FN Thomson Reuters Web of Science™ VR 1.0 PT J AU O'Neill, PM Badhwar, GD Culpepper, WX AF O'Neill, PM Badhwar, GD Culpepper, WX TI Internuclear cascade - Evaporation model for LET spectra of 200 MeV protons used for parts testing SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID SINGLE EVENT UPSETS; HEAVY-IONS; DEPOSITION AB The Linear Energy Transfer (LET) spectrum produced in microelectronic components during testing with 200 MeV protons is calculated with an internuclear cascade evaporation code. This spectrum is compared to the natural space heavy ion environment for various earth orbits. This comparison is used to evaluate the results of proton testing in terms of determining a firm upper bound to the on-orbit heavy ion upset rate and the risk of on-orbit heavy ion failures that would not be detected with protons. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP O'Neill, PM (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 27 TC 47 Z9 48 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2467 EP 2474 DI 10.1109/23.736487 PN 1 PG 8 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200021 PM 11542300 ER PT J AU Johnston, AH Swift, GM Miyahira, T Edmonds, LD AF Johnston, AH Swift, GM Miyahira, T Edmonds, LD TI Breakdown of gate oxides during irradiation with heavy ions SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID CHARGE AB Breakdown of thin gate oxides from heavy ions is investigated using capacitor test structures. Soft breakdown was observed for 45 Angstrom oxides, but not for 75 Angstrom oxides. Lower critical fields were observed when experiments were done with high fluences during each successive step. This implies that oxide defects play an important role in breakdown from heavy ions and that breakdown occurs more readily when an ion strike occurs close to a defect site. Critical fields for 75 Angstrom oxides are low enough to allow gate rupture to occur at normal supply voltages for ions with high LET. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Johnston, AH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 17 TC 52 Z9 52 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2500 EP 2508 DI 10.1109/23.736491 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200025 ER PT J AU Katz, R Wang, JJ Koga, R LaBel, KA McCollum, J Brown, R Reed, RA Cronquist, B Crain, S Scott, T Paolini, W Sin, B AF Katz, R Wang, JJ Koga, R LaBel, KA McCollum, J Brown, R Reed, RA Cronquist, B Crain, S Scott, T Paolini, W Sin, B TI Current radiation issues for programmable elements and devices SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm AB State of the art programmable devices are utilizing advanced processing technologies, non-standard circuit structures, and unique electrical elements in commercial-off-the-shelf (COTS)-based, high-performance devices. This paper will discuss that the above factors, coupled with the systems application environment, have a strong interplay that affect the radiation hardness of programmable devices and have resultant system impacts in (1) reliability of the unprogrammed, biased antifuse for heavy ions (rupture), (2) logic upset manifesting itself as clock upset, and (3) configuration upset. General radiation characteristics of advanced technologies are examined and manufacturers' modifications to their COTS-based and their impact on future programmable devices will be analyzed. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Actel Corp, Sunnyvale, CA 94086 USA. Aerospace Corp, Los Angeles, CA 90009 USA. Lockheed Martin Fed Syst, Manassas, VA USA. RP Katz, R (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 13 TC 18 Z9 19 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2600 EP 2610 DI 10.1109/23.736503 PN 1 PG 11 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200037 ER PT J AU Rax, BG Johnston, AH Lee, CI AF Rax, BG Johnston, AH Lee, CI TI Proton damage effects in linear integrated circuits SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID GAIN DEGRADATION; BIPOLAR; RADIATION AB Proton tests of linear integrated circuits have identified devices where significantly more damage occurs at equivalent total dose levels with protons than with gamma rays. The difference is attributed to displacement damage, and it can be important for hardened devices as well as for unhardened technologies. Proton testing may be required for applications of circuits that use substrate and lateral pnp transistors in critical circuit functions where protons comprise a significant fraction of the space environment. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rax, BG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 18 Z9 18 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2632 EP 2637 DI 10.1109/23.736507 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200041 ER PT J AU Shinn, JL Cucinotta, FA Simonsen, LC Wilson, JW Badavi, FF Badhwar, GD Miller, J Zeitlin, C Heilbronn, T Tripathi, RK Clowdsley, MS Heinbockel, JH Xapsos, MA AF Shinn, JL Cucinotta, FA Simonsen, LC Wilson, JW Badavi, FF Badhwar, GD Miller, J Zeitlin, C Heilbronn, T Tripathi, RK Clowdsley, MS Heinbockel, JH Xapsos, MA TI Validation of a comprehensive space radiation transport code SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID ACCURATE UNIVERSAL PARAMETERIZATION; GALACTIC COSMIC-RADIATION; ABSORPTION CROSS-SECTIONS; HEAVY-ION FRAGMENTATION; TARGET FRAGMENTATION; ENERGY DEPOSITION; MODEL; SPECTRA; SHUTTLE; COLLISIONS AB The HZETRN code has been developed over the past decade to evaluate the local radiation fields within sensitive materials on spacecraft in the space environment. Most of the more important nuclear and atomic processes are now modeled and evaluation within a complex spacecraft geometry with differing material components, including transition effects across boundaries of dissimilar materials, are included. The atomic/nuclear database and transport procedures have received limited validation in laboratory testing with high energy ion beams.,The codes have been applied in design of the SAGE-III instrument resulting in material changes to control injurious neutron production, in the study of the Space Shuttle single event upsets, and in validation with space measurements (particle telescopes, tissue equivalent. proportional counters, CR-39) on Shuttle and Mir. The present paper reviews the code development and presents recent results in laboratory and space flight validation. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Christopher Newport Univ, Newport News, VA 23606 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA USA. Hampton Univ, Hampton, VA 23668 USA. Old Dominion Univ, Norfolk, VA USA. USN, Res Lab, Washington, DC 20375 USA. RP Shinn, JL (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 48 TC 17 Z9 18 U1 0 U2 4 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2711 EP 2719 DI 10.1109/23.736519 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200052 PM 11542474 ER PT J AU LaBel, KA Johnston, AH Barth, JL Reed, RA Barnes, CE AF LaBel, KA Johnston, AH Barth, JL Reed, RA Barnes, CE TI Emerging radiation hardness assurance (RHA) issues: A NASA approach for space might programs SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID HEAVY-ION; DAMAGE; TRANSIENTS; ANALOG AB Spacecraft performance requirements drive the utilization of commercial-off-the-shelf (COTS) components and emerging technologies in systems. The response of these technologies to radiation is often complex. This engenders a set of emerging radiation hardness assurance (RHA) issues which include displacement damage in optocouplers, high-precision and hybrid devices, enhanced low dose rate (ELDR) and proton damage enhancement (PDE) in linear circuits, linear transients, and catastrophic single event effects (SEEs) phenomena. NASA has developed an approach to designing reliable space systems which addresses these emerging RHA issues. This programmatic methodology includes hazard definition, hazard evaluation, requirements definition, evaluation of device usage, and application of radiation engineering techniques with the active involvement of designers. Risk assessment is an integral constituent in the approach as is an established program to assess future technology needs for programs. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP LaBel, KA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 35 TC 28 Z9 28 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2727 EP 2736 DI 10.1109/23.736521 PN 1 PG 10 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200054 ER PT J AU Edmonds, LD Swift, GM Lee, CI AF Edmonds, LD Swift, GM Lee, CI TI Radiation response of a MEMS accelerometer: An electrostatic force SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm AB Particle irradiation on the mechanical sensor of the ADXL50 microelectromechanical accelerometer shifts the output voltage. An earlier conclusion, that a dielectric below the sensor becomes charged, is extended by quantifying the effect of this charge on device output. It is shown that an electrostatic force is consistent with the observation that the output voltage shift is independent of acceleration. Possible charging mechanisms are suggested. An appendix derives a convenient algorithm for calculating electrostatic forces, which may also be used for other MEMS devices. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Edmonds, LD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 TC 41 Z9 42 U1 1 U2 6 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 DEC PY 1998 VL 45 IS 6 BP 2779 EP 2788 DI 10.1109/23.736528 PN 1 PG 10 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200061 ER PT J AU Reed, RA Marshall, PW Johnston, AH Barth, JL Marshall, CJ LaBel, KA D'Ordine, M Kim, HS Carts, MA AF Reed, RA Marshall, PW Johnston, AH Barth, JL Marshall, CJ LaBel, KA D'Ordine, M Kim, HS Carts, MA TI Emerging optocoupler issues with energetic particle-induced transients and permanent radiation degradation SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID DISPLACEMENT DAMAGE AB Radiation-induced permanent degradation and single event transient effects for optocouplers are discussed in this paper. These two effects are independent to the first order and will be addressed separately. Displacement damage-induced degradation of optocoupler current transfer ratio is reviewed. New data are presented that show the importance of application specific testing and that generalized quantification of optocoupler CTR degradation can lead to incorrect predictions of actual circuit performance in a radiation environment. Data are given for various circuit loading and drive current parameters. Previous work that introduces the idea that two mechanisms exist for inducing transients on the optocoupler output is discussed. New data are presented that extends the evidence of this dual mechanism hypothesis. In this work measurements show that single event transient cross sections and transient propagation varies with circuit filtering. Finally, we discuss utilization of the optocouplers in the space environment. New data are applied to two examples: one on permanent degradation and the other on single event transient rates in high bandwidth applications. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SFA Inc, NRL, Landover, MD 20785 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NRL, Washington, DC 20375 USA. Ball Aerosp Syst Grp, Boulder, CO 80301 USA. Jackson & Tull Chartered Engineers, Washington, DC USA. RP Reed, RA (reprint author), NASA, Goddard Space Flight Ctr, Code 562, Greenbelt, MD 20771 USA. NR 14 TC 33 Z9 35 U1 0 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9499 J9 IEEE T NUCL SCI JI IEEE Trans. Nucl. Sci. PD DEC PY 1998 VL 45 IS 6 BP 2833 EP 2841 DI 10.1109/23.736536 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200069 ER PT J AU Marshall, CJ Marshall, PW Carts, MA Reed, RA LaBel, KA AF Marshall, CJ Marshall, PW Carts, MA Reed, RA LaBel, KA TI Proton-induced transient effects in a metal-semiconductor-metal (MSM) photodetector for optical-based data transfer SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID SATELLITE DATA MANAGEMENT; DATA LINKS; GAAS; INGAAS AB We present a study of proton transient effects in metal-semiconductor-metal (MSM) photodetectors, which demonstrates their inherent advantage for minimizing Single Event Effects (SEEs) in proton environments. Upset mechanisms are characterized for 830 nm GaAs and 1300 nm InGaAs detectors. Only protons incident at grazing angles are likely to cause a bit errors by direct ionization. The MSM technology appears to be a more robust to single bit errors than thicker 1300 nm p-i-n diode structures which we have previously shown to be susceptible to errors from direct ionization events at all angles, and also at relatively high optical powers [1]. For a given receiver, the relative contributions of direct ionization and nuclear reaction upset mechanisms at a specific data rate and optical power are determined by the geometry of the charge collection volume of the detector. We show that state-of-the-art p-i-n detectors can also display a reduced sensitivity to direct ionization by incident protons except at grazing angles. C1 NRL, Washington, DC 20375 USA. SFA Inc, Largo, MD 20785 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Marshall, CJ (reprint author), NRL, Code 6611,4555 Overlook Ave SW, Washington, DC 20375 USA. NR 24 TC 13 Z9 13 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 DEC PY 1998 VL 45 IS 6 BP 2842 EP 2848 DI 10.1109/23.736537 PN 1 PG 7 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200070 ER PT J AU Johnston, AH Swift, GM Miyahira, T Guertin, S Edmonds, LD AF Johnston, AH Swift, GM Miyahira, T Guertin, S Edmonds, LD TI Single-event upset effects in optocouplers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID PROTON AB Single-event upset is investigated for optocouplers using heavy ions. The threshold LET for optocouplers with internal high-gain amplifiers is very low, causing output transients to occur even when the optocouplers are irradiated with short-range alpha particles. Although previous work with high energy protons showed that transients were caused by charge collected in the large-area photodetector, transients generated in the high-gain amplifier make a significant contribution to the total cross section when optocouplers are irradiated with heavy ions. The transient pulse width increases with LET, exceeding 400 ns for long-range particles above 7 MeV-cm(2)/mg. This is about an order of magnitude greater than the pulse width that occurs when they are irradiated with protons. The ion range must exceed 50 mu m to characterize the cross section and pulse width in these devices. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Johnston, AH (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 12 Z9 14 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 DEC PY 1998 VL 45 IS 6 BP 2867 EP 2875 DI 10.1109/23.736541 PN 1 PG 9 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200074 ER PT J AU LaBel, KA Marshall, PW Barth, JL Katz, RB Reed, RA Leidecker, HW Kim, HS Marshall, CJ AF LaBel, KA Marshall, PW Barth, JL Katz, RB Reed, RA Leidecker, HW Kim, HS Marshall, CJ TI Anatomy an in-flight anomaly: Investigation of proton-induced SEE test results for stacked IBM DRAMs SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article; Proceedings Paper CT 35th IEEE International Nuclear and Space Radiation Effects Conference (NSREC) CY JUL 20-24, 1998 CL NEWPORT BEACH, CALIFORNIA SP IEEE/NPSS Radiat Effects Comm ID RADIATION AB We present ground test and space flight data describing a single event anomaly that affects multiple bytes in a stacked DRAM module. A 12 Gbit solid state recorder containing 1,440 DRAM die experiences the anomalous events at a rate requiring testing of a large sample set of these modules. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Jackson & Tull Chartered Engineers, Lanham, MD 20706 USA. NRL, Washington, DC 20375 USA. RP LaBel, KA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 11 TC 25 Z9 25 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 DEC PY 1998 VL 45 IS 6 BP 2898 EP 2903 DI 10.1109/23.736545 PN 1 PG 6 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UM UT WOS:000077624200078 ER PT J AU Edmonds, LD AF Edmonds, LD TI Electric currents through ion tracks in silicon devices SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE LA English DT Article DE charge collection from ion tracks; charge transport in doped silicon; funneling; single-event effect ID CHARGE COLLECTION; SIMULATION; UPSET AB A modified form of Ohm's law, describing electric currents through ion tracks, is presented as a tool for future theoretical modeling efforts related to charge collection from ion tracks in silicon devices. The equation is rigorously derived from the drift/diffusion equations and accounts for all currents (electron and hole, drift, and diffusion). While only one quantitative result is given, a fairly complete description of charge collection from ion tracks in silicon diodes is qualitatively discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Edmonds, LD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 38 Z9 39 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 DEC PY 1998 VL 45 IS 6 BP 3153 EP 3164 DI 10.1109/23.736194 PN 3 PG 12 WC Engineering, Electrical & Electronic; Nuclear Science & Technology SC Engineering; Nuclear Science & Technology GA 149UV UT WOS:000077624900001 ER PT J AU Appel, WS LeVan, MD Finn, JE AF Appel, WS LeVan, MD Finn, JE TI Nonideal adsorption equilibria described by pure component isotherms and virial mixture coefficients SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH LA English DT Article ID HIGH-PRESSURE ADSORPTION; GAS-MIXTURES; HETEROGENEOUS SURFACES; ACTIVATED CARBON; WATER AB A novel method is used to describe adsorption equilibria of nonideal mixtures. The two-dimensional virial equation of state is reorganized so that contributions of single components are separated from those of mixed components. Existing single component adsorption isotherm equations, which describe pure component data better and with fewer parameters than a truncated virial series, are substituted for the pure component terms. The remaining equation of state then contains terms corresponding to the pure component isotherms and terms with virial cross-coefficients for the mixture. The method is applied first to a mixture of Langmuirian adsorbates to demonstrate a sound thermodynamic and mathematical basis. We then consider nonideal binary and ternary mixtures of carbon dioxide, hydrogen sulfide, and propane on H-mordenite and a highly nonideal mixture of n-hexane and water on activated carbon. C1 Vanderbilt Univ, Dept Chem Engn, Nashville, TN 37235 USA. NASA, Regenerat Life Support Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP LeVan, MD (reprint author), Vanderbilt Univ, Dept Chem Engn, Box 1604,Stn B, Nashville, TN 37235 USA. NR 27 TC 19 Z9 19 U1 0 U2 9 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0888-5885 J9 IND ENG CHEM RES JI Ind. Eng. Chem. Res. PD DEC PY 1998 VL 37 IS 12 BP 4774 EP 4782 DI 10.1021/ie980257u PG 9 WC Engineering, Chemical SC Engineering GA 146NH UT WOS:000077436600032 ER PT J AU Menzies, T Clancey, WJ AF Menzies, T Clancey, WJ TI the challenge of situated cognition for symbolic knowledge-based systems SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Editorial Material C1 NASA, WVU IVV Fac, Fairmont, WV 26505 USA. NASA, Ames Res Ctr, Computat Sci Div, Moffett Field, CA 94035 USA. RP Menzies, T (reprint author), NASA, WVU IVV Fac, 100 Univ Ave, Fairmont, WV 26505 USA. NR 2 TC 3 Z9 3 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1071-5819 J9 INT J HUM-COMPUT ST JI Int. J. Hum.-Comput. Stud. PD DEC PY 1998 VL 49 IS 6 BP 767 EP 769 DI 10.1006/ijhc.1998.0026 PG 3 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA 154YN UT WOS:000077918600001 ER PT J AU Clancey, WJ Sachs, P Sierhuis, M van Hoof, R AF Clancey, WJ Sachs, P Sierhuis, M van Hoof, R TI Brahms: simulating practice for work systems design SO INTERNATIONAL JOURNAL OF HUMAN-COMPUTER STUDIES LA English DT Article AB A continuing problem in business today is the design of human-computer systems that respect how work actually gets done. The overarching context of work consists of activities, which people conceive as ways of organizing their daily life and especially their interactions with each other. Activities include reading mail, going to workshops, meeting with colleagues over lunch, answering phone calls, and so on. Brahms is a multiagent simulation tool for modeling the activities of groups in different locations and the physical environment consisting of objects and documents, including especially computer systems. A Brahms model of work practice reveals circumstantial, interactional influences on how work actually gets done, especially how people involve each other in their work. In particular, a model of practice reveals how people accomplish a collaboration through multiple and alternative means of communication, such as meetings, computer tools, and written documents. Choices of what and how to communicate are dependent upon social beliefs and behaviors-what people know about each other's activities, intentions, and capabilities and their understanding of the norms of the group. As a result, Brahms models can help human-computer system designers to understand how tasks and information actually flow between people and machines, what work is required to synchronize individual contributions, and how tools hinder or help this process. In particular, workflow diagrams generated by Brahms are the emergent product of local interactions between agents and representational artifacts, not pre-ordained, end-to-end paths built in by a modeler. We developed Brahms as a tool to support the design of work by illuminating how formal flow descriptions relate to the social systems of work; we accomplish this by incorporating multiple views-relating people, information, systems, and geography-in one tool. Applications of Brahms could also include system requirements analysis, instruction, implementing software agents, and a workbench for relating cognitive and social theories of human behavior. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Inst Res Learning, Menlo Pk, CA 94028 USA. Bell Atlantic Sci & Technol Inc, White Plains, NY 10604 USA. RP Clancey, WJ (reprint author), NASA, Ames Res Ctr, MS 269-3, Moffett Field, CA 94035 USA. EM bclancey@mail.arc.nasa.gov; patricia_sachs@irl.org; msierhuis@mail.arc.nasa.gov; rvhoof@basit.com NR 51 TC 51 Z9 52 U1 2 U2 2 PU ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1071-5819 J9 INT J HUM-COMPUT ST JI Int. J. Hum.-Comput. Stud. PD DEC PY 1998 VL 49 IS 6 BP 831 EP 865 DI 10.1006/ijhc.1998.0229 PG 35 WC Computer Science, Cybernetics; Ergonomics; Psychology, Multidisciplinary SC Computer Science; Engineering; Psychology GA 154YN UT WOS:000077918600004 ER PT J AU Xu, K Luo, LS AF Xu, K Luo, LS TI Connection between lattice-Boltzmann equation and beam scheme SO INTERNATIONAL JOURNAL OF MODERN PHYSICS C LA English DT Article; Proceedings Paper CT 7th International Conference on the Discrete Simulation of Fluids CY JUL 14-18, 1998 CL UNIV OXFORD, OXFORD, ENGLAND HO UNIV OXFORD DE lattice-Boltzmann method; beam scheme; finite difference and finite element methods ID NAVIER-STOKES EQUATION; CIRCULAR-CYLINDER; GAS AUTOMATA; FLOW; SIMULATIONS; SYSTEM; MODEL AB In this paper we analyze and compare the lattice-Boltzmann equation with the beam scheme in detail. We notice the similarity and differences between the lattice Boltzmann equation and the beam scheme. We show that the accuracy of the lattice-Boltzmann equation is indeed second order in space. We discuss the advantages and limitations of the lattice-Boltzmann equation and the beam scheme. Based on our analysis, we propose an improved multi-dimensional beam scheme. C1 Hong Kong Univ Sci & Technol, Dept Math, Kowloon, Hong Kong. NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP Xu, K (reprint author), Hong Kong Univ Sci & Technol, Dept Math, Clear Water Bay, Kowloon, Hong Kong. RI Luo, Li-Shi/A-4561-2011; Xu, Kun/F-7627-2011 OI Luo, Li-Shi/0000-0003-1215-7892; NR 27 TC 8 Z9 8 U1 0 U2 5 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE SN 0129-1831 J9 INT J MOD PHYS C JI Int. J. Mod. Phys. C PD DEC PY 1998 VL 9 IS 8 BP 1177 EP 1187 DI 10.1142/S0129183198001072 PG 11 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 199BL UT WOS:000080459500005 ER PT J AU Vahala, G Pavlo, P Vahala, L Martys, NS AF Vahala, G Pavlo, P Vahala, L Martys, NS TI Thermal lattice-Boltzmann models (TLBM) for compressible flows SO INTERNATIONAL JOURNAL OF MODERN PHYSICS C LA English DT Article; Proceedings Paper CT 7th International Conference on the Discrete Simulation of Fluids CY JUL 14-18, 1998 CL UNIV OXFORD, OXFORD, ENGLAND HO UNIV OXFORD DE lattice symmetries; linear stability; Rayleigh-Bernard AB The progress and challenges in thermal lattice-Boltzmann modeling are discussed. In particular, momentum and energy closures schemes are contrasted. Higher order symmetric (but no longer space filling) velocity lattices are constructed for both 2D and 3D flows and shown to have superior stability properties to the standard (but lower) symmetry lattices. While this decouples the velocity lattice from the spatial grid, the interpolation required following free-streaming is just 1D. The connection between fixed lattice vectors and temperature-dependent lattice vectors (obtained in the Gauss-Hermite quadrature approach) is discussed. Some (compressible) Rayleigh-Benard simulations on the 2D octagonal lattice are presented for extended BGK collision operators that allow for arbitrary Prandtl numbers. C1 Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. Acad Sci Czech Republ, Inst Plasma Phys, Prague 8, Czech Republic. Old Dominion Univ, Dept Elect & Comp Engn, Norfolk, VA 23529 USA. NIST, Gaithersburg, MD 20899 USA. RP Vahala, G (reprint author), Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. RI Pavlo, Pavol/G-4214-2014 OI Pavlo, Pavol/0000-0003-1400-1074 NR 14 TC 36 Z9 37 U1 1 U2 8 PU WORLD SCIENTIFIC PUBL CO PTE LTD PI SINGAPORE PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE SN 0129-1831 J9 INT J MOD PHYS C JI Int. J. Mod. Phys. C PD DEC PY 1998 VL 9 IS 8 BP 1247 EP 1261 DI 10.1142/S0129183198001126 PG 15 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 199BL UT WOS:000080459500010 ER PT J AU Halpern, D Ji, M Leetmaa, A Reynolds, RW AF Halpern, D Ji, M Leetmaa, A Reynolds, RW TI Influence of assimilation of subsurface temperature measurements on simulations of equatorial undercurrent and south equatorial current along the Pacific equator SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID GENERAL-CIRCULATION MODEL; TROPICAL PACIFIC; OCEAN MODEL; REDUCED-GRAVITY; WIND STRESS; VARIABILITY; CLIMATE; ERRORS AB Equatorial Pacific current and temperature fields were simulated with and without assimilation of subsurface temperature measurements for April 1992-March 1995 and compared with moored buoy and research vessel current measurements. Data assimilation intensified the mean east-west slope of the thermocline along the equator in the eastern Pacific, shifted eastward the longitude of the mean Equatorial Undercurrent (EUC) maximum speed 800 km to 125 degrees W, and produced a 25% stronger mean EUC core speed in the eastern Pacific. In the eastern Pacific the mean EUC core speed simulated with data assimilation was slightly more representative of observations compared to that computed without data assimilated; in the western Pacific the data assimilation had no impact on mean EUC simulations. Data assimilation intensified the north-south slope of the thermocline south of the equator in the western Pacific to produce a thicker and more intense westward-flowing South Equatorial Current (SEC) in the western Pacific. In the western Pacific the mean SEC transport per unit width simulated with data assimilation was more representative of observations compared to that computed without data assimilation. However, large differences remained between the observed SEC transport per unit width and that simulated with data assimilation. In the eastern Pacific, the data assimilation had no impact on mean SEC simulations. The temporal variability of monthly mean EUC core speeds and SEC transports per unit width were increased significantly by data assimilation. It also increased the representativeness of monthly mean SEC transports per unit width to the observations. However, the data representativeness of monthly mean EUC core speeds was decreased. Results could be explained by the coupling between zonal gradient of temperature and EUC and between meridional gradient of temperature and SEC. Longitudinal variations along the Pacific equator of the impact of data assimilation on the EUC and SEC precludes the choice of a single site to evaluate the effectiveness of data assimilation schemes. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Natl Ctr Environm Predict, Camp Springs, MD USA. RP Halpern, D (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-323, Pasadena, CA 91109 USA. EM halpern@pacific.jpl.nasa.gov NR 31 TC 3 Z9 3 U1 2 U2 5 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 DEC PY 1998 VL 15 IS 6 BP 1471 EP 1477 DI 10.1175/1520-0426(1998)015<1471:IOAOST>2.0.CO;2 PG 7 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 165LM UT WOS:000078522500018 ER PT J AU Le Vine, DM Kao, M Garvine, RW Sanders, T AF Le Vine, DM Kao, M Garvine, RW Sanders, T TI Remote sensing of ocean salinity: Results from the Delaware coastal current experiment SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID APERTURE MICROWAVE RADIOMETER; BUOYANCY; ESTAR AB A comparison is presented of remote and shipboard measurements of sea surface salinity made in the vicinity of the Delaware coastal current, a low salinity band with its source in the mouth of Delaware Bay. The remote sensing measurements were made from an aircraft with the Electronically Scanned Thinned Array Radiometer. The shipboard measurements were made with a thermosalinograph on board the R/V Cape Henlopen. On 29-30 April 1993, the RN Cape Henlopen sailed from the mouth of Delaware Bay south toward Chesapeake Bay in an east-west zig-zag pattern, repeatedly crossing the coastal current. The aircraft, a NASA P-3, flew the same lines on the afternoon of 30 April. Both thermosalinograph- and microwave radiometer-derived salinity maps clearly show the freshwater signature of the coastal current and generally are in agreement to within about 1 psu. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. Univ Delaware, Coll Marine Studies, Newark, DE USA. RP Le Vine, DM (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. EM dmlevine@meneg.gsfc.nasa.gov NR 21 TC 38 Z9 39 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0739-0572 J9 J ATMOS OCEAN TECH JI J. Atmos. Ocean. Technol. PD DEC PY 1998 VL 15 IS 6 BP 1478 EP 1484 DI 10.1175/1520-0426(1998)015<1478:RSOOSR>2.0.CO;2 PG 7 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 165LM UT WOS:000078522500019 ER PT J AU Lean, J Rind, D AF Lean, J Rind, D TI Climate forcing by changing solar radiation SO JOURNAL OF CLIMATE LA English DT Review ID TROPOSPHERE-STRATOSPHERE SYSTEM; SEA-SURFACE TEMPERATURE; IRRADIANCE VARIATIONS; MAUNDER MINIMUM; PRECIPITATION FLUCTUATIONS; LUMINOSITY VARIATIONS; DECADAL VARIABILITY; BRIGHTNESS CHANGES; CIRCULATION MODEL; CYCLE VARIATION AB By how much does changing radiation from the sun influence the earth's climate. presently and in the recent past, compared with other natural and anthropogenic processes? Current knowledge of the amplitudes and timescales of solar radiative output variability needed to address this question is described from contemporary solar monitoring and historical reconstructions. The 17-yr observational database of space-based solar monitoring exhibits an Il-yr irradiance cycle with amplitude of about 0.1%. Larger amplitude solar total radiative output changes-of 0.24% relative to present levels-are estimated for the seventeenth-century Maunder Minimum by parameterizing the variability mechanisms identified for the Il-yr cycle, using proxies of solar and stellar variability. The 11- and 22-yr periods evident in solar activity proxies appear in many climate and paleoclimate records, and some solar and climate time series correlate strongly over multidecadal and centennial timescales. These statistical relationships suggest a response of the climate system to the changing sun. The correlation of reconstructed solar irradiance and Northern Hemisphere (NH) surface temperature anomalies is 0.86 in the pre industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55 degrees C surface warming since 1900 and one-third of the warming since 1970. Climate model simulations using irradiance reconstructions provide a tool with which to identify potential physical mechanism for these implied connections. An equilibrium simulation by the Goddard Institute for Space Studies GCM predicts an NH surface temperature change of 0.51 degrees C for a 0.25% solar irradiance reduction, in general agreement with the preindustrial parameterization. But attributing a significant fraction of recent climate warming to solar forcing presents serious ambiguities about the impact of increasing greenhouse gas concentrations whose radiative forcing has been significantly larger than solar forcing over this time period. Present inability to adequately specify climate forcing by changing solar radiation has implications for policy making regarding anthropogenic global change, which must be detected against natural climate variability. C1 USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Lean, J (reprint author), USN, Res Lab, EO Hulburt Ctr Space Res, Code 7673L, Washington, DC 20375 USA. EM lean@demeter.nrl.navy.mil OI Lean, Judith/0000-0002-0087-9639 NR 145 TC 137 Z9 145 U1 2 U2 23 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 DEC PY 1998 VL 11 IS 12 BP 3069 EP 3094 DI 10.1175/1520-0442(1998)011<3069:CFBCSR>2.0.CO;2 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 151ZY UT WOS:000077751700001 ER PT J AU Yang, S Lau, KM AF Yang, S Lau, KM TI Influences of sea surface temperature and ground wetness on Asian summer monsoon SO JOURNAL OF CLIMATE LA English DT Article ID EURASIAN SNOW COVER; NINO SOUTHERN OSCILLATION; GENERAL-CIRCULATION MODEL; ATMOSPHERE OCEAN SYSTEM; EL-NINO; TROPICAL PACIFIC; INDIAN MONSOON; INTERANNUAL VARIABILITY; NUMERICAL EXPERIMENT; CLIMATE AB The authors have conducted a series of experiments with a general circulation model to understand the influences of sea surface temperature (SST) and ground wetness (GW) (measured by snow amount and soil moisture content) on the Asian summer monsoon. The experiments are designed to illustrate the dominant features of monsoon response to SST and GW forcings and to delineate the relative importance of each forcing function in contributing to the variability of the monsoon. Results indicate that ocean basin-scale SST anomalies exert a stronger control on the interannual variability of the monsoon compared to GW anomalies. The impact of SST anomalies on the monsoon appears nonlinear with respect to warm and cold events. The monsoon is weakened during the warm events but changes less noticeably during the cold events. The diminution of monsoon circulation associated with the warm SST anomalies is accompanied by a broad-scale reduction in water vapor convergence and monsoon rainfall. Results also indicate that, following wet land surface conditions (enhanced snow and soil moisture) in the Asian continent during previous cold seasons, the summer monsoon becomes moderately weaker. Antecedent land surface processes mainly influence the early part of the monsoon. Wetter and colder conditions occur in the Asian continent during warm SST events. This results in reduced land-sea thermal contrast, which reinforces the weak monsoon anomalies produced initially by warm SST forcing. These interactive forcings are also responsible for the changes in the winter-spring westerlies over subtropical Asia, which are key precursory signals for the subsequent summer monsoon. It should be pointed out that this study is conducted for the climate decade of 1979-88 only. The general robustness of the results needs to be explored by further investigations. In addition, chaotic features may have affected the results because of sampling errors. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Yang, S (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Mail Code 913, Greenbelt, MD 20771 USA. RI Yang, Song/B-4952-2009; Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 54 TC 138 Z9 150 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 DEC PY 1998 VL 11 IS 12 BP 3230 EP 3246 DI 10.1175/1520-0442(1998)011<3230:IOSSTA>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 151ZY UT WOS:000077751700009 ER PT J AU Miller, RL Tegen, I AF Miller, RL Tegen, I TI Climate response to soil dust aerosols SO JOURNAL OF CLIMATE LA English DT Article ID BURNING OIL-WELLS; MINERAL DUST; OPTICAL-THICKNESS; ATMOSPHERIC SMOKE; TROPICAL PACIFIC; LIGHT-SCATTERING; TRADE WINDS; MODEL; VARIABILITY; TEMPERATURE AB The effect of radiative forcing by soil dust aerosols upon climate is calculated. Two atmospheric GCM (AGCM) simulations are compared, one containing a prescribed seasonally varying concentration of dust aerosols, and the other omitting dust. Each simulation includes a mixed layer ocean model, which allows SST to change in response to the reduction in surface net radiation by dust. Dust aerosols reduce the surface net radiation both by absorbing and reflecting sunlight. For the optical properties of the dust particles assumed here, the reflection of sunlight is largely offset by the trapping of upwelling longwave radiation, so that the perturbation by dust to the net radiation gain at the top of the atmosphere is small in comparison to the surface reduction. Consequently, the radiative effect of soil dust aerosols is to redistribute healing from the surface to within the dust layer. Beneath the dust layer, surface temperature is reduced on the order of 1 K, typically in regions where deep convection is absent. In contrast, surface temperature remains unperturbed over the Arabian Sea during Northern Hemisphere (NH) summer. even though the dust concentration is highest in this region. It is suggested that the absence of cooling results from the negligible radiative forcing by dust at the top of the atmosphere, along with the frequent occurrence of deep convection, which ties the surface temperature to the unperturbed value at the emitting level. Where convection is absent, cooling at the surface occurs because radiative heating by dust reduces the rate of subsidence land the corresponding mass exchange with the convecting region). Thus, the temperature contrast between these two regions must increase to maintain the original transport of energy, which is unperturbed by dust. It is suggested that cooling over the Arabian Sea during NH winter, despite the much smaller dust loading, is permitted by the absence of convection during this season. Thus, the change in surface temperature forced by dust depends upon the extent of overlap between the dust layer and regions of deep convection, in addition to the magnitude of the radiative forcing. Surface temperature is also reduced outside of the dust cloud, which is unlikely to result solely from natural variability of the AGCM. It is suggested that the perturbation by dust to Indian and African monsoon rainfall may depend upon the extent to which ocean dynamical heat transports are altered by dust. C1 Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Miller, RL (reprint author), Columbia Univ, Dept Appl Phys, Armstrong 550, New York, NY 10027 USA. EM rlm15@columbia.edu RI Miller, Ron/E-1902-2012 NR 56 TC 254 Z9 266 U1 5 U2 28 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 DEC PY 1998 VL 11 IS 12 BP 3247 EP 3267 DI 10.1175/1520-0442(1998)011<3247:CRTSDA>2.0.CO;2 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 151ZY UT WOS:000077751700010 ER PT J AU Tselioudis, G DelGenio, AD Kovari, W Yao, MS AF Tselioudis, G DelGenio, AD Kovari, W Yao, MS TI Temperature dependence of low cloud optical thickness in the GISS GCM: Contributing mechanisms and climate implications SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; MARINE BOUNDARY-LAYER; CUMULUS TRANSITION; TOP ENTRAINMENT; SEASONAL CYCLE; LIQUID WATER; PARAMETERIZATION; FEEDBACK; CONDENSATION; SENSITIVITY AB A current-climate simulation of the Goddard Institute for Space Studies (GISS) GCM, which includes interactive cloud optical properties that depend on the predicted cloud water content, is analyzed to document the variations of low cloud optical thickness with temperature in the model atmosphere. It is found that low cloud optical thickness decreases with temperature in the warm subtropical and tropical latitudes and increases with temperature in the cold midlatitude regions. This behavior is in agreement with the results of two observational studies that analyzed satellite data from the International Satellite Cloud Climatology Project and Special Sensor Microwave/Imager datasets. The increase of low cloud optical thickness with temperature in the midlatitudes is due to vertical extent and cloud water increases, whereas the decrease with temperature in the warm latitudes is due to decreases in cloud water content and happens despite increases in cloud vertical extent. The cloud processes that produce the cloud property changes in the model also vary with latitude. In the midlatitude regions relative-humidity-induced increases of cloud vertical extent with temperature dominate, whereas in the Tropics increases in cloud-top entrainment and precipitation with temperature produce decreases of cloud water content, whose effect on optical thickness outweighs the effect of entrainment-induced increases of cloud vertical extent with temperature. Doubled-CO2 simulations with the GISS GCM suggest that even though low cloud optical thickness changes have little effect on the global climate sensitivity of the model, they redistribute the temperature change and reduce the high-latitude amplification of the greenhouse warming. It is also found that the current climate variations of low cloud optical thickness with temperature reproduce qualitatively but overestimate quantitatively the changes in optical thickness with climate warming. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Sci Syst Applicat Inc, New York, NY USA. RP Tselioudis, G (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM gtselioudis@giss.nasa.gov RI Del Genio, Anthony/D-4663-2012 OI Del Genio, Anthony/0000-0001-7450-1359 NR 35 TC 21 Z9 23 U1 0 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 DEC PY 1998 VL 11 IS 12 BP 3268 EP 3281 DI 10.1175/1520-0442(1998)011<3268:TDOLCO>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 151ZY UT WOS:000077751700011 ER PT J AU Chung, SK Trinh, EH AF Chung, SK Trinh, EH TI Containerless protein crystal growth in rotating levitated drops SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE protein crystal; drop rotation; levitation; microgravity simulation ID MICROGRAVITY; CRYSTALLIZATION; THAUMATIN; KINETICS; VIRUS AB A method for growing protein crystals in a containerless environment using an ultrasonic-electrostatic hybrid levitator is evaluated. In this approach, a single protein solution droplet bearing a surface charge is electrostatically levitated and acoustically rotated along a horizontal axis during the crystal nucleation and growth phases. Sample rotation is induced by ultrasonic streaming and radiation pressure applied in addition to the electrostatic levitation force. This unique approach is developed in order to create controlled crystal growth conditions which would reproduce some of the aspects of the low-gravity environment. We present the outcome of a development effort and feasibility study showing the successful growth of lysozyme and thaumatin crystals suspended within the bulk of quiescent liquid protein solutions inside rotating droplets also containing a Very small concentration of agarose. Even though the crystals are not growing in a completely gelled medium and rotation is required for their long-term suspension, there are indications that a convectionless crystal growth environment has been obtained within the rotating drop, and that artificial flow can be introduced in a controlled manner by imposing drop shape oscillations. (C) 1998 Elsevier Science B.V. All rights reserved. PACS:81.10.-h;81.10.Mx;87.15;43.25.Uv. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chung, SK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM sang.k.chung@jpl.nasa.gov NR 31 TC 64 Z9 68 U1 1 U2 9 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 DEC PY 1998 VL 194 IS 3-4 BP 384 EP 397 DI 10.1016/S0022-0248(98)00542-9 PG 14 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 143WL UT WOS:000077280400016 ER PT J AU Su, YJ Horwitz, JL Moore, TE Giles, BL Chandler, MO Craven, PD Hirahara, M Pollock, CJ AF Su, YJ Horwitz, JL Moore, TE Giles, BL Chandler, MO Craven, PD Hirahara, M Pollock, CJ TI Polar wind survey with the Thermal Ion Dynamics Experiment Plasma Source Instrument suite aboard POLAR SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ELECTRON-TEMPERATURE ANISOTROPY; RETURN CURRENT REGION; SUPRATHERMAL O+ IONS; TOPSIDE IONOSPHERE; KINETIC-MODEL; CENTRIFUGAL ACCELERATION; TRANSPORT MODELS; MAGNETOSPHERE; CAP; OUTFLOW AB In February 1996, the POLAR spacecraft was placed in an elliptical orbit with a 9 R-E geocentric distance apogee in the northern hemisphere and 1.8 R-E perigee in the southern hemisphere. The Thermal Ion Dynamics Experiment (TIDE) on POLAR has allowed sampling of the three-dimensional ion distribution functions with excellent energy, angular, and mass resolution. The Plasma Source Instrument (PSI), when operated, allows sufficient diminution of the electric potential to observe the polar wind at very high altitudes. In this paper, we describe the results of a survey of the polar wind characteristics for H+, He+, and O+ as observed by TIDE at similar to 5000 km and similar to 8 R-E altitudes over the polar cap during April-May 1996. At 5000 km altitude, the H+ polar wind exhibits a supersonic outflow, while O+ shows subsonic downflow, which suggests a cleft ion fountain origin for the O+ ions in the polar cap region. Dramatic decreases of the 5000 km altitude H+ and O+ ion densities and fluxes are seen as the solar zenith angle increases from 90 degrees to 100 degrees for the ionospheric base, which is consistent with solar illumination ionization control. However, the polar cap downward O+ flow and density decline from dayside to nightside in magnetic coordinates suggest a cleft ion fountain origin for the polar cap O+. Cleft ion fountain origin O+ density plumes could also be partially responsible for a similar day-night asymmetry in H+ owing to the charge-exchange reaction. At 8 R-E altitude, both H+ and O+ outflows are supersonic and H+ is the highly dominant ion species. The average bulk ion field-aligned velocities are in the typical ratio VO+ : VHe+: VH+ similar to 2 : 3 : 5, which may suggest a tendency toward comparable energy gains, such as via an electric potential layer. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Rikkyo Univ, Dept Phys, Tokyo 171, Japan. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. SW Res Inst, Instrumentat & Space Res Div, San Antonio, TX 78238 USA. RP Chandler, MO (reprint author), Univ Calif Los Alamos Natl Lab, POB 1663, Los Alamos, NM 87545 USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 78 TC 51 Z9 51 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1998 VL 103 IS A12 BP 29305 EP 29337 DI 10.1029/98JA02662 PG 33 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 149MD UT WOS:000077608400016 ER PT J AU Hinson, DP Kliore, AJ Flasar, FM Twicken, JD Schinder, PJ Herrera, RG AF Hinson, DP Kliore, AJ Flasar, FM Twicken, JD Schinder, PJ Herrera, RG TI Galileo radio occultation measurements of Io's ionosphere and plasma wake SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WAVE OBSERVATIONS; HOT-SPOTS; ATMOSPHERE; TORUS; MODEL; PHOTOCHEMISTRY; METEOROLOGY; SO2 AB Six radio occultation experiments were conducted with the Galileo orbiter in 1997, yielding detailed measurements of the distribution and motion of plasma surrounding Io. This distribution has two components. One is highly asymmetric, consisting of a wake or tail that appears only on the downstream side and extends to distances as large as 10 Io radii. The other resembles a bound ionosphere and is present within a few hundred kilometers of Io's surface throughout the upstream and downstream hemispheres. Motion of plasma within the wake was measured through cross correlation of data acquired simultaneously at two widely separated terrestrial antennas. Plasma near Io's equatorial plane is moving away from Io in the downstream direction. Its speed increases from 30 km s(-1) at a distance of 3 Io radii from the center of Io to 57 km s(-1) at 7 10 radii. The latter corresponds to corotation with Jupiter's magnetic field, which suggests that bulk plasma motion rather than wave motion is being observed. Results for the bound ionosphere include vertical profiles of electron density at 10 locations near Io's terminator. The ionosphere is substantial, with the peak density exceeding 50,000 cm(-3) at 9 out of 10 locations and reaching a maximum of 277,000 cm The peak density varies systematically with Io longitude, with maxima near the center of the hemispheres facing toward (0 degrees W) and away from (180 degrees W) Jupiter and minima near the center of the downstream (90 degrees W) and upstream (270 degrees W) hemispheres. This pattern may be related to the Alfvenic current system induced by Io's motion through magnetospheric plasma. The vertical extent of the bound ionosphere increases from similar to 200 km near the center of the upstream hemisphere to similar to 400 km near the boundary between the leading and trailing hemispheres. There is a close resemblance between one ionospheric profile and a Chapman layer, and the topside scale height implies a plasma temperature of 202 +/- 14 K if Na+ is the principal ion. Two intense volcanic hot spots, Kanehekili and 9606A, may be influencing the atmospheric structure at this location. C1 Stanford Univ, Ctr Radar Astron, Stanford, CA 94305 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RP Flasar, FM (reprint author), Stanford Univ, Ctr Radar Astron, Stanford, CA 94305 USA. RI Flasar, F Michael/C-8509-2012; OI Schinder, Paul/0000-0002-4571-7895 NR 31 TC 46 Z9 46 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 DEC 1 PY 1998 VL 103 IS A12 BP 29343 EP 29357 DI 10.1029/98JA02659 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 149MD UT WOS:000077608400018 ER PT J AU Reiner, MJ Kaiser, ML Fainberg, J Stone, RG AF Reiner, MJ Kaiser, ML Fainberg, J Stone, RG TI A new method for studying remote type II radio emissions from coronal mass ejection-driven shocks SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY SHOCKS; WIND SPACECRAFT; BURSTS; WAVES; ELECTRONS; DENSITY; EVENTS AB Some interplanetary shocks associated with coronal mass ejections (CMEs) generate type II radio emissions at the local plasma frequency and/or its harmonic. These type II radio emissions provide a means of remotely studying and tracking CMEs from the solar corona to 1 AU and beyond. New analysis techniques that inherently reveal the dynamics of a CME as it propagates through the interplanetary medium are used for tracking the CME-associated radio emissions. The techniques make use of dynamic spectra of the radio intensity plotted as a function of inverse frequency and time. When in situ measurements are also available, the analyses determine unequivocally whether the type II radio emissions occurred at the fundamental or harmonic of the local plasma frequency in the upstream or downstream regions of the CME-driven shock. These new analysis techniques are applied to three type II radio bursts that were observed by the WAVES radio experiment on the Wind spacecraft on May 13-14, November 4-5, and November 6-7, 1997; each event corresponded to a CME observed by SOHO LASCO (large angle and spectrometric coronagraph), and each event was observed in situ by Wind. We find that the type II radio emissions for each of the three events were generated at both the fundamental and harmonic of the plasma frequency in the upstream region of the CME-driven shock, that the type II emissions appear, in general, to originate in regions along the shock front of higher than normal densities, and that the radio emission sites along the shock front change with time. In one case, additional radio tracking, provided by the direction-finding analysis, was used to locate the sites of the radio emission along the shock front. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Raytheon STX, Lanham, MD 20706 USA. RP Reiner, MJ (reprint author), Raytheon STX, 4400 Forbes Blvd, Lanham, MD 20706 USA. NR 26 TC 87 Z9 88 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 DEC 1 PY 1998 VL 103 IS A12 BP 29651 EP 29664 DI 10.1029/98JA02614 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 149MD UT WOS:000077608400043 ER PT J AU Hefti, S Grunwaldt, H Ipavich, FM Bochsler, P Hovestadt, D Aellig, MR Hilchenbach, M Kallenbach, R Galvin, AB Geiss, J Gliem, F Gloeckler, G Klecker, B Marsch, E Mobius, E Neugebauer, M Wurz, P AF Hefti, S Grunwaldt, H Ipavich, FM Bochsler, P Hovestadt, D Aellig, MR Hilchenbach, M Kallenbach, R Galvin, AB Geiss, J Gliem, F Gloeckler, G Klecker, B Marsch, E Mobius, E Neugebauer, M Wurz, P TI Kinetic properties of solar wind minor ions and protons measured with SOHO/CELIAS SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HEAVY-IONS; VELOCITY; ACCELERATION AB Using observations of the Charge Time-of-Flight(CTOF) charge and mass spectrometer of the Charge, Element and Isotope Analysis System (CELIAS), and of CELIAS/proton monitor on board the Solar and Heliospheric Observatory (SOHO), we present an overview of speeds and kinetic temperatures of minor ions and protons in the solar wind near solar minimum, covering the Carrington Rotations 1908 to 1912. In the case of a collision-dominated solar wind the speed of minor ions is expected to be lower or equal to the speed of the protons, and all species are expected to have equal temperatures. On the other hand, minor ions can be accelerated and heated by wave-particle interaction. In this: case, equal thermal speeds of all species are expel-ted. CTOF data allow the determination of the kinetic parameters of various ions with high accuracy and with high time resolution. The mean O6+ Speed of the observed period is 390 km s(-1). The speeds of Si7+ and Fe9+ correlate well with O6+, the linear correlation coefficient being 0.96 or higher. Our results also indicate that silicon and iron tend to lag behind oxygen with a speed difference of similar to 20 km s(-1) at 500 km s(-1) At the same time, the kinetic temperature of the ions under investigation exhibit the well-known mass proportionality, which is attributed to wave-particle interactions. During the period of low solar activity in consideration, many cases are observed where the kinetic temperature is extraordinarily low (10(4) K for O6+). C1 Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. Max Planck Inst Aeron, D-37189 Lindau, Germany. Univ Maryland, Dept Space Phys, College Pk, MD 20742 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ New Hampshire, Space Phys Dept, Durham, NH 03824 USA. Int Space Sci Inst, Bern, Switzerland. Tech Univ Braunschweig, Inst Datenverarbeitsanlangen, D-38023 Braunschweig, Germany. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Michigan, Coll Engn, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. RP Hefti, S (reprint author), Univ Michigan, Coll Engn, Dept Atmospher Ocean & Space Sci, 2455 Hayward St, Ann Arbor, MI 48109 USA. RI Galvin, Antoinette/A-6114-2013 NR 15 TC 43 Z9 43 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-SPACE JI J. Geophys. Res-Space Phys. PD DEC 1 PY 1998 VL 103 IS A12 BP 29697 EP 29704 DI 10.1029/1998JA900022 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 149MD UT WOS:000077608400046 ER PT J AU Burlaga, LF Ness, NF AF Burlaga, LF Ness, NF TI Magnetic field strength distributions and spectra in the heliosphere and their significance for cosmic ray modulation: Voyager 1, 1980-1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID LARGE-SCALE FLUCTUATIONS; SOLAR-WIND; 1/F NOISE; INTERPLANETARY; TURBULENCE; EVOLUTION; DISTANCE; ORIGIN; FLOWS; AU AB Annual variations of the hourly averages of the heliospheric magnetic field strength B observed by Voyager 1 (V1) have been analyzed for the 15-year interval 1980-1994 inclusive. During this period, V1 moved from a radial distance of 6.9-58.1 AU and from a heliolatitude of -5.4 to 32.7 degrees. The annual distribution function of B is nearly lognormal. The width of the distribution, w, does not change systematically with time, distance, latitude or solar activity: [w] = 0.61 +/- 0.02. The standard deviation of B, SD(B), normalized by the average, B(av), is also invariant: [SD(B)/B(av)] = 0.67 +/- 0.03. There is a decadal frequency range for which the power spectral density (PSD) of B(t) is well described by a power law with an exponent s that ranges from -2.0 near solar maximum (1980, 1990) when GMIRs were present to -1.5 near solar minimum (1987-1988). A Global Merged Interaction Region (GMIR) is a shell-like region that encircles the Sun, propagates away from the Sun, ha:s a radial thickness of the order of a few AU and contains intense, disturbed magnetic fields. The lower limit of the scaling range corresponds to a period of approximate to 5 days and is invariant in the 15 years studied. The relative amplitude of the PSD at the lower limit of this range is also invariant. However, the relative amplitude of the fluctuations at the solar rotation period of 26 days decreases with increasing distance from the sun as R(-(0.9 +/- 0.2)). These derived observational results in time and frequency domains require theoretical models of the solar wind expansion into the distant heliosphere that include both physical and statistical features. Such models could be based on (1) energy and/or entropy principles or (2) conventional MHD along with temporally complex but statistically simple input functions. Our results suggest an anticorrelation between the annual magnetic field strength and cosmic ray intensity, as is observed during the 15-year period considered here. Statistical models of the magnetic field might provide a basis for new models of cosmic ray modulation. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. RP Burlaga, LF (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. EM u2leb@lepvax.gsfc.nasa.gov NR 57 TC 52 Z9 54 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 DEC 1 PY 1998 VL 103 IS A12 BP 29719 EP 29732 DI 10.1029/98JA02682 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 149MD UT WOS:000077608400048 ER PT J AU Hutjes, RWA Kabat, P Running, SW Shuttleworth, WJ Field, C Bass, B Dias, MAFD Avissar, R Becker, A Claussen, M Dolman, AJ Feddes, RA Fosberg, M Fukushima, Y Gash, JHC Guenni, L Hoff, H Jarvis, PG Kayane, I Krenke, AN Liu, C Meybeck, M Nobre, CA Oyebande, L Pitman, A Pielke, RA Raupach, M Saugier, B Schulze, ED Sellers, PJ Tenhunen, JD Valentini, R Victoria, RL Vorosmarty, CJ AF Hutjes, RWA Kabat, P Running, SW Shuttleworth, WJ Field, C Bass, B Dias, MAFD Avissar, R Becker, A Claussen, M Dolman, AJ Feddes, RA Fosberg, M Fukushima, Y Gash, JHC Guenni, L Hoff, H Jarvis, PG Kayane, I Krenke, AN Liu, C Meybeck, M Nobre, CA Oyebande, L Pitman, A Pielke, RA Raupach, M Saugier, B Schulze, ED Sellers, PJ Tenhunen, JD Valentini, R Victoria, RL Vorosmarty, CJ TI Biospheric aspects of the hydrological cycle - Preface SO JOURNAL OF HYDROLOGY LA English DT Editorial Material DE hydrological cycle; terrestrial biosphere; global carbon balance; natural variability; biogeochemical cycle ID GENERAL-CIRCULATION MODEL; SEMI-ARID REGIONS; ATMOSPHERIC CO2; SCALING CHARACTERISTICS; TERRESTRIAL ECOSYSTEMS; CLIMATIC IMPACTS; FIELD EXPERIMENT; VEGETATION; DROUGHT; FLUXES AB The Core Project Biospheric Aspects of the Hydrological Cycle (BAHC) of the International Geosphere Biosphere Programme (IGBP) addresses the biospheric aspects of the hydrological cycle through experiments and modelling of energy, water, carbon dioxide and sediment fluxes in the soil-vegetation-atmosphere system at a variety of spatial and temporal scales. Active regulation of water, energy and carbon dioxide fluxes by the vegetation make it an important factor in regulating the Earth's hydrological cycle and in the formation of the climate. Consequently, human induced conversion of vegetation cover is an important driver for climate change. A number of recent studies, discussed in this paper, emphasise the importance of the terrestrial biosphere for the climate system. Initially, these studies demonstrate the influence of the land surface on tropical weather and climate, revealing the mechanisms, acting at various scales, that connect increasing temperatures and decreasing rainfall to large-scale deforestation and other forms of land degradation. More recently, the significance of the land surface processes for water cycle and for weather and climate in temperate and boreal zones was demonstrated. In addition the terrestrial biosphere plays a significant role in the carbon dioxide fluxes and in global carbon balance. Recent work suggests that many ecosystems both in the tropics and in temperate zones may act as a substantial sink for carbon dioxide, though the temporal variability of this sink strength is yet unclear. Further, carbon dioxide uptake and evaporation by vegetation are intrinsically coupled leading to Links and feedbacks between land surface and climate that are hardly explored yet. Earth's vegetation cover and its changes owing to human impact have a profound influence on a lateral redistribution of water and transported constituents, such as nutrients and sediments, and acts therefore as an important moderator of Earth's biogeochemical cycles. In the BAHC science programme, the importance of studying the influence of climate and human activities on mobilisation and river-borne transport of constituents is explicitly articulated. The terrestrial water and associated material cycles are studied as highly dynamic in space and time, and reflect a complex interplay among climatic forcing, topography, land cover and vegetation dynamics. Despite a large progress in our understanding of how the terrestrial biosphere interacts with Earth's and climate system and with the terrestrial part of its hydrological cycle, a number of basic issues still remain unresolved. Limited to the scope of BAHC, the paper briefly assesses the present status and identifies the most important outstanding issues, which require further research. Two, arguably most important outstanding issues are identified: a limited understanding of natural variability, especially with respect to seasonal to inter-annual cycles, and of a complex ecosystem behaviour resulting from multiple feedbacks and multiple coupled biogeochemical cycles within the overall climate system. This leads to two major challenges for the future science agenda related to global change research. First, there is a need for a strong multidisciplinary integration of research efforts in both modelling and experiments, the latter extending to inter-annual timescales. Second, the ever increasing complexity in characterisation and modelling of the climate system, which is mainly owing to incorporation of the biosphere's and human feedbacks, may call for a new approach in global change impact studies. Methodologies need to be developed to identify risks to, and vulnerability of environmental systems, taking into account all important interactions between atmospheric, ecological and hydrological processes at relevant scales. With respect to the influence of climate and human activities on mobilisation and river-borne transport of constituents, the main issues for the future are related to declining availability and quality of ground data for quantity and quality of water discharge. Such assessments presented in this paper, in combination with community wide science evaluation, has lead to an update of the science agenda for BAHC, a summary of which is provided in the appendix. (C) 1998 Elsevier Science B.V. All rights reserved. C1 DLO, Winand Staring Ctr Integrat Land Soil & Water Res, NL-6700 AC Wageningen, Netherlands. Univ Montana, Sch Forestry, Missoula, MT 59812 USA. Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Carnegie Inst Washington, Dept Plant Biol, Stanford, CA 94305 USA. Univ Sao Paulo, Dept Geophys & Astron, Sao Paulo, Brazil. Environm Canada, Downsview, ON, Canada. Rutgers State Univ, New Brunswick, NJ 08903 USA. Potsdam Inst Climate Impact Res, Potsdam, Germany. Agr Univ Wageningen, Dept Water Resources Management, Wageningen, Netherlands. Potsdam Inst Climate Impact Res, BAHC Core Project Off, Potsdam, Germany. Nagoya Univ, Inst Hydrospher Atmospher Sci, Nagoya, Aichi, Japan. Inst Hydrol, Wallingford OX10 8BB, Oxon, England. Univ Simon Bolivar, Caracas, Venezuela. Univ Tsukuba, Inst Geosci, Tsukuba, Ibaraki 305, Japan. Russian Acad Sci, Inst Geog, Moscow, Russia. Chinese Acad Sci, Inst Agr Modernisat, Shijiazhuang, Peoples R China. Univ Paris, F-75252 Paris, France. Ctr Weather Predict & Climate Studies, INPE, Cachoeira Paulista, Brazil. Univ Lagos, Hydrol Lab, Lagos, Nigeria. Macquarie Univ, N Ryde, NSW, Australia. Colorado State Univ, Ft Collins, CO 80523 USA. CSIRO, Ctr Environm Mech, Canberra, ACT 2601, Australia. Univ Paris, Ecol Vegetale Lab, F-75252 Paris, France. Max Planck Inst Biogeochem, Jena, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Bayreuth, Dept Plant Ecol, Bayreuth, Germany. Univ Tuscia, Viterbo, Italy. Univ Sao Paulo, CENA, Piracicaba, Brazil. Univ New Hampshire, Durham, NH 03824 USA. RP Hutjes, RWA (reprint author), DLO, Winand Staring Ctr Integrat Land Soil & Water Res, POB 125, NL-6700 AC Wageningen, Netherlands. EM hutjes@sc.dlo.nl RI Pielke, Roger/A-5015-2009; Valentini, Riccardo/D-1226-2010; Pitman, Andrew/A-7353-2011; Victoria, Reynaldo /F-5348-2012; Schulze, Ernst-Detlef/K-9627-2014 OI Valentini, Riccardo/0000-0002-6756-5634; Pitman, Andrew/0000-0003-0604-3274; NR 97 TC 31 Z9 48 U1 2 U2 43 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-1694 J9 J HYDROL JI J. Hydrol. PD DEC PY 1998 VL 212 IS 1-4 BP 1 EP 21 DI 10.1016/S0022-1694(98)00255-8 PG 21 WC Engineering, Civil; Geosciences, Multidisciplinary; Water Resources SC Engineering; Geology; Water Resources GA 151LV UT WOS:000077722300001 ER PT J AU Lipa, JA Swanson, DR Nissen, JA Williamson, PR Geng, ZK Stricker, DA Chui, TCP Israelsson, UE Larson, M AF Lipa, JA Swanson, DR Nissen, JA Williamson, PR Geng, ZK Stricker, DA Chui, TCP Israelsson, UE Larson, M TI Preliminary results from a Shuttle mission to measure the heat capacity of confined helium near the Lambda point SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS ID SUPERFLUID DENSITY; T-LAMBDA; HE-4; TRANSITION AB We describe the preliminary results from a Shuttle mission to measure the heat capacity of helium confined within a stack of evenly spaced silicon plates at temperatures very close to the superfluid transition. Recently developed high resolution thermometry has substantially improved our ability to study dimensional cross-over effects in well-defined geometries. These effects have been of interest to theorists and experimentalists for decades. The main part of the apparatus consists of a high purity copper calorimeter containing a stack of 408 silicon plates spaced 57 microns apart, and a pair of high resolution, fast response, paramagnetic salt thermometers with a noise level of < 10(-10) K in a 1 Hz bandwidth. The resolution of the heat capacity measurements was about 5 x 10(-9) K, allowing the finite size peak to be mapped in detail. In addition, wide range data containing information on the behavior of the surface specific heat was collected. The preliminary analysis shows fair agreement with theory. The results can also be combined with supplementary ground measurements on smaller length scales to perform additional tests of scaling predictions for cross-over to lower dimensional behavior. C1 Stanford Univ, Stanford, CA 94305 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lipa, JA (reprint author), Stanford Univ, Stanford, CA 94305 USA. NR 15 TC 24 Z9 24 U1 1 U2 1 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD DEC PY 1998 VL 113 IS 5-6 BP 849 EP 860 DI 10.1023/A:1022598705146 PG 12 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 140RA UT WOS:000077101100031 ER PT J AU Duncan, RV Day, PK McCready, SS Moeur, WA Liu, FC Sergatskov, DA AF Duncan, RV Day, PK McCready, SS Moeur, WA Liu, FC Sergatskov, DA TI Gravitational effects on nonlinear heat transport near the superfluid transition in He-4 SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS ID THERMAL-CONDUCTIVITY; VAPOR-PRESSURE; DEPRESSION; HELIUM; BARS AB We have recently observed nonlinear heat transport within 30 nK of the superfluid transition temperature using heat flux Q, in the range 0.1 < Q < 2 erg/(s cm(2)). While Haussmann and Dohm (HD) accurately predict the initial departure of the thermal conductivity, kappa, from the linear response region, kappa, is greater than expected very close to T-lambda. We anticipate that the nature of the thermal conductivity's nonlinearity may depend upon Earth's gravity in the low heat flux limit (Q < 0.5 erg/(s cm(2))). Comparison of our data to similar data to be taken in a microgravity laboratory will provide an experimental determination of the effect of gravity on nonlinear heat transport near the superfluid transition. The microgravity measurements will also permit the first experimental test of theories that do not consider gravitational effects, such as those by HD. C1 Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Duncan, RV (reprint author), Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA. NR 22 TC 7 Z9 7 U1 0 U2 1 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD DEC PY 1998 VL 113 IS 5-6 BP 861 EP 866 DI 10.1023/A:1022550821984 PG 6 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 140RA UT WOS:000077101100032 ER PT J AU Liu, YM Larson, M Israelsson, U AF Liu, YM Larson, M Israelsson, U TI He-4 experiments near T-lambda in a low-gravity simulator SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS ID HELIUM AB We report on our latest measurements of gravity cancellation in the low-gravity simulator using a magnetostrictive force. We made these measurements using a new thermal conductivity cell design that is 0.5cm in diameter and 0.5cm in height. Gravity cancellation was verified by measuring both the reduction in the T-lambda variation across the cell and the suppression of thermal convection as a function of the magnetic field. Full gravity cancellation was achieved in the simulator with B(dB/dz) approximate to 21 T-2/cm, agreeing well with the calculated value and the valve found from levitating drops of helium. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Liu, YM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 7 TC 6 Z9 6 U1 0 U2 0 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD DEC PY 1998 VL 113 IS 5-6 BP 867 EP 872 DI 10.1023/A:1022502906055 PG 6 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 140RA UT WOS:000077101100033 ER PT J AU Barmatz, M Hahn, I Zhong, F AF Barmatz, M Hahn, I Zhong, F TI Recent high resolution measurements of the specific heat and isothermal compressibility near the He-3 liquid-gas critical point SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS AB Measurements of the specific heat at constant volume and isothermal compressibility have been made along a near critical isochore in the liquid-gas critical region of He-3. The critical density was determined to within 0.1% from pressure-density measurements along a near critical isotherm in the single phase region. The specific heat was measured in the gravity affected region in the reduced temperature range /T/T-c - 1/ less than or equal to 3 x 10(-4) using a slow cooling drift technique. A new electrostriction technique was developed to measure the isothermal compressibility along isochores and isotherms near the critical point. Initial measurements that validate this new technique will also be presented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Barmatz, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 10 Z9 10 U1 0 U2 0 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD DEC PY 1998 VL 113 IS 5-6 BP 891 EP 896 DI 10.1023/A:1022511107872 PG 6 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 140RA UT WOS:000077101100037 ER PT J AU Mohazzab, M Mulders, N Larson, M Nash, A AF Mohazzab, M Mulders, N Larson, M Nash, A TI Second sound measurements near the tricritical point in He-3-He-4 mixtures SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS ID LOGARITHMIC CORRECTIONS; UNIVERSALITY AB In this paper we discuss a pulsed second sound experiment, aimed at determining accurately the critical exponent zeta, and the predicted logarithmic correction to scaling, for the superfluid density along a tricritical path in the He-3-He-4 phase diagram. We present an accurate estimate for the limits for closest approach to the tricritical point, as set by gravitationally induced sample inhomogeneities and finite size effects, and discuss some of the complications associated with measurements close to the tricritical point. C1 Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mohazzab, M (reprint author), Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA. NR 18 TC 6 Z9 6 U1 0 U2 2 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD DEC PY 1998 VL 113 IS 5-6 BP 1031 EP 1036 DI 10.1023/A:1022508501937 PG 6 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 140RA UT WOS:000077101100060 ER PT J AU Naser, J Smith, JE Kuruvilla, AK AF Naser, J Smith, JE Kuruvilla, AK TI Effect of microgravity on grain coarsening during liquid phase sintering in the Fe-Cu system SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID VOLUME FRACTION; SUSPENSIONS; COALESCENCE; PARTICLES; ALUMINA; GRAVITY; ALLOYS AB Samples within the Fe-Cu system with th ree different volume fractions of solid (50, 60 and 70 vol% Fe) and four different sintering times (2.5, 5, 17 and 66 min) were liquid phase sintered (LPS) in microgravity. Particle coarsening during LPS is generally known to increase with increasing volume fraction of solid. Contrary to expectations, there was an enhancement in particle coarsening with a decrease in the volume fraction of solid. The agglomerated microstructures observed in these samples (especially those with a lower volume fraction of solid) also exhibited a higher grain growth constant consistent with their higher 3D coordination number. The relevant analysis discussed in this paper strongly suggests that agglomeration is promoted by Brownian motion that dominates any density-driven force in the absence of gravity. The observed particle growth characteristics were in excellent agreement with the Lifshitz-Slyozov encounter modified theory, which incorporates the effect of higher solid volume fraction and particle coalescence into the LSW theory. The particle distributions appear to remain unchanged with processing time beyond 2.5 min, suggesting thereby, that agglomeration promotes an equilibrium particle configuration early on in the process and enables scaled grain growth with time. (C) 1998 Kluwer Academic Publishers. C1 Univ Alabama, Consortium Mat Dev Space, Huntsville, AL 35899 USA. Univ Alabama, Dept Chem & Mat Engn, Huntsville, AL 35899 USA. George C Marshall Space Flight Ctr, IITRI, Huntsville, AL 35812 USA. RP Naser, J (reprint author), Univ Alabama, Consortium Mat Dev Space, Huntsville, AL 35899 USA. EM jesmith@ebs.330.eb.uah.edu NR 45 TC 9 Z9 9 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD DEC 1 PY 1998 VL 33 IS 23 BP 5573 EP 5580 DI 10.1023/A:1004403912910 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 170YF UT WOS:000078834200008 ER PT J AU Ahumada, A AF Ahumada, A TI Resting models for perceptual discrimination using repeatable noise. SO JOURNAL OF MATHEMATICAL PSYCHOLOGY LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2496 J9 J MATH PSYCHOL JI J. Math. Psychol. PD DEC PY 1998 VL 42 IS 4 BP 510 EP 511 PG 2 WC Mathematics, Interdisciplinary Applications; Social Sciences, Mathematical Methods; Psychology, Mathematical SC Mathematics; Mathematical Methods In Social Sciences; Psychology GA 153KX UT WOS:000077833200095 ER PT J AU Holland, FA Zaretsky, EV Melis, ME AF Holland, FA Zaretsky, EV Melis, ME TI Probabilistic failure prediction of SCS-6/Ti-15-3 MMC ring SO JOURNAL OF MECHANICAL DESIGN LA English DT Article AB Two parameter Weibull analysis was used to predict the fracture strength and fatigue life of an SCS-6/Ti-15-3 metal matrix composite (MMC) ring from coupon samples. Two methods were used. One method was to calculate an effective volume for an idealized ring on the basis of a theoretical approximation of the stress distribution. Fracture strength and fatigue life of the coupon samples wee then scaled to the effective volume of the ring. The other method used finite-element analysis (FEA) to determine a stress distribution in the actual, geometrically imperfect ring. The total ring reliability was then determined by multiplying the element reliabilities. Experimental fracture strengths were obtained for two MMC rings, each having an O.D. of 176.5 mm (6.95 in.) and I.D. of 146.0 mm (5.75 in.) and a 15.2 mm (0.60 in.) width. The median value of the experimental ring fracture strength data ws 173.1 MPa (25.1 ksi). Fracture strength predictions by the effective-volume and finite-element methods were 5 and 17 percent lower than the experimental value, respectively. The effective-volume and finite-element methods predicted ring fatigue lives of 2700 and 4800 cycles, respectively, at a 50 percent probability of failure and 154.4 MPa (22.4 ksi) maximum ring internal pressure. No ring fatigue data were available for comparison. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Holland, FA (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 10 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 1050-0472 J9 J MECH DESIGN JI J. Mech. Des. PD DEC PY 1998 VL 120 IS 4 BP 714 EP 720 DI 10.1115/1.2829336 PG 7 WC Engineering, Mechanical SC Engineering GA 147AL UT WOS:000077466000029 ER PT J AU Lubecke, VM McGrath, WR Tai, YC Rutledge, DB AF Lubecke, VM McGrath, WR Tai, YC Rutledge, DB TI Microfabrication of linear translator tuning elements in submillimeter-wave integrated circuits SO JOURNAL OF MICROELECTROMECHANICAL SYSTEMS LA English DT Article DE backshort; coplanar; MEMS; micromachining; millimeter wave; monolithic integrated circuit; planar tuning element; submillimeter wave ID RECEIVER; MIXERS AB A micromechanical planar tuning element has been developed and demonstrated in a fully monolithic 620-GHz integrated circuit, It allows for the mechanical variation of the electrical length of a coplanar transmission line tuner and is called a sliding planar backshort (SPB). It consists of a movable patterned rectangular metal plate confined by polyimide flanges along two of its edges to allow guided linear translation along the length of a dielectric-coated coplanar transmission line. Its fabrication involves an application of sacrificial-layer and molding techniques to materials and processes which are compatible with the fabrication of a nide range of submillimeter-wave integrated circuits. This is the first reported micromechanically adjustable tuning element demonstrated at submillimeter wavelengths. [319]. C1 CALTECH, Div Engn & Appl Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Lubecke, VM (reprint author), RIKEN, Inst Phys & Chem Res, Photodynam Res Ctr, Sendai, Miyagi 980, Japan. EM victor@postman.riken.co.jp NR 24 TC 0 Z9 0 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 1057-7157 J9 J MICROELECTROMECH S JI J. Microelectromech. Syst. PD DEC PY 1998 VL 7 IS 4 BP 404 EP 410 DI 10.1109/84.735348 PG 7 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Physics, Applied SC Engineering; Science & Technology - Other Topics; Instruments & Instrumentation; Physics GA 145ZB UT WOS:000077401800008 ER PT J AU Stoner, AW Mehta, N Ray-Culp, M AF Stoner, AW Mehta, N Ray-Culp, M TI Mesoscale distribution patterns of Queen Conch (Strombus gigas linne) in Exuma Sound, Bahamas: Links in recruitment from larvae to fishery yields SO JOURNAL OF SHELLFISH RESEARCH LA English DT Article DE fishery; habitat; larval supply; mesoscale; oceanography; postsettlement; presettlement; recruitment ID CORAL-REEF FISH; BENTHIC MARINE-INVERTEBRATES; DEEP-WATER HABITATS; POPULATION-STRUCTURE; SEAGRASS MEADOWS; POSTSETTLEMENT PROCESSES; STOCK ENHANCEMENT; FLORIDA-KEYS; SETTLEMENT; MORTALITY AB Populations of benthic species that produce pelagic larvae are sustained through a complex interaction of factors, including larval supply, variable transport mechanisms, and a host of postsettlement processes that affect differential recruitment and abundance. We report distributional data for the larvae, juveniles, adults, and a time-averaged index of fishery yield (shell middens) of the economically important marine gastropod Strombus gigas (queen conch) in the Exuma Sound, Bahamas. All life history stages and the fishery yields were heterogeneously distributed around this semienclosed system, with higher densities of benthic stages in the northern part of the sound than in the south and east. Distribution of shell middens closely reflected abundance patterns of shallow-water juvenile aggregations and abundance of adults in depth-stratified surveys; therefore, midden distribution provided a good indicator of long-term productivity around the periphery of the sound. Although patterns of fishery productivity around the system were closely related to both juvenile and adult distributions, and density of newly-hatched larvae reflected the distribution of adults and shell middens, as would be expected, benthic stages and the fishery yields were completely decoupled from the abundance of settlement-stage larvae. When transplants of newly settled conch were made to four seagrass sites in the eastern Exuma Sound with characteristics typical of conch nurseries, low growth rates resulted in all but one location. All of these results suggest that conch abundance and distribution in Exuma Sound is determined in the benthos, either during settlement or in the first year of postsettlement life. Therefore, although larval supply has been shown to influence benthic recruitment on a small scale (i.e., size and location of juvenile aggregations), and juvenile populations will always depend upon a reliable source of competent larvae, high quality habitat plays an equally important role in the recruitment of this important fishery resource. C1 Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Highlands, NJ 07732 USA. Caribbean Marine Res Ctr, Vero Beach, FL 32963 USA. RP Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Highlands, NJ 07732 USA. NR 69 TC 7 Z9 7 U1 2 U2 16 PU NATL SHELLFISHERIES ASSOC PI GROTON PA C/O DR. SANDRA E. SHUMWAY, UNIV CONNECTICUT, 1080 SHENNECOSSETT RD, GROTON, CT 06340 USA SN 0730-8000 EI 1943-6319 J9 J SHELLFISH RES JI J. Shellfish Res. PD DEC PY 1998 VL 17 IS 4 BP 955 EP 969 PG 15 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 184RY UT WOS:000079628200008 ER PT J AU Sherif, JS Sanderson, P AF Sherif, JS Sanderson, P TI Metrics for object-oriented software projects SO JOURNAL OF SYSTEMS AND SOFTWARE LA English DT Article ID DESIGN AB This paper puts forward an analysis of two software projects developed at the Jet Propulsion Laboratory (JPL). The two projects are The Micro Generic Controller (UGC) and The Sequence Generator (SEQGEN). Both projects use the object-oriented paradigm and the C++ programming language. Object-oriented metrics and other measures are implemented to analyze and compare the two projects. (C) 1998 Elsevier Science Inc. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SW Missouri State Univ, Springfield, MI USA. RP Sherif, JS (reprint author), CALTECH, Jet Prop Lab, Mail Stop 144-210, Pasadena, CA 91109 USA. EM jsherif@fullerton.edu NR 21 TC 4 Z9 4 U1 0 U2 1 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0164-1212 J9 J SYST SOFTWARE JI J. Syst. Softw. PD DEC PY 1998 VL 44 IS 2 BP 147 EP 154 PG 8 WC Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA 149CA UT WOS:000077586500007 ER PT J AU Lee, KN AF Lee, KN TI Contamination effects on interfacial porosity during cyclic oxidation of mullite-coated silicon carbide SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID CORROSION; CERAMICS; COATINGS AB Plasma-sprayed mullite (3Al(2)O(3). 2SiO(2)) and mullite/yttria-stabilized zirconia (mullite/YSZ) dual-layer coatings have been developed to protect silicon-based ceramics from environmental attack. The mullite/SiC system develops interfacial pores during cyclic oxidation. The development of pores at the mullite/sintered SiC interface in air has been investigated as a function of the purity of mullite at 1230 degrees-1350 degrees C in an atmospheric-pressure furnace. The silica scale is readily contaminated by impurities of alkali or alkaline-earth metal oxides from the mullite coating. The contamination enhances oxidation and reduces the scale viscosity by forming alkali or alkaline-earth metal silicates. The porosity increases as the temperature and contamination increase and decreases as the purity of the mullite increases. C1 Cleveland State Univ, Dept Chem Engn, Cleveland, OH 44115 USA. RP Lee, KN (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 16 TC 17 Z9 20 U1 1 U2 5 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0002-7820 J9 J AM CERAM SOC JI J. Am. Ceram. Soc. PD DEC PY 1998 VL 81 IS 12 BP 3329 EP 3332 DI 10.1111/j.1151-2916.1998.tb02777.x PG 4 WC Materials Science, Ceramics SC Materials Science GA 149CR UT WOS:000077588000039 ER PT J AU Manney, GL Orsolini, YJ Pumphrey, HC Roche, AE AF Manney, GL Orsolini, YJ Pumphrey, HC Roche, AE TI The 4-day wave and transport of UARS tracers in the austral polar vortex SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID ATMOSPHERE RESEARCH SATELLITE; MICROWAVE LIMB SOUNDER; SOUTHERN-HEMISPHERE; BAROTROPIC INSTABILITY; PLANETARY-WAVES; OZONE LAMINAE; STRATOSPHERE; WINTER; TEMPERATURE; VALIDATION AB Upper Atmosphere Research Satellite tracer data and isentropic transport calculations using U.K. Meteorological Office winds initialized with these data show evidence of eastward-traveling waves in the polar upper stratosphere in late austral winter 1992. Microwave Limb Sounder (MLS) H2O from prototype iterative retrievals shows a 4-day wave signal at levels from similar to 1.5 to 0.1 hPa; a 4-day wave signal was not obvious in production retrievals of MLS H2O. At 1800 K, the 4-day wave signal in MLS H2O has a double-peaked structure in latitude, which is reproduced in isentropic transport calculations. The time evolution,amplitude, and phase of the 3-day wave in the transport calculations agree well with observations at high latitudes; the position and shape of the polar vortex and of H2O drawn up around the vortex are reproduced by the transport calculations. Spectral analyses of the Cryogen Limb Array Etalon Spectrometer (CLAES) CH4 are dominated by more slowly eastward-moving waves (similar or equal to 6-10 days), but a weak 4-day wave signature is also present between similar to 1.5 and 4 hPa. Transport calculations initialized with CH4 Show similar eastward-traveling signals, good agreement with the phase of the observed signals, and overall agreement with the observed position of the vortex. The qualitative success of the transport calculations in reproducing the phase and overall time evolution of high-latitude eastward-traveling waves in the polar upper stratosphere indicates that the winds used for the transport calculations are generally reliable, and that the eastward-traveling waves identified in the MLS H2O and CLAES CH4 originate to a large extent from horizontal transport processes. Examination of the vertical structure of potential vorticity shows periods when at the highest levels studied (around 1800 K), the;4-day wave is responsible for the main motion of the vortex, whereas at lower levels (at and below similar to 1400 K) the vortex motion is characterized by a lower eastward progression, and the 4-day wave signal contributes to motions that are confined inside the vortex. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Ctr Natl Rech Meteorol, Toulouse, France. Univ Edinburgh, Dept Meteorol, Edinburgh, Midlothian, Scotland. Lockheed Martin Palo Alto Res Lab, Palo Alto, CA USA. RP Manney, GL (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 183-701, Pasadena, CA 91109 USA. NR 25 TC 14 Z9 14 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 DEC 1 PY 1998 VL 55 IS 23 BP 3456 EP 3470 DI 10.1175/1520-0469(1998)055<3456:TDWATO>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 145NH UT WOS:000077377500005 ER PT J AU Lee, HK Chu, PS Sui, CH Lau, KM AF Lee, HK Chu, PS Sui, CH Lau, KM TI On the annual cycle of latent heat fluxes over the equatorial Pacific using TAO buoy observations SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID SEA-SURFACE TEMPERATURE; TROPICAL PACIFIC; TURBULENT FLUXES; OCEAN; EVAPORATION; CONVECTION; INTERFACE; MOISTURE; WIND AB In this paper, we describe the annual cycle in the latent heat flux (LHF) and its associated bulk variables (sea surface temperature, wind speed, humidity difference) over the equatorial Pacific. The in-situ, daily-averaged TAO buoy observations between 8 degrees N and 8 degrees S during the period 1992-1996 form the database. LHF was computed using a modified bulk parameterization scheme to account for active convection and low wind speed frequently observed in the western Pacific. Harmonic analysis was used to help quantify the phase and amplitude of the annual and semiannual cycles. The annual cycle of LHF was found to be conspicuous in two regions, namely, the northeastern and western/central Pacific. For the former region, the maximum LHF occurs in boreal summer and early fall, when surface wind speeds are strong and the temperature difference between sea surface and air near the bottom of the atmospheric boundary layer is large. For the western/central Pacific, maximum LHF occurs in boreal winter, when the winter monsoon is strong. In contrast to the aforementioned two regions, the annual cycle in LHF in the equatorial cold tongue is weak and low LHF prevails throughout the year. Also noted in this study is a westward propagation of the maximum LHF region from the northeastern Pacific around July to the western Pacific by the following March. We also ascertained the relative importance of dynamic and thermodynamic processes in regulating the month-to-month variations of the LHF along two meridional transects, one in the eastern and another in the western Pacific. In the eastern Pacific, except to the north of the cold tongue, variations in humidity difference (i.e., thermodynamic process) seem to be of primary importance to the annual variations in LHF. On the other hand, variations in wind speed (i.e., dynamic process) are more important to the LHF in the western/central Pacific. C1 Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Dept Meteorol, Honolulu, HI 96822 USA. NASA, Climate & Radiat Branch, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD USA. RP Chu, PS (reprint author), Univ Hawaii Manoa, Sch Ocean & Earth Sci & Technol, Dept Meteorol, 2525 Correa Rd, Honolulu, HI 96822 USA. RI Lau, William /E-1510-2012; OI Lau, William /0000-0002-3587-3691; SUI, CHUNG-HSIUNG/0000-0003-2842-5660 NR 29 TC 3 Z9 3 U1 0 U2 0 PU METEOROLOGICAL SOC JAPAN PI TOKYO PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO, 100-0004, JAPAN SN 0026-1165 EI 2186-9057 J9 J METEOROL SOC JPN JI J. Meteorol. Soc. Jpn. PD DEC PY 1998 VL 76 IS 6 BP 909 EP 923 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 166AE UT WOS:000078553400006 ER PT J AU Zhang, GF Tsang, L Pak, K AF Zhang, GF Tsang, L Pak, K TI Angular correlation function and scattering coefficient of electromagnetic waves scattered by a buried object under a two-dimensional rough surface SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION LA English DT Article ID MONTE-CARLO SIMULATIONS; BACKSCATTERING ENHANCEMENT; LIGHT; RADAR AB We study three-dimensional (3-D) electromagnetic wave scattering from a buried object under a two-dimensional (2-D) random rough surface. The surface integral equations of wave fields are used for the rough surface and the surface of the buried object. The surface fields are then solved by the method of moments. The scattered wave field from the object is represented by the rough-surface field so that the matrix equation can be salved efficiently by means of the sparse-matrix canonical-grid method. Numerical simulations are illustrated for a perfectly conducting sphere buried under a 2-D rough surface. Both the scattering coefficient (normalized radar cross section) and the angular correlation function (ACF) are calculated. The study of 3-D electromagnetic scattering allows the use of azimuthal angular averaging and the study of cross polarization and the polarization angular correlation function (PACF). It is found that the ACF is more effective in suppressing the clutter that is due to the rough-surface scattering, and the PACF is more useful for the detection of the buried object. (C) 1998 Optical Society of America [S0740-3232(98)00412-8]. C1 Univ Washington, Dept Elect Engn, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zhang, GF (reprint author), Natl Ctr Atmospher Res, Pob 3000, Boulder, CO 80307 USA. RI Zhang, Guifu/M-3178-2014 OI Zhang, Guifu/0000-0002-0261-2815 NR 26 TC 39 Z9 39 U1 0 U2 6 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 DEC PY 1998 VL 15 IS 12 BP 2995 EP 3002 DI 10.1364/JOSAA.15.002995 PG 8 WC Optics SC Optics GA 146JB UT WOS:000077424600006 ER PT J AU Siebert, MW Keith, TG Ferguson, DC Wilt, DM Kolecki, JC Hepp, AF AF Siebert, MW Keith, TG Ferguson, DC Wilt, DM Kolecki, JC Hepp, AF TI Mars Pathfinder Wheel Abrasion Experiment - Ground and flight results SO LUBRICATION ENGINEERING LA English DT Article AB The Mars Pathfinder conducted scientific and technology experiments with a rover and a lander One of the technology experiments carried by the rover was a tribological experiment, called the wheel abrasion experiment, designed to evaluate the abrasiveness of Martian surface material. The experiment was carried on one of the wheels of the rover; Sojourner. Wear was detected by a photodetector through the reduction of reflectance of three types of metal films (Al, Pt, and Ni) on a black anodized substrate attached to the wheel. The Pathfinder mission showed that significant wear occurred on the metal wheel strips, with the most wear on the thinnest aluminum samples, mid the least on the thickest nickel and platinum samples. The depth of dig during a wheel abrasion experiment showed that the surface material is, in some places, very loose, and in other places tightly packed. Laboratory tests using a spare flight wheel demonstrated that the surface simulants used for wear testing adhered to the wheel and that electrostatic charging of the wheel occurred. C1 Univ Toledo, Toledo, OH 43606 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Siebert, MW (reprint author), Univ Toledo, 2801 W Bancroft St, Toledo, OH 43606 USA. NR 11 TC 1 Z9 1 U1 0 U2 0 PU SOC TRIBOLOGISTS & LUBRICATION ENGINEERS PI PARK RIDGE PA 840 BUSSE HIGHWAY, PARK RIDGE, IL 60068 USA SN 0024-7154 J9 LUBR ENG JI Lubric. Eng. PD DEC PY 1998 VL 54 IS 12 BP 20 EP 26 PG 7 WC Engineering, Mechanical SC Engineering GA 149UW UT WOS:000077625100005 ER PT J AU Anastasi, RF Friedman, AD Hinders, MK Madaras, EI AF Anastasi, RF Friedman, AD Hinders, MK Madaras, EI TI NDE of damage in thick stitched composites using laser-based ultrasound with optical fibers for remote generation and detection SO MATERIALS EVALUATION LA English DT Article DE composites; ultrasound; laser; optical fibers ID CONFOCAL FABRY-PEROT AB As design engineers implement new composite systems such as thick, load bearing, composite structures, they must have certifiable confidence in the structure's durability and worthiness. This confidence builds from understanding the structural response and failure characteristics of simple components loaded in testing machines to tests on full scale sections. Nondestructive evaluation is an important element that can provide quantitative information on the damage initiation, propagation, and final failure modes for the composite structural components. Although ultrasound is generally accepted as a test method, the use of conventional ultrasound for in situ monitoring of damage during tests of large structures is not practical. The use of lasers to generate and defect ultrasound extends the application of ultrasound to in situ sensing of damage in a deformed structure remotely and without contact. The goal of this research is to utilize this technology to monitor damage progression during testing. This paper describes and demonstrates the application of laser based ultrasound to quantify damage in thick stitched composite structural elements. This method involves using a Q-switched laser to generate a rapid, local thermal strain on the surface of the structure, causing the generation of ultrasonic waves into the material. A second laser used with a Fabry-Perot interferometer detects the surface deflections. The use of fiber optics provides safety for eyes and a convenient method of delivering the laser over long distances to the specimens. The composite material comprises several stacks of graphite assembled by stitching through the laminate thickness, then infiltrated with a resin and cured. The specimens used for these nondestructive evaluation studies had either impact damage or skin/stiffener interlaminar failure. Although little or no surface damage was visible, internal damage was detected by laser based ultrasound. C1 NASA, USA, Vehicle Technol Ctr,Langley Res Ctr, ARL,AMSRL VT S,Nondestruct Evaluat Sci Branch, Hampton, VA 23681 USA. Coll William & Mary, Dept Appl Sci, Williamsburg, VA 23187 USA. NASA, Nondestruct Evaluat Sci Branch, Langley Res Ctr, Hampton, VA 23681 USA. RP Anastasi, RF (reprint author), NASA, USA, Vehicle Technol Ctr,Langley Res Ctr, ARL,AMSRL VT S,Nondestruct Evaluat Sci Branch, Hampton, VA 23681 USA. NR 16 TC 2 Z9 3 U1 2 U2 8 PU AMER SOC NON-DESTRUCTIVE TEST PI COLUMBUS PA 1711 ARLINGATE LANE PO BOX 28518, COLUMBUS, OH 43228-0518 USA SN 0025-5327 J9 MATER EVAL JI Mater. Eval. PD DEC PY 1998 VL 56 IS 12 BP 1402 EP 1406 PG 5 WC Materials Science, Characterization & Testing SC Materials Science GA 150GU UT WOS:000077656700006 ER PT J AU Kim, Q Kayali, S AF Kim, Q Kayali, S TI Microchannel gate temperature analysis SO MICROELECTRONICS RELIABILITY LA English DT Article ID QUANTUM AB Photoemission spectra of a GaAs gate material of a metal semiconductor field effect transistor (MESFET) were analyzed to nondestructively assess the submicron-size local gate temperature. Utilizing the micromanipulator, the laser beam was precisely adjusted to probe the exact position of the device gate. The emission spectral bands due to the interaction among photons, free excitons and impurity bound excitons in GaAs gate materials were measured and identified both at 299.1 K and 84.8 K. The shift of the band was found to be 16.30 meV for the free excitons when the device was not powered, while the band shift of the gate was 7.38 meV when the device was powered at 84.8 K. Simple first order calculations based on the theory of temperature shift of the bound excitons, predicts an inversely proportional relationship between the emission bandshift and temperature. Measurements using this technique found an increase of 97.0 K. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kim, Q (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 303-210, Pasadena, CA 91109 USA. EM quiesup.kim@jpl.nasa.gov NR 9 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0026-2714 J9 MICROELECTRON RELIAB JI Microelectron. Reliab. PD DEC PY 1998 VL 38 IS 12 BP 1823 EP 1827 DI 10.1016/S0026-2714(98)00190-5 PG 5 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 154DP UT WOS:000077873600003 ER PT J AU Zdziarski, AA Poutanen, J Mikolajewska, J Gierlinski, M Ebisawa, K Johnson, WN AF Zdziarski, AA Poutanen, J Mikolajewska, J Gierlinski, M Ebisawa, K Johnson, WN TI Broad-band X-ray/gamma-ray spectra and binary parameters of GX 339-4 and their astrophysical implications SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Review DE accretion, accretion discs; binaries : general; stars : individual : GX 339-4; gamma-rays : observations; gamma-rays : theory; X-rays : stars ID ACTIVE GALACTIC NUCLEI; RELATIVISTIC THERMAL PLASMAS; BLACK-HOLE CANDIDATES; ACCRETION DISKS; CYGNUS X-1; NEUTRON-STARS; THIN CLOUDS; OPTICAL OBSERVATIONS; CENTRAL REGIONS; COLD MATTER AB We present X-ray/gamma-ray spectra of the binary GX 339-4 observed in the hard state simultaneously by Ginga and CGRO OSSE during an outburst in 1991 September. The Ginga X-ray spectra are well represented by a power law with a photon spectral index of Gamma similar or equal to 1.75 and a Compton reflection component with a fluorescent Fe K alpha line corresponding to a solid angle of an optically thick, ionized medium of similar to 0.3 x 2 pi. The OSSE data (greater than or equal to 50 keV) require a sharp high-energy cut-off in the power-law spectrum. The broad-band spectra are very well modelled by repeated Compton scattering in a thermal plasma with an optical depth of tau similar to 1 and kT similar or equal to 50 keV. We also study the distance to the system and find it to be 23 kpc, ruling out earlier determinations of similar to 1 kpc. Using this limit, the observed reddening and the orbital period, we find the allowed range of the mass of the primary is consistent with it being a black hole. We find the data are inconsistent with models of either homogenous or patchy coronae above the surface of an accretion disc. Rather, they are consistent with the presence of an inner hot disc with the viscosity parameter of alpha - 1 accreting at a rate close to the maximum set by advection. The hot disc is surrounded by a cold outer disc, which gives rise to the reflection component and a soft X-ray excess, also present in the data. The seed photons for Comptonization are unlikely to be due to thermal synchrotron radiation. Rather, they are supplied by the outer cold disc and/or cold clouds within the hot disc. e(+/-) pair production is negligible if electrons are thermal. The hot disc model, fur which scaled parameters are independent of the black hole mass, is supported by the similarity of the spectrum of GX 339-4 to those of other black hole binaries and Seyfert is. On the other hand, their spectra in the soft gamma-ray regime are significantly harder than those of weakly magnetized neutron stars. Based on this difference, we propose that the presence of broad-band spectra corresponding to thermal Comptonization with kT greater than or similar to 50 keV represents a black hole signature. C1 N Copernicus Astron Ctr, PL-00716 Warsaw, Poland. Stockholm Observ, S-13336 Saltsjobaden, Sweden. Jagiellonian Univ, Astron Observ, PL-30244 Krakow, Poland. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. RP Zdziarski, AA (reprint author), N Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw, Poland. EM aaz@camk.edu.pl RI Johnson, Neil/G-3309-2014; Poutanen, Juri/H-6651-2016; OI Poutanen, Juri/0000-0002-0983-0049; Gierlinski, Marek/0000-0001-9149-3514 NR 123 TC 136 Z9 136 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 DEC 1 PY 1998 VL 301 IS 2 BP 435 EP 450 DI 10.1046/j.1365-8711.1998.02021.x PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 156AA UT WOS:000077978200018 ER PT J AU Karyampudi, VM Lai, GS Manobianco, J AF Karyampudi, VM Lai, GS Manobianco, J TI Impact of initial conditions, rainfall assimilation, and cumulus parameterization on simulations of Hurricane Florence (1988) SO MONTHLY WEATHER REVIEW LA English DT Article ID NUMERICAL WEATHER PREDICTION; CONVECTIVE ADJUSTMENT SCHEME; TROPICAL CYCLONE; PHYSICAL INITIALIZATION; DROPWINDSONDE DATA; CLOUD CLUSTERS; SPECTRAL MODEL; FORECAST MODEL; GLOBAL-MODEL; RATES AB Numerical simulations were performed with the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model Version 5 (MM5) to study the impact of initial conditions, satellite-derived rain assimilation, and cumulus parameterization on Hurricane Florence (1988). A few modifications were made to the J. Manobianco et al. (MKKN) rain assimilation scheme, which was developed originally for midlatitude weather systems, to successfully simulate organized tropical weather systems such as Florence. These changes consist of replacing latent heating scaring with convective rainfall in the Kuo-Anthes scheme in areas where both the model-predicted and satellite-derived rainfall coincide, and specifying a normalized parabolic heating profile in deep convective regions where there is satellite rain but no model rain. Restoration of the original Kuo-Anthes heating distribution function in lieu of the fixed heating profile specified in the MM5 model is another change implemented in the Kuo-Anthes scheme. Results from the sensitivity simulations made with the modified rain assimilation scheme show that 1) the enhanced initial conditions with the omega dropsonde data yield a positive impact on the development of Florence for both the Betts-Miller and the modified Kuo-Anthes schemes, 2) the effect of ingesting continuous (Special Sensor Microwave/Imager and Geostationary Operational Environmental Satellite Infrared) satellite-derived rainfall rates as latent heating by the modified rain assimilation scheme is much greater with the modified Kuo-Anthes scheme than with the Betts-Miller scheme, and 3) the combined impact of enhanced initial conditions and rain assimilation yields a superior simulation of Florence, particularly with the Kuo-Anthes scheme. The weak response of the Betts-Miller scheme to rain assimilation, compared to the large impact with the Kuo-Anthes scheme, appears to be related mainly to the differences in the treatment of convective rainfall and its latent heat release in respective cumulus parameterization schemes. Since the MKKN scheme mainly invokes latent heat scaling to ingest satellite rainfall, the Kuo-Anthes scheme responds to increased latent heating from satellite rainfall rates more favorably through conditional instability of the second kind (CISK)-type feedback effects than the Betts-Miller scheme. The latter result clearly suggests that the success of the modified rain assimilation scheme on development of organized tropical systems such as Hurricane Florence depends to a large extent on the choice of cumulus parameterization scheme. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. ENSCO Inc, Cocoa Beach, FL USA. Sci Syst & Applicat Inc, Lanham, MD USA. RP Karyampudi, VM (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. NR 52 TC 37 Z9 40 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 DEC PY 1998 VL 126 IS 12 BP 3077 EP 3101 DI 10.1175/1520-0493(1998)126<3077:IOICRA>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 150GZ UT WOS:000077657300003 ER PT J AU Song, YT AF Song, YT TI A general pressure gradient formulation for ocean models. Part I: Scheme design and diagnostic analysis SO MONTHLY WEATHER REVIEW LA English DT Article ID PRIMITIVE EQUATION; HORIZONTAL GRADIENTS; COORDINATE SYSTEM; SIGMA; SIMULATION; TOPOGRAPHY; ERROR; FORCE AB A Jacobian formulation of the pressure gradient farce for use in models with topography-following coordinates is proposed. II can be used in conjunction with any vertical coordinate system and is easily implemented. Vertical variations in the pressure gradient are expressed in terms of a vertical integral of the Jacobian of density and depth with respect to the vertical computational coordinate. Finite difference approximations are made on the density held, consistent with piecewise linear and continuous fields, and accurate pressure gradients are obtained by vertically integrating the discrete Jacobian from sea surface. Two discrete schemes are derived and examined in detail: the first using standard centered differencing in the generalized vertical coordinate and the second using a vertical weighting such that the finite differences are centered with respect to the Cartesian z coordinate. Both schemes achieve second-order accuracy for any vertical coordinate system and are significantly more accurate than conventional schemes based on estimating the pressure gradients by finite differencing a previously determined pressure field. The standard Jacobian formulation is constructed to give exact pressure gradient results, independent of the bottom topography, if the buoyancy field varies bilinearly with horizontal position, x, and the generalized vertical coordinate, s, over each grid cell. Similarly, the weighted Jacobian scheme is designed to achieve exact results, when the buoyancy field varies linearly with z and arbitrarily with x, that is, b(x,z) = b(0)(x) + b(1)(x)z. When horizontal resolution cannot be made fine enough to avoid hydrostatic inconsistency, errors can be substantially reduced by the choice of an appropriate vertical coordinate. Tests with horizontally uniform, vertically varying, and with horizontally and vertically varying buoyancy fields show that the standard Jacobian formulation achieves superior results when the condition for hydrostatic consistency is satisfied, but when coarse horizontal resolution causes this condition to be strongly violated, the weighted Jacobian may give superior results. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. RP Song, YT (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. NR 34 TC 41 Z9 45 U1 3 U2 4 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 DEC PY 1998 VL 126 IS 12 BP 3213 EP 3230 DI 10.1175/1520-0493(1998)126<3213:AGPGFF>2.0.CO;2 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 150GZ UT WOS:000077657300011 ER PT J AU Song, YT Wright, DG AF Song, YT Wright, DG TI A general pressure gradient formulation for ocean models. Part II: Energy, momentum, and bottom torque consistency SO MONTHLY WEATHER REVIEW LA English DT Article ID CIRCULATION MODEL; WIND-DRIVEN; PRIMITIVE EQUATIONS; COORDINATE SYSTEM; SEPARATION; TOPOGRAPHY; ATLANTIC; JEBAR AB A new formulation of the pressure gradient force for use in models with topography-following coordinates is proposed and diagnostically analyzed in Part I. Here, iris shown that important properties of the continuous equations are retained by the resulting numerical schemes, and their performance in prognostic simulations is examined. Numerical consistency is investigated with respect to global energy conservation, depth-integrated momentum changes, and the representation of the bottom pressure torque. The performances of the numerical schemes are tested in prognostic integrations of an ocean model to demonstrate numerical accuracy and longterm integral stability. Two typical geometries, an isolated tall seamount and an unforced basin with sloping boundaries, are considered for the special case of no external forcing and horizontal isopycnals to test numerical accuracy. These test problems confirm that the proposed schemes yield accurate approximations to the pressure gradient force. Integral consistency conditions are verified and the energetics of the "advective elimination" of the pressure gradient error (Mellor el al.) is considered. A large-scale wind-driven basin with and without topography is used to test the model's long-term integral performance and the effects of bottom pressure torque on the transport in western boundary currents. Integrations are carried out for 10 years in each case and results show that the schemes are stable, and the steep topography causes no obvious numerical problems. A realistic meandering western boundary current is well developed with detached cold cyclonic and warm anticyclonic eddies as it extends across the basin. In addition, the results with topography show earlier separation and enhanced transport in the western boundary currents due to the bottom pressure torque. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. Fisheries & Oceans Canada, Bedford Inst Oceanog, Dartmouth, NS B2Y 4A2, Canada. RP CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. EM song@pacific.jpl.nasa.gov NR 30 TC 31 Z9 32 U1 0 U2 2 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 EI 1520-0493 J9 MON WEATHER REV JI Mon. Weather Rev. PD DEC PY 1998 VL 126 IS 12 BP 3231 EP 3247 DI 10.1175/1520-0493(1998)126<3231:AGPGFF>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 150GZ UT WOS:000077657300012 ER PT J AU Dzegilenko, FN Srivastava, D Saini, S AF Dzegilenko, FN Srivastava, D Saini, S TI Simulations of carbon nanotube tip assisted mechano-chemical reactions on a diamond surface SO NANOTECHNOLOGY LA English DT Article ID SCANNING TUNNELING MICROSCOPE; INDIVIDUAL MOLECULES; ATOMISTIC MECHANISMS; NANOMETER-SCALE; SINGLE ATOMS; DYNAMICS; STM; SI; NANOSTRUCTURES; MANIPULATION AB The interaction of a carbon nanotube tip with two chemically modified caps with a single-height-stepped C{001} (2 x 1) diamond surface is studied by performing molecular dynamics simulations. The C-2 and C6H2 radicals are attached to the end cap of a nanotube. The forces for solving the classical equations of motion are derived from Brenner's many-body reactive potential. Depending on the surface impact site, the nanotube initial velocity towards the diamond surface, and the nanotube withdrawal rate a variety of mechano-chemical reactions have been observed. The strong tip-surface interaction results in creation of chemically different nanostructures on the diamond surface for C6H2 tip, while the tip with C-2 allows us to remove a dimer of carbon atoms from the upper terrace of diamond. The possibility of using a nanotube with chemically modified caps for selective etching and nanolithography on different semiconductor surfaces is discussed. C1 NASA, Ames Res Ctr, NAS MRJ, IT Modeling & Simulat Grp, Moffett Field, CA 94035 USA. RP Dzegilenko, FN (reprint author), NASA, Ames Res Ctr, NAS MRJ, IT Modeling & Simulat Grp, Moffett Field, CA 94035 USA. NR 39 TC 10 Z9 10 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0957-4484 J9 NANOTECHNOLOGY JI Nanotechnology PD DEC PY 1998 VL 9 IS 4 BP 325 EP 330 DI 10.1088/0957-4484/9/4/004 PG 6 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied SC Science & Technology - Other Topics; Materials Science; Physics GA 152AL UT WOS:000077753000004 ER PT J AU Goldburg, WI Min, KY AF Goldburg, WI Min, KY TI The effect of shear on nucleation: Experiments in a binary mixture SO NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA D-CONDENSED MATTER ATOMIC MOLECULAR AND CHEMICAL PHYSICS FLUIDS PLASMAS BIOPHYSICS LA English DT Article; Proceedings Paper CT International Conference on the Morphology and Kinetics of Phase Separating Complex Fluids CY JUN 24-28, 1997 CL MESSINA, ITALY ID FLUIDS AB Phase separation in a near-critical binary mixture is strongly altered if the fluid is being continually exposed to a shearing force. Of interest here is the effect of uniform shear on the nucleation of spherical droplets out of a background phase. Shear of magnitude S will rupture all droplets having a radius R that exceeds a certain value R-max that is inversely proportional to S and directly proportional to the surface tension of the droplet. Increasing S in small steps will decrease R-max to a value R-c, the critical radius of the supercooled system. Since there can be no droplets present of size R less than R-c and none larger, R-c becomes measurable under steady-state conditions. We describe light scattering experiments of this type and also report experiments carried out immediately after the shear has been switched off. It appears that strong shear not only destroys existing droplets, but it also suppresses concentration fluctuations which would other wise grow to become spherical droplets. Where possible, the results will be compared with existing theories. C1 Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Goldburg, WI (reprint author), Univ Pittsburgh, Dept Phys & Astron, Pittsburgh, PA 15260 USA. NR 15 TC 0 Z9 0 U1 0 U2 2 PU EDITRICE COMPOSITORI BOLOGNA PI BOLOGNA PA VIA STALINGRADO 97/2, I-40128 BOLOGNA, ITALY SN 0392-6737 J9 NUOVO CIMENTO D JI Nuovo Cimento Soc. Ital. Fis. D-Condens. Matter At. Mol. Chem. Phys. Fluids Plasmas Biophys. PD DEC PY 1998 VL 20 IS 12BIS BP 2083 EP 2094 PG 12 WC Physics, Multidisciplinary SC Physics GA 214WU UT WOS:000081351200014 ER PT J AU Cucka, P Netanyahu, NS Rosenfeld, A AF Cucka, P Netanyahu, NS Rosenfeld, A TI "Robotic" estimation: The inefficiency of random-walk sampling SO PATTERN RECOGNITION LA English DT Article DE sampling; estimation; random walks AB Pattern recognition often involves estimation of statistics of a data ensemble by taking samples of the data and using sample statistics as estimates of the ensemble statistics. Ideally, the samples should be chosen randomly from the ensemble. In some situations, however, random sampling may not be practical. For example, if a robot is required to obtain samples of its environment, it would be inefficient for the robot to go to a sequence of randomly chosen locations to collect samples. In moving through the environment, the robot must follow a continous path, and it can obtain large numbers of samples as it moves along the path. This "robotic sampling" process can be made (somewhat) random by letting the path be a random walk through the environment. Unfortunately, if successive samples along the path are correlated, taking samples along the path is less efficient (from a sampling-theoretic standpoint) than taking random samples. This paper studies the inefficiency of "robotic" estimation, based on a random-walk path, relative to estimation based on random sampling. (C) 1998 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved. C1 Univ Maryland, Ctr Automat Res, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Ctr Excellence Space Data & Informat Sci, Greenbelt, MD 20771 USA. RP Rosenfeld, A (reprint author), Univ Maryland, Ctr Automat Res, College Pk, MD 20742 USA. NR 4 TC 1 Z9 1 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0031-3203 J9 PATTERN RECOGN JI Pattern Recognit. PD DEC PY 1998 VL 31 IS 12 BP 2091 EP 2102 DI 10.1016/S0031-3203(98)00024-7 PG 12 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 132UM UT WOS:000076648700023 ER PT J AU Bhatia, AK Drachman, RJ AF Bhatia, AK Drachman, RJ TI Optical properties of helium including relativistic corrections SO PHYSICAL REVIEW A LA English DT Article ID POLARIZABILITIES AB We have obtained very accurately calculated nonrelativistic values of the index of refraction and the Verdet constant of helium gas. We have used the Breit-Pauli operator to obtain corrections of order alpha(2) to the same optical quantities. This required us to analyze the scattering of light by helium atoms correct up to third order: second order in the electromagnetic field and first order in the Breit-Pauli operator. We compare these results with experimental values and find some significant discrepancies. [S1050-2947(98)06212-X]. 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, Greenbelt, MD 20771 USA. NR 7 TC 14 Z9 14 U1 3 U2 5 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 DEC PY 1998 VL 58 IS 6 BP 4470 EP 4472 DI 10.1103/PhysRevA.58.4470 PG 3 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 145CD UT WOS:000077352700030 ER PT J AU Zhou, Y Speziale, CG Rubinstein, R AF Zhou, Y Speziale, CG Rubinstein, R TI Some remarks concerning recent work on rotating turbulence SO PHYSICS OF FLUIDS LA English DT Editorial Material ID DYNAMICAL MODEL; ISOTROPIC TURBULENCE AB Some aspects of a recent paper on rotating turbulence by Canuto and Dubovikov [Phys. Fluids 9, 2132 (1997)] are examined from historical and scientific perspectives. Their claim to have discovered a new energy spectrum scaling law for rotating turbulence is examined in light of previous publications on this subject. We answer an objection raised to the consistency of this spectral scaling law with the Bardina-type dissipation rate transport equation derived from this law by two of the authors [Phys. Fluids 8, 3172 (1996)]. Finally, some difficulties with the alternative model for the dissipation rate transport equation proposed by Canuto and Dubovikov are described in both the weak and strong rotation limits. (C) 1998 American Institute of Physics. [S1070-6631(98)01012-5]. C1 IBM Corp, Div Res, TJ Watson Res Ctr, Yorktown Heights, NY 10598 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. Boston Univ, Dept Aerosp & Mech Engn, Boston, MA 02215 USA. RP Zhou, Y (reprint author), IBM Corp, Div Res, TJ Watson Res Ctr, POB 218, Yorktown Heights, NY 10598 USA. NR 17 TC 4 Z9 4 U1 0 U2 4 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 DEC PY 1998 VL 10 IS 12 BP 3242 EP 3244 DI 10.1063/1.869854 PG 3 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 141PD UT WOS:000077151600027 ER PT J AU Canuto, VM Dubovikov, MS AF Canuto, VM Dubovikov, MS TI Response to "Some remarks concerning recent work on rotating turbulence" [Phys. Fluids 10, 3242 (1998)] SO PHYSICS OF FLUIDS LA English DT Editorial Material C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 9 TC 0 Z9 0 U1 0 U2 1 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 DEC PY 1998 VL 10 IS 12 BP 3245 EP 3246 DI 10.1063/1.869855 PG 2 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 141PD UT WOS:000077151600028 ER PT J AU Oughton, S Matthaeus, WH Ghosh, S AF Oughton, S Matthaeus, WH Ghosh, S TI Scaling of spectral anisotropy with magnetic field strength in decaying magnetohydrodynamic turbulence SO PHYSICS OF PLASMAS LA English DT Article ID SOLAR-WIND FLUCTUATIONS; POLARIZED ALFVEN-WAVE; MHD TURBULENCE; INTERSTELLAR TURBULENCE; NONLINEAR EVOLUTION; EQUATIONS; MODEL; BETA AB Space plasma measurements, laboratory experiments, and simulations have shown that magnetohydrodynamic (MHD) turbulence exhibits a dynamical tendency towards spectral anisotropy given a sufficiently strong background magnetic field. Here the undriven decaying initial-value problem for homogeneous MHD turbulence is examined with the purpose of characterizing the variation of spectral anisotropy of the turbulent fluctuations with magnetic field strength. Numerical results for both incompressible and compressible MHD are presented. A simple model for the scaling of this spectral anisotropy as a function of the fluctuating magnetic field over total magnetic field is offered. The arguments are based on ideas from reduced MHD (RMHD) dynamics and resonant driving of certain non- RMHD modes. The results suggest physical bases for explaining variations of the anisotropy with compressibility, Reynolds numbers, and spectral width of the initial conditions. (C) 1998 American Institute of Physics. (isotropic) [S1070-664X(98)02912-7]. C1 UCL, Dept Math, London WC1E 6BT, England. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. Space Applicat Corp, Vienna, VA 22180 USA. RP Oughton, S (reprint author), NASA, Goddard Space Flight Ctr, Code 692, Greenbelt, MD 20771 USA. EM sean@math.ucl.ac.uk RI Oughton, Sean/A-3380-2012 OI Oughton, Sean/0000-0002-2814-7288 NR 36 TC 56 Z9 56 U1 0 U2 0 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 1070-664X J9 PHYS PLASMAS JI Phys. Plasmas PD DEC PY 1998 VL 5 IS 12 BP 4235 EP 4242 DI 10.1063/1.873159 PG 8 WC Physics, Fluids & Plasmas SC Physics GA 139LX UT WOS:000077031000017 ER PT J AU Loewenstein, M White, RE AF Loewenstein, M White, RE TI Do elliptical galaxies have dark matter? SO PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS LA English DT Article; Proceedings Paper CT Workshop on Primordial Black Holes and Hawking Radiation/3rd International Symposium on Sources and Detection of Dark Matter in the Universe CY FEB 17-20, 1998 CL MARINA DEL REY, CALIFORNIA ID UNIVERSAL AB We present constraints on the structure of dark matter halos in elliptical galaxies from the relationship between X-ray temperature and velocity dispersion observed in an optically complete sample. We demonstrate the ubiquity of dark matter in L > L-* galaxies, present limits on the dark matter structural parameters, and discuss the scaling of these parameters with optical luminosity. We find that the dark matter is characterized by velocity dispersions that are greater than those of the luminous stars, and that the mass-to-light ratio within six half-light radii for bright elliptical galaxies has a universal value, M/L-v approximate to 25h(80)M./L-v.. The latter conclusion is consistent with gravitational lensing studies, but conflicts with the simplest extension of CDM theories of large scale structure formation to galactic scales. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Alabama, Dept Phys & Astron, Tuscaloosa, AL 35487 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Loewenstein, M (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-1573 J9 PHYS REP JI Phys. Rep.-Rev. Sec. Phys. Lett. PD DEC PY 1998 VL 307 IS 1-4 BP 75 EP 81 DI 10.1016/S0370-1573(98)00059-3 PG 7 WC Physics, Multidisciplinary SC Physics GA 155GE UT WOS:000077937700010 ER PT J AU Carr, BJ MacGibbon, JH AF Carr, BJ MacGibbon, JH TI Cosmic rays from primordial black holes and constraints on the early universe SO PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS LA English DT Article; Proceedings Paper CT Workshop on Primordial Black Holes and Hawking Radiation/3rd International Symposium on Sources and Detection of Dark Matter in the Universe CY FEB 17-20, 1998 CL MARINA DEL REY, CALIFORNIA DE cosmic rays; primordial black holes; early Universe ID GLUON-JET EMISSION; DENSITY PERTURBATIONS; QUARK-JET; INFLATION; ANTIPROTONS; EXPLOSIONS; ENERGIES; SPECTRA; RELICS; BURSTS AB The constraints on the number of evaporating primordial black holes imposed by observations of the cosmological gamma-ray background do not exclude their making a significant contribution to the Galactic flux of cosmic ray photons, electrons, positrons and antiprotons. Even if this contribution is small, cosmic ray data place important limits on the number of evaporating black holes and thereby on models of the early Universe. Evaporating black holes are unlikely to be detectable in their final explosive phase unless new physics is invoked at the QCD phase transition. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Univ London Queen Mary & Westfield Coll, Sch Math Sci, London E1 4NS, England. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Carr, BJ (reprint author), Univ London Queen Mary & Westfield Coll, Sch Math Sci, Mile End Rd, London E1 4NS, England. EM b.j.carr@qmw.ac.uk NR 66 TC 45 Z9 45 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-1573 J9 PHYS REP JI Phys. Rep.-Rev. Sec. Phys. Lett. PD DEC PY 1998 VL 307 IS 1-4 BP 141 EP 154 DI 10.1016/S0370-1573(98)00039-8 PG 14 WC Physics, Multidisciplinary SC Physics GA 155GE UT WOS:000077937700017 ER PT J AU Wichoski, UF MacGibbon, JH Brandenberger, RH AF Wichoski, UF MacGibbon, JH Brandenberger, RH TI Astrophysical constraints on primordial black hole formation from collapsing cosmic strings SO PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS LA English DT Article; Proceedings Paper CT Workshop on Primordial Black Holes and Hawking Radiation/3rd International Symposium on Sources and Detection of Dark Matter in the Universe CY FEB 17-20, 1998 CL MARINA DEL REY, CALIFORNIA ID EMISSION; RELICS AB Primordial black holes (PBH) may have formed from the collapse of cosmic string loops. The spectral shape of the PBH mass spectrum can be determined by the scaling argument for string networks. Limits on the spectral amplitude derived from extragalactic gamma-ray and galactic gamma-ray and cosmic ray flux observations as well as constraints from the possible formation of stable black holes remnants are reanalyzed. The new constraints are remarkably close to those derived from the normalization of the cosmic string model to the cosmic microwave background anisotropies. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Brown Univ, Dept Phys, Providence, RI 02912 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Wichoski, UF (reprint author), Brown Univ, Dept Phys, Providence, RI 02912 USA. NR 24 TC 4 Z9 4 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0370-1573 J9 PHYS REP JI Phys. Rep.-Rev. Sec. Phys. Lett. PD DEC PY 1998 VL 307 IS 1-4 BP 191 EP 196 DI 10.1016/S0370-1573(98)00070-2 PG 6 WC Physics, Multidisciplinary SC Physics GA 155GE UT WOS:000077937700022 ER PT J AU Kadambi, JR Martin, WT Amirthaganesh, S Wernet, MP AF Kadambi, JR Martin, WT Amirthaganesh, S Wernet, MP TI Particle sizing using particle imaging velocimetry for two-phase flows SO POWDER TECHNOLOGY LA English DT Article; Proceedings Paper CT AIChE Annual Meeting CY NOV 16-21, 1997 CL LOS ANGELES, CALIFORNIA SP AIChE DE PTV; laser; defocus; sizing; intensity weighting; diffraction AB The major factors influencing the successful measurement of particle size from Particle Imaging Velocimetry (PIV) image data are described. Components of a standard PN system, a high resolution CCD camera and argon ion laser, are used to capture images of stationary particles. The image data are used to ascertain the limitations of estimating particle size. The effects of the Gaussian distributed intensity variation across the depth of the light sheet and the optical collection system's depth of field are investigated. These effects provide insight into designing a balanced illumination and collection optical system necessary to obtain constant particle size estimates, independent of their position within the light sheet. Using a 'balanced' optical set-up, monodisperse particle images are shown to be reproducible and predictable over a range of particle sizes and fields of view. Accuracy in the particle size estimates on the order of 9% are obtained consistently. It is also shown that size distributions in a mixture of polydisperse particles can be obtained with a maximum deviation of 10-20% from the true size distribution. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Kadambi, JR (reprint author), Case Western Reserve Univ, Dept Mech & Aerosp Engn, 10900 Euclid Ave, Cleveland, OH 44106 USA. NR 10 TC 16 Z9 33 U1 3 U2 10 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0032-5910 J9 POWDER TECHNOL JI Powder Technol. PD DEC 1 PY 1998 VL 100 IS 2-3 BP 251 EP 259 DI 10.1016/S0032-5910(98)00146-6 PG 9 WC Engineering, Chemical SC Engineering GA 134FZ UT WOS:000076733500018 ER PT J AU Cucinotta, FA Katz, R Wilson, JW AF Cucinotta, FA Katz, R Wilson, JW TI Radial distribution of electron spectra from high-energy ions SO RADIATION AND ENVIRONMENTAL BIOPHYSICS LA English DT Article ID ULTRASOFT X-RAYS; TRACK STRUCTURE; MUTATION-INDUCTION; HEAVY-IONS; V79 CELLS; INACTIVATION; RADIOBIOLOGY; DEPOSITION; PROTONS; BEAMS AB The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 mu m sites. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Nebraska, Lincoln, NE 68558 USA. NASA, Langley Res Ctr, Hampton, VA 23668 USA. RP Cucinotta, FA (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN, Houston, TX 77058 USA. NR 35 TC 34 Z9 35 U1 0 U2 6 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0301-634X J9 RADIAT ENVIRON BIOPH JI Radiat. Environ. Biophys. PD DEC PY 1998 VL 37 IS 4 BP 259 EP 265 DI 10.1007/s004110050127 PG 7 WC Biology; Biophysics; Environmental Sciences; Radiology, Nuclear Medicine & Medical Imaging SC Life Sciences & Biomedicine - Other Topics; Biophysics; Environmental Sciences & Ecology; Radiology, Nuclear Medicine & Medical Imaging GA 162PZ UT WOS:000078357100005 PM 10052675 ER PT J AU Gitelson, AA Kaufman, YJ AF Gitelson, AA Kaufman, YJ TI MODIS NDVI optimization to fit the AVHRR data series spectral considerations SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID LEAF-AREA INDEX; REFLECTANCE SPECTRA; VEGETATION INDEX; EOS-MODIS; CHLOROPHYLL; LEAVES; MODELS AB In early 1999 about when this article win hit the press. NASA is scheduled to launch its first Earth Observing satellite System (EOS) with array of instructions for precise, scientific, remote sensing of the Earth land ocean, and atmospheres. One of the main instruments, MODIS, will monitor daily vegetation dynamics with seven specially selected and highly characterized and calibrated spectral channels in the solar spectrum, with spatial resolution from 250 m to 500 m. These MODIS data, together with multiangular observations from the MISR instrument (also on EOS), will generate a much better picture of vegetation dynamic than previous satellite data records. But studying changes on, the Earth surface takes years and decades. To do it in our scientific lifetime, there is a need to be able to develop a data series that combines the traditional NDVI-AVHRR data sets that was used to monitor vegetation dynamics with the new MODIS data with its narrower channels. Here we propose that due to spectral differences between the AVHRR and MODIS, a combination of the MODIS red and green channels should be used to represent the AVHRR red channel in such long term data series, to avoid a step in the NDVI of delta NDVI of up to 0.05. We use both leaf spectra and full canopy spectra to develop and test this optimization. Optimization of the MODIS sensitivity for monitoring the dynamics of vegetation chlorophyll content is also discussed. (C) Elsevier Science Inc., 1998. C1 Ben Gurion Univ Negev, Jacob Blaustein Inst Desert Res, Dept Environm Phys & Energy Res, IL-84990 Sede Boqer, Israel. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Gitelson, AA (reprint author), Ben Gurion Univ Negev, Jacob Blaustein Inst Desert Res, Dept Environm Phys & Energy Res, Sede Boker Campus, IL-84990 Sede Boqer, Israel. RI Gitelson, Anatoly/G-3452-2012 NR 19 TC 70 Z9 85 U1 0 U2 10 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 DEC PY 1998 VL 66 IS 3 BP 343 EP 350 DI 10.1016/S0034-4257(98)00065-0 PG 8 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 142CX UT WOS:000077183300008 ER PT J AU Shahinpoor, M Bar-Cohen, Y Simpson, JO Smith, J AF Shahinpoor, M Bar-Cohen, Y Simpson, JO Smith, J TI Ionic polymer-metal composites (IPMCs) as biomimetic sensors, actuators and artificial muscles - a review SO SMART MATERIALS & STRUCTURES LA English DT Review ID GELS; MICROELECTROMECHANICS; MEMBRANE; DESIGN AB This paper presents an introduction to ionic polymer-metal composites and some mathematical modeling pertaining to them. It further discusses a number of recent findings in connection with ion-exchange polymer-metal composites (IPMCs) as biomimetic sensors and actuators. Strips of these composites can undergo large bending and flapping displacement if an electric field is imposed across their thickness. Thus, in this sense they are large motion actuators. Conversely by bending the composite strip, either quasi-statically or dynamically, a voltage is produced across the thickness of the strip. Thus, they are also large motion sensors. The output voltage can be calibrated for a standard size sensor and correlated to the applied loads or stresses. They can be manufactured and cut in any size and shape. In this paper first the sensing capability of these materials is reported. The preliminary results show the existence of a linear relationship between the output voltage and the imposed displacement for almost all cases. Furthermore, the ability of these IPMCs as large motion actuators and robotic manipulators is presented. Several muscle configurations are constructed to demonstrate the capabilities of these IPMC actuators. This paper further identifies key parameters involving the vibrational and resonance characteristics of sensors and actuators made with IPMCs. When the applied signal frequency varies, so does the displacement up to a critical frequency called the resonant frequency where maximum deformation is observed, beyond which the actuator response is diminished. A data acquisition system was used to measure the parameters involved and record the results in real time basis. Also the load characterizations of the IPMCs were measured and it was shown that these actuators exhibit good force to weight characteristics in the presence of low applied voltages. Finally reported are the cryogenic properties of these muscles for potential utilization in an outer space environment of a few Torrs and temperatures of the order of -140 degrees Celsius. These muscles are shown to work quite well in such harsh cryogenic environments and thus present a great potential as sensors and actuators that can operate at cryogenic temperatures. C1 Univ New Mexico, Artificial Muscles Res Inst, Albuquerque, NM 87131 USA. CALTECH, Jet Prop Lab, NASA, Pasadena, CA 91109 USA. NASA, Langley Res Ctr, Composites & Polymers Branch, Hampton, VA 23681 USA. NR 68 TC 533 Z9 538 U1 22 U2 177 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0964-1726 J9 SMART MATER STRUCT JI Smart Mater. Struct. PD DEC PY 1998 VL 7 IS 6 BP R15 EP R30 DI 10.1088/0964-1726/7/6/001 PG 16 WC Instruments & Instrumentation; Materials Science, Multidisciplinary SC Instruments & Instrumentation; Materials Science GA 158FQ UT WOS:000078105700001 ER PT J AU Neudeck, PG Huang, W Dudley, M AF Neudeck, PG Huang, W Dudley, M TI Breakdown degradation associated with elementary screw dislocations in 4H-SiC p(+)n junction rectifiers SO SOLID-STATE ELECTRONICS LA English DT Article ID 6H-SIC SINGLE-CRYSTALS; DEFECTS; ELECTRONICS AB It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector>2c). 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = 1c with no hollow core) in densities on the order of thousands per cm(2), nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p(+)n diodes. First, synchrotron white beam X-ray topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p+n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast, devices that contained at least one elementary screw dislocation exhibited 5-35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. SUNY Stony Brook, Dept Mat Sci & Engn, Stony Brook, NY 11794 USA. RP Neudeck, PG (reprint author), NASA, Lewis Res Ctr, MS 77-1,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 29 TC 61 Z9 61 U1 1 U2 7 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD DEC PY 1998 VL 42 IS 12 BP 2157 EP 2164 DI 10.1016/S0038-1101(98)00211-1 PG 8 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA 147NM UT WOS:000077573500006 ER PT J AU Chen, LY Hunter, GW Neudeck, PG Knight, D AF Chen, LY Hunter, GW Neudeck, PG Knight, D TI Surface and interface properties of PdCr/SiC Schottky diode gas sensor annealed at 425 degrees C SO SOLID-STATE ELECTRONICS LA English DT Article AB The surface and interface properties of Pd0.9Cr0.1/SiC Schottky diode gas sensors both before and after annealing are investigated using Anger electron spectroscopy (AES), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). At room temperature the alloy reacted with SIC and formed PdxSi only in a very narrow interfacial region. After annealing for 250 h at 425 degrees C, the surface of the Schottky contact area has much less silicon and carbon contamination than that found on the surface of an annealed Pd/SiC structure. Palladium silicides (PdxSi) formed at a broadened interface after annealing, but a significant layer of alloy film is still free of silicon and carbon. The chromium concentration with respect to palladium is quite uniform down to the deep interface region. A stable catalytic surface and a clean layer of Pd0.9Cr0.1 film are likely responsible for significantly improved device sensitivity. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Chen, LY (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 12 Z9 12 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD DEC PY 1998 VL 42 IS 12 BP 2209 EP 2214 DI 10.1016/S0038-1101(98)00217-2 PG 6 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA 147NM UT WOS:000077573500012 ER PT J AU Ardel, G Golodnitsky, D Peled, E Wang, YF Wang, G Bajue, S Greenbaum, S AF Ardel, G Golodnitsky, D Peled, E Wang, YF Wang, G Bajue, S Greenbaum, S TI Bulk and interfacial ionic conduction in LiI/Al2O3 mixtures SO SOLID STATE IONICS LA English DT Article; Proceedings Paper CT 11th International Conference on Solid State Ionics (SSI-11) CY NOV 16-21, 1997 CL HONOLULU, HI SP Int Soc Solid State Ion, Univ Hawaii, Coll Engn DE lithium iodide; nano-crystalline alumina; complex impedance; interfacial effects; lithium-7 NMR ID POLYMER ELECTROLYTES AB We have studied physical mixtures of LiI and nanoscale particles of Al2O3, prepared in pellet form under pressure, by X-ray diffraction, complex impedance, and wide-line Li-7 and I-127 and high resolution Li-7 NMR spectroscopy. Enhancement in ionic conductivity by the addition of Al2O3, is observed, although there is also an increase in grain boundary resistance. The high resolution (MAS) NMR method clearly resolves two or more distinct Li+ sites, one characteristic of bulk LiI and the rest associated with surface/interface regions. The site populations depend strongly on mix composition and temperature, and are correlated with the ionic conductivity behavior. (C) 1998 Published by Elsevier Science BN. All rights reserved. C1 CUNY Hunter Coll, Dept Phys & Astron, New York, NY 10021 USA. CUNY Medgar Evers Coll, Dept Nat Sci & Comp Sci, Brooklyn, NY 11225 USA. Tel Aviv Univ, Sch Chem, IL-69978 Tel Aviv, Israel. RP Greenbaum, S (reprint author), NASA Jet Prop Lab, Electrochem Technol Grp, Mail Stop 277-207, Pasadena, CA 91109 USA. EM steve.greenbaum@hunter.cuny.edu NR 11 TC 25 Z9 25 U1 2 U2 14 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-2738 J9 SOLID STATE IONICS JI Solid State Ion. PD DEC PY 1998 VL 113 SI SI BP 477 EP 485 DI 10.1016/S0167-2738(98)00313-0 PG 9 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 154BU UT WOS:000077868800068 ER PT J AU Szewczyk, ZP AF Szewczyk, ZP TI A knowledge-based search framework for designing composite structures SO STRUCTURAL OPTIMIZATION LA English DT Article ID DISTRIBUTED-MEMORY COMPUTERS; GENETIC ALGORITHMS; OPTIMIZATION; DECOMPOSITION AB In this paper, a search framework is presented that makes a genetic algorithm (GA) a practical engineering tool for searching discrete and nonconvex design spaces. It is shown that "near optimal" designs can be relatively quickly found if three problems are addressed: (i) the dimensionality of a design space is reasonably reduced, (ii) fast function evaluations are available, and (iii) genetic operators are tailored to the application art hand. In our work, the number of active design variables is reduced by using a rule-based fuzzy logic inference engine to process knowledge about the structure's behaviour. The use of a parallel computing environment for structural analysis in conjunction with data retrieval from binary-like trees effectively reduces the time required to perform Genetic searching. Three different selection operators along with a permutation-like operator for the reduced problem are evaluated for their effectiveness in locating the global optimum. As an example, the stacking sequence for maximising a budding load for a stiffened square panel with a circular cut-out and subject to thermal and shear loading is designed. C1 NASA, Computat Struct Branch, Langley Res Ctr, Hampton, VA 23681 USA. RP Szewczyk, ZP (reprint author), NASA, Computat Struct Branch, Langley Res Ctr, Hampton, VA 23681 USA. NR 32 TC 1 Z9 1 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0934-4373 J9 STRUCT OPTIMIZATION JI Struct. Optim. PD DEC PY 1998 VL 16 IS 4 BP 289 EP 299 PG 11 WC Computer Science, Interdisciplinary Applications; Engineering, Multidisciplinary; Mechanics SC Computer Science; Engineering; Mechanics GA 147PP UT WOS:000077575900007 ER PT J AU Angood, PB Doarn, CR Holaday, L Nicogossian, AE Merrell, RC AF Angood, PB Doarn, CR Holaday, L Nicogossian, AE Merrell, RC TI The spacebridge to Russia project: Internet-based telemedicine SO TELEMEDICINE JOURNAL LA English DT Article AB The National Aeronautics and Space Administration (NASA) has been a pioneer in telemedicine since the beginning of the human spaceflight program in the early 1960s. With the rapid evolution in computer technology and equally rapid development of computer networks, NASA and the Department of Surgery in Yale University's School of Medicine created a telemedicine testbed with the Russia Space Agency, the Spacebridge to Russia Project, using multimedia computers connected via the Internet. Clinical consultations were evaluated in a store-and-forward mode using a variety of electronic media, packaged as digital files, and transmitted using Internet and World Wide Web tools. These systems allow real-time Internet video teleconferencing between remotely located users over computer systems. This report describes the project and the evaluation methods utilized for monitoring effectiveness of the communications. The Spacebridge to Russia Project is a testbed for Internet-based telemedicine. The Internet and current computer technologies (hardware and software) make telemedicine readily accessible and affordable for most health care providers. Internet-based telemedicine is a communication tool that should become integral to global health care. C1 Yale Univ, Sch Med, Dept Surg, New Haven, CT 06520 USA. NASA, Washington, DC 20546 USA. RP Angood, PB (reprint author), Yale Univ, Sch Med, Dept Surg, 333 Cedar St LH 118, New Haven, CT 06520 USA. NR 2 TC 13 Z9 14 U1 0 U2 0 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 WIN PY 1998 VL 4 IS 4 BP 305 EP 311 DI 10.1089/tmj.1.1998.4.305 PG 7 WC Health Care Sciences & Services SC Health Care Sciences & Services GA 160XM UT WOS:000078257400005 PM 10220470 ER PT J AU Aucar, JA Doarn, CR Sargsyan, A Samuelson, DA Odonnell, MJ DeBakey, ME AF Aucar, JA Doarn, CR Sargsyan, A Samuelson, DA Odonnell, MJ DeBakey, ME TI Use of the Internet for long-term clinical follow-up SO TELEMEDICINE JOURNAL LA English DT Article AB Use of the Internet for patient-specific consultation across international boundaries has been demonstrated. This report describes the efforts of Baylor College of Medicine and NASA to conduct a telemedicine consultation with Moscow, Russia. Consultation between Russian and American physicians was performed over the Internet with a combination of real-time and store-and-forward techniques. The clinical focus involved a 65-year old Russian scientist who had undergone mitral valve replacement in the United States 5 years earlier. Development of new activity-related chest pain, dyspnea, and intermittent atrial fibrillation led to a consultation with his American cardiologist and cardiac surgeon. Real-time video was supplemented with telephone voice communication to overcome bandwidth limitations. Prior to the video link, the patient's recent history and clinical data were made available via the Internet using file transfer protocol (FTP). The patient's medications, new electrocardiographic findings, and activity status were reviewed. Specific clinical recommendations were made as a result of this telemedicine consultation. This case illustrates the technical factors, clinical implications, and confidentiality issues related to using the Internet for telemedicine consultations and demonstrates that the Internet may provide an alternative means for long-term clinical follow-up of patients. C1 Baylor Coll Med, Dept Surg, Houston, TX 77030 USA. Baylor Coll Med, Dept Informat Technol, Houston, TX 77030 USA. Baylor Coll Med, Dept Med, Houston, TX 77030 USA. NASA Headquarters, Washington, DC USA. KRUG Life Sci, Houston, TX USA. RP Aucar, JA (reprint author), Bethany Clin Whites Mill, 3604 Peters Court, High Point, NC 27265 USA. NR 11 TC 12 Z9 12 U1 0 U2 0 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 WIN PY 1998 VL 4 IS 4 BP 371 EP 374 DI 10.1089/tmj.1.1998.4.371 PG 4 WC Health Care Sciences & Services SC Health Care Sciences & Services GA 160XM UT WOS:000078257400013 PM 10220478 ER PT J AU Cox, JS Brentner, KS Rumsey, CL AF Cox, JS Brentner, KS Rumsey, CL TI Computation of vortex shedding and radiated sound for a circular cylinder: Subcritical to transcritical Reynolds numbers SO THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS LA English DT Article ID ROBUST METHOD; TURBULENCE; NOISE; LIFT; WAKE; FLOW; EFFICIENT; LAMINAR; SMOOTH AB The Lighthill acoustic analogy combined with Reynolds-averaged Navier-Stokes flow computations are used to investigate the ability of existing technology to predict the tonal noise generated by vortex shedding from a circular cylinder for a range of Reynolds numbers (100 less than or equal to Re less than or equal to 5 million). Computed mean drag, mean coefficient of pressure, Strouhal number, and fluctuating lift are compared with experiment. Two-dimensional calculations produce a Reynolds number trend similar to experiment but incorrectly predict many of the flow quantities. Different turbulence models give inconsistent results in the critical Reynolds number range (Re approximate to 100 000). The computed flow field is used as input for noise prediction. Two-dimensional inputs overpredict both noise amplitude and frequency; however, if an appropriate correlation length is used, predicted noise amplitudes agree with experiment. Noise levels and frequency content agree much better with experiment when three-dimensional flow computations are used as input data. C1 George Washington Univ, JIAFS, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Cox, JS (reprint author), George Washington Univ, JIAFS, Hampton, VA 23681 USA. NR 41 TC 40 Z9 47 U1 0 U2 6 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0935-4964 J9 THEOR COMP FLUID DYN JI Theor. Comput. Fluid Dyn. PD DEC PY 1998 VL 12 IS 4 BP 233 EP 253 DI 10.1007/s001620050108 PG 21 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 154BP UT WOS:000077868400003 ER PT J AU Mason, BH Haftka, RT Johnson, ER Farley, GL AF Mason, BH Haftka, RT Johnson, ER Farley, GL TI Variable complexity design of composite fuselage frames by response surface techniques SO THIN-WALLED STRUCTURES LA English DT Article DE composite fuselage frames; response surface techniques; variable complexity design ID INTERLAMINAR STRESSES; DELAMINATION; INITIATION; CRITERION AB Curved frame structures are often used as part of the internal skeletal structure in aircraft. Laminated composite materials offer potential weight savings for such structures, but composite frames have different and more complex failure mechanisms than metallic frames. In particular, failure mechanisms involving interlaminar stresses are important in composite structures. Interlaminar stresses can be directly computed from three-dimensional finite element models, but the computational expense of these models is prohibitive. In this work, two- and three-dimensional (2D and 3D) finite element models are combined to reduce the computational expense associated with designing composite frames. A response surface design approach is used to approximate the failure response of curved composite C-section frames subjected to an axial tensile loading using a minimum number of finite element analyses. Results are presented for two examples with two and five design variables, respectively. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Virginia Polytech Inst & State Univ, Dept Aerosp & Ocean Engn, Blacksburg, VA 24060 USA. USA, Vehicle Struct Directorate, NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Mason, BH (reprint author), Virginia Polytech Inst & State Univ, Dept Aerosp & Ocean Engn, Blacksburg, VA 24060 USA. NR 25 TC 18 Z9 18 U1 0 U2 1 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0263-8231 J9 THIN WALL STRUCT JI Thin-Walled Struct. PD DEC PY 1998 VL 32 IS 4 BP 235 EP 261 DI 10.1016/S0263-8231(98)00016-0 PG 27 WC Engineering, Civil SC Engineering GA 156EJ UT WOS:000077988200001 ER PT J AU Houser, PR Shuttleworth, WJ Famiglietti, JS Gupta, HV Syed, KH Goodrich, DC AF Houser, PR Shuttleworth, WJ Famiglietti, JS Gupta, HV Syed, KH Goodrich, DC TI Integration of soil moisture remote sensing and hydrologic modeling using data assimilation SO WATER RESOURCES RESEARCH LA English DT Article ID MONSOON 90; SURFACE AB The feasibility of synthesizing distributed fields of soil moisture by the novel application of four-dimensional data assimilation (4DDA) applied in a hydrological model is explored. Six 160-km(2) push broom microwave radiometer (PBMR) images gathered over the Walnut Gulch experimental watershed in southeast Arizona were assimilated into the Topmodel-based Land-Atmosphere Transfer Scheme (TOPLATS) using several alternative assimilation procedures. Modification of traditional assimilation methods was required to use these high-density PBMR observations. The images were found to contain horizontal correlations that imply length scales of several tens of kilometers, thus allowing information to be advected beyond the area of the image. Information on surface soil moisture also was assimilated into the subsurface using knowledge of the surface-subsurface correlation. Newtonian. nudging assimilation procedures are preferable to other techniques because they nearly preserve the observed patterns within the sampled region but also yield plausible patterns in unmeasured regions and allow information to be advected in time. C1 Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. Univ Texas, Dept Geol Sci, Austin, TX 78712 USA. ARS, SW Watershed Res Ctr, USDA, Tucson, AZ 85719 USA. RP Houser, PR (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. RI Gupta, Hoshin/D-1642-2010; Goodrich, David/B-1763-2009; Houser, Paul/J-9515-2013 OI Gupta, Hoshin/0000-0001-9855-2839; Goodrich, David/0000-0001-7735-1448; Houser, Paul/0000-0002-2991-0441 NR 20 TC 260 Z9 285 U1 5 U2 41 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 DEC PY 1998 VL 34 IS 12 BP 3405 EP 3420 DI 10.1029/1998WR900001 PG 16 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 145VV UT WOS:000077393000016 ER PT J AU Kara, AB Elsner, JB Ruscher, PH AF Kara, AB Elsner, JB Ruscher, PH TI Numerical models of boundary layer processes over and around the Gulf of Mexico during a return-flow event SO WEATHER AND FORECASTING LA English DT Article ID MASS TRANSFORMATION MODEL; SOIL HYDROLOGY; PARAMETERIZATION; EVAPORATION; SENSITIVITY AB The return-flow of low-level air from the Gulf of Mexico over the southeast United States during the cool season is studied using numerical models. The key models are a newly developed airmass transformation (AMT) model and a one-dimensional planetary boundary layer (PBL) model. Both are employed to examine the thermodynamic structure over and to the north of the Gulf. Model errors for predicting minimum, maximum, and dewpoint temperatures at the surface during both offshore and onshore phases of the return-few cycle are analyzed. PBL model forecasts indicate soil moisture values obtained from the Era Model improve accuracy. It is shown that forecasts of maximum temperature for coastal locations are sensitive to the soil moisture used in the PBL model. The AMT model performs well in determining boundary layer parameters since it includes horizontal advective processes. The AMT model is also able to predict the regional differences caused by different surface forcing while passing over land or sea. Results lead to a strategy for making predictions during cool-season return-flow events over and around the Gulf of Mexico. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. RP Kara, AB (reprint author), NASA, Army Ammunizat Plant, Bldg 9101, Stennis Space Ctr, MS 39529 USA. EM kara@nrlssc.navy.mil NR 35 TC 4 Z9 4 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0882-8156 J9 WEATHER FORECAST JI Weather Forecast. PD DEC PY 1998 VL 13 IS 4 BP 921 EP 933 DI 10.1175/1520-0434(1998)013<0921:NMOBLP>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 150KC UT WOS:000077663200002 ER PT J AU Jata, KV Vasudevan, AK Bales, TT AF Jata, KV Vasudevan, AK Bales, TT TI International Conference on Crystallographic Texture and Mechanical Anisotropy - 1-5 September 1997 - Hyannis, Masschusetts - Preface SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Editorial Material C1 USAF, Res Lab, Mat Directorate, Washington, DC 20330 USA. Off Naval Res, Arlington, VA 22217 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Jata, KV (reprint author), USAF, Res Lab, Mat Directorate, Washington, DC 20330 USA. NR 0 TC 0 Z9 0 U1 0 U2 1 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD NOV 30 PY 1998 VL 257 IS 1 BP XI EP XI PG 1 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 147LZ UT WOS:000077570400002 ER PT J AU Crooks, R Wang, Z Levit, VI Shenoy, RN AF Crooks, R Wang, Z Levit, VI Shenoy, RN TI Microtexture, microstructure and plastic anisotropy of AA2195 SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT International Conference on Crystallographic Texture and Mechanical Anisotropy CY SEP 01-05, 1997 CL CAPE COD, MASSACHUSETTS SP USAF, Res Lab Adv Metall, NASA, Off Naval Res, Engn Fdn DE microtexture; anisotropy; plastic deformation ID TEXTURE; EXTRUSION; ALLOYS AB The anisotropic tensile behavior of a commercial lithium-containing aluminum alloy was studied in both rolled plate and extruded forms in solution-treated and quenched and T8 tempers. Microtexture and other electron microscopy techniques were used to correlate grain orientation and morphology, load direction and inhomogeneous plastic deformation in T8 material. The ratio of yield strengths between 45 degrees and 0 degrees test directions was the same for as-quenched and T8 material. The plate and extruded materials had strong Brass, {110}[112], textures. Pronounced slip bands were found in Brass oriented grains after 45 degrees loading, on slip planes parallel to both the working direction and long axis of the grains; in a range from 0.02 to 20% average strain. An attempt to increase the area fraction of the T-1 precipitate variant on these planes had no effect on anisotropy. The intergranular fracture surfaces show coarse, linear features which suggest a connection between the planar slip bands and delamination fracture. (C) 1998 Published by Elsevier Science S.A. All rights reserved. C1 Analyt Serv & Mat Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Crooks, R (reprint author), Analyt Serv & Mat Inc, 107 Res Dr, Hampton, VA 23666 USA. NR 12 TC 21 Z9 23 U1 1 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD NOV 30 PY 1998 VL 257 IS 1 BP 145 EP 152 DI 10.1016/S0921-5093(98)00833-8 PG 8 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 147LZ UT WOS:000077570400017 ER PT J AU Hales, SJ Hafley, RA AF Hales, SJ Hafley, RA TI Texture and anisotropy in Al-Li alloy 2195 plate and near-net-shape extrusions SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article; Proceedings Paper CT International Conference on Crystallographic Texture and Mechanical Anisotropy CY SEP 01-05, 1997 CL CAPE COD, MASSACHUSETTS SP USAF, Res Lab Adv Metall, NASA, Off Naval Res, Engn Fdn DE Al-Li alloy; extrusion; orientation; texture; anisotropy ID ALUMINUM-LITHIUM SHEET AB Low density aluminum-lithium (Al-Li) alloys, such as 2195. are candidate materials for reducing the structural weight of cryogenic tanks on launch vehicles. The objective of this investigation was to establish the relationship between mechanical anisotropy, microstructure and texture in a near-net-shape 'T-stiffened' extrusion and in two gauges of plate. In both product forms, in-plane properties were measured as a function of orientation to the extrusion/rolling direction; tensile properties in increments of 15 degrees and fracture toughness properties at 0, 45 and 90 degrees to the principal axis. Mechanical behavior was evaluated at two locations in the skin of the extrusion, namely midway between and directly beneath the stiffeners. The microstructures of the plate and extruded product were characterized using cross-polarized light imaging of anodically etched metallographic sections. The textural characteristics were quantified as a function of location within the respective cross-sections using orientation distribution function (ODF) analysis. Tensile and fracture properties were correlated with microstructural and textural characteristics in the 2195 near-net-shape extrusion and compared with plate product. Published by Elsevier Science S.A. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Hales, SJ (reprint author), NASA, Langley Res Ctr, MS 188A,2 W Reid St, Hampton, VA 23681 USA. NR 35 TC 29 Z9 30 U1 3 U2 9 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD NOV 30 PY 1998 VL 257 IS 1 BP 153 EP 164 DI 10.1016/S0921-5093(98)00834-X PG 12 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 147LZ UT WOS:000077570400018 ER PT J AU Levit, C Sarfatti, J AF Levit, C Sarfatti, J TI Reply to comment by I.P. Hamilton on: "Are the Bader Laplacian and the Bohm quantum potential equivalent?" SO CHEMICAL PHYSICS LETTERS LA English DT Editorial Material C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Internet Sci Educ Project, San Francisco, CA 94133 USA. RP Sarfatti, J (reprint author), NASA, Ames Res Ctr, MS T27A, Moffett Field, CA 94035 USA. EM sarfatti@well.com NR 12 TC 7 Z9 7 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD NOV 27 PY 1998 VL 297 IS 3-4 BP 263 EP 264 PG 2 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 142HZ UT WOS:000077196000015 ER PT J AU Appa, K Argyris, J Guruswamy, GP Martin, CA AF Appa, K Argyris, J Guruswamy, GP Martin, CA TI Synergistic aircraft design using CFD air loads SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article AB A novel approach to the art of optimal design of modem flying vehicles including the application of multiple objective functions and constraints is presented. The method employs a two stage optimization procedure so that local minima and global minima of multiple objective functions can be determined synergistically. The concept of system identification is also used to characterize a nonlinear system in terms of generalized state space coordinates. Next, the modern optimal control theory is applied to design concurrently the multidisciplinary functional elements of an advanced aircraft system. Hence, the procedure proposed here should hopefully advance the art of modern aircraft design and reduce the period of design cycle and cost by an order of magnitude. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Northrop Grumman Corp, Hawthorne, CA 90250 USA. Univ Stuttgart, Inst Comp Applicat, D-70569 Stuttgart, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Appa, K (reprint author), Northrop Grumman Corp, 1 Northrop Ave, Hawthorne, CA 90250 USA. NR 12 TC 1 Z9 1 U1 0 U2 1 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 NOV 27 PY 1998 VL 166 IS 3-4 BP 247 EP 259 DI 10.1016/S0045-7825(98)00073-5 PG 13 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 150GL UT WOS:000077655900005 ER PT J AU Wang, PH Cunnold, DM Zawodny, JM Pierce, RB Olson, JR Kent, GS Skeens, KM AF Wang, PH Cunnold, DM Zawodny, JM Pierce, RB Olson, JR Kent, GS Skeens, KM TI Seasonal ozone variations in the isentropic layer between 330 and 380 K as observed by SAGE II: Implications of extratropical cross-tropopause transport SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC OZONE; TROPOSPHERIC OZONE; CHEMISTRY; AEROSOL; CIRCULATION; EXCHANGE; ATLANTIC; PACIFIC; CLOUDS; REGION AB To provide observational evidence on the extratropical cross-tropopause transport between the stratosphere and the troposphere via quasi-isentropic processes in the middleworld (the part of the atmosphere in which the isentropic surfaces intersect the tropopause), this report presents an analysis of the seasonal variations of the ozone latitudinal distribution in the isentropic layer between 330 K and 380 K based on the measurements from the Stratospheric Aerosol and Gas Experiment (SAGE) II. The results from SAGE II data analysis are consistent with (1) the buildup of ozone-rich air in the extratropical middleworld through the large-scale descending mass circulation during winter, (2) the spread of ozone-rich air in the isentropic layer from midlatitudes to subtropics via quasi-isentropic transport during spring, (3) significant photochemical ozone removal and the absence of an ozone-rich supply of air to the layer during summer, and (4) air mass exchange between the subtropics and the extratropics during the summer monsoon period. Thus the SAGE II observed ozone seasonal variations in the middleworld are consistent with the existing model calculated annual cycle of the diabatic circulation as well as the conceptual role of the eddy quasi-adiabatic transport in the stratosphere-troposphere exchange reported in the literature. C1 Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampden Sydney, VA 23681 USA. Sun Microsyst Inc, Mclean, VA 22101 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. RP Wang, PH (reprint author), Sci & Technol Corp, 101 Res Dr, Hampton, VA 23666 USA. EM p.wang@larc.nasa.gov; cunnold@eas.gatech.edu; r.b.pierce@larc.nasa.gov; j.r.olson@larc.nasa.gov; kent@larc.nasa.gov; Kristi.Skeens@East.Sun.COM RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 43 TC 18 Z9 18 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 NOV 27 PY 1998 VL 103 IS D22 BP 28647 EP 28659 DI 10.1029/98JD02797 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 142JB UT WOS:000077196200003 ER PT J AU McDermid, IS Bergwerff, JB Bodeker, G Boyd, IS Brinksma, EJ Connor, BJ Farmer, R Gross, MR Kimvilakani, P Matthews, WA McGee, TJ Ormel, FT Parrish, A Singh, U Swart, DPJ Tsou, JJ Wang, PH Zawodny, J AF McDermid, IS Bergwerff, JB Bodeker, G Boyd, IS Brinksma, EJ Connor, BJ Farmer, R Gross, MR Kimvilakani, P Matthews, WA McGee, TJ Ormel, FT Parrish, A Singh, U Swart, DPJ Tsou, JJ Wang, PH Zawodny, J TI OPAL: Network for the Detection of Stratospheric Change ozone profiler assessment at Lauder, New Zealand 1. Blind intercomparison SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID LIDAR AB An intercomparison of ozone-profiling instruments, two differential absorption lidars, a microwave radiometer, electrochemical concentration sondes, and the SAGE II satellite instrument is presented. The ground-based instruments were located at the Network for the Detection of Stratospheric Change (NDSC) primary station at Lauder, New Zealand. The campaign, which took place between April 15 and 29, 1995, strictly followed the NDSC guidelines for a blind intercomparison. Agreement between the measurements was within 15% for single profiles and within 10% for the campaign average, in the region from 20 to 40 km altitude. Outside of this region the differences were greater but can generally be ascribed to the limits of a particular instrument. C1 CALTECH, Jet Propuls Lab, Table Mt Facil, Wrightwood, CA 92397 USA. Natl Inst Publ Hlth & Environm, RIVM, Air Res Lab, NL-3720 BA Bilthoven, Netherlands. NIWA, Omakau 50061, Central Otago, New Zealand. Vrije Univ Amsterdam, Fac Phys & Astron, NL-1081 HV Amsterdam, Netherlands. ARC, Lanham, MD 20785 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21228 USA. IDEA Corp, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. Millitech Corp, South Deerfield, MA 01373 USA. GATS Inc, Hampton, VA 23666 USA. Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, ASD, Aerosol Res Branch, Hampton, VA 23681 USA. RP Bergwerff, JB (reprint author), CALTECH, Jet Propuls Lab, Table Mt Facil, POB 367, Wrightwood, CA 92397 USA. RI Bodeker, Greg/A-8870-2008; McGee, Thomas/G-4951-2013 OI Bodeker, Greg/0000-0003-1094-5852; NR 15 TC 16 Z9 16 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1998 VL 103 IS D22 BP 28683 EP 28692 DI 10.1029/98JD02706 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 142JB UT WOS:000077196200005 ER PT J AU McDermid, IS Bergwerff, JB Bodeker, G Boyd, IS Brinksma, EJ Connor, BJ Farmer, R Gross, MR Kimvilakani, P Matthews, WA McGee, TJ Ormel, FT Parrish, A Singh, U Swart, DPJ Tsou, JJ AF McDermid, IS Bergwerff, JB Bodeker, G Boyd, IS Brinksma, EJ Connor, BJ Farmer, R Gross, MR Kimvilakani, P Matthews, WA McGee, TJ Ormel, FT Parrish, A Singh, U Swart, DPJ Tsou, JJ TI OPAL: Network for the Detection of Stratospheric Change ozone profiler assessment at Lauder, New Zealand 2. Intercomparison of revised results SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MICROWAVE AB Following a blind intercomparison of ozone profiling instruments in the Network for the Detection of Stratospheric Change at Lauder, New Zealand, revisions to the analyses were made resulting in a new data set. This paper compares the revised results from two differential absorption lidars (RIVM and GSFC), a microwave radiometer (Millitech/LaRC), and electrochemical concentration cell (ECC) balloon sondes (NIWA). In general, the results are substantially improved compared to the earlier blind intercomparison. The level of agreement was similar both for single profiles and for the campaign average profile and was approximately 5% for the lidars and the sondes over the altitude range from 15 to 42 km (32 km for sondes). The revised microwave data show a bias of 5-10% high in the region from 22 to 42 km. Starting at 42 km, the lidar errors increase significantly, and comparisons of the microwave results were not possible above this altitude. C1 CALTECH, Jet Prop Lab, Table Mt Facil, Wrightwood, CA 92397 USA. Natl Inst Publ Hlth & Environm, RIVM, Air Res Lab, NL-3720 BA Bilthoven, Netherlands. NIWA, Omakau, Central Otago, New Zealand. Free Univ Amsterdam, Dept Phys & Astron, NL-1081 HV Amsterdam, Netherlands. ARC, Lanham, MD 20785 USA. IDEA Corp, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Millitech Corp, S Deerfield, MA 01373 USA. Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Hughes STX Corp, Lanham, MD USA. RP McDermid, IS (reprint author), CALTECH, Jet Prop Lab, Table Mt Facil, POB 367, Wrightwood, CA 92397 USA. RI Bodeker, Greg/A-8870-2008; McGee, Thomas/G-4951-2013 OI Bodeker, Greg/0000-0003-1094-5852; NR 10 TC 14 Z9 14 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1998 VL 103 IS D22 BP 28693 EP 28699 DI 10.1029/98JD02707 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 142JB UT WOS:000077196200006 ER PT J AU Harshvardhan Ridgway, W Ramaswamy, V Freidenreich, SM Batey, M AF Harshvardhan Ridgway, W Ramaswamy, V Freidenreich, SM Batey, M TI Spectral characteristics of solar near-infrared absorption in cloudy atmospheres SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOCUMULUS CLOUDS; AIRCRAFT OBSERVATIONS; OPTICAL-PROPERTIES; RADIATION; WATER; CONSTANTS; SURFACE; ALBEDO; FIELDS; MODEL AB Theoretical and experimentally derived estimates of the atmospheric absorption of solar energy in the presence of clouds have been reported to be at variance for quite a long time. A detailed set of near-monochromatic computations of the reflectance, transmittance, and absorptance of a standard midlatitude atmosphere with embedded water clouds is used to identify spectral features in the solar near-infrared that can be utilized to study this discrepancy. The results are framed in terms of the cloud radiative forcing both at the surface and at the top of the atmosphere, and it is shown that water vapor windows are the most sensitive to variations in cloud optical properties and cloud placement in the vertical. The ratio of the cloud radiative forcing at the surface to that at the top of the atmosphere, R, varies from near zero in the band centers at small wavenumbers for high clouds to similar to 1 in the band centers at larger wavenumbers for low clouds and to values in excess of 2 in the water vapor windows at small wavenumbers. The possibility of using measurements from space with the future Moderate Resolution Imaging Spectroradiometer (MODIS) and simultaneous surface measurements is discussed. It is also shown that horizontal inhomogeneities in the cloud layers do not alter appreciably the estimates of the R factor, but areal mean cloud absorption is lower for an inhomogeneous cloud having the same mean liquid water as the corresponding homogeneous cloud. C1 Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN USA. Princeton Univ, NOAA, Geophys Fluid Dynam Lab, Princeton, NJ 08542 USA. NASA, Goddard Space Flight Ctr, SM&A Corp, Greenbelt, MD 20771 USA. RP Harshvardhan (reprint author), Purdue Univ, Dept Earth & Atmospher Sci, W Lafayette, IN USA. EM harsh@purdue.edu NR 38 TC 0 Z9 0 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 27 PY 1998 VL 103 IS D22 BP 28793 EP 28799 DI 10.1029/1998JD200013 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 142JB UT WOS:000077196200015 ER PT J AU Asner, GP Bateson, CA Privette, JL El Saleous, N Wessman, CA AF Asner, GP Bateson, CA Privette, JL El Saleous, N Wessman, CA TI Estimating vegetation structural effects on carbon uptake using satellite data fusion and inverse modeling SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NET PRIMARY PRODUCTION; LEAF-AREA INDEX; RADIATIVE-TRANSFER; REFLECTANCE MODEL; BIOMASS DYNAMICS; HONEY MESQUITE; CANOPY; PATTERNS; NDVI; FIRE AB Regional analyses of biogeochemical processes can benefit significantly from observational information on land cover, vegetation structure (e.g., leaf area index), and biophysical properties such as fractional PAR absorption. Few remote sensing efforts have provided a suite of plant attributes needed to link vegetation structure to ecosystem function at high spatial resolution. In arid and semiarid ecosystems (e.g., savannas), high spatial heterogeneity of land cover results in significant functional interaction between dominant vegetation types, requiring new approaches to resolve their structural characteristics for regional-scale biogeochemical research. We developed and tested a satellite data fusion and radiative transfer inverse modeling approach to deliver estimates of vegetation structure in a savanna region of Texas. Spectral mixture analysis of Landsat data provided verifiable estimates of woody plant, herbaceous, bare soil, and shade fractions at 28.5 m resolution. Using these subpixel cover fractions, a geometric-optical model was inverted to estimate overstory stand density and crown dimensions with reasonable accuracy. The Landsat cover estimates were then used to spectrally unmix the contribution of woody plant and herbaceous canopies to AVHRR multiangle reflectance data. These angular reflectances were used with radiative transfer model inversions to estimate canopy leaf area index (LAI). The suite of estimated canopy and landscape variables indicated distinct patterns in land cover and structural attributes related to land use. These variables were used to calculate diurnal PAR absorption and carbon uptake by woody and herbaceous canopies in contrasting land cover and land use types. We found that both LAI and the spatial distribution of vegetation structural types exert strong control on carbon fluxes and that intercanopy shading is an important factor controlling functional processes in spatially heterogeneous environments. C1 Univ Colorado, CSES, Cooperat Inst Res Environm Sci, Boulder, CO 80309 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Asner, GP (reprint author), Univ Colorado, CSES, Cooperat Inst Res Environm Sci, Campus Box 216, Boulder, CO 80309 USA. EM asner@cses.colorado.edu RI Privette, Jeffrey/G-7807-2011; Asner, Gregory/G-9268-2013 OI Privette, Jeffrey/0000-0001-8267-9894; Asner, Gregory/0000-0001-7893-6421 NR 62 TC 34 Z9 34 U1 1 U2 9 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 NOV 27 PY 1998 VL 103 IS D22 BP 28839 EP 28853 DI 10.1029/98JD02459 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 142JB UT WOS:000077196200019 ER PT J AU Kent, GS Trepte, CR Lucker, PL AF Kent, GS Trepte, CR Lucker, PL TI Long-term Stratospheric Aerosol and Gas Experiment I and II measurements of upper tropospheric aerosol extinction SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID AIRCRAFT SULFUR EMISSIONS; OPTICAL-THICKNESS; OCCULTATION DATA; SULFATE AEROSOL; CLOUD; BACKSCATTER; SAGE; CLIMATE; MODEL; LIDAR AB A detailed analysis has been made of Stratospheric Aerosol and Gas Experiment I and II aerosol extinction data for the upper troposphere (6-km altitude to the seasonally averaged tropopause) taken between 1979 and 1998. An improved method of separation of the volcanic and surface-derived components of the aerosol optical depth has been used. The mean extinction, at a wavelength of 1.02 mu m, of the nonvolcanic component of the upper tropospheric aerosol is found to increase from approximately 1 x 10(-4) km(-1) at 70 degrees S to about 7 times that value at 70 degrees N. Maximum downward transfer of volcanic material into the upper troposphere is observed to take place in local spring in each hemisphere, occurring at a latitude of 70 degrees S or greater in the southern hemisphere and at about 50 degrees N in the northern hemisphere. The almost 20-year data sequence (1979-1981, 1984-1991, 1994-1998) has been examined for evidence of any long-term trends in the aerosol optical depth of the upper troposphere. It is unlikely that any change in the upper tropospheric 1-mu m aerosol optical depth greater than 1% per year has taken place when averaged over either hemisphere. C1 Sci & Technol Corp, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Kent, GS (reprint author), Sci & Technol Corp, 101 Res Dr, Hampton, VA 23666 USA. EM g.s.kent@larc.nasa.gov; c.r.trepte@larc.nasa.gov; p.l.lucker@larc.nasa.gov NR 49 TC 27 Z9 29 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 NOV 27 PY 1998 VL 103 IS D22 BP 28863 EP 28874 DI 10.1029/98JD02583 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 142JB UT WOS:000077196200021 ER PT J AU Murphy, DM Thomson, DS Mahoney, TMJ AF Murphy, DM Thomson, DS Mahoney, TMJ TI In situ measurements of organics, meteoritic material, mercury, and other elements in aerosols at 5 to 19 kilometers SO SCIENCE LA English DT Article ID CONDENSATION NUCLEI; PARTICLE FORMATION; LOWER STRATOSPHERE; TROPOSPHERE; ORIGIN; METALS; DUST AB In situ measurements of the chemical composition of individual aerosol particles at altitudes between 5 and 19 kilometers reveal that upper tropospheric aerosols often contained more organic material than sulfate. Although stratospheric aerosols primarily consisted of sulfuric acid and water, many also contained meteoritic material. Just above the tropopause, small amounts of mercury were found in over half of the aerosol particles that were analyzed. Overall, there was tremendous variety in aerosol composition. One measure of this diversity is that at Least 45 elements were detected in aerosol particles. These results have wide implications for the complexity of aerosol sources and chemistry. They also offer possibilities for understanding the transport of atmospheric aerosols. C1 NOAA, Aeron Lab, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Murphy, DM (reprint author), NOAA, Aeron Lab, 325 Broadway, Boulder, CO 80303 USA. EM murphyd@al.noaa.gov RI Murphy, Daniel/J-4357-2012 OI Murphy, Daniel/0000-0002-8091-7235 NR 48 TC 421 Z9 425 U1 2 U2 52 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 NOV 27 PY 1998 VL 282 IS 5394 BP 1664 EP 1669 DI 10.1126/science.282.5394.1664 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 143GJ UT WOS:000077246600035 ER PT J AU Ramalingam, S Maroudas, D Aydil, ES Walch, SP AF Ramalingam, S Maroudas, D Aydil, ES Walch, SP TI Abstraction of hydrogen by SiH3 from hydrogen-terminated Si(001)-(2x1) surfaces SO SURFACE SCIENCE LA English DT Letter DE growth; hydrogen; molecular dynamics; density functional calculations; plasma deposition; plasma processing; semiconductor-semiconductor thin film structures; silicon; surface chemical reaction ID MOLECULAR-DYNAMICS SIMULATIONS; PLASMA-INDUCED DEPOSITION; AMORPHOUS-SILICON; FILM GROWTH; SILANE; POTENTIALS; RADICALS; SYSTEMS AB We present the dynamics and energetics of an Eley-Rideal reaction by which SiH3 radicals impinging on a H-terminated Si(001)-(2 x 1) surface during plasma deposition abstract hydrogen atoms from the surface and return to the gas phase as silane molecules. The reactions were observed during classical molecular-dynamics simulations of hydrogenated amorphous silicon deposition from SiH3, radicals impinging on H-terminated Si(001)-(2 x 1) surfaces maintained at temperatures over the range 500 K less than or equal to T less than or equal to 773 K. The H-abstraction reaction introduces dangling bonds at the surface that impinging SiHx (0 less than or equal to x less than or equal to 3) radicals can attach to; thus, it is a crucial reaction for deposition. The computed activation energy barrier for the reaction and the exothermic reaction energy are 0.09 eV and 0.23 eV, respectively. The energetics of the reaction as computed based on an empirical classical potential are in good agreement with density-functional-theory pseudopotential calculations using a cluster model. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Univ Calif Santa Barbara, Dept Chem Engn, Santa Barbara, CA 93106 USA. NASA, Thermosci Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Maroudas, D (reprint author), Univ Calif Santa Barbara, Dept Chem Engn, Santa Barbara, CA 93106 USA. EM dimitris@calypso.ucsb.edu NR 22 TC 53 Z9 53 U1 0 U2 5 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD NOV 27 PY 1998 VL 418 IS 1 BP L8 EP L13 DI 10.1016/S0039-6028(98)00703-1 PG 6 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 148VM UT WOS:000077554300003 ER PT J AU Simons, RN Lee, RQ AF Simons, RN Lee, RQ TI Impedance matching of tapered slot antenna using a dielectric transformer SO ELECTRONICS LETTERS LA English DT Article AB A new impedance matching technique for tapered slot antennas using a dielectric transformer is presented. The technique is demonstrated by measuring the input impedence, VSWR and the gain of a Vivaldi antenna (VA). Measured results at Ka-Band frequencies are presented and discussed. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Simons, RN (reprint author), NASA, Lewis Res Ctr, MS 54-8,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 4 TC 5 Z9 5 U1 2 U2 4 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 0013-5194 J9 ELECTRON LETT JI Electron. Lett. PD NOV 26 PY 1998 VL 34 IS 24 BP 2287 EP 2289 DI 10.1049/el:19981612 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 148DT UT WOS:000077490000003 ER PT J AU Reipurth, B Bally, L Fesen, RA Devine, D AF Reipurth, B Bally, L Fesen, RA Devine, D TI Protostellar jets irradiated by massive stars SO NATURE LA English DT Article ID ENERGY-SOURCE; YOUNG STARS AB The formation of solar-type stars is a gradual process during which they accrete mass from the dense disks and cloud cores that surround them. This accretion requires the release of angular momentum, and an important mechanism for achieving this seems to be the production of jets along the polar axes of the young stars(1,2), But the presence of massive, luminous stars within the same star-forming region can affect the forming stars by stripping away their circumstellar envelopes with ultraviolet radiation, thereby removing the reservoir of gas from which the stars are built up and exposing the disks to photoerosion(3). Here we present observations of four highly collimated jets from young stars that appear to have been stripped of their circumstellar molecular cloud cores in this way. The production of jets seems to have been largely unaffected. If these jets are also photoionized, their mass loss rates can be determined from observations with much greater accuracy than for normal shock-excited jets. C1 Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Dartmouth Coll, Dept Phys & Astron, Hanover, NH 03755 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Reipurth, B (reprint author), Univ Colorado, Ctr Astrophys & Space Astron, Campus Box 389, Boulder, CO 80309 USA. NR 29 TC 72 Z9 72 U1 0 U2 3 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD NOV 26 PY 1998 VL 396 IS 6709 BP 343 EP 345 DI 10.1038/24562 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 142MJ UT WOS:000077204000041 ER PT J AU Farmer, J AF Farmer, J TI Thermophiles, early biosphere evolution, and the origin of life on Earth: Implications for the exobiological exploration of Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID ECOSYSTEMS; ATMOSPHERE; HABITATS; DOMAINS; SEARCH C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Farmer, J (reprint author), Arizona State Univ, Dept Geol, Box 871404, Tempe, AZ 85287 USA. EM jfarmer@asu.edu NR 49 TC 37 Z9 39 U1 1 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 NOV 25 PY 1998 VL 103 IS E12 BP 28457 EP 28461 DI 10.1029/98JE01542 PG 5 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 144AK UT WOS:000077290100001 ER PT J AU Haberle, RM AF Haberle, RM TI Early Mars climate models SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID EARLY MARTIAN ATMOSPHERE; CARBON-DIOXIDE; PRIMORDIAL ATMOSPHERE; TERRESTRIAL PLANETS; IMPACT EROSION; LIQUID WATER; EVOLUTION; EARTH; CO2; GREENHOUSE AB It is often stated that Mars and Earth had similar environmental conditions early in their history and that life might therefore have originated on Mars as well as on Earth. However, the atmospheric conditions required to produce and sustain a warm, wet climate on early Mars remain uncertain. State-of-the-art greenhouse models predict global mean surface temperatures early in Mars' history that differ little from today's, unless special conditions are invoked. The greatest difficulty the models have is coping with a faint early Sun. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Haberle, RM (reprint author), NASA, Ames Res Ctr, Div Space Sci, MS 245-3, Moffett Field, CA 94035 USA. NR 66 TC 93 Z9 93 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 NOV 25 PY 1998 VL 103 IS E12 BP 28467 EP 28479 DI 10.1029/98JE01396 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 144AK UT WOS:000077290100003 ER PT J AU Doran, PT Wharton, RA Des Marais, DJ McKay, CP AF Doran, PT Wharton, RA Des Marais, DJ McKay, CP TI Antarctic paleolake sediments and the search for extinct life on Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID COVERED LAKE-HOARE; MARINE-PHYTOPLANKTON; VALLES MARINERIS; ICE; EVOLUTION; CARBON; WATER; FRACTIONATION; DEPOSITS; CLIMATE AB Evidence of lakes in Mars history is substantial. The proposed similarities between the ancient Martian environment and certain modern environments on Earth have led exobiologists to study antarctic lakes as analogs to those purported to have existed on Mars. We have investigated modern sedimentation processes (especially with respect to delta(13)C of carbonate and organic matter) in lakes in the McMurdo Dry Valleys region df east Antarctica and assessed various paleolake deposits with respect to their utility as Martian analogs and targets for future Mars exobiology missions. Three main types of paleolake deposit were identified and assessed: strand lines, perched deltas, and lacustrine sand mounds. Deltas are usually identified as good targets, but our research shows that authigenic carbonates are not readily identifiable in the sediments. Large deltas, although most likely to attract attention through remote sensing, generally are difficult sites for discovery of paleobiological matter, and delta(13)C signals follow no coherent pattern. Lacustrine sand mounds, on the other hand, contain abundant authigenic carbonate and freeze-dried organic matter and appear to be excellent records of paleolimnological conditions. The advantage of studying lake bottom deposits versus lake edge deposits is retrieval of a stable lake-wide signal. Deltas are therefore most useful in that they are generally large-scale features capable of drawing attention to a region of potential for the discovery of smaller lacustrine sand mounds. C1 Univ Illinois, Dept Earth & Environm Sci, Chicago, IL 60607 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Nevada, Desert Res Inst, Ctr Biol Sci, Reno, NV 89506 USA. RP Doran, PT (reprint author), Univ Illinois, Dept Earth & Environm Sci, 845 W Taylor St, Chicago, IL 60607 USA. EM pdoran@uic.edu; wharton@dri.edu; david_desmarais@qmgate.arc.nasa.gov; mckay@gal.arc.nasa.gov NR 50 TC 37 Z9 38 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 NOV 25 PY 1998 VL 103 IS E12 BP 28481 EP 28493 DI 10.1029/98JE01713 PG 13 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 144AK UT WOS:000077290100004 ER PT J AU Sleep, NH Zahnle, K AF Sleep, NH Zahnle, K TI Refugia from asteroid impacts on early Mars and the early Earth SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARTIAN METEORITE ALH84001; BACILLUS-SUBTILIS SPORES; EARLY EVOLUTION; GIANT IMPACT; TEMPERATURE ORIGIN; EARLY ATMOSPHERE; OXIDATION-STATE; SNC METEORITES; 2060 CHIRON; LIFE AB impacts of asteroids and comets posed a major hazard to the continuous existence of early life on Mars, as on Earth. The chief danger was presented by globally distributed ejecta, including transient thick rock vapor atmospheres. On Earth, much of the thermal radiation is absorbed by boiling the oceans. Any surviving life is either in deep water or well below the surface. Global thermal excursions are buffered by the heat capacity of the oceans. But when impacts are large enough to vaporize the oceans (>10(28) J), thermal buffering serves only to prolong the disaster for thousands of years, while the oceans rain out. Without oceans, thermal buffering does not occur on Mars. Relatively small impacts (10(26) J) frequently heat the surface everywhere to the melting point. However, owing to the low Martian escape velocity, the most energetic ejecta (including the rock vapor) more easily escape to spade, while massive quantities of less energetic ejecta are globally distributed Survival. in deep subsurface environments is more likely on Mars because (1) Mars' lower background heat flow and lower gravity allow deeper colonies, and (2) the thermal heat pulse from a major impact is briefer. Only thermophile organisms could have survived impacts of asteroids large enough to leave heat or boil the entire terrestrial ocean. Studies of terrestrial microorganisms indicate that the last common ancestor may have been thermophile and the survivor of such a catastrophe. This organism should be distinguished from the first common ancestor. An additional refugium is ejection of rock to space by impacts and thier return to a habitable planet. C1 Stanford Univ, Dept Geophys, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Mt View, CA USA. RP Sleep, NH (reprint author), Stanford Univ, Dept Geophys, 373-A Mitchell Hall, Stanford, CA 94305 USA. EM norm@pangea.stanford.edu NR 99 TC 82 Z9 81 U1 2 U2 13 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 NOV 25 PY 1998 VL 103 IS E12 BP 28529 EP 28544 DI 10.1029/98JE01809 PG 16 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 144AK UT WOS:000077290100007 ER PT J AU Stoker, C AF Stoker, C TI The search for life on Mars: The role of rovers SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID MARTIAN NORTHERN PLAINS; HYDROTHERMAL SYSTEMS; GROUND ICE; EVOLUTION; ORIGIN; EARTH; EXPLORATION; ATMOSPHERE; PALEOLAKES; SUBMARINE AB The search for evidence of life on Mars will require highly capable revers. The strategy for the search for life divides into four major objectives: understanding the history of the Martian climate, finding evidence of chemical evolution, searching for evidence of past life, and searching for evidence of living organisms. To achieve these objectives, revers will need to traverse distances of the order of 10 km to study a variety of relevant features (e.g., fluvial channels, shorelines,, eskers, hydrothermal deposits) in sufficient detail to diagnose their formation processes. Requirements for revers include color imaging at a range of spatial scales (wide angle for geologic context, high resolution for resolving millimeter- to centimeter-scale textures, submillimeter resolution of selected areas); in situ capabilities to perform chemical, mineralogical, and organic analysis; and the ability to collect samples of rocks, soils, and subsurface samples for return to Earth for detailed laboratory analysis. Simulations of rover missions to Mars and the Moon were performed for 3 days each in February 1995 using the Marsokhod rover deployed on Kilauea volcano, Hawaii, and operated via satellite communications from Moffett Field, California. During the simulations, science teams analyzed images taken by the Marsokhod and deduced the geologic setting and history of the field site. Imaging for the Mars mission simulation used mast-mounted monochrome stereo cameras with 30 degrees field of view, 1.4 mrad/pixel resolution, 1.7 m height, 1 m horizontal spacing, and fixed pointing. A camera mounted on a manipulator arm was capable of resolving 1 mm features. During 18 hours of operation, the rover traversed 800 m of terrain, made observations at eight science targets, and obtained 52 stereo images and 18 arm camera images. For the lunar mission simulation, stereo cameras were mounted on a mast with a pointable platform at 1.5 m height and 10 cm horizontal spacing. Stereo color video was transmitted to mission operations. Command cycles with 1.5 s time delay allowed live teleoperation. In 15 hours of operation the rover traversed 1.2 km, and nine science targets were studied in detail. These experiments show that revers can be used to successfully perform field geology on other planets. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Stoker, C (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM cstoker@mail.arc.nasa.gov NR 86 TC 12 Z9 12 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 NOV 25 PY 1998 VL 103 IS E12 BP 28557 EP 28575 DI 10.1029/98JE01723 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 144AK UT WOS:000077290100009 ER PT J AU DeVincenzi, DL Race, MS Klein, HP AF DeVincenzi, DL Race, MS Klein, HP TI Planetary protection, sample return missions and Mars exploration: History, status, and future needs SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SEARCH; LIFE AB As the prospect grows for a Mars sample return mission early in the next millennium, it will be important to ensure that appropriate planetary protection (PP) controls are incorporated into the mission design and implementation from the start. The need for these PP controls is firmly based on scientific considerations and backed by a number of national and international agreements and guidelines aimed at preventing harmful cross contamination of planets and extraterrestrial bodies. The historical precedent for the use of PP measures on both unmanned and manned missions traces from post-Sputnik missions to the present; with periodic modifications as new information was obtained. In consideration of the anticipated attention to PP questions by both the scientific/technical community and the public, this paper presents a comprehensive review of the major issues and problems surrounding PP for a Mars Sample Return (MSR) mission, including an analysis of arguments that have been raised for and against the imposition of PP measures. Also discussed are the history and foundations for PP policies and requirements; important research areas needing attention prior to defining detailed PP requirements for a MSR mission; and legal and public awareness issues that must be considered with mission planning. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. SETI Inst, Mt View, CA 94043 USA. RP DeVincenzi, DL (reprint author), NASA, Ames Res Ctr, MS 245-1, Moffett Field, CA 94035 USA. NR 66 TC 16 Z9 16 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 NOV 25 PY 1998 VL 103 IS E12 BP 28577 EP 28585 DI 10.1029/98JE01600 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 144AK UT WOS:000077290100010 ER PT J AU Chipot, C Pohorille, A AF Chipot, C Pohorille, A TI Folding and translocation of the undecamer of poly-L-leucine across the water-hexane interface. A molecular dynamics study SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY LA English DT Article ID ALANINE-BASED PEPTIDES; HYDROPHOBIC TRANSMEMBRANE SEGMENTS; ALPHA-HELIX FORMATION; LIPID BILAYERS; FREE-ENERGY; 3(10)-HELICAL CONFORMATION; PHOSPHOLIPID-BILAYERS; AMPHIPATHIC PEPTIDES; MEMBRANE INSERTION; AQUEOUS-SOLUTION AB The undecamer of poly-L-leucine at the water-hexane interface is studied by molecular dynamics simulations. This represents a simple model relevant to folding and insertion of hydrophobic peptides into membranes. The peptide, initially placed in a random coil conformation on the aqueous side of the system, rapidly translocates toward the hexane phase and undergoes interfacial folding into an alpha-helix in the subsequent 36 ns. Folding is nonsequential and highly dynamic. The initially formed helical segment at the N-terminus of the undecamer becomes transiently broken and, subsequently, reforms before the remainder of the peptide folds from the C-terminus. The formation of intramolecular hydrogen bonds during the folding of the peptide is preceded by a dehydration of the participating polar groups, as they become immersed in hexane. Folding proceeds through a short-lived intermediate, a 3(10)-helix, which rapidly interconverts to an alpha-helix. Both helices contribute to the equilibrium ensemble of folded structures. The helical peptide is largely buried in hexane, yet remains adsorbed at the interface. Its preferred orientation is parallel to the interface, although the perpendicular arrangement with the N-terminus immersed in hexane is only slightly less favorable. In contrast, the reversed orientation is highly unfavorable, because it would require dehydration of C-terminus carbonyl groups that do not participate in intramolecular hydrogen bonding. For the same reason, the transfer of the undecamer from the interface to the bulk hexane is also unfavorable. The results suggest that hydrophobic peptides fold in the interfacial region and, simultaneously, translocate into the nonpolar side of the interface. It is further implied that peptide insertion into the membrane is accomplished by rotating from the parallel to the perpendicular orientation, most likely in such a way that the N-terminus penetrates the bilayer. C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. Univ Nancy 1, URA CNRS 510, Chim Theor Lab, F-54506 Vandoeuvre Nancy, France. Univ Calif San Francisco, Dept Pharmaceut Chem, San Francisco, CA 94143 USA. RP Pohorille, A (reprint author), NASA, Ames Res Ctr, Exobiol Branch, MS 239-4, Moffett Field, CA 94035 USA. NR 100 TC 59 Z9 59 U1 0 U2 3 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 NOV 25 PY 1998 VL 120 IS 46 BP 11912 EP 11924 DI 10.1021/ja980010o PG 13 WC Chemistry, Multidisciplinary SC Chemistry GA 142QD UT WOS:000077210900010 PM 11542762 ER PT J AU Moore, CE Cardelino, BH Frazier, DO Niles, J Wang, XQ AF Moore, CE Cardelino, BH Frazier, DO Niles, J Wang, XQ TI Molecular static third-order polarizabilities of carbon-cage fullerenes and their correlation with three geometric properties: symmetry, aromaticity, and size SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE LA English DT Article; Proceedings Paper CT Conference on Current Trends in Computational Chemistry (CCTCC) CY NOV, 1997 CL VICKSBURG, MS DE hyperpolarizability; third-order polarizability; fullerenes; C-60; C-70; C-78; C-84; aromaticity; nonlinear optics ID NONLINEAR-OPTICAL-PROPERTIES; 2ND-ORDER HYPERPOLARIZABILITY; C-60 MOLECULE; C60; C-84; C-70; DISPERSION; NANOTUBES; FILMS; MODEL AB The static third-order polarizabilities (gamma) of C-60, C-70, five isomers of C-78 and two isomers of C-84 were analyzed in terms of three properties, from a geometric point of view: symmetry; aromaticity; and size. The polarizability values were based on the finite field approximation using a semiempirical Hamiltonian (AMI) and applied to molecular structures obtained from density functional theory calculations. Symmetry was characterized by the molecular group order. The selection of six-member rings as aromatic was determined from an analysis of bond lengths. Maximum interatomic distance and surface area were the parameters considered with respect to size. Based on triple linear regression analysis, it was found that the static linear polarizability (alpha) and gamma in these molecules respond differently to geometrical properties: alpha depends almost exclusively on surface area while gamma is affected by a combination of number of aromatic rings, length and group order, in decreasing importance. In the case of alpha, valence electron contributions provide the same information as all-electron estimates. For gamma, the best correlation coefficients are obtained when all-electron estimates are used and when the dependent parameter is ln(gamma) instead of gamma. Published by Elsevier Science B.V. C1 Spelman Coll, Dept Chem, Atlanta, GA 30314 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Clark Atlanta Univ, Dept Phys, Atlanta, GA 30314 USA. Clark Atlanta Univ, NSF, Ctr Theoret Studies Phys Syst, Atlanta, GA 30314 USA. RP Cardelino, BH (reprint author), Spelman Coll, Dept Chem, Atlanta, GA 30314 USA. NR 66 TC 8 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-1280 J9 THEOCHEM-J MOL STRUC JI Theochem-J. Mol. Struct. PD NOV 23 PY 1998 VL 454 IS 2-3 BP 135 EP 148 DI 10.1016/S0166-1280(98)00284-X PG 14 WC Chemistry, Physical SC Chemistry GA 146QU UT WOS:000077442500005 ER PT J AU Pohorille, A Wilson, MA New, MH Chipot, C AF Pohorille, A Wilson, MA New, MH Chipot, C TI Concentrations of anesthetics across the water-membrane interface; the Meyer-Overton hypothesis revisited SO TOXICOLOGY LETTERS LA English DT Article; Proceedings Paper CT 5th International Conference on Molecular and Cellular Mechanisms of Anaesthesia CY JUN 18-20, 1997 CL UNIV CALGARY, CALGARY, CANADA HO UNIV CALGARY DE water-membrane interface; water-oil interface; free energy; Meyer-Overton relation; mechanism of anesthetic action ID GENERAL-ANESTHESIA; SITES; MECHANISMS; POTENCY; NMR AB The free energies of transferring a variety of anesthetic and nonanesthetic compounds across water-oil and water-membrane interfaces were obtained using computer simulations. Anesthetics exhibit greatly enhanced concentrations at these interfaces, compared to nonanesthetics. The substitution of the interfacial solubilites of the anesthetics for their bulk lipid solubilities in the Meyer-Overton relation, was found to give a better correlation, indicating that the potency of an anesthetic is directly proportional to its solubility at the interface. (C) 1998 Published by Elsevier Science Ireland Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Exobiol Branch, Moffett Field, CA 94035 USA. Univ Calif San Francisco, Dept Pharmaceut Chem, San Francisco, CA 94143 USA. RP Pohorille, A (reprint author), NASA, Ames Res Ctr, Exobiol Branch, MS 239-4, Moffett Field, CA 94035 USA. NR 24 TC 17 Z9 17 U1 1 U2 4 PU ELSEVIER IRELAND LTD PI CLARE PA ELSEVIER HOUSE, BROOKVALE PLAZA, EAST PARK SHANNON, CO, CLARE, 00000, IRELAND SN 0378-4274 EI 1879-3169 J9 TOXICOL LETT JI Toxicol. Lett. PD NOV 23 PY 1998 VL 101 BP 421 EP 430 PG 10 WC Toxicology SC Toxicology GA 160EL UT WOS:000078217400059 PM 10049175 ER PT J AU Scott, GBI Fairley, DA Freeman, CG McEwan, MJ Anicich, VG AF Scott, GBI Fairley, DA Freeman, CG McEwan, MJ Anicich, VG TI Gas-phase reactions of some positive ions with atomic and molecular nitrogen SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID ASSOCIATION REACTIONS; FLOW-TUBE; KINETICS; CO+; OXYGEN; O2+ AB The reactions of the cations CN+, HCN+, HCNH+, HC3N+, HC3NH+, H-3(+), H2O+, H3O+, N-2(+), CO+, HCO+, O-2(+), CO2+, HCO2+ and C2H2+ with atomic and molecular nitrogen have been characterized using a selected ion flow tube (SIFT) operating at room temperature. Rate coefficient and branching ratio data are reported for all ion-neutral reactions studied. Constraints arising from spin conservation considerations are found to be unimportant in cation-N atom processes. (C) 1998 American Institute of Physics. [S0021-9606(98)01044-7]. C1 Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Scott, GBI (reprint author), Univ Canterbury, Dept Chem, Christchurch 1, New Zealand. NR 30 TC 41 Z9 41 U1 0 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 NOV 22 PY 1998 VL 109 IS 20 BP 9010 EP 9014 DI 10.1063/1.477571 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 139QE UT WOS:000077039900034 ER PT J AU Gross, MAK Somerville, RS Primack, JR Holtzman, J Klypin, A AF Gross, MAK Somerville, RS Primack, JR Holtzman, J Klypin, A TI Cold dark matter variant cosmological models - I. Simulations and preliminary comparisons SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE cosmic microwave background; cosmology : theory; dark matter; large-scale; structure of Universe ID LARGE-SCALE STRUCTURE; MICROWAVE BACKGROUND ANISOTROPIES; ANGULAR POWER SPECTRUM; X-RAY-ANALYSIS; GALAXY FORMATION; PLUS HOT; MASS FLUCTUATIONS; VELOCITY BIAS; EVOLUTION; CLUSTERS AB We present two matched sets of five dissipationless simulations each, including four presently favoured minimal modifications to the standard cold dark matter (CDM) scenario. One simulation suite, with a linear box size of 75 h(-1) Mpc, is designed for high resolution and good statistics on the group/poor cluster scale, and the other, with a box size of 300 h(-1) Mpc, is designed for good rich cluster statistics. All runs had 57 million cold particles, and models with massive neutrinos (CHDM-2 nu) had an additional 113 million hot particles. We consider separately models with massive neutrinos, tilt, curvature, and a non-zero cosmological constant (Lambda drop 3H(0)(2)Omega(Lambda)) in addition to the standard CDM model. We find that the dark matter in each of our tilted Omega(0) + Omega(Lambda) = 1 (TACDM) model with Omega(0) = 0.4, our tilted Omega(0) = I model (TCDM), and our open Lambda = 0 (OCDM) model with Omega(0) = 0.5 has too much small-scale power by a factor of similar to 2, while CHDM-2 nu and SCDM are acceptable fits. In addition, we take advantage of the large dynamic range in detectable halo masses afforded by the combination of the two sets of simulations to test the Press-Schechter approximation. We find good fits at cluster masses for delta(c,g) = 1.27-1.35 for a Gaussian filter and delta(c,t) = 1.57-1.73 for a top hat filter. However, when we adjust delta(c) to obtain a good fit at cluster mass scales, we find that the Press-Schechter model overpredicts the number density of haloes compared to the simulations by a weakly cosmology-dependent factor of 1.5-2 at galaxy and group masses. It is impossible to obtain a good fit over the entire range of masses simulated by adjusting delta(c) within reasonable bounds. C1 Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. NASA, Goddard Space Flight Ctr, Earth & Space Data Comp Div, Greenbelt, MD 20771 USA. Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel. New Mexico State Univ, Dept Astron, Las Cruces, NM 88001 USA. RP Gross, MAK (reprint author), Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. EM gross@fozzie.gsfc.nasa.gov; rachels@alf.fiz.huji.ac.il; joel@ucolick.org; holtz@nmsu.edu; aklypin@nmsu.edu NR 85 TC 97 Z9 98 U1 1 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 21 PY 1998 VL 301 IS 1 BP 81 EP 94 DI 10.1046/j.1365-8711.1998.01998.x PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 147MB UT WOS:000077570600014 ER PT J AU Magdziarz, P Blaes, OM Zdziarski, AA Johnson, WN Smith, DA AF Magdziarz, P Blaes, OM Zdziarski, AA Johnson, WN Smith, DA TI A spectral decomposition of the variable optical, ultraviolet and X-ray continuum of NGC 5548 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; galaxies : individual : NGC 5548; galaxies : Seyfert; ultraviolet : galaxies; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; BROAD-LINE REGION; SHORT-TIMESCALE VARIABILITY; AGNS ACCRETION DISK; NON THERMAL SOURCE; SEYFERT-GALAXIES; MULTIWAVELENGTH OBSERVATIONS; ANISOTROPIC ILLUMINATION; CORONA MODEL; BLACK-HOLES AB We present an analysis and decomposition of the broad-band optical/UV/X-ray/gamma-ray spectrum of the Seyfert 1 galaxy NGC 5548. The spectrum consists of an average of simultaneous optical/IUE/Ginga observations accompanied by ROSAT and CGRO/OSSE data from non-simultaneous observations. We show that the overall optical/UV/X-ray/gamma-ray spectrum can be deconvolved into three basic continuum components: a cool multitemperature blackbody, a hard thermal Comptonized component and an EUV/soft X-ray component well described by a thermal Comptonization continuum. Assuming that the opticaL/IUE spectrum comes from a cold disc, the maximum disc temperature is very well constrained by the data to be kT(disc) = 3.2(-0.2)(+0.2) eV. This rules out models explaining the soft excess as a far tail of the disc spectrum. We show that the soft excess inferred by the data requires a separate continuum component, which is consistent with thermal Comptonization in optically thick (tau similar to 30), warm (similar to 0.3 keV) plasma. This Comptonization component contains a significant fraction of the source energy. The plasma parameters of the hard continuum (tau similar to 2, kT(HC) similar to 50 keV) are consistent with those suggested for the average spectrum of Seyferts, On the basis of the broad-band spectral model, we also re-analyse the simultaneous IUE/Ginga campaign. We find that the fluxes in all three continuum components are positively correlated, The total flux emitted in the hard component is positively correlated with both the spectral index and the solid angle of cold matter seen by the hot source. Such a correlation suggests that the variability mechanism is related to changes in the geometry of the continuum-emitting regions, and an excess in the amount of reflection requires deviations from a simple plane disc picture. The variations in the hard spectral index can then be explained by increased cooling of the hot plasma caused by the increased number of seed photons. We suggest that the geometry variations may be related to a transition region between a cold and a hot disc. C1 Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. Nicholas Copernicus Astron Ctr, PL-00716 Warsaw, Poland. USN, Res Lab, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Jagiellonian Univ, Astron Observ, Krakow, Poland. RI Johnson, Neil/G-3309-2014 NR 90 TC 80 Z9 80 U1 0 U2 1 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 21 PY 1998 VL 301 IS 1 BP 179 EP 192 DI 10.1046/j.1365-8711.1998.02015.x PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 147MB UT WOS:000077570600024 ER PT J AU Krizmanic, JF AF Krizmanic, JF TI GLAST: The Gamma-ray Large Area Space Telescope SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article; Proceedings Paper CT 6th International Workshop on Vertex Detectors CY AUG 31-SEP 05, 1997 CL MANGARATIBA, BRAZIL SP Brazilian Res Council (CNPq), FAPERJ AB Initiated by the spectacular successes of the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory, the Gamma ray Large Area Space Telescope (GLAST) collaboration has been developing a next generation, high-energy gamma ray experiment. The goal of the GLAST mission is to image photons with sufficient angular resolution for unique, point source identification in the energy range of 10 MeV to greater than 100 GeV with good energy resolution and with a large field of view. Operating as a pair-conversion telescope, GLAST will use silicon microstrip detectors interspersed with thin layers of high-Z material to form an upper, tracker section which will be followed by a 10 radiation length deep, segmented calorimeter. The large area required to achieve the desired sensitivity and the development of ultralow-power electronics has led to a baseline configuration employing over 87 m(2) of silicon microstrip detectors with approximately 1.3 x 10(6) channels. The GLAST instrument will operate with the tracker and the calorimeter acquiring data asynchronously and semi-independently, thus self-triggering on events as they occur. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. RP Krizmanic, JF (reprint author), NASA, Goddard Space Flight Ctr, USRA, Code 661, Greenbelt, MD 20771 USA. NR 23 TC 1 Z9 1 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 NOV 21 PY 1998 VL 418 IS 1 BP 161 EP 172 DI 10.1016/S0168-9002(98)00730-X PG 12 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 142UM UT WOS:000077218800021 ER PT J AU Patel, DN Reddy, RB Nash-Stevenson, SK AF Patel, DN Reddy, RB Nash-Stevenson, SK TI Diode-pumped violet energy upconversion in BaF2 : Er3+ SO APPLIED OPTICS LA English DT Article ID TO-VISIBLE CONVERSION; RARE-EARTH IONS; UP-CONVERSION; MULTIPHONON RELAXATION; FLUORIDE; LASER; GLASSES; ERBIUM AB Under 805-nm diode-laser excitation we detected intense upconversion signals at 410, 380, and 275 nm in BaF2:Er3+. Energy up conversion schemes and efficiencies are discussed in detail. Intensity parameters of Er3+ in BaF2 were derived as Omega(2) = 1.048 +/- 0.117 x 10(-20) cm(2), Omega(4), = 1.418 +/- 0.180 x 10-20 cm2, and Omega(6) = 1.009 +/- 0.127 x 10(-20) cm(2). (C) 1998 Optical Society of America. OCIS codes: 160.3380, 300.6410, 190.7220, 300.2530, 160.2540, 160.3220. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Alabama A&M Univ, Dept Phys, POB 1268, Normal, AL 35762 USA. EM brreddy@aamu.edu NR 22 TC 34 Z9 41 U1 1 U2 6 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD NOV 20 PY 1998 VL 37 IS 33 BP 7805 EP 7808 DI 10.1364/AO.37.007805 PG 4 WC Optics SC Optics GA 138ZQ UT WOS:000077003300022 PM 18301622 ER PT J AU Hauser, MG Arendt, RG Kelsall, T Dwek, E Odegard, N Weiland, JL Freudenreich, HT Reach, WT Silverberg, RF Moseley, SH Pei, YC Lubin, P Mather, JC Shafer, RA Smoot, GF Weiss, R Wilkinson, DT Wright, EL AF Hauser, MG Arendt, RG Kelsall, T Dwek, E Odegard, N Weiland, JL Freudenreich, HT Reach, WT Silverberg, RF Moseley, SH Pei, YC Lubin, P Mather, JC Shafer, RA Smoot, GF Weiss, R Wilkinson, DT Wright, EL TI The COBE Diffuse Infrared Background Experiment search for the cosmic infrared background. I. Limits and detections SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; diffuse radiation; infrared : general ID ROCKET-BORNE OBSERVATION; GAMMA-RAYS; DIRBE MAPS; SKY; RADIATION; SPECTRUM; ANISOTROPY; GALAXIES; MODEL; LIGHT AB The Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) spacecraft was designed primarily to conduct a systematic search for an isotropic cosmic infrared background (CIB) in 10 photometric bands from 1.25 to 240 mu m. The results of that search are presented here. Conservative limits on the CIB are obtained from the minimum observed brightness in all-sky maps at each wavelength, with the faintest limits in the DIRBE spectral range being at 3.5 mu m (vI(v) < 64 nW m(-2) sr(-1), 95% confidence level) and at 240 mu m (vI(v) < 28 nW m(-2) sr(-1), 95% confidence level). The bright foregrounds from interplanetary dust scattering and emission, stars, and interstellar dust emission are the principal impediments to the DIRBE measurements of the GIB. These foregrounds have been modeled and removed from the sky maps. Assessment of the random and systematic uncertainties in the residuals and tests for isotropy show that only the 140 and 240 mu m data provide candidate detections of the GIB. The residuals and their uncertainties provide CIB upper limits more restrictive than the dark sky limits at wavelengths from 1.25 to 100 mu m. No plausible solar system or Galactic source of the observed 140 and 240 mu m residuals can be identified, leading to the conclusion that the CIB has been detected at levels of vI(v) = 25 +/- 7 and 14 +/- 3 nW m(-2) sr(-1) at 140 and 240 mu m, respectively. The integrated energy from 140 to 240 mu m, 10.3 nW m(-2) sr(-1), is about twice the integrated optical light from the galaxies in the Hubble Deep Field, suggesting that star formation might have been heavily enshrouded by dust at high redshift. The detections and upper limits reported here provide new constraints on models of the history of energy-releasing processes and dust production since the decoupling of the cosmic microwave background from matter. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Rayetheon STX, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Dept Phys, Space Sci Lab, Berkeley, CA 94720 USA. MIT, Dept Phys, Cambridge, MA 02139 USA. Princeton Univ, Dept Phys, Princeton, NJ 08544 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. RP Hauser, MG (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. RI Reach, William/C-4710-2008; Moseley, Harvey/D-5069-2012; Dwek, Eli/C-3995-2012; OI Reach, William/0000-0001-8362-4094 NR 60 TC 540 Z9 542 U1 1 U2 9 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 NOV 20 PY 1998 VL 508 IS 1 BP 25 EP 43 DI 10.1086/306379 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000004 ER PT J AU Kelsall, T Weiland, JL Franz, BA Reach, WT Arendt, RG Dwek, E Freudenreich, HT Hauser, MG Moseley, SH Odegard, NP Silverberg, RF Wright, EL AF Kelsall, T Weiland, JL Franz, BA Reach, WT Arendt, RG Dwek, E Freudenreich, HT Hauser, MG Moseley, SH Odegard, NP Silverberg, RF Wright, EL TI The COBE Diffuse Infrared Background Experiment search for the cosmic infrared background. II. Model of the interplanetary dust cloud SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; diffuse radiation; infrared : general; infrared : solar system; interplanetary medium ID ZODIACAL DUST; THERMAL EMISSION; PHYSICAL MODEL; ASTEROID BELT; SOLAR-SYSTEM; EVOLUTION; BANDS; IRAS; PARTICLES; DENSITY AB The COBE Diffuse Infrared Background Experiment (DIRBE) was designed to search for the cosmic infrared background (CIB) radiation. For an observer confined to the inner solar system, scattered light and thermal emission from the interplanetary dust (IPD) are major contributors to the diffuse sky brightness at most infrared wavelengths. Accurate removal of this zodiacal light foreground is a necessary step toward a direct measurement of the GIB. The zodiacal light foreground contribution in each of the 10 DIRBE wavelength bands ranging from 1.25 to 240 mu m is distinguished by its apparent seasonal variation over the whole sky. This contribution has been extracted by fitting the brightness calculated from a parameterized physical model to the time variation of the all-sky DIRBE measurements over 10 months of liquid He cooled observations. The model brightness is evaluated as the integral along the line of sight of the product of a source function and a three-dimensional dust density distribution function. The dust density distribution is composed of multiple components: a smooth cloud, three asteroidal dust bands, and a circumsolar ring near 1 AU. By using a directly measurable quantity that relates only to the IPD cloud, we exclude other contributors to the sky brightness from the IPD model. High-quality maps of the infrared sky with the zodiacal foreground removed have been generated using the IPD model described here. Imperfections in the model reveal themselves as low-level systematic artifacts in the residual maps that correlate with components of the IPD. The most evident of these artifacts are located near the ecliptic plane in the mid-IR and are less than 2% of the zodiacal foreground brightness. Uncertainties associated with the model are discussed, including implications for the CIB search. C1 NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. RP Kelsall, T (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX, Code 685, Greenbelt, MD 20771 USA. EM kelsall@stars.gsfc.nasa.gov RI Moseley, Harvey/D-5069-2012; Dwek, Eli/C-3995-2012; Franz, Bryan/D-6284-2012; OI Franz, Bryan/0000-0003-0293-2082; Reach, William/0000-0001-8362-4094 NR 53 TC 340 Z9 340 U1 2 U2 6 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 NOV 20 PY 1998 VL 508 IS 1 BP 44 EP 73 DI 10.1086/306380 PN 1 PG 30 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000005 ER PT J AU Arendt, RG Odegard, N Weiland, JL Sodroski, TJ Hauser, MG Dwek, E Kelsall, T Moseley, SH Silverberg, RF Leisawitz, D Mitchell, K Reach, WT Wright, EL AF Arendt, RG Odegard, N Weiland, JL Sodroski, TJ Hauser, MG Dwek, E Kelsall, T Moseley, SH Silverberg, RF Leisawitz, D Mitchell, K Reach, WT Wright, EL TI The COBE diffuse infrared background experiment search for the Cosmic Infrared Background. III. Separation of galactic emission from the infrared sky brightness SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; Galaxy : general; infrared : ISM : continuum; infrared : stars; ISM : general ID H-ALPHA EMISSION; MILKY-WAY; INTERSTELLAR-MEDIUM; DIRBE OBSERVATIONS; COLUMN DENSITY; X-RAY; DUST; GALAXY; LATITUDE; CIRRUS AB The Cosmic Infrared Background (CIB) is hidden behind veils of foreground emission from our own solar system and Galaxy. This paper describes procedures for removing the Galactic IR emission from the 1.25-240 mu m COBE DIRBE maps as steps toward the ultimate goal of detecting the GIB. The Galactic emission models are carefully chosen and constructed so that the isotropic CIB is completely retained in the residual sky maps. We start with DIRBE data from which the scattered light and thermal emission of the interplanetary dust (IPD) cloud have already been removed. Locations affected by the emission from bright compact and stellar sources are excluded from the analysis. The unresolved emission of faint stars at near- and mid-IR wavelengths is represented by a model based on Galactic source counts. The 100 mu m DIRBE observations are used as the spatial template for the interstellar medium (ISM) emission at high latitudes. Correlation of the 100 mu m data with H I column density allows us to isolate the component of the observed emission that is associated with the ISM. Limits are established on the far-IR emissivity of the diffuse ionized medium, which indicate a lower emissivity per H nucleus than in the neutral medium. At 240 mu m, we find that adding a second spatial template to the ISM model can greatly improve the accuracy of the model at low latitudes. The crucial product of this analysis is a set of all-sky IR maps from which the Galactic land IPD) emission has been removed. We discuss systematic uncertainties and potential errors in the foreground subtraction process that may have an impact on studies seeking to detect the CIB in the residual maps. C1 NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Sci Applicat Corp, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. CALTECH, IPAC, Pasadena, CA 91125 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. RP Arendt, RG (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX, Code 685, Greenbelt, MD 20771 USA. EM arendt@stars.gsfc.nasa.gov RI Moseley, Harvey/D-5069-2012; OI Reach, William/0000-0001-8362-4094 NR 92 TC 129 Z9 130 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 NOV 20 PY 1998 VL 508 IS 1 BP 74 EP 105 DI 10.1086/306381 PN 1 PG 32 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000006 ER PT J AU Dwek, E Arendt, RG Hauser, MG Fixsen, D Kelsall, T Leisawitz, D Pei, YC Wright, EL Mather, JC Moseley, SH Odegard, N Shafer, R Silverberg, RF Weiland, JL AF Dwek, E Arendt, RG Hauser, MG Fixsen, D Kelsall, T Leisawitz, D Pei, YC Wright, EL Mather, JC Moseley, SH Odegard, N Shafer, R Silverberg, RF Weiland, JL TI The COBE Diffuse Infrared Background Experiment search for the cosmic infrared background. IV. Cosmological implications SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; diffuse radiation; dust, extinction; galaxies : evolution; infrared : general ID SPECTRAL ENERGY-DISTRIBUTIONS; HIGH-REDSHIFT GALAXIES; STAR-FORMATION HISTORY; HUBBLE DEEP FIELD; LUMINOSITY FUNCTION; INTERSTELLAR DUST; ELLIPTIC GALAXIES; SOLAR-SYSTEM; DIRBE MAPS; EVOLUTION AB A direct measurement of the extragalactic background light (EBL) can provide important constraints on the integrated cosmological history of star formation, metal and dust production, and the conversion of starlight into infrared emission by dust. In this paper we examine the cosmological implications of the recent detection of the EEL in the 125 to 5000 mu m wavelength region by the Diffuse Infrared Background Experiment (DIRBE) and Far Infrared Absolute Spectrophotometer (FIRAS) on board the Cosmic Background Explorer (COBE). We first show that the 140 and 240 mu m isotropic residual emission found in the DIRBE data cannot be produced by foreground emission sources in the solar system or the Galaxy. The DIRBE 140 and 240 mu m isotropic residuals, and by inference the FIRAS residuals as well, are therefore extragalactic. Assuming that most of the 140 and 240 mu m emission is from dust yields a 2 sigma lower limit of vI(v) approximate to 5 nW m(-2) sr(-1) for the EBL at 100 mu m. The integrated EBL detected by the COBE between 140 and 5000 mu m is similar to 16 nW m(-2) sr(-1), roughly 20%-50% of the integrated EEL intensity expected from energy release by nucleosynthesis throughout cosmic history. This also implies that at least similar to 5%-15% of the baryonic mass density implied by big bang nucleosynthesis has been processed through stars. The COBE observations provide important constraints on the cosmic star formation rate, and we calculate the EEL spectrum for various star formation histories. The results show that the UV and optically determined cosmic star formation rates fall short in producing the observed 140 to 5000 mu m background. The COBE observations require the star formation rate at redshifts of z approximate to 1.5 to be larger than that inferred from UV-optical observations by at least a factor of 2. This excess stellar energy must be mainly generated by massive stars, since it otherwise would result in a local K-band luminosity density that is larger than observed. The energy sources could either be yet undetected dust-enshrouded galaxies, or extremely dusty star-forming regions in observed galaxies, and they may be responsible for the observed iron enrichment in the intracluster medium. The exact star formation history or scenarios required to produce the EEL at far-IR wavelengths cannot be unambiguously resolved by the COBE observations and must await future observations. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. RP Dwek, E (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Code 685, Greenbelt, MD 20771 USA. EM eli.dwek@gsfc.nasa.gov RI Moseley, Harvey/D-5069-2012 NR 89 TC 185 Z9 185 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 NOV 20 PY 1998 VL 508 IS 1 BP 106 EP 122 DI 10.1086/306382 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000007 ER PT J AU Fixsen, DJ Dwek, E Mather, JC Bennett, CL Shafer, RA AF Fixsen, DJ Dwek, E Mather, JC Bennett, CL Shafer, RA TI The spectrum of the extragalactic far-infrared background from the COBE FIRAS observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; diffuse radiation; infrared : general; interplanetary medium ID INSTRUMENT; DESIGN; CLOUDS; GALAXY AB The COBE FIRAS data contain foreground emission from interplanetary, Galactic interstellar dust and extragalactic background emission. We use three different methods to separate the Various emission components, and derive the spectrum of the extragalactic far-infrared background (FIRB). Each method relies on a different set of assumptions, which affect the FIRE spectrum in different ways. Despite this, the FIRE spectra derived by these different methods are remarkably similar. The average spectrum that we derive in the v = 5-80 cm(-1) (2000-125 mu m) frequency interval is I(v) = (1.3 +/- 0.4) x 10(-5)(v/v(o))P-0.64+/-0.12(v)(18.5 +/- 1.2 K), where v(o) = 100 cm(-1) (lambda(o) = 100 mu m), and P is the Planck function. The derived FIRE spectrum is consistent with the (DIRBE) 140 and 240 mu m detections. The total intensity received in the 5-80 cm(-1) frequency interval is 14 nW m(-2) sr(-1) and comprises about 20% of the total intensity expected from the energy release from nucleosynthesis throughout the history of the universe. C1 NASA, Goddard Space Flight Ctr, Hughes STX Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Fixsen, DJ (reprint author), NASA, Goddard Space Flight Ctr, Hughes STX Corp, Code 685, Greenbelt, MD 20771 USA. EM fixsen@stars.gsfc.nasa.gov RI Dwek, Eli/C-3995-2012 NR 27 TC 556 Z9 556 U1 2 U2 8 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 NOV 20 PY 1998 VL 508 IS 1 BP 123 EP 128 DI 10.1086/306383 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000008 ER PT J AU Kraemer, SB Ruiz, JR Crenshaw, DM AF Kraemer, SB Ruiz, JR Crenshaw, DM TI Physical conditions in the inner narrow-line region of the Seyfert 2 galaxy NGC 1068 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 1068); galaxies : Seyfert; ultraviolet : galaxies ID GAS-COMPOSITION; NGC-1068; ULTRAVIOLET; NUCLEUS; SPECTROPOLARIMETRY; SPECTRUM AB The physical conditions in the inner narrow-line region (NLR) of the Seyfert 2 galaxy NGC 1068 are examined using ultraviolet and optical spectra and photoionization models. The spectra are Hubble Space Telescope archive data obtained with the Faint Object Spectrograph (FOS). We selected spectra of four regions, taken through the 0." 3 FOS aperture covering the full FOS 1200-6800 Angstrom wave band. Each region is approximately 20 pc in extent, and all are within 100 pc of the apparent nucleus of NGC 1068. The spectra show similar emission-line ratios from a wide range of ionization states for the most abundant elements. After extensive photoionization modeling, we interpret this result as an indication that each region includes a range of gas densities, which we included in the models as separate components. Supersolar abundances were required for several elements to fit the observed emission-line ratios. Dust was included in the models, but apparently dust-to-gas fraction varies within these regions. The low-ionization lines in these spectra can be best explained as arising in gas that is partially shielded from the ionizing continuum. Although the predicted line ratios from the photoionization models provide a good fit to the observed ratios, it is apparent that the model predictions of electron temperatures in the ionized gas are too low. We interpret this as an indication of additional collisional heating due to shocks and/or energetic particles associated with the radio jet that traverses the NLR of NGC 1068. The density structure within each region may also be the result of compression by the jet. C1 NASA, Catholic Univ Amer, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kraemer, SB (reprint author), NASA, Catholic Univ Amer, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. EM stiskraemer@yancey.gsfc.nasa.gov NR 38 TC 40 Z9 40 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 NOV 20 PY 1998 VL 508 IS 1 BP 232 EP 242 DI 10.1086/306389 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000017 ER PT J AU Simpson, JP Witteborn, FC Price, SD Cohen, M AF Simpson, JP Witteborn, FC Price, SD Cohen, M TI Midcourse Space Experiment spectra of the Orion Nebula and the implications for abundances in the interstellar medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE infrared : ISM : continuum; infrared : ISM : lines and bands; ISM : individual (Orion Nebula) ID INFRARED-EMISSION BANDS; EFFECTIVE COLLISION STRENGTHS; AROMATIC HYDROCARBON CATIONS; FINE-STRUCTURE TRANSITION; PURE-ROTATIONAL EMISSION; LOW-DENSITY PLASMAS; I LINE-INTENSITIES; ATOMIC DATA; IRON PROJECT; CHEMICAL-COMPOSITION AB Spectra of the Orion Nebula were obtained with the Midcourse Space Experiment Spirit III interferometer from 370 to 2000 cm(-1) with 2 cm(-1) resolution in a 6' x 9' held of view (FOV) in 1996 November. Lines were detected of [S III] 534.4 cm(-1), [Ne III] 642.9 cm(-1), [Ne II] 780.4 cm(-1), [S IV] 951.4 cm(-1), [Ar III] 1112.2 cm(-1), [Ar II] 1431.6 cm(-1), H (7-6) 808.3 cm(-1), H (8-6) 1332.9 cm(-1), H (6-5) 1340.5 cm(-1), H-2(S1) 587.0 cm(-1), H-2(S2) 814.4 cm(-1), H-2(S3) 1034.7 cm(-1), H-2(S4) 1246.1 cm(-1), and H-2(S5) 1447.3 cm(-1). The following abundances were determined from these lines: Ne/H = 9.9 +/- 1.1 x 10(-5), S/H = 8.1 +/- 1.1 x 10(-6), and Ar/H = 2.5 +/- 0.2 x 10(-6). These abundances are all less than solar and confirm that the Sun is overabundant in heavy elements without the need for correction for the composition of interstellar dust. The low sulfur abundance compared with solar is an indication that a significant amount of the sulfur in Orion is in dust grains. The FOV-averaged molecular hydrogen column density is similar to 1.6 x 10(20) cm(-2) for an excitation temperature of similar to 670 K and an extinction correction corresponding to an optical depth of 1.5 at 9.7 mu m. The unidentified infrared emission features at 6.2, 7.7, 8.6, 11.3, and 12.7 mu m, attributable to polycyclic aromatic hydrocarbons, were also detected. A prominent, broad silicate feature centered near 18 mu m and additional weak features were detected and are discussed. C1 NASA, Ames Res Ctr, Astrophys Branch, Moffett Field, CA 94035 USA. SETI Inst, Moffett Field, CA 94035 USA. USAF, Res Lab, VSBC, Hanscom AFB, MA 01731 USA. Univ Calif Berkeley, Radio Astron Lab, Berkeley, CA 94720 USA. RP Simpson, JP (reprint author), NASA, Ames Res Ctr, Astrophys Branch, MS 245-6, Moffett Field, CA 94035 USA. NR 51 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 NOV 20 PY 1998 VL 508 IS 1 BP 268 EP 274 DI 10.1086/306388 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000021 ER PT J AU Harding, AK Muslimov, AG AF Harding, AK Muslimov, AG TI Particle acceleration zones above pulsar polar caps: Electron and positron pair formation fronts SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; MHD; pulsars : general; stars : neutron ID STRONG MAGNETIC-FIELDS; GAMMA-RAY PULSARS; INVERSE COMPTON-SCATTERING; NEUTRON-STAR; CONDENSED MATTER; INNER-GAP; RADIATION; EMISSION; ENERGY; ELECTRODYNAMICS AB We investigate self-consistent particle acceleration near a pulsar polar cap (PC) by the electrostatic field due to the effect of inertial frame dragging. Test particles gain energy from the electric field parallel to the open magnetic field lines and lose energy by both curvature radiation (CR) and resonant and nonresonant inverse Compton scattering (ICS) with soft thermal X-rays from the neutron star (NS) surface. Gamma rays radiated by electrons accelerated from the stellar surface produce pairs in the strong magnetic field, which screen the electric field beyond a pair formation front (PFF). Some of the created positrons can be accelerated back toward the surface and produce gamma-rays and pairs that create another PFF above the surface. We find that ICS photons control PFF formation near the surface, but because of the different angles at which the electron and positron scatter the soft photons, positron-initiated cascades develop above the surface and may screen the accelerating electric field. Stable acceleration from the NS surface is therefore not possible in the presence of dominant ICS energy losses. However, we rind that stable acceleration zones may occur at some distance above the surface, where CR dominates the electron and positron energy losses and there is up-down symmetry between the electron and positron PFFs. We examine the dependence of CR-controlled acceleration zone voltage, width, and height above the surface on parameters of the pulsar and its soft X-ray emission. For most pulsars, we find that acceleration will start at a height of 0.5-1 stellar radii above the NS surface. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Harding, AK (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Harding, Alice/D-3160-2012 NR 48 TC 160 Z9 162 U1 0 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1998 VL 508 IS 1 BP 328 EP 346 DI 10.1086/306394 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LX UT WOS:000077780000027 ER PT J AU Canuto, VM AF Canuto, VM TI Overshooting and the mu-barrier SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; stars : evolution; stars : interiors; Sun : evolution; Sun : interior; turbulence ID CONVECTION AB Using general arguments and without numerical calculations. we present three complementary "proofs" that the extent of overshooting (OV) outside a convective region is decreased by a gradient of the mean molecular weight. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP Canuto, VM (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 12 TC 8 Z9 8 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1998 VL 508 IS 1 BP L103 EP L104 DI 10.1086/311722 PN 2 PG 2 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152MA UT WOS:000077780300024 ER PT J AU Dwek, E Arendt, RG AF Dwek, E Arendt, RG TI A Tentative detection of the cosmic infrared background at 3.5 mu m from COBE/DIRBE observations SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; diffuse radiation; infrared : general AB Foreground emission and scattered light from interplanetary dust (IPD) particles and emission from Galactic stellar sources are the greatest obstacles to determining the cosmic infrared background (CIB) from diffuse sky measurements in the similar to 1-5 mu m range. We use ground-based observational limits on the K-band intensity of the CIB in conjunction with sky maps obtained by the Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer satellite to reexamine the limits on the CIB at 1.25, 3.5, and 4.9 mu m. Adopting a CIB intensity of 7.4 nW m(-2) sr(-1) at 2.2 mu m, and using the 2.2 mu m DIRBE sky map from which the emission from the IPD cloud has been subtracted, we create a spatial template of the Galactic stellar contribution to the diffUse infrared sky. This template is then used to subtract the contribution of the diffuse Galactic stellar emission from the IPD emission-subtracted DIRBE sky maps at 1.25, 3.5, and 4.9 mu m. The DIRBE 100 mu m data are used to estimate the small contribution of emission from interstellar dust at 3.5 and 4.9 mu m. Our method significantly reduces the errors associated with the subtraction of Galactic starlight, leaving only the IPD emission component as the primary obstacle to the detection of the CIB at these wavelengths. The analysis leads to a tentative detection of the CIB at 3.5 mu m with an intensity of vI(v) = (9.9 +/- 0.312[v(o)I(CIB)(v(o)) - 7.4]} +/- 2.9 nW m(-2) sr(-1), where v(o)I(CIB)(v(o)) is the CIB intensity at 2.2 mu m in units of nW m(-2) sr(-1). The analysis also yields new upper Limits (95% confidence limit) on the CIB at 1.25 and 4.9 mu m of 68 and 36 nW m(-2) sr(-1), respectively The cosmological implications of these results are discussed in this Letter. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Raytheon STX, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dwek, E (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Code 685, Greenbelt, MD 20771 USA. EM eli.dwek@gsfc.nasa.gov NR 11 TC 115 Z9 115 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 20 PY 1998 VL 508 IS 1 BP L9 EP L12 DI 10.1086/311714 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152MA UT WOS:000077780300003 ER PT J AU Ji, Q Shaw, GE Cantrell, W AF Ji, Q Shaw, GE Cantrell, W TI A new instrument for measuring cloud condensation nuclei: Cloud condensation nucleus "remover" SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article AB This communique describes a new and novel instrument for measuring concentrations of natural cloud condensation nuclei (CCN) from the free atmosphere. It simultaneously provides the size spectrum of nucleated particles, a useful parameter for gaining insight into the composition of the CCN. The supersaturation spectrum N(S), where N is the number concentration of droplets nucleated at supersaturation S, is readily obtained. This parameter is one of the keys to evaluating aerosol influence on cloud microphysics and on the possible modulations of cloud albedo. Laboratory evaluations show that the instrument has good measurement accuracy and precision, even at low CCN concentrations found in the clean troposphere. The instrument is rugged and reliable. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. RP Ji, Q (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM ji@climate.gsfc.nasa.gov; shaw@gi.alaska.edu; cantrell@gi.alaska.edu NR 17 TC 21 Z9 22 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 NOV 20 PY 1998 VL 103 IS D21 BP 28013 EP 28019 DI 10.1029/98JD01884 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700001 ER PT J AU Chatfield, RB Vastano, JA Li, L Sachse, GW Connors, VS AF Chatfield, RB Vastano, JA Li, L Sachse, GW Connors, VS TI The Great African plume from biomass burning: Generalizations from a three-dimensional study of TRACE A carbon monoxide SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HIGH-RESOLUTION RADIOMETER; SOUTH-ATLANTIC; METEOROLOGICAL CONDITIONS; TROPOSPHERIC OZONE; REACTIVE NITROGEN; TRANSPORT; MODEL; AEROSOLS; CHEMISTRY; EMISSIONS AB The "Great African Plume" flows westward from a wind divergence line over Central Africa to pollute the Equatorial Atlantic Ocean. The plume arises from agricultural burning fumes which mix in a 3-4 km deep boundary layer over Africa, then override cooler rainforest air, and finally swerve westward, where their progress into the Atlantic is "gated" by southern storm systems. Another prominent elevated "Global Burning Plume" from Tropical South America flows past South Africa above 8 km altitude. Joining elevated African plumes, it influences the South Indian and Southern Oceans. These are results from our GRACES (Global Regional Atmospheric Chemistry Event Simulator), which was used to study carbon monoxide during an intensive experimental period, September-October 1992. Traces of the plumes are also evident in observations of CO in the Measurement of Air Pollution from Satellites (MAPS) samples of October, 1994, suggesting a general phenomena. To arrive at these conclusions, we used the detailed weather reconstructions afforded by MM5 meteorological model dynamics to drive GRACES. Both statistical and detailed (event) comparisons of CO and observed aboard the NASA DC-8 are good, especially < 6 km altitude. The following model adaptations that we required may inform global analysis and global models: (I) Parameterized vertical transport like planetary boundary layer convection and deep cumulonimbus convection strongly control CO, allowing far more precision than trajectory studies and models using only large scale motions. (2) CO sources during this period were consistent with the Hao and Liu [1994] report-based carbon-burn rates; (3) deep convection is even more active than as parameterized by MMS's Grell-scheme: on the large scale: mass fluxes effective for CO redistribution may be over twice core-updraft values diagnosed strengths. C1 NASA, Ames Res Ctr, Earth Syst Sci Div, Moffett Field, CA 94035 USA. San Jose State Univ Fdn, San Jose, CA 95172 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Chatfield, RB (reprint author), NASA, Ames Res Ctr, Earth Syst Sci Div, MS 245-5, Moffett Field, CA 94035 USA. EM chatfield@clio.arc.nasa.gov NR 51 TC 30 Z9 30 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1998 VL 103 IS D21 BP 28059 EP 28077 DI 10.1029/97JD03363 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700006 ER PT J AU Smirnov, A Holben, BN Slutsker, I Welton, EJ Formenti, P AF Smirnov, A Holben, BN Slutsker, I Welton, EJ Formenti, P TI Optical properties of Saharan dust during ACE 2 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SKY BRIGHTNESS MEASUREMENTS; SIZE DISTRIBUTION; AEROSOLS; SCATTERING; OCEAN AB The Aerosol Robotic Network (AERONET) of automatic Sun/sky radiometers collected data on Tenerife, Canary Islands, in June-July 1997 during the second Aerosol Characterization Experiment (ACE 2). Initially, two instruments were deployed at Izana observatory (2360 m above sea level) and one at a mountain station Teide (3570 m above sea level). Repeatability of the calibration constants (Langley method) for all instruments was less than 0.5%. Aerosol optical depths measured by colocated sunphotometers and column size distributions, retrieved from spectral sky radiance data, were in good agreement. Later, one of the instruments was relocated at sea level. On July 8, 17, and 25, Saharan dust outbreaks were observed. Diurnal variations of spectral aerosol optical depth are presented. Relative diurnal stability of Saharan dust optical properties has been observed. Volume size distributions at various heights (sea level and 2360 m above sea level) show that the main portion of coarse particles is situated above 2360 m level. Measurements on July 25 showed how incoming dust has changed the magnitude and spectral dependence of aerosol optical depth and volume spectra of columnar aerosol. Mean optical depth and Angstrom parameter values for Saharan dust outbreaks during the ACE 2 experiment agree well with the Atlantic Ocean and Bermuda data obtained during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) in July 1996, as well as with previously reported Atlantic Ocean results. Also, there is a good agreement between ACE 2 data for Saharan air masses and data obtained on certain sites of the AERONET network. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Greenbelt, MD 20771 USA. Max Planck Inst Chem, Dept Biochem, D-55020 Mainz, Germany. Univ Miami, Dept Phys, Coral Gables, FL 33146 USA. RP Smirnov, A (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. EM asmimov@spamer.gsfc.nasa.gov RI Smirnov, Alexander/C-2121-2009; Welton, Ellsworth/A-8362-2012 OI Smirnov, Alexander/0000-0002-8208-1304; NR 15 TC 50 Z9 50 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 NOV 20 PY 1998 VL 103 IS D21 BP 28079 EP 28092 DI 10.1029/98JD01930 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700007 ER PT J AU Ko, MKW Sze, ND Scott, C Rodriguez, JM Weisenstein, DK Sander, SP AF Ko, MKW Sze, ND Scott, C Rodriguez, JM Weisenstein, DK Sander, SP TI Ozone depletion potential of CH3Br SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID STRATOSPHERIC HBR; ATMOSPHERIC CH3BR; LIFETIME; MODEL; HOBR; SPECTROSCOPY; DEGRADATION; KINETICS; SPECTRA; IMPACT AB The ozone depletion potential (ODP) of methyl bromide (CH3Br) can be determined by combining the model-calculated bromine efficiency factor (BEF) for CH3Br and its atmospheric lifetime. This paper examines how changes in several key kinetic data affect BEF. The key reactions highlighted in this study include the reaction of BrO + HO2, the absorption cross section of HOBr, the absorption cross section and the photolysis products of BrONO2, and the heterogeneous conversion of BrONO2 to HOBr and HNO3 on aerosol particles. By combining the calculated BEF with the latest estimate of 0.7 year for the atmospheric lifetime of CH3Br, the likely value of ODP for CH3Br is 0.39. The model-calculated concentration of HBr (similar to 0.3 pptv) in the lower stratosphere is substantially smaller than the reported measured value of about 1 pptv. Recent publications suggested models can reproduce the measured value if one assumes a yield for HBr from the reaction of BrO + OH or from the reaction of BrO + HO2. Although the DeMore et al. [1997] evaluation concluded any substantial yield of HBr from BrO + HO2 is unlikely, for completeness, we calculate the effects of these assumed yields on BEF for CH3Br. Our calculations show that the effects are minimal: practically no impact for an assumed 1.3% yield of HBr from BrO + OH and 10% smaller for an assumed 0.6% yield from BrO + HO2. C1 Atmospher & Environm Res Inc, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ko, MKW (reprint author), Atmospher & Environm Res Inc, 840 Mem Dr, Cambridge, MA 02139 USA. EM mko@aer.com; ssander@jpl.nasa.gov RI Rodriguez, Jose/G-3751-2013; Ko, Malcolm/D-5898-2015 OI Rodriguez, Jose/0000-0002-1902-4649; NR 36 TC 9 Z9 9 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 NOV 20 PY 1998 VL 103 IS D21 BP 28187 EP 28195 DI 10.1029/98JD02537 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700015 ER PT J AU Rinsland, CP Jones, NB Connor, BJ Logan, JA Pougatchev, NS Goldman, A Murcray, FJ Stephen, TM Pine, AS Zander, R Mahieu, E Demoulin, P AF Rinsland, CP Jones, NB Connor, BJ Logan, JA Pougatchev, NS Goldman, A Murcray, FJ Stephen, TM Pine, AS Zander, R Mahieu, E Demoulin, P TI Northern and southern hemisphere ground-based infrared spectroscopic measurements of tropospheric carbon monoxide and ethane SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID SOLAR ABSORPTION-SPECTRA; ATMOSPHERIC TRACE GASES; TOTAL COLUMN ABUNDANCE; SEASONAL-VARIATIONS; NEW-ZEALAND; KITT PEAK; NONMETHANE HYDROCARBONS; VERTICAL-DISTRIBUTION; PHOTOCHEMICAL MODEL; TORSIONAL SPECTRUM AB crime series of CO and C2H6 measurements have been derived from high-resolution infrared solar spectra recorded in Lauder, New Zealand (45.0 degrees S, 169.7 degrees E, altitude 0.37 km), and at the U.S. National Solar Observatory (31.9 degrees N, 111.6 degrees W, altitude 2.09 km) on Kitt Peak. Lauder observations were obtained between July 1993 and November 1997, while the Kitt Peak measurements were recorded between May 1977 and December 1997. Both databases were analyzed with spectroscopic parameters that included significant improvements for C2H6 relative to previous studies. Target CO and C2H6 lines were selected to achieve similar vertical samplings based on averaging kernels. These calculations show that partial columns from layers extending from the surface to the mean tropopause and from the mean tropopause to 100 km are nearly independent. Retrievals based on a semiempirical application of the Rodgers optimal estimation technique are reported for the lower laver, which has a broad maximum in sensitivity in the upper troposphere. The Lauder CO and C2H6 partial columns exhibit highly asymmetrical seasonal cycles with minima in austral autumn and sharp peaks in austral spring. The spring maxima are the result of tropical biomass burning emissions followed by deep convective vertical transport to the upper troposphere and long-range horizontal transport. Significant year-to-year variations are observed for both CO and C2H6, but the measured trends, (+0.37 +/- 0.57)% yr(-1) and (-0.64 +/- 0.79)% yr(-1), 1 sigma, respectively, indicate no significant long-term changes. The Kitt Peak data also exhibit CO and C2H6 seasonal variations in the lower layer with trends equal to (-0.27 +/- 0.17)% yr(-1) and (-1.20 +/- 0.35')% yr(-1), 1 sigma, respectively. Hence a decrease in the Kitt Peak tropospheric C2H6 column has been detected, though the CO trend is not significant. Both measurement sets are compared with previous observations, reported trends, and three-dimensional model calculations. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. NIWA Climate, Lauder 9182, New Zealand. Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium. Univ Denver, Dept Phys, Denver, CO 80208 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Alpine Technol, Germantown, MD 20874 USA. Christopher Newport Univ, Dept Phys, Newport News, VA 23606 USA. Harvard Univ, Div Appl Sci, Cambridge, MA 02138 USA. RP Rinsland, CP (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 401A, Hampton, VA 23681 USA. EM rinsland@riscbox.larc.nasa.gov; jones@kea.lauder.cri.nz; connor@kea.lauder.cri.nz; jal@io.harvard.edu; nikita@riscbox.larc.nasa.gov; goldman@acd.ucar.edu; fmucray@acd.ucar.edu; tstephen@du.edu; alanpine@erols.com; zander@astro.ulg.ac.be RI Jones, Nicholas/G-5575-2011; OI Jones, Nicholas/0000-0002-0111-2368; Mahieu, Emmanuel/0000-0002-5251-0286 NR 107 TC 162 Z9 165 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1998 VL 103 IS D21 BP 28197 EP 28217 DI 10.1029/98JD02515 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700016 ER PT J AU Singh, HB Viezee, W Chen, Y Thakur, AN Kondo, Y Talbot, RW Gregory, GL Sachse, GW Blake, DR Bradshaw, JD Wang, Y Jacob, DJ AF Singh, HB Viezee, W Chen, Y Thakur, AN Kondo, Y Talbot, RW Gregory, GL Sachse, GW Blake, DR Bradshaw, JD Wang, Y Jacob, DJ TI Latitudinal distribution of reactive nitrogen in the free troposphere over the Pacific Ocean in late winter early spring SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HNO3/NOX RATIO; NITRIC-ACID; STRATOSPHERE; AEROSOLS; FATE; NOX AB The late winter/early spring (February/March, 1994) measurements of Pacific Exploratory Mission-West (PEM-W) B have been analyzed to show latitudinal distributions (45 degrees N to 10 degrees S) of the mixing ratios of reactive nitrogen species (NO, peroxyacetylnitrate (PAN), HNO3, and NOy), ozone, and chemical tracers (CO, NMHCs, acetone, and C2Cl4) with a focus on the upper troposphere. Mixing ratios of all species are relatively low in the warm tropical and subtropical air south of the polar jetstream (approximate to 28 degrees N) but increase sharply with latitude in the cold polar air north of the jetstream. Noteworthy is the continuous increase in reservoir species (PAN and HNO3) and the simultaneous decrease in NOx toward the northern midlatitudes. The Harvard global three-dimensional model of tropospheric chemistry has been used to compare these observations with predictions. In the upper troposphere the magnitude and distribution of measured NOy and PAN as a function of latitude is well represented by this model, while NOx (measured NO + model calculated NO2) is underpredicted, especially in the tropics. Unlike several previous studies, where model-predicted HNO3 exceeded observations by as much as a factor of 10, the present data/model comparison is improved to within a factor of 2. The predicted upper tropospheric HNO3 is generally below or near measured values, and there is little need to invoke particle reactions as a means of removing or recycling HNO3. Comparison between measured NOy and the sum of its three main constituents (PAN + NOx + HNO3) on average show a small mean shortfall (<15%). This shortfall could be attributed to the presence of known but unmeasured species (e.g., peroxynitric acid and alkyl nitrates) as well as to instrument errors. C1 NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Div Earth Sci, Hampton, VA 23665 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02139 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Georgia Inst Technol, Sch Atmospher Sci, Atlanta, GA 30332 USA. RP Singh, HB (reprint author), NASA, Ames Res Ctr, Div Earth Sci, Moffett Field, CA 94035 USA. EM hsingh@mail.arc.nasa.gov RI Kondo, Yutaka/D-1459-2012; Wang, Yuhang/B-5578-2014 NR 32 TC 35 Z9 35 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 NOV 20 PY 1998 VL 103 IS D21 BP 28237 EP 28246 DI 10.1029/98JD01891 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700018 ER PT J AU Michelsen, HA Manney, GL Gunson, MR Zander, R AF Michelsen, HA Manney, GL Gunson, MR Zander, R TI Correlations of stratospheric abundances of NOy, O-3, N2O, and CH4 derived from ATMOS measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TOTAL REACTIVE NITROGEN; HALOGEN OCCULTATION EXPERIMENT; NORTH POLAR VORTEX; WINTER 1992 93; ARCTIC STRATOSPHERE; OZONE DEPLETION; ANTARCTIC STRATOSPHERE; 2-DIMENSIONAL MODEL; TROPICAL STRATOSPHERE; AIRCRAFT MEASUREMENTS AB Correlations are presented for [NOy] relative to [N2O] and [O-3] derived from measurements from the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument from a wide range of altitudes and latitudes, including the tropics for which previous analyses have not extended above similar to 20 km, Relationships for [O-3] versus [N2O] are also given. The results are shown to be in good agreement with aircraft- and balloon-based observations. Distinct correlations are observed for the tropics, the springtime polar vortex, and the extratropics-extravortex regions, These correlations demonstrate rapid production of NOy and O-3 in the tropical middle stratosphere and episodic export of air from this region to higher latitudes. Isolation of air within the developing polar vortices in the fall is also shown. Arctic vortex data from April 1993 appear to indicate denitrification of 25-30%, which is evident as a 3.0-4.5 ppb deficit in [NOy] when the vortex [NOy]:[N2O] correlation is compared with the extravortex correlation. A mixture of air descended from above 40 km with air from lower altitudes can fully account for this deficit in [NOy], in addition to approximately half of art apparent Arctic ozone loss of 50-60%, as inferred by comparison of the vortex and extravortex [O-3]:[N2O] correlations. Comparison of Antarctic vortex and extravortex correlations from November 1994 similarly show a 60-80% deficit in [NOy] and 80-100% deficit in [O-3]; at least half of this apparent denitrification and ozone loss can be attributed to mixing of air descended from higher altitudes with air from lower altitudes. C1 AER Inc, San Ramon, CA 94583 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium. RP Michelsen, HA (reprint author), AER Inc, 2682 Bishop Dr,Ste 120, San Ramon, CA 94583 USA. EM ham@aer.com; manney@iguana.jpl.nasa.gov; mrg@caesar.jpl.nasa.gov; zander@atmosfer.astro.ulg.ac.be NR 78 TC 102 Z9 103 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1998 VL 103 IS D21 BP 28347 EP 28359 DI 10.1029/98JD02850 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700023 ER PT J AU Callis, LB Natarajan, M Evans, DS Lambeth, JD AF Callis, LB Natarajan, M Evans, DS Lambeth, JD TI Solar atmospheric coupling by electrons (SOLACE) 1. Effects of the May 12, 1997 solar event on the middle atmosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID THERMOSPHERIC NITRIC-OXIDE; CORONAL MASS EJECTIONS; HELIOGRAPHIC LATITUDES; REACTIVE NITROGEN; OZONE DEPLETION; COOLING RATES; PROTON EVENTS; ODD NITROGEN; WIND; STRATOSPHERE AB An analysis is carried out of the effects on middle atmospheric NOy and O-3 of a coronal mass ejection (CME) event which occurred on May 12, 1997, and which is coupled with observed solar wind fluctuations. Observations of electron fluxes by instruments aboard the SAMPEX and NOAA 12 satellites indicate large enhancements of magnetospheric electron fluxes occurring with the arrival of the high-speed solar wind. Calculations suggest that significant formation rates of NOy should occur in the mesosphere and the lower thermosphere at mid to high latitudes. Halogen Occultation Experiment (HALOE) NO observations reveal increases of more than an order of magnitude between 85 and 120 km in both hemispheres within 1-2 days after the electron flux increases. Two dimensional chemical transport simulations were carried out to assess the fate of the NO, increases. Northern hemispheric increases were lost to photochemical destruction shortly after the event ended. Southern hemispheric increases were transported in part into the stratosphere by advective descent. By October 1997, high-latitude NOy increases of 20-40% were calculated near 25 km leading to O-3 reductions of up to approximate to 20% when compared to a simulation with no electron precipitation. A solar atmospheric coupling by electrons precipitating from the outer trapping and auroral regions of the magnetosphere, and which affects middle atmospheric NO, is clearly demonstrated by the observations alone. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. NOAA, Space Environm Ctr, Boulder, CO USA. RP Callis, LB (reprint author), NASA, Langley Res Ctr, Mail Stop 410B, Hampton, VA 23681 USA. EM lbc@jaguar.larc.nasa.gov NR 49 TC 40 Z9 40 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD NOV 20 PY 1998 VL 103 IS D21 BP 28405 EP 28419 DI 10.1029/98JD02408 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700027 ER PT J AU Callis, LB Natarajan, M Lambeth, JD Baker, DN AF Callis, LB Natarajan, M Lambeth, JD Baker, DN TI Solar atmospheric coupling by electrons (SOLACE) 2. Calculated stratospheric effects of precipitating electrons, 1979-1988 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID EXPERIMENT-II MEASUREMENTS; MIDDLE ATMOSPHERE; COOLING RATES; PROTON EVENTS; NITRIC-OXIDE; ODD NITROGEN; OZONE; AEROSOL; CLIMATOLOGY; MODEL AB An analysis has been carried out of the effects of energetic electron precipitation (EEP) on stratospheric NOy, NO2, and O-3. Solar wind observations used together with precipitating electron fluxes observed aboard TIROS spacecraft show a close relationship between the long- and short-term fluctuations in the solar wind and EEP over a period of 16 years. Daily electron energy spectra for 4.25 less than or equal to E less than or equal to 1050 keV and energy deposition profiles are developed for both hemispheres for L greater than or equal to 5 and used in two-dimensional chemical transport simulations for the period January 15, 1979, through December 31, 1987. Results indicate that globally averaged column NOy (from 25 to 40 km) increases by approximate to 12% between 1979 and 1983-1985 with a rapid decline to 1979 levels between early 1985 and 1987. Day-by-day comparisons of the results with the Stratospheric Aerosol and Gas Experiment (SAGE II) column NO2 and O-3 for the period October 24, 1984, and December 31, 1987, show good agreement with the inclusion of EEP in the simulations. Northern near-hemispheric decreases of column NO2 of approximate to 35% observed by SAGE II between early 1985 and 1987 are well simulated with the inclusion of EEP. Comparisons of several simulations with one another and with SAGE II: NO2 data and Solar Backscattered Ultraviolet (SBUV) (V6) O-3 data suggest that SOLACE represents a solar- terrestrial coupling mechanism which, for solar cycle 21, is as important to stratospheric O-3 as solar UV flux variations. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. RP Callis, LB (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 401B, Hampton, VA 23681 USA. EM lbc@jaguar.larc.nasa.gov NR 56 TC 50 Z9 50 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 NOV 20 PY 1998 VL 103 IS D21 BP 28421 EP 28438 DI 10.1029/98JD02407 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 140GF UT WOS:000077078700028 ER PT J AU Guedry, FE Rupert, AR Reschke, MF AF Guedry, FE Rupert, AR Reschke, MF TI Motion sickness and development of synergy within the spatial orientation system. A hypothetical unifying concept SO BRAIN RESEARCH BULLETIN LA English DT Article DE motion sickness; spatial orientation; well-being; development ID VESTIBULOOCULAR REFLEX AB Adaptation to research paradigms such as rotating rooms and optical alteration of visual feedback during movement results in development of perceptual-motor programs that provide the reflexive assistance that is necessary to skilled control of movement and balance. The discomfort and stomach awareness that occur during the adaptation process has been attributed to conflicting sensory information about the state of motion. Vestibular signals depend on the kinematics of head movements irrespective of the presence or absence of signals from other senses. We propose that sensory conflict when vestibular signals are at least one component of the conflict are innately disturbing and unpleasant. This innate reaction is part of a continuum that operates early in life to prevent development of inefficient perceptual-motor programs. This reaction operates irrespective of and in addition to reward and punishment from parental guidance or goal attainment to yield efficient control of whole body movement in the operating environment of the individual, The same mechanism is involved in adapting the spatial orientation system to strange environments. This conceptual model "explains"' why motion sickness is associated with adaptation to novel environments and is in general consistent with motion sickness literature. (C) 1999 Elsevier Science Inc. C1 Univ W Florida, Pensacola, FL 32503 USA. NASA, Lyndon B Johnson Space Ctr, Space Biomed Res Inst, Houston, TX 77058 USA. RP Guedry, FE (reprint author), Univ W Florida, 3861 Ochuse Dr, Pensacola, FL 32503 USA. EM fguedry@namrl.navy.mil NR 60 TC 19 Z9 20 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0361-9230 J9 BRAIN RES BULL JI Brain Res. Bull. PD NOV 15 PY 1998 VL 47 IS 5 BP 475 EP 480 DI 10.1016/S0361-9230(98)00087-2 PG 6 WC Neurosciences SC Neurosciences & Neurology GA 166WU UT WOS:000078601500012 PM 10052577 ER PT J AU Harm, DL Parker, DE Reschke, MF Skinner, NC AF Harm, DL Parker, DE Reschke, MF Skinner, NC TI Relationship between selected orientation rest frame, circular vection and space motion sickness SO BRAIN RESEARCH BULLETIN LA English DT Article DE spatial orientation; motion sickness; vection ID MICROGRAVITY AB Space motion sickness (SMS) and spatial orientation and motion perception disturbances occur in 70-80% of astronauts. People select "rest frames" to create the subjective sense of spatial orientation. In microgravity, the astronaut's rest frame may be based on visual scene polarity cues and on the internal head and body z axis (vertical body axis). The data reported here address the following question: Can an astronaut's orientation rest frame be related and described by other variables including circular vection response latencies and space motion sickness? The astronaut's microgravity spatial orientation rest frames were determined from inflight and postflight verbal reports. Circular vection responses were elicited by rotating a virtual room continuously at 35 degrees/s in pitch, roll and yaw with respect to the astronaut. Latency to the onset of vection was recorded from the time the crew member opened their eyes to the onset of vection. The astronauts who used visual cues exhibited significantly shorter vection latencies than those who used internal z axis cues. A negative binomial regression model was used to represent the observed total SMS symptom scores for each subject for each flight day. Orientation reference type had a significant effect, resulting in an estimated three-fold increase in the expected motion sickness score on flight day 1 for astronauts who used visual cues. The results demonstrate meaningful classification of astronauts' rest frames and their relationships to sensitivity to circular vection and SMS. Thus, it may be possible to use vection latencies to predict SMS severity and duration. (C) 1999 Elsevier Science Inc. C1 NASA, Lyndon B Johnson Space Ctr, Neurosci Labs, Houston, TX 77058 USA. Univ Washington, Seattle, WA 98195 USA. KRUG Life Sci Div, Houston, TX USA. RP Harm, DL (reprint author), NASA, Lyndon B Johnson Space Ctr, Neurosci Labs, Mail Code SD3,2101 Nasa Rd 1, Houston, TX 77058 USA. EM harm@sdmail.jsc.nasa.gov NR 11 TC 7 Z9 7 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0361-9230 J9 BRAIN RES BULL JI Brain Res. Bull. PD NOV 15 PY 1998 VL 47 IS 5 BP 497 EP 501 DI 10.1016/S0361-9230(98)00096-3 PG 5 WC Neurosciences SC Neurosciences & Neurology GA 166WU UT WOS:000078601500015 PM 10052580 ER PT J AU Tsurutani, BT Arballo, JK Lakhina, GS Ho, CM Buti, B Pickett, JS Gurnett, DA AF Tsurutani, BT Arballo, JK Lakhina, GS Ho, CM Buti, B Pickett, JS Gurnett, DA TI Plasma waves in the dayside polar cap boundary layer: Bipolar and monopolar electric pulses and whistler mode waves SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PARTICLE INTERACTIONS; SOLITARY WAVES; MAGNETOPAUSE AB We report four different types of plasma waves detected in and near the dayside polar cap boundary layer (PCBL) region at high altitudes (> 6 R-E) One wave type is narrowband whistler-mode emission at frequencies just below f(ce) (5.5 kHz). These emissions could be locally generated by resonant wave-particle interactions involving an electron beam of similar to 100 eV energy. A second type is a low frequency (200-300 Hx) whistler mode wave, which may be locally generated by similar to 25 keV electrons or similar to 45 keV ions. It is also possible that these latter waves are generated at low altitudes near the ionosphere and then converted from the ion cyclotron mode into whistler-mode during propagation from the generation region to the spacecraft. Two further types of waves are large-amplitude bipolar and monopolar solitary "electrostatic" waves. The bipolar wave structures are possibly generated all along the magnetic field lines in the field-aligned current regions (at all local times). The monopolar structures could be evolved bipolar solitary waves. A one-d schematic is presented to explain the paired monopolar structures as a result of splitting of an electron hole into two parts. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Indian Inst Geomagnetism, Bombay 400005, Maharashtra, India. RP Tsurutani, BT (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lakhina, Gurbax /C-9295-2012; OI Lakhina, Gurbax /0000-0002-8956-486X NR 15 TC 63 Z9 63 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 15 PY 1998 VL 25 IS 22 BP 4117 EP 4120 DI 10.1029/1998GL900114 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 139GH UT WOS:000077019300004 ER PT J AU Sofia, S Fox, P Schatten, K AF Sofia, S Fox, P Schatten, K TI Forecast update for activity cycle 23 from a dynamo-based method SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR AB In this paper we update a prediction of the solar activity for cycle 23 on the basis of a general framework derived from simple dynamo considerations. We estimate an expected maximum smoothed International Sunspot Number of 143+/-30, or a smoothed 2800 MHz radio flux (F10.7) of 190+/-30 x 10(-22) Watts/m(2)/Hz. These values should allow us to test the reliability of the various forecasting methods. C1 Yale Univ, Dept Astron, New Haven, CT 06520 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. GSFC, NASA, Terr Phys Lab, Greenbelt, MD USA. RP Sofia, S (reprint author), Yale Univ, Dept Astron, New Haven, CT 06520 USA. OI Fox, Peter/0000-0002-1009-7163 NR 13 TC 15 Z9 15 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 NOV 15 PY 1998 VL 25 IS 22 BP 4149 EP 4152 DI 10.1029/1998GL900138 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 139GH UT WOS:000077019300012 ER PT J AU Nagy, AF Kim, J Cravens, TE Kliore, AJ AF Nagy, AF Kim, J Cravens, TE Kliore, AJ TI Hot oxygen corona at Europa SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID UPPER ATMOSPHERES; HYDROGEN; ATOMS; VENUS; MARS AB A model of the hot oxygen exosphere at Europa was constructed. The source term for the hot atoms was assumed to be dissociative recombination of O-2(+) and Liouville's theorem was used to calculate their altitude distribution. It was found that near the surface the hot oxygen density is in excess of 200 cm(-3), dropping to a value on the order of 50 cm(-3) at 1500 km. These calculations indicate that the hot atomic oxygen densities are considerably less than the thermal molecular oxygen ones, but slightly larger than the measured sodium values. The escape flux of the hot oxygen atoms was calculated to be on the order of 1.4x10(8) atoms cm(-2) sed(-1). This corresponds to a global escape rate of 4.4x10(25) atoms sec(-1), which is more than an order of magnitude less than the estimated atmospheric sputtering rate. C1 Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Korean Aerosp Res Inst, Space Div, Yusong Gu, Taejon, South Korea. Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Nagy, AF (reprint author), Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. NR 15 TC 10 Z9 10 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 NOV 15 PY 1998 VL 25 IS 22 BP 4153 EP 4155 DI 10.1029/1998GL900139 PG 3 WC Geosciences, Multidisciplinary SC Geology GA 139GH UT WOS:000077019300013 ER PT J AU Dessler, AE AF Dessler, AE TI A reexamination of the "stratospheric fountain" hypothesis SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER-VAPOR; ANNUAL CYCLE; BUDGET; SYSTEM AB We reexamine the "stratospheric fountain" hypothesis by comparing estimates of the annually and zonally averaged volume mixing ratio (vmr) of water vapor entering the stratosphere to annually and zonally averaged estimates of the saturation vmr of the tropical tropopause-region. We find that the vmr of water vapor entering the stratosphere (3.8+/-0.3 ppmv) agrees well with the saturation vmr of the tropical, tropopause-region (4.0+/-0.8 ppmv). Consequently, our analysis provides no support for the "stratospheric fountain" hypothesis, which required troposphere-to-stratosphere transport to occur preferentially in regions where the tropical tropopause is colder than average. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dessler, AE (reprint author), Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. EM dessler@atmos.umd.edu RI Dessler, Andrew/G-8852-2012 OI Dessler, Andrew/0000-0003-3939-4820 NR 23 TC 82 Z9 83 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 NOV 15 PY 1998 VL 25 IS 22 BP 4165 EP 4168 DI 10.1029/1998GL900120 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 139GH UT WOS:000077019300016 ER PT J AU Tabazadeh, A Jacobson, MZ Singh, HB Toon, OB Lin, JS Chatfield, RB Thakur, AN Talbot, RW Dibb, JE AF Tabazadeh, A Jacobson, MZ Singh, HB Toon, OB Lin, JS Chatfield, RB Thakur, AN Talbot, RW Dibb, JE TI Nitric acid scavenging by mineral and biomass burning aerosols SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CHEJU ISLAND; HNO3; TROPOSPHERE; NITRATE; KOREA; ICE; AIR AB The abundance of gas phase nitric acid in the upper troposphere is overestimated by global chemistry-transport models, especially during the spring and summer seasons. Recent aircraft data obtained over the central US show that mineral aerosols were abundant in the upper troposphere during spring. Chemical reactions on mineral dust may provide an important sink for nitric acid. In regions where the mineral dust abundance is low in the upper troposphere similar HNO3 removal processes may occur on biomass burning aerosols. We propose that mineral and biomass burning aerosols may provide an important global sink for gas phase nitric acid, particularly during spring and summer when aerosol composition in the upper troposphere may be greatly affected by dust storms from east Asia or tropical biomass burning plumes. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Civil & Environm Engn, Palo Alto, CA 94304 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Bay Area Environm Res Inst, San Francisco, CA USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RP Tabazadeh, A (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. NR 28 TC 74 Z9 77 U1 0 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 15 PY 1998 VL 25 IS 22 BP 4185 EP 4188 DI 10.1029/1998GL900062 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 139GH UT WOS:000077019300021 ER PT J AU Cantrell, JH Zhang, XG AF Cantrell, JH Zhang, XG TI Nonlinear acoustic response from precipitate-matrix misfit in a dislocation network SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID HARMONIC-GENERATION AB An analytical model is presented for the effects on the acoustic nonlinearity of the interaction of matrix dislocations with precipitate coherency strains in metallic alloys. The acoustic nonlinearity parameters are shown to depend linearly on the dislocation density, volume fraction of precipitates and precipitate-matrix misfit parameters, and on the fourth power of the dislocation loop length. The model predicts changes in the acoustic nonlinearity parameter associated with the growth of precipitates during the artificial aging of aluminum alloy 2024 that are in good agreement with experimental measurements reported in the literature. [S0021-8979(98)04222-4]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Oak Ridge Natl Lab, Computat Phys & Engn Div, Oak Ridge, TN 37831 USA. RP Cantrell, JH (reprint author), NASA, Langley Res Ctr, Mail Stop 231, Hampton, VA 23681 USA. NR 12 TC 21 Z9 23 U1 0 U2 11 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 NOV 15 PY 1998 VL 84 IS 10 BP 5469 EP 5472 DI 10.1063/1.368309 PG 4 WC Physics, Applied SC Physics GA 133CP UT WOS:000076669100010 ER PT J AU Bauschlicher, CW Partridge, H AF Bauschlicher, CW Partridge, H TI A comparison of ZnO and ZnO- SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID GAUSSIAN-BASIS SETS; COUPLED-CLUSTER THEORY; MOLECULAR CALCULATIONS; ELECTRON CORRELATION; WAVE-FUNCTIONS; ATOMS; ENERGIES; THERMOCHEMISTRY AB Ab initio electronic structure calculations are performed to support and to help interpret the experimental work reported in the preceding manuscript. The coupled cluster singles and doubles [CCSD(T)] approach, in conjunction with a large basis set, is used to compute spectroscopic constants for the X(1)Sigma(+) and (3)Pi states of ZnO and the X(2)Sigma(+) State of ZnO-. The spectroscopic constants, including the electron affinity (E.A.) are in good agreement with experiment. The ZnO E.A. is significantly larger than that of O, thus relative to the atomic ground-state asymptotes, ZnO- has a larger D-0 than the (1)Sigma(+) state, despite the fact that the extra electron goes into an antibonding orbital. The changes in spectroscopic constants can be understood in terms of the X(1)Sigma(+) formally dissociating to Zn S-1 + O D-1, while the (3)Pi and (2)Sigma(+) states dissociate to Zn S-1(+) O P-3 and Zn S-1 and O- P-2, respectively. (C) 1998 American Institute of Physics. [S0021-9606(98)01943-6]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. EM bauschli@pegasus.arc.nasa.gov; partridg@pegasus.arc.nasa.gov NR 23 TC 33 Z9 33 U1 1 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0021-9606 J9 J CHEM PHYS JI J. Chem. Phys. PD NOV 15 PY 1998 VL 109 IS 19 BP 8430 EP 8434 DI 10.1063/1.477506 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 139AJ UT WOS:000077005000033 ER PT J AU Gilson, J Roemmich, D Cornuelle, B Fu, LL AF Gilson, J Roemmich, D Cornuelle, B Fu, LL TI Relationship of TOPEX/Poseidon altimetric height to steric height and circulation in the North Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID EXPENDABLE BATHYTHERMOGRAPH AB TOPEX/Poseidon altimetric height is compared with 20 transpacific eddy-resolving realizations of steric height. The latter are calculated from temperature (expendable bathythermograph (XBT)) and salinity (expendable conductivity and temperature profiler (XCTD)) profiles along a precisely repeating ship track over a period of 5 years. The overall difference between steric height and altimetric height is 5.2 cm RMS. On long wavelengths (lambda < 500 km), the 3.5 cm RMS difference is due mainly to altimetric measurement errors but also has a component from steric variability deeper than the 800 m limit of the XBT. The data sets are very coherent in the long wavelength band, with coherence amplitude of 0.89. This band contains 65% of the total variance in steric height. On short wavelengths (lambda > 500 km), containing 17% of the steric height variance, the 3.0 cm RMS difference and lowered coherence are due to the sparse distribution of altimeter ground tracks along the XBT section. The 2.4 cm RMS difference in the basin-wide spatial mean appears to be due to fluctuations in bottom pressure. Differences between steric height and altimetric height increase near the western boundary, but data variance increases even more, and so the signal-to-noise ratio is highest in the western quarter of the transect. Basin-wide integrals of surface geostrophic transport from steric height and altimetric height are in reasonable agreement. The 1.9 x 10(4) m(2) s(-1) RMS difference is mainly because the interpolated altimetric height lacks spatial resolution across the narrow western boundary current. A linear regression is used to demonstrate the estimation of subsurface temperature from altimetric data. Errors diminish from 0.8 degrees C at 200 m to 0.3 degrees C at 400 m. Geostrophic volume transport, 0-800 m, shows agreement that is similar to surface transport, with 4.8 Sverdrup (Sv) (10(6) m(3) s(-1)) RMS difference. The combination of altimetric height with subsurface temperature and salinity profiling is a powerful tool for observing variability in circulation and transport of the upper ocean. The continuing need for appropriate subsurface data for verification and for statistical estimation is emphasized. This includes salinity measurements, which significantly reduce errors in specific volume and steric height. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Gilson, J (reprint author), Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. NR 20 TC 71 Z9 74 U1 1 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD NOV 15 PY 1998 VL 103 IS C12 BP 27947 EP 27965 DI 10.1029/98JC01680 PG 19 WC Oceanography SC Oceanography GA 139AF UT WOS:000077004700026 ER PT J AU Bansal, NP Chen, YL AF Bansal, NP Chen, YL TI Chemical, mechanical and microstructural characterization of low-oxygen containing silicon carbide fibers with ceramic coatings SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID HIGH-TEMPERATURES; TENSILE-STRENGTH; WEIBULL MODULUS; NICALON AB Room temperature tensile strengths of as-received Hi-Nicalon fibers and those having BN/SiC, p-BN/SiC, and p-B(Si)N/SiC surface coatings, deposited by chemical vapor deposition, were measured using an average fiber diameter of 13.5 mu m. The Weibull statistical parameters were determined for each fiber. The average tensile strength of uncoated Hi-Nicalon was 3.19 +/- 0.73 GPa with a Weibull modulus of 5.41. Strength of fibers coated with BN/SiC did not change. However, fibers coated with p-BN/SiC and p-B(Si)N1SiC surface layers showed strength loss of similar to 10% and 35%, respectively, compared with the as-received fibers. The elemental compositions of the fibers and the coatings were analyzed using scanning Auger microprobe and energy dispersive X-ray spectroscopy. The BN coating was contaminated with a large concentration of carbon and some oxygen. In contrast, p-BN, p-B(Si)N, and SiC coatings did not show any contamination. Microstructural analyses of the fibers and the coatings were done by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction. Hi-Nicalon fiber consists of fine beta-SiC nanocrystals ranging in size from 1 to 30 nm embedded in an amorphous matrix. TEM analysis of the BN coating revealed four distinct layers with turbostratic structure. The p-BN layer was turbostratic and showed considerable preferred orientation. The p-B(Si)N was glassy and the silicon and boron were uniformly distributed. The silicon carbide coating was polycrystalline with a columnar structure along the growth direction. The p-B(Si)N/SiC coatings were more uniform, less defective and of better quality than the BN/SiC or the p-BN/SiC coatings. (C) 1998 Kluwer Academic Publishers. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Dynacs Inc, Lewis Res Ctr Grp, Brookpark, OH 44142 USA. RP Bansal, NP (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 11 TC 12 Z9 14 U1 0 U2 4 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0022-2461 J9 J MATER SCI JI J. Mater. Sci. PD NOV 15 PY 1998 VL 33 IS 22 BP 5277 EP 5289 DI 10.1023/A:1004404812485 PG 13 WC Materials Science, Multidisciplinary SC Materials Science GA 170YE UT WOS:000078834100001 ER PT J AU Ritzert, FJ Yun, HM Miner, RV AF Ritzert, FJ Yun, HM Miner, RV TI Single crystal fibers of yttria-stabilized cubic zirconia with ternary oxide additions SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID STRENGTH AB Single crystal fibers of yttria (Y2O3)-stabilized cubic zirconia (ZrO2) with ternary oxide additions were grown using the laser float zone fiber processing technique. Ternary additions to the ZrO2-Y2O3 binary system were studied aimed at increasing strength while maintaining the high coefficient of thermal expansion of the binary system. Statistical methods aided in identifying the most promising ternary oxide candidate (Ta2O5, Sc2O3, and HfO2) and optimum composition. The yttria range investigated was 14 to 24 mol% and the ternary oxide component ranged from 1 to 5 mol %. Hafnium oxide was the most promising ternary oxide component based on 816 degrees C tensile strength results and ease of fabrication. The optimum com position for development was 81ZrO(2)-14Y(2)O(3)-5HfO(2) based upon the same elevated temperature strength tests. Preliminary results indicate process improvements could improve the fiber performance. We also investigated the effect of crystal orientation on strength. (C) 11998 Kluwer Academic Publishers. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Ritzert, FJ (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 30 TC 2 Z9 3 U1 2 U2 3 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 NOV 15 PY 1998 VL 33 IS 22 BP 5339 EP 5349 DI 10.1023/A:1004438031140 PG 11 WC Materials Science, Multidisciplinary SC Materials Science GA 170YE UT WOS:000078834100006 ER PT J AU Coon, DN Calomino, AM AF Coon, DN Calomino, AM TI Effective static stress of a sinusoidal cyclic waveform SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article ID REINFORCED SILICON-NITRIDE; CALCIUM ALUMINOSILICATE COMPOSITE; TENSILE CREEP; RECOVERY BEHAVIOR; FATIGUE BEHAVIOR; HIGH-TEMPERATURE; ALUMINA; MECHANISMS; CERAMICS; FAILURE C1 Univ Wyoming, Dept Mech Engn, Laramie, WY 82071 USA. NASA, Lewis Res Ctr, Struct & Mat Branch, Cleveland, OH 44135 USA. RP Coon, DN (reprint author), Univ Wyoming, Dept Mech Engn, Laramie, WY 82071 USA. NR 19 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 NOV 15 PY 1998 VL 17 IS 22 BP 1881 EP 1882 DI 10.1023/A:1006627619446 PG 2 WC Materials Science, Multidisciplinary SC Materials Science GA 170ZW UT WOS:000078838200005 ER PT J AU Minnis, P Garber, DP Young, DF Arduini, RF AF Minnis, P Garber, DP Young, DF Arduini, RF TI Parameterizations of reflectance and effective emittance for satellite remote sensing of cloud properties SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID CIRRUS CLOUDS; ICE CRYSTALS; RADIATIVE PROPERTIES; INFRARED RADIANCES; OPTICAL-CONSTANTS; SINGLE-SCATTERING; AVHRR CHANNELS; TEMPERATURE; INFERENCE; REGION AB The interpretation of satellite-observed radiances to derive cloud optical depth and effective particle size requires radiative transfer calculations relating these parameters to the reflectance, transmittance, and emittance of the cloud. Such computations can be extremely time consuming when used in an operational mode to analyze routine satellite data. Adding-doubling (AD) radiative transfer models are used here to compute reflectance and effective emittance at wavelengths commonly used by operational meteorological satellite imagers for droplet effective radii ranging from 2 to 32 mu m and for distributions of randomly-oriented hexagonal ice crystals with effective diameters varying from 6 to 135 mu m. Cloud reflectance lookup tables were generated at the typical visible-channel wavelength of 0.65 mu m and the solar-infrared (SI) at wavelengths of 3.75 and 3.90 mu m A combination of four-point Lagrangian and linear interpolation between the model nodal points is the most accurate and economical method for estimating reflectance as a function of particle size for any set of solar zenith, viewing zenith, and relative azimuth angles. Compared to exact AD calculations, the four-point method retrieves the reflectance to within +/-3%-9% for water droplets and ice crystals, respectively. Most of the error is confined to scattering angles near distinct features in the phase functions. The errors are reduced to similar to 2% for ice when the assessment is constrained to only those angles that are actually useful in satellite retrievals. Effective emittance, which includes absorption and scattering effects, was computed at SI, infrared (IR; 10.7 and 10.8 mu m), and split-window (WS; 11.9 and 12.0 mu m) wavelengths for a wide range of surface and cloud temperatures using the same ice crystal and water droplet distributions. The results were parameterized with a 32-term polynomial model that depends on the clear-cloud radiating temperature difference, the clear-sky temperature, and viewing zenith angle. A four-point Lagrangian method is used to interpolate between optical depth nodes. The model reproduces the adding-doubling results with an overall accuracy better than +/-2%, 0.4%, and 0.3%, respectively, for the SI, IR, and WS emittances, a substantial reduction in the error compared to earlier parameterizations. Temperatures simulated with the emittance models are within 0.6 and 1 K for water droplets and ice crystals, respectively, in the SI channels. The IR temperatures are accurate to better than +/-0.05 K. During the daytime, the simulations of combined reflectance and emittance for the SI channels are as accurate as the emittance models alone except at particular scattering angles. The magnitudes of the errors depend on the angle, particle size, and solar zenith angle. Examples are given showing the parameterizations applied to satellite data. Computational time exceeds that of previous models but the accuracy gain should yield emittances that are more reliable for retrieval of global cloud microphysical properties. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA USA. Univ Calif Los Angeles, Los Angeles, CA USA. RP Minnis, P (reprint author), NASA, Langley Res Ctr, MS 420, Hampton, VA 23681 USA. RI Garber, Donald/D-7427-2015; Minnis, Patrick/G-1902-2010 OI Minnis, Patrick/0000-0002-4733-6148 NR 40 TC 147 Z9 148 U1 0 U2 5 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 NOV 15 PY 1998 VL 55 IS 22 BP 3313 EP 3339 DI 10.1175/1520-0469(1998)055<3313:PORAEE>2.0.CO;2 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 141YE UT WOS:000077171300001 ER PT J AU Murr, LE Quinones, SA Ferreyra, E Ayala, A Valerio, OL Horz, F Bernhard, RP AF Murr, LE Quinones, SA Ferreyra, E Ayala, A Valerio, OL Horz, F Bernhard, RP TI The low-velocity-to-hypervelocity penetration transition for impact craters in metal targets SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE SEM; soda-lime glass; TEM ID THICK COPPER TARGETS; INITIAL MICROSTRUCTURE; PROJECTILES AB Projectile/target behavior for 1100 Al/Cu, soda-lime glass/Cu, soda-lime glass/1100 Al, ferritic stainless steel/Cu, and ferritic stainless steel/1100 Al for spherical (3.18 mm diameter) projectiles at impact velocities ranging from 0.8 to similar to 6 km s(-1) has been examined by light metallography, SEM, and TEM. At a reference velocity of 1 km s(-1), the crater depth/crater diameter ratio (p/D-c) is observed to be linearly related to bulk density ratios Co,lp,)liz and elastic modulus ratios (E-p/E-t)(rho(p)/rho(t))(1/2), and to vary from about 0.2 to 2.95. The hypervelocity (u(o) > 5 km s(-1)) threshold value for p/D-c is also shown to be linearly related to these functionalities and ranges from p/D-c = 0.4 for the 1100 Al/Cu system and 0.85 for the ferritic stainless steel/1100 Al system. The residual crater microstructures are all characterized by a zone of dynamic recrystallization at the crater wall (which thickens with impact velocity), and decreasing dislocation density beyond this zone; consistent with residual hardness profiles whose amplitudes decrease with distance from the crater wall. Computer simulations and validation of these simulations utilizing the ranges of experimentally measured crater geometries with impact velocity were developed which fairly accurately represented residual crater shapes and related features. These results also demonstrate the importance of appropriate projectile/target strength ratios in computer simulations; and illustrate the potential for extrapolations to new systems, and for impact velocities well beyond those achievable in the laboratory. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. Univ Texas, Inst Mat Res, El Paso, TX 79968 USA. NASA, Lyndon B Johnson Space Ctr, Solar Syst Explorat Div, Houston, TX 77058 USA. Lockheed Engn & Sci Co, Houston, TX 77058 USA. RP Murr, LE (reprint author), Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. OI Murr, Lawrence/0000-0001-5942-8376 NR 20 TC 32 Z9 35 U1 1 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0921-5093 J9 MAT SCI ENG A-STRUCT JI Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process. PD NOV 15 PY 1998 VL 256 IS 1-2 BP 166 EP 182 DI 10.1016/S0921-5093(98)00796-5 PG 17 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 142RF UT WOS:000077213600018 ER PT J AU Kolb, EW Singh, A Srednicki, M AF Kolb, EW Singh, A Srednicki, M TI Quantum fluctuations of axions SO PHYSICAL REVIEW D LA English DT Article ID FINITE-TEMPERATURE; PARTICLE-PRODUCTION; FIELD-THEORY; PHASE-TRANSITIONS; SCALAR FIELD; REAL-TIME; SYMMETRY RESTORATION; INVISIBLE AXION; HARMLESS AXION; INFLATION AB We study the time evolution of the quantum fluctuations of the axion field for both the QCD axion as well as axions arising in the context of supergravity and string theories. We explicitly keep track not only of the coherently oscillating zero momentum mode of the axion but also of the higher non-zero momentum modes using the full axion potential. The full axion potential makes possible two kinds of instabilities: spinodal instabilities and parametric resonance instabilities, The presence of either of these instabilities can lead to a quasi-exponential increase in the occupation of non-zero momentum modes and the build-up of the quantum fluctuations of the axions. If either of these becomes a significant effect then axions would no longer be a suitable cold dark matter candidate. Our results confirm the conventional wisdom that these effects are not significant in the setting of an expanding FRW universe and hence axions are indeed cold dark matter candidates, [S0556-2821(98)04820-6]. C1 Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. RP Kolb, EW (reprint author), Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, POB 500, Batavia, IL 60510 USA. NR 60 TC 7 Z9 7 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD NOV 15 PY 1998 VL 58 IS 10 AR 105004 DI 10.1103/PhysRevD.58.105004 PG 7 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 140UN UT WOS:000077106900055 ER PT J AU Scherrer, RJ Vilenkin, A AF Scherrer, RJ Vilenkin, A TI "Lattice-free" simulations of topological defect formation SO PHYSICAL REVIEW D LA English DT Article ID COSMIC-STRING FORMATION; LARGE-SCALE STRUCTURE; DOMAIN-WALLS; EVOLUTION; MONOPOLES; UNIVERSE AB We examine simulations of the formation of domain walls, cosmic strings, and monopoles on a cubic lattice, in which the topological defects are assumed to lie at the zeros of a piecewise constant 1, 2, or 3 component Gaussian random field, respectively. We derive analytic expressions for the corresponding topological defect densities in the continuum limit and show that they fail to agree with simulation results, even when the fields are smoothed on small scales to eliminate lattice effects. We demonstrate that this discrepancy, which is related to a classic geometric fallacy, is due to the anisotropy of the cubic lattice, which cannot be eliminated by smoothing. This problem can be resolved by linearly interpolating the field values on the lattice, which gives results in good agreement with the continuum predictions. We use this procedure to obtain a lattice-free estimate (for Gaussian smoothing) of the fraction of the total length of string in the form of infinite strings: f(infinity) = 0.716+/-0.015. [S0556-2821(98)03122-1]. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Tufts Univ, Inst Cosmol, Dept Phys & Astron, Medford, MA 02155 USA. RP Scherrer, RJ (reprint author), NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. NR 15 TC 11 Z9 11 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD NOV 15 PY 1998 VL 58 IS 10 AR 103501 DI 10.1103/PhysRevD.58.103501 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 140UN UT WOS:000077106900008 ER PT J AU Tinto, M AF Tinto, M TI Spacecraft to spacecraft coherent laser tracking as a xylophone interferometer detector of gravitational radiation SO PHYSICAL REVIEW D LA English DT Article ID DOPPLER TRACKING AB Searches far gravitational radiation can be performed in space with two spacecraft tracking each other with coherent laser light. Four observables can be measured: two one-way Doppler data (each spacecraft transmits a light beam and the other reads out the Doppler data with an onboard laser), and two two-way Doppler data (light is coherently transponded by the other spacecraft and the Doppler effect is extracted by comparing the phases of transmitted and transponded lights). One-way and two-way tracking data recorded on board the two spacecraft are time tagged and telemetered back to Earth for data analysis. By linearly combining the four data sets, we derive a method for reducing by several orders of magnitude, at selected Fourier components, the frequency fluctuations due to the lasers. The gravitational wave signal remaining at these frequencies makes this spacecraft to spacecraft coherent laser tracking technique the equivalent of a xylophone interferometer detector of gravitational radiation. Estimates for the strain sensitivities achievable with these experiments are presented for gravitational wave bursts, monochromatic signals, and a stochastic background of gravitational radiation. This experimental technique could be implemented with two spacecraft carrying an appropriate optical payload, or with the proposed broadband, space-based laser interferometer detectors of gravitational waves operated in this non-infereometric mode. [S0556-2821(98)08520-8]. 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 mtinto@pop.jpl.nasa.gov NR 20 TC 8 Z9 8 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD NOV 15 PY 1998 VL 58 IS 10 AR 102001 DI 10.1103/PhysRevD.58.102001 PG 12 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 140UN UT WOS:000077106900005 ER PT J AU Hujeirat, A Yorke, HW AF Hujeirat, A Yorke, HW TI On the MHD structure of the solar tachocline. Steady and dynamical solutions SO NEW ASTRONOMY LA English DT Article DE MHD; turbulence; sun : rotation; sun : magnetic fields; sun : interior; methods : numerical ID ANGULAR-MOMENTUM TRANSPORT; CONVECTION ZONE; ROTATION; DEPENDENCE; FIELD; SUN AB Using recent helioseismology measurements, we carry out a parameter study to investigate the steady and unsteady configurations of the solar tachocline (hereafter ST) between the differentially rotating convection zone and the underlying solid-body rotating core. It is shown that in the case of steady solutions, a poloidal magnetic field of quadrupole type topology generates toroidal flux tubes (hereafter B-T) that are three times stronger than in the dipole case. In both cases however, B-T acquires values that are far below those required to overcome distortion via convective turbulence. These values remain rather sensitive to the conditions imposed on the boundaries and on the underlying viscosity prescription. They appear however to have a weak dependence on the width of the ST. For example, imposing a 50 G poloidal field or stronger on the outer boundary yields unsteady solutions only. Using the above-obtained steady configurations as initial conditions, we carried out several calculations to follow the evolution of the flow over several hundred dynamical time scales. It appears that the final dynamical solutions obtained differ significantly from their corresponding initial profiles. Moreover, a large scale polewards oriented motion always results independent of whether magnetic effects are in- or excluded. The numerical results indicate that the ST is likely to be governed by purely hydrodynamical or weakly magnetized flows in order to re-produce Omega-profiles that are consistent with the helioseismology measurements. The storage of a strong B-T in the near-equator region as a possible scenario for the evolution of the sun spots is numerically investigated as well. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Landessternwarte Koenigstuhl, D-69117 Heidelberg, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Astron Inst, D-97074 Wurzburg, Germany. RP Landessternwarte Koenigstuhl, D-69117 Heidelberg, Germany. EM A.Hujeirat@lsw.uni-heidelberg.de; Harold.Yorke@jpl.nasa.gov NR 19 TC 4 Z9 4 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 1384-1076 EI 1384-1092 J9 NEW ASTRON JI New Astron. PD NOV 12 PY 1998 VL 3 IS 8 BP 671 EP 685 DI 10.1016/S1384-1076(98)00036-0 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 139UE UT WOS:000077047400004 ER PT J AU Stothers, RB AF Stothers, RB TI Galactic disc dark matter, terrestrial impact cratering and the law of large numbers SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Review DE methods : statistical; comets : general; Earth; ISM : clouds; Galaxy : kinematics and dynamics; solar neighbourhood ID TELESCOPE STAR COUNTS; SURFACE MASS DENSITY; OORT COMET CLOUD; PERIODICITY HYPOTHESIS; STATISTICAL TEST; EXTINCTIONS; RECORD; SUN; SHOWERS; EVENTS AB A new approach is used to study the old question of missing mass in the Galactic disc. Invoking the law of large numbers, a simple average is formed of the many independent published values of the volume density of solar neighbourhood matter deduced from observational analyses of the gravitational force perpendicular to the Galactic plane. This average value is 0.15 +/- 0.01 M. pc(-3), which should be compared with 0.10 +/- 0.01 Mo pc-3 in known visible matter. The estimated 30 per cent dark matter significantly increases the Galactic z-force, thereby reducing the average half-period of vertical oscillation of the Solar system about the Galactic plane to 37 +/- 4 Myr. A number of previously proposed Galactic mechanisms can both trigger and modulate the rate of gravitational perturbations of the Oort halo of comets. These mechanisms include encounters with massive interstellar clouds and the vertical Galactic tides. Predicted impacts of Oort halo comets on the Earth are broadly compatible with the terrestrial record of large impact craters. A specifically Galactic signature may appear in the 36 +/- 1 Myr mean periodicity of cratering detected in Grieve's updated List of the ages of large impact craters. 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 119 TC 28 Z9 28 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 11 PY 1998 VL 300 IS 4 BP 1098 EP 1104 DI 10.1046/j.1365-8711.1998.02001.x PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 140YD UT WOS:000077097500021 ER PT J AU Barbier, LM Karageorge, E Singh, S AF Barbier, LM Karageorge, E Singh, S TI The POEMS strip detector ASIC chip SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article DE silicon strip detectors; ASIC; magnetic spectrometer ID ELECTRONS AB In this paper we report on the design and performance of a new Application Specific Integrated Circuit (ASIC) for use with silicon strip detectors. This ASIC chip was designed for the Positron-Electron Magnet Spectrometer experiment (POEMS), which has been proposed as a NASA small explorer payload. The ASIC performs as designed, with a noise figure of 800 electrons ENC with a 10 pF load, while using only 170 mu W per channel. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Prime Circuits Inc, Greenbelt, MD 20771 USA. RP Barbier, LM (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. NR 12 TC 1 Z9 1 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 NOV 11 PY 1998 VL 417 IS 2-3 BP 354 EP 359 DI 10.1016/S0168-9002(98)00739-6 PG 6 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 138FG UT WOS:000076960200015 ER PT J AU Poon, TC Juday, R Hara, T AF Poon, TC Juday, R Hara, T TI Spatial light modulators - research, development, and applications: introduction to the feature issue SO APPLIED OPTICS LA English DT Editorial Material C1 Virginia Polytech Inst & State Univ, Bradley Dept Elect Engn, Opt Image Proc Lab, Blacksburg, VA 24061 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Hamamatsu Photon KK, Cent Res Lab, Hamakita 434, Japan. RP Poon, TC (reprint author), Virginia Polytech Inst & State Univ, Bradley Dept Elect Engn, Opt Image Proc Lab, Blacksburg, VA 24061 USA. NR 0 TC 5 Z9 5 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD NOV 10 PY 1998 VL 37 IS 32 BP 7471 EP 7471 DI 10.1364/AO.37.007471 PG 1 WC Optics SC Optics GA 137LK UT WOS:000076916100001 PM 18301580 ER PT J AU Ferrarese, L Bresolin, F Kennicutt, RC Saha, A Stetson, PB Freedman, WL Mould, JR Madore, BF Sakai, S Ford, HC Gibson, BK Graham, JA Han, MS Hoessel, JG Huchra, J Hughes, SM Illingworth, GD Phelps, R Prosser, CF Silbermann, NA AF Ferrarese, L Bresolin, F Kennicutt, RC Saha, A Stetson, PB Freedman, WL Mould, JR Madore, BF Sakai, S Ford, HC Gibson, BK Graham, JA Han, MS Hoessel, JG Huchra, J Hughes, SM Illingworth, GD Phelps, R Prosser, CF Silbermann, NA TI The Hubble Space Telescope key project on the extragalactic distance scale. XII. The discovery of Cepheids and a new distance to NGC 2541 SO ASTROPHYSICAL JOURNAL LA English DT Article DE Cepheids; galaxies : distances and redshifts; galaxies : individual (NGC 2541) ID ABSOLUTE PEAK BRIGHTNESS; BVRI CCD PHOTOMETRY; VARIABLE-STARS; NEARBY GALAXIES; INFRARED PHOTOMETRY; CALIBRATION; CONSTANT; PERFORMANCE; EXTINCTION; WFPC2 AB We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). A total of 25 exposures (divided into 13 epochs) were obtained using the F555W filter (transformed to Johnson V), and nine exposures were obtained (divided into five epochs) using the F814W filter (transformed to Cousins I). Photometric reduction of the data is performed using two independent packages, DoPHOT and DAOPHOT II/ALLFRAME, which give very good agreement in the measured magnitudes. A total of 34 bona fide Cepheids, with periods ranging from 12 to over 60 days, are identified based on both sets of photometry. By fitting V and I period-luminosity relations, apparent distance moduli are derived assuming a Large Magellanic Cloud distance modulus and mean color excess of mu(LMC) = 18.50 +/- 0.10 mag and E(B - V) = 0.10 mag, respectively. Adopting A(V)/E(V - I) = 2.45, we obtain a true distance modulus to NGC 2541 of mu(0) = 30.47 +/- 0.11 (random) +/- 0.12 (systematic) mag (D = 12.4 +/- 0.6 [random] +/- 0.7 [systematic] Mpc), and a total (Galactic plus internal) mean color excess E(B - V) = 0.08 +/- 0.05 (internal error) mag. C1 CALTECH, Pasadena, CA 91125 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. European So Observ, D-8046 Garching, Germany. Kitt Peak Natl Observ, Natl Opt Astron Observ, Tucson, AZ 85726 USA. Dominion Astrophys Observ, Victoria, BC V8X 4M6, Canada. Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Inst Adv Studies, Weston, ACT 2611, Australia. NASA, IPAC Extragalact Database, Pasadena, CA 91125 USA. Carnegie Inst Washington, Dept Terr Magnetism, Baltimore, MD 21218 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 Ferrarese, L (reprint author), CALTECH, Pasadena, CA 91125 USA. RI Gibson, Brad/M-3592-2015 OI Gibson, Brad/0000-0003-4446-3130 NR 70 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 NOV 10 PY 1998 VL 507 IS 2 BP 655 EP 690 DI 10.1086/306364 PN 1 PG 36 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LU UT WOS:000077779700010 ER PT J AU Piner, BG Kingham, KA AF Piner, BG Kingham, KA TI Geodetic VLBI observations of EGRET blazars SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : jets; quasars : individual (0202+149, CTA 26, 1156+295, 1606+106); radio continuum : galaxies ID ACTIVE GALACTIC NUCLEI; EXTRAGALACTIC RADIO-SOURCES; FREQUENCY VARIABLE SOURCES; REFERENCE FRAME SOURCES; GAMMA-RAY EMISSION; MILLIARCSECOND STRUCTURE; SUPERLUMINAL MOTION; BL-LACERTAE; BRIGHTNESS TEMPERATURES; VLA OBSERVATIONS AB We present VLBI observations of the EGRET quasars 0202+149, CTA 26, and 1606+106, as well as additional analysis of VLBI observations of 1156+295 presented in a previous letter. We have produced 8 and 2 GHz VLBI images at II epochs, 8 epochs, and 12 epochs, spanning the years 1989-1996, of 0202+149, CTA 26, and 1606+106, respectively. The VLBI data have been taken from the Washington VLBI correlator's geodetic database. We have measured the apparent velocities of the jet components and find that CTA 26 and 1606+106 are superluminal sources, with average apparent speeds of 8.9 and 2.9 h(-1) c, respectively (H-0 = 100 h km s(-1) Mpc(-1), q(0) = 0.5). The components in 0202+149 are stationary, and we identify this source as a compact F double. These sources all have apparently bent jets, and we detected nonradial motion of components in CTA 26 and 1156 + 295. We have not yet detected any components emerging subsequent to the gamma-ray flares in CTA 26, 1156+295, and 1606+106, and we derive lower limits on the ejection times of any such components. The misalignment angle distribution of the EGRET sources is compared to the distribution for blazars as a whole, and we find that EGRET sources belong preferentially to neither the aligned nor the misaligned population. We also compare the average values for the apparent velocities and Doppler beaming factors for the EGRET and non-EGRET blazars, and find no significant differences. We thus find no indication, within the measurement errors, that EGRET blazars are any more strongly beamed than their counterparts that have not been detected in gamma-rays. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. RP Piner, BG (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,M-S 238-332, Pasadena, CA 91109 USA. NR 75 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 NOV 10 PY 1998 VL 507 IS 2 BP 706 EP 725 DI 10.1086/306346 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LU UT WOS:000077779700012 ER PT J AU Durouchoux, P Vilhu, O Corbel, S Wallyn, P Dwarakanath, KS Huovelin, J Anantharamaiah, KR Grindlay, J Chapuis, C Park, YS Bally, J Mahoney, W AF Durouchoux, P Vilhu, O Corbel, S Wallyn, P Dwarakanath, KS Huovelin, J Anantharamaiah, KR Grindlay, J Chapuis, C Park, YS Bally, J Mahoney, W TI Multiwavelength observation of a new black hole candidate: EXS 1737.9-2952 SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; Galaxy : center; gamma rays : theory; ISM : molecules ID GALACTIC-CENTER; LINE EMISSION; CLOUDS AB We report a multiwavelength analysis of an unusual high-energy transient: EXS 1737.9 - 2952. Due to the features this source exhibited in the hard X-ray domain similar to another source in the Galactic center region (1E1740.9 - 2952), and in order to study the molecular gas toward this X-ray source, we performed an observation of the EXS region in 1993 August, using the Swedish-ESO Submillimeter Telescope (SEST) located in La Silla (Chilean Andes). We observed a cloud, at the "forbidden" velocity of 135 km s(-1), using (CO)-C-12 (1-0) transitions, giving a maximum column density of 8 x 10(21) cm(-2). In 1994 we conducted other observations to search for higher density regions inside the cloud, using HCO+ and CS lines, but they were unsuccessful: we concluded that the cloud could be associated with the X-ray source and its mean density is of the order of approximate to 10(3) cm(-3). In 1994 April, we performed a set of observations of the held containing EXS, at 20 cm and 6 cm, using the VLA in its A configuration, and found four possible radio candidates for an association with the EXS X-ray source, one of them (source 3) being extended, exhibiting a head-tail morphology, and a having a thermal spectrum with a spectral index approximate to -0.7. We reproduced our observation in 1994 November and December, using the C configuration at 6 cm, in order to investigate on possible variability and extension of these sources and found a marginal indication in the 20 cm image that source 3 may have a weak second component displaced about 15 ". Nevertheless, this indication is too faint to associate this source definitely with EXS since no significant variation was detected. In addition, during the 1994 November-December observation, two more extended sources were detected but their association with EXS is unlikely. We also analyzed the Einstein/IPC image of the 5 sigma EXS error box which does not exhibit, at the time of the observation, any significant low-energy X-ray counterpart to EXS. A nearby pulsar PSR 1737 - 30 in the ROSAT catalog is outside this error box. Finally, IRAS maps of the EXS region do not show any IR contribution at the location of the radio sources. We conclude that (1) EXS 1737.9 - 2952 is a high-energy transient, (2) a persistent counterpart at other wavelengths is not demonstrated, and (3) EXS, when flaring, as well as other GC gamma-ray sources, could possibly contribute to the 511 keV bulge emission. C1 Ctr Etud Saclay, DSM, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. Univ Helsinki, Observ, FIN-00014 Helsinki, Finland. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Raman Res Inst, Bangalore 560080, Karnataka, India. Harvard Univ, Ctr Astrophys, Cambridge, MA 02138 USA. Daeduk Radio Telescope, Daejon 305348, South Korea. Univ Colorado, APAS, Boulder, CO 80309 USA. RP Durouchoux, P (reprint author), Ctr Etud Saclay, DSM, DAPNIA, Serv Astrophys, F-91191 Gif Sur Yvette, France. RI Dwarakanath, K /D-4876-2012; Anantharamaiah , K. R./E-5369-2012; Astronomy & Astrophysics Group, Raman Res Institute/D-4046-2012; M, Manjunath/N-4000-2014 OI M, Manjunath/0000-0001-8710-0730 NR 22 TC 2 Z9 2 U1 1 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 NOV 10 PY 1998 VL 507 IS 2 BP 781 EP 793 DI 10.1086/306337 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LU UT WOS:000077779700018 ER PT J AU Smith, MA Robinson, RD Hatzes, AP AF Smith, MA Robinson, RD Hatzes, AP TI A multiwavelength campaign on gamma Cassiopeiae. II. The case for corotating, circumstellar clouds SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; stars : activity; stars : emission-line, Be; stars : individual (gamma Cassiopeiae); stars : rotation ID VARIABILITY; STARS; SPECTRUM AB Simultaneous X-ray/UV observations over a full day on 1996 March 14-15 have been made of the prototypical B0.5e star gamma Cas using the Rossi X-Ray Timing Explorer satellite and the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope. The GHRS spectra, taken in the region of the Si Iv lambda lambda 1394-1403 doublet, also permitted the construction of an extremely precise light curve from a nearby "pseudocontinuum" region. The continuum UV and X-ray light curves reveal a pair of X-ray maxima similar to 10 hr apart that coincide in time with UV continuum flux "dips" of similar to 1%. In the first paper in this series we attributed the long-term X-ray Variations to magnetic activity sites on the surface of the star that undergo rotational modulation on a similar to 1.125 days period. In the current study we find that flux and color curves generated from a 33 hr sequence of Inter national Ultraviolet Explorer (IUE) echellegrams obtained in 1996 January display dip features similar to those in the GHRS data. Comparing the timings of the continuum flux dips and the Si Iv line strength variations in both the GHRS and IUE data sets gives a slightly revised period of 1.123 days for both the UV and X-ray activities. This strengthens the argument that high-energy activity on gamma Cas is modulated by rotation of long-lived structures close to its surface. Analysis of the pseudocontinuum light curves constructed from the GHRS and IUE light curves shows at least two surprising characteristics for the flux dips: (1) the dips last only similar to 0.3 cycles, which is too brief for rotation modulation of surface features, and (2) their amplitudes increase from long to short wavelengths, which attain a maximum near 1206 Angstrom. The character of the variations of the photospheric Si Iv line profiles is unexpected in that the equivalent width fluctuations do not correlate with the slow undulations of the continuum flux. Moreover, the profile variations do not show an expected blue-to-red migration of microfeatures. We show that the continuum characteristics and absence of migration of features in the Si Iv lines can be explained by the presence of very cool, optically thin clouds that corotate with the star. Assuming a tilt of the rotational axis of +45 degrees to the observer's line of sight, our model simulations of the two major dips in the UV light curves indicate that the clouds have radii of a few tenths of a stellar radius and are attached to points on the surface at low to mid-latitudes on the near hemisphere. These findings support the conclusion of the first paper in this series that gamma Cas is a member of a small group of OB stars that have magnetospheres associated with X-ray activity. C1 Space Telescope Sci Inst, STScI CSC, Baltimore, MD 21218 USA. Catholic Univ Amer, Washington, DC 20064 USA. Goddard Space Flight Ctr, LASP, Greenbelt, MD USA. Univ Texas, Dept Astron, Austin, TX 78712 USA. RP Smith, MA (reprint author), Space Telescope Sci Inst, STScI CSC, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 24 TC 27 Z9 27 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 NOV 10 PY 1998 VL 507 IS 2 BP 945 EP 954 DI 10.1086/306347 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LU UT WOS:000077779700029 ER PT J AU Malbet, F Berger, JP Colavita, MM Koresko, CD Beichman, C Boden, AF Kulkarni, SR Lane, BF Mobley, DW Pan, XP Shao, M Van Belle, GT Wallace, JK AF Malbet, F Berger, JP Colavita, MM Koresko, CD Beichman, C Boden, AF Kulkarni, SR Lane, BF Mobley, DW Pan, XP Shao, M Van Belle, GT Wallace, JK TI FU Orionis resolved by infrared long-baseline interferometry at a 2 AU scale SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; circumstellar matter; infrared : stars; instrumentation : interferometers; stars : individual (FU Orionis); stars : pre-main-sequence ID STARS; OBJECTS; ENVELOPES; DISKS AB We present the first infrared interferometric observations of a young stellar object with a spatial projected resolution better than 2 AU. The observations were obtained with the Palomar Testbed Interferometer (PTI). FU Orionis exhibits a visibility of V-2 = 0.72 +/- 0.07 for a 103 +/- 5 m-projected baseline at lambda = 2.2 mu m. On the spatial scale probed by the PTI, the data are consistent with both a binary system scenario (a maximum magnitude difference of 2.7 +/- 0.5 mag and the smallest separation of 0.35 +/- 0.05 AU) and a standard luminous accretion disk model ((M)over dot similar to 6 x 10(-5) M. yr(-1)), where the thermal emission dominates the stellar scattering, and are inconsistent with a single stellar photosphere. C1 Observ Grenoble, Astrophys Lab, UMR UJF CNRS 5571, F-38041 Grenoble 9, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Palomar Observ, Pasadena, CA 91125 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. RP Malbet, F (reprint author), Observ Grenoble, Astrophys Lab, UMR UJF CNRS 5571, BP 53, F-38041 Grenoble 9, France. NR 15 TC 35 Z9 35 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 NOV 10 PY 1998 VL 507 IS 2 BP L149 EP L152 DI 10.1086/311688 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LW UT WOS:000077779900012 ER PT J AU Willacy, K Langer, WD Velusamy, T AF Willacy, K Langer, WD Velusamy, T TI Dust emission and molecular depletion in L1498 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dust, extinction; infrared : ISM : continuum; ISM : clouds; ISM : individual (L1498) ID STAR-FORMING REGIONS; PROTOSTARS; CLOUD; CORE AB We present 100 and 200 mu m ISOPHOT observations of the dense core L1498. We have mapped the central core by using Delta I-200 = I-200 - I-100/theta, where Delta I-200 is a measure of the emission from the cold dust and theta = I-100/I-200 in the outer regions. The dust continuum emission provides information about the chemical depletion and the properties of cold cores where there is a lack of gas tracers. Previous observations of L1498 show that the emission from CS and CCS lies outside of the NH3 core. The peak in Delta I-200 lies close to the previously observed NH3 peak. A comparison with high spatial resolution observations of (CO)-O-18 emission shows that the Delta I-200 maximum coincides with a dip in the (CO)-O-18 emission at the core center. We estimate that the depletion factor for (CO)-O-18 in this region is at least 8 and is likely to be much larger. Such high depletion has significant implications for studies of gas-grain chemistry and protostellar cores. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Willacy, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 169-506, Pasadena, CA 91109 USA. NR 18 TC 57 Z9 58 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 NOV 10 PY 1998 VL 507 IS 2 BP L171 EP L175 DI 10.1086/311695 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LW UT WOS:000077779900017 ER PT J AU Goyal, SK Seyfried, MS O'Neill, PE AF Goyal, SK Seyfried, MS O'Neill, PE TI Effect of digital elevation model resolution on topographic correction of airborne SAR SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID SOIL-MOISTURE; RADAR IMAGERY; DEPENDENCE AB Topography in high relief mountainous areas may mask the signal variation in airborne Synthetic Aperture Radar (SAR) data caused by soil moisture, surface roughness and vegetation. It also affects the quality of image calibration and registration. Good quality calibration and registration are required for the use of SAR in the estimation of soil water. To address the problem of topographic effects, the widely available standard 30 m x 30 m United States Geological Survey (USGS) Digital Elevation Model(DEM) has been incorporated into SAR calibration and registration programs. The topographic resolution of SAR imagery relative to the USGS DEM was examined by comparing the correlation between incident angle (theta) and SAR backscatter (sigma(0)) in a high resolution DEM (mapped at 1:4800 and 1:600 from aerial photography for two small areas) to that in the USGS DEM (mapped at 1:240<(00)over bar>). We found that SAR resolved topographic features not resolved by the USGS DEM. Filtering and aggregation techniques were applied to reduce speckle, the apparent noise due to small topographic features resolved by SAR but not resolved by the USGS DEM, and the registration error. Increasing the filter window from 3 x 3 to 5 x 5 to 9 x 9 and the cell size from 6 m x 12 m to 30 m x 30 m to 90 m x 90 m, reduced the unexplained variability in backscatter by 50%. However, there was considerable unexplained variability at all levels of filtering and aggregation. Aggregation to 90 m x 90 m cell size resulted in blurred or obscured surface features of hydrological interest. Filtering with a 9 x 9 window and resolution cell size of 30 m x 30 m was found to be optimal in terms of the amount of variability explained and the kinds of landscape features retained. Even after applying filtering and aggregation techniques, the correlation between sigma(0) and theta for the high resolution DEM (r = 0.54) was much better than for the USGS DEM (r = 0.36). Correction functions for the numerical estimation of terrain influence on the backscatter variation in the SAR image were derived using empirical imaging models. Topographic effects on sigma(0) were further reduced in the corrected images. However, even after correction there was considerable unexplained sigma(0) variability, some of which could be attributed to major topographic features. Thus, landscape features other than theta need to be incorporated in topographic correction procedures. C1 Idaho Dept Water Resources, Boise, ID 83706 USA. ARS, USDA, Boise, ID 83712 USA. NASA, Hydrol Sci Branch 974, Lab Hydrospher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Goyal, SK (reprint author), Idaho Dept Water Resources, 1301 N Orchard St, Boise, ID 83706 USA. RI O'Neill, Peggy/D-2904-2013 NR 29 TC 14 Z9 16 U1 1 U2 2 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD NOV 10 PY 1998 VL 19 IS 16 BP 3075 EP 3096 DI 10.1080/014311698214190 PG 22 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 137UG UT WOS:000076934300004 ER PT J AU Na, Y Moin, P AF Na, Y Moin, P TI Direct numerical simulation of a separated turbulent boundary layer SO JOURNAL OF FLUID MECHANICS LA English DT Article ID FLOW AB A separated turbulent boundary layer over a flat plate was investigated by direct numerical simulation of the incompressible Navier-Stokes equations. A suction-blowing velocity distribution was prescribed along the upper boundary of the computational domain to create an adverse-to-favourable pressure gradient that produces a closed separation bubble. The Reynolds number based on inlet free-stream velocity and momentum thickness is 300. Neither instantaneous detachment nor reattachment points are fixed in space but fluctuate significantly. The mean detachment and reattachment locations determined by three different definitions, i.e. (i) location of 50% forward flow fraction, (ii) mean dividing streamline (phi = 0), (iii) location of zero wall-shear stress (<(tau)over bar>(w) = 0), are in good agreement. Instantaneous vorticity contours show that the turbulent structures emanating upstream of separation move upwards into the shear layer in the detachment region and then turn around the bubble. The locations of the maximum turbulence intensities as well as Reynolds shear stress occur in the middle of the shear layer. In the detached flow region, Reynolds shear stresses and their gradients are large away from the wall and thus the largest pressure fluctuations are in the middle of the shear layer. Iso-surfaces of negative pressure fluctuations which correspond to the core region of the vortices show that large-scale structures grow in the shear layer and agglomerate. They then impinge on the wall and subsequently convect downstream. The characteristic Strouhal number St = f(in)(delta)*/U(0) associated with this motion ranges from 0.0025 to 0.01. The kinetic energy budget in the detachment region is very similar to that of a plane mixing layer. C1 Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Na, Y (reprint author), Stanford Univ, Dept Mech Engn, Stanford, CA 94305 USA. NR 30 TC 113 Z9 113 U1 0 U2 17 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD NOV 10 PY 1998 VL 374 BP 379 EP 405 DI 10.1017/S0022112098009987 PG 27 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 141KL UT WOS:000077142900014 ER PT J AU Sakimoto, SEH Zuber, MT AF Sakimoto, SEH Zuber, MT TI Flow and convective cooling in lava tubes SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID KILAUEA VOLCANO; ALBA-PATERA; HAWAII; KUPAIANAHA; MARS; CONSTRAINTS; EMPLACEMENT; ERUPTIONS; FIELD AB Tube-fed basaltic lava flows with lengths ranging from 10 to 200 km are inferred to exhibit similar amounts of cooling. To explain the wide range of implied cooling rates, we consider forced convection as a dominant cooling process in lava tubes and present solutions that express mean temperature versus distance down the tube as a function of flow rate and flow cross section. Our models treat forced convective thermal losses in steady laminar flow through a lava tube with constant temperature walls and constant material properties. We explore the effects of different wall temperature and heat flux rate boundary conditions for circular tube and parallel plate flows over a range of tube sizes, plate spacings, eruption temperatures, and volume flow rates. Results show that nonlinear cooling rates over distance are characteristic of constant wall temperature for a piecewise parallel plate/circular tube model. This provides the best fit to temperature observations for Hawaiian tubes. Such a model may also provide an explanation for the very low (similar to 10 degrees C) cooling observed in similar to 10 km long Hawaii tube flows and inferred in longer similar to 50 to 150 km tube-fed flows in Queensland. The forced convective cooling model may also explain similar flow morphologies for long tube-fed basaltic lava flows in a wide variety of locations, since small variations in eruption temperature or flow rate can accommodate the entire range of flow lengths and cooling rates considered. Our results are consistent with previous suggestions that long basaltic flows may be a reflection of low slopes, a particularly steady moderate eruption rate, and well-insulated flow, rather than of high discharge rates. C1 NASA, Geodynam Branch, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA USA. NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Sakimoto, SEH (reprint author), NASA, Geodynam Branch, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 921, Greenbelt, MD 20771 USA. EM sakimoto@denali.gsfc.nasa.gov; zuber@tharsis.gsfc.nasa.gov NR 80 TC 45 Z9 46 U1 2 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD NOV 10 PY 1998 VL 103 IS B11 BP 27465 EP 27487 DI 10.1029/97JB03108 PG 23 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 137MQ UT WOS:000076918900037 ER PT J AU Chung, DJH Kolb, EW Riotto, A AF Chung, DJH Kolb, EW Riotto, A TI Nonthermal supermassive dark matter SO PHYSICAL REVIEW LETTERS LA English DT Article ID PARTICLE-PRODUCTION; BUBBLE COLLISIONS; INFLATION; UNIVERSE; DECAY AB We discuss several cosmological production mechanisms for nonthermal supermassive dark matter and argue that dark matter may be elementary particles of mass much greater than the weak scale. Searches for dark matter should not be limited to weakly interacting particles with mass of the order of the weak scale, but should extend into the supermassive range as well. [S0031-9007(98)07529-2]. C1 Univ Chicago, Dept Phys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Chicago, IL 60637 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. CERN, Div Theory, CH-1211 Geneva 23, Switzerland. RP Chung, DJH (reprint author), Univ Chicago, Dept Phys, Chicago, IL 60637 USA. EM djchung@theory.uchicago.edu; rocky@rigoletto.fnal.gov; riotto@nxth04.cern.ch NR 27 TC 153 Z9 154 U1 1 U2 2 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 NOV 9 PY 1998 VL 81 IS 19 BP 4048 EP 4051 DI 10.1103/PhysRevLett.81.4048 PG 4 WC Physics, Multidisciplinary SC Physics GA 139CW UT WOS:000077011000005 ER PT J AU Matsunaga, H Orito, S Matsumoto, H Yoshimura, K Moiseev, A Anraku, K Golden, R Imori, M Makida, Y Mitchell, J Motoki, M Nishimura, J Nozaki, M Ormes, J Saeki, T Sanuki, T Streitmatter, R Suzuki, J Tanaka, K Ueda, I Yajima, N Yamagami, T Yamamoto, A Yoshida, T AF Matsunaga, H Orito, S Matsumoto, H Yoshimura, K Moiseev, A Anraku, K Golden, R Imori, M Makida, Y Mitchell, J Motoki, M Nishimura, J Nozaki, M Ormes, J Saeki, T Sanuki, T Streitmatter, R Suzuki, J Tanaka, K Ueda, I Yajima, N Yamagami, T Yamamoto, A Yoshida, T TI Measurement of low-energy cosmic-ray antiprotons at solar minimum SO PHYSICAL REVIEW LETTERS LA English DT Article ID BLACK-HOLES; FLUX AB The absolute fluxes of the cosmic-ray antiprotons at solar minimum are measured in the energy range 0.18 to 1.4 GeV, based on 43 events unambiguously detected in BESS 1995 data. The resultant energy spectrum appears to be flat below 1 GeV, compatible with a possible admixture of primary antiproton component with a soft energy spectrum, while the possibility of secondary antiprotons alone explaining the data cannot be excluded with the present accuracy. Further improvement of statistical accuracy and extension of the energy range are planned in future BESS flights. [S0031-9007(98)07573-5]. C1 Univ Tokyo, Tokyo 1130033, Japan. Kobe Univ, Kobe, Hyogo 6578501, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. KEK, High Energy Accelerator Res Org, Tsukuba, Ibaraki 3050801, Japan. Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. RP Matsunaga, H (reprint author), Univ Tokyo, Tokyo 1130033, Japan. EM oriton@icepp.s.u-tokyo.ac.jp RI MOTOKI, Masakazu/B-4212-2009 NR 23 TC 62 Z9 62 U1 1 U2 2 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 NOV 9 PY 1998 VL 81 IS 19 BP 4052 EP 4055 DI 10.1103/PhysRevLett.81.4052 PG 4 WC Physics, Multidisciplinary SC Physics GA 139CW UT WOS:000077011000006 ER PT J AU Doshi, B Brennan, KF Bicknell-Tassius, R Grunthaner, F AF Doshi, B Brennan, KF Bicknell-Tassius, R Grunthaner, F TI The effect of strain-induced polarization fields on impact ionization in a multiquantum-well structure SO APPLIED PHYSICS LETTERS LA English DT Article ID INGAAS/INALAS SUPERLATTICE; AVALANCHE PHOTODIODE; GAN; HETEROSTRUCTURE; ENHANCEMENT; ZINCBLENDE; CHARGE; APD AB We present a mechanism for enhancing the electron impact ionization rate based on the strain-induced polarization fields in a strained multiquantum-well system. To illustrate the concept, the electron ionization rate is calculated for a strained GaN and Al0.3Ga0.7N multiquantum-well device. The presence of the polarization fields within the Al0.3Ga0.7N layers provides an additional mechanism for carrier heating to the conduction band edge discontinuity of earlier simple multiquantum-well avalanche photodiode designs. It is found that the ionization rate is substantially enhanced over both its bulk GaN value and that for an unstrained multiquantum-well structure. (C) 1998 American Institute of Physics. [S0003-6951(98)01445-4]. C1 Georgia Tech, Sch Elect & Comp Engn, Atlanta, GA 30332 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Brennan, KF (reprint author), Georgia Tech, Sch Elect & Comp Engn, Atlanta, GA 30332 USA. NR 25 TC 10 Z9 10 U1 1 U2 5 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 NOV 8 PY 1998 VL 73 IS 19 BP 2784 EP 2786 DI 10.1063/1.122590 PG 3 WC Physics, Applied SC Physics GA 134HF UT WOS:000076736900028 ER PT J AU Babinski, A Wysmolek, A Tomaszewicz, T Baranowski, JM Leon, R Lobo, C Jagadish, C AF Babinski, A Wysmolek, A Tomaszewicz, T Baranowski, JM Leon, R Lobo, C Jagadish, C TI Electrically modulated photoluminescence in self-organized InGaAs/GaAs quantum dots SO APPLIED PHYSICS LETTERS LA English DT Article ID LASERS; SPECTROSCOPY; SYSTEMS AB Results of photoluminescence (PL) study of the self-organized InGaAs/GaAs quantum dots (QDs) in a field-effect structure grown by metalorganic vapor phase epitaxy are presented. It has been found that the PL from the QDs strongly depends on the bias voltage. No PL from the QDs ground state can be observed from the reverse biased structure, whereas the PL signal recovers in the forward biased structure. It is proposed that the bias dependence of the PL signal results from the QDs electron occupancy changes driven by the electric field within the structure. Due to a long thermalization time, the photogenerated electrons are swept out of the QDs by the electric field before radiative recombination. The electrically modulated PL (e-m PL), making use of the bias dependence of PL signal, is proposed as a tool for QD investigation. The e-m PL spectra at T=300 and T=4.2 K are analyzed and discussed. (C) 1998 American Institute of Physics. [S0003-6951(98)02345-6]. C1 Univ Warsaw, Inst Expt Phys, PL-00681 Warsaw, Poland. Australian Natl Univ, Res Sch Phys Sci & Engn, Inst Adv Studies, Dept Elect Mat Engn, Canberra, ACT 0200, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Babinski, A (reprint author), Univ Warsaw, Inst Expt Phys, Hoza 69, PL-00681 Warsaw, Poland. EM adam.babinski@fuw.edu.pl; cxj109@rsphysse.anu.edu.au RI Lobo, Charlene/B-3977-2013; Lobo, Charlene/G-5003-2011; OI Lobo, Charlene/0000-0002-2746-1363; Lobo, Charlene/0000-0002-2746-1363; Babinski, Adam/0000-0002-5591-4825 NR 19 TC 6 Z9 6 U1 0 U2 3 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 NOV 8 PY 1998 VL 73 IS 19 BP 2811 EP 2813 PG 3 WC Physics, Applied SC Physics GA 134HF UT WOS:000076736900037 ER PT J AU Showalter, MR AF Showalter, MR TI Detection of centimeter-sized meteoroid impact events in Saturn's F ring SO SCIENCE LA English DT Article ID B-RING; SPOKES; PLANETARY; EVOLUTION; SATELLITES AB Voyager images reveal that three prominent clumps in Saturn's F ring were short-lived, appearing rapidly and then spreading and decaying in brightness over periods of similar to 2 weeks. These features arise from hypervelocity impacts by similar to 10-centimeter meteoroids into F ring bodies. Future ring observations of these impact events could constrain the centimeter-sized component of the meteoroid population, which is otherwise unmeasurable but plays an import ant role in the evolution of rings and surfaces in the outer solar system. The F ring's numerous other trumps are much longer lived and appear to be unrelated to impacts. C1 Stanford Univ, Space Telecommun & Radiosci Lab, Stanford, CA 94305 USA. RP Showalter, MR (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 29 TC 37 Z9 37 U1 0 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD NOV 6 PY 1998 VL 282 IS 5391 BP 1099 EP 1102 DI 10.1126/science.282.5391.1099 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 136YY UT WOS:000076887700043 PM 9804543 ER PT J AU Patnaik, SN Hopkins, DA AF Patnaik, SN Hopkins, DA TI Optimality of a fully stressed design SO COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING LA English DT Article AB For a truss a fully stressed state is reached when all its members are utilized to their full strength capacity. Historically, engineers considered such a design optimum. But recently this optimality has been questioned, especially since the weight of the structure is not explicitly used in fully stressed design calculations. This paper examines optimality of the fully stressed design (FSD) with analytical and graphical illustrations. Solutions for a set of examples obtained by using the FSD method and optimization methods numerically confirm the optimality of the FSD. The FSD, which can be obtained with a small amount of calculation, can be extended to displacement constraints and to nontruss-type structures. (C) 1998 Elsevier Science S.A. All rights reserved. C1 Ohio Aerosp Inst, Cleveland, OH 44142 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Patnaik, SN (reprint author), Ohio Aerosp Inst, Cleveland, OH 44142 USA. NR 12 TC 16 Z9 18 U1 1 U2 2 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 NOV 2 PY 1998 VL 165 IS 1-4 BP 215 EP 221 DI 10.1016/S0045-7825(98)00041-3 PG 7 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications; Mechanics SC Engineering; Mathematics; Mechanics GA 147XW UT WOS:000077523700010 ER PT J AU Jaworske, DA AF Jaworske, DA TI Correlation of predicted and observed optical properties of multilayer thermal control coatings SO THIN SOLID FILMS LA English DT Article; Proceedings Paper CT 25th International Conference on Metallurgical Coatings and Thin Films CY APR 25-MAY 01, 1998 CL SAN DIEGO, CALIFORNIA SP Vacuum Met, Thin Film Div, AVS DE thermal control coatings; optical properties AB Thermal control coatings on spacecraft will be increasingly important as spacecraft grow smaller and more compact. New thermal control coatings will be needed to meet the demanding requirements of next generation spacecraft. Computer programs are now available to design optical coatings, and one such program was used to design several thermal control coatings consisting of alternating layers of WO3 and SiO2. The coatings were subsequently manufactured with electron beam evaporation and characterized with both optical and thermal techniques. Optical data were collected in both the visible region of the spectrum and the infrared. Solar absorptance values were predicted in the range of 0.177-0.196 and were observed in the range of 0.155-0.228. Infrared emittance values were predicted in the range of 0.074-0.083 and were observed optically in the range 0.048-0.093 and calorimetrically in the range of 0.069-0.100. (C) 1998 Elsevier Science S.A. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Jaworske, DA (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 15 Z9 16 U1 0 U2 3 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0040-6090 J9 THIN SOLID FILMS JI Thin Solid Films PD NOV 2 PY 1998 VL 332 IS 1-2 BP 30 EP 33 DI 10.1016/S0040-6090(98)01043-8 PG 4 WC Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 142LT UT WOS:000077202500007 ER PT J AU Fieseler, PD AF Fieseler, PD TI A method for solar sailing in a low earth orbit SO ACTA ASTRONAUTICA LA English DT Article ID SPACECRAFT TRAJECTORIES; COEFFICIENTS AB It has been widely accepted that solar sails are incapable of operating in low earth orbits due to drag from the residual atmosphere overcoming the sunlight induced thrust. This limitation seems to require that a solar sail always maintain an altitude greater than approximately 1000 km above the earth's surface. Placing a sail at this altitude first requires a fairly large launch Vehicle which increases the cost of any proposed solar sail mission or proof of concept flight. The inability to access low altitudes also has effectively negated the possibility of using a solar sail as a low cost orbital transfer vehicle. This paper describes a new configuration of solar sail that will allow operation in high inclination earth orbits from under 350 km circular out to interplanetary space. Two possible sail configurations are described and their operation, advantages over previous sail designs and limitations are discussed: Spacecraft drag reduction technique involving the use of a shield made of a solar sail like material is: developed. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Fieseler, PD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 31 TC 12 Z9 14 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD NOV PY 1998 VL 43 IS 9-10 BP 531 EP 541 DI 10.1016/S0094-5765(98)00175-1 PG 11 WC Engineering, Aerospace SC Engineering GA 154JH UT WOS:000077885400009 ER PT J AU Frink, NT AF Frink, NT TI Tetrahedral unstructured Navier-Stokes method for turbulent flows SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 34th Aerospace Sciences Meeting and Exhibit CY JAN 15-19, 1996 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut ID EULER EQUATIONS; GRIDS AB A method is presented for solving the Navier-Stokes equations for turbulent how problems on three-dimensional unstructured grids, Spatial discretization is accomplished by a cell-centered, finite volume formulation using an accurate linear reconstruction scheme and upwind flux differencing. Time is advanced by an implicit backward Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model (Spalart, P. R,, and Allmaras, S. R,, "A One-Equation Turbulence Model for Aerodynamic Flows," AIAA Paper 92-0439, Jan. 1992), which is coupled with a wall function to reduce the number of cells in the sublayer region of the boundary layer. A systematic assessment of the method is presented to devise guidelines for more strategic application of the technology to complex problems. The assessment includes the accuracy in predictions of the skin-friction coefficient, law-of-the-wall behavior, and surface pressure for a flat-plate turbulent boundary layer and for the ONERA M6 wing under a high-Reynolds-number, transonic, separated flow condition. C1 NASA, Langley Res Ctr, Configurat Aerodynam Branch, Aerodynam & Gas Dynam Div, Hampton, VA 23681 USA. RP Frink, NT (reprint author), NASA, Langley Res Ctr, Configurat Aerodynam Branch, Aerodynam & Gas Dynam Div, Mail Stop 499, Hampton, VA 23681 USA. NR 28 TC 36 Z9 38 U1 3 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1998 VL 36 IS 11 BP 1975 EP 1982 DI 10.2514/2.324 PG 8 WC Engineering, Aerospace SC Engineering GA 139EB UT WOS:000077014000005 ER PT J AU Tsynkov, SV Vatsa, VN AF Tsynkov, SV Vatsa, VN TI Improved treatment of external boundary conditions for three-dimensional flow computations SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA 13th Computational Fluid Dynamics Conference CY JUN 29-JUL 02, 1997 CL SNOWMASS VILLAGE, COLORADO SP Amer Inst Aeronaut & Astronaut AB An innovative numerical approach is presented for setting highly accurate nonlocal boundary conditions at the external computational boundaries when calculating three-dimensional compressible viscous flows over finite bodies. The approach is based on application of the special boundary operators analogous to Calderon's projections (Calderon, A. P., "Boundary-Value Problems for Elliptic Equations:" Proceedings of the Soviet-American Conference on Partial Differential Equations at Novosibirsk, Fizmatgiz, Moscow 1963, pp. 303, 304) and the difference potentials method by Ryaben'kii [Ryaben'kii, V. S.,"Boundary Equations with Projections:" Russian Mathematical Surveys, Vol. 40, No. 2, 1985, pp. 147-183; Ryaben'kii, V. S., Difference Potentials Method for Some Problems of Continuous Media Mechanics, Nauka, Moscow 1987 (in Russian); and Ryaben'kii, V. S., "Differcnce Potentials Method and Its Applications:" Mathematische Nachrichten, Vol. 177, Feb. 1996, pp. 251-264]; it extends the previous technique developed for the two-dimensional case. The new boundary conditions methodology has been successfully combined with the NASA-developed code TLNS3D and used for the analysis of wing-shaped configurations in subsonic and transonic how regimes. As demonstrated by the computational experiments, the improved external boundary conditions allow one to greatly reduce the size of the computational domain while still maintaining high accuracy of the numerical solution. Moreover, they may provide for a noticeable speedup of convergence of the multigrid iterations. C1 NASA, Langley Res Ctr, Aerodynam & Acoust Methods Branch, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. RP Tsynkov, SV (reprint author), Tel Aviv Univ, Sch Math Sci, Dept Math Appl, IL-69978 Tel Aviv, Israel. NR 26 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 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1998 VL 36 IS 11 BP 1998 EP 2004 DI 10.2514/2.327 PG 7 WC Engineering, Aerospace SC Engineering GA 139EB UT WOS:000077014000008 ER PT J AU Rohloff, TJ Whitmore, SA Catton, I AF Rohloff, TJ Whitmore, SA Catton, I TI Air data sensing from surface pressure measurements using a neural network method SO AIAA JOURNAL LA English DT Article AB Neural networks have been successfully developed to estimate freestream static and dynamic pressures from an array of pressure measurements taken from ports located flush on the nose of an aircraft. Specific techniques were developed for extracting a proper set of neural network training patterns from an abundant archive of data. Additionally, the specific techniques used to train the neural networks for this project were reported, including the scheduled adjustments to learning rate parameters during the training process. The performance of the trained networks was compared to the accuracy of the aerodynamic model that is currently being applied to these flush air data sensing systems. C1 Univ Calif Los Angeles, Dept Mech & Aerosp Engn, Los Angeles, CA 90095 USA. NASA, Dryden Flight Res Ctr, Vehicle Dynam Grp, Aerodynam Branch, Edwards, 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 9 TC 8 Z9 8 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD NOV PY 1998 VL 36 IS 11 BP 2094 EP 2101 DI 10.2514/2.312 PG 8 WC Engineering, Aerospace SC Engineering GA 139EB UT WOS:000077014000020 ER PT J AU Visscher, PT Reid, RP Bebout, BM Hoeft, SE Macintyre, IG Thompson, JA AF Visscher, PT Reid, RP Bebout, BM Hoeft, SE Macintyre, IG Thompson, JA TI Formation of lithified micritic laminae in modern marine stromatolites (Bahamas): The role of sulfur cycling SO AMERICAN MINERALOGIST LA English DT Article ID SOLAR LAKE SINAI; CYANOBACTERIAL MATS; SULFATE REDUCTION; SUBTIDAL STROMATOLITES; MICROBIAL MATS; EXUMA-CAYS; SEDIMENTS; SULFIDE; DISSOLUTION; OXYGEN AB Microbial mats on the surfaces of modern, marine stromatolites at Highborne Gay, Bahamas, were investigated to assess the role of microbial processes in stromatolite formation. The Highborne Cay stromatolitic mats contain Schizothix as the dominant cyanobacterium and show millimeter-scale lamination: Some layers in the mat are soft (unlithified), whereas other layers are crusty (lithified). Lithified layers within the mats correspond to micritic horizons composed of thin (20-50 mu m) micritic crusts, which commonly overlie truncated, micritized carbonate sand grains. These features are identical to lithified laminae in the underlying stromatolite; the micritic crusts are similar in thickness to micritic laminae in many ancient stromatolites. Biogeochemical parameters in a representative stromatolitic mat from Highborne Cay were measured to identify the role of bacteria in precipitation and dissolution of CaCO3. Depth distributions of O-2, HS-, and pH were determined with microelectrode measurements in the field. Oxygen profiles were used to calculate photosynthesis and aerobic respiration. Sulfate reduction was determined using (SO42-)-S-35 and sulfide oxidation potential was measured in homogenized samples. Our results indicate that cyanobacterial photosynthesis, sulfate reduction, and anaerobic sulfide oxidation in stromatolitic mats at Highborne Cay are responsible for CaCO3 precipitation, whereas aerobic respiration and aerobic sulfide oxidation cause CaCO3 dissolution. A close coupling of photosynthesis and aerobic respiration in the uppermost few millimeters of the mats results in no, or very little, net lithification. Sulfur cycling, on the other hand, shows a close correlation with the formation of lithified micritic layers. Photosynthesis, combined with sulfate reduction and sulfide oxidation results in net lithification. Sulfate reduction rates are high in the uppermost lithified layer and, on a diel basis, consume 33-38% of the CO2 fixed by the cyanobacteria. In addition, this lithified layer contains a significant population of sulfide-oxidizing bacteria and shows a high sulfide oxidation potential. These findings argue that photosynthesis coupled to sulfate reduction and sulfide oxidation is more important than photosynthesis coupled to aerobic respiration in the formation of lithified micritic laminae in Highborne Cay stromatolites. C1 Univ Connecticut, Dept Marine Sci, Groton, CT 06340 USA. Univ Miami, Rosenstiel Sch Marine & Atmospher Sci, Div Marine Geol & Geophys, Miami, FL 33149 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Smithsonian Inst, Natl Museum Nat Hist, Dept Paleobiol, Washington, DC 20560 USA. Tabor Acad, Marion, MA 02738 USA. RP Visscher, PT (reprint author), Univ Connecticut, Dept Marine Sci, Groton, CT 06340 USA. EM visscher@uconnvm.uconn.edu NR 46 TC 156 Z9 160 U1 3 U2 19 PU MINERALOGICAL SOC AMER PI CHANTILLY PA 3635 CONCORDE PKWY STE 500, CHANTILLY, VA 20151-1125 USA SN 0003-004X EI 1945-3027 J9 AM MINERAL JI Am. Miner. PD NOV-DEC PY 1998 VL 83 IS 11-12 BP 1482 EP 1493 PN 2 PG 12 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA 145YE UT WOS:000077399200009 ER PT J AU Larsen, I Little, B Nealson, KH Ray, R Stone, A Tian, JH AF Larsen, I Little, B Nealson, KH Ray, R Stone, A Tian, JH TI Manganite reduction by Shewanella putrefaciens MR-4 SO AMERICAN MINERALOGIST LA English DT Article ID MANGANESE(IV) OXIDES; MICROBIAL REDUCTION; DISSOLUTION; GROWTH; ORGANICS; SULFUR AB Previous studies have documented dissimilatory growth of bacteria on solid Mn4+ oxide, but Mn3+ oxides have not been previously studied; here we have demonstrated for the first time the bacterial reduction of manganite. Strain MR-4 of Shewanella putrefaciens was able to grow on and rapidly reduce insoluble needle-shaped crystals of synthetic manganite (MnOOH), converting them to soluble Mn2+ in the process. The rate of Mn3+ reduction was optimal at pH of 7.0 and 26 degrees C consistent with an enzymatic reaction. In addition the rates of reduction were in proportion to the amount of manganite added, but nearly independent of the cell concentration present (e.g., cell number had only a small effect on the rate of Mn3+ reduction at early stages of growth) suggesting that surface properties were dictating the rates of metal reduction. This thesis was supported by major differences in reduction rates when Mn oxides of different surface areas were studied. Removal of the carbon source (formate or lactate) or addition of metabolic inhibitors reduced the rate of metal reduction. No Mn3+ reduction was observed when the samples were oxygenated, nor when the cells were separated from the Mn3+ oxide by a dialysis membrane. Environmental scanning electron microscopy (ESEM) images showed close contact of the cells with the needle-shaped crystals during early stages of reduction. In later stages, the closely associated cells were coated with a layer of extracellular polymeric material that obscured the cells when viewed by ESEM. When manganite crystals were dried and gold coated, and viewed by standard scanning electron microscopy (SEM), abundant bacteria could be seen on the surface of the metal oxide in a thin biofilm-like layer. The layer of extracellular polymer is a new finding, and neither the composition, function, nor importance in the manganese reduction process have been elucidated. C1 Univ Wisconsin, Ctr Great Lakes Studies, Milwaukee, WI 53204 USA. USN, Res Lab, Stennis Space Ctr, MS 39529 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Johns Hopkins Univ, Dept Geog & Environm Engn, Baltimore, MD 21218 USA. RP Larsen, I (reprint author), Univ Wisconsin, Ctr Great Lakes Studies, 600 E Greenfield Ave, Milwaukee, WI 53204 USA. RI Stone, Alan/A-2569-2010 OI Stone, Alan/0000-0002-3660-1129 NR 17 TC 16 Z9 16 U1 0 U2 9 PU MINERALOGICAL SOC AMER PI WASHINGTON PA 1015 EIGHTEENTH ST, NW SUITE 601, WASHINGTON, DC 20036 USA SN 0003-004X J9 AM MINERAL JI Am. Miner. PD NOV-DEC PY 1998 VL 83 IS 11-12 BP 1564 EP 1572 PN 2 PG 9 WC Geochemistry & Geophysics; Mineralogy SC Geochemistry & Geophysics; Mineralogy GA 145YE UT WOS:000077399200017 ER PT J AU Mouroulis, P Wilson, DW Maker, PD Muller, RE AF Mouroulis, P Wilson, DW Maker, PD Muller, RE TI Convex grating types for concentric imaging spectrometers SO APPLIED OPTICS LA English DT Article ID DIFFRACTIVE OPTICAL-ELEMENTS; RAPID FABRICATION; EFFICIENCY; HOLOGRAMS AB The properties of convex gratings fabricated by electron-beam lithography are investigated. Three grating types are shown. The first is a single-panel, true blazed grating in which the blaze angle stays constant relative to the local surface normal. This grating provides high peak efficiencies of approximately 88% in the first order and 85% in the second order. The second grating has two concentric panels, with each panel blazed at a different angle. This type permits flexibility in matching the grating response to a desired form. The third type has a groove shape that departs from the sawtooth blazed profile to increase the second-order bandwidth. All these types are difficult or impossible to produce with conventional techniques. The gratings compare favorably with conventional (holographic and ruled) types in terms of efficiency and scatter. Simple scalar models are shown to predict the wavelength response accurately. These gratings allow the optical designer to realize fully the considerable advantages of concentric spectrometer forms. (C) 1998 Optical Society of America OCIS codes: 050.1940, 050.1950, 050.2770, 120.6200, 220.4000. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Mouroulis, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 42 Z9 58 U1 2 U2 9 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD NOV 1 PY 1998 VL 37 IS 31 BP 7200 EP 7208 DI 10.1364/AO.37.007200 PG 9 WC Optics SC Optics GA 134VJ UT WOS:000076764100005 PM 18301546 ER PT J AU Ponder, JM Burstein, D O'Connell, RW Rose, JA Frogel, JA Wu, CC Crenshaw, DM Rieke, MJ Tripicco, M AF Ponder, JM Burstein, D O'Connell, RW Rose, JA Frogel, JA Wu, CC Crenshaw, DM Rieke, MJ Tripicco, M TI Integrated ultraviolet spectra and line indices of M31 globular clusters and the cores of elliptical galaxies SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : elliptical and lenticular, cD; galaxies : stellar content ID OLD STELLAR POPULATIONS; ENERGY-DISTRIBUTIONS; NITROGEN ABUNDANCES; STARS; SPECTROSCOPY; PHOTOMETRY; PARAMETERS; RESOLUTION; CATALOG; SYSTEMS AB We present observations of the integrated light of four M31 globular clusters (MIV, MII, K280, and K58) and of the cores of six elliptical galaxies (NGC 3605, 3608, 5018, 5831, 6127, and 7619) made with the Faint Object Spectrograph on the Hubble Space Telescope. The spectra cover the range 2200-4800 Angstrom at a resolution of 8 Angstrom with signal-to-noise ratio of more than 20 and flux accuracy of similar to 5%. To these data we add from the literature IUE observations of the dwarf elliptical galaxy M32, Galactic globular clusters, and Galactic stars. The stellar populations in these systems are analyzed with the aid of mid-UV and near-UV colors and absorption line strengths. Included in the measured indices is the key NH feature at 3360 8, We compare these line index measures with the 2600 - 3000 colors of these stars and stellar populations. We find that the M31 globular clusters, Galactic globular clusters/Galactic stars, and elliptical galaxies represent three distinct stellar populations, based on their behavior in color-line strength correlations involving Mg II, NH, CN, and several UV metallic blends. In particular, the M31 globular cluster MIV, as metal-poor as the Galactic globular M92, shows a strong NH 3360 Angstrom feature. Other line indices, including the 3096 Angstrom blend that is dominated by lines of Mg I and Al I, show intrinsic differences as well. We also find that the broadband line indices often employed to measure stellar population differences in faint objects, such as the 4000 Angstrom and the Mg 2800 breaks, are disappointingly insensitive to these stellar population differences. We find that the hot (T > 20,000 EC) stellar component responsible for the "UV upturn" at shorter wavelengths can have an important influence on the mid-UV spectral range (2400-3200 Angstrom) as well. The hot component can contribute over 50% of the flux at 2600 Angstrom in some cases and affects both continuum colors and line strengths. Mid-UV spectra of galaxies must be corrected for this effect before they can be used as age and abundance diagnostics. Of the three stellar populations studied here, M31 globular clusters and elliptical galaxies are more similar to each other than either is to the Galactic stellar populations defined by globular clusters and nearby stars. Similarities between the abundance-pattern differences currently identified among these stellar populations and those among globular cluster stars (N, Al enhancements) present a curious coincidence that deserves future investigation. C1 Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85728 USA. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Comp Sci Corp, Space Telescope Sci Inst, Sci Programs, Baltimore, MD 21218 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ponder, JM (reprint author), Arizona State Univ, Dept Phys & Astron, Box 871504, Tempe, AZ 85728 USA. NR 62 TC 41 Z9 42 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD NOV PY 1998 VL 116 IS 5 BP 2297 EP 2314 DI 10.1086/300590 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134UZ UT WOS:000076763200019 ER PT J AU Mewe, R Drake, SA Kaastra, JS Schrijver, CJ Drake, JJ Gudel, M Schmitt, JHMM Singh, KP White, NE AF Mewe, R Drake, SA Kaastra, JS Schrijver, CJ Drake, JJ Gudel, M Schmitt, JHMM Singh, KP White, NE TI alpha Centauri: coronal temperature structure and abundances from ASCA observations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : coronae; stars : individual : alpha Cen; stars : abundances; X-rays : stars ID EXTREME-ULTRAVIOLET-SPECTRA; SOLAR-LIKE STARS; EMISSION MEASURE; COOL STARS; EUV SPECTROSCOPY; EVOLUTION; SYSTEM; LINES; IONIZATION; ATMOSPHERE AB We have analyzed the X-ray spectrum of the nearby binary alpha Cen AB (G2V + K1V) that has been obtained from observations with ASCA. The coronal temperature structure and abundances have been derived from multi-temperature fitting and confirmed by a differential emission measure analysis. The corona as seen by ASCA is essentially isothermal with a temperature around 0.3 keV, consistent with the evolutionary picture of coronae of aging solar-type stars. A comparison between the measurements from various instruments indicates a source variability in the coronal flux (which precludes the joint fitting of data from different instruments taken at different epochs) and temperature structure consistent with that discovered in a series of ROSAT observations. The elemental abundances agree with solar photospheric abundances for Ne, Si, and Fe at 1 sigma level, while O appears to be underabundant by a factor of about 3 relative to solar photospheric values, and Mg overabundant by a factor of a few. The abundance ratios with respect to Fe are better determined: [O/Fe] = 0.4+/-0.14(x solar, etc.), [Mg/Fe] = 4+/-1, [Ne/Fe] = 1+/-0.3, and [Si/Fe] = 6+/-4. C1 SRON, NL-3584 CA Utrecht, Netherlands. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Stanford Lockheed Inst Space Res, Dept H112, Palo Alto, CA 94304 USA. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. Paul Scherrer Inst, CH-5232 Villigen, Switzerland. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. RP Mewe, R (reprint author), SRON, Sorbonnelaan 2, NL-3584 CA Utrecht, Netherlands. EM R.Mewe@sron.nl RI White, Nicholas/B-6428-2012; Guedel, Manuel/C-8486-2015 OI White, Nicholas/0000-0003-3853-3462; Guedel, Manuel/0000-0001-9818-0588 NR 62 TC 5 Z9 5 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 NOV PY 1998 VL 339 IS 2 BP 545 EP 552 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 139ED UT WOS:000077014200030 ER PT J AU Angelini, L Church, MJ Parmar, AN Balucinska-Church, M Mineo, T AF Angelini, L Church, MJ Parmar, AN Balucinska-Church, M Mineo, T TI Discovery of a new 170 s X-ray pulsar 1SAXJ1324.4-6200 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE X-ray : stars; stars : rotation; pulsar : general; stars : individual : 1SAX J1324.4-6200 ID PERSEI AB We report the discovery with BeppoSAX of a new 170.84 +/- 0.04s X-ray pulsar, 1SAXJ1324.4-6200, found serendipitously in the field of the X-ray binary XB 1323-619 in 1997 August. The source and periodicity are also detected in archival ASCA data taken in 1994. The X-ray spectrum is modeled by a power-law with a photon index of 1.0 +/- 0.4 and absorption of (7.8+/-(2.7)(1.1)) x 10(22) atom cm(-2). The source is located close to the galactic plane and within 3' of the direction of the dark cloud DC 306.8+0.6. The measured interstellar absorption and cloud size imply a distance >3.4 kpc. This implies a 1-10 keV source luminosity of >1.1 x 10(34) erg s(-1) during the BeppoSAX observation. The source is not detected in earlier Einstein IPC and EXOSAT CMA observations, most probably due to reduced detector efficency and lower sensitivity to highly absorbed sources. The X-ray properties suggest that 1SAX J1324.4-6200 is an accreting neutron star with a Be star companion. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Birmingham, Sch Phys & Astron, Birmingham B15 2TT, W Midlands, England. European Space Agcy, Estec, Dept Space Sci, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. Inst IFCAI, I-90146 Palermo, Italy. NR 21 TC 14 Z9 14 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD NOV PY 1998 VL 339 IS 2 BP L41 EP L44 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 139ED UT WOS:000077014200003 ER PT J AU Lellouch, E Crovisier, J Lim, T Bockelee-Morvan, D Leech, K Hanner, MS Altieri, B Schmitt, B Trotta, F Keller, HU AF Lellouch, E Crovisier, J Lim, T Bockelee-Morvan, D Leech, K Hanner, MS Altieri, B Schmitt, B Trotta, F Keller, HU TI Evidence for water ice and estimate of dust production rate in comet Hale-Bopp at 2.9 AU from the Sun SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE comets : general; comet : individual : C/1995 O1 (Hale-Bopp); infrared : solar system ID C/1995-O1; GRAINS; PERIHELION; CONTINUUM; NUCLEUS AB We report observational evidence for water ice in comet C/1995 O1 (Hale-Bopp) when it was at 2.9 AU from the Sun, from emission features at 44 and 65 mu m, and possibly an absorption feature at 3.1 mu m, observed with ISO/LWS and PHT. We find that icy grains have mean radii of 15 mu m within a factor of 2, lifetimes of similar to 2 days, a temperature of similar to 153 K, and a total mass of similar to 2 x 10(9) kg. From investigation of the continuum spectrum at 43-195 mu m, we also infer a production rate of large particles (similar to 100 mu m) dust of about 4 x 10(4) kg s(-1). C1 Observ Paris, F-92195 Meudon, France. ESA, Div Astrophys, ISO Sci Operat Ctr, Villafranca, Spain. Queen Mary Univ London, London E1 4NS, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Lab Glaciol & Geophys Environm, F-38402 St Martin Dheres, France. Max Planck Inst Aeron, D-37189 Katlenburg Lindau, Germany. RP Crovisier, J (reprint author), Observ Paris, F-92195 Meudon, France. RI Schmitt, Bernard/A-1064-2009 OI Schmitt, Bernard/0000-0002-1230-6627 NR 33 TC 58 Z9 58 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 NOV 1 PY 1998 VL 339 IS 1 BP L9 EP L12 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134GU UT WOS:000076735600003 ER PT J AU Sekanina, Z AF Sekanina, Z TI A double nucleus of comet Evans-Drinkwater (C/1996 J1) SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE comet Evans-Drinkwater; double nucleus; nontidal splitting; brightness variations; new comets AB The nucleus of comet C/1996 J1, whose duplicity was first detected in early May 1997, similar to 4 months after perihelion, is found to have split nontidally similar to 70 days before perihelion at 1.65 AU from the Sun. The secondary nucleus, discovered when in outburst and subsequently observed for 8-1/2 months, had separated from the primary nucleus at a rate of 1.7 m/s and drifted away from it with a radial nongravitational deceleration of similar to 31 x 10(-5) the Sun's attraction, typical for the short-lived companions. At the time of splitting, this dynamically new comet was near conjunction with the Sun and therefore unobservable from Earth. In late 1997 and early 1998, when last seen, the companion was greater than or similar to 100 times fainter relative to the primary component than it had been when first reported. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sekanina, Z (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 26 TC 1 Z9 1 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 NOV 1 PY 1998 VL 339 IS 1 BP L25 EP L28 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134GU UT WOS:000076735600007 ER PT J AU Hill, RS Fanelli, MN Smith, DA Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Smith, AM Stecher, TP AF Hill, RS Fanelli, MN Smith, DA Bohlin, RC Neff, SG O'Connell, RW Roberts, MS Smith, AM Stecher, TP TI Ultraviolet imaging of the irregular galaxy NGC 4449 with the ultraviolet imaging telescope: Photometry and recent star formation history SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 4449); galaxies : irregular; galaxies : photometry; galaxies : stellar content; ultraviolet : galaxies ID EMISSION-LINE; STARBURST GALAXIES; OB ASSOCIATIONS; IONIZED-GAS; NGC-4449; EXTINCTION; KINEMATICS; FILAMENTS; NGC-4214; CLUSTERS AB The bright Magellanic irregular galaxy NGC 4449 was observed during the Astro-2 Space Shuttle mission by the Ultraviolet Imaging Telescope (UIT), which obtained images of a 40' field centered on the galaxy in two broad far-ultraviolet (FUV) bands centered at 1520 and 1620 Angstrom, with 3 "-5 " spatial resolution. Together with H alpha and H beta fluxes from ground-based Fabry-Perot images, these data are analyzed in order to explore the recent star formation history of NGC 4449. Maps of the H alpha-to-FUV and FUV-to-blue continuum flux ratios are presented and interpreted using evolutionary synthesis models. Photometry is presented both for 22 apertures containing large OB complexes and for 57 small apertures containing compact FUV-emitting knots. The OB complexes along the northern edge of the visible system have high H alpha-to-FUV ratios and thus appear to be more dominated by the current generation of stars than are other parts of the galaxy. However, young sources do exist elsewhere and are particularly conspicuous along the bar. The small-aperture analysis shows three candidate regions for sequential star formation. Surface brightness profiles are consistent with an exponential disk in both the FUV and the optical continuum. C1 NASA, Raytheon STX Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Virginia, Charlottesville, VA 22903 USA. Natl Radio Astron Observ, Charlottesville, VA 22903 USA. RP Hill, RS (reprint author), NASA, Raytheon STX Corp, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 57 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 NOV 1 PY 1998 VL 507 IS 1 BP 179 EP 198 DI 10.1086/306302 PN 1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LQ UT WOS:000077779400017 ER PT J AU Chiar, JE Pendleton, YJ Geballe, TR Tielens, AGGM AF Chiar, JE Pendleton, YJ Geballe, TR Tielens, AGGM TI Near-infrared spectroscopy of the proto-planetary nebula CRL 618 and the origin of the hydrocarbon dust component in the interstellar medium SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; dust, extinction; ISM : individual (CRL 618); ISM : molecules; line : profiles; stars : AGE and post-AGB ID POLYCYCLIC AROMATIC-HYDROCARBONS; HYDROGENATED AMORPHOUS-CARBON; MICRON EMISSION FEATURES; CIRCUMSTELLAR ENVELOPES; MOLECULAR CLOUDS; ORGANIC-MATTER; STELLAR WIND; MU-M; ABSORPTION; GRAINS AB A new 2.8-3.8 mu m spectrum of the carbon-rich protoplanetary nebula CRL 618 confirms the previous detection of a circumstellar 3.4 mu m absorption feature in this object (Lequeux & Jourdain de Muizon). The high resolution and high signal-to-noise ratio of our spectrum allow us to derive the detailed profile of this absorption feature, which is very similar to that observed in the spectrum of the Galactic center and also resembles the strong 3.4 mu m emission feature in some post-asymptotic giant branch stars. A weak 3.3 mu m unidentified infrared band, marginally detected in the CRL 618 spectrum of Lequeux & Jourdain de Muizon, is present in our spectrum. The existence of the 3.4 pm feature implies the presence of relatively short-chained, aliphatic hydrocarbon materials (-CH2-/-CH3 similar or equal to 2-2.5) in the circumstellar environment around CRL 618. It also implies that the carriers of the interstellar 3.4 pm feature are produced at least in part in circumstellar material, and it calls into question whether any are produced by the processing of interstellar ices in dense interstellar clouds, as has been previously proposed. Other features in the spectrum are recombination lines of hydrogen, rotational and vibration-rotation lines of molecular hydrogen, and a broad absorption probably due to a blend of HCN and C2H2 bands. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Joint Astron Ctr, Hilo, HI 96720 USA. RP NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 54 TC 73 Z9 73 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 NOV 1 PY 1998 VL 507 IS 1 BP 281 EP 286 DI 10.1086/306318 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LQ UT WOS:000077779400027 PM 11542820 ER PT J AU Pohl, M Esposito, JA AF Pohl, M Esposito, JA TI Electron acceleration in supernova remnants and diffuse gamma rays above 1 GeV SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; gamma rays : theory; supernova remnants ID GALAXIES COLD GAS; COSMIC-RAY; SPIRAL GALAXIES; GALACTIC PLANE; EGRET OBSERVATIONS; DARK-MATTER; MILKY-WAY; EMISSION; PROPAGATION; TRANSPORT AB The recently observed X-ray synchrotron emission from four supernova remnants (SNRs) has strengthened the evidence that cosmic-ray electrons are accelerated in SNRs. We show that if this is indeed the case, the local electron spectrum will be strongly time-dependent, at least above roughly 30 GeV. The time dependence stems from the Poisson fluctuations in the number of SNRs within a certain volume and within a certain time interval. As far as cosmic-ray electrons are concerned, the Galaxy looks like actively bubbling Swiss cheese rather than a steady, homogeneously filled system. Our finding has important consequences for studies of the Galactic diffuse gamma-ray emission, for which a strong excess over model predictions above 1 GeV has recently been reported. While these models relied on an electron injection spectrum with index 2.4 (chosen to fit the local electron flux up to 1 TeV), we show that an electron injection index of around 2.0 would (1) be consistent with the expected Poisson fluctuations in the locally observable electron spectrum and (2) explain the above-mentioned gamma-ray excess above 1 GeV. An electron injection index of around 2 would also correspond to the average radio synchrotron spectrum of individual SNRs. We use a three-dimensional propagation code to calculate the spectra of electrons throughout the Galaxy and show that the longitude and latitude distribution of the leptonic gamma-ray production above 1 GeV is in accord with the respective distributions for the gamma-ray excess. Finally, we point out that our model implies a strong systematic uncertainty in the determination of the spectrum of the extragalactic gamma-ray background. C1 Danish Space Res Inst, DK-2100 Copenhagen O, Denmark. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Pohl, M (reprint author), Danish Space Res Inst, Juliane Marie Vej 30, DK-2100 Copenhagen O, Denmark. EM mkp@dsri.dk NR 92 TC 124 Z9 125 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 NOV 1 PY 1998 VL 507 IS 1 BP 327 EP 338 DI 10.1086/306298 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LQ UT WOS:000077779400032 ER PT J AU Baring, MG Harding, AK AF Baring, MG Harding, AK TI Radio-quiet pulsars with ultrastrong magnetic fields SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : theory; magnetic fields; pulsars : general; radiation mechanisms : nonthermalstars : neutron ID PAIR CREATION; POLAR CAPS; PHOTON; GAPS; CASCADES AB The notable absence of radio pulsars having measured magnetic dipole surface field strengths above B-0 similar to x 10(13) G naturally raises the question of whether this forms an upper limit to pulsar magnetization. Recently there has been increasing evidence that neutron stars possessing higher dipole spin-down fields do in fact exist, including a growing list of anomalous X-ray pulsars (AXPs) with long periods and spinning down with high-period derivatives, which imply surface fields of 10(14)-10(15) G. Furthermore, the recently reported X-ray period and period derivative for the soft gamma-ray repeater (SGR) source SGR 1806-20 suggest a surface field around 10(15) G. None of these high-field pulsars have yet been detected as radio pulsars. We propose that high-field pulsars should be radio quiet because electron-positron pair production in their magnetospheres, thought to be essential for radio emission, is efficiently suppressed in ultrastrong fields (B-0 greater than or similar to x 10(13) G) by the action of photon splitting, a quantum electrodynamical process in which a photon splits into two. Our computed radio quiescence boundary in the radio pulsar P-(P) over dot diagram, where photon splitting overtakes pair creation, is located just above the boundary of the known radio pulsar population, neatly dividing them from the AXPs. We thus identify a physical mechanism that defines a new class of high-field radio-quiet neutron stars that should be detectable by their pulsed emission at X-ray and perhaps gamma-ray energies. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RI Harding, Alice/D-3160-2012 NR 32 TC 111 Z9 114 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 NOV 1 PY 1998 VL 507 IS 1 BP L55 EP L58 DI 10.1086/311679 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LR UT WOS:000077779500014 ER PT J AU Lamarre, JM Giard, M Pointecouteau, E Bernard, JP Serra, G Pajot, F Desert, FX Ristorcelli, I Torre, JP Church, S Coron, N Puget, JL Bock, JJ AF Lamarre, JM Giard, M Pointecouteau, E Bernard, JP Serra, G Pajot, F Desert, FX Ristorcelli, I Torre, JP Church, S Coron, N Puget, JL Bock, JJ TI First measurement of the submillimeter Sunyaev-Zeldovich effect SO ASTROPHYSICAL JOURNAL LA English DT Article DE balloons; cosmic microwave background; dust, extinction; galaxies : clusters : individual (A2163); infrared : general ID X-RAY-PROPERTIES; HUBBLE CONSTANT; GAS AB We report the first detection of the Sunyaev-Zeldovich (S-Z) increment on the cosmic microwave background at submillimeter wavelengths in the direction of a cluster of galaxies. It was achieved toward the rich cluster Abell 2163, using the PRONAOS 2 m stratospheric telescope. Together with data from the SuZIE, Diabolo, and ISO-PHT experiments, these measurements, for the first time, give a complete picture of the far-infrared-to-millimeter spectral energy distribution of the diffuse emission toward a cluster of galaxies. It clearly shows the positive and negative parts of the S-Z effect and also a positive signal at short wavelengths that can be attributed to foreground dust in our Galaxy. C1 Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France. Ctr Etud Spatiale Rayonnements, F-31028 Toulouse, France. CNRS, Serv Aeron, F-91371 Verrieres Buisson, France. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lamarre, JM (reprint author), Univ Paris 11, Inst Astrophys Spatiale, Batiment 121, F-91405 Orsay, France. NR 22 TC 46 Z9 46 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 NOV 1 PY 1998 VL 507 IS 1 BP L5 EP L8 DI 10.1086/311678 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LR UT WOS:000077779500002 ER PT J AU Teplitz, HI Gardner, JP Malumuth, EM Heap, SR AF Teplitz, HI Gardner, JP Malumuth, EM Heap, SR TI Galaxy morphology from NICMOS parallel imaging SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; galaxies : evolution; galaxies : fundamental parameters; galaxies : irregular; infrared : galaxies; surveys ID HUBBLE DEEP FIELD; PHOTOMETRY; EVOLUTION AB We present high-resolution Near-Infrared Camera and Multiobject Spectrometer images of random fields obtained in parallel to other Hubble Space Telescope observations. We present galaxy number counts reaching H-1.6 = 24. The H-1.6-band galaxy counts show good agreement with the deepest I- and K-band counts obtained from ground-based data. We present the distribution of galaxies with morphological type to H-1.6 < 23. We find relatively fewer irregular galaxies compared with an I-band sample from the Hubble Deep Field, which we attribute to their blue color rather than to morphological K-corrections. We conclude that the irregulars are intrinsically faint blue galaxies at z < 1. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Teplitz, HI (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 27 TC 34 Z9 34 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 NOV 1 PY 1998 VL 507 IS 1 BP L17 EP L20 DI 10.1086/311665 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LR UT WOS:000077779500005 ER PT J AU Terebey, S Van Buren, D Padgett, DL Hancock, T Brundage, M AF Terebey, S Van Buren, D Padgett, DL Hancock, T Brundage, M TI A candidate protoplanet in the Taurus star-forming region SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : general; circumstellar matter; infrared : stars; planetary systems; stars : formation; stars : individual (TMR-1) ID AURIGA MOLECULAR CLOUD; EMBEDDED YOUNG STARS; SYSTEMS AB Hubble Space Telescope/Near-Infrared Camera and Multiobject Spectrometer images of the class I protostar TMR-I (IRAS 04361+2547) reveal a faint companion with 10." 0 = 1400 AU projected separation. The central protostar is itself resolved as a close binary with 0." 31 = 42 AU separation, surrounded by circumstellar reflection nebulosity. A long narrow filament seems to connect the protobinary to the faint companion TMR-1C, suggesting a physical association. If the sources are physically related, then we hypothesize that TMR-1C has been ejected by the protobinary. If TMR-1C has the same age and distance as the protobinary, then current models indicate that its flux is consistent with a young giant planet of several Jovian masses. C1 Extrasolar Res Corp, Pasadena, CA 91101 USA. CALTECH, Jet Prop Lab, IPAC 100 22, Pasadena, CA 91125 USA. RP Terebey, S (reprint author), Extrasolar Res Corp, 569 S Marengo Ave, Pasadena, CA 91101 USA. NR 24 TC 36 Z9 36 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD NOV 1 PY 1998 VL 507 IS 1 BP L71 EP L74 DI 10.1086/311671 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LR UT WOS:000077779500018 ER PT J AU Bellan, J Harstad, K AF Bellan, J Harstad, K TI Dispersion (electrostatic/mechanical) and fuel properties effects on soot propensity in clusters of drops SO ATOMIZATION AND SPRAYS LA English DT Article ID EVAPORATION AB Soot propensity is studied numerically for an initially binary size, axisymmetric cluster of evaporating drops by defining it as the propensity for nucleation reactions to occur; the study does not address physical or chemical processes ensuing after soot nucleation, such as soot oxidation effects resulting from be fuel molecular structure. The relative magnitude of the fuel vapor partial density is taken as an indication of the soot nucleation magnitude,. thus; the effect of drop dispersion on soot (precursor) formation is isolated from that of soot production resulting from formation/destruction by oxidation. The cluster is embedded in an inviscid vortex and exchanges mass, momentum species, and energy with its surroundings. The vortical motion disperses the drops and the initial cluster evolves into a cylindrical shell with an inner and an outer boundary. In addition to the forces resulting from the vortical motion, an electrostatic force acts on the cluster when the drops are charged; in this situation, the drops might become small enough to reach the Rayleigh limit Results are obtained for typical vortical motion times having the same order of magnitude as the drop lifetime. Analysis of the results shows that the motion of uncharged drops is determined primarily by centrifugation, whereas for charged drops the electrostatic dispersion becomes the dominant influence in the outer part of the cluster. Tn the range of parameters investigated mechanical dispersion cannot rival electrostatically induced dispersion for decreasing the fuel vapor partial density. An additional feature of drop charging is the maintenance of a finite slip velocity in the outer part of the cluster, thereby compounding the advantage of increased dispersion to enhanced evaporation. The results also show that mechanical dispersion combined with electrostatic dispersion does not have a substantial advantage over electrostatic dispersion alone. For uncharged drops it has been found that the latent heat governs soot propensity at small drop dispersion, whereas the liquid density becomes increasingly important with increasing drop dispersion. Drop charging does not affect the influence of fuel physical properties on soot propensity. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 6 Z9 6 U1 2 U2 2 PU BEGELL HOUSE INC PI NEW YORK PA 79 MADISON AVE, SUITE 1205, NEW YORK, NY 10016-7892 USA SN 1044-5110 J9 ATOMIZATION SPRAY JI Atom. Sprays PD NOV-DEC PY 1998 VL 8 IS 6 BP 601 EP 624 PG 24 WC Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA 147HB UT WOS:000077482300001 ER PT J AU Lindgren, KN Kraft, D Ballard, RE Tucker, A Hargens, AR AF Lindgren, KN Kraft, D Ballard, RE Tucker, A Hargens, AR TI Venoconstrictive thigh cuffs impede fluid shifts during simulated microgravity SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID LEG COMPLIANCE; SPACEFLIGHT; ADAPTATION; VOLUME; TILT; SIZE AB Background: This study determined the efficacy of venoconstrictive thigh cuffs, inflated to 50 mmHg, on impeding fluid redistributions during simulated microgravity. Methods: There were 10 healthy male subjects who were exposed to a 2-h tilt protocol which started in the standing position, and was followed by 30 min supine, 30 min standing, 30 min supine, 30 min of -12 degrees head down tilt (HDT, to simulate microgravity), 15 min of HDT with venoconstrictive thigh cuffs inflated, a further 10 min of HDT, 5 min supine, and 10 min standing. To increase the sensitivity of the techniques in an Earth-based model, 12 degrees HDT was used to simulate microgravity effects on body fluid shifts. Volume changes were measured with anthropometric sleeve plethysmography. Results: Transition to the various tilt positions resulted in concomitant decrements in leg volume (Stand [STD] to Supine [SUP], -3.0%; SUP to HDT, -2.0%). inflation of the venoconstrictive thigh cuffs to 50 mmHg, during simulated microgravity, resulted in a significant 3.0% increase in leg volume from that seen in HDT (p < 0.01). No significant changes in systemic cardiovascular parameters were noted during cuff inflation. Conclusions: We conclude that venoconstrictive thigh cuffs, inflated to 50 mmHg for 15 min during 12 degrees HDT, can create a more Earth-like fluid distribution. Cuffs could potentially be used to ameliorate the symptoms of cephalad edema seen with space adaptation syndrome and to potentiate existing fluid volume countermeasure protocols. C1 Colorado State Univ, Dept Physiol, Ft Collins, CO 80523 USA. NASA, Ames Res Ctr, Space Physiol Lab, Moffett Field, CA 94035 USA. RP Tucker, A (reprint author), Colorado State Univ, Dept Physiol, Ft Collins, CO 80523 USA. NR 27 TC 14 Z9 14 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 NOV PY 1998 VL 69 IS 11 BP 1052 EP 1058 PG 7 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 133PA UT WOS:000076693900004 PM 9819160 ER PT J AU McGinnis, PJ Harris, BA AF McGinnis, PJ Harris, BA TI The re-emergence of space medicine as a distinct discipline SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Editorial Material AB Space Medicine is a discipline whose scope will encompass primary and advanced medical care amidst the environmental constraints of space. At one time, there was a Department of Space Medicine associated with the U.S. Air Force School of Aviation Medicine. Until 1993, an academic, university-based training program dedicated to space medicine did not exist. This paper reviews the history of space medicine in the United States. It presents the current conceptions of space medicine, and postulates the need for space medicine to mature as a distinct discipline. C1 NASA, Lyndon B Johnson Space Ctr, Flight Med Clin, Houston, TX 77058 USA. RP McGinnis, PJ (reprint author), NASA, Lyndon B Johnson Space Ctr, Flight Med Clin, Mail Code SD-26, Houston, TX 77058 USA. NR 17 TC 5 Z9 5 U1 3 U2 4 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 NOV PY 1998 VL 69 IS 11 BP 1107 EP 1111 PG 5 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 133PA UT WOS:000076693900015 PM 9819171 ER PT J AU Daunton, NG Tang, F Corcoran, ML Fox, RA Man, SY AF Daunton, NG Tang, F Corcoran, ML Fox, RA Man, SY TI Chronic exposure to hypergravity affects thyrotropin-releasing hormone levels in rat brainstem and cerebellum SO BIOLOGICAL SIGNALS AND RECEPTORS LA English DT Article DE brainstem; cerebellum; hypothalamus; striatum; cortex; thyrotropin-releasing hormone; met-enkephalin; substance P; centrifugation, chronic ID SPINAL-CORD INJURY; VESTIBULAR COMPENSATION; SUBSTANCE-P; NEUROPEPTIDES; RECEPTORS; PITUITARY; TRH; CHOLECYSTOKININ; SOMATOSTATIN; YM-14673 AB In studies to determine the neurochemical mechanisms underlying adaptation to altered gravity we have investigated changes in neuropeptide levels in brainstem, cerebellum, hypothalamus, striatum, hippocampus, and cerebral cortex by radioimmunoassay. Fourteen days of hypergravity (hyperG) exposure resulted in significant increases in thyrotropin-releasing hormone (TRH) content of brainstem and cerebellum, but no changes in levels of other neuropeptides (beta-endorphin, cholecystokinin, met-enkephalin, somatostatin, and substance P) examined in these areas were found, nor were TRH levels significantly changed in any other brain regions investigated. The increase in TRH in brainstem and cerebellum was not seen in animals exposed only to the rotational component of centrifugation, suggesting that this increase was elicited by the alteration in the gravitational environment. The only other neuropeptide affected by chronic hyperG exposure was met-enkephalin, which was significantly decreased in the cerebral cortex. However, this alteration in met-enkephalin was found in both hyperG and rotation control animals and thus may be due to the rotational rather than the hyperG component of centrifugation. Thus it does not appear as if there is a generalized neuropeptide response to chronic hyperG following 2 weeks of exposure. Rather, there is an increase only of TRH and that occurs only in areas of the brain known to be heavily involved with vestibular inputs and motor control (both voluntary and autonomic). These results suggest that TRH may play a role in adaptation to altered gravity as it does in adaptation to altered vestibular input following labyrinthectomy, and in cerebellar and vestibular control of locomotion, as seen in studies of ataxia. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Hong Kong, Dept Physiol, Hong Kong, Hong Kong. San Jose State Univ, San Jose, CA 95192 USA. RP Daunton, NG (reprint author), NASA, Ames Res Ctr, MS 261-3, Moffett Field, CA 94035 USA. NR 33 TC 7 Z9 7 U1 0 U2 0 PU KARGER PI BASEL PA ALLSCHWILERSTRASSE 10, CH-4009 BASEL, SWITZERLAND SN 1422-4933 J9 BIOL SIGNAL RECEPT JI Biol. Signal Recept. PD NOV-DEC PY 1998 VL 7 IS 6 BP 337 EP 344 PG 8 WC Biochemistry & Molecular Biology; Biophysics; Cell Biology SC Biochemistry & Molecular Biology; Biophysics; Cell Biology GA 152TU UT WOS:000077793500004 PM 9873155 ER PT J AU Ross, MD Tomko, DL AF Ross, MD Tomko, DL TI Effect of gravity on vestibular neural development SO BRAIN RESEARCH REVIEWS LA English DT Article; Proceedings Paper CT Workshop on Space Neuroscience Research CY APR 22-24, 1997 CL PARIS, FRANCE SP NASA, CNES, ESA, DARA, NASDA, CSA DE vestibular macula; altered gravity; critical period; synaptogenesis ID EXPERIENCE-DEPENDENT PLASTICITY; COMPUTER GENERATED IMAGERY; SOMATOSENSORY CORTEX; SENSORY EPITHELIUM; RECEPTIVE-FIELDS; AUDITORY SPACE; 3-D COMPONENTS; BARREL CORTEX; CHICK-EMBRYO; INNER-EAR AB The timing, molecular basis, and morphophysiological and behavioral consequences of the interaction between external environment and the internal genetic pool that shapes the nervous system over a lifetime remain important questions in basic neuroscientific research. Space station offers the opportunity to study this interaction over several life cycles in a variety of organisms. This short review considers past work in altered gravity, particularly on the vestibular system, as the basis for proposing future research on space station, and discusses the equipment necessary to achieve goals. It is stressed that, in keeping with the international investment being made in this research endeavor, both the questions asked and the technologies to be developed should be bold. Advantage must be taken of this unique research environment to expand the frontiers of neuroscience. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Biocomputat Ctr, Moffett Field, CA 94035 USA. RP Ross, MD (reprint author), NASA, Ames Res Ctr, Mail Stop 239-11, Moffett Field, CA 94035 USA. EM ross@biocomp.arc.nasa.gov NR 61 TC 22 Z9 23 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0165-0173 J9 BRAIN RES REV JI Brain Res. Rev. PD NOV PY 1998 VL 28 IS 1-2 BP 44 EP 51 DI 10.1016/S0165-0173(98)00025-3 PG 8 WC Neurosciences SC Neurosciences & Neurology GA 141MH UT WOS:000077147400007 PM 9795127 ER PT J AU Reschke, MF Bloomberg, JJ Harm, DL Paloski, WH Layne, C McDonald, V AF Reschke, MF Bloomberg, JJ Harm, DL Paloski, WH Layne, C McDonald, V TI Posture, locomotion, spatial orientation, and motion sickness as a function of space flight SO BRAIN RESEARCH REVIEWS LA English DT Article; Proceedings Paper CT Workshop on Space Neuroscience Research CY APR 22-24, 1997 CL PARIS, FRANCE SP NASA, CNES, ESA, DARA, NASDA, CSA DE posture; locomotor; motion perception; space motion sickness; space flight ID CANADIAN VESTIBULAR EXPERIMENTS; TRANSDERMAL SCOPOLAMINE; PROLONGED WEIGHTLESSNESS; HEAD STABILIZATION; EQUILIBRIUM CONTROL; PARABOLIC FLIGHT; TTS-SCOPOLAMINE; SELF-MOTION; MICROGRAVITY; MECHANISMS AB This article summarizes a variety of newly published findings obtained by the Neuroscience Laboratory, Johnson Space Center, and attempts to place this work within a historical framework of previous results on posture, locomotion, motion sickness, and perceptual responses that have been observed in conjunction with space flight. In this context we have taken the view that correct transduction and integration of signals from all sensory systems is essential to maintaining stable vision, postural and locomotor control, and eye-hand coordination as components of spatial orientation. The plasticity of the human central nervous system allows individuals to adapt to altered stimulus conditions encountered in a microgravity environment. However, until some level of adaptation is achieved, astronauts and cosmonauts often experience space motion sickness, disturbances in motion control and eye-hand coordination, unstable vision, and illusory motion of the self, the visual scene, or both. Many of the same types of disturbances encountered in space flight reappear immediately after crew members return to earth. The magnitude of these neurosensory, sensory-motor and perceptual disturbances, and the time needed to recover from them, tend to vary as a function of mission duration and the space travelers prior experience with the stimulus rearrangement of space flight. To adequately chart the development of neurosensory changes associated with space flight, we recommend development of enhanced eye movement systems and body position measurement. We also advocate the use of a human small radius centrifuge as both a research tool and as a means of providing on-orbit countermeasures that will lessen the impact of living for long periods of time with out exposure to altering gravito-inertial forces. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Neurosci Lab, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP NASA, Neurosci Lab, Lyndon B Johnson Space Ctr, SD3, Houston, TX 77058 USA. EM mreschke@ems.jsc.nasa.gov NR 188 TC 90 Z9 98 U1 2 U2 9 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0165-0173 EI 1872-6321 J9 BRAIN RES REV JI Brain Res. Rev. PD NOV PY 1998 VL 28 IS 1-2 BP 102 EP 117 DI 10.1016/S0165-0173(98)00031-9 PG 16 WC Neurosciences SC Neurosciences & Neurology GA 141MH UT WOS:000077147400014 PM 9795167 ER PT J AU Rozas, LP Minello, TJ AF Rozas, LP Minello, TJ TI Nekton use of salt marsh, seagrass, and nonvegetated habitats in a south Texas (USA) estuary SO BULLETIN OF MARINE SCIENCE LA English DT Article ID CRABS CALLINECTES-SAPIDUS; JUVENILE BLUE CRABS; PENAEUS-AZTECUS; DECAPOD CRUSTACEANS; FISH COMMUNITIES; BROWN SHRIMP; SPECIES COMPOSITION; SEASONAL ABUNDANCE; UNVEGETATED AREAS; NATANT MACROFAUNA AB We quantified nekton densities to estimate relative nursery values of Spartina alterniflora salt marsh, seagrass dominated by Ruppia maritima and Halodule wrightii, and shallow (<1 m deep) nonvegetated habitat in the Aransas National Wildlife Refuge in Texas. In each of two seasons of high nekton abundance, fall (September 1993) and spring (May 1994), we took 100 quantitative samples using a 1-m(2) drop sampler. We collected a total of 38 species of fishes and 19 species of decapod crustaceans. Vegetated habitats supported significantly higher densities of most numerically dominant species. Densities of total crustaceans, daggerblade grass shrimp Palaemonetes pugio, blue crabs Callinectes sapidus, and brackish grass shrimp Palaemonetes intermedius were significantly higher in salt marsh than seagrass. However, densities of total fishes, naked gobies Gobiosoma bosc, spotted seatrout Cynoscion nebulosus, pinfish Lagodon rhomboides, gulf pipefish Syngnathus scovelli, brown shrimp Farfantepenaeus aztecus (fall), white shrimp Litopenaeus setiferus, and pink shrimp Farfantepanaeus duorarum were not significantly different in salt marsh and seagrass. In spring, brown shrimp densities were higher in seagrass than salt marsh. In contrast to other abundant species, mean densities of bay anchovies Anchoa mitchilli were higher over nonvegetated bottom than in vegetated habitats in both seasons. Nekton size also differed among habitats, and organisms generally were smaller in seagrass beds than in marsh habitat. Our results provide further documentation that shallow vegetated habitats are important nurseries for many estuarine species. Furthermore, our study showed that where salt marsh and seagrass co-occur, most decapod crustaceans either selected for marsh habitat or showed no preference between these two vegetated habitats. C1 NOAA, Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, Galveston, TX 77551 USA. RP Rozas, LP (reprint author), NOAA, Natl Marine Fisheries Serv, SE Fisheries Sci Ctr, 4700 Ave U, Galveston, TX 77551 USA. EM Lawrence.Rozas@noda.gov NR 76 TC 101 Z9 106 U1 4 U2 22 PU ROSENSTIEL SCH MAR ATMOS SCI PI MIAMI PA 4600 RICKENBACKER CAUSEWAY, MIAMI, FL 33149 USA SN 0007-4977 J9 B MAR SCI JI Bull. Mar. Sci. PD NOV PY 1998 VL 63 IS 3 BP 481 EP 501 PG 21 WC Marine & Freshwater Biology; Oceanography SC Marine & Freshwater Biology; Oceanography GA 163LR UT WOS:000078407600003 ER PT J AU Hasler, AF Palaniappan, K Kambhammetu, C Black, P Uhlhorn, E Chesters, D AF Hasler, AF Palaniappan, K Kambhammetu, C Black, P Uhlhorn, E Chesters, D TI High-resolution wind fields within the inner core and eye of a mature tropical cyclone from GOES 1-min images SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SATELLITE AB Mesoscale wind fields have been determined for a mature hurricane with high spatial and temporal resolution, continuity, and coherency. These wind fields, near the tropopause in the inner core and at low levels inside the eye, allow the evolution of mesoscale storm features to be observed. Previously, satellite-derived winds near hurricanes have been determined only at some distance from the eye over a typical time period of 1-2 h. Hurricane reconnaissance aircraft take 30 min to 1 h to complete an inner-core pattern. With the long observation periods of these previous methods, steady-state conditions must be assumed to give a complete description of the observed region. With the advent of 1-min interval imagery, and fourfold improvement of image dynamic range from NOAA's current generation of GOES satellites, there is a new capability to measure inner-core tropical cyclone wind fields near the tropopause and within the eye, enabling mesoscale dynamical processes to be inferred. These measurements give insights into the general magnitude and structure of the hurricane vortex, along with very detailed measurements of the cloud-top wind's variations in response to convective outbursts. This paper describes the new techniques used to take advantage of the GOES satellite improvements that, in turn, allowed the above innovations to occur. The source of data for this study is a nearly continuous 12-h sequence of 1-min visible images from NOAA GOES-9 on 6 September 1995. These images are centered on Hurricane Luis with maximum winds of 120 kt (CAT4) when it was 250 km northeast of Puerto Rico. A uniform distribution of long-lived cirrus debris with detailed structure is observed in the central dense overcast (CDO), which has been tracked using the 1-min images. The derived wind field near the tropopause at approximately 15 km in the CDO region has a strong closed circulation with speeds up to 25 m s(-1), which pulses in response to the convective outbursts in the eyewall. Cloud displacements are computed at every pixel in every image, resulting in a quarter-million u-v winds in each of 488 hurricane images observed at 1- to 4-min intervals over 12 h. For analysis and presentation, these ultradense wind fields are reduced to 8- or 16-km grids using a 7-min time base by smoothing displacement vectors in space and time. Cloud structures were tracked automatically on a massively parallel processing computer, but with manual spot-checking. Manual tracking has been used to follow CDO structure over long time periods, up to 90 min for a small test sample. Cloud tracking for the wind fields presented here is accomplished using a Massively Parallel Semi-Fluid Motion Analysis (MPSMA) automatic technique. This robust deformable surface-matching algorithm has been implemented on the massively parallel Maspar supercomputer. MPSMA automatic tracking typically follows a feature for 7 min. For this time base the error of these winds is estimated to be 1.5 m s(-1). However, systematic navigation and height assignment errors in the moderately sheared hurricane environment must still be considered. Spatial and temporal smoothing of the wind field have been performed to reduce systematic navigation errors and small-scale turbulent noise. The synthesis used here to compute the wind fields gives an order of magnitude reduction in the amount of data presented compared to the amount of data processed. Longer tracking could give higher accuracy but would smooth out the smaller-scale spatial and temporal features that appear dynamically significant. The authors believe that the techniques described in this paper have great potential for further research on tropical cyclones and severe weather as well as in operational use for nowcasting and forecasting. United States and foreign policymakers are urged to augment the GOES, GMS, FY2, and Meteosat geostationary satellite systems with dual imaging systems such that I-min observations are routinely taken. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Delaware, Dept Comp & Informat Sci, Newark, DE 19716 USA. NOAA, Atlantic Oceanog & Meteorol Lab, Hurricane Res Div, Miami, FL 33149 USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Hasler, AF (reprint author), NASA, Goddard Space Flight Ctr, Code 912, Greenbelt, MD 20771 USA. RI Palaniappan, Kannappan/A-3231-2008; Uhlhorn, Eric/B-1336-2014 OI Uhlhorn, Eric/0000-0002-4759-5342 NR 27 TC 31 Z9 31 U1 1 U2 7 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 EI 1520-0477 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD NOV PY 1998 VL 79 IS 11 BP 2483 EP 2496 DI 10.1175/1520-0477(1998)079<2483:HRWFWT>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 143BL UT WOS:000077235200003 ER PT J AU Ord, GN Gualtieri, JA AF Ord, GN Gualtieri, JA TI Fractal paths and Schrodinger's equation in an electromagnetic field SO CHAOS SOLITONS & FRACTALS LA English DT Article ID RANDOM-WALKS; QUANTUM-MECHANICS; DIRAC-EQUATION; INTERFERENCE; ANALOG; TIME AB It is well known that the trajectories of random walks on discrete lattices have a fractal dimension of 2 when viewed on scales much greater than the lattice spacing and that these walks provide a microscopic model for the diffusion equation. Less well known is the fact that some instances of Schrodinger's equation occur naturally in the description of the statistics of these same walks and, thus, have classical contexts which ape distinct from their usual association with quantum mechanics. In this article, we show that Schrodinger's equation for a particle in an electromagnetic field in 1+1 dimensions is one such instance. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Ryerson Polytech Univ, MPCS, Toronto, ON M5K 25B, Canada. NASA, Goddard Space Flight Ctr, Appl Informat Sci Branch, Greenbelt, MD 20771 USA. RP Ord, GN (reprint author), Ryerson Polytech Univ, MPCS, Toronto, ON M5K 25B, Canada. NR 20 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 0960-0779 J9 CHAOS SOLITON FRACT JI Chaos Solitons Fractals PD NOV PY 1998 VL 9 IS 11 BP 1921 EP 1929 DI 10.1016/S0960-0779(98)00230-6 PG 9 WC Mathematics, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Mathematics; Physics GA 148WH UT WOS:000077556300012 ER PT J AU D'Eath, P Sornborger, A AF D'Eath, P Sornborger, A TI Persistence amplitudes from numerical quantum gravity SO CLASSICAL AND QUANTUM GRAVITY LA English DT Article ID MASSLESS SCALAR FIELD; GRAVITATIONAL COLLAPSE; SUPERGRAVITY AB The Euclidean quantum amplitude to go between data specified on an initial and a final hypersurface may be approximated by the tree amplitude exp(-I-classical/(h) over bar), (1) where I-classical is the Euclidean action of the classical solution joining the initial and final data. In certain cases the tree amplitude is exact. We study I-classical and hence the quantum amplitude, in the case of a spherically symmetric Riemannian gravitational field coupled to a spherically symmetric scalar field. The classical scalar field obeys an elliptic equation, which we solve using relaxation techniques. in conjunction with the field equations giving the gravitational field. An example of the transition from linearity to nonlinearity is presented and power-law behaviour of the action is demonstrated. C1 Univ Cambridge, DAMTP, Cambridge CB3 9EW, England. NASA, Fermi Natl Accelerator Lab, Fermilab Astrophys Grp, Batavia, IL 60510 USA. RP D'Eath, P (reprint author), Univ Cambridge, DAMTP, 3 Silver St, Cambridge CB3 9EW, England. NR 23 TC 4 Z9 4 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0264-9381 J9 CLASSICAL QUANT GRAV JI Class. Quantum Gravity PD NOV PY 1998 VL 15 IS 11 BP 3435 EP 3447 DI 10.1088/0264-9381/15/11/010 PG 13 WC Astronomy & Astrophysics; Physics, Multidisciplinary; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 141CX UT WOS:000077126000010 ER PT J AU Engelke, KA Convertino, VA AF Engelke, KA Convertino, VA TI Restoration of peak vascular conductance after simulated microgravity by maximal exercise SO CLINICAL PHYSIOLOGY LA English DT Article DE bedrest; blood flow; fatigue; hyperaemia; vasodilation ID CARDIOPULMONARY BAROREFLEX CONTROL; BLOOD-VOLUME; MONONUCLEAR-CELLS; ISCHEMIC EXERCISE; VASODILATION; RESISTANCE; RECEPTORS; RESPONSES; MUSCLE; MEN AB We sought to determine if (i) peak vascular conductance of the calf was reduced following prolonged exposure to simulated microgravity, and (ii) if maximal cycle ergometry performed at the end of microgravity exposure stimulated a restoration of peak calf vascular conductance. To do this, peak vascular conductance of the calf was recorded following ischaemic plantar flexion exercise to fatigue. in seven men after 16 days of head-down tilt (HDT) under two conditions: (i) after one bout of maximal supine cycle ergometry completed 24 h prior to performance of ischaemic plantar flexion exercise, and (ii) in a control (no cycle ergometry) condition. Following HDT, peak vascular conductance was reduced in the control condition (0.38 +/- 0.02 to 0.24 +/- 0.02 ml 100 ml(-1) min(-1) mmHg(-1); P = 0.04), but was restored when subjects performed cycle ergometry (0.33 +/- 0.05 to 0.28 +/- 0.04 ml 100 ml(-1) min(-1) mmHg(-1); P = 0.46). After HDT, time to fatigue during ischaemic plantar flexion exercise was not different from pre-HDT 24 h after performance of exhaustive cycle ergometry (120 +/- 24 vs. 122 +/- 19 s), but was decreased in the control condition (116 +/- 11 vs. 95 +/- 8 s; P = 0.07). These data suggest that a single bout of maximal exercise can provide a stimulus to restore peak vascular conductance and maintain time to fatigue during performance of ischaemic plantar flexion exercise. C1 Univ Florida, Dept Physiol, Gainesville, FL 32610 USA. USA, Inst Surg Res, Ft Sam Houston, TX 78234 USA. NASA, Biomed Engn Off, Kennedy Space Ctr, FL 32899 USA. RP Convertino, VA (reprint author), AL AOCY, Physiol Res Branch, 2507 Kennedy Circle, Brooks AFB, TX 78235 USA. NR 37 TC 7 Z9 7 U1 0 U2 2 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0144-5979 J9 CLIN PHYSIOL JI Clin. Physiol. PD NOV PY 1998 VL 18 IS 6 BP 544 EP 553 DI 10.1046/j.1365-2281.1998.00133.x PG 10 WC Physiology SC Physiology GA 137XY UT WOS:000076943400008 PM 9818160 ER PT J AU Povitsky, A AF Povitsky, A TI Efficient parallelization of a parabolized flow solver SO COMPUTERS & FLUIDS LA English DT Article AB This article describes application of our theory of parallelization of implicit ADI schemes to parabolized flows. A parallel multi-domain version of a turbulent developing flow in a straight duct (case A) and viscous flow in a curved duct (case B) are presented. Semi-implicit and explicit methods for the determination of boundary values for the auxiliary ADI functions on the interfaces between the sub-domains are utilized. Numerical runs show that the proposed algorithm is valid in the regions with rapidly varying fields of governing variables (near-entrance region for the case A, region 30 degrees < theta < 60 degrees for the case B) as well as in the regions with slow axial modification of the flowfield. The algorithm is suitable for small transverse velocity (case A) and for transverse velocity of order of streamwise velocity (case B). A simplified version of our theoretical model of parallel efficiency is developed and utilized for optimal multidomain partitioning. Computer runs of the multi-domain code are done on a Meiko CS and on a DEC Alpha farm with PVM communication software. The predictions of parallel efficiency obtained by the model compare well with those of actual computer runs. The parallelization parameters obtained are quite different for two considered MIMD machines. This fact confirms the importance of a priori estimation of parallelization efficiency of an algorithm and correct choice of a parallel computer. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. RP NASA, Langley Res Ctr, ICASE, Hampton, VA 23681 USA. NR 10 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 EI 1879-0747 J9 COMPUT FLUIDS JI Comput. Fluids PD NOV PY 1998 VL 27 IS 8 BP 985 EP 1000 DI 10.1016/S0045-7930(98)00010-3 PG 16 WC Computer Science, Interdisciplinary Applications; Mechanics SC Computer Science; Mechanics GA 115WH UT WOS:000075689000007 ER PT J AU Bryson, S AF Bryson, S TI Practical visualization - How visualization can lead us astray SO COMPUTERS IN PHYSICS LA English DT Article C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bryson, S (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 3 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0894-1866 J9 COMPUT PHYS JI Comput. Phys. PD NOV-DEC PY 1998 VL 12 IS 6 BP 585 EP 587 PG 3 WC Computer Science, Interdisciplinary Applications; Physics, Multidisciplinary; Physics, Mathematical SC Computer Science; Physics GA 149NP UT WOS:000077611900019 ER PT J AU Wang, LP Huang, RX AF Wang, LP Huang, RX TI A homogeneous model of the Deacon cell in a circumpolar ocean SO DYNAMICS OF ATMOSPHERES AND OCEANS LA English DT Article DE deacon cell; inter-basin water mass exchange; wind forcing; zonal through-channel transport ID WIND-DRIVEN CIRCULATION; CHANNEL; WATER; THERMOCLINE; TRANSPORT; GYRE AB Dynamics of the three-dimensional structure of the wind-driven Deacon cell in a beta-plane channel are discussed in a homogeneous model in the presence of a sufficiently high ridge. The emphasis is on the water mass balance: how the northward surface Ekman drift is returned. It is demonstrated that a sufficiently high ridge can break up the geostrophic constraint and a net geostrophic volume flux across the open latitude band is allowed. It is found that: (1) the Deacon cell is a fundamentally three-dimensional structure, (2) wind forcing can drive an inter-basin water mass exchange in the Southern Ocean, and (3) zonal through-channel transport in the circumpolar ocean varies at different longitudes. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA. RP Wang, LP (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. NR 27 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0377-0265 J9 DYNAM ATMOS OCEANS JI Dyn. Atmos. Oceans PD NOV PY 1998 VL 28 IS 3-4 BP 157 EP 177 DI 10.1016/S0377-0265(98)00051-7 PG 21 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Oceanography SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Oceanography GA 147KX UT WOS:000077568100003 ER PT J AU Whorton, MS Calise, AJ Hsu, CC AF Whorton, MS Calise, AJ Hsu, CC TI A study of fixed-order mixed norm designs for a benchmark problem in structural control SO EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS LA English DT Article; Proceedings Paper CT 1st World Conference on Structural Control (1WCSC) CY AUG 03-SEP 05, 1994 CL LOS ANGELES, CALIFORNIA SP Int Assoc Struct Control (IASC) DE robust control; mixed H-2/mu control; parametric uncertainty; homotopy methods; structural control ID FEEDBACK AB This study investigates the use of H-2, mu-synthesis, and mixed H-2/mu methods to construct full-order controllers and optimized controllers of fixed dimensions. The benchmark problem definition is first extended to include uncertainty within the controller bandwidth in the form of parametric uncertainty representative of uncertainty in the natural frequencies of the design model. The sensitivity of H-2 design to unmodelled dynamics and parametric uncertainty is evaluated for a range of controller levels of authority. Next, mu-synthesis methods are applied to design full-order compensators that are robust to both unmodelled dynamics and to parametric uncertainty. Finally, a set of mixed H-2/mu compensators are designed which are optimized for a fixed compensator dimension. These mixed norm designs recover the H-2 design performance levels while providing the same levels of robust stability as the mu designs. It is shown that designing with the mixed norm approach permits higher levels of controller authority for which the H-2 designs are destabilizing. The benchmark problem is that of an active tendon system. The controller designs are all based on the use of acceleration feedback. (C) 1998 John Wiley & Sons, Ltd. This paper was produced under the auspices of the U.S. Government and it is therefore not subject to copyright in the U.S. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Georgia Inst Technol, Sch Aerosp Engn, Atlanta, GA 30332 USA. RP Whorton, MS (reprint author), NASA, George C Marshall Space Flight Ctr, ED12, Huntsville, AL 35812 USA. NR 21 TC 8 Z9 10 U1 1 U2 2 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0098-8847 J9 EARTHQUAKE ENG STRUC JI Earthq. Eng. Struct. Dyn. PD NOV PY 1998 VL 27 IS 11 BP 1315 EP 1330 DI 10.1002/(SICI)1096-9845(1998110)27:11<1315::AID-EQE786>3.0.CO;2-9 PG 16 WC Engineering, Civil; Engineering, Geological SC Engineering GA 138HM UT WOS:000076966500014 ER PT J AU Wu, XR Newman, JC Zhao, W Swain, MH Ding, CF Phillips, EP AF Wu, XR Newman, JC Zhao, W Swain, MH Ding, CF Phillips, EP TI Small crack growth and fatigue life predictions for high-strength aluminium alloys: Part I - Experimental and fracture mechanics analysis SO FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES LA English DT Article DE surface cracks; corner cracks; weight-function method; crack closure; small crack effect; total fatigue life prediction ID STRESS-INTENSITY FACTORS; WEIGHT FUNCTION-METHOD; FINITE-THICKNESS PLATES; SEMICIRCULAR NOTCH; SURFACE CRACKS; CORNER CRACKS; GRADIENTS; BODIES AB The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack rests were conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plasticity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions. Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminium alloys was developed and demonstrated using the crack-closure model. C1 Inst Aeronaut Mat, Beijing 100095, Peoples R China. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Wu, XR (reprint author), Inst Aeronaut Mat, Beijing 100095, Peoples R China. NR 30 TC 29 Z9 40 U1 1 U2 10 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 8756-758X J9 FATIGUE FRACT ENG M JI Fatigue Fract. Eng. Mater. Struct. PD NOV PY 1998 VL 21 IS 11 BP 1289 EP 1306 PG 18 WC Engineering, Mechanical; Materials Science, Multidisciplinary SC Engineering; Materials Science GA 153ZJ UT WOS:000077863300002 ER PT J AU Atkinson, S Ragen, TJ Gilmartin, WG Becker, BL Johanos, TC AF Atkinson, S Ragen, TJ Gilmartin, WG Becker, BL Johanos, TC TI Use of a GnRH agonist to suppress testosterone in wild male Hawaiian monk seals (Monachus schauinslandi) SO GENERAL AND COMPARATIVE ENDOCRINOLOGY LA English DT Article DE GnRH agonist; testosterone; Hawaiian monk seals; Monachus schauinslandi ID HORMONE-RELEASING HORMONE; MICROCAPSULES; INHIBITION AB A gonadotropin-releasing hormone (GnRH) agonist, D-Trp(6)-LHRH, was evaluated for its effectiveness in reducing circulating testosterone concentrations in wild Hawaiian monk seals (Monachus schauinslandi). Twenty-eight adult male seals were randomly divided into three groups: 10 were captured and treated with 7.5 mg of the GnRH agonist, 9 were captured but did not receive the agonist, and 9 were captured near the end of the study to serve as handling controls. Blood samples were taken from all 28 seals. From 14 to 58 days after initial capture, 8 of the treated seals and 8 of the untreated seals were recaptured and a second sample of blood was taken. For comparison, blood was also collected from 4 captive adult male seals during the same months as the field study In the treated group, the agonist induced a significant decline in mean circulating testosterone concentrations, from 1.01 ng/ml (first sample) to 0.21 ng/ml (second sample, taken approximately 38 days later). In the untreated group, mean testosterone concentrations of the first and second samples were statistically indistinguishable (1.11 vs 1.16 ng/ml). The mean concentration of the untreated group (second sample) was also indistinguishable from the mean concentration of seals in the control group (1.16 vs 0.82 ng/ml). Also, mean testosterone concentration in the initial samples from the four captive seals was not statistically different from that of untreated wild seals (1.38 vs 1.11 ng/ml). These results suggest that (1) the GnRH agonist suppresses the production of testosterone in wild adult male Hawaiian monk seals, (2) a single handling of adult malt seals does not affect their testosterone levels, and (3) testosterone concentrations in captive male seals appear to be consistent with concentrations in wild seals. Further evaluation of this GnRH agonist is necessary before it is used in the management of this endangered species, but these results suggest it may be a useful tool for reducing mortality of monk seals from adult male aggression related to reproduction and mating behavior. (C) 1998 Academic Press. C1 Univ Hawaii, Hawaii Inst Marine Biol, Kaneohe, HI 96744 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP Atkinson, S (reprint author), Univ Hawaii, Hawaii Inst Marine Biol, POB 1346, Kaneohe, HI 96744 USA. NR 17 TC 8 Z9 9 U1 1 U2 9 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0016-6480 J9 GEN COMP ENDOCR JI Gen. Comp. Endocrinol. PD NOV PY 1998 VL 112 IS 2 BP 178 EP 182 DI 10.1006/gcen.1998.7173 PG 5 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 135NW UT WOS:000076809900005 PM 9784300 ER PT J AU Thomas-Keprta, KL McKay, DS Wentworth, SJ Stevens, TO Taunton, AE Allen, CC Coleman, A Gibson, EK Romanek, CS AF Thomas-Keprta, KL McKay, DS Wentworth, SJ Stevens, TO Taunton, AE Allen, CC Coleman, A Gibson, EK Romanek, CS TI Bacterial mineralization patterns in basaltic aquifers: Implications for possible life in martian meteorite ALH84001 SO GEOLOGY LA English DT Article ID MICROORGANISMS; NANNOBACTERIA; ECOSYSTEMS; SEDIMENTS; MARS; DEEP AB To explore the formation and preservation of biogenic features in igneous rocks, we have examined the organisms in experimental basaltic microcosms using scanning and transmission electron microscopy, Four types of microorganisms were recognized on the basis of size, morphology, and chemical composition, Some of the organisms mineralized rapidly, whereas others show no evidence of mineralization. Many mineralized cells are hollow and do not contain evidence of microstructure. Filaments, either attached or no longer attached to organisms, are common. Unattached filaments are mineralized and are most likely bacterial appendages (e,g., prosthecae). Features similar in size and morphology to unattached, mineralized filaments are recognized in martian meteorite ALH84001. C1 Lockheed Martin Space Mission Syst & Serv, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Pacific NW Lab, Richland, WA 99352 USA. Univ Wisconsin, Dept Geol, Madison, WI 53706 USA. Brown Univ, Biomed Dept, Providence, RI 02912 USA. Univ Georgia, Savannah River Ecol Lab, Aiken, SC 29802 USA. RP Thomas-Keprta, KL (reprint author), Lockheed Martin Space Mission Syst & Serv, 2400 NASA Rd 1, Houston, TX 77058 USA. NR 22 TC 32 Z9 35 U1 1 U2 2 PU ASSOC ENGINEERING GEOLOGISTS GEOLOGICAL SOCIETY AMER PI COLLEGE STN PA TEXAS A & M UNIV, DEPT GEOLOGY & GEOPHYSICS, COLLEGE STN, TX 77843-3115 USA SN 0091-7613 J9 GEOLOGY JI Geology PD NOV PY 1998 VL 26 IS 11 BP 1031 EP 1034 DI 10.1130/0091-7613(1998)026<1031:BMPIBA>2.3.CO;2 PG 4 WC Geology SC Geology GA 135MX UT WOS:000076807000018 PM 11541429 ER PT J AU Cofer, WR Winstead, EL Stocks, BJ Goldammer, JG Cahoon, DR AF Cofer, WR Winstead, EL Stocks, BJ Goldammer, JG Cahoon, DR TI Crown fire emissions of CO(2), CO, H(2), CH(4), and TNMHC from a dense jack pine boreal forest fire SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID BIOMASS-BURNING EMISSIONS; TRACE GAS EMISSIONS AB Samples of high-intensity crown fire smoke were collected using a helicopter during the International Crown Fire Modeling Experiment near Fort Providence, Northwest Territories, Canada. The samples were analyzed for carbon dioxide (CO(2)), carbon monoxide (CO), hydrogen (H(2)), methane (CH(4)), and total nonmethane hydrocarbons (TNMHC). CO(2)-normalized mean emission ratios (ERs) and emission factors (g product/kg fuel burned)were determined for CO(2), CO, H(2), CH(4), and TNMHC. Carbon monoxide production was determined to increase during high-intensity crowning. Unlike CO, corresponding increase in the production of H(2), CH(4), and TNMHC during crowning was not detected. This represents the first clear indication that we know of where relative increases in CO production from vegetation fires are not positively correlated with corresponding increases in CH(4), H(2), and TNMHC production. These results may be important to the atmospheric carbon budget, and to the potential use of CO as a normalizing parameter for boreal forest fire emissions. C1 NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. Canadian Forest Serv, Sault Ste Marie, ON P6A 5M7, Canada. Univ Freiburg, Max Planck Inst Chem, D-79085 Freiburg, Germany. RP Cofer, WR (reprint author), NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. NR 17 TC 69 Z9 76 U1 1 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1998 VL 25 IS 21 BP 3919 EP 3922 DI 10.1029/1998GL900042 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 136CE UT WOS:000076839800001 ER PT J AU Jucks, KW Johnson, DG Chance, KV Traub, WA Margitan, JJ Osterman, GB Salawitch, RJ Sasano, Y AF Jucks, KW Johnson, DG Chance, KV Traub, WA Margitan, JJ Osterman, GB Salawitch, RJ Sasano, Y TI Observations of OH, HO2, H2O, and O-3 in the upper stratosphere: implications for HOx photochemistry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OZONE AB Balloon-borne observations of concentrations of OH, HO2, H2O, and O-3 in the middle and upper stratosphere are used to test our understanding of HOx photochemistry. Assuming our photochemical model is complete, the measured [OH] and [HO2] above 38 km (where HOx partitioning is no longer dependent on [NO]) are modeled best by calculations that use a 25% reduction in the ratio of the reaction rate constants for O+HO2 and O+OH as well as either a 25% reduction Of the rate constant of OH+HO2 (the primary HOx sink) or a 25% increase in HOx production. All of these changes are consistent with the uncertainties in the recommended rate constants. The kinetic parameters required to explain our observations of [OH] and [HO2] do not lead to a resolution of the long-standing "ozone deficit problem" above 45 km. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Japan Environm Agcy, Natl Inst Environm Studies, Ibaraki 305, Japan. RP Jucks, KW (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI Salawitch, Ross/B-4605-2009; Sasano, Yasuhiro/C-2927-2009; Johnson, David/F-2376-2015; OI Salawitch, Ross/0000-0001-8597-5832; Sasano, Yasuhiro/0000-0001-7470-5642; Johnson, David/0000-0003-4399-5653; Chance, Kelly/0000-0002-7339-7577 NR 11 TC 60 Z9 61 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 NOV 1 PY 1998 VL 25 IS 21 BP 3935 EP 3938 DI 10.1029/1998GL900009 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 136CE UT WOS:000076839800005 ER PT J AU Danilin, MY Fahey, DW Schumann, U Prather, MJ Penner, JE Ko, MKW Weisenstein, DK Jackman, CH Pitari, G Kohler, I Sausen, R Weaver, CJ Douglass, AR Connell, PS Kinnison, DE Dentener, FJ Fleming, EL Berntsen, TK Isaksen, ISA Haywood, JM Karcher, B AF Danilin, MY Fahey, DW Schumann, U Prather, MJ Penner, JE Ko, MKW Weisenstein, DK Jackman, CH Pitari, G Kohler, I Sausen, R Weaver, CJ Douglass, AR Connell, PS Kinnison, DE Dentener, FJ Fleming, EL Berntsen, TK Isaksen, ISA Haywood, JM Karcher, B TI Aviation fuel tracer simulation: Model intercomparison and implications SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRCRAFT SULFUR EMISSIONS; SUPERSONIC AIRCRAFT; LOWER STRATOSPHERE; TRANSPORT MODEL; AEROSOL; OZONE; SULFATE; IMPACT AB An upper limit for aircraft-produced perturbations to aerosols and gaseous exhaust products in the upper troposphere and lower stratosphere (UT/LS) is derived using the 1992 aviation fuel tracer simulation performed by eleven global atmospheric models. Key findings are that subsonic aircraft emissions: 1) have not be responsible for the observed water vapor trends at 40 degrees N; 2) could be a significant source of soot mass near 12 km, but not at 20 km, 3) might cause a noticeable increase in the background sulfate aerosol surface area and number densities (but not mass density) near the northern mid-latitude tropopause, and 4) could provide a global, annual mean top of the atmosphere radiative forcing up to +0.006 W/m(2) and -0.013 W/m(2) due to emitted soot and sulfur, respectively. C1 AER Inc, Cambridge, MA 02139 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. DLR, Inst Atmospher Phys, Oberpfaffenhofen, Germany. Univ Calif Irvine, Irvine, CA 92717 USA. Univ Michigan, Ann Arbor, MI 48109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD USA. Univ Aquila, I-67100 Laquila, Italy. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA USA. Univ Utrecht, Utrecht, Netherlands. Space Applicat Corp, Vienna, VA USA. Ctr Int Climate & Environm Res, Oslo, Norway. Univ Oslo, Oslo, Norway. Meteorol Off, Bracknell, Berks, England. RP Danilin, MY (reprint author), AER Inc, 840 Mem Dr, Cambridge, MA 02139 USA. RI Jackman, Charles/D-4699-2012; Karcher, Bernd/D-5325-2014; Ko, Malcolm/D-5898-2015; Douglass, Anne/D-4655-2012; Fahey, David/G-4499-2013; Pitari, Giovanni/O-7458-2016; Penner, Joyce/J-1719-2012 OI Karcher, Bernd/0000-0003-0278-4980; Fahey, David/0000-0003-1720-0634; Pitari, Giovanni/0000-0001-7051-9578; Schumann, Ulrich/0000-0001-5255-6869; NR 30 TC 44 Z9 45 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 NOV 1 PY 1998 VL 25 IS 21 BP 3947 EP 3950 DI 10.1029/1998GL900058 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 136CE UT WOS:000076839800008 ER PT J AU Lundgren, P Giardini, D Russo, RM AF Lundgren, P Giardini, D Russo, RM TI A geodynamic framework for eastern Mediterranean kinematics SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GRAVITATIONAL POTENTIAL-ENERGY; CRUSTAL DEFORMATION; ACTIVE DEFORMATION; AEGEAN REGION; TECTONICS; EXTENSION; DYNAMICS; GREECE; SCALE; ASIA AB We use a finite element model incorporating plate motion boundary conditions, fault constraints, and space geodetic velocities to calculate eastern Mediterranean plate kinematics and to estimate the motion of the region's major faults. We then use subsets of these constraints to generate models testing different scenarios of driving forces (slab roll-back at the Hellenic are, Arabian plate push, gravitational collapse of W. Anatolia) to match the expected pattern of deformation. We find that models combining only trench rollback and Arabian push are unable to provide a good match to the observed deformation across western Anatolia and the Aegean and that we need to introduce the effects of mantle corner flow and gravitational collapse to fit observations. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. ETH Zurich, Inst Geophys, CH-8093 Zurich, Switzerland. Northwestern Univ, Dept Geol Sci, Evanston, IL 60208 USA. RP Lundgren, P (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Giardini, Domenico/F-5406-2011 NR 23 TC 33 Z9 33 U1 1 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD NOV 1 PY 1998 VL 25 IS 21 BP 4007 EP 4010 DI 10.1029/1998GL900096 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 136CE UT WOS:000076839800023 ER PT J AU Goldstein, RM Werner, CL AF Goldstein, RM Werner, CL TI Radar interferogram filtering for geophysical applications SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ICE-SHEET MOTION; INTERFEROMETRIC RADAR AB The use of SAR interferometry is often impeded by decorrelation from thermal noise, temporal change, and baseline geometry. Power spectra of interferograms are typically the sum of a narrow-band component combined with broad-band noise. We describe a new adaptive filtering algorithm that dramatically lowers phase noise, improving both measurement accuracy and phase unwrapping, while demonstrating graceful degradation in regions of pure noise. The performance of the filter is demonstrated with SAR data from the ERS satellites over the Jakobshavns glacier of Greenland. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goldstein, RM (reprint author), CALTECH, Jet Prop Lab, MS 300-227,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM goldstein@kahuna.jpl.nasa.gov RI zhang, yonglei/G-1045-2011 NR 14 TC 474 Z9 530 U1 1 U2 22 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 NOV 1 PY 1998 VL 25 IS 21 BP 4035 EP 4038 DI 10.1029/1998GL900033 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 136CE UT WOS:000076839800030 ER PT J AU Daniels, RA Peteet, D AF Daniels, RA Peteet, D TI Fish scale evidence for rapid post-glacial colonization of an Atlantic coastal pond SO GLOBAL ECOLOGY AND BIOGEOGRAPHY LA English DT Article DE Allamuchy Pond; Atlantic coastal refugia; Atlantic salmon; fish scale; Phoxininae; postglacial fish migration; sunfish; yellow perch; white sucker ID NORTHEASTERN USA AB Fish scales from the sediment of Allamuchy Pond, New Jersey, USA, indicate that fishes were present in the pond within 400 years of the time of the first deposition of organic material, at approximate to 12, 600 years sp. The earliest of the scales, from a while sucker, Catostomus commersoni, appears in sediment dared 12,260+/-220 years BP. Presence of scales in sediment deposited before 10,000 years BP indicates that Atlantic salmon, Salmo salar, sunfish, Lepomis sp., and yellow perch, Perca flavescens were also early inhabitants of the pond. The timing of the arrival of each of these fishes suggests that they migrated out from Atlantic coastal refugia, A minnow scale, referred to Phoxininae, was also retrieved, it could not be matched to any cyprinid currently found in northeastern North America. The species present historically in this pond are from five families found currently in ponds throughout the North-east and suggest that the lentic palaeo-environment was similar to present mid-elevation or high-latitude lentic systems. C1 New York State Museum & Sci Serv, Albany, NY 12230 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Lamont Doherty Earth Observ, New Core Lab, Palisades, NY 10964 USA. RP Daniels, RA (reprint author), New York State Museum & Sci Serv, CEC 3140, Albany, NY 12230 USA. NR 43 TC 6 Z9 6 U1 1 U2 4 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0960-7447 J9 GLOBAL ECOL BIOGEOGR JI Glob. Ecol. Biogeogr. PD NOV PY 1998 VL 7 IS 6 BP 467 EP 476 DI 10.1046/j.1466-822X.1998.00313.x PG 10 WC Ecology; Geography, Physical SC Environmental Sciences & Ecology; Physical Geography GA 178PT UT WOS:000079275600005 ER PT J AU Brooke, TY Knacke, RF Encrenaz, T Drossart, P Crisp, D Feuchtgruber, H AF Brooke, TY Knacke, RF Encrenaz, T Drossart, P Crisp, D Feuchtgruber, H TI Models of the ISO 3-mu m reflection spectrum of Jupiter SO ICARUS LA English DT Article DE Jupiter; atmosphere; general; composition; infrared observations; spectroscopy ID CLOUD STRUCTURE; INFRARED OBSERVATIONS; VERTICAL STRUCTURE; JOVIAN ATMOSPHERE; EQUATORIAL BELT; ZONE; PHOTOCHEMISTRY; SCATTERING; ABSORPTION; PHOTOMETRY AB A spectrum of Jupiter in the 3-mu m region obtained with the Infrared Space Observatory (ISO) shows evidence for the long-sought spectral signature of NH3 ice particles in the jovian atmosphere. We calculated Jupiter 3-mu m reflection spectrum, including multiple scattering by spherical cloud particles. Models containing reflection from two cloud decks along with NH3 gas absorption reproduce the sharp drop in Jupiter's reflectance longward of 2.7 mu m. Inclusion of cloud particles composed of NH3 ice in the upper cloud near 0.55 bar improves the it to the spectrum near 3.0 mu m, due to the N-H stretch absorption of solid NH3. For models with a single size for the NH3 ice, particles with radius a approximate to 10 mu m give the best fit. For a model with a bimodal distribution of a = 1 mu m and a = 10 mu m NH3 ice particles, the large particles need to dominate the 3-mu m NH3 ice particle opacity to provide absorption that is sufficiently broad. (C) 1998 Academic Press. C1 Penn State Erie, Div Sci, Erie, PA 16563 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Penn State Erie, Behrend Coll, Div Sci, Erie, PA 16563 USA. Observ Paris, DESPA, F-92195 Meudon, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. ESA, ISO Sci Operat Ctr, Div Astrophys, E-28080 Madrid, Spain. MPI Extraterrestr Phys, D-85740 Garching, Germany. RP Brooke, TY (reprint author), Penn State Erie, Div Sci, Stn Rd, Erie, PA 16563 USA. NR 40 TC 38 Z9 38 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 NOV PY 1998 VL 136 IS 1 BP 1 EP 13 DI 10.1006/icar.1998.6013 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 148CP UT WOS:000077535500001 ER PT J AU Emery, JP Sprague, AL Witteborn, FC Colwell, JE Kozlowski, RWH Wooden, DH AF Emery, JP Sprague, AL Witteborn, FC Colwell, JE Kozlowski, RWH Wooden, DH TI Mercury: Thermal modeling and mid-infrared (5-12 mu m) observations SO ICARUS LA English DT Article DE thermal modeling; Mercury surface composition; Mercury; planetary surfaces ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; SPECTRAL IRRADIANCE CALIBRATION; PLANETARY SURFACES; RADIOMETRIC METHOD; EMISSION-SPECTRA; RECALIBRATION; WAVELENGTHS; PLAGIOCLASE; DEPENDENCE; GRADIENTS AB We present and use a new rough-surface thermal model to aid in the analysis of new mid-infrared spectral measurements of Mercury from 5-12.5 mu m. The model calculates spatially resolved thermal emission from slowly rotating, airless bodies. The Mercury data contain the first spectral measurements of Mercury between 5-7.5 mu m, a region not accessible from ground-based telescopes, and are also the first observations of Mercury to be made while flying on the Kuiper Airborne Observatory (KAO). They were obtained with the High-efficiency Infrared Faint Object Grating Spectrometer (HIFOGS). Our rough surface thermal model which best fit the KAO data has a Hapke <(theta)over bar> of 20 degrees. A strong 5-mu m emission feature was present during both observing periods. We suggest the 5-mu m excess may be a result of near surface thermal gradients in regolith materials with a 30 to 100-mu m grainsize, but cannot entirely rule out an observational artifact resulting from our instrumentation or the telescope on the KAO, Other features in the spectra are consistent with a feldspathic and feld-spathoidal surface composition. (C) 1998 Academic Press. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Susquehanna Univ, Selingsgrove, PA 17870 USA. NASA, Ames Res Ctr, Mt View, CA 94035 USA. RP Emery, JP (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NR 48 TC 62 Z9 62 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 NOV PY 1998 VL 136 IS 1 BP 104 EP 123 DI 10.1006/icar.1998.6012 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 148CP UT WOS:000077535500007 ER PT J AU Hilland, JE Stuhr, FV Freeman, A Imel, D Shen, Y Jordan, RL Caro, ER AF Hilland, JE Stuhr, FV Freeman, A Imel, D Shen, Y Jordan, RL Caro, ER TI Future NASA spaceborne SAR missions SO IEEE AEROSPACE AND ELECTRONIC SYSTEMS MAGAZINE LA English DT Article DE radar; interferometry; topography; vegetation; remote sensing; ScanSAR; synthetic-aperture ID RADAR AB Two Earth-orbiting radar missions are planned for the near future by NASA - Shuttle Radar Topography Mission (SRTM) and LightSAR. The SRTM will fly aboard the Shuttle using interferometric synthetic aperture radar (IFSAR) to provide a global digital elevation map. SRTM is jointly sponsored by NASA and the National Imagery and Mapping Agency (NIMA). The LightSAR will utilize emerging technology to reduce mass and life-cycle costs for a mission to acquire SAR data for Earth science and civilian applications and to establish commercial utility. LightSAR is sponsored by NASA and industry partners. The use of IFSAR to measure elevation is one of the most powerful and practical applications of radar. A properly equipped spaceborne IFSAR system can produce a highly accurate global digital elevation map, including cloud-covered areas, in significantly less time and at significantly lower cost than other systems. For accurate topography over a large area, the interferometric measurements can be performed simultaneously in physically separate receive systems. The Spaceborne Imaging Radar C (SIR-C), successfully flown twice in 1994 aboard the Space Shuttle Endeavour, offers a unique opportunity for global multifrequency elevation mapping by the year 2000. The addition of a C-band receive antenna of approximately 60 m length, extended from the Shuttle bay on a mast, and operating in concert with the existing SIR-C antenna, produces an interferometric pair. It is estimated that the 90% linear absolute elevation error achievable is less than 16 meters for elevation postings of 30 meters. The SRTM will be the first single-pass spaceborne IFSAR instrument and will produce a near-global high-resolution digital topography data set. Since LightSAR offers important benefits to both the science community and US industry, an innovative government-industry teaming approach is being explored, with industry sharing the cost of developing LightSAR in return for commercial rights to its data and operational responsibility. LightSAR will enable mapping of surface change. The instrument's high-resolution mapping, along with its quad polarization, dual polarization, interferometric and ScanSAR modes will enable continuous monitoring of natural hazards, Earth's surface deformation, surface vegetation change, and ocean mesoscale features to provide commercially viable and scientifically valuable data products. Advanced microelectronics and lightweight materials will increase LightSAR's functionality without increasing the mass. Dual frequency L/X-band designs have been examined. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hilland, JE (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 12 Z9 12 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0885-8985 J9 IEEE AERO EL SYS MAG JI IEEE Aerosp. Electron. Syst. Mag. PD NOV PY 1998 VL 13 IS 11 BP 9 EP 16 DI 10.1109/62.730609 PG 8 WC Engineering, Aerospace; Engineering, Electrical & Electronic SC Engineering GA 134AM UT WOS:000076720000003 ER PT J AU Lai, R Barsky, M Huang, T Sholley, M Wang, H Kok, YL Streit, DC Block, T Liu, PH Gaier, T Samoska, L AF Lai, R Barsky, M Huang, T Sholley, M Wang, H Kok, YL Streit, DC Block, T Liu, PH Gaier, T Samoska, L TI An InP HEMT MMIC LNA with 7.2-dB gain at 190 GHz SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article AB We present the highest frequency performance of any solid-state monolithic microwave integrated circuit (MMIC) amplifier. A 2-stage 80-nm gate length InGaAs/InAlAs/InP HEMT MMIC balanced amplifier has a measured on-wafer peak gain of 7.2 dB at 190 GHz and greater than 5 dB gain from 170 to 194 GHz, The circuit was fabricated using a pseudomorphic 20-nm In0.65Ga0.35As channel HEMT structure grown on a 3-in InP substrate by MBE. Based on the measured circuit results, the intrinsic exhibits an F-max greater than 400 GHz. C1 TRW Elect Space & Technol Div, Redondo Beach, CA 90277 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lai, R (reprint author), TRW Elect Space & Technol Div, Redondo Beach, CA 90277 USA. NR 7 TC 29 Z9 30 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 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD NOV PY 1998 VL 8 IS 11 BP 393 EP 395 DI 10.1109/75.736257 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 151BZ UT WOS:000077702100013 ER PT J AU Shieh, W Maleki, L AF Shieh, W Maleki, L TI Phase noise of optical interference in photonic RF systems SO IEEE PHOTONICS TECHNOLOGY LETTERS LA English DT Article DE frequency stability; microwave; optical fiber applications; phased array radar; phase noise ID INTENSITY NOISE; LASER AB Close-in optical interferometric noise spectrum and its conversion to RF close-in phase noise are theoretically and experimentally studied. The optical 1/f frequency noise is the dominant source of the close-in interferometric phase noise and is converted into the 1/f(upsilon) noise, where upsilon is determined by the time delay sealed to the coherence time of the 1/f noise. The study also indicates that reflective type devices and optically amplified links exacerbate the interferometric phase noise degradation. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Shieh, W (reprint author), Lucent Technol, Opt Networking, Holmdel, NJ 07733 USA. OI Shieh, William/0000-0003-1777-5403 NR 8 TC 24 Z9 24 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 1041-1135 J9 IEEE PHOTONIC TECH L JI IEEE Photonics Technol. Lett. PD NOV PY 1998 VL 10 IS 11 BP 1617 EP 1619 DI 10.1109/68.726768 PG 3 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA 129TY UT WOS:000076480200031 ER PT J AU Neat, GW Melody, JW AF Neat, GW Melody, JW TI Vibration attenuation approach for spaceborne optical interferometers SO IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY LA English DT Article DE active optical control; flexible structures; interferometry; vibration attenuation; vibration isolation AB This paper proposes a vibration attenuation strategy for spaceborne optical interferometers to meet their submicron positional stability requirements. Specifically, the Stellar Interferometer Mission requires 10-nm level stabilization of optical elements distributed across a 10-m flexible structure in the presence of the primary disturbance source, spinning reaction wheel assemblies. The proposed strategy incorporates the high-frequency attenuation of six-axis vibration isolation with low-frequency attenuation of active optical control, The strategy is implemented on the Micro-Precision Interferometer testbed, a fully functional hardware model of a future spaceborne interferometer. Combining measured testbed disturbance transfer functions with a stochastic model of reaction wheel disturbances enables evaluation of the vibration attenuation strategy in the expected on-orbit disturbance environment. Results indicate that the requirement of 10 nm is satisfied. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Neat, GW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 32 Z9 34 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 1063-6536 J9 IEEE T CONTR SYST T JI IEEE Trans. Control Syst. Technol. PD NOV PY 1998 VL 6 IS 6 BP 689 EP 700 DI 10.1109/87.726529 PG 12 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 133TZ UT WOS:000076703000001 ER PT J AU Joshi, SM Kelkar, AG AF Joshi, SM Kelkar, AG TI Inner loop control of supersonic aircraft in the presence of aeroelastic modes SO IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY LA English DT Article DE aeroelastic mode control; aircraft control; linear-quadratic control; robustness; robust control; supersonic aircraft ID SYSTEMS; BOUNDS; REDUCTION; STABILITY AB Longitudinal control system design is considered for a linearized dynamic model of a supersonic transport aircraft concept characterized by relaxed static stability and significant aeroelastic interactions. Two LQG-type controllers are designed using the frequency-domain additive uncertainty formulation to ensure robustness to unmodeled flexible modes. The first controller is based on a fourth-order model containing only the rigid-body modes, while the second controller is based on an eighth-order model that additionally includes the two most prominent flexible modes. The performance obtainable from the fourth-order controller is not adequate, while the eighth-order controller is found to provide better performance, Frequency-domain and time-domain (Lyapunov) methods are subsequently used to assess the robustness of the eighth-order controller to parametric uncertainties in the design model. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Kansas State Univ, Manhattan, KS 66506 USA. RP Joshi, SM (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 17 TC 12 Z9 12 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1063-6536 J9 IEEE T CONTR SYST T JI IEEE Trans. Control Syst. Technol. PD NOV PY 1998 VL 6 IS 6 BP 730 EP 739 DI 10.1109/87.726534 PG 10 WC Automation & Control Systems; Engineering, Electrical & Electronic SC Automation & Control Systems; Engineering GA 133TZ UT WOS:000076703000005 ER PT J AU Simard, M DeGrandi, G Thomson, KPB Benie, GB AF Simard, M DeGrandi, G Thomson, KPB Benie, GB TI Analysis of speckle noise contribution on wavelet decomposition of SAR images SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE multiscale; speckle; synthetic aperture radar (SAR); texture; wavelet ID CLUTTER TEXTURES; COHERENT IMAGES; RADAR IMAGES; COMPRESSION; STATISTICS; MODEL; REPRESENTATION; SCATTERING; TRANSFORM; RAYLEIGH AB This paper describes the use of the wavelet transform for multiscale texture analysis. One of the basic problems is that texture measures have to adapt to the peculiarity of radar images that contain multiplicative speckle noise. In this paper, the focus is on the effect of speckle on the wavelet transform. The effect is first assessed analytically, It is shown that the wavelet coefficients are modulated by the multiplicative character of the speckle in a manner that is proportional to the target mean backscattering coefficient. The effect of speckle correlation is also demonstrated. Wavelet decomposition is then applied to a simulated radar image generated by a Monte Carlo approach and based on a statistical model. Modeling shows that the correlation properties of speckle have an effect up to a scale that corresponds to its granular size, The results also show that the main contribution to the wavelet transform for an homogeneous area is the first-order statistical distribution of speckle, which remains important even at large scales. The results are then compared to a ERS-1 synthetic aperture radar (SAR) image of a primary tropical forest region. C1 Univ Laval, Ctr Rech Geomat, Ste Foy, PQ G1K 7P4, Canada. Commiss European Communities, Joint Res Ctr, Space Applicat Inst, I-21020 Ispra, Italy. Univ Sherbrooke, CARTEL, Sherbrooke, PQ J1K 2R1, Canada. RP Simard, M (reprint author), CALTECH, Jet Prop Lab, NASA, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM simard@bacchus.jpl.nasa.gov; gianfranco.degrandi@jrc.it; keith.thomson@scg.ulaval.ca RI Simard, Marc/H-3516-2013 OI Simard, Marc/0000-0002-9442-4562 NR 52 TC 47 Z9 55 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 NOV PY 1998 VL 36 IS 6 BP 1953 EP 1962 DI 10.1109/36.729367 PG 10 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 139UT UT WOS:000077048600013 ER PT J AU Imhoff, ML Carson, S Johnson, P AF Imhoff, ML Carson, S Johnson, P TI A low-frequency radar experiment for measuring vegetation biomass SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE biomass measurement; forest stands; low-frequency radar; vegetation; VHF radar ID FOREST BIOMASS; SAR; BACKSCATTER; MICHIGAN AB Optical depth and backscatter measures were made at 18 frequencies between 50 and 450 MHz on two forest stands having dry biomass densities of 323 and 87 tons/ha to identify radar frequencies capable of penetrating heavy stands of vegetation, Good separation between stands was only achieved below 120 MHz. C1 NASA, Biospher Sci Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. SAIC, Arlington, VA 22203 USA. Amer Elect Inc, Zimmerman Associates Inc, Vienna, VA 22182 USA. RP Imhoff, ML (reprint author), NASA, Biospher Sci Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 19 TC 16 Z9 17 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 NOV PY 1998 VL 36 IS 6 BP 1988 EP 1991 DI 10.1109/36.729374 PG 4 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 139UT UT WOS:000077048600019 ER PT J AU Wang, H Lai, R Kok, YL Huang, TW Aust, MV Chen, YCC Siegel, PH Gaier, T Dengler, RJ Allen, BR AF Wang, H Lai, R Kok, YL Huang, TW Aust, MV Chen, YCC Siegel, PH Gaier, T Dengler, RJ Allen, BR TI A 155-GHz monolithic low-noise amplifier SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE InP; LNA; MMIC; pHEMT AB This paper presents the design, fabrication, and test results of a three-stage 155-GHz monolithic low-noise amplifier (LNA) fabricated with the 0.1-mu m pseudomorphic (PM) InAlAs/InGaAs/InP HEMT technology. With this amplifier in a test fixture, a small-signal gain of 12 dB was measured at 155 GHz, and more than 10-dB gain from 151 to 156 GHz, When the amplifier was biased for a low noise figure (NF), an NF of 5.1 dB with an associated gain of 10.1 dB was achieved at 155 GHz, All the results above are referred to the monolithic-microwave integrated-circuit (MMIC) chip with the input and output waveguide-to-microstrip-line transition losses corrected. C1 TRW Co Inc, Space & Technol Grp, Redondo Beach, CA 90278 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wang, H (reprint author), Natl Taiwan Univ, Dept Elect Engn, Taipei 10617, Taiwan. NR 13 TC 19 Z9 20 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 NOV PY 1998 VL 46 IS 11 BP 1660 EP 1666 DI 10.1109/22.734551 PN 1 PG 7 WC Engineering, Electrical & Electronic SC Engineering GA 140DP UT WOS:000077071800009 ER PT J AU Harvey, JF Brown, ER AF Harvey, JF Brown, ER TI Special issue on innovative integration techniques for microwave and millimeter-wave circuits - Foreword SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Editorial Material C1 USA, Res Off, Washington, DC 20310 USA. Univ Calif Los Angeles, Los Angeles, CA 90024 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Harvey, JF (reprint author), USA, Res Off, Washington, DC 20310 USA. NR 6 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD NOV PY 1998 VL 46 IS 11 BP 1817 EP 1820 PN 2 PG 4 WC Engineering, Electrical & Electronic SC Engineering GA 140RC UT WOS:000077101300001 ER PT J AU Moussessian, A Rosenberg, JJ Rutledge, DB AF Moussessian, A Rosenberg, JJ Rutledge, DB TI Properties of periodic arrays of symmetric complementary structures and their application to grid amplifiers SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE grid amplifiers; quasi-optics; self-complementary ID 100-ELEMENT AB Deschamps' theorem for n-terminal complementary structures is reviewed. An extension to Deschamps' theorem for a class of three-terminal bounded structures with one axis of symmetry is presented. It is shown that, for these structures, a simple relationship between the impedances of the odd mode of the original structure and the admittances of the even mode of the complementary structure exists, and that these modes are orthogonal. Using this, a self-complementary grid amplifier is designed and the measured results are presented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvey Mudd Coll, Dept Engn, Claremont, CA 91711 USA. CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. RP Moussessian, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 6 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 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD NOV PY 1998 VL 46 IS 11 BP 1956 EP 1963 DI 10.1109/22.734518 PN 2 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 140RC UT WOS:000077101300016 ER PT J AU Moussessian, A Wanke, MC Li, YJ Chiao, JC Allen, SJ Crowe, TW Rutledge, DB AF Moussessian, A Wanke, MC Li, YJ Chiao, JC Allen, SJ Crowe, TW Rutledge, DB TI A terahertz grid frequency doubler SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Article DE frequency doubler; multiplier grid; quasi-optics; terahertz ID THZ AB We present a 144-element terahertz quasi-optical grid frequency doubler. The grid is a planar structure with bowtie antennas as a unit cell, each loaded with a planar Schottky diode. The maximum output power measured for this grid is 24 mW at 1 THz for 3.1-mu s 500-GHz input pulses with a peak input power of 47 W. An efficiency of 0.17% for an input pow er of 6.3 W and output power of 10.8 mW is measured. To date, this is the largest recorded output power for a multiplier at terahertz frequencies. Input and output tuning curves are presented and an output pattern is measured and compared to theory. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. Univ Virginia, Dept Elect Engn, Charlottesville, VA 22903 USA. Univ Hawaii Manoa, Dept Elect Engn, Honolulu, HI 96822 USA. CALTECH, Dept Elect Engn, Pasadena, CA 91125 USA. RP Moussessian, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 15 Z9 16 U1 1 U2 3 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9480 J9 IEEE T MICROW THEORY JI IEEE Trans. Microw. Theory Tech. PD NOV PY 1998 VL 46 IS 11 BP 1976 EP 1981 DI 10.1109/22.734524 PN 2 PG 6 WC Engineering, Electrical & Electronic SC Engineering GA 140RC UT WOS:000077101300018 ER PT J AU Feather, MS AF Feather, MS TI Rapid application of lightweight formal methods for consistency analyses SO IEEE TRANSACTIONS ON SOFTWARE ENGINEERING LA English DT Article DE consistency checking; formal methods; interlace checking; test-log checking; database-based analysis; NASA AB Lightweight formal methods promise to yield modest analysis results in an extremely rapid manner. To fulfill this promise, they must be able to work with existing information sources, be able to analyze for manifestly desirable properties, be highly automated (especially if dealing with voluminous amounts of information), and be readily customizable and flexible in the face of emerging needs and understanding. Two pilot studies investigate the feasibility of lightweight formal methods that employ a database as the underlying reasoning engine to perform the analyses. The first study concerns aspects of software module interfaces, the second test logs' adherence to required and expected conditions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 125-233, Pasadena, CA 91109 USA. EM martin.s.feather@jpl.nasa.gov NR 13 TC 12 Z9 12 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 0098-5589 EI 1939-3520 J9 IEEE T SOFTWARE ENG JI IEEE Trans. Softw. Eng. PD NOV PY 1998 VL 24 IS 11 BP 949 EP 959 DI 10.1109/32.730544 PG 11 WC Computer Science, Software Engineering; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 139CL UT WOS:000077010000005 ER PT J AU Lee, TS Ghosh, S AF Lee, TS Ghosh, S TI RYNSORD: A novel decentralized algorithm for railway networks with "soft reservation" SO IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY LA English DT Article DE autonomous systems; congestion mitigation; coordinating processes; decentralized algorithms; decision making; distributed algorithm; distributed decision making; distributed optimization; flexible negotiation; hard reservation; lookahead; scheduling; soft reservation; train network; resource allocation ID TRAIN CONTROL-SYSTEM; SIMULATION; DESIGN AB This paper presents a novel Decentralized algorithm with SOft Reservation for efficient scheduling and congestion mitigation in RailwaY Networks (RYNSORD), wherein every train utilizes lookahead to dynamically replan its route. Thus, a train, currently at position X and headed for the ultimate destination Y, first requests and reserves N tracks, i.e., the lookahead, ahead of its current position for use at appropriate future times. The train moves through the N tracks and, upon completion, it again requests and reserves N subsequent tracks ahead of itself. The process continues until the train reaches its destination. The reservation process is characterized as "soft," i.e., less abrupt and more flexible in negotiation between the trains and stations, in contrast to the traditional rigid "hard" reservations. RYNSORD is modeled and implemented on a network of SUN spare workstations, configured as a loosely coupled parallel processor. Experimental results, obtained from simulating realistic example train networks and utilizing stochastic input train traffic data, reveal that: 1) soft reservation is superior to hard reservations in achieving both fast train travel times and higher quality of routing and 2) while trains under low lookahead experience higher average hop count and high probability of doublebacks, relative to large lookahead values, they also have lower travel times. C1 NASA, Ames Res Ctr, Network Res Grp, Moffett Field, CA 94035 USA. Arizona State Univ, Dept Comp Sci & Engn, Tempe, AZ 85287 USA. RP Lee, TS (reprint author), NASA, Ames Res Ctr, Network Res Grp, Moffett Field, CA 94035 USA. NR 19 TC 8 Z9 8 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9545 J9 IEEE T VEH TECHNOL JI IEEE Trans. Veh. Technol. PD NOV PY 1998 VL 47 IS 4 BP 1350 EP 1364 DI 10.1109/25.728526 PG 15 WC Engineering, Electrical & Electronic; Telecommunications; Transportation Science & Technology SC Engineering; Telecommunications; Transportation GA 136QK UT WOS:000076870500025 ER PT J AU Harstad, K Bellan, J AF Harstad, K Bellan, J TI Isolated fluid oxygen drop behavior in fluid hydrogen at rocket chamber pressures SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID VAPORIZATION; COMBUSTION AB A model has been developed for the behavior of an isolated fluid drop of a single compound immersed into another compound in finite, quiescent surroundings at supercritical conditions. The model is based upon fluctuation theory which accounts for both Soret and Dufour effects in the calculation of the transport matrix relating molar and heat fluxes to the transport properties and the thermodynamic variables. The transport properties have been modeled over a wide range of pressure and temperature variation applicable to LOx-H-2 conditions in rocket chambers, and the form of the chemical potentials is valid for a general fluid. The equations of state have been calculated using a previously-derived, computationally-efficient and accurate protocol. Results obtained for the LOx-H-2 system show that the supercritical behavior is essentially one of diffusion. The temperature profile relaxes fastest followed by the density and lastly by the mass fraction profile. An effective Lewis number calculated using theory derived elsewhere shows that it is larger by approximately a factor of 40 than the traditional Lewis number. The parametric variations show that gradients increasingly persist with increasing fluid drop size or pressure, and with decreasing temperature. The implication of these results upon accurate measurements of fluid drop size under supercritical conditions is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 31 TC 54 Z9 54 U1 0 U2 6 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 NOV PY 1998 VL 41 IS 22 BP 3537 EP 3550 DI 10.1016/S0017-9310(98)00049-0 PG 14 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 120WN UT WOS:000075980500017 ER PT J AU Harstad, K Bellan, J AF Harstad, K Bellan, J TI Interactions of fluid oxygen drops in fluid hydrogen at rocket chamber pressures SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID MULTIPLE AB A model of fluid drop behavior in clusters has been developed including the interactions induced by the drop proximity. The model is based upon the global conservation equations for the interstitial cluster region coupled to isolated fluid drop equations previously developed. Heat and mass transfer to the cluster are modeled using the Nusselt number concept. Results from calculations for the LOx-H-2 system show the predictions to be insensitive to the value of the Nusselt number over three orders of magnitude. The results also show that at fixed pressure, increased drop proximity induces increased accumulation of LO, in the interstitial space inside the cluster. At fixed initial drop proximity, the gradients of the dependent variables become increasingly smeared as the pressure increases; an opposite result from that obtained for isolated drops (Harstad K, Bellan J. Isolated fluid oxygen drop behavior in fluid hydrogen at rocket chamber pressure. Int J Heat Mass Transfer 1998;41.3537-50). It is thus inferred that clusters of drops might be a desirable aspect in supercritical combustion because they aid interdiffusion of the reactive components. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 13 TC 21 Z9 21 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD NOV PY 1998 VL 41 IS 22 BP 3551 EP 3558 DI 10.1016/S0017-9310(98)00048-9 PG 8 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 120WN UT WOS:000075980500018 ER PT J AU Hause, T Librescu, L Johnson, TF AF Hause, T Librescu, L Johnson, TF TI Non-linear response of geometrically imperfect sandwich curved panels under thermomechanical loading SO INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS LA English DT Article DE thermomechanical postbuckling; snap-through; load-carrying capacity ID COMPOSITE AB This paper deals with the non-linear response of sandwich curved panels exposed to thermomechanical loadings. The mechanical loads consist of compressive/tensile edge loads, and a lateral pressure while the temperature field is assumed to exhibit a linear variation through the thickness of the panel. Towards obtaining the equations governing the postbuckling response, the Extended Galerkin's Method is used. The numerical illustrations concern doubly curved, circular cylindrical and as a special case, flat panels, all the edges being simply supported. Moveable and immoveable tangential boundary conditions in the directions normal to the edges are considered and their implications upon the thermomechanical load-carrying capacity are emphasized. Effects of the radii of curvature and of initial geometric imperfections on the load-carrying capacity of sandwich panels are also considered and their influence upon the intensity of the snap-through buckling are discussed. It is shown that in special cases involving the thermomechanical loading and initial geometric imperfection, the snap-through phenomenon can occur also in the case of hat sandwich panels. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. NASA, Langley Res Ctr, Struct Div, Thermal Struct Branch, Hampton, VA 23681 USA. RP Hause, T (reprint author), Virginia Polytech Inst & State Univ, Dept Engn Sci & Mech, Blacksburg, VA 24061 USA. NR 11 TC 12 Z9 12 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0020-7462 J9 INT J NONLINEAR MECH JI Int. J. Non-Linear Mech. PD NOV PY 1998 VL 33 IS 6 BP 1039 EP 1059 DI 10.1016/S0020-7462(97)00067-X PG 21 WC Mechanics SC Mechanics GA ZQ613 UT WOS:000073885600008 ER PT J AU Mathias, DL Roth, KR Ross, JC Rogers, SE Cummings, RM AF Mathias, DL Roth, KR Ross, JC Rogers, SE Cummings, RM TI Navier-Stokes analysis of the flow about a flap edge SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA 33rd Aerospace Sciences Meeting CY JAN 09-12, 1995 CL RENO, NEVADA SP Amer Inst Aeronaut & Astronaut AB The current study computationally examines one of the principal three-dimensional features of the flow over a high-lift system, the now associated with a flap edge. Structured, overset grids were used in conjunction with an incompressible Navier-Stokes solver to compute the flow over a two-element high-lift configuration. The computations were run in a fully turbulent mode using the one-equation Baldwin-Barth model. Specific emphasis was given to the details of the now in the vicinity of the flap edge, and so the geometry was simplified to isolate this region. The geometry consisted of an unswept wing, which spanned a wind-tunnel test section, equipped with a single-element flap. Two flap configurations were computed: a full-span and a half-span Fowler flap. The chord-based Reynolds number was 3.7 x 10(6) for all eases. The results for the full-span flap agreed with two-dimensional experimental results and verified the method. Grid topologies and related issues for the had-span flap geometry are discussed. Results of the half-span flap case are compared with three-dimensional experimental results, with emphasis on the how features associated with the nap edge. The results show the effect of the vortex created by the flap edge, including the impact on flow separation and spanwise Lift distribution. C1 Calif Polytech State Univ San Luis Obispo, Dept Aeronaut Engn, San Luis Obispo, CA 93407 USA. NASA, Ames Res Ctr, Aerodynam Directorate, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Computat Algorithms & Applicat Branch, Moffett Field, CA 94035 USA. RP Mathias, DL (reprint author), MCAT Inc, Moffett Field, CA 94035 USA. NR 21 TC 7 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 NOV-DEC PY 1998 VL 35 IS 6 BP 833 EP 838 DI 10.2514/2.2384 PG 6 WC Engineering, Aerospace SC Engineering GA 148PX UT WOS:000077542000001 ER PT J AU Patnaik, SN Guptill, JD Hopkins, DA Lavelle, TM AF Patnaik, SN Guptill, JD Hopkins, DA Lavelle, TM TI Neural network and regression approximations in high-speed civil aircraft design optimization SO JOURNAL OF AIRCRAFT LA English DT Article ID STRUCTURAL OPTIMIZATION AB Nonlinear mathematical-programming-based design optimization can be an elegant method. However, the calculations required to generate the merit function, constraints, and their gradients, which are frequently required, make the process computationally intensive. The computational burden can be substantially reduced by using approximating analyzers derived from an original analyzer utilizing neural networks and linear regression methods. The experience gained from using both of these approximation methods in the design optimization of a high-speed civil transport aircraft is the subject of this paper. The NASA Langley Research Center's Flight Optimization System was selected for tbe aircraft analysis. This software was exercised to generate a set of training data with which a neural network and regression method were trained, thereby producing the two approximating analyzers. The derived analyzers were coupled to the NASA Lewis Research Center's CometBoards test bed to provide the optimization capability, Both approximation methods were examined for use in aircraft design optimization, and both performed satisfactorily. The CPU time for solution of the problem, which had been measured in hours, was reduced to minutes with the neural network approximation and to seconds with the regression method. Instability encountered in the aircraft analysis software at certain design points was also eliminated. However, there were costs and difficulties associated with training the approximating analyzers. The CPU time required to generate the I/O pairs and to train the approximating analyzers was seven times that required for solution of the problem. C1 NASA, Lewis Res Ctr, Machine Dynam Branch, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Propuls Syst Anal Off, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Computat Sci Branch, Cleveland, OH 44135 USA. RP Patnaik, SN (reprint author), Ohio Aerosp Inst, 22800 Cedar Point Rd, Brook Pk, OH 44142 USA. NR 35 TC 4 Z9 5 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1998 VL 35 IS 6 BP 839 EP 850 DI 10.2514/2.2395 PG 12 WC Engineering, Aerospace SC Engineering GA 148PX UT WOS:000077542000002 ER PT J AU Toomer, CA Topliss, ME Hills, DP AF Toomer, CA Topliss, ME Hills, DP TI Aerodynamic optimization using analytic descriptions of the design space SO JOURNAL OF AIRCRAFT LA English DT Article; Proceedings Paper CT AIAA/USAF/NASA/ISSMO 6th Symposium on Multidisciplinary Analysis and Optimization CY SEP 04-06, 1996 CL BELLEVUE, WASHINGTON SP AIAA, USAF, NASA, ISSMO ID SENSITIVITY DERIVATIVES AB This paper discusses a strategy for performing aerodynamic single-point and multipoint optimization studies. The approach uses a combination of three methods: an Euler computational fluid dynamics (CFD) code that provides accurate information at one chosen point in the design space, a linear approximation method of the quasianalytic type that rapidly evaluates data at many design points, and a function-fitting algorithm that maps aerodynamic and geometric data across the whole design space. As the method proceeds, a good quality database of aerodynamic and geometric quantities is rapidly constructed at a fraction of the cost of using conventional methods. The availability of this database and the analytic representation of the quantities over the whole design space permits optimizations to be performed using constraints on specific aerodynamic parameters, e.g,, maximum surface Mach number and pressure gradients, over chosen regions of the aerofoil, The approach is also highly flexible, enabling optimization problems of increasing complexity to be built up quickly, and is easily integrated within modern engineering methods. Results are presented for a typical transonic aerofoil giving comparisons with individual CFD analyses. C1 British Aerosp Operat Ltd, Sowerby Res Ctr, CFD Grp, Bristol BS12 7QW, Avon, England. RP Toomer, CA (reprint author), NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, M-S 403, Hampton, VA 23681 USA. NR 9 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0021-8669 J9 J AIRCRAFT JI J. Aircr. PD NOV-DEC PY 1998 VL 35 IS 6 BP 882 EP 890 DI 10.2514/2.2408 PG 9 WC Engineering, Aerospace SC Engineering GA 148PX UT WOS:000077542000007 ER PT J AU Ribner, HS AF Ribner, HS TI Wake forces implied in the Theodorsen and Goldstein theories of propellers SO JOURNAL OF AIRCRAFT LA English DT Article AB This study examines wake edge forces and normal forces implied, but overlooked, respectively, in the Theodorsen and Goldstein theories of the optimum efficiency of propellers. It is argued that the postulated trailing vortex sheets must coincide with real rigid surfaces to support forces exerted by the fluid, In the rigidized Theodorsen model, edge suction forces are tilted backward and circumferentially in the region of contraction. These are implicitly included in the predictions of propeller thrust and torque. The corrections are estimated herein. The resulting change in efficiency, a gain, is normally less than 1%, but can reach over 2% in extreme examples. In the rigidized Goldstein model, the wake does not contract, but the streamlines do. The crossflow component, acting on the bound trailing vortices, generates lift; hence, thrust and torque components. These corrections to the Goldstein-based predictions (using Theodorsen's formulas) are found to be compatible with the contraction correction of the Theodorsen theory: the Goldstein theory, when rigidized, appears equivalent to the Theodorsen theory. In the Theodorsen theory, the required wake forces are seen to be so small that their neglect (by neglect of wake rigidity) is of conceptual significance only. C1 Univ Toronto, Inst Aerosp Studies, N York, ON M3H 5T6, Canada. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Ribner, HS (reprint author), Univ Toronto, Inst Aerosp Studies, 4925 Dufferin St, N York, ON M3H 5T6, Canada. NR 15 TC 2 Z9 2 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 NOV-DEC PY 1998 VL 35 IS 6 BP 930 EP 935 DI 10.2514/2.2388 PG 6 WC Engineering, Aerospace SC Engineering GA 148PX UT WOS:000077542000013 ER PT J AU Jegley, DC AF Jegley, DC TI Behavior of compression-loaded composite panels with stringer terminations and impact damage SO JOURNAL OF AIRCRAFT LA English DT Article AB The results of an analytical and experimental study of graphite-epoxy stiffened panels with impact-damaged stringer terminations are presented. Five stitched graphite-epoxy panels with stiffeners with a gradual reduction in either thickness or height were examined. Panels were analyzed using finite element analysis and tested by loading them in axial compression to a predetermined load. The panels were then subjected to impact damage and loaded to failure. Axial midplane strains, surface strains, interlaminar strains, and failure results are discussed. C1 NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, Hampton, VA 23681 USA. RP Jegley, DC (reprint author), NASA, Langley Res Ctr, Struct Mech Branch, Struct Div, M-S 190, Hampton, VA 23681 USA. NR 6 TC 1 Z9 2 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 NOV-DEC PY 1998 VL 35 IS 6 BP 942 EP 948 DI 10.2514/2.2390 PG 7 WC Engineering, Aerospace SC Engineering GA 148PX UT WOS:000077542000015 ER PT J AU Gao, BC Han, W Tsay, SC Larsen, NF AF Gao, BC Han, W Tsay, SC Larsen, NF TI Cloud detection over the Arctic region using airborne imaging spectrometer data during the daytime SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID WATER-VAPOR BAND; PATTERN-RECOGNITION; COVER ANALYSIS; POLAR-REGIONS; SURFACE; IMAGERY; CLASSIFICATION AB Detection of clouds over arctic regions from current satellite radiometric measurements in the visible and IR atmospheric window regions, such as those of Advanced Very High Resolution Radiometer and Landsat, is often difficult due to the high albedos of snow- and ice-covered surfaces in the visible and the nearly isothermal temperature profiles in the lower atmosphere. In this paper the authors show that the water vapor absorption channel at 1.38 mu m is effective in detecting high clouds over snow- and ice-covered surfaces in the Arctic. Low-level clouds can be detected from surface snow and sea ice using a narrow channel centered at 1.5 mu m with a width of approximately 10 nm because of the dark background that results from strong absorption by snow and sea ice. Imaging data with contiguous spectral coverage between 0.4 and 2.5 mu m acquired with the Airborne Visible/Infrared Imaging Spectrometer during the Arctic Radiation Measurements in Column Atmosphere-Surface System in Alaska in 1995 are analyzed. The authors have observed that as wavelength increases from 1.38 mu m the atmospheric water vapor absorption becomes weaker and weaker and the low-level clouds and surface tundra are increasingly seen. It is always possible to locate a narrow channel in the spectral range of 1.38-1.50 mu m with appropriate water vapor absorption strength to separate water and ice clouds from surface snow, sea ice, and tundra. The simple cloud-masking technique described here is directly applicable to cloud detection during the daytime from hyperspectral imaging data over arctic regions, which will be acquired with future satellite sensors. C1 USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. SFA Inc, Largo, MD USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. Univ Alaska, Inst Geophys, Fairbanks, AK USA. Univ Alaska, Dept Phys, Fairbanks, AK USA. RP Gao, BC (reprint author), USN, Res Lab, Remote Sensing Div, Code 7212,4555 Overlook Dr SW, Washington, DC 20375 USA. RI Tsay, Si-Chee/J-1147-2014 NR 24 TC 12 Z9 12 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 NOV PY 1998 VL 37 IS 11 BP 1421 EP 1429 DI 10.1175/1520-0450(1998)037<1421:CDOTAR>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 144CH UT WOS:000077295800004 ER PT J AU Schlegel, TT Benavides, EW Barker, DC Brown, TE Harm, DL DeSilva, SJ Low, PA AF Schlegel, TT Benavides, EW Barker, DC Brown, TE Harm, DL DeSilva, SJ Low, PA TI Cardiovascular and Valsalva responses during parabolic flight SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE Valsalva maneuver; baroreflex; microgravity; hypergravity ID CENTRAL VENOUS-PRESSURE; ACUTE HEMODYNAMIC-RESPONSES; IMPEDANCE CARDIOGRAPHY; HEART-RATE; HUMANS; REFLEX; WEIGHTLESSNESS; MANEUVER; STIMULATION; SENSITIVITY AB We investigated the integrated cardiovascular responses of 15 human subjects to the acute gravitational changes (micro- and hypergravity portions) of parabolic flight. Measurements were made with subjects quietly seated and while subjects performed controlled Valsalva maneuvers. During quiet, seated, parabolic flight, mean arterial pressure increased during the transition into microgravity but decreased as microgravity was sustained. The decrease in mean arterial pressure was accompanied by immediate reflexive increases in heart rate but by absent (or later-than-expected) reflexive increases in total vascular resistance. Mean arterial pressure responses in Valsalva phases II1, III, and IV were accentuated in hypergravity relative to microgravity (P < 0.01, P < 0.01, and P < 0.05, respectively), but accentuations differed qualitatively and quantitatively from those induced by a supine-to-seated postural change in 1 G. This study is the first systematic evaluation of temporal and Valsalva-related changes in cardiovascular parameters during parabolic flight. Results suggest that arterial baroreflex control of vascular resistance may be modified by alterations of cardiopulmonary, vestibular, and/or other receptor activity. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Wyle Labs, Houston, TX 77058 USA. Albert Einstein Med Ctr, Philadelphia, PA 19141 USA. Mayo Clin & Mayo Fdn, Auton Reflex Lab, Rochester, MN 55905 USA. RP Schlegel, TT (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Mail Code SD8, Houston, TX 77058 USA. NR 49 TC 16 Z9 18 U1 2 U2 3 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 NOV PY 1998 VL 85 IS 5 BP 1957 EP 1965 PG 9 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 136TU UT WOS:000076875900048 PM 9804604 ER PT J AU Dzegilenko, F Bowman, JM Carter, S AF Dzegilenko, F Bowman, JM Carter, S TI Vibrational spectrum of (CO)(2) on Cu(100): Quantum calculations with 18 coupled modes SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID LASER-INDUCED DESORPTION; HELIUM ATOM SCATTERING; INFRARED-SPECTROSCOPY; ENERGY-TRANSFER; LINE-SHAPES; CO; CO/CU(100); SURFACE; EXCITATION; RELAXATION AB We report calculations of the vibrational frequencies of CO dimer on Cu(100) using the recently developed vibrational self-consistent field code. Eighteen modes are treated explicitly within a three-mode representation of the potential. Nine symmetry-distinct doublets are observed and the corresponding frequencies are computed. The thermally broadened spectrum of the GO-stretch fundamental is calculated at various temperatures. Both the temperature and coverage dependence of both the average GO-stretch frequency and the corresponding linewidth are consistent with experimentally observed trends. (C) 1998 American Institute of Physics. [S0021-9606(98)70141-2]. C1 NASA, Ames Res Ctr, IT Modeling & Simulat Grp, MRJ, Moffett Field, CA 94035 USA. Emory Univ, Dept Chem, Atlanta, GA 30322 USA. Emory Univ, Cherry L Emerson Ctr Sci Computat, Atlanta, GA 30322 USA. Univ Reading, Dept Chem, Reading RG6 2AD, Berks, England. RP Dzegilenko, F (reprint author), NASA, Ames Res Ctr, IT Modeling & Simulat Grp, MRJ, Mail Stop T27A-1, Moffett Field, CA 94035 USA. NR 41 TC 11 Z9 11 U1 0 U2 3 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 NOV 1 PY 1998 VL 109 IS 17 BP 7506 EP 7510 DI 10.1063/1.477373 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 132KY UT WOS:000076630100049 ER PT J AU Janowiak, JE Gruber, A Kondragunta, CR Livezey, RE Huffman, GJ AF Janowiak, JE Gruber, A Kondragunta, CR Livezey, RE Huffman, GJ TI A comparison of the NCEP-NCAR reanalysis precipitation and the GPCP rain gauge-satellite combined dataset with observational error considerations SO JOURNAL OF CLIMATE LA English DT Article ID GLOBAL PRECIPITATION; CLIMATOLOGY PROJECT; NASA/DAO REANALYSES; TROPICAL PACIFIC; NCEP/NCAR; OSCILLATION; HEMISPHERE; PATTERNS AB The Global Precipitation Climatology Project (GPCP) has released monthly mean estimates of precipitation that comprise gauge observations and satellite-derived precipitation estimates. Estimates of standard random error for each month at each grid location are also provided in this data release. One of the primary intended uses of this dataset is the validation of climatic-scale precipitation fields that are produced by numerical models. Nearly coincident with this dataset development, the National Centers for Environmental Prediction and the National Center for Atmospheric: Research have joined in a cooperative effort to reanalyze meteorological fields from the present back to the 1940s using a fixed state-of-the-art data assimilation system and large input database. In this paper, monthly accumulations of reanalysis precipitation are compared with the GPCP combined rain gauge-satellite dataset over the period 1988-95. A unique feature of this comparison is the use of standard error estimates that are contained in the GPCP combined dataset. These errors are incorporated into the comparison to provide more realistic assessments of the reanalysis model performance than could be attained by using only the mean fields. Variability on timescales from intraseasonal to interannual are examined between the GPCP and reanalysis precipitation. While the representation of large-scale features compares well between the two datasets, substantial differences are observed on regional scales. This result is not unexpected since present-day data assimilation systems are not designed to incorporate observations of precipitation. Furthermore, inferences of deficiencies in the reanalysis precipitation should nor be projected to other fields in which observations have been assimilated directly into the reanalysis model. C1 NOAA, NWS, NCEP, Climate Predict Ctr, Camp Springs, MD USA. NOAA, NESDIS, Res Off, Camp Springs, MD USA. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Sci Syst & Applicat Inc, Greenbelt, MD USA. RP Janowiak, JE (reprint author), NOAA, Natl Weather Serv, NCEP, Climate Predict Ctr, 4700 Silver Hill Rd,Room 605,Stop 9910, Washington, DC 20233 USA. EM John.janowiak@noaa.gov RI Huffman, George/F-4494-2014 OI Huffman, George/0000-0003-3858-8308 NR 39 TC 100 Z9 103 U1 0 U2 6 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD NOV PY 1998 VL 11 IS 11 BP 2960 EP 2979 DI 10.1175/1520-0442(1998)011<2960:ACOTNN>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 141YF UT WOS:000077171400016 ER PT J AU Wang, JH Rossow, WB AF Wang, JH Rossow, WB TI Effects of cloud vertical structure on atmospheric circulation in the GISS GCM SO JOURNAL OF CLIMATE LA English DT Article ID UPPER-AIR OBSERVATIONS; LARGE-SCALE DYNAMICS; GENERAL-CIRCULATION; NUMERICAL EXPERIMENTS; ENERGY TRANSPORTS; RADIATION BUDGET; CIRRUS CLOUDS; TIME SCALES; CLIMATE; MODEL AB Thirteen experiments have been performed using the Goddard Institute for Space Studies General Circulation Model (GISS GCM) to investigate the response of the large-scale circulation to different macroscale cloud vertical structures (CVS). The overall effect of clouds, the role of their geographic variation, and difference between the transient and equilibrium responses of the atmospheric circulation are also studied. Clouds act to suppress the Hadley circulation in the transient response, but intensify it in the equilibrium state. Changing CVS affects the atmospheric circulation directly by modifying the radiative cooling profile and atmospheric static stability, but the effect is opposed, on average. by an indirect effect on the latent healing profile produced by deep (moist) convection, Different interactions of radiation and convection with land and ocean surfaces mean that this cancellation of CVS effects on radiative and latent heating is not the same at all locations. All three parameters of the CVS seem equally important: the cloud-top height of the uppermost cloud layer, the presence of multiple layers, and the separation distance between two consecutive layers in a multilayered cloud system, In experiments with a globally uniform, single-layered cloud, the one with the cloud located somewhere at middle levels (720-550 mb in this model) results in the strongest Hadley circulation: with a single-layered cloud located above or below this level, both the circulation intensity and its vertical extent decrease. Inserting another cloud layer below a cloud in the upper troposphere also intensifies the Hadley circulation, the effect increasing with decreasing separation distance. Separately vertical gradients in the cloud distribution appear to be more important to the circulation strength than horizontal gradients. but horizontal variations in the CVS are needed to explain the strength of the mean circulation in the model atmosphere. The results also suggest that explicitly resolving cloud-top radiative cooling and base warming for each cloud layer is important to modeling the Hadley circulation. C1 Univ Colorado, Dept Engn Sci, Program Atmospher & Ocean Sci, Boulder, CO 80309 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Wang, JH (reprint author), Univ Colorado, Dept Engn Sci, Program Atmospher & Ocean Sci, Campus Box 429, Boulder, CO 80309 USA. RI Rossow, William/F-3138-2015 NR 48 TC 37 Z9 52 U1 0 U2 4 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 NOV PY 1998 VL 11 IS 11 BP 3010 EP 3029 DI 10.1175/1520-0442(1998)011<3010:EOCVSO>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 141YF UT WOS:000077171400019 ER PT J AU Ohsaka, K Trinh, EH AF Ohsaka, K Trinh, EH TI Apparatus for measuring the growth velocity of dendritic ice in undercooled water SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE dynamic nucleation; dendritic ice; growth velocity; undercooling; interface kinetics ID SOLIDIFICATION AB A unique apparatus for measuring the dendritic growth velocity of ice crystals in undercooled water is described and a preliminary result at undercooling levels between 5 and 8.5 K is presented. The result appears to show a significant deviation from the theoretical prediction based on the thermal diffusion model possibly due to sluggish interface kinetics which start playing a role in dendritic growth at these undercooling levels. Discussion includes necessary modifications of the diagnostic technique in order to eliminate uncertainties in the preliminary data and improve the accuracy in future measurements. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ohsaka, K (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 9 TC 26 Z9 29 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 NOV PY 1998 VL 194 IS 1 BP 138 EP 142 DI 10.1016/S0022-0248(98)00661-7 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 137DM UT WOS:000076899600019 ER PT J AU LaCombe, JC Koss, MB Tennenhouse, LA Winsa, EA Glicksman, ME AF LaCombe, JC Koss, MB Tennenhouse, LA Winsa, EA Glicksman, ME TI The Clapeyron effect in succinonitrile: applications to crystal growth SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE apparatus for crystal growth; dendritic growth; melt growth by pressure; Clapeyron effect AB This paper describes experiments that measure the Clapeyron effect, i.e., the change in melting temperature with static pressure in succinonitrile (SCN), a common model material used in crystal growth experiments. The Clapeyron results also yield information about the density change upon solidification - a parameter that is difficult to measure accurately and directly in SCN due to void formation in the solid. Furthermore, making a pressure change in an experimental environment presents researchers with a way to change more rapidly and uniformly the supercooling of a melt than by using conventional heating and cooling techniques. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Rensselaer Polytech Inst, Dept Mat Sci & Engn, Troy, NY 12180 USA. NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. RP Koss, MB (reprint author), Rensselaer Polytech Inst, Dept Mat Sci & Engn, Troy, NY 12180 USA. OI Glicksman, Martin/0000-0002-2675-2759 NR 7 TC 18 Z9 18 U1 0 U2 4 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 NOV PY 1998 VL 194 IS 1 BP 143 EP 148 DI 10.1016/S0022-0248(98)00611-3 PG 6 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 137DM UT WOS:000076899600020 ER PT J AU Knipp, DJ Emery, BA Engebretson, M Li, X McAllister, AH Mukai, T Kokubun, S Reeves, GD Evans, D Obara, T Pi, X Rosenberg, T Weatherwax, A McHarg, MG Chun, F Mosely, K Codrescu, M Lanzerotti, L Rich, FJ Sharber, J Wilkinson, P AF Knipp, DJ Emery, BA Engebretson, M Li, X McAllister, AH Mukai, T Kokubun, S Reeves, GD Evans, D Obara, T Pi, X Rosenberg, T Weatherwax, A McHarg, MG Chun, F Mosely, K Codrescu, M Lanzerotti, L Rich, FJ Sharber, J Wilkinson, P TI An overview of the early November 1993 geomagnetic storm SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EQUATORIAL SPREAD-F; SOLAR-WIND; IONOSPHERIC ELECTRODYNAMICS; MAGNETIC STORMS; POLAR-CAP; PHASE FLUCTUATIONS; PLASMA SHEET; MARCH 28-29; FIELD; THERMOSPHERE AB This paper describes the development of a major space storm during November 2-11, 1993. We discuss the history of the contributing high-speed stream, the powerful combination of solar wind transients and a corotating interaction region which initiated the storm, the high-speed flow which prolonged the storm and the near-Earth manifestations of the storm. The 8-day storm period was unusually long; the result of a high-speed stream (maximum speed 800 km/s) emanating from st distended coronal hole. Storm onset was accompanied by a compression of the entire dayside magnetopause to within geosynchronous Earth orbit(GEO). For nearly 12 hours the near-Earth environment was in a state of tumult. A super-dense plasma sheet was observed at GEO, and severe spacecraft charging was reported. The effects of electrons precipitating into the atmosphere penetrated into the stratosphere. Subauroral electron content varied by 100% and F layer heights oscillated by 200 km. Equatorial plasma irregularities extended in plumes to heights of 1400 km. Later, energetic particle fluxes at GEO recovered and rose by more than an order of magnitude. A satellite anomaly was reported during the interval of high energetic electron flux. Model results indicate an upper atmospheric temperature increase of 200 degrees K within 24 hours of storm onset. Joule heating for the first 24 hours of the storm was more than 3 times that for typical active geomagnetic conditions. We estimate that total global ionospheric heating for the full storm interval was similar to 190 PJ, with 30% of that generated within 24 hours of storm onset. C1 USAF Acad, Dept Phys, Colorado Springs, CO 80840 USA. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. Augsburg Coll, Dept Phys, Minneapolis, MN 55454 USA. Nagoya Univ, Solar Terr Environm Lab, Aichi, Japan. AT&T Bell Labs, Lucent Technol, Murray Hill, NJ 07974 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Hiraiso Solar Terr Res Ctr, Ibaraki, Osaka, Japan. CALTECH, Jet Prop Lab, Pasadena, CA USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. USAF, Res Lab, Space Vehicles Dirctorate, Hanscom AFB, MA 01731 USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. SW Res Inst, San Antonio, TX 78228 USA. IPS Radio & Space Serv, Haymarket, NSW, Australia. RP Knipp, DJ (reprint author), USAF Acad, Dept Phys, Colorado Springs, CO 80840 USA. EM knippdj.dfp@usafa.af.mil; emery@ncar.ucar.edu; engebret@augsburg.edu; lix@kitron.Colorado.edu; ahm@ncar.ucar.edu; mukai@fujitubo.gtl.isas.ac.jp; reeves@lanl.gov; T.Obara@crl.go.jp; xqp@cobra.jpl.nasa.gov; rosenberg@uap.umd.edu; allanw@polar.umd.edu; mchargmg.dfp@usafa.af.mil; chunflc.dfp@usafa.af.mil; codrescu@sec.noaa.gov; ljl@physics.belllabs.com; rich@plh.af.mil; sharb@broccoli.space.swri.edu; phil@ips.gov.au RI Reeves, Geoffrey/E-8101-2011 OI Reeves, Geoffrey/0000-0002-7985-8098 NR 92 TC 67 Z9 69 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26197 EP 26220 DI 10.1029/98JA00762 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500002 ER PT J AU Ho, CM Mannucci, AJ Sparks, L Pi, X Lindqwister, UJ Wilson, BD Iijima, BA Reyes, MJ AF Ho, CM Mannucci, AJ Sparks, L Pi, X Lindqwister, UJ Wilson, BD Iijima, BA Reyes, MJ TI Ionospheric total electron content perturbations monitored by the GPS global network during two northern hemisphere winter storms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID DISTURBANCE DYNAMO; F-REGION; FIELDS; LATITUDES; MIDDLE; MAPS AB The global evolution of two major ionospheric storms, occurring on November 4, 1993, and November 26, 1994, respectively, is studied using measurements of total electron content (TEC) obtained from a worldwide network of ground-based GPS receivers. The time-dependent features of ionospheric storms are identified using TEC difference maps based on the percent change of TEC during storm time relative to quiet time. The onset of each ionospheric storm is indicated by the appearance of auroral/subauroral TEC enhancements which occur within 1 hour of the beginning of the geomagnetic storm main phase. Significant TEC enhancements (> 100%) are observed in the winter northern hemisphere. The rate at which TEC enhancements appear is found to correlate with gradients in the Dst index. The large scale ionospheric structures identified during the storms are (1) nightside auroral/subauroral enhancements which surround the auroral oval, (2) dayside (around noon) high-latitude and middle-latitude enhancements associated with traveling ionospheric disturbances, and (3) conjugate latitudinal enhancements. For the November 1993 storm, a short positive phase (about 15 hours) is followed by a long negative phase (similar to 60 hours). In the November 1994 storm, we have identified the clear signature of a traveling ionospheric disturbance (TID) which propagated at a speed of similar to 460 m/s from similar to 60 degrees N to similar to 40 degrees N. The motion of this disturbance appears to conserve angular momentum. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ho, CM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Mannucci, Anthony/A-1349-2007 OI Mannucci, Anthony/0000-0003-2391-8490 NR 30 TC 57 Z9 58 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26409 EP 26420 DI 10.1029/98JA01237 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500018 ER PT J AU Hesse, M Winske, D AF Hesse, M Winske, D TI Electron dissipation in collisionless magnetic reconnection SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID 2-DIMENSIONAL MAGNETOTAIL EQUILIBRIA; HYBRID DRIFT INSTABILITY; PARTICLE SIMULATION; MHD SIMULATIONS; CURRENT SHEETS; TEARING MODE; FIELD; DYNAMICS; SUBSTORM; PLASMAS AB A study of the electron dynamics in the dissipation region of collisionless magnetic reconnection is presented. The investigation is based on a new 2.5-dimensional electromagnetic particle-in-cell simulation code. This code is applied to the problem of reconnection in two differently sized current sheets: one with a thickness of the ion inertial length and the other with electron inertial length thickness. The complete set of contributions to the reconnection electric field is calculated directly from the particle information. The two cases lead to quite different results. In the ion scale, sheet reconnection is significantly slower, and the dissipation is provided virtually exclusively by electron quasi-viscous effects. The electron scale sheet reconnects much faster, involving a bifurcation of the reconnection region and the formation of a magnetic island. In this latter case, dissipation appears to be primarily provided by electron inertial effects and here foremost by bulk electron acceleration. Finally, an attempt to represent the effects of electron pressure-based dissipation in a transport model is presented also. C1 NASA, Goddard Space Flight Ctr, Electrodynam Branch, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Hesse, M (reprint author), NASA, Goddard Space Flight Ctr, Electrodynam Branch, Code 661, Greenbelt, MD 20771 USA. RI Hesse, Michael/D-2031-2012 NR 48 TC 76 Z9 77 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26479 EP 26486 DI 10.1029/98JA01570 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500022 ER PT J AU Song, P Zhu, Z Russell, CT Anderson, RR Gurnett, DA Ogilvie, KW Strangeway, RJ AF Song, P Zhu, Z Russell, CT Anderson, RR Gurnett, DA Ogilvie, KW Strangeway, RJ TI Properties of ELF emissions in the dayside magnetopause SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY MAGNETIC-FIELD; HYBRID DRIFT INSTABILITY; FLUX-TRANSFER EVENTS; SUBSOLAR MAGNETOPAUSE; PLASMA-WAVES; ISEE 1; MAGNETOSPHERE; LAYER; SHAPE; SIZE AB We undertake a comprehensive study of the extremely low frequency emissions within the magnetopause current layer using measurements obtained with ISEE 1 spacecraft. Since the emissions vary greatly, both spatially and temporally, to derive meaningful and robust statistical results is challenging. We design an averaging procedure and choose the normalized wave amplitudes for a correlation analysis. Also, we separate the parameters for the correlation with local or global properties. We found that most of the wave power in the current layer is carried by the magnetic field fluctuations, while the electric field carries relatively little energy. These emissions are best correlated with the local magnetic field shear and electron plasma beta. The power increases as the shear and beta increase. The wave is correlated with the global interplanetary magnetic field (IMF) clock angle, although it is weaker than with the local shear. The wave is weakly correlated with the IMF B-z and is not correlated with the electron temperature anisotropy. The con-elation of the electric wave field with our chosen parameters is weaker than and varying from that of the magnetic wave field. These ELF emissions have the characteristics of the whistler mode dispersion with an increasing phase velocity above the lower hybrid frequency and with a cutoff at the electron cyclotron frequency. The wavelength is similar to 20 to 100 lan. In a case study, the electric field is polarized nearly perpendicular to the background magnetic field. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. RP Song, P (reprint author), Univ Michigan, Space Phys Res Lab, 2455 Hayward St, Ann Arbor, MI 48109 USA. NR 34 TC 8 Z9 8 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26495 EP 26506 DI 10.1029/98JA02396 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500024 ER PT J AU Turner, NE Baker, DN Pulkkinen, TI Singer, HJ Mozer, F Lepping, RP AF Turner, NE Baker, DN Pulkkinen, TI Singer, HJ Mozer, F Lepping, RP TI High-altitude polar cap electric field responses to southward turnings of the interplanetary magnetic field SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID IONOSPHERIC CONVECTION PATTERN; MAGNETOSPHERE; RECONNECTION; SUBSTORMS; MODEL AB Interplanetary electric field coupling with the magnetosphere has been analyzed predominantly using data from the Wind magnetometer and the Polar electric field instrument. The coupling was investigated using the Polar Electric Field Instrument (EFI) to measure the electric field in the northern polar cap immediately following sharp southward turnings of the IMF as observed by Wind. Southward turnings were chosen which exhibited a sudden change of the IMF north-south component from B-z > 0 to B-z < 0 (GSM coordinates) after an hour or more of relatively stable conditions, and for which Polar was in the northern polar cap. These Bz changes correspond to B-y changes in the interplanetary electric field. For each of the 30 identified events, a time was estimated for the arrival of the IMF change at the magnetopause using the solar wind speed observed by the Wind Solar Wind Experiment (SWE), and Polar electric field data were examined to identify responses. For many of the selected events (about one third), abrupt changes of state in the magnetospheric electric field were evident with timing that matched the expected solar wind arrival time at Earth. For events for which additional data were available, we conducted in-depth examination of the individual events using IMP 8, Geotail, and GOES 9. In one such event, GOES 9 data showed a substorm growth phase and onset which also corresponded to features in the solar wind observed by Wind, Geotail, and IMP 8. In addition to the individual event studies, a superposed epoch analysis of all available events revealed a consistent rise in the mean polar cap electric field about 15 min following sharp IMF southward turnings. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. NOAA, Space Environm Ctr, Boulder, CO 80303 USA. RP Turner, NE (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. RI Pulkkinen, Tuija/D-8403-2012; OI Pulkkinen, Tuija/0000-0002-6317-381X; Turner, Niescja/0000-0002-3280-4260 NR 21 TC 2 Z9 2 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26533 EP 26545 DI 10.1029/98JA01743 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500027 ER PT J AU Taguchi, S Slavin, JA Kiyohara, M Nose, M Reeves, GD Lepping, RP AF Taguchi, S Slavin, JA Kiyohara, M Nose, M Reeves, GD Lepping, RP TI Temporal relationship between midtail traveling compression regions and substorm onset: Evidence for near-Earth neutral line formation in the late growth phase SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID BURSTY BULK FLOWS; PLASMA SHEET; MAGNETOSPHERIC SUBSTORMS; GEOTAIL OBSERVATIONS; CURRENT DISRUPTION; IMP-8 OBSERVATIONS; CURRENT WEDGE; MAGNETOTAIL; EXPANSION; MODEL AB The timing of the near-Earth neutral line (NENL) formation relative to substorm onset signatures has been a central debate in substorm research for some time. Several recent studies have suggested that the direct identification of the reconnection site, at least in its initial stage, is difficult because it may be a very limited region spatially. Our approach to this timing problem is the examination of the midtail lobe traveling compression regions (TCRs) relative to onset during substorm events. Fifty-nine midtail TCRs in the IMP 8 magnetotail observations are analyzed. These midtail TCRs differ from the distant tail TCRs in that they lack the first half of the north and south tilting of the field during the compression. The flat B-Z phase preceding the south tilting interval in these midtail compression regions has been interpreted as being due to the close proximity to the growing plasmoid bulge just prior to plasmoid ejection down the tail. The results of our analysis show that these TCRs start a few minutes before or simultaneously (accuracy of 1 min) with Pi2 onset at low-latitude or midlatitude ground stations and the particle injection at the geosynchronous orbit. Before the plasmoid bulge formation starts, the NENL must start to form in the plasma sheet; that is, the formation of NENL must initially occur on closed field lines to form the plasmoids which compress the lobes to cause the TCRs. Our results support this view and allow us to conclude that NENL forms before ground and geosynchronous substorm onset signatures, i.e., in the late growth phase. The implications of these results for magnetospheric substorm models are discussed. C1 Univ Electrocommun, Dept Elect Engn, Tokyo 1828585, Japan. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. RP Taguchi, S (reprint author), Univ Electrocommun, Dept Elect Engn, Tokyo 1828585, Japan. EM taguchi@ee.uec.ac.jp RI Slavin, James/H-3170-2012; Nose, Masahito/B-1900-2015; Reeves, Geoffrey/E-8101-2011 OI Slavin, James/0000-0002-9206-724X; Nose, Masahito/0000-0002-2789-3588; Reeves, Geoffrey/0000-0002-7985-8098 NR 35 TC 16 Z9 16 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26607 EP 26612 DI 10.1029/98JA02617 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500033 ER PT J AU Higgins, CA Thieman, JR Fung, SF Green, JL Candey, RM AF Higgins, CA Thieman, JR Fung, SF Green, JL Candey, RM TI Latitudinal structure within Jovian hectometric radiation SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID RADIO ASTRONOMY OBSERVATIONS; SOLAR-WIND CONTROL; IO PLASMA TORUS; EMISSIONS; LOCATIONS; VOYAGER; JUPITER AB Jovian hectometric radio emission (HOM: 300-3000 kHz) has a number of persistent structural features associated with it as observed by the Voyager 1, Voyager 2, Ulysses, and Galileo spacecraft for specific jovigraphic latitudes (-4 degrees to +7.1 degrees) and local times (0.3 to 10.5 hours). Most notable are the presence of HOM emission between 270 degrees and 120 degrees central meridian longitude (CML) and the region of reduced emission intensity (a "gap") between 120 degrees and 270 degrees. We displayed the Ulysses and Galileo data using time-frequency occurrence probability spectrograms and show that the observed HOM emission features are nearly identical to those observed by the Voyager spacecraft. This implies that the HOM structure is long-lived and fixed in its longitudinal position within the Jovian magnetosphere. HOM structure depends on small changes in the observer's jovigraphic latitude, so the different jovigraphic latitudes of the spacecraft were used to probe the HOM beam structure. From this analysis we found that the CML width of the main HOM gap is directly correlated to the latitude of the spacecraft. We conclude that the latitudinal thickness of the HOM beam is about 12 degrees, extending from -5 degrees to +7 degrees magnetic latitude. C1 NASA, Goddard Space Flight Ctr, Natl Res Council, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Space Sci Data Operat Off, Greenbelt, MD 20771 USA. RP Higgins, CA (reprint author), NASA, Goddard Space Flight Ctr, Natl Res Council, Code 633-0, Greenbelt, MD 20771 USA. RI Candey, Robert/D-4639-2012; Fung, Shing/F-5647-2012 NR 24 TC 10 Z9 10 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26679 EP 26686 DI 10.1029/98JA02393 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500039 ER PT J AU Liu, XM Shemansky, DE Ahmed, SM James, GK Ajello, JM AF Liu, XM Shemansky, DE Ahmed, SM James, GK Ajello, JM TI Electron-impact excitation and emission cross sections of the H-2 Lyman and Werner systems SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MOLECULAR-HYDROGEN; OSCILLATOR-STRENGTHS; CURRENT DENSITIES; BAND SYSTEMS; ULTRAVIOLET EMISSION; EXTREME-ULTRAVIOLET; VACUUM ULTRAVIOLET; TRANSITION MOMENTS; RYDBERG SERIES; ION SOURCES AB Excitation functions of the H-2 Lyman (Ly) (B (1)Sigma(u)(+) - X (1)Sigma(g)(+)) and Werner (W) (C (1)Pi(u) - X (1)Sigma(g)(+)) band systems have been reanalyzed using a combination of measurements and theoretical considerations. These systems are prominent emitters in outer planet atmospheric dayglow and auroral activity and can be used to infer energy deposition and heating rates. Earlier measurements of the cross sections reported by Shemansky et al. [1985a] have been found to be inaccurate in the threshold energy region. A combination of high-resolution spectral and shape function measurements obtained at the Jet Propulsion Laboratory (JPL) in low- and medium-energy regions have been used to obtain relative excitation shape functions of the two systems. At energies above 250 eV, we have used the measurements obtained earlier by De Heer and Carriere [1971] in order to define the first two terms of the Born electric dipole collision strength. The complete set of collision strength terms is obtained by combining: the: JPL and De Heer and Carriere [1971] data. We have found that, contrary to results of,Shemansky et al. [1985a], the shape functions of the Ha Ly and W systems, expressed in units of threshold energy, are the same: within experimental error. Absolute cross sections of the Ha Ly and W systems are established using the theoretical oscillator strengths of Abgrall et al. [1987, 1993a, b, c] and Abgrall and Roueff [1989]. The atomic hydrogen H-2 Ly a emission cross section resulting fi om dissociative excitation of Ha at 100 eV obtained from relative! intensities of H2 W emission lines is also derived and compared with other experimental measurements. At a gas temperature of 300 K and electron energy of 100 eV, the cross sections for the H Ly alpha, H-2 Ly, and W emissions are (0.716 +/- 0.095) x 10(-17), (2.62 +/- 0.34) x 10-17, and (2.41 +/- 0.31) x 10-17 cm(2), respectively. The accuracy of the absolute values and shape functions is limited primarily by electron gun performance, as was the case for Shemansky et al. The rotational dependence of the, transition dipole matrix elements and perturbations between the B (1)Sigma(u)(+) and C (1)Pi(u)(+) states have a significant effect on the cross sections. C1 Univ So Calif, Dept Aerosp Engn, Los Angeles, CA 90089 USA. Inst Plasma Res, Bhat 382428, Gandhinagar, India. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ahmed, SM (reprint author), Univ So Calif, Dept Aerosp Engn, Los Angeles, CA 90089 USA. EM xliu@jpluvs.jpl.nasa.gov; dons@hippolyta.usc.edu; ahmed@plasma.ernet.in; gjames@jpluvs.jpl.nasa.gov; jajello@jpluvs.jpl.nasa.gov NR 48 TC 48 Z9 48 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26739 EP 26758 DI 10.1029/98JA02721 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500045 ER PT J AU Kucharek, H Ipavich, FM Kallenbach, R Bochsler, P Hovestadt, D Grunwaldt, H Hilchenbach, M Axford, WI Balsiger, H Burgi, A Coplan, MA Galvin, AB Geiss, J Gliem, F Gloeckler, G Hsieh, KC Judge, DJ Klecker, B Lee, MA Livi, S Managadze, GG Marsch, E Mobius, E Neugebauer, M Ogawa, HS Reiche, KU Scholer, M Verigin, MI Wilken, B Wurz, P AF Kucharek, H Ipavich, FM Kallenbach, R Bochsler, P Hovestadt, D Grunwaldt, H Hilchenbach, M Axford, WI Balsiger, H Burgi, A Coplan, MA Galvin, AB Geiss, J Gliem, F Gloeckler, G Hsieh, KC Judge, DJ Klecker, B Lee, MA Livi, S Managadze, GG Marsch, E Mobius, E Neugebauer, M Ogawa, HS Reiche, KU Scholer, M Verigin, MI Wilken, B Wurz, P TI Magnesium isotopic composition as observed with the CELIAS/MTOF experiment on the SOHO spacecraft SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID THIN CARBON FOILS; CHARGE-EXCHANGE; SOLAR-WIND; ABUNDANCES; IONS; NEON AB Solar wind abundance ratios of magnesium isotopes measured with the high resolution Mass Time-of-Flight spectrometer (MTOF) of the Charge, Element, and Isotope Analysis System (CELIAS) experiment on board the Solar and Heliospheric Observatory (SOHO) are presented. MTOF, as part of CELIAS, is, because of its high time and mass resolution, an excellent tool for isotope abundance measurements in the solar wind. From the data analysis we have found that the isotopic composition of magnesium in the solar wind agrees with the terrestrial composition within the experimental uncertainty. We have obtained isotopic ratios of Mg-24/Mg-25 = 7.7 +/- 0.4 and Mg-24/Mg-26 = 7.0 +/- 0.5. These values are consistent with the terrestrial values of Mg-24/Mg-25 = 7.90 +/- 0.01 and Mg-24/Mg-26 = 7.17 +/- 0.03. Furthermore, these investigations also show that with the given uncertainties the abundance ratios do not vary significantly within a solar wind velocity range from 375 km/s to 530 km/s. C1 Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Univ Maryland, Dept Phys & Astron, College Pk, MD 20742 USA. Int Space Sci Inst, CH-3012 Bern, Switzerland. Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. Max Planck Inst Aeron, D-37189 Kaltenburg Lindau, Germany. Arias Luftreinhaltung & Umweltberatung, CH-3012 Bern, Switzerland. Tech Univ Braunschweig, Inst Datenverarbeitung, D-38023 Braunschweig, Germany. Univ Arizona, Dept Phys, Tucson, AZ 85721 USA. Univ So Calif, Ctr Space Sci, Los Angeles, CA 90089 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Inst Space Phys, Moscow, Russia. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Axford, WI (reprint author), Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. EM hak@mpe-garching.mpg.de; ipavich@umtof.umd.edu; reinald.kallenbach@soho.unibe.ch; gruenwaldt@linax1.dnet.gwdg.de; arias-bern@bluewin.ch; gliem@ida.ing.tu-bs.de; hsieh@soliton.physics.arizona.edu; gmanagad@esoc.bitnet; moebius@rotor.sr.unh.edu; mneugebauer@jplsp.jpl.nasa.gov; peter.wurz@soho.unibe.ch RI Galvin, Antoinette/A-6114-2013 NR 28 TC 12 Z9 12 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26805 EP 26812 DI 10.1029/98JA02542 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500052 ER PT J AU Pryor, WR Witte, M Ajello, JM AF Pryor, WR Witte, M Ajello, JM TI Interplanetary Lyman alpha remote sensing with the Ulysses Interstellar Neutral Gas Experiment SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID GALILEO ULTRAVIOLET SPECTROMETER; HYDROGEN DENSITY; SOLAR-CYCLE; HELIOSPHERIC INTERFACE; LATITUDINAL VARIATIONS; MULTIPLE-SCATTERING; WIND; MODULATION; FLUX; MARINER-10 AB The Ulysses neutral gas instrument obtained celestial sphere maps of interplanetary Lyman ex emission from neutral hydrogen in 1991-1996. These maps are unique because the spacecraft was located at a wide range of heliocentric ecliptic latitudes. Eleven of these maps are compared with the predictions of an interstellar wind hydrogen model previously used to study Galileo and Pioneer Venus Lyman alpha data obtained near the ecliptic plane. The model provides reasonable agreement with the Ulysses maps. The lifetime of the interstellar hydrogen atoms against charge exchange with solar wind protons is shown to be more latitudinally isotropic at solar maximum in 1991 than at solar minimum in 1994 and 1995. This result agrees with white light coronagraph data that generally show a more isotropic coronal brightness pattern at solar maximum. The transition from a more symmetric to a more asymmetric solar wind charge exchange rate also explains differences between published Galileo data from solar maximum and Solar and Heliospheric Observatory (SOHO) Solar Wind Anisotropy Experiment (SWAN) data from solar minimum. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Max Planck Inst Aeron, D-37191 Katlenburg Lindau, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ajello, JM (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80303 USA. NR 38 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26813 EP 26831 DI 10.1029/98JA01459 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500053 ER PT J AU Pryor, WR Lasica, SJ Stewart, AIF Hall, DT Lineaweaver, S Colwell, WB Ajello, JM White, OR Tobiska, WK AF Pryor, WR Lasica, SJ Stewart, AIF Hall, DT Lineaweaver, S Colwell, WB Ajello, JM White, OR Tobiska, WK TI Interplanetary Lyman alpha observations from Pioneer Venus over a solar cycle from 1978 to 1992 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID ORBITER ULTRAVIOLET SPECTROMETER; WIND TERMINATION SHOCK; LATITUDINAL VARIATIONS; INTERSTELLAR HYDROGEN; MULTIPLE-SCATTERING; OUTER HELIOSPHERE; NEUTRAL HYDROGEN; VOYAGER UVS; GALILEO; DENSITY AB The Pioneer Venus Orbiter ultraviolet spectrometer (PVOUVS) routinely obtained interplanetary hydrogen Lyman alpha data while viewing ecliptic latitudes near 30 degrees S from 1978 to 1992 (during solar cycles 21 and 22). We describe "hot" models for this interplanetary Lyman alpha data that include the solar cycle variation of (1) the solar flux, as a function of latitude and longitude; (2) the radiation pressure on hydrogen atoms; (3) the salar wind flux; (4) the solar EUV flux; and (5) the multiple scattering correction to an optically thin radiative transfer model. These models make use of solar radiation flux parameters (solar wind, solar EUV, and solar Lyman alpha) from spacecraft and ground-based solar proxy observations. Comparison of the upwind data and model indicates that the ratio of the solar Lyman alpha line center flux (responsible for the interplanetary signal) to the observed solar Lyman alpha integrated flux is constant to within similar to 20%, with an effective line width near 1.1 Angstrom. Averaging the solar radiation pressure and hydrogen atom lifetime over 1 year before the observation reproduces the upwind intensity time variation but not the downwind. A better fit to the downwind time series is found using the 1 year average appropriate for the time that the atoms passed closest to the sun. Solar Lyman alpha measurements from two satellites are used in our models. Upper Atmosphere Research Satellite (UARS) solar Lyman alpha measurements are systematically higher than Solar Mesosphere Explorer (SME) values and have a larger solar maximum to solar minimum ratio. UARS-based models work better than SME-based models in fitting the PVOUVS downwind time series Lyman alpha data. C1 Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA. CALTECH, Jet Prop Lab, Fed Data Corp, Pasadena, CA 91109 USA. Natl Ctr Atmospher Res, High Altitude Observ, Boulder, CO 80307 USA. RP Ajello, JM (reprint author), Univ Colorado, Lab Atmospher & Space Phys, 1234 Innovat Dr, Boulder, CO 80303 USA. NR 51 TC 17 Z9 17 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD NOV 1 PY 1998 VL 103 IS A11 BP 26833 EP 26849 DI 10.1029/98JA01918 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500054 ER PT J AU Crooker, NU McAllister, AH Fitzenreiter, RJ Linker, JA Larson, DE Lepping, RP Szabo, A Steinberg, JT Lazarus, AJ Mikic, Z Lin, RP AF Crooker, NU McAllister, AH Fitzenreiter, RJ Linker, JA Larson, DE Lepping, RP Szabo, A Steinberg, JT Lazarus, AJ Mikic, Z Lin, RP TI Sector boundary transformation by an open magnetic cloud SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID HELIOSPHERIC CURRENT SHEET; CORONAL MASS EJECTIONS; SOLAR-WIND; ELECTRONS; FIELD; STREAMER; TOPOLOGY; RECONNECTION; EVENTS AB A magnetic cloud observed by the Wind spacecraft on February 8, 1995, was remarkable for its impact on the interplanetary sector structure. The magnetic field data imply that the cloud occurred in the middle of a sector and that the arrival of the following sector boundary on February 10 coincided with the arrival time predicted from the corresponding source surface map. The electron heat flux data, however, give incontrovertible evidence that instead the cloud brought the sector boundary, well ahead of the predicted arrival time. The electron heat flux data show little counterstreaming within the cloud, indicating predominantly open helical field lines. Under the assumption that the cloud originally had the form of a closed flux rope loop with legs rooted to the Sun, observational constraints dictate that the sector boundary was displaced not because it was pushed aside by the cloud but because reconnection in the leading leg opened field lines there, creating a topological change spanning 45 degrees of heliographic longitude. The solar source of the cloud was deduced from an associated eruptive arcade event extending northeastward from an active region in Yohkoh soft X ray data on February 4. On February 8, the same active region was the source of impulsive energetic electron events observed at Wind during a brief counterstreaming interval, consistent with magnetic connection in the leading leg at that time. The cloud's helicity matches that predicted from the skew of the arcade fields in the February, 4 X ray event, but the predicted alignment of the arcade and cloud axes was off by 35 degrees. We use an MHD model with boundary conditions derived from solar magnetograms to illustrate the tilted arcade configuration in the corona that gave rise to the magnetic cloud and the lesser tilt of the heliospheric current sheet stemming from it. C1 Boston Univ, Ctr Space Phys, Boston, MA 02215 USA. Helio Res, Le Crescenta, CA USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Sci Applicat Int Corp, San Diego, CA 92121 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. RP Crooker, NU (reprint author), Boston Univ, Ctr Space Phys, 725 Commonwealth Ave, Boston, MA 02215 USA. EM crooker@buasta.bu.edu; ahm@hao.ucar.edu; u3rjf@leprjf.gsfc.nasa.gov; linker@iris023.saic.mit.edu; davin@ssl.berkeley.edu; rpl@leprpl1.gsfc.nasa.gov; asz@leprpl1.gsfc.nasa.gov; jts@space.mit.edu; ajl@space.mit.edu; mikic@iris023.saic.com; rlin@ssl.berkeley.edu NR 37 TC 28 Z9 28 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 NOV 1 PY 1998 VL 103 IS A11 BP 26859 EP 26868 DI 10.1029/98JA02391 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 133UX UT WOS:000076705500056 ER PT J AU Brenner, M Lind, R AF Brenner, M Lind, R TI Wavelet-processed flight data for robust aeroservoelastic stability margins SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID SYSTEM-IDENTIFICATION; TRANSFORM AB Wavelet analysis for filtering and system identification is used to improve the estimation of aeroservoelastic (ASE) stability margins. Computation of robust stability margins for stability boundary prediction depends on uncertainty descriptions derived from the test data for model validation. Nonideal test conditions, data acquisition errors, and signal processing algorithms cause uncertainty descriptions to be intrinsically conservative. The conservatism of the robust stability margins is reduced with parametric and nonparametric time-frequency analysis of flight data in the model validation process. Nonparametric wavelet processing of data is used to reduce the effects of external disturbances and unmodeled dynamics. Parametric estimates of modal stability are also extracted using the wavelet transform. F-18 High Alpha Research Vehicle ASE flight test data are used to demonstrate improved robust stability prediction by extension of the stability boundary from within the flight envelope to conditions sufficently beyond the actual flight regime. Stability within the flight envelope is confirmed by flight test. Practical aspects and guidelines for efficiency of these procedures are presented for on-line implementation. C1 NASA, Dryden Flight Res Ctr, Aerostruct Branch, Edwards, CA 93523 USA. RP Brenner, M (reprint author), NASA, Dryden Flight Res Ctr, Aerostruct Branch, MS 4840D-RS, Edwards, CA 93523 USA. NR 26 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 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1998 VL 21 IS 6 BP 823 EP 829 DI 10.2514/2.4331 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 139HB UT WOS:000077021500002 ER PT J AU Bar-Itzhack, I Montgomery, PY Garrick, JC AF Bar-Itzhack, I Montgomery, PY Garrick, JC TI Algorithms for attitude determination using the global positioning system SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference CY AUG 11-13, 1997 CL NEW ORLEANS, LOUISIANA SP Amer Inst Aeronaut & Astronaut ID VECTOR OBSERVATIONS AB Techniques are discussed for attitude determination using the global positioning system (GPS) differential phase measurements, assuming that the cycle integer ambiguities are known. The problem of attitude determination is posed as a parameter optimization problem. One proposed set of optimal solutions, which includes solutions of Wahba's problem, is based on least-squares fit of some attitude parameters to a set of vector measurements. The use of these algorithms requires the conversion of the basic GPS scalar phase measurements into unit vectors. It is shown that when the GPS antennas constitute tao axes of a Cartesian coordinate system, the conversion is immediate. When this is not the case, a more elaborate transformation is required. The necessary conversion formulae for both cases are developed and demonstrated in an example. Another possible approach is based on a least squares fit of the attitude quaternion to the GPS phase measurements themselves. The cost function of the fit is given in the literature in the most straightforward formulation as a function of the attitude matrix. Conversion is presented of the matrix-based cost function to a quaternion-based cost function that corresponds to the cost function minimized by QUEST. However, unlike the QUEST cost function, the converted cost function is not a simple quadratic form; therefore, the simple QUEST solution is not applicable in this case. An iterative solution for finding the optimal quaternion is derived and demonstrated through numerical examples. The algorithms can handle cases of planar antenna arrays and, thus, cover a deficiency in earlier algorithms. C1 NASA, Goddard Space Flight Ctr, Flight Dynam Anal Branch, Greenbelt, MD 20771 USA. Stanford Univ, Dept Aeronaut & Astronaut, Stanford, CA 94305 USA. RP Bar-Itzhack, I (reprint author), Technion Israel Inst Technol, Fac Aerosp Engn, IL-32000 Haifa, Israel. EM ibaritz@tx.technion.ac.il NR 14 TC 27 Z9 29 U1 1 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1998 VL 21 IS 6 BP 846 EP 852 DI 10.2514/2.4347 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 139HB UT WOS:000077021500005 ER PT J AU Ballin, MG Erzberger, H AF Ballin, MG Erzberger, H TI Potential benefits of terminal airspace traffic automation for arrivals SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article; Proceedings Paper CT AIAA Guidance, Navigation, and Control Conference and Exhibit CY JUL 29-31, 1996 CL SAN DIEGO, CALIFORNIA SP AIAA AB Advanced air traffic management systems such as the Center/TRACON Automation System should yield a wide range of benefits, including increased airport arrival capacity and reduced aircraft delays, To estimate the traffic flow benefits achievable from future terminal airspace automation, live radar information was used to perform an analysis of current aircraft landing rates and separations at the Dallas/Fort Worth International Airport. Separation statistics that result when controllers balance complex procedural constraints against the need to maintain high landing rates are presented. In addition, the analysis estimates the potential for airport capacity improvements by determining the unused landing opportunities that occur during rush traffic periods. Results suggest a large potential for balancing runway loads and improving the accuracy and consistency of spacing between arrivals on final approach, leading to a potential increase in arrival capacity of at least 15% for the Dallas/Fort Worth International Airport and similar airports. This capacity increase may lower operating costs for airport users and substantially reduce the need for future airport expansions. C1 NASA, Ames Res Ctr, Flight Management & Human Factors Div, Automat Concepts Res Branch, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, Flight Management & Human Factors Div, Air Traff Management Branch, Moffett Field, CA 94035 USA. RP Ballin, MG (reprint author), NASA, Langley Res Ctr, Flight Dynam & Control Div, Crew Syst & Operat Branch, Hampton, VA 23681 USA. NR 8 TC 2 Z9 2 U1 1 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1998 VL 21 IS 6 BP 909 EP 915 DI 10.2514/2.4324 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 139HB UT WOS:000077021500013 ER PT J AU Chou, HC Ardema, MD Bowles, JV AF Chou, HC Ardema, MD Bowles, JV TI Near-optimal entry trajectories for reusable launch vehicles SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID OPERATION; ALTITUDE AB A near-optimal guidance law for the descent trajectory of a fully reusable single-stage-to-orbit rocket launch vehicle is derived. A methodology is developed to investigate using both bank angle and altitude as control variables and selecting parameters that maximize various performance functions. The method is based on the energy-state model of the aircraft equations of motion. The major task of this paper is to obtain optimal entry trajectories under a variety of performance goals: minimum time, minimum surface temperature, minimum heat load, and maximum heading change. Four classes of trajectories were investigated: no banking, optimal left turn banking, optimal right turn banking, and optimal bank chattering. The cost function is in general a weighted sum of all performance goals. In particular, the tradeoff between minimizing heat load into the vehicle and maximizing cross-range distance is investigated. The results show that the optimization methodology can be used to derive a wide variety of near-optimal trajectories. C1 Santa Clara Univ, Dept Engn Mech, Santa Clara, CA 95053 USA. NASA, Ames Res Ctr, Syst Anal Branch, Moffett Field, CA 94035 USA. RP Chou, HC (reprint author), Appl Mat, Hsinchu 300, Taiwan. NR 15 TC 5 Z9 5 U1 0 U2 3 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1998 VL 21 IS 6 BP 983 EP 990 DI 10.2514/2.4335 PG 8 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 139HB UT WOS:000077021500023 ER PT J AU Davidson, JB Andrisani, D AF Davidson, JB Andrisani, D TI Gain-weighted eigenspace assignment SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article ID EIGENSTRUCTURE ASSIGNMENT; MULTIVARIABLE SYSTEMS C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Purdue Univ, Sch Aeronaut & Astronaut, W Lafayette, IN 47907 USA. RP Davidson, JB (reprint author), NASA, Langley Res Ctr, Mail Stop 132, Hampton, VA 23681 USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0731-5090 J9 J GUID CONTROL DYNAM JI J. Guid. Control Dyn. PD NOV-DEC PY 1998 VL 21 IS 6 BP 1009 EP 1012 DI 10.2514/2.4341 PG 4 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 139HB UT WOS:000077021500029 ER PT J AU Harter, AW Lee, RAM Chui, TCP Goodstein, DL AF Harter, AW Lee, RAM Chui, TCP Goodstein, DL TI Measuring the heat capacity of superfluid He-4 in the presence of a heat flux near T lambda: Progress and prospects SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS ID FLOW INDUCED ANOMALIES; TRANSITION; DEPRESSION AB It has been predicted that the heat capacity of superfluid He-4 will diverge strongly at a depressed transition temperature in the presence of a constant heat flux, Q. We have built a cell to measure this effect, and have taken preliminary measurements at various heat flux values. Our data indicate an enhancement of the heat capacity that varies as a function of Q. However, the temperature dependence of our measurements leads us to believe that our initial findings were affected by spurious heat flow. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Harter, AW (reprint author), CALTECH, Pasadena, CA 91125 USA. NR 18 TC 0 Z9 0 U1 1 U2 1 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD NOV PY 1998 VL 113 IS 3-4 BP 549 EP 554 DI 10.1023/A:1022528901745 PG 6 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 139ZH UT WOS:000077060800058 ER PT J AU Larson, M Liu, YM Israelsson, UE AF Larson, M Liu, YM Israelsson, UE TI Simulations of the behavior of helium in a thermal conductivity cell SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article; Proceedings Paper CT International Symposium on Quantum Fluids and Solids (QFS98) CY JUN 09-14, 1998 CL AMHERST, MASSACHUSETTS ID SUPERFLUID TRANSITION; HE-4 AB We have performed numerical simulations of the behavior in a one-dimensional thermal conductivity cell of helium, as it is ramped through the superfluid transition from below. The goal of the simulations is to be able to at least qualitatively, if not quantitatively, predict the behavior of helium in a reduced gravitational environment. These numerical simulations can model helium cells with effective gravitational fields of \a/g\ > 0 by changing the distribution of local transition temperatures to match the desired gravitational environment. The numerical results for the simulated behavior show excellent qualitative agreement with the observed experimental data under a variety of effective gravity values. PACS numbers: 67.40 Pm, 67.40.Kh, 02.60 Lj, 02.70 Bf. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Larson, M (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 0 Z9 0 U1 0 U2 0 PU PLENUM PUBL CORP PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0022-2291 J9 J LOW TEMP PHYS JI J. Low Temp. Phys. PD NOV PY 1998 VL 113 IS 3-4 BP 561 EP 566 DI 10.1023/A:1022533002653 PG 6 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 139ZH UT WOS:000077060800060 ER PT J AU Wolfenden, A Miller, CM Hebsur, MG AF Wolfenden, A Miller, CM Hebsur, MG TI Dynamic Young's modulus and vibration damping for cryomilled NiAl-AlN composites: 5-20% AlN concentrations SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article C1 Texas A&M Univ, Dept Mech Engn, Adv Mat Lab, College Stn, TX 77843 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Wolfenden, A (reprint author), Texas A&M Univ, Dept Mech Engn, Adv Mat Lab, College Stn, TX 77843 USA. NR 12 TC 5 Z9 5 U1 1 U2 1 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 NOV 1 PY 1998 VL 17 IS 21 BP 1861 EP 1864 DI 10.1023/A:1006650813994 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA 170ZU UT WOS:000078838000022 ER PT J AU Susskind, J Iredell, L Blass, WE Reuter, DC Halsey, GW Jennings, DE AF Susskind, J Iredell, L Blass, WE Reuter, DC Halsey, GW Jennings, DE TI Torsional splittings in the band nu(9)+nu(4)-nu(4) of ethane SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID VIBRATION-ROTATION INTERACTION; + V4; SPECTRA; JUPITER AB Torsional splittings of the C2H6 hot band upsilon(9) + upsilon(4) - upsilon(4) have been determined based on measurements taken with the Kitt Peak National Observatory Fourier transform spectrometer with .0025 cm(-1) resolution. The measured splittings range from -.2347 cm(-1) (the sign is relative to that of the observed splitting in the upsilon(9) band of C2H6) to .0682 cm(-1), with a standard deviation of the observed splittings of .0251 cm(-1). The splittings call be explained as a result of xy Coriolis interaction of upsilon(9) + upsilon(4) with the excited torsional states tau upsilon(4), with the major effect arising from the "forbidden" interaction with the nearly degenerate state 5 upsilon(4)sigma = 2. The rms error of the predicted splittings is .00422 cm(-1), if parameters determined from theory and previous work are used, and is .00217 cm(-1), if small refinements to the parameters are made based on the measured splittings themselves. (C) 1998 Academic Press. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Gen Sci Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Tennessee, Dept Phys & Astron, Mol Spect Lab, Knoxville, TN 37996 USA. RP Susskind, J (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 910-4, Greenbelt, MD 20771 USA. RI Blass, William/A-2792-2008; Jennings, Donald/D-7978-2012 NR 19 TC 7 Z9 7 U1 0 U2 0 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 NOV PY 1998 VL 192 IS 1 BP 119 EP 138 DI 10.1006/jmsp.1998.7675 PG 20 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 136NM UT WOS:000076865700015 ER PT J AU Chackerian, C Freedman, RS Giver, LP Brown, LR AF Chackerian, C Freedman, RS Giver, LP Brown, LR TI The NO vibrational fundamental band: O-2-broadening coefficients SO JOURNAL OF MOLECULAR SPECTROSCOPY LA English DT Article ID PARAMETERS; FREQUENCY AB The first measurements of O-2 broadening of NO lines is reported. For the NO fundamental vibration-rotation band, polynomial representations for this broadening at 299 K are given for Omega = 3/2 and Omega = 1/2e and f transitions, respectively: gamma(3/2)(\m\) = 0.06463 - 0.00262\m\ + 0.000147\m\(2) - 0.00000327\m\(3), g(1/2)(f)(\m\) = 0.06515 - 0.00381\m\ + 0.000271\m\(2) - 0.00000665\m\(3), and gamma(1/2)(e)(\m\) = 0.06433 - 0.00343\m\ + 0.000214\m\(2) - 0.00000497\m\(3). These broadening coefficients are on the order of 17% smaller than the comparable coefficients found for N-2 broadening of NO. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chackerian, C (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 15 TC 9 Z9 9 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0022-2852 J9 J MOL SPECTROSC JI J. Mol. Spectrosc. PD NOV PY 1998 VL 192 IS 1 BP 215 EP 219 DI 10.1006/jmsp.1998.7679 PG 5 WC Physics, Atomic, Molecular & Chemical; Spectroscopy SC Physics; Spectroscopy GA 136NM UT WOS:000076865700025 ER PT J AU Mompean, G Jongen, T Deville, MO Gatski, TB AF Mompean, G Jongen, T Deville, MO Gatski, TB TI On algebraic extra-stress models for the simulation of viscoelastic flows SO JOURNAL OF NON-NEWTONIAN FLUID MECHANICS LA English DT Article DE viscoelastic; extra-stress; Oldroyd-B fluid; algebraic ID CONTRACTION; TURBULENCE; PLANAR AB A methodology is presented for the formulation of an algebraic extra-stress model derivable from the Oldroyd-B constitutive equation for a viscoelastic fluid. An implicit algebraic tensor relation is derived directly from the differential constitutive relation by involving a slow variation condition on the evolution of the deviatoric part of the extra-stress tensor. An explicit solution to this algebraic constitutive equation is then obtained using representation bases developed previously for the turbulent flow of Newtonian fluids. A series of validation flows are then studied to assess the accuracy and range of applicability of the algebraic extra-stress model. (C) 1998 Elsevier Science B.V. All rights reserved. C1 Swiss Fed Inst Technol, DGM, LMF, CH-1015 Lausanne, Switzerland. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Deville, MO (reprint author), Swiss Fed Inst Technol, DGM, LMF, CH-1015 Lausanne, Switzerland. NR 17 TC 6 Z9 6 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0377-0257 J9 J NON-NEWTON FLUID JI J. Non-Newton. Fluid Mech. PD NOV PY 1998 VL 79 IS 2-3 BP 261 EP 281 DI 10.1016/S0377-0257(98)00111-6 PG 21 WC Mechanics SC Mechanics GA 139AB UT WOS:000077004300011 ER PT J AU Kumar, N Srivastava, KM AF Kumar, N Srivastava, KM TI The effect of neutral-gas friction on Alfven surface waves propagating along a plasma-vacuum interface SO JOURNAL OF PLASMA PHYSICS LA English DT Article AB The effect of neutral-gas friction on Alfven surface waves propagating along an infinitely conducting viscous plasma-vacuum interface has been investigated. a dispersion relation is obtained for such waves. For different values of the neutral-gas friction parameter S = upsilon(c)/omega (where upsilon(c) is the collisional frequency between two components of the composite plasma), the variations of the real and imaginary parts k(r) and k(i) of the wavenumber k with the viscosity parameter vp = mu(1)omega/rho(01)v(A1)(2) (where mu(1) and rho(01) are the coefficient of viscosity and the density of plasma media 1) are shown graphically. It is concluded that a three-mode structure of Alfven surface waves results owing to neutral-gas friction. It is suggested that our results are useful for both laboratory and astrophysical plasmas (e.g. photospheres, chromospheres and cool interstellar clouds). C1 Univ Roorkee, Dept Math, Roorkee 247667, Uttar Pradesh, India. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kumar, N (reprint author), KGK Coll, Dept Math, Moradabad 244001, India. NR 18 TC 1 Z9 1 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 40 WEST 20TH STREET, NEW YORK, NY 10011-4211 USA SN 0022-3778 J9 J PLASMA PHYS JI J. Plasma Phys. PD NOV-DEC PY 1998 VL 60 BP 731 EP 742 DI 10.1017/S0022377898007144 PN 4 PG 12 WC Physics, Fluids & Plasmas SC Physics GA 159TJ UT WOS:000078190300004 ER PT J AU Steinetz, BM Adams, ML AF Steinetz, BM Adams, ML TI Effects of compression, staging, and braid angle on braided rope seal performance 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 Future turbine engines will operate at increased temperatures to achieve more demanding efficiency and performance goals. Seals are being developed to seal and serve as compliant mounts allowing for relative thermal growths between high-temperature but brittle primary structures and the surrounding support structures. The hybrid seal was constructed of an all-ceramic (alumina-silica) core overbraided with a superalloy wire sheath (cobalt-based superalloy), The all-ceramic seal was constructed of an all-ceramic (alumina-silica) core overbraided with multiple ceramic (alumina-silica) sheath layers. The current report studies the test results of baseline and modified hybrid seals, two-stage hybrid and two-stage all-ceramic seal configurations, and single-stage hybrid and single-stage all-ceramic seal configurations for a range of seal crush conditions. Hybrid seal modifications include increasing the sheath braid angle and core coverage. For the same percent seal cross-sectional crush, results show that increasing the hybrid seal braid angle increased seal stiffness and seal unit load, resulting in flows approximately one-third of the baseline hybrid seal flows. For both hybrid and all-ceramic seals, two-stage seal configurations significantly outperformed single-stage configurations. Two-stage seal flows were at least 30% less than the single-stage seal flows for the same seal crush. Flow results are presented for a range of pressures and temperatures from ambient to 1300 degrees F, before and after scrubbing. Compression test results show that for both all-ceramic and hybrid seals, seal preload and stiffness increase with seal crush, but residual seal interference remains constant. C1 NASA, Lewis Res Ctr, MechComponents Branch, Cleveland, OH 44135 USA. Modern Technol Corp, Middleburg Hts, OH 44130 USA. RP Steinetz, BM (reprint author), NASA, Lewis Res Ctr, MechComponents Branch, Cleveland, OH 44135 USA. EM bruce.steinetz@lerc.nasa.gov NR 8 TC 5 Z9 5 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 NOV-DEC PY 1998 VL 14 IS 6 BP 934 EP 940 DI 10.2514/2.5387 PG 7 WC Engineering, Aerospace SC Engineering GA 139HK UT WOS:000077022300009 ER PT J AU Perkins, HD Thomas, SR DeBonis, JR AF Perkins, HD Thomas, SR DeBonis, JR TI Rocket-based combined cycle propulsion system testing 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 C1 NASA, Lewis Res Ctr, Hyperson Projects Off, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Engine Syst Technol Branch, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Nozzle Branch, Cleveland, OH 44135 USA. RP Perkins, HD (reprint author), NASA, Lewis Res Ctr, Hyperson Projects Off, Cleveland, OH 44135 USA. NR 5 TC 0 Z9 0 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD NOV-DEC PY 1998 VL 14 IS 6 BP 1065 EP 1067 DI 10.2514/2.5375 PG 3 WC Engineering, Aerospace SC Engineering GA 139HK UT WOS:000077022300026 ER PT J AU Rothman, LS Rinsland, CP Goldman, A Massie, ST Edwards, DP Flaud, JM Perrin, A Camy-Peyret, C Dana, V Mandin, JY Schroeder, J McCann, A Gamache, RR Wattson, RB Yoshino, K Chance, KV Jucks, KW Brown, LR Nemtchinov, V Varanasi, P AF Rothman, LS Rinsland, CP Goldman, A Massie, ST Edwards, DP Flaud, JM Perrin, A Camy-Peyret, C Dana, V Mandin, JY Schroeder, J McCann, A Gamache, RR Wattson, RB Yoshino, K Chance, KV Jucks, KW Brown, LR Nemtchinov, V Varanasi, P TI The HITRAN molecular spectroscopic database and HAWKS (HITRAN Atmospheric Workstation): 1996 edition SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Review ID ABSORPTION CROSS-SECTIONS; COLLISION-INDUCED ABSORPTION; FAR-INFRARED SPECTRUM; SCHUMANN-RUNGE BANDS; NONLOCAL THERMODYNAMIC-EQUILIBRIUM; FOURIER-TRANSFORM SPECTROSCOPY; HIGH-RESOLUTION SPECTROSCOPY; AIR-BROADENING COEFFICIENTS; 720-NM WAVELENGTH REGION; DIODE-LASER SPECTROSCOPY AB Since its first publication in 1973, the HITRAN molecular spectroscopic database has been recognized as the international standard for providing the necessary fundamental spectroscopic parameters for diverse atmospheric and laboratory transmission and radiance calculations. There have been periodic editions of HITRAN over the past decades as the database has been expanded and improved with respect to the molecular species and spectral range covered, the number of parameters included, and the accuracy of this information. The 1996 edition not only includes the customary line-by-line transition parameters familiar to HITRAN users, but also cross-section data, aerosol indices of refraction, software to filter and manipulate the data, and documentation. This paper describes the data and features that have been added or replaced since the previous edition of HITRAN. We also cite instances of critical data that are forthcoming. Published by Elsevier Science Ltd. C1 VSBM, AF Res Lab, Bedford, MA 01731 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Denver, Dept Phys, Denver, CO 80208 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Paris 11, Photophys Mol Lab, CNRS, F-91405 Orsay, France. Univ Paris 06, LPMA, F-75252 Paris 05, France. Ontar Corp, N Andover, MA 01845 USA. Univ Lowell, Dept Environm Earth & Atmospher Sci, Lowell, MA 01854 USA. Utah State Univ, Stewart Radiance Lab, Bedford, MA 01730 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SUNY Stony Brook, Stony Brook, NY 11794 USA. RP Rothman, LS (reprint author), VSBM, AF Res Lab, 29 Randolph Rd, Bedford, MA 01731 USA. OI Chance, Kelly/0000-0002-7339-7577; Rothman, Laurence/0000-0002-3837-4847 NR 291 TC 1556 Z9 1597 U1 9 U2 81 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 NOV PY 1998 VL 60 IS 5 BP 665 EP 710 DI 10.1016/S0022-4073(98)00078-8 PG 46 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100002 ER PT J AU Devi, VM Benner, DC Rinsland, CP Smith, MAH AF Devi, VM Benner, DC Rinsland, CP Smith, MAH TI Absolute rovibrational intensities of (CO2)-C-12-O-16 absorption bands in the 3090-3850 cm(-1) spectral region SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID CARBON-DIOXIDE BANDS; INFRARED ENERGY-LEVELS; LINE-INTENSITIES; CO2 BANDS; CM-1; TEMPERATURE; N2O AB A multispectrum nonlinear least-squares fitting technique has been used to determine the absolute intensities for approximately 1500 spectral lines in 36 vibration-rotation bands of (CO2)-C-12-O-16 between 3090 and 3850 cm(-1). A total of six absorption spectra of a high-purity (99.995% minimum) natural sample of carbon dioxide were used in the analysis. The spectral data (0.01 cm(-1) resolution) were recorded at room temperature and low pressure(1 to 10 Torr) using the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak. The absorption path lengths for these spectra varied between 24.86 and 385.76 m. The first experimental determination of the intensity of the theoretically predicted 2 nu(2)(2) + nu(3) "forbidden" band has been made. The measured line intensities obtained for each band have been analyzed to determine the vibrational band intensity, S-nu, in cm(-1)/(molecule cm(-2)) at 296 K, square of the rotationless transition dipole moment \R\(2) in Debye(2), as well as the nonrigid rotor coefficients. The results are compared to the values listed in the 1996 HITRAN database which are obtained using the direct numerical diagonalization (DND) technique as well as to other published values where available. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Devi, VM (reprint author), Coll William & Mary, Dept Phys, Box 8795, Williamsburg, VA 23187 USA. NR 34 TC 20 Z9 20 U1 0 U2 3 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 NOV PY 1998 VL 60 IS 5 BP 741 EP 770 DI 10.1016/S0022-4073(98)00080-6 PG 30 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100004 ER PT J AU Devi, VM Benner, DC Smith, MAH Rinsland, CP AF Devi, VM Benner, DC Smith, MAH Rinsland, CP TI Pressure broadening and pressure shift coefficients in the 2v(2)(0) and v(1) bands of (OCO)-O-16-C-13-O-18 SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID STRENGTHS; REGION AB In this study we report the first measurements of the pressure broadening and the pressure-induced line shift coefficients due to air and nitrogen for 93 individual rovibrational lines, P(46) to R(46) and P(50) to R(45), respectively, belonging to the 2 nu(2)(0) and nu(1) bands of (OCO)-O-16-C-13-O-18. The results were obtained by analyzing ten long path, high-resolution laboratory absorption spectra using a multispectrum nonlinear least-squares technique. Broadening due to nitrogen was about 4% larger than by air. Similar to broadening coefficients, the pressure-shift coefficients were found to be transition dependent, but different for the P- and R-branch lines with the same rotational quantum number, J. Except for a few R-branch lines, the measured shift coefficients were negative. The shift coefficients varied from +4 x 10(-3) cm(-1)atm(-1) at 296 K to - 5.6 x 10(-3) cm(-1)atm(-1) at 296 K. Comparisons of the broadening and shift coefficients between the two bands, between the P and R branches, and between the two broadening gases are reported. No significant difference between shift coefficients of the two bands or the two broadening gases was observed. The results obtained were compared with those reported in the literature for the more abundant (CO2)-C-12-O-16 species. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Devi, VM (reprint author), Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NR 7 TC 12 Z9 12 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 771 EP 783 DI 10.1016/S0022-4073(98)00081-8 PG 13 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100005 ER PT J AU Rinsland, CP Flaud, JM Goldman, A Perrin, A Camy-Peyret, C Smith, MAH Devi, VM Benner, DC Barbe, A Stephen, TM Murcray, FJ AF Rinsland, CP Flaud, JM Goldman, A Perrin, A Camy-Peyret, C Smith, MAH Devi, VM Benner, DC Barbe, A Stephen, TM Murcray, FJ TI Spectroscopic parameters for ozone and its isotopes: Current status, prospects for improvement, and the identification of (OOO)-O-16-O-16-O-17 and (OOO)-O-16-O-17-O-16 lines in infrared ground-based and stratospheric solar absorption spectra SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID NU(3) ROVIBRATIONAL TRANSITIONS; CROSS-SECTION MEASUREMENTS; ROBERT-BONAMY FORMALISM; TEMPERATURE-DEPENDENCE; BROADENING COEFFICIENTS; ABSOLUTE ABSORPTION; WAVELENGTH REGION; HEAVY OZONE; SHIFT COEFFICIENTS; TROPOSPHERIC OZONE AB We describe the updates to the spectroscopic parameters of ozone and its isotopes in the 1996 HITRAN compilation. Recent published studies not included in HITRAN are also summarized, Finally, we report the identification of infrared lines of the gamma(3) bands of (OOO)-O-16-O-16-O-17 and (OOO)-O-16-O-17-O-16 in high-resolution sole; spectra recorded by stratospheric balloon-borne and ground-based Fourier transform spectrometers. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Paris Sud, CNRS, Photophys Mol Lab, F-91405 Orsay, France. Univ Denver, Dept Phys, Denver, CO 80208 USA. Univ Paris 06, CNRS, Lab Phys Mol & Applicat, F-75252 Paris 05, France. Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. Univ Reims, Grp Spectrometrie Mol & Atmospher, CNRS,UPRESA Q 6089 & D1434, UFR Sci, F-51687 Reims 2, France. RP Rinsland, CP (reprint author), NASA, Langley Res Ctr, Mail Stop 401A, Hampton, VA 23681 USA. NR 93 TC 11 Z9 12 U1 1 U2 5 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 NOV PY 1998 VL 60 IS 5 BP 803 EP 814 DI 10.1016/S0022-4073(98)00083-1 PG 12 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100007 ER PT J AU Devi, VM Benner, DC Smith, MAH Rinsland, CP AF Devi, VM Benner, DC Smith, MAH Rinsland, CP TI Self-broadening and self-shift coefficients in the fundamental band of (CO)-C-12-O-16 SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID DIODE-LASER MEASUREMENTS; PRESSURE-INDUCED LINESHIFTS; CARBON-MONOXIDE; LOW-TEMPERATURES; LINE STRENGTHS; CO; N-2; HE; WIDTHS; PARAMETERS AB High quality and precise measurements of self-broadened and self-shift coefficients in the fundamental band of (CO)-C-12-O-16 were made using spectra recorded at room temperature with the high-resolution (0.0027 cm(-1)) McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. The spectral region under investigation (2008-2247 cm(-1)) contains the P(31) to R(31) transitions. The data were obtained using a high-purity natural isotopic sample of carbon monoxide and two absorption cells with pathlengths of 4.08 and 9.98 cm, respectively. Various pressures of CO were used, ranging between 0.25 and 201.2 Torr. The results were obtained by analyzing five spectra simultaneously using a multispectrum nonlinear least-squares fitting technique. The self-broadened coefficients ranged from 0.0426(2) cm(-1) atm(-1) at 296 K to 0.0924(2) cm(-1) atm(-1) at 296 K, while the pressure-induced shift coefficients varied between -0.0042(3) cm(-1) atm(-1) at 296 K and +0.0005(1) cm(-1) atm(-1) at 296 K. The value in parentheses is the estimated uncertainty in units of the last digit. The self-broadened coefficients of lines with same values of m in the P and R branches agree close to within experimental uncertainties while the self-shift coefficients showed considerable variation within and between the two branches. The mean value of the ratios of P branch to R branch self-broadened coefficients was found to be 1.01 with a standard deviation of +/-0.01. Comparisons of the results with other published data were made. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Devi, VM (reprint author), Coll William & Mary, Dept Phys, Williamsburg, VA 23187 USA. NR 34 TC 18 Z9 19 U1 0 U2 2 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 NOV PY 1998 VL 60 IS 5 BP 815 EP 824 DI 10.1016/S0022-4073(98)00084-3 PG 10 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100008 ER PT J AU Goldman, A Brown, LR Schoenfeld, WG Spencer, MN Chackerian, C Giver, LP Dothe, H Rinsland, CP Coudert, LH Dana, V Mandin, JY AF Goldman, A Brown, LR Schoenfeld, WG Spencer, MN Chackerian, C Giver, LP Dothe, H Rinsland, CP Coudert, LH Dana, V Mandin, JY TI Nitric oxide line parameters: Review of 1996 HITRAN update and new results SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID HETERODYNE FREQUENCY MEASUREMENTS; FUNDAMENTAL-BAND; TEMPERATURE-RANGE; DIPOLE-MOMENT; NO; INTENSITIES; EXTRAPOLATION; SPECTROSCOPY; LINEWIDTHS; STRENGTHS AB The 1996 HITRAN database incorporated an extensive update of NO line parameters in the 5.3 mu m region. Hyperfine lines associated with the 0-1 band up to J = 46.5 were included and accuracies were greatly improved. Better air- and self-broadened widths were also included for a number of the infrared entries but erroneously omitted for others. These changes, as well as the complete NO database, are critically reviewed. Recent results not yet incorporated into the HITRAN database are described along with ongoing studies and needs for corrections and future improvements. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Mei Associates, Lexington, MA 02173 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Paris Sud, Photophys Mol Lab, F-91405 Orsay, France. Univ Paris 06, CNRS, Lab Phys Mol & Applicat, F-75252 Paris 05, France. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. NR 59 TC 18 Z9 19 U1 1 U2 11 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 NOV PY 1998 VL 60 IS 5 BP 825 EP 838 DI 10.1016/S0022-4073(98)00085-5 PG 14 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100009 ER PT J AU Perrin, A Flaud, JM Goldman, A Camy-Peyret, C Lafferty, WJ Arcas, P Rinsland, CP AF Perrin, A Flaud, JM Goldman, A Camy-Peyret, C Lafferty, WJ Arcas, P Rinsland, CP TI NO2 and SO2 line parameters: 1996 HITRAN update and new results SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID HIGH-RESOLUTION MEASUREMENTS; ABSORPTION CROSS-SECTION; ELECTRON-SPIN ROTATION; TEMPERATURE-DEPENDENCE; CONTACT RESONANCES; NITROGEN-DIOXIDE; SPECTRAL REGION; SULFUR-DIOXIDE; (NO2)-N-14-O-16; INTENSITIES AB The purpose of the present paper is to describe recent progress in the study of two molecules of atmospheric interest, namely nitrogen dioxide (NO2) and sulfur dioxide (SO2). This progress has led to updates in the 1996 version of the HITRAN database. Also some recommendations for the future will be given. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Paris Sud, CNRS, Photophys Mol Lab, F-91405 Orsay, France. Univ Denver, Dept Phys, Denver, CO 80208 USA. Univ Paris Sud, CNRS, Lab Phys Mol & Applicat, F-91405 Orsay, France. Natl Inst Stand & Technol, Opt Technol Div, Gaithersburg, MD 20899 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23682 USA. RP Perrin, A (reprint author), Univ Paris Sud, CNRS, Photophys Mol Lab, Bat 210,Campus Orsay, F-91405 Orsay, France. NR 56 TC 20 Z9 20 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 839 EP 850 DI 10.1016/S0022-4073(98)00086-7 PG 12 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100010 ER PT J AU Goldman, A Rinsland, CP Perrin, A Flaud, JM AF Goldman, A Rinsland, CP Perrin, A Flaud, JM TI HNO3 line parameters: 1996 HITRAN update and new results SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID TUNABLE DIODE-LASER; RESOLUTION SPECTRAL MEASUREMENT; NITRIC-ACID; ATMOSPHERIC SPECTRA; 2-NU(9) BANDS; INTENSITIES; MODEL; NU(5); NU(9); RESONANCE AB The 1996 HITRAN update of HNO3 absorption parameters is reviewed, for both discrete lines and cross-sections. Recent results not incorporated into the HITRAN database are described, as well as ongoing studies and needs for further improvements. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Paris Sud, CNRS, Photophys Mol Lab, F-91405 Orsay, France. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. NR 30 TC 29 Z9 29 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 851 EP 861 DI 10.1016/S0022-4073(98)00087-9 PG 11 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100011 ER PT J AU Coffey, MT Goldman, A Hannigan, JW Mankin, WG Schoenfeld, WG Rinsland, CP Bernardo, C Griffith, DWT AF Coffey, MT Goldman, A Hannigan, JW Mankin, WG Schoenfeld, WG Rinsland, CP Bernardo, C Griffith, DWT TI Improved vibration-rotation (0-1) HBr line parameters for validating high resolution infrared atmospheric spectra measurements SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID EMISSION-SPECTROSCOPY; BAND AB Improved line parameters are generated for the HBr (0-1) fundamental band. These new parameters, which include hyperfine structure, allow fitting of HBr absorption features from gas cells used for long-term validation of infrared high-resolution spectrometers. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Wollongong, Dept Chem, Wollongong, NSW 2522, Australia. RP Coffey, MT (reprint author), Natl Ctr Atmospher Res, Div Atmospher Chem, POB 3000, Boulder, CO 80307 USA. NR 13 TC 16 Z9 16 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 863 EP 867 DI 10.1016/S0022-4073(98)00088-0 PG 5 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100012 ER PT J AU Goldman, A Chance, KV Coffey, MT Hannigan, JW Mankin, WG Rinsland, CP AF Goldman, A Chance, KV Coffey, MT Hannigan, JW Mankin, WG Rinsland, CP TI Improved line parameters for the X-1 Sigma(+) (0-0) and (0-1) bands of HI SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID HIGH-RESOLUTION MEASUREMENTS; METHYL-IODIDE; OZONE; TRANSITIONS; EMISSIONS; SPECTRUM; REGION; OCEAN; SEAS AB Hyperfine lines associated with the X(1)Sigma(+) (0-0) and (0-1) bands of (HI)-I-127 are generated. Discussion of the HI line parameters in the HITRAN and SAO databases is presented. The new (0-0) line parameters are based on previously published far-infrared constants. High-resolution laboratory spectra in the infrared fundamental band region are presented and analyzed for new fine structure spectroscopic constants, which are combined with available hyperfine structure constants for calculating the new (0-1) line parameters. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. Harvard Smithsonian Ctr Astrophys, Atom & Mol Phys Div, Cambridge, MA 02138 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. NR 27 TC 5 Z9 5 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 869 EP 874 DI 10.1016/S0022-4073(98)00089-2 PG 6 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100013 ER PT J AU Goldman, A Rinsland, CP Flaud, JM Orphal, J AF Goldman, A Rinsland, CP Flaud, JM Orphal, J TI ClONO2: Spectroscopic line parameters and cross-sections in 1996 HITRAN SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID HARMONIC FORCE-FIELD; LONG-TERM TREND; CHLORINE NITRATE; HIGH-RESOLUTION; STRATOSPHERIC TEMPERATURES; ABSORPTION-COEFFICIENTS; INFRARED-SPECTRA; PROFILES; MILLIMETER; EMISSION AB The 1996 HITRAN update of ClONO2 line parameters and cross-sections are reviewed. Recent results not yet incorporated into the HITRAN database are described along with ongoing studies and needs for improvements. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Univ Denver, Dept Phys, Denver, CO 80208 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Univ Paris Sud, CNRS, Photophys Mol Lab, F-91405 Orsay, France. Univ Bremen, Inst Environm Phys, D-28334 Bremen, Germany. RP Goldman, A (reprint author), Univ Denver, Dept Phys, Denver, CO 80208 USA. RI Orphal, Johannes/A-8667-2012 OI Orphal, Johannes/0000-0002-1943-4496 NR 37 TC 11 Z9 11 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 875 EP 882 DI 10.1016/S0022-4073(98)00090-9 PG 8 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100014 ER PT J AU Pickett, HM Poynter, RL Cohen, EA Delitsky, ML Pearson, JC Muller, HSP AF Pickett, HM Poynter, RL Cohen, EA Delitsky, ML Pearson, JC Muller, HSP TI Submillimeter, millimeter, and microwave spectral line catalog SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article AB This paper describes a computer-accessible catalog of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10 000 GHz (i.e. wavelengths longer than 30 mu m). The catalog can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines in the interstellar medium, the Earth's atmosphere, and the atmospheres of other planets. The information listed for each spectral line includes the frequency and its estimated error, the intensity, the lower state energy, and the quantum number assignment. The catalog is continuously updated and at present has information on 331 atomic and molecular species and includes a total of 1 845 866 lines. The catalog has been constructed by using theoretical least-squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariance. Future versions of this catalog will add more atoms and molecules and update the present listings as new data appear. The catalog is available on-line via anonymous FTP at spec.jpl.nasa.gov and on the world wide web at http://spec.jpl.nasa.gov. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Pickett, HM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. OI Mueller, Holger/0000-0002-0183-8927 NR 3 TC 904 Z9 908 U1 4 U2 32 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 NOV PY 1998 VL 60 IS 5 BP 883 EP 890 DI 10.1016/S0022-4073(98)00091-0 PG 8 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100015 ER PT J AU Rinsland, CP Gunson, MR Wang, PH Arduini, RF Baum, BA Minnis, P Goldman, A Abrams, MC Zander, R Mahieu, E Salawitch, RJ Michelsen, HA Irion, FW Newchurch, MJ AF Rinsland, CP Gunson, MR Wang, PH Arduini, RF Baum, BA Minnis, P Goldman, A Abrams, MC Zander, R Mahieu, E Salawitch, RJ Michelsen, HA Irion, FW Newchurch, MJ TI ATMOS/ATLAS 3 infrared profile measurements of trace gases in the November 1994 tropical and subtropical upper troposphere SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID BIOMASS BURNING EMISSIONS; SOUTH-ATLANTIC; REACTIVE NITROGEN; SHUTTLE MISSIONS; ATMOS EXPERIMENT; SOLAR SPECTRA; AIR; OZONE; REDISTRIBUTION; STRATOSPHERE AB Vertical mixing ratio profiles of four relatively long-lives gases, HCN, C2H2, CO, and C2H6, have been retrieved from 0.01 cm(-1) resolution infrared solar occultation spectra recorded between latitudes of 5.3 degrees N and 31.4 degrees N. The observations were obtained by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Science (ATLAS) 3 shuttle flight, 3-12 November 1994. Elevated mixing ratios below the tropopause were measured for these gases during several of the occultations. The positive correlations obtained between the simultaneously measured mixing ratios suggest that the enhancements are likely the result of surface emissions, most likely biomass burning and/or urban industrial activities, followed by common injection via deep convective transport of the gases to the upper troposphere. The elevated levels of HCN may account for at least part of the "missing NOy" in the upper troposphere. Comparisons of the observations with values measured during a recent aircraft campaign are presented. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Sci & Technol Corp, Hampton, VA 23666 USA. Sci Applicat Int Corp, Hampton, VA 23666 USA. Univ Denver, Dept Phys, Denver, CO 80208 USA. ITT Def & Elect, Ft Wayne, IN 46801 USA. Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. Harvard Univ, Div Appl Sci, Cambridge, MA 02138 USA. Univ Alabama, Dept Atmospher Sci, Huntsville, AL 35899 USA. RP Rinsland, CP (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RI Salawitch, Ross/B-4605-2009; Baum, Bryan/B-7670-2011; Minnis, Patrick/G-1902-2010; OI Salawitch, Ross/0000-0001-8597-5832; Baum, Bryan/0000-0002-7193-2767; Minnis, Patrick/0000-0002-4733-6148; Mahieu, Emmanuel/0000-0002-5251-0286 NR 36 TC 28 Z9 28 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 891 EP 901 DI 10.1016/S0022-4073(98)00092-2 PG 11 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100016 ER PT J AU Rinsland, CP Gunson, MR Wang, PH Arduini, RF Baum, BA Minnis, P Goldman, A Abrams, MC Zander, R Mahieu, E Salawitch, RJ Michelsen, HA Irion, FW Newchurch, MJ AF Rinsland, CP Gunson, MR Wang, PH Arduini, RF Baum, BA Minnis, P Goldman, A Abrams, MC Zander, R Mahieu, E Salawitch, RJ Michelsen, HA Irion, FW Newchurch, MJ TI ATMOS/ATLAS 3 infrared profile measurements of clouds in the tropical and subtropical upper troposphere SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID POLAR STRATOSPHERIC CLOUDS; SUBVISIBLE CIRRUS CLOUDS; OPTICAL-CONSTANTS; SHUTTLE MISSIONS; ATMOS EXPERIMENT; ICE CRYSTALS; WARM POOL; SPECTRA; EXTINCTION; TROPOPAUSE AB Vertical profiles of infrared cirrus extinction have been derived from tropical and subtropical upper tropospheric solar occultation spectra. The measurements were recorded by the Atmospheric Trace Molecule Spectroscopy (ATMOS) Fourier transform spectrometer during the Atmospheric Laboratory for Applications and Sciences (ATLAS) 3 shuttle flight in November 1994. The presence of large numbers of small ice crystals is inferred from the appearance of broad extinction features in the 8-12 mu m region. These features were observed near the tropopause and at lower altitudes. Vertical profiles of the ice extinction (km(-1)) in microwindows at 831, 957, and 1204 cm(-1) have been retrieved from the spectra and analyzed with a model for randomly oriented spheroidal ice crystals. An area-equivalent spherical radius of 6 mu m is estimated from the smallest ice crystals observed in the 8-12 mu m region. Direct penetration of clouds into the lower stratosphere is inferred from observations of cloud extinction extending from the upper troposphere to 50 mbar (20 km altitude). Cloud extinction between 3 and 5 mu m shows very little wavelength dependence, at least for the cases observed by the ATMOS instrument in the tropics and subtropics during ATLAS 3. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Sci & Technol Corp, Hampton, VA 23666 USA. Univ Denver, Dept Phys, Denver, CO 80208 USA. ITT Def & Elect, Ft Wayne, IN 46801 USA. Univ Liege, Inst Astrophys, B-4000 Liege, Belgium. Harvard Univ, Div Appl Sci, Cambridge, MA 02138 USA. Univ Alabama, Dept Atmospher Sci, Huntsville, AL 35899 USA. RP Rinsland, CP (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RI Salawitch, Ross/B-4605-2009; Baum, Bryan/B-7670-2011; Minnis, Patrick/G-1902-2010; OI Salawitch, Ross/0000-0001-8597-5832; Baum, Bryan/0000-0002-7193-2767; Minnis, Patrick/0000-0002-4733-6148; Mahieu, Emmanuel/0000-0002-5251-0286 NR 42 TC 15 Z9 15 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD NOV PY 1998 VL 60 IS 5 BP 903 EP 919 DI 10.1016/S0022-4073(98)00093-4 PG 17 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 129YR UT WOS:000076492100017 ER PT J AU Springer, A AF Springer, A TI Evaluating aerodynamic characteristics of wind-tunnel models produced by rapid prototyping methods SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB Initial studies of the aerodynamic characteristics of proposed launch vehicles can be made more accurately if lower-cost, high-fidelity aerodynamic models are available for wind-tunnel testing early in the development phase. The results of a study undertaken at NASA Marshall Space Flight Center are discussed to determine whether four rapid prototyping methods using a variety of materials are suitable for the design and manufacture of high-speed wind-tunnel models in direct testing applications. Also presented is an analysis of whether these materials and processes are of sufficient strength and fidelity to withstand the testing environment. In addition to test data, costs and turnaround times for the various models are given. On the basis of this study's results, one can conclude that rapid prototyping models show promise in limited, direct application for preliminary aerodynamic development studies at subsonic, transonic, and supersonic speeds. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Springer, A (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 4 TC 18 Z9 22 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 NOV-DEC PY 1998 VL 35 IS 6 BP 755 EP 759 DI 10.2514/2.3412 PG 5 WC Engineering, Aerospace SC Engineering GA 156HZ UT WOS:000077996700005 ER PT J AU Vayner, BV Doreswamy, CV Ferguson, DC Galofaro, JT Snyder, DB AF Vayner, BV Doreswamy, CV Ferguson, DC Galofaro, JT Snyder, DB TI Arcing on aluminum anodized plates immersed in low-density plasmas SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID LOW-EARTH-ORBIT; SOLAR-ARRAYS; VOLTAGE; ENVIRONMENT; SPACECRAFT AB A number of experiments have been done to study characteristics of the plasma contamination and electromagnetic radiation generated by arcing on anodized aluminum plates immersed in low-density plasma. The low-Earth-orbit plasma environment was simulated in a plasma vacuum chamber, where the parameters could be controlled precisely. Diagnostic equipment included two antennas, a mass spectrometer, a spherical langmuir probe, a wire probe, and a very sensitive current probe to measure are current. All data except for mass spectrometry were obtained in digital form with a sampling interval of 2.5 ns that allowed us to study the radiation spectrum at frequencies up to 200 MHz, We found that the level of interference considerably exceeds the limitations on the level of electromagnetic noise set by technical requirements on Space Shuttle operation, Experiments with two independently biased plates have shown that the arcing onset on one plate generates a pulse of current on the second plate and that the secondary current pulse has a significant amplitude. The sampling interval for mass spectrometry was 250 ms. This allow ed us to obtain the rate of plasma contamination due to arcing. A significant degradation of the coating layer was determined by measurement of the resistance of the plate, which had experienced a few hundred arcs. C1 NASA, Lewis Res Ctr, Ohio Aerosp Inst, Photovoltaic & Space Environm Effects Branch, Cleveland, OH 44135 USA. RP Vayner, BV (reprint author), NASA, Lewis Res Ctr, Ohio Aerosp Inst, Photovoltaic & Space Environm Effects Branch, Cleveland, OH 44135 USA. NR 32 TC 6 Z9 6 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 NOV-DEC PY 1998 VL 35 IS 6 BP 805 EP 811 DI 10.2514/2.3403 PG 7 WC Engineering, Aerospace SC Engineering GA 156HZ UT WOS:000077996700013 ER PT J AU Joshi, PB Malonson, MR Green, BD McKay, J Brinza, D Arnold, G AF Joshi, PB Malonson, MR Green, BD McKay, J Brinza, D Arnold, G TI Spacecraft environment and effects monitoring instrumentation for small satellites SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID CONTAMINATION AB Future satellite systems will be required to survive and function in the space environment for much longer durations (10-15 years) than their present counterparts to achieve greater cost effectiveness, Therefore, the characterization of orbital space environment and its effects on spacecraft systems have received considerable attention in the recent years. Instrumentation is described for long-term measurement of key physical parameters characterizing the low-Earth-orbit environment and its effects on degradation of spacecraft materials and solar arrays. These measurements enable active, real-time monitoring of the spacecraft environment and the health of spacecraft and payload systems. The instrumentation, called Space Active Modular Materials Experiments, is designed to be compact, low power and lightweight. It is ideally suited for applications to small satellites, especially those designed for long-term, autonomous operation. C1 Phys Sci Inc, Dept Appl Sci, Andover, MA 01810 USA. Res Support Instruments, Hunt Valley, MD 21031 USA. CALTECH, Jet Prop Lab, Space Environm Effects Grp, Pasadena, CA 91109 USA. Aerospace Corp, Surface Sci Dept, El Segundo, CA 90245 USA. RP Joshi, PB (reprint author), Phys Sci Inc, Dept Appl Sci, 20 New England Business Ctr, Andover, MA 01810 USA. NR 10 TC 1 Z9 1 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 NOV-DEC PY 1998 VL 35 IS 6 BP 821 EP 829 DI 10.2514/2.3405 PG 9 WC Engineering, Aerospace SC Engineering GA 156HZ UT WOS:000077996700015 ER PT J AU Comfort, RH Moore, TE Craven, PD Pollock, CJ Mozer, FS Williamson, WS AF Comfort, RH Moore, TE Craven, PD Pollock, CJ Mozer, FS Williamson, WS TI Spacecraft potential control by the plasma source instrument on the POLAR satellite SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NASA, Goddard Space Flight Ctr, Interplanetary Phys Branch, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. SW Res Inst, San Antonio, TX 78284 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Hughes Res Labs, Sensors & Mat Lab, Malibu, CA 90265 USA. RP Comfort, RH (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RI Moore, Thomas/D-4675-2012 OI Moore, Thomas/0000-0002-3150-1137 NR 12 TC 15 Z9 15 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 NOV-DEC PY 1998 VL 35 IS 6 BP 845 EP 849 DI 10.2514/2.7586 PG 5 WC Engineering, Aerospace SC Engineering GA 156HZ UT WOS:000077996700018 ER PT J AU Boltz, FW AF Boltz, FW TI Space Shuttle family: Shuttle II, Mini Shuttle, and Micro Shuttles SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article ID MILITARY C1 NASA, Ames Res Ctr, Aeronaut Div, Moffett Field, CA 94035 USA. NR 15 TC 1 Z9 1 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1998 VL 35 IS 6 BP 852 EP 855 DI 10.2514/2.7588 PG 4 WC Engineering, Aerospace SC Engineering GA 156HZ UT WOS:000077996700020 ER PT J AU Hwu, SU Gomez, SF Panneton, RJ AF Hwu, SU Gomez, SF Panneton, RJ TI Multipath effects on International Space Station global positioning system performance SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 Lockheed Martin Space Mission Syst & Serv, Commun Syst Anal & Test Sect, Houston, TX 77258 USA. NASA, Lyndon B Johnson Space Ctr, Guidance & Navigat Branch, Houston, TX 77258 USA. NASA, Lyndon B Johnson Space Ctr, Avion Test & Anal Branch, Houston, TX 77258 USA. RP Hwu, SU (reprint author), Lockheed Martin Space Mission Syst & Serv, Commun Syst Anal & Test Sect, 2400 NASA Rd 1, Houston, TX 77258 USA. NR 5 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD NOV-DEC PY 1998 VL 35 IS 6 BP 858 EP 859 DI 10.2514/2.7591 PG 2 WC Engineering, Aerospace SC Engineering GA 156HZ UT WOS:000077996700023 ER PT J AU Arya, S Mount, DM Netanyahu, NS Silverman, R Wu, AY AF Arya, S Mount, DM Netanyahu, NS Silverman, R Wu, AY TI An optimal algorithm for approximate nearest neighbor searching in fixed dimensions SO JOURNAL OF THE ACM LA English DT Article DE approximation algorithms; box-decomposition trees; closest-point queries; nearest neighbor searching; post-office problem; priority search ID CLOSEST-POINT QUERIES; VECTOR QUANTIZATION; TREES AB Consider a set S of n data points in real d-dimensional space, R(d), where distances are measured using any Minkowski metric. In nearest neighbor searching, we preprocess S into a data structure, so that given any query point q epsilon R(d), is the closest point of S to q can be reported quickly. Given any positive real epsilon, a data point p is a (1 + epsilon)-approximate nearest neighbor of q if its distance from q is within a factor of (1 + epsilon) Of the distance to the true nearest neighbor. We show that it is possible to preprocess a set of n points in R(d) in O(dn log n) time and O(dn) space, so that given a query point q epsilon R(d), and epsilon > 0, a (1 + epsilon)-approximate nearest neighbor of q can be computed in O(c(d,epsilon) log n) time, where c(d,epsilon) less than or equal to d [1 + 6d/epsilon](d) is a factor depending only on dimension and epsilon. In general, we show that given an integer k greater than or equal to 1 (1 + epsilon)-approximations to the k nearest neighbors of q cart be computed in additional O(kd log n) time. C1 Univ Maryland, Dept Comp Sci, College Pk, MD 20742 USA. Univ Maryland, Inst Adv Comp Studies, College Pk, MD 20742 USA. Univ Maryland, Ctr Automat Res, College Pk, MD 20742 USA. Univ Dist Columbia, Dept Comp Sci, Washington, DC USA. American Univ, Dept Comp Sci & Informat Syst, Washington, DC 20016 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Hong Kong Univ Sci & Technol, Kowloon, Peoples R China. RP Arya, S (reprint author), Hong Kong Univ Sci & Technol, Dept Comp Sci, Hong Kong, Peoples R China. EM arya@cs.wst.hk; mount@cs.umd.edu; nathan@macs.biu.ac.il; ruth@cfar.umd.edu; awu@american.edu NR 58 TC 921 Z9 972 U1 4 U2 69 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 2 PENN PLAZA, STE 701, NEW YORK, NY 10121-0701 USA SN 0004-5411 J9 J ACM JI J. ACM PD NOV PY 1998 VL 45 IS 6 BP 891 EP 923 DI 10.1145/293347.293348 PG 33 WC Computer Science, Hardware & Architecture; Computer Science, Information Systems; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA 180PP UT WOS:000079394600001 ER PT J AU Ogbuji, LUJT AF Ogbuji, LUJT TI A pervasive mode of oxidative degradation in a SiC-SiC composite SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID CERAMIC-MATRIX COMPOSITES; SILICON-CARBIDE; FIBER; NICALON; CARBON; EMBRITTLEMENT; TEMPERATURE; KINETICS AB The oxidative durability of a SiC-SiC composite with Hi-Nicalon fiber and a BN interphase was investigated at 800 degrees C (where pesting is known to occur in SiC-SiC composites) for exposure durations of up to 500 h and in a variety of oxidant mixes and flow rates, ranging from quasi-stagnant room air, through slow-flowing oxygen that contained 30%-90% H2O, to the high-velocity flame of a burner rig. Degradation of the composite was determined from residual strength and fracture stain in post-exposure mechanical tests and correlated with microstructural evidence of damage to the fiber and interphase. The most-severe degradation of composite behavior occurred in the burner rig and has been shown to be associated with the high oxidant velocity and substantial moisture content, as well as a thin sublayer of carbon that is indicated to form between the fiber and the interphase during composite processing. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Ogbuji, LUJT (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 23 TC 49 Z9 50 U1 1 U2 8 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 NOV PY 1998 VL 81 IS 11 BP 2777 EP 2784 PG 8 WC Materials Science, Ceramics SC Materials Science GA 137BV UT WOS:000076895000002 ER PT J AU Barnes, NP Walsh, BM Murray, KE Quarles, GJ Castillo, VK AF Barnes, NP Walsh, BM Murray, KE Quarles, GJ Castillo, VK TI Nd : LuLF operating on the F-4(3/2) -> I-4(11/2) and F-4(3/2) -> I-4(13/2) transitions SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article ID LASER-OSCILLATOR; HIGH-EFFICIENCY; MODE; YLF; CRYSTAL; ND-3+; LIYF4 AB Nd:LuLF, that is, Nd:LuLiF4, was grown with a Czochralski technique and characterized spectroscopically to include absorption and emission data and lifetime. Evaluation of this laser material for operation on the F-4(3/2) -->I-4(11/2) and the F-4(3/2)-->I-4(13/2) transitions was performed. Normal-mode laser performance was achieved on both the pi and the sigma polarizations for both transitions by use of a simple polarization-selective resonator. Both normal-mode and Q-switched performance was characterized on the F-4(3/2) --> I-4(11/2) transition. (C) 1998 Optical Society of America [S0740-3224(98)01411-8]. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Boston Coll, Chestnut Hill, MA 02167 USA. VLOC, New Port Richey, FL 34655 USA. RP Barnes, NP (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 24 TC 14 Z9 14 U1 0 U2 2 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD NOV PY 1998 VL 15 IS 11 BP 2788 EP 2793 DI 10.1364/JOSAB.15.002788 PG 6 WC Optics SC Optics GA 136NF UT WOS:000076865100023 ER PT J AU Walsh, BM Barnes, NP Hutcheson, RL Equall, RW Di Bartolo, B AF Walsh, BM Barnes, NP Hutcheson, RL Equall, RW Di Bartolo, B TI Spectroscopy and lasing characteristics of Nd-doped Y3GaxAl(5-x)O-12 materials: application toward a compositionally tuned 0.94-mu m laser SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS LA English DT Article AB Nd-doped Y3GaxAl(5-x)O-12 (YGAG) materials are investigated for their usefulness as compositionally tuned laser materials. An analysis of Line-center wavelength, line broadening, and Line strength with Ga concentration is conducted to assess the feasibility of constructing a compositionally tuned 0.94-mu m laser. Spectroscopic results on this analysis are presented. A laser rod of Nd:Y3Ga1.35Al3.65O12 was made to lase at 0.94465 mu m and its performance characterized. This represents the first such laser demonstration on the F-4(3/2) --> I-4(9/2) laser transition in Nd:YGAG. Improved optical quality and the use of compositional variations of the YGAG structure is expected to improve the laser performance as these materials are more fully developed. (C) 1998 Optical Society of America [S0740-3224(98)01511-2]. C1 Boston Coll, Dept Phys, Chestnut Hill, MA 02167 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci Mat Corp, Bozeman, MT 59715 USA. RP Walsh, BM (reprint author), Boston Coll, Dept Phys, Chestnut Hill, MA 02167 USA. NR 11 TC 32 Z9 32 U1 0 U2 1 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0740-3224 J9 J OPT SOC AM B JI J. Opt. Soc. Am. B-Opt. Phys. PD NOV PY 1998 VL 15 IS 11 BP 2794 EP 2801 DI 10.1364/JOSAB.15.002794 PG 8 WC Optics SC Optics GA 136NF UT WOS:000076865100024 ER PT J AU Park, DG Wang, ZH Morkoc, H Alterovitz, SA Smith, DJ Tsen, SCY AF Park, DG Wang, ZH Morkoc, H Alterovitz, SA Smith, DJ Tsen, SCY TI Interface characterization of Si3N4/Si/GaAs heterostructures after high temperature annealing SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B LA English DT Article ID CHEMICAL-VAPOR-DEPOSITION; INSULATOR-SEMICONDUCTOR STRUCTURES; MOLECULAR-BEAM EPITAXY; SPECTROSCOPIC ELLIPSOMETRY; VARIABLE ANGLE; SI INTERLAYER; GAAS; CAPACITANCE; TRANSISTORS; DENSITY AB We present data on interface characteristics of Si3N4/Si/GaAs metal-insulator-semiconductor (MIS) structures and correlate electrical properties with spectroscopic ellipsometry, x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) observations. The interface of Si3N4/Si/GaAs heterostructures was electrically characterized by a combination of capacitance-voltage and conductance methods. The nature of an insulator/GaAs interface and the microstructure of Si3N4/Si/GaAs interfaces after high temperature annealing were investigated by variable angle spectroscopic ellipsometry and high resolution TEM, respectively. The evolution of chemical species in Si3N4/Si/GaAs heterostructures was examined using in situ angle-resolved XPS. The interface trap density (D-it) of the Si3N4/Si MIS capacitor was in the 2 x 10(10) eV(-1) cm(-2) range near the Si midgap after rapid thermal annealing at 550 degrees C in N-2 However, this density increased to high 10(10) eV(-1) cm-2 with annealing at 800 degrees C. The interface characteristics of Si3N4/Si/GaAs structures with D-it in the 7x10(10) eV(-1) cm(-2) range also degraded after annealing at 750 degrees C in N-2 with D-it increasing to 5 X 10(11) eV(-1) cm(-2) near the GaAs midgap. The spectroscopic ellipsometry results together with high resolution TEM observations appear to suggest that the degradation is due in part to the interface changing from crystalline to amorphous through chemical reaction. XPS measurements revealed that the as-deposited Si interlayer is nitridated during the initial stages of silicon nitride deposition, thus the thinned Si cannot prevent the outdiffusion of Ga and As species. We circumvented thermally induced interface degradation of Si3N4/Si/GaAs structures by employing a novel ex situ/in situ growth approach. (C) 1998 American Vacuum Society. [S0734-211X(98)19606-3]. C1 Univ Illinois, Coordinated Sci Lab, Urbana, IL 61801 USA. Univ Illinois, Mat Res Lab, Urbana, IL 61801 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Arizona State Univ, Ctr Solid State Sci, Tempe, AZ 85287 USA. RP Park, DG (reprint author), Hyundai Elect Ind, Proc Res Dept 4, Semicond Adv Res Div, Kyungki Do 467701, South Korea. NR 31 TC 5 Z9 5 U1 1 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 NOV-DEC PY 1998 VL 16 IS 6 BP 3032 EP 3040 DI 10.1116/1.590338 PG 9 WC Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Physics, Applied SC Engineering; Science & Technology - Other Topics; Physics GA 148QA UT WOS:000077542300021 ER PT J AU Stowe, RP Cubbage, ML Sams, CF Pierson, DL Barrett, ADT AF Stowe, RP Cubbage, ML Sams, CF Pierson, DL Barrett, ADT TI Detection and quantification of Epstein-Barr virus EBER1 in EBV-infected cells by fluorescent in situ hybridization and flow cytometry SO JOURNAL OF VIROLOGICAL METHODS LA English DT Article DE herpesvirus; Epstein-Barr virus; fluorescent in situ hybridization; flow cytometry ID INSITU HYBRIDIZATION; CARRIER STATE; SMALL RNAS; B-CELLS; EXPRESSION; INDIVIDUALS; ANTIGEN; LATENCY; BLOOD; DNA AB A rapid and highly sensitive fluorescent in situ hybridization (FISH) assay was developed to detect Epstein-Barr virus (EBV)-infected cells in peripheral blood. Multiple fluorescein-labeled antisense oligonucleotide probes were designed to hybridize to the EBER1 transcript, which is highly expressed in latently infected cells. After a rapid (30 min) hybridization, the cells were analyzed by flow cytometry. EBER1 was detected in several positive control cell lines that have variable numbers of EBV genome copies. No EBER1 was detected in two known EBV-negative cell lines. Northern blot analyses confirmed the presence and quantity of EBER1 transcripts in each cell line. This method was used to quantify the number of EBV-infected cells in peripheral blood from a patient with chronic mononucleosis. These results indicate that EBV-infected cells can be detected at the single cell level? and that this assay can be used to quantify the number of EBV-infected cells in clinical samples. (C) 1998 Published by Elsevier Science B.V. All rights reserved. C1 Univ Texas, Med Branch, Dept Pathol, Galveston, TX 77555 USA. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. KRUG Life Sci, Houston, TX USA. RP Barrett, ADT (reprint author), Univ Texas, Med Branch, Dept Pathol, Galveston, TX 77555 USA. NR 34 TC 11 Z9 11 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0166-0934 J9 J VIROL METHODS JI J. Virol. Methods PD NOV PY 1998 VL 75 IS 1 BP 83 EP 91 PG 9 WC Biochemical Research Methods; Biotechnology & Applied Microbiology; Virology SC Biochemistry & Molecular Biology; Biotechnology & Applied Microbiology; Virology GA 132MT UT WOS:000076634400009 PM 9820577 ER PT J AU Hendricks, RC Wilson, J Wu, T Flower, R AF Hendricks, RC Wilson, J Wu, T Flower, R TI Two-way brush seals catch a wave SO MECHANICAL ENGINEERING LA English DT Article C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Hendricks, RC (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD NOV PY 1998 VL 120 IS 11 BP 78 EP 80 PG 3 WC Engineering, Mechanical SC Engineering GA 134LM UT WOS:000076744500035 ER PT J AU Cintala, MJ Grieve, RAF AF Cintala, MJ Grieve, RAF TI Scaling impact melting and crater dimensions: Implications for the lunar cratering record (vol 33, pg 889, 1998) SO METEORITICS & PLANETARY SCIENCE LA English DT Correction C1 NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. Geol Survey Canada, Ottawa, ON K1A 0E8, Canada. RP Cintala, MJ (reprint author), NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Code SN2, Houston, TX 77058 USA. NR 3 TC 6 Z9 6 U1 1 U2 2 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 NOV PY 1998 VL 33 IS 6 BP 1343 EP 1343 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 147YY UT WOS:000077526400015 ER PT J AU Reinsch, S Wilhelm, H Senger, F Sawyer, A Mitchison, T Karsenti, E Walczak, C AF Reinsch, S Wilhelm, H Senger, F Sawyer, A Mitchison, T Karsenti, E Walczak, C TI XCTK1: a new xenopus C-terminal kinesin-like protein localizes to centrosomes SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 European Mol Biol Lab, D-69117 Heidelberg, Germany. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Harvard Univ, Sch Med, Dept Cell Biol, Boston, MA 02115 USA. Indiana Univ, Med Sci Program, Bloomington, IN 47405 USA. NR 0 TC 1 Z9 1 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1998 VL 9 SU S MA 49 BP 9A EP 9A PG 1 WC Cell Biology SC Cell Biology GA 137GQ UT WOS:000076906700048 ER PT J AU Hammond, TG Goodwin, TJ Lewis, FC Linnehan, RM Wolf, DA Hire, KP Campbell, WC Benes, E O'Reilly, KC Kaysen, JH AF Hammond, TG Goodwin, TJ Lewis, FC Linnehan, RM Wolf, DA Hire, KP Campbell, WC Benes, E O'Reilly, KC Kaysen, JH TI Genetic analysis of tissue engineering studies in microgravity. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 Tulane Univ, Med Ctr, New Orleans, LA USA. VAMC, New Orleans, LA USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 1 U2 1 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1998 VL 9 SU S MA 723 BP 125A EP 125A PG 1 WC Cell Biology SC Cell Biology GA 137GQ UT WOS:000076906700723 ER PT J AU Haddad, RS Sognier, MA Tsao, YD Lee, W Gonda, SR AF Haddad, RS Sognier, MA Tsao, YD Lee, W Gonda, SR TI Reuse of mammalian cell culture medium: Assessment of relevant issues. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 Wyle Labs, El Segundo, CA 90245 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1998 VL 9 SU S MA 734 BP 127A EP 127A PG 1 WC Cell Biology SC Cell Biology GA 137GQ UT WOS:000076906700737 ER PT J AU Johnson-Wint, B Cobb, M AF Johnson-Wint, B Cobb, M TI Temperature increase may mediate vibration stimulation of collagen gel contraction by rat tendon fibroblasts and done forming cells. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 No Illinois Univ, De Kalb, IL 60115 USA. Lockheed Martin Engn & Sci Co, Moffett Field, CA USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1998 VL 9 SU S MA 993 BP 172A EP 172A PG 1 WC Cell Biology SC Cell Biology GA 137GQ UT WOS:000076906700996 ER PT J AU Searby, ND Komarova, SV Globus, RK AF Searby, ND Komarova, SV Globus, RK TI Mechanical loading by centrifugation rearranges the cytoskeleton and stimulates bioenergetics in osteoblasts. SO MOLECULAR BIOLOGY OF THE CELL LA English DT Meeting Abstract C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER SOC CELL BIOLOGY PI BETHESDA PA PUBL OFFICE, 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 1059-1524 J9 MOL BIOL CELL JI Mol. Biol. Cell PD NOV PY 1998 VL 9 SU S MA 1008 BP 174A EP 174A PG 1 WC Cell Biology SC Cell Biology GA 137GQ UT WOS:000076906701009 ER PT J AU Nicholson, KL Reichert, GA Mason, KO Puchnarewicz, EM Ho, LC Shields, JC Filippenko, AV AF Nicholson, KL Reichert, GA Mason, KO Puchnarewicz, EM Ho, LC Shields, JC Filippenko, AV TI Evidence for low-level AGN activity in the nucleus of the LINER galaxy NGC 4594 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE line : formation; galaxies : individual : NGC 4594; ultraviolet : galaxies; X-rays : galaxies ID ADVECTION-DOMINATED ACCRETION; DWARF SEYFERT NUCLEI; X-RAY-PROPERTIES; GALACTIC NUCLEI; STARBURST GALAXIES; COMPLETE SAMPLE; EMISSION; ULTRAVIOLET; QUASARS; SEARCH AB We investigate the properties of the low-ionization nuclear emission-line region (LINER) galaxy, NGC 4594, using data taken with the Faint Object Spectrograph on the Hubble Space Telescope (HST) and with the ASCA X-ray observatory. The ultraviolet spectrum shows only narrow-line emission (FWHM approximate to 800-1000 km s(-1)) with no evidence for broad emission-line components. The emission-line data are compared with shock and photoionization model predictions. Fast shock models are incompatible with the UV emission-line spectrum and the best fit is found with a model, devised by Shull & McKee, where slow shocks (100 km s(-1)) are incident on a relatively dense medium (n(0) = 100 cm(-3)). Among photoionization models the best agreement is obtained with a CLOUDY model which has an ionization parameter of U = 3.2 x 10(-4). The hard X-Pay ASCA data on NGC4594 yield a spectral index of alpha(X) = 0.62 +/- 0.03 which extrapolates, within the errors, to the soft X-ray spectrum measured with the ROSAT PSPC. When the ASCA and ROSAT data are combined, the best-fitting column density is N(H) = 5.3 x 10(20) cm(-2), slightly higher than the Galactic value in this direction. However, allowing for contamination by soft extended emission close to the nucleus, the column density to the nuclear source may be as high as 2.9 x 10(21) cm(-2). The multiwavelength spectrum of the NGC 4594 differs from those of luminous active galactic nuclei (AGN) in the relative weakness of the UV continuum. This is consistent with the Siemiginowska model for a low-state accretion disc. Advection-dominated disc models, which have been applied to low-luminosity AGN, also agree qualitatively with our data. C1 UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Ohio Univ, Dept Phys & Astron, Athens, OH 45701 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. RP Nicholson, KL (reprint author), UCL, Mullard Space Sci Lab, Holmbury St Mary, Dorking RH5 6NT, Surrey, England. NR 51 TC 33 Z9 33 U1 0 U2 1 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD NOV 1 PY 1998 VL 300 IS 3 BP 893 EP 906 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 137AX UT WOS:000076892200021 ER PT J AU Schwarz, GJ Hauschildt, PH Starrfield, S Whitelock, PA Baron, E Sonneborn, G AF Schwarz, GJ Hauschildt, PH Starrfield, S Whitelock, PA Baron, E Sonneborn, G TI A multiwavelength study of the early evolution of the classical nova LMC 1988 #1 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE stars : abundances; stars : individual : LMC 1988 #1; novae, cataclysmic variables ID LARGE MAGELLANIC CLOUD; MODEL ATMOSPHERE ANALYSIS; RADIATIVE-TRANSFER; HERCULIS 1991; CYGNI 1992; DUST; PHOTOMETRY; SPECTRA; GAS AB LMC 1988 #1 was a moderately fast, CO, dust-forming classical nova. It was observed extensively in many different wavelength regions during its early evolution. The UV, optical and infrared light curves of LMC 1988 #1 are very similar to those of the Galactic Nova V1668 Cyg 1978. As in V1668 Cyg, LMC 1988 #1 showed the presence of an optically thin dust shell similar to 55 d after visual maximum which lasted for about two months. We successfully fit the UV and optical spectra of LMC 1988 #1 taken within the first two months of its outburst (when the atmosphere was still optically thick) with synthetic spectra computed using PHOENIX nova model atmospheres. The synthetic spectra reproduce most of the features seen in the observations and provide V-band magnitudes consistent with the observed light curve. From the synthetic spectral fits to the observed data, we find that the bolometric luminosity was approximately constant at (3.0 +/- 0.3) x 10(38) erg s(-1) (assuming a distance of 53 kpc to the LMC) during the first 45 d after visual maximum. The fits are improved by increasing the CNO abundances to similar to 10 times their solar values, implying that the ejecta were enriched in CNO elements. C1 Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Georgia, Dept Phys & Astron, Athens, GA 30602 USA. Univ Georgia, Ctr Simulat Phys, Athens, GA 30602 USA. S African Astron Observ, ZA-7935 Cape Town, South Africa. Univ Oklahoma, Dept Phys & Astron, Norman, OK 73019 USA. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Schwarz, GJ (reprint author), Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. EM schwarz@hydro.la.asu.edu; yeti@hal.physast.uga.edu; sumner.starrfield@asu.edu; paw@saao.ac.za; baron@physast.nhn.ou.edu; sonneborn@fornax.gsfc.nasa.gov RI Baron, Edward/A-9041-2009 OI Baron, Edward/0000-0001-5393-1608 NR 45 TC 20 Z9 20 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 NOV 1 PY 1998 VL 300 IS 3 BP 931 EP 944 DI 10.1046/j.1365-8711.1998.01964.x PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 137AX UT WOS:000076892200024 ER PT J AU Cohn, SE da Silva, A Guo, J Sienkiewicz, M Lamich, D AF Cohn, SE da Silva, A Guo, J Sienkiewicz, M Lamich, D TI Assessing the effects of data selection with the DAO physical-space statistical analysis system SO MONTHLY WEATHER REVIEW LA English DT Article ID DATA ASSIMILATION SYSTEM; RANGE FORECAST ERRORS; RADIOSONDE DATA; INTERPOLATION; CIRCULATION; COVARIANCE; PREDICTION; EQUATIONS; DYNAMICS; MODELS AB Conventional optimal interpolation (OI) analysis systems solve the standard statistical analysis equations approximately, by invoking a local approximation and a data selection procedure. Although solution of the analysis equations is essentially exact in the recent generation of global spectral variational analysis systems, these new systems also include substantial changes in error covariance modeling, making it difficult to discern whether improvements in analysis and forecast quality are due to exact, global solution of the analysis equations, or to changes in error covariance modeling. The formulation and implementation of a new type of global analysis system at the Data Assimilation Office, termed the Physical-space Statistical Analysis System (PSAS), is described in this article. Since this system operates directly in physical space, it is capable of employing error covariance models identical to those of the predecessor OI system, as well as more advanced models. To focus strictly on the effect of global versus local solution of the analysis equations, a comparison between PSAS and Of analyses is carried out with both systems using identical error covariance models and identical data. Spectral decomposition of the analysis increments reveals that, relative to the PSAS increments, the OI increments have too little power at large horizontal scales and excessive power at small horizontal scales. The OI increments also display an unrealistically large ratio of divergence to vorticity. Dynamical imbalances in the OI-analyzed state can therefore be attributed in part to the approximate local method of solution, and are not entirely due to the simple geostrophic constraint built into the forecast error covariance model. Root-mean-square observation minus 6-h forecast errors in the zonal wind component are substantially smaller for the PSAS system than for the OI system. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. RP Cohn, SE (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Code 910-3, Greenbelt, MD 20771 USA. RI da Silva, Arlindo/D-6301-2012; Cohn, Stephen/K-1954-2012; Sienkiewicz, Meta/P-8168-2016 OI da Silva, Arlindo/0000-0002-3381-4030; Cohn, Stephen/0000-0001-8506-9354; Sienkiewicz, Meta/0000-0002-9267-4568 NR 48 TC 159 Z9 165 U1 2 U2 5 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 NOV PY 1998 VL 126 IS 11 BP 2913 EP 2926 DI 10.1175/1520-0493(1998)126<2913:ATEODS>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 137TP UT WOS:000076932600010 ER PT J AU Tripathi, RK Wilson, JW Cucinotta, FA AF Tripathi, RK Wilson, JW Cucinotta, FA TI Nuclear absorption cross sections using medium modified nucleon-nucleon amplitudes SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS LA English DT Article ID MICROSCOPIC CALCULATION; SCATTERING; C-12 AB We extract the in-medium nucleon-nucleon amplitudes from the available proton-nucleus total reaction cross sections data. The retrieval of the information from the experiment makes these estimates very reliable. Simple expressions are then given for the in-medium nucleon-nucleon amplitudes for any system of colliding nuclei as a function of energy. Excellent agreement is demonstrated in ion-nucleus absorption cross sections. (C) 1998 Elsevier Science B.V. kll rights reserved. C1 Hampton Univ, Hampton, VA 23668 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Tripathi, RK (reprint author), Hampton Univ, Hampton, VA 23668 USA. FU NCPDCID CDC HHS [NCCI-242] NR 24 TC 9 Z9 9 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 NOV PY 1998 VL 145 IS 3 BP 277 EP 282 DI 10.1016/S0168-583X(98)00420-0 PG 6 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Atomic, Molecular & Chemical; Physics, Nuclear SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 140FF UT WOS:000077076100003 PM 11542671 ER PT J AU Lane, HW Gretebeck, RJ Smith, SM AF Lane, HW Gretebeck, RJ Smith, SM TI Nutrition, endocrinology, and body composition during space flight SO NUTRITION RESEARCH LA English DT Review DE energy; protein; bed rest; metabolism; muscle ID SHORT-TERM SPACEFLIGHT; BED-REST; ENERGY-EXPENDITURE; PROTEIN-METABOLISM; ASTRONAUTS; MUSCLE; MICROGRAVITY; CORTISOL; INSULIN; BEDREST AB Space flight induces endocrine changes that perturb metabolism. This altered metabolism affects both the astronauts' body composition and the nutritional requirements necessary to maintain their health. During the last 25 years, a combination of studies conducted on Skylab (the first U.S. space laboratory), U.S. Shuttle flights, and Soviet and Russian flights provides a range of data from which general conclusions about energy and protein requirements can be drawn. We have reviewed the endocrine data from those studies and related it to changes in body composition. From these data it appears that protein and energy intake of astronauts are similar to those on Earth. However, a combination of measures, including exercise, appropriate diet, and, potentially, drugs, is required to provide the muscle health needed for long duration space flight. Published by Elsevier Science Inc. C1 NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, Houston, TX 77058 USA. Purdue Univ, W Lafayette, IN 47907 USA. RP Lane, HW (reprint author), NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, Houston, TX 77058 USA. NR 48 TC 13 Z9 14 U1 3 U2 8 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0271-5317 J9 NUTR RES JI Nutr. Res. PD NOV PY 1998 VL 18 IS 11 BP 1923 EP 1934 DI 10.1016/S0271-5317(98)00162-6 PG 12 WC Nutrition & Dietetics SC Nutrition & Dietetics GA 130MW UT WOS:000076524700011 PM 11541547 ER PT J AU Brunett, S Gottschalk, T AF Brunett, S Gottschalk, T TI A large-scale metacomputing framework for the ModSAF real-time simulation SO PARALLEL COMPUTING LA English DT Article DE simulation; distributed systems; metacomputing; scalable communications; interest management ID DISTRIBUTED INTERACTIVE SIMULATION; TECHNOLOGY; DIS AB A distributed, parallel implementation of the widely-used Modular Semi-Automated Forces (ModSAF) Distributed Interactive Simulation (DIS) is presented, with Scalable Parallel Processors (SPPs) used to simulate more than 50,000 individual vehicles. The single-SPP version is described and shown to be scalable. This code is portable and has been run on a variety of different SPP architectures. Results for simulations with up to 15,000 vehicles are presented for a number of distinct SPP architectures. The initial multi-SPP (metacomputing) run used explicit Gateway communication processes to exchange data among several SPPs simulating separate portions of the full battle space. The 50K-vehicle simulations utilized 1904 processors on SPPs at six sites across seven time zones, including platforms from three computer manufacturers. (Four of the SPP sites in the large run used the single-SPP code described in this work, with a somewhat different single-SPP ModSAF implementation used at the other two sites.) Particular attention is given to analyses of inter-SPP data rates and Gateway performance in the multi-SPP runs. An alternative, next-generation implementation based on Globus is presented, including discussions of initial experiments, comparisons to the Gateway model, and planned near-term extensions. Finally, comparisons are made between this work and ongoing mainstream DIS activities. (C) 1998 Elsevier Science B.V. All rights reserved. C1 CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. Oak Ridge Ctr Computat Sci, Oak Ridge, TN USA. USA, Corps Engineers, Waterways Expt Stn, Informat Technol Lab, Washington, DC USA. NASA, Ames Res Ctr, Numer Aerodynam Simulat Syst Div, Moffett Field, CA USA. Indiana Univ, Bloomington, IN 47405 USA. RP Brunett, S (reprint author), CALTECH, Ctr Adv Comp Res, Pasadena, CA 91125 USA. NR 21 TC 4 Z9 4 U1 0 U2 3 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0167-8191 J9 PARALLEL COMPUT JI Parallel Comput. PD NOV PY 1998 VL 24 IS 12-13 BP 1873 EP 1900 DI 10.1016/S0167-8191(98)00082-9 PG 28 WC Computer Science, Theory & Methods SC Computer Science GA 137FW UT WOS:000076904900010 ER PT J AU Welch, RB Bridgeman, B Williams, JA Semmler, R AF Welch, RB Bridgeman, B Williams, JA Semmler, R TI Dual adaptation and adaptive generalization of the human vestibulo-ocular reflex SO PERCEPTION & PSYCHOPHYSICS LA English DT Article ID EYE-MOVEMENTS; FLOCCULUS; HEAD AB In two experiments, we examined the possibility that the human vestibule-ocular reflex (VOR) is subject to dual adaptation (the ability to adapt to a sensory rearrangement more rapidly and/or more completely after repeated experience with it) and adaptive generalization (the ability to adapt more readily to a novel sensory rearrangement as a result of prior dual adaptation training). In Experiment 1, the subjects actively turned the head during alternating exposure to a visual-vestibular rearrangement (target/head gain = 0.5) and the normal situation (target/head gain = 0.0). These conditions produced both adaptation and dual adaptation of the VOR but no evidence of adaptive generalization when tested with a target/head gain of 1.0. Experiment 2, in which exposure to the 0.5 gain entailed externally controlled (i.e., passive) whole body rotation, resulted in VOR adaptation but no dual adaptation. As in Experiment 1, no evidence of adaptive generalization was found. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Calif Santa Cruz, Santa Cruz, CA 95064 USA. Tech Univ Clausthal, D-3392 Clausthal Zellerfeld, Germany. RP Welch, RB (reprint author), NASA, Ames Res Ctr, Mail Stop 239-11, Moffett Field, CA 94035 USA. NR 28 TC 15 Z9 15 U1 0 U2 0 PU PSYCHONOMIC SOC INC PI AUSTIN PA 1710 FORTVIEW RD, AUSTIN, TX 78704 USA SN 0031-5117 J9 PERCEPT PSYCHOPHYS JI Percept. Psychophys. PD NOV PY 1998 VL 60 IS 8 BP 1415 EP 1425 DI 10.3758/BF03208002 PG 11 WC Psychology; Psychology, Experimental SC Psychology GA 147TA UT WOS:000077512800011 PM 9865081 ER PT J AU Hou, TY Wu, XH Chen, SY Zhou, Y AF Hou, TY Wu, XH Chen, SY Zhou, Y TI Effect of finite computational domain on turbulence scaling law in both physical and spectral spaces SO PHYSICAL REVIEW E LA English DT Article AB The well-known translation between the power law of the energy spectrum and that of the correlation function or the second order structure function has been widely used in analyzing random data. Here, we show that the translation is valid only in proper scaling regimes. The regimes of valid translation are different for the correlation function and the structure function. Indeed, they do not overlap. Furthermore, in practice, the power laws exist only for a finite range of scales. We show that this finite range makes the translation inexact even in the proper scaling regime. The error depends on the scaling exponent. The current findings are applicable to data analysis in fluid turbulence and other stochastic systems. [S1063-651X(98)13911-9]. C1 Univ Calif Los Alamos Natl Lab, Ctr Nonlinear Studies, Los Alamos, NM 87545 USA. IBM Corp, Res Ctr, Div Res, Yorktown Heights, NY 10598 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. CALTECH, Pasadena, CA 91125 USA. RP Hou, TY (reprint author), CALTECH, Pasadena, CA 91125 USA. RI Chen, Shiyi/A-3234-2010 NR 3 TC 12 Z9 12 U1 0 U2 4 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 NOV PY 1998 VL 58 IS 5 BP 5841 EP 5844 DI 10.1103/PhysRevE.58.5841 PN A PG 4 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 139VU UT WOS:000077052100080 ER PT J AU Yeung, PK Zhou, Y AF Yeung, PK Zhou, Y TI Numerical study of rotating turbulence with external forcing SO PHYSICS OF FLUIDS LA English DT Article ID ISOTROPIC TURBULENCE; HOMOGENEOUS TURBULENCE; ENERGY-TRANSFER; TRIADIC INTERACTIONS; SCALES; SIMULATIONS; DYNAMICS; MODEL; DISSIPATION; FLOWS AB Direct numerical simulations at 256(3) resolution have been carried out to study the response of isotropic turbulence to the concurrent effects of solid-body rotation and stochastic, isotropic forcing at the large scales. Because spectral transfer to the smaller scales is weakened by rotation, energy input from forcing gradually builds up at the large scales, causing the overall kinetic energy to increase. At intermediate wave numbers the energy spectrum undergoes a transition from a limited k(-5/3) inertial range to k(-2) scaling recently predicted in the literature. Although the Reynolds stress tensor remains approximately isotropic and three-component, evidence for anisotropy and quasi-two-dimensionality in length scales and spectra in different velocity components and directions is strong. The small scales are found to deviate from local isotropy, primarily as a result of anisotropic transfer from the large scales. To understand the spectral dynamics of this flow, we study the detailed behavior of nonlinear triadic interactions in wave number space. Spectral transfer in the velocity component parallel to the axis of rotation is qualitatively similar to that in nonrotating turbulence; however, the perpendicular component is characterized by a much weakened energy cascade at high wave numbers and a local reverse transfer at the largest scales. The broader implications of this work are briefly addressed. (C) 1998 American Institute of Physics. [S1070-6631(98)02611-7]. C1 Georgia Inst Technol, Sch Aerosp Engn, Atlanta, GA 30332 USA. IBM Corp, Div Res, Thomas J Watson Res Ctr, Yorktown Heights, NY 10598 USA. NASA, Inst Comp Applicat Sci & Engn, Langley Res Ctr, Hampton, VA 23681 USA. RP Yeung, PK (reprint author), Georgia Inst Technol, Sch Aerosp Engn, Atlanta, GA 30332 USA. NR 50 TC 53 Z9 54 U1 0 U2 4 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 NOV PY 1998 VL 10 IS 11 BP 2895 EP 2909 DI 10.1063/1.869810 PG 15 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 131QV UT WOS:000076587500018 ER PT J AU Kowitt, ME AF Kowitt, ME TI Exchange about news story on particles ends in photon finish SO PHYSICS TODAY LA English DT Letter C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kowitt, ME (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0031-9228 J9 PHYS TODAY JI Phys. Today PD NOV PY 1998 VL 51 IS 11 BP 86 EP 86 DI 10.1063/1.882067 PG 1 WC Physics, Multidisciplinary SC Physics GA 133RC UT WOS:000076698700027 ER PT J AU Tennant, AF Wu, KW O'Dell, SL Weisskopf, MC AF Tennant, AF Wu, KW O'Dell, SL Weisskopf, MC TI Simulating AXAF grating spectra of accreting white dwarfs SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF AUSTRALIA LA English DT Article DE accretion; stars : binaries : close; stars : white dwarfs; data analysis ID ASTROPHYSICS FACILITY AXAF; RAY; SPECTROMETER; ENERGY; SHOCKS; STARS AB We present simulated AXAF spectra of accreting white dwarfs, using parameters appropriate for magnetic cataclysmic variables. The very high spectral resolution that can be obtained with the High-Energy Transmission Grating of AXAF can resolve the keV X-ray emission lines that characterise the temperature, density and velocity profiles of the shock-heated emission regions of these systems. These simulations demonstrate that actual spectra will allow us to place constraints on the white-dwarf mass and the accretion rate of the systems. The high-resolution spectra also allow the measurement of the velocity of the accretion flow in regions close to the white-dwarf surface. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab ES84, Huntsville, AL 35812 USA. Univ Sydney, Sch Phys, Sydney, NSW 2006, Australia. NASA, George C Marshall Space Flight Ctr, Space Sci Lab ES01, Huntsville, AL 35812 USA. RP Tennant, AF (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab ES84, Huntsville, AL 35812 USA. OI O'Dell, Stephen/0000-0002-1868-8056 NR 23 TC 5 Z9 5 U1 0 U2 0 PU C S I R O PUBLISHING PI COLLINGWOOD PA 150 OXFORD ST, PO BOX 1139, COLLINGWOOD, VICTORIA 3066, AUSTRALIA SN 1323-3580 J9 PUBL ASTRON SOC AUST JI Publ. Astron. Soc. Aust. PD NOV PY 1998 VL 15 IS 3 BP 339 EP 347 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 176PN UT WOS:000079160800011 ER PT J AU Gaidos, EJ AF Gaidos, EJ TI Nearby young solar analogs. I. Catalog and stellar characteristics SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Review ID MAIN-SEQUENCE STARS; X-RAY-EMISSION; T-TAURI STARS; URSA-MAJOR GROUP; ICCD SPECKLE OBSERVATIONS; ALL-SKY SURVEY; CIRCUMSTELLAR DISKS; LITHIUM ABUNDANCE; OPEN CLUSTER; CHROMOSPHERIC EMISSION AB We present a catalog of 38 young solar analogs within 25 pc, stars that are uniquely well suited for observations of their circumstellar environments to improve our understanding of conditions within the solar system during the Hadean/early Archean eons (prior to 3.8 Gyr ago). These G and early K stars were selected from the Hipparcos astrometric catalog based on lack of known stellar companions within 800 AU, bolometric luminosities close to that of the zero-age Sun and consistent with the zero-age main sequence, and ROSAT X-ray luminosities commensurate with the higher rotation rate and level of dynamo-driven activity in solar-mass stars less than 0.8 Gyr old. While many of these objects have been previously identified, this sample is novel in two respects: The selection criteria specifically consider the planetary environment, and the selection is uniform and all-sky. The X-ray emission from these young analogs is spectrally soft and consistent with a coronal origin. Calcium H and K emission, rotation periods, Lithium abundances, and kinematics support an age range of 0.2-0.8 Gyr for most of these stars. Three stars have exceptionally high space motions with respect to the local standard of rest and may be old disk or halo stars that are anomalously X-ray luminous. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Gaidos, EJ (reprint author), CALTECH, Jet Prop Lab, MS 170-25, Pasadena, CA 91125 USA. NR 143 TC 68 Z9 68 U1 1 U2 1 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 NOV PY 1998 VL 110 IS 753 BP 1259 EP 1276 DI 10.1086/316251 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 147GM UT WOS:000077480800001 ER PT J AU Valdivia, JA Milikh, GM Papadopoulos, K AF Valdivia, JA Milikh, GM Papadopoulos, K TI Model of red sprites due to intracloud fractal lightning discharges SO RADIO SCIENCE LA English DT Article ID RADIATION; SIMULATION; TORTUOSITY; IONIZATION; BREAKDOWN; AIRCRAFT; FLASHES; SPECTRA AB A new and improved model of red sprites is presented. Emphasis is placed on accounting for the puzzling observation of the spatial structure in the emissions. The model relies on the electromagnetic pulse (EMP) fields created by a horizontal lightning discharge and includes the observed fractal structure of such discharges in the computation of the EMP power density. It is shown that the model can account for the observed spatial structure of the red sprites while reducing the typical charge required to approximately 100 C. C1 NASA, Goddard Space Flight Ctr, NRC, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. RP Valdivia, JA (reprint author), NASA, Goddard Space Flight Ctr, NRC, Greenbelt, MD 20771 USA. RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 35 TC 19 Z9 20 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD NOV-DEC PY 1998 VL 33 IS 6 BP 1655 EP 1668 DI 10.1029/98RS02201 PG 14 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 145HR UT WOS:000077365500014 ER PT J AU Armstrong, JW AF Armstrong, JW TI Radio wave phase scintillation and precision Doppler tracking of spacecraft SO RADIO SCIENCE LA English DT Article ID OCCULTATION OBSERVATIONS; GRAVITATIONAL RADIATION; SCIENCE INVESTIGATIONS; GALILEO; GRAVITY; SYSTEM; VLBI AB Phase scintillation caused by propagation through solar wind, ionospheric, and tropospheric irregularities is a noise process for many spacecraft radio science experiments. In precision Doppler tracking observations, scintillation can be the dominant noise process. Scintillation statistics are necessary for experiment planning and in design of signal processing procedures. Here high-precision tracking data taken with operational spacecraft (Mars Observer, Galileo, and Mars Global Surveyor) and ground systems are used to produce temporal statistics of tropospheric and plasma phase scintillation. The variance of Doppler frequency fluctuations is approximately decomposed into two propagation processes. The first, associated with distributed scattering along the sight line in the solar wind, has a smooth spectrum. The second, associated principally with localized tropospheric scattering for X-band experiments, has a marked autocorrelation peak at the two-way light time between the Earth and the spacecraft (thus a cosine-squared modulation of the fluctuation power spectrum). For X-band data taken in the antisolar hemisphere the average noise levels of this process are in good agreement with average tropospheric noise levels determined independently from water vapor radiometer observations and radio interferometic data. The variance of the process having a smooth spectrum is consistent: with plasma noise levels determined independently from dual-frequency observations of the Viking spacecraft made at comparable Sun-Earth-spacecraft angles. The observations reported here are used to refine the propagation noise model for Doppler tracking of deep space probes. In particular, they can be used to predict propagation noise levels for high-precision X- and Ka-band tracking observations (e.g., atmosphere/ionosphere/ring occultations; celestial mechanics experiments, and gravitational wave experiments) to be done using the Cassini spacecraft. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Armstrong, JW (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 238-725, Pasadena, CA 91109 USA. NR 38 TC 11 Z9 11 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD NOV-DEC PY 1998 VL 33 IS 6 BP 1727 EP 1738 DI 10.1029/98RS02317 PG 12 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 145HR UT WOS:000077365500018 ER PT J AU Cummer, SA Inan, US Bell, TF AF Cummer, SA Inan, US Bell, TF TI Ionospheric D region remote sensing using VLF radio atmospherics SO RADIO SCIENCE LA English DT Article ID TWEEK ATMOSPHERICS; WAVE-GUIDE; SPECTRA AB Lightning discharges radiate the bulk of their electromagnetic energy in the very low frequency (VLF, 3-30 kHz) and extremely low frequency (ELF, 3-3000 Hz) bands. This energy, contained in impulse-like signals called radio atmospherics or sferics, is guided for long distances by multiple reflections from the ground and lower ionosphere. This suggests that observed sferic waveforms radiated from lightning and received at long distances (>1000 km) from the source stroke contain information about the state of the ionosphere along the propagation path. The focus of this work is on the extraction of nighttime D region electron densities (in the altitude range of similar to 70-95 km) from observed VLF sferics. In order to accurately interpret observed sferic characteristics, we develop a model of sferic propagation which is based on an existing frequency domain subionospheric VLF propagation code. The model shows that the spectral characteristics of VLF sferics depend primarily on the propagation path averaged ionospheric D region electron density profile, covering the range of electron densities from similar to 10(0) to 10(3) cm(-3). To infer the D region density from observed VLF sferics, we find the electron density profile that produces a modeled sferic spectrum that most closely matches an observed sferic spectrum. In most nighttime cases the quality of the agreement and the uncertainties involved allow the height of an exponentially varying electron density profile to be inferred with a precision of similar to 0.2 km. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Stanford Univ, Space Telecommun & Radiosci Lab, Stanford, CA 94305 USA. RP Cummer, SA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 690, Greenbelt, MD 20771 USA. RI Cummer, Steven/A-6118-2008 OI Cummer, Steven/0000-0002-0002-0613 NR 38 TC 95 Z9 99 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0048-6604 J9 RADIO SCI JI Radio Sci. PD NOV-DEC PY 1998 VL 33 IS 6 BP 1781 EP 1792 DI 10.1029/98RS02381 PG 12 WC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications SC Astronomy & Astrophysics; Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Remote Sensing; Telecommunications GA 145HR UT WOS:000077365500023 ER PT J AU Hall, DK Foster, JL Verbyla, DL Klein, AG Benson, CS AF Hall, DK Foster, JL Verbyla, DL Klein, AG Benson, CS TI Assessment of snow-cover mapping accuracy in a variety of vegetation-cover densities in central Alaska SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID SURFACE ALBEDO AB Field and aircraft measurements are acquired in April 1995 in central Alaska to map snow; cover with MODIS Airborne Simulator (MAS) data, acquired from high-altitude aircraft. The Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer (MODIS) is a 36-channel system that will be launched on the EOS-AM-1 platform in 1999. A vegetation-density map derived from integrated reflectances (R(i)), from MAS data, is compared with an independently-produced vegetation type and density map derived from Thematic Mapper (TM) and ancillary data. The maps agreed to within 13%, thus corroborating the effectiveness of using the reflectance technique for mapping vegetation density. Snow cover was mapped on a 13 April 1995 MAS image, using the original MODIS prototype algorithm and an enhanced MODIS prototype algorithm. Field measurements revealed that the area was completely snow covered. With the original algorithm, snow teas mapped in 96% of the pixels having <50% vegetation-cover density according to the R(i) map, while in the areas having vegetation-cover densities greater than or equal to 50%, snow was mapped in only 71% of the pixels. When the enhanced MODIS snow-mapping algorithm was employed, 99% of the pixels having <50% vegetation-cover density were mapped, and 98% of the pixels with greater than or equal to 50% vegetation-cover density were mapped as snow covered. These results demonstrate that. the enhanced algorithm represents a significant improvement over the original MODIS prototype algorithm especially in the mapping of snow; In dense vegetation. The enhanced algorithm will thus be adopted as the MODIS at-launch snow-cover algorithm. Using this simple method for estimating vegetation density from pixel reflectance, it rc;ill be possible to analyze the accuracy of the MODIS snow-cover algorithm in a range of vegetation-cover in places where information on vegetation-cover density is not available from ground measurements. (C) Elsevier Science Inc., 1998. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Greenbelt, MD 20771 USA. Univ Alaska, Dept Forest Sci, Fairbanks, AK 99701 USA. Texas A&M Univ, Dept Geog, College Stn, TX USA. Univ Alaska, Inst Geophys, Fairbanks, AK 99701 USA. RP Hall, DK (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. EM dhall@glacier.gsfc.nasa.gov RI Hall, Dorothy/D-5562-2012 NR 24 TC 88 Z9 98 U1 1 U2 7 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 NOV PY 1998 VL 66 IS 2 BP 129 EP 137 DI 10.1016/S0034-4257(98)00051-0 PG 9 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 132FG UT WOS:000076619200003 ER PT J AU Sandmeier, S Muller, C Hosgood, B Andreoli, G AF Sandmeier, S Muller, C Hosgood, B Andreoli, G TI Physical mechanisms in hyperspectral BRDF data of grass and watercress SO REMOTE SENSING OF ENVIRONMENT LA English DT Article ID BIDIRECTIONAL REFLECTANCE; VEGETATION CANOPIES; DISTRIBUTIONS; EQUATION; MODEL AB A hyperspectral bidirectional reflectance data set of grass lawn and watercress canopies acquired under controlled laboratory conditions at the JRC European Goniometric Facility, at Ispra, Italy was analyzed with respect to basic physical reflectance mechanisms and factors influencing reflectance anisotropy. By normalizing reflectance data with the nadir reflectance as a reference, a strong influence of reflectance intensity on observed reflectance an isotropy is demonstrated for both vegetation canopies. This is explained by multiple scattering effects inside vegetation canopies as a function of canopy spectral absorbance characteristics. Two quantities based on canopy reflectances are utilized for characterizing the spectrally variable dynamics of BRDF effects: the anisotropy factor (ANIF), which is simply a normalization with nadir reflectance, and the anisotropy index (ANIX) defined as the ratio between the maximum and minimum reflectance values In the principal plane (or defined azimuth plane) per spectral band. Using these two quantities the study revealed that the basic physical reflectance mechanisms described by Kimes (1983) for broad spectral bands are extendable to hyperspectral bidirectional reflectance data. In addition, the influences of canopy geometry and multiple scattering on BRDF are clearly demonstrated for the erectophile grass lawn and the planophile watercress canopy. Since multiple scattering effects and canopy geometry are dominant factors regulating BRDF effects, vegetation canopy architecture parameters such as the leaf area index might be derived from hyperspectral BRDF data. (C) Elsevier Science Inc., 1998. C1 Univ Zurich, Dept Geog, RSL, Zurich, Switzerland. Joint Res Ctr, Space Applicat Inst, Ispra, Italy. RP Sandmeier, S (reprint author), NASA, Goddard Space Flight Ctr, Biospher Sci Branch, Code 923, Greenbelt, MD 20771 USA. NR 17 TC 91 Z9 100 U1 4 U2 10 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 NOV PY 1998 VL 66 IS 2 BP 222 EP 233 DI 10.1016/S0034-4257(98)00060-1 PG 12 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 132FG UT WOS:000076619200010 ER PT J AU Satava, RM AF Satava, RM TI The virtual surgeon SO SCIENCES-NEW YORK LA English DT Article C1 Yale Univ, Sch Med, New Haven, CT 06520 USA. Def Adv Res Projects Agcy, Washington, DC USA. NASA, Commercial Space Ctr Med Informat & Technol Appli, Washington, DC 20546 USA. RP Satava, RM (reprint author), Yale Univ, Sch Med, New Haven, CT 06520 USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU NEW YORK ACAD SCIENCES PI NEW YORK PA 2 E 63RD ST, NEW YORK, NY 10021 USA SN 0036-861X J9 SCIENCES JI Sci.-New York PD NOV-DEC PY 1998 VL 38 IS 6 BP 34 EP 39 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 173FM UT WOS:000078970600017 ER PT J AU Ito, K Ravindran, SS AF Ito, K Ravindran, SS TI Optimal control of thermally convected fluid flows SO SIAM JOURNAL ON SCIENTIFIC COMPUTING LA English DT Article DE flow control; temperature control; optimization; Navier-Stokes equations; finite element methods ID NAVIER-STOKES EQUATIONS; FINITE-ELEMENT APPROXIMATION AB We examine the optimal control of stationary thermally convected fluid flows from the theoretical and numerical point of view. We use thermal convection as control mechanism; that is, control is effected through the temperature on part of the boundary. Control problems are formulated as constrained minimization problems. Existence of optimal control is given and a first-order necessary condition of optimality from which optimal solutions can be obtained is established. We develop numerical methods to solve the necessary condition of optimality and present computational results for control of cavity- and channel-type flows showing the feasibility of the proposed approach. C1 N Carolina State Univ, Dept Math, Ctr Res Sci Computat, Raleigh, NC 27695 USA. NASA, Langley Res Ctr, Fluid Dynam & Acoust Div, Flow Modeling & Control Branch, Hampton, VA 23681 USA. RP Ito, K (reprint author), N Carolina State Univ, Dept Math, Ctr Res Sci Computat, Box 8205, Raleigh, NC 27695 USA. NR 20 TC 57 Z9 58 U1 0 U2 1 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 1064-8275 J9 SIAM J SCI COMPUT JI SIAM J. Sci. Comput. PD NOV PY 1998 VL 19 IS 6 BP 1847 EP 1869 DI 10.1137/S1064827596299731 PG 23 WC Mathematics, Applied SC Mathematics GA 107LZ UT WOS:000075211900005 ER PT J AU Gary, GA Davis, JM Moore, R AF Gary, GA Davis, JM Moore, R TI On analysis of dual spacecraft stereoscopic observations to determine the three-dimensional morphology and plasma properties of solar coronal flux tubes SO SOLAR PHYSICS LA English DT Article ID MAGNETIC-FIELDS; 3-DIMENSIONAL RECONSTRUCTION; ACTIVE REGIONS; EMISSION; TOMOGRAPHY; ALGORITHMS; IMAGES; YOHKOH AB By using two spacecraft equipped with multi-bandpass X-ray telescopes, it is possible to obtain direct 3-dimensional morphology of coronal structures which is essential for understanding the energetics and dynamics of the solar atmosphere. X-ray observations taken only in orbit about the Earth are inadequate to fully resolve the 3-dimensional nature of the solar corona. These Earth-orbit observations produce 2-dimensional images and an appropriate model must be included to derive the 3-dimensional structures from the line-of-sight information. Stereoscopic observations from space will remove this limitation and are needed if we are to improve our knowledge of the 3-dimensional morphology of the corona. Several important points regarding a stereoscopic mission are investigated and illustrated using model coronal flux tubes and image-rendering techniques. Synthesized images are formed by integrating the emission from volume elements along the line-of-sight path through a 3-dimensional volume in which a set of model flux tubes are located. The flux tubes are defined by (I) a plasma model defining the emissivity for a specific density, temperature, and pressure distribution, and (2) a magnetic field model from which a set of field lines are selected to define the geometry of the flux tubes. The field lines are used to define the flux-tube volume by assuming an initial base radius and conservation of flux. An effective instrumental spectral-response function is folded into the integration. Analysis of pairs of these synthesized images with various angular perspectives are used to investigate the effect of angular separation on mission objectives. The resulting images and analysis provide guidelines for developing a stereoscopic mission. Our study produced four important results, namely: (1) An angular separation of similar to 30 degrees maximizes the scientific return by direct triangulation analysis because of the tradeoff between increased line-of-sight resolution of position and decreased recognition of individual loop structures arising from the overlapping of multiple loops with increasing angular separation. (2) The analysis benefits from the use of time-differential images to select flux tubes from the collection of numerous overlapping systems by selecting only recently heated or cooled flux tubes. (3) An analysis needs to be developed for algebraic reconstruction techniques applying a priori information, specific to the solar coronal structures, i.e., flux-tube continuity, maximum emission strength, non-negative emission, previous history, and maximum gradients of emission. (4) An analysis strategy combining triangulation, modeling techniques, and algebraic restoration is necessary to derive a complete understanding of the 3-dimensional morphology of the magnetic field. In the same way that helioseismology is classical viewing of the Sun with a tailored set of analysis tools for probing the interior of the Sun, heliostereoscopy is classical viewing of the X-ray emitting corona and requires a tailored set of analysis tools to deduce the true 3-dimensional structure of the corona. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES82, Huntsville, AL 35812 USA. EM Allen.Gary@msfc.nasa.gov NR 45 TC 9 Z9 9 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 NOV PY 1998 VL 183 IS 1 BP 45 EP 76 DI 10.1023/A:1005018925963 PG 32 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 161GT UT WOS:000078281400004 ER PT J AU Wang, HM Chae, JC Gurman, JB Kucera, TA AF Wang, HM Chae, JC Gurman, JB Kucera, TA TI Comparison of prominences in H alpha AND He II 304 angstrom SO SOLAR PHYSICS LA English DT Article ID QUIESCENT PROMINENCE; ERUPTION AB In this letter, we bring attention to prominences which show different morphology in H alpha and Be Il 304 Angstrom, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two kinds of anomaly: (1) prominences showing strong H alpha emissions in the lower part and strong He II emissions in the upper part, and (2) erupting prominences showing extensive He rr emission, but nothing in H alpha. Our results indicate that a part or the whole of a prominence may be too hot to emit H alpha radiation, possibly due to heating or thermal instability. Please note that these are not just two isolated cases, many other prominences show the similar differences in H alpha and He It 304 Angstrom. C1 New Jersey Inst Technol, Big Bear Solar Observ, Big Bear City, CA 92314 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wang, HM (reprint author), New Jersey Inst Technol, Big Bear Solar Observ, Big Bear City, CA 92314 USA. RI Kucera, Therese/C-9558-2012 NR 13 TC 24 Z9 24 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD NOV PY 1998 VL 183 IS 1 BP 91 EP 96 DI 10.1023/A:1005010504873 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 161GT UT WOS:000078281400006 ER PT J AU Ofman, L Kucera, TA Mouradian, Z Poland, AI AF Ofman, L Kucera, TA Mouradian, Z Poland, AI TI SUMER observations of the evolution and the disappearance of a solar prominence SO SOLAR PHYSICS LA English DT Article ID RESONANT ABSORPTION; CORONAL LOOPS; ALFVEN WAVES; DRIVEN; SPECTRUM AB The mechanisms that lead to the formation and the disappearance of prominences are poorly understood, at present. An arch-shaped prominence was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric Observatory (SOHO) on 31 March-1 April 1996. The observations were per-formed at three wave-bands in the Lyman continuum. Ten successive images were obtained at il l-minute time intervals. Based on computed models of Gouttebroze, Heinzel, and Vial (1993), we have determined the temperature distribution of the prominence using the intensity ratio of 876 Angstrom and 907 Angstrom. The observed time sequence shows that parts of the prominence disappear possibly by heating, while other parts exhibit heating and cooling with apparent outward motion. We model the heat input with the linearized MHD equations using a prescribed initial density and a broad-band spectrum of Alfven waves. We find a good qualitative agreement with observations. In the model the prominence is heated by the resonant absorption of Alfven waves with frequencies that match the resonant condition for a particular flux tube structure that is determined by the magnetic field topology and plasma density. C1 NASA, Goddard Space Flight Ctr, Raytheon STX, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, SAC, Greenbelt, MD 20771 USA. Observ Paris, DASOP, CNRS URA 2080, F-92195 Meudon, France. RP Ofman, L (reprint author), NASA, Goddard Space Flight Ctr, Raytheon STX, 682, Greenbelt, MD 20771 USA. RI Kucera, Therese/C-9558-2012 NR 10 TC 16 Z9 16 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 NOV PY 1998 VL 183 IS 1 BP 97 EP 106 DI 10.1023/A:1005052923972 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 161GT UT WOS:000078281400007 ER PT J AU Kucera, TA Andretta, V Poland, AI AF Kucera, TA Andretta, V Poland, AI TI Neutral hydrogen column depths in prominences using EUV absorption features SO SOLAR PHYSICS LA English DT Article ID SOLAR PROMINENCES; CROSS-SECTIONS; HELIUM AB Observations of prominence regions in hot coronal Lines (greater than or similar to 10(6) K) at wavelengths below the hydrogen Lyman absorption Limit show what appear to be absorption features. Other authors have suggested that these observed features may be due to H and He continuum absorption. But there has, as yet, been no conclusive evidence that this is indeed the case. In this paper we present new Solar and Heliospheric Observatory (SOHO) observations that allow us to address this problem in a quantitative manner. We find that continuum absorption is the best explanation for the absorption observed in imaging data from the Coronal Diagnostic Spectrometer (CDS) on board SOHO. Furthermore, we discuss a new technique to measure the column depth of neutral hydrogen in a prominence, and use it to obtain estimates of the prominence filling factors as well. We calculate the column depth of neutral hydrogen, xi H similar to 10(18) cm(-2), and the filling factor, f greater than or similar to 0.3. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Kucera, TA (reprint author), Space Applicat Corp, Vienna, VA 22183 USA. RI Kucera, Therese/C-9558-2012; OI Kucera, Therese/0000-0001-9632-447X NR 16 TC 63 Z9 63 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD NOV PY 1998 VL 183 IS 1 BP 107 EP 121 DI 10.1023/A:1005077417572 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 161GT UT WOS:000078281400008 ER PT J AU Jain, RK Landis, GA AF Jain, RK Landis, GA TI Transient response of gallium arsenide and silicon solar cells under laser pulse SO SOLID-STATE ELECTRONICS LA English DT Article AB Solar cells can be used as receivers in laser power beaming applications[1]. Power beamed to a photovoltaic array could power a satellite, an orbital transfer vehicle or a lunar base. Understanding solar cell response to the pulsed output of a free-electron laser (FEL) is important for evaluation of power-beaming applications. In this work we investigate the time response of gallium arsenide and silicon solar cells to a 25 ns monochromatic pulse input. The PC-ID computer code is used to analyze the cell current during and after the pulse for various conditions. For GaAs cells, current decay was studied at 511, 840 and 870 nm, Most of the results have been calculated for a peak intensity of 50 W cm(-2) which corresponds to roughly 500 suns peak concentration. Silicon cells have a longer minority carrier lifetime and weaker optical absorption, resulting in longer characteristic time constants. Si cell performance was studied at 900, 950 and 1060 nm wavelengths. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Photovolta Branch, Cleveland, OH 44135 USA. RP Jain, RK (reprint author), NASA, Lewis Res Ctr, Photovolta Branch, MS 302-1, Cleveland, OH 44135 USA. NR 10 TC 0 Z9 0 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD NOV PY 1998 VL 42 IS 11 BP 1981 EP 1983 DI 10.1016/S0038-1101(98)00143-9 PG 3 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA 138WC UT WOS:000076995500013 ER PT J AU Dong, P Hong, JK Rogers, P AF Dong, P Hong, JK Rogers, P TI Analysis of residual stresses in Al-Li repair welds and mitigation techniques SO WELDING JOURNAL LA English DT Article DE Al-Li alloys; finite element analysis; mitigation techniques; multipass welds; repair weld; residual stresses; shell element model; thermal stretching technique AB In this paper, the recent results based on a comprehensive study on repair weld residual stresses are presented. Advanced finite element techniques were used to characterize the residual stress evolution in Al-Li alloy weldments, particularly under repair welding conditions. The present analysis procedures considered three-dimensional residual stress characteristics in the repair welds using a shell element model. Local residual stress details were analyzed by a generalized plane-strain model with prescribed translation and rotation conditions established form the global shell element model. Experimental residual stress measurements were conducted using X-ray diffraction methods. A good agreement between the finite element results and experimental measurements was obtained. Finally, a novel welding repair procedure (termed as a "thermal stretching" technique) was proposed to mitigate the weld residual stresses in repair. C1 Battelle Mem Inst, Ctr Welded Struct Res, Columbus, OH 43201 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Dong, P (reprint author), Battelle Mem Inst, Ctr Welded Struct Res, 505 King Ave, Columbus, OH 43201 USA. NR 25 TC 21 Z9 21 U1 0 U2 0 PU AMER WELDING SOC PI MIAMI PA PO BOX 351040, MIAMI, FL 33135 USA SN 0043-2296 J9 WELD J JI Weld. J. PD NOV PY 1998 VL 77 IS 11 BP 439S EP 445S PG 7 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA 136XJ UT WOS:000076884100015 ER PT J AU Hodis, HN Mack, WJ Selhub, J LaBree, L Selzer, RH Liu, CR Li, YJ Kwong-Fu, H Lee, Z Liu, CH AF Hodis, HN Mack, WJ Selhub, J LaBree, L Selzer, RH Liu, CR Li, YJ Kwong-Fu, H Lee, Z Liu, CH TI Gender, hormones, homocysteine, and atherosclerosis SO CIRCULATION LA English DT Meeting Abstract C1 Univ So Calif, Sch Med, Los Angeles, CA USA. Tufts Univ, Boston, MA 02111 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 27 PY 1998 VL 98 IS 17 SU S MA 1960 BP 373 EP 373 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA 131UV UT WOS:000076594401985 ER PT J AU Mack, WJ Ottesen, R Selzer, RH Kwong-Fu, H Liu, CR Liu, CH Li, YJ Lee, Z Hodis, HN AF Mack, WJ Ottesen, R Selzer, RH Kwong-Fu, H Liu, CR Liu, CH Li, YJ Lee, Z Hodis, HN TI Passive and active exposure to tobacco smoke and subclinical carotid artery atherosclerosis SO CIRCULATION LA English DT Meeting Abstract C1 Univ So Calif, Sch Med, Los Angeles, CA USA. City Hope Natl Med Ctr, Duarte, CA 91010 USA. Cal Tech Jet Prop Lab, Pasadena, CA USA. NR 0 TC 2 Z9 2 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 27 PY 1998 VL 98 IS 17 SU S MA 3061 BP 582 EP 582 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA 131UV UT WOS:000076594403081 ER PT J AU Hodis, HN Mack, WJ Selhub, J LaBree, L Selzer, RH Liu, CR Li, YJ Kwong-Fu, H Lee, Z Liu, CH AF Hodis, HN Mack, WJ Selhub, J LaBree, L Selzer, RH Liu, CR Li, YJ Kwong-Fu, H Lee, Z Liu, CH TI Plasma homocysteine levels, multivitamin use, and subclinical atherosclerosis SO CIRCULATION LA English DT Meeting Abstract C1 Univ So Calif, Sch Med, Los Angeles, CA USA. Tufts Univ, Boston, MA 02111 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 227 EAST WASHINGTON SQ, PHILADELPHIA, PA 19106 USA SN 0009-7322 J9 CIRCULATION JI Circulation PD OCT 27 PY 1998 VL 98 IS 17 SU S MA 3161 BP 602 EP 602 PG 1 WC Cardiac & Cardiovascular Systems; Peripheral Vascular Disease SC Cardiovascular System & Cardiology GA 131UV UT WOS:000076594403179 ER PT J AU Sandor, BJ Read, WG Waters, JW Rosenlof, KH AF Sandor, BJ Read, WG Waters, JW Rosenlof, KH TI Seasonal behavior of tropical to midlatitude upper tropospheric water vapor from UARS MLS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MICROWAVE LIMB SOUNDER; RELATIVE-HUMIDITY; STRATOSPHERE; CLIMATE; ATMOSPHERE; GREENHOUSE; TRANSPORT AB Measurements of upper tropospheric water vapor made during 1991-1997 with the Microwave Limb Sounder instrument on the Upper Atmospheric Research Satellite are described. Zonal mean results versus day of year are presented for tropical to midlatitudes on pressure surfaces 316, 215, and 147 hPa. The latitude of greatest upper tropospheric humidity (UTH) varies with season, following the Intertropical Convergence Zone. Annual maximum UTH occurs in northern summer at north tropical latitudes, coincident with the Indian monsoon ana with a June-August maximum of water vapor transport to the lower stratosphere [Rosenlof et al., 1997]. Comparison with lower stratospheric studies supports the Rosenlof et al. [1997] conclusion that water vapor transport is a maximum from the summer northern hemisphere tropical troposphere. Seasonally adjusted UTH is higher in the northern hemisphere than at equivalent southern hemisphere latitudes. The midlatitude secondary maximum in relative humidity seen in other (lower altitude) data sets is' seen on the 316 hPa surface throughout the year, only in northern hemisphere spring-summer at 215 hPa, and does not occur at 147 hPa. These observations characterize seasonal and interhemispheric differences in strengths of midlatitude convection and of subtropical subsidence. Frequency distribution analysis of tropical measurements shows the peak (mode) of the frequency distribution to be much drier than mean and median values at 316 and 215 hPa and marginally drier than mean and median values at 147 hPa. The frequency distribution mode is drier in the tropical wet than in the dry season at 316 hPa, consistent with other data sets at 300-500 hPa [Spencer and Braswell, 1997; Chiou et al., 1997] but is wetter in the tropical wet than in the dry season at 215 and 147 hPa. The wettest values of the frequency distribution mode occur in April-May, corresponding to neither the tropical wet nor the dry season. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NOAA, Aeron Lab, Cooperat Inst Res Environm Sci, Boulder, CO 80303 USA. RP Natl Ctr Atmospher Res, Div Atmospher Chem, Pob 3000, Boulder, CO 80307 USA. EM sandor@acd.ucar.edu RI Rosenlof, Karen/B-5652-2008 OI Rosenlof, Karen/0000-0002-0903-8270 NR 30 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 OCT 27 PY 1998 VL 103 IS D20 BP 25935 EP 25947 DI 10.1029/98JD02272 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 132BH UT WOS:000076609600006 ER PT J AU Tegen, I Miller, R AF Tegen, I Miller, R TI A general circulation model study on the interannual variability of soil dust aerosol SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NORTH-ATLANTIC OSCILLATION; MINERAL DUST; DESERT DUST; CLIMATE; SIMULATIONS; ATMOSPHERE; VALIDATION; FREQUENCY; SAHARA AB To assess interannual soil dust aerosol variability, we computed dust as a tracer in the Goddard Institute for Space Studies general circulation model. I Comparisons of dust model results with results from an off-line tracer model, satellite retrievals, and ground observations show mostly good agreement, but also reveal problems with the model results and difficulties with such comparisons. Two 15-year runs with prescribed sea surface temperatures were carried out, one with identical dust sources for each year and one with varying dust sources in order to investigate the-contribution of dust sources and transport to the variability of dust concentrations in different regions. Specifically;for the North Atlantic and the Mediterranean region, 70-90% of the dust variability is attributable to transport variability. Correlation coefficients between dust concentrations with precipitation and surface winds were calculated to find controlling factors for dust concentration for different regions of the world. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. RP NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. EM itegen@giss.nasa.gov RI Miller, Ron/E-1902-2012 NR 45 TC 88 Z9 91 U1 2 U2 6 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 OCT 27 PY 1998 VL 103 IS D20 BP 25975 EP 25995 DI 10.1029/98JD02345 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 132BH UT WOS:000076609600010 ER PT J AU Liu, HS AF Liu, HS TI Glacial-interglacial changes induced by pulse modulation of the incoming solar radiation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID EARTHS ORBITAL PARAMETERS; LAST CLIMATIC CYCLE; VOSTOK ICE CORE; DEVILS-HOLE; INSOLATION; RECORDS; PLEISTOCENE; EVOLUTION; CALCITE; SYSTEM AB The Milankovitch insolation equation as an astronomical forcing function for climate change is modified to include the frequency variation effect of the Earth's obliquity on insolation. To establish the criterion that frequency variation of the obliquity is responsible for major paleoclimatic changes, the cooperative phenomena between the obliquity frequency and the Milankovitch insolation are defined as frequency-insolation resonances. Coupling of the orbital frequency and insolation variations has established an especially new and interesting series of these resonances, which may induce pulsation of insolation. In this paper we show that insolation pulses would modulate the Milankovitch insolation in such a way that the mode (phase or period) of the insolation variations could be locked into a 100-kyr cycle. The pulse-modulated Milankovitch insolation forcing is tested by energy balance climate models. The physical mechanism behind this forcing for glacial-interglacial changes is explained and clarified in terms of pulse duration in the incoming solar radiation. It is concluded that the frequency-insolation resonances may be the key to the puzzle of the 100-kyr paleoclimate cycle. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Geodynam Branch, Code 921, Greenbelt, MD 20771 USA. EM hanshou@denali.gsfc.nasa.gov NR 62 TC 6 Z9 8 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 OCT 27 PY 1998 VL 103 IS D20 BP 26147 EP 26164 DI 10.1029/98JD02477 PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 132BH UT WOS:000076609600022 ER PT J AU Hansen, JE Sato, M Lacis, A Ruedy, R Tegen, I Matthews, E AF Hansen, JE Sato, M Lacis, A Ruedy, R Tegen, I Matthews, E TI Climate forcings in the Industrial era SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article ID RADIATION BUDGET; AEROSOL; TEMPERATURE; SENSITIVITY; INCREASE; CLOUDS; CYCLE AB The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHGs alone. Current trends in GHG climate forcings are smaller than in popular "business as usual" or 1% per year CO(2) growth scenarios. The summary implication is a paradigm change for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Hansen, JE (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. EM jhansen@giss.nasa.gov RI Lacis, Andrew/D-4658-2012 NR 46 TC 236 Z9 245 U1 2 U2 44 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 OCT 27 PY 1998 VL 95 IS 22 BP 12753 EP 12758 DI 10.1073/pnas.95.22.12753 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 134RT UT WOS:000076757300007 PM 9788985 ER PT J AU Huang, W Shen, Z Huang, NE Fung, YC AF Huang, W Shen, Z Huang, NE Fung, YC TI Use of intrinsic modes in biology: Examples of indicial response of pulmonary blood pressure to +/- step hypoxia SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA LA English DT Article DE nonstationary; stochastic process; Fourier spectrum; Hilbert spectrum; nonlinear oscillations ID ZERO-STRESS STATE; GENE-EXPRESSION; ELASTIC LAMINAE; HYPERTENSION; RAT; ARTERIES; ENDOTHELIN-1; RECOVERY; VESSELS AB Recently, a new method to analyze biological nonstationary stochastic variables has been presented. The method is especially suitable to analyze the variation of one biological variable with respect to changes of another variable. Here, it is illustrated by the change of the pulmonary blood pressure in response to a step change of oxygen concentration in the gas that an animal breathes, The pressure signal is resolved into the sum of a set of oscillatory intrinsic mode functions, which have zero "local mean," and a final nonoscillatory mode. With this device, we obtain a set of "mean trends," each of which represents a "mean" in a definitive sense, and together they represent the mean trend systematically with different degrees of oscillatory content. Correspondingly, the oscillatory content of the signal about any mean trend can be represented by a set of partial sums of intrinsic mode functions, When the concept of "indicial response function" is used to describe the change of one variable in response to a step change of another variable, we now have a set of indicial response functions of the mean trends and another set of indicial response functions to describe the energy or intensity of oscillations about each mean trend. Each of these can be represented by an analytic function whose coefficients can be determined by a least-squares curve-fitting procedure. In this way, experimental results are stated sharply by analytic functions. C1 Univ Calif San Diego, Dept Bioengn, La Jolla, CA 92093 USA. Univ Calif Irvine, Dept Civil & Environm Engn, Irvine, CA 92697 USA. NASA, Goddard Space Flight Ctr, Oceans & Ice Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. CALTECH, Div Engn & Appl Sci, Pasadena, CA 91125 USA. RP Fung, YC (reprint author), Univ Calif San Diego, Dept Bioengn, La Jolla, CA 92093 USA. FU NHLBI NIH HHS [HL 43026, P01 HL043026] NR 26 TC 39 Z9 47 U1 1 U2 2 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 OCT 27 PY 1998 VL 95 IS 22 BP 12766 EP 12771 DI 10.1073/pnas.95.22.12766 PG 6 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 134RT UT WOS:000076757300009 PM 9788987 ER PT J AU Jimenez, J Wray, AA AF Jimenez, J Wray, AA TI On the characteristics of vortex filaments in isotropic turbulence SO JOURNAL OF FLUID MECHANICS LA English DT Article ID FULLY-DEVELOPED TURBULENCE; HOMOGENEOUS TURBULENCE; PROBABILITY DENSITY; REYNOLDS-NUMBER; VELOCITY INCREMENTS; INTENSE VORTICITY; FLOWS; INTERMITTENCY; LAYERS; FLUID AB The statistical properties of the strong coherent vortices observed in numerical simulations of isotropic turbulence are studied. When compiled at axial vorticity levels omega/omega' similar to Re(lambda)(1/2), where omega' is the r.m.s. vorticity magnitude for the flow as a whole, they have radii of the order of the Kolmogorov scale and internal velocity differences of the order of the r.m.s. velocity of the flow u'. Theoretical arguments are given to explain these scalings. It is shown that the filaments are inhomogeneous Burgers' vortices driven by an axial stretching which behaves like the strain fluctuations of the background flow. It is suggested that they are the strongest members in a class of coherent objects, the weakest of which have radii of the order of the Taylor microscale, and indirect evidence is presented that they are unstable. A model is proposed in which this instability leads to a cascade of coherent filaments whose radii are below the dissipative scale of the flow as a whole. A family of such cascades separates the self-similar inertial range from the dissipative limit. At the vorticity level given above, the filaments occupy a volume fraction which scales as Re(lambda)(-2), and their total length increases as O(Re(lambda)). The length of individual filaments scales as the integral length of the flow, but there is a shorter internal length of the order of the Taylor microscale. C1 Univ Politecn Madrid, Sch Aeronaut, E-28040 Madrid, Spain. Stanford Univ, Ctr Turbulent Res, Stanford, CA 94305 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jimenez, J (reprint author), Univ Politecn Madrid, Sch Aeronaut, E-28040 Madrid, Spain. RI jimenez, javier/A-6691-2008 OI jimenez, javier/0000-0003-0755-843X NR 52 TC 112 Z9 112 U1 2 U2 14 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-1120 J9 J FLUID MECH JI J. Fluid Mech. PD OCT 25 PY 1998 VL 373 BP 255 EP 285 DI 10.1017/S0022112098002341 PG 31 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 139GP UT WOS:000077020000008 ER PT J AU Weislogel, MM Lichter, S AF Weislogel, MM Lichter, S TI Capillary flow in an interior corner SO JOURNAL OF FLUID MECHANICS LA English DT Article ID SQUARE CROSS-SECTION; WETTING LIQUID; FREE SURFACES; LAMINAR-FLOW; TUBES; GRAVITY; BUBBLES; MENISCI; RISE; DROP AB The design of fluids management processes in the low-gravity environment of space requires an accurate description of capillarity-controlled flow in containers. Here we consider the spontaneous redistribution of fluid along an interior corner of a container due to capillary forces. The analytical portion of the work presents an asymptotic formulation in the limit of a slender fluid column, slight surface curvature along the flow direction z, small inertia, and low gravity. The scaling introduced explicitly accounts for much of the variation of how resistance due to geometry and so the effects of corner geometry can be distinguished from those of surface curvature. For the special cases of a constant height boundary condition and a constant flow condition, the similarity solutions yield that the length of the fluid column increases as t(1/2) and t(3/5), respectively. In the experimental portion of the work, measurements from a 2.2 s drop tower are reported. An extensive data set, collected over a previously unexplored range of flow parameters, includes estimates of repeatability and accuracy, the role of inertia and column slenderness, and the effects of corner angle, container geometry, and fluid properties. At short times, the fluid is governed by inertia (t less than or similar to t(Lc)) Afterwards, an intermediate regime (t(Lc) less than or similar to t less than or similar to t(H)) can be shown to be modelled by a constant-flow-like similarity solution. For t greater than or equal to t(H) it is found that there exists a location z(H) at which the interface height remains constant at a value h(z(H), t) = H which can be shown to be well predicted. Comprehensive comparison is made between the analysis and measurements using the constant height boundary condition. As time increases, it is found that the constant height similarity solution describes the how over a lengthening interval which extends from the origin to the invariant tip solution. For t much greater than t(H), the constant height solution describes the entire flow domain. A formulation applicable throughout the container (not just in corners) is presented in the limit of long times. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Northwestern Univ, Dept Mech Engn, Evanston, IL 60208 USA. RP Weislogel, MM (reprint author), TDA Res, 12345 W 52nd Ave, Wheat Ridge, CO 80033 USA. RI Lichter, Seth/B-7598-2009 NR 38 TC 99 Z9 106 U1 0 U2 17 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 OCT 25 PY 1998 VL 373 BP 349 EP 378 DI 10.1017/S0022112098002535 PG 30 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 139GP UT WOS:000077020000011 ER PT J AU Albright, TP Painter, TH Roberts, DA Shi, JC Dozier, J Fielding, E AF Albright, TP Painter, TH Roberts, DA Shi, JC Dozier, J Fielding, E TI Classification of surface types using SIR-C/X-SAR, Mount Everest Area, Tibet SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID SYNTHETIC-APERTURE RADAR; SNOW; IMAGERY; REGIONS AB Imaging radar is a promising tool for mapping snow and ice cover in alpine regions. It combines a high-resolution, day or night, all-weather imaging capability with sensitivity to hydrologic and climatic snow and ice parameters. We use the spaceborne imaging radar-C/X-band synthetic aperture radar (SIR-C/X-SAR) to map snow and glacial ice on the rugged north slope of Mount Everest. From interferometrically derived digital elevation data, we compute the terrain calibration factor and cosine of the local illumination angle. We then process and terrain-correct radar data sets acquired on April 16, 1994. In addition to the spectral data, we include surface slope to improve discrimination among several surface types. These data sets are then used in a decision tree to generate an image classification. This method is successful in identifying and mapping scree/talus, dry snow, dry snow-covered glacier, wet snow-covered glacier, and rock-covered glacier, as corroborated by comparison with existing surface cover maps and other ancillary information. Application of the classification scheme to data acquired on October 7 of the same year yields accurate results for most surface types but underreports the extent of dry snow cover. C1 Univ Calif Santa Barbara, Sch Environm Sci & Management, Santa Barbara, CA 93106 USA. Univ Calif Santa Barbara, Inst Computat Earth Syst Sci, Santa Barbara, CA 93106 USA. Univ Calif Santa Barbara, Dept Geog, Santa Barbara, CA 93106 USA. Jet Prop Lab, Pasadena, CA 91103 USA. RP Albright, TP (reprint author), US Geol Survey, Raytheon STX Corp, Sci & Applicat Branch, EROS Data Ctr, Sioux Falls, SD 57198 USA. RI Dozier, Jeff/B-7364-2009; Painter, Thomas/B-7806-2016; Fielding, Eric/A-1288-2007 OI Dozier, Jeff/0000-0001-8542-431X; Fielding, Eric/0000-0002-6648-8067 NR 22 TC 10 Z9 10 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 OCT 25 PY 1998 VL 103 IS E11 BP 25823 EP 25837 DI 10.1029/98JE01893 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VD UT WOS:000078713100008 ER PT J AU Foster, JL Chang, ATC Hall, DK Wergin, WP Erbe, EF Barton, J AF Foster, JL Chang, ATC Hall, DK Wergin, WP Erbe, EF Barton, J TI Carbon dioxide crystals: An examination of their size, shape, and scattering properties at 37 GHz and comparisons with water ice (snow) measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID DISCRETE-DIPOLE APPROXIMATION; SOUTH POLAR-CAP; DRY SNOW; MARS; CO2; TEMPERATURES; EMISSIVITY; MODEL AB On Earth, the temperature regime is such that water is generally fairly close to its freezing point, and thus relatively small differences in climate affect how much snow and ice are present and whether or not the snow covering will be seasonal or last from one year to the next. On Mars, as on Earth, the presence of ice also plays a role in large-scale climate processes and it is important in controlling the abundance of atmospheric carbon dioxide (CO(2)) and water vapor. Passive microwave radiometry has been used to derive snow extent and snow depth on Earth, where scattering by snow (H(2)O) crystals is the dominant effect on the microwave radiation emanating from the ground and emerging from the snowpack. Microwave remote sensing may also prove to be useful for assessing the coverage and thickness of the frozen H(2)O and CO(2) on Mars, but more exact information is needed on how both H(2)O crystals and frozen CO(2) crystals scatter and absorb passive microwave radiation. In this study, CO(2) crystals have been produced in a laboratory cold chamber with temperature conditions similar to those found on the polar caps of Mars, and detailed three-dimensional images of their size and shape have been made with a low-temperature scanning electron microscope. Unlike the much larger H(2)O snow crystals found on Earth, which typically range in size between 0.1 mm and 1.0 mm (radius), CO(2) crystals are differently shaped and considerably smaller. Bipyramid crystals (base to base four-sided pyramids) are commonly observed, some as small as 1.0 mu m. A discrete dipole model was employed to calculate the passive microwave radiation scattered and absorbed by crystals of various sizes and shapes. Modeling results indicate that the shape of the crystal, whether for frozen CO(2) or H(2)O, is of-little consequence in affecting extinction efficiency. However, owing to their smaller size, frozen CO(2) crystals are more emissive than the H(2)O crystals in the 37 GHz region of the microwave spectrum. For the larger sizes of the modeled crystals, scattering dominates over absorption since the particles approach the size of the wavelength. The scattering values are 2 orders of magnitude larger than absorption for the 900 mu m size snow particles. For CO(2) crystals of 3.0 mu m in size,absorption is 7 orders of magnitude greater than scattering. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. ARS, Nematol Lab, USDA, Beltsville, MD 20770 USA. Gen Sci Corp, Laurel, MD 20707 USA. RP Foster, JL (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. EM jfoster@glacier.gsfc.nasa.gov RI Hall, Dorothy/D-5562-2012 NR 44 TC 9 Z9 9 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 OCT 25 PY 1998 VL 103 IS E11 BP 25839 EP 25850 DI 10.1029/98JE02493 PG 12 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 168VD UT WOS:000078713100009 ER PT J AU Khurana, KK Kivelson, MG Stevenson, DJ Schubert, G Russell, CT Walker, RJ Polanskey, C AF Khurana, KK Kivelson, MG Stevenson, DJ Schubert, G Russell, CT Walker, RJ Polanskey, C TI Induced magnetic fields as evidence for subsurface oceans in Europa and Callisto SO NATURE LA English DT Article ID INTERNAL STRUCTURE; OUTER PLANETS; GANYMEDE; SIGNATURE; WATER; IO AB The Galileo spacecraft has been orbiting Jupiter since 7 December 1995, and encounters one of the four galilean satellites-Io, Europa, Ganymede and Callisto-on each orbit. Initial results from the spacecraft's magnetometer(1,2) have indicated that neither Europe nor Callisto have an appreciable internal magnetic field, in contrast to Ganymede(3) and possibly Io(4). Here we report perturbations of the external magnetic fields (associated with Jupiter's inner magnetosphere) in the vicinity of both Europe and Callisto. We interpret these perturbations as arising from induced magnetic fields, generated by the moons in response to the periodically varying plasma environment. Electromagnetic induction requires eddy currents to now within the moons, and our calculations show that the most probable explanation is that there are layers of significant electrical conductivity just beneath the surfaces of both moons. We argue that these conducting layers may best be explained by the presence of salty liquid-water oceans, for which there is already indirect geological evidence(5,6) in the case of Europa. C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Khurana, KK (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RI Kivelson, Margaret/I-9019-2012; OI Kivelson, Margaret/0000-0003-3859-8581; Russell, Christopher/0000-0003-1639-8298 NR 34 TC 244 Z9 252 U1 7 U2 53 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD OCT 22 PY 1998 VL 395 IS 6704 BP 777 EP 780 DI 10.1038/27394 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 132AL UT WOS:000076607400049 PM 9796812 ER PT J AU Leyderman, A Cui, YL Penn, BG AF Leyderman, A Cui, YL Penn, BG TI Electro-optical effects in thin single-crystalline organic films grown from the melt SO JOURNAL OF PHYSICS D-APPLIED PHYSICS LA English DT Article AB Single-crystalline films of meta-nitroaniline (mNA) and 2-cyclo-octylamino-5-nitropyridine (COANP) 5-20 mu m thick were grown between two transparent fused quartz plates on which layers of indium tin oxide had been deposited. Both linear and quadratic electro-optical effects of the crystals were examined by an ac modulation method. The figures of merit for mNA and COANP are estimated to be (3.6 +/- 2.0) x 10(-12) and (4.2 +/- 0.5) x 10(-12) m V-1, respectively. The crystals were of high quality due to the excellent protection provided by the cells and the figures of merit of the crystals did not decrease with time. It is believed that the method adopted in the paper is applicable to fabrication of electro-optical cells with other compounds if growth of those crystals from the melt is feasible. It is suggested that the electro-optical cells have excellent potential use for device fabrication because of their durability and relatively easy manipulation during crystal growth. C1 UPR RUM, Dept Phys, Mayaguez, PR 00681 USA. NASA, SSL, MSFC, Huntsville, AL 35812 USA. RP Leyderman, A (reprint author), UPR RUM, Dept Phys, Mayaguez, PR 00681 USA. NR 21 TC 8 Z9 8 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0022-3727 J9 J PHYS D APPL PHYS JI J. Phys. D-Appl. Phys. PD OCT 21 PY 1998 VL 31 IS 20 BP 2711 EP 2717 DI 10.1088/0022-3727/31/20/002 PG 7 WC Physics, Applied SC Physics GA 136EQ UT WOS:000076845900002 ER PT J AU Stassinopoulos, EG Stauffer, CA Brucker, GJ AF Stassinopoulos, EG Stauffer, CA Brucker, GJ TI Miniature high-let radiation spectrometer for space and avionics applications SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article DE radiation; dose; space; avionics; LET spectrometer AB This paper reports on the design and characterization of a small, low-power, and low-weight instrument, a High-LET Radiation Spectrometer (HiLRS), that measures energy deposited by heavy ions in microelectronic devices. The HiLRS operates on pulse-height analysis principles and is designed for space and avionics applications. The detector component in the instrument is based on large scale arrays of p-n junctions. In this system, the pulse amplitude from a particle hit is directly proportional to the particle LET. A prototype flight unit has been fabricated and calibrated using several heavy ions with varying LETs and protons with several energies. The unit has been delivered to the Ballistic Missile Defense Organization (BMDO) c/o the Air Force Research Laboratory in Albuquerque, NM, for integration into the military Space Technology Research Vehicle (STRV), a US-UK cooperative mission. Another version of HiLRS is being prepared for delivery in April to the Hubble Space Telescope (HST) project, to fly on the HST Orbital Systems Test (HOST) platform on a shuttle mission. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Radiat Phys Off, Greenbelt, MD 20771 USA. Syst Engn & Secur, Greenbelt, MD 20770 USA. Radiat Effects Consultants Inc, Long Branch, NJ 07764 USA. RP Stassinopoulos, EG (reprint author), NASA, Goddard Space Flight Ctr, Radiat Phys Off, Greenbelt, MD 20771 USA. NR 2 TC 1 Z9 1 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 OCT 21 PY 1998 VL 416 IS 2-3 BP 531 EP 535 DI 10.1016/S0168-9002(98)00633-0 PG 5 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 135YZ UT WOS:000076831700038 ER PT J AU Jarzembski, MA Srivastava, V AF Jarzembski, MA Srivastava, V TI Comparison of continuous-wave CO2 lidar calibration by use of Earth-surface targets in laboratory and airborne measurements SO APPLIED OPTICS LA English DT Article ID ATMOSPHERIC AEROSOL; CLOUD BACKSCATTER; WINDS AB Backscatter of several Earth surfaces was characterized in the laboratory as a function of incidence angle with a focused continuous-wave 9.1-mu m CO2 Doppler lidar for use as possible calibration targets. Some targets showed negligible angular dependence, while others showed a slight increase with decreasing angle. The Earth-surface signal measured over the complex Californian terrain during a 1995 NASA airborne mission compared well with laboratory data. Distributions of the Earth's surface signal shows that the lidar efficiency can be estimated with a fair degree of accuracy, preferably with uniform Earth-surface targets during flight for airborne or space-based lidar. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Univ Space Res Assoc, Inst Global Change Res & Educ, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. RP Jarzembski, MA (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. EM maurice.jarzembski@msfc.nasa.gov; vandana.srivastava@msfc.nasa.gov NR 17 TC 5 Z9 5 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0003-6935 J9 APPL OPTICS JI Appl. Optics PD OCT 20 PY 1998 VL 37 IS 30 BP 7120 EP 7127 DI 10.1364/AO.37.007120 PG 8 WC Optics SC Optics GA 130ZE UT WOS:000076549900019 PM 18301536 ER PT J AU Willacy, K Klahr, HH Millar, TJ Henning, T AF Willacy, K Klahr, HH Millar, TJ Henning, T TI Gas and grain chemistry in a protoplanetary disk SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : formation; stars : pre-main sequence; accretion, accretion disks; molecular processes; dust, extinction ID ACCRETION DISKS; EXPLOSIVE DESORPTION; CHEMICAL-REACTIONS; CLOUDS; DUST; EVOLUTION; DESTRUCTION; APPEARANCE; OUTBURSTS; MANTLES AB The chemistry in a protoplanetary accretion disk is modelled between a radius of 100 and 0.1 AU of the central object. We find that interaction of the gas with the dust grains is very important, both by removing a large fraction of the material from the gas in the outer regions and through the chemical reactions which can occur on the dust grain surfaces. In addition, collision with grains neutralises gaseous ions effectively and keeps the ionization fraction low. This results in a chemistry which is dominated by neutral-neutral reactions, even if ionization is provided by cosmic rays or by the decay of radioactive isotopes. We model the effects of two desorption processes with very different efficiencies and find that while these produce similar results over much of the disk for many species, some molecules are extremely sensitive to the nature of the desorption and may one day be used as an observational test for the desorption process. C1 Univ Manchester, Dept Phys, Manchester M60 1QD, Lancs, England. Univ Observ, D-07745 Jena, Germany. Inst Astrophys, D-07745 Jena, Germany. RP Willacy, K (reprint author), CALTECH, Jet Prop Lab, MS 169-327, Pasadena, CA 91109 USA. OI Millar, Tom/0000-0001-5178-3656 NR 37 TC 95 Z9 95 U1 1 U2 3 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT 20 PY 1998 VL 338 IS 3 BP 995 EP 1005 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134GT UT WOS:000076735400034 ER PT J AU Jevremovic, D Butler, CJ Drake, SA O'Donoghue, D van Wyk, F AF Jevremovic, D Butler, CJ Drake, SA O'Donoghue, D van Wyk, F TI Ultraviolet and optical flares on Gl 866 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : activity; binaries : spectroscopic; stars : chromospheres; stars : flare; stars : late-type ID X-RAY EMISSION; STELLAR FLARES; SOLAR-FLARES; STARS; TEMPERATURE; BALMER; BINARY AB We present simultaneous ultraviolet and optical observations of five flares on the very late type M dwarf Gl 866 (dM5.5e). A procedure to estimate the physical parameters of the flaring plasma has been developed using a simplified model of the flare and a comparison of observed and computed Balmer decrements. With this procedure we have determined the optical thickness, electron temperature and electron density of the flaring plasma at flare maximum for three spectroscopically observed flares. The three spectroscopically observed flares cover up to 5 percent of the stellar surface and have areas similar to solar flares. C1 Armagh Observ, Armagh BT61 9DG, North Ireland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Cape Town, Dept Astron, ZA-7700 Rondebosch, South Africa. S African Astron Observ, ZA-7935 Cape Town, South Africa. Astron Observ, YU-11070 Belgrade, Yugoslavia. RP Jevremovic, D (reprint author), Armagh Observ, Coll Hill, Armagh BT61 9DG, North Ireland. EM djc@star.arm.ac.uk; cjb@star.arm.ac.uk NR 26 TC 11 Z9 11 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 OCT 20 PY 1998 VL 338 IS 3 BP 1057 EP 1065 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134GT UT WOS:000076735400039 ER PT J AU Teplitz, HI Malkan, M McLean, IS AF Teplitz, HI Malkan, M McLean, IS TI An infrared search for star-forming galaxies at z > 2 SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; galaxies : evolution; galaxies : Seyfert; infrared : galaxies ID HUBBLE DEEP FIELD; HIGH-REDSHIFT GALAXIES; LUMINOSITY FUNCTION; KECK SPECTROSCOPY; ABSORPTION; EVOLUTION; SPECTRA; QUASARS; QSOS; PHOTOMETRY AB We report the cumulative results of an ongoing near-infrared search for redshifted H alpha emission from normal galaxies at z > 2. An infrared search reduces the bias due to reddening. Using narrowband imaging with the Near Infrared Camera on the Keck I 10 m telescope, a survey area of almost 12 arcmin(2) has been covered. Target regions were selected by matching the redshifts of QSO emission and metal-line absorptions to our available filters. The survey depth is 7 x 10(-17) ergs cm(-2) s(-1) (3 sigma) in Ha and K' similar or equal to 22. Eleven H alpha emitters plus two Seyfert I objects have been discovered. The high density of galaxy detections, corresponding to a comoving volume density of 0.0135 +/- (0.0055)(0.0035) Mpc(-3), makes it unlikely that all of the H alpha flux in these objects is the result of active nuclei. There is a strong suggestion of clustering in the environments of metal-line absorbers. Each candidate galaxy lies typically within a projected distance of 250 kpc of the QSO line of sight and is resolved but compact. The average star formation rate inferred for the galaxies from the H alpha flux is 50 M. yr(-1), significantly higher than present-day star-forming galaxies but consistent with other estimates for galaxies at high redshift. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Dept Phys & Astron, Div Astron, Los Angeles, CA 90095 USA. RP NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. EM hit@binary.gsfc.nasa.gov; malkan@astro.ucla.edu; mclean@astro.ucla.edu NR 50 TC 42 Z9 42 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 OCT 20 PY 1998 VL 506 IS 2 BP 519 EP 532 DI 10.1086/306255 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LM UT WOS:000077779100006 ER PT J AU Bloomer, JD Watson, DM Pipher, JL Forrest, WJ Ali, B Greenhouse, MA Satyapal, S Smith, HA Fischer, J AF Bloomer, JD Watson, DM Pipher, JL Forrest, WJ Ali, B Greenhouse, MA Satyapal, S Smith, HA Fischer, J TI A near-infrared study of NGC 7538 IRS 1, 2, and 3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE H II regions; infrared : ISM : lines and bands; infrared : stars; ISM : individual (NGC 7538); open clusters and associations : individual (NGC 7538); stars : formation ID FE-II EMISSION; MOLECULAR CLOUDS; SUPERNOVA-REMNANTS; STAR-FORMATION; H-2 EMISSION; ORION NEBULA; WEAK LINES; REGIONS; INTERSTELLAR; NGC-7538 AB We present images of the cluster of embedded young stars designated NGC 7538 IRS 1, 2, and 3 in the J (1.25 mu m), H (1.64 mu m), and K (2.16 mu m) broad bands; the 1.64 mu m line of [Fe II]; the 2.12 mu m and 2.25 mu m lines of H-2; the 2.17 mu m Brackett gamma H-recombination line; and the 3.29 mu m "unidentifed" dust feature. The NGC 7538 IRS 2 compact H II region, as seen in Brackett gamma line emission, possesses a cometary morphology. We find evidence for a shell-like distribution of [Fe II] line emission along the periphery of the compact H II region. This morphology and the observed intensity ratio [Fe II] 1.64 mu m)I(Br gamma) imply that the [Fe II] line emission emanates from shocked stellar wind material. We observe arcs of H, line emission immediately exterior to the [Fe II] line emission shell and suggest that these arcs delineate molecular cloud material shocked via collision with the stellar wind. We observe larger area with centers of curvature displaced from each other and IRS 2, in broad-band-continuum, H-2-line, and 3.29 mu m feature emission, and suggest that these arcs represent molecular gas (either shocked or UV-excited) and dust swept up during distinct episodes of stellar mass ejection. We submit that the morphological and energetic evidence favors a "stellar wind bow shock" interpretation, in which the motion of the central O star with respect to the surrounding molecular cloud, in conjunction with the star's high-velocity stellar wind and episodic mass ejection, gives rise to the observed general cometary morphology and circum-H II region emission. C1 Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. USN, Res Lab, Remote Sensing Div, Washington, DC 20375 USA. Univ Wyoming, Dept Phys & Astron, Laramie, WY 82071 USA. RP Bloomer, JD (reprint author), Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA. NR 57 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 OCT 20 PY 1998 VL 506 IS 2 BP 727 EP 742 DI 10.1086/306268 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LM UT WOS:000077779100022 ER PT J AU Feibelman, WA AF Feibelman, WA TI The IUE spectrum, electron density, and terminal wind velocity of the "O VI sequence" planetary nebula NGC 5315 SO ASTROPHYSICAL JOURNAL LA English DT Article DE line : identification; planetary nebulae : individual (NGC 5315); ultraviolet : ISM ID RATIOS AB Extensive archival and new IUE data obtained during the last (19th) year episode of the "O VI sequence" planetary nebula NGC 5315 and its central star have been analyzed. A large number of high-excitation emission lines have been identified, and their fluxes were determined. These yield electron densities from C III], Si III], and N III], and terminal wind velocities from C IV lambda 1549 low- and high-dispersion spectra. The values are quite high, in the range of log N-e = 4.9 +/- 0.1 cm(-3) from C III] and Si III] diagnostics, and terminal wind velocities are in the range of - 3600 +/- 100 km s(-1). C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 19 TC 5 Z9 5 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 20 PY 1998 VL 506 IS 2 BP 773 EP 779 DI 10.1086/306281 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LM UT WOS:000077779100025 ER PT J AU Ghosh, P AF Ghosh, P TI Viscous stability of relativistic Keplerian accretion disks SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; black hole physics; gravitation; relativity; X-rays : stars ID BLACK-HOLES; COMPACT OBJECTS; BINARY-SYSTEMS; INSTABILITY AB We investigate the viscous stability of thin, Keplerian accretion disks in regions in which general relativistic (GR) effects are essential. For gas pressure-dominated (GPD) disks, we show that the Newtonian conclusion that such disks are viscously stable is reversed by GR modifications in the behaviors of viscous stress and surface density over a significantly large annular region not far from the innermost stable orbit at r = r(ms). For slowly rotating central objects, this region spans a range of radii 14 less than or similar to r less than or similar to 19 in units of the central object's mass M. For radiation pressure-dominated (RPD) disks, the Newtonian conclusion that they are viscously unstable remains valid after including the above GR modifications, except in a very small annulus around rm 14 M, which has a negligible influence. Inclusion of the stabilizing effect of the mass inflow through the disk's inner edge via a GR analog of Roche lobe overflow adds a small, stable region around r,, for RPD disks but leaves GPD disks unchanged. We mention possible astrophysical relevance of these results, particularly to the high-frequency Xray variabilities observed by the Rossi X-Ray Timing Explorer. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Ghosh, P (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 18 TC 6 Z9 6 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 OCT 20 PY 1998 VL 506 IS 2 BP L109 EP L112 DI 10.1086/311659 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LP UT WOS:000077779300008 ER PT J AU Bindschadler, R AF Bindschadler, R TI Geoscience - Future of the west Antarctic ice sheet SO SCIENCE LA English DT Editorial Material ID SEA-LEVEL RISE; COLLAPSE C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Sci, Oceans & Ice Branch, Greenbelt, MD 20771 USA. RP Bindschadler, R (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Sci, Oceans & Ice Branch, Greenbelt, MD 20771 USA. NR 19 TC 55 Z9 58 U1 0 U2 5 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD OCT 16 PY 1998 VL 282 IS 5388 BP 428 EP 429 DI 10.1126/science.282.5388.428 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 129TT UT WOS:000076479600039 ER PT J AU Chua, D Brittnacher, M Parks, G Germany, G Spann, J AF Chua, D Brittnacher, M Parks, G Germany, G Spann, J TI A new auroral feature: The nightside gap SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID HARANG DISCONTINUITY; ULTRAVIOLET IMAGER; SUBSTORM; CURRENTS AB Using images from the Ultraviolet Imager (UVI) aboard the Polar spacecraft, we identify an un-(UVI) aboard the Polar spacecraft, we identify an unusual morphological feature of the auroral oval marked by roughly a factor of four decrease in auroral luminosity near local midnight during some substorms. This feature has not been previously described in detail. The nightside gap appears in roughly 7% of the substorms observed by UVI during our study period from December, 1996 to February, 1997. Two nightside gap events from this period are characterized in detail as case studies of this phenomenon. We suggest that the nightside gap may be due to a significant reduction in field-aligned currents along with an insufficient ionospheric potential to accelerate precipitating electrons within the gap region, perhaps associated with the Harang discontinuity. C1 Univ Washington, Geophys Program, Seattle, WA 98195 USA. Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Chua, D (reprint author), Univ Washington, Geophys Program, Box 351650, Seattle, WA 98195 USA. EM damien@geophys.washington.edu NR 15 TC 8 Z9 8 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 OCT 15 PY 1998 VL 25 IS 20 BP 3747 EP 3750 DI 10.1029/98GL02806 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 130CV UT WOS:000076502400002 ER PT J AU Ray, RD AF Ray, RD TI Diurnal oscillations in atmospheric pressure at twenty-five small oceanic islands SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-ENERGY; ABSORPTION AB The diurnal oscillation in atmospheric surface pressure-the S-1(p) tide-is estimated at 25 oceanic stations. The estimated mean amplitudes and phases are compared to two theoretical predictions of the migrating S-1 component recently computed by Braswell and Lindzen and to the older wavenumber-1 decomposition of Haurwitz and Cowley. The new S-1 amplitudes are weaker than the Haurwitz-Cowley amplitudes everywhere, suggesting that their model may have been unduly influenced by nonmigrating components from continental stations. The observations show best agreement with a theoretical model having 25 W m(-2) additional atmospheric energy absorption relative to that inferred from general circulation models. Stations polewards of the S-1 critical latitude are somewhat anomalous. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. RP Ray, RD (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Code 926, Greenbelt, MD 20771 USA. RI Ray, Richard/D-1034-2012 NR 17 TC 11 Z9 11 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 OCT 15 PY 1998 VL 25 IS 20 BP 3851 EP 3854 DI 10.1029/1998GL900039 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 130CV UT WOS:000076502400029 ER PT J AU Chandra, S Ziemke, JR Min, W Read, WG AF Chandra, S Ziemke, JR Min, W Read, WG TI Effects of 1997-1998 El Nino on tropospheric ozone and water vapor SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PACIFIC; DATASET AB This paper analyzes the impact of the 1997-1998 El Nino on tropospheric column ozone and tropospheric water vapor derived respectively from the Total Ozone Mapping Spectrometer (TOMS) on Earth Probe and the Microwave Limb Scanning instrument on the Upper Atmosphere Research Satellite. The 1997-1998 El Nino, characterized by an anomalous increase in sea-surface temperature (SST) across the eastern and central tropical Pacific Ocean, is one of the strongest EI Nino Southern Oscillation (ENSO) events of the century, comparable in magnitude to the 1982-1983 episode. The major impact of the SST change has been the shift in the convection pattern from the western to the eastern Pacific affecting the response of rain-producing cumulonimbus. As a result, there has been a significant increase in rainfall over the eastern Pacific and a decrease over the western Pacific and Indonesia. The dryness in the Indonesian region has contributed to large-scale burning by uncontrolled wildfires in the tropical rainforests of Sumatra and Borneo. Our study shows that tropospheric column ozone decreased by 4-8 Dobson units (DU) in the eastern Pacific and increased by about 10-20 DU in the western Pacific largely as a result of the eastward shift of the tropical convective activity as inferred from National Oceanic and Atmospheric Administration (NOAA) outgoing longwave radiation (OLR) data The effect of this shift is also evident in the upper tropospheric water vapor mixing ratio which varies inversely as ozone (O-3). These conclusions are qualitatively consistent with the changes in atmospheric circulation derived from zonal and vertical wind data obtained from the Goddard Earth Observing System data assimilation analyses. The changes in tropospheric column O-3 during the course of the 1997-1998 El Nino appear to be caused by a combination of large-scale circulation processes associated with the shift in the tropical convection pattern and surface/boundary layer processes associated with forest fires in the Indonesian region. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Software Corp Amer, Lanham, MD 20706 USA. Gen Sci Corp, Laurel, MD 20707 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chandra, S (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. NR 15 TC 117 Z9 117 U1 0 U2 14 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 OCT 15 PY 1998 VL 25 IS 20 BP 3867 EP 3870 DI 10.1029/98GL02695 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 130CV UT WOS:000076502400033 ER PT J AU van der Veen, CJ Krabill, WB Csatho, BM Bolzan, JF AF van der Veen, CJ Krabill, WB Csatho, BM Bolzan, JF TI Surface roughness on the Greenland ice sheet from airborne laser altimetry SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB High resolution airborne laser altimetry is used to determine the small-scale surface relief in central Greenland and estimate the contribution from spatial noise to stratigraphic records. The standard deviation of the surface roughness is 1.6 cm water equivalent, corresponding to a standard deviation of annual layer thickness of 2.3 cm we. This estimate agrees with an independent assessment of the spatial variability (2.5 cm we) based on nine shallow ice cores. The agreement suggests that the statistical nature of the surface in central Greenland remains unchanged throughout the year. By conducting airborne altimetry around proposed drilling sites, the expected noise level in the core can be evaluated and sites Selected where this level is lowest. C1 Ohio State Univ, Byrd Polar Res Ctr, Columbus, OH 43210 USA. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Bolzan, JF (reprint author), Ohio State Univ, Byrd Polar Res Ctr, 108 Scott Hall,1090 Carmack Rd, Columbus, OH 43210 USA. NR 18 TC 14 Z9 14 U1 0 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 15 PY 1998 VL 25 IS 20 BP 3887 EP 3890 DI 10.1029/1998GL900041 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 130CV UT WOS:000076502400038 ER PT J AU Russell, WS Eiseman, PR AF Russell, WS Eiseman, PR TI A boundary conforming structured grid for global ocean circulation studies SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article DE numerical grid generation; block structure; ocean circulation; finite difference equations; boundary currents ID COORDINATE AB A boundary conforming two-dimensional structured grid for the irregular domain of the world's ocean is generated numerically using differential equation techniques. It is calculated using block structured methods which allow the inclusion of all major bodies of water including seas and basins, and which preserve slope continuity of the co-ordinate lines across the global domain. The block structure is coupled with an innovative blown-up cube model of the Earth which permits all areas of the global ocean to be modeled with the same resolution, eliminating problems associated with polar singularities. The grid is generated on the curved surface of the Earth (rather than the longitude-latitude plane) by employing the Beltrami operator instead of the standard Laplacian operator. Application of the grid to a steady state heat conduction problem shows the relative computational accuracy and the potential to resolve the complex, smaller scale oceanographic phenomena of great importance to global circulation studies. (C) 1998 John Wiley & Sons, Ltd. C1 Columbia Univ, Dept Appl Phys, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Program Dev Corp, White Plains, NY 10601 USA. RP Russell, WS (reprint author), Columbia Univ, Dept Appl Phys, 2880 Broadway, New York, NY 10025 USA. EM bill@haggis.giss.nasa.gov NR 22 TC 1 Z9 1 U1 0 U2 1 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 OCT 15 PY 1998 VL 28 IS 5 BP 761 EP + DI 10.1002/(SICI)1097-0363(19981015)28:5<761::AID-FLD696>3.0.CO;2-W PG 29 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA 129VY UT WOS:000076485800001 ER PT J AU O'Reilly, JE Maritorena, S Mitchell, BG Siegel, DA Carder, KL Garver, SA Kahru, M McClain, C AF O'Reilly, JE Maritorena, S Mitchell, BG Siegel, DA Carder, KL Garver, SA Kahru, M McClain, C TI Ocean color chlorophyll algorithms for SeaWiFS SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID REMOTE-SENSING REFLECTANCE; CROSS-SPECTRUM ANALYSIS; OPTICAL-PROPERTIES; COASTAL WATERS; SARGASSO SEA; PHYTOPLANKTON ABSORPTION; COCCOLITHOPHORE BLOOMS; PRIMARY PRODUCTIVITY; BIOGENOUS MATTER; LIGHT-ABSORPTION AB A large data set containing coincident in situ chlorophyll and remote sensing reflectance measurements was used to evaluate the accuracy, precision, and suitability of a wide variety of ocean color chlorophyll algorithms for use by SeaWiFS (Sea-viewing Wide Field-of-view Sensor). The radiance-chlorophyll data were assembled from various sources during the SeaWiFS Bio-optical Algorithm Mini-Workshop (SeaBAM) and is composed of 919 stations encompassing chlorophyll concentrations between 0.019 and 32.79 mu g L(-1). Most of the observations are from Case I nonpolar waters, and similar to 20 observations are from more turbid coastal waters. A variety of statistical and graphical criteria were used to evaluate the performances of 2 semianalytic and 15 empirical chlorophyll/pigment algorithms subjected to the SeaBAM data. The empirical algorithms generally performed better than the semianalytic. Cubic polynomial formulations were generally superior to other kinds of equations. Empirical algorithms with increasing complexity (number of coefficients and wavebands), were calibrated to the SeaBAM data, and evaluated to illustrate the relative merits of different formulations. The ocean chlorophyll 2 algorithm (OC2), a modified cubic polynomial (MCP) function which uses Rrs490/Rrs555, well simulates the sigmoidal pattern evident between log-transformed radiance ratios and chlorophyll, and has been chosen as the at-launch SeaWiFS operational chlorophyll a algorithm. Improved performance was obtained using the ocean chlorophyll 4 algorithm (OC4), a four-band (443, 490, 510, 555 nm), maximum band ratio formulation. This maximum band ratio (MBR) is a new approach in empirical ocean color algorithms and has the potential advantage of maintaining the highest possible satellite sensor signal:noise ratio over a 3-orders-of-magnitude range in chlorophyll concentration. C1 NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, Narragansett, RI 02882 USA. Univ S Florida, St Petersburg, FL 33701 USA. Calif State Polytech Univ Pomona, Pomona, CA 91768 USA. Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Calif Santa Barbara, Dept Geog, Santa Barbara, CA 93106 USA. RP O'Reilly, JE (reprint author), NOAA, Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, 28 Tarzwell Dr, Narragansett, RI 02882 USA. EM oreilly@fish1.gso.uri.edu RI Siegel, David/C-5587-2008 NR 93 TC 1076 Z9 1122 U1 17 U2 114 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 OCT 15 PY 1998 VL 103 IS C11 BP 24937 EP 24953 DI 10.1029/98JC02160 PG 17 WC Oceanography SC Oceanography GA 127XB UT WOS:000076374900023 ER PT J AU Ray, RD AF Ray, RD TI Spectral analysis of highly aliased sea-level signals SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OCEAN TIDE MODELS; TOPEX/POSEIDON ALTIMETRY; VARIABILITY; ERRORS AB Observing high-wavenumber ocean phenomena with a satellite altimeter generally calls for "along-track" analyses of the data: measurements along a repeating satellite ground track are analyzed in a point-by-point fashion, as opposed to spatially averaging data over multiple tracks. The sea-level aliasing problems encountered in such analyses can be especially challenging. For TOPEX/POSEIDON, all signals with frequency greater than 18 cycles per year (cpy), including both tidal and subdiurnal signals, are folded into the 0-18 cpy band. Because the tidal bands are wider than 18 cpy, residual tidal cusp energy, plus any subdiurnal energy, is capable of corrupting any low-frequency signal of interest. The practical consequences of this are explored here by using real sea-level measurements from conventional tide gauges, for which the true oceanographic spectrum is known and to which a simulated "satellite-measured" spectrum, based on coarsely subsampled data, may be compared. At many locations the spectrum is sufficently red that interannual frequencies remain unaffected. Intra-annual frequencies, however, must be interpreted with greater caution, and even interannual frequencies can be corrupted if the spectrum is flat. The results also suggest that whenever tides must be estimated directly from the altimetry, response methods of analysis are preferable to harmonic methods, even in nonlinear regimes; this will remain so for the foreseeable future. We concentrate on three example tide gauges: two coastal stations on the Malay Peninsula where the closely aliased K-1 and Ssa tides are strong and at Canton Island where trapped equatorial waves are aliased. C1 NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Space Geodesy Branch, Code 926, Greenbelt, MD 20771 USA. EM richard.ray@gsfc.nasa.gov RI Ray, Richard/D-1034-2012 NR 32 TC 23 Z9 23 U1 1 U2 5 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 OCT 15 PY 1998 VL 103 IS C11 BP 24991 EP 25003 DI 10.1029/98JC02545 PG 13 WC Oceanography SC Oceanography GA 127XB UT WOS:000076374900027 ER PT J AU Elfouhaily, T Vandemark, D Gourrion, J Chapron, B AF Elfouhaily, T Vandemark, D Gourrion, J Chapron, B TI Estimation of wind stress using dual-frequency TOPEX data SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID SIGNIFICANT WAVE HEIGHT; GEOSAT ALTIMETER; SPEED ALGORITHM; SEA; DEPENDENCE; ROUGHNESS; RAIN AB The TOPEX/POSEIDON satellite carries the first dual-frequency radar altimeter. Monofrequency (Ku-band) algorithms are presently used to retrieve: surface wind speed from the altimeter's radar cross-section measurement (sigma(Ku)(o)). These algorithms work reasonably well, but it is also known that altimeter wind estimates can be contaminated by residual effects, such as sea state, embedded in the sigma(Ku)(o) measurement. Investigating the potential benefit of using two frequencies for wind retrieval, it is shown that a simple evaluation of TOPEX data yields previously unavailable information, particularly for high and low wind speeds. As the wind speed increases, the dual-frequency data provides a measurement more directly linked to the short-scale surface roughness, which in turn is associated with the local surface wind stress. Using a global TOPEX sigma(o) data set and TOPEX's significant wave height (H(s)) estimate as a surrogate for the sea state's degree of development, it is also shown that differences between the two TOPEX sigma(o) measurements strongly evidence nonlocal sea state signature. A composite scattering theory is used to show how the dual-frequency data can provide an improved friction velocity model, especially for winds above 7 m/s. A wind speed conversion is included using a sea state dependent drag coefficient fed with TOPEX H(s) data. Two colocated TOPEX-buoy data sets (from the National Data Buoy Center (NDBC) and the Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) campaign) are employed to test the new wind speed algorithm. A measurable improvement in wind speed estimation is obtained when compared to the monofrequency Witter and Chelton [1991] model. C1 NASA, Univ Space Res Assoc, Greenbelt, MD USA. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Isl, VA 23337 USA. IFREMER, Ctr Brest, F-29280 Plouzane, France. RP Elfouhaily, T (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. EM elfoutm1@nansen.jhuapl.edu; bchapron@ifremer.fr RI Chapron, Bertrand/O-6527-2015 NR 31 TC 34 Z9 34 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-OCEANS JI J. Geophys. Res.-Oceans PD OCT 15 PY 1998 VL 103 IS C11 BP 25101 EP 25108 DI 10.1029/98JC00193 PG 8 WC Oceanography SC Oceanography GA 127XB UT WOS:000076374900034 ER PT J AU Faughnan, P Bryan, C Gan, Y Aglan, H AF Faughnan, P Bryan, C Gan, Y Aglan, H TI Correlation between the dynamic mechanical properties and the fatigue behavior of filled and unfilled PTFE materials SO JOURNAL OF MATERIALS SCIENCE LETTERS LA English DT Article ID BLENDS C1 NASA, John F Kennedy Space Ctr, Kennedy Space Ctr, FL 32899 USA. Tuskegee Univ, Dept Mech Engn, Tuskegee, AL 36088 USA. RP Faughnan, P (reprint author), NASA, John F Kennedy Space Ctr, Kennedy Space Ctr, FL 32899 USA. NR 26 TC 9 Z9 9 U1 1 U2 6 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0261-8028 J9 J MATER SCI LETT JI J. Mater. Sci. Lett. PD OCT 15 PY 1998 VL 17 IS 20 BP 1743 EP 1746 DI 10.1023/A:1006695723138 PG 4 WC Materials Science, Multidisciplinary SC Materials Science GA 170ZR UT WOS:000078837800014 ER PT J AU Shankar, K AF Shankar, K TI A study of the dynamic stress concentration factors of a flat plate for sea applications SO JOURNAL OF SOUND AND VIBRATION LA English DT Article ID BORNE SOUND-TRANSMISSION AB Statistical Energy Analysis (SEA) methods have been used to obtain the mean square vibrational energy levels of connected structures under certain conditions of coupling and excitation by random, uncorrelated forcing. Simple relationships between spatially averaged energies or velocities to stress and strain have been developed. However, the prediction of spatial variations in dynamic stress distribution at boundaries and discontinuities is more difficult and very few studies have been made in the SEA context. This paper first compares SEA predicted spatially averaged mean square stress to that of a FEA model of a simple two-plate system. Then it studies the behaviour of the dynamic stress concentration factors at the clamped boundary and also at the corner of a square hole in a hat plate at different frequency ranges using FEA models. The method used here is particulary useful for SEA applications, the stresses being normalized to unit power input. Certain assumptions for stress prediction at boundaries from SEA derived uniform stresses are also verified. (C) 1998 Academic Press. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Shankar, K (reprint author), NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 12 TC 6 Z9 8 U1 0 U2 1 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-460X J9 J SOUND VIB JI J. Sound Vibr. PD OCT 15 PY 1998 VL 217 IS 1 BP 97 EP 111 DI 10.1006/jsvi.1998.1730 PG 15 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 130EU UT WOS:000076507600006 ER PT J AU Galama, TJ Vreeswijk, PM van Paradijs, J Kouveliotou, C Augusteijn, T Bohnhardt, H Brewer, JP Doublier, V Gonzalez, JF Leibundgut, B Lidman, C Hainaut, OR Patat, F Heise, J in't Zand, J Hurley, K Groot, PJ Strom, RG Mazzali, PA Iwamoto, K Nomoto, K Umeda, H Nakamura, T Young, TR Suzuki, T Shigeyama, T Koshut, T Kippen, M Robinson, C de Wildt, P Wijers, RAMJ Tanvir, N Greiner, J Pian, E Palazzi, E Frontera, F Masetti, N Nicastro, L Feroci, M Costa, E Piro, L Peterson, BA Tinney, C Boyle, B Cannon, R Stathakis, R Sadler, E Begam, MC Ianna, P AF Galama, TJ Vreeswijk, PM van Paradijs, J Kouveliotou, C Augusteijn, T Bohnhardt, H Brewer, JP Doublier, V Gonzalez, JF Leibundgut, B Lidman, C Hainaut, OR Patat, F Heise, J in't Zand, J Hurley, K Groot, PJ Strom, RG Mazzali, PA Iwamoto, K Nomoto, K Umeda, H Nakamura, T Young, TR Suzuki, T Shigeyama, T Koshut, T Kippen, M Robinson, C de Wildt, P Wijers, RAMJ Tanvir, N Greiner, J Pian, E Palazzi, E Frontera, F Masetti, N Nicastro, L Feroci, M Costa, E Piro, L Peterson, BA Tinney, C Boyle, B Cannon, R Stathakis, R Sadler, E Begam, MC Ianna, P TI An unusual supernova in the error box of the gamma-ray burst of 25 April 1998 SO NATURE LA English DT Article ID 28 FEBRUARY 1997; AFTERGLOW; REDSHIFT AB The discovery of afterglows associated with gamma-ray bursts at X-ray(1), optical(2) and radio(3) wavelengths and the measurement of the redshifts of some of these events(4,5) has established that gamma-ray bursts lie at extreme distances, making them the most powerful photon-emitters known in the Universe. Here we report the discovery of transient optical emission in the error box of the gamma-ray burst GRB980425, the Light curve of which Mras very different from that of previous optical afterglows associated with gamma-ray bursts. The optical transient is located in a spiral arm of the galaxy ES0184-G82, which has a redshift velocity of only 2,550 km s(-1) (ref, 6). Its optical spectrum and location indicate that it is a very luminous supernova(7), which has been identified as SN1998bw. If this supernova and GRB980425 are indeed associated, the energy radiated in gamma-rays is at least four orders of magnitude less than in other gamma-ray bursts, although its appearance was otherwise unremarkable: this indicates that very different mechanisms can give rise to gamma-ray bursts. But independent of this association, the supernova is itself unusual, exhibiting an unusual light curve at radio wavelengths that requires that the gas emitting the radio photons be expanding relativistically(8,9). C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Space Res Assoc, Huntsville, AL 35812 USA. European So Observ, Santiago 19, Chile. SRON, Space Res Lab, NL-3584 CA Utrecht, Netherlands. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Netherlands Fdn Res Astron, NL-7990 AA Dwingeloo, Netherlands. Osservatorio Astron Trieste, I-13431 Trieste, Italy. Univ Tokyo, Sch Sci, Dept Astron, Tokyo 111, Japan. Univ Tokyo, Sch Sci, Res Ctr Early Universe, Tokyo 111, Japan. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Inst Astrophys, Potsdam, Germany. CNR, Ist tecnol & Sudio Rasiaz Extraterr, Bologna, Italy. CNR, Ist Fis Cosm & Applicaz Informat, I-90146 Palermo, Italy. CNR, Ist Astrofis Spaziale, Rome, Italy. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston Creek, ACT 2611, Australia. Anglo Australian Observ, Epping, NSW 2121, Australia. Univ Sydney, Sch Phys A29, Sydney, NSW 2006, Australia. Univ Virginia, Dept Astron, Charlottesville, VA 22903 USA. RP Galama, TJ (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. RI Gonzalez, Jean-Francois/B-7189-2008; Galama, Titus/D-1429-2014; PIRO, LUIGI/E-4954-2013; SHIGEYAMA, TOSHIKAZU/G-4894-2014; Palazzi, Eliana/N-4746-2015; Groot, Paul/K-4391-2016; OI Gonzalez, Jean-Francois/0000-0001-9423-6062; Galama, Titus/0000-0002-1036-396X; PIRO, LUIGI/0000-0003-4159-3984; Groot, Paul/0000-0002-4488-726X; Costa, Enrico/0000-0003-4925-8523; Feroci, Marco/0000-0002-7617-3421; Palazzi, Eliana/0000-0002-8691-7666 NR 28 TC 1234 Z9 1248 U1 4 U2 25 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD OCT 15 PY 1998 VL 395 IS 6703 BP 670 EP 672 DI 10.1038/27150 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 129PR UT WOS:000076472600043 ER PT J AU Iwamoto, K Mazzali, PA Nomoto, K Umeda, H Nakamura, T Patat, F Danziger, IJ Young, TR Suzuki, T Shigeyama, T Augusteijn, T Doublier, V Gonzalez, JF Boehnhardt, H Brewer, J Hainaut, OR Lidman, C Leibundgut, B Cappellaro, E Turatto, M Galama, TJ Vreeswijk, PN Kouveliotou, C van Paradijs, J Pian, E Palazzi, E Frontera, F AF Iwamoto, K Mazzali, PA Nomoto, K Umeda, H Nakamura, T Patat, F Danziger, IJ Young, TR Suzuki, T Shigeyama, T Augusteijn, T Doublier, V Gonzalez, JF Boehnhardt, H Brewer, J Hainaut, OR Lidman, C Leibundgut, B Cappellaro, E Turatto, M Galama, TJ Vreeswijk, PN Kouveliotou, C van Paradijs, J Pian, E Palazzi, E Frontera, F TI A hypernova model for the supernova associated with the gamma-ray burst of 25 April 1998 SO NATURE LA English DT Article ID PROGENITOR; SPECTRA AB The discovery of the unusual supernova SN1998bw, and its possible association with the gamma-ray burst GRB980425(1-3), provide new insights into the explosion mechanism of very massive stars and the origin of some classes of gamma-ray bursts. Optical spectra indicate that SN1998bw is a type Ic supernova(3,4), but its peak luminosity is unusually high compared with typical type Ic supemovae(3). Here we report our findings that the optical spectra and the light curve of SN1998bw can be well reproduced by an extremely energetic explosion of a massive star composed mainly of carbon and oxygen (having lost its hydrogen and helium envelopes). The kinetic energy of the ejecta is as large as (2-5) x 10(52) erg; more than ten times that of previously observed supernovae, This type of supernova could therefore be termed 'hypernova'. The extremely large energy suggests the existence of a new mechanism of massive star explosion that can also produce the relativistic shocks necessary to generate the observed gamma-rays. C1 Univ Tokyo, Sch Sci, Dept Astron, Tokyo 1130033, Japan. Univ Tokyo, Sch Sci, Res Ctr Early Universe, Tokyo 1130033, Japan. Osservatorio Astron Trieste, I-34131 Trieste, Italy. European So Observ, Santiago 19, Chile. European So Observ, D-85748 Garching, Germany. Osservatorio Astron Padova, I-35122 Padua, Italy. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. CNR, Ist Tecnol & Studio Rasiaz Extraterr, Bologna, Italy. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. RP Nomoto, K (reprint author), Univ Tokyo, Sch Sci, Dept Astron, Tokyo 1130033, Japan. RI Gonzalez, Jean-Francois/B-7189-2008; Galama, Titus/D-1429-2014; SHIGEYAMA, TOSHIKAZU/G-4894-2014; Palazzi, Eliana/N-4746-2015; OI Gonzalez, Jean-Francois/0000-0001-9423-6062; Galama, Titus/0000-0002-1036-396X; Cappellaro, Enrico/0000-0001-5008-8619; Palazzi, Eliana/0000-0002-8691-7666; Turatto, Massimo/0000-0002-9719-3157 NR 19 TC 500 Z9 502 U1 1 U2 11 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD OCT 15 PY 1998 VL 395 IS 6703 BP 672 EP 674 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 129PR UT WOS:000076472600044 ER PT J AU Barabash, T Dykman, MI Platzman, PM Smelyanskiy, VN AF Barabash, T Dykman, MI Platzman, PM Smelyanskiy, VN TI Ripplon-induced tunneling transverse to the magnetic field SO PHYSICAL REVIEW B LA English DT Article ID 2D ELECTRON-SYSTEM; HELIUM SURFACE; SUPPRESSION AB We analyze single-electron tunneling from the bound state above the surface of liquid helium. For strong enough magnetic fields parallel to the surface, the tunneling must be accompanied by ripplon scattering. The effective width of the tunneling barrier strongly and nonmonotonically depends on the momentum transferred to ripplons. The escape rate is affected by Landau quantization of the states behind the barrier. The results obtained here also apply to electrons on other cryogenic substrates. [S0163-1829(98)50444-4]. C1 Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. AT&T Bell Labs, Lucent Technol, Murray Hill, NJ 07974 USA. NASA, Ames Res Ctr, Caelum Res Co, Moffett Field, CA 94035 USA. RP Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. RI Sharpee, Tatyana/E-8663-2010 NR 13 TC 0 Z9 0 U1 0 U2 0 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2469-9950 EI 2469-9969 J9 PHYS REV B JI Phys. Rev. B PD OCT 15 PY 1998 VL 58 IS 16 BP R10214 EP R10217 DI 10.1103/PhysRevB.58.R10214 PG 4 WC Physics, Condensed Matter SC Physics GA 133ZB UT WOS:000076716500032 ER PT J AU Anantram, MP AF Anantram, MP TI Charging effects in the alternating-current conductance of a double-barrier resonant tunnelling structure SO JOURNAL OF PHYSICS-CONDENSED MATTER LA English DT Article ID ADMITTANCE; DEVICES AB There have been many studies of the linear response ac conductance of a double-barrier resonant tunnelling structure. While these studies are important, they fail to self-consistently include the effect of time-dependent charge density in the well. In this paper, we calculate the ac conductance by including the effect of time-dependent charge density in the well in a self-consistent manner. The charge density in the well contributes to both the how of displacement currents and the time-dependent potential in the well. We find that including these effects can make a significant difference to the ac conductance, and that the total ac current is not equal to the average of non-self-consistently calculated conduction currents in the two contacts, an assumption often made. This is illustrated by comparing the results obtained with and without the effect of the time-dependent charge density included properly. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Anantram, MP (reprint author), NASA, Ames Res Ctr, Mail Stop T27-A, Moffett Field, CA 94035 USA. NR 16 TC 2 Z9 2 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-8984 J9 J PHYS-CONDENS MAT JI J. Phys.-Condes. Matter PD OCT 12 PY 1998 VL 10 IS 40 BP 9015 EP 9027 DI 10.1088/0953-8984/10/40/008 PG 13 WC Physics, Condensed Matter SC Physics GA 130GP UT WOS:000076512100008 ER PT J AU Lopez, RE Dodelson, S Scherrer, RJ Turner, MS AF Lopez, RE Dodelson, S Scherrer, RJ Turner, MS TI Probing unstable massive neutrinos with current cosmic microwave background observations SO PHYSICAL REVIEW LETTERS LA English DT Article ID DARK-MATTER; INFLATION; ANISOTROPIES; CONSTRAINTS; PARTICLES AB The pattern of anisotropies in the cosmic microwave background depends upon the masses and lifetimes of the three neutrino species. A neutrino species of mass greater than 10 eV with lifetime between 10(13) and 10(17) sec leaves a very distinct signature (due to the integrated Sachs-Wolfe effect): the anisotropies at large angles are predicted to be comparable to those on degree scales. Present data exclude such a possibility and hence this region of parameter space. For m(v) similar or equal to 30 eV, tau similar or equal to 10(13) sec, we find an interesting possibility: the integrated Sachs-Wolfe peak produced by the decaying neutrino in low-Omega models mimics the acoustic peak expected in an Omega = 1 model. [S0031-9007(98)07347-5]. C1 Univ Chicago, Dept Phys, Chicago, IL 60637 USA. NASA, Fermi Natl Accelerator Lab, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Univ Chicago, Dept Astron & Astrophys, Enrico Fermi Inst, Chicago, IL 60637 USA. RP Lopez, RE (reprint author), Univ Chicago, Dept Phys, Chicago, IL 60637 USA. NR 34 TC 23 Z9 23 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 OCT 12 PY 1998 VL 81 IS 15 BP 3075 EP 3078 DI 10.1103/PhysRevLett.81.3075 PG 4 WC Physics, Multidisciplinary SC Physics GA 127UR UT WOS:000076369400007 ER PT J AU Stecker, FW AF Stecker, FW TI Comment on "On the origin of the highest energy cosmic rays" - Stecker replies SO PHYSICAL REVIEW LETTERS LA English DT Article C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Stecker, FW (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 6 TC 15 Z9 15 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 OCT 12 PY 1998 VL 81 IS 15 BP 3296 EP 3296 DI 10.1103/PhysRevLett.81.3296 PG 1 WC Physics, Multidisciplinary SC Physics GA 127UR UT WOS:000076369400063 ER PT J AU Hynes, RI Haswell, CA Shrader, CR Chen, W Horne, K Harlaftis, ET O'Brien, K Hellier, C Fender, RP AF Hynes, RI Haswell, CA Shrader, CR Chen, W Horne, K Harlaftis, ET O'Brien, K Hellier, C Fender, RP TI The 1996 outburst of GRO J1655-40: the challenge of interpreting the multiwavelength spectra SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; binaries : close; stars : individual : Nova Sco 1994 (GRO J1655-40); ultraviolet : stars; X-rays : stars ID X-RAY BINARIES; NOVA-MUSCAE 1991; BLACK-HOLE; CATACLYSMIC VARIABLES; SUPERLUMINAL SOURCE; BOWEN FLUORESCENCE; SECONDARY MAXIMA; ACCRETION DISKS; LIGHT CURVES; ULTRAVIOLET AB We report on the results of a multiwavelength campaign to observe the soft X-ray transient (SXT) and superluminal jet source GRO J1655-40 in outburst using HST, RXTE and CGRO together with ground-based facilities. This outburst was qualitatively quite different from other SXT outbursts and from previous outbursts of this source, The onset of hard X-ray activity occurred very slowly, over several months, and was delayed relative to the soft X-ray rise. During this period, the optical fluxes declined steadily. This apparent anticorrelation is not consistent with the standard disc instability model of SXT outbursts, nor is it expected if the optical output is dominated by reprocessed X-rays, as in persistent low-mass X-ray binaries. Based on the strength of the 2175-Angstrom interstellar absorption feature we constrain the reddening to be E(B - V) - 1.2 +/- 0.1, a result which is consistent with the known properties of the source and with the strength of interstellar absorption lines. Using this result we find that our dereddened spectra are dominated by a component peaking, in the optical, with the expected nu(1/3) disc spectrum seen only in the ultraviolet. We consider possible interpretations of this spectrum in terms of thermal emission from the outer accretion disc and/or secondary star, both with and without X-ray irradiation, and also as non-thermal optical synchrotron emission from a compact self-absorbed central source. In addition to the prominent He Ir 4686-Angstrom line, we see Bowen fluorescence Lines of N III and O III, and possible P Cygni profiles in the ultraviolet resonance lines, which can be interpreted in terms of an accretion disc wind. The X-ray spectra broadly resemble the high-soft state commonly seen in black hole candidates, but evolve through two substates. Taken as a whole, the outburst data set cannot readily be interpreted by any standard model for SXT outbursts. We suggest that many of the characteristics could be interpreted in the context of a model combining X-ray irradiation with the limit-cycle disc instability, but with the added ingredient of a very large disc in this long-period system. C1 Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. Univ Keele, Dept Phys, Keele ST5 5BG, Staffs, England. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Amsterdam, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. RP Hynes, RI (reprint author), Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. NR 66 TC 47 Z9 47 U1 0 U2 1 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD OCT 11 PY 1998 VL 300 IS 1 BP 64 EP 82 DI 10.1046/j.1365-8711.1998.01835.x PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 134CU UT WOS:000076725900009 ER PT J AU Fonte, P Peskov, V Ramsey, BD AF Fonte, P Peskov, V Ramsey, BD TI A study of breakdown limits in microstrip gas counters with preamplification structures SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID RESOLUTION; DETECTORS; FEEDBACK; CHAMBER; GEM AB We have studied the charge and breakdown limits of Microstrip Gas Counters (MSGC's) with two different preamplification structures: the Gas Electron Multiplier (GEM) and the Parallel-Plate Avalanche Counter (PPAC). It was found that in both cases the breakdown limit was increased by 1-2 orders of magnitude compared to the bare MSGC and that this was due to the spreading of the primary electron cloud during pre-amplification. This spreading reduces the charge density in the final MSGC avalanche, permitting much higher total gains before streamers form. The real practical gain limitations in these two-stage detectors arose not from sparking, but from a loss of proportionality due to space charge effects. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Coimbra, LIP, Coimbra, Portugal. Inst Super Engn Coimbra, Coimbra, Portugal. RP Ramsey, BD (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RI Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 19 TC 13 Z9 13 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 OCT 11 PY 1998 VL 416 IS 1 BP 23 EP 31 DI 10.1016/S0168-9002(98)00649-4 PG 9 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 132TZ UT WOS:000076647300004 ER PT J AU Wechsler, RH Gross, MAK Primack, JR Blumenthal, GR Dekel, A AF Wechsler, RH Gross, MAK Primack, JR Blumenthal, GR Dekel, A TI Implications of spikes in the redshift distribution of z similar to 3 galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; cosmology : theory; dark matter; galaxies : clusters : general; galaxies : formation; large-scale structure of universe ID CLUSTERS AB We address the high peaks found by Steidel and coworkers in the redshift distribution of "Lyman-break" objects (LBOs) at redshift z similar or equal to 3. The highest spike represents a relative overdensity of 2.6 in the distribution of LBOs in pixels of comoving size similar to 10 h(-1) Mpc. We examine the likelihood of such a spike in the redshift distribution within a suite of models for the evolution of structure in the universe, including models with Omega = 1 (a standard cold dark matter [SCDM] and a cold plus hot dark matter model [CHDM]) and with Omega(0) = 0.4-0.5 (a flat cold dark matter model with a nonzero cosmological constant Lambda [Lambda CDM] and an open cold dark matter model [OCDM]). Using high-resolution dissipationless N-body simulations, we analyze deep pencil-beam surveys from these models in the same way that they are actually observed, identifying LBOs with the most massive dark matter halos. We find that all the models (with SCDM as a marginal exception) have a substantial probability of producing spikes similar to those observed, because the massive halos are much more clumped than the underlying matter; i.e., they are biased. Therefore, the likelihood of such a spike is not a good discriminator among these models. We find in these models that the mean biasing parameter b of LBOs with respect to dark matter varies within a range b similar or equal to 2-5 on a scale of similar to 10 h(-1) Mpc. However, all models show considerable dispersion in their biasing, with the local biasing parameter reaching values as high as ten. We also compute the two-body correlation functions of LBOs predicted in these models. The LBO correlation functions are less steep than galaxies today (gamma approximate to -1.4) but show similar or slightly longer correlation lengths. C1 Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Santa Cruz, Dept Astron, Santa Cruz, CA 95064 USA. Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel. RP Wechsler, RH (reprint author), Univ Calif Santa Cruz, Dept Phys, Santa Cruz, CA 95064 USA. NR 28 TC 42 Z9 42 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 OCT 10 PY 1998 VL 506 IS 1 BP 19 EP 32 DI 10.1086/306229 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LJ UT WOS:000077778800002 ER PT J AU Kippen, RM Briggs, MS Kommers, JM Kouveliotou, C Hurley, K Robinson, CR van Paradijs, J Hartmann, DH Galama, TJ Vreeswijk, PM AF Kippen, RM Briggs, MS Kommers, JM Kouveliotou, C Hurley, K Robinson, CR van Paradijs, J Hartmann, DH Galama, TJ Vreeswijk, PM TI On the association of gamma-ray bursts with supernovae SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; supernovae : general ID 28 FEBRUARY 1997; AFTERGLOW AB The recent discovery of a supernova (SN 1998bw) seemingly associated with GRB 980425 adds a new twist to the decades-old debate over the origin of gamma-ray bursts. To investigate the possibility that some (or all) bursts are associated with supernovae, we performed a systematic search for temporal/angular correlations using catalogs of BATSE and BATSE/Ulysses burst locations. We find no associations with any of the precise BATSE/Ulysses locations, which allows us to conclude that the fraction of high-fluence gamma-ray bursts from known supernovae is small (less than 0.2%). For the more numerous weaker bursts, the corresponding limiting fraction of 1.5% is less constraining due to the imprecise locations of these events. This limit (1.5% similar or equal to 18 bursts) allows that a large fraction of the recent supernovae used as a comparison data set (18 supernovae similar or equal to 20%) could have associated gamma-ray bursts. Thus, although we find no significant evidence to support a burst/supernova association, the possibility cannot be excluded for weak bursts. C1 Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. MIT, Dept Phys, Cambridge, MA 02139 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Space Res Assoc, Huntsville, AL 35805 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. RP Kippen, RM (reprint author), Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. RI Galama, Titus/D-1429-2014 OI Galama, Titus/0000-0002-1036-396X NR 27 TC 34 Z9 34 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 OCT 10 PY 1998 VL 506 IS 1 BP L27 EP L30 DI 10.1086/311634 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LL UT WOS:000077779000007 ER PT J AU Uemizu, K Bock, JJ Kawada, M Lange, AE Matsumoto, T Watabe, T Yost, SA AF Uemizu, K Bock, JJ Kawada, M Lange, AE Matsumoto, T Watabe, T Yost, SA TI A search for a near-infrared halo around NGC 4565 SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; galaxies : halos; galaxies : individual (NGC 4565) stars : low-mass, brown dwarfs ID SPIRAL GALAXY NGC5907; COOL BROWN DWARF; SURFACE PHOTOMETRY; DARK-MATTER; NGC-4565; LIGHT; ATMOSPHERES; MODEL; STARS; FIELD AB We present a near-infrared (3.5-5 mu m) search for the integrated emission from low-mass stars and/or brown dwarfs in the halo of the nearby edge-on spiral galaxy NGC 4565. The observation was made with a liquid-helium-cooled rocket-borne telescope using a 256 x 256 InSb array with a pixel scale of 17 ". Images of NGC 4565 were successfully obtained with sensitivity near the natural background limit. Our search reveals no evidence of a faint halo around the galaxy, in contrast with the previous reports of a halo around NGC 5907. The lower limit of the mass-to-light ratio for the halo of NGC 4565 is 260 (2 sigma) in solar units at 3.5-5 mu m. This implies that hydrogen-burning stars do not contribute significantly to the mass of the dark halo in NGC 4565. C1 Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. Nagoya Univ, Chikusa Ku, Nagoya, Aichi 4648602, Japan. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Pasadena, CA 91125 USA. RP Uemizu, K (reprint author), Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 2298510, Japan. NR 26 TC 7 Z9 7 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 OCT 10 PY 1998 VL 506 IS 1 BP L15 EP L18 DI 10.1086/311640 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LL UT WOS:000077779000004 ER PT J AU Ozyoruk, Y Long, LN Jones, MG AF Ozyoruk, Y Long, LN Jones, MG TI Time-domain numerical simulation of a flow-impedance tube SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE flow-impedance tube; computational aeroacoustics; impedance conditions; z-transforms; nonreflecting boundary conditions; finite difference ID COMPUTATIONAL AEROACOUSTICS; BOUNDARY-CONDITIONS; SOUND AB An efficient method has been developed for. the application of the surface acoustic impedance condition in time-domain solutions of aeroacoustic problems, such as the broadband-frequency simulation of a flow-impedance tube, The basis for this method is the standard impedance condition stated in the frequency domain as the particle displacement continuity equation. The development of the time-domain impedance condition follows the relations among the frequency. z-, and discrete-time domains and a rational function representation of the impedance in the z-domain. The resultant impedance condition consists of finite, infinite-impulse-response type, digital filter operations in the time domain, which is very suitable to computational aeroacoustics algorithms. This paper describes the present approach and discusses the time-domain numerical simulations of the NASA Langley how-impedance tube with a constant depth ceramic tubular liner. Both single and broadband-frequency simulations are performed. Excellent agreement is shown with experimental data at various frequencies and flow conditions. (C) 1998 Academic Press. C1 Middle E Tech Univ, Dept Aeronaut Engn, TR-06531 Ankara, Turkey. Penn State Univ, Dept Aerosp Engn, University Pk, PA 16802 USA. NASA, Langley Res Ctr, Lockheed Martin Engn & Sci Serv, Hampton, VA 23681 USA. RP Ozyoruk, Y (reprint author), Middle E Tech Univ, Dept Aeronaut Engn, TR-06531 Ankara, Turkey. NR 21 TC 48 Z9 56 U1 1 U2 2 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 OCT 10 PY 1998 VL 146 IS 1 BP 29 EP 57 DI 10.1006/jcph.1998.5919 PG 29 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 129DN UT WOS:000076448100002 ER PT J AU Zhu, DM Miller, RA AF Zhu, DM Miller, RA TI Sintering and creep behavior of plasma-sprayed zirconia- and hafnia-based thermal barrier coatings SO SURFACE & COATINGS TECHNOLOGY LA English DT Article; Proceedings Paper CT 25th International Conference on Metallurgical Coatings and Thin Films CY APR 25-MAY 01, 1998 CL SAN DIEGO, CALIFORNIA SP Vacuum Met, Thin Film Div, AVS DE thermal barrier coatings; ceramic sintering and creep; defect structure; dilatometry ID STABILIZED ZIRCONIA AB The sintering and creep of plasma-sprayed ceramic thermal barrier coatings under high temperature conditions are complex phenomena. Changes in thermomechanical and thermophysical properties and in the stress response of these coating systems as a result of the sintering and creep processes are detrimental to coating thermal fatigue resistance and performance. In this paper, the sintering characteristics of ZrO2-8wt%Y2O3, ZrO2-25wt%CeO2-2.5wt%Y2O3, ZrO2-6w%NiO-9wt%Y2O3, ZrO2-6wt%Sc2O3-2wt%Y2O3 and HfO2-27wt%Y2O3 coating materials were investigated using dilatometry. It was found that the KfO(2)-Y2O3 and baseline ZrO2-Y2O3 exhibited the best sintering resistance, while the NiO-doped ZrO2-Y2O3 showed the highest shrinkage strain rates during the tests. Higher shrinkage strain rates of the coating materials were also observed when the specimens were tested in Ar+5%H-2 as compared to in air. This phenomenon was attributed to an enhanced metal cation interstitial diffusion mechanism under the reducing conditions. It is proposed that increased chemical stability of coating materials will improve the material sintering resistance. (C) 1998 Elsevier Science S.A. All rights reserved. C1 NASA, Lewis Res Ctr, Ohio Aerosp Inst, Cleveland, OH 44135 USA. RP Zhu, DM (reprint author), NASA, Lewis Res Ctr, Ohio Aerosp Inst, Cleveland, OH 44135 USA. EM Dongming.Zhu@lerc.nasa.gov NR 25 TC 109 Z9 111 U1 6 U2 43 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0257-8972 J9 SURF COAT TECH JI Surf. Coat. Technol. PD OCT 10 PY 1998 VL 108 IS 1-3 BP 114 EP 120 DI 10.1016/S0257-8972(98)00669-0 PG 7 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 142LY UT WOS:000077203000018 ER PT J AU Bauschlicher, CW Ricca, A AF Bauschlicher, CW Ricca, A TI Atomization energies of SO and SO(2): Basis set extrapolation revisited SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; WAVE-FUNCTIONS; ATOMS; 1ST-ROW; WATER AB The addition of tight functions to sulfur and extrapolation to the complete basis set limit are required to obtain accurate atomization energies. Six different extrapolation procedures are tried. The best atomization energies come from the series of basis sets that yield the most consistent results for all extrapolation techniques. In the variable ct approach, a values larger than 4.5 or smaller than 3 appear to suggest that the extrapolation may not be reliable. It does not appear possible to determine a reliable basis set series using only the triple and quadruple-zeta based sets. The scalar relativistic effects reduce the atomization of SO and SO(2) by 0.34 and 0.81 kcal/mol, respectively, and clearly must be accounted for if a highly accurate atomization energy is to be computed. The magnitude of the core-valence (CV) contribution to the atomization is affected by missing diffuse valence functions. The CV contribution is much more stable if basis set superposition errors are accounted for. A similar study of SF, SF(+), and SF(6) shows that the best family of basis sets varies with the nature of the S bonding. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Thermosci Inst, STC-230-3, Moffett Field, CA 94035 USA. NR 28 TC 59 Z9 59 U1 0 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD OCT 8 PY 1998 VL 102 IS 41 BP 8044 EP 8050 DI 10.1021/jp9819691 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 132EF UT WOS:000076616800023 ER PT J AU Flasar, FM AF Flasar, FM TI Planetary science - Titan weather report SO NATURE LA English DT Editorial Material ID ATMOSPHERE; SURFACE C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Flasar, FM (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Flasar, F Michael/C-8509-2012 NR 14 TC 1 Z9 1 U1 0 U2 2 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON, ENGLAND N1 9XW SN 0028-0836 J9 NATURE JI Nature PD OCT 8 PY 1998 VL 395 IS 6702 BP 541 EP + DI 10.1038/26847 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 127QW UT WOS:000076362900020 PM 9783575 ER PT J AU Kacsich, T Kolawa, E Fleurial, JP Caillat, T Nicolet, MA AF Kacsich, T Kolawa, E Fleurial, JP Caillat, T Nicolet, MA TI Films of ni-7 at% V, Pd, Pt and Ta-Si-N as diffusion barriers for copper on Bi2Te3 SO JOURNAL OF PHYSICS D-APPLIED PHYSICS LA English DT Article ID AMORPHOUS (MO; METALLIZATIONS AB Films of Ni-7 at% V, Pt, Pd, and Ta40Si14N46, each approximately 100 nm thick, were magnetron-deposited and Interposed between about 250 nm thick copper overlayers and Bi2Te3 single-crystalline substrates. The samples were then annealed in vacuum up to 350 degrees C. The performance of the metal and the tantalum-silicon-nitride films as diffusion barriers for in-diffusion of Cu and out-diffusion of Bi and Te was evaluated by 2.0 MeV He-4 backscattering spectrometry and x-ray diffraction. The Ni-7 at%:V, Pd and Pt films all fail to prevent interdiffusion of Cu and Bi2Te3 after a few hours of annealing at 200 degrees C. However, the Ta40Si14N46 barrier preserves the integrity of the contact: after 250 degrees C for 50 h and 350 degrees C for 1 h anneals. These results confirm the superior characteristics of the metal-silicon-nitride films as diffusion barriers. C1 CALTECH, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kacsich, T (reprint author), CALTECH, Pasadena, CA 91125 USA. NR 19 TC 21 Z9 21 U1 1 U2 10 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0022-3727 J9 J PHYS D APPL PHYS JI J. Phys. D-Appl. Phys. PD OCT 7 PY 1998 VL 31 IS 19 BP 2406 EP 2411 DI 10.1088/0022-3727/31/19/007 PG 6 WC Physics, Applied SC Physics GA 131WG UT WOS:000076597800007 ER PT J AU Anderson, JD Laing, PA Lau, EL Liu, AS Nieto, MM Turyshev, SG AF Anderson, JD Laing, PA Lau, EL Liu, AS Nieto, MM Turyshev, SG TI Indication, from Pioneer 10/11, Galileo, and Ulysses data, of an apparent anomalous, weak, long-range acceleration SO PHYSICAL REVIEW LETTERS LA English DT Article ID MATTER AB Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft indicate an apparent anomalous, constant, acceleration acting on the spacecraft with a magnitude similar to 8.5 x 10(-8) cm/s(2), directed towards the Sun. Two independent codes and physical strategies have been used to analyze the data. A number of potential causes have been ruled out. We discuss future kinematic tests and possible origins of the signal. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Aerospace Corp, El Segundo, CA 90245 USA. Astrodynam Sci, Los Angeles, CA 90039 USA. Univ Calif Los Alamos Natl Lab, Div Theoret MSB285, Los Alamos, NM 87545 USA. RP Anderson, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 18 TC 362 Z9 366 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 OCT 5 PY 1998 VL 81 IS 14 BP 2858 EP 2861 DI 10.1103/PhysRevLett.81.2858 PG 4 WC Physics, Multidisciplinary SC Physics GA 125HR UT WOS:000076231900006 ER PT J AU Clarke, AD Davis, D Kapustin, VN Eisele, F Chen, G Paluch, I Lenschow, D Bandy, AR Thornton, D Moore, K Mauldin, L Tanner, D Litchy, M Carroll, MA Collins, J Albercook, C AF Clarke, AD Davis, D Kapustin, VN Eisele, F Chen, G Paluch, I Lenschow, D Bandy, AR Thornton, D Moore, K Mauldin, L Tanner, D Litchy, M Carroll, MA Collins, J Albercook, C TI Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources SO SCIENCE LA English DT Article ID CLOUD CONDENSATION NUCLEI; AEROSOL-SIZE DISTRIBUTION; DIMETHYL SULFIDE; ATMOSPHERIC SULFUR; PACIFIC; SULFATE; CYCLES; ENTRAINMENT; SAGA-3; OCEAN AB New particle formation in a tropical marine boundary Layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being Linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions. C1 Univ Hawaii, Sch Ocean & Earth Sci & Technol, Honolulu, HI 96822 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Natl Ctr Atmospher Res, Div Atmospher Chem, Boulder, CO 80307 USA. Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA. Univ Michigan, Ann Arbor, MI 48109 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Clarke, AD (reprint author), Univ Hawaii, Sch Ocean & Earth Sci & Technol, Honolulu, HI 96822 USA. OI LENSCHOW, DONALD/0000-0003-4353-0098 NR 37 TC 149 Z9 151 U1 3 U2 20 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 OCT 2 PY 1998 VL 282 IS 5386 BP 89 EP 92 DI 10.1126/science.282.5386.89 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 126LM UT WOS:000076294900043 ER PT J AU Graf, J Sasaki, C Winn, C Liu, WT Tsai, W Freilich, M Long, D AF Graf, J Sasaki, C Winn, C Liu, WT Tsai, W Freilich, M Long, D TI NASA Scatterometer experiment SO ACTA ASTRONAUTICA LA English DT Article ID OCEAN AB Satellite scatterometers are microwave radars capable of measuring near-surface vector winds (both speed and direction) over the oceans under all weather conditions. The ata generated from these instruments are used in scientific studies of upper ocean circulation tropospheric dynamics, air-sea interaction and climate change; in operational meteorology as a means to increase numerical weather forecast skill and the accuracy of storm warning predictions; and in commercial applications such as ship routing. The scatterometer wind measurement technique was demonstrated with the flight of the Seasat Scatterometer in 1978. This paper summarizes the scatterometry measurement technique, describes the design of the NASA Scatterometer (NSCAT) instrument recently launched aboard the National Space Development Agency of Japan's (NASDA) Advanced Earth Observing Satellite (ADEOS), presents first results from the NSCAT instrument, and describes the future U.S. program for measuring surface marine wind vectors. (C) 1996 International Astronautical Federation. Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Graf, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Long, David/K-4908-2015 OI Long, David/0000-0002-1852-3972 NR 6 TC 32 Z9 34 U1 0 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 OCT PY 1998 VL 43 IS 7-8 BP 397 EP 407 DI 10.1016/S0094-5765(97)00180-X PG 11 WC Engineering, Aerospace SC Engineering GA 142AT UT WOS:000077178300006 ER PT J AU Singh, M AF Singh, M TI Ceramic joining technology SO ADVANCED MATERIALS & PROCESSES LA English DT Article C1 NASA, Lewis Res Ctr, FDC NYMA Inc, Cleveland, OH 44135 USA. RP Singh, M (reprint author), NASA, Lewis Res Ctr, FDC NYMA Inc, MS 106-5,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 0 TC 3 Z9 4 U1 2 U2 2 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 0026-0665 J9 ADV MATER PROCESS JI Adv. Mater. Process. PD OCT PY 1998 VL 154 IS 4 BP 89 EP 90 PG 2 WC Materials Science, Multidisciplinary SC Materials Science GA 126TG UT WOS:000076309300006 ER PT J AU Chandrasekhara, MS Wilder, MC Carr, LW AF Chandrasekhara, MS Wilder, MC Carr, LW TI Unsteady stall control using dynamically deforming airfoils SO AIAA JOURNAL 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 An experiment documenting the compressible flow over a dynamically deforming airfoil is presented. This airfoil, which has a leading edge radius that can be dynamically changed, was tested at various deformation rates for fixed airfoil angle of attack. Selected leading-edge shapes were also tested during airfoil oscillation. These tests show that for a range of Mach numbers observed on the retreating blades of helicopter rotors the dynamic stall vortex can be avoided by a judicious variation of leading-edge curvature. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. USN, Postgrad Sch, Navy NASA Joint Inst Aeronaut, Dept Aeronaut & Astronaut, Monterey, CA 93943 USA. MCAT Inc, Navy NASA Joint Inst Aeronaut, Mt View, CA 94043 USA. RP Chandrasekhara, MS (reprint author), NASA, Ames Res Ctr, MS 260-1, Moffett Field, CA 94035 USA. NR 9 TC 26 Z9 26 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD OCT PY 1998 VL 36 IS 10 BP 1792 EP 1800 DI 10.2514/2.294 PG 9 WC Engineering, Aerospace SC Engineering GA 126VQ UT WOS:000076315500004 ER PT J AU Koch, GJ Petros, M AF Koch, GJ Petros, M TI A simple overhead Denisyuk configuration for making reflection holograms with a diode laser SO AMERICAN JOURNAL OF PHYSICS LA English DT Article ID ATOMIC PHYSICS C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci & Technol Corp, Hampton, VA 23666 USA. RP Koch, GJ (reprint author), NASA, Langley Res Ctr, MS 468, Hampton, VA 23681 USA. NR 10 TC 5 Z9 5 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0002-9505 J9 AM J PHYS JI Am. J. Phys. PD OCT PY 1998 VL 66 IS 10 BP 933 EP 934 DI 10.1119/1.18983 PG 2 WC Education, Scientific Disciplines; Physics, Multidisciplinary SC Education & Educational Research; Physics GA 125JM UT WOS:000076234500022 ER PT J AU Brooks, VL Quesnell, RR Kane, CM Keil, LC AF Brooks, VL Quesnell, RR Kane, CM Keil, LC TI Hemodynamic and hormonal responses to hemorrhage in conscious rabbits at mid- and late gestation SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE arterial pressure; heart rate; vasopressin; renin; angiotensin II; baroreceptor reflex ID PREGNANT RABBIT; PRESSURE; RENIN; BAROREFLEX; PLASMA; SHEEP; PROGESTERONE; HYPOTENSION; HYPOVOLEMIA; SECRETION AB This study tests the hypothesis that conscious rabbits late in pregnancy (P), but not at midgestation (MP), are less able to maintain arterial pressure during hemorrhage. Blood volume (BV) was elevated (P < 0.05) by an average of 13 +/- 4 (MP) and 35 +/- 3% (P). Rabbits were bled in both the nonpregnant (NP) and P state at 2% of the initial BV per minute. The hemorrhage was stopped after arterial pressure decreased. In NP rabbits, arterial pressure was well maintained near control pressures of 70 +/- 2 mmHg until 38 +/- 2% of the initial BV was removed and then rapidly fell to reach a nadir at 35 +/- 2 mmHg. In contrast, in P rabbits, basal arterial pressure was lower (61 +/- 2 mmHg; P < 0.05) and gradually decreased to below control after <25% of the initial BV was removed, Moreover, the rapid hypotensive phase was triggered with a lower percent BV removal (33 +/- 2%; P < 0.05). Basal heart rate was higher during P (149 +/- 5 vs. 189 +/- 9 beats/min; P < 0.05), and reflex increases were delayed. The slope of the relationship between arterial pressure and vasopressin was not modified during P, although the line was shifted to a lower pressure (P < 0.05). Larger increases in plasma renin activity and ANG II concentration were produced during hemorrhage in P rabbits. In contrast, no differences in the changes in arterial pressure, heart rate, and vasopressin were found between NP and MP rabbits during hemorrhage, although increases in renin and ANG II were greater at MP (P < 0.05). In summary, although P conscious rabbits are less able to maintain blood pressure during hemorrhage, this change is not evident at MP. These data suggest that the factors that mediate the P-induced alterations in arterial pressure regulation are not operative until late in gestation. C1 Oregon Hlth Sci Univ, Dept Physiol & Pharmacol, Portland, OR 97201 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Brooks, VL (reprint author), Oregon Hlth Sci Univ, Dept Physiol & Pharmacol, L-334, Portland, OR 97201 USA. FU NHLBI NIH HHS [HL-39923] NR 43 TC 14 Z9 15 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0363-6119 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD OCT PY 1998 VL 275 IS 4 BP R1082 EP R1090 PG 9 WC Physiology SC Physiology GA 125KB UT WOS:000076235800018 PM 9756537 ER PT J AU Wade, CE Morey-Holton, E AF Wade, CE Morey-Holton, E TI Alteration of renal function of rats following spaceflight SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE urinary sodium and potassium excretion; aldosterone; free water clearance; osmolal clearance ID FLUID-ELECTROLYTE METABOLISM; HEAD-DOWN TILT; WEIGHTLESSNESS; BODY; MICROGRAVITY; MECHANISM; FLIGHT AB Following spaceflight, changes in renal function of humans have been suggested. To assess the effects of readaptation on renal function, urine was collected from male rats (similar to 245 g) over a 2-wk period following a 14-day spaceflight. Rats were assigned to three groups: flight animals (n = 6), flight controls (n = 6) housed in the flight cages on the ground, and vivarium controls (n = 5) housed in standard shoe box cages. Animals were placed into individual metabolic cages for urine collection. Urine output was significantly increased for 3 days following flight. Excretion rates of Na+ and K+ were increased, resulting in an increased osmotic excretion rate. Creatinine excretion rate increased over the first two postflight days. Glomerular filtration rate increased immediately following spaceflight without changes in plasma creatinine, Na+, K+, or osmolality. Increased excretion of solute was thus the result of increased delivery and a decreased percent reabsorption of the filtered load. Osmolal clearance was increased immediately postflight while free water clearance was decreased. In growing rats, the diuresis after short-duration spaceflight is the result of an increase in solute excretion with an accompanying reduction in free water clearance. C1 NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. Univ Calif Davis, Davis, CA 95616 USA. Univ Calif San Francisco, San Francisco, CA 94143 USA. RP Wade, CE (reprint author), NASA, Ames Res Ctr, Div Life Sci, Moffett Field, CA 94035 USA. NR 32 TC 16 Z9 20 U1 0 U2 0 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0363-6119 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD OCT PY 1998 VL 275 IS 4 BP R1058 EP R1065 PG 8 WC Physiology SC Physiology GA 125KB UT WOS:000076235800015 PM 9756534 ER PT J AU Work, TM Raskin, RE Balazs, GH Whittaker, SD AF Work, TM Raskin, RE Balazs, GH Whittaker, SD TI Morphologic and cytochemical characteristics of blood cells from Hawaiian green turtles SO AMERICAN JOURNAL OF VETERINARY RESEARCH LA English DT Article ID CHELONIA-MYDAS; SEA-TURTLE; LEUKOCYTES AB Objective-To identify and characterize blood cells from free-ranging Hawaiian green turtles, Chelonia mydas. Sample Population-26 green turtles from Puako on the island of Hawaii and Kaneohe Bay an the island of Oahu. Procedure-Blood was examined, using light and electron microscopy and cytochemical stains that included benzidine peroxidase, chloroacetate esterase, alpha naphthyl butyrate esterase, acid phosphatase, Sudan black B, periodic acid-Schiff, and toluidine blue. Results-6 types of WBC were identified: lymphocytes, monocytes, thrombocytes, heterophils, basophils, and eosinophils (small and large). Morphologic characteristics of mononuclear cells and most granulocytes were similar to those of cells from other reptiles except that green turtles have both large and small eosinophils. Conclusions-Our classification of green turtle blood cells clarifies improper nomenclature reported previously and provides a reference for future hematologic studies in this species. C1 US Geol Survey, Biol Resource Div, Natl Wildlife Hlth Ctr, Honolulu Field Stn, Honolulu, HI 96850 USA. Univ Florida, Coll Vet Med, Dept Physiol Sci, Gainesville, FL 32610 USA. NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. Univ Florida, Interdiscilinary Ctr Biotechnol Res, Electron Microscopy Core Lab, Gainesville, FL 32611 USA. RP Work, TM (reprint author), US Geol Survey, Biol Resource Div, Natl Wildlife Hlth Ctr, Honolulu Field Stn, POB 50167, Honolulu, HI 96850 USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 NR 20 TC 51 Z9 58 U1 2 U2 6 PU AMER VETERINARY MEDICAL ASSOC PI SCHAUMBURG PA 1931 N MEACHAM RD SUITE 100, SCHAUMBURG, IL 60173-4360 USA SN 0002-9645 J9 AM J VET RES JI Am. J. Vet. Res. PD OCT PY 1998 VL 59 IS 10 BP 1252 EP 1257 PG 6 WC Veterinary Sciences SC Veterinary Sciences GA 135QR UT WOS:000076814600011 PM 9781457 ER PT J AU Malik, M Dang, HH AF Malik, M Dang, HH TI Vibration analysis of continuous systems by differential transformation SO APPLIED MATHEMATICS AND COMPUTATION LA English DT Article DE differential transformation; continuous system vibration; Bernoulli-Euler beam AB This paper demonstrates the application of the technique of differential transformation to free vibration of continuous systems. The specific problem chosen for this purpose is that of thin beams. The transformation technique is employed for deriving frequency equations and mode functions. The frequencies and mode shapes obtained from the differential-transformation solutions are compared with the exact analytical solutions. It is shown that the solutions obtained from the technique have a very high degree of accuracy. (C) 1998 Published by Elsevier Science Inc, All rights reserved. C1 Univ Oklahoma, Sch Aerosp & Mech Engn, Norman, OK 73019 USA. RP Malik, M (reprint author), NASA, Langley Res Ctr, UVA Ctr Adv Computat Technol, Mail Stop 201, Hampton, VA 23665 USA. NR 3 TC 46 Z9 46 U1 0 U2 2 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0096-3003 J9 APPL MATH COMPUT JI Appl. Math. Comput. PD OCT PY 1998 VL 96 IS 1 BP 17 EP 26 DI 10.1016/S0096-3003(97)10076-5 PG 10 WC Mathematics, Applied SC Mathematics GA 116PF UT WOS:000075733200002 ER PT J AU Browell, EV Ismail, S Grant, WB AF Browell, EV Ismail, S Grant, WB TI Differential absorption lidar (DIAL) measurements from air and space SO APPLIED PHYSICS B-LASERS AND OPTICS LA English DT Article ID TROPOSPHERIC WATER-VAPOR; WINTERTIME ARCTIC STRATOSPHERE; AIRBORNE LIDAR; AEROSOL DISTRIBUTIONS; TECHNOLOGY EXPERIMENT; OZONE; PROFILES; SYSTEM; VALIDATION; SATELLITE AB Differential absorption lidar (DIAL) systems have been used for the measurement of ozone, water vapor, and aerosols from aircraft platforms for over 18 years, yielding new insights into atmospheric chemistry, composition, and dynamics in large-scale field experiments conducted all over the world. The successful deployment of the lidar in-space technology experiment (LITE) in September 1994 demonstrated that space-based lidars can also collect valuable information on the global atmosphere. This paper reviews some of the contributions of the NASA Langley Research Center's airborne ozone and water vapor DIAL systems and space-based LITE system to the understanding of the atmosphere and discusses the feasibility and advantages of putting DIAL systems in space for routine atmospheric measurements off ozone and/or water vapor and aerosols and clouds. The technology and applications of the differential absorption lidar (DIAL) technique have progressed significantly since the first DIAL measurements of Schotland [1], and airborne DIAL measurements of ozone and water vapor are frequently being made in a wide range of field experiments. In addition, plans are underway to develop DIAL systems for use on satellites for continuous global measurements. This paper will highlight the history of airborne lidar and DIAL systems, summarize the major accomplishments of the NASA Langley DIAL program, and discuss specifications and goals for DIAL systems in space. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Browell, EV (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, MS 401A, Hampton, VA 23681 USA. RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 88 TC 115 Z9 117 U1 0 U2 13 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 OCT PY 1998 VL 67 IS 4 BP 399 EP 410 DI 10.1007/s003400050523 PG 12 WC Optics; Physics, Applied SC Optics; Physics GA 133YA UT WOS:000076714100001 ER PT J AU Durand, D Dalrymple, B Eaton, L Spargo, J Wire, M Dowdy, M Ressler, M AF Durand, D Dalrymple, B Eaton, L Spargo, J Wire, M Dowdy, M Ressler, M TI 10 KNbN ADC for IR sensor applications SO APPLIED SUPERCONDUCTIVITY LA English DT Article ID A/D CONVERTER; DESIGN AB The authors report the design, fabrication and lest results of a 12-bit NbN SFQ counting A/D converter operating at 9 to 10 K and its insertion into a test IR focal plane array sensor system. The NbN IC is based on a linearized SQUID front-end which generates SFQ pulses at a frequency proportional to the signal. A gated SFQ counter integrates the signal over the sample time and the data is driven off chip through a serializing latching voltage state logic (MVTL) output shift register. The TRW A/D converter chip has been packaged and inserted into an IR focal plane array sensor test facility, or test bed, at the NASA Jet Propulsion Laboratory. The entire system has been successfully demonstrated producing IR images at 100 frames/s with the NbN A/D converter operating at 9 K, dissipating 0.3 mW. Performance of the A/D converter chip, the package including magnetic shielding and medium/high speed signal I/O, and the integrated test bed system are discussed. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 TRW Co Inc, Redondo Beach, CA 90278 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Durand, D (reprint author), TRW Co Inc, 1 Space Pk, Redondo Beach, CA 90278 USA. NR 7 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 0964-1807 J9 APPL SUPERCOND JI Appl. Supercond. PD OCT-DEC PY 1998 VL 6 IS 10-12 BP 741 EP 750 PG 10 WC Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter SC Materials Science; Physics GA 251VE UT WOS:000083466400037 ER PT J AU Miller, S Schlegel, EM Petre, R Colbert, E AF Miller, S Schlegel, EM Petre, R Colbert, E TI X-ray properties of NGC 1313: Second-epoch PSPC observations SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 1313); galaxies : spiral; supernovae : individual (SN 1978K); X-rays : galaxies ID SPIRAL GALAXY NGC-1313; SN 1978K; EMISSION; M33; SUPERNOVA; SPECTRUM; SN-1978K; CLOUD AB Second-epoch ROSAT PSPC observations of the nearby barred spiral galaxy NGC 1313 show that the extended X-ray emission surrounding the bright "nuclear" source can be mostly attributed to at least three individual sources, each with L(X(0.1-2,4 keV)) approximate to 10(38-39) ergs s(-1) and lying within similar to 2.6 kpc from the central source. One of these three sources shows up only as an extension of the nuclear source in the east-west direction but becomes more apparent after subtracting out the main source. We find no evidence for X-ray emission from hot, interstellar gas and show that if such emission is present, it has a surface brightness less than or equal to 5 x 10(36) ergs s(-1) arcmin(-2) and an integrated X-ray luminosity less than similar to 5 x 10(38) ergs s(-1). We find that of the 10 point sources detected, four of them show definite signs of variability between the two epochs of PSPC data. We also discuss an attempted revision of the description of the point-spread function of the PSPC. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Miller, S (reprint author), Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NR 38 TC 9 Z9 9 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD OCT PY 1998 VL 116 IS 4 BP 1657 EP 1670 DI 10.1086/300551 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 128NP UT WOS:000076413100011 ER PT J AU Van Buren, D Brundage, M Ressler, M Terebey, S AF Van Buren, D Brundage, M Ressler, M Terebey, S TI 10 micron search for cool companions of nearby stars SO ASTRONOMICAL JOURNAL LA English DT Article DE planetary systems; stars : low-mass, brown dwarfs; techniques : image processing ID PLANETS; DWARFS AB We present 10 mu m broadband images of the nearby stars Gliese 15, 71, 628, 699, 725A, 725B, 729, and 820A from an experiment designed to detect cool companions. The observations establish upper limits for the presence of companion objects with separations between 2 " and 10 " at or below the hydrogen burning limit for Gliese 15, 699, and 729. C1 CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Extrasolar Res Corp, Pasadena, CA 91106 USA. RP Van Buren, D (reprint author), CALTECH, Ctr Infrared Proc & Anal, Mail Stop 100-22, Pasadena, CA 91125 USA. NR 11 TC 3 Z9 3 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD OCT PY 1998 VL 116 IS 4 BP 1992 EP 1997 DI 10.1086/300530 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 128NP UT WOS:000076413100044 ER PT J AU Levison, HF Lissauer, JJ Duncan, MJ AF Levison, HF Lissauer, JJ Duncan, MJ TI Modeling the diversity of outer planetary systems SO ASTRONOMICAL JOURNAL LA English DT Article DE celestial mechanics, stellar dynamics; solar system : formation; solar system : general ID LARGE-SCALE CHAOS; SOLAR-SYSTEM; STABILITY; ACCRETION; COMPANION; 16-CYGNI-B; EVOLUTION; DYNAMICS; STAR AB In order to better understand the range of dynamically long-lived giant planet systems, we present the results of a set of bottom-up numerical simulations designed to generate plausible giant planet systems from a large number of planetary embryos. Our simulations produced systems that are stable for at least a billion years and that exhibit a wide range of characteristics. Some of these systems are reminiscent of the outer solar system. The number of planets ranged from one to seven. Many systems contained only Uranus-mass objects. We constructed systems that were more compact than the outer solar system and systems that were much sparser, with planets on very eccentric orbits. Perhaps most surprisingly, some of the systems that we constructed were stable for at least a billion years despite undergoing macroscopic orbital changes on much shorter timescales. C1 SW Res Inst, Dept Space Sci, Boulder, CO 80302 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada. RP Levison, HF (reprint author), SW Res Inst, Dept Space Sci, Boulder, CO 80302 USA. EM hal@gort.boulder.swri.edu; lissauer@ringside.arc.nasa.gov; duncan@astro.queensu.ca RI Levison, Harold/C-6061-2013 OI Levison, Harold/0000-0001-5847-8099 NR 43 TC 145 Z9 146 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 J9 ASTRON J JI Astron. J. PD OCT PY 1998 VL 116 IS 4 BP 1998 EP 2014 DI 10.1086/300557 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 128NP UT WOS:000076413100045 ER PT J AU Frink, S Roser, S Alcala, JM Covino, E Brandner, W AF Frink, S Roser, S Alcala, JM Covino, E Brandner, W TI Kinematics of T Tauri stars in Chamaeleon SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : kinematics; stars : formation; stars : premain sequence; stars : late-type; astrometry ID MAIN-SEQUENCE STARS; ALL-SKY SURVEY; POINT-SOURCE CATALOG; HIGH-VELOCITY CLOUDS; X-RAY OBSERVATIONS; CHAMELEON-I; FORMING REGION; DARK CLOUD; MOLECULAR CLOUDS; ORIONIS STAR AB We study the kinematics of T Tauri stars (TTS) located in the cores of the Chamaeleon clouds as well as far off these clouds. Our sample comprises 2 early type stars known to be related to Cha I, 6 classical (CTTS) and 6 weak-line T Tauri stars (WTTS) known before the ROSAT mission, and 8 bonafide pre-main sequence (PMS) stars as well as 23 presumably older stars discovered with ROSAT (Alcala et al. 1995; Covino et al. 1997). Altogether we present proper motions for 45 stars, taken from the Hipparcos, ACT and STARNET catalogues. For 12 stars of our sample parallaxes measured by Hipparcos are available, and we use them to derive constraints on the distance distribution of the other stars in our sample. Our analysis of the proper motions allows us to divide the sample into several subgroups. We analyse the motions of the stars in connection with different star formation scenarios and find them consistent with both the high velocity cloud (HVC) impact model (Lepine & Duvert 1994) and the cloudlet model (Feigelson 1996), whereas the data seem to be inconsistent with any kind of a dynamical ejection model. C1 Astron Rechen Inst Heidelberg, D-69120 Heidelberg, Germany. Osservatorio Astron Capodimonte, I-80131 Naples, Italy. Inst Nacl Astrofis Opt & Elect, Puebla 72000, Mexico. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. RP Frink, S (reprint author), Astron Rechen Inst Heidelberg, Monchhofstr 12-14, D-69120 Heidelberg, Germany. EM sabine@ari.uni-heidelberg.de NR 48 TC 33 Z9 33 U1 0 U2 1 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1998 VL 338 IS 2 BP 442 EP 451 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 132CF UT WOS:000076611900015 ER PT J AU Deeg, HJ Doyle, LR Kozhevnikov, VP Martin, EL Oetiker, B Palaiologou, E Schneider, J Afonso, C Dunham, EW Jenkins, JM Ninkov, Z Stone, RPS Zakharova, PE AF Deeg, HJ Doyle, LR Kozhevnikov, VP Martin, EL Oetiker, B Palaiologou, E Schneider, J Afonso, C Dunham, EW Jenkins, JM Ninkov, Z Stone, RPS Zakharova, PE TI Near-term detectability of terrestrial extrasolar planets: TEP network observations of CM Draconis SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : individual : CM Dra; planetary systems; binaries : eclipsing; stars : low mass, brown dwarfs; stars : flare; techniques : photometric ID RESOLVED CCD PHOTOMETRY; SYSTEMS; STARS AB Results from a photometric search for extrasolar planetary transits across the eclipsing binary CM Dra are presented. The TEP (Transits of Extrasolar Planets) network has observed this star since 1994, and a lightcurve with 617 hours of coverage has been obtained. The data give a complete phase coverage of the CM Dra system at each of the 3 years of observations, with a noise of less than 5 mmag. New epoch and period values for CM Dra are derived, and a low flare rate of 0.25 hr(-1) has been confirmed. The absence of periodic variations in eclipse minimum times excludes the presence of very massive planets with periods of less than a few years. The lightcurve was visually scanned for the presence of unusual events which may be indicative of transits of extrasolar planets with 'massive earth' sizes. Six suspicious events were found which are being followed up for future transits, by planets with sizes between 1.5 and 2.5 R(E) (Earth Radii). However, none of these events has amplitudes compatible with planets larger than 2.5 R(E). Coplanar planets larger than 2.5 R(E) and with orbital periods of less than 60 days can therefore be ruled out with a confidence of about 80%. Planets smaller than 1.5 R(E) cannot be detected in the data without a sub-noise detection algorithm. A preliminary signal detection analysis shows that there is a 50% detection confidence for 2 R(E) planets with a period from 10 to 30 days with the current data. This data-set demonstrates that it is possible to detect terrestrial sized planets with ground based photometry, and that strong constraints on the sizes of planets orbiting in the plane of the CM Dra system can be set. C1 Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Tenerife, Spain. NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. Ural State Univ, Astron Observ, Ekaterinburg 620083, Russia. Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA. Univ Crete, Skinakas Observ, GR-71110 Iraklion, Crete, Greece. Observ Paris, CNRS, F-92195 Meudon, France. Lowell Observ, Flagstaff, AZ 86001 USA. Rochester Inst Technol, Ctr Imaging Sci, Rochester, NY 14623 USA. Univ Calif Santa Cruz, Lick Observ, Mt Hamilton, CA 95140 USA. RP Deeg, HJ (reprint author), Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Tenerife, Spain. EM hdeeg@bigfoot.com; doyle@gal.arc.nasa.gov RI Jenkins, James/I-5284-2016 NR 27 TC 54 Z9 54 U1 1 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD OCT PY 1998 VL 338 IS 2 BP 479 EP 490 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 132CF UT WOS:000076611900019 ER PT J AU Delfosse, X Forveille, T Mayor, M Perrier, C Naef, D Queloz, D AF Delfosse, X Forveille, T Mayor, M Perrier, C Naef, D Queloz, D TI The closest extrasolar planet - A giant planet around the M4 dwarf Gl 876 SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE giant planet formation; extrasolar planets; giant planets; M dwarf stars ID LOW-MASS STARS; ORIGIN; NEARBY AB Precise radial velocity observations of the nearby M4 dwarf G1 876 with the Observatoire de Haute Provence 1.93 m telescope and the new 1.20 m swiss telescope at la Silla indicate the presence of a jovian mass companion to this star. The orbital fit to the data gives a period of 60.8 days, a velocity amplitude of 246m.s(-1) and an eccentricity of 0.34. Assuming that G1 876 has a mass of 0.3 M., the mass function implies a mass for the companion of 2/sin i Jupiter masses. C1 Observ Geneva, CH-1290 Sauverny, Switzerland. Observ Grenoble, F-38041 Grenoble, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Delfosse, X (reprint author), Observ Geneva, 51 Ch Maillettes, CH-1290 Sauverny, Switzerland. EM Xavier.Delfosse@obs.unige.ch NR 27 TC 98 Z9 99 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 OCT PY 1998 VL 338 IS 2 BP L67 EP L70 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 132CF UT WOS:000076611900007 ER PT J AU Lang, MJ Buckley, JH Carter-Lewis, DA Catanese, M Cawley, MF Colombo, E Connaughton, V Fegan, DJ Finley, JP Gaidos, JA Gillanders, GH Hillas, AM Kertzman, MP Krennrich, F Lessard, RW Moriarty, P Quinn, J Rose, HJ Sembroski, G Weekes, TC AF Lang, MJ Buckley, JH Carter-Lewis, DA Catanese, M Cawley, MF Colombo, E Connaughton, V Fegan, DJ Finley, JP Gaidos, JA Gillanders, GH Hillas, AM Kertzman, MP Krennrich, F Lessard, RW Moriarty, P Quinn, J Rose, HJ Sembroski, G Weekes, TC TI A search for TeV emission from AE Aquarii SO ASTROPARTICLE PHYSICS LA English DT Article DE VHE gamma-ray astronomy; cataclysmic variables; AE Aquarii ID GAMMA-RAY OBSERVATIONS; WHITE-DWARF; MARKARIAN-421 AB We have observed the cataclysmic variable AE Aqr for a total of 68.7 hours over the epoch 1991-95 using the Whipple Observatory 10 m gamma-ray telescope. An analysis of these data has revealed no evidence for any steady, pulsed or episodic TeV emission. We have calculated an upper limit for steady emission of 4.0 x 10(-12) photons cm(-2)s(-1) at an energy threshold of 900 GeV, This is three orders of magnitude less than the flux reported by others during burst activity. Our upper limits for coherent pulsed emission at the first and second harmonics of the white dwarf frequency are 1.5 x 10(-12) photons cm(-2)s(-1) in each case. (C) 1998 Elsevier Science B.V. C1 Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland. Washington Univ, Dept Phys, St Louis, MO 63130 USA. Iowa State Univ Sci & Technol, Dept Phys & Astron, Ames, IA 50011 USA. Natl Univ Ireland, Dept Phys, Maynooth, Kildare, Ireland. CONAE, RA-1063 Buenos Aires, DF, Argentina. NASA, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Natl Univ Ireland Univ Coll Dublin, Dept Phys, Dublin 4, Ireland. Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA. Univ Leeds, Dept Phys, Leeds LS2 9JT, W Yorkshire, England. Depauw Univ, Dept Phys, Greencastle, IN 46135 USA. Galway Mayo Inst Technol, Sch Sci, Galway, Ireland. Harvard Smithsonian CfA, FL Whipple Observ, Amado, AZ 85645 USA. RP Lang, MJ (reprint author), Natl Univ Ireland Univ Coll Galway, Dept Phys, Galway, Ireland. OI Lang, Mark/0000-0003-4641-4201 NR 24 TC 13 Z9 13 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD OCT PY 1998 VL 9 IS 3 BP 203 EP 211 DI 10.1016/S0927-6505(98)00020-6 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 134FR UT WOS:000076732700003 ER PT J AU Platania, P Bensadoun, M Bersanelli, M De Amici, G Kogut, A Levin, S Maino, D Smoot, GF AF Platania, P Bensadoun, M Bersanelli, M De Amici, G Kogut, A Levin, S Maino, D Smoot, GF TI A determination of the spectral index of galactic synchrotron emission in the 1-10 GHz range SO ASTROPHYSICAL JOURNAL LA English DT Article DE diffuse radiation; radiation mechanisms : nonthermal ID DIFFERENTIAL MICROWAVE RADIOMETER; COSMIC BACKGROUND-RADIATION; CONTINUUM EMISSION; TEMPERATURE; FLUCTUATIONS; FREQUENCY; SKY; MHZ AB We present an analysis of simultaneous multifrequency measurements of the Galactic emission in the 1-10 GHz range with 18 degrees angular resolution taken from a high-altitude site. Our data yield a determination of the synchrotron spectral index between 1.4 and 7.5 GHz of beta(syn) = 2.81 +/- 0.16. Combining our data with maps made by Haslam et al. and Reich & Reich, we find beta(syn) = 2.76 +/- 0.11 in the 0.4-7.5 GHz range. These results are in agreement with the few previously published measurements. The variation of beta(syn) with frequency based on our results and compared with other data found in the literature suggests a steepening of the synchrotron spectrum toward high frequencies, as expected from theory because of the steepening of the parent cosmic-ray electron energy spectrum. Comparison between the Haslam data and the 19 GHz map of Cottingham also indicates a spatial variation of the spectral index on large angular scales. Additional high-quality data are necessary to provide a serious study of these effects. C1 CNR, Ist Fis Cosm, I-20133 Milan, Italy. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. TRW Co Inc, Space & Technol Div, Redondo Beach, CA 90278 USA. NASA, Goddard Space Flight Ctr, Hughes STX, Greenbelt, MD 20771 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SISSA, Sch Adv Int Studies, I-34014 Trieste, Italy. RP Platania, P (reprint author), CNR, Ist Fis Cosm, Via Bassini 15, I-20133 Milan, Italy. RI Kogut, Alan/D-6293-2012 NR 27 TC 85 Z9 85 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 OCT 1 PY 1998 VL 505 IS 2 BP 473 EP 483 DI 10.1086/306175 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500001 ER PT J AU Potekhin, AY Ivanchik, AV Varshalovich, DA Lanzetta, KM Baldwin, JA Williger, GM Carswell, RF AF Potekhin, AY Ivanchik, AV Varshalovich, DA Lanzetta, KM Baldwin, JA Williger, GM Carswell, RF TI Testing cosmological variability of the proton-to-electron mass ratio using the spectrum of PKS 0528-250 SO ASTROPHYSICAL JOURNAL LA English DT Article DE atomic data; cosmology : observations; elementary particles; quasars : absorption lines; quasars : individual (PKS 0528-250) ID FUNDAMENTAL CONSTANTS; MOLECULAR-HYDROGEN; PHYSICAL CONSTANTS; TIME-VARIATION; ABSORPTION-LINES; BAND SYSTEM; DIMENSIONS; EVOLUTION; REDSHIFT; LIMITS AB Multidimensional cosmologies allow for variations of fundamental physical constants over the course of cosmological evolution, and different versions of the theories predict different time dependences. In particular, such variations could manifest themselves as changes of the proton-to-electron mass ratio mu = m(p)/m(e) over the period of similar to 10(10) yr since the moment of formation of high-redshift QSO spectra. Here we analyze a new high-resolution spectrum of the z = 2.81080 molecular hydrogen absorption system toward the QSO PKS 0528-250 to derive a new observational constraint to the time-averaged variation rate of the proton-to-electron mass ratio. We find \(mu) over dot/mu\ < 1.5 x 10(-14) yr(-1), which is much tighter than previously measured limits. C1 AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Cerro Tololo Interamer Observ, La Serena, Chile. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England. RP Potekhin, AY (reprint author), AF Ioffe Phys Tech Inst, Politekhnicheskaya 26, St Petersburg 194021, Russia. RI Potekhin, Alexander/B-9747-2014; Ivanchik, Alexandre/C-1049-2014 OI Potekhin, Alexander/0000-0001-9955-4684; NR 32 TC 45 Z9 45 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 OCT 1 PY 1998 VL 505 IS 2 BP 523 EP 528 DI 10.1086/306211 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500005 ER PT J AU Hubeny, I Hubeny, V AF Hubeny, I Hubeny, V TI Non-LTE models and theoretical spectra of accretion disks in active galactic nuclei. II. Vertical structure of the disk SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies : active; galaxies : nuclei; radiative transfer ID KERR BLACK-HOLE; STELLAR ATMOSPHERES; LYMAN EDGE; QUASARS AB We have calculated several representative models of vertical structure of an accretion disk around a supermassive Kerr black hole. The interaction of radiation and matter is treated self-consistently, taking into account departures from LTE for calculating both the disk structure and the radiation held. The structural equations are described in detail, and various approximations are discussed. We have demonstrated that departures from LTE are very important for determining the disk structure, even at the midplane, as well as the emergent radiation, particularly for hot and electron-scattering-dominated disks, We have shown that at least for the disk parameters studied in this paper, non-LTE effects tend to reduce the value of the Lyman jump with respect to the LTE predictions, regardless whether LTE predicts an emission or absorption jump. We have studied the effects of various values of viscosity on the model structure and predicted spectral energy distribution. The viscosity is parameterized through a parameter alpha(o) that describes the vertically averaged viscous stress, two power-law exponents, zeta(0) and zeta(1), and the division point m(d) between these two forms. The disk structure and emergent radiation is sensitive mainly to the values of alpha(o), while the other parameters influence the disk structure to a much lesser extent. However, although the detailed shape of the predicted spectrum is sensitive to adopted value of alpha(o), the overall appearance of the spectrum is quite similar. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. RP Hubeny, I (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. EM hubeny@tlusty.gsfc.nasa.gov; veronika@physics.ucsb.edu NR 47 TC 59 Z9 59 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 OCT 1 PY 1998 VL 505 IS 2 BP 558 EP 576 DI 10.1086/306207 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500008 ER PT J AU Wilson, AS Roy, AL Ulvestad, JS Colbert, EJM Weaver, KA Braatz, JA Henkel, C Matsuoka, M Xue, S Iyomoto, N Okada, K AF Wilson, AS Roy, AL Ulvestad, JS Colbert, EJM Weaver, KA Braatz, JA Henkel, C Matsuoka, M Xue, S Iyomoto, N Okada, K TI The ionization fraction in the obscuring "torus" of an active galactic nucleus SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies : active; galaxies : individual (NGC 2639); galaxies : nuclei; galaxies : Seyfert; radio continuum : galaxies ID WATER MASER EMISSION; SEYFERT-GALAXIES; H2O MEGAMASERS; DISK; QUASARS; REGIONS; SAMPLE AB The LINER galaxy NGC 2639 contains a water vapor megamaser, suggesting the presence of a nuclear accretion disk or torus viewed close to edge-on. This galaxy is thus a good candidate for revealing absorption by the torus of any compact nuclear continuum emission. In this paper, we report VLBA radio maps at three frequencies and an ASCA X-ray spectrum obtained to search for free-free and photoelectric absorptions, respectively. The radio observations reveal a compact (<0.2 pc) nuclear source with a spectrum that turns over sharply near 5 GHz. This turnover may reflect either synchrotron self-absorption or free-free absorption. The galaxy is detected by ASCA with an observed luminosity of 1.4 x 10(41) ergs s(-1) in the 0.6-10 keV band. The X-ray spectrum shows emission in excess of a power-law model at energies greater than 4 keV; we interpret this excess as compact, nuclear, hard X-ray emission with the lower energies photoelectrically absorbed by an equivalent hydrogen column of similar or equal to 5 x 10(23) cm(-2). If we assume that the turnover in the radio spectrum is caused by free-free absorption and that both the free-free and photoelectric absorptions are produced by the same gaseous component, the ratio integral n(e)(2) dl/integral n(H)dl may be determined. If the masing molecular gas is responsible for both absorptions, the required ionization fraction is greater than or similar to 1.3 x 10(-5), which is comparable to the theoretical upper limit derived by Neufeld, Maloney, and Conger for X-ray heated molecular gas. The two values may be reconciled if the molecular gas is very dense: n(H2) greater than or similar to 10(9) cm(-3). The measured ionization fraction is also consistent with the idea that both absorptions occur in a hot (similar to 6000 K), weakly ionized (ionization fraction a few times 10(-2)) atomic region that may coexist with the warm molecular gas. If this is the case, the absorbing gas is similar to 1 pc from the nucleus. We rule out the possibility that both absorptions occur in a fully ionized gas near 10(4) K. If our line of sight passes through more than one phase, the atomic gas probably dominates the free-free absorption, while the molecular gas may dominate the photoelectric absorption. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Natl Radio Astron Observ, Socorro, NM 87801 USA. NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Natl Radio Astron Observ, Green Bank, WV 24944 USA. Max Planck Inst Radioastron, D-53121 Bonn, Germany. RIKEN, Inst Phys & Chem Res, Wako, Saitama 35101, Japan. Univ Tokyo, Dept Phys, Bunkyo Ku, Tokyo 113, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 229, Japan. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Wilson, AS (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. EM awilson@stsci.edu; aroy@aoc.nrao.edu; julvesta@aoc.nrao.edu; colbert@lheamail.gsfc.nasa.gov; kim.weaver@pha.jhu.edu; jbraatz@nrao.edu; p220hen@mpifr-bonn.mpg.de; matsuoka@postman.riken.go.jp; xue@crab.riken.go.jp; iyomoto@miranda.phys.s.u-tokyo.ac.jp; okada@astro.isas.ac.jp NR 32 TC 21 Z9 21 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 OCT 1 PY 1998 VL 505 IS 2 BP 587 EP 593 DI 10.1086/306210 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500010 ER PT J AU Nandra, K Clavel, J Edelson, RA George, IM Malkan, MA Mushotzky, RF Peterson, BM Turner, TJ AF Nandra, K Clavel, J Edelson, RA George, IM Malkan, MA Mushotzky, RF Peterson, BM Turner, TJ TI New constraints on the continuum emission mechanism of active galactic nuclei: Intensive monitoring of NGC 7469 in the x-ray and ultraviolet SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 7469); ultraviolet : galaxies; x-rays : galaxies ID BROAD-LINE REGION; ACCRETION-DISK MODELS; K-ALPHA-LINES; SEYFERT-GALAXIES; COLD MATTER; MULTIWAVELENGTH OBSERVATIONS; BLACK-HOLES; VARIABILITY; SPECTRA; NGC-7469 AB We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7469 in the X-ray with RXTE over a similar to 30 day baseline. The source shows strong variability with a root mean square (rms) amplitude of similar to 16% and peak-to-peak variations of a factor of order 2. Simultaneous data over this period were obtained in the ultraviolet (UV) using IUE; making this the most intensive X-ray WUV/X-ray variability campaign performed for any active galaxy. Comparison of the continuum light curves reveals very similar amplitudes of variability but different variability characteristics, with the X-rays showing much more rapid variations. The data are not strongly correlated at zero lag. The largest absolute value of the correlation coefficient occurs for an anticorrelation between the two bands, with the X-ray variations leading the UV by similar to 4 days. The largest positive correlation is for the ultraviolet to lead the X-rays by similar to 4 days. Neither option appears to be compatible with any simple interband transfer function. The peak positive correlation at similar to 4 days occurs because the more prominent peaks in the UV light curve appear to lead those in the X-rays by this amount. However, the minima of the light curves are near simultaneous. These observations provide new constraints on theoretical models of the central regions of active galactic nuclei. Models in which the observed UV emission is produced solely by reradiation of absorber X-rays are ruled out by our data, as are those in which the X-rays are produced solely by Compton upscattering of the observed UV component by a constant distribution of particles. New or more complex models must be sought to explain the data. We require at least-two variability mechanisms, which have no simple relationship. We briefly explore means by which these observations could be reconciled with theoretical models. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. European Space Agcy, ISO Observ, Madrid 28080, Spain. Univ Leicester, Dept Phys & Astron, Xray Astron Grp, Leicester LE1 7RH, Leics, England. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. RP Nandra, K (reprint author), NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Code 660, Greenbelt, MD 20771 USA. NR 68 TC 95 Z9 96 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 OCT 1 PY 1998 VL 505 IS 2 BP 594 EP 606 DI 10.1086/306181 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500011 ER PT J AU Esin, AA Narayan, R Cui, W Grove, JE Zhang, SN AF Esin, AA Narayan, R Cui, W Grove, JE Zhang, SN TI Spectral transitions in Cygnus X-1 and other black hole X-ray binaries SO ASTROPHYSICAL JOURNAL LA English DT Review DE accretion, accretion disks; black hole physics; stars : individual (Cygnus X-1, GRO J0422+32, GRO J1719-24); X-rays : stars ID ADVECTION-DOMINATED ACCRETION; ACTIVE GALACTIC NUCLEI; 226868 = CYGNUS-X-1; NOVA-MUSCAE 1991; HDE 226868; GRO J0422+32; DISK MODEL; OPTICAL COUNTERPART; SPHERICAL ACCRETION; INTERMEDIATE STATE AB We show that the model proposed by Esin, McClintock, & Narayan for the low state, intermediate stale, and high state of the black hole soft X-ray transient, Nova Muscae 1991, is consistent with the spectral evolution of the black hole X-ray binary, Cyg X-1, during the hard-to-soft slate transition observed in 1996. We also apply the model to the outbursts of two other black hole X-ray transients, GRO J0422 + 32 and GRO J1719 - 24. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. USN, Res Lab, Washington, DC 20375 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Esin, AA (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. NR 120 TC 205 Z9 208 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 OCT 1 PY 1998 VL 505 IS 2 BP 854 EP 868 DI 10.1086/306186 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500029 ER PT J AU Bohm-Vitense, E Evans, NR Carpenter, K Albrow, MD Cottrell, PL Robinson, R Beck-Winchatz, B AF Bohm-Vitense, E Evans, NR Carpenter, K Albrow, MD Cottrell, PL Robinson, R Beck-Winchatz, B TI The mass of the Cepheid binary V636 Scorpii SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : spectroscopic; Cepheids; stars : evolution; stars : individual (V636 Scorpii) ID DYNAMICAL MASS; S-MUSCAE; STARS; MODELS; ORBIT AB The mass-luminosity relation for Cepheids depends on the degree of mixing in their main-sequence progenitors. Masses of Cepheids can be inferred by using different aspects of pulsation theory. These methods have in the past led to diverging results, showing that something was wrong in either evolution theory or pulsation theory or both. For some binary Cepheids dynamical masses, which are independent of pulsation and evolution theories, can be determined. V636 Sco is one of a handful of Cepheid binaries whose companions are bright enough in the ultraviolet that orbital radial velocities can be measured. We have here attempted to determine the radial velocity of the companion V636 Sco B to the Cepheid V636 Sco A by means of two Hubble Space Telescope (HST) spectra taken at phases of minimum and maximum Cepheid orbital velocities. The ratio of the orbital velocity of the companion and the Cepheid (which is the inverse of their mass ratio) came out to be 1.25 +/- 0.17. V636 Sco B has a spectral type B9.5 V, for which we expect a stellar mass of 2.5 M-.. For the Cepheid we thus determine a mass of 3.1 +/- 0.4 Mo, which is surprisingly low. If true, such a low mass would indicate an extremely large amount of excess mixing, which is very unlikely. We discuss the likely possibility that V636 Sco B may itself be a binary with an unseen secondary, in which case the mass derived from the two measurements discussed above is not correct. Although the error limits for the mass of each Cepheid are rather large, the combined mass-luminosity relation for all Cepheids studied by us so far by means of HST spectra indicates excess mixing corresponding to core convective overshoot by 0.25 to about 0.5 pressure scale height in the main-sequence progenitors of the Cepheids. C1 Univ Washington, Dept Astron, Seattle, WA 98195 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Canterbury, Dept Phys & Astron, Mt John Univ Observ, Christchurch 1, New Zealand. S African Astron Observ, ZA-7935 Cape Town, South Africa. Comp Sci Corp, Greenbelt, MD 20771 USA. RP Bohm-Vitense, E (reprint author), Univ Washington, Dept Astron, Seattle, WA 98195 USA. EM erica@astro.washington.edu; evans@cfambl.harvard.edu; hrscarpenter@tmal.gasfc.nasa.gov; cottrell@cantva.canterbury.ac.nz; hrsrobinson@tmal.gsfc.nasa.gov RI Carpenter, Kenneth/D-4740-2012 NR 28 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 OCT 1 PY 1998 VL 505 IS 2 BP 903 EP 909 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500033 ER PT J AU Gwinn, CR Britton, MC Reynolds, JE Jauncey, DL King, EA McCullough, PM Lovell, JEJ Preston, RA AF Gwinn, CR Britton, MC Reynolds, JE Jauncey, DL King, EA McCullough, PM Lovell, JEJ Preston, RA TI Interstellar optics SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : general; radiative transfer; scattering; techniques : interferometric; telescopes ID SCATTER-BROADENED IMAGE; DENSITY TURBULENCE; ANGULAR DIAMETER; INNER SCALE; SCINTILLATION; PRINCIPLES; RESOLUTION; CYGNUS-X-3; COHERENCE; SPECTRUM AB We discuss the effects of finite source size on the diffraction pattern produced by scattering in a thin screen, particularly as applied to radio-wave scattering by density fluctuations in the interstellar plasma. Using the stationary phase approximation, we express the Kirchhoff integral for the diffracted electric field as a phasor sum and show that source structure introduces correlations between such sums, combined to form intensity or interferometric visibility. We obtain expressions for the probability distribution functions of intensity of a source of finite size and of interferometric visibility on a baseline shorter than the scale of the diffraction pattern. We also present expressions for the first and second moments of intensity and visibility, for arbitrary source structure, and for sources with Gaussian distribution of intensity. We also present results for sources that radiate Gaussian beams, possibly with imperfect spatial coherence. With these results, observations of the diffracted electric field yield information on the structure of the scattered source with angular resolution corresponding to the diffraction limit of the scattering disk. These results are of interest for studies of pulsars and other extremely compact radio sources. C1 Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. Australia Telescope Natl Facil, Epping, NSW 2121, Australia. Univ Tasmania, Dept Phys, Hobart, Tas 7001, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Gwinn, CR (reprint author), Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA. RI King, Edward/A-1473-2012 OI King, Edward/0000-0002-6898-2130 NR 47 TC 36 Z9 36 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 OCT 1 PY 1998 VL 505 IS 2 BP 928 EP 940 DI 10.1086/306178 PN 1 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500036 ER PT J AU Aschwanden, MJ Kliem, B Schwarz, U Kurths, J Dennis, BR Schwartz, RA AF Aschwanden, MJ Kliem, B Schwarz, U Kurths, J Dennis, BR Schwartz, RA TI Wavelet analysis of solar flare hard X-rays SO ASTROPHYSICAL JOURNAL LA English DT Article DE methods : statistical; Sun : flares; Sun : X-rays, gamma rays; waves ID COUNTING DETECTOR IMAGES; OF-FLIGHT MEASUREMENTS; 1992 JANUARY 13; 1980 JUNE 7; RADIO SPIKES; PARTICLE-ACCELERATION; MAGNETIC RECONNECTION; FRACTAL DIMENSIONS; BULK ENERGIZATION; ELECTRON-BEAMS AB We apply a multiresolution analysis to hard X-ray (HXR) time profiles f(t) of solar flares. This method is based on a wavelet transform (with triangle-shaped wavelets), which yields a dynamic decomposition of the power at different timescales T, the scalogram P(T, t). For stationary processes, time-averaged power coefficients, the scalegram S(T), can be calculated. We develop an algorithm to transform these (multiresolution) scalegrams S(T) into a standard distribution function of physical timescales, N(T). We analyze 647 solar flares observed with the Compton Gamma Ray Observatory (CGRO), recorded at energies greater than or equal to 25 keV with a time resolution of 64 ms over 4 minutes in each flare. The main findings of our wavelet analysis are: 1. In strong flares, the shortest detected timescales are found in the range T-min approximate to 0.1-0.7 s. These minimum timescales are found to correlate with the flare loop size r (measured from Yohkoh images in 46 flares), according to the relation T-min(r) approximate to 0.5(r/10(9) cm) s. Moreover, these minimum timescales are subject to a cutoff, T-min(n(e)) greater than or similar to T-Defl(n(e)), which corresponds to the electron collisional deflection time at the loss-cone site of the hare loops (inferred from energy-dependent time delays in CGRO data). 2. In smoothly varying flares, the shortest detected timescales are found in the range T-min approximate to 0.5-5 s. Because these smoothly varying flares exhibit also large trap delays, the lack of detected fine structure is likely to be caused by the convolution with trapping times. 3. In weak flares, the shortest detected timescales cover a large range, T-min approximate to 0.5-50 s, mostly affected by Poisson noise. 4. The scalegrams S(T) show a power-law behavior with slopes of beta(max) approximate to 1.5-3.2 (for strong hares) over the timescale range of [T-min, T-peak]. Dominant peaks in the timescale distribution N(T) are found in the range T-peak approximate to 0.5-10(2) s, often coinciding with the upper cutoff of N(T). These observational results indicate that the fastest significant HXR time structures detected with wavelets tin strong flares) are related to physical parameters of propagation and collision processes. If the minimum timescale T-min is associated with an Alfvenic crossing time through elementary acceleration cells, we obtain sizes of r(acc) approximate to 75-750 km, which have a scale-invariant ratio r(acc)/r approximate to 0.03 to flare loops and are consistent with cell sizes inferred from the frequency bandwidth of decimetric millisecond spikes. C1 Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Astrophys Inst Potsdam, D-14482 Potsdam, Germany. Univ Potsdam, Inst Theoret Phys & Astrophys, D-14469 Potsdam, Germany. NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Aschwanden, MJ (reprint author), Lockheed Martin, Solar & Astrophys Lab, Dept H112, Bldg 252,3251 Hanover St, Palo Alto, CA 94304 USA. RI Dennis, Brian/C-9511-2012 NR 89 TC 48 Z9 48 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD OCT 1 PY 1998 VL 505 IS 2 BP 941 EP 956 DI 10.1086/306200 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LF UT WOS:000077778500037 ER PT J AU Marcy, GW Butler, RP Vogt, SS Fischer, D Lissauer, JJ AF Marcy, GW Butler, RP Vogt, SS Fischer, D Lissauer, JJ TI A planetary companion to a nearby M4 dwarf, Gliese 876 SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary systems; stars : individual (Gliese 876) ID ECHELLE-SPECTROMETER; STARS; SYSTEMS; ORIGIN AB Doppler measurements of the M4 dwarf star Obese 876 taken at both Lick and Keck Observatories reveal periodic, Keplerian velocity variations with a period of 61 days. The orbital fit implies that the companion has a mass of M = 2.1 M-JUP/sin i, an orbital eccentricity of e = 0.27 +/- 0.03, and a semimajor axis of a = 0.21 AU. The planet is the first found around an M dwarf and was drawn from a survey of 24 such stars at Lick Observatory. It is the closest extrasolar planet yet found, providing opportunities for follow-up detection. The presence of a giant planet on a noncircular orbit, 0.2 AU from a 0.32 M. star, presents a challenge to planet formation theory. This planet detection around an M dwarf suggests that giant planets are numerous in the Galaxy. C1 San Francisco State Univ, Dept Phys & Astron, San Francisco, CA 94132 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Anglo Australian Observ, Epping, NSW 2121, Australia. Univ Calif Santa Cruz, UCO Lick Observ, Santa Cruz, CA 95064 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Marcy, GW (reprint author), San Francisco State Univ, Dept Phys & Astron, San Francisco, CA 94132 USA. RI Butler, Robert/B-1125-2009 NR 23 TC 148 Z9 148 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 OCT 1 PY 1998 VL 505 IS 2 BP L147 EP L149 DI 10.1086/311623 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LH UT WOS:000077778700019 ER PT J AU Simpson, C Meadows, V AF Simpson, C Meadows, V TI The nuclear spectrum of the radio galaxy NGC 5128 (Centaurus A) SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : individual (NGC 5128, Centaurus A); galaxies : nuclei; infrared : galaxies ID MASSIVE BLACK-HOLE; SUPERNOVA-REMNANTS; GALACTIC NUCLEI; IONIZED-GAS; NGC-5128; DISK; SPECTROSCOPY; EMISSION; SHOCK; TELESCOPE AB We present near-infrared spectra of the nuclear disk in the nearby radio galaxy NGC 5128 (Centaurus A). On the basis of the observed strengths of the [S III] 0.9532 mu m and [Fe II] 1.2567 mu m lines, we classify NGC 5128 as a LINER. Modeling of the strengths of these and additional Lines suggests that the nuclear region is powered by shocks rather than by photoionization. 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 40 TC 3 Z9 3 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 OCT 1 PY 1998 VL 505 IS 2 BP L99 EP L102 DI 10.1086/311616 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LH UT WOS:000077778700008 ER PT J AU Yaqoob, T George, IM Turner, TJ Nandra, K Ptak, A Serlemitsos, PJ AF Yaqoob, T George, IM Turner, TJ Nandra, K Ptak, A Serlemitsos, PJ TI A peculiar emission-line feature in the X-ray spectrum of the quasar PKS 0637-752 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; quasars : emission lines; quasars : individual (PKS 0637-752); X-rays : galaxies ID SEYFERT-GALAXIES; EXOSAT AB We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 0637-752 (redshift 0.654), covering the 0.8-15 keV band in the quasar frame. We find the source to have a luminosity of similar to 10(46) ergs s(-1) in the 2-10 keV band, which is a factor of similar to 3 lower than during a previous Ginga observation. The continuum appears to be well modeled by a simple power law with Gamma = 1.64 +/- 0.07, with no evidence for absorption by material intrinsic to the quasar or Fe-K emission (with an equivalent width less than or similar to 80 eV at 90% confidence). However, we do find evidence for a narrow emission line at an energy 1.60 +/- 0.07 keV and equivalent width 59(-34)(+38) eV (both in the quasar frame). Line emission at these energies has not been observed in any other active galaxy or quasar to date. We reject the possibility that this line is the result of instrumental artifacts and briefly explore possible identifications. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. Natl Acad Sci, Natl Res Council Res Associate, Washington, DC USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. RP Yaqoob, T (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 36 TC 24 Z9 24 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 OCT 1 PY 1998 VL 505 IS 2 BP L87 EP L90 DI 10.1086/311618 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 152LH UT WOS:000077778700005 ER PT J AU Schaefer, BE Cline, TL Hurley, KC Laros, JG AF Schaefer, BE Cline, TL Hurley, KC Laros, JG TI Gamma-ray burst counterparts: Optical data SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxies, photometry; gamma rays, bursts ID HUBBLE-SPACE-TELESCOPE; 28 FEBRUARY 1997; ERROR BOX; 1978 NOVEMBER; STANDARD STARS; FY AQUILAE; TRANSIENT; LOCALIZATIONS; SEARCH; ULTRAVIOLET AB The surest solution of the gamma-ray burst (GRB) mystery is to find an unambiguous low-energy quiescent counterpart. To this end, we have intensively searched within the smallest GRB error boxes for any counterpart candidates. This paper reports on 255 hr of exposure with ground-based telescopes since 1981. We report our results in the U, B, V, R. I, J, H, and K bands. We find the usual array of mildly unusual sources in the boxes, but none is sufficiently unusual to suggest a causal connection. We find that the smallest boxes are empty to fairly deep magnitudes. This fact can be of significance since virtually all cosmological models place bright bursters inside normal host galaxies at moderate distances. To allow for quantitative evaluation of the predictions of these models, we have compiled a list of limits on the brighest galaxy inside each of the 26 regions in various bands. This list was compiled from our own results as well as from the published literature. The limits on host galaxy luminosities from these data are substantially more restrictive than the limits from recent optical transients because the bursts we report on are much brighter than the bursts with optical transients. C1 Yale Univ, Dept Phys, New Haven, CT 06520 USA. NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Schaefer, BE (reprint author), Yale Univ, Dept Phys, POB 208121, New Haven, CT 06520 USA. EM schaefer@grb2.physics.yale.edu; cline@lheavx.gsfc.nas.gov; khurley@sunspot.ssl.berkeley.edu; jlaros@lpl.arizona.edu NR 82 TC 11 Z9 11 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD OCT PY 1998 VL 118 IS 2 BP 353 EP 389 DI 10.1086/313141 PG 37 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 130JQ UT WOS:000076517300004 ER PT J AU Laros, JG Hurley, KC Fenimore, EE Klebesadel, RW Briggs, MS Kouveliotou, C McCollough, ML Fishman, GJ Meegan, CA Cline, TL Boer, M Niel, M AF Laros, JG Hurley, KC Fenimore, EE Klebesadel, RW Briggs, MS Kouveliotou, C McCollough, ML Fishman, GJ Meegan, CA Cline, TL Boer, M Niel, M TI Gamma-ray burst arrival time localizations: Simultaneous observations by Pioneer Venus Orbiter, Compton Gamma-Ray Observatory, and Ulysses SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE gamma rays, bursts; methods, observational ID RADIO AB Between the Compton Gamma Ray Observatory (CGRO) launch in 1991 April and the Pioneer Venus Orbiter (PVO) demise in 1992 October, concurrent coverage by CGRO, PVO, and Ulysses was obtained for several hundred gamma-ray bursts (GRBs). Although most of these were below the PVO and UIysses thresholds, 37 were positively detected by all three spacecraft, with data quality adequate for quantitative localization analysis. All were localized independently to similar to 2 degrees accuracy by the CGRO Burst and Transient Source Experiment (BATSE), and three were also localized by COMPTEL. we computed arrival-time error boxes, whose larger dimensions range from about 2' to several degrees and whose smaller dimensions are in the arcminute range. Twelve have areas less than 10 arcmin(2), and only four have areas greater than 1 deg(2). The area of the smallest box is 0.44 arcmin(2). We find that the overall BATSE localization accuracy for these events is consistent with the most recent stated uncertainties. This work indicates that the ROSAT soft X-ray source found within a preliminary IPN error box for GB920501 (Trig 1576) (Hurley et al.) is less likely to be the GRB counterpart than previously reported. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Alabama, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, USRA, Huntsville, AL 35812 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Ctr Etud Spatiale Rayonnements, F-31029 Toulouse, France. RP Laros, JG (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. OI Boer, Michel/0000-0001-9157-4349 NR 18 TC 19 Z9 19 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5801 S ELLIS AVENUE, CHICAGO, IL 60637 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD OCT PY 1998 VL 118 IS 2 BP 391 EP 399 DI 10.1086/313139 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 130JQ UT WOS:000076517300005 ER PT J AU Greenleaf, JE Farrell, PA Loomis, JL Fedele, MJ West, J Rossler, A Hinghofer-Szalkay, H AF Greenleaf, JE Farrell, PA Loomis, JL Fedele, MJ West, J Rossler, A Hinghofer-Szalkay, H TI Sodium chloride citrate beverages attenuate hypovolemia in men resting 12 h at 2800 m altitude SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article ID ACUTE PSYCHOLOGICAL STRESS; PLASMA-VOLUME; HUMANS AB Background: The mechanism for reduction and restoration of total body water and plasma volume (PV) during initial exposure to acute altitude (ALT) is not clear but may involve involuntary dehydration; i.e., delayed voluntary fluid intake. Method: Ten men (24 +/- SD 3 yr, 180.8 +/- 8.1 cm height, 78.8 +/- 12.8 kg weight, 1.99 +/- 0.19 m(2) surface area, and 12.2 +/- 4.0% body fat) were in a semi-reclining position for 12 h in a chamber at 2800 m (539 mmHg) ALT or at 321 m (732 mmHg; ground). They ate a controlled breakfast (450 kcal + 3 ml . kg(-1) H2O) on the ground, and lunch and dinner at ALT (or on the ground) for a total daily intake of 2850 kcal (14% PRO, 67% CHO, 16% fat, 2.6g NaCl). At hour 10 they consumed fluid-electrolyte beverages or water (72 ml . kg(-1), 948 ml . d(-1)) in 4 sessions at weekly intervals. Beverage compositions were: a) 185 mEq . L-1 Na+, 283 mOsm . kg(-1) b) 21.6 mEq . L-1 Na+, 365 mOsm . kg(-1); c) water at ALT; and d) water on the ground. Results: After 10 h at ALT % Delta PV (Hb-Hct] decreased (p < 0.05) by: a) 9.0 +/- SE 1.5%; b) 6.2 +/- 1.7%; c) 7.4 +/- 2.2%; and d) by 9.0 +/- 2.4%, respectively. After drinking hom 1000-1030 h, PV at 1200 h changed by: a) +8.3 +/- SE 2.0% (p < 0.05); b) +2.8 +/- 2.7% (NS); c) -0.9 +/- 1.5% (NS); and d) by +0.8 +/- 3.5% (NS), respectively. The similar ground-induced hypovolemia suggests a response to confinement rather than an ALT effect and involuntary dehydration does not appear to be implicated. Conclusion: The significant increase in PV after consuming the (a) NaCl-NaCitrate beverage indicates that drink ionic composition appears to be more important than its osmolality for restoring PV in these conditions. Practical considerations: Because this hypovolemia was probably due to the confinement rather that reduced ambient pressure, appropriate countermeasures could be consumption of isotonic beverages, elastic stockings, leg exercise, and leg elevation. C1 NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. Penn State Univ, Noll Physiol Res Ctr, University Pk, PA 16802 USA. Karl Franzens Univ Graz, Dept Physiol, Graz, Austria. Austrian Soc Aerosp Med, Inst Adapt & Spaceflight Physiol, Graz, Austria. RP Greenleaf, JE (reprint author), NASA, Ames Res Ctr, Gravitat Res Branch 239 11, Lab Human Environm Physiol, Moffett Field, CA 94035 USA. RI Roessler, Andreas/A-5751-2008 NR 25 TC 7 Z9 7 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 OCT PY 1998 VL 69 IS 10 BP 936 EP 943 PG 8 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 123KY UT WOS:000076125400002 PM 9773893 ER PT J AU Stone, RP Johnson, SW AF Stone, RP Johnson, SW TI Prolonged exposure to mine tailings and survival and reproductive success of ovigerous tanner crabs (Chionoecetes bairdi) SO BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY LA English DT Article C1 NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, Juneau, AK 99801 USA. RP Stone, RP (reprint author), NOAA, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 19 TC 1 Z9 1 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0007-4861 J9 B ENVIRON CONTAM TOX JI Bull. Environ. Contam. Toxicol. PD OCT PY 1998 VL 61 IS 4 BP 548 EP 556 PG 9 WC Environmental Sciences; Toxicology SC Environmental Sciences & Ecology; Toxicology GA 124NA UT WOS:000076187600019 PM 9811962 ER PT J AU Servain, J Busalacchi, AJ McPhaden, MJ Moura, AD Reverdin, G Vianna, M Zebiak, SE AF Servain, J Busalacchi, AJ McPhaden, MJ Moura, AD Reverdin, G Vianna, M Zebiak, SE TI A Pilot Research Moored Array in the Tropical Atlantic (PIRATA) SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID SEA-SURFACE TEMPERATURE; GENERAL-CIRCULATION MODEL; NINO SOUTHERN-OSCILLATION; PACIFIC WARM POOL; EQUATORIAL ATLANTIC; NORTHEAST BRAZIL; DECADAL VARIABILITY; MIXED-LAYER; WIND STRESS; OCEAN AB The tropical Atlantic Ocean is characterized by a large seasonal cycle around which there are climatically significant interannual and decadal timescale variations. The most pronounced of these interannual variations are equatorial warm events, somewhat similar to the El Nino events for the Pacific, and the so-called Atlantic sea surface temperature dipole. Both of these phenomena in turn may be related to El Nino-Southern Oscillation variability in the tropical Pacific and other modes of regional climatic variability in ways that are not yet fully understood. PIRATA (Pilot Research Moored Array in the Tropical Atlantic) will address the lack of oceanic and atmospheric data in the tropical Atlantic, which limits our ability to make progress on these important climate issues. The PIRATA array consists of 12 moored Autonomous Temperature Line Acquisition System buoy sites to be occupied during the years 1997-2000 for monitoring the surface variables and upper-ocean thermal structure at key locations in the tropical Atlantic. Meteorological and oceanographical measurements are transmitted via satellite in real time and are available to all interested users in the research or operational communities. The total number of moorings is a compromise between the need to put out a large enough array for a long enough period of time to gain fundamentally new insights into coupled ocean-atmosphere interactions in the region, while at the same time recognizing the practical constraints of resource limitations in terms of funding, ship time, and personnel. Seen as a pilot Global Ocean Observing System/Global Climate Observing System experiment, PIRATA contributes to monitoring the tropical Atlantic in real time and anticipates a comprehensive observing system that could be operational in the region for the 2000s. C1 ORSTOM, Ctr Brest, F-29280 Plouzane, France. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. NOAA, Pacific Marine Environm Lab, Seattle, WA 98115 USA. Lamont Doherty Earth Observ, Int Res Inst Climate Predict, Palisades, NY 10964 USA. LEGOS, GRGS, Toulouse, France. INPE, Sao Paulo, Brazil. RP Servain, J (reprint author), ORSTOM, Ctr Brest, BP 70, F-29280 Plouzane, France. EM servain@orstom.fr RI McPhaden, Michael/D-9799-2016; OI Vianna, Marcio/0000-0002-3616-7772 NR 57 TC 131 Z9 133 U1 0 U2 11 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0003-0007 EI 1520-0477 J9 B AM METEOROL SOC JI Bull. Amer. Meteorol. Soc. PD OCT PY 1998 VL 79 IS 10 BP 2019 EP 2031 DI 10.1175/1520-0477(1998)079<2019:APRMAI>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 132PK UT WOS:000076638600001 ER PT J AU Ohmura, A Dutton, EG Forgan, B Frohlich, C Gilgen, H Hegner, H Heimo, A Konig-Langlo, G McArthur, B Muller, G Philipona, R Pinker, R Whitlock, CH Dehne, K Wild, M AF Ohmura, A Dutton, EG Forgan, B Frohlich, C Gilgen, H Hegner, H Heimo, A Konig-Langlo, G McArthur, B Muller, G Philipona, R Pinker, R Whitlock, CH Dehne, K Wild, M TI Baseline Surface Radiation Network (BSRN/WCRP): New precision radiometry for climate research SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY LA English DT Article ID CONTINUUM ABSORPTION; IRRADIANCE; SYSTEM; MODEL AB To support climate research, the World Climate Research Programme (WCRP) initiated a new radiometric network, the Baseline Surface Radiation Network (BSRN). The network aims at providing validation material for satellite radiometry and climate models. It further aims at detecting long-term variations in irradiances at the earth's surface, which are believed to play an important role in climate change. The network and its instrumentation are designed 1) to cover major climate zones, 2) to provide the accuracy required to meet the objectives, and 3) to ensure homogenized standards for a long period in the future. The limits of the accuracy are defined to reach these goals. The suitable instruments and instrumentations have been determined and the methods for observations and data management have been agreed on at all stations. Measurements of irradiances are at 1 Hz, and the 1-min statistics (mean, standard deviation, and extreme values) with quality flags are stored at a centralized data archive at the WCRP's World Radiation Monitoring Center (WRMC) in Zurich, Switzerland. The data are quality controlled both at stations and at the WRMC. The original 1-min irradiance statistics will be stored at the WRMC for 10 years, while hourly mean values will be transferred to the World Radiation Data Center in St. Petersburg, Russia. The BSRN, consisting of 15 stations, covers the earth's surface from 80 degrees N to 90 degrees S, and will soon be joined by seven more stations. The data are available to scientific communities in various ways depending on the communication environment of the users. The present article discusses the scientific base, organizational and technical aspects of the network, and data retrieval methods; shows various application possibilities; and presents the future tasks to be accomplished. C1 ETH Zurich, Inst Geog, CH-8057 Zurich, Switzerland. NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Bur Meteorol, Melbourne, Vic, Australia. Phys Meteorol Observ, World Radiat Ctr, Davos, Switzerland. Swiss Meteorol Inst, Payerne Aerol Stn, Payerne, Switzerland. Alfred Wegener Inst Polar & Marine Res, D-2850 Bremerhaven, Germany. Atmospher Environm Serv, Downsview, ON, Canada. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Deutsch Wetterdienst, Observ Potsdam, Potsdam, Germany. RP Ohmura, A (reprint author), ETH Zurich, Inst Geog, Winterthurerstr 190, CH-8057 Zurich, Switzerland. EM ohmura@geo.umnw.ethz.ch RI Pinker, Rachel/F-6565-2010; Wild, Martin/J-8977-2012; Konig-Langlo, Gert/K-5048-2012 OI Konig-Langlo, Gert/0000-0002-6100-4107 NR 42 TC 445 Z9 450 U1 4 U2 30 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 OCT PY 1998 VL 79 IS 10 BP 2115 EP 2136 DI 10.1175/1520-0477(1998)079<2115:BSRNBW>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 132PK UT WOS:000076638600006 ER PT J AU Carls, MG Marty, GD Meyers, TR Thomas, RE Rice, SD AF Carls, MG Marty, GD Meyers, TR Thomas, RE Rice, SD TI Expression of viral hemorrhagic septicemia virus in prespawning Pacific herring (Clupea pallasi) exposed to weathered crude oil SO CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES LA English DT Article ID EXXON-VALDEZ OIL; PRINCE-WILLIAM-SOUND; PETROLEUM-HYDROCARBONS; MARINE FISH; SPILL; SEDIMENTS; HISTOPATHOLOGY; SEAWATER; TISSUES; ALASKA AB Expression of subclinical viral infection in response to toxicant exposure has not previously been reported, but evidence presented herein indicates that activation of viral hemorrhagic septicemia virus (VHSV) may occur in Pacific herring (Clupea pallasi) exposed to crude oil encountered after an oil spill. Decreased incidence of hepatic inflammatory cells as a function of total polynuclear aromatic hydrocarbon (TPAH) concentration was evidence for immunosuppression in exposed fish, and decreased immune surveillance is a possible mechanism by which subclinical VHSV could be reactivated. Adult Pacific herring of unknown status regarding infection by VHSV were captured from the wild and exposed to weathered crude oil for 16-18 days. TPAH concentration in tissue, VHSV prevalence, and mortality were correlated with dose. Histopathologic lesions were significantly correlated with TPAH concentration and prevalence of VHSV, but not gender or length. Significant lesions included increased hepatocelIular necrosis, splenic thrombosis, and decreased inflammation in the liver. C1 NOAA, Natl Marine Fisheries Serv, Auke Bay Lab, Juneau, AK 99801 USA. Univ Calif Davis, Sch Vet Med, Dept Anat Physiol & Cell Biol, Davis, CA 95616 USA. Alaska Dept Fish & Game, Juneau Fish Pathol Lab, CFMD Div, Juneau, AK 99802 USA. Calif State Univ Chico, Dept Biol Sci, Chico, CA 95959 USA. RP Carls, MG (reprint author), NOAA, Natl Marine Fisheries Serv, Auke Bay Lab, 11305 Glacier Highway, Juneau, AK 99801 USA. EM mark.carls@noaa.gov NR 30 TC 25 Z9 27 U1 1 U2 7 PU CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS PI OTTAWA PA 1200 MONTREAL ROAD, BUILDING M-55, OTTAWA, ON K1A 0R6, CANADA SN 0706-652X J9 CAN J FISH AQUAT SCI JI Can. J. Fish. Aquat. Sci. PD OCT PY 1998 VL 55 IS 10 BP 2300 EP 2309 DI 10.1139/cjfas-55-10-2300 PG 10 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 143KA UT WOS:000077253300010 ER PT J AU Lau, KM Bua, W AF Lau, KM Bua, W TI Mechanisms of monsoon Southern Oscillation coupling: insights from GCM experiments SO CLIMATE DYNAMICS LA English DT Article ID ASIAN SUMMER MONSOON; SEA-SURFACE TEMPERATURES; BIENNIAL OSCILLATION; CLIMATE; VARIABILITY; OCEAN; ENSO; RAINFALL; SYSTEM; LAND AB The relative roles of internal atmospheric dynamics, land surface evaporation and sea surface temperature (SST) forcings on the coupling between the Asian monsoon (AM) and the Southern Oscillation (SO) are investigated in a series of GCM experiments. Results confirm previous studies indicating that the characteristic large-scale pattern of the SO is due primarily to SST anomaly (SSTA) forcing. The AM circulation anomalies are coupled to the SO via a characteristic upper level circulation couplet over the equatorial central Pacific. This couplet acts as a radiating node for teleconnection signals originating from the AM region to the extratropics. Generally, a weak AM is associated with warm SST over the eastern equatorial Pacific, concomitant with the negative phase of the SO, i.e., low (high) surface pressure over Tahiti (Darwin). The reverse holds for strong AM. Two wavetrains associated with the AM fluctuation have been identified: one arcing over northeastern Asia via the Aleutians to North American, and another emanating from northwestern Europe, via Siberia to northern India. Internal dynamics appear to underpin the origin of these wavetrains, which are strongly tempered by SSTA forcing and to a lesser degree by interactive land processes. Regionally, land-atmosphere interaction seems to have the strongest impact over East Asia/Indochina and the adjacent oceanic region of the South China Sea. Here, land-atmosphere interaction is responsible for the enhancement of a subseasonal scale see-saw oscillation in precipitation between land and the adjacent oceans. A local land-atmosphere feedback mechanism involving strong coupling between the hydrologic and energy cycles is identified. It is suggested that the interaction among precipitation, moisture convergence and land surface turbulent heat fluxes and radiation processes play key roles in determining the fast (subseasonal and shorter scales) response of the AM. On these time scales, the occurrences of cool/wet and hot/dry states associated with the precipitation seesaw appear to be chaotic. However, the preferred occurrence of a given state and the abrupt transition between states are dependent on the large-scale circulation and radiation forcings induced by the SO. One of the more provocative findings here is that effects of land-atmosphere interaction do not seem to alter the basic planetary scale features of the AM-SO system. As a result, the interannual variability of the coupled AM-SO is relatively small in the absence of anomalous SST forcing. Yet, the local effect of land-atmosphere interaction on AM is quite pronounced and dependent upon the large-scale forcings related to SO. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. RP Lau, KM (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. EM lau@climate.gsfc.nasa.gov RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 33 TC 45 Z9 45 U1 0 U2 7 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0930-7575 J9 CLIM DYNAM JI Clim. Dyn. PD OCT PY 1998 VL 14 IS 11 BP 759 EP 779 DI 10.1007/s003820050253 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 129GE UT WOS:000076454800001 ER PT J AU Goldin, DS Venneri, SL Noor, AK AF Goldin, DS Venneri, SL Noor, AK TI Beyond incremental change SO COMPUTER LA English DT Article AB In the next 25 years NASA has ambitious goals: It wants to accurately predict climate and resources over decades, not just daps. It wants to detect Earth-sized planets 600 trillion miles away with a telescope powerful enough to determine signs of life. It wants to use the International Space Station as a platform for an astronaut to visit Mars. This is the big vision, and to many it may sound more like science fiction. To help achieve these goals, in 1997 NASA and the University of Virginia's Center for Advanced Computational Technology began planning and developing the Intelligent Synthesis Environment. The ISE aims to link scientists, design teams, manufacturers, suppliers, and consultants in the creation and operation of an aerospace system and in synthesizing its missions. The ultimate goal is to significantly increase creativity and knowledge and eventually dissolve rigid cultural boundaries among diverse engineering and science teams. C1 Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, Hampton, VA 23681 USA. NASA, US Civil Space Program, Washington, DC USA. NASA, Adv Civil Aeroanut Technol Programs, Washington, DC USA. NASA Headquarters, Technol Leadership Council, Washington, DC USA. RP Goldin, DS (reprint author), Univ Virginia, NASA, Langley Res Ctr, Ctr Adv Computat Technol, 11 W Taylor St, Hampton, VA 23681 USA. EM a.k.noor@larc.nasa.gov NR 11 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 OCT PY 1998 VL 31 IS 10 BP 31 EP + DI 10.1109/2.722277 PG 10 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering SC Computer Science GA 125BZ UT WOS:000076218700011 ER PT J AU Wainwright, TC Waples, RS AF Wainwright, TC Waples, RS TI Prioritizing Pacific salmon stocks for conservation: Response to Allendorf et al. SO CONSERVATION BIOLOGY LA English DT Editorial Material ID TRENDS C1 NOAA, Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Conservat Biol Div, Seattle, WA 98112 USA. RP Wainwright, TC (reprint author), Natl Marine Fisheries Serv, NW Fisheries Sci Ctr, Fishery Anal & Monitoring Div, 2030 S Marine Sci Dr, Newport, OR 97365 USA. EM Thomas.Wainwright@NOAA.gov RI Wainwright, Thomas/F-4550-2010; Waples, Robin/K-1126-2016 OI Wainwright, Thomas/0000-0001-5147-479X; NR 18 TC 7 Z9 7 U1 1 U2 4 PU BLACKWELL SCIENCE INC PI MALDEN PA 350 MAIN ST, MALDEN, MA 02148 USA SN 0888-8892 J9 CONSERV BIOL JI Conserv. Biol. PD OCT PY 1998 VL 12 IS 5 BP 1144 EP 1147 DI 10.1046/j.1523-1739.1998.97385.x PG 4 WC Biodiversity Conservation; Ecology; Environmental Sciences SC Biodiversity & Conservation; Environmental Sciences & Ecology GA 126BL UT WOS:000076272800030 ER PT J AU Glass, DE AF Glass, DE TI Cryogenic mechanical properties of Gore-Tex (R) fabric SO CRYOGENICS LA English DT Article DE PTFE; mechanical properties AB Mechanical properties of a Gore-Tex(R) woven fabric were determined at ambient, elevated, liquid nitrogen, and liquid helium temperatures. Data is presented for both creep and static strength testing at temperatures from 20 K to 450 K, and showed an increasing strength with decreasing temperature. The material appears well suited for applications where a strong and flexible material is required at cryogenic temperatures. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Analyt Serv & Mat Inc, Hampton, VA 23666 USA. RP Glass, DE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 3 TC 0 Z9 0 U1 0 U2 3 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD OCT PY 1998 VL 38 IS 10 BP 983 EP 987 DI 10.1016/S0011-2275(98)00090-3 PG 5 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 151VM UT WOS:000077741400006 ER PT J AU Turner, RT Evans, GL Cavolina, JM Halloran, B Morey-Holton, E AF Turner, RT Evans, GL Cavolina, JM Halloran, B Morey-Holton, E TI Programmed administration of parathyroid hormone increases bone formation and reduces bone loss in hindlimb-unloaded ovariectomized rats SO ENDOCRINOLOGY LA English DT Article ID CANCELLOUS BONE; GROWING-RATS; INTERMITTENT TREATMENT; SEXUALLY MATURE; TRABECULAR BONE; HISTOMORPHOMETRY; SPACEFLIGHT; ADAPTATION; TURNOVER; ESTROGEN AB Gonadal insufficiency and reduced mechanical usage are two important risk factors for osteoporosis. The beneficial effects of PTH therapy to reverse the estrogen deficiency-induced bone loss in the laboratory rat are well known, but the influence of mechanical usage in this response has not been established. In this study, the effects of programed administration of PTH on cancellous bone volume and turnover at the proximal tibial metaphysis were determined in hindlimb-unloaded, ovariectomized (OVX), 3-month-old Sprague-Dawley rats. PTH was administered to weight-bearing and hindlimb-unloaded OVX rats with osmotic pumps programed to deliver 20 mu g human PTH (similar to 80 mu g/kg.day) during a daily l-h infusion for 7 days. Compared with sham-operated rats, OVX increased longitudinal and radial bone growth, increased indexes of cancellous bone turnover, and resulted in net resorption of cancellous bone. Hindlimb unloading of OVX rats decreased longitudinal and radial bone growth, decreased osteoblast number, increased osteoclast number, and resulted in a further decrease in cancellous bone volume compared with those in weight-bearing OVX rats. Programed administration of PTH had no effect on either radial or longitudinal bone growth in weight-bearing and hindlimb-unloaded OVX rats. PTH treatment had dramatic effects on selected cancellous bone measurements; PTH maintained cancellous bone volume in OVX weight-bearing rats and greatly reduced cancellous bone loss in OVX hindlimb-unloaded rats. In the latter animals, PTH treatment prevented the hindlimb unloading-induced reduction in trabecular thickness, but the hormone was ineffective in preventing either the increase in osteoclast number or the loss of trabecular plates. Importantly, PTH treatment increased the retention of a baseline flurochrome label, osteoblast number, and bone formation in the proximal tibial metaphysis regardless of the level of mechanical usage. These findings demonstrate that programed administration of PTH is effective in increasing osteoblast number and bone formation and has beneficial effects on bone volume in the absence of weight-bearing and gonadal hormones. We conclude that the actions of PTH on cancellous bone are independent of the level of mechanical usage. C1 Mayo Clin & Mayo Fdn, Dept Orthoped, Rochester, MN 55905 USA. Mayo Clin & Mayo Fdn, Dept Biochem & Mol Biol, Rochester, MN 55905 USA. Vet Adm Med Ctr, San Francisco, CA 94121 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Turner, RT (reprint author), Mayo Clin & Mayo Fdn, Dept Orthoped, Room 3-69 Med Sci Bldg,200 1st St SW, Rochester, MN 55905 USA. NR 38 TC 55 Z9 55 U1 0 U2 1 PU ENDOCRINE SOC PI CHEVY CHASE PA 8401 CONNECTICUT AVE, SUITE 900, CHEVY CHASE, MD 20815-5817 USA SN 0013-7227 EI 1945-7170 J9 ENDOCRINOLOGY JI Endocrinology PD OCT PY 1998 VL 139 IS 10 BP 4086 EP 4091 DI 10.1210/en.139.10.4086 PG 6 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 121WE UT WOS:000076038100009 PM 9751486 ER PT J AU Stoner, AW Ray-Culp, M O'Connell, SM AF Stoner, AW Ray-Culp, M O'Connell, SM TI Settlement and recruitment of queen conch, Strombus gigas, in seagrass meadows: Associations with habitat and micropredators SO FISHERY BULLETIN LA English DT Article ID SP-I LARVAE; POPULATION-STRUCTURE; BIOLOGICAL DATA; STILL WATER; FLUME FLOWS; GROWTH; MORTALITY; PREDATION; GASTROPOD; BAHAMAS AB A suction dredge survey was conducted in the Bahamas in a tidal flow field system which contained a nursery ground for the economically significant gastropod Strombus gigas (queen conch). Settlement of larval conch within the system was associated with the specific location of the nursery and positively correlated with subsequent recruitment to the juvenile population (<45 mm shell length). Settlement was relatively independent of habitat features including depth, sediment characteristics, and macrophytes. Conversely, densities of micro-predators (small crabs, shrimp, and predaceous gastropods) capable of consuming early postsettlement conch were often correlated with habitat features such as seagrass shoot density, seagrass detritus, and organic content of the sediment. The density of small xanthid crabs (mode=1.5 mm carapace width) was positively correlated with density of live postsettlement conch (mean less than or equal to 4/m(2)), suggesting that conch settle in predator-prone areas or that the crabs respond numerically to small conch (or both). Densities of xanthids were very high (to >200/m(2)), and the crabs probably represent an important source of mortality for small conch in the primary nursery ground. Shells of dead conch indicated that molluscan and asteroid predators probably caused most of the predatory mortality on young conch that settled outside the nursery. Because critical settlement and recruitment habitats for queen conch are associated with particular hydrographic conditions, these habitats cannot be identified or predicted simply by mapping obvious features such as seagrass cover, depth, or sediment type. An understanding of dynamic processes, such as larval transport and retention, selective settlement mechanisms, and trophic ecology, will be required to identify critical nursery habitats. C1 Caribbean Marine Res Ctr, Vero Beach, FL 32963 USA. RP Stoner, AW (reprint author), Natl Marine Fisheries Serv, NE Fisheries Sci Ctr, NOAA, 74 Magruder Rd, Highlands, NJ 07732 USA. NR 52 TC 11 Z9 11 U1 1 U2 15 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 USA SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD OCT PY 1998 VL 96 IS 4 BP 885 EP 899 PG 15 WC Fisheries SC Fisheries GA 131UJ UT WOS:000076593400016 ER PT J AU Moles, A Heifetz, J Love, DC AF Moles, A Heifetz, J Love, DC TI Metazoan parasites as potential markers for selected Gulf of Alaska rockfishes SO FISHERY BULLETIN LA English DT Article C1 Natl Marine Fisheries Serv, Auke Bay Lab, Alaska Fisheries Sci Ctr, NOAA, Juneau, AK 99801 USA. RP Moles, A (reprint author), Natl Marine Fisheries Serv, Auke Bay Lab, Alaska Fisheries Sci Ctr, NOAA, 11305 Glacier Highway, Juneau, AK 99801 USA. NR 7 TC 14 Z9 16 U1 0 U2 1 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 USA SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD OCT PY 1998 VL 96 IS 4 BP 912 EP 916 PG 5 WC Fisheries SC Fisheries GA 131UJ UT WOS:000076593400019 ER PT J AU Gornostyrev, YN Marchenkov, VV Levit, VI Kaufman, M Veber, KV AF Gornostyrev, YN Marchenkov, VV Levit, VI Kaufman, M Veber, KV TI Effect of plastic deformation on the resistivity and point-defect distribution in the intermetallic compound NiAl SO FIZIKA METALLOV I METALLOVEDENIE LA Russian DT Article ID SINGLE-CRYSTALS; ELONGATION; BEHAVIOR; FEAL C1 Russian Acad Sci, Inst Met Phys, Ekaterinburg 620219, Russia. Univ Vienna, Inst Atom, A-1020 Vienna, Austria. Wroclaw Intense Magnet Fields & Low Temp Int Lab, PL-53529 Wroclaw, Poland. Univ Florida, Gainesville, FL USA. NASA, Langley Res Ctr, Analyt Lab, Hampton, VA 23665 USA. RP Gornostyrev, YN (reprint author), Russian Acad Sci, Inst Met Phys, Ul S Kovalevskoi 18, Ekaterinburg 620219, Russia. RI Gornostyrev, Yuri/K-5100-2013; Marchenkov, Vyacheslav/J-7698-2013 OI Gornostyrev, Yuri/0000-0001-7765-9805; Marchenkov, Vyacheslav/0000-0003-2044-1789 NR 12 TC 0 Z9 0 U1 0 U2 1 PU GOSUDARSTVENNOE NAUCHNO-TEKH PI MOSCOW PA IZDATELSTVO LITERATURY PO CHERNOI I TSYETNOI METALLURGII, MOSCOW, RUSSIA SN 0015-3230 J9 FIZ MET METALLOVED+ JI Fiz. Metallov Metalloved. PD OCT PY 1998 VL 86 IS 4 BP 62 EP 70 PG 9 WC Metallurgy & Metallurgical Engineering SC Metallurgy & Metallurgical Engineering GA 150KD UT WOS:000077663300006 ER PT J AU Anderson, SW Stofan, ER Plaut, JJ Crown, DA AF Anderson, SW Stofan, ER Plaut, JJ Crown, DA TI Block size distributions on silicic lava flow surfaces: Implications for emplacement conditions SO GEOLOGICAL SOCIETY OF AMERICA BULLETIN LA English DT Article ID LONG-VALLEY CALDERA; MOUNT-ST-HELENS; MEDICINE LAKE VOLCANO; OBSIDIAN DOME; NORTHERN CALIFORNIA; EASTERN CALIFORNIA; MAGMA ASCENT; CHAIN; CRYSTALLIZATION; CONSTRAINTS AB We determined block size distributions on the surfaces of Holocene silicic lava flows at the Inyo domes and the Medicine Lake volcano, and studied the development of blocks on the active Mount St. Helens and Mount Unzen lava domes to better understand the emplacement history of young viscous flows. We measured block chord lengths along perpendicular 25 m long transects within vent,jumbled, and ridged morphologic units. Vent regions generally contain the largest average block sizes and largest range of average blocks, whereas ridged areas tend to have the smallest average blocks. Observations at the active Mount St. Helens and Mount Unzen lava domes show that block size distributions reflect stress conditions during dow High extrusion rates produce small primary blocks and lead to rapid fracturing of the flow surface, whereas low extrusion rates allow large slabs to form in the vent area and lead to less severe fragmentation. A dramatic increase in the size of blocks evident in active vent regions may indicate a significant decrease in eruption rate, and thus could signal the cessation of extrusion. However, if the extrusion rate is too high or the cooling rate too low, a rigid crust and accompanying blocks will not form on an eruptive time scale, Blocks may fracture through mechanical and thermal processes as they move downslope, Most silicic lava flows reach a steady state downslope, where the average block size at the surface remains in the 20-30 cm size range with increasing distance from the vent. Fines (blocks <12 cm) do not accumulate on the flow surface because they slip toward the now interior through void spaces between surface blocks. We therefore expect long silicic lava flows to have blocky surfaces throughout their lengths, an important consideration for evaluation of planetary lava-flow emplacement. C1 Black Hills State Univ, Dept Phys Sci, Spearfish, SD 57799 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Pittsburgh, Dept Geol & Planetary Sci, Pittsburgh, PA 15260 USA. RP Anderson, SW (reprint author), Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. EM steve@hwr.arizona.edu NR 49 TC 32 Z9 32 U1 0 U2 3 PU ASSOC ENGINEERING GEOLOGISTS GEOLOGICAL SOCIETY AMER PI COLLEGE STN PA TEXAS A & M UNIV, DEPT GEOLOGY & GEOPHYSICS, COLLEGE STN, TX 77843-3115 USA SN 0016-7606 J9 GEOL SOC AM BULL JI Geol. Soc. Am. Bull. PD OCT PY 1998 VL 110 IS 10 BP 1258 EP 1267 DI 10.1130/0016-7606(1998)110<1258:BSDOSL>2.3.CO;2 PG 10 WC Geosciences, Multidisciplinary SC Geology GA 125AF UT WOS:000076214700003 ER PT J AU Meyer, B Tapponnier, P Bourjot, L Metivier, F Gaudemer, Y Peltzer, G Shunmin, G Zhitai, C AF Meyer, B Tapponnier, P Bourjot, L Metivier, F Gaudemer, Y Peltzer, G Shunmin, G Zhitai, C TI Crustal thickening in Gansu-Qinghai, lithospheric mantle subduction, and oblique, strike-slip controlled growth of the Tibet plateau SO GEOPHYSICAL JOURNAL INTERNATIONAL LA English DT Review DE deformation; fault propagation; fold and mountain growth; plate tectonics; plateau building; Tibet ID BENEATH SOUTHERN TIBET; HUI AUTONOMOUS REGION; CONTINENTAL COLLISION; CENTRAL-ASIA; TECTONIC IMPLICATIONS; CENOZOIC TECTONICS; ACTIVE TECTONICS; HAIYUAN FAULT; LATERAL SHEAR; EASTERN TIBET AB Fieldwork complemented by SPOT image analysis throws light on current crustal shortening processes in the ranges of northeastern Tibet (Gansu and Qinghai provinces, China). The ongoing deformation of Late-Pleistocene bajada aprons in the forelands of the ranges involves folding, at various scales, and chiefly north-vergent, seismogenic thrusts. The most active thrusts usually break the ground many kilometres north of the range-fronts, along the northeast limbs of growing, asymmetric ramp-anticlines. Normal faulting at the apex of other growing anticlines, between the range fronts and the thrust breaks, implies slip on blind ramps connecting distinct active decollement levels that deepen southwards. The various patterns of uplift of the bajada surfaces can be used to constrain plausible links between contemporary thrusts downsection. Typically, the foreland thrusts and decollements appear to splay from master thrusts that plunge at least 15-20 km down beneath the high ranges. Plio-Quaternary anticlinal ridges rising to more than 3000 m a.s.l. expose Palaeozoic metamorphic basement in their core. In general, the geology and topography of the ranges and forelands imply that structural reliefs of the order of 5-10 km have accrued at rates of 1-2 mm yr(-1) in approximately the last 5 Ma. From hill to range size, the elongated reliefs that result from such Late-Cenozoic, NE-SW shortening appear to follow a simple scaling law, with roughly constant length/width ratio, suggesting that they have grown self-similarly. The greatest mountain ranges, which are over 5.5 km high, tens of kilometres wide and hundreds of kilometres long may thus be interpreted to have formed as NW-trending ramp anticlines, at the scale of the middle-upper crust. The fairly regular, large-scale arrangement of those ranges, with parallel crests separated by piggy-back basins, the coevality of many parallel, south-dipping thrusts, and a change in the scaling ratio (from approximate to 5 to 8) for range widths greater than approximate to 30 km further suggests that they developed as a result of the northeastward migration of large thrust ramps above a broad decollement dipping SW at a shallow angle in the middle lower crust, This, in turn, suggests that the 400-500 km-wide crustal wedge that forms the northeastern edge of the Tibet-Qinghai plateau shortens and thickens as a thick-skinned accretionary prism decoupled from the stronger upper mantle underneath. Such a thickening process must have been coupled with propagation of the Altyn Tagh fault towards the ENE because most thrust traces merge northwestwards with active branches of this fault, after veering clockwise. This process appears to typify the manner in which the Tibet-Qinghai highlands have expanded their surface area in the Neogene, The present topography and structure imply that, during much of that period, the Tibet plateau grew predominantly towards the northeast or east-northeast, but only marginally towards the north-northwest. This was accomplished by the rise, in fairly fast succession. of the Arka Tagh, Qiman Tagh, Mahan shan, Tanghenan Shan, and other NW-trending mountain ranges splaying southeastwards from the Altyn Tagh, isolating the Aqqik-Ayakkum Kol, Qaidam, Suhai and other catchments and basins that became incorporated into the highland mass as intermontane troughs. The tectonic cut-off of catchments and the ultimate infilling of basins by debris from the adjacent ranges, a result of tectonically forced internal drainage, have thus been essential relief-smoothing factors, yielding the outstandingly flat topography that makes Tibet a plateau. Using Late-Mesozoic and Neogene horizons as markers, the retrodeformation of sections across the West Qilian Ranges and Qaidam basin implies at least approximate to 150 km of N30 degrees E Neogene shortening. On a broader scale, taking erosion into account, and assuming isostatic compensation and an initial crustal thickness comparable to that of the Gobi platform (47.5 +/- 5 km), minimum amounts of Late-Cenozoic crustal shortening on NE sections between the Kunlun fault and the Hexi corridor are estimated to range between 100 and 200 km. In keeping with the inference of a deep crustal decollement and with the existence of Mid-Miocene to Pliocene plutonism and volcanism south of the Kunlun range, such values suggest that the lithospheric mantle of the Qaidam plunged obliquely into the asthenosphere south of that range to minimum depths of the order of 200-300 km. A minimum of approximate to 150 km of shortening in the last approximate to 10 Ma, consistent with the average age of the earliest volcanic-plutonic rocks just south of the Kunlun (approximate to 10.8 Ma) would imply average Late-Cenozoic rates of shortening and regional uplift in NE Tibet of at least approximate to 15 mm yr(-1) and approximate to 0.2 mm yr(-1), respectively. Such numbers are consistent with a cumulative sinistral offset and slip rate of at least approximate to 200 km and approximate to 2 cm yr(-1), respectively, on the Altyn Tagh fault east of 88 degrees E. The fault may have propagated more than 1000 km, to 102 degrees E, in the last 10 Ma. Our study of ongoing tectonics in northeast Tibet is consistent with a scenario in which, while the Himalayas-Gangdese essentially 'stagnated' above India's subducting mantle, much of Tibet grew by thickening of the Asian crust, as propagation of large, lithospheric, strike-slip shear zones caused the opposite edge of the plateau to migrate far into Asia. The Asian lithospheric mantle, decoupled from the crust, appears to have subducted southwards along the two Mesozoic sutures that cut Tibet north of the Gangdese, rather than to have thickened. The Bangong-Nujiang suture was probably reactivated earlier than the Jinsha-Kunlun suture, located farther north. Overall, the large-scale deformation bears a resemblance to plate tectonics at obliquely convergent margins, including slip-partioning along large strike-slip faults such as the Altyn Tagh and Kunlun faults. Simple mechanisms at the level of the lithospheric mantle are merely hidden by the broader distribution and greater complexity of strain in the crust. C1 Inst Phys Globe, CNRS, Lab Tecton, UMR 7578, F-75252 Paris 05, France. Univ Savoie, F-73000 Chambery, France. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. State Seismol Bur, Beijing, Peoples R China. Inst Seismol, Lanzhou, Peoples R China. RP Meyer, B (reprint author), Inst Phys Globe, CNRS, Lab Tecton, UMR 7578, 4 Pl Jussieu, F-75252 Paris 05, France. RI Metivier, Francois/B-4202-2011; Tapponnier, .Paul/B-7033-2011; Meyer, Bertrand/E-6903-2011; Gaudemer, Yves/K-3921-2012 OI Tapponnier, .Paul/0000-0002-7135-1962; NR 133 TC 491 Z9 611 U1 10 U2 108 PU BLACKWELL SCIENCE LTD PI OXFORD PA P O BOX 88, OSNEY MEAD, OXFORD OX2 0NE, OXON, ENGLAND SN 0956-540X J9 GEOPHYS J INT JI Geophys. J. Int. PD OCT PY 1998 VL 135 IS 1 BP 1 EP 47 DI 10.1046/j.1365-246X.1998.00567.x PG 49 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 127UZ UT WOS:000076370100001 ER PT J AU Chen, JL Wilson, CR Chambers, DP Nerem, RS Tapley, BD AF Chen, JL Wilson, CR Chambers, DP Nerem, RS Tapley, BD TI Seasonal global water mass budget and mean sea level variations SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Analysis of TOPEX/Poseidon satellite altimeter data indicates that the global mean sea level variation has a clear seasonal signal with an amplitude of about 2 to 3 mm, along with a long term drift. This seasonal variation is associated with mass redistribution within the global hydrological cycle plus steric thermal contributions. We investigate seasonal variations of water vapor in the atmosphere and water storage on land using both assimilated atmospheric models and climatological data, and to estimate the corresponding global mean sea level changes. The predicted seasonal global mean sea level changes are then compared with the seasonal variabilities observed by TOPEX/Poseidon altimetry data, after the latter are corrected for the steric effect using a simplified thermal model derived from the NOAA World Ocean Atlas 1994. The good agreement in both amplitude and phase indicates that the T/P altimeter may provide key information for the global water mass budget by placing observational constraints on the mass budget variations predicted by global atmospheric and hydrological models. C1 Univ Texas, Tapley Ctr Space Res, Austin, TX 78712 USA. NASA Headquarters, Washington, DC 20546 USA. Univ Texas, Dept Geol Sci, Austin, TX USA. RP Chen, JL (reprint author), Univ Texas, Tapley Ctr Space Res, Austin, TX 78712 USA. OI Chambers, Don/0000-0002-5439-0257 NR 10 TC 71 Z9 77 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 OCT 1 PY 1998 VL 25 IS 19 BP 3555 EP 3558 DI 10.1029/98GL02754 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 125KJ UT WOS:000076236500004 ER PT J AU Zheng, QN Yan, XH Liu, WT Klemas, V Greger, D Wang, ZM AF Zheng, QN Yan, XH Liu, WT Klemas, V Greger, D Wang, ZM TI A solitary wave packet in the atmosphere observed from space SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERNAL WAVES; OCEAN AB A group of parallel cloud lines was identified in seven successive space shuttle photographs taken over the Pakistani offshore zone in the northern Arabian Sea on April 29, 1993. There are a total of 19 lines aligned with the length of the leading line longer than 250 km and an average separation distance (wavelength) of 1 km We suggest that the lines are generated by an atmospheric solitary wave packet characterized by decreases in amplitudes and wavelengths from the front to the rear. These features are comparable with the dnoidal soliton solution to the Korteweg-de Vries (KdV) equation The land breeze and katabatic flow are proposed as a possible generation mechanism. C1 Univ Delaware, Coll Marine Studies, Newark, DE 19716 USA. CALTECH, Jet Prop Lab 300 323, Pasadena, CA 91109 USA. RP Zheng, QN (reprint author), Univ Delaware, Coll Marine Studies, Newark, DE 19716 USA. RI Zheng, Quanan/F-9025-2010 NR 13 TC 11 Z9 11 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 OCT 1 PY 1998 VL 25 IS 19 BP 3559 EP 3562 DI 10.1029/98GL02319 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 125KJ UT WOS:000076236500005 ER PT J AU Haines, BJ Bar-Sever, YE AF Haines, BJ Bar-Sever, YE TI Monitoring the TOPEX microwave radiometer with GPS: Stability of columnar water vapor measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SEA-LEVEL; TOPEX/POSEIDON AB Using data from terrestrial global positioning system (GPS) receivers, we describe an anomalous drift in columnar water vapor measurements from the TOPEX microwave radiometer (TMR). Based on their long-occupation histories and proximity to open-water TOPEX/POSEIDON (T/P) ground tracks, we identified four geodetic-quality GPS stations that are suitable for calibrating the TMR. We constructed time series at each site based on the differences of instantaneous vertical wet tropospheric path delay (PDwet) derived independently from GPS and TMR data at T/P overflight times. The ensemble results span 1992-1997 and suggest that the TMR measurements of PDwet are gradually drifting lower. Our nominal estimate of the drift is -1.2 +/- 0.4 mm yr(-1) (one standard error). Accounting for this would increase the estimated rate of change in global mean sea level from T/P by the same amount. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Haines, BJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 238-600, Pasadena, CA 91109 USA. NR 15 TC 33 Z9 33 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD OCT 1 PY 1998 VL 25 IS 19 BP 3563 EP 3566 DI 10.1029/98GL02757 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 125KJ UT WOS:000076236500006 ER PT J AU Murphy, N Smith, EJ Wolf, J Intriligator, DS AF Murphy, N Smith, EJ Wolf, J Intriligator, DS TI A reexamination of "interstellar ion waves" previously identified in Pioneer 10 magnetic field data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-WIND; PICK-UP; HYDROGEN AB Pioneer 10 magnetic field measurements, believed to include waves associated with the pick-up of interstellar hydrogen atoms, have been further analyzed. Power spectra and waveform data reveal that the signals previously interpreted as waves are an artifact. They resulted from a very low telemetry/sampling rate, associated with the large distance of Pioneer 10 from Earth, which caused aliasing of a sinusoidal signal at the spacecraft spin frequency to a low frequency just above the proton gyrofrequency. Thus the Pioneer 10 plasma analyzer evidence for interstellar pickup ions must be considered separately from the magnetometer data: The validity of the plasma measurements is not affected by this data artifact. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Carmel Res Ctr, Space Plasma Lab, Santa Monica, CA 90406 USA. RP Murphy, N (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 5 TC 3 Z9 3 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 OCT 1 PY 1998 VL 25 IS 19 BP 3721 EP 3724 DI 10.1029/98GL02802 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 125KJ UT WOS:000076236500046 ER PT J AU Chang, SW Scudder, JD Fuselier, SA Fennell, JF Trattner, KJ Pickett, JS Spence, HE Menietti, JD Peterson, WK Lepping, RP Friedel, R AF Chang, SW Scudder, JD Fuselier, SA Fennell, JF Trattner, KJ Pickett, JS Spence, HE Menietti, JD Peterson, WK Lepping, RP Friedel, R TI Cusp energetic ions: A bow shock source SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SUPRATHERMAL IONS; PLASMA INSTRUMENT; UPSTREAM; SPACECRAFT; DIFFUSE; EVENTS; WIND; ACCELERATION; MISSION; WAVES AB Recent interpretations of cusp energetic ions observed by the POLAR spacecraft have suggested a new energization process in the cusp [Chen et al., 1997; 1998]. Simultaneous enhancement of H+, He+2, and O>+2 fluxes indicates that they are of solar wind origin. In the present study, we examine H+ and He+2 energy spectra from 20 eV to several 100 keV measured by the Hydra, Toroidal Imaging Mass-Angle Spectrograph (TIMAS), and Charge and Mass Magnetospheric Ion Composition Experiment (CAM-MICE) on POLAR. The combined spectrum for each species is shown to be continuous with a thermal distribution below 10 keV/e and an energetic component above 20 keV/e. Energetic ions with comparable fluxes and a similar spectral shape are commonly observed downstream from the Earth's quasi-parallel (Q(parallel to)) bow Shock. In addition to the similarity in the ion spectra, electric and magnetic field noise and turbulence detected in the cusp by the Plasma Wave Instrument (PWI) and Magnetic Field Experiment (MFE) onboard POLAR are similar to the previously reported observations at the bow shock. The waves appear to be coincidental to the cusp energetic ions rather than causal. We suggest that these ions are not accelerated locally in the cusp. Rather, they are accelerated at the Q(parallel to) bow shock and enter the cusp along open magnetic field lines connecting both regions. C1 Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. Aerospace Corp, Los Angeles, CA 90009 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. Lockheed Martin Adv Technol Ctr, Dept H1 11, Palo Alto, CA 94304 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Boston Univ, Dept Space Phys & Astron, Ctr Space Phys, Boston, MA 02215 USA. RP Chang, SW (reprint author), Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA. RI Friedel, Reiner/D-1410-2012; Scudder, Jack/D-8417-2013; Spence, Harlan/A-1942-2011; Peterson, WK/A-8706-2009; OI Friedel, Reiner/0000-0002-5228-0281; Scudder, Jack/0000-0001-7975-5630; Peterson, WK/0000-0002-1513-6096; Spence, Harlan/0000-0002-2526-2205 NR 22 TC 46 Z9 46 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 OCT 1 PY 1998 VL 25 IS 19 BP 3729 EP 3732 DI 10.1029/98GL52808 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 125KJ UT WOS:000076236500048 ER PT J AU Nunes, AC Zaidi, AA Ravi, TS Talia, JE AF Nunes, AC Zaidi, AA Ravi, TS Talia, JE TI Microparticulate emissions in 2195 aluminum-lithium alloy weldments SO HIGH TEMPERATURE MATERIALS AND PROCESSES LA English DT Article AB Microparticulate Emission (MPE) from Variable Polarity Plasma Are (VPPA) welds in 2195 aluminum-lithium alloy is described. It takes various forms herein labelled "Smut", "Snow", and "Lava". It is attributed to a gas generating reaction taking place at molten grain boundaries or crack surfaces. The reaction could be a release of hydrogen displaced from lithium-hydride by an influx of dissolved nitrogen. There appears to be a close link between cracking and MPE. C1 NASA, George C Marshall Space Flight Ctr, Mat & Proc Lab, Huntsville, AL 35812 USA. Wichita State Univ, Dept Mech Engn, Wichita, KS 67260 USA. RP Nunes, AC (reprint author), NASA, George C Marshall Space Flight Ctr, Mat & Proc Lab, EH 23, Huntsville, AL 35812 USA. NR 5 TC 1 Z9 1 U1 3 U2 3 PU FREUND PUBLISHING HOUSE LTD PI LONDON PA STE 500, CHESHAM HOUSE, 150 REGENT ST, LONDON W1R 5FA, ENGLAND SN 0334-6455 J9 HIGH TEMP MATER PROC JI High Temp. Mater. Process. PD OCT-DEC PY 1998 VL 17 IS 4 BP 313 EP 318 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA 142VQ UT WOS:000077221400013 ER PT J AU Dello Russo, N DiSanti, MA Mumma, MJ Magee-Sauer, K Rettig, TW AF Dello Russo, N DiSanti, MA Mumma, MJ Magee-Sauer, K Rettig, TW TI Carbonyl sulfide in comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp): Evidence for an extended source in Hale-Bopp SO ICARUS LA English DT Article DE comets; spectroscopy; infrared; carbonyl sulfide; production rates ID PARENT MOLECULES; EMISSION FEATURE; MU-M; SPECTRA; OCS; ATMOSPHERES; HALLEY; SULFUR; RATES; WEST AB Carbonyl sulfide was detected in Comet Hale-Bopp (C/1995 O1) using high dispersion infrared spectroscopy at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. Six lines (P10, P11, P12, P14, P15, and P17) of the nu(3) fundamental band near 4.85 mu m were detected on UT April 16.0, April 30.0, and May 1.2, 1997, and two additional lines (P18 and P22) were detected on April 30.0. Water was detected directly through emission lines of its nu(1)-nu(2) hot band on UT April 16.0, April 30.0, and May 1.2, with a rotational temperature of 93 +/- 16 K on May 1.2. Adopting a rotational temperature of 100 K for OCS, our derived production rates are (3.80 +/- 0.67) and (1.77 +/- 0.85) x 10(28) molecules s(-1) on April 16.0 and May 1.2, respectively. The measured production rates imply mixing ratios (Q(OCS)/Q(H2O)) of (4.58 +/- 0.77) and (2.76 +/- 1.34) x 10(-3) on April 16.0 and May 1.2, respectively. Comparison of spatial profiles for OCS, H2O, and the dust continuum derived from spectra taken less than 1 h apart suggests that on April 16.0 a significant amount of OCS (similar to 70% of the total) was released as an extended source. On April 30.0 and May 1.2 the quality of the data prevent a firm conclusion regarding an extended source contribution. If the nature of the OCS source did not change between April 16.0 and May 1.2, the weighted mean mixing ratio is (4.13 +/- 0.77) x 10(-3). We searched for lines P1 through P8 of the nu(3) band of OCS in Comet Hyakutake (C/1996 B2) on UT March 24.5, 1996. Our upper limit (3 sigma) for the OCS production rate in Hyakutake is 1.0 x 10(27) molecules s(-1) (Q(OCS)/Q(H2O) < 5.3 x 10(-3)). (C) 1998 Academic Press. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. Rowan Univ, Dept Chem & Phys, Glassboro, NJ 08028 USA. Univ Notre Dame, Dept Phys & Astron, Notre Dame, IN 46556 USA. RP Dello Russo, N (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 690-2, Greenbelt, MD 20771 USA. EM neil@kuiper.gsfc.nasa.gov RI mumma, michael/I-2764-2013; Magee-Sauer, Karen/K-6061-2015; Dello Russo, Neil/G-2727-2015 OI Magee-Sauer, Karen/0000-0002-4979-9875; Dello Russo, Neil/0000-0002-8379-7304 NR 40 TC 73 Z9 73 U1 0 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 OCT PY 1998 VL 135 IS 2 BP 377 EP 388 DI 10.1006/icar.1998.5990 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 138UD UT WOS:000076990700001 ER PT J AU Cruikshank, DP Roush, TL Bartholomew, MJ Geballe, TR Pendleton, YJ White, SM Bell, JF Davies, JK Owen, TC de Bergh, C Tholen, DJ Bernstein, MP Brown, RH Tryka, KA Dalle Ore, CM AF Cruikshank, DP Roush, TL Bartholomew, MJ Geballe, TR Pendleton, YJ White, SM Bell, JF Davies, JK Owen, TC de Bergh, C Tholen, DJ Bernstein, MP Brown, RH Tryka, KA Dalle Ore, CM TI The composition of Centaur 5145 Pholus SO ICARUS LA English DT Review DE asteroids; composition; comets; composition; ices; centaurs; prebiotic chemistry ID OUTER SOLAR-SYSTEM; SPECTRAL REFLECTANCE PROPERTIES; CHARGED-PARTICLE IRRADIATION; NEAR-INFRARED SPECTROSCOPY; COMET HALE-BOPP; OPTICAL-CONSTANTS; WATER ICE; ABSOLUTE CALIBRATION; ABSORPTION FEATURES; ORGANIC MATERIAL AB We present a new spectrum of the Centaur object 5145 Pholus between 1.15 and 2.4 Gem. We model this, and the previously published (0.4- to 1.0-mu m) spectrum, using Hapke scattering theory. Seen in absorption are the 2.04-mu m band of H(2)O ice and a strong band at 2.27 mu m, interpreted as frozen methanol and/or a photolytic product of methanol having small molecular weight. The presence of small molecules is indicative of a chemically primitive surface, since heating and other processes remove the light hydrocarbons in favor of macromolecular carbon of the kind found in carbonaceous meteorites. The unusually red slope of Pholus' spectrum is matched by fine grains of a refractory organic solid (tholin), as found previously by M. Hoffmann et al, (1993, J. Geophys. Res. 98, 7403-7407) and P. D. Wilson et al. (1994, Icarus 107, 288-303). Olivine (which we model with Fo 82) also appears to be present on Pholus. We present a live-component model for the composite spectrum of all spectroscopic and photometric data available for 5145 Pholus and conclude that this is a primitive object which hips not yet been substantially processed by solar heat. The properties of Pholus are those of the nucleus of a large comet that has never been active. (C) 1998 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sterling Software, Moffett Field, CA 94035 USA. Joint Astron Ctr, Hilo, HI 96720 USA. Cornell Univ, CRSR, Ithaca, NY 14853 USA. Joint Astron Ctr, Hilo, HI 96720 USA. Inst Astron, Honolulu, HI 96822 USA. Observ Paris, F-92195 Meudon, France. SETI Inst, Moffett Field, CA 94035 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. No Arizona Univ, Dept Phys, Flagstaff, AZ 86011 USA. RP Cruikshank, DP (reprint author), NASA, Ames Res Ctr, MS 245-6, Moffett Field, CA 94035 USA. EM cruikshank@ssa1.arc.nasa.gov OI Tryka, Kimberly/0000-0002-5399-4235 NR 114 TC 175 Z9 175 U1 0 U2 4 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 OCT PY 1998 VL 135 IS 2 BP 389 EP 407 DI 10.1006/icar.1998.5997 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 138UD UT WOS:000076990700002 ER PT J AU Hudson, RS Ostro, SJ AF Hudson, RS Ostro, SJ TI Photometric properties of Asteroid 4179 Toutatis from lightcurves and a radar-derived physical model SO ICARUS LA English DT Article DE asteroids; photometry; radar; surfaces ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; GALILEO PHOTOMETRY; SPIN-STATE; SHAPE; GASPRA; 4179-TOUTATIS; ROUGHNESS; SURFACE; IMAGES; IDA AB Optical lightcurves reported by J. R. Spencer et al. (1995, Icarus 117, 71-89) and a radar-derived shape and spin-state model (R. S. Hudson and S. J. Ostro, 1995, Science 270, 84-86) are used to estimate the Hapke parameters of the Earth-crossing Asteroid 4179 Toutatis. We find a particle single-scattering albedo w = 0.261 +/- 0.019, opposition surge width h = 0.036 +/- 0.023 and amplitude B-0 = 1.20 +/- 0.32, particle phase function asymmetry factor g = -0.29 +/- 0.06, and macroscopic roughness parameter <(theta)over bar> = 32 +/- 8 degrees. The synthetic lightcurves generated with this model provide a good fit (rms residual = 0.12 mag) to the optical data which span phase angles from 0.2 degrees to 121.4 degrees. The addition of optical data in the modeling process results in a slight refinement of the radar-derived estimate of the parameters that describe Toutatis's non-principal-axis spin state. Analysis of the opposition surge width in light of recent radar results supports the hypothesis that a significant fraction of Toutatis's surface is covered by a fine particulate regolith. (C) 1998 Academic Press. C1 Washington State Univ, Sch Elect Engn & Comp Sci, Pullman, WA 99164 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Hudson, RS (reprint author), Washington State Univ, Sch Elect Engn & Comp Sci, Pullman, WA 99164 USA. NR 27 TC 19 Z9 21 U1 2 U2 9 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 OCT PY 1998 VL 135 IS 2 BP 451 EP 457 DI 10.1006/icar.1998.5991 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 138UD UT WOS:000076990700007 ER PT J AU Moore, MH Hudson, RL AF Moore, MH Hudson, RL TI Infrared study of ion-irradiated water-ice mixtures with hydrocarbons relevant to comets SO ICARUS LA English DT Article DE comet; ice; organics; infrared; irradiation ID CHARGED-PARTICLE IRRADIATION; HALE-BOPP C/1995-O1; PROTON IRRADIATION; OPTICAL-CONSTANTS; FROZEN METHANE; B2 HYAKUTAKE; SPECTROSCOPY; CHEMISTRY; SPACE; SPECTRUM AB Ethane, methane, and acetylene were detected in Comets C/1996 B2 Hyakutake and C/1995 O1 Hale-Bopp. In order to investigate the possibility of condensed-phase synthesis of C(2)H(6) in interstellar ices, we have examined the role of CH(4) and C(2)H(2) in the radiation synthesis of C(2)H(6) in laboratory-formed low-temperature ices. Mixtures such as H(2)O + CH(4), H(2)O + C(2)H(2), H(2)O + CH(4) + C(2)H(2) were irradiated. Many mixtures were investigated using different concentrations of hydrocarbons. Results showed that yields of C(2)H(6) from CH(4) due to dimerization, were similar to yields of C(2)H(6) from C(2)H(2) due to H-addition reactions. However, CH(4) was not a source of C(2)H(2), suggesting that C(2)H(2) is part of the natal chemistry of these comets. Both CH(3)OH and C(2)H(5)OH were identified in our experiments along with CO, CO(2), HCO, H(2)CO, and CH(3)CHO. (C) 1998 Academic Press. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Eckerd Coll, Dept Chem, St Petersburg, FL 33733 USA. RP Moore, MH (reprint author), NASA, Goddard Space Flight Ctr, Code 691, Greenbelt, MD 20771 USA. EM ummhm@lepvax.gsfc.nasa.gov RI Hudson, Reggie/E-2335-2012 NR 39 TC 121 Z9 121 U1 2 U2 17 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 OCT PY 1998 VL 135 IS 2 BP 518 EP 527 DI 10.1006/icar.1998.5996 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 138UD UT WOS:000076990700012 ER PT J AU Chang, S Zdanowicz, VS Murchelano, RA AF Chang, S Zdanowicz, VS Murchelano, RA TI Associations between liver lesions in winter flounder (Pleuronectes americanus) and sediment chemical contaminants from north-east United States estuaries SO ICES JOURNAL OF MARINE SCIENCE LA English DT Article DE contaminants; liver lesions; winter flounder ID SOLE PAROPHRYS-VETULUS; TROUT SALMO-GAIRDNERI; HEPATIC-LESIONS; ENGLISH SOLE; MARINE FISH; PUGET-SOUND; CARCINOGENIC AGENTS; AQUATIC ANIMALS; BOSTON HARBOR; NEW-YORK AB Neoplastic diseases, particularly of bottom-dwelling fishes, are more prevalent in coastal areas than in areas that are relatively pristine. Although sediments in many urbanized estuaries contain high concentrations of contaminants, there is little evidence linking a specific organic or inorganic chemical to a particular liver lesion in winter flounder (Pleuronectes americanus), despite increasing study in recent years. Between 1984 and 1986, sediments and winter flounder were collected from 10 sites in the north-east United States ranging from grossly polluted to relatively unimpacted. Sediments were analysed for polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides, polychlorinated biphenyls (PCBs), and metals. Gross and microscopic pathological examinations were conducted on winter flounder liver sections. Factor and canonical correlation analyses were used to explore associations between biological and chemical measurements. Hepatitis, cholangitis, phlebitis, and macrophage aggregate hyperplasia showed positive associations with low molecular weight, petroleum-derived PAHs (naphthalene, anthracene, l-methylnaphthalene, 2-methylnaphthalene. 2,6-dimethylnaphthalene, acenaphthene, phenanthrene, biphenyl, fluorene, and 1-methylphenanthrene), the pesticides lindane, hexachlorobenzene, heptachlor epoxide, and o,p'-DDD, tri- to hexachlorobiphenyls, and chromium, cadmium, lead, thallium, and selenium, but were negatively associated with the pesticides o,p'-DDT, p,p'-DDT, p,p'-DDE, and mirex. Cytoplasmic hepatocellular vacuolation, cytoplasmic bile duct vacuolation, neoplasms, and pre-neoplasms showed positive associations with most PAHs measured, whether petroleum-derived or combustion-derived (benzo[a]pyrene, benzo[e]pyrene, benzo[a]anthracene, dibenzo[a,h]anthracene, perylene, chrysene, and ftuoranthene), the pesticides dieldrin, trans-nonachlor and alpha-chlordane, and silver, copper, antimony, and tin, but no associations with PCBs were found. Coagulative necrosis, single cell necrosis and haemorrhagic necrosis showed positive associations with hepta- to nonachlorobiphenyls and arsenic, zinc, nickel, and mercury, and negative associations with high molecular weight, combustion-derived PAHs and DDT compounds and metabolites. C1 NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. NOAA, Natl Marine Fisheries Serv, Woods Hole Lab, Woods Hole, MA 02543 USA. RP Chang, S (reprint author), NOAA, Natl Marine Fisheries Serv, James J Howard Marine Sci Lab, Highlands, NJ 07732 USA. NR 69 TC 25 Z9 25 U1 2 U2 11 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 1054-3139 J9 ICES J MAR SCI JI ICES J. Mar. Sci. PD OCT PY 1998 VL 55 IS 5 BP 954 EP 969 DI 10.1006/jmsc.1998.0354 PG 16 WC Fisheries; Marine & Freshwater Biology; Oceanography SC Fisheries; Marine & Freshwater Biology; Oceanography GA 140JQ UT WOS:000077084500012 ER PT J AU Lanari, R Hensley, S Rosen, PA AF Lanari, R Hensley, S Rosen, PA TI Chirp z-transform based SPECAN approach for phase-preserving ScanSAR image generation SO IEE PROCEEDINGS-RADAR SONAR AND NAVIGATION LA English DT Article DE ScanSAR mode; SAR processing; SPECAN algorithm; chirp z-transform ID SYNTHETIC APERTURE RADAR; SAR; ALGORITHMS; MIGRATION AB The scan mode synthetic aperture radar (ScanSAR) image impulse response is derived in the time domain, and particular attention is given to the analysis of the phase, which is important for several applications, and especially in interferometric ScanSAR systems. A new algorithm for phase-preserving azimuth focusing of ScanSAR data, that extends the basic SPECAN procedure, is presented. The proposed algorithm avoids the interpolation step needed to achieve constant azimuth pixel spacing by replacing the standard Fourier transform used in the SPECAN procedure with an appropriate chirp z-transform. The relationship between the modified SPECAN algorithm and the standard range-Doppler approach is also discussed. Experiments on real and simulated data are carried out to validate the theory. C1 CNR, IRECE, I-80124 Naples, Italy. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lanari, R (reprint author), CNR, IRECE, Via Diocleziano 328, I-80124 Naples, Italy. NR 16 TC 39 Z9 45 U1 1 U2 4 PU IEE-INST ELEC ENG PI HERTFORD PA MICHAEL FARADAY HOUSE SIX HILLS WAY STEVENAGE, HERTFORD SG1 2AY, ENGLAND SN 1350-2395 J9 IEE P-RADAR SON NAV JI IEE Proc.-Radar Sonar Navig. PD OCT PY 1998 VL 145 IS 5 BP 254 EP 261 DI 10.1049/ip-rsn:19982218 PG 8 WC Telecommunications SC Telecommunications GA 138LN UT WOS:000076973500002 ER PT J AU Clarke, KC Gaydos, LJ AF Clarke, KC Gaydos, LJ TI Loose-coupling a cellular automaton model and GIS: long-term urban growth prediction for San Francisco and Washington/Baltimore SO INTERNATIONAL JOURNAL OF GEOGRAPHICAL INFORMATION SCIENCE LA English DT Article; Proceedings Paper CT Research Workshop on GIS in Spatial Population Analysis and Regional Economic Development CY MAR 24-25, 1997 CL CHINESE UNIV HONG KONG, HONG KONG, HONG KONG SP Chinese Univ Hong Kong, Hong Kong Inst, Geog Dept, Chinese Univ Hong Kong, Hong Kong Inst, S China Program HO CHINESE UNIV HONG KONG AB Prior research developed a cellular automaton model, that was calibrated by using historical digital maps of urban areas and can be used to predict the future extent of an urban area. The model has now been applied to two rapidly growing, but remarkably different urban areas: the San Francisco Bay region in California and the Washington/Baltimore corridor in the Eastern United States. This paper presents the calibration and prediction results for both regions, reviews their data requirements, compares the differences in the initial configurations and control parameters for the model in the two settings, and discusses the role of GIS in the applications. The model has generated some long term predictions that appear useful for urban planning and are consistent with results from other models and observations of growth. Although the GIS was only loosely coupled with the model, the model's provision of future urban patterns as data layers for GIS description and analysis is an important outcome of this type of calculation. C1 Univ Calif Santa Barbara, Santa Barbara, CA 93106 USA. NASA, US Geol Survey, EROS Data Ctr, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Clarke, KC (reprint author), Univ Calif Santa Barbara, Santa Barbara, CA 93106 USA. RI Clarke, Keith/E-1863-2011 OI Clarke, Keith/0000-0001-5805-6056 NR 31 TC 421 Z9 493 U1 10 U2 89 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 1365-8816 J9 INT J GEOGR INF SCI JI Int. J. Geogr. Inf. Sci. PD OCT-NOV PY 1998 VL 12 IS 7 BP 699 EP 714 PG 16 WC Computer Science, Information Systems; Geography; Geography, Physical; Information Science & Library Science SC Computer Science; Geography; Physical Geography; Information Science & Library Science GA 126GX UT WOS:000076286500005 PM 12294536 ER PT J AU Potter, CS Brooks, V AF Potter, CS Brooks, V TI Global analysis of empirical relations between annual climate and seasonality of NDVI SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID AVHRR VEGETATION INDEX; SATELLITE-OBSERVATIONS; PRIMARY PRODUCTIVITY; SURFACE TEMPERATURE; LAND-SURFACE; DATA SET; MODEL; PHOTOSYNTHESIS; DYNAMICS; FORESTS AB This paper describes the use of satellite data to calibrate a new climate-vegetation greenness relation for global change studies. We examined statistical relations between annual climate indexes (temperature, precipitation, and surface radiation) and seasonal attributes of the AVHRR Normalized Difference Vegetation Index (NDVI) time series for the mid-1980s in order to refine our understanding of intra-annual patterns and global controls on natural vegetation dynamics. Multiple linear regression results using global 1 degrees gridded data sets suggest that three climate indexes: degree days (growing/chilling), annual precipitation total, and an annual moisture index together can account to 70-80% of the geographical variation in the NDVI seasonal extremes (maximum and minimum values) for the calibration year 1984. Inclusion of the same annual climate index values from the previous year explains no substantial additional portion of the global scale variation in NDVI seasonal extremes. The monthly timing of NDVI extremes is closely associated with seasonal patterns in maximum and minimum temperature and rainfall, with lag times of 1 to 2 months. We separated well-drained areas from 1 degrees grid cells mapped as greater than 25% inundated coverage for estimation of both the magnitude and timing of seasonal NDVI maximum values. Predicted monthly NDVI, derived from our climate-based regression equations and Fourier smoothing algorithms, shows good agreement with observed NDVI for several different years at a series of ecosystem test locations from around the globe. Regions in which NDVI seasonal extremes are not accurately predicted are mainly high latitude zones, mixed and disturbed vegetation types, and other remote locations where climate station data are sparse. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Ames Operat, Johnson Controls World Serv, Moffett Field, CA 94035 USA. RP Potter, CS (reprint author), NASA, Ames Res Ctr, Mail Stop 242-4, Moffett Field, CA 94035 USA. NR 44 TC 87 Z9 108 U1 2 U2 24 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD OCT PY 1998 VL 19 IS 15 BP 2921 EP 2948 DI 10.1080/014311698214352 PG 28 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 127MG UT WOS:000076354300007 ER PT J AU Wang, SG Lin, SB Shieh, LS Sunkel, JW AF Wang, SG Lin, SB Shieh, LS Sunkel, JW TI Observer-based controller for robust pole clustering in a vertical strip and disturbance rejection in structured uncertain systems SO INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL LA English DT Article DE robust pole-placement; pole clustering; robust stability; robust performance; uncertain linear systems; disturbance rejection observers ID H-INFINITY-CONTROL; TIME-VARYING UNCERTAINTY; LINEAR-SYSTEMS; STATE-SPACE; STABILIZATION; FEEDBACK; PERFORMANCE; SENSITIVITY; STABILITY; DESIGN AB This paper presents an observer-based multi-objective robust feedback controller to achieve robust pole clustering within a vertical strip and disturbance rejection with an H-infinity-norm constraint for the uncertain linear systems, The systems of interest include both matched and mismatched uncertain linear systems with structured uncertainties existing in both the system and input matrices. The controller is obtained by solving two Riccati equations (one for the controller and the other for the observer) and checking three conditions (two for robust pole clustering), A set of tuning parameters is incorporated to enhance flexibility in finding the controller. (C) 1998 John Wiley & Sons, Ltd. C1 Univ N Carolina, Coll Engn, Charlotte, NC 28223 USA. Prairie View A&M Univ, Coll Engn & Architecture, Prairie View, TX 77446 USA. Univ Houston, Dept Elect Engn, Houston, TX 77204 USA. NASA, Avion Syst Div, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Wang, SG (reprint author), Univ N Carolina, Coll Engn, Charlotte, NC 28223 USA. NR 27 TC 10 Z9 11 U1 0 U2 4 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 OCT PY 1998 VL 8 IS 12 BP 1073 EP 1084 PG 12 WC Automation & Control Systems; Engineering, Electrical & Electronic; Mathematics, Applied SC Automation & Control Systems; Engineering; Mathematics GA 129TW UT WOS:000076479900004 ER PT J AU Sarrazin, P Blake, D Bish, D Vaniman, D Collins, S AF Sarrazin, P Blake, D Bish, D Vaniman, D Collins, S TI A miniature XRD/XRF instrument for in-situ characterization of Martian soils and rocks SO JOURNAL DE PHYSIQUE IV LA English DT Article; Proceedings Paper CT Conference on X-Rays and Matter (RX 97) CY OCT 14-16, 1997 CL STRASBOURG, FRANCE SP Ecole Nationale Superieure Arts & Industries AB In the context of the exploration of Mars, the availability of an instrument for in-situ mineralogical characterization of the surface of the planet is of the highest importance. We are developing a miniature X-ray diffraction / fluorescence instrument for this specific purpose. The concept of the instrument is based on the use of a single CCD detector exposed directly to the X-rays diffracted and fluoresced by a sample. A first prototype has been realized to test the concept of simultaneous XRD and XRF measurement with a single CCD detector. This paper presents the result obtained after refinement of this instrument. The capability of the technique has been proven. Further developments are planned to propose a miniature XRD/XRF instrument for planetary exploration. The concept utilized in this project could find a range cg applications as laboratory instruments or portable instruments. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. ENESAD, LGAP, F-21036 Dijon, France. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Sarrazin, P (reprint author), NASA, Ames Res Ctr, MS 239-4, Moffett Field, CA 94035 USA. NR 10 TC 6 Z9 6 U1 4 U2 8 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 1155-4339 J9 J PHYS IV JI J. Phys. IV PD OCT PY 1998 VL 8 IS P5 BP 465 EP 470 DI 10.1051/jp4:1998559 PG 6 WC Physics, Multidisciplinary SC Physics GA 134WQ UT WOS:000076767100060 ER PT J AU Chamis, CC AF Chamis, CC TI Thermostructural approach for low cost fabrication processing SO JOURNAL OF ADVANCED MATERIALS LA English DT Article AB A new approach is described which is based on adapting coupled thermal/structural computer codes for low cost fabrication processing. The coupled thermal structural behavior is simulated by using a coupled multidisciplinary computer code. Through this approach the temperature gradients during processing and the respective evolution of thermomechanical properties during cooling are simultaneously evaluated. The approach is demonstrated by applying it to ice forming and casting process to fabricate a simple and a complex component. The volume of the part and its respective mold is modeled by 3-D mixed field finite elements which accommodate solidification, heat transfer, stress/structural analysis. Results obtained show that the temperature gradients are functions of the pouring ports and built-up rapidly in the mold reaching magnitudes approaching those of the melt. The approach is amenable to formal optimization for mold material and multiple pouring ports in order to minimize the thermal gradients which reduce residual stresses and thereby increase part service life. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Chamis, CC (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 0 Z9 0 U1 0 U2 0 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER JI J. Adv. Mater. PD OCT PY 1998 VL 30 IS 4 BP 64 EP 73 PG 10 WC Materials Science, Multidisciplinary SC Materials Science GA 209HX UT WOS:000081043100005 ER PT J AU Mendell, WW AF Mendell, WW TI Role of lunar development in human exploration of the solar system SO JOURNAL OF AEROSPACE ENGINEERING LA English DT Article AB Human exploration of the solar system can be said to have begun with the Apollo missions. The Apollo Project was publicly funded with the narrow technical objective of landing human beings on the Moon. The transportation and life support systems were specialized technical designs, developed in a project management environment tailored to that objective. Most scenarios for future human exploration assume a similar longterm commitment of public funds to a narrowly focused project managed by a government organization, which becomes a single customer for a large industrial complex supporting the mission. Advocates of human exploration of space have not yet been successful in generating the political momentum required to initiate such a project to return to the Moon or to explore Mars. Alternative scenarios of exploration may relax some or all of the parameters of organizational complexity, great expense, narrow technical focus, required public funding, and control by a single organization. Development of the Moon using private investment is quite possibly a necessary condition for alternative scenarios to succeed. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Mendell, WW (reprint author), NASA, Lyndon B Johnson Space Ctr, SN2, Houston, TX 77058 USA. NR 15 TC 0 Z9 0 U1 0 U2 1 PU ASCE-AMER SOC CIVIL ENGINEERS PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2398 USA SN 0893-1321 J9 J AEROSPACE ENG JI J. Aerosp. Eng. PD OCT PY 1998 VL 11 IS 4 BP 106 EP 110 DI 10.1061/(ASCE)0893-1321(1998)11:4(106) PG 5 WC Engineering, Aerospace; Engineering, Civil SC Engineering GA 121WD UT WOS:000076038000002 ER PT J AU Suggs, RJ Jedlovec, GJ Guillory, AR AF Suggs, RJ Jedlovec, GJ Guillory, AR TI Retrieval of geophysical parameters from GOES: Evaluation of a split-window technique SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID PRECIPITABLE WATER; SURFACE; MODEL AB The performance of a physical split-window retrieval algorithm used to retrieve skin temperature (ST) and precipitable water (PW) from Geostationary Operational Environmental Satellites' (GOES) infrared measurements is evaluated. The evaluation assesses the potential of using GOES measurements to provide accurate retrieval products for climate research studies. Several algorithm performance issues are addressed, including the time of retrieval (diurnal effects), sensitivity to the first-guess field, and an evaluation of performance differences associated with the split-window channel characteristics of the GOES-7 VISSR (Visible and Infrared Spin Scan Radiometer) Atmospheric Sounder (VAS) and the GOES-8 imager and sounder. The investigation used a mesoscale model, initialized by radiosonde data, to generate a simulated atmosphere representative of a case study characterized by summertime conditions over the east-central United States. Synthetic GOES channel radiances were developed from the surrogate atmosphere using GOES channel response functions and an appropriate radiative transfer code. The model fields also provided the necessary ground truth and first-guess field for the retrieval algorithm. Retrievals of ST and PW were made from the simulated channel radiances associated with the VAS and GOES-8 imager and sounder split-window channels. Retrieval methodologies were applied to address issues of importance in climate research studies, such as long-term trends and diurnal variability of ST and PW. The performance was measured by comparing the retrieved values with the model values at each of the retrieval locations. The algorithm performance for both ST and PW was found to be sensitive to the quality of the first-guess field and to the channel characteristics of the GOES sensors. An estimate of the lower bound on ST and PW retrieval errors was determined. The ST retrievals in all cases showed a significant improvement over the first-guess values. The GOES-8 imager ST retrieval errors, which were about half of the VAS values, ranged from about 0.2 to 0.6 K, exhibiting little diurnal effect. The PW retrieval errors ranged from about 2.0 to 7.0 mm with a modest sensitivity to the different sensor channels. However, a significant diurnal trend in the PW retrieval errors that correlated with the presence of surface- and low-level temperature inversions was observed. The algorithm performance results provide insight into the application of GOES split-window retrieval methodologies for climate variability studies and may have implications for operational applications of similar retrieval techniques. C1 NASA, Global Hydrol & Climate Ctr, George C Marshall Space Flight Ctr, Huntsville, AL 35806 USA. RP Suggs, RJ (reprint author), NASA, Global Hydrol & Climate Ctr, George C Marshall Space Flight Ctr, 977 Explorer Blvd, Huntsville, AL 35806 USA. NR 18 TC 11 Z9 11 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD OCT PY 1998 VL 37 IS 10 BP 1205 EP 1227 DI 10.1175/1520-0450(1998)037<1205:ROGPFG>2.0.CO;2 PN 2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 128CM UT WOS:000076387700001 ER PT J AU Rosenfeld, D Amitai, E AF Rosenfeld, D Amitai, E TI Comparison of WPMM versus regression for evaluating Z-R relationships SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID INTEGRALS; RAINFALL; RADAR AB The accuracy of the estimation of Z-R relationships is evaluated for the Window Probability Matching Method (WPMM) and regression methods. The evaluation is based on experiments of random subsampling of disdrometer-obtained 1-min reflectivity Z and rain-rate R pairs. The simulation of the disparity between the radar and the rain gauge measurement volumes was done by 3-min time averaging of the reflectivity data. Geometrical mismatch and synchronization inaccuracies between the radar and rain gauges are simulated by desynchronization of dt minutes, that is, shifting the R and Z time series with respect to each other by dt minutes. The WPMM and bias-corrected regression methods have similar skill in estimating rainfall accumulation even when geometrical and synchronization errors are introduced. However, the WPMM has significant advantage in estimating the rain intensities when geometrical and synchronization errors are introduced to the radar-gauge-measured Z-R pairs for simulating real-world radar and rain gauge comparisons. Regression-based Z-R relationships tend to overestimate the low rain intensities and underestimate the high rain intensities with the crossover at the estimated median rain volume intensity. This trend becomes more severe with the increased desynchronization. This reduction of the dynamic range of R does not occur when using WPMM. Although rain gauge bias correction may render the overall rain accumulation insensitive to the power of the Z-R law, its appropriate selection has a major effect on the partition of rainfall amounts between weak and strong intensities or the partition between convective and stratiform rainfall. C1 Hebrew Univ Jerusalem, Inst Earth Sci, IL-91904 Jerusalem, Israel. NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD USA. RP Rosenfeld, D (reprint author), Hebrew Univ Jerusalem, Inst Earth Sci, IL-91904 Jerusalem, Israel. RI Rosenfeld, Daniel/F-6077-2016 OI Rosenfeld, Daniel/0000-0002-0784-7656 NR 7 TC 15 Z9 17 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD OCT PY 1998 VL 37 IS 10 BP 1241 EP 1249 DI 10.1175/1520-0450(1998)037<1241:COWVRF>2.0.CO;2 PN 2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 128CM UT WOS:000076387700003 ER PT J AU Tabib-Azar, M Hubbard, SM Schnabel, CM Bailey, S AF Tabib-Azar, M Hubbard, SM Schnabel, CM Bailey, S TI Mapping of crystal defects and the minority carrier diffusion length in 6H-SiC using a novel electron beam induced current technique SO JOURNAL OF APPLIED PHYSICS LA English DT Article ID SILICON-CARBIDE; DIODES AB We report on a mapping technique used to correlate the structure of defects with their electrical characteristics in semiconductors. Interesting results that directly and clearly show the influence of micropipes on the minority carrier diffusion length were obtained in both p- and n-type 6H-SiC. The method is based on electron-beam induced current (EBIC) measurements in planar structures. Values of hole diffusion length in defect free regions of n-type 6H-SiC, with a doping concentration of 1.7 x 10(17) cm(-3), ranged from 1.46 to 0.68 mu m. These values were reduced to below 0.1 mu m at the center of large defects. In addition, measurements on p- type 6H-SiC resulted in electron diffusion lengths ranging from 1.42 to 0.8 mu m which also showed drastic reductions near defects. Our planar mapping technique measures diffusion lengths along a linescan. This linear map is then overlaid onto the EBIC image, allowing direct visualization of defects and their effect on minority carrier diffusion lengths. (C) 1998 American Institute of Physics. [S0021-8979(98)01919-7]. C1 Case Western Reserve Univ, Dept Elect Engn & Appl Phys, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Tabib-Azar, M (reprint author), Case Western Reserve Univ, Dept Elect Engn & Appl Phys, Cleveland, OH 44106 USA. NR 25 TC 13 Z9 13 U1 0 U2 5 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 OCT 1 PY 1998 VL 84 IS 7 BP 3986 EP 3992 DI 10.1063/1.368578 PG 7 WC Physics, Applied SC Physics GA 124LX UT WOS:000076184800073 ER PT J AU Moran, MM Roy, RR Wade, CE Corbin, BJ Grindeland, RE AF Moran, MM Roy, RR Wade, CE Corbin, BJ Grindeland, RE TI Size constraints of telemeters in rats SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE telemetry; seromas; microgravity ID SPONTANEOUSLY HYPERTENSIVE RATS; BLOOD-PRESSURE; HEART-RATE; BONE MASS; RADIOTELEMETRY; EXPOSURE; EXERCISE; STRENGTH; STRESS; LOAD AB This study was designed to determine the maximum-size subcutaneous telemeter that would enable long-term and multichannel data collection in a 170-g rat for 90 days. In phase 1, rats with implants weighing 5 (2.5 cm(3)), 15 (7.5 cm(3)), 25 (12.5 cm(3)), 35 (17.5 cm(3)), or 45 (22.5 cm(3))g were compared with sham-operated (SOC) and nonoperated (NOC) control animals. Severe skin lesions, seromas, and lower growth rates were observed in rats having implants greater than or equal to 35 g. Thus, in phase 2, rats implanted with 23.5 g (17.5 cm(3); 11-g active telemeter and 12.5-g implant) were compared with rats implanted with 11 g (6 cm(3); telemeter only) and with the SOC and NOC groups. No differences were found among implanted groups in mean arterial pressure (MAP), heart rate (HR), subcutaneous temperature, or spontaneous activity under standard housing conditions. All groups were more active and had a higher MAP during the dark than the light phase of the daily cycle. During 2 h of cold exposure (3 degrees C), both telemetered groups exhibited similar changes in HR, MAP, temperature, and activity levels. Adrenal glands were larger in the 23.5-g group (51 +/- 1.6 mg) than in the SOC (46 +/- 1.0 mg) and the NOC groups (41 +/- 2.0 mg). No other significant differences were found in organ, muscle, or bone weights. These data verify the feasibility of using 23.5-g (17.5 cm(3)) subcutaneous telemeters for chronic recordings in young adult rats. C1 NASA, Ames Res Ctr, Life Sci Res Div, Moffett Field, CA 94035 USA. GB Tech, Houston, TX 77258 USA. Univ Calif Los Angeles, Brain Res Inst, Los Angeles, CA 90095 USA. RP Wade, CE (reprint author), NASA, Ames Res Ctr, Life Sci Res Div, MS 239-11, Moffett Field, CA 94035 USA. NR 31 TC 14 Z9 14 U1 0 U2 1 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 OCT PY 1998 VL 85 IS 4 BP 1564 EP 1571 PG 8 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 126RJ UT WOS:000076306700050 PM 9760354 ER PT J AU Siconolfi, SF Gretebeck, RJ Wong, WW Moore, SS Gilbert, JH AF Siconolfi, SF Gretebeck, RJ Wong, WW Moore, SS Gilbert, JH TI Determining bone and total body mineral content from body density and bioelectrical response spectroscopy SO JOURNAL OF APPLIED PHYSIOLOGY LA English DT Article DE multicompartment models; body composition; underwater weighing; osteoporosis ID X-RAY ABSORPTIOMETRY; NEUTRON-ACTIVATION ANALYSIS; ACCURACY; WATER AB We hypothesized that one could assess total body mineral (TBM) and bone mineral content (BMC) from measurements of body density and bioelectrical response spectroscopy (BRS)-determined total body water by using a three-compartment (3C) model. We compared TBM and BMC computed from measurements of water ((H2O)-H-2 dilution or BRS) and body density (underwater weighing) with [4-compartment (4C)] and without (3C) mineral (dual X-ray absorptiometry) in 15 women and 16 men. BRS used multifrequency or single-frequency estimates of water. Mean differences between the 3C and 4C models ranged from -6.1 to 2.2%. Correlations between models were 0.82-0.91. Standard errors of the estimate of 8.5-9.3% were within the range of those previously reported, i.e., 4.9-13%. Use of BRS did not significantly decrease the strength of the correlations between the models. A significant mean difference (only in women) was found only with 3C single-frequency BRS estimates of TBM and BMC. We concluded that investigators can assess TBM and BMC 3C multifrequency BRS estimates in men and women. C1 NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Res Labs SD3, Neurosci Neuromuscular Lab, Houston, TX 77058 USA. Baylor Coll Med, Dept Pediat, USDA ARS, Childrens Nutr Res Ctr,Stable Isotope Program, Houston, TX 77030 USA. Univ Space Res Assoc, Houston, TX 77058 USA. Aerosp Consultant Enterprises, Houston, TX 77059 USA. Purdue Univ, Dept Foods & Nutr, W Lafayette, IN 47907 USA. RP Siconolfi, SF (reprint author), Wayne State Univ, Coll Pharm & Allied Hlth Profess, 121 Shapero Hall, Detroit, MI 48202 USA. NR 21 TC 3 Z9 3 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 OCT PY 1998 VL 85 IS 4 BP 1578 EP 1582 PG 5 WC Physiology; Sport Sciences SC Physiology; Sport Sciences GA 126RJ UT WOS:000076306700052 PM 9760356 ER PT J AU Durden, SL Haddad, ZS AF Durden, SL Haddad, ZS TI Comparison of radar rainfall retrieval algorithms in convective rain during TOGA COARE SO JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY LA English DT Article ID DUAL-FREQUENCY ALGORITHMS; SINGLE-FREQUENCY; SPACEBORNE RADAR; AIRBORNE; ATTENUATION; PROFILES; TESTS AB The authors compare deterministic and stochastic rain-rare retrieval algorithms by applying them to 14-GHz nadir-looking airborne radar reflectivity profiles acquired in tropical convective rain during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. The deterministic algorithms both use the path-integrated attenuation (PIA), measured by the surface reference technique, as a constraint. One deterministic algorithm corrects the k-R relation, while the second corrects the Z-R relation. The stochastic algorithms are based on applying an extended Kalman filter to the reflectivity profile. One employs radar reflectivity only; the other additionally uses the PIA. The authors find that the stochastic algorithm, which uses the PIA, is the most robust algorithm with regard to incorrect assumptions about the drop size distribution (DSD). The deterministic algorithm that uses the PIA to adjust the Z-R relation is also fairly robust and produces rain rates similar to the stochastic algorithm that uses the PIA. The deterministic algorithm that adjusts only the k-R relation and the stochastic radar-only algorithm are more sensitive to assumptions about the DSD. It is likely that they underestimate convective rainfall, especially if the DSD is erroneously assumed to be appropriate for stratiform rain conditions. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Durden, SL (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-227,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 16 TC 9 Z9 9 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 OCT PY 1998 VL 15 IS 5 BP 1091 EP 1096 DI 10.1175/1520-0426(1998)015<1091:CORRRA>2.0.CO;2 PG 6 WC Engineering, Ocean; Meteorology & Atmospheric Sciences SC Engineering; Meteorology & Atmospheric Sciences GA 120NH UT WOS:000075962100002 ER PT J AU Omidvar, K Menard, R Buonsanto, MJ AF Omidvar, K Menard, R Buonsanto, MJ TI Empirical determination of the O+O collision frequency SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS LA English DT Article ID AERONOMICAL MEASUREMENTS; CROSS-SECTION AB The collision frequency between an oxygen atom and its singly charged ion controls the transfer of energy between the solar radiation and the thermosphere. We define a factor F, often called the Burnside factor, as the ratio of the empirical to the theoretical collision frequencies whose deviation from unity is a measure of inconsistency between theory and observation. Assuming given values for the theoretical parameters, here we apply the observational data to the empirical determination of this factor. The data are taken at the Millstone Hill Observatory, which consist of two distinct sets of data A and B. Three methods of analysis have been used. These are the method of linear-least-squares, a method due to Hines et (1997), and a third method based on lognormal distribution of the data. While the linear-least-squares and lognormal distribution methods are based on Gaussian and lognormal distributions, respectively, no distribution assumption is made in the Hines et al. method, and this makes the method more general. The linear-least-squares and the Hines ct al. methods give consistent estimates for F, differing in values from each other by only a few units in their third decimal places. Based on Pesnell et al. (1993) calculated collision frequency, the F estimates for the sets A and B are 0.91 and 1.06, respectively. In addition. Hines et al. (1997) and lognormal distribution methods set rigorous upper and lower bounds on estimates of F. The bounds in the two methods are consistent with each other. Designating the true value of F by based on Pesnell et al. calculated collision frequency, we obtain 0.89 < F < 1.02, and 1.06 < F < 1.17 for the two sets A and B, respectively. Thus, the inequalities for the set A brackets the correct value of F = 1.0. We have also shown that the deviation of F for each measurement from F is lognormally distributed. It is shown that a shift of about 15% of the F estimates between the two sets indicated above is principally due systematic errors in the oxygen atom densities in the two sets, which is of the order of 11%. An alternative way to find the atomic oxygen density by calculation is suggested here. To recommend a realistic formula for the user to calculate the collision frequency, without rigorous justification, average the two estimates of F, leading to (F) over bar = 0.98. Since the Pesnell et al. (1993) formula is valid to two significant figures, we recommend their formula with an uncertainty of 8% attached to it, which is due to the difference the two estimates of F. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. MIT, Haystack Observ, Westford, MA 01886 USA. RP Omidvar, K (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. EM omidvar@dao.gsfc.nasa.gov NR 17 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 1364-6826 J9 J ATMOS SOL-TERR PHY JI J. Atmos. Sol.-Terr. Phys. PD OCT PY 1998 VL 60 IS 15 BP 1485 EP 1496 DI 10.1016/S1364-6826(98)00086-8 PG 12 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences GA 155XK UT WOS:000077971600006 ER PT J AU Speers, RA Paloski, WH Kuo, AD AF Speers, RA Paloski, WH Kuo, AD TI Multivariate changes in coordination of postural control following spaceflight SO JOURNAL OF BIOMECHANICS LA English DT Article DE posture; balance; joint coordination; multivariate analysis; spaceflight; spatial orientation; sensory organization test ID WEIGHTLESSNESS; MICROGRAVITY AB Postural and gait instabilities in astronauts returning from spaceflight are thought to result from in-flight adaptation of central nervous system processing of sensory inputs from the vestibular, proprioceptive, and visual systems. We hypothesized that reorganization of posture control relying on these multiple inputs would result in not only greater amounts of sway, but also changes in interjoint coordination. We tested this hypothesis by examining the multivariate characteristics of postural sway and comparing the postural control gain used for maintenance of upright stance during the altered sensory conditions of the Sensory Organization Test (EquiTest, Neurocom Intl.). We used the covariance of hip and ankle kinematics as a measure of joint motion and interjoint coordination, and then utilized discriminant analysis to further examine these characteristics in a group of 10 first-time astronauts. In five of the six conditions, the most important difference was an increased relative utilization of the hip strategy, which would not be evident using conventional balance measures such as peak or root-mean-square sway. This finding was supported by indications of increased hip torque gains relative to lower extremity and neck motion in at least four conditions (p < 0.05). In contrast, ankle torque gains to these motions did not appear to change. These results suggest that after spaceflight, astronauts exhibit significant multivariate changes in multijoint coordination, of which increased sway is only one component. These changes are consistent with reweighting of vestibular inputs and changes in control strategy in a multivariable control system. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. C1 Univ Michigan, Dept Biomed Engn, Ann Arbor, MI 48109 USA. Univ Michigan, Dept Otolaryngol, Vestibular Testing Ctr, Ann Arbor, MI 48109 USA. NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Univ Michigan, Dept Mech Engn & Appl Mech, Ann Arbor, MI 48109 USA. RP Speers, RA (reprint author), Univ Michigan, Dept Biomed Engn, Ann Arbor, MI 48109 USA. EM rspeers@umich.edu RI Kuo, Arthur/L-3359-2013 OI Kuo, Arthur/0000-0001-5233-9709 FU NIDCD NIH HHS [1R29DC02312-01A1] NR 17 TC 19 Z9 20 U1 5 U2 5 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0021-9290 J9 J BIOMECH JI J. Biomech. PD OCT PY 1998 VL 31 IS 10 BP 883 EP 889 DI 10.1016/S0021-9290(98)00065-7 PG 7 WC Biophysics; Engineering, Biomedical SC Biophysics; Engineering GA 139ZR UT WOS:000077061600003 PM 9840753 ER PT J AU Schubert, SD Helfand, HM Wu, CY Min, W AF Schubert, SD Helfand, HM Wu, CY Min, W TI Subseasonal variations in warm-season moisture transport and precipitation over the central and eastern United States SO JOURNAL OF CLIMATE LA English DT Article ID LOW-LEVEL JET; GREAT-PLAINS; METEOROLOGICAL CONDITIONS; DIURNAL-VARIATIONS; HEAT WAVES; CLIMATE; SUMMER; CONVECTION; FREQUENCY; DROUGHTS AB Subseasonal variations in warm-season (May-August) precipitation over the central and eastern1 United States are shown to be strongly linked to variations in the moisture entering the continent from the Gulf of Mexico within a longitudinally confined "channel" (referred to here as the Texas corridor or TC). These variations reflect the development of low-level southerly wind maxima (or jets) on a number of different timescales in association with distinct subcontinental and larger-scale phenomena. On the diurnal timescale, the TC moisture flux variations are tied to the development of the Great Plains low-level jet. The composite nighttime anomalies are characterized by a strong southerly moisture flux covering northeast Mexico and the southern Great Plains, and enhanced boundary layer convergence and precipitation over much of the upper Great Plains. The strongest jets tend to be associated with an anomalous surface low over the Great Plains, reflecting a predilection for periods when midlatitude weather systems are positioned to produce enhanced southerly how over this region. On subsynoptic (2-4 days) timescales the TC moisture flux variations are associated with the development and evolution of a warm-season lee cyclone. These systems, which are most prevalent during the early part of the warm season (May and June), form over the central Great Plains in association with an upper-level shortwave and enhanced upper-tropospheric cross-mountain westerly flow. A low-level southerly wind maximum or jet develops underneath and perpendicular to the advancing edge of enhanced midtropospheric westerlies. The clash of anomalous southerly moisture Aux and a deep intrusion of anomalous northerly low-level winds results in enhanced precipitation eventually stretching from Texas to the Great Lakes. On synoptic (4-8 days) timescales the TC moisture Bur variations are associated with the propagation and intensification of a warm-season midlatitude cyclone. This system, which also occurs preferentially during May and June, develops offshore and intensifies as it crosses the Rocky Mountains and taps moisture from the Gulf of Mexico. Low-level southerly wind anomalies develop parallel to the mid- and upper-level winds on the leading edge of the trough. Widespread precipitation anomalies move with the propagating system with reduced rainfall occurring over the anomalous surface high, and enhanced rainfall occurring over the anomalous surface low. On still longer timescales (8-16 days) the variations in the TC moisture transport are tied to slow eastward-moving systems. The evolution and structure of the mid- and low-level winds are similar to those of the synoptic-scale system with, however, a somewhat larger zonal scale and spatially more diffuse southerly moisture flux and precipitation anomalies. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Schubert, SD (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Atmospheres Lab, Mail Code 910-3, Greenbelt, MD 20771 USA. NR 55 TC 37 Z9 37 U1 0 U2 10 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD OCT PY 1998 VL 11 IS 10 BP 2530 EP 2555 DI 10.1175/1520-0442(1998)011<2530:SVIWSM>2.0.CO;2 PG 26 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 130TM UT WOS:000076536500005 ER PT J AU Smith, SM Nillen, JL Leblanc, A Lipton, A Demers, LM Lane, HW Leach, CS AF Smith, SM Nillen, JL Leblanc, A Lipton, A Demers, LM Lane, HW Leach, CS TI Collagen cross-link excretion during space flight and bed rest SO JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM LA English DT Article ID BONE TURNOVER; URINARY-EXCRETION; N-TELOPEPTIDES; I COLLAGEN; MARKERS; RESORPTION; CALCIUM; OSTEOPOROSIS; PYRIDINOLINE; QUANTITATION AB Extended exposure to weightlessness results in bone loss. However, little information exists as to the precise nature or time course of this hone loss. Bone resorption results in the release of collagen breakdown products, including N-telopeptide and the pyridinium (PM) cross-links, pyridinoline and deoxypyridinoline. Urinary pyridinoline and deoxypyridinoline are known to increase during bed rest. We assessed excretion of PYD cross-links and N-telopeptide before, during, and after long (28-day, 59-day, and 84-day) Skylab missions, as well as during short(14-day) and long(119-day) bed-rest studies. During space flight: the urinary cross-link excretion level was twice those observed before flight. Urinary excretion levels of the collagen breakdown products were also 40-50% higher, during short and long bed rest, than before. These results clearly show that the changes in bone metabolism associated with space flight involve increased resorption. The rate of response (i.e. within days to weeks) suggests that alterations in bone metabolism are an early effect of weightlessness. These studies are important for a better understanding of bone metabolism in space crews and in those who are bedridden. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs SD3, Houston, TX 77058 USA. Lyndon B Johnson Space Ctr, Enterprise Advisory Serv Inc, Houston, TX 77058 USA. Baylor Coll Med, Houston, TX 77030 USA. Penn State Univ, Milton S Hershey Med Ctr, Hershey, PA 17033 USA. RP Smith, SM (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs SD3, Houston, TX 77058 USA. EM smsmith@ems.jsc.nasa.gov NR 29 TC 97 Z9 100 U1 0 U2 4 PU ENDOCRINE SOC PI CHEVY CHASE PA 8401 CONNECTICUT AVE, SUITE 900, CHEVY CHASE, MD 20815-5817 USA SN 0021-972X EI 1945-7197 J9 J CLIN ENDOCR METAB JI J. Clin. Endocrinol. Metab. PD OCT PY 1998 VL 83 IS 10 BP 3584 EP 3591 DI 10.1210/jc.83.10.3584 PG 8 WC Endocrinology & Metabolism SC Endocrinology & Metabolism GA 126CN UT WOS:000076275500035 PM 9768669 ER PT J AU O'Brien, TK Sen, JK AF O'Brien, TK Sen, JK TI Tension-torsion behavior of glass epoxy flexbeam laminates SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE glass epoxy; fatigue AB Quasi-static tension-torsion and tension-torsion fatigue tests were conducted on several candidate S2/F584 glass-epoxy flex-beam layups to establish their torsional strength and fatigue behavior in the presence of an axial load, determine typical damage mechanisms, and provide a database for developing predictive analytical methods. Tension-torsion specimens contained 0 degrees longitudinal plies and 15, 30, or 45 degrees angle plies in seven different stacking sequences. The angle plies were +/- 45 woven cloth in one layup and prepreg tape in the other layups. In the tape laminates, fatigue failures began with matrix cracks forming on the edge that initiated delaminations in the interfaces between the angle plies and 0 degrees plies. In the cloth laminates, a series of small "stair step" delaminations formed between the +/-45 cloth layers and initiated delaminations in the neighboring 0/45 interfaces. Tests indicated that the three layups with only 0 degrees and +/-45 degrees plies had the highest torsional strength in the presence of a constant axial load. Of the three strongest layups, the one in which the +/- 45 degrees plies were made of woven cloth fabric instead of prepreg tape was the strongest and had the longest fatigue life. C1 USA, Res Lab, Vehicle Technol Ctr, NASA Langley Res Ctr, Hampton, VA USA. McDonnell Douglas Helicopter Syst, Mesa, AZ USA. RP O'Brien, TK (reprint author), USA, Res Lab, Vehicle Technol Ctr, NASA Langley Res Ctr, Hampton, VA USA. NR 1 TC 5 Z9 5 U1 2 U2 6 PU AMER SOC TESTING MATERIALS PI W CONSHOHOCKEN PA 100 BARR HARBOR DR, W CONSHOHOCKEN, PA 19428-2959 USA SN 0884-6804 J9 J COMPOS TECH RES JI J. Compos. Technol. Res. PD OCT PY 1998 VL 20 IS 4 BP 221 EP 226 PG 6 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA 137MF UT WOS:000076918000003 ER PT J AU Sen, S Dhindaw, BK Curreri, PA Peters, P Kaukler, WF AF Sen, S Dhindaw, BK Curreri, PA Peters, P Kaukler, WF TI Measurement of interfacial undercooling in a dilute Pb-Sn alloy near the regime of morphological instability SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID CELLULAR SOLIDIFICATION; SUCCINONITRILE-SALOL; DENDRITIC GROWTH; LEAD AB The solid/liquid (s/l) interfacial Seebeck technique was used to measure interfacial undercooling in a Pb-1 wt% Sn alloy. For plane front solidification an undercooling in the range of 0.54-0.57 degrees C was recorded. However, for growth velocities between 6 and 15 mu m/s the undercooling increased with increase in velocity. This is in contradiction to the theoretical predictions based on growth at the extremum condition. A modified analytical expression was developed based on the marginal stability criterion to predict undercooling for growth velocities immediately over the limit of morphological stability. Between 6 and 15 mu m/s the trend predicted by this modified expression is in qualitative agreement with the experimental results. This model is more consistent with the analysis of Venugopal and Kirkaldy which states that the extremum condition criterion is not applicable in the marginal stability regime. At higher growth velocities between 20 and 50 mu m/s where stable cellular growth is expected the undercooling decreased with increase in velocity. The predictions of Burden and Hunt based on extremum criterion agree reasonably well with the experimental results in this velocity range. Finally, the importance of nonequilibrium phase diagram parameters such as partition coefficient and liquidus slope were also evaluated using the experimental undercooling results obtained in this investigation. (C) 1998 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Indian Inst Technol, Kharagpur 721302, W Bengal, India. Univ Alabama, CMMR, Huntsville, AL 35899 USA. RP Sen, S (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. OI Dhindaw, Brij Kumar/0000-0001-6991-9793; Kaukler, William/0000-0002-7758-269X NR 20 TC 8 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD OCT PY 1998 VL 193 IS 4 BP 692 EP 700 DI 10.1016/S0022-0248(98)00518-1 PG 9 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 134CJ UT WOS:000076725000033 ER PT J AU Costen, RC Miller, LJ AF Costen, RC Miller, LJ TI Pulsing inertial oscillation, supercell storms, and surface mesonetwork data SO JOURNAL OF ENGINEERING MATHEMATICS LA English DT Article DE modeling; supercell storm; nonlinear; inertial oscillation; mesonetwork data ID THUNDERSTORM; EVOLUTION; DYNAMICS AB The pulsing inertial oscillation (PIO) model is a nonlinear, time-dependent, translating vortex solution of the inviscid, compressible fluid dynamic equations in the middle troposphere. The translation of this vortex during a pulse is strikingly similar to that of a supercell storm - a rotating thunderstorm that can generate tornadoes and hail. Two studies were performed to test the hypothesis that some supercell storms are manifestations of a PIO pulse. The first study applied the model to an intense interior draft whose buoyancy was bounded by a temperature excess of +/-12 K. The peak updraft speed achieved was 41.5 ms(-1) and the peak Rossby number was 92.9. The study also pointed to an advanced concept for attaining higher values. The second study applied the PIO model to a supercell storm as a whole and succeeded in replicating its bulk properties, such as mesocylonic circulation, net mass and moisture influxes, and time track. This study also identified a critical feature of the PIO model that could be tested against storm data: The average vertical draft is downward before the turn in the storm track and upward afterwards. In the conventional theory, the average vertical draft is upward from storm inception until dissipation. These differing draft predictions were compared with the best available data, which are surface mesonetwork data. These data were found to support the PIO model. However, surface data alone are not conclusive, and further measurements are warranted. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Costen, RC (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 32 TC 0 Z9 0 U1 1 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0022-0833 J9 J ENG MATH JI J. Eng. Math. PD OCT PY 1998 VL 34 IS 3 BP 277 EP 299 DI 10.1023/A:1004319330013 PG 23 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 127KU UT WOS:000076350800002 ER PT J AU Olla, BL Davis, MW Schreck, CB AF Olla, BL Davis, MW Schreck, CB TI Temperature magnified postcapture mortality in adult sablefish after simulated trawling SO JOURNAL OF FISH BIOLOGY LA English DT Article DE by-catch; physiology; survival; stress ID ANOPLOPOMA-FIMBRIA; EL-NINO; ACCLIMATION; CALIFORNIA; FECUNDITY; WATERS; OREGON AB For sablefish Anoplopoma fimbria that had been transferred abruptly from ambient (5.7 degrees C) to temperatures ranging from 15 to 20 degrees C for 30 min followed by 15 min in air (19.5 degrees C), mortality increased with temperature. Mortality occurred at lower temperatures for sablefish that were net-towed for 4 h at ambient temperature before exposure to a rapid increase in temperature. A clear relationship was apparent between serum lactate and temperature with lactate increasing as temperature increased. For treatments in which mortality did not occur, lactate decreased sharply within 24 h, suggesting recovery. It would appear that the critical postcapture temperature for sablefish that reside and are captured at 4-6 degrees C, would be between 12 and 15 degrees C. The results of this study suggest that fishery management strategies designed to increase postcapture survival of sablefish bycatch should include a consideration of the impact of exposure to seasonal thermoclines and seasonally elevated air temperatures. C1 Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Newport, OR 97365 USA. Oregon State Univ, US Geol Survey, Oregon Cooperat Fishery Res Unit, Biol Resources Div,Dept Fisheries & Wildlife, Corvallis, OR 97331 USA. RP Olla, BL (reprint author), Oregon State Univ, Hatfield Marine Sci Ctr, Natl Marine Fisheries Serv, Alaska Fisheries Sci Ctr, Newport, OR 97365 USA. NR 21 TC 36 Z9 37 U1 0 U2 2 PU ACADEMIC PRESS LTD PI LONDON PA 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND SN 0022-1112 J9 J FISH BIOL JI J. Fish Biol. PD OCT PY 1998 VL 53 IS 4 BP 743 EP 751 DI 10.1111/j.1095-8649.1998.tb01829.x PG 9 WC Fisheries; Marine & Freshwater Biology SC Fisheries; Marine & Freshwater Biology GA 125QA UT WOS:000076247500005 ER PT J AU Sitar, RJ Baker, JB Clauer, CR Ridley, AJ Cumnock, JA Papitashvili, VO Spann, J Brittnacher, MJ Parks, GK AF Sitar, RJ Baker, JB Clauer, CR Ridley, AJ Cumnock, JA Papitashvili, VO Spann, J Brittnacher, MJ Parks, GK TI Multi-instrument analysis of the ionospheric signatures of a hot flow anomaly occurring on July 24, 1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID EARTHS BOW SHOCK; TRAVELING CONVECTION VORTICES; INTERPLANETARY MAGNETIC-FIELD; DIAMAGNETIC CAVITIES UPSTREAM; TWIN VORTICES; EVENTS; BOUNDARY; REVERSAL; WAVES AB We present the analysis of a coordinated set of observations from the POLAR ultraviolet imager (UVI), ground magnetometers, incoherent scatter radar, solar wind monitors, and the DMSP satellite, focused on a traveling convection vortex (TCV) event on July 24, 1996. Starting at approximately 1036 UT, ground magnetometers in Greenland and eastern Canada observe pulsations consistent with the passing overhead of a series of TCV field-aligned current pairs. Azimuthal scans by the Sondrestrom incoherent scatter radar located near Kangerlussuaq (formerly Sondrestrom), Greenland, at this time show strong modulation in the strength and direction of ionospheric plasma flow. The magnetometer pulsations grow in magnitude over the next hour, peaking in intensity at 1137 UT. Images from the UVI instrument show a localized intensification of auroral emissions over central and western Greenland at 1139 UT. Subsequent images show the intensification grow in strength and propagate westward (tailward) until approximately 1158 UT, at which time the intensification fades, These observations are consistent with the westward passage of four pairs of TCVs over central Greenland. The intensification of auroral emissions at 1139 UT is associated with the leading vortex of the fourth TCV pair, thought to be the result of an upward field-aligned current. The modulated flow observed by the radar is the result of the strong electric fields associated with the field-aligned current systems responsible for the impulsive TCV as they pass through the field of view of the radar. Measurements taken in the solar wind by the Wind spacecraft suggest that a pressure change triggers the onset of TCV activity. A subsequent sudden change in the orientation of the interplanetary magnetic field produces a hot flow anomaly which forms at the bow shock. We believe that the interaction of the hot flow anomaly with the magnetopause intensified the fourth TCV pair and. produced the associated auroral brightening. DMSP particle data indicate that the TCVs occur on field lines which map to the boundary plasma sheet-low latitude boundary layer interface. The ground observations associated with the hot flow anomaly are the first of their kind and provide a mechanism to tie an interplanetary magnetic field orientation change into the existing theory that TCVs result from a deformation of the magnetopause. C1 Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA. SW Res Inst, San Antonio, TX 78238 USA. Univ Texas, Ctr Space Sci, Richardson, TX 75083 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Washington, Geophys Program, Seattle, WA 98195 USA. RP Sitar, RJ (reprint author), Univ Michigan, Space Phys Res Lab, 2455 Hayward, Ann Arbor, MI 48109 USA. RI Ridley, Aaron/F-3943-2011 OI Ridley, Aaron/0000-0001-6933-8534 NR 28 TC 31 Z9 31 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23357 EP 23372 DI 10.1029/98JA01916 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300003 ER PT J AU Gumbel, J Murtagh, DP Espy, PJ Witt, G Schmidlin, FJ AF Gumbel, J Murtagh, DP Espy, PJ Witt, G Schmidlin, FJ TI Odd oxygen measurements during the Noctilucent Cloud 93 rocket campaign SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID POLAR MESOSPHERIC CLOUDS; ATOMIC OXYGEN; LOWER THERMOSPHERE; MIDDLE ATMOSPHERE; OZONE; MODEL; REGION; PHOTOCHEMISTRY; FLUCTUATIONS; TRANSPORT AB The NLC-93 campaign at Esrange, Sweden, addressed the chemical, dynamical and electrical environment of the summer mesopause in the presence of noctilucent clouds (NLC). A major topic was the detailed investigation of odd oxygen abundances and their structure in the vicinity of the cloud layer. Applying independent in situ measurements, we have obtained consistent profiles of atomic oxygen, ozone, and mesospheric total density. Atomic oxygen was measured on two rocket flights by means of a newly developed probe utilizing the 1304 Angstrom resonance fluorescence / absorption technique. Detailed Monte Carlo simulations of the radiative transfer and the instrument aerodynamics are included in the data analysis. We find relatively low atomic oxygen densities with a peak of 2 x 10(11) cm(-3) at 96 km. An airglow radiometer recorded the O-2 IR-atmospheric band emission, allowing the retrieval of ozone densities by means of an inversion model that considers both direct and indirect sources of O-2 (a(1)Delta(g)). The odd oxygen measurements are compared to a steady state photochemical model. While good agreement is found in the mesosphere, the results deviate close to the cold mesopause. Significant vertical structures are found in the atomic oxygen profiles; sharp gradients and distinct minima coincide with the observed NLC layer. Possible influences of heterogeneous chemistry on the odd oxygen abundance are discussed. C1 Univ Stockholm, Dept Meteorol, S-10691 Stockholm, Sweden. NASA, Goddard Space Flight Ctr, Wallops Flight Facil, Wallops Island, VA 23337 USA. RP Gumbel, J (reprint author), Univ Stockholm, Dept Meteorol, S-10691 Stockholm, Sweden. EM gumbel@misu.su.se RI Murtagh, Donal/F-8694-2011 OI Murtagh, Donal/0000-0003-1539-3559 NR 57 TC 29 Z9 30 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23399 EP 23414 DI 10.1029/98JA02155 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300007 ER PT J AU Khazanov, GV Liemohn, MW Kozyra, JU Moore, TE AF Khazanov, GV Liemohn, MW Kozyra, JU Moore, TE TI Inner magnetospheric superthermal electron transport: Photoelectron and plasma sheet electron sources SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MONTE-CARLO METHOD; RING CURRENT IONS; AURORAL ELECTRONS; GEOSYNCHRONOUS ORBIT; SUBSTORM INJECTIONS; SYNCHRONOUS ORBIT; UPPER-ATMOSPHERE; IONOSPHERE; EQUATION; FLUXES AB Two time-dependent kinetic models of superthermal electron transport are combined to conduct global calculations of the nonthermal electron distribution function throughout the inner magnetosphere. It is shown that the energy range of validity for this combined model extends down to the superthermal-thermal intersection at a few eV, allowing for the calculation of the entire distribution function and thus an accurate heating rate to the thermal plasma. Because of the linearity of the formulas, the source terms are separated to calculate the distributions from the various populations, namely photoelectrons (PEs) and plasma sheet electrons (PSEs). These distributions are discussed in detail, examining the processes responsible for their formation in the various regions of the inner magnetosphere. It is shown that convection, corotation, and Coulomb collisions are the dominant processes in the formation of the PE distribution function and that PSEs are dominated by the interplay between the drift terms. Of note is that the PEs propagate around the nightside in a narrow channel at the edge of the plasmasphere as Coulomb collisions reduce the fluxes inside of this and convection compresses the flux tubes inward. These distributions are then recombined to show the development of the total superthermal electron distribution function in the inner magnetosphere and their influence on the thermal plasma. PEs usually dominate the dayside heating, with integral energy fluxes to the ionosphere reaching 10(10) eV cm(-2) in the plasmasphere, while heating from the PSEs typically does not exceed 10(8) eV cm(-2) s(-1) On the nightside, the inner plasmasphere is usually unheated by superthermal electrons. A feature of these combined spectra is that the distribution often has upward slopes with energy, particularly at the crossover from PE to PSE dominance, indicating that instabilities are possible. C1 Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Univ Alaska, Dept Phys, Fairbanks, AK 99775 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Khazanov, GV (reprint author), Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. RI Moore, Thomas/D-4675-2012; Liemohn, Michael/H-8703-2012; feggans, john/F-5370-2012 OI Moore, Thomas/0000-0002-3150-1137; Liemohn, Michael/0000-0002-7039-2631; NR 85 TC 20 Z9 20 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23485 EP 23501 DI 10.1029/98JA02291 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300013 ER PT J AU Nagai, T Fujimoto, M Nakamura, R Saito, Y Mukai, T Yamamoto, T Nishida, A Kokubun, S Reeves, GD Lepping, RP AF Nagai, T Fujimoto, M Nakamura, R Saito, Y Mukai, T Yamamoto, T Nishida, A Kokubun, S Reeves, GD Lepping, RP TI Geotail observations of a fast tailward flow at X-GSM=-15 R-E SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SUBSTORM GROWTH-PHASE; MAGNETOTAIL; ONSET; PSEUDOBREAKUP; PARTICLE AB Geotail observed a fast tailward flow burst (a speed of >600 km/s) with southward B-z in the Earth's magnetotail at a radial distance of 15.5 R-E on March 30, 1995. Ions in this burst consisted of a single-component plasma showing convection motion, and these ions were confined near the neutral sheet. This flow burst was likely associated with a pseudobreakup rather than a major substorm onset. In this event, magnetic reconnection appeared to take place only for the field lines near the neutral sheet. The magnetic reconnection was quenched soon and resulted in a short-lived tailward flow burst embedded in the plasma sheet. C1 Tokyo Inst Technol, Dept Earth & Planetary Sci, Tokyo 1528551, Japan. Nagoya Univ, Solar Terr Environm Lab, Toyokawa 4428507, Japan. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Nagai, T (reprint author), Tokyo Inst Technol, Dept Earth & Planetary Sci, Tokyo 1528551, Japan. EM nagai@geo.titech.ac.jp RI Nakamura, Rumi/I-7712-2013; Reeves, Geoffrey/E-8101-2011 OI Nakamura, Rumi/0000-0002-2620-9211; Reeves, Geoffrey/0000-0002-7985-8098 NR 15 TC 22 Z9 22 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23543 EP 23550 DI 10.1029/98JA02246 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300016 ER PT J AU Tsyganenko, NA AF Tsyganenko, NA TI Modeling of twisted/warped magnetospheric configurations using the general deformation method SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MAGNETIC-FIELD; TAIL; MAGNETOPAUSE; DIPOLE; SHAPE; SHEET AB A new method is developed for modeling the effects of the planetary dipole tilt and of the interplanetary magnetic field (IMF) related twisting of the cross-tail current sheet. The method extends the field deformation technique of Stern [1987] and makes it possible to easily represent a wide variety of warped magnetospheric configurations, starting from simple models with an axially symmetric magnetopause and a planar tail current sheet. The proposed transformations do not violate the condition del.B = 0 and allow one to retain a desired distribution of the normal component of the total field at the magnetospheric boundary. Furthermore, the method makes it possible to add flexibility to the model magnetopause, so that the effects of the dipole tilt and of the IMF upon its shape can be reproduced. In particular, the transformation with a radially dependent rotation of the X and Z axes, while providing the desired tilt-related bending of the cross-tail current sheet, can also deform the magnetopause and reproduce its tilt-related asymmetry, indicated by observations and reported here for the first time. The deformation technique also allows algorithms that are more compact and faster than the currently used ones. Because of the general nature of the proposed approach it should be possible to extend it to the modeling of other (e.g., Jovian) planetary magnetospheres. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Raytheon STX Corp, Greenbelt, MD 20771 USA. RP Tsyganenko, NA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Raytheon STX Corp, Code 690-2, Greenbelt, MD 20771 USA. RI Tsyganenko, Nikolai/J-7377-2012 OI Tsyganenko, Nikolai/0000-0002-5938-1579 NR 31 TC 37 Z9 38 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23551 EP 23563 DI 10.1029/98JA02292 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300017 ER PT J AU Sergeev, VA Kamide, Y Kokubun, S Nakamura, R Deehr, CS Hughes, TJ Lepping, RP Mukai, T Petrukovich, AA Shue, JH Shinokawa, K Troshichev, OA Yumoto, K AF Sergeev, VA Kamide, Y Kokubun, S Nakamura, R Deehr, CS Hughes, TJ Lepping, RP Mukai, T Petrukovich, AA Shue, JH Shinokawa, K Troshichev, OA Yumoto, K TI Short-duration convection bays and localized interplanetary magnetic field structures on November 28, 1995 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; MAGNETOSPHERIC SUBSTORMS; CURRENT SYSTEMS; DYNAMICS; PHYSICS; PHASES AB We present ground-based, plasma sheet, and magnetosheath observations of two subsequent short-duration (10-20 min) increases of the postmidnight westward electrojet on November 28, 1995. Appearing: as though small (150-200 nT) substorms, they were not accompanied by any substorm expansion onset signatures. Auroral breakup, worldwide Pi2 pulsations, and the corresponding plasma sheet activity, such as fast flows, current disruption, and plasmoid generation, were all observed only at the recovery of the second electrojet increase. These convection bays were associated with the equatorward expansion of the auroras and simultaneous magnetic variations in the polar cap and middle latitudes. Growth phase signatures of the lobe field increase and tailward stretching of magnetic field were also observed in the plasma sheet. Bursty bulk flows in the plasma sheet seem to be quenched at the onset of first convection bay and did not resume until the auroral breakup which concluded the second convection bay, A point of interest of this event was the "incomplete" convection/current system with a well-developed dawn vortex in the absence of well-defined dusk vortex; instead, a complicated transient activity dominated over the afternoon-dusk local time sector. We interpret this asymmetry either in terms of the magnetopause encounter with the edge of the solar wind driver, i.e., strong southward IMF, which hits only the dawn part of the magnetosphere, or with an extremely slant interplanetary discontinuity. This unique configuration was inferred from observations of uncorrelated strong southward B-z events by the Wind and IMP 8 spacecraft in the dusk and dawn magnetosheath, respectively, as well as from the directional analysis of the interplanetary discontinuities which form the edges of these structures, We suggest that interaction of the magnetosphere with very slant solar wind discontinuities may bring various specific features to magnetospheric and ionospheric dynamics that have not been reported. C1 Nagoya Univ, Solar Terr Environm Lab, Aichi 442, Japan. Univ Alaska, Inst Geophys, Fairbanks, AK 99775 USA. Natl Res Council Canada, Herzberg Inst Astrophys, Ottawa, ON K1A 0R6, Canada. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Kanagawa 229, Japan. Russian Acad Sci, Space Res Inst, IKI, Moscow 117810, Russia. Arctic & Antarctic Res Inst, Dept Geophys, St Petersburg 191104, Russia. Kyushu Univ, Dept Phys, Fukuoka 810, Japan. RP Sergeev, VA (reprint author), St Petersburg State Univ, Inst Phys, St Petersburg 198904, Russia. RI Nakamura, Rumi/I-7712-2013; Petrukovich, Anatoly/G-8764-2011; Sergeev, Victor/H-1173-2013 OI Nakamura, Rumi/0000-0002-2620-9211; Petrukovich, Anatoly/0000-0002-5344-2967; Sergeev, Victor/0000-0002-4569-9631 NR 26 TC 16 Z9 16 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23593 EP 23609 DI 10.1029/98JA01747 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300020 ER PT J AU Farrell, WM Kaiser, ML Steinberg, JT Bale, SD AF Farrell, WM Kaiser, ML Steinberg, JT Bale, SD TI A simple simulation of a plasma void: Applications to wind observations of the lunar wake SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID PARTICLE DISTRIBUTIONS; BOW WAVE; SPACECRAFT; MOON AB Previously, the formation of the lunar wake was considered from a magnetohydrodynamic perspective. However, recent Wind particle and field observations suggest the lunar wake may be formed by kinetic processes: those microphysical processes not considered in an MHD formalism. Unfortunately, a full multidimensional and self-consistent kinetic simulation of the lunar wake is beyond current means. However, some elements of the kinetic structure can be simulated via a simple one-dimensional electrostatic particle-in-cell simulation. We present a self-consistent simulation of a cross-sectional element of a plasma void. Essentially, wakeward directed ion beams are formed at the flanks of the simulated void, consistent with the Wind observations of counterstreaming ion beams in the wake region. These wakeward directed beams are generated by ambipolar electric fields formed at the wake edges. Other structures observed by Wind are also seen in the simulation, including an electrostatically turbulent central wake region that causes the wake to fill-in and a rarefaction wave emanating outward from the wake. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. MIT, Ctr Space Res, Cambridge, MA 02139 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Farrell, WM (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Bale, Stuart/E-7533-2011; Farrell, William/I-4865-2013 OI Bale, Stuart/0000-0002-1989-3596; NR 16 TC 57 Z9 57 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23653 EP 23660 DI 10.1029/97JA03717 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300024 ER PT J AU Ofman, L Davila, JM AF Ofman, L Davila, JM TI Solar wind acceleration by large-amplitude nonlinear waves: Parametric study SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID WKB ALFVEN WAVES; CORONAL HOLES; STELLAR ATMOSPHERES; MHD TURBULENCE; SOLITARY WAVES; MODELS; FLUCTUATIONS; PROPAGATION; REFLECTION AB We investigate the parametric dependence of the solar wind acceleration by large-amplitude nonlinear (LAN) magnetohydrodynamic waves. For this purpose we model numerically the self-consistent problem of the solar wind with waves by solving time-dependent, nonlinear, resistive 2.5-dimensional (three-dimensional with azimuthal symmetry) MHD equations driven by Alfven waves. We find that when the Alfven wave amplitude is above a parameter-dependent threshold, LAN waves are generated in the model coronal hole. For typical coronal parameters the solar wind speed and density fluctuate considerably on a timescale of similar to 10-40 min and with an amplitude of up to several hundred kmilometers per second near the Sun (r less than or similar to 10 R-S) in agreement with recent interplanetary scintillation observations, The solar wind speed is inversely dependent on the driving frequency in the range 0.35-3 mHz. The amplitude of the velocity fluctuations increases with the amplitude of the magnetic field and the driving Alfven waves at the base of the corona and decreases with the coronal temperature. We found that for the same-typical solar wind and Alfven wave parameters and an isothermal initial atmosphere, the WKB model predicts 30% higher flow velocities far from the Sun (32 R-S) than our self-consistent wave model with high-frequency Alfven waves (f = 2.78 mHz), conforming to the WKB approximation. However, our model predicts significantly higher average flow speed near the Sun, When low-frequency non-WKB waves drive the wind, our model predicts 25% higher solar wind speed than the WKB model far from the Sun. This result of our model is in agreement with linear studies of solar wind acceleration by Alfven waves that take into account Alfven wave reflection. C1 NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD USA. RP Ofman, L (reprint author), NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Code 682, Greenbelt, MD 20771 USA. NR 50 TC 67 Z9 67 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23677 EP 23690 DI 10.1029/98JA01996 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300026 ER PT J AU Ghosh, S Matthaeus, WH Roberts, DA Goldstein, ML AF Ghosh, S Matthaeus, WH Roberts, DA Goldstein, ML TI The evolution of slab fluctuations in the presence of pressure-balanced magnetic structures and velocity shears SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND FLUCTUATIONS; INTERPLANETARY ALFVENIC FLUCTUATIONS; MHD TURBULENCE; NONLINEAR EVOLUTION; HIGH-BETA; FIELD; MAGNETOHYDRODYNAMICS; ANISOTROPY; TRANSPORT; MODEL AB The traditional view that solar wind fluctuations are well-described as a spectrum of parallel-propagating Alfven waves has been challenged many times but is still a frequently encountered perspective. Here we examine whether it remains consistent to view most of the fluctuation energy as resident in parallel-propagating Alfven waves in situations in which there are also present either transverse pressure-balanced (PB) magnetic structures or transverse velocity shears. We address these questions through direct simulation of compressible magnetohydrodynamics, with expansion effects neglected. We show that parallel-propagating Alfven waves are redirected to large oblique angles after refractive interactions with PB structures or advective interactions with velocity shears, reflecting the nonequilibrium nature of the initial spectral distribution. The timescale for these processes ranges from 2-8 eddy-turnover times or characteristic nonlinear times. Relatively small amounts of PB structure and/or shear energy can redirect initially parallel-propagating Alfven waves to highly oblique angles. Velocity microstreams appear to be particularly efficient at creating highly oblique waves. Even though the excited wave vectors are eventually primarily oblique, the magnetic variance ratios show a minimum variance in the mean magnetic field direction. C1 Space Applicat Corp, Appl Res Div, Largo, MD 20774 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ghosh, S (reprint author), Space Applicat Corp, Appl Res Div, 9315 Large Dr W,Suite 250, Largo, MD 20774 USA. EM ron.ghosh@gsfc.nasa.gov; yswhm@bartol.udel.edu; aaron.roberts@gsfc.nasa.gov; melvyn.goldstein@gsfc.nasa.gov RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 44 TC 48 Z9 48 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23691 EP 23704 DI 10.1029/98JA02195 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300027 ER PT J AU Ghosh, S Matthaeus, WH Roberts, DA Goldstein, ML AF Ghosh, S Matthaeus, WH Roberts, DA Goldstein, ML TI Waves, structures, and the appearance of two-component turbulence in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID MEAN MAGNETIC-FIELD; MHD TURBULENCE; ALFVEN WAVES; MAGNETOHYDRODYNAMICS; FLUCTUATIONS; ANISOTROPY; MODEL AB Spacecraft observations of magnetic field fluctuations in the solar wind reveals a "Maltese Cross" pattern in the two-dimensional correlation function measurements of solar wind fluctuations [Matthaeus et al., 1990]. This pattern suggests the presence of two components: fluctuations with their (Fourier) wave vector approximately parallel to the ambient magnetic field (e.g., slab turbulence) and fluctuations with their (Fourier) wave vector approximately perpendicular to the ambient magnetic field (e.g,, quasi two-dimensional turbulence). To date, the appearance of such a pattern has never been reproduced from numerical simulation studies. Here we present results of several MHD simulations that address this issue using both two-and-one-half dimensional and three-dimensional compressible models and a wide variety of initial states and plasma parameters. Slab turbulence and quasi two-dimensional turbulence appear in various runs, however, their simultaneous appearance is difficult to achieve and seems to rely upon their separate existence in the initial data. In contrast, the presence of transverse pressure-balanced magnetic structures causes slab turbulence to evolve in such a manner that a two-component correlation function emerges through time averaging. We suggest that the Maltese Cross and similar observations may be a consequence of either the initial data or of averaging over different parcels of solar wind. C1 Space Applicat Corp, Appl Res Div, Largo, MD 20774 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ghosh, S (reprint author), Space Applicat Corp, Appl Res Div, 9315 Large Dr W,Suite 250, Largo, MD 20774 USA. EM ron.ghosh@gsfc.nasa.nov; yswhm@bartol.udel.edu; aaron.roberts@gsfc.nasa.gov; melvyn.goldstein@gsfc.nasa.gov RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 21 TC 62 Z9 62 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 OCT 1 PY 1998 VL 103 IS A10 BP 23705 EP 23715 DI 10.1029/98JA02194 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300028 ER PT J AU Burlaga, LF Ness, NF Wang, YM Sheeley, NR AF Burlaga, LF Ness, NF Wang, YM Sheeley, NR TI Heliospheric magnetic field strength out to 66 AU: Voyager 1, 1978-1996 SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND SPEED; RADIAL IMF COMPONENT; ULYSSES OBSERVATIONS; LATITUDINAL DEPENDENCE; OUTER HELIOSPHERE; EXPANSION FACTOR; CYCLE; GRADIENTS; PIONEER-11; EVOLUTION AB We discuss Voyager 1 (V1) observations of the heliospheric magnetic field strength from 1978 through 1996. During this period the distance of V1 from the Sun increased from approximate to 3 AU to 66 AU and its heliographic latitude increased from approximate to 5 degrees S to 33 degrees N. The magnetic field strength profile observed by V1 is consistent with Parker's spiral field model when one considers (1) the solar cycle variation of the observed magnetic field strength at 1 AU, B-1(t) (which is a measure of the source field strength) and (2) the latitudinal and solar cycle variations of the solar wind speed, V(t, theta), Both B-1(t) and V(t, theta) make significant contributions to the variation of the magnetic field strength variations observed by V1. There is no evidence for a "magnetic flux deficit" increasing with distance from the Sun. There is a solar cycle variation of the magnetic field strength in the outer heliosphere, which will affect the modulation of cosmic rays. C1 NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA. USN, EO Hulburt Ctr Space Res, Res Lab, Washington, DC 20375 USA. RP Burlaga, LF (reprint author), NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 48 TC 19 Z9 19 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD OCT 1 PY 1998 VL 103 IS A10 BP 23727 EP 23732 DI 10.1029/98JA01433 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 125XL UT WOS:000076262300030 ER PT J AU Chen, PS Kuruvilla, AK Malone, TW Stanton, WP AF Chen, PS Kuruvilla, AK Malone, TW Stanton, WP TI The effects of artificial aging on the microstructure and fracture toughness of Al-Cu-Li alloy 2195 SO JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE LA English DT Article DE Alloy 2195; aluminum; heal treatment; lithium alloys; microstructure; spacecraft hardware ID ALUMINUM-LITHIUM ALLOYS; CRYOGENIC TEMPERATURES; BEHAVIOR; AMBIENT AB Aluminum-lithium alloys have shown promise for aerospace applications, and National Aeronautics and Space Administration (NASA) has selected the aluminum-lithium Alloy 2195 for the main structural alloy of the super light weight tank (SLWT) for the space shuttle, This alloy has significantly higher strength than conventional 2xxx alloys (such as 2219) at both ambient and cryogenic temperatures. If properly processed and heat treated, this alloy can display higher fracture toughness at cryogenic temperature than at ambient temperature. However, the properties of production materials have shown greater variation than those of other established alloys, as is the case with any new alloy that is being transitioned to a demanding application. Recently, some commercial 2195 plates for the SLWT program were rejected, mostly due to low CFT or FTR at ambient and cryogenic temperatures, Investigation of the microstructure property relationships of Al-Cu-Li based alloys indicates that the poor fracture toughness properties can be attributed to excessive T-1 precipitation at subgrain boundaries. Lowering the aging temperature is one way to avoid excessive T-1 precipitation at subgrain boundaries. However, this approach results In a significant drop in yield strength, In addition, low-temperature aging is associated with sluggish aging kinetics, which are not desirable for industrial mass production. Therefore, the present study was undertaken to develop an aging process that can improve fracture toughness without sacrificing yield and tensile strength. A multistep heating-rate controlled (MSRC) aging treatment has been developed that can improve the cryogenic fracture toughness of aluminum-lithium Alloy 2195, At the same levels of yield strength (YS), this treatment results in considerably higher fracture toughness than that found in Alloy 2195, which has received conventional (isothermal) aging. Transmission electron microscopy revealed that the new treatment greatly reduces the size and density of subgrain-boundary T-1 precipitates. In addition, it promotes T-1 and theta " nucleation, resulting in a fine and dense distribution of precipitate particles in the matrix. The MSRC aging treatment consists of(a) aging at 127 degrees C (260 degrees F) for 5 h, (b) heating continuously from 127 degrees C (260 degrees F) to 135 degrees C (275 degrees F) at a rate of 0.556 degrees C/h (1 degrees F/h), (c) holding at 135 degrees C (275 degrees F) for 5 h, (d) heating continuously from 135 to 143 degrees C (275 to 290 degrees F) at a rate of 0.556 degrees C/h (1 degrees F/h), and (e) holding at 143 degrees C (290 degrees F) for 25 h to obtain a near peak-aged condition. C1 NASA, George C Marshall Space Flight Ctr, IIT Res Inst, Met Res Facil, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Met Proc Branch, Mat & Proc Lab, Huntsville, AL 35812 USA. RP Chen, PS (reprint author), NASA, George C Marshall Space Flight Ctr, IIT Res Inst, Met Res Facil, Bldg 4628, Huntsville, AL 35812 USA. NR 14 TC 31 Z9 33 U1 3 U2 19 PU ASM INTERNATIONAL PI MATERIALS PARK PA SUBSCRIPTIONS SPECIALIST CUSTOMER SERVICE, MATERIALS PARK, OH 44073-0002 USA SN 1059-9495 J9 J MATER ENG PERFORM JI J. Mater. Eng. Perform. PD OCT PY 1998 VL 7 IS 5 BP 682 EP 690 DI 10.1361/105994998770347576 PG 9 WC Materials Science, Multidisciplinary SC Materials Science GA 124YP UT WOS:000076210600015 ER PT J AU Tseng, AA Watson, WL Chen, JS Orth, NW AF Tseng, AA Watson, WL Chen, JS Orth, NW TI Melt spinning of a shape memory alloy SO JOURNAL OF MATERIALS PROCESSING & MANUFACTURING SCIENCE LA English DT Article ID TRANSFORMATION AB Rapidly solidified Ti70Ni30 ribbons for shape memory applications have been produced by melt spinning. The effects of spinning speeds on the structure and transformation behavior of the alloy were investigated. The martensitic transformation characteristics of melt-spun ribbons were studied using a thermal analysis technique. The microstructural and mechanical properties of the ribbons are studied. The paper details the making of the master alloys, production of rapidly solidified ribbons, and evaluation of ingot and ribbon properties. It was found that this is not an easy alloy to melt spin. A narrow operating window for temperature was noted for this alloy. C1 Arizona State Univ, Mfg Inst, Tempe, AZ 85287 USA. Temple Univ, Dept Mech Engn, Philadelphia, PA 19122 USA. NASA, Lewis Res Ctr, Intermet Mat Branch, Cleveland, OH 44135 USA. NR 12 TC 0 Z9 0 U1 0 U2 0 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 1062-0656 J9 J MATER PROCESS MANU JI J. Mater. Process. Manuf. Sci. PD OCT PY 1998 VL 7 IS 2 BP 135 EP 144 DI 10.1106/8VF3-1XFK-0NDM-H7LP PG 10 WC Materials Science, Multidisciplinary SC Materials Science GA 258MB UT WOS:000083842000001 ER PT J AU Tang, W Guo, X McClure, JC Murr, LE AF Tang, W Guo, X McClure, JC Murr, LE TI Heat input and temperature distribution in friction stir welding SO JOURNAL OF MATERIALS PROCESSING & MANUFACTURING SCIENCE LA English DT Article AB In this paper the heat input and temperature distribution during friction stir welding is investigated. The temperatures at different positions in the specimen thickness direction and perpendicular to the pin tool travel direction were recorded during welding under various welding conditions. It was found that the highest temperature in the welding seam is less that 0.8T(m). For the conditions used in this work, the temperature does not change appreciably in the specimen thickness direction. The temperature distribution perpendicular to the weld is nearly isothermal under the pin tool shoulder. Furthermore, increasing welding pressure and pin tool rotational speed increases the peak welding temperature. Finally, it is shown that the shoulder of the pin tool plays a very important role in the welding process. C1 Univ Texas, Dept Met & Mat Engn, El Paso, TX 79968 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RI Tang, Wei/E-3613-2017; OI Tang, Wei/0000-0002-9274-9574; Murr, Lawrence/0000-0001-5942-8376 NR 12 TC 149 Z9 168 U1 11 U2 49 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 1062-0656 J9 J MATER PROCESS MANU JI J. Mater. Process. Manuf. Sci. PD OCT PY 1998 VL 7 IS 2 BP 163 EP 172 DI 10.1106/55TF-PF2G-JBH2-1Q2B PG 10 WC Materials Science, Multidisciplinary SC Materials Science GA 258MB UT WOS:000083842000003 ER PT J AU Bansal, NP AF Bansal, NP TI Solid state synthesis and properties of monoclinic celsian SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID KINETICS AB Monoclinic celsian of Ba0.75Sr0.25Al2Si2O8 (BSAS-1) and Ba0.85Sr0.15Al2Si2O8 (BSAS-2) compositions have been synthesized from metal carbonates and oxides by solid state reaction. A mixture of BaCO3, SrCO3, Al2O3, and SiO2 powders was precalcined at similar to 900-940 degrees C to decompose the carbonates followed by hot pressing at similar to 1300 degrees C. The hot pressed BSAS-1 material was almost fully dense and contained the monoclinic celsian phase, with complete absence of the undesirable hexacelsian as indicated by X-ray diffraction, In contrast, a small fraction of hexacelsian was still present in hot pressed BSAS-2. However, on further heat treatment at 1200 degrees C for 24 h, the hexacelsian phase was completely eliminated. The average linear thermal expansion coefficients of BSAS-1 and BSAS-2 compositions, having the monoclinic celsian phase, were measured to be 5.28 x 10(-6) degrees C-1 and 5.15 x 10(-6) degrees C-1, respectively, from room temperature to 1200 degrees C, The hot-pressed BSAS-1 celsian showed room temperature flexural strength of 131 MPa, elastic modulus of 96 GPa and was stable in air up to temperatures as high as similar to 1500 degrees C. (C) 1998 Kluwer Academic Publishers. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Bansal, NP (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 18 TC 39 Z9 42 U1 1 U2 2 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 OCT 1 PY 1998 VL 33 IS 19 BP 4711 EP 4715 DI 10.1023/A:1004484903436 PG 5 WC Materials Science, Multidisciplinary SC Materials Science GA 170XY UT WOS:000078833400007 ER PT J AU Robinson, DH Arrigo, KR Kolber, Z Gosselin, M Sullivan, CW AF Robinson, DH Arrigo, KR Kolber, Z Gosselin, M Sullivan, CW TI Photophysiological evidence of nutrient limitation of platelet ice algae in McMurdo Sound, Antarctica SO JOURNAL OF PHYCOLOGY LA English DT Article DE Antarctic; nutrient limitation; photoacclimation; pump-probe fluorometry; sea ice algae ID PHOTOSYNTHESIS-IRRADIANCE RELATIONSHIPS; DENSE MICROALGAL BLOOM; SEA-ICE; MICROBIAL COMMUNITIES; CARBON ASSIMILATION; HIGH-RESOLUTION; SPECTRAL IRRADIANCE; ENERGY-CONVERSION; LIGHT-ABSORPTION; MARINE DIATOMS AB Seasonally changing photophysiological and biochemical characteristics of sea ice microalgae are interpreted with respect to light availability and measurements of nutrient concentration made at high vertical resolution (12.5 cm) during a dense bloom in the platelet ice layer of McMurdo Sound during a 6-week study in austral spring of 1989. Platelet ice algae remained highly shade adapted throughout the spring as shown by their low photoadaptive index (E-k, 3.7-8.4 mu mol photons.m(-2).s(-1)), low mean specific absorption coefficient (<0.009 m(2) mg(-1) Chl a), high optical cross-sectional area of photosystem II (sigma(PSII) 3.0-8.2), and high molar ratio of fucoxanthin:chlorophyll a (mean 1.62 +/- 0.25 SD). Between 24 October and 8 November, the algae exhibited a photoacclimative response that was marked by a 30% decrease in photosynthetic efficiency (alpha(B)), a 75% decrease in maximum photosynthetic rate (P-m(B)), and a 60% increase in sigma(PSII). The photochemical conversion efficiency at photosystem II (F-v/F-m = ca. 0.5) and the quantum yield of photosynthesis (empty set(C) = 0.062-0.078 mol C mol(-1) photons) were ca. 80% of their maximal values. After 8 November, changes in algal photophysiology and biochemistry, which were inconsistent with a photoacclimation response, suggest that tice platelet ice alg-ae near the platelet/congelation ice interface became increasingly nutrient limited. The number of pennate diatoms increased threefold to 150 X 10(9) cells m(-3) between 8 and 14 November, then remained unchanged throughout the remainder of the field season. Following the increase in cell number, F-v/F-m, empty set(C), and C:Chla decreased by >40%, sigma(PSII) increased by 70%; and the biochemical ratios C:N and C:Si increased 25%-30%. Nutrient depletion was apparent from the high-resolution vertical profiles, but nutrient concentrations limiting algal growth were not observed. However, nutrient concentrations at the likely site of nutrient limitation near the platelet/congelation ice interface were not measured, indicating that higher resolution sampling is necessary to fully characterize this highly variable habitat. C1 NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Brookhaven Natl Lab, Upton, NY 11973 USA. Univ Quebec, Dept Oceanog, Rimouski, PQ G5L 3A1, Canada. Univ So Calif, Los Angeles, CA 90089 USA. RP Robinson, DH (reprint author), NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. EM dale@neptune.gsfc.nasa.gov RI Gosselin, Michel/B-4477-2014 OI Gosselin, Michel/0000-0002-1044-0793 NR 49 TC 27 Z9 29 U1 2 U2 13 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 OCT PY 1998 VL 34 IS 5 BP 788 EP 797 DI 10.1046/j.1529-8817.1998.340788.x PG 10 WC Plant Sciences; Marine & Freshwater Biology SC Plant Sciences; Marine & Freshwater Biology GA 133AQ UT WOS:000076664600011 ER PT J AU Goodman, ML AF Goodman, ML TI A class of driven, dissipative, energy-conserving magnetohydrodynamic equilibria with flow SO JOURNAL OF PLASMA PHYSICS LA English DT Article ID H-MODE; TRANSPORT; TOKAMAK; TURBULENCE; CURRENTS; PLASMAS; SYSTEMS AB The classical transport coefficients provide an accurate description of transport processes in collision-dominated plasmas. These transport coefficients are used in a cylindrically symmetric, electrically driven, steady-state magnetohydrodynamic (MHD) model with flow and an energy equation to study the effects of transport processes on MHD equilibria. The transport coefficients: which are functions of number density, temperature and magnetic field strength, are computed self-consistently as functions of radius R. The model has plasma-confining solutions characterized by the existence of an inner region of plasma with values of temperature, pressure and current density that are orders of magnitude larger than in the surrounding, outer region of plasma that extends outward to the boundary of the cylinder at R = a. The inner and outer regions are separated by a boundary layer that is an electric-dipole layer in which the relative charge separation is localized, and in which the radial electric field, temperature: pressure and axial current density vary rapidly. By analogy with laboratory fusion plasmas in confinement devices, the plasma in the inner region is confined plasma, and the plasma in the outer region is unconfined plasma. The solutions studied demonstrate that the thermoelectric current density, driven by the temperature gradient, can make the main contribution to the current density, and that the thermoelectric component of the electron heat flux, driven by an effective electric field, can make a large contribution to the total heat flux. These solutions also demonstrate that the electron pressure gradient and Hall terms in Ohm's law can make dominant contributions to the radial electric field. These results indicate that the common practice of neglecting thermoelectric effects and the Hall and electron pressure-gradient terms in Ohm's law is not always justified, and can lead to large errors. The model has three, intrinsic; universal values of beta at which qualitative changes in the solutions occur. These values are universal in that they only depend on the ion charge number and the electron-to-ion mass ratio. The first such value of beta (about 3.2% for a hydrogen plasma), when crossed, signals a change in sign of the radial gradient of the number density, and must be exceeded in order that a plasma-confining solution exist for a plasma with no flow. The second such value of beta (about 10.4% for a hydrogen plasma), when crossed, signals a change in sign of the poloidal current density. Some of the solutions presented exhibit this current reversal. The third such value of beta is about 2.67 for a hydrogen plasma. When beta is greater than or equal to this value, the thermoelectric, effective electric-field-driven component of the electron heat flux cancels 50% or more of the temperature-gradient-driven ion heat flux. If appropriate boundary conditions are given on the axis R = 0 of the cylinder, the equilibrium is uniquely determined. Analytical evidence is presented that, together with earlier work, strongly suggests that if appropriate boundary conditions are enforced at the outer boundary R = a then the equilibrium exhibits a bifurcation into two states, one of which exhibits plasma confinement and carries a larger axial current than the other state, which is close to global thermodynamic equilibrium, and so is not plasma-confining. Exact expressions for the two values of the axial current in the bifurcation are presented. Whether or not a bifurcation can occur is determined by the values of a critical electric field determined by the boundary conditions at R = a, and the constant driving electric field, which is specified. An exact expression for the critical electric field is presented. Although the ranges of the physical quantities computed by the model are a subset of those describing fusion plasmas in tokamaks, the model may be applied to any two-component, electron-ion, collision-dominated plasma for which the ion cyclotron frequency is much larger than the ion-ion Coulomb collision frequency such as the plasma in magnetic flux tubes in the solar interior, photosphere, lower transition region, and possibly the upper transition region and lower corona. C1 NASA, Goddard Space Flight Ctr, Comp Sci Corp, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, Comp Sci Corp, Greenbelt, MD 20771 USA. NR 23 TC 4 Z9 4 U1 0 U2 0 PU CAMBRIDGE UNIV PRESS PI NEW YORK PA 32 AVENUE OF THE AMERICAS, NEW YORK, NY 10013-2473 USA SN 0022-3778 EI 1469-7807 J9 J PLASMA PHYS JI J. Plasma Phys. PD OCT PY 1998 VL 60 BP 587 EP 625 DI 10.1017/S0022377898006928 PN 3 PG 39 WC Physics, Fluids & Plasmas SC Physics GA 146YD UT WOS:000077460700011 ER PT J AU Bhatia, AK Kastner, SO AF Bhatia, AK Kastner, SO TI Local Doppler-profile escape factors within the cylinder SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID PROBABILITIES AB Local escape factors for photons emitted within a Doppler (Gaussian) frequency profile, at specified radial locations within the homogenous infinite cylinder, are calculated and tabulated. They have been checked for numerical accuracy against a previously calculated global (integrated) escape factor. Their general behavior is illustrated in figures, which show also the expected approach of the surface escape factor to the plane-parallel value of 1/2 as opacity increases. (C) 1998 Published by Elsevier Science Ltd. All right reserved. 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, Greenbelt, MD 20771 USA. NR 11 TC 1 Z9 1 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD OCT PY 1998 VL 60 IS 4 BP 543 EP 549 DI 10.1016/S0022-4073(97)00204-5 PG 7 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 114DP UT WOS:000075594100005 ER PT J AU Pardo, JR Gerin, M Prigent, C Cernicharo, J Rochard, G Brunel, P AF Pardo, JR Gerin, M Prigent, C Cernicharo, J Rochard, G Brunel, P TI Remote sensing of the mesospheric temperature profile from close-to-nadir observations: Discussion about the capabilities of the 57.5-62.5 GHz frequency band and the 118.75 GHz single O-2 line SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article ID OXYGEN AB The new generation of atmospheric temperature sounders at frequencies around 60 GHz plan to include channels for scanning at altitudes above similar to 45 km (AMSU-C of NOAA and SSM/IS of DMSP). The thermal emission of O-2 at such altitudes is affected by the interaction of the permanent magnetic moment of O-2 in its ground electronic state je with the Earth's magnetic field resulting in a Zeeman splitting of the rotational lines. This physical phenomenon is polarization dependent. Thus, the magnetic field makes the analysis of data coming from channels sensitive to it much more complicated than in the case of low atmospheric channels (temperature weighting functions peaking below similar to 45 km) around 60 GHz. This paper discusses the choice of frequencies and polarizations in the spin-rotation oxygen lines around 60 and 119 GHz to cover the goals of the future temperature sounders above similar to 45 km. (C) 1998 Elsevier Science Ltd. All rights reserved. C1 Observ Paris, DEMIRM, F-75014 Paris, France. ENS, URA 336 CNRS, F-75005 Paris, France. CSIC, IEM, Dpto Fis Mol, E-28006 Madrid, Spain. Meteo France, Ctr Meteorol Spatiale, F-22302 Lannion, France. RP Pardo, JR (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. NR 15 TC 4 Z9 4 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0022-4073 J9 J QUANT SPECTROSC RA JI J. Quant. Spectrosc. Radiat. Transf. PD OCT PY 1998 VL 60 IS 4 BP 559 EP 571 DI 10.1016/S0022-4073(97)00235-5 PG 13 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 114DP UT WOS:000075594100007 ER PT J AU Wang, PKC Yee, J Hadaegh, FY Lau, K AF Wang, PKC Yee, J Hadaegh, FY Lau, K TI Experimental study of formation alignment of multiple autonomous air-levitated vehicles with rule-based controls SO JOURNAL OF ROBOTIC SYSTEMS LA English DT Article ID NAVIGATION STRATEGIES; MOBILE ROBOTS AB An experimental study is made on the alignment of three autonomous air-levitated vehicles with air-jet controls to achieve an equilateral-triangle formation. The vehicles are equipped with lasers, optical sensors, radio transceivers, and on-board power sources. The attitude and displacement of each vehicle are controlled by air-jets, simple rule-based controls activated by discrete optical sensors with binary outputs and special geometric configuration for formation alignment. The main objective is to determine the feasibility of using control rules derived by making use of the sensor data only for formation alignment. The sensors consist of discrete, binary optical detectors arranged in a certain geometric pattern. The vehicle design, including estimation of levitation lifetime, sensor design, and vehicle excursion due to an air-jet pulse, are discussed first. Then the control rules are described in detail. The effectiveness of the proposed sensor-control combination in formation alignment is determined both experimentally and via computer simulation. (C) 1998 John Wiley & Sons, Inc. C1 Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Wang, PKC (reprint author), Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. NR 10 TC 6 Z9 6 U1 0 U2 0 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0741-2223 J9 J ROBOTIC SYST JI J. Robot. Syst. PD OCT PY 1998 VL 15 IS 10 BP 559 EP 580 DI 10.1002/(SICI)1097-4563(199810)15:10<559::AID-ROB3>3.3.CO;2-6 PG 22 WC Robotics SC Robotics GA 124CB UT WOS:000076162700003 ER PT J AU Roberts, RG Graham, T Lippitt, T AF Roberts, RG Graham, T Lippitt, T TI On the inverse kinematics, statics, and fault tolerance of cable-suspended robots SO JOURNAL OF ROBOTIC SYSTEMS LA English DT Article AB This paper examines some issues concerning the inverse kinematics and statics of cable-suspended robots and studies some of the inherent workspace Limitations that result from the fact that the robot is cable actuated. The paper presents necessary and sufficient conditions for a cable-suspended robot to stay in a given configuration (i.e., to achieve static equilibrium). Another important issue is the extent to which the cables constrain the robot. For example, fully constraining the robot is critical for space applications in which the robot must work in a zero-gravity environment. Conditions for completely constraining the robot are derived. The problems of achieving static equilibrium and fully constraining the robot are formulated in terms of the left null space of a manipulator inverse Jacobian. This null space formulation is also used to study the fault tolerance of cable-suspended robots that are redundantly actuated. (C) 1998 John Wiley & Sons, Inc. C1 Florida State Univ, Coll Engn, FAMU, Dept Elect Engn, Tallahassee, FL 32310 USA. NASA, Adv Syst & Anal Div, Kennedy Space Ctr, FL 32899 USA. RP Roberts, RG (reprint author), Florida State Univ, Coll Engn, FAMU, Dept Elect Engn, Tallahassee, FL 32310 USA. NR 9 TC 121 Z9 127 U1 1 U2 7 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0741-2223 J9 J ROBOTIC SYST JI J. Robot. Syst. PD OCT PY 1998 VL 15 IS 10 BP 581 EP 597 DI 10.1002/(SICI)1097-4563(199810)15:10<581::AID-ROB4>3.3.CO;2-O PG 17 WC Robotics SC Robotics GA 124CB UT WOS:000076162700004 ER PT J AU Hindson, WS Chen, RTN AF Hindson, WS Chen, RTN TI Operational tests of noise abatement approaches for rotorcraft using differential GPS for guidance SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT 51st Annual Forum of the American-Helicopter-Society CY MAY 09-11, 1995 CL FT WORTH, TEXAS SP Amer Helicopter Soc AB The NASA/Army Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) UH-60A Black Hawk helicopter was used to test the feasibility of using operational techniques to alleviate helicopter noise during approach to landing. Decelerating approaches were flown using multi-segment glidepaths, The approaches were designed to avoid flight conditions known to generate noise due to blade-vortex-interaction (BVI). A Local Differential Global Positioning System (LDGPS) was used for precision navigation, and guidance calculations were performed in an on-board computer. Steering commands were presented to the pilot using the existing electromechanical flight instruments of the UH-60A. Operational aspects of the noise abatement approaches were evaluated by pilots from NASA, FAA, and the helicopter industry. The methodology used to design the noise abatement trajectories is described, and navigation system and flight technical error data are reported. RP Hindson, WS (reprint author), NASA, Ames Res Ctr, Rotorcraft & Powered Lift Branch, Civil Rotorcraft Grp, Moffett Field, CA 94035 USA. NR 18 TC 4 Z9 4 U1 0 U2 1 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD OCT PY 1998 VL 43 IS 4 BP 352 EP 359 PG 8 WC Engineering, Aerospace SC Engineering GA 137UN UT WOS:000076934900008 ER PT J AU Steif, PS Rubal, MP Gray, GT Pereira, JM AF Steif, PS Rubal, MP Gray, GT Pereira, JM TI Damage in gamma titanium aluminides due to small particle impacts SO JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS LA English DT Article; Proceedings Paper CT Symposium on the Dynamic Deformation and Failure Mechanics of Materials, Honoring Professor R J Clifton on the Occasion of his 60th Birthday CY MAY 22-24, 1997 CL PASADENA, CALIFORNIA DE ductility; contact mechanics; finite elements; plate impact; intermetallics (not included in list) AB Initiation of cracking due to small particle impacts on low ductility intermetallics is investigated experimentally and theoretically. The gamma titanium aluminide alloys of interest which are being considered for elevated temperature structural applications in aircraft engines exhibit tensile ductilities on the order of 1-2%. Cracking due to any source, including small particle impacts, is of concern given the rapid growth of cracks in fatigue. This investigation focuses on a model geometry which reproduces the rear face cracking that is induced by a small particle impinging on an air foil leading edge. Small steer spheres are projected onto thin plates at velocities ranging from 76 to 305 m/s; cracking is thereby induced on the rear surface of the plates. Through finite element analyses of the dynamic impact event and some analytical estimates, we examine the hypothesis that crack initiation due to small particle impacts can be correlated with material ductility and with the severity and spatial extent of the straining during the impact event. In addition, with the use of static indentation tests in which similar strain distributions are present, some insight is gained into the difference in ductility between high and low strain rates. (C) 1998 Elsevier Science Ltd: All rights reserved. C1 Carnegie Mellon Univ, Dept Mech Engn, Pittsburgh, PA 15213 USA. Univ Calif Los Alamos Natl Lab, MST Grp 5, Los Alamos, NM 87545 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Steif, PS (reprint author), Carnegie Mellon Univ, Dept Mech Engn, Schenley Pk, Pittsburgh, PA 15213 USA. RI Steif, Paul/D-2459-2013 NR 19 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 0022-5096 J9 J MECH PHYS SOLIDS JI J. Mech. Phys. Solids PD OCT PY 1998 VL 46 IS 10 BP 2069 EP 2086 PG 18 WC Materials Science, Multidisciplinary; Mechanics; Physics, Condensed Matter SC Materials Science; Mechanics; Physics GA 146GC UT WOS:000077420100021 ER PT J AU Kim, YJ Farrara, JD Mechoso, CR AF Kim, YJ Farrara, JD Mechoso, CR TI Sensitivity of AGCM simulations to modifications in the ozone distribution and refinements in selected physical parameterizations SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID GENERAL-CIRCULATION MODEL; GRAVITY-WAVE DRAG; WEATHER PREDICTION MODELS; PLANETARY BOUNDARY-LAYER; LOWER STRATOSPHERE; NUMERICAL FORECASTS; TROPOSPHERE; CLIMATE; WINTER; PARAMETRIZATION AB The sensitivity of the stratospheric circulation simulated by an atmospheric general circulation model (UCLA. AGCM) to modifications in the parameterization of several key physical processes is investigated. The focus is on the northern hemisphere winter circulation simulated by the troposphere-stratosphere version of the model. The parameterization of ozone mixing ratio is first investigated by comparing multi-year simulations with distributions of ozone mixing ratio that are either prescribed according to an observed climatology, or predicted using a scheme with a simple photochemistry formulation. The prescribed ozone mixing ratios produce a considerably more realistic circulation, although the results are degraded in some regions of the stratosphere. This leads to a closer look into the radiation parameterization. Several simulations for the northern winter season are performed with adjustments to obtain more realistic radiative cooling rates mainly in the upper stratosphere. It is found that the simulation of the stratospheric polar night jet is very sensitive to these adjustments. Additional experiments performed by adding Rayleigh friction and Newtonian cooling reveal a similar sensitivity. The results of these experiments emphasize a need for caution when ad-hoc adjustments are applied in the model. They also confirm that the performance of an AGCM in the stratosphere can depend on several different model aspects, and that this dependence is not always straightforward. In addition, the authors argue that their results support the notion that parameterizations of orographic gravity wave drag that neglect or underestimate the drag in the troposphere may overestimate the drag in the stratosphere. C1 Univ Calif Los Angeles, Dept Atmospher Sci, Los Angeles, CA 90095 USA. RP Kim, YJ (reprint author), CALTECH, Jet Prop Lab, Mail Stop 300-319,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM young-joon.kim@jpl.nasa.gov NR 48 TC 9 Z9 9 U1 0 U2 2 PU METEOROLOGICAL SOC JAPAN PI TOKYO PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO, 100-0004, JAPAN SN 0026-1165 EI 2186-9057 J9 J METEOROL SOC JPN JI J. Meteorol. Soc. Jpn. PD OCT PY 1998 VL 76 IS 5 BP 695 EP 709 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 149JX UT WOS:000077602900003 ER PT J AU Prabhakara, C Meneghini, R Short, DA Weinman, JA Iacovazzi, R Oki, R Cadeddu, M AF Prabhakara, C Meneghini, R Short, DA Weinman, JA Iacovazzi, R Oki, R Cadeddu, M TI A TRMM microwave radiometer rain retrieval method based on fractional rain area SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID CONVECTIVE RAINFALL; CLOUD CLUSTERS; NIMBUS-7 SMMR; RADAR; PROFILES; OCEANS; RATES AB Recent studies based on aircraft observations made over ocean by radar and multi-channel passive microwave radiometer, each with a held of view (fov) of a few kilometers, indicate significant problems in relating the radar derived rain rate with the brightness temperature measurements of the microwave radiometer. We arrive at a similar conclusion from extensive observations of rain rate made by ship borne radars and rain rate deduced from observations of the satellite-borne, multi-channel Special Sensor Microwave Imager (SSM/I) radiometer, which has a much larger fov (similar to 30 km). The principal reason for these problems is that the signal due to rain drops contained in the radiometer measurements is nonlinearly mixed with that of other hydrometeors that could be present in the radiometer fov. These other hydrometeors include liquid droplets, and dry and melting ice and snow particles of different densities, sizes, and shapes in clouds. Observations made by SSM/I are not adequate to uncouple the rain signal satisfactorily from such a non-linear mix of signals on the scale of the radiometer footprint. These problems are complicated further by meteorological conditions, which can significantly alter the amount and spatial distribution of these other hydrometeors. For these reasons an empirical method is developed to estimate area-average rain rate in a mesoscale region of about 300 x 300 km(2), based on SSM/I data. One parameter of this empirical method f(R) relates to the fractional rain area in a mesoscale region, while the second parameter, chi, reflects in a weak way the scattering and emission properties of the hydrometeors in that region. This method requires tuning with the help of radar data. Over the TOGA-COARE area, the rain rates retrieved from this method can reproduce the radar observed rain rates with a correlation coefficient of about 0.85. Furthermore, monthly total rainfall estimated from this method for the TOGA-COARE area has an error of about 13 %. This rain retrieval method is applicable to the Tropical Rainfall Measuring Mission (TRMM), in which multi-channel dual-polarization microwave radiometer observations over a 760 km wide swath are overlapped with those of radar, which has a swath of 220 km. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Tokyo, Cen Clim Sys Res, Tokyo, Japan. Univ Space Res Assoc, Greenbelt, MD USA. RP Prabhakara, C (reprint author), NASA, Goddard Space Flight Ctr, Code 913, Greenbelt, MD 20771 USA. EM cuddapah@climate.gsfc.nasa.gov RI Iacovazzi Jr, Robert/G-3867-2010; PMM, JAXA/K-8537-2016 NR 37 TC 3 Z9 3 U1 0 U2 1 PU METEOROLOGICAL SOC JAPAN PI TOKYO PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO, 100-0004, JAPAN SN 0026-1165 EI 2186-9057 J9 J METEOROL SOC JPN JI J. Meteorol. Soc. Jpn. PD OCT PY 1998 VL 76 IS 5 BP 765 EP 781 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 149JX UT WOS:000077602900008 ER PT J AU Scott, CD Blackwell, HE Arepalli, S Akundi, MA AF Scott, CD Blackwell, HE Arepalli, S Akundi, MA TI Techniques for estimating rotational and vibrational temperature in nitrogen arcjet flow SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 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 Molecular nitrogen and molecular nitrogen ion spectra are used to infer vibrational and rotational temperatures in an arcjet shock layer under the assumption of Boltzmann populations, Various techniques correlate spectral features with temperatures, among which are determining intensity integrals and forming ratios that are then correlated with rotational and vibrational temperatures. Sensitivity factors, determined by correlating these ratios with temperature, are indicators of the potential accuracy of different spectrum regions for determining temperature. In another technique, least-squares fits of measured spectra are made to fit temperature-dependent computed spectra, including global fits to computed spectra as a function of temperature or fits to vibrational-level basis spect-ra, Technique accuracy is described and precision improved by combining the results of several techniques. When results from the various techniques are combined, overall temperature determination accuracy at a single point in an arcjet shock layer is about +/-4% for vibrational temperature and +/-10% for rotational temperature. C1 NASA, Lyndon B Johnson Space Ctr, Struct & Mech Div, Houston, TX 77058 USA. BSA Serv, Houston, TX 77045 USA. GB Tech Lockheed Martin, Struct & Mech Div, Houston, TX 77058 USA. Xavier Univ, Dept Phys, New Orleans, LA 70125 USA. RP Scott, CD (reprint author), NASA, Lyndon B Johnson Space Ctr, Struct & Mech Div, ES3, Houston, TX 77058 USA. RI Arepalli, Sivaram/A-5372-2010 NR 19 TC 11 Z9 11 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 457 EP 464 DI 10.2514/2.6369 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500001 ER PT J AU Blackwell, HE Scott, CD Arepalli, S AF Blackwell, HE Scott, CD Arepalli, S TI Measured shock-layer vibrational populations and temperatures in arcjet nitrogen flow SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 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 DISTRIBUTIONS; DISSOCIATION; N-2 AB Radiation is analyzed from a highly nonequilibrium shock layer produced by a blunt body in a low-density arcjet now of nitrogen. Populations of vibrational states are obtained at several locations in the shock layer through fits of basis spectra to measured spectra, Several techniques determine the rotational and vibrational temperature corresponding to Boltzmann fits to low vibrational state populations for N-2 and N-2(+) molecules. These techniques include correlations of ratios of intensity integrals, fits of calculated vibrational basis sets to measurements, and minimization of the deviation between calculated and measured spectra, Analyses of basis set fits yield vibrational populations that deviate from a Boltzmann distribution at vibrational quantum numbers greater than about 6-8, Differences in rotational and vibrational temperatures are found, together with temperature differences between the neutral molecule and the ion. Temperature profiles and non-Boltzmann vibrational populations indicate the nonequilibrium character of the layer, Experimentally determined population distributions should interest anyone modeling nonequilibrium vibrational kinetics, These distributions, up to nu' = 20, should be of interest, and temperature profiles generally should be useful when validating the gas models used for high-enthalpy nonequilibrium nitrogen flows. C1 BSA Serv, Houston, TX 77045 USA. NASA, Lyndon B Johnson Space Ctr, Struct & Mech Div, Houston, TX 77058 USA. GB Tech Lockheed Martin, Struct & Mech Div, Houston, TX 77058 USA. RP Blackwell, HE (reprint author), BSA Serv, Houston, TX 77045 USA. RI Arepalli, Sivaram/A-5372-2010 NR 24 TC 1 Z9 1 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 465 EP 472 DI 10.2514/2.6380 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500002 ER PT J AU Copeland, RA Pallix, JB Stewart, DA AF Copeland, RA Pallix, JB Stewart, DA TI Surface-catalyzed production of NO from recombination of N and O atoms SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID LASER-INDUCED FLUORESCENCE; NITROGEN-ATOMS; 2-PHOTON AB An experimental method has been developed that uses laser-induced fluorescence detection of N atoms to monitor NO formation from a surface-catalyzed reaction on quartz. Well-characterized mixtures of N and O atoms were generated through NO titration of N atoms produced in a microwave discharge. Experiments were carried out in a diffusion reactor designed for measurement of atom recombination coefficients on surfaces exhibiting low catalytic activity. The results have shown that a significant concentration of NO is generated in the room temperature reaction of N and O atoms on quartz surfaces. This work has demonstrated that N- and O-atom recombination on surfaces cannot be treated independently. C1 SRI Int, Aeron Program, Mol Phys Lab, Menlo Park, CA 94025 USA. NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Thermosci Inst, Moffett Field, CA 94035 USA. RP Copeland, RA (reprint author), SRI Int, Aeron Program, Mol Phys Lab, 333 Ravenswood Ave, Menlo Park, CA 94025 USA. RI Copeland, Richard/E-2201-2011 NR 13 TC 13 Z9 13 U1 2 U2 6 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 496 EP 499 DI 10.2514/2.6395 PG 4 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500007 ER PT J AU Stallcop, JR Levin, E Partridge, H AF Stallcop, JR Levin, E Partridge, H TI Transport properties of hydrogen SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID CROSS-SECTIONS; COLLISION INTEGRALS; COEFFICIENTS; ENERGY; SCATTERING; NITROGEN; VALUES; ATOMS; H2 AB Transport cross sections and collision integrals have been calculated for interactions of hydrogen atoms and diatomic molecules. These results were determined using accurate potential energies and quantum mechanical formulations of the scattering. Collision integrals have been tabulated for H-H and H(2)-H(2), and have been applied to determine diffusion and viscosity. The variation of transport properties with temperature and relative composition is examined for a gas formed from H atoms and H(2) molecules. The inversion temperature is found to be about a factor 3 lower than that of earlier estimates. C1 NASA, Ames Res Ctr, Computat Chem Branch, Space Technol Div, Moffett Field, CA 94035 USA. Eloret Corp, Thermosci Inst, Moffett Field, CA 94035 USA. RP Stallcop, JR (reprint author), NASA, Ames Res Ctr, Computat Chem Branch, Space Technol Div, Moffett Field, CA 94035 USA. NR 35 TC 32 Z9 33 U1 0 U2 2 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091-4344 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 514 EP 519 DI 10.2514/2.6370 PG 6 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500010 ER PT J AU Darby, SP Landrum, DB Coleman, HW AF Darby, SP Landrum, DB Coleman, HW TI Assessment of uncertainty in the determination of activation energy for polymeric materials SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID THERMOGRAVIMETRIC DATA; KINETIC-ANALYSIS AB An assessment of the experimental uncertainty in obtaining the kinetic activation energy from thermogravimetric analysis (TGA) data is presented. A neat phenolic resin, Borden SC1008, was heated at three heating rates to obtain weight loss vs temperature data. Activation energy was calculated by two methods: the traditional Flynn and Wall method based on the slope of log(q) versus 1/T, and a modification of this method where the ordinate and abscissa are reversed in the linear regression. The modified method produced a more accurate curve fit of the data, was more sensitive to data nonlinearity, and gave a value of activation energy 75% greater than the original method. An uncertainty analysis using the modified method yielded a 60% uncertainty in the average activation energy. Based on this result, the activation energy for a carbon-phenolic material was doubled and used to calculate the ablation rate in a typical solid rocket environment. Doubling the activation energy increased surface recession by 3%, Current TGA data reduction techniques that use the traditional Flynn and Wall approach to calculate activation energy should be changed to the modified method. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Mech & Aerosp Engn, Prop Res Ctr, Huntsville, AL 35899 USA. RP Darby, SP (reprint author), NASA, George C Marshall Space Flight Ctr, EH42, Huntsville, AL 35812 USA. NR 36 TC 0 Z9 0 U1 0 U2 4 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 520 EP 527 DI 10.2514/2.6371 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500011 ER PT J AU Marschall, J Milos, FS AF Marschall, J Milos, FS TI Gas permeability of rigid fibrous refractory insulations SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB An experimental procedure is developed for measuring the gas permeability of rigid fibrous tile insulations. Permeability data are documented for a variety of ceramic fiber insulations from the LI, AIM, FRCI, and AETB families, as well as for the commercial carbon fiber insulation FiberForm(R). It is demonstrated that rarefied-now effects are significant for gas flow through such materials and that the pressure dependence of gas permeability is well represented by the Klinkenberg formulation. Continuum permeabilities ranging from 3 to 63 x 10(-12) m(2) are found for all materials except FiberForm, which has a significantly higher continuum permeability on the order of 10(-10) m(2). The room temperature permeability slip parameter for air is found to range from 603 to 7940 Pa. A scaling relation that allows calculation of permeability slip parameters for other gases and for varying temperature is validated by experiment. The dependency of the permeability on material density, anisotropic microstructure, and constituent fiber size is presented. To illustrate an application of this permeability data, representative computations for the gas now through a rigid fibrous vent of a space probe during launch and atmospheric entry are given. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. RP Marschall, J (reprint author), Eloret Corp, Thermosci Inst, Moffett Field, CA 94035 USA. EM jmarschall@mail.arc.nasa.gov; fmilos@mail.arc.nasa.gov NR 11 TC 18 Z9 18 U1 2 U2 8 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 528 EP 535 DI 10.2514/2.6372 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500012 ER PT J AU Rooke, S Fralick, G Liebert, C AF Rooke, S Fralick, G Liebert, C TI Heat transfer analysis of a plug-type heat flux gauge SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB An analysis of a miniature plug-type heat flux gauge is presented. The analysis provides previously unavailable quantitative details of the heat transfer within this gauge type. The analysis is performed using a two-dimensional, axisymmetric numerical model with temperature-dependent thermal properties. The model is solved using the alternating direction implicit finite difference solution procedure. Details of the comparison of the model results with experimental data are presented. Isotherms, gauge centerline temperature distributions, and heat fluxes computed at various locations within the gauge are presented and discussed. For the cases studied, the numerical analysis reveals that the measured heat flux indicated by the gauge is not the same as the heat flux at the gauge hot active surface. Using temperatures measured by the gauge as input, the numerical model enables one to compute the heat flux into the surface in which the gauge is mounted, at positions that are thermally undisturbed by the presence of the gauge. This can be done regardless of whether or not the heat flux at the gauge hot active surface is the same as the heat nux into thermally undisturbed portions of the surface. C1 CSO Engineers, Indianapolis, IN 46240 USA. NASA, Lewis Res Ctr, Sensors & Elect Technol Branch, Div Instrumentat & Controls, Cleveland, OH 44135 USA. RP Rooke, S (reprint author), CSO Engineers, 9100 Keystone Crossing,Suite 200, Indianapolis, IN 46240 USA. NR 12 TC 4 Z9 4 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0887-8722 J9 J THERMOPHYS HEAT TR JI J. Thermophys. Heat Transf. PD OCT-DEC PY 1998 VL 12 IS 4 BP 536 EP 542 DI 10.2514/2.6373 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 132CM UT WOS:000076612500013 ER PT J AU Weigl, HJ Paduano, JD Frechette, LG Epstein, AH Greitzer, EM Bright, MM Strazisar, AJ AF Weigl, HJ Paduano, JD Frechette, LG Epstein, AH Greitzer, EM Bright, MM Strazisar, AJ TI Active stabilization of rotating stall and surge in a transonic single-stage axial compressor SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID ROBUST-CONTROL; SUPPRESSION; MODELS AB Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the signal to an annular an-ny of twelve separately modulated air injectors. At lip relative Mach numbers of 1.0 and 1.5 the control achieved 11 and 3.5 percent reductions in stalling mass flow, respectively, with injection adding 3.6 percent of the design compressor mass flow. The aerodynamic effects of the injection have also been examined At a tip Mach number, M-tip of 1.0, the stall inception dynamics and effective active control strategies are similar to results for low-speed axial compressors. The range extension was achieved by individually damping the first and second spatial harmonics of the prestall perturbations using constant gain feedback, At a M-tip of 1.5 (design rotor speed), the prestall dynamics are different than at the lower speed. Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations needed to be stabilized to increase the compressor operating range. Ar design speed the instability was initiated by approximately ten rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis, the zeroth, first, and second spatial harmonics each include mole than one lightly damped mode, which can grow into the large amplitude instability. Forced response testing identified several modes traveling up to 150 percent of rotor speed for the first three spatial harmonics; simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor at this speed. A dynamic model-based robust controller was therefore used to stabilize the multiple modes that comprise the first three harmonic perturbations ill this transonic region of operation. C1 MIT, Dept Aeronaut & Astronaut, Gas Turbine Lab, Cambridge, MA 02139 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Weigl, HJ (reprint author), MIT, Dept Aeronaut & Astronaut, Gas Turbine Lab, Cambridge, MA 02139 USA. RI Frechette, Luc/D-1920-2014 OI Frechette, Luc/0000-0001-7138-0811 NR 29 TC 73 Z9 88 U1 2 U2 10 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1998 VL 120 IS 4 BP 625 EP 636 PG 12 WC Engineering, Mechanical SC Engineering GA 132ZY UT WOS:000076663000001 ER PT J AU Ameri, AA Steinthorsson, E Rigby, DL AF Ameri, AA Steinthorsson, E Rigby, DL TI Effect of squealer tip on rotor heat transfer and efficiency SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID TRANSITION AB Calculations were preformed to simulate the tip flow and heat transfer on the GE-E-3 first-stage turbine, which represents a modern gas turbine blade geometry. Cases considered were a smooth tip 2 percent recess, and 3 percent recess. In addition, a two-dimensional cavity problem was calculated. Good agreement with experimental results was obtained for the cavity calculations, demonstrating that the k-omega turbulence model used is capable of representing flows of the present type. In the rotor calculations, two dominant flow structures were shown to exist within the recess. Also areas of large heat transfer rate were identified on the blade tip and the mechanisms of heat transfer enhancement were discussed. No significant difference in adiabatic efficiency was observed for the three tip treatments investigated. C1 AYT Corp, Brook Pk, OH 44135 USA. NASA, Inst Computat Mech Prop, Lewis Res Ctr, Brook Pk, OH 44142 USA. NASA, NYMA Inc, Lewis Grp, Brook Pk, OH 44142 USA. RP Ameri, AA (reprint author), AYT Corp, Brook Pk, OH 44135 USA. NR 18 TC 109 Z9 118 U1 2 U2 6 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0889-504X J9 J TURBOMACH JI J. Turbomach.-Trans. ASME PD OCT PY 1998 VL 120 IS 4 BP 753 EP 759 PG 7 WC Engineering, Mechanical SC Engineering GA 132ZY UT WOS:000076663000015 ER PT J AU Chen, P AF Chen, P TI Telescope mirrors successfully lose weight SO LASER FOCUS WORLD LA English DT Article AB Replicating mirrors with graphite-fiber-reinforced composites keeps them thin. C1 NASA, Goddard Space Flight Ctr, CUA, CMA, Greenbelt, MD 20771 USA. RP Chen, P (reprint author), NASA, Goddard Space Flight Ctr, CUA, CMA, Code 684-9, Greenbelt, MD 20771 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU PENNWELL PUBL CO PI NASHUA PA 5TH FLOOR TEN TARA BOULEVARD, NASHUA, NH 03062-2801 USA SN 0740-2511 J9 LASER FOCUS WORLD JI Laser Focus World PD OCT PY 1998 VL 34 IS 10 BP 69 EP 72 PG 4 WC Optics SC Optics GA 126DB UT WOS:000076276700027 ER PT J AU Mohan, SK AF Mohan, SK TI Pictures vs. a thousand words SO MECHANICAL ENGINEERING LA English DT Letter C1 CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Mohan, SK (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD OCT PY 1998 VL 120 IS 10 BP 8 EP 8 PG 1 WC Engineering, Mechanical SC Engineering GA 125FU UT WOS:000076227400005 ER PT J AU Newman, PA AF Newman, PA TI Preserving earth's stratosphere SO MECHANICAL ENGINEERING LA English DT Article C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Newman, PA (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RI Newman, Paul/D-6208-2012 OI Newman, Paul/0000-0003-1139-2508 NR 0 TC 2 Z9 2 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0025-6501 J9 MECH ENG JI Mech. Eng. PD OCT PY 1998 VL 120 IS 10 BP 88 EP 91 PG 4 WC Engineering, Mechanical SC Engineering GA 125FU UT WOS:000076227400028 ER PT J AU Fichter, WB AF Fichter, WB TI Stress decay in an orthotropic half-plane under local self-equilibrated edge loading SO MECHANICS OF COMPOSITE MATERIALS AND STRUCTURES LA English DT Article AB An exact solution is presented for the stresses in a specially orthotropic half-plane under a localized, symmetric, self-equilibrated combination of uniform normal edge loadings. "Smeared" orthotropic material properties are used to represent a broad range of balanced angle-ply graphite-epoxy laminates. Expressions for the three stresses in the half-plane are presented for isotropic material and for two orthotropic material families that contain marry of the practical laminates. Particular attention is given to the diffusion of the edge loading into the half-space and to the shear stresses caused by the discontinuous edge loading, both of which are strongly influenced by material properties. Of special interest to designers of composite structures may be a simple approximate formula, in terms of material properties, which is proposed for a lower bound on the normalized 90%-decay distance for the normal stress. Also, the results serve as further illustration of the fact that the meaningful application of Saint-Venant's principle to specially orthotropic materials requires knowledge of their elastic properties. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Fichter, WB (reprint author), NASA, Langley Res Ctr, Mail Stop 190, Hampton, VA 23681 USA. NR 7 TC 2 Z9 2 U1 1 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 1075-9417 J9 MECH COMPOS MATER ST JI Mech. Compos. Mater. Struct. PD OCT-DEC PY 1998 VL 5 IS 4 BP 355 EP 370 DI 10.1080/10759419808945906 PG 16 WC Materials Science, Multidisciplinary; Materials Science, Characterization & Testing; Materials Science, Composites SC Materials Science GA 124EB UT WOS:000076167400003 ER PT J AU Buckley, DAH Barrett, PE Haberl, F Sekiguchi, K AF Buckley, DAH Barrett, PE Haberl, F Sekiguchi, K TI A ROSAT observation of the dipping, flaring and eclipsing polar MN Hya (RX J0929.1-2404) SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE accretion, accretion discs; stars : individual : MN Hya (RX J0929.1-2404); stars : magnetic fields; novae, cataclysmic variables; white dwarfs; X-rays : stars ID EMISSION; AM AB We present the results of a 22.5 ks pointed ROSAT PSPC observation of the 3.4-h period eclipsing polar MN Hya (RX J0929.1-2404). The X-ray light curve exhibits a 'double-humped' shape, with a secondary minimum occuring at phi similar to 0.45, a morphology consistent with two-pole accretion. Strong aperiodic flaring activity, with flux enhancements of similar to 6x the quiescent level, is also observed. A pre-eclipse 'dip' occurs in the phase interval phi = 0.87-0.95 with the X-rays becoming harder, indicative of photoelectric absorption by the pre-shock flow. There is also evidence of a secondary spectrally hard 'dip' near phi = 0.45-0.55, which might be associated with a second accretion stream flowing to the other magnetic pole. The X-ray spectrum is best represented by a combination of a similar to 50 eV blackbody and a thermal bremsstrahlung component of kT greater than or similar to 1.6 keV, with a total absorption column of N-H = 2.9 x 10(20)cm(-2). The primary maximum (phi similar to 0.65) has a slightly larger column and normalization compared to the secondary maximum. Although there are few photons, the dip spectrum is very flat in comparison to other phases, and is best represented by a single bremsstrahlung component. This is indicative of the spectral hardening seen in the light curves attributed to photoabsorption. The ratio of unabsorbed bremsstrahlung and blackbody luminosities is similar to 0.1 for the best-fitting average spectral models. This implies a magnetic field strength less than or similar to 30 MG on the basis of the empirical L-hard/L-soft - B relationships, although consideration of the cyclotron flux and aspect effects could allow for an even higher field (less than or similar to 55 MG). C1 S African Astron Observ, ZA-7935 Cape Town, South Africa. NASA, Goddard Space Flight Ctr, High Energy Astrophys Archive, Greenbelt, MD 20771 USA. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. Natl Astron Observ Japan, Subaru Telescope, Hilo, HI 96720 USA. RP Buckley, DAH (reprint author), S African Astron Observ, POB 9, ZA-7935 Cape Town, South Africa. NR 25 TC 4 Z9 4 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 OCT 1 PY 1998 VL 299 IS 4 BP 998 EP 1006 DI 10.1046/j.1365-8711.1998.01851.x PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 131AU UT WOS:000076554200010 ER PT J AU Hynes, RI O'Brien, K Horne, K Chen, W Haswell, CA AF Hynes, RI O'Brien, K Horne, K Chen, W Haswell, CA TI Echoes from an irradiated disc in GRO J1655-40 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Letter DE accretion, accretion discs; binaries : close; stars : individual : Nova Sco 1994; (GRO J1655-40); ultraviolet : stars; X-rays : stars ID ACTIVE GALACTIC NUCLEI; VARIABILITY AB We demonstrate correlated rapid variability between the optical/UV and X-ray emission for the first time in a soft X-ray transient, GRO J1655-40: Hubble Space Telescope (HST) light curves show similar features to those seen by the Rossi X-my Timing Explorer (RXTE), but with mean delay of up to 10-20 s. We interpret the correlations as the result of reprocessing of X-rays into optical and UV emission, with a delay owing to finite light travel time, and thus perform echo mapping of the system. The time-delay distribution has a mean of 14.6 +/- 1.4 s and dispersion (i.e. the standard deviation of the distribution) of 10.5 +/- 1.9 s at binary phase 0.4. Hence we identify the reprocessing region as the accretion disc rather than the mass donor star. C1 Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. RP Hynes, RI (reprint author), Univ Sussex, Ctr Astron, Brighton BN1 9QH, E Sussex, England. NR 18 TC 32 Z9 32 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 OCT 1 PY 1998 VL 299 IS 4 BP L37 EP L41 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 131AU UT WOS:000076554200001 ER PT J AU McGill, MJ Spinhirne, JD AF McGill, MJ Spinhirne, JD TI Comparison of two direct-detection Doppler lidar techniques SO OPTICAL ENGINEERING LA English DT Article DE lidar; Doppler lidar; wind measurement; Fabry-Perot; direct-detection lidar ID EDGE TECHNIQUE; ATMOSPHERIC WIND; MIDDLE ATMOSPHERE; RESOLUTION; PROFILES; ACCURACY; SYSTEMS; CIRCLE AB Two types of direct-detection Doppler lidars are described: the multichannel spectral resolving approach and the edge technique approach. The two methods are compared in terms of fundamental system characteristics. The equations necessary to model the instruments and predict noise-limited performance are developed in forms that enable an easy comparison of the methods. Using those equations, simulation results are presented to compare the performance of the receiver systems. Results are shown for both aerosol Doppler and molecular Doppler systems. Instrument design considerations are discussed to clarify the choice of realistic values for the model parameters. (C) 1998 Society of Photo-Optical instrumentation Engineers. [S0091-3286(98)01310-5]. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. RP McGill, MJ (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Code 912, Greenbelt, MD 20771 USA. RI McGill, Matthew/D-8176-2012 NR 34 TC 29 Z9 36 U1 5 U2 12 PU SPIE - INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING PI BELLINGHAM PA POB 10, BELLINGHAM, WA 98227-0010 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD OCT PY 1998 VL 37 IS 10 BP 2675 EP 2686 DI 10.1117/1.601804 PG 12 WC Optics SC Optics GA 128GY UT WOS:000076398600003 ER PT J AU Salama, F AF Salama, F TI The diffuse interstellar bands: A tracer for organics in the diffuse interstellar medium? SO ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES LA English DT Article; Proceedings Paper CT 1996 ISSOL Meeting CY JUL 08-13, 1996 CL ORLEANS, FRANCE SP ISSOL ID POLYCYCLIC AROMATIC-HYDROCARBONS; 2-PHOTON ABSORPTION; MOLECULES; CARRIERS; SEARCH; SPECTROSCOPY; HYPOTHESIS; CORONENE; OVALENE; CATIONS AB The diffuse interstellar bands (DIBs) are absorption bands seen in the spectra of stars obscured by interstellar dust. DIBs are recognized as a tracer for free, organic molecules in the diffuse interstellar medium (ISM). The potential molecular carriers for the DIBs are discussed with an emphasis on neutral and ionized polycyclic aromatic hydrocarbons (PAHs) for which the most focused effort has been made to date. From the combined astronomical, laboratory and theoretical study, it is concluded that a distribution of free neutral and ionized complex organics (PAHs, fullerenes, unsaturated hydrocarbons) represents the most promising class of candidates to account for the DIBs. The case for aromatic hydrocarbons appears particularly strong. The implied widespread distribution of complex organics in the diffuse ISM bears profound implications for our understanding of the chemical complexity of the ISM, the evolution of prebiotic molecules and its impact on the origin and the evolution of life on early Earth through the exogenous delivery (cometary encounters and metoritic bombardments) of prebiotic organics. C1 NASA, Div Space Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Salama, F (reprint author), NASA, Div Space Sci, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Salama, Farid/A-8787-2009 OI Salama, Farid/0000-0002-6064-4401 NR 48 TC 8 Z9 8 U1 0 U2 2 PU SPRINGER PI DORDRECHT PA VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD OCT PY 1998 VL 28 IS 4-6 BP 349 EP 364 DI 10.1023/A:1006506620752 PG 16 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 115HL UT WOS:000075658100002 PM 9742721 ER PT J AU Bishop, JL AF Bishop, JL TI Biogenic catalysis of soil formation on Mars? SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article; Proceedings Paper CT 1996 ISSOL Meeting CY JUL 08-13, 1996 CL ORLEANS, FRANCE SP ISSOL ID REFLECTANCE SPECTROSCOPY; CARBONACEOUS CHONDRITES; MAGNETOTACTIC BACTERIA; AQUEOUS ALTERATION; ANALOG MATERIALS; MU-M; LIFE; MONTMORILLONITE; MINERALOGY; METEORITE AB The high iron abundance and the weak ferric iron spectral features of martian surface material are consistent with nanophase (nm sized) iron oxide minerals as a major source of iron in the bright region soil on Mars. Nanophase iron oxide minerals, such as ferrihydrite and schwertmannite, and nanophase forms of hematite and goethite are formed by both biotic and abiotic processes on Earth. The presence of these minerals on Mars does not indicate biological activity on Mars, but it does raise the possibility. This work includes speculation regarding the possibility of biogenic soils on Mars based on previous observations and analyses. A remote sensing goal of upcoming missions should be to determine if nanophase iron oxide minerals, clay silicates and carbonates are present in the martian surface material. These minerals are important indicators for exobiology and their presence on Mars would invoke a need for further investigation and sample return from these sites. C1 NASA, Ames Res Ctr, Moffett Field, CA 94305 USA. RP Bishop, JL (reprint author), NASA, Ames Res Ctr, Mail Stop 239-4, Moffett Field, CA 94305 USA. NR 70 TC 1 Z9 1 U1 0 U2 4 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD OCT PY 1998 VL 28 IS 4-6 BP 449 EP 459 DI 10.1023/A:1006544110215 PG 11 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 115HL UT WOS:000075658100007 PM 9742725 ER PT J AU Simoneit, BRT Summons, RE Jahnke, LL AF Simoneit, BRT Summons, RE Jahnke, LL TI Biomarkers as tracers for life on early Earth and Mars SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article; Proceedings Paper CT 1996 ISSOL Meeting CY JUL 08-13, 1996 CL ORLEANS, FRANCE SP ISSOL ID HOT-SPRING ENVIRONMENTS; CYANOBACTERIAL MATS; HYDROTHERMAL VENT; ORGANIC-MATTER; BIOGEOCHEMISTRY; 21-DEGREES-N; CHEMISTRY; LIPIDS AB Biomarkers in geological samples are products derived from biochemical (natural product) precursors by reductive and oxidative processes (e.g., cholestanes from cholesterol). Generally, lipids, pigments and biomembranes are preserved best over longer geological times and labile compounds such as amino acids, sugars, etc. are useful biomarkers for recent times. Thus, the detailed characterization of biomarker compositions permits the assessment of the major contributing species of extinct and/or extant life. In the case of the early Earth, work has progressed to elucidate molecular structure and carbon isotopic signals preserved in ancient sedimentary rocks. In addition, the combination of bacterial biochemistry with the organic geochemistry of contemporary and ancient hydrothermal ecosystems permits the modeling of the nature, behavior and preservation potential of primitive microbial communities. This approach uses combined molecular and isotopic analyses to characterize lipids produced by cultured bacteria (representative of ancient strains) and to test a variety of culture conditions which affect their biosynthesis. On considering Mars, the biomarkers from lipids and biopolymers would be expected to be preserved best if life flourished there during its early history (3.5-4 x 10(9) yr ago). Both oxidized and reduced products would be expected. This is based on the inferred occurrence of hydrothermal activity during that time with the concomitant preservation of biochemically-derived organic matter. Both known biomarkers (i.e., as elucidated for early terrestrial samples and for primitive terrestrial microbiota) and novel, potentially unknown compounds should be characterized. C1 Oregon State Univ, Coll Ocean & Atmospher Sci, Petroleum & Environm Geochem Grp, Corvallis, OR 97331 USA. Australian Geol Survey, Canberra, ACT 2601, Australia. NASA, Planetary Biol Branch, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Simoneit, BRT (reprint author), Oregon State Univ, Coll Ocean & Atmospher Sci, Petroleum & Environm Geochem Grp, Corvallis, OR 97331 USA. RI SIMONEIT, BERND/A-2008-2013 NR 42 TC 20 Z9 21 U1 2 U2 9 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0169-6149 J9 ORIGINS LIFE EVOL B JI Orig. Life Evol. Biosph. PD OCT PY 1998 VL 28 IS 4-6 BP 475 EP 483 DI 10.1023/A:1006508012904 PG 9 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 115HL UT WOS:000075658100009 PM 9776659 ER PT J AU Hodgson, ME Davis, BA AF Hodgson, ME Davis, BA TI PE & RS special issue - Remote sensing and GIS for hazards - Foreword SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Editorial Material C1 Univ S Carolina, Dept Geog, Columbia, SC 29208 USA. NASA, CRSP, Stennis Space Ctr, MS 39529 USA. RP Hodgson, ME (reprint author), Univ S Carolina, Dept Geog, Columbia, SC 29208 USA. NR 0 TC 3 Z9 3 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 OCT PY 1998 VL 64 IS 10 BP 976 EP 976 PG 1 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 127GJ UT WOS:000076342300004 ER PT J AU Ambrosia, VG Buechel, SW Brass, JA Peterson, JR Davies, RH Kane, RJ Spain, S AF Ambrosia, VG Buechel, SW Brass, JA Peterson, JR Davies, RH Kane, RJ Spain, S TI An integration of remote sensing, GIS, and information distribution for wildfire detection and management SO PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING LA English DT Article AB A disaster mitigation feasibility study, entitled "WILDFIRE," was initiated in 1997. Project WILDFIRE demonstrated the feasibility of integrating civil and commercial communications and information technology it, provide operational resources to firefighters attacking wildland fires. The demonstration of various technologies occurred during an actual "controlled" burn in a wildland environment in northern California. Real-time data transfer of thermal line scanner data from an airborne platform via a cellular data phone transmission was accomplished, and near-real-time map integration and development was demonstrated using portable uplink/downlink systems to "move" data and asset information (such as vehicle and personnel locations) to a fire camp and a disaster control center. Vehicle tracking was accomplished with the Global Positioning System (GPS) and radio communications to track both fire equipment and field personnel in real time. We focus on the utility and melding of these "off-the-shelf" and emerging technologies in the context of disaster mitigation and response. C1 NASA, Ames Res Ctr, Johnson Controls World Serv Inc, Moffett Field, CA 94035 USA. Terra Mar Resources Informat Serv, Mt Ranch, CA 95246 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. TRW Co Inc, Sunnyvale, CA 94088 USA. Western Disaster Ctr, Moffett Field, CA 94035 USA. TERA Res Inc, Sunnyvale, CA 94086 USA. RP Ambrosia, VG (reprint author), NASA, Ames Res Ctr, Johnson Controls World Serv Inc, MS 242-4, Moffett Field, CA 94035 USA. NR 13 TC 18 Z9 18 U1 2 U2 13 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 OCT PY 1998 VL 64 IS 10 BP 977 EP 985 PG 9 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 127GJ UT WOS:000076342300005 ER PT J AU Chang, ES Geller, M AF Chang, ES Geller, M TI Improved experimental energy levels of carbon I from solar infrared spectra SO PHYSICA SCRIPTA LA English DT Article ID LASER MAGNETIC-RESONANCE; FINE-STRUCTURE; ATOMIC CARBON; FE-I AB We have improved the energy levels in neutral carbon using high resolution infrared solar spectra The main source is the space-based ATMOS spectrum measured by the Fourier transform spectroscopy technique from 600 to 4800 cm(-1). From these infrared data, we have determined 19 new energy levels in the 5f, 5g 6g and 6h configurations. To extend measurements to higher frequencies, we also use other FTS solar spectra: the MARK IV balloon data, covering from 4700 to 5700 cm(-1), and the ground-based NOAO spectra, up to 9000 cm(-1) of Livingston and Wallace and 8900 to 13 600 cm(-1) of Wallace et al. For completeness' sake, we include the 63 new levels found by Feldman et al. plus 8 new levels derived from the VUV data. Utilizing all existing carbon spectra from the far infrared to the vacuum ultraviolet, we have revised Johansson's energy levels and the ionization potential, resulting in improving the accuracy by about an order of magnitude to about 3 mK. C1 Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chang, ES (reprint author), Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. NR 31 TC 7 Z9 7 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 OCT PY 1998 VL 58 IS 4 BP 326 EP 340 DI 10.1088/0031-8949/58/4/008 PG 15 WC Physics, Multidisciplinary SC Physics GA 129PM UT WOS:000076472200008 ER PT J AU Bhatia, AK AF Bhatia, AK TI Properties of the ground state of the hydrogen molecular ion SO PHYSICAL REVIEW A LA English DT Article AB The ground-state energies of the ions H-2(+) and D-2(+) have been calculated without making use of the Born-Oppenheimer approximation. Instead, the ions are treated as three-body systems whose ground states are spherically symmetric. The wave function of the ground state is taken to be a generalized Hylleraas form, but it is necessary to use high powers of the internuclear coordinate to simulate the localized motion of the nuclei. We obtain good values of the ground-state energies and compare them with those obtained from earlier calculations. Expectation values are calculated for various operators, the Fermi contact parameter, and the permanent quadrupole moment. The cusp condition is also calculated. The results are compared with the results of other calculations, where available. [S1050-2947(98)05410-9]. 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, Greenbelt, MD 20771 USA. NR 9 TC 27 Z9 27 U1 4 U2 6 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 OCT PY 1998 VL 58 IS 4 BP 2787 EP 2789 DI 10.1103/PhysRevA.58.2787 PG 3 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 127WQ UT WOS:000076373900028 ER PT J AU Rossler, T Indik, RA Harkness, GK Moloney, JV Ning, CZ AF Rossler, T Indik, RA Harkness, GK Moloney, JV Ning, CZ TI Modeling the interplay of thermal effects and transverse mode behavior in native-oxide-confined vertical-cavity surface-emitting lasers SO PHYSICAL REVIEW A LA English DT Article ID SEMICONDUCTOR-LASERS; NUMERICAL-SIMULATION; GAIN; THRESHOLD; PERFORMANCE; POLARIZATION; DYNAMICS; LIGHT; FABRICATION; VCSELS AB We present a microscopically based vertical-cavity surface-emitting laser (VCSEL) model that treats plasma and lattice heating self-consistently and includes gain dispersion in a fashion facilitating the incorporation of many-body effects. This model is used to investigate the interplay of thermal effects and transverse mode behavior observed in recent experiments with large-aperture selectively oxidized VCSELs. We confirm that the highly divergent single-mode emission seen experimentally at low ambient temperatures may be caused by a redshift of the cavity resonance frequency relative to the quantum-well gain peak. Moreover, due to the dependence of the gain spectrum on temperature our model qualitatively reproduces the measured increase of the dominant spatial scale of the low-temperature steady-state field patterns with pumping. Finally, we demonstrate that spatial hole burning plays a significant role at larger ambient temperatures and explains the decrease of the spatial wavelength with pumping, in agreement with the experiments. [S1050-2947(98)02410-X]. C1 Univ Arizona, Dept Math, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Rossler, T (reprint author), Univ Arizona, Dept Math, Tucson, AZ 85721 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 49 TC 67 Z9 67 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 OCT PY 1998 VL 58 IS 4 BP 3279 EP 3292 DI 10.1103/PhysRevA.58.3279 PG 14 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 127WQ UT WOS:000076373900083 ER PT J AU Artoni, M Bulatov, A Seery, BD AF Artoni, M Bulatov, A Seery, BD TI Nonclassical phase of the electromagnetic field in a nonstationary dielectric SO PHYSICAL REVIEW A LA English DT Article ID QUANTUM; FREQUENCY; RADIATION; PLASMA; MODULATION; LIGHT AB The quantum state of the electromagnetic field propagating in a nonstationary dielectric can acquire a phase shift that arises from modifications in the quantum fluctuations of the field. The shift could be observed, even for quite weak modifications, as a fringe displacement in an interference experiment. [S1050-2947(98)00408-9]. C1 CSIC, Inst Estructura Mat, Madrid 28006, Spain. Princeton Univ, Dept Chem, Princeton, NJ 08544 USA. NASA, Goddard Space Flight Ctr, Photon Div, Greenbelt, MD 20771 USA. RP Artoni, M (reprint author), CSIC, Inst Estructura Mat, C Serrano 125, Madrid 28006, Spain. RI Boulatov, Alexei/A-7096-2014 NR 20 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 1050-2947 J9 PHYS REV A JI Phys. Rev. A PD OCT PY 1998 VL 58 IS 4 BP 3345 EP 3348 DI 10.1103/PhysRevA.58.3345 PG 4 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 127WQ UT WOS:000076373900093 ER PT J AU Zaman, KBMQ AF Zaman, KBMQ TI Asymptotic spreading rate of initially compressible jets - experiment and analysis SO PHYSICS OF FLUIDS LA English DT Article ID CIRCULAR JET; TURBULENCE; FIELD; FLOW AB Experimental results for the spreading and centerline velocity decay rates for round, compressible jets, from a convergent and a convergent-divergent nozzle, are presented. The spreading rate is determined from the variation of streamwise mass flux obtained from Pitot probe surveys. Results for the far asymptotic region show that both spreading and centerline velocity decay rates;when nondimensionalized by parameters at the nozzle exit, decrease with increasing "jet Mach number" M-J. Dimensional analysis with the assumption of momentum conservation, together with compressible flow calculations for the conditions at the nozzle exit, predict this Mach number dependence well. The analysis also demonstrates that an increase in the;"potential core length" of the jet occurring with increasing M-J, a commonly observed trend, is largely accounted for simply by the variations in the density and static pressure at the nozzle exit. The effect of decreasing mixing efficiency with increasing compressibility is inferred to contribute only partially to the latter trend. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Zaman, KBMQ (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 20 TC 23 Z9 23 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 OCT PY 1998 VL 10 IS 10 BP 2652 EP 2660 DI 10.1063/1.869778 PG 9 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 122DP UT WOS:000076056900020 ER PT J AU Backes, PG Peters, SF Phan, L Tso, KS AF Backes, PG Peters, SF Phan, L Tso, KS TI Task lines and motion guides SO PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS LA English DT Article ID SYSTEM AB The new task lines and motion guides approaches to telerobotics are described. Motion guides is a new paradigm for teleoperation of a robot where the path is teleoperated rather than the robot, and the robot is constrained to follow the path. Continuous commands to the robot are only one-dimensional: forward, back, or halt along the motion guide. Task lines have subtasks attached to motion guides. The task lines and motion guides have been implemented in a virtual reality environment to enable task description and execution in a natural, virtual reality graphics environment rather than via direct interaction with a command program. Subtasks are represented in the virtual reality environment by icons attached to the motion guides. The combination of task lines and motion guides is valuable for ground control of Space Station robots, which is the initial application for this technology. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SoHaR Inc, Beverly Hills, CA USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM backes@telerobotics.jpl.nasa.gov NR 17 TC 2 Z9 2 U1 0 U2 0 PU MIT PRESS PI CAMBRIDGE PA ONE ROGERS ST, CAMBRIDGE, MA 02142-1209 USA SN 1054-7460 EI 1531-3263 J9 PRESENCE-TELEOP VIRT JI Presence-Teleoper. Virtual Env. PD OCT PY 1998 VL 7 IS 5 BP 494 EP 502 DI 10.1162/105474698565875 PG 9 WC Computer Science, Cybernetics; Computer Science, Software Engineering SC Computer Science GA 135BF UT WOS:000076779000005 ER EF