasa.gov; bchapron@ifremer.fr RI Chapron, Bertrand/O-6527-2015 NR 16 TC 21 Z9 23 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-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1999 VL 104 IS C4 BP 7641 EP 7647 DI 10.1029/1998JC900128 PG 7 WC Oceanography SC Oceanography GA 187KA UT WOS:000079784700003 ER PT J AU Carton, JA Chao, Y AF Carton, JA Chao, Y TI Caribbean Sea eddies inferred from TOPEX/POSEIDON altimetry and a 1/6 degrees Atlantic Ocean model simulation SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTH BRAZIL CURRENT; CURRENT RETROFLECTION; CIRCULATION MODEL; GEOSAT ALTIMETRY; WORLD OCEAN; GULF AB Large cyclonic and anticyclonic eddies are found in the Caribbean Sea. Analysis of sea level data from the TOPEX/POSEIDON altimeter shows that the eddies are quite regular, appearing at near 3-month intervals west of the southern Lesser Antilles. These eddies progress westward at average speeds of 12 cm s(-1), growing in amplitude up to 20 cm. Many eddies dissipate in the coastal waters of Nicaragua a half year after they appear. A 1/6 degrees x 1/6 degrees general circulation model of the Atlantic is shown to reproduce major features of the eddy life cycle, including their amplitudes, temporal scales, and propagation speed. Analysis of the model output further suggests that the eddies are mainly limited to the thermocline and above, with little phase lag in the vertical. The simulated eddies have sufficiently strong currents that the horizontal gradient of total vorticity changes sign, suggesting that conversions from mean to eddy kinetic energy may be contributing to their growth. Analysis of the simulation links eddies in the Caribbean with eddies formed outside the Caribbean at the confluence of the North Brazil Current and North Equatorial Countercurrent systems. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20743 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Carton, JA (reprint author), Univ Maryland, Dept Meteorol, 3433 Comp & Space Sci Bldg, College Pk, MD 20743 USA. EM carton@atmos.umd.edu; ye@pacific.jpl.nasa.gov RI carton, james/C-4807-2009 OI carton, james/0000-0003-0598-5198 NR 30 TC 46 Z9 46 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9275 EI 2169-9291 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD APR 15 PY 1999 VL 104 IS C4 BP 7743 EP 7752 DI 10.1029/1998JC900081 PG 10 WC Oceanography SC Oceanography GA 187KA UT WOS:000079784700010 ER PT J AU DeMore, WB Bayes, KD AF DeMore, WB Bayes, KD TI Rate constants for the reactions of hydroxyl radical with several alkanes, cycloalkanes, and dimethyl ether SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID HYDROGEN-ATOM ABSTRACTION; RELATIVE RATE MEASUREMENTS; OH RADICALS; GAS-PHASE; TROPOSPHERIC CHEMISTRY; TEMPERATURE-RANGE; RATE COEFFICIENTS; KINETICS; SERIES; CYCLOPROPANE AB Relative rate experiments were used to measure ratios of rate constants as a function of temperature for the reactions of OH with propane, n-butane, n-pentane, n-hexane, cyclopropane, cyclobutane, cyclopentane, cyclohexane, and dimethyl ether. To assure internal consistency, ratios were measured for seventeen reactant pairs among these reactants. All of the derived rate constants are based on an absolute rate constant of the OH + C2H6 reaction using k(ethane) = 1.0 x 10(-11) exp(-1094/T) cm(3)/molecule s. The rate constants obtained are as follows. propane: 1.29 x 10(-11) exp(-730/T), k(298 K) = 1.11 x 10(-12). n-butane: 1.68 x 10(-11) exp(-584/T), k(298 K) = 2.37 x 10(-12). n-pentane: 1.94 x 10(-11) exp(-494/T), k(298 K) = 3.70 x 10(-12) n-hexane: 2.60 x 10(-11) exp(-480/T), k(298 K) = 5.19 x 10(-12), cyclopropane: 5.15 x 10(-12) exp(-1255/T, k(298 K) = 7.64 x 10(-14). cyclobutane: 1.62 x 10(-11) exp(-611/T), k(298 K) = 2.08 x 10(-12). cyclopentane: 2.57 x 10(-11) exp(-498/T), k(298 K) = 4.83 x 10-(12). cyclohexane: 3.58 x 10(-11) exp(-500/T), k(298 K) 6.69 x 10(-12). dimethylether: 1.51 x 10(-11) exp(-496/T), k(298 K) = 2.86 x 10(-12). These results are compared with previous literature data and are discussed in terms of trends in preexponential factors and activation energies. Also, rate constants and Arrhenius parameters are derived for methylene groups in the alkanes and cycloalkanes. In the low temperature regime, the present data illustrate a persistent discrepancy between absolute and relative rate measurements. The relative data show less curvature at low temperatures, and can be adequately fit with two-parameter Arrhenius expressions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP DeMore, WB (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 28 TC 64 Z9 65 U1 1 U2 47 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD APR 15 PY 1999 VL 103 IS 15 BP 2649 EP 2654 DI 10.1021/jp983273d PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 189YH UT WOS:000079933500022 ER PT J AU Cho, H Kang, W AF Cho, H Kang, W TI Negative Hall plateaus and quantum Hall effect in (TMTSF)(2)PF6 SO PHYSICAL REVIEW B LA English DT Article ID DENSITY-WAVE PHASES; MAGNETIC-FIELD; BECHGAARD SALTS; SIGN REVERSALS; CONDUCTORS; (TMTSF)2CLO4; STATES; TRANSITIONS; STABILITY AB We present our study of negative Hall plateaus associated with the magnetic-field-induced spin-density waves (FISDW). Slightly above the the pressure necessary to stabilize superconductivity, the quantum Hall effect associated with the field-induced spin density waves is interrupted by several negative Hall plateaus and an in-between phase. Quantizations of the negative Hall plateaus suggests that these states may be identified as FISDW states with negative quantum numbers. The in-between phase occurs from splitting of a phase boundary deep inside the FISDW diagram and is reminiscent of the previously suggested arborescence. [S0163-1829(99)05915-9]. C1 Univ Chicago, James Franck Inst, Chicago, IL 60637 USA. Univ Chicago, Dept Phys, Chicago, IL 60637 USA. RP Cho, H (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 26 TC 8 Z9 8 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD APR 15 PY 1999 VL 59 IS 15 BP 9814 EP 9817 DI 10.1103/PhysRevB.59.9814 PG 4 WC Physics, Condensed Matter SC Physics GA 190JG UT WOS:000079958900034 ER PT J AU Guo, XZ Khakoo, MA Mathews, DF Mikaelian, G Crowe, A Kanik, I Trajmar, S Zeman, V Bartschat, K Fontes, CJ AF Guo, XZ Khakoo, MA Mathews, DF Mikaelian, G Crowe, A Kanik, I Trajmar, S Zeman, V Bartschat, K Fontes, CJ TI Differential cross section ratios for low-energy electron-impact excitation of the 4p(5)5s levels of krypton - sensitive tests of relativistic effects for heavy noble gases SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Letter ID CLOSE-COUPLING CALCULATIONS; NEAR-THRESHOLD; R-MATRIX; SPIN-ORBIT; SCATTERING; STATES; KR; XE; HELIUM; ATOMS AB We present new experimental measurements and theoretical calculations of R-matrix and unitarized first-order many-body theory for electron-impact excitation of krypton. The usefulness of differential cross section ratios in providing sensitive tests of electron scattering models for the excitation of the np(5)(n + 1)s configuration of the heavy rare gases is demonstrated. In addition to differential cross sections alone, these ratios provide interesting physical insights into the details of the collision process. Comparisons of the measured ratios with predictions from the present and other available calculations show some agreement, but also reveal that significant improvements of these models are required. C1 Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Nottingham, Dept Math, Nottingham NG7 2RD, England. Drake Univ, Dept Phys & Astron, Des Moines, IA 50311 USA. Univ Calif Los Alamos Natl Lab, Appl Theoret & Computat Phys Div, Los Alamos, NM 87545 USA. Univ Newcastle Upon Tyne, Dept Phys, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England. RP Guo, XZ (reprint author), Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. RI Bartschat, Klaus/I-2527-2012 NR 28 TC 12 Z9 12 U1 0 U2 2 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 14 PY 1999 VL 32 IS 7 BP L155 EP L163 DI 10.1088/0953-4075/32/7/002 PG 9 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 189PN UT WOS:000079913900002 ER PT J AU Wolfe, DB Oldenburg, SJ Westcott, SL Jackson, JB Paley, MS Halas, NJ AF Wolfe, DB Oldenburg, SJ Westcott, SL Jackson, JB Paley, MS Halas, NJ TI Photodeposition of molecular layers on nanoparticle substrates SO LANGMUIR LA English DT Article ID RAY PHOTOELECTRON-SPECTROSCOPY; COATED POLYSTYRENE LATEXES; SURFACE CHARACTERIZATION; DIACETYLENE; PARTICLES; CLUSTERS; FILMS AB We report the photodeposition of polymeric layers of nanometer scale thickness onto silica nanoparticle substrates. This was accomplished by ultraviolet irradiation of a solution of functionalized diacetylene monomers in which the silica nanoparticles were suspended. Following photodeposition, the coated nanoparticles were analyzed using transmission electron microscopy and UV-visible spectroscopy. Highly regular polydiacetylene films with thicknesses from 2.5 to 25 nm were produced. The thickness measurements were facilitated by the attachment of small gold nanoparticles onto the surface of the silica nanoparticle substrates prior to photodeposition, to provide contrast in the final TEM image. W-visible spectroscopy of the deposited films indicates that approximately 40% less conjugation is present relative to that of macroscopic polydiacetylene thin films grown with the same approach. This process yields a unique "nanolaminate" coating which may be useful in the modification of the physical, chemical, or optical properties of nanoparticles. C1 Rice Univ, Rice Quantum Inst, Dept Elect & Comp Engn, Houston, TX 77005 USA. Rice Univ, Dept Chem, Houston, TX 77005 USA. Rice Univ, Ctr Nanotechnol Sci & Technol, Houston, TX 77005 USA. NASA, Univ Space Res Assoc, Space Sci Lab, ES 76, Huntsville, AL 35812 USA. RP Halas, NJ (reprint author), Rice Univ, Rice Quantum Inst, Dept Elect & Comp Engn, 6100 S Main, Houston, TX 77005 USA. RI Halas, Naomi/D-2935-2011 NR 19 TC 6 Z9 6 U1 2 U2 5 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0743-7463 J9 LANGMUIR JI Langmuir PD APR 13 PY 1999 VL 15 IS 8 BP 2745 EP 2748 DI 10.1021/la981593i PG 4 WC Chemistry, Multidisciplinary; Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA 187FF UT WOS:000079775700022 ER PT J AU Silbermann, NA Harding, P Ferrarese, L Stetson, PB Madore, BF Kennicutt, RC Freedman, WL Mould, JR Bresolin, F Ford, H Gibson, BK Graham, JA Han, MS Hoessel, JG Hill, RJ Huchra, J Hughes, SMG Illingworth, GD Kelson, D Macri, L Phelps, R Rawson, D Sakai, S Turner, A AF Silbermann, NA Harding, P Ferrarese, L Stetson, PB Madore, BF Kennicutt, RC Freedman, WL Mould, JR Bresolin, F Ford, H Gibson, BK Graham, JA Han, MS Hoessel, JG Hill, RJ Huchra, J Hughes, SMG Illingworth, GD Kelson, D Macri, L Phelps, R Rawson, D Sakai, S Turner, A TI The hubble space telescope key project on the extragalactic distance scale. XIV. The cepheids in NGC 1365 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cepheids; galaxies, distances and redshifts; galaxies, individual (NGC 1365) ID TULLY-FISHER RELATION; RR-LYRAE STARS; H-II-REGIONS; STELLAR PHOTOMETRY; SPIRAL GALAXIES; FORNAX CLUSTER; CCD PHOTOMETRY; DISCOVERY; PERFORMANCE; CALIBRATION AB We report the detection of Cepheid variable stars in the barred spiral galaxy NGC 1365, located in the Fornax cluster, using the Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 (WFPC2). Twelve V (F555W) and four I (F814W) epochs of observation were obtained. The two photometry packages ALLFRAME and DoPHOT were separately used to obtain profile-fitting photometry of all the stars in the HST held. The search for Cepheid variable stars resulted in a sample of 52 variables, with periods between 14 and 60 days, common to both data sets. ALLFRAME photometry and light curves of the Cepheids are presented. A subset of 34 Cepheids were selected on the basis of period, light curve shape, similar ALLFRAME and DoPHOT periods, color, and relative crowding, to lit the Cepheid period-luminosity relations in V and I for both ALLFRAME and DoPHOT. The measured distance modulus to NGC 1365 from the ALLFRAME photometry is 31.31 +/- 0.20 (random) +/- 0.18 (systematic) mag, corresponding to a distance of 18.3 +/- 1.7 (random) +/- 1.6 (systematic) Mpc. The reddening is measured to be E(V - I) = 0.16 +/- 0.08 mag. These values are in excellent agreement with those obtained using the DoPHOT photometry, namely a distance modulus of 31.26 +/- 0.10 mag and a reddening of 0.15 +/- 0.10 mag (internal errors only). C1 CALTECH, Jet Prop Lab, Infrared Proc & Anal Ctr, NASA Extragalact Database, Pasadena, CA 91125 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Johns Hopkins Univ, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Wisconsin, Madison, WI 53706 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 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. RP Silbermann, NA (reprint author), CALTECH, Jet Prop Lab, Infrared Proc & Anal Ctr, NASA Extragalact Database, MS 100-22, Pasadena, CA 91125 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 59 TC 41 Z9 41 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP 1 EP 28 DI 10.1086/307002 PN 1 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AF UT WOS:000080226400001 ER PT J AU Madore, BF Freedman, WL Silbermann, N Harding, P Huchra, J Mould, JR Graham, JA Ferrarese, L Gibson, BK Han, MS Hoessel, JG Hughes, SM Illingworth, GD Phelps, R Sakai, S Stetson, P AF Madore, BF Freedman, WL Silbermann, N Harding, P Huchra, J Mould, JR Graham, JA Ferrarese, L Gibson, BK Han, MS Hoessel, JG Hughes, SM Illingworth, GD Phelps, R Sakai, S Stetson, P TI The Hubble Space Telescope key project on the extragalactic distance scale. XV. A Cepheid distance to the Fornax cluster and its implications SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; distance scale; galaxies : clusters : individual (Fornax); galaxies : distances and redshifts; galaxies : individual (NGC 1365) ID TULLY-FISHER RELATION; LINE-WIDTH RELATIONS; LOCAL SUPERCLUSTER; SPIRAL GALAXIES; VELOCITY-FIELD; EXPANSION RATE; CONSTANT; IA; CALIBRATION; BRIGHTNESS AB Using the Hubble Space Telescope, 37 long-period Cepheid variables have been discovered in the Fornax Cluster spiral galaxy NGC 1365. The resulting V and I period-luminosity relations yield a true distance modulus of mu(0) = 31.35 +/- 0.07 mag, which corresponds to a distance of 18.6 +/- 0.6 Mpc. This measurement provides several routes for estimating the Hubble constant. (1) Assuming this distance for the Fornax Cluster as a whole yields a local Hubble constant of 70 +/- 18 (random) +/- 7 (systematic) km s(-1) Mpc(-1). (2) Nine Cepheid-based distances to groups of galaxies out to and including the Fornax and Virgo Clusters yield H-0 = 73 +/- 16 (random) +/- 7 (systematic) km s(-1) Mpc(-1). (3) Recalibrating the I-band Tully-Fisher relation using NGC 1365 and six nearby spiral galaxies, and applying it to 15 galaxy clusters out to 100 Mpc, give H-0 = 76 +/- 3 (random) is (systematic) km s(-1) Mpc(-1). (4) Using a broad-based set of differential cluster distance moduli ranging from Fornax to Abell 2147 gives H-0 = 72 +/- 3 (random) +/- 6(systematic) km s(-1) Mpc(-1). Finally, (5) assuming the NGC 1365 distance for the two additional Type Ia supernovae in Fornax; and adding them to the SN Ia calibration (correcting for light-curve shape) gives H-0 = 67 +/- 6 (random) +/- 7 (systematic) km s(-1) Mpc(-1) out to a distance in excess of 500 Mpc. All five of these H-0 determinations agree to within their statistical errors. The resulting estimate of the Hubble constant, combining all of these determinations, is H-0 = 72 +/- 5 (random) +/- 7 (systematic) km s(-1) Mpc(-1). An extensive tabulation of identified systematic and statistical errors, and their propagation, is given. C1 CALTECH, Jet Prop Lab, NASA, IPAC Extragalact Database,Infrares Proc & Anal Ct, Pasadena, CA 91125 USA. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20015 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Royal Greenwich Observ, Cambridge CB3 0HA, England. Univ Calif Santa Cruz, Lick Observ, Santa Cruz, CA 95064 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. RP Madore, BF (reprint author), CALTECH, Jet Prop Lab, NASA, IPAC Extragalact Database,Infrares Proc & Anal Ct, MS 100-22, Pasadena, CA 91125 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 74 TC 76 Z9 76 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP 29 EP 41 DI 10.1086/307004 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AF UT WOS:000080226400002 ER PT J AU Valinia, A Henriksen, MJ Loewenstein, M Roettiger, K Mushotzky, RF Madejski, G AF Valinia, A Henriksen, MJ Loewenstein, M Roettiger, K Mushotzky, RF Madejski, G TI Rossi X-Ray Timing Explorer hard X-ray observation of Abell 754: Constraining the hottest temperature component and the intracluster magnetic field SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : clusters : individual (Abell 754); intergalactic medium; magnetic fields; X-rays : galaxies ID COOLING FLOWS; COMA CLUSTER; VLA SURVEY; GALAXIES; PERFORMANCE; MORPHOLOGY; CM AB Abell 754, a cluster undergoing merging, was observed in hard X-rays with the Rossi X-Ray Tinting Explorer (RXTE) in order to constrain its hottest temperature component and search for evidence of nonthermal emission. Simultaneous modeling of RXTE data and those taken with previous missions yields an average intracluster temperature of similar to 9 keV in the 1-50 keV energy band. A multitemperature component model derived from numerical simulations of the evolution of a cluster undergoing a merger produces similar quality of fit, indicating that the emission measure from the very hot gas component is sufficiently small that it renders the two models indistinguishable. No significant nonthermal emission was detected. However, our observations set an upper limit of 7.1 x 10(-14) ergs cm(-2) s(-1) keV(-1) (90% confidence limit) to the nonthermal emission flux at 20 keV. Combining this result with the radio synchrotron emission flux, we find a lower limit of 0.2 mu G for the intracluster magnetic field. We discuss the implications of our results for the theories of magnetic field amplifications in cluster mergers. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ N Dakota, Dept Phys, Grand Forks, ND 58202 USA. Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA. RP Valinia, A (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 33 TC 22 Z9 22 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP 42 EP 49 DI 10.1086/307022 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AF UT WOS:000080226400003 ER PT J AU Pahre, MA Mould, JR Dressler, A Holtzman, JA Watson, AM Gallagher, JS Ballester, GE Burrows, CJ Casertano, S Clarke, JT Crisp, D Griffiths, RE Grillmair, CJ Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Westphal, JA AF Pahre, MA Mould, JR Dressler, A Holtzman, JA Watson, AM Gallagher, JS Ballester, GE Burrows, CJ Casertano, S Clarke, JT Crisp, D Griffiths, RE Grillmair, CJ Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Westphal, JA TI Detection of surface brightness fluctuations in NGC 4373 using the Hubble Space Telescope SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : distances and redshifts; galaxies : elliptical and lenticular, cD; galaxies : individual (NGC 4373); galaxies : stellar content ID MEASURING EXTRAGALACTIC DISTANCES; VIRGO CLUSTER; ELLIPTICAL GALAXIES; SAMPLE SELECTION; PHOTOMETRY; CALIBRATION; CONSTANT; WFPC2; FIELD; SPECTROSCOPY AB Surface brightness fluctuations (SBF) have been detected for three elliptical galaxies-NGC 3379 in the Leo group, NGC 4406 in the Virgo cluster, and NGC 4373 in the Hydra-Centaurus supercluster-using marginally sampled, deep images taken with the Planetary Camera of the WFPC2 instrument on the Hubble Space Telescope (HST). The power spectrum of the fluctuations image is well fitted by an empirical model of the point-spread function constructed using point sources identified in the held. Comparison with high-quality ground-based observations of all three galaxies show excellent agreement in the measurement of the distance modulus over a substantial range in distance. This demonstrates the capability of the Planetary Camera of WFPC2 to measure distances using the SBF technique despite the marginal sampling and small spatial coverage of the images. The residual variance due to unresolved sources in all three galaxies is only 2%-5% of the detected fluctuations signal, which confirms the advantage of HST imaging in minimizing the uncertainty of this SBF correction. Extensive consistency checks, including an independent SBF analysis using an alternate software package, suggest that our internal uncertainties are <0.02 mag. The fluctuations magnitude for NGC 4373 is I-F814W = 31.31 +/- 0.05 mag, corresponding to a distance modulus of (m-M)(0) = 32.99 +/- 0.11. This implies a peculiar velocity for this galaxy of 415 +/- 330 km s(-1), which is smaller than derived from the D-n-sigma relation. C1 CALTECH, Palomar Observ, Pasadena, CA 91125 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Johns Hopkins Univ, Dept Astron, Baltimore, MD 21218 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Pahre, MA (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St,Mail Stop 20, Cambridge, MA 02138 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 36 TC 21 Z9 21 U1 0 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP 79 EP 88 DI 10.1086/306998 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AF UT WOS:000080226400006 ER PT J AU Boden, AF Koresko, CD van Belle, GT Colavita, MM Dumont, PJ Gubler, J Kulkarni, SR Lane, BF Mobley, D Shao, M Wallace, JK Henry, GW AF Boden, AF Koresko, CD van Belle, GT Colavita, MM Dumont, PJ Gubler, J Kulkarni, SR Lane, BF Mobley, D Shao, M Wallace, JK Henry, GW CA PTI Collaboration TI The visual orbit of iota Pegasi SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : spectroscopic; stars : fundamental parameters; stars : individual (iota Pegasi); techniques : interferometric ID LINE OPTICAL INTERFEROMETRY; SOLAR-TYPE STARS; TESTBED INTERFEROMETER; COMPONENT MASSES; ANGULAR DIAMETER; STANDARD STARS; PRECISION; PHOTOMETRY; ANDROMEDAE; SYSTEM AB We have determined the visual orbit for the spectroscopic binary I Pegasi with interferometric visibility data obtained by the Palomar Testbed Interferometer in 1997. l Peg is a double-lined binary system whose minimum masses and spectral typing suggests the possibility of eclipses. Our orbital and component diameter determinations do not favor the eclipse hypothesis: the limb-to-limb separation of the two components is 0.151+/-0.069 mas at conjunction. Our conclusion that the 1 Peg system does not eclipse is supported by high-precision photometric observations. The physical parameters implied by our visual orbit and the spectroscopic orbit of Fekel & Tomkin are in good agreement with those inferred by other means. In particular, the orbital parallax of the system is determined to be 86.9 +/- 1.0 mas, and masses of the two components are determined to be 1.326 +/- 0.016 and 0.819 +/- 0.009 M., respectively. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. Univ Calif San Diego, San Diego, CA 92103 USA. Tennessee State Univ, Ctr Excellence Informat Syst, Nashville, TN 37203 USA. RP Boden, AF (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 44 TC 50 Z9 50 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP 356 EP 364 DI 10.1086/307030 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AF UT WOS:000080226400029 ER PT J AU Steiman-Cameron, TY Imamura, JN AF Steiman-Cameron, TY Imamura, JN TI V2301Ophiuchi: An X-ray-bright eclipsing AM Herculis object SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : eclipsing; novae, cataclysmic variables; radiation mechanisms : nonthermal; stars : individual (V2301 Ophiuchi); X-rays : stars ID QUASI-PERIODIC OSCILLATIONS; DWARF RADIATIVE SHOCKS; MAGNETIC WHITE-DWARFS; STABILITY PROPERTIES; DEGENERATE DWARFS; TIMING EXPLORER; UV-RADIATION; 1H 1752+081; ACCRETION; PERFORMANCE AB We present hard X-ray and optical observations of the eclipsing AM Her system V2301 Oph. The X-ray data were obtained using the PCA detector of the Rossi X-Ray Timing Explorer satellite during 1997 May, and the optical data were obtained using the 1 and 1.5 m telescopes of the Cerro Tololo Inter-American Observatory during 1996 May and 1997 June. V2301 Oph was bright in both the optical and hard X-rays during our observations. This, when coupled with its eclipsing nature, makes V2301 Oph an ideal testbed for theories of the large-scale topology of AM Her hows and the radiative shocks in AM Her systems. The X-ray emission from V2301 Oph was modulated strongly on the orbital period. During the bright orbital phases, the X-ray flux was Fx approximate to 3.6 x 10(-11) ergs cm(-2) s(-1) over the energy range E = 2-10 keV. The X-ray emission did not go to zero during the faint orbital phases; it was similar to 10% of the bright phase level. The X-ray spectrum could be fitted by (1) optically thin thermal bremsstrahlung (temperature kT(x) approximate to 9-19 keV) models with an absorption line at 5.1-5.2 keV or an emission line at similar to 7 keV, and (2) power-law continuum tinder approximate to 2) models with an absorption Line at 5.1-5.2 keV or an emission line at similar to 7 keV. The absorption columns were large for all fits, n(H) similar to (3-10) x 10(22) Cm-2 The n(H) are model dependent, but their large sizes are secure because they are set by the rollover in the X-ray spectrum at 3-4 keV. The hardness of the X-ray spectrum was roughly constant during the bright orbital phases. During the faint orbital phases, the X-ray spectral properties were not well determined, but it did appear that the spectrum hardened. There were total eclipses in both the X-ray and optical light curves. The X-ray light curves and eclipses were consistent with a dominant hot spot and a secondary hot spot. The dominant hot spot was not a point source; it had to cover about 50 degrees in longitude on the surface of the white dwarf. We argue that the X-ray light curve and eclipse shape also suggest that the accretion occurs in a sheetlike geometry rather than in a columnar geometry. The optical light curves and eclipses were consistent with emission from the white dwarf photosphere, an extended emission region that sat above the surface of the white dwarf, and the X-ray-heated face of the companion star. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Oregon, Dept Phys, Eugene, OR 97403 USA. Univ Oregon, Inst Theoret Sci, Eugene, OR 97403 USA. RP Steiman-Cameron, TY (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 22 TC 10 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP 404 EP 413 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AF UT WOS:000080226400033 ER PT J AU Cha, AN Sembach, KR Danks, AC AF Cha, AN Sembach, KR Danks, AC TI The distance to the Vela supernova remnant SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : individual (Vela Supernova Remnant); line : profiles; supernova remnants ID LOCAL INTERSTELLAR-MEDIUM; CA-II; NA-I; GAS; PULSARS; NEBULA AB We have obtained high-resolution Ca II and Na I absorption-line spectra toward 68 OB stars in the direction of the Vela supernova remnant. The stars lie at distances of 190-2800 pc as determined by Hipparcos and spectroscopic parallax estimations. The presence of high-velocity absorption attributable to the remnant along some of the sight lines constrains the remnant distance to 250 +/- 30 pc. This distance is consistent with several recent investigations that suggest that the canonical remnant distance of 500 pc is too large. C1 Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. RP Cha, AN (reprint author), Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. NR 27 TC 85 Z9 86 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP L25 EP L28 DI 10.1086/311968 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AH UT WOS:000080226600007 ER PT J AU Krist, JE Stapelfeldt, KR Burrows, CJ Hester, JJ Watson, AM Ballester, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT AF Krist, JE Stapelfeldt, KR Burrows, CJ Hester, JJ Watson, AM Ballester, GE Clarke, JT Crisp, D Evans, RW Gallagher, JS Griffiths, RE Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Trauger, JT TI Hubble Space Telescope WFPC2 imaging of XZ Tauri: Time evolution of a Herbig-Haro bow shock SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; circumstellar matter; ISM : jets and outflows; stars : individual (XZ Tauri); stars : pre-main-sequence AB We report observations of dramatic morphological changes in the extremely young Herbig-Haro object ejected by the pre-main-sequence binary XZ Tauri. Nubble Space Telescope images taken in 1995 showed a filled bubble of emission nebulosity extending 4" north-northeast of the system in the direction of a previously known jet. New images obtained in 1998 show that the bubble has undergone a remarkable transition into a limb-brightened structure as it continues its motion away from the binary. The new images suggest that we may be witnessing the initial formation of the postshock cooling zone in a newly emerging Herbig-Haro bow shock system, probably accompanied by significant temporal evolution in the nebula's emission line spectrum. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. European Space Agcy, Div Astrophys, Dept Space Sci, F-75738 Paris, France. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Univ Wisconsin, Dept Astron, Madison, WI 53705 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. RP Krist, JE (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 9 TC 33 Z9 33 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP L35 EP L38 DI 10.1086/311961 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AH UT WOS:000080226600009 ER PT J AU Savaglio, S Ferguson, HC Brown, TM Espey, BR Sahu, KC Baum, SA Carollo, CM Kaiser, ME Stiavelli, M Williams, RE Wilson, J AF Savaglio, S Ferguson, HC Brown, TM Espey, BR Sahu, KC Baum, SA Carollo, CM Kaiser, ME Stiavelli, M Williams, RE Wilson, J TI The Ly alpha forest of the quasar in the Hubble Deep Field South SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; quasars : absorption lines; quasars : individual (J2233-606) ID STATISTICS; QSO AB The quasar in the Hubble Deep Field South (HDF-S), J2233-606 (z(em) = 2.23), has been observed exhaustively by ground-based telescopes and by the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope at low, medium, and high resolution in the spectral interval from 1120 to 10000 Angstrom. The combined data give continuous coverage of the Ly alpha forest from redshift 0.9 to 2.24. This very large baseline represents a unique opportunity to study in detail the distribution of clouds associated with emitting structures in the field of the quasar and in nearby fields already observed as part of the HDF-S campaign. Here we report on the main properties obtained from the large spectroscopic data set that is available for the Ly alpha clouds in the intermediate-redshift range of 1.20-2.20, where our present knowledge has been complicated by the difficulty in producing good data. The number density is shown to be higher than what is expected by extrapolating the results from both lower and higher redshifts: 63 +/- 8 lines with logN(HI) greater than or equal to 14.0 are found (including metal systems) at (z) = 1.7, compared with the similar to 40 lines predicted by extrapolating from previous studies. The redshift distribution of the Ly alpha clouds shows a region spanning z similar or equal to 1.383-1.460 (comoving size of 94 h(65)(-1) Mpc, Omega(0) = 1) with a low density of absorption lines; we detect five lines in this region, compared with the 16 expected from an average density along the line of sight. The two-point correlation function shows a positive signal up to scales of about 3 h(65)(-1) Mpc and an amplitude that is larger for larger H I column densities. The average Doppler parameter is about 27 km s(-1), which is comparable to the mean value found at z > 3, thus casting doubts on the temperature evolution of the Ly alpha clouds. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Baltimore, MD 21218 USA. Scuola Normale Super Pisa, I-56126 Pisa, Italy. RP Savaglio, S (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 16 TC 28 Z9 29 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 10 PY 1999 VL 515 IS 1 BP L5 EP L8 DI 10.1086/311963 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AH UT WOS:000080226600002 ER PT J AU Tessler, A Riggs, HR Dambach, M AF Tessler, A Riggs, HR Dambach, M TI A novel four-node quadrilateral smoothing element for stress enhancement and error estimation SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE error estimation; adaptive mesh refinement; stress recovery; smoothing technique; penalty method; penalty constraints ID SUPERCONVERGENT PATCH RECOVERY; EQUILIBRIUM; SHEAR; REP AB A four-node, quadrilateral smoothing element is developed based upon a penalized-discrete-least-squares variational formulation. The smoothing methodology recovers C-1-continuous stresses, thus enabling effective a posteriori error estimation and automatic adaptive mesh refinement. The element formulation is originated with a five-node macro-element configuration consisting of four triangular anisoparametric smoothing elements in a cross-diagonal pattern. This element pattern enables a convenient closed-form solution for the degrees of freedom of the interior node, resulting from enforcing explicitly a set of natural edge-wise penalty constraints. The degree-of-freedom reduction scheme leads to a very efficient formulation of a four-node quadrilateral smoothing element without any compromise in robustness and accuracy of the smoothing analysis. The application examples include stress recovery and error estimation in adaptive mesh refinement solutions for an elasticity problem and an aerospace structural component. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 NASA, Langley Res Ctr, Computat Struct Branch, Hampton, VA 23681 USA. Univ Hawaii Manoa, Dept Civil Engn, Honolulu, HI 96822 USA. George Washington Univ, NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Tessler, A (reprint author), NASA, Langley Res Ctr, Computat Struct Branch, Mail Stop 240, Hampton, VA 23681 USA. RI Tessler, Alexander/A-4729-2009 NR 28 TC 10 Z9 10 U1 0 U2 2 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 10 PY 1999 VL 44 IS 10 BP 1527 EP 1543 DI 10.1002/(SICI)1097-0207(19990410)44:10<1527::AID-NME497>3.0.CO;2-1 PG 21 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 177CF UT WOS:000079189300007 ER PT J AU Miller, RS Bellan, J AF Miller, RS Bellan, J TI Direct numerical simulation of a confined three-dimensional gas mixing layer with one evaporating hydrocarbon-droplet-laden stream SO JOURNAL OF FLUID MECHANICS LA English DT Article ID FREE SHEAR-LAYER; PARTICLE DISPERSION; TURBULENCE MODIFICATION; PREFERENTIAL CONCENTRATION; ISOTROPIC TURBULENCE; SOLID PARTICLES; FLOW; 2-PHASE; PLANE; VORTEX AB Direct numerical simulations are performed of a confined three-dimensional, temporally developing, initially isothermal gas mixing layer with one stream laden with as many as 7.3 x 10(5) evaporating hydrocarbon droplets, at moderate gas temperature and subsonic Mach number. Complete two-way phase couplings of mass, momentum and energy are incorporated which are based on a thermodynamically self-consistent specification of the vapour enthalpy, internal energy and latent heat of vaporization. Effects of the initial liquid mass loading ratio (ML), initial Stokes number (St(0)), initial droplet temperature and flow three-dimensionality on the mixing layer growth and development are discussed. The dominant parameter governing flow modulation is found to be the liquid mass loading ratio. Variations in the initial Stokes number over the range 0.5 less than or equal to St(0) less than or equal to 2.0 do not cause significant modulations of either first- or second-order gas phase statistics. The mixing layer growth rate and kinetic energy are increasingly attenuated for increasing liquid loadings in the range 0 less than or equal to ML less than or equal to 0.35. The laden stream becomes saturated before evaporation is completed for all but the smallest liquid loadings owing to. (i) latent heat effects which reduce the gas temperature, and (ii) build up of the evaporated vapour mass fraction. However, droplets continue to be entrained into the layer where they evaporate owing to contact with the relatively higher-temperature vapour-free gas stream. The droplets within the layer are observed to be centrifuged out of high-vorticity regions and to migrate towards high-strain regions of the flow. This results in the formation of concentration streaks in spanwise braid regions which are wrapped around the periphery of secondary streamwise vortices. Persistent regions of positive and negative slip velocity and slip temperature are identified. The velocity component variances in both the streamwise and spanwise directions are found to be larger for the droplets than for the gas phase on the unladen stream side of the layer; however, the cross-stream velocity and temperature variances are larger for the gas. Finally, both the mean streamwise gas velocity and droplet number density profiles are observed to coincide for all ML when the cross-stream coordinate is normalized by the instantaneous vorticity thickness; however, first-order thermodynamic profiles do not coincide. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Miller, RS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 125-21, Pasadena, CA 91109 USA. NR 54 TC 123 Z9 123 U1 1 U2 13 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 APR 10 PY 1999 VL 384 BP 293 EP 338 DI 10.1017/S0022112098004042 PG 46 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 200VK UT WOS:000080560600013 ER PT J AU Shindell, D Rind, D Balachandran, N Lean, J Lonergan, P AF Shindell, D Rind, D Balachandran, N Lean, J Lonergan, P TI Solar cycle variability, ozone, and climate SO SCIENCE LA English DT Article ID WINTER STRATOSPHERIC CIRCULATION; MIDDLE ATMOSPHERE; INTERANNUAL VARIABILITY; NORTHERN-HEMISPHERE; UV VARIABILITY; TROPOSPHERE; MODEL; TEMPERATURE; IMPACT; QBO AB Results from a global climate model including an interactive parameterization of stratospheric chemistry show how upper stratospheric ozone changes may amplify observed, 11-year solar cycle irradiance changes to affect climate. In the model, circulation changes initially induced in the stratosphere subsequently penetrate into the troposphere, demonstrating the importance of the dynamical coupling between the stratosphere and troposphere. The model reproduces many observed 11-year oscillations, including the relatively Long record of geopotential height variations; hence, it implies that these oscillations are likely driven, at Least in part, by solar variability. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. Space Sci & Applicat Inc, New York, NY 10025 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Shindell, D (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM dshindell@giss.nasa.gov RI Shindell, Drew/D-4636-2012; lionel, Scotto /K-8141-2012 NR 29 TC 378 Z9 390 U1 2 U2 34 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 9 PY 1999 VL 284 IS 5412 BP 305 EP 308 DI 10.1126/science.284.5412.305 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 184WH UT WOS:000079636400039 ER PT J AU Yang, L Srolovitz, DJ Yee, AF AF Yang, L Srolovitz, DJ Yee, AF TI Molecular dynamics study of isobaric and isochoric glass transitions in a model amorphous polymer SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID SIMULATIONS; SYSTEMS; POLYETHYLENE; TEMPERATURE; CONSTRAINTS; ENSEMBLE; MOTION AB We perform molecular dynamics simulations of the glass transition through isobaric and isochoric cooling of a model polymeric material. In general, excellent agreement between the simulation results and the existing experimental trends is observed. The glass transition temperature (T (g)) is found to be a function of pressure under isobaric conditions and specific volume under isochoric conditions. Under both isobaric and isochoric conditions, the trans-state fraction and the torsional contributions to the energy undergo abrupt changes at the glass transition temperature. We analyze these data to show that the glass transition is primarily associated with the freezing of the torsional degrees of the polymer chains which is strongly coupled to the degree of freedom associated with the nonbonded Lennard-Jones potential. We attribute the greater strength of the glass transition under constant pressure conditions to the fact that the nonbonded Lennard-Jones potential is sensitive to the specific volume, which does not change during cooling under isochoric conditions. Comparison of the isochoric and isobaric data demonstrate that the thermodynamic state is independent of cooling path above T (g), while path-dependent below T (g). The simulation data show that the free volume at the isobaric glass transition temperature is pressure dependent. We also find that a glass transition occurs under isochoric conditions, even though the free volume actually increases with decreasing temperature. (C) 1999 American Institute of Physics. C1 Univ Michigan, Dept Mat Sci & Engn, Ann Arbor, MI 48109 USA. RP Yang, L (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. RI Yee, Albert/E-5398-2010 OI Yee, Albert/0000-0002-5762-6042 NR 26 TC 29 Z9 30 U1 2 U2 6 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD APR 8 PY 1999 VL 110 IS 14 BP 7058 EP 7069 DI 10.1063/1.478611 PG 12 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 183ER UT WOS:000079541700049 ER PT J AU Rind, D AF Rind, D TI Global energy and water cycles SO NATURE LA English DT Book Review C1 NASA, Goddard Inst Space Studies, Goddard Inst Space Studies, New York, NY 10025 USA. RP Rind, D (reprint author), NASA, Goddard Inst Space Studies, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 1 TC 0 Z9 0 U1 1 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 8 PY 1999 VL 398 IS 6727 BP 480 EP 480 PG 1 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 185HQ UT WOS:000079662800037 ER PT J AU Nepstad, DC Verissimo, A Alencar, A Nobre, C Lima, E Lefebvre, P Schlesinger, P Potter, C Moutinho, P Mendoza, E Cochrane, M Brooks, V AF Nepstad, DC Verissimo, A Alencar, A Nobre, C Lima, E Lefebvre, P Schlesinger, P Potter, C Moutinho, P Mendoza, E Cochrane, M Brooks, V TI Large-scale impoverishment of Amazonian forests by logging and fire SO NATURE LA English DT Article ID BRAZILIAN AMAZONIA; SATELLITE DATA; EASTERN AMAZON; CLIMATE-CHANGE; DEFORESTATION; MANAGEMENT; PASTURES; FRONTIER AB Amazonian deforestation rates are used to determine human effects on the global carbon cycle(1-3) and to measure Brazil's progress in curbing forest impoverishment(1,4,5). But this widely used measure of tropical land use tells only part of the story. Here we present field surveys of wood mills and forest burning across Brazilian Amazonia which show that logging crews severely damage 10,000 to 15,000 km(2) yr(-1) of forest that are not included in deforestation mapping programmes. Moreover, we find that surface fires burn additional large areas of standing forest, the destruction of which is normally not documented. Forest impoverishment due to such fires may increase dramatically when severe droughts provoke forest leaf-shedding and greater flammability; our regional water-balance model indicates that an estimated 270,000 km(2) of forest became vulnerable to fire in the 1998 dry season. Overall, we find that present estimates of annual deforestation for Brazilian Amazonia capture less than half of the forest area that is impoverished each year, and even less during; years of severe drought. Both logging and fire increase forest vulnerability to future burning(6,7) and release forest carbon stocks to the atmosphere, potentially doubling net carbon emissions from regional land-use during severe El Nino episodes. If this forest impoverishment is to be controlled, then logging activities need to be restricted or replaced with low-impact timber harvest techniques, and more effective strategies to prevent accidental forest fires need to be implemented. C1 Woods Hole Res Ctr, Woods Hole, MA 02543 USA. UFPa, Inst Pesquisa Ambiental Amazonia Campus Guama, BR-66075970 Belem, Para, Brazil. IMAZON, Inst Homem & Meio Ambiente Amazonia, BR-66017000 Belem, Para, Brazil. Inst Nacl Pesquisas Espaciais, BR-12201970 Sao Jose Dos Campos, Brazil. NASA, Ecosyst Sci & Technol Branch, Ames Res Ctr, San Francisco, CA 94110 USA. Univ Fed Acre, Parque Zoobot, BR-69000 Acre, Brazil. RP Nepstad, DC (reprint author), Woods Hole Res Ctr, POB 296, Woods Hole, MA 02543 USA. NR 28 TC 697 Z9 735 U1 25 U2 194 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD APR 8 PY 1999 VL 398 IS 6727 BP 505 EP 508 DI 10.1038/19066 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 185HQ UT WOS:000079662800046 ER PT J AU Romanini, D Biennier, L Salama, F Kachanov, A Allamandola, LJ Stoeckel, F AF Romanini, D Biennier, L Salama, F Kachanov, A Allamandola, LJ Stoeckel, F TI Jet-discharge cavity ring-down spectroscopy of ionized polycyclic aromatic hydrocarbons: progress in testing the PAH hypothesis for the diffuse interstellar band problem SO CHEMICAL PHYSICS LETTERS LA English DT Article ID ABSORPTION-SPECTROSCOPY; CORONENE; OVALENE; CATIONS; SEARCH AB Naphthalene cations (C10H8+ were produced in a slit jet coupled with an electronic discharge, and cavity ring down was used to obtain its absorption spectrum in the region 645-680 nm. Two of the strongest C10H8+ bands previously characterized by matrix isolation spectroscopy were found, both with a fractional blue shift of about 0.5%. This is the first gas-phase electronic absorption spectrum of an ionized polycyclic aromatic hydrocarbon (PAH). This work opens the way for a direct comparison of laboratory PAH spectra with the diffuse interstellar bands (DIB), the origin of which still constitutes an open problem in astrophysics. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Grenoble 1, Spectrometrie Phys Lab, CNRS, UMR 5588, F-38402 St Martin Dheres, France. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Romanini, D (reprint author), Univ Grenoble 1, Spectrometrie Phys Lab, CNRS, UMR 5588, BP 87, F-38402 St Martin Dheres, France. RI Romanini, Daniele/C-6602-2008; Salama, Farid/A-8787-2009; Biennier, Ludovic/O-1618-2014 OI Salama, Farid/0000-0002-6064-4401; NR 19 TC 95 Z9 95 U1 2 U2 17 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 2 PY 1999 VL 303 IS 1-2 BP 165 EP 170 DI 10.1016/S0009-2614(99)00210-9 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 182YN UT WOS:000079525900025 PM 11542872 ER PT J AU Rind, D AF Rind, D TI Complexity and climate SO SCIENCE LA English DT Editorial Material ID ICE AB The climate that we experience results from both ordered forcing and chaotic behavior; the result is a system with characteristics of each. in forecasting prospective climate changes for the next century, the focus has been on the ordered system's responses to anthropogenic forcing. The chaotic component may be much harder to predict, but at this point it is not known how important it will be. C1 NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Rind, D (reprint author), NASA, Goddard Space Flight Ctr, Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 13 TC 82 Z9 100 U1 1 U2 6 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 2 PY 1999 VL 284 IS 5411 BP 105 EP 107 DI 10.1126/science.284.5411.105 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 182QE UT WOS:000079509000042 ER PT J AU Goldin, DS Venneri, SL Noor, AK AF Goldin, DS Venneri, SL Noor, AK TI New frontiers in design synthesis SO ACTA ASTRONAUTICA LA English DT Article ID COMPUTERS AB The Intelligent Synthesis Environment (ISE), which is one of the major strategic technologies under development at NASA centers and the University of Virginia, is described. One of the major objectives of ISE is to significantly enhance the rapid creation of innovative affordable products and missions. ISE uses a synergistic combination of leading-edge technologies, including high performance computing, high capacity communications and networking, human-centered computing, knowledge-based engineering, computational intelligence, virtual product development, and product information management. The environment will link scientists, design teams, manufacturers, suppliers, and consultants who participate in the mission synthesis as well as in the creation and operation of the aerospace system. It will radically advance the process by which complex science missions are synthesized, and high-tech engineering systems are designed, manufactured and operated. The five major components critical to ISE are human-centered computing infrastructure for distributed collaboration rapid synthesis and simulation tools, life cycle integration and validation, and cultural change in both the engineering and science creative process. The five components and their subelements are described. Related U.S. government programs are outlined and the future impact of ISE on engineering research and education is discussed. (C) 1998 American Institute of Aeronautics and Astronautics Inc. Published by Elsevier Science Ltd. AII rights reserved. C1 NASA Headquarters, Washington, DC 20546 USA. RP Goldin, DS (reprint author), NASA Headquarters, Washington, DC 20546 USA. NR 29 TC 2 Z9 3 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 EI 1879-2030 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR-JUN PY 1999 VL 44 IS 7-12 SI SI BP 407 EP 418 DI 10.1016/S0094-5765(99)00087-9 PG 12 WC Engineering, Aerospace SC Engineering GA 235RB UT WOS:000082555400012 PM 11542518 ER PT J AU Huntoon, CL AF Huntoon, CL TI New challenges for life sciences flight project management SO ACTA ASTRONAUTICA LA English DT Article AB Scientists have conducted studies involving human spaceflight crews for over three decades. These studies have progressed from simple observations before and after each flight to sophisticated experiments during flights of several weeks up to several months. The findings from these experiments are available in the scientific literature. Management of these flight experiments has grown into a system fashioned from the Apollo Program style, focusing on budgeting, scheduling and allocation of human and material resources. While these areas remain important to the future, the International Space Station (ISS) requires that the Life Sciences spaceflight experiments expand the existing project management methodology. The use of telescience with state-of-the-art information technology and the multi-national crews and investigators challenges the former management processes. Actually conducting experiments an board the ISS will be an enormous undertaking and International Agreements and Working Groups will be essential in giving guidance to the flight project management. Teams forged in this matrix environment must be competent to make decisions and qualified to work with the army of engineers, scientists, and the spaceflight crews. In order to undertake this complex task, data systems not previously used for these purposes must be adapted so that the investigators and the project management personnel can all share in important information as soon as it is available. The utilization of telescience and distributed experiment operations will allow the investigator to remain involved in their experiment as well as to understand the numerous issues faced by other elements of the program. The complexity in formation and management of project teams will be a new kind of challenge for international science programs. Meeting that challenge is essential to assure success of the International Space Station as a laboratory in space. (C) 1998 International Astronautical Federation Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Washington, DC 20546 USA. RP Huntoon, CL (reprint author), NASA, Washington, DC 20546 USA. NR 4 TC 0 Z9 0 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR-JUN PY 1999 VL 44 IS 7-12 SI SI BP 583 EP 584 DI 10.1016/S0094-5765(99)00066-1 PG 2 WC Engineering, Aerospace SC Engineering GA 235RB UT WOS:000082555400028 PM 11542522 ER PT J AU Loftus, JP AF Loftus, JP TI The management of the geostationary environment SO ACTA ASTRONAUTICA LA English DT Article AB The population in the geostationary orbit is increasing at the rate of about 25 spacecraft a year and operating lifetimes are increasing. The size of the spacecraft is increasing, as is the power level. The only way to protect the operational are is to reboost spacecraft at end of life to a burial orbit. While most operators do some reboost maneuver at end of mission there has been no agreed upon criterion for the maneuver. The ITU-R S, 1003(1) recommends reboost of not less than 300 km with the apogee as high as possible. The Interagency Debris Coordination Working Group (IADC) has recently achieved a consensus on a recommendation that the minimum maneuver be 235 km + Cr 1000 A/M. The concept is that this accommodates the +/-3 7.5 km variance in normal radial positioning and a 167.5 km corridor above the are for repositioning or supersynchronous delivery and establishes a criterion by which the dispositioned spacecraft will never enter that zone after its completion of the maneuver. It also deals with the fact the area mass ratio of spacecraft has been evolving to higher values. Earlier spacecraft had characteristic values of 0.03 but the average now is closer to 0.05 and there are some as great as 0.10. Disposition of the upper stage should be the same as the spacecraft if it is delivered to GSO, It is preferable to have the stage deliver the spacecraft supersynchronous and then have the spacecraft maneuver down to the GSO, (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Loftus, JP (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 6 TC 1 Z9 1 U1 1 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR-JUN PY 1999 VL 44 IS 7-12 SI SI BP 645 EP 648 DI 10.1016/S0094-5765(99)00097-1 PG 4 WC Engineering, Aerospace SC Engineering GA 235RB UT WOS:000082555400034 ER PT J AU Bartoe, JDF Jacobs, D Hall, E AF Bartoe, JDF Jacobs, D Hall, E TI International Space Station: Ready to fly SO ACTA ASTRONAUTICA LA English DT Article AB The International Space Station (ISS) is no longer a paper program, focused on design, development and planning. It is an operational program, with hardware soon to be launched and ground systems in place. Additional modules, components and elements are now under construction in almost all of the 16 ISS International Partner and Participant countries, with metal being bent, software being written, and testing ongoing. Crew members for the first four crews are in training in the U.S. and Russia, with the first crew launching in mid 1999. Mission control centers are fully functioning in Houston and Moscow, with operations centers in St. Hubert, Darmstadt, Tsukuba, Turino, and Huntsville going on line as they are required. The International Space Station, as the largest international civil program in history, features unprecedented technical, managerial, and international complexity. Seven international partners and participants encompassing 15 countries are involved in the ISS. Each partner is contributing and will be operating separate pieces of hardware, to be integrated on-orbit into a single orbital station. Mission control centers, launch vehicles, astronauts/cosmonauts, and support services will be provided by partners across the globe, but must function in a coordinated, integrated fashion. This paper will review the accomplishments of the ISS Program and each of the Partners and Participants over the past year, focusing on completed milestones and hardware. It will also give a status report on the development of the remainder of the ISS modules and components by each Partner and Participant, and discuss upcoming challenges. Published by Elsevier Science Ltd. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Bartoe, JDF (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 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 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR-JUN PY 1999 VL 44 IS 7-12 SI SI BP 657 EP 665 PG 9 WC Engineering, Aerospace SC Engineering GA 235RB UT WOS:000082555400036 ER PT J AU Sumrall, J Lane, C Cusic, R AF Sumrall, J Lane, C Cusic, R TI VentureStar (TM) ... Reaping the benefits of the X-33 program SO ACTA ASTRONAUTICA LA English DT Article AB Major X-33 flight hardware has been delivered, and assembly of the vehicle is well underway in anticipation of its flight test program commencing in the summer of 1999. Attention has now turned to the operational VentureStar(TM) the first single-stage-to-orbit (SSTO) reusable launch vehicle. Activities are grouped under two broad categories: (1) vehicle development and (2) market/business planning, each of which is discussed. The mission concept is presented for direct payload delivery to the International Space Station and to Low Earth orbit, as well as payload delivery with an upper stage to Geosynchronous Transfer Orbit (GTO) and other high energy orbits. System requirements include flight segment and ground segment. Vehicle system sizing and design status is provided including the application of X-33 traceability and lessons learned. Technology applications to the VentureStar(TM) are described including the structure, propellant tanks, thermal protection system, aerodynamics, subsystems, payload bay and propulsion. Developing a market driven low cost launch services system for the 21st Century requires traditional and non-traditional ways of being able to forecast the evolution of the potential market. The challenge is balancing both the technical and financial assumptions of the market. This involves the need to provide a capability to meet market segments that in some cases are very speculative, while at the same time providing the financial community with a credible revenue stream. Furthermore, the market derived requirements need to be assessed so as not to impose unnecessary requirements on the vehicle design that add unreasonable cost to the development of the system, yet provides the right capabilities for new markets that could be triggered by dramatically lower space transportation prices. (C) 1998 International Astronautical Federation Published by Elsevier Science Ltd. All rights reserved. C1 NASA Headquarters, Washington, DC 20546 USA. RP Sumrall, J (reprint author), NASA Headquarters, Washington, DC 20546 USA. NR 0 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 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD APR-JUN PY 1999 VL 44 IS 7-12 SI SI BP 727 EP 736 DI 10.1016/S0094-5765(99)00092-2 PG 10 WC Engineering, Aerospace SC Engineering GA 235RB UT WOS:000082555400044 ER PT J AU Hueter, U AF Hueter, U TI Creating an airline to the stars SO AEROSPACE AMERICA LA English DT Article C1 NASA Marshall, Adv Reusable Technol Project, Huntsville, AL 35812 USA. RP Hueter, U (reprint author), NASA Marshall, Adv Reusable Technol Project, Huntsville, AL 35812 USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD APR PY 1999 VL 37 IS 4 BP 40 EP 44 PG 5 WC Engineering, Aerospace SC Engineering GA 182BL UT WOS:000079478600014 ER PT J AU Jasinski, MF Crago, RD AF Jasinski, MF Crago, RD TI Estimation of vegetation aerodynamic roughness of natural regions using frontal area density determined from satellite imagery SO AGRICULTURAL AND FOREST METEOROLOGY LA English DT Article DE canopy area index; aerodynamic roughness; remote sensing; coniferous forest ID HAPEX-MOBILHY; LANDES FOREST; CANOPY; INDEX; REFLECTANCE; SENSITIVITY; SURFACES; BUDGET; FLUXES; SCALE AB Parameterizations of the frontal area index and canopy area index of natural or randomly distributed plants are developed and applied to the estimation of local aerodynamic roughness using satellite imagery. The formulas are expressed in terms of the subpixel fractional vegetation cover and one non-dimensional geometric parameter that characterizes the plant's shape. Geometrically similar plants and Poisson distributed plant centers are assumed. An appropriate averaging technique to extend satellite pixel-scale estimates to larger scales is provided. The parameterization is applied to the estimation of aerodynamic roughness using satellite imagery for a 2.3 km(2) coniferous portion of the Landes Forest near Lubbon, France, during the 1986 HAPEX-Mobilhy Experiment. The canopy area index is estimated first for each pixel in the scene based on previous estimates of fractional cover obtained using Landsat Thematic Mapper imagery. Next, the results are incorporated into Raupach's [Raupach, M.R., 1994. Boundary-Layer Meteorol. 71, 211-216] analytical formulas for momentum roughness and zero-plane displacement height. The estimates compare reasonably well to reference values determined from measurements taken during the experiment and to published literature values. The approach offers the potential for estimating regionally variable vegetation aerodynamic roughness lengths over natural regions using satellite imagery when there exists only limited knowledge of the vegetated surface, (C) 1999 Elsevier Science B.V, All rights reserved. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. Univ Illinois, Dept Civil & Mat Engn, Chicago, IL 60607 USA. RP Jasinski, MF (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. NR 37 TC 26 Z9 29 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-1923 J9 AGR FOREST METEOROL JI Agric. For. Meteorol. PD APR 1 PY 1999 VL 94 IS 1 BP 65 EP 77 DI 10.1016/S0168-1923(98)00129-4 PG 13 WC Agronomy; Forestry; Meteorology & Atmospheric Sciences SC Agriculture; Forestry; Meteorology & Atmospheric Sciences GA 189AV UT WOS:000079882700005 ER PT J AU Villante, U Lepidi, S Francia, P Vellante, M Meloni, A Lepping, RP Mariani, F AF Villante, U Lepidi, S Francia, P Vellante, M Meloni, A Lepping, RP Mariani, F TI Pc3 pulsations during variable IMF conditions SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Article DE magnetospheric physics (MHD waves and; instabilities; solar wind - magnetosphere interactions) ID LOW GEOMAGNETIC LATITUDES; PC-3 MAGNETIC PULSATIONS; FIELD LINE RESONANCES; LONG-PERIOD; CONE ANGLE; MAGNETOSPHERE; POLARIZATION; FREQUENCIES; WAVES AB Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy) during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica) provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes. C1 Univ Aquila, Dipartimento Fis, I-67100 Laquila, Italy. Ist Nazl Geofis, I-00161 Rome, Italy. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Roma Tor Vergata, Dipartimento Fis, I-00173 Rome, Italy. RP Villante, U (reprint author), Univ Aquila, Dipartimento Fis, I-67100 Laquila, Italy. OI Villante, Umberto/0000-0002-3630-7958 NR 29 TC 5 Z9 6 U1 0 U2 1 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 APR PY 1999 VL 17 IS 4 BP 490 EP 496 DI 10.1007/s00585-999-0490-x PG 7 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 188QY UT WOS:000079860900004 ER PT J AU Purucker, ME von Frese, RRB Taylor, PT AF Purucker, ME von Frese, RRB Taylor, PT TI Mapping and interpretation of satellite magnetic anomalies from POGO data over the Antarctic region SO ANNALI DI GEOFISICA LA English DT Article DE Antarctic; geomagnetic field; magnetic field satellites; magnetic anomalies ID REMANENT MAGNETIZATION; FIELD; COMPONENTS; OCEANS; MODEL; MAPS AB A satellite magnetic anomaly map made using the POGO magnetic field data is compared to three maps made using Magsat data. A total of 14 anomalies with magnitudes greater than 3 nT can be identified in all four of the maps poleward of 60 degrees S latitude. Forward models of the Antarctic continental and oceanic lithosphere are produced which use magnetic crustal thickness based on seismic and heat flow data, and which also use the distribution of the Cretaceous Quiet Zone from marine geophysics. These simple models can explain significant parts of eight of the 14 identified anomalies. The remaining anomalies may be caused by lateral variations of magnetization, inadequate models of the magnetic crustal thickness, or remanent magnetizations in directions other than the present field. In addition, contamination of the magnetic anomaly maps by fields of time-varying external origin (and their corresponding internal parts) is still a significant problem in the Antarctic region. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Raytheon ITSS, Greenbelt, MD 20771 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. Ohio State Univ, Dept Geol Sci, Columbus, OH 43210 USA. RP Purucker, ME (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, Raytheon ITSS, Greenbelt, MD 20771 USA. RI Taylor, Patrick/D-4707-2012 OI Taylor, Patrick/0000-0002-1212-9384 NR 29 TC 4 Z9 4 U1 1 U2 2 PU EDITRICE COMPOSITORI BOLOGNA PI BOLOGNA PA VIA STALINGRADO 97/2, I-40128 BOLOGNA, ITALY SN 0365-2556 J9 ANN GEOFIS JI Ann. Geofis. PD APR PY 1999 VL 42 IS 2 BP 215 EP 227 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 204KL UT WOS:000080763400008 ER PT J AU von Frese, RRB Kim, HR Tan, L Kim, JW Taylor, PT Purucker, ME Alsdorf, DE Raymond, CA AF von Frese, RRB Kim, HR Tan, L Kim, JW Taylor, PT Purucker, ME Alsdorf, DE Raymond, CA TI Satellite magnetic anomalies of the Antarctic crust SO ANNALI DI GEOFISICA LA English DT Article DE Antarctic; crust; magnetic anomalies; ADMAP; satellite surveys; airborne surveys ID FIELD; BOUNDARY; GRAVITY; INVERSION; MOHO AB Spatially and temporally static crustal magnetic anomalies are contaminated by static core field effects above spherical harmonic degree 12 and dynamic, large-amplitude external fields. To extract crustal magnetic anomalies from the measurements of NASA's Magsat mission, we separate crustal signals from both core and external field effects. In particular, we define Magsat anomalies relative to the degree 11 field and use spectral correlation theory to reduce them for external field effects. We obtain a model of Antarctic crustal thickness by comparing the region's terrain gravity effects to free-air gravity anomalies derived from the Earth Gravity Model 1996 (EGM96). To separate core and crustal magnetic effects, we obtain the pseudo-magnetic effect of the crustal thickness variations from their gravity effect via Poisson's theorem for correlative potentials. We compare the pseudo-magnetic effect of the crustal thickness variations to field differences between degrees 11 and 13 by spectral correlation analysis. We thus identify and remove possible residual core field effects in the Magsat anomalies relative to the degree 11 core field. The resultant anomalies reflect possible Antarctic contrasts due both to crustal thickness and intracrustal variations of magnetization. In addition, they provide important constraints on the geologic interpretation of aeromagnetic survey data, such as are available for the Weddell Province. These crustal anomalies also may be used to correct for long wavelength errors in regional compilations of near-surface magnetic survey data. However, the validity of these applications is limited by the poor quality of the Antarctic Magsat data that were obtained during austral Summer and Fall when south polar external field activity was maximum. Hence an important test and supplement for the Antarctic crustal Magsat anomaly map will be provided by the data from the recently launched Orsted mission, which will yield coverage over austral Winter and Spring periods when external field activity is minimal. C1 Ohio State Univ, Dept Geol Sci, Columbus, OH 43210 USA. Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. Sejong Univ, Dept Earth Sci, Seoul, South Korea. NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, RSTX, Greenbelt, MD 20771 USA. Cornell Univ, Dept Geol Sci, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP von Frese, RRB (reprint author), Ohio State Univ, Dept Geol Sci, 125 S Oval Mall, Columbus, OH 43210 USA. RI Taylor, Patrick/D-4707-2012 OI Taylor, Patrick/0000-0002-1212-9384 NR 42 TC 12 Z9 12 U1 0 U2 0 PU EDITRICE COMPOSITORI BOLOGNA PI BOLOGNA PA VIA STALINGRADO 97/2, I-40128 BOLOGNA, ITALY SN 0365-2556 J9 ANN GEOFIS JI Ann. Geofis. PD APR PY 1999 VL 42 IS 2 BP 309 EP 326 PG 18 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 204KL UT WOS:000080763400016 ER PT J AU Ovryn, B Andrews, JH AF Ovryn, B Andrews, JH TI Measurement of changes in optical path length and reflectivity with phase-shifting laser feedback interferometry SO APPLIED OPTICS LA English DT Article ID TIME HOLOGRAPHIC-INTERFEROMETRY; REAL-TIME; MICROSCOPY; DIODE AB The operating characteristics of a novel phase-shifting interferometer are presented. Interference arises by reflecting the light from a sample back into the cavity of a cw He-Ne laser. Changes in phase and fringe visibility are calculated from an overdetermined set of phase-shifted intensity measurements with the phase shifts being introduced with an electro-optic modulator. The interferometer is sensitive enough to measure displacements below 1 Hz with a rms error of approximately 1 nm from a sample that reflects only 3% of the 28 mu W that is incident on its surface. The interferometer is applied to the determination of cantilever bending of a piezoelectric bimorph. (C) 1999 Optical Society of America. C1 Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Natl Ctr Micrograv Res Fluids & Combust, Cleveland, OH 44135 USA. Youngstown State Univ, Dept Phys & Astron, Ctr Photon Induced Proc, Youngstown, OH 44555 USA. RP Ovryn, B (reprint author), Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NR 23 TC 20 Z9 22 U1 0 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD APR 1 PY 1999 VL 38 IS 10 BP 1959 EP 1967 DI 10.1364/AO.38.001959 PG 9 WC Optics SC Optics GA 184TU UT WOS:000079630200008 PM 18319751 ER PT J AU Phanord, DD Koshak, WJ Solakiewicz, RJ Blakeslee, RJ AF Phanord, DD Koshak, WJ Solakiewicz, RJ Blakeslee, RJ TI Calculation of the bulk electromagnetic properties of thunderclouds using a two-space scattering formalism SO APPLIED PHYSICS B-LASERS AND OPTICS LA English DT Article AB A two-space scatterer formalism and equivalent medium approach of Twersky are used to obtain formulas for the bulk electromagnetic parameters of a thundercloud medium. For simplicity, linearly polarized excitation is considered, and we assume that the thundercloud medium is composed only of monodispersed liquid water droplets and moist air, i.e., we neglect complications due to the presence of ice particles. A modified WKB approximation is applied to derive the two-space scattering amplitude. Optical constants of dry air, moist atmosphere, and water are employed to obtain results by iteration. The numerical values of the bulk parameters are required to replace the actual thundercloud medium with an equivalent medium, thereby simplifying the solution to future forward lightning radiative transfer studies. C1 Univ Wisconsin, Dept Math & Comp Sci, Whitewater, WI 53190 USA. NASA, Global Hydrol & Climate Ctr, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Chicago State Univ, Dept Math & Comp Sci, Chicago, IL USA. RP Phanord, DD (reprint author), Univ Wisconsin, Dept Math & Comp Sci, Whitewater, WI 53190 USA. NR 14 TC 0 Z9 0 U1 0 U2 0 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0946-2171 J9 APPL PHYS B-LASERS O JI Appl. Phys. B-Lasers Opt. PD APR PY 1999 VL 68 IS 4 BP 731 EP 734 DI 10.1007/s003400050695 PG 4 WC Optics; Physics, Applied SC Optics; Physics GA 181HB UT WOS:000079434500014 ER PT J AU Olivas, JD Acosta, E Barrera, EV AF Olivas, JD Acosta, E Barrera, EV TI Surface study of the bonding nature of ambient adsorbates to nickel alloy substrates using thermal desorption and X-ray photoelectron spectroscopy SO APPLIED SURFACE SCIENCE LA English DT Article DE X-ray photoelectron spectroscopy; contamination; desorption; cleaning ID CHEMISORBED CO; XPS; SPECTRA; DECOMPOSITION; ADSORPTION; ALUMINUM; TITANIUM AB The present study analyzed the surface effects resulting from cleaning of a Ni alloy with different solvents using an approach involving thermal desorption and X-ray photoelectron spectroscopy. The study focused on contaminant O and C species interactions with the polycrystalline substrate resulting from various solvent/ambient interactions. Each solvent resulted in evaporation and ambient adsorption behavior which produced contaminants characteristic of the solvent used. Combining desorption theory and surface spectroscopic techniques, a method of determining desorption behavior, independent of weight measurements, was developed. By comparison of ambient O species to substrate oxides, changes in adsorbate coverage were estimated for the denuding surfaces. Experimental values for desorption behaviors and relative desorption energetics were determined for ambient air on a polycrystalline substrate resulting from solvent/substrate interactions. Differences were discriminated between the preparation methods and shown to vary as a function of solvent used. The nature of a surface with contamination was explained on this basis. (C) 1999 Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91101 USA. Div Phys Sci, Kelly AFB, TX 78241 USA. Rice Univ, Rice Quantum Inst, Dept Mech Engn & Mat Sci, Houston, TX 77005 USA. RP Olivas, JD (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 40 TC 4 Z9 4 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0169-4332 J9 APPL SURF SCI JI Appl. Surf. Sci. PD APR PY 1999 VL 143 IS 1-4 BP 153 EP 168 DI 10.1016/S0169-4332(98)00373-0 PG 16 WC Chemistry, Physical; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Chemistry; Materials Science; Physics GA 192JB UT WOS:000080074200020 ER PT J AU Carlson, MN Holtzman, JA Grillmair, CJ Mould, JR Griffiths, RE Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Gallagher, JS Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Watson, AM Westphal, JA AF Carlson, MN Holtzman, JA Grillmair, CJ Mould, JR Griffiths, RE Ballester, GE Burrows, CJ Clarke, JT Crisp, D Evans, RW Gallagher, JS Hester, JJ Hoessel, JG Scowen, PA Stapelfeldt, KR Trauger, JT Watson, AM Westphal, JA TI Deep Hubble Space Telescope observations of blue star clusters in NGC 3597 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : star clusters ID GLOBULAR-CLUSTERS; GALAXY MERGERS; PERFORMANCE; CALIBRATION; NGC-1275; COUNTS; WFPC2 AB We have analyzed HST/WFPC2 images of NGC 3597 and find similar to 700 compact objects surrounding the galaxy with an average (B-R)(o) similar to 0.6. We propose that the majority of these objects are young globular clusters. They have a spread in colors that is consistent with that expected for a population of young clusters with a common age and spread induced by photometric errors and reddening within NGC 3597. If these objects were similar to the Galactic globular cluster system seen at a younger age, we would predict a turnover in the luminosity function at B similar to 23. However, we find that the luminosity function for the clusters is increasing to the limits of our photometry (B similar to 27). C1 New Mexico State Univ, Dept Astron, Dept 4500, Las Cruces, NM 88003 USA. CALTECH, SIRTF Sci Ctr, Pasadena, CA 91125 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. ESA, Dept Space Sci, Div Astrophys, F-75738 Paris 15, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP New Mexico State Univ, Dept Astron, Dept 4500, Box 30001, Las Cruces, NM 88003 USA. EM mcarlson@nmsu.edu; holtz@nmsu.edu; carl@bugaboo.ipac.caltech.edu; jrm@mso.anu.edu.au; gilda@sunshine.sprl.umich.edu; burrows@stsci.edu; clarke@sunshine.sprl.umich.edu; dc@crispy.jpl.nasa.gov; rwe@wfpc2-mail.jpl.nasa.gov; jsg@tiger.astro.wisc.edu; jjh@cosmos.la.asu.edu; hoessel@jth.astro.wisc.edu; scowen@tycho.la.asu.edu; krs@wfpc2-mail.jpl.nasa.gov; jtt@wfpc2-mail.jpl.nasa.gov; alan@astrosmo.unam.mx; jaw@sol1.gps.caltech.edu RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 21 TC 17 Z9 17 U1 0 U2 4 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD APR PY 1999 VL 117 IS 4 BP 1700 EP 1707 DI 10.1086/300819 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZK UT WOS:000080224500006 ER PT J AU Bottke, WF Richardson, DC Michel, P Love, SG AF Bottke, WF Richardson, DC Michel, P Love, SG TI 1620 Geographos and 433 Eros: Shaped by planetary tides? SO ASTRONOMICAL JOURNAL LA English DT Article DE celestial mechanics, stellar dynamics; minor planets, asteroids ID NEAR-EARTH ASTEROIDS; LINEAR SECULAR RESONANCES; SEMIMAJOR AXES SMALLER; TIDAL FORCES; CROSSING ASTEROIDS; DOUBLET CRATERS; 2 AU; DISRUPTION; 1620-GEOGRAPHOS; DYNAMICS AB Until recently, most asteroids were thought to be solid bodies whose shapes were determined largely by collisions with other asteroids. Recent work by Burns and others has shown that many asteroids may be little more than rubble piles, held together by self-gravity; this means that their shapes may be strongly distorted by tides during close encounters with planets. Here we report on numerical simulations of encounters between an ellipsoid-shaped rubble-pile asteroid and Earth. After an encounter, many of the simulated asteroids develop the same rotation rate and distinctive shape as 1620 Geographos (i.e., highly elongated with a single convex side, tapered ends, and small protuberances swept back against the rotation direction). Since our numerical studies show that these events occur with some frequency, we suggest that Geographos may be a tidally distorted object. In addition, our work shows that 433 Eros, which will be visited by the NEAR spacecraft in 1999, is much like Geographos, suggesting that it too may have been molded by tides in the past. C1 Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. Univ Washington, Dept Astron, Seattle, WA 98195 USA. Osservatorio Astron Torino, I-10025 Pino Torinese, Italy. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Bottke, WF (reprint author), Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. OI Richardson, Derek C/0000-0002-0054-6850 NR 40 TC 29 Z9 29 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1999 VL 117 IS 4 BP 1921 EP 1928 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZK UT WOS:000080224500024 ER PT J AU Kaas, AA Aksnes, K Franklin, F Lieske, J AF Kaas, AA Aksnes, K Franklin, F Lieske, J TI Astrometry from mutual phenomena of the Galilean satellites in 1990-1992 SO ASTRONOMICAL JOURNAL LA English DT Article DE astrometry; ephemerides; planets and satellites : individual (Jupiter) AB This paper derives astrometric data for the Galilean satellites from 213 light curves of 86 mutual eclipses and occultations that occurred in 1990-1992. Comparisons of these data with predictions based on the most precise modern ephemeris (E5) generally show good agreement, although it is rather poorer in the case of J1 (Io). C1 Stockholm Observ, S-13336 Saltsjobaden, Sweden. Univ Oslo, Inst Theoret Astrophys, N-0315 Oslo, Norway. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kaas, AA (reprint author), Stockholm Observ, S-13336 Saltsjobaden, Sweden. NR 7 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD APR PY 1999 VL 117 IS 4 BP 1933 EP 1941 DI 10.1086/300808 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZK UT WOS:000080224500026 ER PT J AU Fioc, M Rocca-Volmerange, B AF Fioc, M Rocca-Volmerange, B TI Far-UV and deep surveys: bursting dwarfs versus normal galaxies SO ASTRONOMY & ASTROPHYSICS LA English DT Review DE galaxies : evolution; galaxies : luminosity function, mass function; galaxies : starburst; cosmology : miscellaneous; ultraviolet : galaxies ID HIGH-REDSHIFT GALAXIES; INITIAL MASS FUNCTION; FAINT BLUE GALAXIES; NUMBER MAGNITUDE COUNTS; K-BAND SURVEY; STARBURST GALAXIES; STAR-FORMATION; FIELD GALAXIES; LUMINOSITY FUNCTIONS; KECK-TELESCOPE AB Galaxy counts from bright ultraviolet (UV) and deep optical spectroscopic surveys have revealed an unexpectedly large number of very blue galaxies (vBG). The colors and luminosities of these objects indicate that they are dwarf galaxies undergoing bursts of star formation. We use a galaxy evolution model (PEGASE, Fioc & Rocca-Volmerange 1997, hereafter FRV) to describe this population as galaxies undergoing cyclical bursts of star formation, thereby determining the luminosity function (LF) of these galaxies. When these bursting galaxies are added to normally evolving populations, the combination reproduces the UV number counts, color distributions and deep optical redshift distributions fairly well. Optical (including the Hubble Deep Field) and near-infrared number counts are fitted assuming an open or a flat, Lambda-dominated, Universe. The high amplitude of the angular correlation function of very blue galaxies discovered by Landy et al. (1996) is also recovered in this modelling. The number of bursting galaxies is only a small fraction of the total number of galaxies at optical and near-infrared wavelengths, even at faintest magnitudes. In our evolution modelling, normal galaxies explain most of the blue excess in a low-Omega Universe. The problem of the blue excess remains in a flat Universe without a cosmological constant. C1 Inst Astrophys, CNRS, F-75014 Paris, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. RP Fioc, M (reprint author), Inst Astrophys, CNRS, 98 Bis Bd Arago, F-75014 Paris, France. EM fioc@iap.fr NR 106 TC 32 Z9 32 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 PY 1999 VL 344 IS 2 BP 393 EP 401 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 189DL UT WOS:000079888800014 ER PT J AU Cappi, M Bassani, L Comastri, A Guainazzi, M Maccacaro, T Malaguti, G Matt, G Palumbo, GGC Blanco, P Dadina, M Dal Fiume, D Di Cocco, G Fabian, AC Frontera, F Maiolino, R Piro, L Trifoglio, M Zhang, N AF Cappi, M Bassani, L Comastri, A Guainazzi, M Maccacaro, T Malaguti, G Matt, G Palumbo, GGC Blanco, P Dadina, M Dal Fiume, D Di Cocco, G Fabian, AC Frontera, F Maiolino, R Piro, L Trifoglio, M Zhang, N TI BeppoSAX observations of Mkn 3: Piercing through the torus of a Seyfert 2 galaxy SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE galaxies : individual : Mkn 3; galaxies : Seyfert; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRUM; COLD MATTER; ASCA OBSERVATIONS; IRON LINE; REFLECTION; EMISSION; COMPLEX; MCG-5-23-16; SCATTERING AB A new BeppoSAX broad-band (0.6-150 keV) spectrum of the Seyfert 2 galaxy Mkn 3 is presented. The spectrum provides a direct measurement of a large, neutral column of gas with N-H similar to 10(24) cm(-2) in the source direction. The source, as bright as 3C 273 above 10 keV, has a steep (Gamma similar to 1.8) spectrum without any evidence of a high-energy cutoff up to at least 150 keV. At lower energies, the data are best modeled with the addition of an unabsorbed reflection component. Combining these data with previous Ginga and ASCA observations, the Fe K-alpha and reflection continuum indicate that the reprocessed emission is responding slower than the intrinsic continuum variations suggesting a size of the reprocessor greater than or similar to 2 pc. Identifying such a reprocessor with a (close to edge-on) obscuring torus, the overall result fits well into unified models since, presumably, one can interpret the strong absorption as due to transmission through the rim of the torus and the unabsorbed (directly viewed) reflection component as due to reprocessing from the torus inner surface. C1 CNR, Ist Tesre, I-40129 Bologna, Italy. Osservatorio Astron Bologna, I-40127 Bologna, Italy. European Space Agcy, ESTEC, SCD, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. Osservatorio Astron Brera, I-20121 Milan, Italy. Univ Roma 3, Dipartimento Fis, I-00146 Rome, Italy. Univ Bologna, Dipartimento Astron, I-40127 Bologna, Italy. UCSD, San Diego, CA USA. ASI, BeppoSAX SDC, I-00131 Rome, Italy. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. Osservatorio Astrofis Arcetri, I-5015 Florence, Italy. Ist Astrofis Spaziale, I-001333 Rome, Italy. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RP Cappi, M (reprint author), CNR, Ist Tesre, Via Gobetti 101, I-40129 Bologna, Italy. EM mcappi@tesre.bo.cnr.it RI PIRO, LUIGI/E-4954-2013; Cappi, Massimo/F-4813-2015; Trifoglio, Massimo/F-5302-2015; Comastri, Andrea/O-9543-2015; OI PIRO, LUIGI/0000-0003-4159-3984; Trifoglio, Massimo/0000-0002-2505-3630; Comastri, Andrea/0000-0003-3451-9970; Cappi, Massimo/0000-0001-6966-8920; Dadina, Mauro/0000-0002-7858-7564 NR 67 TC 46 Z9 46 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 PY 1999 VL 344 IS 3 BP 857 EP 867 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 191NC UT WOS:000080027600019 ER PT J AU Barrow, CH Woan, G MacDowall, RJ AF Barrow, CH Woan, G MacDowall, RJ TI Interplanetary scattering effects in the jovian bKOM radio emission observed by Ulysses SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE interplanetary medium; planets and satellites : individual : Jupiter; radio continuum : solar system ID SOLAR-WIND; PLASMA AB The scattering of radio waves by the interplanetary medium (subsequently referred to simply as 'scattering') imposes limitations on measurements of fine temporal and angular structure at low radio frequencies. The jovian broad-band kilometric radiation (bKOM) is highly structured and observations of this emission, by the Unified Radio and Plasma Experiment (URAP) on board ULYSSES, have been used to study scattering at extremely low frequencies. Structures observed in the bKOM during 1995-6, when the spacecraft was at distances greater than 5 AU from the planet, are compared with observations made in 1991 when the spacecraft was relatively close to Jupiter (similar to 1 AU). Measured values of the e-folding time are compared with theoretical values of temporal broadening and with solar wind electron density measurements made by the SWOOPS experiment on Ulysses. In general, we find that temporal broadening increases with source-observer distance and decreasing frequency, as expected from standard broadening theory, although a few inordinately low values were also observed at distances of 5 to 7 AU. At frequencies close to 45 kHz, an upper limit of about 8 min is clearly visible in observations of the temporal broadening made about 1 AU from Jupiter. Average values of the e-folding time at these same frequencies show a well-defined increase with distance from Jupiter of about 8 min AU(-1). We interpret this as 'saturated scattering,' where all ray paths between source and observer are explored, giving an,upper limit to the temporal broadening which the medium can introduce. These observations establish limits for scattering in the interplanetary medium (IPM), which are relevant to all low frequency radio observations. C1 Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. Univ Glasgow, Dept Phys & Astron, Glasgow G12 8QQ, Lanark, Scotland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Barrow, CH (reprint author), Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. RI MacDowall, Robert/D-2773-2012 NR 23 TC 4 Z9 4 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD APR PY 1999 VL 344 IS 3 BP 1001 EP 1013 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 191NC UT WOS:000080027600035 ER PT J AU Lestrade, JF Preston, PA Jones, DL Phillips, RB Rogers, AEE Titus, MA Rioja, MJ Gabuzda, DC AF Lestrade, JF Preston, PA Jones, DL Phillips, RB Rogers, AEE Titus, MA Rioja, MJ Gabuzda, DC TI High-precision VLBI astrometry of radio-emitting stars SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE techniques : interferometric; astrometry; reference systems; stars : binaries : general; stars : distances; radio continuum : stars ID BASE-LINE INTERFEROMETRY; T-TAURI STARS; REFERENCE-FRAME; HR 1099; SPECTROSCOPIC BINARY; CCD PARALLAXES; UX ARI; HIPPARCOS; SYSTEM; ALGOL AB Multiple-epoch phase-referenced VLBI observations of 11 radio-emitting stars have been conducted as part of an astrometric program to link the Hipparcos optical reference frame to the radio extragalactic reference frame. We present the VLBI positions, proper motions and trigonometric parallaxes from this program in the ICRF (International Celestial Reference Frame). These astrometric parameters are absolute because they are directly measured relative to the distant quasars used as VLBI phase reference calibrators. The mean astrometric precision achieved relative to the calibrators is 0.36 milliarcsecond and the highest precision is for the RS CVn close binary sigma(2) CrB with formal uncertainties of 0.12 milliarcsecond for its relative position, 0.05 milliarcsecond for its annual proper motion and 0.10 milliarcsecond for its trigonometric parallax. In addition to the Hipparcos link, these observations have provided several new results. The distance to the nearby Tau-Auriga star forming region is 148 +/- 5 pc, determined directly through the VLBI trigonometric parallax of the Pre-Main-Sequence star KD283447 of this region. The orthogonality of the 2 orbital planes in the ternary system Algol is supported by new astrometric evidences. The proper motions of HR5110, HR1099 and IM Peg, regarded as possible guide stars for the NASA Gravity Probe B space mission, have formal precisions of 0.16, 0.31 and 0.40 milliarcsecond per year, respectively, and the mission requirement is 0.15 milliarcsecond per year. The close binary UX Ari is the only star that exhibits an acceleration larger than 3 sigma and the most plausible cause is the gravitational interaction of a third body. The distances of the stars HD199178, IM Peg and AR Lac were uncertain by as much as 50% before our observations and are now 116 +/- 4, 97 +/- 6, 41.7 +/- 0.6 pc, respectively. The two X-ray binaries in our program, LSI61303 and Cyg X1, exhibit larger than expected post-fit position residuals. The linear scale of the rms of these residuals is > 10(13) cm, more than 10 times the stellar separations in these systems. For LSI 61303, this scale is consistent with the size of the free-free absorption region of the enshrouding material beyond which radio radiation can escape. This would argue for in situ acceleration of the energetic electrons responsible for the synchrotron emission detected by VLBI as proposed by Vestrand (1983). The space velocities of LSI 61303 and Cyg X1 determined with our VLBI proper motions, radial velocities and distances, are 58 +/- 6 and 70 +/- 3 km s(-1), respectively, and are relatively high. This is expected if a neutron star or a black hole lurk in these systems. C1 Observ Paris, CNRS, URA 1757, F-92195 Meudon, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. MIT, Haystack Observ, Westford, MA 01886 USA. Joint Inst VLBI Europe JIVE, NL-7990 AA Dwingeloo, Netherlands. PN Lebedev Phys Inst, Ctr Astro Space, Moscow 117924, Russia. RP Lestrade, JF (reprint author), Observ Paris, CNRS, URA 1757, F-92195 Meudon, France. EM lestrade@mesioa.obspm.fr NR 75 TC 93 Z9 93 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 PY 1999 VL 344 IS 3 BP 1014 EP 1026 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 191NC UT WOS:000080027600036 ER PT J AU Edelson, R Nandra, K AF Edelson, R Nandra, K TI A cutoff in the X-ray fluctuation power density spectrum of the Seyfert 1 galaxy NGC 3516 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 3516); galaxies : Seyfert; methods : statistical; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; BLACK-HOLE; VARIABILITY; EMISSION; ACCRETION; NGC-4151; NGC-3516; OSCILLATIONS; MODEL; STATE AB During 1997 March-July, the Rossi X-Ray Timing Explorer observed the bright, strongly variable Seyfert 1 galaxy NGC 3516 once every similar to 12.8 hours for 4.5 months and nearly continuously (with interruptions due to South Atlantic Anomaly passage but not Earth occultation) for a 4.2 day period in the middle. These were followed by ongoing monitoring once every similar to 4.3 days. These data are used to construct the first well-determined X-ray fluctuation power density spectrum (PDS) of an active galaxy to span more than four decades of usable temporal frequency. The PDS shows no signs of any strict or quasi-periodicity but does show a progressive flattening of the power-law slope from -1.74 at short timescales to -0.73 at longer timescales. This is the dearest observation to date of the long predicted cutoff in the PDS. The characteristic variability timescale corresponding to this cutoff temporal frequency is similar to 1 month. Although it is unclear how this timescale may be interpreted in terms of a physical size or process, there are several promising candidate models. The PDS appears similar to those seen for Galactic black hole candidates such as Cyg X-1, suggesting that these two classes of objects with very different luminosities and putative black hole masses (differing by more than a factor of 10(5)) may have similar X-ray generation processes and structures. C1 Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90095 USA. Univ Leicester, Xray Astron Grp, Leicester LE1 7RH, Leics, England. Eureka Sci, Oakland, CA 94602 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Edelson, R (reprint author), Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90095 USA. NR 51 TC 137 Z9 137 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1999 VL 514 IS 2 BP 682 EP 690 DI 10.1086/306980 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZQ UT WOS:000080225000015 ER PT J AU Della Ceca, R Griffiths, RE Heckman, TM Lehnert, MD Weaver, KA AF Della Ceca, R Griffiths, RE Heckman, TM Lehnert, MD Weaver, KA TI ASCA observations of the starburst-driven superwind galaxy NGC 2146: Broadband (0.6-9 keV) spectral properties SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : evolution; galaxies : ISM; galaxies : starburst; intergalactic medium; X-rays : galaxies ID X-RAY; ROSAT OBSERVATIONS; GAS; NGC-2146; OUTFLOWS; M82 AB We report ASCA GIS and SIS observations of the nearby (D = 11.6 Mpc), nearly edge-on, starburst galaxy NGC 2146. These X-ray spectral data complement ROSAT PSPC and HRI imaging already discussed in the literature. The broadband (0.6-9 keV) X-ray spectrum of NGC 2146 is best described by a two-component model, the soft X-ray emission being modeled by a Raymond-Smith thermal plasma model with a temperature of kT similar to 0.8 keV, while the hard X-ray emission is modeled by a thermal plasma model with kT similar to 8 keV, or by a power-law model with a photon index of similar to 1.7. We do not find compelling evidence of substantial excess absorption above the Galactic value. The total luminosities of NGC 2146 in the soft (0.5-2.0 keV), hard (2-10 keV), and broad (0.5-10.0 keV) energy bands are similar to 1.3 x 10(40), similar to 1.8 x 10(40), and similar to 3.1 x 10(40) ergs s(-1), respectively. The soft and hard thermal components provide about 30% and 70%, respectively, of the total luminosity in the 0.5-2.0 keV energy band, while in the 2-10 keV energy range only the hard component plays a major role. The spectral results allow us to set tighter constraints on the starburst-driven superwind model, which we show can satisfactorily account for the luminosity, mass, and energy content represented by the soft X-ray spectral component. We estimate that the mass outflow rate (similar to 9 M(.) yr(-1)) is about an order of magnitude greater than the predicted rate at which supernova and stellar winds return mass into the interstellar medium, and therefore we argue that the flow is strongly "mass loaded" with material in and around the starburst. The estimated outflow velocity of the hot gas is close to the escape velocity from the galaxy, so the fate of the gas is not clear. We suggest that the hard X-ray spectral component is due to the combined emission of X-ray binaries and/or young supernova remnants associated with the starburst. C1 Osserv Astron Brera, I-20121 Milan, Italy. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Sterrewacht Leiden, NL-2300 RA Leiden, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Della Ceca, R (reprint author), Osserv Astron Brera, I-20121 Milan, Italy. EM rdc@brera.mi.astro.it; griffith@astro.phys.cmu.edu; heckman@eta.pha.jhu.edu; lehnert@strw.leidenuniv.nl; kweaver@milkway.gsfc.nasa.gov NR 28 TC 40 Z9 40 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 APR 1 PY 1999 VL 514 IS 2 BP 772 EP 780 DI 10.1086/306984 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZQ UT WOS:000080225000021 ER PT J AU Hyung, S Aller, LH Feibelman, WA AF Hyung, S Aller, LH Feibelman, WA TI Spectroscopic observations of the planetary nebula NGC 6818 SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (NGC 6818); ISM : kinematics and dynamics; ultraviolet : ISM ID BRIGHT RING REGION; GASEOUS NEBULAE; EMISSION-LINES; OPTICAL-SPECTRUM; INTERCOMBINATION LINES; ULTRAVIOLET-SPECTRA; CENTRAL STARS; IV; EXCITATION; EVOLUTION AB NGC 6818 is a bright, high-excitation, fairly regular, planetary nebula with a rather rich spectrum. Its rather unusual kinematical structure, studied by Wilson, Weedman, and particularly by Sabbadin, is of special interest. We are here primarily concerned with its high-resolution spectrum as revealed by the Hamilton Echelle Spectrograph at Lick Observatory (resolution similar to 0.2 Angstrom) and supplemented by UV and IR data. These extensive data permit a determination of interstellar extinction, plasma diagnostics, and ionic concentrations. Establishing the chemical composition requires finding the ionization correction factors that may be estimated empirically for only a few elements. In general we rely on a composite theoretical model. The chemical composition appears to be unremarkable. C and N appear to be more abundant than in the Sun. Most other elements seem to have roughly a solar abundance, except for those depleted by grain formation. NGC 6818 may have originated from a star resembling the Sun at least in chemical composition. The central star is rather faint and possibly of the Wolf-Rayet type. Comparisons with model predictions suggest a L-star of about 3,500 L-star and T-star of at least 140,000 K. Comparison with theoretical tracks suggests an age of about 9000 yr. Spectroscopic studies show that the bright shell appears to consist of tangentially moving filaments of differing excitation, a complication that may explain why theoretical nebular models have difficulties. C1 Bohyunsan Opt Astron Observ, Youngcheon 770820, Kyungbuk, South Korea. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Hyung, S (reprint author), Bohyunsan Opt Astron Observ, Jachun POB 1, Youngcheon 770820, Kyungbuk, South Korea. NR 55 TC 13 Z9 13 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1999 VL 514 IS 2 BP 878 EP 894 DI 10.1086/306970 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZQ UT WOS:000080225000030 ER PT J AU Hollis, JM Bertram, R Wagner, RM Lampland, CO AF Hollis, JM Bertram, R Wagner, RM Lampland, CO TI The R Aquarii jet in hindsight SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (R Aquarii); ISM : jets and outflows; ISM : structure ID BINARY-SYSTEM; RADIO JET; MOTION; NEBULA AB The nebulosity surrounding R Aquarii was digitized from optical photographic plates obtained from the Lowell Observatory archive. These data, which span the period 1921-1950, suggest that the R Aqr jet, which was first observed and reported in the 1970s, was already affecting the inner compact nebulosity at earlier epochs. These results are the first observational evidence of an earlier origin for the R Aqr jet and, as such, are consistent with an estimated jet age of similar to 100 yr as determined from the proper motions of the oldest radio-jet components. C1 NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Greenbelt, MD 20771 USA. Univ Arizona, Steward Observ, Dept Astron, Tucson, AZ 85721 USA. Lowell Observ, Flagstaff, AZ 86001 USA. RP Hollis, JM (reprint author), NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Code 930, Greenbelt, MD 20771 USA. NR 27 TC 9 Z9 10 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1999 VL 514 IS 2 BP 895 EP 898 DI 10.1086/306979 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 194ZQ UT WOS:000080225000031 ER PT J AU Chen, W Gehrels, N AF Chen, W Gehrels, N TI The progenitor of the new COMPTEL/ROSAT supernova remnant in Vela SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; supernova remnants; supernovae : general ID GUM NEBULA; GAS AB We show that (1) the newly discovered supernova remnant (SNR) GRO J0852-4642/RX J0852.0-4622 was created by a core-collapse supernova of a massive star and (2) the same supernova event that produced the Ti-44 detected by COMPTEL from this source is probably also responsible for a large fraction of the observed Al-26 emission in the Vela region detected by the same instrument. The first conclusion is based on the fact that the remnant is currently expanding too slowly given its young age for it to be caused by a Type Ia supernova. If the current SNR shell expansion speed is greater than 3000 km s(-1), a 15 M-. Type II supernova with a moderate kinetic energy exploding at about 150 pc away is favored. If the SNR expansion speed is lower than 2000 km s(-1), as derived naively from the X-ray data, a much more energetic supernova is required to have occurred at similar to 250 pc away in a dense environment at the edge of the Gum Nebula. This progenitor has a preferred ejecta mass of less than or equal to 10 M-., and therefore it is probably a Type Ib or Type Ic supernova. However, the required high ambient density of n(H) greater than or equal to 100 cm(-3) in this scenario is difficult to reconcile with the regional CO data. A combination of our estimates of the age/energetics of the new SNR and the almost perfect positional coincidence of the new SNR with the centroid of the COMPTEL Al-26 emission feature of the Vela region strongly favors a causal connection. If confirmed, this will be the first case in which both Ti-44 and Al-26 are detected from the same young SNR, and together they can be used to select preferred theoretical core-collapse supernova models. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Chen, W (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RI Gehrels, Neil/D-2971-2012 NR 15 TC 15 Z9 16 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1999 VL 514 IS 2 BP L103 EP L106 DI 10.1086/311951 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AD UT WOS:000080226200012 ER PT J AU Gotthelf, EV Petre, R Vasisht, G AF Gotthelf, EV Petre, R Vasisht, G TI X-ray variability from the compact source in the supernova remnant RCW 103 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (1E 161348-5055); stars : neutron; supernova remnants; supernovae : individual (RCW 103); X-rays : stars ID NEUTRON-STARS; RCW-103; DISCOVERY; PULSAR; ENVELOPES; EMISSION AB A new ASCA observation of 1E 161348-5055, the central compact X-ray source in the supernova remnant RCW 103, reveals an order-of-magnitude decrease in its 3-10 keV flux since the previous ASCA measurement 4 yr earlier This result is difficult to reconcile with suggestions that the bulk of the emission is simple quasi-blackbody, cooling radiation from an isolated neutron star. Furthermore, archived Einstein and ROSAT data sets spanning 18 yr confirm that this source manifests long-term variability, to a lesser degree. This provides a natural explanation for difficulties encountered in reproducing the original Einstein detection of IE 161348-5055. Spectra from the new data are consistent with no significant spectral change despite the decline in luminosity. We find no evidence for a pulsed component in any of the data sets, with a best upper limit on the pulsed modulation of 13%. We discuss the phenomenology of this remarkable source. C1 Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gotthelf, EV (reprint author), Columbia Univ, Columbia Astrophys Lab, 550 W 120th St, New York, NY 10027 USA. NR 31 TC 52 Z9 52 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1999 VL 514 IS 2 BP L107 EP L110 DI 10.1086/311948 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AD UT WOS:000080226200013 ER PT J AU Sahai, R Hekkert, PT Morris, M Zijlstra, A Likkel, L AF Sahai, R Hekkert, PT Morris, M Zijlstra, A Likkel, L TI The "water-fountain nebula" IRAS 16342-3814: Hubble Space Telescope/very large array study of a bipolar protoplanetary nebula SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; planetary nebulae : general; stars : AGB and post-AGB; stars : mass loss ID MASS-LOSS RATES; PLANETARY-NEBULAE; FOOTPRINT M1-92; EVOLVED STARS; CARBON STARS; EMISSION; CO; PERFORMANCE; OUTFLOW; WFPC2 AB We present Hubble Space Telescope (HST) Wide-Field and Planetary Camera 2 images and VLA OH maser emission-line maps of the cold infrared object IRAS 16342-3814, believed to be a protoplanetary nebula. The HST images show an asymmetrical bipolar nebula, with the lobes separated by a dark equatorial waist. The two bright lobes and the dark waist are simply interpreted as bubble-like reflection nebulae illuminated by starlight escaping through polar holes in a dense, flattened, optically thick cocoon of dust, which completely obscures the central star A faint halo can be seen surrounding each of the lobes. The bubbles are likely to have been created by a fast outflow (evidenced by H2O emission) plowing into a surrounding dense, more slowly expanding, circumstellar envelope of the progenitor asymptotic giant-branch (AGB) star (evidenced by the halo). The IRAS fluxes indicate a circumstellar mass of about 0.7 M-.(D/2 kpc) and an AGE mass-loss rate of about 10(-4) M, yr(-1) (V-exp/15 km s(-1))(D/2 kpc)(2) (assuming a gas-to-dust ratio of 200). OH features with the largest redshifted and blueshifted velocities are concentrated around the bright eastern and western polar lobes, respectively, whereas intermediate-velocity features generally occur at low latitudes, in the dark waist region. We critically examine evidence for the post-AGE classification of IRAS 16342-3814. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Univ Calif Los Angeles, Div Astron & Astrophys, Los Angeles, CA 90095 USA. Inst Astrophys, F-75014 Paris, France. Univ Manchester, Inst Sci & Technol, Dept Phys, Manchester M60 1QD, Lancs, England. Univ Wisconsin, Dept Phys & Astron, Eau Claire, WI 54702 USA. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, MS 183-900, Pasadena, CA 91109 USA. NR 32 TC 80 Z9 80 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD APR 1 PY 1999 VL 514 IS 2 BP L115 EP L119 DI 10.1086/311955 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 195AD UT WOS:000080226200015 ER PT J AU Thakur, AN Singh, HB Mariani, P Chen, Y Wang, Y Jacob, DJ Brasseur, G Muller, JF Lawrence, M AF Thakur, AN Singh, HB Mariani, P Chen, Y Wang, Y Jacob, DJ Brasseur, G Muller, JF Lawrence, M TI Distribution of reactive nitrogen species in the remote free troposphere: data and model comparisons SO ATMOSPHERIC ENVIRONMENT LA English DT Article DE nitrogen oxides; troposphere; ozone; global models ID GLOBAL LIGHTNING DISTRIBUTIONS; ORGANIC-COMPOUND EMISSIONS; GENERAL-CIRCULATION MODEL; DRY DEPOSITION; TRACE GASES; NOX; CHEMISTRY; HYDROCARBONS; CONSTRAINTS; TRANSPORT AB The available reactive nitrogen measurements from the global free troposphere obtained during the period of 1985-1995 have been compiled and analyzed. The species of interest are NO, NOx (NO + NO2), NOy, PAN, HNO3 and O-3. Data extending to 13 km have been gridded with a 5 degrees x 5 degrees horizontal and 1 km vertical resolution. The data have been divided into two seasons, namely "Winter" and "Summer" depending upon the time and location of the observations. Data described here as well as additional analysis have also been archived and are accessible on-line through the World Wide Web at: http://george.arc.nasa.gov/ similar to athakur. Global maps of the reactive nitrogen species distribution are produced in a form that would be most useful for the test and evaluation of models of tropospheric transport and chemistry. Limited comparisons of the observed reactive nitrogen species data with predictions by 3-D global models were performed using three selected models. Significant model to model as well as data to model differences were frequently observed. During summer, models tended to underpredict NO (-25 to -60%) while significantly overpredicting HNO3 (+ 250 to + 400%) especially in the upper troposphere. Similarly, the seasonal HNO3 variations predicted by some models were opposite to those observed. PAN was generally overpredicted, especially in the upper troposphere, while NOy was underpredicted. Ozone on average was better simulated but significant deviations at specific locations were evident. By comparing model predictions with observations, an overall quantitative assessment of the accuracy with which these three models describe the global distribution of measured reactive nitrogen species is provided. No reliable trend information for any of the reactive nitrogen species was possible based on the presently available data set. The reactive nitrogen data currently offer only a limited spatial and temporal coverage for the validation of global models. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Harvard Univ, Cambridge, MA 02139 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Belgian Inst Space Aeron, Brussels, Belgium. Max Planck Inst Chem, D-55128 Mainz, Germany. RP Singh, HB (reprint author), NASA, Ames Res Ctr, MS 245-5, Moffett Field, CA 94035 USA. EM hsingh@mail.arc.nasa.gov RI Wang, Yuhang/B-5578-2014 NR 58 TC 56 Z9 57 U1 1 U2 14 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD APR PY 1999 VL 33 IS 9 BP 1403 EP 1422 DI 10.1016/S1352-2310(98)00281-7 PG 20 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 170BX UT WOS:000078786900007 ER PT J AU Allen, AG Grenfell, JL Harrison, RM James, J Evans, MJ AF Allen, AG Grenfell, JL Harrison, RM James, J Evans, MJ TI Nanoparticle formation in marine airmasses: contrasting behaviour of the open ocean and coastal environments SO ATMOSPHERIC RESEARCH LA English DT Article DE nanoparticles; nucleation; formation mechanisms; troposphere ID CLOUD CONDENSATION NUCLEI; DIMETHYL SULFIDE; BOUNDARY-LAYER; AITKEN NUCLEI; AEROSOL; AIR; SULFUR; METHANESULFONATE; EPIPHANIOMETER; DISTRIBUTIONS AB Massive and rapid increases in nanoparticles have been observed at a remote coastal site in western Ireland. The same phenomenon was not detected aboard a ship situated approximately 160 km off-coast. On-shore nanoparticles correlated remarkably well with the march of the tide, peaking at low-water. This suggests a link between marine biogenic gas emissions (as yet unidentified) and nanoparticle formation events. This paper examines the contrasting behaviour observed at the coast and in the open ocean, with respect to nanoparticle formation. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Birmingham, Inst Publ & Environm Hlth, Birmingham B15 2TT, W Midlands, England. Columbia Univ, NASA, GISS, New York, NY 10025 USA. Univ Cambridge, Dept Chem, Ctr Atmospher Sci, Cambridge CB2 1EW, England. RP Harrison, RM (reprint author), Univ Birmingham, Inst Publ & Environm Hlth, Birmingham B15 2TT, W Midlands, England. RI Harrison, Roy/A-2256-2008; Evans, Mathew/A-3886-2012 OI Harrison, Roy/0000-0002-2684-5226; Evans, Mathew/0000-0003-4775-032X NR 31 TC 15 Z9 15 U1 1 U2 5 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD APR PY 1999 VL 51 IS 1 BP 1 EP 14 DI 10.1016/S0169-8095(98)00111-2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 177UD UT WOS:000079228700001 ER PT J AU Breininger, DR AF Breininger, DR TI Florida Scrub-Jay demography and dispersal in a fragmented landscape SO AUK LA English DT Article ID SUCCESS AB I measured population dynamics and cooperative breeding in an isolated population of Florida Scrub-lays (Aphelocoma coerulescens) on an urban barrier island in southern Brevard County Florida. In 1992, the scrub-jay population consisted of 29 breeding pairs within six population clusters that comprised two subpopulations, By 1998, the population declined to 10 pairs in four clusters because of poor reproductive success. The frequency of breeding by one-year-olds was related to the availability of breeding vacancies that increased as the population declined. Nearly half of the breeding vacancies were filled by jays that had bred previously but lost their mates. Sex differences in dispersal tendencies led to frequent exchanges of females (but not males) among clusters. The largest clusters did not sustain the smallest ones. Mortality of scrub-jays that resided in the smallest subpopulation exceeded reproductive success, but this subpopulation served as a net source of replacement breeders for the largest subpopulation as the population declined. C1 NASA, Biomed Operat Off, Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. RP Breininger, DR (reprint author), NASA, Biomed Operat Off, Dynamac Corp, Kennedy Space Ctr, FL 32899 USA. NR 26 TC 31 Z9 32 U1 2 U2 5 PU AMER ORNITHOLOGISTS UNION PI LAWRENCE PA ORNITHOLOGICAL SOC NORTH AMER PO BOX 1897, LAWRENCE, KS 66044-8897 USA SN 0004-8038 J9 AUK JI AUK PD APR PY 1999 VL 116 IS 2 BP 520 EP 527 PG 8 WC Ornithology SC Zoology GA 191CD UT WOS:000080002900022 ER PT J AU Hoffman, BD Baumgartner, ET Huntsberger, TL Schenker, PS AF Hoffman, BD Baumgartner, ET Huntsberger, TL Schenker, PS TI Improved rover state estimation in challenging terrain SO AUTONOMOUS ROBOTS LA English DT Article DE planetary rovers; range map registration; state estimation; vision-based navigation; real-time path planning ID MOBILE ROBOTS; NAVIGATION AB Given ambitious mission objectives and long delay times between command-uplink/data-downlink sessions, increased autonomy is required for planetary rovers. Specifically, NASA's planned 2003 and 2005 Mars rover missions must incorporate increased autonomy if their desired mission goals are to be realized. Increased autonomy, including autonomous path planning and navigation to user designated goals, relies on good quality estimates of the rover's state, e.g., its position and orientation relative to some initial reference frame. The challenging terrain over which the rover will necessarily traverse tends to seriously degrade a dead-reckoned state estimate, given severe wheel slip and/or interaction with obstacles. In this paper, we present the implementation of a complete rover navigation system. First, the system is able to adaptively construct semi-sparse terrain maps based on the current ground texture and distances to possible nearby obstacles. Second, the rover is able to match successively constructed terrain maps to obtain a vision-based state estimate which can then be fused with wheel odometry to obtain a much improved state estimate. Finally the rover makes use of this state estimate to perform autonomous real-time path planning and navigation to user designated goals. Reactive obstacle avoidance is also implemented for roaming in an environment in the absence of a user designated goal. The system is demonstrated in soft soil and relatively dense rock fields, achieving state estimates that are significantly improved with respect to dead reckoning alone (e.g., 0.38 m mean absolute error vs. 1.34 m), and successfully navigating in multiple trials to user designated goals. C1 Silicon Graph Comp Syst, Mt View, CA 94043 USA. CALTECH, Jet Prop Lab, Sci & Technol Dev Sect, Pasadena, CA 91109 USA. RP Hoffman, BD (reprint author), Silicon Graph Comp Syst, Mt View, CA 94043 USA. NR 30 TC 24 Z9 24 U1 0 U2 2 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0929-5593 J9 AUTON ROBOT JI Auton. Robot. PD APR PY 1999 VL 6 IS 2 BP 113 EP 130 DI 10.1023/A:1008879310128 PG 18 WC Computer Science, Artificial Intelligence; Robotics SC Computer Science; Robotics GA 203YH UT WOS:000080735400002 ER PT J AU Gennery, DB AF Gennery, DB TI Traversability analysis and path planning for a planetary rover SO AUTONOMOUS ROBOTS LA English DT Article DE mobile robots; sensor fusion; terrain mapping; obstacle avoidance; uncertainty ID MOBILE AB A method of analyzing three-dimensional data such as might be produced by stereo vision or a laser range finder in order to plan a path for a vehicle such as a Mars rover is described. In order to produce robust results from data that is sparse and of varying accuracy, the method takes into account the accuracy of each data point, as represented by its covariance matrix. It computes estimates of smoothed and interpolated height, slope, and roughness at equally spaced horizontal intervals, as well as accuracy estimates of these quantities. From this data, a cost function is computed that takes into account both the distance traveled and the probability that each region is traversable. A parallel search algorithm that finds the path of minimum cost also is described. Examples using real data are presented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gennery, DB (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM gennery@robotics.jpl.nasa.gov NR 32 TC 55 Z9 58 U1 0 U2 6 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0929-5593 EI 1573-7527 J9 AUTON ROBOT JI Auton. Robot. PD APR PY 1999 VL 6 IS 2 BP 131 EP 146 DI 10.1023/A:1008831426966 PG 16 WC Computer Science, Artificial Intelligence; Robotics SC Computer Science; Robotics GA 203YH UT WOS:000080735400003 ER PT J AU Geerts, B AF Geerts, B TI Trends in atmospheric science journals: A reader's perspective SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article AB A survey of 22 atmospheric science journals shows that the number of published articles tripled in 30 years during 1965-95, so that it has become increasingly difficult to keep abreast of the literature. A total of 1642 peer-reviewed articles in the journals were categorized numerically in terms of features of the abstracts and the conclusions. Consistent differences were found between journals. Most journals are mediocre in terms of their reader-friendliness, with little or no improvement over recent decades. The abstract and/or the conclusions in many papers have become too long and too discursive, preventing the reader from making a rapid assessment of the papers' usefulness. These trends may retard atmospheric research. Therefore journal editors are urged to insist on some easy improvements. C1 Goddard Space Flight Ctr, Greenbelt, MD USA. RP Geerts, B (reprint author), Sci Sysy & Applicat Inc, NASA, GSFC, Mail Code 912, Greenbelt, MD 20771 USA. NR 18 TC 5 Z9 5 U1 1 U2 8 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 1999 VL 80 IS 4 BP 639 EP 651 DI 10.1175/1520-0477(1999)080<0639:TIASJA>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 189FW UT WOS:000079894800004 ER PT J AU Hard, JJ Hoard, WR AF Hard, JJ Hoard, WR TI Analysis of straying variation in Alaskan hatchery chinook salmon (Oncorhynchus tshawytscha) following transplantation SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID PACIFIC SALMON; COHO SALMON; COLUMBIA RIVER; KISUTCH; PATTERNS; POPULATIONS; BEHAVIOR; STOCKS AB In 1976 chinook salmon (Oncorhynchus tshawytscha) gametes from the Chickamin and Unuk rivers in southeastern Alaska were transplanted 250 km to establish hatchery runs at Little Port Waiter (LPW), Baranof Island. From 1977 to 1989, 1 862 058 marked smelts from 12 broods were released from LPW. Woming and straying were estimated from adult recoveries at 25 locations in Alaska and British Columbia between 1981 and 1989. Of 22 198 LPW fish recovered over this period, 21 934 (98.8%) were collected at LPW. Of 264 fish recovered elsewhere, 38.3% were within 7 km of LPW; 64.4% were within 25 km of LPW. No LPW fish were recovered from the ancestral rivers, but nine fish were recovered from rivers supporting wild chinook salmon. Straying declined with distance from the release site but varied between hatcheries and streams. Straying declined with increasing age and run size. Straying was similar between the populations but varied among broods, and analysis of straying in experimental groups provided evidence for a heritable component. Males strayed more often than females. Population, gender, run size, and recovery age interacted to produce substantial variation in straying, indicating that run composition can produce complex straying responses. C1 NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Seattle, WA 98112 USA. Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Hard, JJ (reprint author), NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, 2725 Montlake Blvd E, Seattle, WA 98112 USA. EM jeff.hard@noaa.gov RI Hard, Jeffrey/C-7229-2009 NR 39 TC 42 Z9 44 U1 1 U2 7 PU CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS PI OTTAWA PA 65 AURIGA DR, SUITE 203, OTTAWA, ON K2E 7W6, CANADA SN 0706-652X EI 1205-7533 J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD APR PY 1999 VL 56 IS 4 BP 578 EP 589 DI 10.1139/cjfas-56-4-578 PG 12 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 209BR UT WOS:000081027900006 ER PT J AU Curran, MD Gedris, TE Stiegman, AE Plett, GA AF Curran, MD Gedris, TE Stiegman, AE Plett, GA TI Synthetic control over the production of multicomponent sol-gel materials: Fabrication of homogeneous vanadia-silica xerogels with high vanadium content SO CHEMISTRY OF MATERIALS LA English DT Article ID RAMAN-SPECTROSCOPY; OXIDE CATALYSTS; V-51 NMR; REDUCTION; TEMPERATURE; V2O5 AB The effect of Bronsted acid catalysts on the gelation times and final homogeneity of vanadia-silica sol-gel derived glass is reported. It was found that the addition of hydrochloric acid reduced the gelation times, especially at high acid concentrations. This acid also caused slow reduction of the V(V) to V(IV) during the process. Drying of the V(IV)containing xerogels at 500 degrees C resulted in their reoxidation to V(V). Characterization of the reoxidized gels by Raman and V-51 solid-state NMR spectroscopies verified that the structure of the vanadium(Tr) sites that were created from the reoxidation of the V(IV) sites were of pseudotetrahedral geometry with a short terminal oxo group and three Si-O-V linkages. This is the same site produced from direct incorporation of oxovanadium(V) into the gel without reduction occurring. A benefit is realized in this reduction-reoxidation process in that relatively high loadings (12.3 mol % or 17 wt % V2O5) Of vanadium can bt incorporated into the silica matrix while homogeneity is still maintained. Use of nonreducing acids such as HNO3 resulted in no particular gains in vanadium loading, and in fact, materials produced with this acid were similar to those made with no added acid. The transition between homogeneous and heterogeneous materials is also discussed. C1 Florida State Univ, Dept Chem, Tallahassee, FL 32306 USA. Florida State Univ, Ctr Mat Res & Technol, Tallahassee, FL 32306 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Stiegman, AE (reprint author), Florida State Univ, Dept Chem, Tallahassee, FL 32306 USA. NR 34 TC 24 Z9 24 U1 0 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0897-4756 J9 CHEM MATER JI Chem. Mat. PD APR PY 1999 VL 11 IS 4 BP 1120 EP 1127 DI 10.1021/cm981119y PG 8 WC Chemistry, Physical; Materials Science, Multidisciplinary SC Chemistry; Materials Science GA 188KN UT WOS:000079845700038 ER PT J AU Pawson, S Fiorino, M AF Pawson, S Fiorino, M TI A comparison of reanalyses in the tropical stratosphere. Part 3: Inclusion of the pre-satellite data era SO CLIMATE DYNAMICS LA English DT Article ID QUASI-BIENNIAL OSCILLATION; TEMPERATURE AB In this study, previous evaluations of the monthly mean structure of the tropical lower stratosphere in reanalyzed datasets are extended to include the period 1958-1978, when no satellite-based observations were available. It is shown that a large discontinuity, in temperatures near the tropical tropopause, in the NCEP data occurred when the Tires Operational Vertical Sounder (TOVS) became operational. When only rawinsonde data were available, the tropopause temperatures in the NCEP dataset are in better agreement with ERA data for TOVS period. Both NCEP and NASA reanalyses show similar deviations from the ERA data in the TOVS renalyses show similar deviations from the ERA data in the TOVS period. There is also a stepwise change in the lower stratospheric meridional velocity when the TOVS data were introduced into the NCEP reanalyses. This discontinuity is such that in the 1958-1978 period, the annual cycle in zonal mean meridional velocity in the NCEP data resembles that of the ERA data in the 1979-1993 period. The differences are shown to result from large changes in the local meridional flow in the Indonesian region. The temporal consistency of the QBO is examined; it is shown that the NCEP assimilation system is sensitive to the data available. There is a change in the zonally asymmetric structure of the zonal wind over time, presumably related to the changes in input data and the inability of the model to represent the three-dimensional structure of the tropical lower stratosphere. These results provide further evidence of the value of rawinsonde data in data assimilation systems as well as the need to use satellite radiance data in an appropriate manner. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Calif Lawrence Livermore Natl Lab, Program Climate Model Diag & Intercomparison, Livermore, CA 94550 USA. RP Pawson, S (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RI Fiorino, Michael/N-4150-2014; Pawson, Steven/I-1865-2014 OI Fiorino, Michael/0000-0002-2819-8157; Pawson, Steven/0000-0003-0200-717X NR 16 TC 41 Z9 43 U1 1 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD APR PY 1999 VL 15 IS 4 BP 241 EP 250 DI 10.1007/s003820050279 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 188UQ UT WOS:000079867400001 ER PT J AU Lohn, JD AF Lohn, JD TI Experiments on evolving software models of analog circuits SO COMMUNICATIONS OF THE ACM LA English DT Hardware Review C1 Caelum Res Corp, NASA Ames Res Ctr, Moffett Field, CA USA. RP Lohn, JD (reprint author), Caelum Res Corp, NASA Ames Res Ctr, Moffett Field, CA USA. NR 6 TC 4 Z9 4 U1 0 U2 0 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 1515 BROADWAY, NEW YORK, NY 10036 USA SN 0001-0782 J9 COMMUN ACM JI Commun. ACM PD APR PY 1999 VL 42 IS 4 BP 67 EP 69 DI 10.1145/299157.299875 PG 3 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA 181AG UT WOS:000079418000020 ER EF