FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Saunders, M AF Saunders, M TI The Discovery experiment - The selection process; results to date SO ACTA ASTRONAUTICA LA English DT Article C1 NASA, Langley Res Ctr, Space Sci Support Off, Hampton, VA 23665 USA. RP Saunders, M (reprint author), NASA, Langley Res Ctr, Space Sci Support Off, Hampton, VA 23665 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 215 EP 225 DI 10.1016/S0094-5765(99)00139-3 PG 11 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100006 ER PT J AU Spear, AJ AF Spear, AJ TI Mars Pathfinder's lessons learned from the Mars Pathfinder Project Manager's perspective and the future road SO ACTA ASTRONAUTICA LA English DT Article AB This paper addresses Mars Pathfinder Project lessons learned from a Project Management perspective. Also, it contrasts the Future Project Development approach relative to the Mars Pathfinder's approach. Mars Pathfinder was initiated by NASA in March 1992 as an experiment in CHEAPER, BETTER, FASTER. Not only was the Mars Pathfinder Team challenged to land on Mars- no easy task- but they were asked to do it under a low price, cost cap and short schedule. The Team was also asked to invent a new way of doing business at JPL. Given Institutional priority at JPL, the Mars Pathfinder Team charged off in many directions, which taken as a whole, resulted in a successful, effective, integrated approach to Project Management. But what we did was really nothing new. It was back to basics, cutting out the "crap", executing a well laid out plan, and following through on the details- extremely important. This paper outlines the Mars Pathfinder key steps to Project Management, reports on the results and presents a Vision for future Project development. (C) 1999 Published by Elsevier Science Ltd. All. rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Spear, AJ (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 0 TC 1 Z9 1 U1 0 U2 4 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 235 EP 247 DI 10.1016/S0094-5765(99)00141-1 PG 13 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100008 ER PT J AU Shirley, DL AF Shirley, DL TI Touching Mars: 1998 status of the Mars Robotic Exploration Program SO ACTA ASTRONAUTICA LA English DT Article AB The ars Robotic Exploration Program is sending missions every 26 months to orbit and land on Mars and, in 2005, to return a sample to Earth. The highly successful Mars Pathfinder and Mars Global Surveyor missions were launched in 1996. Mars surveyor '98 will launch in December 1998 and January 1999, to be followed by an orbiter, lander and rover in 2001 and again in 2003. A sample return mission is planned for a 2005 launch. The primary goal of the program after 2001 is the search for evidence of past or present life; and the strategy of orbiters, sample collecting rovers, and sample returns of designed to enrich the chances that such evidence will be discovered. The program is also pioneering "faster, better, cheaper" project management and implementation techniques for NASA. Frequently updated results of the program are available at http://mars.jpl.nasa.gov. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Mars Explorat Program, Pasadena, CA 91125 USA. RP Shirley, DL (reprint author), CALTECH, Jet Prop Lab, Mars Explorat Program, Pasadena, CA 91125 USA. NR 8 TC 3 Z9 3 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 249 EP 265 DI 10.1016/S0094-5765(99)00142-3 PG 17 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100009 ER PT J AU Jones, JA Saunders, S Blamont, J Yavrouian, A AF Jones, JA Saunders, S Blamont, J Yavrouian, A TI Balloons for controlled roving/landing on Mars SO ACTA ASTRONAUTICA LA English DT Article AB Until now, the only practical balloon systems proposed to explore the martian atmosphere have been superpressure balloons, which fly at a constant altitude, or short-lived helium balloons, which precariously drag a snake through;all types of surface weather, or a day/night combination of the two. For the first time, two novel atmospheric balloon systems now appear quite viable for controlled balloon landings at selected martian surface locations. These balloons could softland payload packages, such as lightweight surface roving vehicles. The two balloon approaches and a land rover concept are described below, along with a combination of the two approaches. Solar Hot-Air Balloons: These "Montgolfiere" balloons are named after the 18th-century French brothers Joseph-Michel and Jacques-Etienne Mongolfier, who first flew hot-air balloons. Using entirely solar heat, they are ideal for landing at the martian poles during summer or for shorter flights at lower latitudes. Recent tests have already confirmed the ease of altitude deployment and filling of these solar hot-air balloons. Furthermore, actual landings and reascents of solar hot-air balloons have been recently demonstrated by JPL, using a novel, lightweight, top air vent that is radio controlled. One particularly useful application of these balloons is their use as a parachute to soft-land packages that are up to 50% of the total entry mass, which represents a fivefold improvement over present retrorocket landing-systems. Variable-Emissivity Balloons: A second atmospheric balloon system uses a variable-emissivity superpressure helium balloon that can land at night at any martian latitude. These balloons would be gold-coated, superpressure helium balloons during both night and day, They could land at prescribed targets by exposing a section of the upper white balloon surface to the radiant cooling of deep space during the night. This reduces the temperature and pressure in the balloon to create negative buoyancy, thus causing descent, while replacement of the gold top cover; causes reascent. Specific areas could be targeted for landings by using atmospheric currents at various altitudes, similar to techniques used by balloonists flying over the Earth. Inflatable Roving Vehicles: JPL has recently fabricated and tested a number of roving vehicles with large inflatable balloons that act as tires. One version, with 75-cm-diameter wheels, has already demonstrated the ability to make large traverses in JPL's simulated "Mars Yard." A full-scale version, with 1.5-m-diameter wheels, should be capable of climbing large rocks (less than or equal to 0.5 m), traveling reasonably fast (approximate to 500 m/h) and far (approximate to 10 km), and yet have very low mass (approximate to 6 kg). Low-Cost Combined Atmospheric/Surface Mission: A simple, solar hot-air balloon would act as a parachute to land a 6-kg inflatable rover. The balloon would then rise to a 3-km altitude while carrying a 2-kg camera/magnetometer/communications package for the remainder of daylight hours. The entire package would then soft-land at dusk. Total Mars entry mass would be about 20 kg, and the mission could be flown to Mars at very low cost (approximate to $5M total launch costs) via one of the CNES Ariane 5 GTO piggyback launches. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Jones, JA (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 17 TC 3 Z9 4 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 293 EP 300 DI 10.1016/S0094-5765(99)00146-0 PG 8 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100013 ER PT J AU Gershman, R Wallace, RA AF Gershman, R Wallace, RA TI Technology needs of future planetary missions SO ACTA ASTRONAUTICA LA English DT Article AB This paper presents the findings of a series of planetary mission studies which supported development of the Space Science Strategic Plan. The studies' evaluated the feasibility, science return, and cost of missions that were candidates for inclusion in the Strategic Plan and also assessed the effects of advanced technology on these parameters. The mission set covered includes high priority missions to planets and/or comets and asteroids subsequent to Pluto Express and Europa Orbiter (i.e., launching after 2004) except for missions to Mars (handled by a different office at JPL). A wide range missions were studied with emphasis on nine mission targets in two priority groups identified in the Strategic Plan. The first group are leading candidates for launch slots in the middle of the next decade: a comet nucleus sample return mission, a Jupiter deep multi-probe mission, and a Mercury Orbiter/solar physics mission; These are feasible today but can use advanced technology to enhance performance and/or reduce cost. The Second group are future technology drivers, high priority science missions that require technology breakthroughs' prior to implementation. These include comet deep coring and advanced sampling, Europa Lander, Io Volcano Observer,Neptune Orbiter, and investigations of the atmospheres and surfaces of Titan and Venus by aerobots or other means. The paper describes the mission concepts and the enabling and enhancing technologies developments identified for each mission. The current trend toward miniaturization of avionics will benefit all of the missions. Several were found to be enabled or strongly enhanced by advances in low thrust propulsion, either solar electric or solar sail. Another critical area is in-situ technologies, including precision approach; landing; surface mobility; sample collection, analyses and packaging; and sample return to Earth. (C) 1999 Published py Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Gershman, R (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 0 TC 7 Z9 7 U1 0 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 329 EP 335 DI 10.1016/S0094-5765(99)00150-2 PG 7 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100017 ER PT J AU Rasky, DJ Tran, HK AF Rasky, DJ Tran, HK TI Low cost entry systems for future planetary exploration missions SO ACTA ASTRONAUTICA LA English DT Article AB Recent developments in materials for spacecraft thermal protection have made it possible to construct high performance, low cost aeroshells for missions requiring atmospheric entry. The new material developments center around the light-weight ceramic ablator family invented and developed at NASA Ames. This presentation will discuss three members of the family, SIRCA, PICA and SPLIT, which have found application on a number of NASA missions. With these advanced materials, a simple fabrication approach is enabled using organic composite construction techniques to produce high performance, low cost, reliable aeroshells which can protect vehicles over a wide range of entry, conditions - ranging from tens to hundreds to thousands of W/cm<^>2 of heating. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. RP Rasky, DJ (reprint author), NASA, Ames Res Ctr, Thermal Protect Mat & Syst Branch, Moffett Field, CA 94035 USA. NR 0 TC 3 Z9 4 U1 3 U2 6 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 347 EP 355 DI 10.1016/S0094-5765(99)00153-8 PG 9 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100019 ER PT J AU Rayman, MD Chadbourne, PA Culwell, JS Williams, SN AF Rayman, MD Chadbourne, PA Culwell, JS Williams, SN TI Mission design for Deep Space 1: a low-thrust technology validation mission SO ACTA ASTRONAUTICA LA English DT Article AB Deep Space 1 (DS1), currently scheduled for launch in July or August 1998, is the first mission of NASA's New Millennium program, chartered to flight validate high-risk, advanced technologies important for future space and Earth science programs. DS1's payload of technologies will be rigorously exercised during the two-year mission. Several features of the project present unique or unusual opportunities and challenges in the design of the mission that are likely to be encountered in future missions. The principal mission-driving technology is solar electric propulsion (SEP); this;will be the first mission to rely on SEP as the primary source of propulsion. Another important technology for the mission design is the autonomous on-board navigation system, which requires frequent (at least weekly) intervals of several hours during which it collects visible images of distant asteroids and stars for its use in orbit determination and maneuver planning. The mission design accommodates the needs of these and other technologies for operational use and for acquiring sufficient validation data to assess their viability for future missions. DS1's mission profile includes encounters with an asteroid and a comet. (C) 1999 Elsevier Science Ltd. AII rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rayman, MD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 3 TC 17 Z9 17 U1 0 U2 4 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 381 EP 388 DI 10.1016/S0094-5765(99)00157-5 PG 8 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100023 ER PT J AU Muirhead, B Kerridge, S AF Muirhead, B Kerridge, S TI The Deep Space 4/Champollion mission SO ACTA ASTRONAUTICA LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Muirhead, B (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 407 EP 414 DI 10.1016/S0094-5765(99)00160-5 PG 8 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100026 ER PT J AU Staehle, RL Brewster, SC Carraway, JB Chatterjee, AK Clark, KB Doyle, RJ Henry, PK Johannesen, JR Johnson, TV Jorgensen, EJ Kemski, RP Ludwinski, JM Maddock, RW Mondt, JF Randolph, JE Terrile, RJ Tsurutani, BT AF Staehle, RL Brewster, SC Carraway, JB Chatterjee, AK Clark, KB Doyle, RJ Henry, PK Johannesen, JR Johnson, TV Jorgensen, EJ Kemski, RP Ludwinski, JM Maddock, RW Mondt, JF Randolph, JE Terrile, RJ Tsurutani, BT TI Ice & fire: Missions to the most difficult solar system destinations ... on a budget SO ACTA ASTRONAUTICA LA English DT Article AB Three radii from the surface of the Sun...more natural radiation around Jupiter than would be encountered immediately following a nuclear war... to the farthest planet and beyond... these challenges are faced by the three "Ice & Fire" missions: Solar Probe, Europa Orbiter, and Pluto-Kuiper Express. These three missions will be beneficiaries of the X2000 and related advanced technology development programs. Technology developments now in progress make these missions achievable at costs recently thought adequate only for missions of relatively short durations to "nearby" destinations. The next mission to Europa after Galileo will determine whether a global subsurface liquid water ocean is currently present, and will identify locations where the ocean, if it exists, may be most accessible to future missions. Pluto-Kuiper Express will complete the reconnaissance of the known planets in our Solar System with geological, compositional, and atmospheric mapping of Pluto and Charon while Pluto remains relatively near the Sun during its 248 year orbit. An extended mission to a Kuiper Disk object may be possible, depending on remaining sciencecraft resources. Using a unique combination of Sun shield/high gain antenna and quadrature encounter geometry, Solar Probe will deeply penetrate our nearest star's atmosphere to make local measurements of the birth of solar wind, and to remotely image features as small as 60 kilometers across on the Sun's surface. Avionics technology, leading to integration of functions among a set of multichip modules with standard interfaces, will enable lower production costs, lower power and mass, and the ability to package with modest shielding to enable survival in orbit around Europa inside Jupiter's intense radiation belts. The same avionics and software can be utilized on the other Ice & Fire missions, Each mission is characterized by a long cruise to its destination, facilitated by planetary flybys. The flight systems will represent a unique early integration of science "payload" and "spacecraft," becoming a more integrated "sciencecraft." To reduce operations and tracking costs, sciencecraft will be more autonomous. They will self-monitor and self-command, while sending a continuous beacon alerting ground receivers to general sciencecraft health and any need for immediate attention. Where solar power proves impractical for achieving mission goals, an advanced radioisotope power source may be utilized with a much smaller amount of fuel than on prior missions. The three missions described are to begin the Outer Planets/Solar Probe exploration program, as first proposed in the FY1998 Federal Budget. Sciencecraft, launch systems and mission operations must all fit within a single program, encouraging system- and program-wide tradeoffs to minimize costs. Some of the system and technological solutions utilized by these missions may find application in a variety of other science-driven missions. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Staehle, RL (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RI Frank, David/E-8213-2012 NR 16 TC 0 Z9 0 U1 1 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 423 EP 439 DI 10.1016/S0094-5765(99)00162-9 PG 17 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100028 ER PT J AU Doyotte, R Love, SG Peterson, CE AF Doyotte, R Love, SG Peterson, CE TI The Zeus Mission Study - An application of automated collaborative design SO ACTA ASTRONAUTICA LA English DT Article AB The purpose of the Zeus Mission Study was threefold. As an element of a graduate course in spacecraft system engineering, its purpose was primarily educational - to allow the students to apply their knowledge in a real mission study. The second purpose was to investigate the feasibility of applying advanced technology (the power antenna and solar electric propulsion concepts) to a challenging mission. Finally, the study allowed evaluation of the benefits of using quality-oriented techniques (Quality Function Deployment (QFD) and Taguchi Methods) for a mission study. To encourage innovation, several constraints were placed on the study from the onset. While the primary goal was to place at least one lander on Europa, the additional constraint of no nuclear power sources posed an additional challenge, particularly when coupled with the mass constraints imposed by using a Delta II class launch vehicle. In spite of these limitations, the team was able to develop a mission and spacecraft design capable of carrying three simple, lightweight, yet capable landers. The science return will more than adequately meet the science goals established. QFD was used to determine the optimal choice of instrumentation. The lander design was selected from several competing lander concepts, including revers. The carrier design was largely dictated by the needs of the propulsion system required to support the mission, although the development of a Project Trades Model (PTM) in software allowed for rapid recalculation of key system parameters as changes were made. Finally, Taguchi Methods (Design of Experiments) were used in conjunction with the PTM allowing for some limited optimization of design features. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Doyotte, R (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 0 TC 3 Z9 3 U1 0 U2 5 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 AUG-NOV PY 1999 VL 45 IS 4-9 BP 441 EP 448 DI 10.1016/S0094-5765(99)00163-0 PG 8 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100029 ER PT J AU Gershman, R Penzo, P Wiercigroch, A AF Gershman, R Penzo, P Wiercigroch, A TI From GTO to the planets SO ACTA ASTRONAUTICA LA English DT Article AB Most Ariane 5 launches will provide slots for auxiliary payloads - up to eight payloads at 100 kg apiece. Recent analysis has established that these slots can be used to send small science payloads to Mars, Venus, or a range of near-Earth and main-belt asteroids. This paper discusses the Ariane 5 configuration, mission analyses, and launch scheduling issues associated with these opportunities and describes some applicable candidate mission concepts, (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Gershman, R (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 517 EP 525 DI 10.1016/S0094-5765(99)00171-X PG 9 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100037 ER PT J AU Leschly, K Sprague, G Rademacher, J AF Leschly, K Sprague, G Rademacher, J TI Carrier spacecraft using ariane-5 GTO piggyback launch SO ACTA ASTRONAUTICA LA English DT Article AB Several design concepts for interplanetary carrier spacecraft (SIC) using the Ariane-5 GTO piggyback launch opportunities have been studied over the past year by JPL and CNES: The study has been fucused on carrier S/C design which will deliver one or more entry probes to Mars/Venus. The probes ranges from 35-90 cm in diameter and weighs 10-50 kg each. A planetary orbiter design has also been identified, which will carry additional fuel for orbit insertion, at the expense of reducing the science payload to between 2-10 kg. The design concepts are:compatible with the Ariane-5 Structure for Auxiliary Payloads (ASAP) launch constraints for the single-mounted (ASAP-standard) and the dual-mounted (ASAP-Banana) secondary payload configurations - carrying up to 100 kg and 180 kg payloads; respectively. The-feasibility of these interplanetary carrier S/C have been confirmed through an industry survey and by Arianespace. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Leschly, K (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 3 TC 0 Z9 0 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 527 EP 531 DI 10.1016/S0094-5765(99)00172-1 PG 5 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100038 ER PT J AU Gershman, R Seybold, C AF Gershman, R Seybold, C TI Propulsion trades for space science missions SO ACTA ASTRONAUTICA LA English DT Article AB This study evaluated the relative benefits of proposed deep space propulsion technology improvements in three areas: advanced chemical, solar electric, and solar sail. Within each area, specific states, representing current technology (present-1999), mid-term (2000-2004), and far term (2005+), were selected for evaluation. The figures of merit used were net spacecraft mass delivered, size of the launch vehicle needed, trip time, cost, and risk. Based on the results, an investment strategy was recommended to NASA headquarters, along with possible scenarios for its implementation. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Gershman, R (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 8 TC 16 Z9 16 U1 0 U2 2 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 541 EP 548 DI 10.1016/S0094-5765(99)00174-5 PG 8 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100040 ER PT J AU Blue, RC AF Blue, RC TI Mars Microprobe Project instrumentation package SO ACTA ASTRONAUTICA LA English DT Article AB The Mars Microprobe Project is a technology validation mission in NASA's New Millennium Program. The project is developing a pair of small, two-piece probes for delivery to the surface,of Mars in December of 1999. Descent from orbit to the surface is accomplished with a passive single-stage non-erosive aeroshell designed specifically for this mission. Upon impact each probe separates into a section that penetrates into the Martian regolith and a section that remains on the surface. This design provides an opportunity to collect scientific data both on and up to two meters beneath the surface. The instrumentation package of the Mars Microprobe includes a meteorological instrument for measuring atmospheric pressure and temperature, accelerometers to measure the atmospheric drag on the probe aeroshell during descent, accelerometers for measuring the forces on the probe at impact, temperature sensors in the penetrator to measure the soil thermal conductivity at depth, and an experiment to collect a small sample of the Martian regolith and determine if water is present in the sample. An overview of the instrument design and implementation is reported along with the results of the environmental tests and instrument calibration. (C) 1999 Published by Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Mars Microprobe Mission, Pasadena, CA 91109 USA. RP Blue, RC (reprint author), CALTECH, Jet Prop Lab, Mars Microprobe Mission, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 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 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD AUG-NOV PY 1999 VL 45 IS 4-9 BP 585 EP 595 DI 10.1016/S0094-5765(99)00179-4 PG 11 WC Engineering, Aerospace SC Engineering GA 263XT UT WOS:000084151100045 ER PT J AU Sobieszczanski-Sobieski, J AF Sobieszczanski-Sobieski, J TI Multidisciplinary design optimisation (MDO) methods: their synergy with computer technology in the design process SO AERONAUTICAL JOURNAL LA English DT Article ID SENSITIVITY; DERIVATIVES; COMPLEX AB The paper identifies speed, agility, human interface, generation of sensitivity information, task decomposition, and data transmission (including storage) as important attributes for a computer environment to have in order to support engineering design effectively. It is argued that when examined in terms of these attributes the presently available environment can be shown to be inadequate. A radical improvement is needed, and it may be achieved by combining new methods that have recently emerged from multidisciplinary design optimisation (MDO) with massively parallel processing computer technology. The caveat is that, for successful use of that technology in engineering computing, new paradigms for computing will have to be developed - specifically, innovative algorithms that are intrinsically parallel so that their performance scales up linearly with the number of processors. It may be speculated that the idea of simulating a complex behaviour by interaction of a large number of very simple models may be an inspiration for the above algorithms; the cellular automata are an example. Because of the long lead time needed to develop and mature new paradigms, development should begin now, even though the widespread availability of massively parallel processing is still a few years away. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Sobieszczanski-Sobieski, J (reprint author), NASA, Langley Res Ctr, MS 139, Hampton, VA 23681 USA. NR 34 TC 7 Z9 7 U1 0 U2 4 PU ROYAL AERONAUTICAL SOC PI LONDON PA 4 HAMILTON PL, LONDON, ENGLAND W1V OBQ SN 0001-9240 J9 AERONAUT J JI Aeronaut. J. PD AUG PY 1999 VL 103 IS 1026 BP 373 EP 382 PG 10 WC Engineering, Aerospace SC Engineering GA 241BW UT WOS:000082863100003 ER PT J AU Powell, CA Preisser, JS AF Powell, CA Preisser, JS TI Research for quieter skies SO AEROSPACE AMERICA LA English DT Article C1 NASA Langley, Fluid Mech & Acoust Div, Hampton, VA 23665 USA. RP Powell, CA (reprint author), NASA Langley, Fluid Mech & Acoust Div, Hampton, VA 23665 USA. NR 0 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 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD AUG PY 1999 VL 37 IS 8 BP 26 EP 29 PG 4 WC Engineering, Aerospace SC Engineering GA 225EQ UT WOS:000081945800010 ER PT J AU Dawson, DL DeMaioribus, CA Hagino, RT Light, JT Bradley, DV Britt, KE Charles, BE AF Dawson, DL DeMaioribus, CA Hagino, RT Light, JT Bradley, DV Britt, KE Charles, BE TI The effect of withdrawal of drugs treating intermittent claudication SO AMERICAN JOURNAL OF SURGERY LA English DT Article; Proceedings Paper CT 27th Annual Meeting of the Society-for-Clinical-Vascular-Surgery CY MAR 24-28, 1999 CL LAKE BUENA VISTA, FLORIDA SP Soc Clin Vasc Surg ID DOUBLE-BLIND TRIAL; ARTERIAL-DISEASE; PENTOXIFYLLINE; CILOSTAZOL; METAANALYSIS; MULTICENTER; MANAGEMENT; PLACEBO AB BACKGROUND: Pharmacologic treatment for intermittent claudication is a management option. This study evaluated the effect of withdrawal of drug therapies, cilostazol and pentoxifylline, on the walking ability of peripheral artery disease patients. METHODS: Single-blind placebo crossover from a randomized, double-blind trial; 45 claudication patients received either cilostazol 100 mg orally twice daily (n = 16), pentoxifylline 400 mg orally three times daily (n = 13), or placebo (n = 16) for 24 weeks. After 24 weeks of double-blind therapy, treatment for all groups was placebo only, and follow-up continued through week 30. Treatment efficacy was established with treadmill testing. RESULTS: Profile analysis demonstrated a highly significant loss of treatment benefit after crossover (P = 0.001) for cilostazol-treated patients, but no significant change after crossover was observed with pentoxifylline. CONCLUSIONS: Drug withdrawal worsened the walking of claudicants who had benefited from cilostazol therapy. This decline with crossover to placebo suggests that the initial improvement with cilostazol treatment was due to the drug's action. Withdrawal of pentoxifylline did not adversely affect walking. Am J Surg. 1999;178: 141-146. (C) 1999 by Excerpta Medica, Inc. C1 Wilford Hall USAF Med Ctr, Dept Gen Surg, Surg Res Serv, Lackland AFB, TX 78236 USA. RP Dawson, DL (reprint author), NASA, Lyndon B Johnson Space Ctr, Div Med Sci, Mail Code SD,2101 NASA Rd 1, Houston, TX 77058 USA. NR 16 TC 35 Z9 37 U1 0 U2 0 PU CAHNERS PUBL CO PI NEW YORK PA 249 WEST 17 STREET, NEW YORK, NY 10011 USA SN 0002-9610 J9 AM J SURG JI Am. J. Surg. PD AUG PY 1999 VL 178 IS 2 BP 141 EP 146 DI 10.1016/S0002-9610(99)00147-6 PG 6 WC Surgery SC Surgery GA 231DG UT WOS:000082292400013 PM 10487267 ER PT J AU Meerkotter, R Schumann, U Doelling, DR Minnis, P Nakajima, T Tsushima, Y AF Meerkotter, R Schumann, U Doelling, DR Minnis, P Nakajima, T Tsushima, Y TI Radiative forcing by contrails SO ANNALES GEOPHYSICAE-ATMOSPHERES HYDROSPHERES AND SPACE SCIENCES LA English DT Article DE atmospheric composition and structure (aerosols and particles); meteorology and atmospheric dynamics (climatology, radiative processes) ID IN-SITU MEASUREMENTS; CIRRUS CLOUDS; OPTICAL-PROPERTIES; ICE CRYSTALS; AIRCRAFT EXHAUST; SOLAR-RADIATION; CLIMATE MODELS; OCTOBER 1989; SCATTERING; PARAMETERIZATION AB A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude., and subarctic summer and winter atmospheres. Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere, a mean contrail covets of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 Wm(-2) daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude. The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover. C1 DLR Oberpfaffenhofen, Inst Phys Atmosphare, Wessling, Germany. NASA, Langley Res Ctr, Hampton, VA 23665 USA. Univ Tokyo, Ctr Climate Syst Res, Tokyo, Japan. RP DLR Oberpfaffenhofen, Inst Phys Atmosphare, Wessling, Germany. EM ulrich.schumann@dlr.de RI Nakajima, Teruyuki/H-2370-2013; Minnis, Patrick/G-1902-2010; OI Nakajima, Teruyuki/0000-0002-9042-504X; Minnis, Patrick/0000-0002-4733-6148; Schumann, Ulrich/0000-0001-5255-6869 NR 79 TC 79 Z9 79 U1 1 U2 6 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0992-7689 J9 ANN GEOPHYS-ATM HYDR JI Ann. Geophys.-Atmos. Hydrospheres Space Sci. PD AUG PY 1999 VL 17 IS 8 BP 1080 EP 1094 DI 10.1007/s005850050833 PG 15 WC Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences SC Astronomy & Astrophysics; Geology; Meteorology & Atmospheric Sciences GA 231DZ UT WOS:000082294000009 ER PT J AU De Propris, R Stanford, SA Eisenhardt, PR Dickinson, M Elston, R AF De Propris, R Stanford, SA Eisenhardt, PR Dickinson, M Elston, R TI The K-band luminosity function in galaxy clusters to z similar to 1 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : dusters : general; galaxies : evolution; galaxies : formation; galaxies : luminosity function, mass function ID PREDICTED STAR COUNTS; REDSHIFT SURVEY; FIELD GALAXIES; ELLIPTIC GALAXIES; DISTANT CLUSTERS; EVOLUTION; POPULATIONS; SPECTROSCOPY; MAGNITUDE; UNIVERSE AB present K-band luminosity functions for galaxies in a heterogeneous sample of 38 clusters at 0.1 < z < 1. Using infrared-selected galaxy samples, which generally reach 2 mag fainter than the characteristic galaxy luminosity LY*, we fitted Schechter functions to background-corrected cluster galaxy counts to determine K* as a function of redshift. Because of the magnitude limit of our data, the faint-end slope a is fixed at -0.9 in the fitting process. We find that K*(z) departs from no-evolution predictions at z > 0.4 and is consistent with the behavior of a simple, passive luminosity evolution model in which galaxies form all their stars in a single burst at z(f) = 2(3) in an H(0) = 65 km s(-1) Mpc(-1), Omega(M) = 0.3, Omega(A), = 0.7(0) universe. This differs from the flat or negative infrared luminosity evolution, which has been reported for high-redshift field galaxy samples. We find that the observed evolution appears to be insensitive to cluster X-ray luminosity or optical richness, implying little variation in the evolutionary history of galaxies over the range of environmental densities spanned by our cluster sample. These results support and extend previous analyses based on the color evolution of high-redshift cluster E/SO galaxies, indicating not only that their stellar populations formed at high-redshift, but that the assembly of the galaxies themselves was largely complete by z approximate to 1 and that subsequent evolution down to the present epoch was primarily passive. C1 Univ New S Wales, Sch Phys, Dept Astron & Opt, Sydney, NSW 2052, Australia. Univ Calif Davis, Livermore, CA 94550 USA. Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. RP De Propris, R (reprint author), Univ New S Wales, Sch Phys, Dept Astron & Opt, Sydney, NSW 2052, Australia. EM propris@edwin.phys.unsw.edu.au; adam@igpp.llnl.gov; prme@kromos.jpl.nasa.gov; med@stsci.edu; elston@astro.ufl.edu NR 71 TC 111 Z9 111 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 AUG PY 1999 VL 118 IS 2 BP 719 EP 729 DI 10.1086/300978 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232JZ UT WOS:000082368700011 ER PT J AU Devine, D Reipurth, B Bally, J AF Devine, D Reipurth, B Bally, J TI L1551 NE or L1551 IRS 5: Which source drives HH 28/29? SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM : jets and outflows; stars : formation; stars : mass loss ID HERBIG-HARO OBJECTS; MOLECULAR OUTFLOW; L1551-IRS-5; REGION; CLOUD; LOBE AB We have obtained deep high-resolution interference filter images of the HH objects in the L1551 molecular cloud in 1990 and 1997, and we suggest that the well-known and well-studied objects HH 28 and 29 are driven by the deeply embedded class 0 source L1551 NE, not by the well-known IRS 5 source. We find a new, small bipolar HH flow, HH 454, surrounding L1551 NE. This new HH flow is aligned along the axis of a highly collimated infrared jet from this source, is blueshifted by 110 km s(-1) southwest of the source, and is redshifted by 100-130 km s(-1) northeast of L1551 NE. A line through the L1551 NE source and along this well-defined how axis passes straight through HH 29 and within parts of the more distant HH 259 and HH 28. The proper motion of HH 29 exhibits a complex flow pattern with some knots appearing to move away from the nearby source IRS 5 while other Darts are moving away from L1551 NE. The HH 29 object encompasses several bright, stationary knots that have faded between the two epoch images. When these stationary knots are excluded from the proper-motion analysis, the resulting overall flow vector points away from L1551 NE, not from IRS 5. Most components of HH 259 and some parts of HH 28 also appear to be moving in a direction pointing away from L1551 NE rather than from IRS 5. In the opposite, redshifted lobe, we find a new, distant HH object, HH 286, but it is unclear whether L1551 NE or IRS 5 is the driving source. Altogether, it appears that L1551 NE plays a much more prominent role than hitherto anticipated in the outflow activity of this highly complex and confused region. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. RP Devine, D (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. OI BALLY, JOHN/0000-0001-8135-6612 NR 29 TC 30 Z9 30 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1999 VL 118 IS 2 BP 972 EP 982 DI 10.1086/300992 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232JZ UT WOS:000082368700034 ER PT J AU Ghosh, K Iyengar, KVK Ramsey, BD Austin, RA AF Ghosh, K Iyengar, KVK Ramsey, BD Austin, RA TI Near-simultaneous spectroscopic and broadband polarimetric observations of Be stars SO ASTRONOMICAL JOURNAL LA English DT Article DE stars : emission-line, Be; techniques : polarimetric; techniques : spectroscopic ID BASE-LINE INTERFEROMETRY; THIN STELLAR ENVELOPES; MULTICOLOR POLARIMETRY; THOMSON SCATTERING; CONTINUUM POLARIZATION; MULTIPLE-SCATTERING; EMISSION-LINES; IR EXCESS; MASS-LOSS; CONSTRAINTS AB Near simultaneous optical spectroscopic (on four nights) and broadband linear continuum (B, V, R, and I bands) polarimetric (on seven nights) observations of 29 Be stars were carried out during 1993 November-December. The program Be stars displayed wavelength dependence of intrinsic polarizations with no frequency dependence of polarimetric position angles. Some of the Be stars displayed long-term polarization variability. The Be and Be-shell stars could not be distinguished from one another solely on the basis of their polarization values. Full widths at half-maximum of the H alpha profiles and the intrinsic linear continuum polarizations are closely correlated with the projected rotational velocities of the program stars. Photospheric-absorption-corrected equivalent widths of H alpha profiles [W(alpha)] and the radii of H alpha-emitting or -absorbing envelopes (R-e or R-a) are nonlinearly correlated with the intrinsic continuum polarizations of these stars. However, W(alpha) and R-e are linearly correlated. With large uncertainties, there is a trend of spectral dependence of polarization. Detailed discussion of these results is presented in this paper. C1 NASA, Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NAS, NRC, Washington, DC USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. RP Ghosh, K (reprint author), NASA, Marshall Space Flight Ctr, Space Sci Lab, Mail Code ES84, Huntsville, AL 35812 USA. NR 65 TC 5 Z9 5 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1999 VL 118 IS 2 BP 1061 EP 1072 DI 10.1086/300953 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232JZ UT WOS:000082368700042 ER PT J AU Stern, SA Colwell, WB Festou, MC Tamblyn, PM Parker, JW Slater, DC Weissman, PR Paxton, LJ AF Stern, SA Colwell, WB Festou, MC Tamblyn, PM Parker, JW Slater, DC Weissman, PR Paxton, LJ TI Comet Hale-Bopp (C/1995 O1) near 2.3 AU postperihelion: Southwest Ultraviolet Imaging System measurements of the H2O and dust production SO ASTRONOMICAL JOURNAL LA English DT Article DE comets : general ID EVOLUTION; OH AB The Southwest Ultraviolet Imaging System (SWUIS) imaged comet C/1995 O1 (Hale-Bopp) in various bandpasses from the Space Shuttle on nine occasions during 1997 August 9-15. These observations occurred when the solar elongation of the comet was too small to permit Hubble Space Telescope and other UV observations. Here we present some first results of the continuum and gas emission measurements collected by SWUIS. We find that Hale-Bopp's dust-production parameter, Afp, was (2.0 +/- 0.8) x 10(5) cm when the comet was 2.33 AU from the Sun. Furthermore, we find that its water production rate, Q(H2O), was (2.6 +/- 0.4) x 10(29) s(-1). Combining this result with both other published H2O production rates and CO production rates, we find that our measurements were made at the beginning of the period when the comet's activity was in transition from a H2O dominated to a CO-dominated state. We also find that the average rate of decrease of the water production between perihelion and 2.33 AU postperihelion was very close to r(h)(-4.0+/-0.6), but concerns over radio data indicate that it may have been shallower immediately postperihelion and then considerably steeper beyond about 2 AU. Such a behavior could indicate a sharply declining H2O production rate beyond 2 AU, but if this is the case, then the H2O production curve's steepening and turnoff occurred approximate to 1 AU closer to the Sun postperihelion than did the H2O turn-on preperihelion. An alternative explanation could be that a seasonal (i.e., obliquity-dependent shadowing) effect may have caused a reduction in illuminated area on Hale-Bopp's irregular nucleus between 1.5 and 2.3 AU outbound. C1 SW Res Inst, Boulder, CO 80302 USA. SW Res Inst, San Antonio, TX 78238 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. RP Stern, SA (reprint author), SW Res Inst, Suite 426,1050 Walnut St, Boulder, CO 80302 USA. RI Paxton, Larry/D-1934-2015 OI Paxton, Larry/0000-0002-2597-347X NR 20 TC 12 Z9 12 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD AUG PY 1999 VL 118 IS 2 BP 1120 EP 1125 DI 10.1086/300968 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 232JZ UT WOS:000082368700046 ER PT J AU Ros, E Marcaide, JM Guirado, JC Ratner, MI Shapiro, II Krichbaum, TP Witzel, A Preston, RA AF Ros, E Marcaide, JM Guirado, JC Ratner, MI Shapiro, II Krichbaum, TP Witzel, A Preston, RA TI High precision difference astrometry applied to the triplet of S5 radio sources B1803+784/Q1928+738/B2007+777 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE techniques : interferometric; astrometry; galaxies : BL Lacertae objects : individual : B1803+784, B2007+777, Q1928+738 ID BL LACERTAE OBJECTS; COMPLETE SAMPLE; SCALE STRUCTURE; MOTION; SYSTEM; MILLIARCSECOND; MAPS; GHZ AB We determined the separations of the radio sources in the triangle formed by the BL Lac objects 1803+784 and 2007+777, and the QSO 1928+738 from intercontinental interferometric observations carried out in November 1991 at the frequencies of 2.3 and 8.4 GHz simultaneously. Difference phase-delay astrometry yielded the following separations: Delta alpha((1803+784)-(1928+738))=-l(h)27(m) 2.(s)811256+/-0.(s)000062 Delta delta((1803+784)-(1928+738))=4 degrees 30' 2." 44833+/-0." 00012 Delta alpha((1928+738)-(2007+777))=-0(h)37(m)42.(s)503305+/-0.(s)000033 Delta delta((1928+738)-(2007+777))=-3 degrees 54'41." 67756+/-0." 00013 Delta alpha((2007+777)-(1803+784))=2(h) 4(m)45.(s)314561+/-0.(s)000052 Delta delta((2007+777)-(1803+784))=-0 degrees 35'20." 77077+/-0." 00013 We successfully connected differenced phase delays over 7 degrees on the sky at 8.4 GHz at an epoch of maximum solar activity. The effects of the ionosphere on these VLBI data were mostly removed by estimates of the total electron content from observations of GPS satellites. The comparison of the estimated separation of QSO 1928+738 and BL 2007+777 with previous such estimates obtained from data at different epochs leads us to a particular alignment of the maps of QSO 1928+738 at different epochs relative to those of BL 2007+777, although with significant uncertainty. For this alignment, that the jet components of QSO 1928+738 show a mean proper motion of 0.32+/-0.10 mas/yr and also suggest an identification for the position of the core of this radio source. C1 Max Planck Inst Radioastron, D-53121 Bonn, Germany. Univ Valencia, Dept Astron & Astrofis, E-46100 Valencia, Spain. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ros, E (reprint author), Max Planck Inst Radioastron, Hugel 69, D-53121 Bonn, Germany. EM ros@mpifr-bonn.mpg.de NR 47 TC 17 Z9 17 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 AUG PY 1999 VL 348 IS 2 BP 381 EP 393 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 231DN UT WOS:000082293000011 ER PT J AU Matsuura, M Yamamura, I Murakami, H Freund, RM Tanaka, M AF Matsuura, M Yamamura, I Murakami, H Freund, RM Tanaka, M TI Water vapor absorption in early M-type stars SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE infrared : stars; stars : late-type; stars : atmospheres; stars : circumstellar matter; stars : variables : general; surveys ID VARIABLES; SPECTRA AB The spectrometers onboard the Infrared Telescope in Space (IRTS) reveal water vapor absorption in early M-type stars, as early as M2. Previous observations detected H2O vapor absorption only in stars later than M6, with the exception of the recent detection of H2O in beta Peg (M2.5 II-III). In our sample of 108 stars, 67 stars have spectral types earlier than M6. The spectral types are established by means of their near-infrared colors on a statistical basis. Among the 67 stars of spectral types earlier than M6, we find water vapor absorption in six stars. The observed absorption features are interpreted using a local thermodynamic equilibrium model. The features are reasonably fitted by model spectra with excitation temperatures of 1000-1500 K and water column densities of 5 x 10(19) to 1 x 10(20) cm(-2). These numbers, imply that the H2O molecules are present in a region of the atmosphere, located above the photosphere. Furthermore, our analysis shows a good correlation between the H2O absorption band strength, and the mid-infrared excess due to the circumstellar dust. We discuss the relation between the outer atmosphere and the mass loss. C1 Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. Univ Tokyo, Sch Sci, Dept Astron, Bunkyo Ku, Tokyo 1130033, Japan. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Matsuura, M (reprint author), Inst Space & Astronaut Sci, 3-1-1 Yoshinodai, Kanagawa 2298510, Japan. EM mikako@astro.isas.ac.jp NR 27 TC 31 Z9 31 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 AUG PY 1999 VL 348 IS 2 BP 579 EP 583 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 231DN UT WOS:000082293000031 ER PT J AU Mann, G Jansen, F MacDowall, RJ Kaiser, ML Stone, RG AF Mann, G Jansen, F MacDowall, RJ Kaiser, ML Stone, RG TI A heliospheric density model and type III radio bursts SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetohydrodynamics (MHD); Sun : corona; Sun : magnetic fields; Sun : radio radiation; inteplanetary medium ID ULYSSES SPACECRAFT; ELECTRON-DENSITY; PLASMA; WAVES AB A heliospheric density model is derived by evaluating the spherical solutions of magnetohydrostatic equations including the thermal pressure and the gravitational force of the Sun. The model resulting as a special solution of Parker's wind equation covers a range from the low corona up to 5 AU and, surprisingly, agrees very well with observations. Such a model is required for the interpretation of solar and interplanetary radio observations since the emission of the radio radiation is regarded to be generated near the local electron plasma frequency, which depends on the electron number density. Thus, the density model yields the radial distance of the radio source from the Sun and, consequently, the radial source velocity from the drift in dynamic radio spectra. The model is applied for estimating the velocity of electron beams generating solar and interplanetary type III radio bursts. C1 Astrophys Inst Potsdam, D-14482 Potsdam, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Astrophys Inst Potsdam, Sternwarte 16, D-14482 Potsdam, Germany. EM GMann@aip.de RI MacDowall, Robert/D-2773-2012 NR 25 TC 125 Z9 125 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 1432-0746 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD AUG PY 1999 VL 348 IS 2 BP 614 EP 620 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 231DN UT WOS:000082293000035 ER PT J AU van den Ancker, ME Wesselius, PR Tielens, AGGM van Dishoeck, EF Spinoglio, L AF van den Ancker, ME Wesselius, PR Tielens, AGGM van Dishoeck, EF Spinoglio, L TI ISO spectroscopy of shocked gas in the vicinity of T Tauri SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : circumstellar matter; stars : individual : T Tau; stars : pre-main sequence; ISM : jets and outflows; infrared : stars ID RADIO-CONTINUUM EMISSION; MAIN-SEQUENCE OBJECTS; YOUNG STELLAR OBJECTS; MOLECULAR-HYDROGEN; WAVELENGTH SPECTROMETER; LABORATORY SIMULATIONS; INFRARED-EMISSION; BINARY-SYSTEM; STARS; LINE AB We present the results of ISO SWS and LWS spectroscopy of the young binary system T Tau. The spectrum shows absorption features due to H2O ice, CO2 ice, gas-phase CO and amorphous silicate dust, which we attribute to the envelope of T Tau S. We derive an extinction of A(V) = 17(m)4 +/- O(m)6 towards this source. Detected emission lines from H I arise in the same region which is also responsible for the optical Hr lines of T Tau N. These lines most likely arise in a partially ionized wind. Emission from the infrared fine-structure transitions of [S I], [ArII], [Ne II], [Fe 11], [Si II], [O I] and [C II] was also detected, which we explain as arising in a approximate to 100 km s(-1) dissociative shock in a fairly dense(5 x 10(4) cm(-3)) medium. Pure rotational and rovibrational emission from molecular hydrogen was detected as well. We show the H-2 emission lines to be due to two thermal components, of 440 and 1500 K respectively, which we attribute to emission from the dissociative shock also responsible for the atomic fine-structure lines and a much slower (approximate to 35 km s(-1)) non-dissociative shock. The 1500 K component shows clear evidence for fluorescent UV excitation. Additionally, we found indications for the presence of a deeply embedded (A(V) > 40 degrees) source of warm Ha emission. We suggest that this component might be due to a shock, caused by either the outflow from T Tau S or by the infall of matter on the circumstellar disk of T Tau S. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. SRON, NL-9700 AV Groningen, Netherlands. Univ Groningen, Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Leiden Observ, NL-2300 RA Leiden, Netherlands. CNR, Ist Fis Spazio Interplanetario, Area Ric Tor Vergata, I-00133 Rome, Italy. RP van den Ancker, ME (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. EM mario@astro.uva.nl OI Spinoglio, Luigi/0000-0001-8840-1551 NR 75 TC 26 Z9 26 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 AUG PY 1999 VL 348 IS 3 BP 877 EP 887 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 235ZV UT WOS:000082574500027 ER PT J AU Lachaume, R Dominik, C Lanz, T Habing, HJ AF Lachaume, R Dominik, C Lanz, T Habing, HJ TI Age determinations of main-sequence stars: combining different methods SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : activity; stars : chromospheres; stars : evolution; stars : rotation ID ROTATION; CATALOG; DEPENDENCE; PARAMETERS; PHOTOMETRY; EVOLUTION; SYSTEM; TERMS; SUN AB We have determined the age of a sample of nearby main-sequence stars with spectral types B9-K9. We have derived the stellar ages from five different age estimators: the location in the HR diagram compared to theoretical isochrones, the rotational velocity, the strength of chromospheric calcium emission lines, the stellar metallicity, and their space velocity. New calibrations consistent with recent theoretical isochrones are provided for the last four indicators. For hot stars, isochrones are the best indicator, while stellar rotation is best for cool stars. However, many stars require in fact a combination of different methods to properly bracket their actual age. We also discuss the uncertainties involved, in particular those in using isochrones, and we find that these uncertainties are often underestimated in the literature. C1 Leiden Univ, Sterrewacht Leiden, NL-2300 RA Leiden, Netherlands. Ecole Normale Super, F-75230 Paris 05, France. Univ Utrecht, Sterrekundig Inst, NL-3508 TA Utrecht, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Dominik, C (reprint author), Leiden Univ, Sterrewacht Leiden, POB 9513, NL-2300 RA Leiden, Netherlands. NR 28 TC 137 Z9 138 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 AUG PY 1999 VL 348 IS 3 BP 897 EP 909 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 235ZV UT WOS:000082574500029 ER PT J AU Neukirch, T Rastatter, L AF Neukirch, T Rastatter, L TI A new method for calculating a special class of self-consistent three-dimensional magnetohydrostatic equilibria SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE sun : magnetic fields; magnetic fields; methods : analytical ID ELECTRIC-CURRENT SYSTEMS; MAGNETOSTATIC ATMOSPHERES; MAGNETIC-FIELD; 3-DIMENSIONAL STRUCTURES; MAGNETOHYDRODYNAMIC EQUILIBRIA; EQUATIONS; CORONA; LINES; EXISTENCE; FORCE AB A new mathematical formulation for calculating a special class of self-consistent three-dimensional magnetohydrostatic equilibria in Cartesian and spherical coordinates is presented. The method uses a representation of the magnetic field in terms of poloidal and toroidal field components which automatically guarantees the solenoidal character of the magnetic field. This representation is commonly used in the theory of linear force-free magnetic fields. One advantage of this representation of the magnetic field is that the calculation involves only one scalar function whereas in previous treatments one was forced to operate with all three components of the magnetic field independently. C1 Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Neukirch, T (reprint author), Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. EM thomas@mcs.st-and.ac.uk; Lutz.Rastatter@gsfc.nasa.gov RI Neukirch, Thomas/C-1981-2009; Rastaetter, Lutz/D-4715-2012 OI Neukirch, Thomas/0000-0002-7597-4980; Rastaetter, Lutz/0000-0002-7343-4147 NR 38 TC 15 Z9 15 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 AUG PY 1999 VL 348 IS 3 BP 1000 EP 1004 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 235ZV UT WOS:000082574500041 ER PT J AU Teplitz, HI McLean, IS Malkan, MA AF Teplitz, HI McLean, IS Malkan, MA TI Near-infrared observations of the environments of radio-quiet QSOs at z greater than or similar to 1 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : Seyfert; infrared : galaxies; quasars : general; radio continuum : galaxies ID LOUD QUASARS; GALAXIES; EMISSION; EVOLUTION; TELESCOPE; REDSHIFTS; CLUSTERS; FIELDS; CAMERA; ALPHA AB We present the results of an infrared survey of QSO fields at z = 0.95, 0.995, and 1.5. Each z < 1 held was imaged to typical continuum limits of J = 20.5, K' = 19 (5 sigma) and line fluxes of 1.3 x 10(-16) ergs cm(-2) s(-1) (1 sigma) in a 1% interference filter. Sixteen fields were chosen with z similar to 0.95 targets, 14 with z similar to 0.995, and six with z similar to 1.5. A total area of 0.05 deg(2) was surveyed, and two emission-line objects were found. We present the infrared and optical photometry of these objects. Optical spectroscopy has confirmed the redshift of one object (at z = 0.989) and is consistent with the other object having a similar redshift, We discuss the density of such objects across a range of redshifts from this survey and others in the literature. We also present number-magnitude counts for galaxies in the fields of radio quiet QSOs, supporting the interpretation that they exist in lower density environments than their radio-loud counterparts. The J-band number counts are among the first to be published in the J = 16-20 range. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Angeles, Dept Phys & Astron, Div Astron, Los Angeles, CA 90095 USA. RP Teplitz, HI (reprint author), NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. EM hit@binary.gsfc.nasa.gov; mclean@astro.ucla.edu; malkan@astro.ucla.edu NR 55 TC 27 Z9 27 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1999 VL 520 IS 2 BP 469 EP 478 DI 10.1086/307480 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218EQ UT WOS:000081540600007 ER PT J AU McCarthy, PJ Yan, L Freudling, W Teplitz, HI Malumuth, EM Weymann, RJ Malkan, MA Fosbury, RAE Gardner, JP Storrie-Lombardi, LJ Thompson, RI Williams, RE Heap, SR AF McCarthy, PJ Yan, L Freudling, W Teplitz, HI Malumuth, EM Weymann, RJ Malkan, MA Fosbury, RAE Gardner, JP Storrie-Lombardi, LJ Thompson, RI Williams, RE Heap, SR TI Emission-line galaxies from the NICMOS/Hubble Space Telescope grism parallel survey SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : distances and redshifts; galaxies : Seyfert; galaxies : statistics; infrared : galaxies; surveys ID FRANCE REDSHIFT SURVEY; EVOLUTION; FIELD AB We present the first results of a survey of random fields with the slitless G141 (lambda(c) = 1.5 mu m, Delta lambda = 0.8 mu m) grism on the near-IR camera and multiobject spectrometer (NICMOS) on board the Hubble Space Telescope (HST). Approximately 64 arcmin(2) have been observed at intermediate and high Galactic latitudes. The 3 sigma limiting line and continuum fluxes in each field vary from 7.5 x 10(-17) to 1 x 10-17 ergs cm(-2) s(-1) and from H = 20 to 22, respectively. Our median and area-weighted 3 sigma limiting line fluxes within a 4 pixel aperture are nearly identical at 4.1 x 10(-17) ergs cm(-2) s(-1) and are 60% deeper than the deepest narrowband imaging surveys from the ground. We have identified 33 emission-line objects and derive their observed wavelengths, fluxes, and equivalent widths. We argue that the most likely line identification is Ho! and that the redshift range probed is from 0.75 to 1.9. The 2 sigma rest-frame equivalent width Limits range from 9 to 130 Angstrom, with an average of 40 Angstrom. The survey probes an effective comoving volume of 10(5) h(50)(-3) Mpc(3) for q(0) = 0.5. Our derived comoving number density of emission-line galaxies in the range 0.7 < z < 1.9 is 3.3 x 10(-4) h(50)(3) Mpc(-3), very similar to that of the bright Lyman break objects at z similar to 3. The objects with detected emission lines have a median F160W magnitude of 20.4 (Vega scale) and a median Ka luminosity of 2.7 x 10(42) ergs s(-1). The implied star formation rates range from 1 to 324 M-circle dot yr(-1), with an average [N II] lambda lambda 6583, 6548 corrected rate of 21 M-circle dot yr(-1) for H-0 = 50 km s(-1) Mpc and q(0) = 0.5 (34 M-circle dot yr(-1) for q(0) = 0.1). C1 Carnegie Inst Washington Observ, Pasadena, CA 91101 USA. Space Telescope European Coordinating Facil, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD 20706 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. Univ Arizona, Steward Observ, Tucson, AZ 85720 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. RP McCarthy, PJ (reprint author), Carnegie Inst Washington Observ, 813 Santa Barbara St, Pasadena, CA 91101 USA. NR 27 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 AUG 1 PY 1999 VL 520 IS 2 BP 548 EP 563 DI 10.1086/307491 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218EQ UT WOS:000081540600013 ER PT J AU Kraemer, SB Ho, LC Crenshaw, DM Shields, JC Filippenko, AV AF Kraemer, SB Ho, LC Crenshaw, DM Shields, JC Filippenko, AV TI Physical conditions in the emission-line gas in the extremely low luminosity Seyfert nucleus of NGC 4395 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : abundances; galaxies : individual (NGC 4395); galaxies : nuclei; galaxies : Seyfert ID SPIRAL GALAXIES; IUE; ABUNDANCES; STARBURST; PROFILES; NGC-4395; NGC-1068; NITROGEN; SPECTRUM; QUASARS AB We have combined Hubble Space Telescope/Faint Object Spectrograph, ground-based, and Infrared Space Observatory spectra of the nucleus of NGC 4395, the least luminous and nearest known type 1 Seyfert galaxy. The spectra show emission lines from a wide range of ionization states and critical densities. We have generated multicomponent photoionization models of both the broad and narrow emission-line regions (BLR and NLR) to investigate the physical conditions in the emission-line gas and test the proposition that the source of ionization is the nonstellar continuum radiation emitted by the central source. We show that, with a minimum of free parameters, the model predictions match the observed emission-line intensity ratios quite well. The elemental abundances appear to be subsolar, with even greater underabundance of nitrogen. From the size of the BLR predicted by the models, we estimate a central mass of a few times 10(5) M-circle dot, in reasonable agreement with estimates from the stellar kinematics. Finally, our results suggest that the covering factor of the emission-line gas is close to unity, and that the observed UV to X-ray continuum is absorbed by intervening NLR gas. We argue that a high covering factor is responsible for the apparent flattening of the Baldwin relation in low-luminosity active galactic nuclei. C1 Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Ohio Univ, Dept Phys & Astron, Athens, OH 45701 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. RP Kraemer, SB (reprint author), Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 48 TC 48 Z9 48 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 AUG 1 PY 1999 VL 520 IS 2 BP 564 EP 573 DI 10.1086/307486 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218EQ UT WOS:000081540600014 ER PT J AU Tateyama, CE Kingham, KA Kaufmann, P Piner, BG Botti, LCL de Lucena, AMP AF Tateyama, CE Kingham, KA Kaufmann, P Piner, BG Botti, LCL de Lucena, AMP TI Observations of OJ 287 from the geodetic-VLBI archive of the Washington correlator SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (OJ 287); galaxies : jets; radio continuum : galaxies ID LACERTAE OBJECT OJ-287; REFERENCE FRAME SOURCES; BL-LACERTAE; POLARIZATION STRUCTURE; RADIO AB We present 27 geodetic VLBI maps of OJ 287 obtained from the archive of the Washington correlator. The observations presented here were made between 1990 October and 1996 December. During this period a sequence of six superluminal components has been identified. We measured the proper motion of these components to be approximately 0.5 mas yr(-1), which is about twice as high as that seen in previous VLBI observations. These results imply a higher component ejection rate than previously observed, in good agreement with the observed occurrences of radio outbursts. We have examined a possible connection between VLBI components and optical flares in the framework of a binary black hole system. C1 INPE, Ctr Radio Astron & Aplicacoes Espacias, Inst Presbiteriano Mackenzie, BR-01302000 Sao Paulo, Brazil. USN Observ, Earth Orientat Dept, Washington, DC 20392 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. INPE, CRAAE, Radio Observ Espacial Nordeste, Eusebio, Fortaleza, Brazil. RP Tateyama, CE (reprint author), INPE, Ctr Radio Astron & Aplicacoes Espacias, Inst Presbiteriano Mackenzie, Rua Consolacao 896, BR-01302000 Sao Paulo, Brazil. NR 29 TC 17 Z9 17 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 AUG 1 PY 1999 VL 520 IS 2 BP 627 EP 633 DI 10.1086/307475 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218EQ UT WOS:000081540600020 ER PT J AU Gibson, SE Biesecker, D Guhathakurta, M Hoeksema, JT Lazarus, AJ Linker, J Mikic, Z Pisanko, Y Riley, P Steinberg, J Strachan, L Szabo, A Thompson, BJ Zhao, XP AF Gibson, SE Biesecker, D Guhathakurta, M Hoeksema, JT Lazarus, AJ Linker, J Mikic, Z Pisanko, Y Riley, P Steinberg, J Strachan, L Szabo, A Thompson, BJ Zhao, XP TI The three-dimensional coronal magnetic field during Whole Sun Month SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; solar wind; Sun : corona; Sun : magnetic fields ID FARADAY-ROTATION MEASUREMENTS; SOLAR-WIND; SHEET CURRENTS; MODEL; MINIMUM; TEMPERATURE; EVOLUTION; STREAMER; PLASMA; VOLUME AB Combining models and observations, we study the three-dimensional coronal magnetic field during a period of extensive coordinated solar observations and analysis known as the Whole Sun Month (WSM) campaign (1996 August 10-September 8). The two main goals of the WSM campaign are addressed in this paper, namely, (1) to use the field configuration to link coronal features observed by coronagraphs and imaging telescopes to solar wind speed variations observed in situ and (2) to study the role of the three-dimensional coronal magnetic field in coronal force balance. Specifically, we consider how the magnetic field connects the two fastest wind streams to the two regions that have been the main foci of the WSM analysis: the equatorial extension of the north coronal hole (known as the Elephant's Trunk) and the axisymmetric streamer belt region on the opposite side of the Sun. We then quantitatively compare the different model predictions of coronal plasma and solar wind properties with observations and consider the implications for coronal force balance and solar wind acceleration. C1 Catholic Univ Amer, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Stanford Univ, Stanford, CA 94305 USA. MIT, Cambridge, MA 02139 USA. Inst Appl Geophys, Moscow, Russia. Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Gibson, SE (reprint author), Univ Cambridge, Dept Appl Math & Theoret Phys, Silver St, Cambridge CB3 9EW, England. RI Gibson, Sarah/A-9189-2011; Thompson, Barbara/C-9429-2012 NR 63 TC 31 Z9 32 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 AUG 1 PY 1999 VL 520 IS 2 BP 871 EP 879 DI 10.1086/307496 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218EQ UT WOS:000081540600048 ER PT J AU Kogut, A AF Kogut, A TI Likelihood analysis of mega-pixel maps SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic microwave background; methods : data analysis AB The derivation of cosmological parameters from astrophysical data sets routinely involves operations counts which scale as O(N-3), where N is the number of data points. Currently planned missions, including Microwave Anisotropy Probe and Planck, will generate sky maps with N-d = 10(6) or more pixels. Simple "brute-force" analysis, applied to such mega-pixel data, would require years of computing even on the fastest computers. We describe an algorithm that allows estimation of the likelihood function in the direct pixel basis. The algorithm uses a conjugate gradient approach to evaluate chi(2) and a geometric approximation to evaluate the determinant. Monte Carlo simulations provide a correction to the determinant, yielding an unbiased estimate of the likelihood surface in an arbitrary region surrounding the likelihood peak. The algorithm requires O(N-d(3/2)) operations and O(N-d) storage for each likelihood evaluation and allows for significant parallel computation. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Kogut, A (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 685, Greenbelt, MD 20771 USA. RI Kogut, Alan/D-6293-2012 NR 9 TC 4 Z9 4 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD AUG 1 PY 1999 VL 520 IS 2 BP L83 EP L86 DI 10.1086/312151 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218ER UT WOS:000081540700002 ER PT J AU Moro-Martin, A Cernicharo, J Noriega-Crespo, A Martin-Pintado, J AF Moro-Martin, A Cernicharo, J Noriega-Crespo, A Martin-Pintado, J TI A molecular counterpart to the HH 1-2 flow SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : individual (HH 1-2); ISM : jets and outflows; ISM : molecules; stars : formation ID HERBIG-HARO OBJECTS; PROPER MOTIONS; HYDROGEN; HH-1-2; EXCITATION; JETS; GAS AB We present high angular resolution (12 "-24 ") and high-sensitivity (12)CO and (13)CO J = 2-1 and J = 1-0 observations of the HH 1-2 outflow; The observations show the molecular counterpart, moving with a velocity of similar or equal to 30 km s(-1), of the optical bipolar system driven by the VLA 1 embedded source. Along with the optical jet there are certain regions where the molecular gas reaches deprojected velocities of 100-200 km s(-1) and that we interpret as the molecular jet. The bipolar CO outflow has a length of similar to 260 " with a curved morphology toward the north where it extends beyond the HH 1 object (similar to 120 "). Two new molecular outflows have been detected, one arising from IRAS 05339-0647, which excites the HH 147 optical flow, and another powered by VLA 2, which drives the HH 144 optical outflow. The molecular outflow driven by the VLA 3 source is also clearly detected and spatially resolved from the VLA 1 main outflow. C1 CSIC, Dept Fis Mol, Inst Estructura Mat, E-28006 Madrid, Spain. CALTECH, Infrared Proc & Anal Ctr, JPL, Pasadena, CA 91125 USA. Observ Astron Nacl, E-28800 Alcala De Henares, Spain. RP Moro-Martin, A (reprint author), CSIC, Dept Fis Mol, Inst Estructura Mat, Serrano 121, E-28006 Madrid, Spain. EM amaya@astro.iem.csic.es; cerni@astro.iem.csic.es; alberto@ipac.caltech.edu; martin@oan.es RI Martin-Pintado, Jesus/H-6107-2015 OI Martin-Pintado, Jesus/0000-0003-4561-3508 NR 25 TC 19 Z9 19 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 AUG 1 PY 1999 VL 520 IS 2 BP L111 EP L114 DI 10.1086/312156 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218ER UT WOS:000081540700009 ER PT J AU Zarro, DM Sterling, AC Thompson, BJ Hudson, HS Nitta, N AF Zarro, DM Sterling, AC Thompson, BJ Hudson, HS Nitta, N TI SOHO EIT observations of extreme-ultraviolet "dimming" associated with a halo coronal mass ejection SO ASTROPHYSICAL JOURNAL LA English DT Article DE sun : corona; sun : flares; sun : UV radiation; sun : X-rays, gamma rays ID MAGNETIC RECONNECTION; SOLAR-FLARE AB A solar flare was observed on 1997 April 7 with the Soft X-ray Telescope (SXT) on Yohkoh. The flare was associated with a "halo" coronal mass ejection (CME). The flaring region showed areas of reduced soft X-ray (SXR) brightness-"dimmings"-that developed prior to the CME observed in white Light and persisted for several hours following the CME. The most prominent dimming regions were located near the ends of a preflare SXR S-shaped (sigmoid) feature that disappeared during the event, leaving behind a postflare SXR arcade and cusp structure. Based upon these and similar soft X-ray observations, it has been postulated that SXR dimming regions are the coronal signatures (i.e., remnants) of magnetic flux ropes ejected during CMEs. This Letter reports new observations of coronal dimming at extreme-ultraviolet (EUV) wavelengths obtained with the Extreme-ultraviolet Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO). A series of EIT observations in the 195 Angstrom Fe XII wavelength band were obtained simultaneously with SXT during the 1997 April 7 flare/CME. The EIT observations show that regions of reduced EW intensity developed at the same locations and at the same time as SXR dimming features. The decrease in EW intensity (averaged over each dimming region) occurred simultaneously with an increase in EUV emission from flaring loops in the active region. We interpret these joint observations within the framework of flux-rope eruption as the cause of EUV and SXR coronal dimmings, and as the source of at least part of the CME. C1 NASA, Goddard Space Flight Ctr, SM&A Syst Solut Grp, Greenbelt, MD 20771 USA. Computat Phys Inc, Fairfax, VA 22031 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. Solar Phys Res Corp, Tucson, AZ 85718 USA. Lockheed Martin Solar & Astrophys Lab, Palo Alto, CA 94304 USA. RP Zarro, DM (reprint author), NASA, Goddard Space Flight Ctr, SM&A Syst Solut Grp, Code 682-3, Greenbelt, MD 20771 USA. RI Thompson, Barbara/C-9429-2012 NR 18 TC 103 Z9 109 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 AUG 1 PY 1999 VL 520 IS 2 BP L139 EP L142 DI 10.1086/312150 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 218ER UT WOS:000081540700016 ER PT J AU Simkin, SM Sadler, EM Sault, R Tingay, SJ Callcut, J AF Simkin, SM Sadler, EM Sault, R Tingay, SJ Callcut, J TI Pictor A (PKS 0518-45): From nucleus to lobes SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE galaxies : individual (Pictor A); galaxies : jets; galaxies : kinematics and dynamics; galaxies : nuclei; galaxies : structure; radio continuum : galaxies ID POWERFUL RADIO GALAXIES; LINE-EMITTING GAS; HUBBLE-SPACE-TELESCOPE; WESTERN HOT-SPOT; MULTIFREQUENCY SYNTHESIS; ACTIVE GALAXIES; CLASSIFICATION; EXCITATION; KINEMATICS; MECHANISM AB We present a variety of new imaging and kinematic data for the double-lobed radio galaxy Pictor A. The new optical data include Hubble Space Telescope (HST) continuum and [O III], emission-line images (at a resolution of 25-100 mas) and ground-based imaging and spectroscopy (at a resolution of similar to 1 ".5). The ground-based images show H alpha filaments and loops which extend to the north and west of the optical core. The radio continuum data include 3 cm Australia Telescope images of the core, at a resolution comparable to that of the optical, ground-based images, and a VLBI image of a jet in the compact core (at a resolution of 2-25 mas), which seems to align with a continuum "jet" found in the HST images. The core radio jet, the HST optical continuum "jet," and the NW H alpha filaments all appear to be aligned with the extended, low-luminosity radio continuum bridge which Perley et al, have traced out to the optical-synchrotron hot spot in the NW lobe of this object. The H alpha filaments which appear to lie in the path of this trajectory are associated with a disrupted velocity field in the extended ionized gas. These filaments (as well as the extended CO mi emission found at mas scales in the HST images) may have been pushed to the north, out of the path of the jet. The ground-based spectra which cover this trajectory also yield line ratios for the ionized gas which have anomalously low CN nl (6564), suggesting either a complex, clumpy structure in the gas with a higher cloud-covering factor at larger radii and with denser clouds than is found in the nuclear regions of most NLRG and Seyfert 2 galaxies, or some other, unmodeled, mechanism for the emergent spectrum from this region. The H alpha emission-line filaments to the north appear to be associated with a 3 cm radio continuum knot which lies in a gap in the filaments similar to 4 " from the nucleus. Altogether, the data in this paper provide good circumstantial evidence for nondisruptive redirection of a radio jet by interstellar gas clouds in the host galaxy. C1 Michigan State Univ, E Lansing, MI 48824 USA. Univ Sydney, Sch Phys, Sydney, NSW 2006, Australia. CSIRO, Australia Telescope Natl Facil, Epping, NSW 1710, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Michigan State Univ, E Lansing, MI 48824 USA. RP Simkin, SM (reprint author), Michigan State Univ, E Lansing, MI 48824 USA. RI Tingay, Steven/B-5271-2013; OI Sadler, Elaine/0000-0002-1136-2555 NR 51 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 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD AUG PY 1999 VL 123 IS 2 BP 447 EP 465 DI 10.1086/313243 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 236PA UT WOS:000082606700004 ER PT J AU Williams, RM Chu, YH Dickel, JR Petre, R Smith, RC Tavarez, M AF Williams, RM Chu, YH Dickel, JR Petre, R Smith, RC Tavarez, M TI Supernova remnants in the magellanic clouds. III. An X-ray atlas of large magellanic cloud supernova remnants SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE atlases; Magellanic Clouds; supernova remnants; surveys; X-rays : ISM ID SCANNING INTERFEROMETER OBSERVATIONS; HONEYCOMB NEBULA; OB-ASSOCIATIONS; EVOLUTION; RADIO; SHELL; N49; MORPHOLOGY; KINEMATICS; HIDDEN AB We have used archival ROSAT data to present X-ray images of 31 supernova remnants (SNRs) in the Large Magellanic Cloud (LMC). We have classified these remnants according to their X-ray morphologies, into the categories of shell-type, diffuse face, centrally brightened, point-source-dominated, and irregular. We suggest possible causes of the X-ray emission for each category and for individual features of some of the SNRs. C1 Univ Illinois, Dept Astron, Urbana, IL 61801 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Cerro Tololo Interamer Observ, La Serena, Chile. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. RP Williams, RM (reprint author), Univ Illinois, Dept Astron, 1002 W Green St, Urbana, IL 61801 USA. NR 62 TC 74 Z9 74 U1 1 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD AUG PY 1999 VL 123 IS 2 BP 467 EP 485 DI 10.1086/313246 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 236PA UT WOS:000082606700005 ER PT J AU Stothers, RB AF Stothers, RB TI Volcanic dry fogs, climate cooling, and plague pandemics in Europe and the Middle East SO CLIMATIC CHANGE LA English DT Article ID TREE-RING RECORD; ICE CORE; ERUPTION; TEMPERATURES; GREENLAND; SIGNAL; PRECIPITATION; TRANSPORT; ICELAND; ASH AB Dry fogs spawned by large volcanic eruptions cool the climate by partially blocking incident sunlight and perturbing atmospheric circulation patterns. The climatic and epidemiological consequences of seven intense volcanic dry fogs of the past 21 centuries, detected in Europe and the Middle East, are investigated by using historical reports, supplemented by tree-ring data and polar-ice acidity measurements. The signal-to-noise ratio in the historical data is very high. In four cases, the first winter following the eruption was exceptionally cold. The eruptions preceding these frigid first winters are known, or strongly suspected, to have occurred at high northern latitudes. Two of the other dry fogs are linked unambiguously to tropical eruptions, after each of which the first winter was comparatively mild. The following few years tended to be cooler on the average in all six of the instances that can be checked. Famine and disease pandemics ensued, with the epidemics in all cases reaching the Mediterranean area within 1 to 5 years after the eruptions. In at least five cases, the contagion responsible for the mass mortality was probably plague. 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 57 TC 46 Z9 49 U1 1 U2 16 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD AUG PY 1999 VL 42 IS 4 BP 713 EP 723 DI 10.1023/A:1005480105370 PG 11 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 218VU UT WOS:000081574400006 ER PT J AU Bryson, S Kenwright, D Cox, M Ellsworth, D Haimes, A AF Bryson, S Kenwright, D Cox, M Ellsworth, D Haimes, A TI Visually exploring gigabyte data sets in real time SO COMMUNICATIONS OF THE ACM LA English DT Article ID TOPOLOGY C1 NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. MIT, Dept Aeronaut & Astronaut, Cambridge, MA 02139 USA. RP NASA, Ames Res Ctr, MRJ Technol Solut, Moffett Field, CA 94035 USA. EM bryson@nas.nasa.gov; davidk@nas.nasa.gov; mbc@nas.nasa.gov; ellswort@nas.nasa.gov; haimes@orville.mit.edu NR 12 TC 7 Z9 7 U1 0 U2 1 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 2 PENN PLAZA, STE 701, NEW YORK, NY 10121-0701 USA SN 0001-0782 EI 1557-7317 J9 COMMUN ACM JI Commun. ACM PD AUG PY 1999 VL 42 IS 8 BP 82 EP 90 DI 10.1145/310930.310977 PG 9 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA 220EJ UT WOS:000081651300026 ER PT J AU Ebert, D Bedwell, E Maher, S Smoliar, L Downing, E AF Ebert, D Bedwell, E Maher, S Smoliar, L Downing, E TI Realizing D-3 visualization using crossed-beam volumetric displays SO COMMUNICATIONS OF THE ACM LA English DT Article C1 Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. Univ Maryland, Ctr Adv Comp Studies, College Pk, MD 20742 USA. NASA, Goddard Space Flight Ctr, Sci Visualizat Studio, Greenbelt, MD 20771 USA. 3D Technol Labs, Res & Dev, Sunnyvale, CA 94086 USA. RP Ebert, D (reprint author), Univ Maryland Baltimore Cty, Baltimore, MD 21228 USA. NR 12 TC 8 Z9 8 U1 0 U2 1 PU ASSOC COMPUTING MACHINERY PI NEW YORK PA 1515 BROADWAY, NEW YORK, NY 10036 USA SN 0001-0782 J9 COMMUN ACM JI Commun. ACM PD AUG PY 1999 VL 42 IS 8 BP 100 EP 107 DI 10.1145/310930.310979 PG 8 WC Computer Science, Hardware & Architecture; Computer Science, Software Engineering; Computer Science, Theory & Methods SC Computer Science GA 220EJ UT WOS:000081651300028 ER PT J AU Larson, M Pearson, D Elliott, S Petrac, D Israelsson, U Luchik, T AF Larson, M Pearson, D Elliott, S Petrac, D Israelsson, U Luchik, T TI The confined helium experiment (CHeX) - The successful return of the low temperature platform facility (LTPF) to space SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1998 Space Cryogenics Workshop CY JUL 20-21, 1998 CL NOORDWIJK, NETHERLANDS SP ESTEC DE HeII systems; cryostats; space cryogenics ID LAMBDA-POINT AB The Low Temperature Platform Facility (LTPF) flew on STS-87 from November 19 to December 5, 1997 as part of the fourth United States Microgravity Payload (USMP-4). During this flight, the LTPF contained the Confined Helium eXperiment (CHeX). The CHeX mission was a success because the LTPF functioned as expected, and the LTPF dewar provided a stable, long lived cooling source for the CHeX instrument. The LTPF is a NASA/JPL facility that is designed to accommodate space shuttle based science experiments or instruments that need cryogenic temperatures near 2 K. The LTPF had flown two times prior to this most recent flight: in 1984 as the Superfluid Helium Experiment on Space Lab-2 and in 1992 as the Lambda Point Experiment (LPE) on USMP-1. The facility has been substantially upgraded between every flight. For the CHeX mission, the improvements to the facility were driven by the need to meet updated Space Shuttle requirements and by the desire to increase the scientific return from the mission. These improvements involved changes to both the cryostat and the facility electronics. We report on the flight performance of the LTPF during the most recent mission (CHeX) and on some of the lessons learned while preparing for this mission. (C) 1999 Elsevier Science Ltd. All rights reserved. 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 6 Z9 6 U1 0 U2 1 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 AUG PY 1999 VL 39 IS 8 BP 671 EP 675 DI 10.1016/S0011-2275(99)00067-3 PG 5 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 264UB UT WOS:000084199600004 ER PT J AU Breon, S Shirron, P Boyle, R Canavan, E DiPirro, M Serlemitsos, A Tuttle, J Whitehouse, P AF Breon, S Shirron, P Boyle, R Canavan, E DiPirro, M Serlemitsos, A Tuttle, J Whitehouse, P TI The XRS low temperature cryogenic system ground performance tests results SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1998 Space Cryogenics Workshop CY JUL 20-21, 1998 CL NOORDWIJK, NETHERLANDS SP ESTEC DE space cryogenics; adiabatic demagnetization; magnetic refrigeration; high Tc superconductors; current leads; superconducting magnets ID HELIUM CRYOSTAT; DESIGN AB The X-Ray Spectrometer (XRS) instrument is part of the Astro-E mission scheduled to launch early in 2000. Its cryogenic system is required to cool a 32-element array of X-ray microcalorimeters to 60-65 mK over a mission lifetime of at least 2 years. This is accomplished using an adiabatic demagnetization refrigerator (ADR) contained within a two-stage superfluid helium/solid neon cooler. Goddard Space Flight Center is providing the ADR and helium dewar. The flight helium dewar was assembled in Sept. 1997 and subjected to extensive thermal performance tests. This paper presents test results at both the subsystem and component levels. In addition, results of the low temperature topoff performed in Japan with the engineering unit neon and helium dewars are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Breon, S (reprint author), NASA, Goddard Space Flight Ctr, Code 552, Greenbelt, MD 20771 USA. NR 13 TC 5 Z9 5 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD AUG PY 1999 VL 39 IS 8 BP 677 EP 690 DI 10.1016/S0011-2275(99)00068-5 PG 14 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 264UB UT WOS:000084199600005 ER PT J AU Bhatia, RS Bock, JJ Ade, PAR Benoit, A Bradshaw, TW Crill, BP Griffin, MJ Hepburn, ID Hristov, VV Lange, AE Mason, PV Murray, AG Orlowska, AH Turner, AD AF Bhatia, RS Bock, JJ Ade, PAR Benoit, A Bradshaw, TW Crill, BP Griffin, MJ Hepburn, ID Hristov, VV Lange, AE Mason, PV Murray, AG Orlowska, AH Turner, AD TI The susceptibility of incoherent detector systems to cryocooler microphonics SO CRYOGENICS LA English DT Article; Proceedings Paper CT 1998 Space Cryogenics Workshop CY JUL 20-21, 1998 CL NOORDWIJK, NETHERLANDS SP ESTEC DE infrared detectors; Joule-Thomson coolers; dilution; stirling; space cryogenics ID READOUT AB Mechanical cryocoolers will be used to provide 4 K cooling for the HFI bolometer instrument in the Planck Surveyor mission for measurement of the anisotropies in the cosmic microwave background. They may also find application in future Earth-observing satellites. We describe an experimental programme to investigate the effects of microphonic vibrations on infrared detectors. Our initial tests have demonstrated the feasibility of operating far-infrared photoconductive detectors in conjunction with a 4 K cryocooler for Earth observing applications. The microphonic susceptibility of a bolometer at 100 mK has also been investigated, using a modified variation of the Planck Surveyor zero gravity flight dilution system. The results of these tests gives us confidence in the proposed use of sensitive bolometers with mechanical cryocoolers for space missions. We also describe development of the bolometers, the readout systems and temperature regulators for improved systems level performance of such instruments. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Observat Cosmol Grp, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ London Queen Mary & Westfield Coll, Dept Phys, Astrophys Lab, London E1 4NS, England. CNRS, Ctr Rech Tres Basses Temp, F-38042 Grenoble 09, France. Rutherford Appleton Lab, Cryogen & Mat Engn Grp, Didcot OX11 0QX, Oxon, England. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. RP Bhatia, RS (reprint author), CALTECH, Observat Cosmol Grp, Mail Code 59-33, Pasadena, CA 91125 USA. EM rsb@astro.caltech.edu NR 19 TC 9 Z9 9 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0011-2275 J9 CRYOGENICS JI Cryogenics PD AUG PY 1999 VL 39 IS 8 BP 701 EP 715 DI 10.1016/S0011-2275(99)00071-5 PG 15 WC Thermodynamics; Physics, Applied SC Thermodynamics; Physics GA 264UB UT WOS:000084199600008 ER PT J AU Argus, DF Heflin, MB Donnellan, A Webb, FH Dong, D Hurst, KS Jefferson, DC Lyzenga, GA Watkins, MM Zumberge, JF AF Argus, DF Heflin, MB Donnellan, A Webb, FH Dong, D Hurst, KS Jefferson, DC Lyzenga, GA Watkins, MM Zumberge, JF TI Shortening and thickening of metropolitan Los Angeles measured and inferred by using geodesy SO GEOLOGY LA English DT Article ID SAN-ANDREAS FAULT; SOUTHERN CALIFORNIA; CRUSTAL DEFORMATION; VENTURA-BASIN; NORTHRIDGE EARTHQUAKE; BIG BEND; REGION; TECTONICS; SLIP AB Geodetic observations using the Global Positioning System (GPS) and other techniques record a high rate of north-south shortening in an east-southeast-trending, 5-40-km-wide belt in northern metropolitan Los Angeles, California. Downtown Los Angeles is observed to be converging upon the southern San Gabriel Mountains at 6 mm/yr. Aside from the elastic strain that will be released during earthquakes rupturing the san Andreas and San Jacinto faults, east-west lengthening across northern metropolitan Los Angeles is minor, <2.5 mm/yr. Therefore north-south shortening is accommodated mainly by vertical crustal thickening. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Argus, Donald/F-7704-2011 NR 20 TC 37 Z9 37 U1 0 U2 4 PU GEOLOGICAL SOC AMER, INC PI BOULDER PA PO BOX 9140, BOULDER, CO 80301-9140 USA SN 0091-7613 EI 1943-2682 J9 GEOLOGY JI Geology PD AUG PY 1999 VL 27 IS 8 BP 703 EP 706 DI 10.1130/0091-7613(1999)027<0703:SATOML>2.3.CO;2 PG 4 WC Geology SC Geology GA 221LY UT WOS:000081729600008 ER PT J AU Wang, LP Koblinsky, C AF Wang, LP Koblinsky, C TI Large change of mesoscale variability in the Kuroshio Extension region during the first 5 years of the TOPEX/Poseidon mission SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID GEOSAT ALTIMETRY AB Analysis of the first 5 years of TOPEX/Poseidon altimetry data reveals that mesoscale variability (MV) in the Kuroshio Extension region has a large, well structured temporal change. The mesoscale variance varies by more than a factor of 2 over the 5-year span. The temporal variation appears to be the combination of two forms: a large-scale standing (from 140 degrees E to 170 degrees E) modulation, and accompanying with it a variation that propagates westward slowly with a phase speed of about 0.7 cm/s. Along with the westward propagation, the center of maximum MV retreats westward. As a comparison, variation of MV in the Gulf Stream region is computed. The analysis shows that MV in the Gulf Stream region also undergoes large temporal change. But it is much less well structured. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, ESSIC, College Pk, MD 20742 USA. RP Wang, LP (reprint author), NASA, Goddard Space Flight Ctr, Code 971, Greenbelt, MD 20771 USA. NR 12 TC 1 Z9 1 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2243 EP 2246 DI 10.1029/1999GL900468 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700006 ER PT J AU Ruzmaikin, A AF Ruzmaikin, A TI Can El Nino amplify the solar forcing of climate? SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID STOCHASTIC RESONANCE; WEATHER AB ENSO (El Nino and the Southern Oscillation) is considered as a stochastic driver that excites the atmospheric anomaly states, such as Pacific North American pattern. This can make 11-year solar activity forcing of climate feasible through stochastic resonance - a mechanism that amplifies a weak input to a nonlinear bistable system by the assistance of noise. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ruzmaikin, A (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 24 TC 11 Z9 13 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2255 EP 2258 DI 10.1029/1999GL900535 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700009 ER PT J AU Wasilewski, P Kletetschka, G AF Wasilewski, P Kletetschka, G TI Lodestone: Natures only permanent magnet - What it is and how it gets charged SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Magnetite and Titanomagnetite exhibit magnetic properties which are attributable to the micro-structures developed during oxidation and exsolution: All magnetite iron ores which are lodestones contain maghemite. These lodestones have He between 10 and 30 mT, SIRM between 8 and 18 Am(2)kg(1), and R-1 between 0.10 and 0.26. Magnetite, titanomagnetite and metals have REM values (ratio of NRM to SWM) < 0.05. Samples (called fulgarites) obtained from the Smithsonian Institution have REM values ranging from 0.45 to 0.92. The REM value serves as a witness parameter to the magnetic fields associated with the lightning bolt. If a high REM value (say >> 0.1) can be verified as not to be due to contamination by man and does not contain MD hematite then the rock has LRM (lightning remanent magnetization). The magnetic field associated with lightning can be revealed from an isothermal remanent acquisition (RA) curve. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wasilewski, P (reprint author), NASA, Goddard Space Flight Ctr, Code 961, Greenbelt, MD 20771 USA. RI Kletetschka, Gunther/C-9996-2011 OI Kletetschka, Gunther/0000-0002-0645-9037 NR 31 TC 27 Z9 28 U1 2 U2 21 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2275 EP 2278 DI 10.1029/1999GL900496 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700014 ER PT J AU Hood, LL Mitchell, DL Lin, RP Acuna, MH Binder, AB AF Hood, LL Mitchell, DL Lin, RP Acuna, MH Binder, AB TI Initial measurements of the lunar induced magnetic dipole moment using lunar prospector magnetometer data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Twenty-one orbits of Lunar Prospector magnetometer data obtained during an extended passage of the Moon through a lobe of the geomagnetic tail in April 1998 are applied to estimate the residual lunar induced magnetic dipole moment. Editing and averaging of individual orbit segments yields a negative induced moment with amplitude -2.4 +/- 1.6 x 10(22) Gauss-cm(3) per Gauss of applied field. Assuming that the induced field is caused entirely by electrical currents near the surface of a highly electrically conducting metallic core, the preferred core radius is 340+/-90 km. For an iron-rich composition, such a core would represent 1 to 3% of the lunar mass. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lunar Res Inst, Gilroy, CA 95020 USA. RP Hood, LL (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NR 10 TC 76 Z9 79 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 AUG 1 PY 1999 VL 26 IS 15 BP 2327 EP 2330 DI 10.1029/1999GL900487 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700027 ER PT J AU Moore, TE Peterson, WK Russell, CT Chandler, MO Collier, MR Collin, HL Craven, PD Fitzenreiter, R Giles, BL Pollock, CJ AF Moore, TE Peterson, WK Russell, CT Chandler, MO Collier, MR Collin, HL Craven, PD Fitzenreiter, R Giles, BL Pollock, CJ TI Ionospheric mass ejection in response to a CME SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-CYCLE; ION AB We report observations of a direct ionospheric plasma outflow response to the incidence of an interplanetary shock and associated coronal mass ejection (CME) upon the earth's magnetosphere. Data from the WIND spacecraft, 185 R-E upstream, document the passage of an interplanetary shock at 23:20 UT on 24 Sept. 1998. The polar cap plasma environment sampled by the POLAR spacecraft changed abruptly at 23:45 UT, reflecting the compressional displacement of the geopause relative to the spacecraft. POLAR left the polar wind outflow region and entered the mantle flows. Descending toward the dayside cusp region, POLAR later returned from the mantle to an enhanced polar wind flux dominated by O+ plasma and eventually containing molecular ions. The enhanced and O+- dominated outflow continued as the spacecraft passed through the high altitude cleft and then the southern cleft at lower altitude. Such a direct response of the ionosphere to solar wind dynamic pressure disturbances may have important impacts on magnetospheric dynamics. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA. NASA, Space Sci Lab, George C Marshall Space Flight Ctr, Huntsville, AL 35802 USA. SW Res Inst, Dept Instrumentat & Space Res, San Antonio, TX 78228 USA. RP Moore, TE (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 692, Greenbelt, MD 20771 USA. RI Moore, Thomas/D-4675-2012; Collier, Michael/I-4864-2013; Peterson, WK/A-8706-2009 OI Moore, Thomas/0000-0002-3150-1137; Collier, Michael/0000-0001-9658-6605; Peterson, WK/0000-0002-1513-6096 NR 11 TC 106 Z9 106 U1 2 U2 6 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2339 EP 2342 DI 10.1029/1999GL900456 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700030 ER PT J AU Russell, CT Zhou, XW Chi, PJ Kawano, H Moore, TE Peterson, WK Cladis, JB Singer, HJ AF Russell, CT Zhou, XW Chi, PJ Kawano, H Moore, TE Peterson, WK Cladis, JB Singer, HJ TI Sudden compression of the outer magnetosphere associated with an ionospheric mass ejection SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID MAGNETIC-FIELD AB On September 24, 1998 at 2345 UT the magnetosphere was suddenly compressed as the dynamic pressure of the solar wind rapidly rose from 2 to 15 nPa At the Polar spacecraft, at high altitudes above the center of the northern polar cap, a remarkably smooth increase in the field strength occurred while the plasma properties changed abruptly, as described in an accompanying paper. Comparisons with models and an examination of the wave amplitudes during the compression indicate that the initial change in plasma properties was most probably due to convection of pre-existing boundary layer plasma to the location of Polar rather than due to local heating by betatron acceleration and ion cyclotron waves. The smoothness of the increase in field strength is attributed to the very high velocity of compressional waves in the tail that outrun the advancing solar wind disturbance. The signatures as measured by GOES 10 at 1444 LT and at GOES 8 at 1846 LT in low latitude geosynchronous orbit are the more familiar sudden jump on the dayside, where the density is high and the compressional wave velocity low, and a weak change on the nightside, where tail current changes oppose the effects of the dayside magnetopause currents. This event is an ideal candidate for collaborative investigation of the effects of a classical sudden storm commencement on the magnetosphere. C1 Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Kyushu Univ 33, Fukuoka 812, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Martin, Palo Alto Res Lab, Palo Alto, CA 94304 USA. NOAA, R E SE, Boulder, CO 80303 USA. RP Russell, CT (reprint author), Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RI Moore, Thomas/D-4675-2012; Peterson, WK/A-8706-2009; OI Moore, Thomas/0000-0002-3150-1137; Peterson, WK/0000-0002-1513-6096; Russell, Christopher/0000-0003-1639-8298 NR 9 TC 32 Z9 33 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 AUG 1 PY 1999 VL 26 IS 15 BP 2343 EP 2346 DI 10.1029/1999GL900455 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700031 ER PT J AU Jensen, EJ Read, WG Mergenthaler, J Sandor, BJ Pfister, L Tabazadeh, A AF Jensen, EJ Read, WG Mergenthaler, J Sandor, BJ Pfister, L Tabazadeh, A TI High humidities and subvisible cirrus near the tropical tropopause SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID TROPOSPHERIC WATER-VAPOR; UARS MLS; CLOUD; PACIFIC AB Measurements of water vapor from the Microwave Limb Sounder on the Upper Atmospheric Research Satellite show that humidities in the extreme tropical upper troposphere are often near saturation with respect to ice. These high humidity values are supported by the available accurate in situ water vapor measurements near the tropical tropopause. A nearly saturated upper troposphere reduces the outgoing longwave radiative flux at the top of the atmosphere by about 1-2 W-m(-2) compared to the radiative flux calculated using a standard atmospheric humidity profile. Subvisible cirrus near the tropopause reduce the outgoing longwave radiation an additional few W-m(-2) as well as increasing the radiative heating near the tropopause. Changes in the humidity frequency distribution in this region of the atmosphere and the associated changes in subvisible cirrus frequency would substantially impact the radiative budget of the tropics. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. Lockheed Martin Inc, Menlo Park, CA USA. Natl Ctr Atmospher Res, Boulder, CO 80307 USA. RP Jensen, EJ (reprint author), NASA, Ames Res Ctr, MS 245-4, Moffett Field, CA 94035 USA. NR 22 TC 39 Z9 39 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 AUG 1 PY 1999 VL 26 IS 15 BP 2347 EP 2350 DI 10.1029/1999GL900266 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700032 ER PT J AU Rodriguez, P Kennedy, EJ Keskinen, MJ Basu, S McCarrick, M Preston, J Zwi, H Engebretson, M Wong, A Wuerker, R Kaiser, ML Desch, MD Goetz, K Bougeret, JL Manning, R AF Rodriguez, P Kennedy, EJ Keskinen, MJ Basu, S McCarrick, M Preston, J Zwi, H Engebretson, M Wong, A Wuerker, R Kaiser, ML Desch, MD Goetz, K Bougeret, JL Manning, R TI A wave interference experiment with HAARP, HIPAS, and WIND SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID F-REGION; IRREGULARITIES; RADIO; LAYER AB We report on the first experiment using two high power, high frequency transmitting facilities in a bistatic, interferometer mode. The HAARP and HIPAS facilities in Alaska radiated at 4525 kHz with total combined power of about 700 kW, in the direction of the WIND spacecraft. The WAVES experiment aboard WIND received the transmissions at a distance of about 25 earth radii. The experimental setup thus resembled Young's two-slit experiment. The expected interference pattern was observed; at the distance of WIND, the fringe size was about 30 km peak to peak. C1 USN, Res Lab, Washington, DC 20375 USA. USAF, Res Lab, Hanscom AFB, MA 01731 USA. Adv Power Technol Inc, Washington, DC 20037 USA. Univ Calif Los Angeles, Dept Phys, Los Angeles, CA 90095 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA. Observ Paris, DESPA, F-92195 Meudon, France. RP Rodriguez, P (reprint author), USN, Res Lab, Code 6750, Washington, DC 20375 USA. NR 10 TC 5 Z9 5 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2351 EP 2354 DI 10.1029/1999GL900525 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700033 ER PT J AU Chang, ATC Chiu, LS Kummerow, C Meng, J Wilheit, TT AF Chang, ATC Chiu, LS Kummerow, C Meng, J Wilheit, TT TI First results of the TRMM microwave imager (TMI) monthly oceanic rain rate: Comparison with SSIM/I SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SSM/I AB We evaluated the performance of the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) at-launch algorithm for monthly oceanic rain rate using six months (January - June 1998) of TMI data. Comparison with oceanic monthly rain rates derived from the Special Sensor Microwave Imager (SSM/I) data shows statistically significant differences. The TMI min rates are lower than the SSM/I rain rates by about 10% overall, except for rain rates lower than 1.4 mm/day. The low TMI bias may be due to an overestimate of the columnar water vapor as indicated by the estimated rain layer thickness. The superior sampling by the TMI improves the algorithm statistics at the low rain rates. The averaged monthly rain rates over the latitudes between 40 degrees S and 40 degrees N are 2.78 and 3.17 mm/day, respectively for TMT and SSM/I, with RMS difference of 1.35 mm/day and correlation coefficient of 0.94. C1 NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. Texas A&M Univ, Dept Meteorol, College Stn, TX 77843 USA. RP Chang, ATC (reprint author), NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. RI Wilheit, Thomas/G-9438-2012 NR 9 TC 31 Z9 34 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2379 EP 2382 DI 10.1029/1998GL900452 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700041 ER PT J AU Ferry, GV Pueschel, RF Strawa, AW Kondo, Y Howard, SD Verma, S Mahoney, MJ Bui, TP Hannan, JR Fuelberg, HE AF Ferry, GV Pueschel, RF Strawa, AW Kondo, Y Howard, SD Verma, S Mahoney, MJ Bui, TP Hannan, JR Fuelberg, HE TI Effects of aircraft on aerosol abundance in the upper troposphere SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID VISIBLE CONTRAILS; EMISSIONS; EXHAUST; PLUMES AB A significant increase in H2SO4 aerosol concentration coincidental with an enhancement in NO was detected above 10 km pressure altitude during a cross-corridor flight out of Shannon on October 23, 1997. The source of this aerosol is ascribed to commercial aircraft operations in flight corridors above 10 km, because (1) a stable atmosphere prevented vertical air mass exchanges and thus eliminated surface sources, (2) air mass back trajectories documented the absence of remote continental sources, and (3) temperature profiler data showed the tropopause at least one kilometer above flight altitude throughout the night, thus excluding stratospheric sources. Particle volatility identified (60-80)% H2SO4, approximate to 20% (NH4)(2)SO4 and approximate to 10% nonvolatile aerosol in the proximity of flight corridors, and (10-30)% H2SO4, up to 50% (NH4)(2)SO4 and (40-60)% nonvolatile aerosols in air that was not affected by aircraft operations below 10 km. The newly formed H2SO4 particles did not measurably affect surface area and volume of the background aerosol due to their small size, hence did not influence radiative transfer directly. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Nagoya Univ, Toyokawa, Japan. Symtech Corp, Arlington, VA 22202 USA. Sci & Technol Corp, Lanham, MD USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Florida State Univ, Tallahassee, FL 32306 USA. RP Ferry, GV (reprint author), NASA, Ames Res Ctr, MS SGP 245-4, Moffett Field, CA 94035 USA. RI Kondo, Yutaka/D-1459-2012 NR 20 TC 15 Z9 15 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2399 EP 2402 DI 10.1029/1999GL900445 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700046 ER PT J AU Levine, JS AF Levine, JS TI The 1997 fires in Kalimantan and Sumatra, Indonesia: Gaseous and particulate emissions (vol 26, pg 815, 1999) SO GEOPHYSICAL RESEARCH LETTERS LA English DT Correction C1 NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. RP Levine, JS (reprint author), NASA, Div Atmospher Sci, Langley Res Ctr, Hampton, VA 23681 USA. NR 1 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD AUG 1 PY 1999 VL 26 IS 15 BP 2407 EP 2407 DI 10.1029/1999GL900543 PG 1 WC Geosciences, Multidisciplinary SC Geology GA 221WT UT WOS:000081750700048 ER PT J AU Lopes-Gautier, R McEwen, AS Smythe, WB Geissler, PE Kamp, L Davies, AG Spencer, JR Keszthelyi, L Carlson, R Leader, FE Mehlman, R Soderblom, L AF Lopes-Gautier, R McEwen, AS Smythe, WB Geissler, PE Kamp, L Davies, AG Spencer, JR Keszthelyi, L Carlson, R Leader, FE Mehlman, R Soderblom, L CA Galileo NIMS Team SSI Team TI Active volcanism on Io: Global distribution and variations in activity SO ICARUS LA English DT Article DE Io; volcanism; infrared observations ID INFRARED MAPPING SPECTROMETER; HOT-SPOTS; SILICATE VOLCANISM; INTERNAL STRUCTURE; HEAT-FLOW; GALILEO; TEMPERATURE; SURFACE; STATE; SSI AB Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the near-infrared mapping spectrometer (NIMS) for the first 10 orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI) and from groundbased observations, and compare them to what was known about Io's volcanic activity from observations made during the two Voyager flybys in 1979. A total of 61 active volcanic centers have been identified from Voyager, groundbased, and Galileo observations. Of these, 41 are hot spots detected by NIMS and/or SSI. Another 25 locations were identified as possible active volcanic centers, mostly on the basis of observed surface changes. Hot spots are correlated with surface colors, particularly dark and red deposits, and generally anti-correlated with white, SO2-rich areas. Surface features corresponding to the hot spots, mostly calderas or flows, were identified from Galileo and Voyager images. Hot spot temperatures obtained from both NIMS and SSI are consistent with silicate volcanism, which appears to be widespread on Io. Two types of hot spot activity are present: persistent-type activity, lasting from months to years, and sporadic events, which may represent either short-lived activity or low-level activity that occasionally flares up. Sporadic events are not often detected, but may make an important contribution to lo's heat flow and resurfacing. The distribution of active volcanic centers on the surface does not show any clear correlation with latitude, longitude, Voyager-derived global topography, or heat flow patterns predicted by the asthenosphere and deep mantle tidal dissipation models. However persistent hot spots and active plumes are concentrated toward lower latitudes, and this distribution favors the asthenosphere rather than the deep mantle tidal dissipation model. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Arizona, Dept Planetary Sci, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Lowell Observ, Flagstaff, AZ 86001 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. US Geol Survey, Branch Astrogeol Studies, Flagstaff, AZ 86001 USA. RP Lopes-Gautier, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Lopes, Rosaly/D-1608-2016 OI Lopes, Rosaly/0000-0002-7928-3167 NR 51 TC 104 Z9 105 U1 0 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 AUG PY 1999 VL 140 IS 2 BP 243 EP 264 DI 10.1006/icar.1999.6129 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900001 ER PT J AU Geissler, PE McEwen, AS Keszthelyi, L Lopes-Gautier, R Granahan, J Simonelli, DP AF Geissler, PE McEwen, AS Keszthelyi, L Lopes-Gautier, R Granahan, J Simonelli, DP TI Global color variations on Io SO ICARUS LA English DT Article DE Io; Galileo; spectroscopy; multispectral imaging ID JUPITERS SATELLITE IO; SURFACE; SULFUR; VOLCANISM; VOYAGER-1; SYSTEM; FROST; MOON; SO2 AB Visible and near-infrared images of Io from the Galileo spacecraft reveal a surface more colorful than previously thought. Red, yellow green, white, and black hues decorate the satellite, presumably caused by a varied composition of sulfur compounds and silicates. Almost a third of Io is covered by red and orange materials, particularly at polar latitudes above +/-30 degrees. These red regions were scarcely distinguishable in the shorter wavelength Voyager observations. Bright red pyroclastic deposits mark the locations of many hot spots, plumes, and visible surface changes, providing a prominent flag of recent volcanic activity. Io's equatorial regions are dominated by yellow materials, which occupy about 40% of the satellite's surface. White and gray materials cover about 27% of Io, primarily in equatorial areas and in localized deposits at high latitudes. These are identified with moderate-to-coarse-grained SO2 as mapped by the NIMS instrument on Galileo (R. W. Carlson et al, 1997, Geophys, Res. Lett. 24, 2479-2482). Greenish-yellow materials in small isolated spots on Io's anti-Jupiter hemisphere were recently discovered in 3 km/pixel color imaging from orbit 14. Unlike other ionian terrains, these regions have a negative near-infrared spectral slope, suggesting contamination by a nonsulfur component. Only about 1.4% of Io's surface is occupied by dark materials, which display a variety of visible colors ranging from black to red and green. Most dark spots have a shallow spectral absorption feature at 0.9 mu m, suggesting magnesium-rich silicates rather than black sulfur. Little large-scale alteration in the global color and albedo pattern has occurred between the Voyager and Galileo eras; 90% of the surface appears unchanged despite the vigorous volcanic activity which must have taken place in the intervening 17 years. This suggests that over a time scale of decades, the bulk of Io's resurfacing is restricted to a few small but persistently active areas. (C) 1999 Academic Press. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SETS Technol Inc, Honolulu, HI 96813 USA. Univ Hawaii, Sci & Technol Int, Honolulu, HI 96813 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. RP Geissler, PE (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RI Lopes, Rosaly/D-1608-2016 OI Lopes, Rosaly/0000-0002-7928-3167 NR 40 TC 84 Z9 85 U1 1 U2 2 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1999 VL 140 IS 2 BP 265 EP 282 DI 10.1006/icar.1999.6128 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900002 ER PT J AU Moore, JM Asphaug, E Morrison, D Spencer, JR Chapman, CR Bierhaus, B Sullivan, RJ Chuang, FC Klemaszewski, JE Greeley, R Bender, KC Geissler, PE Helfenstein, P Pilcher, CB AF Moore, JM Asphaug, E Morrison, D Spencer, JR Chapman, CR Bierhaus, B Sullivan, RJ Chuang, FC Klemaszewski, JE Greeley, R Bender, KC Geissler, PE Helfenstein, P Pilcher, CB TI Mass movement and landform degradation on the icy Galilean satellites: Results of the Galileo nominal mission SO ICARUS LA English DT Article DE Europa; Ganymede; Callisto; satellites of Jupiter; satellite surfaces ID WATER-ICE; HIGH-RESOLUTION; GANYMEDE; EUROPA; CALLISTO; MOBILITY; TERRAINS; SHELL; MARS AB The Galileo mission has revealed remarkable evidence of mass movement and landform degradation on the icy Galilean satellites of Jupiter. Weakening of surface materials coupled with mass movement reduces the topographic relief of landforms by moving surface materials down-slope. Throughout the Galileo orbiter nominal mission we have studied all known farms of mass movement and landform degradation of the icy galilean satellites, of which Callisto, by far, displays the most degraded surface, Callisto exhibits discrete mass movements that are larger and apparently more common than seen elsewhere. Most degradation on Ganymede appears consistent with sliding or slumping, impact erosion, and regolith evolution, Sliding or slumping is also observed at very small (100 m) scale on Europa. Sputter ablation, while probably playing some role in the evolution of Ganymede's and Callisto's debris layers, appears to be less important than other processes. Sputter ablation might play a significant role on Europa only if that satellite's surface is significantly older than 10(8) years, far older than crater statistics indicate. Impact erosion and regolith formation on Europa are probably minimal, as implied by the low density of small craters there. Impact erosion and regolith formation may be important on the dark terrains of Ganymede, though some surfaces on this satellite may be modified by sublimation-degradation. While impact erosion and regolith formation are expected to operate with the same vigor on Callisto as on Ganpmede, most of the areas examined at high resolution on Callisto have an appearance that implies that some additional process is at work, most likely sublimation-driven landform modification and mass wasting. The extent of surface degradation ascribed to sublimation on the outer two Galilean satellites implies that an ice more volatile than H2O is probably involved. (C) 1999 Academic Press. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Lowell Observ, Flagstaff, AZ 86001 USA. SW Res Inst, Boulder, CO 80302 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Univ Arizona, Lunar Planetary Lab, Tucson, AZ 85721 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. NASA, Washington, DC 20546 USA. RP Moore, JM (reprint author), NASA, Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA. NR 56 TC 62 Z9 62 U1 1 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1999 VL 140 IS 2 BP 294 EP 312 DI 10.1006/icar.1999.6132 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900004 ER PT J AU Grazier, KR Newman, WI Kaula, WM Hyman, JM AF Grazier, KR Newman, WI Kaula, WM Hyman, JM TI Dynamical evolution of planetesimals in the outer solar system - I. The Jupiter/Saturn zone SO ICARUS LA English DT Article ID SHORT-PERIOD COMETS; ORIGINAL DISTRIBUTION; STABLE ORBITS; ASTEROIDS; SATURN AB We report on numerical simulations designed to understand the distribution of small bodies in the Solar System and the winnowing of planetesimals accreted from the early solar nebula. The primordial planetesimal swarm evolved in a phase space divided into regimes by separatrices which define their trajectories and fate. This sorting process is driven by the energy and angular momentum and continues to the present day. We reconsider the existence and importance of stable niches in the Jupiter/Saturn zone using highly accurate numerical techniques based on high-order optimized multistep integration schemes coupled to roundoff error minimizing methods. We repeat the investigations of W.M. Weibel et al. (Icarus 83, 382-390, 1990) with one hundred thousand massless particles-nearly 10(3) time more particles than our 1990 investigation. Previous studies of the Jupiter/Saturn zone have employed only hundreds of particles, usually starting on circular and zero inclination orbits. By employing 10(5) particles on both inclinded and eccentric orbits, we can perform a near-exhaustive search for test particle stability as a function of initial orbital elements. The increase in the numbers of test particles also facilitates robust statistical inference and comparison with analytic results. In our simulations, we observed three stages in the planetesimal dynamics. At the start of the simulation many planetesimals are quickly eliminated by close approaches to Jupiter or Saturn. Next there is a gravitational relaxation phase where the surviving particles are exponentially eliminated by random gravitational encounters with Jupiter or Saturn. Finally, the only long-lived particles in the simulation were initially located either at a Lagrange point or in an orbit nearly commensurable with Jupiter or Saturn. We conclude that although niches for planetesimal material are rare, extremely high-accuracy long-duration simulations employing many particles will be able to capture even the qualitative nature of early Solar System planetesimal evolution. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Math, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. RP Grazier, KR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Newman, William/E-5918-2011 OI Newman, William/0000-0002-9835-1428 NR 47 TC 25 Z9 25 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 AUG PY 1999 VL 140 IS 2 BP 341 EP 352 DI 10.1006/icar.1999.6146 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900007 ER PT J AU Grazier, KR Newman, WI Varadi, F Kaula, WM Hyman, JM AF Grazier, KR Newman, WI Varadi, F Kaula, WM Hyman, JM TI Dynamical evolution of planetesimals in the outer solar system - II. The Saturn/Uranus and Uranus/Neptune zones SO ICARUS LA English DT Article ID SECULAR RESONANCES; ORBITS; STABILITY; PLANETS; NEPTUNE; REGION; URANUS; BELT AB We report on numerical simulations exploring the dynamical stability of planetesimals in the gaps between the outer Solar System planets. We search for stable niches in the Saturn/Uranus and Uranus/Neptune zones by employing 10,000 massless particles-many more than previous studies in these two zones-using high-order optimized multistep integration schemes coupled with roundoff error minimizing methods. An additional feature of this study differing from its predecessors, is the fact that our initial distributions contain particles on orbits which are both inclined and noncircular. These initial distributions were also Gaussian distributed such that the Gaussian peaks were at the midpoint between the neighboring perturbers, The simulations showed an initial transient phase where the bulk of the primordial planetesimal swarm was removed from the Solar System within 10(5) years. This is about 10 times longer than we observed in our previous Jupiter/Saturn studies. Next, there was a gravitational relaxation phase where the particles underwent a random walk in momentum space and were exponentially eliminated by random encounters with the planets. Unlike our previous Jupiter/Saturn simulation, the particles did not fully relax into a third Lagrangian niche phase where long-lived particles are at Lagrange points or stable niches. This is either because the Lagrangian niche phase never occurs or because these simulations did not have enough particles for this third phase to manifest. In these simulations, there was a general trend for the particles to migrate outward and eventually to be cleared out by the outermost planet in the zone. We confirmed that particles with higher eccentricities had shorter lifetimes and that the resonances between the jovian planets "pumped up" the eccentricities of the planetesimals with low-inclination orbits more than those with higher inclinations. We estimated the expected lifetime of particles using kinetic theory and even though the time scale of the Uranus/Neptune simulation was 380 times longer than our previous Jupiter/Saturn simulation, the planetesimals in the Uranus/Neptune zone were cleared out more quickly than those in the Saturn/Uranus zone because of the positions of resonances with the jovian planets. These resonances had an even greater effect than random gravitational stirring in the winnowing process and confirm that all the jovian planets are necessary in long simulations. Even though we observed several long-lived zones near 12.5, 14.4, 16, 24.5, and 26 AU, only two particles remained at the end of the 10(9)-year integration: one near the 2:3 Saturn resonance, and the other near the Neptune 1:1 resonance. This suggests that niches for planetesimal material in the jovian planets are rare and may exist either only in extremely narrow bands or in the neighborhoods of the triangular Lagrange points of the outer planets. (C) 1999 Academic Press. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Dept Math, Los Angeles, CA 90095 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. Univ Calif Los Alamos Natl Lab, Div Theoret, Los Alamos, NM 87545 USA. RP Grazier, KR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Newman, William/E-5918-2011 OI Newman, William/0000-0002-9835-1428 NR 34 TC 25 Z9 25 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1999 VL 140 IS 2 BP 353 EP 368 DI 10.1006/icar.1999.6147 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900008 ER PT J AU Hudson, RS Ostro, SJ AF Hudson, RS Ostro, SJ TI Physical model of asteroid 1620 Geographos from radar and optical data SO ICARUS LA English DT Article DE asteroids; radar; photometry; image processing ID PHOTOMETRIC MODELS; GALILEO SHAPE; SPIN-STATE; LIGHTCURVES; 1620-GEOGRAPHOS; DISRUPTION; TOUTATIS; EARTH; IDA AB We develop a physical model of asteroid 1620 Geographos using Goldstone delay-Doppler radar images obtained August 1994 (Ostro et al. 1996, Icarus 121., 46-66) with resolution as fine as 75 m, and optical lightcurves obtained in 1969, 1983, and 1993-1994 (Magnusson et al. 1996, Icarus 123, 227-244). The data set admits a geometric ambiguity that precludes a unique model. Within this constraint, our model has maximum dimensions of (5.0, 2.0, 2.1) +/- 0.15 km and a volume of less than or equal to 8.8 km(3), equivalent to a sphere of less than or equal to 2.56 km diameter. The radar equivalent spherical albedo is greater than or equal to 0.12. The photometric solution provides Hapke parameters w greater than or equal to 0.22, g = -0.34 +/- 0.10, and <(theta)over bar> = 25 +/- 10 degrees with assumed values h = 0.02 and B-0 = 1.32. The spin state solution does not differ significantly from that of Magnusson et al, having lambda = 55 +/- 6 degrees, beta = -46 +/- 4 degrees, and P = 5.2233270 +/- 0.00000072 h. We identify seven main features in the delay-Doppler images and their corresponding locations on the model. (C) 1999 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 19 TC 37 Z9 40 U1 0 U2 4 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1999 VL 140 IS 2 BP 369 EP 378 DI 10.1006/icar.1999.6142 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900009 ER PT J AU Magri, C Ostro, SJ Rosema, KD Thomas, ML Mitchell, DL Campbell, DB Chandler, JF Shapiro, II Giorgini, JD Yeomans, DK AF Magri, C Ostro, SJ Rosema, KD Thomas, ML Mitchell, DL Campbell, DB Chandler, JF Shapiro, II Giorgini, JD Yeomans, DK TI Mainbelt asteroids: Results of Arecibo and Goldstone radar observations of 37 objects during 1980-1995 SO ICARUS LA English DT Article DE asteroids; radar ID SHAPE; LIGHTCURVES; PHOTOMETRY; SPECTRA; MODELS AB We report detailed results of Arecibo and Goldstone radar observations of 30 mainbelt asteroids (MBAs) during 1980-1995, In addition to estimates of radar cross section, radar albedo, and circular polarization ratio, we obtain new constraints on pole direction for several asteroids, with those for 21 Lutetia being particularly restrictive. We carry out statistical analyses of disk-integrated properties (radar albedo and polarization ratio) of all 37 radar-observed MBAs. M asteroids seem to have higher radar albedos and a wider range of albedos than do asteroids from the other taxonomic classes; there is no evidence that C and S MBAs have different albedo distributions; and there is some suggestion, worthy of future study, that primitive B, F, G, and P asteroids are not as radar-bright as C and S objects. There is no statistically significant evidence that different taxonomic classes have different polarization ratio distributions, despite suggestions to the contrary based on visual inspection of these distributions. The similarity between the C and S albedo distributions implies similar near-surface regolith bulk densities. The hypothesis of ordinary chondritic composition for the S-class asteroids is reasonably consistent with the radar data, provided that these asteroids have typical lunar porosities. Nevertheless, it is possible that some of these targets have high-porosity regoliths of stony-iron composition. Our M-class sample presumably contains both metallic objects (such as 216 Kleopatra and, probably, 16 Psyche) and less metallic objects. (C) 1999 Academic Press. C1 Univ Maine, Farmington, ME 04938 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. Ctr Astrophys, Cambridge, MA 02138 USA. RP Magri, C (reprint author), Univ Maine, 39 High St,Preble Hall, Farmington, ME 04938 USA. NR 64 TC 58 Z9 58 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1999 VL 140 IS 2 BP 379 EP 407 DI 10.1006/icar.1999.6130 PG 29 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900010 ER PT J AU Hudson, RL AF Hudson, RL TI Laboratory studies of the formation of methanol and other organic molecules by water plus carbon monoxide radiolysis: Relevance to comets, icy satellites, and interstellar ices SO ICARUS LA English DT Article DE ices; comets; composition; radiation chemistry; organic chemistry; spectroscopy ID INFRARED SPECTRAL PROPERTIES; CLOUD CORES; FAR-IR; ANALOGS; CO; FORMALDEHYDE; CH3O; SPECTROSCOPY; IRRADIATION; DESORPTION AB Radiation processing of cometary, planetary, and interstellar ices has been investigated by irradiating mixtures of H(2)O and CO near 16 K with 0.8-MeV protons. IR spectroscopy and isotopic substitution showed that H and OH, from H(2)O, added to CO to form HCO, H(2)CO, HCOOH, and CH(3)OH. A values (integrated spectral absorbances) for HCOOH and HCO trapped in H(2)O ice were measured for the first time. These new values, along with published A's for H(2)CO and CH(3)OH, were used to calculate radiation yields (G values) and conventional percentage yields. Significantly higher percentage yields of HCOOH and CH(3)OH were observed, compared to previous solid-state H(2)O + CO experiments. This suggests that radiation processing may help explain the discrepancy between the observed gas-phase abundances of small organic molecules and the abundances predicted by current theoretical models and previous laboratory experiments. In contrast to previous experiments on one-component ices, no spectral evidence for long-chain molecules was found in the present work. This demonstrates that ice composition is a critical factor in applying laboratory results to cometary, icy satellite, and interstellar ices. (C) 1999 Academic Press. C1 Eckerd Coll, Dept Chem, St Petersburg, FL 33733 USA. NASA, Astrochem Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Hudson, RL (reprint author), Eckerd Coll, Dept Chem, St Petersburg, FL 33733 USA. EM hudsonrl@eckerd.edu RI Hudson, Reggie/E-2335-2012 NR 52 TC 131 Z9 131 U1 1 U2 19 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD AUG PY 1999 VL 140 IS 2 BP 451 EP 461 DI 10.1006/icar.1999.6144 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 239EB UT WOS:000082754900015 ER PT J AU Morabito, DD AF Morabito, DD TI The characterization of a 34-meter beam-waveguide antenna at Ka band (32.0 GHz) and X band (8.4 GHz) SO IEEE ANTENNAS AND PROPAGATION MAGAZINE LA English DT Article DE beam waveguides; satellite communication earth terminals; multireflector antennas; reflector antenna feeds; reflector antennas; space vehicle communication ID MICROWAVE AB New antennas for the NASA Deep Space Network (DSN) have been built to replace the aging antennas of older designs for deep-space communications. These new antennas incorporate a new dual-shape design as well as a beam waveguide (BWG), which utilize a series of additional secondary mirrors to relocate the focal point into a stationary room below the main reflector. The advantages of using such a design include increased isolation of the feed package from outside environmental factors, such as moisture, wind, and temperature changes; and ease of access to the equipment fur maintenance, troubleshooting and repair purposes. This article reports oil the performance of a beam waveguide antenna at X-band and Ka-band microwave frequencies. The Ka-Band Antenna Performance: Experiment (KaAP) antenna-efficiency measurements presented in this article were acquired at the Goldstone DSS-13 Research anti Development (R&D) beam-waveguide antenna between December, 1993, and November, 1995. The measured antenna efficiency and ground-station figure-of-merit (gain divided by operating system noise temperature) as a function of elevation angle: and their uncertainties are presented. Also described are the station configuration, the measurement technique, the modeling used in the analysis processing, and the historical evolution of the DSS-13 Ka-band antenna-efficiency measurements as progressive improvements and configuration changes were implemented. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Morabito, DD (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. NR 29 TC 6 Z9 7 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 1045-9243 J9 IEEE ANTENNAS PROPAG JI IEEE Antennas Propag. Mag. PD AUG PY 1999 VL 41 IS 4 BP 23 EP 34 DI 10.1109/74.789734 PG 12 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 234ZQ UT WOS:000082514600004 ER PT J AU Tischler, MB Colbourne, JD Morel, MR Biezad, DJ Cheung, KK Levine, WS Moldoveanu, V AF Tischler, MB Colbourne, JD Morel, MR Biezad, DJ Cheung, KK Levine, WS Moldoveanu, V TI A multidisciplinary flight control development environment and its application to a helicopter SO IEEE CONTROL SYSTEMS MAGAZINE LA English DT Article ID SYSTEM-IDENTIFICATION; ROTORCRAFT; BANDWIDTH C1 NASA, Ames Res Ctr, Aviat Res Dev & Engn Ctr, USA,Aeroflightdynam Directorate, Moffett Field, CA 94035 USA. Calif Polytech State Univ San Luis Obispo, Dept Aeronaut Engn, San Luis Obispo, CA USA. Raytheon ITSS, Moffett Field, CA USA. Univ Maryland, Dept Elect Engn, College Pk, MD 20742 USA. RP Tischler, MB (reprint author), NASA, Ames Res Ctr, Aviat Res Dev & Engn Ctr, USA,Aeroflightdynam Directorate, MS 210-5, Moffett Field, CA 94035 USA. NR 21 TC 18 Z9 18 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 0272-1708 J9 IEEE CONTR SYST MAG JI IEEE Control Syst. Mag. PD AUG PY 1999 VL 19 IS 4 BP 22 EP 33 DI 10.1109/37.777786 PG 12 WC Automation & Control Systems SC Automation & Control Systems GA 219VP UT WOS:000081628200002 ER PT J AU Lee, Q Martin, SC Mensa, D Smith, RP Guthrie, J Rodwell, MJW AF Lee, Q Martin, SC Mensa, D Smith, RP Guthrie, J Rodwell, MJW TI Submicron transferred-substrate heterojunction bipolar transistors SO IEEE ELECTRON DEVICE LETTERS LA English DT Article DE heterojunction bipolar transistors; substrate transfer AB We report submicron transferred-substrate AlInAs/GaInAs heterojunction bipolar transistors (HBT's). Devices with 0.4-mu m emitter and 0.4-mu m collector widths have 17.5 dB unilateral gain at 110 GHz, Extrapolating at -20 dB/decade, the power gain cutoff frequency f(max) is 820 GHz, The high f(max) results from the scaling of HBT's junction widths, from elimination of collector series resistance through the use of a Schottky collector contact, and from partial screening of the collector-base capacitance by the collector space charge. C1 Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Lee, Q (reprint author), Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA. NR 8 TC 29 Z9 29 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0741-3106 J9 IEEE ELECTR DEVICE L JI IEEE Electron Device Lett. PD AUG PY 1999 VL 20 IS 8 BP 396 EP 398 DI 10.1109/55.778155 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 222NM UT WOS:000081791700006 ER PT J AU Kok, YL Wang, H Huang, TW Lai, R Barsky, M Chen, YC Sholley, M Block, T Streit, DC Liu, PH Allen, BR Samoska, L Gaier, T AF Kok, YL Wang, H Huang, TW Lai, R Barsky, M Chen, YC Sholley, M Block, T Streit, DC Liu, PH Allen, BR Samoska, L Gaier, T TI 160-190-GHz monolithic low-noise amplifiers SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE high electron mobility transistor (HEMT); LNA; MMIC; noise figure (NF); pseudomorphic (PM) technology ID BAND AB This letter presents the results of two 160-190-GHz monolithic low-noise amplifiers (LNA's) fabricated with 0.07-mu m pseudomorphic (PM) InAlAs/InGaAs/InP HEMT technology using a reactive ion etch (RIE) via hole process, A peak small signal gain of 9 dB was measured at 188 GHz for the first LNA with a 3-dB bandwidth from 164 to 192 GHz while the second LNA has achieved over 6-dB gain from 132 to 180 GHz. The same design (second LNA) was also fabricated with a 0.08-mu m gate and a wet etch process, showing a small-signal gain of 6 dB with 6-dB noise figure. All the measurement results were obtained via on-wafer probing. The LNA noise measurement at 170 GHz is also the first attempt at this frequency. C1 TRW Co Inc, Space & Elect Grp, Redondo Beach, CA 90278 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kok, YL (reprint author), TRW Co Inc, Space & Elect Grp, Redondo Beach, CA 90278 USA. NR 15 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 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD AUG PY 1999 VL 9 IS 8 BP 311 EP 313 DI 10.1109/75.779912 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 225BJ UT WOS:000081935800006 ER PT J AU Asenov, A Saini, S AF Asenov, A Saini, S TI Suppression of random dopant-induced threshold voltage fluctuations in sub-0.1-mu m MOSFET's with epitaxial and delta-doped channels SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE doping; fluctuations; MOSFET; semiconductor device simulation; silicon devices; threshold ID MOS-TRANSISTORS; SIMULATION; MISMATCH AB A detailed three-dimensional (3-D) statistical "atomistic" simulation study of fluctuation-resistant sub-0.1-mu m MOSFET architectures with epitaxial channels and delta doping is presented. The need for enhancing the fluctuation resistance of the sub-0.1-mu m generation transistors is highlighted by presenting summarized results from atomistic simulations of a wide range of conventional devices with uniformly doped channel. According to our atomistic results, the doping concentration dependence of the random dopant-induced threshold voltage fluctuations in conventional devices is stronger than the analytically predicted fourth-root dependence. As a result of this, the scaling of such devices M-ill be restricted by the "intrinsic" random dopant-induced fluctuations earlier than anticipated. Our atomistic simulations confirm that the introduction of a thin epitaxial layer in the MOSFET's channel can efficiently suppress the random dopant-induced threshold voltage fluctuations in sub-0.1-mu m devices. For the first time, we observe an "anomalous" reduction in the threshold voltage fluctuations with an increase in the doping concentration behind the epitaxial channel, which rye attribute to screening effects. Also, for the first time we study the effect of a delta-doping, positioned behind the epitaxial layer, on the intrinsic threshold voltage fluctuations. Above a certain thickness of epitaxial layer, we observe a pronounced anomalous decrease in the threshold voltage fluctuation with the increase of the delta doping, This phenomenon which is also associated with screening, enhances the importance of the delta doping in the design of properly scaled fluctuation-resistant sub-0.1-mu m MOSFET's. C1 Univ Glasgow, Dept Elect & Elect Engn, Device Modeling Grp, Glasgow G12 8LT, Lanark, Scotland. NASA, Ames Res Ctr, Numer Aerosp Simulat Syst Div, Moffett Field, CA 94035 USA. RP Univ Glasgow, Dept Elect & Elect Engn, Device Modeling Grp, Glasgow G12 8LT, Lanark, Scotland. EM A.Asenov@elec.gla.ac.uk NR 28 TC 114 Z9 114 U1 1 U2 9 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9383 EI 1557-9646 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD AUG PY 1999 VL 46 IS 8 BP 1718 EP 1724 DI 10.1109/16.777162 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 220NC UT WOS:000081671200021 ER PT J AU Vaden, KR Heinen, VO Dayton, JA AF Vaden, KR Heinen, VO Dayton, JA TI Three-dimensional modeling of multistage depressed collectors SO IEEE TRANSACTIONS ON ELECTRON DEVICES LA English DT Article DE CAD; multistage depressed collectors; TWT AB The computer modeling of instantaneous currents within a multistage depressed collector is presented, MAFIA, a three-dimensional (3-D) electromagnetic finite integration code, performs the collector analysis. The computational results provide valuable insight into the performance of the collector and show excellent agreement with experimental measurements and with the classic axially symmetric (2 1/2-D), steady-state computations. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Vaden, KR (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 6 TC 6 Z9 7 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0018-9383 J9 IEEE T ELECTRON DEV JI IEEE Trans. Electron Devices PD AUG PY 1999 VL 46 IS 8 BP 1810 EP 1811 DI 10.1109/16.777176 PG 2 WC Engineering, Electrical & Electronic; Physics, Applied SC Engineering; Physics GA 220NC UT WOS:000081671200035 ER PT J AU Seraji, H AF Seraji, H TI Real-time collision avoidance for position-controlled manipulators SO IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION LA English DT Article DE collision avoidance; position-controlled manipulators; real-time control; robot control ID CONFIGURATION CONTROL; IMPLEMENTATION; ROBOT AB A new approach to real-time collision avoidance for position-controlled conventional six-DOP and dexterous seven-DOF arms is developed, and supportive experimental results are presented. The collision avoidance problem Is formulated and solved as a position-based force control problem. Virtual forces representing the intrusion of the arm into the obstacle safety zone are computed in real time using a spring-damper model, These forces are then nullified by employing an outer force control loop which perturbs the Cartesian commands for the arm position control system. The approach is implemented and tested on a seven-nor RRC arm and a set of experiments are conducted in the laboratory. These experiments demonstrate perturbations of the end-effector position and orientation, as well as the arm posture, in order to avoid impending collisions, The proposed approach is simple, computationally fast, requires minimal modification to the arm control system, and applies to whole-arm collision avoidance for seven-DOF arms. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Seraji, H (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 15 TC 33 Z9 36 U1 0 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1042-296X J9 IEEE T ROBOTIC AUTOM JI IEEE Trans. Robot. Autom. PD AUG PY 1999 VL 15 IS 4 BP 670 EP 677 DI 10.1109/70.781972 PG 8 WC Automation & Control Systems; Engineering, Electrical & Electronic; Robotics SC Automation & Control Systems; Engineering; Robotics GA 227EF UT WOS:000082064800008 ER PT J AU Woodard, SE Garg, DP AF Woodard, SE Garg, DP TI A numerical optimization approach for tuning fuzzy logic controllers SO IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART B-CYBERNETICS LA English DT Article DE attitude control; fuzzy logic controllers; numerical optimization; pointing control; spacecraft control AB This paper develops a method to tune fuzzy controllers using numerical optimization. The main attribute of this approach is that it allows fuzzy logic controllers to be tuned to achieve global performance requirements. Furthermore, this approach allows design constraints to be implemented during the tuning process. The method tunes the controller by parameterizing the membership functions for error, change-in-error, and control output. The resulting parameters form a design vector which is iteratively changed to minimize an objective function. The minimal objective function results in an optimal performance of the system. A spacecraft mounted science payload line-of-sight pointing control is used to demonstrate results. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Duke Univ, Dept Mech Engn & Mat Sci, Durham, NC 27708 USA. RP Woodard, SE (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 6 TC 9 Z9 10 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 1083-4419 J9 IEEE T SYST MAN CY B JI IEEE Trans. Syst. Man Cybern. Part B-Cybern. PD AUG PY 1999 VL 29 IS 4 BP 565 EP 569 DI 10.1109/3477.775276 PG 5 WC Automation & Control Systems; Computer Science, Artificial Intelligence; Computer Science, Cybernetics SC Automation & Control Systems; Computer Science GA 218RP UT WOS:000081565700013 PM 18252334 ER PT J AU McCrory, JL Lemmon, DR Sommer, HJ Prout, B Smith, D Korth, DW Lucero, J Greenisen, M Moore, J Kozlovskaya, I Pestov, I Stepansov, V Miyakinchenko, Y Cavanagh, PR AF McCrory, JL Lemmon, DR Sommer, HJ Prout, B Smith, D Korth, DW Lucero, J Greenisen, M Moore, J Kozlovskaya, I Pestov, I Stepansov, V Miyakinchenko, Y Cavanagh, PR CA TVIS Study Grp TI Evaluation of a treadmill with vibration isolation and stabilization (TVIS) for use on the International Space Station SO JOURNAL OF APPLIED BIOMECHANICS LA English DT Article DE microgravity; locomotion; kinematics; running; space station ID EXERCISE COUNTERMEASURES; SPACEFLIGHT AB A treadmill with vibration isolation and stabilization designed for the international Space Station (ISS) was evaluated during Shuttle mission STS-81. Three crew members ran and walked on the device, which floats freely in zero gravity. For the majority of the more than 2 hours of locomotion studied, the treadmill showed peak to peak linear and angular displacements of less than 2.5 cm and 2.5 degrees, respectively. Vibration transmitted to the vehicle was within the microgravity allocation limits that are defined for the ISS. Refinements to the treadmill and harness system are discussed. This approach to treadmill design offers the possibility of generating 1G-like loads on the lower extremities while preserving the microgravity environment of the ISS for structural safety and vibration free experimental conditions. C1 Penn State Univ, Ctr Locomot Studies, University Pk, PA 16802 USA. Lockheed Martin Engn Serv, Houston, TX 77058 USA. Penn State Univ, Dept Kinesiol & Biobehav Hlth, University Pk, PA 16802 USA. Penn State Univ, Dept Orthopaed & Rehabil, University Pk, PA 16802 USA. Penn State Univ, Dept Med, University Pk, PA 16802 USA. Penn State Univ, Dept Med, Hershey, PA 17033 USA. Penn State Univ, Dept Kinesiol & Biobehav Hlth, Hershey, PA 17033 USA. Penn State Univ, Dept Orthopaed & Rehabil, Hershey, PA 17033 USA. Wyle Labs, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Minist Publ Hlth Russia, Inst Biomed Problems, Moscow, Russia. RP McCrory, JL (reprint author), Penn State Univ, Ctr Locomot Studies, University Pk, PA 16802 USA. RI Kozlovskaya, Inesa/R-9729-2016 NR 13 TC 20 Z9 21 U1 0 U2 6 PU HUMAN KINETICS PUBL INC PI CHAMPAIGN PA 1607 N MARKET ST, CHAMPAIGN, IL 61820-2200 USA SN 1065-8483 J9 J APPL BIOMECH JI J. Appl. Biomech. PD AUG PY 1999 VL 15 IS 3 BP 292 EP 302 PG 11 WC Engineering, Biomedical; Sport Sciences SC Engineering; Sport Sciences GA 221KZ UT WOS:000081727400007 PM 11541844 ER PT J AU Hong, Y Kummerow, CD Olson, WS AF Hong, Y Kummerow, CD Olson, WS TI Separation of convective and stratiform precipitation using microwave brightness temperature SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID VERTICAL STRUCTURE INFORMATION; CLOUD-RADIATION MODEL; SATELLITE MEASUREMENTS; ESTIMATING RAINFALL; PACIFIC-OCEAN; LIQUID WATER; REFLECTIVITY; RETRIEVAL; SSM/I; RADAR AB This paper presents a new scheme that classifies convective and stratiform (CIS) precipitation areas over oceans using microwave brightness temperature. In this scheme, data are first screened to eliminate nonraining pixels. For raining pixels, C/S indices are computed from brightness temperatures and their variability for emission (19 and 37 GHz) and scattering (85 GHz). Since lower-resolution satellite data generally contain mixtures of convective and stratiform precipitation, a probability matching method is employed to relate the CIS index to a convective fraction of precipitation area. The scheme has been applied on synthetic data generated from a dynamical cloud model and radiative transfer computations to simulate the frequencies and resolutions of the Tropical Rainfall Measuring Mission (TRMM) Microwave (TMI) Imager as well as the Special Sensor Microwave/Imager (SSM/I). The results from simulated TMI data during the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment agree very well with the ground-based radar classification maps; The classification accuracy degrades when SSM/I data is used, due largely to the lower spatial resolution of the SSM/I. The successful launch of TRMM satellite in November 1997 has made it possible to test this scheme on actual TMI data. Preliminary results of TMI derived CIS classification compared with that from the first spaceborne precipitation radar has shown a very good agreement. Further verification and improvement of this scheme are under way. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Greenbelt, MD 20771 USA. Caelum Res Corp, Silver Spring, MD USA. Univ Maryland Baltimore Cty, JCET, Baltimore, MD 21228 USA. RP Hong, Y (reprint author), NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Code 912, Greenbelt, MD 20771 USA. NR 36 TC 75 Z9 80 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 AUG PY 1999 VL 38 IS 8 BP 1195 EP 1213 DI 10.1175/1520-0450(1999)038<1195:SOCASP>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 233BR UT WOS:000082406100013 ER PT J AU Stubenrauch, CJ Rossow, WB Cheruy, F Chedin, A Scott, NA AF Stubenrauch, CJ Rossow, WB Cheruy, F Chedin, A Scott, NA TI Clouds as seen by satellite sounders (3I) and imagers (ISCCP). Part I: Evaluation of cloud parameters SO JOURNAL OF CLIMATE LA English DT Article ID LEVEL CLOUDS; RETRIEVAL; RADIANCES; RESOLUTION; BUDGET; HIRS; PATH AB The improved initialization inversion (3I) algorithms convert TIROS-N Operational Vertical Sounder observations from the National Oceanic and Atmospheric Administration (NOAA) polar-orbiting environmental satellites into atmospheric temperature and water vapor profiles, together with cloud and surface properties. Their relatively good spectral resolution and coverage make IR sounders a very useful tool for the determination of cloud properties both day and night. The iterative process of detailed comparisons between cloud parameters obtained from this global dataset, which is available in the framework of the NOAA-National Aeronautics and Space Administration Pathfinder Program, with time-space-collocated observations of clouds from the recently reprocessed international Satellite Cloud Climatology Project (ISCCP) dataset has led to an improved 3I cloud analysis scheme based on a weighted-chi(2) method described in the second article of this series. This process also provides a first evaluation of the ISCCP reanalysis. The new 3I cloud scheme obtains cloud properties very similar to those from ISCCP for homogeneous cloud scenes. Improvement is especially notable in the stratocumulus regimes where the new 3I scheme detects much more of the low-level cloudiness. Remaining discrepancies in cloud classification can now be explained by differences in cloud detection sensitivity, differences in temperature profiles used, and inhomogeneous or partly cloudy fields. Cirrus cloud identification during the daytime in the recent ISCCP dataset is improved relative to the first version of ISCCP, but is still an underestimate. At night only multispectral IR analyses like 3I can provide cirrus information. The reprocessed ISCCP dataset also shows considerable improvement in cloud cover at higher latitudes. Differences in 3I and ISCCP summertime cloud cover over deserts may be caused by different sensitivities to dust storms. C1 Ecole Polytech, CNRS, Meteorol Dynam Lab, F-91128 Palaiseau, France. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Stubenrauch, CJ (reprint author), Ecole Polytech, CNRS, Meteorol Dynam Lab, F-91128 Palaiseau, France. RI Rossow, William/F-3138-2015 NR 40 TC 79 Z9 79 U1 1 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 AUG PY 1999 VL 12 IS 8 BP 2189 EP 2213 DI 10.1175/1520-0442(1999)012<2189:CASBSS>2.0.CO;2 PN 1 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232HA UT WOS:000082364100004 ER PT J AU Murtugudde, R Busalacchi, AJ AF Murtugudde, R Busalacchi, AJ TI Interannual variability of the dynamics and thermodynamics of the tropical Indian Ocean SO JOURNAL OF CLIMATE LA English DT Article ID SEA-SURFACE TEMPERATURE; SHALLOW-WATER SIMULATIONS; SUMMER MONSOON RAINFALL; MIXED-LAYER MODEL; ARABIAN SEA; INDONESIAN THROUGHFLOW; SOUTHERN OSCILLATION; SEASONAL CIRCULATION; LEVEL VARIATIONS; SOMALI CURRENT AB Interannual variability of the tropical Indian Ocean is studied with a reduced gravity, primitive equation, ocean general circulation model (OGCM). The OGCM is coupled to an atmospheric mixed layer model for surface beat flux computation. The seasonal simulation of sea surface temperatures (SST), current, and thermocline structures are in good agreement with observations and other models. The seasonal cycle of SST along the equator exhibits an eastward propagation with larger variability in the west. The interannual simulations are carried out over 1980-95 with interannual wind stresses nd wind speeds but climatological data for solar radiation and cloudiness. The SST anomalies are smaller than 1 degrees C over most of the basin and the leading EOF shows an ENSO-related warming. However, the correlation between the Southern Oscillation index and the time series of the leading EOF is only -0.51 and SST anomalies of similar magnitudes as an El Nino year appear irt other years too. ENSO-related equatorial winds determine the SST anomalies along the coast of Sumatra and this anomaly in the eastern southern tropical Indian Ocean (STIO) is typically opposite in sign to the anomaly in the western STIO. The western STIO has some of the largest SSTA because of a shallow thermocline and the entrainment effects associated with wind stress curl anomalies in the region. The quasi-biennial oscillation in the thermocline and the SST gradient in the STIO is correlated with the Somali jet, which in turn is correlated with the Indian summer monsoon. An experiment with climatological wind stresses but interannual wind speeds demonstrates that the wind-driven variations in SST are larger than previously estimated with relaxation type heat fluxes. A parallel experiment with climatological wind speeds but interannual wind stresses shows that there are regions where heat fluxes contribute significantly to SST variability. Another simulation with interannual data for radiation and cloudiness shows that model simulation is affected significantly in some regions by the use of climatological data for solar radiation and cloudiness. A model experiment with an open eastern boundary provides a simplistic illustration of the effects of the Indonesian Throughflow (ITF). The main influence of the ITF is to warm the Indian Ocean and reduce the effect of upwelling on SST. C1 NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, ESSIC, College Pk, MD 20742 USA. RP Murtugudde, R (reprint author), NASA, Lab Hydrospher Proc, Goddard Space Flight Ctr, Code 970,Bldg 33, Greenbelt, MD 20771 USA. NR 67 TC 182 Z9 194 U1 5 U2 20 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 AUG PY 1999 VL 12 IS 8 BP 2300 EP 2326 DI 10.1175/1520-0442(1999)012<2300:IVOTDA>2.0.CO;2 PN 1 PG 27 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232HA UT WOS:000082364100010 ER PT J AU Gupta, SK Ritchey, NA Wilber, AC Whitlock, CH Gibson, GG Stackhouse, PW AF Gupta, SK Ritchey, NA Wilber, AC Whitlock, CH Gibson, GG Stackhouse, PW TI A climatology of surface radiation budget derived from satellite data SO JOURNAL OF CLIMATE LA English DT Article ID GENERAL-CIRCULATION MODEL; DOWNWARD LONGWAVE RADIATION; INCIDENT SOLAR-RADIATION; ICE-CLOUD MICROPHYSICS; ATMOSPHERIC ABSORPTION; SEASONAL-VARIATION; VALIDATION; FLUXES; IMPROVEMENTS; IRRADIANCE AB Climatological averages of surface radiation budget parameters, namely, the shortwave and longwave surface radiative fluxes, have been derived for each month of the year on a global scale. These climatological averages were derived from an 8-yr (96 month) time series of monthly average fluxes. The monthly averages were computed using fast radiation parameterizations and satellite data from the International Satellite Cloud Climatology Project and the Earth Radiation Budget Experiment. Results are presented as time series of hemispheric and global averages and as geographical distributions and time-latitude cross sections of climatological averages. The spatial/temporal variabilities of the results were found to be clearly related to the corresponding variabilities of meteorological and other inputs to the parameterizations. Numerous comparisons of the present results were made with available surface measurements for the purpose of validation. In most cases, the differences were found to be within the uncertainties of the measurements. In some cases, where they were large, the differences were attributable to identifiable deficiencies in the meteorological inputs and/or the surface measurements. However, large differences remained unexplained in a few cases. Anomalies of shortwave and longwave surface fluxes during the 1986/87 El Nino-Southern Oscillation episode show a strong relationship with corresponding top-of-atmosphere anomalies derived from an independent data source. Comparisons with results from several general circulation models showed large differences, but, in most cases, these were attributable to well-recognized deficiencies in model simulations. Global annual average downward and net shortwave fluxes were found to be about 185 and 161 W m(-2), respectively. These values are 10-20 W m(-2) lower than those obtained from the general circulation models, bur they are in good agreement with other satellite-derived estimates. Global annual average downward and net longwave fluxes were found to be about 348 and -48 W m(-2), respectively, which are about 10-15 W m(-2) higher than corresponding values from general circulation models. Atmospheric shortwave absorption derived from the present results is 10-15 W m(-2) larger than from the general circulation models, but it is in good agreement with another estimate based on satellite data. C1 Analyt Serv & Mat Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23665 USA. RP Gupta, SK (reprint author), Analyt Serv & Mat Inc, 1 Enterprise Pkwy,Suite 300, Hampton, VA 23666 USA. NR 59 TC 142 Z9 146 U1 3 U2 16 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 AUG PY 1999 VL 12 IS 8 BP 2691 EP 2710 DI 10.1175/1520-0442(1999)012<2691:ACOSRB>2.0.CO;2 PN 2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 232MM UT WOS:000082374600017 ER PT J AU Ghaddar, CK Lee, CK Motakef, S Gillies, DC AF Ghaddar, CK Lee, CK Motakef, S Gillies, DC TI Numerical simulation of THM growth of CdTe in presence of rotating magnetic fields (RMF) SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE solution growth; CdTe; travelling heater method; rotating magnetic field ID TRAVELING HEATER METHOD; CRYSTAL-GROWTH; CONVECTION; FLOW; SYSTEM; MELT; ZONE AB The influence of rotating magnetic fields (RMF) on flow pattern and compositional uniformity in the solution zone of a traveling heater method (THM) system for growth of CdTe is numerically investigated. The analysis is conducted at the 10(-6) and 10(-1) g(0) as representative of space and ground processing conditions. It is shown that under microgravity conditions application of RMF can be used to overwhelm residual buoyancy-induced convection and to control the uniformity of solution-zone composition at the growth front without appreciable modification of the growth interface shape. At high-gravity levels, RMF is found not to be able to completely dominate buoyancy-induced convection. In this regime, for the range of field strengths studied, RMF is found to result in (a) complex flow structures in the solution zone, (b) enhancement of compositional nonuniformities at the growth front, and (c) increased convexity of the growth interface. A scaling analysis of convection in the solution zone is used to generate a nondimensional map delineating the RMF- and gravity-dominated flow regimes. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Cape Simulat Inc, Newton, MA 02138 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Motakef, S (reprint author), Cape Simulat Inc, 1 Bridge St, Newton, MA 02138 USA. NR 26 TC 30 Z9 31 U1 1 U2 6 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 AUG PY 1999 VL 205 IS 1-2 BP 97 EP 111 DI 10.1016/S0022-0248(99)00206-7 PG 15 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 225LA UT WOS:000081962000013 ER PT J AU Batur, C Srinivasan, A Duval, WMB Singh, NB Golovaty, D AF Batur, C Srinivasan, A Duval, WMB Singh, NB Golovaty, D TI On-line control of solid-liquid interface by state feedback SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID PHASE-CHANGE PROBLEMS; SYSTEMS; SEGREGATION; CONVECTION; DESIGN; GROWTH; SPACE AB This paper deals with the problem of controlling the solid-liquid interface shape during directional solidification of a molten material inside a Bridgman-Stockbarger furnace. The necessary convective boundary conditions that would achieve the desired interface shape are found using feedback controls. A state-space model of the solidification process is determined by employing a modified finite-element technique to the governing conduction equation developed using the apparent heat capacity (AHC) formulation. This model is used to design a dynamic controller that would set up a desired interface share at the desired location and translate it at the desired velocity. The proposed controller is implemented on a multizone transparent Bridgman crystal growth furnace. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Akron, Dept Mech Engn, Akron, OH 44325 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Northrop Grumman Corp, Ctr Sci & Technol, Pittsburgh, PA 15235 USA. Penn State Univ, Dept Math, University Pk, PA 16802 USA. RP Batur, C (reprint author), Univ Akron, Dept Mech Engn, Akron, OH 44325 USA. OI Golovaty, Dmitry/0000-0003-0696-2211 NR 24 TC 6 Z9 7 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0248 J9 J CRYST GROWTH JI J. Cryst. Growth PD AUG PY 1999 VL 205 IS 3 BP 395 EP 409 DI 10.1016/S0022-0248(99)00250-X PG 15 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 229VV UT WOS:000082217200020 ER PT J AU Emardson, TR Elgered, G Johansson, JM AF Emardson, TR Elgered, G Johansson, JM TI External atmospheric corrections in geodetic very-long-baseline interferometry SO JOURNAL OF GEODESY LA English DT Article DE very-long-baseline interferometry (VLBI); global positioning system (GPS); micro wave radiometer; radio wave propagation; atmospheric water vapour ID LINE INTERFEROMETRY; WATER-VAPOR; RADIO INTERFEROMETRY; WET DELAY; IMPROVEMENTS AB Three methods to correct for the atmospheric propagation delay in very-long-baseline interferometry (VLBI) measurements were investigated. In the analysis, the NASA R&D experiments from January 1993 to June 1995 were used. The methods were compared in correcting for the excess propagation delay due to water vapour, the "wet" delay, at one of the sites, the Onsala Space Observatory on the west coast of Sweden. The three methods were: (1) estimating the wet delay using the VLBI data themselves; (2) inferring the wet delay from water vapour radiometer (WVR) data, and (3) using independent estimates based on data from the global positioning system (GPS). Optimum elevation cutoff angles were 22 degrees and 26 degrees when using WVR and GPS data, respectively. The results were found to be similar in terms of reproducibility of the estimated baseline lengths. The shortest baselines tend to benefit from external measurements, whereas the lack of improvement in the longer baselines may be partly due to the large amount of data thrown away when removing observations at low elevation angles. Over a 2 week period of intensive measurements, the two methods using external data showed an overall improvement, for all baseline lengths, compared to the first method. This indicates that there are longterm systematic errors in the wet delay data estimated using WVR and GPS data. C1 Chalmers Univ Technol, Onsala Space Observ, SE-43992 Onsala, Sweden. RP Emardson, TR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 238-600, Pasadena, CA 91109 USA. RI Elgered, Gunnar/B-7052-2016 OI Elgered, Gunnar/0000-0001-5711-0073 NR 22 TC 2 Z9 2 U1 0 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0949-7714 J9 J GEODESY JI J. Geodesy PD AUG PY 1999 VL 73 IS 7 BP 375 EP 383 DI 10.1007/s001900050256 PG 9 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA 236AB UT WOS:000082575100005 ER PT J AU Reiner, MJ Kaiser, ML AF Reiner, MJ Kaiser, ML TI High-frequency type II radio emissions associated with shocks driven by coronal mass ejections SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY SHOCKS; WIND SPACECRAFT; SOLAR; DENSITY; ORIGIN; FLARES; BURST AB We investigate the causal relationship between type II radio emissions in the frequency range from 1 to 14 MHz observed by the WAVES experiment on the Wind spacecraft and metric type II bursts observed by ground-based radio telescopes. We do this by extrapolating, to lower radio frequencies, fits to the frequency drift rates of metric type II bursts, These fits, which describe the shock propagation through the solar corona, are based on coronal density laws derived from white light observations. In order to establish whether the type II radio emissions were generated from the same shock, we explicitly chose events for which the type II radio emissions in the frequency range from 1 to 14 MHz were temporally separated from the associated metric type II bursts. The analyses indicate that some type II radio events observed by WAVES may not be low-frequency continuations of the apparently associated metric type II bursts, We conclude that two temporally separated shocks are required to account for the radio observations for these events, one shock being temporally well associated with the flare maximum, In two cases the observed GOES X-ray flux confirms the presence of two closely spaced solar events. We argue that the type II radio emissions observed by Wind/WAVES are likely generated by coronal mass ejection-driven shocks that form as low as 2 R-S in the solar corona. C1 Raytheon ITSS, Lanham, MD USA. NASA, Extraterr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Reiner, MJ (reprint author), Raytheon ITSS, Lanham, MD USA. NR 25 TC 62 Z9 63 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 AUG 1 PY 1999 VL 104 IS A8 BP 16979 EP 16991 DI 10.1029/1999JA900143 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 222NB UT WOS:000081790700001 ER PT J AU Ko, YK Gloeckler, G Cohen, CMS Galvin, AB AF Ko, YK Gloeckler, G Cohen, CMS Galvin, AB TI Solar wind ionic charge states during the Ulysses pole-to-pole pass SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID INTERPLANETARY SPACE; IRON IONIZATION; CORONAL HOLE; PLASMA; LATITUDES; MODELS AB We analyze and compare the ionic charge composition data for different types of the solar wind (slow wind from equatorial regions, fast wind from low-latitude coronal hole and fast wind from both south and north polar coronal hole) which the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses observed during the pole-to-pole pass of its primary mission. The implications on the electron temperature, electron density, and ion outflow velocity from the corresponding solar wind source regions are also discussed. We find that the electron temperature in the source region of the slow solar wind is higher than that in the coronal hole. We also find a possible north-south asymmetry in the electron temperature that may be correlated to the north-south asymmetry in the solar wind speed found in the SWOOPS/Ulysses data. In particular, we make extensive discussions on the latitudinal variations in the polar coronal hole. On the basis of our data without clear constraints from other coronal observations, the preliminary result is that the electron density may be higher, or the heavy ion outflow velocities may be lower toward lower heliographic latitude. C1 Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. RP Ko, YK (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI Galvin, Antoinette/A-6114-2013 NR 30 TC 21 Z9 21 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 AUG 1 PY 1999 VL 104 IS A8 BP 17005 EP 17019 DI 10.1029/1999JA900112 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 222NB UT WOS:000081790700003 ER PT J AU Ruderman, MS Goldstein, ML Roberts, DA Deane, A Ofman, L AF Ruderman, MS Goldstein, ML Roberts, DA Deane, A Ofman, L TI Alfven wave phase mixing driven by velocity shear in two-dimensional open magnetic configurations SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID FLUX-CORRECTED TRANSPORT; CORONAL HEATING MECHANISMS; SOLAR-WIND; ULYSSES OBSERVATIONS; DISSIPATION; FLUCTUATIONS; HOLES; MAGNETOHYDRODYNAMICS; FLOWS AB Phase mixing of torsional Alfven waves in axisymmetric equilibrium magnetic configurations with purely poloidal magnetic field and stationary flow along the field lines in resistive viscous plasmas is studied. The characteristic wavelength along the magnetic field lines is assumed to be much smaller than the characteristic scale of inhomogeneity in the magnetic field direction, and the WKB method is used to obtain an analytic solution describing phase mixing. The general solution is applied to a particular configuration with the radial magnetic field and flow under the assumptions that the magnetic field and density are independent of the polar angle in the spherical coordinates and the flow velocity is independent of the radial coordinate. The only source of phase mixing in this configuration is velocity shear. The analytical solution is compared with a numerical simulation of the fully nonlinear resistive MHD equations. The numerical and analytical results are in good agreement. Consequences for wave energy deposition into the solar corona and solar wind and for the evolution of the Alfven wave energy spectrum are discussed. C1 Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. NASA, Raytheon STX Corp, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. RP Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. EM melvyn.goldstein@gsfc.nasa.gov RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 36 TC 32 Z9 32 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD AUG 1 PY 1999 VL 104 IS A8 BP 17057 EP 17068 DI 10.1029/1999JA900144 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 222NB UT WOS:000081790700007 ER PT J AU Angelopoulos, V Mozer, FS Lin, RP Mukai, T Tsuruda, K Lepping, R Baumjohann, W AF Angelopoulos, V Mozer, FS Lin, RP Mukai, T Tsuruda, K Lepping, R Baumjohann, W TI Comment on "Geotail survey of ion flow in the plasma sheet: Observations between 10 and 50 R-E" by W. R. Paterson et al. SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Editorial Material ID BURSTY BULK FLOWS; SUBSTORM ONSET; MAGNETIC-FIELD; MAGNETOTAIL; WIND C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2298510, Japan. RP Angelopoulos, V (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Baumjohann, Wolfgang/A-1012-2010 OI Baumjohann, Wolfgang/0000-0001-6271-0110 NR 17 TC 26 Z9 26 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 AUG 1 PY 1999 VL 104 IS A8 BP 17521 EP 17525 DI 10.1029/1999JA900198 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 222NB UT WOS:000081790700045 ER PT J AU Molls, T Molls, F AF Molls, T Molls, F TI Space-time conservation method applied to Saint Venant equations - Closure SO JOURNAL OF HYDRAULIC ENGINEERING-ASCE LA English DT Editorial Material C1 So Illinois Univ, Dept Civil Engn, Carbondale, IL 62901 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Molls, T (reprint author), So Illinois Univ, Dept Civil Engn, Carbondale, IL 62901 USA. NR 0 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 0733-9429 J9 J HYDRAUL ENG-ASCE JI J. Hydraul. Eng.-ASCE PD AUG PY 1999 VL 125 IS 8 BP 892 EP 892 PG 1 WC Engineering, Civil; Engineering, Mechanical; Water Resources SC Engineering; Water Resources GA 218CB UT WOS:000081534700012 ER PT J AU Kiasaleh, K Yan, TY Srinivasan, M AF Kiasaleh, K Yan, TY Srinivasan, M TI Trellis-coded pulse-position modulation for optical communication systems impaired by pulsewidth inaccuracies SO JOURNAL OF LIGHTWAVE TECHNOLOGY LA English DT Article DE avalanche photodiode; pulse-position modulation; trellis-coded modulation ID PERFORMANCE; CHANNELS AB A trellis-coded pulse-position modulation (T-PPM) scheme for direct-detection photon communications' over unguided channels is described. The purpose of this signaling method is to combat performance degradation due to the spreading of received signal pulses caused by transmitting laser distortion and the finite area and bandwidth of optical detectors. The T-PPM scheme relies upon use of a set partitioning methodology to increase minimum distance using a simple convolutional encoder. The Viterbi algorithm is used at the receiver to separate the signaling set as part of the demodulation process. It is shown through both analysis and Monte Carlo simulation of an avalanche photodiode based receiver system that T-PPM can restore performance losses due to reduced peak intensity during the detection process. Furthermore, for a large range of background radiation levels, the average number of required signal photons per information bit for T-PPM is smaller than that of uncoded PPM. Specific examples show that for a symbol error rate of 0.001, when the received pulses extend over 4 PPM slot widths, the average laser energy per symbol for 256-ary T-PPM could be reduced by as much as 2 dB. C1 Univ Texas, Erik Jonsson Sch Engn & Comp Sci, Richardson, TX 75083 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kiasaleh, K (reprint author), Univ Texas, Erik Jonsson Sch Engn & Comp Sci, Richardson, TX 75083 USA. NR 16 TC 3 Z9 4 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 0733-8724 J9 J LIGHTWAVE TECHNOL JI J. Lightwave Technol. PD AUG PY 1999 VL 17 IS 8 BP 1336 EP 1346 DI 10.1109/50.779155 PG 11 WC Engineering, Electrical & Electronic; Optics; Telecommunications SC Engineering; Optics; Telecommunications GA 224FF UT WOS:000081886200008 ER PT J AU Seale, MD Madaras, EI AF Seale, MD Madaras, EI TI Ultrasonic measurements of stiffness in thermal-mechanically fatigued IM7/5260 composites SO JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE LA English DT Article DE aging; Lamb wave; nondestructive; thermal-mechanical; thermoset; ultrasonic ID TRANSVERSE CRACKING; REDUCTION; PREDICTION; DAMAGE AB In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. The Lamb wave velocity is directly related to the material parameters, so an effective method exists to ascertain the stiffness of composites by measuring, the velocity of these waves, In this study, a Lamb wave measurement system was used to measure the bending and out-of-plane stiffness coefficients of thermoset composite laminates undergoing thermal-mechanical loading. A series of 16 ply and 32 ply composite laminates were subjected to thermal-mechanical fatigue (TMF) in load frames equipped with special environmental chambers. The composite system studied was a graphite fiber-reinforced bismaleimide thermoset, IM7/5260. The samples were subjected to both high and low temperature profiles as well as high-strain and low-strain profiles. The bending and out-of-plane stiffnesses for composite samples that have undergone over 6000 cycles of combined thermal and mechanical fatigue are reported. The Lamb wave generated elastic stiffness results have shown decreases of up to 64% at 4706 cycles for samples subjected to TMF at high temperatures and less than a 10% decrease at over 6000 cycles for samples subjected to TMF at low temperatures. C1 Natl Res Council Associate, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Seale, MD (reprint author), Natl Res Council Associate, Mail Stop 231, Hampton, VA 23681 USA. EM m.d.seale@larc.nasa.gov NR 22 TC 3 Z9 3 U1 0 U2 2 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 1059-9495 J9 J MATER ENG PERFORM JI J. Mater. Eng. Perform. PD AUG PY 1999 VL 8 IS 4 BP 429 EP 436 DI 10.1361/105994999770346729 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 224VU UT WOS:000081921300006 ER PT J AU Robinson, MB Li, D Rathz, TJ Williams, G AF Robinson, MB Li, D Rathz, TJ Williams, G TI Undercooling, liquid separation and solidification of Cu-Co alloys SO JOURNAL OF MATERIALS SCIENCE LA English DT Article ID DROP-TUBE; DECOMPOSITION; SYSTEMS AB Large undercooling can induce not only various solidification pathways, but also a precursor reaction, or liquid separation. This paper deals with the latter effect of undercooling using examples of the Cu-Co system which has a flattened liquidus. Bulk Cu-Co alloys (about 7 mm in diameter) at compositions ranging from 10 to 100 wt % Co were highly undercooled using a fluxing technique. Except for compositions above 90 wt % Co, liquid separation was directly observed as undercooling exceeded a critical value depending on the composition. It was also confirmed by a microstructural transition from dendrites to droplets above the critical undercooling. Finally, calculations of the metastable miscibility boundary were made to analyze the experimental results. (C) 1999 Kluwer Academic Publishers. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. RP Robinson, MB (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NR 30 TC 50 Z9 55 U1 2 U2 5 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 AUG PY 1999 VL 34 IS 15 BP 3747 EP 3753 DI 10.1023/A:1004688313591 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA 222UZ UT WOS:000081804900023 ER PT J AU Mulligan, NW Stone, M AF Mulligan, NW Stone, M TI Attention and conceptual priming: Limits on the effects of divided attention in the category-exemplar production task SO JOURNAL OF MEMORY AND LANGUAGE LA English DT Article DE attention and memory; implicit and explicit memory; divided attention ID IMPLICIT MEMORY TESTS; EXPLICIT MEMORY; RETRIEVAL-PROCESSES; INDIVIDUAL-ITEM; TEST AWARENESS; WORDS; INFORMATION; DISTINCTIVENESS; ORGANIZATION; EXPOSURE AB Prior research indicates that dividing attention during encoding reduces conceptual priming. The present study examines a limitation of this effect. Experiment la, in apparent contradiction to earlier research (Mulligan, 1997), found no effect of attentional load on later conceptual priming. Experiments 1b, 2, and 3 indicate that the discrepant results are not due to participant, materials, or power differences among studies, but rather to certain procedural differences. In particular, increased attentional load fails to reduce conceptual priming in the category-exemplar production task only when the categorical structure of the study list is salient (i.e., list items are blocked by category) and when attentional load is manipulated within categories, Experiment 4 indicates that processing earlier examples in the study block under full attention confers immunity to divided attention effects for later examples in the block. In contrast, if the first category members are in a divided-attention condition, then the usual negative effects of divided attention obtain. Experiment 5 verifies that this outcome is not due to within-block serial position effects, which occur for category-cued recall bur not category-exemplar production (rendering a new dissociation between matched conceptual explicit and implicit tests). The results are discussed in terms of item-specific and relational encoding processes. (C) 1999 Academic Press. C1 So Methodist Univ, Dept Psychol, Dallas, TX 75275 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Stanford, CA 94305 USA. RP Mulligan, NW (reprint author), So Methodist Univ, Dept Psychol, Dallas, TX 75275 USA. NR 92 TC 32 Z9 35 U1 1 U2 3 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0749-596X J9 J MEM LANG JI J. Mem. Lang. PD AUG PY 1999 VL 41 IS 2 BP 253 EP 280 DI 10.1006/jmla.1999.2648 PG 28 WC Linguistics; Psychology; Psychology, Experimental SC Linguistics; Psychology GA 219HU UT WOS:000081602500005 ER PT J AU Howden, SD Watts, DR AF Howden, SD Watts, DR TI Jet streaks in the Gulf Stream SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID OBJECTIVE ANALYSIS; CAPE-HATTERAS; 68-DEGREES-W; DISTURBANCES; TRANSPORT; VORTICITY; MEANDERS; MOTION; SHEAR; MODEL AB Mesoscale alongstream speed changes of the Gulf Stream are diagnosed From an array of current meters at depths 400, 700, and 1000 m, near 68 degrees W, during the development of steep [ratio of "amplitude" to "wavelength" O(1)] meanders. Speed maxima (jet streaks) are generally found between trough and crest axes in steep meanders with local speed minima near the trough and crest axes. Speed changes along streamlines can be quite dramatic. Speed changes along the jet axis, between jet streaks and local minima in excess of 0.60, 0.40, and 0.35 m s(-1), are observed at depth 400, 700, and 1000 m, respectively. This is in comparison with peak speeds in a frontal coordinates system mean of 1.22, 0.67, and 0.28 m s(-1), at depth 400, 700, and 1000 m, respectively, from a previous study. The presence of the jet streaks can be explained kinematically as a superposition of the Gulf Stream and barotropic vortices. The development of these jet streaks in relation to the developing steep meanders differs from the canonical picture of jet streak/baroclinic wave development in the atmospheric jet stream in that the jet streaks in the Gulf Stream are predominantly fixed in place with respect to meanders as they steepen. C1 Univ Rhode Isl, Grad Sch Oceanog, Kingston, RI 02881 USA. RP Howden, SD (reprint author), NASA, Goddard Space Flight Ctr, Mailcode 971, Greenbelt, MD 20771 USA. NR 37 TC 5 Z9 5 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD AUG PY 1999 VL 29 IS 8 BP 1910 EP 1924 DI 10.1175/1520-0485(1999)029<1910:JSITGS>2.0.CO;2 PN 2 PG 15 WC Oceanography SC Oceanography GA 236PJ UT WOS:000082607500003 ER PT J AU Hall, CA Glakpe, EK Cannon, JN Kerslake, TW AF Hall, CA Glakpe, EK Cannon, JN Kerslake, TW TI Thermodynamic analysis of space solar dynamic heat receivers with cyclic phase change SO JOURNAL OF SOLAR ENERGY ENGINEERING-TRANSACTIONS OF THE ASME LA English DT Article ID ENERGY-STORAGE AB A physical and thermodynamic model of space solar dynamic heat receivers employing solid-liquid phase change storage is developed. Generalized first and second law efficiencies are defined for cyclic operation. The solar heat receiver of NASA Glenn Research Center's Solar Dynamic Ground Test Demonstration System is used to generate numerical results from startup through balanced-orbit (asymptotic) conditions. In addition, a parametric study is performed to assess changes in receiver first and second law efficiencies due to changes in various system measurable parameters. Results show that parametric changes in system parameters result in maximum deviations of the asymptotic first law efficiency of less than 5 percentage points. The maximum departures of the asymptotic second law efficiency are less than 4 percentage points. Although the NASA receiver configuration is not optimized for cyclic thermodynamic performance, the cycle-integrated first and second law efficiencies compare favorably with steady-state numerical and experimental first and second law efficiencies. C1 Univ New Orleans, Dept Mech Engn, New Orleans, LA 70148 USA. Howard Univ, Coll Engn Architecture & Comp Sci, Washington, DC 20059 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. RP Hall, CA (reprint author), Univ New Orleans, Dept Mech Engn, New Orleans, LA 70148 USA. NR 15 TC 6 Z9 6 U1 0 U2 0 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0199-6231 J9 J SOL ENERG-T ASME JI J. Sol. Energy Eng. Trans.-ASME PD AUG PY 1999 VL 121 IS 3 BP 133 EP 144 DI 10.1115/1.2888424 PG 12 WC Energy & Fuels; Engineering, Mechanical SC Energy & Fuels; Engineering GA 241AD UT WOS:000082858300001 ER PT J AU Zhao, H Sadhal, SS Trinh, EH AF Zhao, H Sadhal, SS Trinh, EH TI Singular perturbation analysis of an acoustically levitated sphere: Flow about the velocity node SO JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA LA English DT Article ID RADIATION FORCE; VISCOUS-FLUID; OSCILLATIONS; BUBBLE; DROPS AB This analysis consists of the development of the fluid flow about a spherical particle placed at the velocity node of a standing wave. High-frequency acoustic fields are being used to levitate particles in Earth gravity, and to stabilize particles in low-gravity situations. While a standing wave in an infinite medium may be purely oscillatory with no net-flow components, the interaction with particles or solid walls leads to nonlinear effects that,create a net steady component of the flow. In the present development, the perturbation method is employed to derive the flow field for the situation when a spherical particle is positioned at the velocity node. As found in an earlier analysis [Riley, Q. J. Mech. Appl. Math 19, 461 (1966)] applicable to a solid sphere at the velocity antinode, there is a thin shear-wave region adjacent to the spherical boundary. However, this thin Stokes layer does not cover the entire sphere in the same manner as in the previous case. In the polar regions flow reversal takes place but the Stokes layer opens to the surrounding field. On an equatorial belt region there are closed streamlines. (C) 1999 Acoustical Society of America. [S0001-4966(99)05807-5]. C1 Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Zhao, H (reprint author), Univ So Calif, Dept Aerosp & Mech Engn, Los Angeles, CA 90089 USA. NR 23 TC 18 Z9 18 U1 0 U2 5 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0001-4966 J9 J ACOUST SOC AM JI J. Acoust. Soc. Am. PD AUG PY 1999 VL 106 IS 2 BP 589 EP 595 DI 10.1121/1.427027 PG 7 WC Acoustics; Audiology & Speech-Language Pathology SC Acoustics; Audiology & Speech-Language Pathology GA 225YN UT WOS:000081993700006 ER PT J AU Das, S Johnson, D Tao, WK AF Das, S Johnson, D Tao, WK TI Single-column and cloud ensemble model simulations of TOGA-COARE convective systems SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID PACIFIC WARM POOL; MEASURING MISSION TRMM; CLIMATE MODELS; RAINFALL; PARAMETERIZATION; RADIATION; CIRCULATION; MICROWAVE; MOISTURE; SCHEME AB A prognostic cloud prediction scheme, designed for large-scale models, has been incorporated into a Single Column Model (SCM) and used to simulate the cloud cluster properties observed during the 19-26 December, 1992 Tropical Oceans Global Atmosphere (TOGA)-Coupled Ocean Atmosphere Response Experiment (COARE). Results from the SCM simulations have been compared with simulated profiles obtained from the Goddard Cumulus Ensemble Model (GCEM). Observed large-scale advective temperature, water vapor, and surface fluxes have been used as forcings to run the SCM and the GCEM. Results indicate that the SCM produces mixed profiles of cooling/warming and drying/moistening in the vertical, which are highly sensitive to the prescribed surface fluxes. Errors in the temperature and moisture profiles simulated by the SCM are about +/-3 K and +/-3 g kg(-1), while those from the GCEM are approximately -2 K and 1 g kg(-1) at most levels. The SCM produced -10 % errors in the relative humidity above 700 mb and -30 % at the surface, while in the GCEM, the errors were about 10 to 15 % at most levels. The distributions of precipitation rates are fairly well simulated, but the high cloud fractions are slightly underestimated by the SCM as compared to the GCEM. The cloud liquid water is underestimated, but the ice contents are slightly overestimated by the SCM. Results show that the SCM has been able to simulate the distributions of temperature, moisture, and precipitation rates fairly well as compared to the GCEM and other GEWEX Cloud System Study (GCSS) model intercomparison products. Sensitivity studies have been carried out to investigate the implications of different physical processes in the SCM. Results indicate that the interactions between various physical processes are nonlinear, and a mere substitution of the heating and moistening profiles from the GCEM may not be able to reproduce the observed temperature and moisture values by the SCM. The SCM has also been used to simulate the distributions of large-scale cloud cluster properties and their diurnal variation during the disturbed and suppressed periods of convection. Results show that the diurnal variations of simulated values are in agreement with many observational studies conducted by different authors over the TOGA-COARE. C1 NASA, Goddard Space Flight Ctr, Mesoscale Atmospher Proc Branch, Greenbelt, MD 20771 USA. RP Das, S (reprint author), Natl Ctr Medium Range Weather Forecasting, POB 3090,Lodhi Rd, New Delhi 110003, India. EM somesh@del3.vsnl.net.in NR 40 TC 12 Z9 12 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 AUG PY 1999 VL 77 IS 4 BP 803 EP 826 PG 24 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 247KA UT WOS:000083218900001 ER PT J AU Weng, HY Lau, KM Xue, YK AF Weng, HY Lau, KM Xue, YK TI Multi-scale summer rainfall variability over China and its long-term link to global sea surface temperature variability SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID TROPICAL WESTERN PACIFIC; 500 HPA HEIGHT; INTERDECADAL VARIABILITY; CLIMATE VARIABILITY; NORTHERN-HEMISPHERE; EAST-ASIA; MONSOON; ASSOCIATION; CONVECTION; ENSO AB Multi-scale summer (Jun-Aug) rainfall variability over China and its long-term link to global sea surface temperature (SST) variability are studied for the period of 1955-1997. First, the dominant spatial and temporal patterns of the observed rainfall anomaly are studied by empirical orthogonal function (EOF) analysis. By a wavelet transform, interannual and decadal-interdecadal variabilities as well as a trend are found, with different dominance, in the first two EOF modes. EOF1 shows a sudden shift in rainfall anomaly over China in the late 1970s, representing overall wetter conditions in central China and drier conditions in northern and southern China in the 1980s than the conditions in the 1960s. This sudden shift is associated with a quasi-in-phase reinforcement between bidecadal and quadridecadal variabilities. EOF2 represents an increasing trend in the rainfall anomaly in broad central and southern China, especially in the Yangtze River valley, without an apparent shift in the late 1970s. The lack of such a shift is associated with an out-of-phase partial cancellation between a bidecadal cycle and the trend around that time. Second, to understand the long-term rainfall variability that is linked to global SST variability, the singular value decomposition (SVD) analysis for the two fields is carried out. SVD1 links drought conditions in northern China and flood conditions in central China to an Fl Nino-like SST anomaly distribution. This mode shows both an apparent trend and a regime shift in the late 1970s, which do not coexist in the rainfall EOF modes. SVD2 links the rainfall anomaly in the area between the Yangtze River and the Yellow River and the opposite anomaly in southern China to a wave-like SST anomaly distribution in the eastern Pacific from tropics to extratropics. SVD3 links the rainfall anomaly in the Yangtze River valley to the SST anomaly in the western Pacific centered near 20 degrees N 140 degrees E. The rainfall variability in different areas of China that can be attributed to SST effects results from the interplay of the SVD modes. The most significant links found from SVD analysis are verified by cross-correlation functions. A scenario for a long-term link on the trend scale between the rainfall over China and global SST variabilities, through the associated large-scale circulation, is presented. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Gen Sci Corp, SAIC, Laurel, MD USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Weng, HY (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. EM weng@climate.gsfc.nasa.gov RI Lau, William /E-1510-2012 OI Lau, William /0000-0002-3587-3691 NR 27 TC 104 Z9 117 U1 0 U2 10 PU METEOROLOGICAL SOC JAPAN PI TOKYO PA C/O JAPAN METEOROLOGICAL AGENCY 1-3-4 OTE-MACHI, CHIYODA-KU, TOKYO, 100-0004, JAPAN SN 0026-1165 EI 2186-9057 J9 J METEOROL SOC JPN JI J. Meteorol. Soc. Jpn. PD AUG PY 1999 VL 77 IS 4 BP 845 EP 857 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 247KA UT WOS:000083218900003 ER PT J AU Prabhakara, C Iacovazzi, R Oki, R Weinman, JA AF Prabhakara, C Iacovazzi, R Oki, R Weinman, JA TI A microwave radiometer rain retrieval method applicable to land areas SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN LA English DT Article ID PRECIPITATION; IMAGER; TRMM AB Multi-spectral, dual-polarization measurements made by the satellite-borne Special Sensor Microwave Imager (SSM/I) and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) radiometers cannot discriminate satisfactorily strong, convective rain from weak, stratiform rain. This degrades the quality of the rain information deduced from these radiometers, particularly over land. With the objective to improve the quality of this rain information on land, in this study we have developed a mesoscale area-average rain retrieval method. This method is derived from ATI concepts outlined by Doneaud ct al. (1984) and Lopez et al. (1989), and it requires tuning based on calibrated radar, and/or surface rain gauges. As a building block of this method, the fractional rain area, f(R), is first determined in a mesoscale grid box of 2 degrees x 3 degrees with the help of a threshold on the 85 GHz scattering depression. Using SSM/I data, f(R) is shown to correlate well with the corresponding ground-truth area-average rain rate, R-g, deduced from 15-minute rain gauge observations. Based on f(R), a method is then developed to retrieve area-average rain rate, R-fR. In order to demonstrate the usefulness of this method, nine-months of R-fR are retrieved from SSM/I data over three grid boxes in the Northeast United States. In the three grid boxes, R-fR can explain about 64 % of the variance contained in the corresponding R-g. When average 85 GHz scattering depression in the rain area is also included as a parameter in this method, the variance explained drops to 55 %. Thus, we find statistically that the algorithm based solely on fractional rain area gives a better result. With the aid of this tunable method, because of the wider TMI swath, one can use this procedure to fill gaps in space and time present in the rain measurements of the Precipitation Radar (PR) in the TRMM mission. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Tokyo, Ctr Climate Syst Res, Tokyo, Japan. 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 27 TC 2 Z9 2 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 AUG PY 1999 VL 77 IS 4 BP 859 EP 871 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 247KA UT WOS:000083218900004 ER PT J AU Ash, TDC Reynolds, AP Roche, P Norton, AJ Still, MD Morales-Rueda, L AF Ash, TDC Reynolds, AP Roche, P Norton, AJ Still, MD Morales-Rueda, L TI The mass of the neutron star in Centaurus X-3 SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE binaries : close; stars : fundamental parameters; stars : individual : Cen X-3 stars : individual : V779 Cen; stars : neutron ID UHURU; GINGA AB We report new radial velocity observations of V779 Cen, the optical companion to the X-ray pulsar Cen X-3. Two sets of results at two epochs yield very different radial velocity amplitudes. We demonstrate there are problems with the first set, not least that they are incompatible with the observed duration of the X-ray eclipse for all inclination angles. The anomalously high radial velocities are probably a result of changes in the outflow behaviour of the companion star, Although there is no reason to doubt the results from the second epoch when viewed in isolation, given the anomalous radial velocities of the first epoch, they must be treated with caution, Using these data, the semi-amplitude of the resulting radial velocity curve is found to be 24.4 +/- 4.1 km s(-1). Given the accurately measured semiamplitude of the orbit of the pulsar, 414.3 +/- 0.9 km s(-1), the mass ratio of the system is 0.059 +/- 0.010. The inclination of the system is found to be 70.degrees 2 +/- 2.degrees 7, assuming that the optical component fills its Roche lobe, and that the system is in synchronous rotation. Hence the mass of the neutron star is 1.21 +/- 0.21M. and the mass of the optical companion is 20.5 +/- 0.7 M., This is a smaller uncertainty than previously reported values, and is consistent with the canonical neutron star mass of 1.4 M.. In addition, we use our spectra to determine the spectral class of V779 Cen to be O6-7II-III. C1 Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. Open Univ, Dept Phys, Milton Keynes MK7 6AA, Bucks, England. European Space Agcy, Estec, Dept Space Sci, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. Univ Sussex, CPES, Ctr Astron, Brighton BN1 9QH, E Sussex, England. Natl Space Sci Ctr, Leicester LE1 5FQ, Leics, England. Univ St Andrews, Dept Phys & Astron, St Andrews KY16 9SS, Fife, Scotland. Goddard Space Flight Ctr, Greenbelt, MD 20772 USA. Univ Southampton, Dept Phys & Astron, Southampton SO17 1BJ, Hants, England. RP Ash, TDC (reprint author), Rutherford Appleton Lab, Didcot OX11 0QX, Oxon, England. OI Norton, Andrew/0000-0001-7619-8269 NR 20 TC 30 Z9 30 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 AUG 1 PY 1999 VL 307 IS 2 BP 357 EP 364 DI 10.1046/j.1365-8711.1999.02605.x PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 224XK UT WOS:000081925100009 ER PT J AU Sherwood, SC Wahrlich, R AF Sherwood, SC Wahrlich, R TI Observed evolution of tropical deep convective events and their environment SO MONTHLY WEATHER REVIEW LA English DT Article ID EQUATORIAL WESTERN PACIFIC; SCALE WAVE DISTURBANCES; CLOUD CLUSTERS; SQUALL-LINE; THERMODYNAMIC STRUCTURE; MESOSCALE; SYSTEMS; GATE; MONSOON; BUDGET AB Using a compositing technique, the temporal progression of tropical convective systems and the mean atmospheric stale in their vicinity is constructed from a time series of geostationary satellite and operational rawinsonde data. The technique establishes the stage in the life cycle of convection prevailing at a given place and time, by a simple objective method using time series of satellite brightness temperature (T-b) histograms collected from a region surrounding the site. Soundings are classified according to their placement in the convective life cycle: and composites formed that represent the areal-mean state of the convecting atmosphere at each stage, for several scales of horizontal averaging. The temporal structure found here for the mesoscale-mean atmosphere closely resembles existing observations of the horizontal structure of a tropical squall line, albeit with certain reductions in amplitude and stabilization rate. This supports the generality of previous findings that the physical mechanisms documented for squall line systems are characteristic of other forms of tropical convection, and quantifies their imprint on thermodynamic mean fields at large spatial scales. The results show an instability decay time during convection of about 3 h at the 120-km horizontal scale. This time grows with scale, as does the duration of the mature stage of convection, which is of similar magnitude. The results also show a column-integrated loss of water vapor and moist static energy following convection. These results may be of use in model validation and theoretical treatments of convective interaction with dynamics. C1 Univ Victoria, Sch Earth Sci, Wellington, New Zealand. RP Sherwood, SC (reprint author), NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA. RI Sherwood, Steven/B-5673-2008 OI Sherwood, Steven/0000-0001-7420-8216 NR 56 TC 65 Z9 65 U1 0 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 AUG PY 1999 VL 127 IS 8 BP 1777 EP 1795 DI 10.1175/1520-0493(1999)127<1777:OEOTDC>2.0.CO;2 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 225FX UT WOS:000081948700004 ER PT J AU Rao, PA Fuelberg, HE Droegemeier, KK AF Rao, PA Fuelberg, HE Droegemeier, KK TI High-resolution modeling of the Cape Canaveral area land-water circulations and associated features SO MONTHLY WEATHER REVIEW LA English DT Article ID SEA-BREEZE FRONT; HORIZONTAL CONVECTIVE ROLLS; GRAVITY CURRENT; SOUTH FLORIDA; BOUNDARY-LAYER; DYNAMICS; SENSITIVITY; DOPPLER; SURFACE; FLOW AB The Advanced Regional Prediction System is used to perform a three-dimensional numerical simulation of land-water circulations near Cape Canaveral, Florida. Three two-way nested grids having spacings of 1.6, 0.4, and 0.1 km are employed. Results show that the structures of both the sea and river breezes compare well with observation and theory. Horizontal convective rolls (HCRs), Kelvin-Helmholtz instability (KHI), and their interactions with the sea and river breezes also are investigated. HCRs form over the heated land surface at periodic intervals. The HCRs have two preferred spatial scales: large and small. Inclusion of both the large and small HCRs yields aspect ratios that are smaller than most previous observations. However, when considering only the larger HCRs, agreement is better. The smaller HCRs eventually dissipate or merge with their larger HCR counterparts. These mergers intensify the vertical motion within the larger circulations. The HCRs are observed to tilt upward in advance of the Indian River breeze (IRB), and then advect over and behind the land-water circulation. There is evidence that an HCR advects 2.5 km behind the surface front. The orientation of the IRE causes its interaction with an HCR to change from an intersection to a merger. This produces positive vertical vorticity that causes the IRE to rotate counterclockwise. The derailed physiography and surface characteristics used in this research allow these complex asymmetric interactions to be simulated. In addition, the configuration of this simulation allows an even smaller-scale feature, KHI, to be observed on top of and behind the Indian River breeze front. It appears as vortices or billows that grow in amplitude and propagate backward relative to the front. The structure of the billows agrees well with previous theoretical and modeling results. Local regions of upward motion associated with the billows may be a preferred area for postfrontal convection. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Univ Oklahoma, Ctr Anal & Predict Storms, Norman, OK 73019 USA. Univ Oklahoma, Sch Meteorol, Norman, OK 73019 USA. RP Rao, PA (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Mesoscale Atmospher Proc Branch, Code 912, Greenbelt, MD 20771 USA. NR 34 TC 26 Z9 26 U1 0 U2 3 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0027-0644 J9 MON WEATHER REV JI Mon. Weather Rev. PD AUG PY 1999 VL 127 IS 8 BP 1808 EP 1821 DI 10.1175/1520-0493(1999)127<1808:HRMOTC>2.0.CO;2 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 225FX UT WOS:000081948700006 ER PT J AU Dee, DP da Silva, AM AF Dee, DP da Silva, AM TI Maximum-likelihood estimation of forecast and observation error covariance parameters. Part I: Methodology SO MONTHLY WEATHER REVIEW LA English DT Article ID ATMOSPHERIC DATA ASSIMILATION; NUMERICAL WEATHER PREDICTION; STATISTICAL INTERPOLATION; RADIOSONDE DATA; WIND AB The maximum-likelihood method for estimating observation and forecast error covariance parameters is described. The method is presented in general terms but with particular emphasis on practical aspects of implementation. Issues such as bias estimation and correction, parameter identifiability, estimation accuracy, and robustness of the method, are discussed in detail. The relationship between the maximum-likelihood method and generalized cross-validation is briefly addressed. The method can be regarded as a generalization of the traditional procedure For estimating covariance parameters from station data. It does not involve any restrictions on the covariance models and can be used with data from moving observers, provided the parameters to be estimated are identifiable. Any available a priori information about the observation and forecast error distributions can be incorporated into the estimation procedure. Estimates of parameter accuracy due to sampling error are obtained as a by-product. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD USA. RP Dee, DP (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Mail Code 910-3, Greenbelt, MD 20771 USA. RI da Silva, Arlindo/D-6301-2012 OI da Silva, Arlindo/0000-0002-3381-4030 NR 30 TC 98 Z9 104 U1 0 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 AUG PY 1999 VL 127 IS 8 BP 1822 EP 1834 DI 10.1175/1520-0493(1999)127<1822:MLEOFA>2.0.CO;2 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 225FX UT WOS:000081948700007 ER PT J AU Dee, DP Gaspari, G Redder, C Rukhovets, L da Silva, AM AF Dee, DP Gaspari, G Redder, C Rukhovets, L da Silva, AM TI Maximum-likelihood estimation of forecast and observation error covariance parameters. Part II: Applications SO MONTHLY WEATHER REVIEW LA English DT Article ID ATMOSPHERIC DATA ASSIMILATION; SYSTEM AB Three different applications of maximum-likelihood estimation of error covariance parameters for atmospheric data assimilation are described. Height error standard deviations, vertical correlation coefficients, and isotropic decorrelation length scales are estimated from rawinsonde height observed-minus-forecast residuals. Sea level pressure error standard deviations and decorrelation length scales are obtained from ship reports, and wind observation error standard deviations and forecast error stream function and velocity potential decorrelation length scales are estimated from aircraft data. These applications serve to demonstrate the ability of the method to estimate covariance parameters using multivariate data from moving observers. Estimates of the parameter uncertainty due to sampling error can be obtained as a by-product of the maximum-likelihood estimation. By bounding this source of error ii is found that many statistical parameters that are usually presumed constant in operational data assimilation systems in fact vary significantly with time. This may well reflect the use of overly simplistic covariance models that cannot adequately describe state-dependent error components such as representativeness error: The sensitivity of the parameter estimates to the treatment of bias, and to the choice of the model representing spatial correlations, is examined in detail. Several experiments emulate an online covariance parameter estimation procedure using a sliding window of data, and it is shown that such a procedure is both desirable and computationally feasible. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Greenbelt, MD 20771 USA. Gen Sci Corp, Laurel, MD USA. RP Dee, DP (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Mail Code 910-3, Greenbelt, MD 20771 USA. RI da Silva, Arlindo/D-6301-2012 OI da Silva, Arlindo/0000-0002-3381-4030 NR 15 TC 40 Z9 43 U1 0 U2 2 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 AUG PY 1999 VL 127 IS 8 BP 1835 EP 1849 DI 10.1175/1520-0493(1999)127<1835:MLEOFA>2.0.CO;2 PG 15 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 225FX UT WOS:000081948700008 ER PT J AU Ghiringhelli, GL Masarati, P Mantegazza, P Nixon, MW AF Ghiringhelli, GL Masarati, P Mantegazza, P Nixon, MW TI Multi-body analysis of a tiltrotor configuration SO NONLINEAR DYNAMICS LA English DT Article DE tiltrotor; multi-body dynamics; finite volume beams AB The paper describes the aeroelastic analysis of a tiltrotor configuration. The 1/5 scale wind tunnel semispan model of the V-22 tiltrotor aircraft is considered. The analysis is performed by means of a multi-body code, based on an original formulation. The differential equilibrium problem is stated in terms of first-order differential equations. The equilibrium equations of every rigid body are written together with the definitions of the momenta. The bodies are connected by kinematic constraints applied in the form of Lagrangian multipliers. Deformable components are mainly modelled by means of beam elements based on an original finite volume formulation. Multi-disciplinary problems can be solved by adding user-defined differential equations. In the presented analysis, the equations related to the control of the swash-plate of the model are considered. Advantages of a multi-body aeroelastic code over existing comprehensive rotorcraft codes include the exact modelling of the kinematics of the hub, the detailed modelling of the flexibility of critical hub components, and the possibility to simulate steady flight conditions as well as wind-up and maneuvers. The simulations described in the paper include (1) the analysis of the aeroelastic stability, with particular regard to the proprotor/pylon instability that is peculiar to tiltrotors, (2) the determination of the dynamic behavior of the system and of the loads due to typical maneuvers, with particular regard to the conversion from helicopter to airplane mode, and (3) the stress evaluation in critical components, such as the pitch links and the conversion downstop spring. C1 Politecn Milan, Dipartimento Ingn Aerospaziale, I-20158 Milan, Italy. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Masarati, P (reprint author), Politecn Milan, Dipartimento Ingn Aerospaziale, Via La Masa 34, I-20158 Milan, Italy. RI Ghiringhelli, Gian Luca/E-5797-2012; Mantegazza, Paolo/E-9254-2012; Masarati, Pierangelo/I-3898-2012 OI Ghiringhelli, Gian Luca/0000-0003-3474-9258; Mantegazza, Paolo/0000-0002-5979-9190; Masarati, Pierangelo/0000-0002-9347-7654 NR 25 TC 18 Z9 22 U1 0 U2 5 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0924-090X J9 NONLINEAR DYNAM JI Nonlinear Dyn. PD AUG PY 1999 VL 19 IS 4 BP 333 EP 357 DI 10.1023/A:1008386219934 PG 25 WC Engineering, Mechanical; Mechanics SC Engineering; Mechanics GA 235FR UT WOS:000082530600003 ER PT J AU Ambriola, ML Barbiellini, G Bartalucci, S Basini, G Bellotti, R Bergstroem, D Bocciolini, M Boezio, M Bravar, U Cafagna, F Carlson, P Casolino, M Castellano, M Ciacio, F Circella, M De Marzo, C De Pascale, MP Finetti, N Francke, T Hof, M Kremer, J Menn, W Mitchell, JW Morselli, A Ormes, JF Papini, P Perego, A Piccardi, S Picozza, P Ricci, M Schiavon, P Simon, M Sparvoli, R Spillantini, P Stephens, SA Stochaj, SJ Streitmatter, RE Suffert, M Vacchi, A Weber, N Zampa, N AF Ambriola, ML Barbiellini, G Bartalucci, S Basini, G Bellotti, R Bergstroem, D Bocciolini, M Boezio, M Bravar, U Cafagna, F Carlson, P Casolino, M Castellano, M Ciacio, F Circella, M De Marzo, C De Pascale, MP Finetti, N Francke, T Hof, M Kremer, J Menn, W Mitchell, JW Morselli, A Ormes, JF Papini, P Perego, A Piccardi, S Picozza, P Ricci, M Schiavon, P Simon, M Sparvoli, R Spillantini, P Stephens, SA Stochaj, SJ Streitmatter, RE Suffert, M Vacchi, A Weber, N Zampa, N TI CAPRICE98: A balloon borne magnetic spectrometer to study cosmic ray antimatter and composition at different atmospheric depths SO NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS LA English DT Article; Proceedings Paper CT 6th International Conference on Advanced Technology and Particle Physics CY OCT 05-09, 1998 CL VILLA OLMO, ITALY SP European Phys Soc, Inst Nazionale Fis Nucleare, Univ Florence, INFN ID PARTICLE IDENTIFICATION CAPABILITY; TRANSITION RADIATION DETECTOR; IMAGING CALORIMETER; ELECTRON RATIO; RICH DETECTOR; PERFORMANCE; POSITRON; FLIGHT; FLUX AB CAPRICE98 is a superconducting magnetic spectrometer built by the WiZard collaboration. It was launched from Ft. Sumner, NM, USA on the 28th of May 1998. For the first time a gas RICH detector has been flown together with a silicon electromagnetic calorimeter. The instrument configuration included a time of flight detector and a drift, chamber stack, which were placed in the region of a magnet field, for rigidity measurement. Science objectives for this experiment include the study of antimatter in cosmic rays and that of cosmic ray composition in the atmosphere with special focus on muons. C1 Univ Bari, INFN Sect, Bari, Italy. Univ Bari, Dept Phys, Bari, Italy. Univ Trieste, INFN Sect, Trieste, Italy. Univ Trieste, Dept Phys, Trieste, Italy. Ist Nazl Fis Nucl, Lab Nazl, Frascati, Italy. Royal Inst Technol, S-10044 Stockholm, Sweden. Univ Florence, INFN Sect, Florence, Italy. Univ Florence, Dept Phys, Florence, Italy. New Mexico State Univ, RL Golden Particle Astrophys Lab, Las Cruces, NM 88003 USA. Univ Roma Tor Vergata, INFN Sect, Rome, Italy. Univ Roma Tor Vergata, Dept Phys, Rome, Italy. Univ Siegen, D-5900 Siegen, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Ctr Rech Nucl, Strasbourg, France. RP Cafagna, F (reprint author), Univ Bari, INFN Sect, Bari, Italy. RI Morselli, Aldo/G-6769-2011; Castellano, Marcello/J-3428-2012; Cafagna, Francesco/A-9299-2010; Vacchi, Andrea/C-1291-2010; OI Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981; Morselli, Aldo/0000-0002-7704-9553; Castellano, Marcello/0000-0002-4211-2903; Cafagna, Francesco/0000-0002-7450-4784; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321 NR 19 TC 15 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0920-5632 J9 NUCL PHYS B-PROC SUP JI Nucl. Phys. B-Proc. Suppl. PD AUG PY 1999 VL 78 BP 32 EP 37 DI 10.1016/S0920-5632(99)00519-8 PG 6 WC Physics, Particles & Fields SC Physics GA 249AJ UT WOS:000083309400006 ER PT J AU Smith, JA Ballard, JR AF Smith, JA Ballard, JR TI Effect of spatial resolution on thermal and near-infrared sensing of canopies SO OPTICAL ENGINEERING LA English DT Article DE remote sensing; thermal infrared; near infrared; canopy model; brightness temperature; normalized difference vegetation index; directional anisotropy; spatial resolution ID SURFACE-TEMPERATURE; VEGETATION INDEX; AIR-TEMPERATURE; RADIANCE; COVER; MODEL AB Satellite observations of agricultural and other plant canopies in the thermal and near IR regime have generally been at spatial scales of tens to hundreds of meters. Advances in sensor technology will extend our capabilities for IR measurements from space to yield improved spatial resolutions. We explore the variability in brightness temperature and the covariation of the normalized difference vegetation index (NDVI) with brightness temperature as a function of viewing geometry and changing spatial resolution. Using 3-D models for both canopy reflectance and thermal infrared exitance, we employ a theoretical analysis for an agricultural scene. The directional viewing effects and correlation between the NDVI and brightness temperature are found to be scale independent and in agreement with experiment. Directional anisotropy in brightness temperature and NDVI are calculated to be less than 7 to 12% respectively for zenith view angles less than 30 deg, but range up to 22 to 40% for zenith view angles of 60 deg. Analysis of variation in local standard deviations with spatial resolution shows a maximum peak corresponding to crop row spacing with rapid fall-off at larger scales. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)00408-0]. C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. USAE, Waterways Expt Stn, Environm Lab, Vicksburg, MS 39180 USA. RP Smith, JA (reprint author), NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 20 TC 10 Z9 10 U1 1 U2 2 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD AUG PY 1999 VL 38 IS 8 BP 1413 EP 1423 DI 10.1117/1.602193 PG 11 WC Optics SC Optics GA 224JZ UT WOS:000081895900021 ER PT J AU Heath, MJ Doyle, LR Joshi, MM Haberle, RM AF Heath, MJ Doyle, LR Joshi, MM Haberle, RM TI Habitability of planets around red dwarf stars SO ORIGINS OF LIFE AND EVOLUTION OF THE BIOSPHERE LA English DT Article ID MICROBIAL ECOSYSTEMS; BASALT AQUIFERS; MAIN-SEQUENCE; AD LEONIS; RADIATION; FLARE; LINES; LIFE; END AB Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible. C1 Biospheres Project, London SE27 9EH, England. SETI Inst, Mt View, CA 94043 USA. NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. RP Heath, MJ (reprint author), Biospheres Project, 47 Tulsemere Rd, London SE27 9EH, England. RI Joshi, Manoj/C-1795-2008 OI Joshi, Manoj/0000-0002-2948-2811 NR 64 TC 51 Z9 52 U1 0 U2 6 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 AUG PY 1999 VL 29 IS 4 BP 405 EP 424 DI 10.1023/A:1006596718708 PG 20 WC Biology SC Life Sciences & Biomedicine - Other Topics GA 215ZJ UT WOS:000081415500006 PM 10472629 ER PT J AU Schmidt, GA AF Schmidt, GA TI Forward modeling of carbonate proxy data from planktonic foraminifera using oxygen isotope tracers in a global ocean model SO PALEOCEANOGRAPHY LA English DT Article ID FRESH-WATER; SEASONAL SUCCESSION; ATLANTIC-OCEAN; INDIAN-OCEAN; SALINITY; SEA; ICE; CIRCULATION; TEMPERATURE; DELTA-O-18 AB The distribution and variation of oxygen isotopes in seawater are calculated using the Goddard Institute for Space Studies' global ocean model. Simple ecological models are used to estimate the planktonic foraminiferal abundance as a function of depth, column temperature, season, light intensity, and density stratification. These models are combined to forward model isotopic signals recorded in calcareous ocean sediment. The sensitivity of the results to the changes in foraminiferal ecology, secondary calcification, and dissolution are also examined. Simulated present-day isotopic values for ecology relevant for multiple species compare well with core-top data. Hindcasts of sea surface temperature and salinity are made from time series of the modeled carbonate isotope values as the model climate changes. Paleoclimatic inferences from these carbonate isotope records are strongly affected by erroneous assumptions concerning the covariations of temperature, salinity, and delta(18)O(w). Habitat-imposed biases are less important, although errors due to temperature-dependent abundances can be significant. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. RP Schmidt, GA (reprint author), NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RI Schmidt, Gavin/D-4427-2012 OI Schmidt, Gavin/0000-0002-2258-0486 NR 58 TC 74 Z9 77 U1 0 U2 9 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0883-8305 J9 PALEOCEANOGRAPHY JI Paleoceanography PD AUG PY 1999 VL 14 IS 4 BP 482 EP 497 DI 10.1029/1999PA900025 PG 16 WC Geosciences, Multidisciplinary; Oceanography; Paleontology SC Geology; Oceanography; Paleontology GA 218QZ UT WOS:000081564300006 ER PT J AU Cerf, NJ Adami, C AF Cerf, NJ Adami, C TI Quantum extension of conditional probability SO PHYSICAL REVIEW A LA English DT Article ID STATES; INFORMATION; ENTROPY AB We analyze properties of the quantum conditional amplitude operator [Phys. Rev. Lett. 74, 5194 (1997)], which plays a role similar to that of the conditional probability in classical information theory. The spectrum of the conditional operator that characterizes a quantum bipartite system is shown to be invariant under local unitary transformations and reflects its inseparability. More specifically, it is proven that the conditional amplitude operator of a separable state cannot have an eigenvalue exceeding 1, which results in a necessary condition for separability. A related separability criterion based on the non-negativity of the von Neumann conditional entropy is also exhibited. [S1050-2947(99)00608-3]. C1 CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Informat Syst Technol Sect, Pasadena, CA 91109 USA. RP Cerf, NJ (reprint author), CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. RI Adami, Christoph/A-5181-2009; Adami, Christoph/A-9675-2011 OI Adami, Christoph/0000-0002-2915-9504 NR 18 TC 46 Z9 48 U1 0 U2 3 PU AMER 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 AUG PY 1999 VL 60 IS 2 BP 893 EP 897 DI 10.1103/PhysRevA.60.893 PG 5 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 227BU UT WOS:000082058900027 ER PT J AU Cerf, NJ Adami, C Gingrich, RM AF Cerf, NJ Adami, C Gingrich, RM TI Reduction criterion for separability SO PHYSICAL REVIEW A LA English DT Article ID MIXED STATES; ENTANGLEMENT; INFORMATION AB We introduce a separability criterion based on the positive map Gamma:rho-->(Tr rho)-rho, where rho is a trace-class Hermitian operator. Any separable state is mapped by the tensor product of r and the identity into a nonnegative operator, which provides a simple necessary condition for separability. This condition is generally not sufficient because it is vulnerable to the dilution of entanglement. In the special case when one subsystem is a quantum bit, r reduces to time reversal, so that this separability condition is equivalent to partial transposition. It is therefore also sufficient for 2x2 and 2x3 systems. Finally, a simple connection between this map for two qubits and complex conjugation in the "magic" basis [Phys. Rev. Lett. 78, 5022 (1997)] is displayed. [S1050-2947(99)00708-8]. C1 CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Informat Syst Technol Sect, Pasadena, CA 91109 USA. RP Cerf, NJ (reprint author), CALTECH, WK Kellogg Radiat Lab, Pasadena, CA 91125 USA. RI Adami, Christoph/A-5181-2009; Adami, Christoph/A-9675-2011 OI Adami, Christoph/0000-0002-2915-9504 NR 16 TC 109 Z9 111 U1 0 U2 1 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1050-2947 EI 1094-1622 J9 PHYS REV A JI Phys. Rev. A PD AUG PY 1999 VL 60 IS 2 BP 898 EP 909 DI 10.1103/PhysRevA.60.898 PG 12 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 227BU UT WOS:000082058900028 ER PT J AU Vasquez, RP Siegal, MP Overmyer, DL Ren, ZF Lao, JY Wang, JH AF Vasquez, RP Siegal, MP Overmyer, DL Ren, ZF Lao, JY Wang, JH TI Chemical bonding in T1 cuprates studied by x-ray photoemission SO PHYSICAL REVIEW B LA English DT Article ID HIGH-TEMPERATURE SUPERCONDUCTORS; CORE-LEVEL; PHOTOELECTRON-SPECTROSCOPY; ELECTRONIC-STRUCTURE; NEUTRON-DIFFRACTION; CRYSTAL-STRUCTURE; BINDING-ENERGIES; THIN-FILMS; TL; SPECTRA AB Epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9 - delta are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl2Ba2CuO6 + delta and TlBa2CaCu2O7 - delta, comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E-s - E-m) and a lower intensity ratio (I-s/I-m) are found to correlate with higher values of T-c. Analysis of these spectra within a simple configuration interaction model suggests that higher values of T-c are related to low values of the O 2p --> Cu 3d charge transfer energy. In the O 1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba2+ ions. For samples near optimum doping, maximum T-c is observed to occur when the Tl 4f(7/2) binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl 4f(7/2) binding energies, corresponding to formal oxidation states nearer Tl1+, are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O is signal associated with Tl-O bonding. [S0163-1829(99)12729-2]. C1 CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. SUNY Buffalo, Dept Chem, Mat Synth Lab, Buffalo, NY 14260 USA. RP Vasquez, RP (reprint author), CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. EM richard.vazquez@jpl.nasa.gov RI Ren, Zhifeng/B-4275-2014 NR 53 TC 12 Z9 12 U1 0 U2 2 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD AUG 1 PY 1999 VL 60 IS 6 BP 4309 EP 4319 DI 10.1103/PhysRevB.60.4309 PG 11 WC Physics, Condensed Matter SC Physics GA 226AA UT WOS:000081997100084 ER PT J AU Hogan, RC Cuzzi, JN Dobrovolskis, AR AF Hogan, RC Cuzzi, JN Dobrovolskis, AR TI Sealing properties of particle density fields formed in simulated turbulent flows SO PHYSICAL REVIEW E LA English DT Article ID FULLY-DEVELOPED TURBULENCE; GENERALIZED DIMENSIONS; SINGULARITY SPECTRUM; ISOTROPIC TURBULENCE; VELOCITY AB Direct numerical simulations of particle concentrations in fully developed three-dimensional turbulence were carried out in order to study the nonuniform structure of the particle density field. Three steady-state turbulent fluid fields with Taylor microscale Reynolds numbers (Re-lambda) of 40, 80, and 140 were generated by solving the Navier-Stokes equations with pseudospectral methods. Large-scale forcing was used to drive the turbulence and maintain temporal stationarity. The response of the particles to the fluid was parametrized by the particle Stokes number St, defined as the ratio of the particle's stopping time to the mean period of eddies on the Kolmogorov scale (eta) In this paper, we consider only passive particles optimally coupled to these eddies (St approximate to 1) because of their tendency to concentrate more than particles with lesser or greater St values. The trajectories of up to 70 x 10(6) particles were tracked in the equilibrated turbulent hows until the particle concentration field reached a statistically stationary state. The nonuniform structure of the concentration fields was characterized by the multifractal singularity spectrum f(alpha), derived from measures obtained after binning particles into cells ranging from 2 eta to 15 eta in size. We observed strong systematic variations of f(alpha) across this scale range in all three simulations and conclude that the particle concentration held is not statistically self-similar across the scale range explored. However, spectra obtained at the 2 eta, 4 eta, and 8 eta scales of each flow case were found to be qualitatively similar;This result suggests that the local structure of the particle concentration field may be flow independent. The singularity spectra found for 2 eta-sized cells were used to predict concentration distributions in good agreement with those obtained directly from the particle data. This singularity spectrum has a shape similar to the analogous spectrum derived for the inertial-range energy dissipation fields sf experimental turbulent flows at Re-lambda = 110 and 1100. Based on this agreement, and the expectation that both dissipation and particle concentration are controlled by the same cascade process, we hypothesize that singularity spectra similar to the ones found in this work provide a good characterization of the spatially averaged statistical properties of preferentially concentrated particles in higher Re-lambda turbulent flows. [S1063-651X(99)00807-7]. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Symtech Inc, Alexandria, VA 22314 USA. Univ Calif Santa Cruz, Santa Cruz, CA 95064 USA. RP Hogan, RC (reprint author), NASA, Ames Res Ctr, Mail Stop 245-3, Moffett Field, CA 94035 USA. NR 24 TC 22 Z9 22 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1063-651X J9 PHYS REV E JI Phys. Rev. E PD AUG PY 1999 VL 60 IS 2 BP 1674 EP 1680 DI 10.1103/PhysRevE.60.1674 PN B PG 7 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 230CW UT WOS:000082235100002 PM 11969949 ER PT J AU Yeh, C Bergman, LA AF Yeh, C Bergman, LA TI Existence of optical solitons on wavelength division multiplexed beams in a nonlinear fiber SO PHYSICAL REVIEW E LA English DT Article ID TRANSMISSION; PULSES AB A simple analytic expression for the initial fundamental optical solitons on wavelength division multiplexed (WDM) beams in a nonlinear fiber has been found. For an ideal fiber with no loss and uniform group-velocity dispersion (GVD) in the anomalous GVD region, the initial form is [1+2(M-1)](-1/2) sech(tau), where M is the number of WDM beams and tau is the normalized time. Computer simulation shows that these initial pulses on WDM beams in this fiber will propagate undistorted without change in their shapes for arbitrarily long distances. The discovery of the existence of solitons on WDM beams presents the ultimate goal for optical fiber communication on multiple wavelength beams in a single fiber. [S1063-651X(99)06208-X]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Yeh, C (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 12 Z9 12 U1 0 U2 0 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1063-651X J9 PHYS REV E JI Phys. Rev. E PD AUG PY 1999 VL 60 IS 2 BP 2306 EP 2308 DI 10.1103/PhysRevE.60.2306 PN B PG 3 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 230CW UT WOS:000082235100079 PM 11970026 ER PT J AU Thangam, S Wang, XH Zhou, Y AF Thangam, S Wang, XH Zhou, Y TI Development of a turbulence model based on the energy spectrum for flows involving rotation SO PHYSICS OF FLUIDS LA English DT Article; Proceedings Paper CT International Conference on Turbulence CY MAR, 1998 CL LOS ALAMOS NATL LAB, LOS ALAMOS, NEW MEXICO HO LOS ALAMOS NATL LAB ID HOMOGENEOUS TURBULENCE; ISOTROPIC TURBULENCE; CHANNEL FLOW; COMPUTATION; EXPLICIT AB A generalized eddy viscosity model is formulated by using the rotation modified energy spectrum. Rotation and mean shear effects are directly included in the eddy viscosity without the use of the local equilibrium assumption. The formulation also includes the modeling of vortex stretching and viscous destruction terms of the dissipation rate equation based on the limit of rotating isotropic turbulence at high Reynolds numbers. The rotation modified energy spectrum includes the contribution of rotation effects on the dissipation and structure of turbulence. The model is shown to reproduce the dominant effects of rotation on turbulence in rotating homogeneous shear flows and turbulent channel flows subject to spanwise rotation. The general applicability of the model and its implications are also addressed. (C) 1999 American Institute of Physics. [S1070-6631(99)02808-1]. C1 Stevens Inst Technol, Dept Mech Engn, Hoboken, NJ 07030 USA. NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. RP Thangam, S (reprint author), Stevens Inst Technol, Dept Mech Engn, Hoboken, NJ 07030 USA. NR 30 TC 9 Z9 10 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 AUG PY 1999 VL 11 IS 8 BP 2225 EP 2234 DI 10.1063/1.870084 PG 10 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 217ZH UT WOS:000081528500028 ER PT J AU Rubinstein, R Zhou, Y AF Rubinstein, R Zhou, Y TI Effects of helicity on Lagrangian and Eulerian time correlations in turbulence SO PHYSICS OF FLUIDS LA English DT Article; Proceedings Paper CT International Conference on Turbulence CY MAR, 1998 CL LOS ALAMOS NATL LAB, LOS ALAMOS, NEW MEXICO HO LOS ALAMOS NATL LAB AB Taylor series expansions of turbulent time correlation functions are applied to show that although to second order, helicity does not affect Lagrangian time correlations, the corresponding helicity effect on Eulerian time correlations is nonzero. This result is applied to two problems in which Eulerian time correlations are relevant: sound radiation and scattering by turbulence. Helicity shifts radiated sound to lower frequencies and increases the angle between scattered and incident sound waves. (C) 1999 American Institute of Physics. [S1070-6631(99)01108-3]. C1 NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. IBM Corp, Div Res, TJ Watson Res Ctr, Yorktown Heights, NY 10598 USA. RP Rubinstein, R (reprint author), NASA, Langley Res Ctr, Inst Comp Applicat Sci & Engn, Hampton, VA 23681 USA. NR 8 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 1070-6631 J9 PHYS FLUIDS JI Phys. Fluids PD AUG PY 1999 VL 11 IS 8 BP 2288 EP 2290 DI 10.1063/1.870035 PG 3 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 217ZH UT WOS:000081528500035 ER PT J AU Stahle, CK McCammon, D Irwin, KD AF Stahle, CK McCammon, D Irwin, KD TI Quantum calorimetry SO PHYSICS TODAY LA English DT Article ID PARTICLE DETECTORS; GERMANIUM AB Novel detectors that operate at 60 millikelvin are now being used to study cosmic gas at millions of kelvin. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Wisconsin, Madison, WI USA. Natl Inst Stand & Technol, Boulder, CO USA. RP Stahle, CK (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 17 TC 36 Z9 36 U1 0 U2 3 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 AUG PY 1999 VL 52 IS 8 BP 32 EP 37 DI 10.1063/1.882776 PN 1 PG 6 WC Physics, Multidisciplinary SC Physics GA 222HT UT WOS:000081779400009 ER PT J AU Siili, T Haberle, RM Murphy, JR Savijarvi, H AF Siili, T Haberle, RM Murphy, JR Savijarvi, H TI Modelling of the combined late-winter ice cap edge and slope winds in Mars' Hellas and Argyre regions SO PLANETARY AND SPACE SCIENCE LA English DT Article ID ANTARCTIC KATABATIC WINDS; HIGH SOUTHERN LATITUDES; POLAR-CAP; MESOSCALE CIRCULATIONS; MARTIAN ATMOSPHERE; THERMAL INERTIA; ALBEDO; FLOW AB Towards the end of southern hemisphere winter (L-s approximate to 180 degrees) the Martian southern polar cap extends equatorward to 40 degrees S and covers at least, the southern slopes of the Hellas and Argyre impact basins. Subsequently, during retreat of the seasonal ice cap, varying configurations of ice coverage on these slopes occur. Since both sloping topography and ice-edge effects can independently drive mesoscale circulations, the superposition of these two processes may then generate interesting wind patterns. A set of numerical experiments has been performed with the University of Helsinki 2-D Mars Mesoscale Circulation Model (MMCM) in order to study the characteristics of circulations driven by these combined forcings. A model-centre latitude of 57 degrees S and a slope angle of 0.6 degrees, both representative of Hellas' southern slope, are used. When compared with the winds arising in the ice-free slope case, ice coverage in the upper extent of the slope results in diminished upslope (daytime) winds, while the down-slope (nighttime) flow is enhanced. Ice coverage in the lower section of the slope in turn causes enhanced upslope (daytime) and attenuated downslope (nocturnal) flows. This arises due to the daytime off-ice near-surface flow induced by the thermal contrast at the ice cap edge. The surface winds are persistently downslope over a fully ice-covered slope. Inclusion of atmospheric dust ( tau = 0.3) reduces the ice-edge forcing. In comparison with the dust-free situation, the resulting circulation is almost unchanged in the case of ice-covered upper part of the slope, in the opposite case the daytime flow is attenuated and the nocturnal downslope flow enhanced. When the entire slope is ice-covered, the flow is amplified due to the increased direct atmospheric heating. Inclusion of a large scale circulation component (7 m/s southerly wind) in conjunction with an ice-covered slope top results in the generation of a downslope windstorm (fohn, or bora-type of event) with near surface winds exceeding 30 m/s. Winds of this magnitude, not realised in any of the other experiments, approach speeds deemed capable of lifting dust from the surface. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Finnish Meteorol Inst, Geophys Res Div, FIN-00101 Helsinki, Finland. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Univ Helsinki, Dept Meteorol, FIN-00014 Helsinki, Finland. RP Siili, T (reprint author), Finnish Meteorol Inst, Geophys Res Div, POB 503, FIN-00101 Helsinki, Finland. NR 55 TC 22 Z9 22 U1 0 U2 5 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG-SEP PY 1999 VL 47 IS 8-9 BP 951 EP 970 DI 10.1016/S0032-0633(99)00016-1 PG 20 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 230CK UT WOS:000082234100002 ER PT J AU Mahapatra, PR Ostro, SJ Benner, LAM Rosema, KD Jurgens, RF Winkler, R Rose, R Giorgini, JD Yeomans, DK Slade, MA AF Mahapatra, PR Ostro, SJ Benner, LAM Rosema, KD Jurgens, RF Winkler, R Rose, R Giorgini, JD Yeomans, DK Slade, MA TI Resent radar observations of asteroid 1566 Icarus SO PLANETARY AND SPACE SCIENCE LA English DT Article ID NEAR-EARTH ASTEROIDS; RADIOMETRY; IMAGES; SHAPE AB We report Doppler-only radar observations of Icarus at Goldstone at a transmitter frequency of 8510 MHz (3.5 cm wavelength) during 8-10 June 1996, the first radar detection of the object since 1968. Optimally filtered and folded spectra achieve a maximum opposite-circular (OC) polarization signal-to-noise ratio of about 10 and help to constrain Icarus' physical properties. We obtain an OC radar cross section of 0.05 km(2) (with a 35% uncertainty), which is less than values estimated by Goldstein (1969) and by Pettengill et al. (1969), and a circular polarization (SC/OC) ratio of 0.5+/-0.2. We analyze the echo power spectrum with a model incorporating the echo bandwidth B and a spectral shape parameter it, yielding a coupled constraint between B and n. We adopt 25 Hz as the lower bound on B, which gives a lower bound on the maximum pole-on breadth of about 0.6 km and upper bounds on the radar and optical albedos that are consistent with Icarus' tentative QS classification. The observed circular polarization ratio indicates a very rough near-surface at spatial scales of the order of the radar wavelength. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Indian Inst Sci, Bangalore 560012, Karnataka, India. RP Ostro, SJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 40 TC 8 Z9 8 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG-SEP PY 1999 VL 47 IS 8-9 BP 987 EP 995 DI 10.1016/S0032-0633(99)00015-X PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 230CK UT WOS:000082234100005 ER PT J AU Landgraf, M Muller, M Grun, E AF Landgraf, M Muller, M Grun, E TI Prediction of the in-situ dust measurements of the stardust mission to comet 81P/Wild 2 SO PLANETARY AND SPACE SCIENCE LA English DT Article ID INTERSTELLAR DUST; ULYSSES; GALILEO; GRAINS; GIOTTO; HALLEY; FLUX; GAS; P/HALLEY AB We predict the amount of cometary, interplanetary, and interstellar cosmic dust that is to be measured by the Cometary and Interstellar Dust Analyzer (CIDA) and the aerogel collector on board the Stardust spacecraft during its fly-by of comet P/Wild 2 and during the interplanetary cruise phase. We give the dust flux on the spacecraft during the encounter with the comet using both, a radially symmetric and an axially symmetric coma model. At closest approach, we predict a total dust flux of 10(6.0) m(-2) s(-1) for the radially symmetric case and 10(6.5) m(-2) s(-1) for th, axially symmetric case. This prediction is based on an observation of the comet at a heliocentric distance of 1.7 AU. We reproduce the measurements of the Giotto and VEGA missions to comet P/Halley using the same model as for the Stardust predictions. The planned measurements of interstellar dust by Stardust have been triggered by the discovery of interstellar dust impacts in the data collected by the Ulysses and Galileo dust detector. Using the Ulysses and Galileo measurements we predict that 25 interstellar particles, mainly with masses of about 10(-12) g, will hit the target of the CIDA experiment. The interstellar side of the aerogel collector will contain 120 interstellar particles, 40 of which with sizes greater than 1 mu m. Furthermore, we investigate the 'contamination' of the CIDA and collector measurements by interplanetary particles during the cruise phase. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Max Planck Inst Kernphys, D-69117 Heidelberg, Germany. RP Landgraf, M (reprint author), NASA, Lyndon B Johnson Space Ctr, Mailcode SN2, Houston, TX 77058 USA. NR 44 TC 42 Z9 42 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG-SEP PY 1999 VL 47 IS 8-9 BP 1029 EP 1050 DI 10.1016/S0032-0633(99)00031-8 PG 22 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 230CK UT WOS:000082234100009 ER PT J AU Donn, B AF Donn, B TI Adventures in the unknown: A path of astronomical research and discovery SO PLANETARY AND SPACE SCIENCE LA English DT Review ID PROTON C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. NR 43 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 0032-0633 J9 PLANET SPACE SCI JI Planet Space Sci. PD AUG-SEP PY 1999 VL 47 IS 8-9 BP 1163 EP 1170 DI 10.1016/S0032-0633(99)00034-3 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 230CK UT WOS:000082234100017 ER PT J AU Rossow, VJ AF Rossow, VJ TI Lift-generated vortex wakes of subsonic transport aircraft SO PROGRESS IN AEROSPACE SCIENCES LA English DT Review ID TURBULENT TRAILING VORTEX; TIP VORTEX; NUMERICAL SIMULATIONS; AMBIENT TURBULENCE; EMPIRICAL-MODEL; LINE VORTEX; WIND-TUNNEL; ROLL-UP; VORTICES; DECAY AB The flow fields of vortices. whether buoyancy-driven or lift-generated, are fascinating fluid-dynamic phenomena which often possess intense swirl velocities and complex time-dependent behavior. As parr of the on-going study of vortex behavior, this paper presents a historical overview of research conducted on the structure and modification of the vortices generated by the lilting surfaces of subsonic transport aircraft. Although primarily presented from an experimental point of view, the derivation and use of relatively compact theoretical formulations and concepts are included. Experience with lift-generated wakes has shown that they are so complex that progress requires application of a combined theoretical and experimental research program, because either alone often leads to incorrect conclusions. The primary purpose of the research to be described is to find a way to reduce the hazard potential of lift-generated vortices shed by subsonic transport aircraft in the vicinity of airports during landing and takeoff operations. The information presented points out that the characteristics of lift-generated vortices are related to the aerodynamic shapes that produce them and that various arrangements of surfaces can be used to produce quite different vortex structures. It is concluded that a satisfactory aerodynamic solution to the wake-vortex problem at airports has not yet been found, but a reduction in the impact of the wake-vortex hazard on airport capacity may soon become available through wake-vortex avoidance concepts currently under study. Published by Elsevier Science Ltd. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Rossow, VJ (reprint author), NASA, Ames Res Ctr, Mail Stop N247-2, Moffett Field, CA 94035 USA. NR 237 TC 102 Z9 105 U1 1 U2 10 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0376-0421 J9 PROG AEROSP SCI JI Prog. Aeosp. Sci. PD AUG PY 1999 VL 35 IS 6 BP 507 EP 660 DI 10.1016/S0376-0421(99)00006-8 PG 154 WC Engineering, Aerospace SC Engineering GA 239BU UT WOS:000082749600001 ER PT J AU Gilliland, RL Goudfrooij, P Kimble, RA AF Gilliland, RL Goudfrooij, P Kimble, RA TI Linearity and high signal-to-noise performance of the STIS CCD SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID TELESCOPE IMAGING SPECTROGRAPH; SOLAR-LIKE OSCILLATIONS; PHOTOMETRY; ENSEMBLE; SEARCH; STARS; M67 AB On-orbit data characteristics of the Space Telescope Imaging Spectrograph (STIS) CCD aboard the Hubble Space Telescope have been explored with early calibrations in a number of limiting conditions. At a gain of 4 e(-) DN-1, STIS CCD data show excellent linearity at high count levels, even for extreme oversaturation of individual central pixels. At low count levels we interpret a position- and intensity-dependent nonlinearity in terms of charge transfer (in)efficiency in the parallel clocking direction and provide a simple model that accounts for this. A short time series of spectra was acquired at short-exposure times and high signal-to-noise ratio (S/N) on the binary system a Cen A and B enabling the shutter repeatability to be quantified at 0.0002 s, A direct demonstration of near-Poisson-limited time series with S/N > 3000 is shown. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. European Space Agcy, Div Astrophys, Dept Space Sci, F-75738 Paris 15, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Gilliland, RL (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. NR 12 TC 19 Z9 19 U1 0 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 AUG PY 1999 VL 111 IS 762 BP 1009 EP 1020 DI 10.1086/316407 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 224YW UT WOS:000081928400010 ER PT J AU Swain, MR AF Swain, MR TI Spectral gradients and u-v sampling SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID KECK INTERFEROMETER; ARRAY; PERFORMANCE; COAST AB I describe a systematic method for characterizing the effects of differences in u-v coverage in terms of inferred spectral gradients in interferometric images. This method is directly applicable to optical acid radio interferometry; it is useful in situations when observations using scaled arrays are not feasible. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Swain, MR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 171-113, Pasadena, CA 91109 USA. NR 14 TC 1 Z9 1 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD AUG PY 1999 VL 111 IS 762 BP 1021 EP 1024 DI 10.1086/316412 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 224YW UT WOS:000081928400011 ER PT J AU Gu, DG Gillespie, A AF Gu, DG Gillespie, A TI Response to Dymond and Shepherd's comment on "Topographic normalization of Landsat TM images of forest based on subpixel sun-canopy-sensor geometry" (Remate Sens. Environ. 64 : 166-175, 1998) SO REMOTE SENSING OF ENVIRONMENT LA English DT Correction C1 Univ Washington, Dept Geol Sci, Seattle, WA 98195 USA. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Gillespie, A (reprint author), Univ Washington, Dept Geol Sci, POB 351310, Seattle, WA 98195 USA. NR 4 TC 3 Z9 3 U1 1 U2 5 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 AUG PY 1999 VL 69 IS 2 BP 195 EP 196 PG 2 WC Environmental Sciences; Remote Sensing; Imaging Science & Photographic Technology SC Environmental Sciences & Ecology; Remote Sensing; Imaging Science & Photographic Technology GA 222NF UT WOS:000081791100010 ER PT J AU Tabib-Azar, M Akinwande, D Ponchak, G LeClair, SR AF Tabib-Azar, M Akinwande, D Ponchak, G LeClair, SR TI Novel physical sensors using evanescent microwave probes SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID TRANSDUCER AB Local probes, such as electron and photon tunneling, atomic force, and capacitance probes, are excellent sensing means for displacement and other related sensors. Here we introduce applications of a new local probe using evanescent microwave probe (EMP) in displacement sensing with a very high vertical spatial resolution (0.01 mu m at 1 GHz), very high bandwidth (100 MHz), and stability. The EMP has been used in the characterization and mapping of the microwave properties of a variety of materials in the past and its application in gas sensing and thermography was recently explored and reported. The interesting feature of the EMP is that its characteristics can be easily altered for a specific sensing application by changing its geometry and frequency of operation. (C) 1999 American Institute of Physics. [S0034-6748(99)04308-7]. C1 Case Western Reserve Univ, Dept Elect Engn & Comp Sci, Cleveland, OH 44106 USA. Case Western Reserve Univ, Dept Macromol Sci, Cleveland, OH 44106 USA. Case Western Reserve Univ, Dept Phys, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. USAF, Res Lab, Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA. RP Tabib-Azar, M (reprint author), Case Western Reserve Univ, Dept Elect Engn & Comp Sci, Cleveland, OH 44106 USA. NR 13 TC 25 Z9 25 U1 0 U2 1 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD AUG PY 1999 VL 70 IS 8 BP 3381 EP 3386 DI 10.1063/1.1149923 PG 6 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 221HE UT WOS:000081720900032 ER PT J AU Tabib-Azar, M Ciocan, R Ponchak, G LeClair, SR AF Tabib-Azar, M Ciocan, R Ponchak, G LeClair, SR TI Transient thermography using evanescent microwave microscope SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article AB Very high spatial resolution thermography is of great importance in electronics, biology, and in many other situations where local variations in temperature are needed to study heat dissipation or to monitor metabolism rate which can be directly related to the heat production. Infrared imaging techniques probably are the best way of obtaining thermal maps of large structures. However, the spatial resolution of infrared imaging techniques is limited to a few 100 mu m and their temperature resolution is usually around 0.1 K. Here we report on a new evanescent microwave method that is capable of mapping temperature distributions with approximate to 1 mu m spatial resolution. The temperature sensitivity of this probe was better than 0.1 V/K with a minimum detectable signal of 0.01 K with a response time faster than 1 mu s. (C) 1999 American Institute of Physics. [S0034-6748(99)01308-8]. C1 Case Western Reserve Univ, Dept Elect Engn & Comp Sci, Cleveland, OH 44106 USA. Case Western Reserve Univ, Dept Macromol Sci, Cleveland, OH 44106 USA. Case Western Reserve Univ, Dept Phys, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. USAF, Res Lab, Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA. RP Tabib-Azar, M (reprint author), Case Western Reserve Univ, Dept Elect Engn & Comp Sci, Cleveland, OH 44106 USA. NR 13 TC 16 Z9 16 U1 1 U2 4 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD AUG PY 1999 VL 70 IS 8 BP 3387 EP 3390 DI 10.1063/1.1149924 PG 4 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 221HE UT WOS:000081720900033 ER PT J AU Rodwell, M Lee, Q Mensa, D Guthrie, J Martin, SC Smith, RP Pullela, R Agarwal, B Jaganathan, S Mathew, T Long, S Long, S Long, S AF Rodwell, M Lee, Q Mensa, D Guthrie, J Martin, SC Smith, RP Pullela, R Agarwal, B Jaganathan, S Mathew, T Long, S Long, S Long, S TI Transferred-substrate HBT integrated circuits SO SOLID-STATE ELECTRONICS LA English DT Article; Proceedings Paper CT Topical Workshop on Heterostructure Microelectronics CY AUG 30-SEP 02, 1998 CL HAYAMA MACHI, JAPAN DE heterojunction bipolar transistor; HBT; transferred-substrate AB Using substrate transfer processes, we have fabricated heterojunction bipolar transistors with submicron emitter-base and collector-base junctions, minimizing RC parasitics and increasing f(max) to 500 GHz. The process also provides a microstrip wiring environment on a low-epsilon(r) dielectric substrate. Demonstrated small-scale ICs in the process include lumped and distribute amplifiers with bandwidths to 85 Hz, 48 GHz static frequency dividers, and 50GHz AGC/limiting amplifiers. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA. Jet Prop Labs, Pasadena, CA USA. RP Rodwell, M (reprint author), Univ Calif Santa Barbara, Dept Elect & Comp Engn, Santa Barbara, CA 93106 USA. NR 12 TC 8 Z9 8 U1 0 U2 0 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD AUG PY 1999 VL 43 IS 8 BP 1489 EP 1495 DI 10.1016/S0038-1101(99)00094-5 PG 7 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA 240KN UT WOS:000082825300026 ER PT J AU Johnson, NL AF Johnson, NL TI Protecting the GEO environment: policies and practices SO SPACE POLICY LA English DT Article AB The geosynchronous orbital regime has long been recognized as a unique space resource, dictating special measures to ensure its continuing use for future generations. During the past 20 yr a variety of national and international policies have been developed to preserve this environment. A review of current practices involving the deployment and disposal of geosynchronous spacecraft, associated upper stages and apogee kick motors, and geosynchronous orbit transfer objects indicates both positive and negative trends. Most spacecraft operators are indeed performing end-of-mission maneuvers, but the boost altitudes normally fall short of policy guidelines. Russia, a major operator in geosynchronous orbit, maneuvers only 1 in 3 spacecraft out of the region, while China has never retired a spacecraft above GEO. The viability of voluntary protection measures for this regime depends upon the responsible actions of the aerospace community as a whole. Published by Elsevier Science Ltd. C1 NASA, Johnson Space Ctr, Orbital Debris Program Off, Houston, TX 77058 USA. RP Johnson, NL (reprint author), NASA, Johnson Space Ctr, Orbital Debris Program Off, SN3, Houston, TX 77058 USA. NR 17 TC 16 Z9 16 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0265-9646 J9 SPACE POLICY JI Space Policy PD AUG PY 1999 VL 15 IS 3 BP 127 EP 135 DI 10.1016/S0265-9646(99)00022-3 PG 9 WC International Relations; Social Sciences, Interdisciplinary SC International Relations; Social Sciences - Other Topics GA 228RM UT WOS:000082149500003 ER PT J AU Chehbouni, A Kerr, YH Watts, C Hartogensis, O Goodrich, D Scott, R Schieldge, J Lee, K Shuttleworth, WJ Dedieu, G De Bruin, HAR AF Chehbouni, A Kerr, YH Watts, C Hartogensis, O Goodrich, D Scott, R Schieldge, J Lee, K Shuttleworth, WJ Dedieu, G De Bruin, HAR TI Estimation of area-average sensible heat flux using a large-aperture scintillometer during the Semi-Arid Land-Surface-Atmosphere (SALSA) experiment SO WATER RESOURCES RESEARCH LA English DT Article ID HETEROGENEOUS TERRAIN; ENERGY-BALANCE; SCINTILLATION; PARAMETERS; MOMENTUM AB The use of a large-aperture scintillometer to estimate sensible heat flux has been successfully tested by several investigators. Most of these investigations, however, have been confined to homogeneous or to sparse with single vegetation-type surfaces. The use of the scintillometer over surfaces made up of contrasting vegetation types is problematic because it requires estimates of effective roughness length and effective displacement height in order to derive area-average sensible heat from measurements of the refractive index. In this study an approach based on a combination of scintillometer measurements and an aggregation scheme has been used to derive area-average sensible heat flux over a transect spanning two adjacent and contrasting vegetation patches: grass and mesquite, The performance of this approach has been assessed using data collected during the 1997 Semi-Arid Land-Surface-Atmosphere field campaign. The results show that the combined approach performed remarkably well, and the correlation coefficient between measured and simulated area-average sensible heat flux was similar to 0.95. This is of interest because this approach offers a reliable means for validating remotely sensed estimates of surface fluxes at comparable spatial scales. C1 Reyes & Aguascalientes Esq, Inst Medio Ambiente & Desarrollo Sustenable, Inst Rech Dev, Hermosillo 83190, Sonora, Mexico. Inst Rech Dev, Paris, France. Ctr Etud Spatiales Biosphere, F-31055 Toulouse, France. Agr Univ Wageningen, Dept Meteorol, NL-6701 AP Wageningen, Netherlands. USDA, ARS, Tucson, AZ 85719 USA. Univ Arizona, Dept Hydrol & Water Resources, Tucson, AZ 85721 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Chehbouni, A (reprint author), Reyes & Aguascalientes Esq, Inst Medio Ambiente & Desarrollo Sustenable, Inst Rech Dev, Col San Benito, Hermosillo 83190, Sonora, Mexico. RI Goodrich, David/B-1763-2009 OI Goodrich, David/0000-0001-7735-1448 NR 38 TC 30 Z9 32 U1 0 U2 2 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 AUG PY 1999 VL 35 IS 8 BP 2505 EP 2511 DI 10.1029/1999WR900111 PG 7 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 221FC UT WOS:000081712500019 ER PT J AU Kruger, A Kucera, PA Krajewski, WF Short, DA AF Kruger, A Kucera, PA Krajewski, WF Short, DA TI TOGA COARE shipborne radar-rainfall products SO WATER RESOURCES RESEARCH LA English DT Article AB Rainfall products derived from radar data often consume vast amounts of storage space and are time-consuming to analyze. Shipborne radar data collected during the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) provide an extensive data set to examine rainfall characteristics in the tropical Western Pacific Ocean. TOGA COARE shipborne radar-rainfall products have been organized into a database with efficient storage and access time characteristics. Software for reading and visually browsing the data has been developed and made available to provide users with a convenient method to study the data set. C1 Univ Iowa, Inst Hydraul Res, Iowa City, IA 52242 USA. NASA, Goddard Space Flight Ctr, Trop Rainfall Measuring Mission Off, Greenbelt, MD 20771 USA. RP Kruger, A (reprint author), Univ Iowa, Inst Hydraul Res, Iowa City, IA 52242 USA. NR 11 TC 2 Z9 2 U1 0 U2 0 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 AUG PY 1999 VL 35 IS 8 BP 2597 EP 2600 DI 10.1029/1999WR900109 PG 4 WC Environmental Sciences; Limnology; Water Resources SC Environmental Sciences & Ecology; Marine & Freshwater Biology; Water Resources GA 221FC UT WOS:000081712500029 ER PT J AU Stibbe, DT Tennyson, J AF Stibbe, DT Tennyson, J TI Potential energy surfaces of excited states of H(2)(-) (vol 285, pg 114, 1998) SO CHEMICAL PHYSICS LETTERS LA English DT Editorial Material ID R-MATRIX METHOD; MOLECULAR-HYDROGEN; ELECTRON-IMPACT; VIBRATIONAL-EXCITATION; DIATOMIC-MOLECULES; CROSS-SECTIONS; RESONANCES; H2; COLLISIONS; SCATTERING AB The H(2)(-) excited state potential curves of Mebel et al. (Chem. Phys. Lett. 285 (1998) 114-120) are re-analysed. They are shown to be artefacts of the method of computation, with little or no relation to real states. The need for caution in the use of bound state electronic structure methods to study resonance parameters is re-emphasized. (C) 1999 Elsevier Science B.V. All rights reserved. C1 UCL, Dept Phys & Astron, London WC1E 6BT, England. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Tennyson, J (reprint author), UCL, Dept Phys & Astron, Mortimer St, London WC1E 6BT, England. EM j.tennyson@ucl.ac.uk RI Tennyson, Jonathan/I-2222-2012 OI Tennyson, Jonathan/0000-0002-4994-5238 NR 37 TC 17 Z9 17 U1 3 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD JUL 30 PY 1999 VL 308 IS 5-6 BP 532 EP 536 DI 10.1016/S0009-2614(99)00628-4 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 221MV UT WOS:000081731600029 ER PT J AU Pope, KO Ocampo, AC Fischer, AG Alvarez, W Fouke, BW Webster, CL Vega, FJ Smit, J Fritsche, AE Claeys, P AF Pope, KO Ocampo, AC Fischer, AG Alvarez, W Fouke, BW Webster, CL Vega, FJ Smit, J Fritsche, AE Claeys, P TI Chicxulub impact ejects from Albion Island, Belize SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE ejecta; impact features; Chicxulub Crater; Belize ID HAITI; STRATIGRAPHY; SPHERULES AB Impact ejecta from the Albion Formation are exposed in northern Belize. The ejecta come from the outer portion of the continuous ejecta blanket of the Chicxulub crater, which is located 360 km to the northwest. The basal unit of the Albion Formation is a similar to 1-m-thick clay and dolomite spheroid bed composed of up to four discrete flows. The clay spheroids are altered impact glass, and the dolomite spheroids are accretionary lapilli. The upper unit is a similar to 15-m-thick coarse diamictite bed containing altered glass, large accretionary blocks, striated, polished, and impacted cobbles, and rare shocked quartz. The abundance of accretionary clasts, evidence for atmospheric drag sorting, and the presence of multiple flows in the Albion Formation indicate that atmospheres play an important role in the formation of the outer portions of continuous ejecta blankets of large craters. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Geo Eco Arc Res, Washington, DC 20007 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ So Calif, Dept Earth Sci, Los Angeles, CA 90089 USA. Univ Calif Berkeley, Dept Geol & Geophys, Berkeley, CA 94720 USA. Univ Illinois, Dept Geol, Urbana, IL 61801 USA. Loma Linda Univ, Geosci Res Inst, Loma Linda, CA 92350 USA. Univ Nacl Autonoma Mexico, Inst Geol, Mexico City 04510, DF, Mexico. Vrije Univ Amsterdam, Inst Earth Sci, NL-1081 HV Amsterdam, Netherlands. Calif State Univ Northridge, Dept Geol Sci, Northridge, CA 91330 USA. Museum Nat Kunde, Inst Mineral, D-10115 Berlin, Germany. RP Pope, KO (reprint author), Geo Eco Arc Res, 3220 N St NW,Suite 132, Washington, DC 20007 USA. RI Claeys, Philippe/B-4895-2008 OI Claeys, Philippe/0000-0002-4585-7687 NR 37 TC 55 Z9 56 U1 0 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD JUL 30 PY 1999 VL 170 IS 4 BP 351 EP 364 DI 10.1016/S0012-821X(99)00123-5 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 222WK UT WOS:000081808200001 ER PT J AU Yee, HC Torczynski, JR Morton, SA Visbal, MR Sweby, PK AF Yee, HC Torczynski, JR Morton, SA Visbal, MR Sweby, PK TI On spurious behavior of CFD simulations SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS LA English DT Article DE computational fluid dynamics; numerical simulation; spurious behavior ID STATE NUMERICAL-SOLUTIONS; NONLINEAR DIFFERENTIAL-EQUATIONS; BACKWARD-FACING STEP; REACTION-CONVECTION EQUATIONS; COMPUTATIONAL FLUID-DYNAMICS; GLOBAL ASYMPTOTIC-BEHAVIOR; ERROR CONTROL; 2-DIMENSIONAL FLOW; SOURCE TERMS; STABILITY AB Spurious behavior in underresolved grids and/or semi-implicit temporal discretizations for four computational fluid dynamics (CFD) simulations are studied. The numerical simulations consist of (a) a 1-D chemically relaxed non-equilibrium flow model, (b) the direct numerical simulation (DNS) of 2D incompressible flow over a backward facing step, (c) a loosely coupled approach for a 2D fluid-structure interaction, and (d) a 3D unsteady compressible flow simulation of vortex breakdown on delta wings. These examples were chosen based on their non-apparent spurious behaviors that were difficult to detect without extensive grid and/or temporal refinement studies and without some knowledge from dynamical systems theory. Studies revealed the various possible dangers of misinterpreting numerical simulation of realistic complex flows that are constrained by available computing power. In large scale computations, underresolved grids, semi-implicit procedures, loosely coupled implicit procedures, and insufficiently long-time integration in DNS are most often unavoidable. Consequently, care must be taken in both computation and in interpretation of the numerical data. The results presented confirm the important role that dynamical systems theory can play in the understanding of the non-linear behavior of numerical algorithms and in aiding the identification of the sources of numerical uncertainties in CFD. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. USAF, Wright Lab, CFD Res Branch, Wright Patterson AFB, OH 45433 USA. Univ Reading, Dept Math, Reading RG6 2AX, Berks, England. RP Yee, HC (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 45 TC 16 Z9 16 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0271-2091 J9 INT J NUMER METH FL JI Int. J. Numer. Methods Fluids PD JUL 30 PY 1999 VL 30 IS 6 BP 675 EP 711 DI 10.1002/(SICI)1097-0363(19990730)30:6<675::AID-FLD857>3.0.CO;2-V PG 37 WC Computer Science, Interdisciplinary Applications; Mathematics, Interdisciplinary Applications; Mechanics; Physics, Fluids & Plasmas SC Computer Science; Mathematics; Mechanics; Physics GA 220TQ UT WOS:000081683900004 ER PT J AU Hwang, SM Ryu, SO De Witt, KJ Rabinowitz, MJ AF Hwang, SM Ryu, SO De Witt, KJ Rabinowitz, MJ TI Rate coefficient measurements of the reaction CH3+O-2=CH3O+O SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID REFLECTED SHOCK-WAVES; CHEMICAL-KINETICS; METHANE OXIDATION; METHYL RADICALS; RATE CONSTANTS; TUBE; TEMPERATURE; IGNITION; MIXTURES; COMBUSTION AB Rate coefficients for the reaction CH3 + Oz = CH3O + O were measured behind reflected shock waves in a series of lean CH4-O-2-Ar mixtures using hydroxyl and methyl radical diagnostics. The rate coefficients are well represented by an Arrhenius expression given as k = (1.60(-0.47)(+0.67)) x 10(13) exp(-15813 +/- 587 K/T) cm(3) mol(-1) s(-1). This expression, which is valid in the temperature range 1575-1822 K, supports the downward trend in the rate coefficients that has been reported in recent determinations. All measurements to date, including the present study, have been to some extent affected by secondary reactions. The complications due to secondary reactions, choice of thermochemical data, and shock-boundary layer interactions that affect the determination of the rate coefficients are examined. C1 NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. Univ Toledo, Dept Chem Engn, Toledo, OH 43606 USA. Yeungnam Univ, Sch Chem Engn & Technol, Kyongsan 712749, South Korea. RP Rabinowitz, MJ (reprint author), NASA, Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. NR 68 TC 22 Z9 23 U1 0 U2 4 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 JUL 29 PY 1999 VL 103 IS 30 BP 5949 EP 5958 DI 10.1021/jp990998o PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 222YU UT WOS:000081813600014 ER PT J AU Swinbank, R Orris, RL Wu, DL AF Swinbank, R Orris, RL Wu, DL TI Stratospheric tides and data assimilation SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID MIDDLE ATMOSPHERE; ANALYSIS SYSTEM; SOLAR TIDES; TEMPERATURES; CLIMATOLOGY; UARS AB In the upper stratosphere the atmosphere exhibits significant diurnal and semidiurnal tidal variations with typical amplitude of about 2 K in midlatitudes. In this paper we examine how well the tidal variations in temperature are represented by the GEOS-2 data assimilation system. It is shown that the GEOS-2 atmospheric model is quite successful at simulating the tidal variations. However, the assimilation of satellite temperature soundings significantly damps the simulated tides; The reason is that the tides are not well represented by the satellite retrievals used by the assimilation system (which have a typical tidal amplitude of about 1 K). As a result of this study, we suggest improvements that should be made to the treatment of satellite sounding data by the assimilation system. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Anne Arundel Community Coll, Dept Sci, Arnold, MD 21012 USA. CALTECH, Jet Prop Lab, Microwave Atmospher Sci Grp, Pasadena, CA 91109 USA. NASA, Goddard Space Flight Ctr, Natl Res Council, Greenbelt, MD 20771 USA. RP Swinbank, R (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Univ Space Res Assoc, Code 910-3, Greenbelt, MD 20771 USA. EM swinbank@dao.gsfc.nasa.gov; rlorris@mail.aacc.cc.md.us; dwu@mls.jpl.nasa.gov RI Wu, Dong/D-5375-2012 NR 33 TC 17 Z9 17 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 27 PY 1999 VL 104 IS D14 BP 16929 EP 16941 DI 10.1029/1999JD900108 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 220ET UT WOS:000081652100023 ER PT J AU Huang, E Williams, E Boldi, R Heckman, S Lyons, W Taylor, M Nelson, T Wong, C AF Huang, E Williams, E Boldi, R Heckman, S Lyons, W Taylor, M Nelson, T Wong, C TI Criteria for sprites and elves based on Schumann resonance observations SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GROUND LIGHTNING FLASHES; RED-SPRITES; ELECTRICAL-DISCHARGE; CONTINUING CURRENTS; AIR BREAKDOWN; FIELD CHANGES; ELF; THUNDERSTORM; IONOSPHERE; MESOSPHERE AB Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the measured time constants for lightning charge transfer with the electrostatic relaxation time at altitudes of nighttime sprite initiation (50-70 km) generally validate the electrostatic assumption in predictions made initially by Wilson [1925]. The measured charge moments (Q dS = 200-2000 C-km) are large in comparison with ordinary negative lightning but are generally insufficient to account for conventional air breakdown at sprite altitudes. The measured charge moments, however, are sufficient to account for electron runaway breakdown, and the long avalanche length in this mechanism also accounts for the exclusive association of sprites with ground flashes of positive polarity. The association of elves with large peak currents (50-200 kA) measured by the National Lightning Detection Network in a band pass beyond the Schumann resonance range is consistent with an electromagnetic pulse mechanism for these events. C1 MIT, Lincoln Lab, Lexington, MA 02173 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA. FMA Res Inc, Ft Collins, CO 80524 USA. Utah State Univ, Space Dynam Lab, Logan, UT 84321 USA. MIT, Parsons Lab, Cambridge, MA 02139 USA. JP Morgan Secur Asia Pte Ltd, Singapore 068809, Singapore. RP Huang, E (reprint author), MIT, Lincoln Lab, 244 Wood St, Lexington, MA 02173 USA. EM everest@mit.edu; earlew@ll.mit.edu; bobb@ll.mit.edu; stan@stanheckman.com; walyons@frii.com; mtaylor@cc.usu.edu; tnelson@frii.com; wong.charles@jpmorgan.com NR 84 TC 157 Z9 159 U1 2 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 JUL 27 PY 1999 VL 104 IS D14 BP 16943 EP 16964 DI 10.1029/1999JD900139 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 220ET UT WOS:000081652100024 ER PT J AU Ning, CZ Hughes, S Citrin, DS AF Ning, CZ Hughes, S Citrin, DS TI Ultrafast modulation of semiconductor lasers through a terahertz field SO APPLIED PHYSICS LETTERS LA English DT Article ID NONLINEAR TRANSPORT; ELECTRON GASES; SWITCH-OFF; DRIVEN AB We demonstrate, by means of numerical simulation, an interesting mechanism to modulate and switch semiconductor lasers at THz and sub-THz frequency rates. A sinusoidal terahertz field applied to a semiconductor laser heats the electron-hole plasma and consequently modifies the optical susceptibility. This allows an almost linear modulation of the output power of the semiconductor laser and leads to a faithful reproduction of the terahertz-field waveform in the emitted laser intensity. (C) 1999 American Institute of Physics. [S0003-6951(99)04330-2]. C1 NASA, Ames Res Ctr, Computat Quantum Optoelect, Moffett Field, CA 94035 USA. Washington State Univ, Dept Phys, Semicond Opt Theory Grp, Pullman, WA 99164 USA. Washington State Univ, Ctr Mat Res, Pullman, WA 99164 USA. RP Ning, CZ (reprint author), NASA, Ames Res Ctr, Computat Quantum Optoelect, Mail Stop T27A-1, Moffett Field, CA 94035 USA. RI Ning, C. Z./D-4699-2009 OI Ning, C. Z./0000-0003-4583-8889 NR 11 TC 7 Z9 7 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD JUL 26 PY 1999 VL 75 IS 4 BP 442 EP 444 DI 10.1063/1.124402 PG 3 WC Physics, Applied SC Physics GA 218UK UT WOS:000081570400002 ER PT J AU Sornborger, A Parry, M AF Sornborger, A Parry, M TI Patterns from preheating SO PHYSICAL REVIEW LETTERS LA English DT Article ID PHASE-TRANSITIONS; INFLATION; BARYOGENESIS; DECAY; EQUILIBRIUM; UNIVERSE AB The formation of regular patterns is a well-known phenomenon in condensed matter physics. Systems that exhibit pattern formation,are typically driven and dissipative with pattern formation occurring in the weakly nonlinear regime and sometimes even in more strongly nonlinear regions of parameter space. In the early universe, parametric resonance can drive explosive particle production called preheating. The fields that are populated then decay quantum mechanically if their particles are unstable. Thus, during: preheating, a driven-dissipative system exists. Motivated by the application to cosmology, we present a case study for pattern formation in relativistic nonlinear wave equations. C1 NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Brown Univ, Dept Phys, Providence, RI 02912 USA. RP Sornborger, A (reprint author), NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. NR 21 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 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD JUL 26 PY 1999 VL 83 IS 4 BP 666 EP 669 DI 10.1103/PhysRevLett.83.666 PG 4 WC Physics, Multidisciplinary SC Physics GA 219KK UT WOS:000081606300002 ER PT J AU Perlmutter, S Turner, MS White, M AF Perlmutter, S Turner, MS White, M TI Constraining dark energy with type Ia supernovae and large-scale structure SO PHYSICAL REVIEW LETTERS LA English DT Article ID COSMOLOGICAL CONSTANT; MASS FLUCTUATIONS; UNIVERSE; COMPONENT AB Measurements of the distances to type Ia supernovae have produced strong evidence that the expansion of the Universe is accelerating, implying the existence of a nearly uniform component of dark energy with negative pressure, We show that constraints to this mysterious component based upon large-scale structure nicely complement the SN Ia data, and that together they require Omega(X) = rho(X)/rho(crit) is an element of (0.6,0.7) and w = rho(X)/rho(X) < -0.6 (95% C.L.), for the favored hat Universe. Other cosmological data support this conclusion. The simplest explanation, a cosmological constant, is consistent with this, while some of the other possibilities are not. C1 EO Lawrence Berkeley Natl Lab, Inst Nucl & Particle Astrophys, Berkeley, CA 94720 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Univ Illinois, Dept Phys, Urbana, IL 61801 USA. RP Perlmutter, S (reprint author), EO Lawrence Berkeley Natl Lab, Inst Nucl & Particle Astrophys, Berkeley, CA 94720 USA. RI Perlmutter, Saul/I-3505-2015; White, Martin/I-3880-2015 OI Perlmutter, Saul/0000-0002-4436-4661; White, Martin/0000-0001-9912-5070 NR 40 TC 338 Z9 343 U1 2 U2 9 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD JUL 26 PY 1999 VL 83 IS 4 BP 670 EP 673 DI 10.1103/PhysRevLett.83.670 PG 4 WC Physics, Multidisciplinary SC Physics GA 219KK UT WOS:000081606300003 ER PT J AU Westall, F AF Westall, F TI The nature of fossil bacteria: A guide to the search for extraterrestrial life SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID AUTOPOIETIC SELF-REPRODUCTION; BARBERTON MOUNTAIN LAND; FATTY-ACID VESICLES; SOUTH-AFRICA; EXPERIMENTAL SILICIFICATION; WESTERN-AUSTRALIA; ONVERWACHT GROUP; MICROFOSSILS; MARS; MICROORGANISMS AB In an attempt to establish reliable criteria for the identification of potential fossil life in extraterrestrial materials, the fossilizable characteristics of bacteria, namely, size, shape, cell wall texture, association, and colony formation, are described, and an overview is given of the ways in which fossil bacteria are preserved las compressions in fine-grained sediments; preservation in amber; permineralized by silica; replacement by minerals such (as silica, pyrite, Fe/Mn oxides, calcite, phosphate, and siderite; or as molds in minerals). The problem of confounding minerally replaced bacteria with non biological structures having a bacterial morphology is addressed. Examples of fossilized bacteria from the Early Archaean through to the Recent are used to illustrate the various modes of preservation and the morphology of fossil bacteria. C1 NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. RP Westall, F (reprint author), NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, SN2, Houston, TX 77058 USA. NR 114 TC 83 Z9 85 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 1999 VL 104 IS E7 BP 16437 EP 16451 DI 10.1029/1998JE900051 PG 15 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 218ZT UT WOS:000081583000001 ER PT J AU Catling, DC AF Catling, DC TI A chemical model for evaporites on early Mars: Possible sedimentary tracers of the early climate and implications for exploration SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Review ID MARTIAN METEORITE ALH84001; LOW-TEMPERATURE; SNC METEORITES; CO2 GREENHOUSE; ATMOSPHERE; SOIL; CARBONATES; MINERALS; RATES; WATER AB Martian geomorphology seems to indicate extensive hydrological activity during the Noachian era. Liquid water at the surface would require a large greenhouse effect that is widely hypothesized to have been caused by a high partial pressure of atmospheric carbon dioxide, P-CO2. A sedimentation model driven by sequential evaporation is used to calculate the evaporite mineral sequence in a closed basin lake subject to high P-CO2. The initial fluid is derived from weathered igneous rock similar to Martian meteorite basalts. Siderite (FeCO3) is always the first major carbonate to precipitate. Thus siderite is predicted to be an important facies component in ancient Martian sediments along with silica, which is also an early precipitate. These would form varves in lakes that undergo cycles of evaporation and water recharge. After silica and siderite, the sequence is magnesian calcite, nearly pure hydromagnesite, and gypsum, followed by highly soluble salts like NaCl. The presence of siderite sediments generally requires an atmospheric P-CO2 level in excess of similar to 0.1 bar, otherwise iron silicates (such as greenalite) would form. This may be used in exploration as an observational test on the past atmospheric composition of Mars, subject to consideration of the depositional environment. At P-CO2 of approximately several bar, gypsum precipitation could occur before calcite upon evaporation if the initial SO42-:Ca2+ ratio is high and there is no water recharge. The predicted carbonate sequence upon evaporation is generally consistent with recent hypotheses suggesting traces of evaporite carbonates in some Martian meteorites. Several mechanisms destroy or obscure carbonates at the Martian surface. Consequently, in situ analysis of the interior of ejecta from recent impact craters lying within sedimentary basins may offer the most practical approach to future exploration of ancient carbonate sediments. C1 NASA, Ames Res Ctr, SETI Inst, Div Space Sci, Moffett Field, CA 94035 USA. RP Catling, DC (reprint author), NASA, Ames Res Ctr, SETI Inst, Div Space Sci, Mail Stop 245-3, Moffett Field, CA 94035 USA. RI Catling, David/D-2082-2009; OI Catling, David/0000-0001-5646-120X NR 106 TC 83 Z9 83 U1 1 U2 10 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 1999 VL 104 IS E7 BP 16453 EP 16469 DI 10.1029/1998JE001020 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 218ZT UT WOS:000081583000002 ER PT J AU Herkenhoff, KE Vasavada, AR AF Herkenhoff, KE Vasavada, AR TI Dark material in the polar layered deposits and dunes on Mars SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID THERMAL MAPPER OBSERVATIONS; PARTICLE-SIZE; PARTICULATE MATERIALS; ASTRONOMICAL THEORY; VIKING 2; DUST; ICE; SURFACE; SAND; CAP AB Viking infrared thermal mapping and bistatic radar data suggest that the bulk density of the north polar erg material is much lower than that of the average Martian surface or of dark dunes at lower latitudes. We have derived a thermal inertia of 245-280 J m(-2) s(-1/2) K-1 (5.9-6.7 x 10(-3) cal cm(-2) s(-1/2) K-1) for the Proctor dune field and 25-150 J m(-2) s(-1/2) K-1 (0.6-3.6 x 10(-3) cal cm(-2) s(-1/2) K-1) for the north polar erg. The uniqueness of the thermophysical properties of the north polar erg material may be due to a unique polar process that has created them. The visible and near-infrared spectral reflectance of the erg suggests that the dark material may be composed of basalt or ferrous clays. These data are consistent with the dark material being composed of basaltic ash or filamentary sublimate residue (FSR) particles derived from erosion of the layered deposits. Dark dust may be preferentially concentrated at the surface of the layered deposits by the formation of FSR particles upon sublimation of water ice. Further weathering and erosion of these areas of exposed layered deposits may form the dark, saltating material that is found in both polar regions. Dark FSR particles may saltate for great distances before eventually breaking down into dust grains, re-mixing with the global dust reservoir, and being recycled into the polar layered deposits via atmospheric suspension. C1 CALTECH, Jet Prop Lab, Pasadena, CA USA. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Herkenhoff, KE (reprint author), US Geol Survey, 2255 N Gemini Dr, Flagstaff, AZ 86001 USA. NR 91 TC 28 Z9 29 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUL 25 PY 1999 VL 104 IS E7 BP 16487 EP 16500 DI 10.1029/1998JE000589 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 218ZT UT WOS:000081583000004 ER PT J AU Ostro, SJ Pravec, P Benner, LAM Hudson, RS Sarounova, L Hicks, MD Rabinowitz, DL Scotti, JV Tholen, DJ Wolf, M Jurgens, RF Thomas, ML Giorgini, JD Chodas, PW Yeomans, DK Rose, R Frye, R Rosema, KD Winkler, R Slade, MA AF Ostro, SJ Pravec, P Benner, LAM Hudson, RS Sarounova, L Hicks, MD Rabinowitz, DL Scotti, JV Tholen, DJ Wolf, M Jurgens, RF Thomas, ML Giorgini, JD Chodas, PW Yeomans, DK Rose, R Frye, R Rosema, KD Winkler, R Slade, MA TI Radar and optical observations of asteroid 1998 KY26 SO SCIENCE LA English DT Article ID NEAR-EARTH ASTEROIDS; DISRUPTION; FRAGMENTS; IMPACT; SHAPE AB Observations of near-Earth asteroid 1998 KY26 shortly after its discovery reveal a slightly elongated spheroid with a diameter of about 30 meters, a composition analogous to carbonaceous chondritic meteorites, and a rotation period of 10.7 minutes. which is an order of magnitude shorter than that measured for any other solar system object. The rotation is too rapid for 1998 KY26 to consist of multiple components bound together just by their mutual gravitational attraction. This monolithic object probably is a fragment derived from cratering or collisional destruction of a much larger asteroid. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Acad Sci Czech Republ, Inst Astron, CZ-25165 Ondrejov, Czech Republic. Washington State Univ, Sch Elect Engn & Comp Sci, Pullman, WA 99164 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Hawaii, Inst Astron, Honolulu, HI 96822 USA. Charles Univ, Astron Inst, CZ-18000 Prague, Czech Republic. RP Ostro, SJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Pravec, Petr/G-9037-2014 NR 38 TC 43 Z9 44 U1 1 U2 1 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD JUL 23 PY 1999 VL 285 IS 5427 BP 557 EP 559 DI 10.1126/science.285.5427.557 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 219LV UT WOS:000081609500029 ER PT J AU Yeomans, DK Antreasian, PG Cheng, A Dunham, DW Farquhar, RW Gaskell, RW Giorgini, JD Helfrich, CE Konopliv, AS McAdams, JV Miller, JK Owen, WM Thomas, PC Veverka, J Williams, BG AF Yeomans, DK Antreasian, PG Cheng, A Dunham, DW Farquhar, RW Gaskell, RW Giorgini, JD Helfrich, CE Konopliv, AS McAdams, JV Miller, JK Owen, WM Thomas, PC Veverka, J Williams, BG TI Estimating the mass of asteroid 433 Eros during the NEAR spacecraft flyby SO SCIENCE LA English DT Article ID 253-MATHILDE; 433-EROS; MISSION; ORBIT AB The Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 3830 kilometers of asteroid 433 Eros on 23 December 1998. The gravitational perturbation on NEAR was evident in the spacecraft tracking data. Ground-based Doppler and range tracking of the spacecraft as well as spacecraft images of the asteroid's center of figure and surface features were used to determine the mass and rotation pole of Eros. The mass of Eros is (7.2 +/- 1.8) x 10(18) grams and, coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a bulk density of 2.5 +/- 0.8 grams per cubic centimeter. The rotation pole position is 15.6 (+/-3.7) degrees in right ascension and 16.4 (+/-1.8) degrees in declination, which is consistent with ground-based and NEAR imaging team observations. C1 CALTECH, Jet Prop Lab, Nav & Flight Mech Sect, Pasadena, CA 91109 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Cornell Univ, Ithaca, NY 14853 USA. RP Yeomans, DK (reprint author), CALTECH, Jet Prop Lab, Nav & Flight Mech Sect, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 12 TC 37 Z9 37 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD JUL 23 PY 1999 VL 285 IS 5427 BP 560 EP 561 DI 10.1126/science.285.5427.560 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 219LV UT WOS:000081609500030 ER PT J AU Veverka, J Thomas, PC Bell, JF Bell, M Carcich, B Clark, B Harch, A Joseph, J Martin, P Robinson, M Murchie, S Izenberg, N Hawkins, E Warren, J Farquhar, R Cheng, A Dunham, D Chapman, C Merline, WJ McFadden, L Wellnitz, D Malin, M Owen, WM Miller, JK Williams, BG Yeomans, DK AF Veverka, J Thomas, PC Bell, JF Bell, M Carcich, B Clark, B Harch, A Joseph, J Martin, P Robinson, M Murchie, S Izenberg, N Hawkins, E Warren, J Farquhar, R Cheng, A Dunham, D Chapman, C Merline, WJ McFadden, L Wellnitz, D Malin, M Owen, WM Miller, JK Williams, BG Yeomans, DK TI Imaging of asteroid 433 Eros during NEAR's flyby reconnaissance SO SCIENCE LA English DT Article ID INFRARED SPECTROMETER; MULTISPECTRAL IMAGER; PHYSICAL-PROPERTIES; RENDEZVOUS MISSION; 433-EROS; 243-IDA; SHAPE; SATELLITE; DISCOVERY; DACTYL AB During the 23 December 1998 flyby of asteroid 433 Eros, the Near-Earth Asteroid Rendezvous (NEAR) spacecraft obtained 222 images of Eros, as well as supporting spectral observations. The images cover slightly more than two-thirds of Eros (best resolution is similar to 400 meters per pixel) and reveal an elongated, cratered body with a linear feature extending for at least 20 kilometers. Our observations show that Eros has dimensions of 33 X 13 X 13 kilometers. The volume, combined with the mass determined by the NEAR radio science experiment, Leads to a density of 2.5 +/- 0.8 grams per cubic centimeter. This relatively high density, and the presence of an extensive Linear feature, suggest that Eros may be a structurally coherent body. C1 Cornell Univ, Ithaca, NY 14853 USA. Northwestern Univ, Dept Geol Sci, Evanston, IL 60208 USA. Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. SW Res Inst, Boulder, CO 80302 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. Main Space Sci Syst Inc, San Diego, CA USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Veverka, J (reprint author), Cornell Univ, Space Sci Bldg, Ithaca, NY 14853 USA. RI Wellnitz, Dennis/B-4080-2012; McFadden, Lucy-Ann/I-4902-2013; Murchie, Scott/E-8030-2015; Izenberg, Noam/F-3952-2015 OI McFadden, Lucy-Ann/0000-0002-0537-9975; Murchie, Scott/0000-0002-1616-8751; Izenberg, Noam/0000-0003-1629-6478 NR 24 TC 45 Z9 45 U1 0 U2 0 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD JUL 23 PY 1999 VL 285 IS 5427 BP 562 EP 564 DI 10.1126/science.285.5427.562 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 219LV UT WOS:000081609500031 ER PT J AU Dyall, KG van Lenthe, E AF Dyall, KG van Lenthe, E TI Relativistic regular approximations revisited: An infinite-order relativistic approximation SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID DIRAC-EQUATION; PERTURBATION-THEORY; HAMILTONIANS AB The concept of the regular approximation is presented as the neglect of the energy dependence of the exact Foldy-Wouthuysen transformation of the Dirac Hamiltonian. Expansion of the normalization terms leads immediately to the zeroth-order regular approximation (ZORA) and first-order regular approximation (FORA) Hamiltonians as the zeroth- and first-order terms of the expansion. The expansion may be taken to infinite order by using an un-normalized Foldy-Wouthuysen transformation, which results in the ZORA Hamiltonian and a nonunit metric. This infinite-order regular approximation, IORA, has eigenvalues which differ from the Dirac eigenvalues by order E-3/c(4) for a hydrogen-like system, which is a considerable improvement over the ZORA eigenvalues, and similar to the nonvariational FORA energies. A further perturbation analysis yields a third-order correction to the IORA energies, TIORA. Results are presented for several systems including the neutral U atom. The IORA eigenvalues for all but the 1s spinor of the neutral system are superior even to the scaled ZORA energies, which are exact for the hydrogenic system. The third-order correction reduces the IORA error for the inner orbitals to a very small fraction of the Dirac eigenvalue. (C) 1999 American Institute of Physics. [S0021-9606(99)30128-8]. C1 NASA, Thermosci Inst, Ames Res Ctr, Moffett Field, CA 94035 USA. Vrije Univ Amsterdam, Afdeling Theoret Chem, NL-1081 HV Amsterdam, Netherlands. RP Dyall, KG (reprint author), NASA, Thermosci Inst, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. NR 9 TC 115 Z9 113 U1 4 U2 12 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 JUL 22 PY 1999 VL 111 IS 4 BP 1366 EP 1372 DI 10.1063/1.479395 PG 7 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 215QQ UT WOS:000081393600004 ER PT J AU Edelson, R Vaughan, S Warwick, R Puchnarewicz, E George, I AF Edelson, R Vaughan, S Warwick, R Puchnarewicz, E George, I TI The ROSAT wide field camera extragalactic survey SO MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY LA English DT Article DE surveys; galaxies : active; BL Lacertae objects : general; galaxies : Seyfert; ultraviolet : galaxies; X-rays : galaxies ID ALL-SKY SURVEY; EXTREME-ULTRAVIOLET SOURCES; LINE SEYFERT-1 GALAXIES; ACTIVE GALACTIC NUCLEI; X-RAY-SPECTRA; SOURCE CATALOG; QUASARS; AGN; SPECTROPHOTOMETRY; IDENTIFICATION AB We report the results of a new analysis of the ROSAT Wide Field Camera (WFC) all-sky survey data, designed to detect extragalactic sources of extreme ultraviolet (EW) radiation in regions of low Galactic N(H). We identify a total of 19 active galactic nuclei (AGN), more than double the number of confirmed AGN in the published WFC (2RE) survey. Our sample contains eight narrow-line Seyfert 1 galaxies, making this the first reasonably sized, complete sample of these extreme AGN, along with six broad-line Seyfert 1s and five BL Lacertae objects. These EUV-selected sources typically have steep soft X-ray spectra with a mean power-law energy index alpha(X) approximate to -2. The derived AGN luminosity function is rather flat and appears to cut off above a luminosity of 10(46) erg s(-1) kev(-1), measured monochromatically at 200 eV. Narrow-line Seyfert Is account for roughly half of the local (z approximate to 0) volume emissivity in the EW band. C1 Univ Leicester, Dept Phys & Astron, Xray Astron Grp, Leicester LE1 7RH, Leics, England. Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA. UCL, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Edelson, R (reprint author), Univ Leicester, Dept Phys & Astron, Xray Astron Grp, Leicester LE1 7RH, Leics, England. EM rae@star.le.ac.uk NR 37 TC 14 Z9 14 U1 0 U2 0 PU WILEY-BLACKWELL PI MALDEN PA COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA SN 0035-8711 J9 MON NOT R ASTRON SOC JI Mon. Not. Roy. Astron. Soc. PD JUL 21 PY 1999 VL 307 IS 1 BP 91 EP 98 DI 10.1046/j.1365-8711.1999.02628.x PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223AU UT WOS:000081818200012 ER PT J AU Scott, DC Herman, RL Webster, CR May, RD Flesch, GJ Moyer, EJ AF Scott, DC Herman, RL Webster, CR May, RD Flesch, GJ Moyer, EJ TI Airborne Laser Infrared Absorption Spectrometer (ALIAS-II) for in situ atmospheric measurements of N2O, CH4, CO, HCl, and NO2 from balloon or remotely piloted aircraft platforms SO APPLIED OPTICS LA English DT Article ID STRATOSPHERIC MEASUREMENTS; NORTHERN-HEMISPHERE; TROPOSPHERIC OZONE; NITROGEN-OXIDES; FAST-RESPONSE; EMISSIONS; TRANSPORT; CHEMISTRY; INCREASE; IMPACT AB The Airborne Laser Infrared Absorption Spectrometer II (ALIAS-II) is a lightweight, high-resolution (0.0003-cm(-1)), scanning, mid-infrared absorption spectrometer based on cooled (80 K) lead-salt tunable diode laser sources. It is designed to make in situ measurements in the lower and middle stratosphere on either a balloon platform or high-altitude remotely piloted aircraft. Chemical species that can be measured precisely include long-lived tracers N2O and CH4, the shorter-lived tracer CO, and chemically active species HCl and NO2. Advances in electronic instrumentation developed for ALIAS-I, with the experience of more than 250 flights on board NASA's ER-2 aircraft., have been implemented in ALIAS-II. The two-channel spectrometer features an open cradle, multipass absorption cell to ensure minimal contamination from inlet and surfaces. Time resolution of the instrument is less than or equal to 3 s, allowing rapid in situ measurements with excellent spatial resolution. ALIAS-II has completed successful balloon flights from New Mexico, Alaska, and Brazil providing CH4 and N2O vertical profiles in the tropics, mid-latitudes, and high northern latitudes up to altitudes of 32 km. (C) 1999 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Scott, DC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM dcscott@igor.jpl.nasa.gov RI Herman, Robert/H-9389-2012 OI Herman, Robert/0000-0001-7063-6424 NR 48 TC 39 Z9 41 U1 0 U2 5 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD JUL 20 PY 1999 VL 38 IS 21 BP 4609 EP 4622 DI 10.1364/AO.38.004609 PG 14 WC Optics SC Optics GA 220MX UT WOS:000081670700022 PM 18323948 ER PT J AU Koshak, WJ Solakiewicz, RJ AF Koshak, WJ Solakiewicz, RJ TI Electro-optic lightning detector SO APPLIED OPTICS LA English DT Article ID FIELD CHANGES; FLORIDA AB The design, alignment, calibration, and field deployment of a solid-state lightning detector is described. The primary sensing component of the detector is a potassium dihydrogen phosphate electro-optic crystal that is attached in series to a flat-plate aluminum antenna: the antenna is exposed to the ambient thundercloud electric field. A semiconductor laser diode (lambda = 685 nm), polarizing optics, and the crystal are arranged in a Pockels cell configuration. Lightning-caused electric field changes are related to small changes in the transmission of laser light through the optical cell. Several hundred lightning electric field change excursions were recorded during five thunderstorms that occurred in the summer of 1998 at the NASA Marshall Space Flight Center in northern Alabama. (C) 1999 Optical Society of America. C1 NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. Chicago State Univ, Dept Math & Comp Sci, Chicago, IL 60628 USA. RP Koshak, WJ (reprint author), NASA, George C Marshall Space Flight Ctr, Global Hydrol & Climate Ctr, Huntsville, AL 35806 USA. EM william.koshak@msfc.nasa.gov NR 37 TC 7 Z9 7 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD JUL 20 PY 1999 VL 38 IS 21 BP 4623 EP 4634 DI 10.1364/AO.38.004623 PG 12 WC Optics SC Optics GA 220MX UT WOS:000081670700023 PM 18323949 ER PT J AU Barnes, RA Eplee, RE Patt, FS McClain, CR AF Barnes, RA Eplee, RE Patt, FS McClain, CR TI Changes in the radiometric sensitivity of SeaWiFS determined from lunar and solar-based measurements SO APPLIED OPTICS LA English DT Article ID ZONE COLOR SCANNER; NIMBUS-7 CZCS; CALIBRATION; RADIANCE; IMAGERY; OCEAN AB We report on the lunar and solar measurements used to determine the changes in the radiometric sensitivity of the Sea-viewing Wide Field-of-view Senses (SeaWiFS). Radiometric sensitivity is defined as the output from the instrument (or from one of the instrument bands) per unit spectral radiance at the instrument's input aperture. Knowledge of the long-term repeatability of the SeaWiFS measurements is crucial to maintaining the quality of the ocean scenes derived from measurements by the instrument. For SeaWiFS bands 1-6 (412-670 nm), the change in radiometric sensitivity is less than 0.2% for the period from November 1997 through November 1998. For band 7 (765 nm), the change is approximately 1.5% and for band 8 (865 nm) approximately SE. The rates of change of bands 7 and 8, which were linear with time for the first eight months of lunar measurements, are now slowing. The scatter in the data points about the trend lines in this analysis is less than 0.3% for all eight SeaWiFS bands. These results are based on monthly measurements of the moon. Daily solar measurements using an onboard diffuser show that the radiometric sensitivities of the SeaWiFS bands have changed smoothly during the time intervals between lunar measurements. Because SeaWiFS measurements have continued past November 1998, the results presented here are considered as a snapshot of the instrument performance as of that date. C1 Gen Sci Corp, Beltsville, MD 20705 USA. NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, SeaWiFS Project, Greenbelt, MD 20771 USA. RP Barnes, RA (reprint author), Gen Sci Corp, Beltsville, MD 20705 USA. EM rbarnes@calval.gsfc.nasa.gov NR 32 TC 80 Z9 83 U1 1 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD JUL 20 PY 1999 VL 38 IS 21 BP 4649 EP 4664 DI 10.1364/AO.38.004649 PG 16 WC Optics SC Optics GA 220MX UT WOS:000081670700026 PM 18323952 ER PT J AU Scoccimarro, R Frieman, JA AF Scoccimarro, R Frieman, JA TI Hyperextended cosmological perturbation theory: Predicting nonlinear clustering amplitudes SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; galaxies : clusters : general; large-scale structure of universe; methods : n-body simulations ID HIGHER-ORDER STATISTICS; LARGE-SCALE STRUCTURE; N-BODY SIMULATIONS; APM GALAXY SURVEY; CORRELATION HIERARCHY; INITIAL CONDITIONS; BBGKY HIERARCHY; DENSITY FIELDS; COSMIC FIELDS; POWER SPECTRA AB We consider the long-standing problem of predicting the hierarchical clustering amplitudes S-p in the strongly nonlinear regime of gravitational evolution. N-body results for the nonlinear evolution of the bispectrum (the Fourier transform of the three-point density correlation function) suggest a physically motivated Ansatz that yields the strongly nonlinear behavior of the skewness, S-3, starting from leading-order perturbation theory. When generalized to higher order (p > 3) polyspectra or correlation functions, this Ansatz leads to a good description of nonlinear amplitudes in the strongly nonlinear regime for both scale-free and cold dark matter models. Furthermore, these results allow us to provide a general fitting formula for the nonlinear evolution of the bispectrum that interpolates between the weakly and strongly nonlinear regimes, analogous to previous expressions for the power spectrum. C1 CITA, McLennan Phys Labs, Toronto, ON M5S 3H8, Canada. Fermi Natl Accelerator Lab, Fermilab Astrophys Ctr, NASA, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. RP Scoccimarro, R (reprint author), CITA, McLennan Phys Labs, 60 St George St, Toronto, ON M5S 3H8, Canada. NR 53 TC 82 Z9 84 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 20 PY 1999 VL 520 IS 1 BP 35 EP 44 DI 10.1086/307448 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RC UT WOS:000081395500003 ER PT J AU Horner, DJ Mushotzky, RF Scharf, CA AF Horner, DJ Mushotzky, RF Scharf, CA TI Observational tests of the mass-temperature relation for galaxy clusters SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : clusters : general; X-rays : galaxies ID X-RAY-CLUSTERS; FLUX-LIMITED SAMPLE; VELOCITY DISPERSION; BARYON FRACTION; VIRIAL MASSES; DARK-MATTER; EVOLUTION; CATALOG; OMEGA AB We examine the relationship between the mass and X-ray gas temperature of galaxy clusters using data drawn from the literature. Simple theoretical arguments suggest that the mass of a cluster is related to the X-ray temperature as M proportional to T-X(3/2). Virial theorem mass estimates based on cluster galaxy velocity dispersions seem to be accurately described by this scaling with a normalization consistent with that predicted by the simulations of Evrard, Metzler, and Navarro. X-ray mass estimates that employ spatially resolved temperature profiles also follow a T-X(3/2) scaling although with a normalization about 40% lower than that of the fit to the virial masses. However, the isothermal beta-model and X-ray surface brightness deprojection masses follow a steeper proportional to T-X(1.8-2.0) scaling. The steepness of the isothermal estimates is due to their implicitly assumed dark matter density profile of rho(r) proportional to r(-2) at large radii, whereas observations and simulations suggest that clusters follow steeper profiles [e.g., rho(r) proportional to r(-2.4)]. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Horner, DJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 46 TC 139 Z9 139 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 JUL 20 PY 1999 VL 520 IS 1 BP 78 EP 86 DI 10.1086/307437 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RC UT WOS:000081395500008 ER PT J AU Weaver, KA Wilson, AS Henkel, C Braatz, JA AF Weaver, KA Wilson, AS Henkel, C Braatz, JA TI X-ray emission from the prototypical LINER galaxy NGC 1052 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : individual (NGC 1052); galaxies : nuclei; galaxies : Seyfert; masers; X-rays : galaxies ID ACTIVE GALACTIC NUCLEI; WATER MASER EMISSION; SEYFERT-2 GALAXY; H2O MEGAMASERS; ASCA; REFLECTION; SPECTRUM; NGC-1068; DISKS; AGN AB We examine the 0.1-10.0 keV X-ray spectrum of the bright nuclear LINER galaxy NGC 1052, one of two elliptical galaxies known to contain a luminous H2O maser. The observed 2.0-10.0 keV spectrum is unusually flat (photon index Gamma similar to 0.2) and is best described as intrinsically power-law shaped nuclear flux that is either (1) attenuated by a complex absorber with similar to 70% of the nuclear flux absorbed by a column density of N-H similar to 3 x 10(23) cm(-2) and similar to 30% absorbed by a column density of N-H similar to 3-5 x 10(22) cm(-2) or (2) reprocessed, with the nuclear source blocked and the X-rays Compton reflected in our direction by high column density (greater than or equal to 10(24) cm(-2)) gas. The moderate equivalent width of the Fe K alpha line favors the dual absorption model as the most likely scenario. The 0.1-2.0 keV spectrum does not resemble the few times 10(6)-10(7) K thermal emission typically found in other elliptical galaxies, but instead is best described as nuclear X-rays leaking through a patchy absorber or scattered in our direction by low-density, ionized gas plus a 15%-20% contribution from a thermal component, which is most likely due to the galaxy. The absorption-corrected 2-10 keV luminosity of the nuclear source is L-X similar to 8 x 10(41) ergs s(-1) or L-X similar to 2 x 10(43) ergs s(-1) for the dual-absorption and Compton-reflection models, respectively. The absorbing and H2O masing gases appear to be spatially separate in this galaxy. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Max Planck Inst Radioastron, D-53121 Bonn, Germany. Natl Radio Astron Observ, Green Bank, WV 24944 USA. Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Weaver, KA (reprint author), NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 34 TC 33 Z9 33 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 JUL 20 PY 1999 VL 520 IS 1 BP 130 EP 136 DI 10.1086/307456 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RC UT WOS:000081395500014 ER PT J AU Jenkins, EB Tripp, TM Wozniak, PR Sofia, UJ Sonneborn, G AF Jenkins, EB Tripp, TM Wozniak, PR Sofia, UJ Sonneborn, G TI Spatial variability in the ratio of interstellar atomic deuterium to hydrogen. I. Observations toward delta Orionis by the interstellar medium absorption profile spectrograph SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : abundances; stars : individual (delta Orionis); ultraviolet : ISM ID BIG-BANG NUCLEOSYNTHESIS; MOLECULAR-HYDROGEN; D/H RATIO; GALACTIC EVOLUTION; CHEMICAL EVOLUTION; ALPHA ABSORPTION; CHARGE-TRANSFER; LYMAN-ALPHA; ABUNDANCE; LINES AB Studies of the abundances of deuterium in different astrophysical sites are of fundamental importance to answering the question about how much deuterium was produced during big bang nucleosynthesis and what fraction of it was destroyed later. With this in mind, we used the Interstellar Medium Absorption Profile Spectrograph (IMAPS) on the ORFEUS-SPAS II mission to observe at a wavelength resolution of 4 km s(-1) (FWHM) the Ly delta and Ly epsilon absorption features produced by interstellar atomic deuterium in the spectrum of delta Ori A. A chi(2) analysis indicated that 0.96 < N(D I) < 1.45 x 10(15) cm(-2) at a 90% level of confidence, and the gas is at a temperature of about 6000 K. In deriving these results, we created a template for the velocity profile defined by seven different N I transitions recorded at a high signal-to-noise ratio. Extra free parameters in the analysis allowed for the additional uncertainties that could arise from various sources of systematic error. To derive a value for D/H, we measured the Ly alpha absorption features in 57 spectra of delta Ori in the IUE archive, with the objective of arriving at an H I column density more accurate than those reported by other investigators. From our measurement of N(H I) = 1.56 x 10(20) cm(-2), we found that N(D I)/N(H I) = 7.4(-1.3)(+1.9) x 10(-6) (90% confidence). Systematic errors in the derivation of N(H I) probably dominate over the very small formal error, but their relative value should be smaller than that for N(D I). Our result for D/H contrasts with the more general finding along other lines of sight that D/H approximate to 1.5 x 10(-5). The underabundance of D toward delta Ori A is not accompanied by an overabundance of N or O relative to H, as one might expect if the gas were subjected to more stellar processing than usual. C1 Princeton Univ Observ, Princeton, NJ 08544 USA. Villanova Univ, Dept Astron & Astrophys, Villanova, PA 19085 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Princeton Univ Observ, Peyton Hall, Princeton, NJ 08544 USA. RI Jenkins, Edward/P-5684-2014 OI Jenkins, Edward/0000-0003-1892-4423 NR 97 TC 84 Z9 84 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 JUL 20 PY 1999 VL 520 IS 1 BP 182 EP 195 DI 10.1086/307447 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RC UT WOS:000081395500020 ER PT J AU Digel, SW Aprile, E Hunter, SD Mukherjee, R Xu, F AF Digel, SW Aprile, E Hunter, SD Mukherjee, R Xu, F TI Egret observations of the diffuse gamma-ray emission in Orion: Analysis through cycle 6 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : observations; ISM : molecules; radio lines : ISM ID MOLECULAR CLOUDS; RADIAL-DISTRIBUTION; GALACTIC PLANE; SOLAR CIRCLE; COSMIC-RAY; MILKY-WAY; CO SURVEY; MONOCEROS; TELESCOPE; GAS AB We present a study of the high-energy diffuse emission observed toward Orion by EGRET on the Compton Gamma Ray Observatory. The total exposure by EGRET in this region has increased by more than a factor of 2 since a previous study. A simple model for the diffuse emission adequately fits the data; no significant point sources are detected in the region studied (l = 195 degrees to 220 degrees and b = -25 degrees to -10 degrees) in either the composite data set or in two separate groups of EGRET viewing periods considered. The gamma-ray emissivity in Orion is found to be (1.65 +/- 0.11) x 10(-26) s(-1) sr(-1) for E > 100 MeV, and the differential emissivity is well described as a combination of contributions from cosmic-ray electrons and protons with approximately the local density. The molecular mass calibrating ratio is N(H-2)/W-CO = (1.35 +/- 0.15) x 10(20) cm(-2) (K km s(-1))(-1). C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. Columbia Univ, Dept Phys, New York, NY 10027 USA. Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA. Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA. RP NASA, Goddard Space Flight Ctr, USRA, Code 660-2, Greenbelt, MD 20771 USA. RI Hunter, Stanley/D-2942-2012 NR 32 TC 24 Z9 24 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 JUL 20 PY 1999 VL 520 IS 1 BP 196 EP 203 DI 10.1086/307455 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RC UT WOS:000081395500021 ER PT J AU Ko, YK Mukai, K Smale, AP White, NE AF Ko, YK Mukai, K Smale, AP White, NE TI ASCA observation of the dipping X-ray source XB 1916-053 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (XB 1916-053); X-rays : stars ID K LINE EMISSION; EXOSAT OBSERVATIONS; GINGA OBSERVATIONS; 4U 1915-05; BINARIES; ABSORPTION; DISCOVERY AB We present the results of timing and spectral studies of the dipping X-ray source XB 1916-053, observed by ASCA during its performance verification phase. The detected dipping activity is consistent with previous observations, with a period of 3008 s and an intermittent secondary dip observed roughly 0.4 out of phase with the primary dip. The energy spectra of different intensity states are fitted with a power law with partial covering fraction absorption and interstellar absorption. The increase in the hardness ratio during the primary and secondary dips, and the increase in the covering fraction and column density with decreasing X-ray intensity, all imply that the dipping is caused by the photoabsorbing materials that have been suggested to be where the accreted flow hits the outer edge of the disk materials. The spectra at all intensity levels show no apparent evidence for Fe or Ne emission lines. This may be due to the low metal abundance in the accretion flow. Alternatively, the X-ray luminosity of the central source may be too weak to excite emission lines, which are assumed to be produced by X-ray photoionization of the disk materials. C1 NASA, High Energy Astrophys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Ko, YK (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. RI White, Nicholas/B-6428-2012 OI White, Nicholas/0000-0003-3853-3462 NR 16 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 JUL 20 PY 1999 VL 520 IS 1 BP 292 EP 297 DI 10.1086/307427 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RC UT WOS:000081395500032 ER PT J AU Kaaret, P Piraino, S Bloser, PF Ford, EC Grindlay, JE Santangelo, A Smale, AP Zhang, W AF Kaaret, P Piraino, S Bloser, PF Ford, EC Grindlay, JE Santangelo, A Smale, AP Zhang, W TI Strong-field gravity and X-ray observations of 4U 1820-30 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; gravitation; relativity; stars : individual (4U 1820-30); stars : neutron; X-rays : stars ID QUASI-PERIODIC OSCILLATIONS; VARIABILITY; BINARIES; SPECTRA AB The behavior of quasi-periodic oscillations (QPOs) at frequencies near 1 kHz in the X-ray emission from the neutron star X-ray binary 4U 1820-30 has been interpreted as evidence for the existence of the marginally stable orbit, a key prediction of strong-field general relativity. The signature of the marginally stable orbit is a saturation in QPO frequency (assumed to track inner disk radius) versus mass accretion rate. Previous studies of 4U 1820-30 have used X-ray count rate as an indicator of mass accretion rate. However, X-ray count rate is known to not correlate robustly with mass accretion rate or QPO frequency in other sources. Here, we examine the QPO frequency dependence on two other indicators of mass accretion rate: energy flux and X-ray spectral shape. Using either of these indicators, we find that the QPO frequency saturates at high mass accretion rates. We interpret this as strong evidence for the existence of the marginally stable orbit. C1 Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. CNR, IFCAI, I-90146 Palermo, Italy. Dipartimento Fis & Astron, I-90123 Palermo, Italy. Univ Amsterdam, Astron Inst Anton Pannekoek, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kaaret, P (reprint author), Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA. NR 26 TC 42 Z9 42 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 JUL 20 PY 1999 VL 520 IS 1 BP L37 EP L40 DI 10.1086/312141 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 215RD UT WOS:000081395600010 ER PT J AU Agena, SM Pusey, ML Bogle, IDL AF Agena, SM Pusey, ML Bogle, IDL TI Protein solubility modeling SO BIOTECHNOLOGY AND BIOENGINEERING LA English DT Article DE protein; equilibrium; crystallization; solubility product; activity coefficient ID LYSOZYME SOLUBILITY; LIQUID-MIXTURES; PRECIPITATION; PH; THERMODYNAMICS AB A thermodynamic framework (UNIQUAC model with temperature dependent parameters) is applied to model the salt-induced protein crystallization equilibrium, i.e., protein solubility. The framework introduces a term for the solubility product describing protein transfer between the liquid and solid phase and a term for the solution behavior describing deviation from ideal solution. Protein solubility is modeled as a function of salt concentration and temperature for a four-component system consisting of a protein, pseudo solvent (water and buffer), cation, and anion (salt). Two different systems, lysozyme with sodium chloride and concanavalin A with ammonium sulfate, are investigated. Comparison of the modeled and experimental protein solubility data results in an average root mean square deviation of 5.8%, demonstrating that the model closely follows the experimental behavior. Model calculations and model parameters are reviewed to examine the model and protein crystallization process. (C) 1999 John Wiley & Sons, Inc. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ London Univ Coll, Dept Chem & Biochem Engn, London WC1E 7JE, England. RP Agena, SM (reprint author), NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. NR 28 TC 19 Z9 21 U1 1 U2 6 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0006-3592 J9 BIOTECHNOL BIOENG JI Biotechnol. Bioeng. PD JUL 20 PY 1999 VL 64 IS 2 BP 144 EP 150 DI 10.1002/(SICI)1097-0290(19990720)64:2<144::AID-BIT3>3.0.CO;2-P PG 7 WC Biotechnology & Applied Microbiology SC Biotechnology & Applied Microbiology GA 205XD UT WOS:000080845100003 PM 10397850 ER PT J AU Garcia-Gorriz, E Vazquez-Cuervo, J AF Garcia-Gorriz, E Vazquez-Cuervo, J TI Ocean-atmosphere coupling in the Mediterranean Sea from TOPEX/POSEIDON, ERS1 and AVHRR data SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID ALBORAN SEA; CIRCULATION; VARIABILITY; STRESS; WIND AB The objective of this work is to evaluate the patterns of the ocean-atmosphere coupling in the Mediterranean sea using the statistical analysis of the time series of three satellite measured variables: wind stress curl computed from the surface wind velocities measured by the European Remote Sensing Satellite-ERS1, sea level anomalies from the merged ERS1-TOPEX/POSEIDON altimetric data and the sea surface temperature from the NOAA/NASA Pathfinder AVHRR Oceans Project. This study examines the ocean-atmosphere coupling patterns in time and space through a canonical correlation analysis of the fields. The wide and exhaustive coverage of the oceanic and atmospheric fields from satellites (such as TOPEX/POSEIDON and ERS1) allow a potential detailed inspection of the coupling. In this study we assess the role of wind stress and/or sea surface temperature space/time variations as forcing mechanisms of the sea level variability for the total 440 day duration (from October 1992 to December 1993) of the three satellite data sets in the different Mediterranean sub-basins. The linear barotropic vorticity equation is computed in order to estimate if the Mediterranean sea level response to wind forcing is barotropic. Results indicate that except for the Strait of Sicily and the Adriatic sea the barotropic response is not dominant. From the canonical correlation analysis, a correlation of 0.57 for the first mode between the sea level anomaly and the wind stress curl indicates a significant local coupling between them, especially in areas of the Eastern Mediterranean. Two uncoupled annual cycles are found in the sea surface temperature data. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Garcia-Gorriz, E (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 23 TC 4 Z9 4 U1 0 U2 0 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 JUL 20 PY 1999 VL 20 IS 11 BP 2127 EP 2147 DI 10.1080/014311699212155 PG 21 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 214CN UT WOS:000081310200001 ER PT J AU Sobieski, PW Craeye, C Bliven, LF AF Sobieski, PW Craeye, C Bliven, LF TI Scatterometric signatures of multivariate drop impacts on fresh and salt water surfaces SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID RING-WAVES; RAIN; SCATTERING; RADAR; VIEW AB Microwave signatures of the ocean surface are affected by wind and rain. To support the development of theoretical models for remote sensing applications, radar scatterometry experiments at 13.5 and 36 GHz with VV polarization were conducted at the Rain-Sea Interaction Facility at NASA Wallops. Backscatterings from rain drop impacts on fresh and salt water surfaces were measured with an incidence angle of 30 degrees for eight different drop sizes. Results are also presented for terminal and non-terminal fall velocities. Surface features were imaged by an ultrahigh-speed digital camera synchronized with radar data acquisition and their geometrical characteristics were determined. Backscattered powers from crowns, craters, stalks and ring-waves were measured and compared. These measurements confirm that for slant radar configurations, ring-waves are the dominant scattering contribution, even though stalk scattering is not negligible. C1 Univ Catholique Louvain, B-1348 Louvain, Belgium. NASA, Goddard Space Flight Ctr, WFF, Lab Hydrospher Proc, Wallops Island, VA 23337 USA. RP Sobieski, PW (reprint author), Univ Catholique Louvain, B-1348 Louvain, Belgium. RI bliven, francis/E-1450-2012 NR 23 TC 27 Z9 27 U1 1 U2 5 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 JUL 20 PY 1999 VL 20 IS 11 BP 2149 EP 2166 DI 10.1080/014311699212164 PG 18 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 214CN UT WOS:000081310200002 ER PT J AU Otterman, J Brakke, TW Fuchs, M Lakshmi, V Cadeddu, M AF Otterman, J Brakke, TW Fuchs, M Lakshmi, V Cadeddu, M TI Longwave emission from a plant soil surface as a function of the view direction: dependence on the canopy architecture SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID SCATTERING; MODEL AB We examine the longwave emission from a structured surface: soil partially covered by an incomplete (not very dense) plane-parallel canopy. The soil(seen through the gaps) is assumed to be at uniform temperature and warmer than the plants. Different canopy architectures are constructed by varying the ratio re of the projection of the vertical elements (thin cylinders, or blades with a uniform distribution in azimuth) to the area of the horizontal facets, while specifying that the gap function (the probability of non-interception, that is, of seeing the soil through the canopy) remains constant (at about 0.5) when viewing the surface at a zenith angle theta(v) of 50 degrees. Assuming initially that the temperature is uniform throughout the canopy, we note that the observed emission (the measured surface temperature) decreases with increasing zenith angle of observation, as more canopy and less soil is seen in the field of view. The pattern of the change is commonly applied to infer both canopy and soil temperatures. When the architecture tends to be more vertical las quantified by a higher kappa), the pattern is modified: the emission becomes appreciably higher in the nadir region (more soil is seen) but lower towards the limb, that is, at larger theta(v) (more plants are seen). Thus, when interpreting the pattern of the emission for a range of theta(v) to estimate the temperature difference between the soil and the canopy, an overestimate results if the tendency to the vertical is underestimated. The analysis of the radiance as a function of the view zenith angle is extended to a canopy with plant-element temperature increasing with the optical depth in the canopy (where the rate specifying the increase of the emission from the plants with the optical depth is adjusted to maintain the continuity of the temperature at the canopy bottom (canopy/soil interface). The pattern with theta(v) of the emitted radiance is, in these cases, closely similar to that for a warm soil/uniform-temperature canopy, especially if the canopy optical depth is large. This analysis indicates that information about the properties of the canopy (optical (radiative transfer) depth, and characterization of the architecture) should be available for an appropriate interpretation of the longwave radiances in terms of the canopy temperature, and through this interpretation, assessment of the evapotranspiration rate. Inversion of the solar bidirectional reflectances measured simultaneously with the longwave measurements is likely to be the best source of this information. C1 NASA, Goddard Space Flight Ctr, LAOR Inc, Greenbelt, MD 20771 USA. Agr Res Org, Volcani Ctr, Inst Soils & Water, IL-50250 Bet Dagan, Israel. NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. RP Otterman, J (reprint author), NASA, Goddard Space Flight Ctr, LAOR Inc, Code 910-4, Greenbelt, MD 20771 USA. RI Lakshmi, Venkat/I-3078-2016 OI Lakshmi, Venkat/0000-0001-7431-9004 NR 13 TC 15 Z9 18 U1 1 U2 5 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 JUL 20 PY 1999 VL 20 IS 11 BP 2195 EP 2201 DI 10.1080/014311699212191 PG 7 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 214CN UT WOS:000081310200005 ER PT J AU Chauhan, NS Lang, RH AF Chauhan, NS Lang, RH TI Radar backscattering from alfalfa canopy: a clump modelling approach SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID ELECTROMAGNETIC BACKSCATTERING; HALF-SPACE; VEGETATION; SCATTERING; LAYER AB Vegetation in the microwave regime can be modelled by replacing vegetation scattering elements (stems, leaflets, etc.) by their dielectric equivalents. Unlike most vegetation, the scattering elements in the alfalfa canopy are not independent of one another at L-band and they also exhibit a unique geometrical structure. This structural feature of the alfalfa canopy has been incorporated into a modelling procedure to predict radar response from the canopy. An alfalfa plant is modelled as a conical clump of stems that are clustered with leaflets. The scattering amplitude of this structural unit (clump) is calculated by the coherent addition of amplitudes from the individual stems. The calculations are done for L-band, where the leaflet size as well as the average distance among the leaflets are small compared to the wavelength. Careful ground and canopy geometry data were collected during the WASHITA'92 experiment conducted in Chickasha, Oklahoma in June 1992. The clump characteristics such as the number of stems with a common root, clump geometry, clustering factor of the leaves, etc., were measured in addition to sizes, density distributions of the stems and the leaves. These measured parameters of the alfalfa canopy have been used in a distorted Born approximation to compute the backscattering coefficient. For comparison, the backscatter from the alfalfa canopy is also computed using a conventional modelling procedure. In this approach, the vegetation is modelled as a random, independent, non-clump distribution of stems and leaflets. The theoretical results with and without the clumping structure are compared with one another and also with the experimental data obtained by the NASA truck based radar. There is a reasonable agreement between the clump model and the data. More importantly, the present study emphasizes the importance of coherence effects among different scattering elements in a canopy and the need to model them by identifying a respective structural unit for a particular canopy. C1 NASA, Goddard Space Flight Ctr, Biospher Sci Branch, GWU, Greenbelt, MD 20771 USA. George Washington Univ, Dept Elect Engn & Comp Sci, Washington, DC 20052 USA. RP Chauhan, NS (reprint author), Raytheon Co, 4400 Forbes Blvd, Lanham, MD 20706 USA. NR 22 TC 15 Z9 16 U1 1 U2 1 PU TAYLOR & FRANCIS LTD PI LONDON PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUL 20 PY 1999 VL 20 IS 11 BP 2203 EP 2220 DI 10.1080/014311699212209 PG 18 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 214CN UT WOS:000081310200006 ER PT J AU Kuang, WJ Bloxham, J AF Kuang, WJ Bloxham, J TI Numerical modeling of magnetohydrodynamic convection in a rapidly rotating spherical shell: Weak and strong field dynamo action SO JOURNAL OF COMPUTATIONAL PHYSICS LA English DT Article DE rotating fluid; convection; magnetohydrodynamics; geomagnetism; dynamo processes ID 3-DIMENSIONAL KINEMATIC DYNAMOS; EARTHS INNER-CORE; THERMAL-CONVECTION; DRIVEN; GEODYNAMO; SIMULATION; SYSTEMS; MANTLE AB In this paper we describe a numerical model for investigating magnetohydrodynamic (MHD) convective flow of a Boussinesq fluid in a rapidly rotating spherical shell, driven by the buoyancy forces arising from incoming buoyant flux at the inner core boundary. The model is designed to investigate the generation of magnetic field in the Earth's fluid outer core. Our model differs from that of G. A. Glatzmaier and P. H. Roberts, who have recently investigated this problem, in several aspects. We apply a different physical approximation in the force balance of the system: instead of viscous stress, we use an axisymmetric inertial force to balance the axial magnetic torque arising from the Lorentz force; we use a mixed spectral-finite difference algorithm for better parallelization of the code; and apply different boundary conditions. We describe our numerical model in detail, and we test it by examining purely thermal convection in a rapidly relating fluid shell and by examining Kumar-Roberts kinematic dynamos (modified for the spherical shell). Our results agree well with those of the previous studies. We also present a weak-field dynamo solution in a very simplified system and strong-field dynamo solutions in a more realistic system. (C) 1999 Academic Press. C1 NASA, Space Geodesy Branch, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. RP NASA, Space Geodesy Branch, Goddard Space Flight Ctr, Code 926, Greenbelt, MD 20771 USA. EM kuang@santafe.gsfc.nasa.gov RI Kuang, Weijia/K-5141-2012 OI Kuang, Weijia/0000-0001-7786-6425 NR 41 TC 115 Z9 119 U1 2 U2 9 PU ACADEMIC PRESS INC ELSEVIER SCIENCE PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0021-9991 EI 1090-2716 J9 J COMPUT PHYS JI J. Comput. Phys. PD JUL 20 PY 1999 VL 153 IS 1 BP 51 EP 81 DI 10.1006/jcph.1999.6274 PG 31 WC Computer Science, Interdisciplinary Applications; Physics, Mathematical SC Computer Science; Physics GA 218DY UT WOS:000081539000004 ER PT J AU Hoell, JM AF Hoell, JM TI Pacific exploratory mission-tropics A, Part 2 - Preface SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Editorial Material ID PEM-WEST-B; FEBRUARY-MARCH 1994; UPPER TROPOSPHERE; CHEMICAL CHARACTERISTICS; CONTINENTAL OUTFLOW; HYDROGEN RADICALS; PHOTOCHEMISTRY; DISTRIBUTIONS; BASIN; OCEAN C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Hoell, JM (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 27 TC 5 Z9 5 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16177 EP 16180 PG 4 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000021 ER PT J AU Board, AS Fuelberg, HE Gregory, GL Heikes, BG Schultz, MG Blake, DR Dibb, JE Sandholm, ST Talbot, RW AF Board, AS Fuelberg, HE Gregory, GL Heikes, BG Schultz, MG Blake, DR Dibb, JE Sandholm, ST Talbot, RW TI Chemical characteristics of air from differing source regions during the Pacific Exploratory Mission-Tropics A (PEM-Tropics A) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID SOUTH-ATLANTIC OCEAN; BIOMASS BURNING EMISSIONS; OZONE PRODUCTION; CONTINENTAL OUTFLOW; BOUNDARY-LAYER; UNITED-STATES; WEST-COAST; TROPOSPHERE; AFRICA; HYDROPEROXIDES AB Ten-day backward trajectories are used to determine the origins of air parcels arriving at airborne DC-8 chemical measurement sites during NASA's Pacific Exploratory Mission-Tropics A (PEM-T) that was conducted during August-October 1996. Those sites at which the air had a common geographical origin and transport history are grouped together, and statistical measures of chemical characteristics are computed. Temporal changes in potential temperature are used to determine whether trajectories experience a significant convective influence during the 10-day period. Those trajectories that do not experience a significant convective influence are divided into four geographical categories depending on their origins and paths. Air parcels originating over Africa and South America are characterized by enhanced mixing ratios of O-3, CO, HNO3, and PAN. The backward trajectories travel at high altitudes (similar to 10-11 km), covering long distances due to strong upper-tropospheric westerly winds. The observed enhancement of combustion-related species is attributed to biomass burning from distant sources to the west, extending even to South America. The relatively large value of Be-7 probably is due either to less efficient removal of aerosols from upper tropospheric air or to small stratospheric contributions. Aged marine parcels are found to have relatively small concentrations of burning-related species. Although these trajectories arrive at a wide range of aircraft altitudes, they do not pass over a land mass during the preceding 10-day period. Air passing over Australia but no other land mass exhibits a combustion signature; however, photochemical product species such as O-3 and PAN are less enhanced than in the long-range transport category. These trajectories travel shorter distances and are at lower altitudes (similar to 5-8 km) than those reaching Africa and/or South America. The combustion influence on these parcels is attributed to biomass burning emissions injected over Australia. That burning is less widespread than in Africa and South America. Finally, trajectories originating over Southeast Asia appear to receive a weak combustion influence. However, compared to Africa and South America, Southeast Asia has a relatively small incidence of biomass burning. There is little combustion input from Australia due to the high transport altitudes compared to the lower heights of the convection. The Southeast Asian parcels exhibit the greatest NOx to Sigma NOi ratio of any category, perhaps due to lightning. Parcels experiencing a significant convective influence also are examined. Most of these parcels pass through widespread, persistent convection along either the South Pacific Convergence Zone or Intertropical Convergence Zone approximately 5 days prior to arriving at the aircraft locations, Thus the category mostly represents marine convection. Mixing ratios of peroxides and acids in the convective category are found to be smaller than in parcels not experiencing convection. Small mixing ratios of Be-7 and Pb-210 suggest particle removal by precipitation. C1 Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. Georgia Inst Technol, Dept Earth & Atmospher Sci, Atlanta, GA 30332 USA. Harvard Univ, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Fuelberg, HE (reprint author), Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. EM fuelberg@met.fsu.edu RI Schultz, Martin/I-9512-2012 OI Schultz, Martin/0000-0003-3455-774X NR 66 TC 23 Z9 23 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 JUL 20 PY 1999 VL 104 IS D13 BP 16181 EP 16196 DI 10.1029/1999JD900021 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000022 ER PT J AU Fenn, MA Browell, EV Butler, CF Grant, WB Kooi, SA Clayton, MB Gregory, GL Newell, RE Zhu, Y Dibb, JE Fuelberg, HE Anderson, BE Bandy, AR Blake, DR Bradshaw, JD Heikes, BG Sachse, GW Sandholm, ST Singh, HB Talbot, RW Thornton, DC AF Fenn, MA Browell, EV Butler, CF Grant, WB Kooi, SA Clayton, MB Gregory, GL Newell, RE Zhu, Y Dibb, JE Fuelberg, HE Anderson, BE Bandy, AR Blake, DR Bradshaw, JD Heikes, BG Sachse, GW Sandholm, ST Singh, HB Talbot, RW Thornton, DC TI Ozone and aerosol distributions and air mass characteristics over the South Pacific during the burning season SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; POTENTIAL VORTICITY; DIAL MEASUREMENTS; ATLANTIC; LIDAR; PROFILES AB In situ and laser remote measurements of gases and aerosols were made with airborne instrumentation to establish a baseline chemical signature of the atmosphere above the South Pacific Ocean during the NASA Global Tropospheric Experiment (GTE)/Pacific Exploratory Mission-Tropics A (PEM-Tropics A) conducted in August-October 1996. This paper discusses general characteristics of the air masses encountered during this experiment using an airborne lidar system for measurements of the large-scale variations in ozone (O-3) and aerosol distributions across the troposphere, calculated potential vorticity (PV) from the European Centre for Medium Range Weather Forecasting (ECMWF), and in situ measurements for comprehensive air mass composition. Between 8 degrees S and 52 degrees S, biomass burning plumes containing elevated levels of O-3, over 100 ppbv, were frequently encountered by the aircraft at altitudes ranging from 2 to 9 km. Air with elevated O-3 was also observed remotely up to the tropopause, and these air masses were observed to have no enhanced aerosol loading. Frequently, these air masses had some enhanced PV associated with them, but not enough to explain the observed O-3 levels. A relationship between PV and O-3 was developed from cases of clearly defined O-3 from stratospheric origin, and this relationship was used to estimate the stratospheric contribution to the air masses containing elevated O-3 in the troposphere. The frequency of observation of the different air mass types and their average chemical composition is discussed in this paper. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Drexel Univ, Philadelphia, PA 19104 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Georgia Inst Technol, Atlanta, GA 30332 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. Univ Rhode Isl, Grad Sch Oceanog, Narragansett, RI 02882 USA. MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Fenn, MA (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM m.a.fenn@larc.nasa.gov; e.v.browell@larc.nasa.gov; c.f.butler@larc.nasa.gov; w.b.grant@larc.nasa.gov; s.a.kooi@larc.nasa.gov; m.b.clayton@larc.nasa.gov; g.l.gregory@larc.nasa.gov; newell@newell1.mit.edu; zhu@newell1.mit.edu; Jack.Dibb@grg.sr.unh.edu; fuelberg@huey.met.fsu.edu; b.e.anderson@larc.nasa.gov; arb@ac1.chemistry.drexel.edu; dblake@orion.oac.uci.edu; ss27@prism.gatech.edu; zagar@notos.gso.uri.edu; g.w.sachse@larc.nasa.gov; ss27@prism.gatech.edu; hsingh@mail.arc.nasa.gov; rwt@christa.unh.edu; dct@ac2.chemistry.drexel.edu RI Grant, William/B-8311-2009 OI Grant, William/0000-0002-1439-3285 NR 33 TC 32 Z9 32 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16197 EP 16212 DI 10.1029/1999JD900065 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000023 ER PT J AU Blake, NJ Blake, DR Wingenter, OW Sive, BC McKenzie, LM Lopez, JP Simpson, IJ Fuelberg, HE Sachse, GW Anderson, BE Gregory, GL Carroll, MA Albercook, GM Rowland, FS AF Blake, NJ Blake, DR Wingenter, OW Sive, BC McKenzie, LM Lopez, JP Simpson, IJ Fuelberg, HE Sachse, GW Anderson, BE Gregory, GL Carroll, MA Albercook, GM Rowland, FS TI Influence of southern hemispheric biomass burning on midtropospheric distributions of nonmethane hydrocarbons and selected halocarbons over the remote South Pacific. SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID TROPOSPHERIC OZONE; WESTERN PACIFIC; CARBON-MONOXIDE; SAVANNA FIRES; CHEMISTRY; ATLANTIC; IMPACT AB Aircraft measurements of nonmethane hydrocarbons (NMHCs) and halocarbons were made over the remote South Pacific Ocean during late August-early October 1996 for NASA's Global Tropospheric Experiment (GTE) Pacific Exploratory Mission-Tropics A (PEM-Tropics A). This paper discusses the large-scale spatial distributions of selected trace gases encountered during PEM-Tropics A. The PEM-Tropics A observations are compared to measurements made over the southwestern pacific in early November 1995 as part of Aerosol Characterization Experiment (ACE 1). Continental pollution in the form of layers containing elevated levels of O-3 was observed during a majority of PEM-Tropics flights, as well as during several ACE 1 flights. The chemical composition of these air masses indicates that they were not fresh and were derived from nonurban combustion sources. The substantial impact of biomass burning on the vertical structure of the South Pacific troposphere is discussed. C1 Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. Florida State Univ, Dept Meteorol, Tallahassee, FL 32306 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Michigan, Ann Arbor, MI 48109 USA. RP Blake, NJ (reprint author), Univ Calif Irvine, Dept Chem, Irvine, CA 92697 USA. EM drblake@uci.edu; nblake@uci.edu; oliver@eas.gatech.edu; bcsive@uci.edu; jplopez@uci.edu; isimpson@uci.edu; rowland@uci.edu RI McKenzie, Lisa/D-4501-2014 NR 45 TC 54 Z9 54 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16213 EP 16232 DI 10.1029/1999JD900067 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000024 ER PT J AU Dibb, JE Talbot, RW Meeker, LD Scheuer, EM Blake, NJ Blake, DR Gregory, GL Sachse, GW AF Dibb, JE Talbot, RW Meeker, LD Scheuer, EM Blake, NJ Blake, DR Gregory, GL Sachse, GW TI Constraints on the age and dilution of Pacific Exploratory Mission-Tropics biomass burning plumes from the natural radionuclide tracer Pb-210 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HYDROCARBON AB During the NASA Global Troposphere Experiment Pacific Exploratory Mission-Tropics (PEM-Tropics) airborne sampling campaign we found unexpectedly high concentrations of aerosol-associated Pb-210 throughout the free troposphere over the South Pacific. Because of the remoteness of the study region, we expected specific activities to be generally less than 35 mu Bq m(-3) but found an average in the free troposphere of 107 mu Bq m(-3). This average was elevated by a large number of very active (up to 405 mu Bq m(-3)) samples that were associated with biomass burning plumes encountered on nearly every PEM-Tropics flight in the southern hemisphere. We use a simple aging and dilution model, which assumes that Rn-222 and primary combustion products are pumped into the free troposphere in wet convective systems over fire regions (most likely in Africa), to explain the elevated Pb-210 activities. This model reproduces the observed Pb-210 activities very well, and predicts the ratios of four hydrocarbon species (emitted by combustion) to CO to better than 20% in most cases. Plume ages calculated by the model depend strongly on the assumed Rn-222 activities in the initial plume, but using values plausible for continental boundary layer air yields ages that are consistent with travel times from Africa to the South Pacific calculated with a back trajectory model. The model also shows that despite being easily recognized through the large enhancements of biomass burning tracers, these plumes must have entrained large fractions of the surrounding ambient air during transport. C1 Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Dibb, JE (reprint author), Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA. EM jack.dibb@unh.edu NR 14 TC 10 Z9 11 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16233 EP 16241 DI 10.1029/1999JD900066 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000025 ER PT J AU Smyth, S Sandholm, S Shumaker, B Mitch, W Kanvinde, A Bradshaw, J Liu, S McKeen, S Gregory, G Anderson, B Talbot, R Blake, D Rowland, S Browell, E Fenn, M Merrill, J Bachmeier, S Sachse, G Collins, J AF Smyth, S Sandholm, S Shumaker, B Mitch, W Kanvinde, A Bradshaw, J Liu, S McKeen, S Gregory, G Anderson, B Talbot, R Blake, D Rowland, S Browell, E Fenn, M Merrill, J Bachmeier, S Sachse, G Collins, J TI Characterization of the chemical signatures of air masses observed during the PEM experiments over the western Pacific SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID CONTINENTAL OUTFLOW; TRACER MODEL; AEROSOLS; PHASE AB Extensive observations of tropospheric trace species during the second NASA Global Tropospheric Experiment Western Pacific Exploratory Mission (PEM-West B) in February-March 1994 showed significant seasonal variability in comparison with the first mission (PEM-West A), conducted in September-October 1991. In this study we adopt a previously established analytical method, i.e., the ratio C2H2/CO as a measure of the relative degree of atmospheric processing, to elucidate the key similarities and variations between the two missions, In addition, the C2H2/CO ratio scheme is combined with the back-trajectory-based and the LIDAR-based air mass classification schemes, respectively, to make in-depth analysis of the seasonal variation between PEM-West A and PEM-West B (hereinafter referred to as PEM-WA and PEM-WB). A large number of compounds, including long-lived NMHCs, CH4, and CO2, are, as expected, well correlated with the ratio C2H2/CO. In comparison with PEM-WA, a significantly larger range of observed C2H2/CO values at the high end for the PEM-WB period indicates that the western Pacific was more impacted by "fresher" source emissions, i.e., faster or mote efficient continental outflow. As in the case of PEM-WA, the C2H2/CO scheme complements the back-trajectory air mass classification scheme very well. By combining the two schemes, we found that the atmospheric processing in the region is dominated by atmospheric mixing for the trace species analyzed. This PEM-WB wintertime result is similar to that found in PEM-WA for the autumn. In both cases, photochemical reactions are found to play a significant role in determining the background mixing ratios of trace gases, and in this way the two processes are directly related and dependent upon each other. This analysis also indicates that many of the upper tropospheric air masses encountered over the western Pacific during PEM-WB may have had little impact from eastern Asia's continental surface sources. NOx mixing ratios were significantly enhanced during PEM-WB when compared with PEM-WA, in the upper troposphere's more atmospherically processed air masses. These high levels of NOx resulted in a substantial amount of photochemical production of O-3. A lack of corresponding enhancements in surface emission tracers strongly implies that in situ atmospheric sources such as lightning are responsible for the enhanced upper tropospheric NOx. The similarity in NOx values between the northern (higher air traffic) and southern continental air masses together with the indications of a large seasonal shift suggests that aircraft emissions are not the dominant source. However, photochemical recycling cannot be ruled out as this in situ source of NOx. C1 Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. Univ Rhode Isl, Grad Sch Oceanog, Ctr Atmospher Chem Studies, Narragansett, RI 02882 USA. Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03820 USA. RP Smyth, S (reprint author), Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. RI McKeen, Stuart/H-9516-2013 NR 25 TC 19 Z9 19 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 JUL 20 PY 1999 VL 104 IS D13 BP 16243 EP 16254 DI 10.1029/1999JD900115 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000026 ER PT J AU Crawford, J Davis, D Olson, J Chen, G Liu, S Gregory, G Barrick, J Sachse, G Sandholm, S Heikes, B Singh, H Blake, D AF Crawford, J Davis, D Olson, J Chen, G Liu, S Gregory, G Barrick, J Sachse, G Sandholm, S Heikes, B Singh, H Blake, D TI Assessment of upper tropospheric HOx sources over the tropical Pacific based on NASA GTE/PEM data: Net effect on HOx and other photochemical parameters SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID NORTH PACIFIC; HYDROGEN-PEROXIDE; ODD-HYDROGEN; OZONE; NITROGEN; OH; CHEMISTRY; TRANSPORT; WESTERN; ACETONE AB Data for the tropical upper troposphere (8-12 km, 20 degrees N-20 degrees S) collected during NASA's Pacific Exploratory Missions have been used to carry out a detailed examination of the photochemical processes controlling HOx (OH+HO2). Of particular significance is the availability of measurements of nonmethane hydrocarbons, oxygenated hydrocarbons (i.e., acetone, methanol, and ethanol) and peroxides (i.e., H2O2 and CH3OOH). These observations have provided constraints on model calculations permitting an assessment of the potential impact of these species on the levels of HO2, CH3O2 CH2O, as well as ozone budget parameters. Sensitivity calculations using a time-dependent photochemical box model show that when constrained by measured values of the above oxygenated species, model estimated HOx levels are elevated relative to unconstrained calculations. The impact of constraining these species was found to increase with altitude, reflecting the systematic roll-off in water vapor mixing ratios with altitude. At 11-12 km, overall increases in HOx approached a factor of 2 with somewhat larger increases being found for gross and net photochemical production of ozone. While significant, the impact on HOx due to peroxides appears to be less than previously estimated. In particular, observations of elevated H2O2 levels may be more influenced by local photochemistry than by convective transport. Issues related to the uncertainty in high-altitude water vapor levels and the possibility of other contributing sources of HOx are discussed. Finally, it is noted that the uncertainties in gas kinetic rate coefficients at the low temperatures of the upper troposphere and as well as OH sensor calibrations should be areas of continued investigation. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Calif Irvine, Dept Chem, Irvine, CA 92717 USA. Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA. Univ Rhode Isl, Ctr Atmospher Chem Studies, Narragansett, RI 02882 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Crawford, J (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. EM j.h.crawford@larc.nasa.gov RI Crawford, James/L-6632-2013 OI Crawford, James/0000-0002-6982-0934 NR 54 TC 89 Z9 89 U1 0 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16255 EP 16273 DI 10.1029/1999JD900106 PG 19 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000027 ER PT J AU Cho, JYN Newell, RE Barrick, JD AF Cho, JYN Newell, RE Barrick, JD TI Horizontal wavenumber spectra of winds, temperature, and trace gases during the Pacific Exploratory Missions: 2. Gravity waves, quasi-two-dimensional turbulence, and vortical modes SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PEM-WEST-A; NUMBER SPECTRA; STRATIFIED TURBULENCE; ATMOSPHERIC VELOCITY; COMMERCIAL AIRCRAFT; ROTATING TURBULENCE; MESOSCALE SPECTRUM; RADAR OBSERVATIONS; NASA DC-8; MOTIONS AB We examine the horizontal wavenumber spectra of horizontal velocity and potential temperature collected by aircraft above the Pacific Ocean to determine whether gravity waves, quasi-two-dimensional (Q-2-D) turbulence, or vortical modes dominate atmospheric fluctuations at scale sizes of 1-100 km and altitudes of 2-12 km. We conclude from the study of Doppler-shifting effects that Q-2-D turbulence and/or vortical modes are more prevalent than gravity waves over the ocean, except. in the equatorial zone. The results are consistent with recent numerical simulations of Q-2-D turbulence, which show that the characteristic inverse cascade of energy is greatly facilitated by the presence of background rotation. Furthermore, a Stokes-parameter analysis reveals the general paucity of coherent wavelike motions, although specific cases of gravity-wave propagation are observed. Finally, a case study of a long flight segment displays a k(-3) horizontal velocity variance spectrum at scales longer than about 100 km. A Stokes-parameter analysis indicates that these large-scale fluctuations were likely due to vortical modes rather than inertio-gravity waves. C1 MIT, Dept Earth Atmospher & Planetary Sci, Cambridge, MA 02139 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Cho, JYN (reprint author), MIT, Dept Earth Atmospher & Planetary Sci, 77 Massachusetts Ave,54-1823, Cambridge, MA 02139 USA. EM jcho@pemtropics.mit.edu; newell@newell1.mit.edu; j.d.barrick@larc.nasa.gov NR 52 TC 37 Z9 37 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16297 EP 16308 DI 10.1029/1999JD900068 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000029 ER PT J AU Bacmeister, JT Kuell, V Offermann, D Riese, M Elkins, JW AF Bacmeister, JT Kuell, V Offermann, D Riese, M Elkins, JW TI Intercomparison of satellite and aircraft observations of ozone, CFC-11, and NOy using trajectory mapping SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID ER-2 AIRCRAFT; INSTRUMENTS ABOARD; ARCTIC WINTER; STRATOSPHERE; ASHOE/MAESA; TRANSPORT; ATMOS AB The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) satellite measured global distributions of over 15 trace constituents at high horizontal resolution (<500 km), The CRISTA mission began shortly before the end of the Airborne Southern Hemisphere Ozone Experiment and Measurements to Assess the Effects of Stratospheric Aircraft (ASHOE/MAESA) airborne measurement campaign. CRISTA measurements of ozone, CFC-11, and HNO3 are available below 20 km, in the altitude range sampled by the ER-2 aircraft during ASHOE/MAESA. However, the time separation between the two missions makes a direct comparison of the data impossible. In this study, trajectory techniques are used to compare CRISTA measurements of ozone, CFC-11, and HNO3 with ER-2 measurements taken during the last two flights of ASHOE/MAESA on November 2 and 4, 1994. Visual comparison of CRISTA and ER-2 data from the November 4 flight is generally good. Mean tracer gradients across scales of similar to 1000 km, as well as absolute mixing ratios agree well with those measured from the ER-2, Correlation coefficients for coincident pairs of ER-2 and CRISTA measurements are between 0.68 and 0.80. The comparison for the November 2 flight is poor. We argue that the poor agreement for this flight maybe due to both smaller CRISTA measurement density as well as rapid stretching in the air mass sampled by the ER-2 on November 2. C1 NOAA, Climate Monitoring & Diagnost Lab, Boulder, CO 80303 USA. Berg Univ Wuppertal, Dept Phys, D-42097 Wuppertal, Germany. USN, Res Lab, Washington, DC 20375 USA. RP Bacmeister, JT (reprint author), NASA, Goddard Space Flight Ctr, Mail Code 913, Greenbelt, MD 20771 USA. EM bacmj@janus.gsfc.nasa.gov RI Riese, Martin/A-3927-2013 OI Riese, Martin/0000-0001-6398-6493 NR 26 TC 16 Z9 16 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUL 20 PY 1999 VL 104 IS D13 BP 16379 EP 16390 DI 10.1029/1999JD900173 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 218CE UT WOS:000081535000035 ER PT J AU Chen, CL Feng, HH Zhang, Z Brazdeikis, A Huang, ZJ Chu, WK Chu, CW Miranda, FA Van Keuls, FW Romanofsky, RR Liou, Y AF Chen, CL Feng, HH Zhang, Z Brazdeikis, A Huang, ZJ Chu, WK Chu, CW Miranda, FA Van Keuls, FW Romanofsky, RR Liou, Y TI Epitaxial ferroelectric Ba0.5Sr0.5TiO3 thin films for room-temperature tunable element applications SO APPLIED PHYSICS LETTERS LA English DT Article ID CHEMICAL-VAPOR-DEPOSITION; ELECTRICAL-PROPERTIES; CAPACITORS AB Perovskite Ba0.5Sr0.5TiO3 thin films have been synthesized on (001) LaAlO3 substrates by pulsed laser ablation. Extensive x-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of [100](BSTO)//[100](LAO). Rutherford backscattering spectrometry studies indicate that the epitaxial films have excellent crystalline quality with an ion beam minimum yield chi(min) of only 2.6%. The dielectric property measurements by the interdigital technique at 1 MHz show room-temperature values of the relative dielectric constant, epsilon(r), and loss tangent, tan delta, of 1430 and 0.007 with no bias, and 960 and 0.001 with 35 V bias, respectively. The obtained data suggest that the as-grown Ba0.5Sr0.5TiO3 films can be used for development of room-temperature tunable microwave elements. (C) 1999 American Institute of Physics. [S0003-6951(99)01529-6]. C1 Univ Houston, Texas Ctr Superconduct, Houston, TX 77204 USA. Univ Houston, Dept Phys, Houston, TX 77204 USA. NASA, Lewis Res Ctr, Commun Technol Div, Cleveland, OH 44135 USA. Acad Sinica, Inst Phys, Taipei 11529, Taiwan. RP Chen, CL (reprint author), Univ Houston, Texas Ctr Superconduct, Houston, TX 77204 USA. EM clchen@uh.edu RI Brazdeikis, Audrius/H-3837-2015 OI Brazdeikis, Audrius/0000-0001-9536-1586 NR 19 TC 158 Z9 164 U1 1 U2 25 PU AMER INST PHYSICS PI MELVILLE PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA SN 0003-6951 J9 APPL PHYS LETT JI Appl. Phys. Lett. PD JUL 19 PY 1999 VL 75 IS 3 BP 412 EP 414 DI 10.1063/1.124392 PG 3 WC Physics, Applied SC Physics GA 215XP UT WOS:000081409000036 ER PT J AU Linthicum, KJ Anyamba, A Tucker, CJ Kelley, PW Myers, MF Peters, CJ AF Linthicum, KJ Anyamba, A Tucker, CJ Kelley, PW Myers, MF Peters, CJ TI Climate and satellite indicators to forecast Rift Valley fever epidemics in Kenya SO SCIENCE LA English DT Article ID DIFFERENCE VEGETATION INDEX; SEA-SURFACE TEMPERATURE; NEAR-INFRARED CHANNELS; DOMESTIC-ANIMALS; EL-NINO; RAINFALL; AVHRR; CALIBRATION; AFRICA; VIRUS AB All known Rift Valley fever virus outbreaks in East Africa from 1950 to May 1998, and probably earlier, followed periods of abnormally high rainfall. Analysis of this record and Pacific and Indian Ocean sea surface temperature anomalies, coupled with satellite normalized difference vegetation index data, shows that prediction of Rift Valley fever outbreaks may be made up to 5 months in advance of outbreaks in East Africa. Concurrent near-real-time monitoring with satellite normalized difference vegetation data may identify actual affected areas. C1 Walter Reed Army Med Ctr, Walter Reed Army Inst Res, Dept Def, Washington, DC 20307 USA. NASA, Goddard Space Flight Ctr, Earth Sci Directorate, Greenbelt, MD 20771 USA. Ctr Dis Control & Prevent, Special Pathogens Branch, Atlanta, GA 30333 USA. RP Anyamba, A (reprint author), Walter Reed Army Med Ctr, Walter Reed Army Inst Res, Dept Def, Washington, DC 20307 USA. NR 30 TC 302 Z9 315 U1 5 U2 34 PU AMER ASSOC ADVANCEMENT SCIENCE PI WASHINGTON PA 1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA SN 0036-8075 J9 SCIENCE JI Science PD JUL 16 PY 1999 VL 285 IS 5426 BP 397 EP 400 DI 10.1126/science.285.5426.397 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 216VV UT WOS:000081465900051 PM 10411500 ER PT J AU Tanizaki, S Mavri, J Partridge, H Jordan, PC AF Tanizaki, S Mavri, J Partridge, H Jordan, PC TI Unusual distributed charge models of water's electric potential SO CHEMICAL PHYSICS LA English DT Article DE multipolar site; wave functions; oxygen atom ID MOLECULAR-DYNAMICS SIMULATIONS; ATOMIC CHARGES; LIQUID WATER; ELECTROSTATIC POTENTIALS; GRAMICIDIN CHANNEL; POLARIZABLE MODEL; ION-TRANSPORT; ENERGY; FIELD; FREQUENCY AB Based on wave functions determined from high level quantum mechanical theory, we critically evaluate some distributed charge models for the electrical potential of a water molecule. In three cases we find that for optimal parameterization several charges coalesce to form a multipole, reducing to four site descriptions, each of three point charges and a multipolar site. In two cases, the multipole is located at the distributed charge; in the third it is sited at the oxygen atom. All three limiting models are considerably superior to simple four site point charge approximations. The description of water's electrical potential can be dramatically improved, even close to the H and O atoms, if distributed charges are described as diffuse spherical charge densities. Some models constructed in this way can admit of intuitive 'chemical' interpretations. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Brandeis Univ, Dept Chem, Waltham, MA 02454 USA. Natl Inst Chem, Ljubljana 1000, Slovenia. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Jordan, PC (reprint author), Brandeis Univ, Dept Chem, MS-015,POB 9110, Waltham, MA 02454 USA. NR 39 TC 2 Z9 2 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0301-0104 J9 CHEM PHYS JI Chem. Phys. PD JUL 15 PY 1999 VL 246 IS 1-3 BP 37 EP 47 DI 10.1016/S0301-0104(99)00158-5 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 227FP UT WOS:000082068600003 ER PT J AU Draper, DS Green, TH AF Draper, DS Green, TH TI P-T phase relations of silicic, alkaline, aluminous liquids: new results and applications to mantle melting and metasomatism SO EARTH AND PLANETARY SCIENCE LETTERS LA English DT Article DE mantle; xenoliths; glasses; P-T conditions; metasomatism; melting ID SOLIDUS PERIDOTITE MELTS; OCEANIC BASALTS; WEST-EIFEL; RICH MELTS; XENOLITHS; GLASSES; ORIGIN; EQUILIBRIA; OLIVINE; DIAMOND AB We report new experimental results obtained under nominally anhydrous conditions at 1.0-1.5 GPa on a synthetic melt whose composition is typical of extreme-composition xenolith glasses. These results demonstrate that part of this extreme compositional range is in equilibrium with a lherzolitic assemblage (olivine, orthopyroxene, and clinopyroxene on the liquidus), extending our earlier findings [D.S. Draper, T.H. Green P-T phase relations of silicic, alkaline, aluminous mantle-xenolith glasses under anhydrous and C-O-H fluid-saturated conditions, J. Petrol. 38 (1997) 1187-1224] showing saturation with harzburgite minerals (olivine and orthopyroxene on the liquidus). The new results strengthen the view that such liquids can readily coexist with upper mantle rocks. Our results also bear on the current debate regarding the nature of low-degree mantle melts between proponents of the diamond-aggregate technique [who argue for comparatively silica- and alkali-rich low-degree melts; e.g., M.B. Baker, M.M. Hirschmann, M.S. Ghiorso, E.M. Stolper, Compositions of near-solidus peridotite melts from experiments and thermodynamic calculations, Nature 375 (1995) 308-311; M.B. Baker, M.M. Hirschmann, L.E. Wasylenki, E.M. Stolper, M.S. Ghiorso, Quest for low-degree mantle melts, Nature 381 (1996) 286] and those favoring the sandwich technique [who question the value of the diamond-aggregate work and argue that near-solidus melts must be nepheline- and olivine-normative; T.J. Falloon, D.H. Green, H.St.C. O'Neill, C.G. Ballhaus, Quest for low-degree mantle melts, Nature 381 (1996) 285; T.J. Falloon, D.H. Green, H.St.C. O'Neill, W.O. Hibberson, Experimental tests of low degree peridotite partial melt compositions: implications for the nature of anhydrous near-solidus peridotite melts at 1 GPa, Earth Planet. Sci. Lett. 152 (1997) 149-162]. Our results support aspects of both views. The sandwich-technique view is supported, for example, because all our liquids coexisting with mantle minerals are nepheline- and olivine-normative; and our olivine-liquid Fe-Mg exchange K-D values fall on a trend similar to that supported by those workers. The diamond-aggregate view is supported, for example, because we find equilibrium between highly silicic, alkaline liquids and mantle minerals, showing the effect of high alkali contents to allow high silica contents at silica activities buffered by magnesian olivine and orthopyroxene at low pressure [M.M. Hirschmann, M.B. Baker, E.M. Stolper, The effect of alkalis on the silica content of mantle-derived melts, Geochim. Cosmochim. Acta 62 (1998) 883-902]. Additionally, the melting trends put forward by the sandwich-technique workers include revised low-degree melt compositions, as reported by Hirschmann et al., and our compositions fall on extensions of these trends. These new analyses also yield an olivine-liquid K-D that more closely follows the trend of K-D vs. melt alkali contents. The views of both sides of this controversy appear to permit, under certain conditions, the existence of small amounts of melt in the upper mantle with compositions similar to the extreme-composition xenolith glasses that are the focus of our work. On the basis of our new results, we conclude that extreme-composition xenolith glasses can act as agents of cryptic metasomatism in the upper mantle. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Macquarie Univ, Sch Earth Sci, GEMOC ARC Natl Key Ctr Geochem Evolut & Metalloge, N Ryde, NSW 2109, Australia. RP Draper, DS (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN2,2101 NASA Rd 1, Houston, TX 77058 USA. RI GAU, geochemist/H-1985-2016 NR 38 TC 36 Z9 36 U1 0 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0012-821X J9 EARTH PLANET SC LETT JI Earth Planet. Sci. Lett. PD JUL 15 PY 1999 VL 170 IS 3 BP 255 EP 268 DI 10.1016/S0012-821X(99)00111-9 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 215DY UT WOS:000081367700008 ER PT J AU Keller, RM Dungan, JL AF Keller, RM Dungan, JL TI Meta-modeling: a knowledge-based approach to facilitating process model construction and reuse SO ECOLOGICAL MODELLING LA English DT Article DE modeling methodology; knowledge-based modeling; model documentation; model reuse; model construction tools; process models; biogeochemical cycling ID ECOSYSTEM; INTERFACE; CARBON; SYSTEM; WATER; POWER AB We introduce a new modeling approach called meta-modeling and illustrate its practical applicability to the construction of physically-based ecosystem process models. As a critical adjunct to the computer modeling code, meta-modeling requires explicit specification of certain background information related to the construction and conceptual underpinnings of a model. This information formalizes the heretofore tacit relationship between the computer source code and the underlying real-world phenomena being investigated, and gives insight into the process by which the model was constructed. We show how the explicit availability of such information can make models more understandable and reusable, and less subject to misinterpretation. In particular, background information enables potential users to better interpret an implemented ecosystem model without direct assistance from the model author. Additionally, we show how the discipline involved in specifying background information leads to improved management of model complexity and fewer implementation errors. We illustrate the meta-modeling approach in the context of the Scientists' Intelligent Graphical Modeling Assistant (SIGMA), a new model construction environment. As the user constructs a model using SIGMA, the system adds appropriate background information that ties the executable model to the underlying physical phenomena being investigated. Not only does this information improve the understandability of the final model, it also serves to reduce the overall time and programming expertise necessary to initially build and subsequently modify models. Furthermore, SIGMA's use of background information helps eliminate coding errors resulting from scientific and dimensional inconsistencies that are otherwise difficult to avoid when building complex models. As a demonstration of SIGMA's utility, the system was used to reimplement and extend a well-known forest ecosystem dynamics model: Forest-BGC (Running, S.W., Coughlan, J.C., 1988. Ecol. Model. 42, 125-154). (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Computat Sci Div, Ames Res Ctr, Moffett Field, CA 94035 USA. Calif State Univ Monterey Bay, Ecosyst Sci & Technol Branch, NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Keller, RM (reprint author), NASA, Computat Sci Div, Ames Res Ctr, Mail Stop 269-2, Moffett Field, CA 94035 USA. RI Dungan, Jennifer/G-9921-2016 OI Dungan, Jennifer/0000-0002-4863-1616 NR 32 TC 13 Z9 14 U1 0 U2 4 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0304-3800 J9 ECOL MODEL JI Ecol. Model. PD JUL 15 PY 1999 VL 119 IS 2-3 BP 89 EP 116 PG 28 WC Ecology SC Environmental Sciences & Ecology GA 222WX UT WOS:000081809300001 ER PT J AU Feynman, J Ruzmaikin, A AF Feynman, J Ruzmaikin, A TI Modulation of cosmic ray precipitation related to climate SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SOLAR-CYCLE; TEMPERATURE; WIND AB High energy cosmic rays may influence the formation of clouds and thus impact weather and climate. Due to systematic solar wind changes, the intensity of cosmic rays incident on the magnetopause has decreased markedly during this century. The pattern of cosmic ray precipitation through the magnetosphere to the upper troposphere has also changed. Early in the century, the part of the troposphere open to cosmic rays of all energies was typically confined to a relatively small high-latitude region. As the century progressed the size of this region increased by over 25% and there was a 6.5 degrees equatorward shift in the yearly averaged latitudinal position of the subauroral region in which cloud cover has been shown to be cosmic ray flux dependent. We suggest these changes in cosmic ray intensity and latitude distribution may have influenced climate change during the last 100 years. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Feynman, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 19 TC 16 Z9 16 U1 0 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 15 PY 1999 VL 26 IS 14 BP 2057 EP 2060 DI 10.1029/1999GL900326 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 217YT UT WOS:000081527100006 ER PT J AU Gross, RS Vondrak, J AF Gross, RS Vondrak, J TI Astrometric and space-geodetic observations of polar wander SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID EARTH ORIENTATION PARAMETERS; HIPPARCOS REFERENCE FRAME; LATITUDE SERVICE DATA; ROTATION; MOTION; SERIES; ICE AB Optical astrometric measurements of star positions taken during the past century have been recently re-reduced using the final Hipparcos star catalog in order to determine variations in the mean location of the Earth's rotation pole with respect to the Earth's crust. This newly available polar motion series, which is the longest homogeneous polar motion series currently available, allows the drift in the pole path to be newly estimated. During the 1900.0 to 1992.0 span of the smoothed Hipparcos polar motion series, the Earth's rotation pole is observed to drift at a mean linear rate of 3.51 +/- 0.01 milliarcseconds/year (mas/yr) towards 79.2 +/- 0.2 degrees W longitude. This new estimate for the observed trend in the pole path, which can be considered to be the present-day expression of true polar wander, is nearly the same as that estimated in previous studies using the homogeneous ILS polar motion series. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Acad Sci Czech Republ, Inst Astron, Prague 14131 4, Czech Republic. RP Gross, RS (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 238-332, Pasadena, CA 91109 USA. RI Vondrak, Jan/G-9057-2014 NR 27 TC 38 Z9 41 U1 1 U2 4 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 15 PY 1999 VL 26 IS 14 BP 2085 EP 2088 DI 10.1029/1999GL900422 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 217YT UT WOS:000081527100013 ER PT J AU Tylka, AJ Reames, DV Ng, CK AF Tylka, AJ Reames, DV Ng, CK TI Observations of systematic temporal evolution in elemental composition during gradual solar energetic particle events SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID ACCELERATION; ABUNDANCES; SHOCKS; TRANSPORT; FLARES; WAVES AB The WIND/EPACT experiment offers a similar to 100 fold increase in collecting power over instruments flown in previous solar cycles, thus allowing unprecedented detailed studies of temporal evolution in gradual solar energetic particle (SEP) events. We present hourly WIND/EPACT observations at similar to 2-10 MeV/nuc from the 20 April 1998 and 26 August 1998 SEP events. These observations show striking patterns in elemental composition which evolve in a systematic fashion throughout the events' several-day durations. These data, combined with theoretical modeling in a companion Letter [Ng et al. 1999], suggest that a dynamic Alfven. wave field, generated primarily by streaming energetic protons, is responsible for the complex behavior which is observed. C1 USN, Res Lab, EO Hulburt Ctr Space Sci, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Tylka, AJ (reprint author), USN, Res Lab, EO Hulburt Ctr Space Sci, Code 7654, Washington, DC 20375 USA. RI Tylka, Allan/G-9592-2014 NR 19 TC 76 Z9 77 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 JUL 15 PY 1999 VL 26 IS 14 BP 2141 EP 2144 DI 10.1029/1999GL900458 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 217YT UT WOS:000081527100027 ER PT J AU Ng, CK Reames, DV Tylka, AJ AF Ng, CK Reames, DV Tylka, AJ TI Effect of proton-amplified waves on the evolution of solar energetic particle composition in gradual events SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID SHOCKS; ACCELERATION; ABUNDANCES; TRANSPORT AB We present a model of the coupled evolution of energetic ions and Alfven waves, incorporating magnetic focusing, pitch-angle diffusion, wave amplification, and a traveling ion source. Ion transport through proton-amplified waves with non-Kolmogorov spectra produces the contrasting three-stage evolution of Fe/O and He/H ratios at several MeV/amu observed by Wind/EPACT in the 20 April 1998 gradual solar energetic particle event [Tylka et al., 1999]. C1 USN, Res Lab, EO Hulburt Ctr Space Sci, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Ng, CK (reprint author), USN, Res Lab, EO Hulburt Ctr Space Sci, Code 7654, Washington, DC 20375 USA. RI Tylka, Allan/G-9592-2014 NR 14 TC 105 Z9 107 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 JUL 15 PY 1999 VL 26 IS 14 BP 2145 EP 2148 DI 10.1029/1999GL900459 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 217YT UT WOS:000081527100028 ER PT J AU Cane, HV Richardson, IG St Cyr, OC AF Cane, HV Richardson, IG St Cyr, OC TI Correction to "The interplanetary events of January-May, 1997 as inferred from energetic particle data, and their relationship with solar events" by H. V. Cane, I. G. Richardson, and O. C. St. Cyr (vol 26, pg 2149, 1999) SO GEOPHYSICAL RESEARCH LETTERS LA English DT Correction C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Computat Phys Inc, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Tasmania, Sch Math & Phys, Hobart, Tas, Australia. Univ Maryland, Dept Astron, College Pk, MD 20742 USA. RP Cane, HV (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 4 TC 7 Z9 7 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 JUL 15 PY 1999 VL 26 IS 14 BP 2149 EP 2150 DI 10.1029/1999GL900467 PG 2 WC Geosciences, Multidisciplinary SC Geology GA 217YT UT WOS:000081527100029 ER PT J AU Tabazadeh, A Toon, OB Jensen, EJ AF Tabazadeh, A Toon, OB Jensen, EJ TI A surface chemistry model for nonreactive trace gas adsorption on ice: Implications for nitric acid scavenging by cirrus SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID WATER-ICE; HNO3; PARTICLES; CLOUDS AB According to recent measurements HNO3 nearly saturates laboratory ice films in flow tubes for vapor pressures ka above 10(-7) torr and temperatures below 230 K. In the upper troposphere the HNO3 vapor pressure is in the range of 1 to 3 x 10(-8) torr and therefore the current laboratory estimates of saturation may not hold in the atmosphere. Here, with the aid of a surface chemistry model and laboratory data we estimate that the binding energy for HNO3 adsorbed on ice is about -14.2 +/- 0.2 kcal mol(-1). Using the surface model, we explore the sensitivity of HNO3 scavenging efficiency to cirrus cloud temperature, ice number density, and HCl competitive coadsorption. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. RP Tabazadeh, A (reprint author), NASA, Ames Res Ctr, MS-245-4, Moffett Field, CA 94035 USA. NR 20 TC 41 Z9 41 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 15 PY 1999 VL 26 IS 14 BP 2211 EP 2214 DI 10.1029/1999GL900501 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 217YT UT WOS:000081527100045 ER PT J AU Ray-Culp, M Davis, M Stoner, AW AF Ray-Culp, M Davis, M Stoner, AW TI Predation by xanthid crabs on early post-settlement gastropods: the role of prey size, prey density, and habitat complexity SO JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY LA English DT Article DE conch; predation; seagrass; Strombus gigas; xanthid crab ID JUVENILE QUEEN CONCH; EARLY POSTSETTLEMENT MORTALITY; BENTHIC MARINE-INVERTEBRATES; STROMBUS-GIGAS LINNAEUS; DEPENDENT MORTALITY; DECAPOD CRUSTACEANS; RECRUITMENT; GROWTH; BEHAVIOR; MICROPREDATORS AB Small predators in marine benthic communities create a hazardous environment for newly settled invertebrates, especially for the smallest individuals. To explore the effects of predation on a newly settled gastropod, queen conch (Strombus gigas Linnaeus), by a xanthid crab (Micropanope sp.), prey size, prey density, and habitat complexity were manipulated in five laboratory experiments. All crabs > 3.1 mm CW killed all conch < 2 mm SL when individual crabs (< 14 mm carapace width (CW)) were offered individual conch that were 2-35 days old after metamorphosis (1.2-8.8 mm shell length (SL)). Only 10% of the crabs > 5.0 mm CW, however, killed conch that were > 5.0 mm SL, suggesting that conch may reach a size refuge from xanthid crabs at 5 mm SL. Furthermore, when given a choice, crabs (4.8 mm CW) preferred smaller conch (2.0 mm SL) to larger (3.7 mm SL), suggesting that 1 week of additional growth in shell length is advantageous to survivorship. Proportional mortality decreased as conch density increased when crabs were offered conch at seven different densities (two to 96 individuals). Crabs proved to be effective predators regardless of the amount of seagrass structure provided in a microcosm experiment, and could consume two conch in 10 s. The high densities of xanthid crabs that occur in the wild, their effectiveness as predators, and their large appetites point to the important role that small predators may potentially play in structuring the population dynamics of their small prey immediately after settlement. (C) 1999 Elsevier Science BN. All rights reserved. C1 Caribbean Marine Res Ctr, Vero Beach, FL 32963 USA. RP Stoner, AW (reprint author), NW Fisheries Sci Ctr, Natl Marine Fisheries Serv, 74 Magruder Rd, Highlands, NJ 07732 USA. EM al.stoner@noaa.gov NR 51 TC 32 Z9 33 U1 3 U2 14 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0022-0981 J9 J EXP MAR BIOL ECOL JI J. Exp. Mar. Biol. Ecol. PD JUL 15 PY 1999 VL 240 IS 2 BP 303 EP 321 DI 10.1016/S0022-0981(99)00065-9 PG 19 WC Ecology; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 218KY UT WOS:000081552800008 ER PT J AU Markus, T AF Markus, T TI Results from an ECMWF-SSM/I forced mixed layer model of the Southern Ocean SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID MARGINAL ICE-ZONE; SEA-ICE; THERMODYNAMIC MODEL; WEDDELL POLYNYA; HEAT-FLUX; SIMULATION; CLIMATE; SYSTEM AB A hulk mixed layer model of the entire Southern Ocean forced by European Centre for Medium-Range Weather Forecasts (ECMWF) near-surface air temperatures and winds is presented. In addition, the Southern Ocean sea ice concentration determined from daily Defense Meteorological Satellite Program special sensor microwave imager (SSM/I) observations obviates the need for a dynamic-thermodynamic sea ice model. The oceanic mixed layer serves as the interface between the deep ocean and the atmosphere or sea ice. Measurements have shown that in the Southern Ocean entrainment of relatively warm deep water into the mixed layer has a significant impact on the oceanic stability and is the primary reason for the thinness of its sea ice cover. The use of satellite-derived ice concentrations reduces greatly the required accuracy in air temperature and wind needed by the model compared to the accuracy needed by coupled sea ice ocean models because these data are only needed here in the calculation of salt and heat fluxes and not to derive ice cover or ice dynamics. The results show that the seasonal cycle and the spatial distribution of mixed layer temperature, salinity, and depth can be reproduced and are in good agreement with in situ observations. Limitations in accuracy result predominantly still from uncertainties in air temperature, cloud cover, and wind speed during the summer months for areas with no or little ice coverage, ice concentration, and snow depth during the winter months as well as ocean currents. C1 NASA, Goddard Space Flight Ctr, UMD, Joint Ctr Earth Syst Sci, Greenbelt, MD 20771 USA. RP Markus, T (reprint author), NASA, Goddard Space Flight Ctr, UMD, Joint Ctr Earth Syst Sci, Code 971, Greenbelt, MD 20771 USA. EM thorsten@beaufort.gsfc.nasa.gov RI Markus, Thorsten/D-5365-2012 NR 57 TC 23 Z9 23 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-OCEANS JI J. Geophys. Res.-Oceans PD JUL 15 PY 1999 VL 104 IS C7 BP 15603 EP 15620 DI 10.1029/1999JC900080 PG 18 WC Oceanography SC Oceanography GA 217RD UT WOS:000081512000008 ER PT J AU Cavalieri, DJ Parkinson, CL Gloersen, P Comiso, JC Zwally, HJ AF Cavalieri, DJ Parkinson, CL Gloersen, P Comiso, JC Zwally, HJ TI Deriving long-term time series of sea ice cover from satellite passive-microwave multisensor data sets SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID REDUCTION AB We have generated consistent sea ice extent and area data records spanning 18.2 years from passive-microwave radiances obtained with the Nimbus 7 scanning multichannel microwave radiometer and with the Defense Meteorological Satellite Program F8, F11, and F13 special sensor microwave/imagers. The goal in the creation of these data was to produce a long-term, consistent set of sea ice extents and areas that provides the means for reliably determining sea ice variability over the 18.2-year period and also serves as a baseline for future measurements. We describe the method used to match the sea ice extents and areas from these four multichannel sensors and summarize the problems encountered when working with radiances from sensors having different frequencies, different footprint sizes, different visit times, and different calibrations. A major obstacle to adjusting for these differences is the lack of a complete year of overlapping data from sequential sensors. Nonetheless, our procedure reduced ice extent differences during periods of sensor overlap to less than 0.05% and ice area differences to 0.6% or less. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RP Cavalieri, DJ (reprint author), NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Greenbelt, MD 20771 USA. RI Parkinson, Claire/E-1747-2012 OI Parkinson, Claire/0000-0001-6730-4197 NR 22 TC 158 Z9 163 U1 1 U2 18 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 JUL 15 PY 1999 VL 104 IS C7 BP 15803 EP 15814 DI 10.1029/1999JC900081 PG 12 WC Oceanography SC Oceanography GA 217RD UT WOS:000081512000021 ER PT J AU Bauschlicher, CW Zhou, MF Andrews, L Johnson, JRT Panas, I Snis, A Roos, BO AF Bauschlicher, CW Zhou, MF Andrews, L Johnson, JRT Panas, I Snis, A Roos, BO TI A further study of the products of scandium and dioxygen reactions SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID DENSITY-FUNCTIONAL CALCULATIONS; 2ND-ORDER PERTURBATION-THEORY; MOLECULAR WAVE-FUNCTIONS; TRANSITION-METAL ATOMS; GAUSSIAN-BASIS SETS; ABLATED IRON ATOMS; ANO BASIS-SETS; INFRARED-SPECTRA; SOLID ARGON; ELECTRON CORRELATION AB The products of the reaction of Sc and dioxygen have been reinvestigated. By adding the electron-trapping molecule CCl4 additional information about the IR spectra has been obtained, as well as the observation of new bands. New ab initio calculations are also performed on possible products of the Sc plus O-2 reaction. The previously observed band at 722.5 cm(-1) is assigned as the b(2) mode of ScO2-. Bands arising from ScO+, Sc(O-2)(+), and(O-2)ScO are also assigned. We are still unable to assign any bands to OScO. The problems associated with the computational study of ScO2 are discussed. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Univ Virginia, Charlottesville, VA 22901 USA. Univ Gothenburg, Dept Chem, S-41296 Gothenburg, Sweden. Ctr Chem, Dept Theoret Chem, S-22100 Lund, Sweden. RP Bauschlicher, CW (reprint author), NASA, Ames Res Ctr, Mail Stop 230-3, Moffett Field, CA 94035 USA. OI Panas, Itai/0000-0002-6679-075X NR 37 TC 57 Z9 57 U1 0 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD JUL 15 PY 1999 VL 103 IS 28 BP 5463 EP 5467 DI 10.1021/jp9908808 PG 5 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 219FX UT WOS:000081598200009 ER PT J AU Chuang, KC Scheiman, DA Fu, J Crawford, M AF Chuang, KC Scheiman, DA Fu, J Crawford, M TI Synthesis and characterization of polyimides with ether linkages SO JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY LA English DT Article DE polyimides; ether linkages; BAPP; BAPD AB Thermoplastic and thermoset polyimides derived from 2,2-bis[4-(4-aminophenoxy)phenyl] propane (BAPP) and 4,4'-bis(4-aminophenoxy)-2,2'-dimethylbiphenyl (BAPD) were prepared and characterized. Their physical and thermal properties as well as the polyelectrolyte effect exhibited by BTDA-BAPP polyamic acids in NMP solution were discussed. (C) 1999 John Wiley & Sons, Inc. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Dynac Engn Co Inc, Cleveland, OH 44135 USA. Harvard Radcliffe Coll, Cambridge, MA 02138 USA. Morehouse Coll, Atlanta, GA 30314 USA. RP Chuang, KC (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 15 TC 4 Z9 5 U1 0 U2 3 PU JOHN WILEY & SONS INC PI NEW YORK PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA SN 0887-624X J9 J POLYM SCI POL CHEM JI J. Polym. Sci. Pol. Chem. PD JUL 15 PY 1999 VL 37 IS 14 BP 2559 EP 2567 DI 10.1002/(SICI)1099-0518(19990715)37:14<2559::AID-POLA29>3.0.CO;2-Z PG 9 WC Polymer Science SC Polymer Science GA 207NR UT WOS:000080943400029 ER PT J AU Miller, RL Tegen, I AF Miller, RL Tegen, I TI Radiative forcing of a tropical direct circulation by soil dust aerosols SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID MINERAL DUST; OPTICAL-THICKNESS; SURFACE-TEMPERATURE; TRADE WINDS; WATER-VAPOR; EL-NINO; MODEL; CLIMATE; ATMOSPHERE; CLOUDS AB The effect of soil dust aerosols upon the tropical climate is estimated by forcing a simple model of a tropical direct circulation. The model consists of a region vertically mixed by deep convection and a nonconvecting region, for which budgets of dry static energy and moisture are constructed. Dynamical effects are included implicitly, by prohibiting horizontal temperature contrasts above the boundary layer. Dust aerosols absorb sunlight to a greater extent than industrial sulfate and sea-salt aerosols. In a companion study, where the climate response to dust is calculated using an atmospheric general circulation model, the global-average dust radiative forcing is negligible at the top of the dust layer,in comparison to the large reduction of the net flux at the surface. Thus, dust aerosols redistribute radiative heating from the surface into the dust layer, unlike industrial sulfates and sea salt, which through reflection reduce the total radiative energy gained by the column. The simple model is perturbed by a reduction in the net radiative flux at the surface. Forcing at the top of the dust layer is idealized to be zero. Cooling occurs at the surface of the nonconvecting region, but surface temperature within the convecting region is only slightly perturbed. It is shown that the disproportionately small response within the convecting region is a consequence of the trivial radiative forcing at the top of the dust layer, and the occurrence of deep convection, which prevents the surface temperature from changing without a corresponding change of the emitting temperature in the upper troposphere. Additional experiments, where the absorptivity of the dust particles is varied, indicate that the anomalous surface temperature is most sensitive to the radiative forcing at the top of the dust layer. The reduction of the surface net radiation is less important per se but introduces an asymmetry in the response between the convecting and nonconvecting regions through the radiative forcing within the dust layer, which is the difference between the forcing at the surface and the layer top. This heating can offset radiative cooling above the boundary layer, reducing the strength of the circulation that links the nonconvecting and convecting regions. The weakened circulation requires cooling of the nonconvecting region relative to the convecting region in order to maintain the export of energy from the latter to the former. It is suggested that the "semi-indirect" effect of aerosols, wherein cloud cover is changed in response to aerosol heating, is sensitive to the vertical extent and magnitude of the aerosol forcing. The experiments suggest that dust optical properties (to which the top of the atmosphere forcing is sensitive) should be allowed to vary with the mineral composition of the source region in a computation of the climate response. More extensive measurements of the dust optical properties, along with the vertical distribution of the dust layer, are needed to reduce the uncertainty of the climate response to dust aerosols. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 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 64 TC 39 Z9 41 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 JUL 15 PY 1999 VL 56 IS 14 BP 2403 EP 2433 DI 10.1175/1520-0469(1999)056<2403:RFOATD>2.0.CO;2 PG 31 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 222DP UT WOS:000081768400010 ER PT J AU Becker, L Bunch, TE Allamandola, LJ AF Becker, L Bunch, TE Allamandola, LJ TI Higher fullerenes in the Allende meteorite SO NATURE LA English DT Letter ID C-60 C1 Univ Hawaii, Hawaii Inst Geophys & Planetary Sci, Honolulu, HI 96822 USA. NASA, Ames Res Ctr, Div Space Sci, Stanford, CA 94305 USA. RP Becker, L (reprint author), Univ Hawaii, Hawaii Inst Geophys & Planetary Sci, 2525 Correa Rd, Honolulu, HI 96822 USA. NR 11 TC 38 Z9 41 U1 0 U2 7 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUL 15 PY 1999 VL 400 IS 6741 BP 227 EP 228 DI 10.1038/22250 PG 2 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 217MP UT WOS:000081503800034 PM 10421363 ER PT J AU Froggat, M Erdogan, T AF Froggat, M Erdogan, T TI All-fiber wavemeter and Fourier-transform spectrometer SO OPTICS LETTERS LA English DT Article AB An all-fiber Fourier-transform spectrometer is proposed and demonstrated, based on the diffraction of light through the side of a standard optical fiber by a UV-induced fiber grating. The interference pattern, whose Fourier transform yields the optical spectrum, is formed by light diffracted from counterpropagating modes in the fiber. The device is simple and compact and functions as a wavemeter, a fiber-optic network monitor, or a tool for fabrication and testing of long fiber Bragg gratings. (C) 1999 Optical Society of America OCIS codes: 050.2770, 060.2340, 120.6200, 230.1950. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Univ Rochester, Inst Opt, Rochester, NY 14627 USA. RP Froggat, M (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 6 TC 7 Z9 7 U1 0 U2 3 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD JUL 15 PY 1999 VL 24 IS 14 BP 942 EP 944 DI 10.1364/OL.24.000942 PG 3 WC Optics SC Optics GA 222FG UT WOS:000081772300006 PM 18073903 ER PT J AU Hui, L Stewart, ED AF Hui, L Stewart, ED TI Superheavy dark matter from thermal inflation SO PHYSICAL REVIEW D LA English DT Article ID MEDIATED SUPERSYMMETRY-BREAKING; COSMOLOGICAL MODULI PROBLEM; DISCRETE GAUGE ANOMALIES; STANDARD MODEL; COSMIC-RAYS; PARTICLES; SCALE; BARYOGENESIS; SUPERGRAVITY; CONSTRAINT AB It is quite plausible that the mass of the dark matter particle increases significantly after its freeze-out, due to a scalar field rolling to large values. We describe a realization of this scenario in the context of thermal inflation which naturally gives a cold dark matter particle with the correct cosmological abundance and a mass around 10(10) GeV, evading the conventional upper bound of 10(5) GeV. We also discuss another realization which could produce a cosmologically interesting abundance of near Planck mass, possibly electromagnetically charged, particles. The detection and observational consequences of superheavy cold dark matter or wimpzillas are briefly examined. [S0556-2821(99)04314-3]. C1 NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Box 500, Batavia, IL 60510 USA. EM lhui@fnal.gov; ewand@fnal.gov RI Stewart, Ewan/C-1565-2011 NR 58 TC 12 Z9 12 U1 1 U2 1 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 2470-0010 EI 2470-0029 J9 PHYS REV D JI Phys. Rev. D PD JUL 15 PY 1999 VL 60 IS 2 AR 023518 DI 10.1103/PhysRevD.60.023518 PG 6 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 216WP UT WOS:000081467700025 ER PT J AU Kaplinghat, M Scherrer, RJ Turner, MS AF Kaplinghat, M Scherrer, RJ Turner, MS TI Constraining variations in the fine-structure constant with the cosmic microwave background SO PHYSICAL REVIEW D LA English DT Article ID TIME-VARIATION; FUNDAMENTAL CONSTANTS; PHYSICAL CONSTANTS; ANISOTROPIES; NUCLEOSYNTHESIS; LIMITS AB Any time variation in the fine-structure constant alters the ionization history of the universe and therefore changes the pattern of cosmic microwave background fluctuations. We calculate the changes in the spectrum of these fluctuations as a function of the change in cu, and we find that these changes are dominated by the change in the redshift of recombination due to the shift in the binding energy of hydrogen. We estimate the accuracy with which the next generation of cosmic microwave background experiments might constrain any variation in ct at z similar to 1000. We find that such experiments could potentially be sensitive to \Delta alpha/alpha\ similar to 10(-2)-10(-3) [S0556-2821(99)02114-1]. C1 Ohio State Univ, Dept Phys, Columbus, OH 43210 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA. Univ Chicago, Enrico Fermi Inst, Dept Phys, Chicago, IL 60637 USA. RP Kaplinghat, M (reprint author), Ohio State Univ, Dept Phys, 174 W 18th Ave, Columbus, OH 43210 USA. NR 26 TC 91 Z9 91 U1 0 U2 2 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0556-2821 J9 PHYS REV D JI Phys. Rev. D PD JUL 15 PY 1999 VL 60 IS 2 AR 023516 DI 10.1103/PhysRevD.60.023516 PG 5 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 216WP UT WOS:000081467700023 ER PT J AU Brage, T Proffitt, CR Leckrone, DS AF Brage, T Proffitt, CR Leckrone, DS TI Relativistic ab initio calculations of oscillator strengths and hyperfine structure constants in TlII SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID ISOELECTRONIC SEQUENCE; EXCITATION-ENERGIES; TRANSITIONS; THALLIUM; PACKAGE AB We present accurate calculations of oscillator strengths and hyperfine structure splitting for a set of transitions in Tl II, and discuss how they can be used in stellar atmosphere models of chemically peculiar stars. The results are in good agreement with recent experiments. The predicted uncertainty for oscillator strengths ranges from about 5 to 20% and in most cases less than 10% for hyperfine structure constants. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Lund, Dept Phys, S-22100 Lund, Sweden. RP Brage, T (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. OI Brage, Tomas/0000-0003-3985-767X NR 20 TC 1 Z9 1 U1 0 U2 2 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD JUL 14 PY 1999 VL 32 IS 13 BP 3183 EP 3192 DI 10.1088/0953-4075/32/13/308 PG 10 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 222XW UT WOS:000081811500015 ER PT J AU Kurczynski, P Pehl, RH Hull, EL Palmer, D Harris, MJ Seifert, H Teegarden, BJ Gehrels, N Cline, TL Ramaty, R Sheppard, D Madden, NW Luke, PN Cork, CP Landis, DA Molone, DF Hurley, K AF Kurczynski, P Pehl, RH Hull, EL Palmer, D Harris, MJ Seifert, H Teegarden, BJ Gehrels, N Cline, TL Ramaty, R Sheppard, D Madden, NW Luke, PN Cork, CP Landis, DA Molone, DF Hurley, K TI Long-term radiation damage to a spaceborne germanium spectrometer SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID FAST-NEUTRON DAMAGE; DETECTORS AB The Transient Gamma-Ray Spectrometer aboard the Wind spacecraft in deep space has observed gamma-ray bursts and solar events for four years. The germanium detector in the instrument has gradually deteriorated from exposure to the approximate to 10(8) p/cm(2)/yr( > 100 MeV) cosmic-ray flux. Low-energy tailing and loss of efficiency, attributed to hole trapping and conversion of the germanium from n- to p-type as a result of crystal damage, were observed. Raising the detector bias voltage ameliorated both difficulties and restored the spectrometer to working operation. Together, these observations extend our understanding of the effects of radiation damage to include the previously unsuccessfully studied regime of long-term operation in space. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Kurczynski, P (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. NR 12 TC 22 Z9 22 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 JUL 11 PY 1999 VL 431 IS 1-2 BP 141 EP 147 DI 10.1016/S0168-9002(99)00283-1 PG 7 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 216WY UT WOS:000081468500014 ER PT J AU Fonte, P Carolino, N Costa, L Ferreira-Marques, R Mendiratta, S Peskov, V Policarpo, A AF Fonte, P Carolino, N Costa, L Ferreira-Marques, R Mendiratta, S Peskov, V Policarpo, A TI A spark-protected high-rate detector SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article ID RESISTIVE-PLATE CHAMBER; BREAKDOWN AB We developed a very low resistivity RPC-type detector, the anode of which was a plate made from materials with resistivity up to 5 x 10(7) Ohm cm, the cathode being a metallic mesh preceded by a drift region. In such a detector it was actually possible to combine the versatility and high counting-rate capability of metallic PPACs with the extreme robustness and "protectiveness" of Resistive Plate Chambers. Occasional discharges triggered by large deposits of primary ionisation or by extreme counting rates are quenched by the resistive anode and are constrained to the streamer phase of the sparking process. The study shows that this discharge affects the detector only locally and that the charge released if limited to a few tens of nC. Proportional counting rates up to 10(5) Hz/mm(2) were achieved at gains above 10(4). The energy resolution at 6 keV was 20% FWHM. The observed gain-rate trade-off is well described by an analytic model and further improvements may be expected by lowering the resistivity of the anode material. The properties of several custom-made, controllable resistivity, anode materials are described and prospects of improvement in the performance of the detector are discussed. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Coimbra, Dept Fis, LIP, P-3000 Coimbra, Portugal. ISEC, P-3000 Coimbra, Portugal. Univ Aveiro, Dept Fis, P-3800 Aveiro, Portugal. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Fonte, P (reprint author), CERN, EP, CH-1211 Geneva 23, Switzerland. RI Universidade Aveiro, Departamento Fisica/E-4128-2013; Fonte, Paulo/B-1842-2008 OI Fonte, Paulo/0000-0002-2275-9099 NR 21 TC 36 Z9 36 U1 1 U2 3 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 JUL 11 PY 1999 VL 431 IS 1-2 BP 154 EP 159 DI 10.1016/S0168-9002(99)00221-1 PG 6 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 216WY UT WOS:000081468500016 ER PT J AU Haiman, Z Loeb, A AF Haiman, Z Loeb, A TI Determining the redshift of reionization from the spectra of high-redshift sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; galaxies : formation; intergalactic medium; quasars : absorption lines; radiative transfer ID INTERGALACTIC MEDIUM; UNIVERSE; GALAXIES; METALS; QUASAR; FIELD AB The redshift at which the universe was reionized is currently unknown. We examine the optimal strategy for extracting this redshift, z(reion), from the spectra of early sources. For a source located at a redshift z(s) beyond but close to the reionization redshift, (1 + z(reion)) < (1 + z(s)) < 32/27(1 + z(reion)), the Gunn-Peterson trough splits into disjoint Ly alpha, Ly beta, and possibly higher Lyman series troughs, with some transmitted flux between these troughs. We show that although the transmitted flux is suppressed considerably by the dense Ly alpha forest at high redshifts, it could still be detectable as long as z(reion) less than or similar to 8. If the ionizing sources are bright and have a short duty cycle (e.g., if they are miniquasars or starbursts with a lifetime less than or similar to 10(6) yr), then breakthrough occurs shortly after the H II regions around them overlap, and the transmitted flux provides a measurement of z(reion). The Next Generation Space Telescope will reach the spectroscopic sensitivity required for such a measurement. C1 Harvard Univ, Dept Astron, Cambridge, MA 02138 USA. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. RP Haiman, Z (reprint author), Harvard Univ, Dept Astron, 60 Garden St, Cambridge, MA 02138 USA. NR 27 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 JUL 10 PY 1999 VL 519 IS 2 BP 479 EP 485 DI 10.1086/307393 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000005 ER PT J AU Hui, L Gaztanaga, E AF Hui, L Gaztanaga, E TI Biased estimations of variance and skewness SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : statistics; methods : statistical ID LARGE-SCALE STRUCTURE; HIGHER-ORDER STATISTICS; APM GALAXY SURVEY; POWER-SPECTRUM; PERTURBATION-THEORY; REDSHIFT SURVEYS; COUNTS; CELLS; SIMULATIONS; MOMENTS AB Nonlinear combinations of direct observables are often used to estimate quantities of theoretical interest. Without sufficient caution, this could lead to biased estimations. An example of great interest is the skewness S-3 of the galaxy distribution, defined as the ratio of the third moment <(zeta)over bar>(3) and the variance squared <(zeta)over bar>(2)(2) smoothed at some scale R. Suppose one is given unbiased estimators for <(zeta)over bar>(3) and <(zeta)over bar>(2)(2) respectively; taking a ratio of the two does not necessarily result in an unbiased estimator of S-3. Exactly such an estimation bias (distinguished from the galaxy bias) affects most existing measurements of S-3 from galaxy surveys. Furthermore, common estimators for <(zeta)over bar>(3) and <(zeta)over bar>(2) suffer also from this kind of estimation bias themselves because of a division by the estimated mean counts in cell. In the case of <(zeta)over bar>(2), the bias is equivalent to what is commonly known as the integral constraint. We present a unifying treatment allowing all these estimation biases to be calculated analytically. These estimation biases are in general negative, and decrease in significance as the survey volume increases, for a given smoothing scale. We present a preliminary reanalysis of some existing measurements of the variance and skewness (from the APM, CfA, SSRS, and IRAS) and show that most of the well-known systematic discrepancies between surveys with similar selection criteria, but different sizes, can be attributed to the volume-dependent estimation biases. This affects the inference of the galaxy bias(es) from these surveys. Our methodology can be adapted to measurements of the variance and skewness of, for instance, the transmission distribution in quasar spectra and the convergence distribution in weak-lensing maps. We discuss generalizations to N > 3, suggest methods to reduce the estimation bias, and point out other examples in large-scale structure studies that might suffer from this type of a nonlinear estimation bias. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. CSIC, Inst Estudis Espacials Catalunya, ES-08034 Barcelona, Spain. RP Hui, L (reprint author), NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. OI Gaztanaga, Enrique/0000-0001-9632-0815 NR 51 TC 56 Z9 56 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 JUL 10 PY 1999 VL 519 IS 2 BP 622 EP 636 DI 10.1086/307401 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000019 ER PT J AU Rastatter, L Schindler, K AF Rastatter, L Schindler, K TI Magnetized accreting stars: Studies of the inner accretion disk edge by a magnetohydrodynamical approach. I. Construction and analysis of magnetopause equilibria SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; galaxies : active; MHD; stars : neutron ID LOCAL SHEAR INSTABILITY; NEUTRON STARS; PERTURBATIONS; RECONNECTION AB In this paper a numerical model of the interaction between the accretion disk and the magnetosphere of an accreting object (e.g., a neutron star) is used to study mechanisms that can lead to fast accretion of matter due to magnetic forces. The framework of magnetohydrodynamics (MHD) provides a simple but powerful tool for such a study on a semiglobal scale. The aim of this work is the construction of stationary states that describe the inner-edge region of the accretion disk with the star's rotating magnetosphere supporting the inner disk edge against gravitation. The equilibrium magnetic fields are computed numerically by a finite difference scheme using the magnetofriction method within ideal magnetohydrodynamics. To study the mass loading onto the magnetosphere we vary disk mass density and pressure. Magnetosphere rotation speed and magnetopause thickness are additonal variables contributing to the shape of the magnetosphere and the currents in the magnetopause at the disk edge. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Ruhr Univ Bochum, D-44780 Bochum, Germany. RP Rastatter, L (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Rastaetter, Lutz/D-4715-2012 OI Rastaetter, Lutz/0000-0002-7343-4147 NR 19 TC 3 Z9 3 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1999 VL 519 IS 2 BP 658 EP 666 DI 10.1086/307382 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000023 ER PT J AU Feibelman, WA AF Feibelman, WA TI Stellar CIII emissions as a new classification parameter for [WC] central stars SO ASTROPHYSICAL JOURNAL LA English DT Article DE planetary nebulae : general; stars : fundamental parameters; stars : Wolf-Rayet; ultraviolet : stars ID IUE SPECTRUM; PLANETARY-NEBULAE; SANDULEAK-3; NGC-6751; NUCLEI AB We report detection of stellar C III lambda 1909 emission in IUE echelle spectra of early-type [WC] central stars of planetary nebulae (CSPNs). Additionally, stellar C III emission at 2297 Angstrom is observed in early- and late-type [WC] CSPNs. Inclusion of these C III features for abundance determinations may resolve a conflict of underabundance of C/O for early-type [WC2]-[WC4] CSPNs. A linear dependence on stellar C III lambda 2297 equivalent widths can be used to indicate a new classification of type-[WCUV] central stars. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. RP Feibelman, WA (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 21 TC 2 Z9 2 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 JUL 10 PY 1999 VL 519 IS 2 BP 726 EP 732 DI 10.1086/307411 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000028 ER PT J AU Kazanas, D Hua, XM AF Kazanas, D Hua, XM TI Modeling the time variability of accreting compact sources SO ASTROPHYSICAL JOURNAL LA English DT Article DE black hole physics; radiation mechanisms : nonthermal; stars : neutron; X-rays : stars ID ACTIVE GALACTIC NUCLEI; X-RAY VARIABILITY; CYGNUS X-1; COMPTONIZATION MODELS; SPECTRA; DISKS; STATE AB We present model light curves for accreting black hole candidates (BHCs) based on a recently proposed model for their spectre-temporal properties. According to this model, the observed light curves and aperiodic variability of BHCs are due to a series of soft photon injections at random (Poisson) intervals near the compact object and their reprocessing into hard radiation in an extended but nonuniform hot plasma corona surrounding the compact object. We argue that the majority of the timing characteristics of these light curves are due to the stochastic nature of the Comptonization process in the extended corona, whose properties, most notably its radial density dependence, are imprinted in them. We compute the corresponding power spectral densities (PSD), autocorrelation functions, time skewness of the light curves, and time lags between the light curves of the sources at different photon energies and compare our results to observation. Our model light curves compare well with observations, providing good fits to their overall morphology, as manifest by the autocorrelation and skewness functions. The lags and PSDs of the model light curves are also in good agreement with those observed (the model can even accommodate the presence of quasi-periodic oscillations). Finally, while most of the variability power resides at timescales approximately a few seconds, at the same time, the model allows also for shots of a few milliseconds in duration, in accordance with observation. We suggest that refinements of this type of model along with spectral and phase lag information can be used to probe the structure of this class of high-energy sources. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 30 TC 18 Z9 18 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1999 VL 519 IS 2 BP 750 EP 761 DI 10.1086/307379 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000031 ER PT J AU Krucker, S Larson, DE Lin, RP Thompson, BJ AF Krucker, S Larson, DE Lin, RP Thompson, BJ TI On the origin of impulsive electron events observed at 1 AU SO ASTROPHYSICAL JOURNAL LA English DT Article DE Sun : flares; Sun : particle emission; Sun : radio radiation; Sun : X-rays, gamma rays ID WIND SPACECRAFT; SOLAR; PLASMA; FLARES AB A statistical survey of 12 impulsive electron events detected at energies down below 1 keV and 58 events detected above 25 keV observed at 1 AU by the 3-D Plasma and Energetic Particles experiment on the Wind spacecraft is presented. Timing analysis of the velocity dispersion reveals two different kinds of electron events: (1) events released from the Sun at the onset of a radio type IU: burst, which suggest that these electrons are part of the population producing the type III radio emission; and (2) events in which the electrons are released up to half an hour Later than the onset of the type III burst. These electrons therefore may be produced by a different acceleration mechanism than the population producing the radio emission. Both types of behavior can be observed during the same impulsive electron event at different energies, but most events show the same timing at all energies. At lower energies (<25 keV), type Iii-related impulsive electron events are more often observed (nine of 12 events), whereas at higher energies (>25 keV), events not related to type III bursts are more numerous (41 of 58). However, events of both classes are observed below 1 keV. Impulsive electron events not related to type III radio bursts are observed to be proton rich, with an order-of-magnitude lower electron-to-proton ratio than events related to type III bursts. For roughly 3/4 of the events not related to type III bursts, large-scale coronal transient waves, also called EIT waves or coronal Moreton waves, are observed by the Extreme Ultraviolet Imaging Telescope (EIT) on board SOHO. Temporal and spatial correlations together with hydromagnetic simulations show that at least some impulsive electron events are more likely related to the propagating Moreton wave than to the hare phenomenon itself. C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, Goddard Space Flight Ctr, Space Applicat Corp, Greenbelt, MD 20771 USA. RP Krucker, S (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Thompson, Barbara/C-9429-2012 NR 18 TC 176 Z9 179 U1 0 U2 3 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1999 VL 519 IS 2 BP 864 EP 875 DI 10.1086/307415 PN 1 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000042 ER PT J AU Kondrashov, D Feynman, J Liewer, PC Ruzmaikin, A AF Kondrashov, D Feynman, J Liewer, PC Ruzmaikin, A TI Three-dimensional magnetohydrodynamic simulations of the interaction of magnetic flux tubes SO ASTROPHYSICAL JOURNAL LA English DT Article DE MHD; Sun : magnetic fields ID RECONNECTION; HELICITY; LOOPS AB We use a three-dimensional Cartesian resistive MHD code to investigate three-dimensional aspects of the interaction of magnetic flux tubes as observed in the solar atmosphere and studied in laboratory experiments. We present here the first results from modeling the reconnection of two Gold-Hoyle magnetic flux tubes that follow the system. evolution to a final steady state. The energy evolution and reconnection rate for flux tubes with both parallel and antiparallel axial fields and with equal and nonequal strengths are studied. For the first time, we calculate a gauge-invariant relative magnetic helicity of the system and compare its evolution for all the above cases. We observed that the rate at which helicity is dissipated may vary significantly for different cases, and it may be comparable with the energy dissipation rate. The footpoints of the interacting flux tubes were held fixed or allowed to move to simulate different conditions in the solar photosphere. The cases with fixed footpoints had lower magnetic energy release and reached a steady state faster than cases with moving footpoints. For all computed cases the magnetic energy was released mostly through work done on the plasma by the electromagnetic forces rather than through resistive dissipation. The reconnection rate of the poloidal magnetic field is faster for the case with antiparallel flux tubes than for the case with parallel flux tubes, consistent with laboratory experiments. We find that during reconnection supersonic (but sub-Alfvenic) flows develop, and it may take a considerably longer time for the system to reach a steady state than for magnetic Bur to reconnect. It is necessary to retain the pressure gradient in the momentum equation; the plasma pressure may be significant for the final equilibrium steady state even with low-beta initial conditions, and the work done on the plasma by compression is important in energy exchange. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Kondrashov, D (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Kondrashov, Dmitri/E-2067-2016 OI Kondrashov, Dmitri/0000-0002-3471-7275 NR 22 TC 19 Z9 19 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 JUL 10 PY 1999 VL 519 IS 2 BP 884 EP 898 DI 10.1086/307383 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XF UT WOS:000081298000044 ER PT J AU Fender, R Corbel, S Tzioumis, T McIntyre, V Campbell-Wilson, D Nowak, M Sood, R Hunstead, R Harmon, A Durouchoux, P Heindl, W AF Fender, R Corbel, S Tzioumis, T McIntyre, V Campbell-Wilson, D Nowak, M Sood, R Hunstead, R Harmon, A Durouchoux, P Heindl, W TI Quenching of the radio jet during the X-ray high state of GX 339-4 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; ISM : jets and outflows; radio continuum : stars; stars : individual (GX 339-4) ID GRO J1655-40; GX-339-4; OUTBURSTS; ACCRETION AB We have observed the black hole candidate X-ray binary GX 339-4 at radio wavelengths before, during, and after the 1998 high/soft X-ray state transition. We find that the radio emission from the system is strongly correlated with the hard X-ray emission and is reduced by a factor of greater than or equal to 25 during the high/soft state compared with the more usual low/hard state. At the points of state transition, we note brief periods of unusually optically thin radio emission that may correspond to discrete ejection events. We propose that in the low/hard state, black hole X-ray binaries produce a quasi-continuous outflow, that in the high/soft state, this outflow is suppressed, and that state transitions often result in one or more discrete ejection events. Future models for low/hard states, such as advection-dominated solutions, need to take into account the strong outflow of relativistic electrons from the system. We propose that the inferred Comptonizing corona and the base of the jetlike outflow are the same thing, based on the strong correlation between radio and hard X-ray emission in GX 339-4 and other X-ray binaries and on the similarity in inferred location and composition of these two components. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Amsterdam, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. CEA Saclay, Serv Astrophys, F-91191 Gif Sur Yvette, France. Paul Wild Observ, CSIRO, Australia Telescope Natl Facil, Narrabri, NSW 2390, Australia. Univ Sydney, Sch Phys, Dept Astrophys, Sydney, NSW 2006, Australia. Univ Sydney, Sch Phys, Dept Astrophys, Molonglo Radio Observ, Sydney, NSW 2006, Australia. Univ Colorado, JILA, Boulder, CO 80309 USA. Australian Def Force Acad, Sch Phys, Canberra, ACT 2600, Australia. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. RP Fender, R (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. NR 40 TC 161 Z9 163 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 JUL 10 PY 1999 VL 519 IS 2 BP L165 EP L168 DI 10.1086/312128 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XK UT WOS:000081298400015 ER PT J AU Goldsmith, PF Langer, WD Velusamy, T AF Goldsmith, PF Langer, WD Velusamy, T TI Detection of methanol in a class 0 protostellar disk SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; ISM : individual (L1157); ISM : molecules; stars : formation; stars : pre-main-sequence ID SPECTRAL ENERGY-DISTRIBUTIONS; T-TAURI STARS; CIRCUMSTELLAR DISKS; PROTOPLANETARY DISK; MOLECULAR OUTFLOW; L1157 OUTFLOW; CHEMISTRY; SIO; GAS; PARAMETERS AB We report the detection of emission from methanol in a compact source coincident with the position of the L1157 infrared source, which we attribute to molecules in the disk surrounding this young, class 0 protostellar object. Using the Caltech Owens Valley Millimeter Array with a synthesized beam size of 2 ", we detect spatially unresolved methanol emission in the 2(k)-1(k) transitions at 3 mm wavelength, which is coincident in position with the peak of the continuum emission. The gas-phase methanol could be located in the central region (<100 AU radius) of a flat disk or in an extended heated surface layer (similar to 200 AU radius) of a flared disk. The fractional abundance of methanol X(CH3OH) is similar to 2 x 10(-8) in the flat disk model and similar to 3 x 10(-7) for the surface layer of a flared disk. The large variation in the fractional abundance between the warm portion of the flared disk and the disk as a whole makes it plausible that substantial chemical processing via depletion and desorption has occurred. C1 Cornell Univ, Natl Astron & Ionosphere Ctr, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Goldsmith, PF (reprint author), Cornell Univ, Natl Astron & Ionosphere Ctr, Dept Astron, Space Sci Bldg, Ithaca, NY 14853 USA. RI Goldsmith, Paul/H-3159-2016 NR 29 TC 26 Z9 26 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 JUL 10 PY 1999 VL 519 IS 2 BP L173 EP L176 DI 10.1086/312125 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XK UT WOS:000081298400017 ER PT J AU Hurley, K Kouveliotou, C Woods, P Mazets, E Golenetskii, S Frederiks, DD Cline, T van Paradijs, J AF Hurley, K Kouveliotou, C Woods, P Mazets, E Golenetskii, S Frederiks, DD Cline, T van Paradijs, J TI Precise interplanetary network localization of a new soft gamma repeater, SGR 1627-41 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; stars : neutron; supernova remnants; X-rays : stars ID SGR1806-20; IDENTIFICATION; COINCIDENT; TRANSIENT AB We present Ulysses, Konus-Wind, and BATSE observations of bursts from a new soft gamma repeater that was active in 1998 June and July. Triangulation of the bursts results in a similar to 1.degrees 8 by 16 " error box whose area is similar to 7.6 arcmin(2) and which contains the Galactic supernova remnant G337.0-0.1. This error box intersects the position of a BeppoSAX X-ray source that is also consistent with the position of G337.0-0.1 and is thought to be the quiescent counterpart to the repeater. If so, the resulting error box is similar to 2' x 16 " and has an area of similar to 0.6 arcmin(2). The error box location within the supernova remnant suggests that the neutron star has a transverse velocity of similar to 200-2000 hm s(-1). C1 Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Alabama, Huntsville, AL 35899 USA. AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1012 WX Amsterdam, Netherlands. RP Hurley, K (reprint author), Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RI Frederiks, Dmitry/C-7612-2014; Golenetskii, Sergey/B-3818-2015 NR 25 TC 35 Z9 35 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1999 VL 519 IS 2 BP L143 EP L145 DI 10.1086/312115 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XK UT WOS:000081298400010 ER PT J AU Mazets, EP Aptekar, RL Butterworth, PS Cline, TL Frederiks, DD Golenetskii, SV Hurley, K Il'inskii, VN AF Mazets, EP Aptekar, RL Butterworth, PS Cline, TL Frederiks, DD Golenetskii, SV Hurley, K Il'inskii, VN TI Unusual burst emission from the new soft gamma repeater SGR 1627-41 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; stars : neutron ID TRANSIENT AB In 1998 June-July, the Konus-Wind burst spectrometer observed a series of bursts from the new soft gamma repeater SGR 1627-41. Time histories and energy spectra of the bursts have been studied, revealing fluences and peak fluxes in the ranges 3 x 10(-7) to 7.5 x 10(-6) ergs cm(-2) and 10(-5) to 10(-4) ergs cm(-2) s(-1), respectively. One event, 18 June 6153.5 s UT, stands out dramatically from this series. Its fluence is similar to 7 x 10(-4) ergs cm(-2) and its peak flux is similar to 2 x 10(-2) ergs cm(-2) s(-1). These values from a source at a distance of 5.8 kpc yield an energy output of similar to 3 x 10(42) ergs and a maximum luminosity of similar to 8 x 10(43) ergs s(-1) for isotropic emission, similar to the values for the famous 1979 March 5 and 1998 August 27 events. In terms of energy, this event is another giant outburst seen in a third soft gamma repeater! However, this very energetic burst differs significantly from the other giant outbursts. It exhibits no separate initial pulse with a fast rise time, no extended tail, and no pulsations. It is rather similar to ordinary repeated bursts, but is a few hundred times stronger in intensity. According to the magnetar model by Thompson & Duncan, such a burst may be initiated by a strong starquake when a crust fracture propagates over the whole surface of a neutron star. C1 AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Mazets, EP (reprint author), AF Ioffe Phys Tech Inst, Politekhnicheskaya 26, St Petersburg 194021, Russia. RI Frederiks, Dmitry/C-7612-2014; Aptekar, Raphail/B-3456-2015; Golenetskii, Sergey/B-3818-2015 NR 30 TC 37 Z9 37 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 10 PY 1999 VL 519 IS 2 BP L151 EP L153 DI 10.1086/312118 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XK UT WOS:000081298400012 ER PT J AU Woods, PM Kouveliotou, C van Paradijs, J Hurley, K Kippen, RM Finger, MH Briggs, MS Dieters, S Fishman, GJ AF Woods, PM Kouveliotou, C van Paradijs, J Hurley, K Kippen, RM Finger, MH Briggs, MS Dieters, S Fishman, GJ TI Discovery of a new soft gamma repeater, SGR 1627-41 SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (SAX J1635.8-4736; SGR 1627-41); stars : neutron; X-rays : bursts ID MAGNETIZED NEUTRON-STARS; X-RAY PULSAR; IDENTIFICATION; SGR1806-20; COINCIDENT; TRANSIENT; CATALOG; BURSTS AB We report the discovery of a new soft gamma repeater (SGR), SGR 1627-41, and present BATSE observations of the burst emission and BeppoSAX Narrow-Field Instrument observations of the probable persistent X-ray counterpart to this SGR. All but one burst spectrum are well fit by an optically thin thermal bremsstrahlung model with kT values between 25 and 35 keV. The spectrum of the X-ray counterpart, SAX J1635.8-4736, is similar to that of other persistent SGR X-ray counterparts. We find weak evidence for a periodic signal at 6.41 s in the light curve for this source. Like other SGRs, this source appears to be associated with a young supernova remnant, G337.0-0.1. Based upon the peak luminosities of bursts observed from this SGR, we find a lower limit on the dipole magnetic field of the neutron star of B-dipole greater than or similar to 5 x 10(14) G. C1 Univ Alabama, Dept Phys, Ctr Space Plasma Aeronom & Astrophys Res, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Woods, PM (reprint author), Univ Alabama, Dept Phys, Ctr Space Plasma Aeronom & Astrophys Res, Huntsville, AL 35899 USA. NR 35 TC 102 Z9 102 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 JUL 10 PY 1999 VL 519 IS 2 BP L139 EP L142 DI 10.1086/312124 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 213XK UT WOS:000081298400009 ER PT J AU Giglio, L Kendall, JD AF Giglio, L Kendall, JD TI Evaluation of global fire detection algorithms using simulated AVHRR infrared data SO INTERNATIONAL JOURNAL OF REMOTE SENSING LA English DT Article ID HIGH-RESOLUTION RADIOMETER; TERRESTRIAL MATERIALS; ATMOSPHERIC WINDOW; DATA SETS; EMISSIVITY; VEGETATION AB This paper provides a comparison of selected algorithms that have been proposed for global active fire monitoring using data from the NOAA Advanced Very High Resolution Radiometer (AVHRR). A simple theoretical model was used to generate scenes of AVHRR infrared channel 3 and channel 4 data containing fires of various sizes and temperatures in a wide range bf terrestrial biomes and climates. Three active fire detection algorithms were applied to the simulated AVHRR images and their performance was characterized in terms of probability of fire detection and false alarm as functions of fire temperature and area, solar and viewing geometry, visibility, season and biome. Additional comparisons were made using AVHRR imagery. Results indicate that while each algorithm has a comparable probability of detecting large (>1000 m(2)) fires in most biomes, substantial differences exist in their ability to detect small fires, their tolerance of smoke and neighbouring fires, the number of false alarms, and their overall suitability for global application. An improved automatic algorithm is finally presented. It offers enhanced active fire detection with comparable or reduced false alarm rates in most biomes. C1 NASA, Sci Syst & Applicat Inc, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Virginia, Dept Environm Sci, Charlottesville, VA 22903 USA. RP Giglio, L (reprint author), NASA, Sci Syst & Applicat Inc, Goddard Space Flight Ctr, Code 923, Greenbelt, MD 20771 USA. EM giglio@hades.gsfc.nasa.gov NR 38 TC 127 Z9 132 U1 2 U2 16 PU TAYLOR & FRANCIS LTD PI ABINGDON PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND SN 0143-1161 J9 INT J REMOTE SENS JI Int. J. Remote Sens. PD JUL 10 PY 1999 VL 20 IS 10 BP 1947 EP 1985 DI 10.1080/014311699212290 PG 39 WC Remote Sensing; Imaging Science & Photographic Technology SC Remote Sensing; Imaging Science & Photographic Technology GA 211HL UT WOS:000081154800003 ER PT J AU Menon, M Srivastava, D AF Menon, M Srivastava, D TI Structure of boron nitride nanotubes: tube closing versus chirality SO CHEMICAL PHYSICS LETTERS LA English DT Article ID MOLECULAR-DYNAMICS; CARBON NANOTUBES; TUBULES; MICROTUBULES; FILAMENTS; GROWTH; SCHEME AB The structure of boron nitride nanotubes is investigated using a generalized tight-binding molecular dynamics method. It is shown that dynamic relaxation results in a wave-like or 'rippled' surface in which the B atoms rotate inward and the N atoms move outward, reminiscent of the surface relaxation of the III-V semiconductors. More importantly, the three different morphologies of the tube closing with flat, conical and amorphous ends, as observed in experiments, are shown to be directly related to the tube chiralities. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NASA, Ames Res Ctr, NAS Syst Div, NAS Computat Facil, Moffett Field, CA 94035 USA. Univ Kentucky, Ctr Computat Sci, Lexington, KY 40506 USA. RP Menon, M (reprint author), Univ Kentucky, Dept Phys & Astron, Lexington, KY 40506 USA. NR 25 TC 112 Z9 115 U1 0 U2 6 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0009-2614 J9 CHEM PHYS LETT JI Chem. Phys. Lett. PD JUL 9 PY 1999 VL 307 IS 5-6 BP 407 EP 412 DI 10.1016/S0009-2614(99)00552-7 PG 6 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 214KC UT WOS:000081326300019 ER PT J AU Luchinsky, DG Mannella, R McClintock, PVE Dykman, MI Smelyanskiy, VN AF Luchinsky, DG Mannella, R McClintock, PVE Dykman, MI Smelyanskiy, VN TI Thermally activated escape of driven systems: the activation energy SO JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL LA English DT Letter ID DISSIPATIVE DYNAMICAL-SYSTEMS; STOCHASTIC RESONANCE; NOISE; FLUCTUATIONS; STATE AB Thermally activated escape in the presence of a periodic external field is investigated theoretically and through analogue experiments and digital simulations. The observed variation of the activation energy for escape with driving force parameters is accurately described by the logarithmic susceptibility (LS). The frequency dispersion of the LS is shown to differ markedly from the standard linear susceptibility. Experimental data on the dispersion are in quantitative agreement with the theory. Switching between different branches of the activation energy is demonstrated for a nonsinusoidal (biharmonic) force. C1 Univ Lancaster, Dept Phys, Lancaster LA1 4YB, England. Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. NASA, Ames Res Ctr, Caelum Res Co, Moffett Field, CA 94035 USA. Russian Res Inst Metrol Serv, Moscow 119361, Russia. Univ Pisa, Dipartimento Fis, I-56100 Pisa, Italy. INFM, UdR Pisa, I-56100 Pisa, Italy. RP Luchinsky, DG (reprint author), Univ Lancaster, Dept Phys, Lancaster LA1 4YB, England. RI Mannella, Riccardo/B-8798-2012; Luchinsky, Dmitry/N-4177-2014 NR 27 TC 14 Z9 14 U1 1 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0305-4470 J9 J PHYS A-MATH GEN JI J. Phys. A-Math. Gen. PD JUL 9 PY 1999 VL 32 IS 27 BP L321 EP L327 DI 10.1088/0305-4470/32/27/105 PG 7 WC Physics, Multidisciplinary; Physics, Mathematical SC Physics GA 221LJ UT WOS:000081728300005 ER PT J AU Tang, WP AF Tang, WP TI Toward an effective sparse approximate inverse preconditioner SO SIAM JOURNAL ON MATRIX ANALYSIS AND APPLICATIONS LA English DT Article DE approximate inverse; globally coupled local inverse; ILU preconditioner; exponential decay ID NONSYMMETRIC LINEAR-SYSTEMS; CONJUGATE-GRADIENT METHODS; BAND MATRICES AB Sparse approximate inverse preconditioners have attracted much attention recently, because of their potential usefulness in a parallel environment. In this paper, we explore several performance issues related to effective sparse approximate inverse preconditioners (SAIPs) for the matrices derived from PDEs. Our refinements can significantly improve the quality of existing SAIPs and/or reduce the cost of computing them. For the test problems from the Harwell-Boeing collection and some other applications, the performance of our preconditioners can be comparable or superior to incomplete LU (ILU) preconditioners with similar preconditioning cost. C1 Univ Waterloo, Dept Comp Sci, Waterloo, ON N2L 3G1, Canada. NASA, Ames Res Ctr, Adv Comp Sci Res Inst, Moffett Field, CA 94035 USA. RP Tang, WP (reprint author), Univ Waterloo, Dept Comp Sci, Waterloo, ON N2L 3G1, Canada. NR 50 TC 28 Z9 28 U1 0 U2 2 PU SIAM PUBLICATIONS PI PHILADELPHIA PA 3600 UNIV CITY SCIENCE CENTER, PHILADELPHIA, PA 19104-2688 USA SN 0895-4798 J9 SIAM J MATRIX ANAL A JI SIAM J. Matrix Anal. Appl. PD JUL 9 PY 1999 VL 20 IS 4 BP 970 EP 986 DI 10.1137/S0895479897320071 PG 17 WC Mathematics, Applied SC Mathematics GA 222WJ UT WOS:000081808100009 ER PT J AU Vilnrotter, V Simon, M Srinivasan, M AF Vilnrotter, V Simon, M Srinivasan, M TI Maximum likelihood detection of PPM signals governed by arbitrary point-process plus additive Gaussian noise SO ELECTRONICS LETTERS LA English DT Article AB The maximum likelihood decision statistic for pulse-position modulated (PPM) signals governed by an arbitrary discrete point process in the presence of additive Gaussian noise is derived. Sufficient conditions are given for determining when the optimum PPM symbol detection strategy is to choose the PPM symbol corresponding to the maximum slot statistic. In particular, it is shown that for the important case of Webb distributed avalanche photodiode output electrons in the presence of Gaussian noise, the optimum decision rule is to choose the largest slot observable. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91107 USA. RP Vilnrotter, V (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91107 USA. NR 6 TC 1 Z9 1 U1 2 U2 2 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 JUL 8 PY 1999 VL 35 IS 14 BP 1132 EP 1133 DI 10.1049/el:19990772 PG 2 WC Engineering, Electrical & Electronic SC Engineering GA 226QM UT WOS:000082031900009 ER PT J AU Chillier, XDF Stone, BM Salama, F Allamandola, LJ AF Chillier, XDF Stone, BM Salama, F Allamandola, LJ TI First detection of an ultraviolet transition in an ionized polycyclic aromatic hydrocarbon SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID RADICAL CATIONS; ELECTRONIC-SPECTRA; ABSORPTION-SPECTRA; RED RECTANGLE; NAPHTHALENE; BANDS AB We report the first measurement of a polycyclic aromatic hydrocarbon cation electronic transition in the ultraviolet spectral region. The UV excitation spectrum of the D-n-XD0 transition of the perylene cation (C20H12+) isolated in an argon matrix was pumped with tunable, coherent radiation and monitored using the vibronic bands of the D-1(B-2(3g)) --> ((2)A(u))D-0 system. The two component band peaks at 244 and 250.2 nm, close to the S-2(B-1(3u)) <-- ((1)A(g))S-0 transition in neutral perylene. (C) 1999 American Institute of Physics. [S0021-9606(99)02226-6]. C1 NASA, Astrochem Lab, Ames Res Ctr, Moffett Field, CA 94035 USA. San Jose State Univ, Dept Chem, San Jose, CA 95192 USA. RP Chillier, XDF (reprint author), NASA, Astrochem Lab, Ames Res Ctr, M-S 245-6, Moffett Field, CA 94035 USA. OI Salama, Farid/0000-0002-6064-4401 NR 15 TC 15 Z9 15 U1 0 U2 1 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 JUL 8 PY 1999 VL 111 IS 2 BP 449 EP 451 DI 10.1063/1.479323 PG 3 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 209UM UT WOS:000081067300002 ER PT J AU Farassat, F Dunn, MH AF Farassat, F Dunn, MH TI A simple derivation of the acoustic boundary condition in the presence of flow SO JOURNAL OF SOUND AND VIBRATION LA English DT Letter C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Old Dominion Univ, Norfolk, VA 23508 USA. RP Farassat, F (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 4 TC 5 Z9 5 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 JUL 8 PY 1999 VL 224 IS 2 BP 384 EP 386 DI 10.1006/jsvi.1998.2142 PG 3 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 214UX UT WOS:000081346900013 ER PT J AU Greenfield, MA AF Greenfield, MA TI Maintaining space shuttle safety within an environment of change SO ACTA ASTRONAUTICA LA English DT Article AB In the 10 years since the Challenger accident, NASA has developed a set of stable and capable processes to prepare the Space Shuttle for safe launch and return. Capitalizing on the extensive experience gained from a string of over 50 successful flights, NASA today is changing the way it does business in an effort to reduce cost. A single Shuttle Flight Operations Contractor (SFOC) has been chosen to operate the Shuttle. The Government role will change from direct "oversight" to "insight" gained through understanding and measuring the contractor's processes. This paper describes the pro gram management changes underway and the NASA Safety and Mission Assurance (S&MA) organization's philosophy, role, and methodology for pursuing this new approach. It describes how audit and surveillance will replace direct oversight and how meaningful performance metrics will be implemented. Published by Elsevier Science Ltd. C1 NASA, Off Safety & Mission Assurance, Washington, DC 20546 USA. RP Greenfield, MA (reprint author), NASA, Off Safety & Mission Assurance, Code Q, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 1 U2 4 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD JUL PY 1999 VL 45 IS 1 BP 31 EP 37 DI 10.1016/S0094-5765(99)00029-6 PG 7 WC Engineering, Aerospace SC Engineering GA 239DQ UT WOS:000082753900004 ER PT J AU Stanford, M Jones, JA AF Stanford, M Jones, JA TI Space radiation concerns for manned exploration SO ACTA ASTRONAUTICA LA English DT Article AB Spaceflight exposes astronaut crews to natural ionizing radiation. To date, exposures in manned spaceflight have been well below the carter limits recommended to NASA by the National Council of Radiation Protection and Measurements (NCRP). This will not be the case for long-duration exploratory class missions. Additionally, International Space Station (ISS) crews will receive higher doses than earlier flight crews. Uncertainties in our understanding of long-term bioeffects, as well as updated analyses of the Hiroshima, Nagasaki and Chernobyl tumorigenesis data, have prompted the NCRP to recommend further reductions by 30-50% for career dose limit guidelines. Intelligent space craft design and material selection can provide a shielding strategy capable of maintaining crew exposures within recommended guidelines, Current studies on newer radioprotectant compounds may find combinations of agents which further diminish the risk of radiation-induced bioeffects to the crew. Published by Elsevier Science Ltd. All rights reserved. C1 Univ Texas, Med Branch, Ctr Aerosp Med & Physiol, Galveston, TX 77555 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Jones, JA (reprint author), NASA, Lyndon B Johnson Space Ctr, SD26,2101 Nasa Rd 1, Houston, TX 77058 USA. NR 20 TC 16 Z9 18 U1 1 U2 3 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0094-5765 J9 ACTA ASTRONAUT JI Acta Astronaut. PD JUL PY 1999 VL 45 IS 1 BP 39 EP 47 DI 10.1016/S0094-5765(99)00055-7 PG 9 WC Engineering, Aerospace SC Engineering GA 239DQ UT WOS:000082753900005 PM 11542526 ER PT J AU Rogers, JL Salas, AO AF Rogers, JL Salas, AO TI Toward a more flexible Web-based framework for multidisciplinary design SO ADVANCES IN ENGINEERING SOFTWARE LA English DT Article DE multidisciplinary design; framework; World Wide Web; process management; optimization; design structure matrix AB In today's competitive environment, both industry and government agencies are under pressure to reduce the time and cost of multidisciplinary design projects. New tools have been introduced to assist in this process by facilitating the integration of and communication among diverse disciplinary codes. One such tool, a framework for multidisciplinary design, is defined as a hardware-software architecture that enables integration, execution, and communication among diverse disciplinary processes. An examination of current frameworks reveals weaknesses in various areas, such as sequencing, monitoring, controlling, and displaying the design process. The objective of this research is to explore how Web technology can improve these areas of weakness and lead toward a more flexible framework. This article describes a Web-based system that optimizes and controls the execution sequence of design processes in addition to monitoring the project status and displaying the design results. Published by Elsevier Science Ltd. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Rogers, JL (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 17 TC 13 Z9 13 U1 0 U2 0 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0965-9978 J9 ADV ENG SOFTW JI Adv. Eng. Softw. PD JUL PY 1999 VL 30 IS 7 BP 439 EP 444 DI 10.1016/S0965-9978(99)00006-X PG 6 WC Computer Science, Interdisciplinary Applications; Computer Science, Software Engineering; Engineering, Multidisciplinary SC Computer Science; Engineering GA 198UL UT WOS:000080442600001 ER PT J AU Generazio, ER Harris, CE AF Generazio, ER Harris, CE TI The role of modelling and simulation in the development of advanced non-destructive evaluation systems SO AERONAUTICAL JOURNAL LA English DT Article ID CERAMIC COMPONENTS; DURABILITY AB Non-destructive evaluation (NDE) technologies are a critical component of a collaborative engineering environment. The role of NDE simulations in component design, manufacturing, certification, integrity and repair are identified and discussed in the context of a futuristic intelligent synthesis environment (ISE) that facilitates collaborative engineering. Each of these critical areas needs to be simulated in a virtual reality environment and is expected to have a large effect on the cost, life, safety, and risk of aerospace products. In a collaborative engineering environment, NDE simulations will provide 'real-time' feedback to component designers and systems engineers. This feedback is necessary to achieve optimum overall system-level benefits. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Generazio, ER (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 9 TC 2 Z9 2 U1 0 U2 0 PU ROYAL AERONAUTICAL SOC PI LONDON PA 4 HAMILTON PL, LONDON, ENGLAND W1V OBQ SN 0001-9240 J9 AERONAUT J JI Aeronaut. J. PD JUL PY 1999 VL 103 IS 1025 BP 325 EP 328 PG 4 WC Engineering, Aerospace SC Engineering GA 234VF UT WOS:000082504500002 ER PT J AU Dickinson, RM Grey, J AF Dickinson, RM Grey, J TI Lasers that beam power to Earth SO AEROSPACE AMERICA LA English DT Article C1 NASA, Wireless Power Transmiss Working Grp, Washington, DC 20546 USA. RP Dickinson, RM (reprint author), NASA, Wireless Power Transmiss Working Grp, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD JUL PY 1999 VL 37 IS 7 BP 50 EP 54 PG 5 WC Engineering, Aerospace SC Engineering GA 219QX UT WOS:000081619200010 ER PT J AU Watson, WR Jones, MG Parrott, TL AF Watson, WR Jones, MG Parrott, TL TI Validation of an impedance eduction method in flow SO AIAA JOURNAL LA English DT Article AB Results are reported for validating a method for educing the normal incidence impedance of a locally reacting liner in a grazing incidence, nonprogressive acoustic wave environment with flow. The results demonstrate the ability of the method to reproduce the normal incidence admittance of a solid steel plate and normal incidence impedance of two soft test liners in a uniform flow. The selected test liners are known to be locally reacting and exhibit no amplitude-dependent impedance nonlinearities and only minimal how effects. Baseline results for these liners are, therefore, established from measurements in a conventional normal Incidence impedance tube. A key feature of the method is the expansion of the unknown impedance function as a piecewise continuous polynomial with undetermined coefficients. Stewart's adaptation (Stewart, G, W., III, "A Modification of Davidon's Minimization Method to Accept Difference Approximations of Derivatives," Journal of ACM, Vol 14, No. 1, 1967, Dg. 72-83) of the Davidon-Fletcher-Powell optimization algorithm is used to educe the normal incidence impedance at each Mach numbs by optimizing an objective function, The method very nearly reproduces the normal incidence impedance spectrum for each of the test liners; thus, its usefulness for determining the normal incidence impedance of test liners for a broad range of source frequencies and flow Mach numbers is demonstrated. C1 NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Aero & Acoust Methods Branch, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Struct Acoust Branch, Fluid Mech & Acoust Div, Hampton, VA 23681 USA. RP Watson, WR (reprint author), NASA, Langley Res Ctr, Fluid Mech & Acoust Div, Aero & Acoust Methods Branch, Hampton, VA 23681 USA. NR 15 TC 11 Z9 12 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD JUL PY 1999 VL 37 IS 7 BP 818 EP 824 DI 10.2514/2.7529 PG 7 WC Engineering, Aerospace SC Engineering GA 212DM UT WOS:000081201600005 ER PT J AU Khavaran, A AF Khavaran, A TI Role of anisotropy in turbulent mixing noise SO AIAA JOURNAL LA English DT Article; Proceedings Paper CT AIAA/CEAS 4th Aeroacoustics Conference CY JUN 02-04, 1998 CL TOULOUSE, FRANCE SP AIAA, CEAS ID MODEL; LAYER AB The objective is to explore the role of anisotropy on aerodynamic mixing noise because of fine-scale turbulence. The usual assumption of isotropic turbulence is replaced with that of axisymmetric turbulence. The analysis is based on source terms of Lilley's equation. In addition, flow/acoustic interaction is accounted for in terms of a high-frequency solution to the axisymmetric Lilley's equation. In the limiting case of isotropy, various source correlation terms derived here simplify to those obtained with an isotropic turbulence model of Batchelor. A Reynolds-averaged Navier-Stokes solution with a k-epsilon turbulence model for a Mach 1.0 jet is used to make flow and acoustic predictions. A parametric study of the turbulence scales indicates that anisotropy increases the peak noise level. C1 NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. RP Khavaran, A (reprint author), Dynacs Engn Co Inc, Mail Stop 2K1,21000 Brookpark Rd, Renton, WA USA. NR 18 TC 35 Z9 36 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 JUL PY 1999 VL 37 IS 7 BP 832 EP 841 DI 10.2514/2.7531 PG 10 WC Engineering, Aerospace SC Engineering GA 212DM UT WOS:000081201600007 ER PT J AU Smith, SM Wastney, ME Morukov, BV Larina, IM Nyquist, LE Abrams, SA Taran, EN Shih, CY Nillen, JL Davis-Street, JE Rice, BL Lane, HW AF Smith, SM Wastney, ME Morukov, BV Larina, IM Nyquist, LE Abrams, SA Taran, EN Shih, CY Nillen, JL Davis-Street, JE Rice, BL Lane, HW TI Calcium metabolism before, during, and after a 3-mo spaceflight: kinetic and biochemical changes SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE weightlessness; calcium absorption; mathematical modeling; stable isotope; microgravity ID BED REST; SPACE-FLIGHT; BONE-FORMATION; WEIGHTLESSNESS; EXCRETION; MARKERS; ABSORPTION; RESORPTION; TURNOVER; PLASMA AB The loss of bone during spaceflight is considered a physiological obstacle for the exploration of other planets. This report of calcium metabolism before, during, and after long-duration spaceflight extends results from Skylab missions in the 1970s. Biochemical and endocrine indexes of calcium and bone metabolism were measured together with calcium absorption, excretion, and bone turnover using stable isotopes. Studies were conducted before, during, and after flight in three male subjects. Subjects varied in physical activity, yet all lost weight during flight. During flight, calcium intake and absorption decreased up to 50%, urinary calcium excretion increased up to 50%, and bone resorption (determined by kinetics or bone markers) increased by over 50%. Osteocalcin and bone-specific alkaline phosphatase, markers of bone formation, increased after flight. Subjects lost similar to 250 mg bone calcium per day during flight and regained bone calcium at a slower rate of similar to 100 mg/day for up to 3 mo after landing. Further studies are required to determine the time course of changes in calcium homeostasis during flight to develop and assess countermeasures against flight-induced bone loss. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Nutr Biochem Lab, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Space & Life Sci Directorate, Houston, TX 77058 USA. Baylor Coll Med, Dept Pediat, USDA ARS, Childrens Nutr Res Ctr, Houston, TX 77030 USA. Lockheed Martin Corp, Houston, TX 77058 USA. Enterprise Advisory Serv Inc, Houston, TX 77058 USA. Georgetown Univ, Ctr Med, Dept Pediat, Washington, DC 20007 USA. Minist Publ Hlth Russia, Inst Biomed Problems, Moscow 123007, Russia. Gagarin Cosmonaut Training Ctr, Star City 141160, Russia. 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 36 TC 110 Z9 118 U1 1 U2 6 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 JUL PY 1999 VL 277 IS 1 BP R1 EP R10 PG 10 WC Physiology SC Physiology GA 213EQ UT WOS:000081259900001 PM 10409251 ER PT J AU Serabyn, E AF Serabyn, E TI Nanometer-level path-length control scheme for nulling interferometry SO APPLIED OPTICS LA English DT Article ID PLANETS AB A method of stabilizing a dual-output rotational shearing inteferometer to the nanometer-level accuracy required for deep starlight nulling in planet searches is presented. In this approach one of the nulling beam combiner's two balanced outputs is used to control the other through a combination of external and internal path-length offsets. The path-length offsets sum to zero for the nulling output and to lambda/4 for the control, or the quadrature, output. In the quadrature output a 1-nm path-length error corresponds to a 1% output-power variation, thus allowing subanometer control. (C) 1999 Optical Society of America. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Serabyn, E (reprint author), CALTECH, Jet Prop Lab, MS 171-113,4800 Oak Grove Dr, Pasadena, CA 91109 USA. EM eserabyn@jpl.nasa.gov NR 7 TC 14 Z9 14 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD JUL 1 PY 1999 VL 38 IS 19 BP 4213 EP 4216 DI 10.1364/AO.38.004213 PG 4 WC Optics SC Optics GA 212GF UT WOS:000081208400031 PM 18323903 ER PT J AU Rosati, P Stanford, SA Eisenhardt, PR Elston, R Spinrad, H Stern, D Dey, A AF Rosati, P Stanford, SA Eisenhardt, PR Elston, R Spinrad, H Stern, D Dey, A TI An X-ray-selected galaxy cluster at z=1.26 SO ASTRONOMICAL JOURNAL LA English DT Article DE galaxies : clusters : general; galaxies : evolution; galaxies : formation; X-rays ID COLOR-MAGNITUDE RELATION; SPECTROPHOTOMETRIC STANDARDS; ELLIPTIC GALAXIES; EVOLUTION AB We report the discovery of an X-ray-luminous galaxy cluster at z = 1.26. RX J0848.9 + 4452 was selected as an X-ray cluster candidate in the ROSAT Deep Cluster Survey on the basis of its spatial extent. Deep optical and near-IR imaging have revealed a galaxy overdensity around the peak of the X-ray emission, with a significant excess of red objects with J-K colors typical of elliptical galaxies at z > 1. Spectroscopic observations at the Reck II Telescope have secured six galaxy redshifts in the range 1.257 < z < 1.267 ([z] = 1.261) within a 35 " radius around the peak X-ray emission. This system lies only 4.'2 away (54.0 h(50)(-1) comoving Mpc, q(0) = 0.5) from the galaxy cluster ClG J0848 + 4453, which was identified at z = 1.273 in a near-IR field galaxy survey and is also known to be X-ray luminous. Assuming that the X-ray emission is entirely due to hot intracluster gas, both these systems have similar rest-frame luminosities L(X) approximate to 1 x 10(44) ergs s(-1) (0.5-2.0 keV band). In combination with our spectrophotometric data for the entire 30 arcmin(2) field, this suggests the presence of a superstructure consisting of two collapsed, possibly virialized, clusters, the first detected to date at z > 1. C1 European So Observ, D-85748 Garching, Germany. Lawrence Livermore Natl Lab, Inst Geophys & Planetary Phys, Livermore, CA 94550 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Florida, Dept Astron, Gainesville, FL 32611 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Natl Opt Astron Observ, Tucson, AZ 85726 USA. RP Rosati, P (reprint author), Univ Calif Davis, Dept Phys, Davis, CA 95616 USA. EM prosati@eso.org; adam@igpp.llnl.gov; prme@kromos.jpl.nasa.gov; elston@astro.ufl.edu; spinrad@bigz.berkeley.edu; dan@bigz.berkeley.edu; dey@noao.edu NR 44 TC 144 Z9 144 U1 0 U2 1 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 JUL PY 1999 VL 118 IS 1 BP 76 EP 85 DI 10.1086/300934 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223WF UT WOS:000081864000006 ER PT J AU Matthews, LD Gallagher, JS Krist, JE Watson, AM Burrows, CJ Griffiths, RE Hester, JJ Trauger, JT Ballester, GE Clarke, JT Crisp, D Evans, RW Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Stapelfeldt, KR Westphal, JA AF Matthews, LD Gallagher, JS Krist, JE Watson, AM Burrows, CJ Griffiths, RE Hester, JJ Trauger, JT Ballester, GE Clarke, JT Crisp, D Evans, RW Hoessel, JG Holtzman, JA Mould, JR Scowen, PA Stapelfeldt, KR Westphal, JA TI WFPC2 observations of compact star cluster nuclei in low-luminosity spiral galaxies SO ASTRONOMICAL JOURNAL LA English DT Review DE galaxies : active; galaxies : nuclei; galaxies : spiral ID ACTIVE GALACTIC NUCLEI; HUBBLE-SPACE-TELESCOPE; PLANETARY CAMERA OBSERVATIONS; DWARF SEYFERT NUCLEI; HIGH-RESOLUTION; SURFACE BRIGHTNESS; NEARBY GALAXIES; STELLAR POPULATIONS; UV OBSERVATIONS; CCD PHOTOMETRY AB We have used the Wide Field Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope to obtain F450W and F814W (B- and I-band) observations of the compact star cluster nuclei of the nearby, late-type, low-luminosity spiral galaxies NGC 4395, NGC 4242, and ESO 359-029. In addition, we analyze archival WFPC2 observations of the compact star cluster nucleus of M33. All of these galaxies are structurally diffuse, with moderately low surface brightnesses and little or no discernible bulge component. Here we present a comparative analysis of the structural and photometric properties of their nuclei. NGC 4395 contains a Seyfert 1 nucleus; M33 has some signatures of weak nuclear activity; the other two galaxies are not known to be active. All of the nuclei have M(I) similar to -11; hence these represent a little explored low-luminosity extension of the galactic nuclear activity sequence in a class of host galaxy not traditionally associated with galactic nuclear phenomena. These kinds of compact nuclei appear to be quite common in low luminosity, late-type spirals. Our Planetary Camera 2 images partially resolve the nuclei of all four galaxies. A simple model consisting of an isothermal sphere plus a point source provides a good model for the observed radial intensity distribution in all cases and permits an exploration of the underlying nuclear structures and spatial scales. Despite their low luminosities, all of the nuclei are very compact. In all cases the luminosity densities are increasing at small radii to the resolution limit of our data. In spite of having similar size scales and luminosities, the nuclei in our sample span a wide range of B-I color. This may be a signature of different evolutionary phases. The M33 nucleus exhibits complex structure; its isophotes are elongated, and it has a possible jetlike component. The Seyfert nucleus of NGC 4395 has an extremely blue color (B-I = -0.16) and is the most structurally complex nucleus in our sample. Circularly symmetric fits to its underlying structure reveal a distinct bipolar pattern. A pair of bright filaments located on one side of the nucleus are probably due to [O III] emission from gas within a nuclear ionization cone. NGC 4395 appears to contain an underlying normal star cluster nucleus that is hosting activity. NGC 4242 shows evidence of a slightly elongated, bar-shaped feature at its center. The ESO 359-029 nucleus appears relatively symmetric and featureless at the resolution limit of our data, but it is clearly very compact. The circumnuclear environments of all four of our program galaxies are extremely diffuse, have only low to moderate star formation, and appear to be devoid of large quantities of dust. The central gravitational potentials of the galaxies are also quite shallow making the origin of these types of "naked" nuclei problematic. C1 SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA. RP Matthews, LD (reprint author), Natl Radio Astron Observ, 520 Edgemont Rd, Charlottesville, VA 22903 USA. EM lmatthew@nrao.edu RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 128 TC 70 Z9 70 U1 1 U2 6 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 JUL PY 1999 VL 118 IS 1 BP 208 EP 235 DI 10.1086/300909 PG 28 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223WF UT WOS:000081864000015 ER PT J AU Sahai, R Dayal, A Watson, AM Trauger, JT Stapelfeldt, KR Burrows, CJ Gallagher, JS Scowen, PA Hester, JJ Evans, RW Ballester, GE Clarke, JT Crisp, D Griffiths, RE Hoessel, JG Holtzman, JA Krist, J Mould, JR AF Sahai, R Dayal, A Watson, AM Trauger, JT Stapelfeldt, KR Burrows, CJ Gallagher, JS Scowen, PA Hester, JJ Evans, RW Ballester, GE Clarke, JT Crisp, D Griffiths, RE Hoessel, JG Holtzman, JA Krist, J Mould, JR TI The etched hourglass nebula MyCn 18. I. Hubble Space Telescope observations SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; ISM : kinematics and dynamics; planetary nebulae : individual (MyCn 18); stars : AGB and post-AGB; stars : mass loss ID PLANETARY-NEBULAE; MASS-LOSS; RING-NEBULA; STARS; BIPOLAR; EVOLUTION; EMISSION; CRL-2688; WINDS; SHOCK AB We have obtained emission-line and continuum images of the young planetary nebula MyCn 18 with the Wide Field Planetary Camera 2 on the Hubble Space Telescope (HST). Although from the ground MyCn 18 appeared to have a triple-ring structure similar to SN 1987A, the HST images show that MyCn 18 has an overall hourglass shape. A series of arcs appear to be etched on the walls of the hourglass near its rims. In the complex central region of the nebula we find a small, inner hourglass structure and two rings. Ring 1 is a bright elliptical ring, and ring 2 a smaller, higher excitation ring. The outer and inner hourglass, and ring 1 and ring 2, all have different centers, and none are coincident with the central star. The hourglass shape of the main nebula is consistent with the predictions of the generalized interacting-winds hypothesis for planetary nebula formation. However, the complex inner nebular structure of MyCn 18 and the offset of the central star from the center of the nebula remain a mystery. We discuss several mechanisms for producing the offset of the central star. Although none are found to be completely satisfactory, those involving a binary central star probably offer the best hope of successful explanation. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. Space Telescope Sci Inst, Baltimore, MD 21218 USA. Univ Wisconsin, Dept Astron, Madison, WI 53706 USA. Arizona State Univ, Dept Phys & Astron, Tempe, AZ 85287 USA. Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA. Carnegie Mellon Univ, Dept Phys, Pittsburgh, PA 15213 USA. New Mexico State Univ, Dept Astron, Las Cruces, NM 88003 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-900,4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Stapelfeldt, Karl/D-2721-2012; Clarke, John/C-8644-2013 NR 42 TC 55 Z9 55 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 1999 VL 118 IS 1 BP 468 EP 476 DI 10.1086/300939 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223WF UT WOS:000081864000032 ER PT J AU Liou, JC Zook, HA AF Liou, JC Zook, HA TI Signatures of the giant planets imprinted on the Edgeworth-Kuiper belt dust disk SO ASTRONOMICAL JOURNAL LA English DT Article DE circumstellar matter; interplanetary medium; Kuiper belt, Oort cloud; planetary systems ID BETA-PICTORIS; SOLAR-SYSTEM; CIRCUMSTELLAR DISK; INTERSTELLAR DUST; PARTICLES; PERTURBATIONS; EVOLUTION; MODEL; RING; RESONANCES AB One method to detect extrasolar planetary systems is to deduce the perturbations of planets on the observed circumstellar dust disks. Our solar system, with its known con figuration of planets, provides an excellent example to study how the distribution of dust in the Edgeworth-Kuiper belt (EKB) dust disk is affected by the existence of multiple and different planets. Numerical simulations of the orbital evolution of dust particles from EKB objects show that Neptune, by trapping dust particles in mean motion resonances, creates a ringlike structure along its orbit. Jupiter and Saturn, by ejecting dust particles from the solar system, create a radial brightness profile inside 10 AU that is quite different from that of a dust disk without their perturbations. On the other hand, Uranus and the terrestrial planets do not produce significant signatures on the EKB dust disk. Our solar system would be recognized as a system with at least two planets if observed from afar. C1 GB Tech Inc, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Liou, JC (reprint author), GB Tech Inc, Mail Code C104,2400 NASA Rd 1, Houston, TX 77058 USA. NR 44 TC 152 Z9 153 U1 2 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 1999 VL 118 IS 1 BP 580 EP 590 DI 10.1086/300938 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223WF UT WOS:000081864000042 ER PT J AU Garcia-Sanchez, J Preston, RA Jones, DL Weissman, PR Lestrade, JF Latham, DW Stefanik, RP AF Garcia-Sanchez, J Preston, RA Jones, DL Weissman, PR Lestrade, JF Latham, DW Stefanik, RP TI Stellar encounters with the Oort cloud based on Hipparcos data (vol 117, pg 1042, 1999) SO ASTRONOMICAL JOURNAL LA English DT Correction C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Observ Paris, Sect Meudon, Paris, France. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Garcia-Sanchez, J (reprint author), CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. NR 1 TC 2 Z9 2 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-6256 J9 ASTRON J JI Astron. J. PD JUL PY 1999 VL 118 IS 1 BP 600 EP 600 DI 10.1086/300905 PG 1 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 223WF UT WOS:000081864000044 ER PT J AU Smith, IA Tilanus, RPJ van Paradijs, J Galama, TJ Groot, PJ Vreeswijk, P Kouveliotou, C Wijers, RAMJ Tanvir, N AF Smith, IA Tilanus, RPJ van Paradijs, J Galama, TJ Groot, PJ Vreeswijk, P Kouveliotou, C Wijers, RAMJ Tanvir, N TI SCUBA sub-millimeter observations of gamma-ray bursters - I. GRB 970508, 971214, 980326, 980329, 980519, 980703, 981220, 981226 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE gamma rays : bursts; radio continuum : general; infrared : general ID 14 DECEMBER 1997; OPTICAL AFTERGLOW; HIGH-REDSHIFT; GRB-970508; MODEL; COUNTERPART; EVOLUTION; EMISSION; GALAXY AB We discuss our ongoing program of Target of Opportunity observations of gamma-ray bursts (GRBs) using the SCUBA instrument on the James Clerk Maxwell Telescope. We present observations of GRB 970508, 971214, 980326, 980329, 980519, 980703, 981220, and 981226. Our most important result to date is the detection of a fading counterpart to GRB 980329 at 850 mu m. Although it proved to be difficult to find the infrared counterpart to this burst, the sub-millimeter flux was relatively bright. This indicates that the brightness of this counterpart (corrected for absorption) was very similar to GRB 970508. The radio through sub-millimeter spectrum of GRB 980329 is well fit by a power law with index alpha = +0.9. However, we cannot exclude a nu(1/3) power law attenuated by synchrotron self-absorption. An alpha similar to +1 VLA-SCUBA power law spectrum is definitely ruled out for GRB 980703, and possibly also for GRB 980519. We cannot rule out that part of the sub-millimeter flux from GRB 980329 comes from a dusty star-forming galaxy at high redshift, such as the ones recently discovered by SCUBA. Any quiescent dust contribution will be much larger at submillimeter than at radio wavelengths. Both a high redshift and large dust extinction would help explain the reddening of the counterpart to GRB 980329. The large intensity of this burst might then indicate that beaming is important. C1 Rice Univ, Dept Space Phys & Astron, Houston, TX 77005 USA. Joint Astron Ctr, Hilo, HI 96720 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Natl Inst Nucl & High Energy Phys, Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA. Univ Hertfordshire, Dept Phys Sci, Hatfield AL10 9AB, Herts, England. RP Smith, IA (reprint author), Rice Univ, Dept Space Phys & Astron, MS-108,6100 S Main, Houston, TX 77005 USA. RI Galama, Titus/D-1429-2014; Groot, Paul/K-4391-2016 OI Galama, Titus/0000-0002-1036-396X; Groot, Paul/0000-0002-4488-726X NR 89 TC 31 Z9 31 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1999 VL 347 IS 1 BP 92 EP 98 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219RJ UT WOS:000081620600013 ER PT J AU Strassmeier, KG Lupinek, S Dempsey, RC Rice, JB AF Strassmeier, KG Lupinek, S Dempsey, RC Rice, JB TI Doppler imaging of stellar surface structure - X. The FK Comae-type star HD 199178=V 1794 Cygni SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : activity; stars : imaging; stars : individual : HD 199178; stars : late-type; stars : starspots ID RS CANUM-VENATICORUM; EFFECTIVE TEMPERATURES; DIFFERENTIAL ROTATION; SPOT ACTIVITY; AB DORADUS; COOL STARS; CVN STARS; BINARY; COLORS; EVOLUTION AB Doppler imaging is used to derive the surface temperature distribution of the Fit Comae star HD 199178 for five observing epochs between 1988 and 1997. Our maps are mainly based on Ca I 6439-Angstrom line profiles and simultaneous and contemporary BV and VI photometry. All images of HD 199178 are characterized by a large polar spot and several low-latitude spots with an average surface temperature difference, photosphere minus spots, of 710+/-260(rms) K for the equatorial spots, approximate to 1700 K for the polar spot, and 1300+/-300(rms)K for the polar-spot appendages. The lifetime of some of the low-latitude spots was found to be as short as one month or even less. The Lifetime of the polar spot and most of its very cool appendages must exceed the time of our observations, i.e. 9 years or approximately 1000 stellar rotations, and could be as long as 12 years since its discovery by Vogt in 1985. Two consecutive Doppler maps in 1989 show no evidence for differential surface rotation, nor is there substantial evidence for the existence of active longitudes in any of our five images. Instead, we suspect that most of the time variability of the surface features on HD 199178 is short term and possibly chaotic in origin. We conclude that spot lifetimes estimated from the timing of light-curve minima could lead to grossly overestimated lifetimes of individual spots. With the aid of our optical spectra and the Hipparcos parallax, we redetermine the absolute stellar parameters of HD 199178 and confirm it to be a single G5III-IV star and find 1.65 M. and 11 L. with T-eff approximate to 5450 K, log g = 2.5, and solar abundances. C1 Univ Vienna, Inst Astron, A-1180 Vienna, Austria. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77598 USA. Brandon Univ, Dept Phys, Brandon, MB R7A 6A9, Canada. RP Strassmeier, KG (reprint author), Univ Vienna, Inst Astron, Turkenschanzstr 17, A-1180 Vienna, Austria. EM strassmeier@astro.univie.ac.at; lupinek@astro.univie.ac.at; robert.c.dempseyl@jsc.nasa.gov; rice@brandonU.ca NR 74 TC 28 Z9 28 U1 1 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 JUL PY 1999 VL 347 IS 1 BP 212 EP 224 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219RJ UT WOS:000081620600027 ER PT J AU Ireland, J Walsh, RW Harrison, RA Priest, ER AF Ireland, J Walsh, RW Harrison, RA Priest, ER TI A wavelet analysis of active region oscillations SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : chromosphere; Sun : corona; Sun : oscillations; Sun : transition region; Sun : UV radiation ID SOLAR CORONAL LOOPS; RESONANT ABSORPTION; ALFVEN WAVES; SURFACE-WAVES; TIME-SERIES; ATMOSPHERE; MECHANISMS; PLASMAS; DRIVEN; POWER AB The wavelet transform is applied to the analysis of active region oscillations. The localised (in time) nature of the wavelet transform allows us to study both the duration of any statistically significant oscillations as well as their period. Time series arising from SOHO (Solar and Heliospheric Observatory) CDS-NIS (Coronal Diagnostic Spectrometer Normal Incidence Spectrometer) active region observations on 14th-15th November 1996 are used to demonstrate the applicability of wavelet methods. High cadence (approximately 14 seconds) observations were made in He I 584.33 Angstrom (log T-e = 4.3), O V 629.73 Angstrom (log T-e = 5.3), Mg IX 368.06 Angstrom (log T-e = 6.0), Fe XVI 360.76 Angstrom (log T-e = 6.4) provide detailed intensity information on the active region over a wide range of temperatures. The distribution of statistically significant periods found varies from line to line, as does their duration. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. Rutherford Appleton Lab, Dept Space Sci, Didcot OX11 0QX, Oxon, England. RP Ireland, J (reprint author), NASA, Goddard Space Flight Ctr, Room G-1,Bldg 26,Mail Code 682-3, Greenbelt, MD 20771 USA. EM ireland@esa.nascom.nasa.gov NR 49 TC 37 Z9 37 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1999 VL 347 IS 1 BP 355 EP 365 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219RJ UT WOS:000081620600040 ER PT J AU Beegle, LW Ajello, JM James, GK Dziczek, D Alvarez, M AF Beegle, LW Ajello, JM James, GK Dziczek, D Alvarez, M TI High resolution emission spectroscopy of the A (1)Pi-X (1)Sigma(+) fourth positive band system of CO excited by electron impact SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE molecular data; ISM : molecules; ultraviolet : ISM ID EXTREME-ULTRAVIOLET EMISSION; OSCILLATOR-STRENGTHS; CARBON-MONOXIDE; CROSS-SECTIONS; ZETA-OPHIUCHI; DISSOCIATIVE EXCITATION; INTERSTELLAR CO; LINE-PROFILE; N-2; TRANSITIONS AB We report electron-impact-induced medium resolution fluorescence spectra of CO [310 m Angstrom and 366 m Angstrom full width at half maximum (FWHM)] at 100 eV over the spectral region from 1300 to 2050 Angstrom. Features in the far ultraviolet (FUV) emission spectra correspond to the Fourth Positive band system of CO (A (1)Pi - X (1)Sigma(+)), together with atomic multiplets from C and O and their ions. The absolute electronic transition moment as a function of internuclear distance was determined from relative band intensities scaled to oscillator strength measurements. A model of the vibronic structure of the band system was developed using the laboratory measurement of the electronic transition moment. In addition, we have obtained high resolution spectra (approximate to 34 m Angstrom FWHM) of the CO (A-X) (5,1) band at 1435 Angstrom and the (3,0) band at 1447 Angstrom and accurately modeled the rotational line structure. The excitation function of the (0,1) band at 1597 Angstrom was measured in the electron impact energy range from threshold to 750 eV and normalized at 100 eV using the relative flow technique with the standard NI (1200 Angstrom) cross section from dissociative excitation of NS The CO (A-X) band system emission cross section was established from a measurement of the relative band intensities of CO at 100 eV. The total Fourth Positive band system cascade cross section, arising from (B --> A) and (C --> A) transitions, is similar to 6% Of the emission cross section at 100 eV The high resolution line profile of the 1152 Angstrom atomic O multiplet (D-1(0)-D-1) resulting from dissociative excitation of CO was measured at similar to 22 m Angstrom FWHM. Kinetic energy distributions of the atomic O fragments at 30 eV and 100 eV impact energies were obtained from an analysis of the deconvolved true line profiles. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Ajello, JM (reprint author), CALTECH, Jet Prop Lab, Mail Stop 183-601, Pasadena, CA 91109 USA. RI Beegle, Luther/A-6354-2010; Dziczek, Dariusz/G-3620-2014 NR 56 TC 19 Z9 19 U1 1 U2 9 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1999 VL 347 IS 1 BP 375 EP 390 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219RJ UT WOS:000081620600043 ER PT J AU Gopalswamy, N Nitta, N Manoharan, PK Raoult, A Pick, M AF Gopalswamy, N Nitta, N Manoharan, PK Raoult, A Pick, M TI X-ray and radio manifestations of a solar eruptive event SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE Sun : corona; Sun : filaments; Sun : flares; Sun : radio radiation; Sun : X-rays, gamma rays ID CORONAL MASS EJECTION; PROMINENCE ERUPTION; FILAMENT; TELESCOPE; FLARE AB e report on a study of the changes in the vicinity of a disappearing solar filament (DSF) that occurred on 1993 April 30. The DSF was associated with a long duration X-ray event (LDE) observed by the GOES and Yohkoh spacecraft. A detailed analysis of the X-ray images obtained by the Yohkoh Soft Xray Telescope revealed that X-ray manifestations of the eruption were wide-spread: (i) X-ray enhancement over a coronal volume several times larger than that of the eruption region, probably the X-ray counterpart of a coronal mass ejection (CME), (ii) Xray ejecta accelerating to 670 km s(-1) into the corona, and (iii) quasi-stationary X-ray loops as in long decay events (LDEs) were observed. One of the important findings of this study is the large-scale X-ray enhancement which we identify with the frontal structure of a CME, apart from the well-known X-ray ejecta and post-eruption arcade formation. There is evidence for triggering of a sympathetic flare in an adjoining active region due to the X-ray ejecta from the eruption region. Stationary metric radio continuum observed by the Nancay Radioheliograph was found to be associated with the brightest X-ray loops that formed following the filament eruption. The unpolarized continuum radio emission was found to be bremsstrahlung radiation from the hot plasma observed in X-rays. The event was also associated with a low frequency metric type II radio burst due to a coronal shock wave from the eruption region. The onset time of the type II emission precludes the possibility of a CME-driven shock causing it. Although we do not have positional information for the type II burst, we found that the X-ray ejecta was fast enough to drive the coronal shock. We confirmed this by comparing the speed of the X-ray ejecta with the shock speed obtained from the radio data which agreed within 10%. C1 Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Lockheed Martin Adv Technol Ctr, Palo Alto, CA 94304 USA. Radio Astron Ctr, Ooty, India. Observ Meudon, Sect Astrophys, F-92195 Meudon, France. RP Gopalswamy, N (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. RI Gopalswamy, Nat/D-3659-2012 NR 25 TC 37 Z9 37 U1 0 U2 2 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1999 VL 347 IS 2 BP 684 EP 695 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219RK UT WOS:000081620700034 ER PT J AU Dulk, GA Leblanc, Y Sault, RJ Bolton, SJ Waite, JH Connerney, JEP AF Dulk, GA Leblanc, Y Sault, RJ Bolton, SJ Waite, JH Connerney, JEP TI Jupiter's magnetic field as revealed by the synchrotron radiation belts - I. Comparison of a 3-D reconstruction with models of the field SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetic fields; plasmas; radiation mechanisms : non-thermal; planets and satellites : individual : Jupiter; radio continuum : solar system ID RADIO DATA; MAGNETOSPHERE; 13-CM; 22-CM AB We use tomographic techniques to make a 3-D reconstruction of Jupiter's synchrotron radiation belts from Very Large Array observations at 20 cm. As in earlier observations with the Australia Telescope Compact Array, this reconstruction shows that the equatorial belt is not symmetric or planar, but is warped. The warp is related to the phi component of the magnetic field, or equivalently the magnetic declination at Jupiter's magnetic equator: D-mag. We show that there is a well defined maximum of intensity at a radius that ranges from about 1.4 to 1.7 R-J, and that the brightness variation with longitude is anticorrelated with \D-mag\ at the magnetic equator. The observed magnetic equatorial radius, jovicentric latitude and brightness are compared with calculations of radius, jovicentric latitude and magnetic declination at the magnetic equator on a locus of constant B = 1.2 G in two field models: H4 and VIP4. The agreement between the observed and model quantities is generally good. However, there are discrepancies that suggest inadequacies in the models, particularly at longitudes where the non-dipolar field elements are pronounced. Until now, observations have provided very few constraints at small radii (R less than or similar to 2) and low latitudes (less than or similar to 15 degrees) for the generation of magnetic field models. Therefore it is not surprising that they are accurate at high latitudes but not at low. The observations of this paper should provide useful constraints for improved models. C1 CNRS, Observ Paris, Dept Rech Spatiale, URA 264, F-92195 Meudon, France. CSIRO, Australia Telescope Natl Facil, Epping, NSW 1710, Australia. CALTECH, Jet Prop Lab, Pasadena, CA USA. SW Res Inst, San Antonio, TX USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dulk, GA (reprint author), CNRS, Observ Paris, Dept Rech Spatiale, URA 264, F-92195 Meudon, France. RI connerney, john/I-5127-2013 NR 13 TC 12 Z9 12 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1999 VL 347 IS 3 BP 1029 EP 1038 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 224AK UT WOS:000081873600033 ER PT J AU Dulk, GA Leblanc, Y Sault, RJ Bolton, SJ AF Dulk, GA Leblanc, Y Sault, RJ Bolton, SJ TI Jupiter's magnetic field as revealed by the synchrotron radiation belts - II. Change of the 2-D brightness distribution with D-E SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetic fields; plasmas; radiation mechanisms : non-thermal; planets and satellites : individual : Jupiter; radio continuum : solar system ID RECONSTRUCTION; 13-CM; 22-CM AB We analyze the magnetic equatorial component of Jupiter's radio synchrotron radiation belts using two-dimensional images recorded by the Australia Telescope Compact Array and the Very Large Array over a period of several years, during which D-E, the Earth's declination seen from Jupiter, changed from D-E = -2.9 degrees to near 0 degrees. The brightness distribution of the belts changed markedly. When D-E = -2.9 degrees there is a pronounced east-west asymmetry where the brightness of a region traversing the east limb is markedly different from that of the same region traversing the west limb, 180 degrees of rotation later. At most longitudes lambda(III) the brightness at east limb passage is larger than at west limb passage. However, when D-E approximate to 0 degrees, the east-west asymmetry essentially disappears. When D-E = +2.9 degrees it is predicted that the east-west asymmetry will be as at -2.9 degrees, but reversed. We show how these changes of appearance are simply related to D-E and the warp of Jupiter's field as described by the "magnetic declination". The radius, latitude and brightness of the locus of maximum intensity is determined by electrons of pitch angle alpha(eq) approximate to 90 degrees, and its longitudinal variation depends entirely on the magnetic field of Jupiter, and not on the energy distribution of the relativistic electrons. We compare the observations with calculations from three magnetic field models and find them to be consistent in general but discrepant in detail. The differences are attributed to uncertainties in the field models, which were generated with few constraints coming from the low latitudes and small radii of the synchrotron radiation belts. C1 Observ Paris, CNRS, Dept Rech Spatiale, URA 264, F-92195 Meudon, France. CSIRO, Australia Telescope Natl Facil, Epping, NSW 1710, Australia. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Dulk, GA (reprint author), Observ Paris, CNRS, Dept Rech Spatiale, URA 264, F-92195 Meudon, France. NR 3 TC 13 Z9 13 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUL PY 1999 VL 347 IS 3 BP 1039 EP 1045 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 224AK UT WOS:000081873600034 ER PT J AU Kraemer, SB Turner, TJ Crenshaw, DM George, IM AF Kraemer, SB Turner, TJ Crenshaw, DM George, IM TI The effect of intrinsic ultraviolet absorbers on the ionizing continuum and narrow emission line ratios in Seyfert galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : Seyfert; X-rays : galaxies ID SOFT-X-RAY; ACTIVE GALACTIC NUCLEI; C-IV; ABSORPTION; NGC-4151; REGIONS; BROAD; SPECTRUM; QUASARS; GAS AB We explore the effects of UV-absorbing material on the shape of the EUV continuum radiation emitted by the active galactic nucleus and on the relative strengths of emission lines, formed in the narrow-line regions of Seyfert galaxies, excited by this continuum. Within a sample of Seyfert 1.5 galaxies, objects with flatter soft X-ray slopes tend to have lower values of He II lambda 4686/H beta, which implies a correlation between the observed spectral energy distribution of the ionizing continuum and the narrow emission line strengths. Objects with the flattest soft X-ray continua tend to possess high-column density UV absorption, and it is plausible that the differences in narrow emission line ratios among these galaxies are an indication of the effects of absorbing material internal to the narrow-line region, rather than intrinsic differences in continuum shape. We have generated a set of photoionization models to examine the effect of a range of UV absorbers on the ionizing continuum and, hence, the resulting conditions in a typical narrow-line cloud. Our results indicate that a low-ionization UV absorber with large covering factor will indeed produce the combination of narrow-line ratios and soft X-ray spectral characteristics observed in several Seyfert 1.5 galaxies. Our results also suggest that low-ionization UV absorption may be more common than currently believed. C1 Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Kraemer, SB (reprint author), Catholic Univ Amer, NASA, Goddard Space Flight Ctr, Code 681, Greenbelt, MD 20771 USA. NR 53 TC 17 Z9 17 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 JUL 1 PY 1999 VL 519 IS 1 BP 69 EP 79 DI 10.1086/307352 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TH UT WOS:000081177600008 ER PT J AU Colbert, EJM Mushotzky, RF AF Colbert, EJM Mushotzky, RF TI The nature of accreting black holes in nearby galaxy nuclei SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; X-rays : galaxies ID X-RAY-EMISSION; ADVECTION-DOMINATED ACCRETION; ACTIVE GALACTIC NUCLEI; SPIRAL GALAXY; CONTINUUM OBSERVATIONS; ASCA OBSERVATIONS; BRIGHT GALAXIES; DWARF GALAXIES; ENERGY-SPECTRA; IONIZED-GAS AB We have found compact X-ray sources in the center of 21 (54%) of 39 nearby face-on spiral and elliptical galaxies with available ROSAT HRI data. ROSAT X-ray luminosities (0.2-2.4 keV) of these compact X-ray sources are similar to 10(37)-10(40) ergs s(-1) (with a mean of 3 x 10(39) ergs s(-1)). The mean displacement between the location of the compact)(-ray source and the optical photometric center of the galaxy is similar to 390 pc. The fact that compact nuclear sources were found in nearly all (five of six) galaxies with previous evidence for a black hole or an active galactic nucleus (AGN) indicates that at least some of the X-ray sources are accreting supermassive black holes. ASCA spectra of six of the 21 galaxies show the presence of a hard component with relatively steep (Gamma approximate to 2.5) spectral slope. A multicolor disk blackbody model fits the data from the spiral galaxies well, suggesting that the X-ray object in these galaxies may be similar to a black hole candidate in its soft thigh) state. ASCA data from the elliptical galaxies indicate that hot (kT approximate to 0.7 keV) gas dominates the emission. The fact that (for both spiral and elliptical galaxies) the spectral slope is steeper than in normal type 1 AGNs and that relatively low absorbing columns (N-H approximate to 10(21) cm(-2)) were found to the power-law component indicates that these objects are somehow geometrically and/or physically different from AGNs in normal active galaxies. The X-ray sources in the spiral and elliptical galaxies may be black hole X-ray binaries, low-luminosity AGNs, or possibly young X-ray luminous supernovae. Assuming the sources in the spiral galaxies are accreting black holes in their soft state, we estimate black hole masses similar to 10(2)-10(4) M.. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Colbert, EJM (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 82 TC 407 Z9 411 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 JUL 1 PY 1999 VL 519 IS 1 BP 89 EP 107 DI 10.1086/307356 PN 1 PG 19 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TH UT WOS:000081177600010 ER PT J AU Boroson, B Kallman, T McCray, R Vrtilek, SD Raymond, J AF Boroson, B Kallman, T McCray, R Vrtilek, SD Raymond, J TI Models of X-ray photoionization in LMC X-4: Slices of a stellar wind SO ASTROPHYSICAL JOURNAL LA English DT Article DE binaries : close; stars : individual (LMC X-4); stars : mass loss; X-rays : stars ID RADIATION-DRIVEN WINDS; HOT LUMINOUS STARS; O-STARS; TERMINAL VELOCITIES; ABSORPTION-SPECTRUM; ROSAT OBSERVATIONS; MAGELLANIC CLOUDS; MASS-LOSS; VELA X-1; EMISSION AB We show that the orbital variation in the UV P Cygni lines of the X-ray binary LMC X-4 results when X-rays photoionize nearly the entire region outside of the X-ray shadow of the normal star. We ht models to Goddard High Resolution Spectrograph (GHRS) observations of N v and C Iv P Cygni line profiles. Analytic methods assuming a spherically symmetric wind show that the wind velocity law is well fitted by v proportional to (1 - 1/r)P, where beta is likely approximate to 1.4-1.6 and definitely less than 2.5. Escape probability models can fit the observed P Cygni profiles and provide measurements of the stellar wind parameters. The fits determine L-X/M = 2.6 +/- 0.1 x 10(43) ergs s(-1) M-circle dot(-1), yr, where L-X is the X-ray luminosity and M; is the mass-loss rate of the star. Allowing an inhomogeneous wind improves the fits. IUE spectra show greater P Cygni absorption during the second half of the orbit than during the first. We discuss possible causes of this effect. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Colorado, JILA, Boulder, CO 80309 USA. Ctr Astrophys, Cambridge, MA 02138 USA. RP Boroson, B (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 64 TC 12 Z9 12 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1999 VL 519 IS 1 BP 191 EP 205 DI 10.1086/307336 PN 1 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TH UT WOS:000081177600018 ER PT J AU van der Hooft, F Kouveliotou, C van Paradijs, J Paciesas, WS Lewin, WHG van der Klis, M Crary, DJ Finger, MH Harmon, BA Zhang, SN AF van der Hooft, F Kouveliotou, C van Paradijs, J Paciesas, WS Lewin, WHG van der Klis, M Crary, DJ Finger, MH Harmon, BA Zhang, SN TI Hard X-ray lags in GRO J1719-24 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; binaries : close; stars : individual (GRO J1719-24); X-rays : stars ID CYGNUS X-1; NOVA-OPHIUCHI-1993; GRS-1716-249; VARIABILITY; RADIO AB We have used the Fourier cross spectra of GRO J1719-24, obtained with BATSE, to estimate the phase lags between the X-ray flux variations in the 20-50 and 50-100 keV energy bands as a function of Fourier frequency in the interval 0.002-0.488 Hz. Our analysis covers the entire similar to 80 day X-ray outburst of this black hole candidate, following the first X-ray detection on 1993 September 25. The X-ray variations in the 50-100 keV band lag those in the 20-50 keV energy band by an approximately constant phase difference of 0.072+/-0.010 rad in the frequency interval 0.02-0.20 Hz. The peak phase lags in the interval 0.02-0.20 Hz are about twice those of Cyg X-l and GRO J0422+32. These results are consistent with models for Comptonization regions composed of extended nonuniform clouds around the central source. C1 Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. Univ Space Res Assoc, Huntsville, AL 35806 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. MIT, Cambridge, MA 02139 USA. Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. NASA, NRC, Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP van der Hooft, F (reprint author), Univ Amsterdam, Astron Inst Anton Pannekoek, Kruislaan 403, NL-1098 SJ Amsterdam, Netherlands. NR 25 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 JUL 1 PY 1999 VL 519 IS 1 BP 332 EP 335 DI 10.1086/307346 PN 1 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TH UT WOS:000081177600031 ER PT J AU Brown, RH Cruikshank, DP Pendleton, Y AF Brown, RH Cruikshank, DP Pendleton, Y TI Water ice on Kuiper Belt object 1996 TO66 SO ASTROPHYSICAL JOURNAL LA English DT Article DE minor planets, asteroids ID SHORT-PERIOD COMETS; OUTER SOLAR-SYSTEM; OPTICAL-CONSTANTS AB The 1.40-2.45 mu m spectrum of Kuiper Belt object 1996 TO66 was measured at the Keck Observatory in 1998 September. Its spectrum shows the strong absorptions near 1.5 and 2.0 mu m that are characteristic of water ice-the first such detection on a Kuiper Belt object. The depth of the absorption bands and the continuum reflectance of 1996 TO66 suggest the presence of a black- to slightly blue-colored, spectrally featureless particulate material as a minority component mixed with the water ice. In addition, there is evidence that the intensity of the water bands in the spectrum of 1996 TO66 varies with rotational phase, suggesting a "patchy" surface. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Brown, RH (reprint author), Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. NR 19 TC 71 Z9 71 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1999 VL 519 IS 1 BP L101 EP L104 DI 10.1086/312098 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TK UT WOS:000081177800025 ER PT J AU Fruchter, AS Thorsett, SE Metzger, MR Sahu, KC Petro, L Livio, M Ferguson, H Pian, E Hogg, DW Galama, T Gull, TR Kouveliotou, C Macchetto, D van Paradijs, J Pedersen, H Smette, A AF Fruchter, AS Thorsett, SE Metzger, MR Sahu, KC Petro, L Livio, M Ferguson, H Pian, E Hogg, DW Galama, T Gull, TR Kouveliotou, C Macchetto, D van Paradijs, J Pedersen, H Smette, A TI Hubble Space Telescope and Palomar imaging of GRB 990123: Implications for the nature of gamma-ray bursts and their hosts SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : observations; gamma rays : bursts; stars : formation AB We report on Hubble Space Telescope and Palomar optical images of the field of GRB 990123, obtained in 1999 February 8 and 9. We find that the optical transient (OT) associated with GRB 990123 is located on an irregular galaxy, with a magnitude of V = 24.20 +/- 0.15. The strong metal absorption lines seen in the spectrum of the OT, along with the low probability of a chance superposition, lead us to conclude that this galaxy is the host of the gamma-ray burst (GRB). The OT is projected within the similar to 1" visible stellar field of the host, nearer the edge than the center. We cannot, on this basis, rule out the galactic nucleus as the site of the GRB, since the unusual morphology of the host may be the result of an ongoing galactic merger, but our demonstration that this host galaxy has extremely blue optical-to-infrared colors more strongly supports an association between GRBs and star formation. We find that the OT magnitude in 1999 February 9.05, V = 25.45 +/- 0.15, is about 1.5 mag fainter than expected from the extrapolation of the decay rate found in earlier observations. A detailed analysis of the OT light curve suggests that its fading has gone through three distinct phases: an early, rapid decline (f(nu) proportional to t(-1.6) for t < 0.1 days); a slower, intermediate decline power-law decay (f(nu) proportional to t(-1.1) for 0.1 < t < 2 days); and then a more rapid decay (at least as steep as f(nu) proportional to t(-18) for t > 2 days). The break to a steeper slope at late times may provide evidence that the optical emission from this GRB was highly beamed. C1 Space Telescope Sci Inst, Baltimore, MD 21218 USA. Princeton Univ, Joseph Henry Labs, Dept Phys, Princeton, NJ 08544 USA. CALTECH, Astron Opt, Pasadena, CA 91125 USA. CNR, Ist Tecnol & Studio Radiaz Extraterr, I-40129 Bologna, Italy. Inst Adv Study, Princeton, NJ 08540 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. European Space Agcy, Div Astrophys, Dept Space Sci, F-75738 Paris 15, France. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Copenhagen, Astron Observ, DK-2100 Copenhagen, Denmark. Natl Opt Astron Observ, Tucson, AZ 85726 USA. RP Fruchter, AS (reprint author), Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA. RI Gull, Theodore/D-2753-2012; Galama, Titus/D-1429-2014; OI Gull, Theodore/0000-0002-6851-5380; Galama, Titus/0000-0002-1036-396X; Petro, Larry/0000-0001-8879-528X NR 48 TC 128 Z9 130 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 JUL 1 PY 1999 VL 519 IS 1 BP L13 EP L16 DI 10.1086/312094 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TK UT WOS:000081177800004 ER PT J AU Hui, L AF Hui, L TI Weighing the cosmological energy contents with weak gravitational lensing SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; gravitational lensing; large-scale structure of universe ID LY-ALPHA FOREST; DENSITY DISTRIBUTION; NONLINEAR EVOLUTION; POWER SPECTRUM; FLUCTUATIONS; STATISTICS; GALAXIES AB Using perturbation theory, Bernardeau, Van Waerbeke, & Mellier show that the skewness of the large-scale lensing convergence, or projected mass density, could be used to constrain Omega(m), the matter content of the universe. However, deep weak-lensing field surveys in the near future will likely measure the convergence on small angular scales (less than or similar to 10'), where the signal will be dominated by highly nonlinear fluctuations. We develop a method far computing the small-scale convergence skewness that gives predictions that agree well with existing results from ray-tracing N-body simulations but is significantly faster. We demonstrate that the small-scale convergence skewness is insensitive to the shape and normalization of the primordial (cold dark matter-type) power spectrum, making it dependent almost entirely on the cosmological energy contents. Moreover, nonlinear clustering appears to enhance the differences between predictions of the convergence skewness for a range of models. Hence, in addition to constraining Omega(m), the small-scale convergence skewness from future deep and several degrees wide surveys can be used to differentiate between curvature-dominated and cosmological constant (Lambda)-dominated models, as well as to constrain the equation of state of a quintessence component, thereby distinguishing Lambda from quintessence. Finally, our method can be easily generalized to other measures such as the aperture mass statistics. C1 NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. RP NASA, Fermilab Astrophys Ctr, Fermi Natl Accelerator Lab, POB 500, Batavia, IL 60510 USA. EM lhui@fnal.gov NR 32 TC 45 Z9 45 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUL 1 PY 1999 VL 519 IS 1 BP L9 EP L12 DI 10.1086/312095 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TK UT WOS:000081177800003 ER PT J AU Williams, GG Park, HS Ables, E Band, DL Barthelmy, SD Bionta, R Butterworth, PS Cline, TL Ferguson, DH Fishman, GJ Gehrels, N Hartmann, DH Hurley, K Kouveliotou, C Meegan, CA Ott, L Parker, E Porrata, R AF Williams, GG Park, HS Ables, E Band, DL Barthelmy, SD Bionta, R Butterworth, PS Cline, TL Ferguson, DH Fishman, GJ Gehrels, N Hartmann, DH Hurley, K Kouveliotou, C Meegan, CA Ott, L Parker, E Porrata, R TI LOTIS search for early-time optical afterglows: GRB 971227 SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts ID GAMMA-RAY-BURST; TRANSIENT IMAGING-SYSTEM; EMISSION AB We report on the very early time search for an optical afterglow from GRB 971227 with the Livermore Optical Transient Imaging System (LOTIS). LOTIS began imaging the "original" BATSE error box of GRB 971227 similar to 14 s after the onset of gamma-ray emission. Continuous monitoring of the position throughout the evening yielded a total of 499 images (10 s integration). Analysis of these images revealed no steady optical afterglow brighter than R = 12.3 +/- 0.2 in any single image. Go-addition of the LOTIS images also failed to uncover transient optical emission. In particular, assuming a constant early-time flux, no optical afterglow brighter than R = 14.2 +/- 0.2 was present within the first 1200 s, and no optical afterglow brighter than R = 15.0 +/- 0.2 was present in the first 6.0 hr. Follow-up observations by other groups revealed a likely X-ray afterglow and a possible optical afterglow. Although subsequent deeper observations could not confirm a fading source, we show that these transients are not inconsistent with our present knowledge of the characteristics of gamma-ray burst afterglows. We also demonstrate that with the upgraded thermoelectrically cooled CCDs, LOTIS is capable of either detecting very early time optical afterglow or placing stringent constraints on the relationship between the gamma-ray emission and the longer wavelength afterglow in relativistic blast-wave models. C1 Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94550 USA. Univ Calif San Diego, Ctr Astrophys & Space Sci, La Jolla, CA 92093 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Columbia, MD 21044 USA. Raytheon Syst, Lanham, MD 20706 USA. Calif State Univ Hayward, Dept Phys, Hayward, CA 94542 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA. RP Williams, GG (reprint author), Clemson Univ, Dept Phys & Astron, Clemson, SC 29634 USA. RI Barthelmy, Scott/D-2943-2012 NR 43 TC 17 Z9 17 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 JUL 1 PY 1999 VL 519 IS 1 BP L25 EP L29 DI 10.1086/312092 PN 2 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TK UT WOS:000081177800007 ER PT J AU Yan, L McCarthy, PJ Freudling, W Teplitz, HI Malumuth, EM Weymann, RJ Malkan, MA AF Yan, L McCarthy, PJ Freudling, W Teplitz, HI Malumuth, EM Weymann, RJ Malkan, MA TI The H alpha luminosity function and global star formation rate from redshifts of 1-2 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : evolution; galaxies : luminosity function, mass function ID HUBBLE DEEP FIELD; STARBURST GALAXIES; EMISSION AB We present a luminosity function for H alpha emission from galaxies at redshifts between 0.7 and 1.9 based on slitless spectroscopy with the near-infrared camera and multiobject spectrometer on the Hubble Space Telescope. The luminosity function is well fit by a Schechter function over the range 6 x 10(41) < L (H alpha) < 2 x 10(43) ergs s(-1) with L* = 7 x 10(42) ergs s(-1) and phi* = 1.7 x 10(-3) Mpc(-3) for H-0 = 50 km s(-1) Mpc(-1) and q(0) = 0.5. We derive a volume-averaged star formation rate at z = 1.3 +/- 0.5 of 0.13 M. yr(-1) Mpc(-3) without correction for extinction. The star formation rate that we derive at similar to 6500 Angstrom is a factor of 3 higher than that deduced from 2800 Angstrom continua. If this difference is caused entirely by reddening, the extinction correction at 2800 Angstrom is quite significant. The precise magnitude of the total extinction correction at rest-frame UV wavelengths (e.g., 2800 and 1500 Angstrom) is sensitive to the relative spatial distribution of the stars, gas, and dust, as well as to the extinction law. In the extreme case of a homogeneous foreground dust screen and a Milky Way or LMC extinction law, we derive a total extinction at 2800 Angstrom of 2.1 mag, or a factor of 7 correction to the UV luminosity density. If we use the Calzetti reddening curve, which was derived for the model in which stars, gas, and dust are well mixed and nebular gas suffers more extinction than stars, our estimate of A(2800) is increased by more than 1 mag. C1 Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Space Telescope European Coordinating Facil, D-85748 Garching, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Raytheon STX Corp, Lanham, MD 20706 USA. Univ Calif Los Angeles, Dept Astron, Los Angeles, CA 90024 USA. NOAO, Tucson, AZ USA. RP Yan, L (reprint author), Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA. NR 37 TC 111 Z9 111 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 JUL 1 PY 1999 VL 519 IS 1 BP L47 EP L50 DI 10.1086/312099 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211TK UT WOS:000081177800012 ER PT J AU Hartman, RC Bertsch, DL Bloom, SD Chen, AW Deines-Jones, P Esposito, JA Fichtel, CE Friedlander, DP Hunter, SD McDonald, LM Sreekumar, P Thompson, DJ Jones, BB Lin, YC Michelson, PF Nolan, PL Tompkins, WF Kanbach, G Mayer-Hasselwander, HA Mucke, A Pohl, M Reimer, O Kniffen, DA Schneid, EJ von Montigny, C Mukherjee, R Dingus, BL AF Hartman, RC Bertsch, DL Bloom, SD Chen, AW Deines-Jones, P Esposito, JA Fichtel, CE Friedlander, DP Hunter, SD McDonald, LM Sreekumar, P Thompson, DJ Jones, BB Lin, YC Michelson, PF Nolan, PL Tompkins, WF Kanbach, G Mayer-Hasselwander, HA Mucke, A Pohl, M Reimer, O Kniffen, DA Schneid, EJ von Montigny, C Mukherjee, R Dingus, BL TI The third EGRET catalog of high-energy gamma-ray sources SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE catalogs; galaxies : active; gamma rays : observations; pulsars : general; Sun : flares ID GALACTIC PLANE; BL-LACERTAE; SUPERNOVA-REMNANTS; POINT SOURCES; EMISSION; PULSARS; TELESCOPE; GRO AB The third catalog of high-energy gamma-ray sources detected by the EGRET telescope on the Compton Gamma Ray Observatory includes data from 1991 April 22 to 1995 October 3 (cycles 1, 2, 3, and 4 of the mission). In addition to including more data than the second EGRET catalog and its supplement, this catalog uses completely reprocessed data (to correct a number of mostly minimal errors and problems). The 271 sources (E > 100 MeV) in the catalog include the single 1991 solar flare bright enough to be detected as a source, the Large Magellanic Cloud, five pulsars, one probable radio galaxy detection (Cen A), and 66 high-confidence identifications of blazars (BL Lac objects, flat-spectrum radio quasars, or unidentified hat-spectrum radio sources). In addition, 27 lower confidence potential blazar identifications are noted. Finally, the catalog contains 170 sources not yet identified firmly with known objects, although potential identifications have been suggested for a number of those. A figure is presented that gives approximate upper limits for gamma-ray sources at any point in the sky, as well as information about sources listed in the second catalog and its supplement, that do not appear in this catalog. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Stanford Univ, Dept Phys, Stanford, CA 94305 USA. Max Planck Inst Extraterr Phys, D-85748 Garching, Germany. Hampden Sydney Coll, Dept Phys, Hampden Sydney, VA 23943 USA. Northrup Grumman Corp, Bethpage, NY 11714 USA. Landessternwarte Heidelberg, D-69117 Heidelberg, Germany. Columbia Univ Barnard Coll, New York, NY 10027 USA. Columbia Univ, Dept Phys, New York, NY 10027 USA. RP Hartman, RC (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013; OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385; Dingus, Brenda/0000-0001-8451-7450 NR 48 TC 1465 Z9 1486 U1 2 U2 13 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUL PY 1999 VL 123 IS 1 BP 79 EP 202 DI 10.1086/313231 PG 124 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219QN UT WOS:000081618400004 ER PT J AU Esposito, JA Bertsch, DL Chen, AW Dingus, BL Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Mayer-Hasselwander, HA McDonald, LM Michelson, PF von Montigny, C Mukherjee, R Nolan, PL Reimer, OL Schneid, E Sreekumar, P Thompson, DJ Tompkins, WF Willis, TD AF Esposito, JA Bertsch, DL Chen, AW Dingus, BL Fichtel, CE Hartman, RC Hunter, SD Kanbach, G Kniffen, DA Lin, YC Mayer-Hasselwander, HA McDonald, LM Michelson, PF von Montigny, C Mukherjee, R Nolan, PL Reimer, OL Schneid, E Sreekumar, P Thompson, DJ Tompkins, WF Willis, TD TI In-flight calibration of EGRET on the Compton Gamma-Ray Observatory SO ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES LA English DT Article DE gamma rays : observations; instrumentation : detectors; methods : observational ID GALACTIC PLANE; EMISSION; TELESCOPE AB The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory has been operating for over 7 yr since its launch in 1991 April. This span of time far exceeds the design lifetime of 2 yr. As the instrument has aged, several changes have occurred owing to spark chamber gas exchanges as well as some hardware degradation and failures, all of which have an influence on the instrument sensitivity. This paper describes postlaunch measurements and analysis that are done to calibrate the instrument response functions. The updated instrument characteristics are incorporated into the analysis software. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Utah, Dept Phys, Salt Lake City, UT 84112 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. Hampden Sydney Coll, Hampden Sydney, VA 23943 USA. Stanford Univ, WW Hansen Expt Phys Lab, Stanford, CA 94305 USA. Sci & Comp, D-72070 Tubingen, Germany. Columbia Univ Barnard Coll, Dept Phys & Astron, New York, NY 10027 USA. Northrup Grumman Corp, Bethpage, NY 11714 USA. RP Esposito, JA (reprint author), Res & Data Syst Corp, Suite 104,7501 Forbes Blvd, Lanham, MD 20706 USA. RI Nolan, Patrick/A-5582-2009; Hunter, Stanley/D-2942-2012; Thompson, David/D-2939-2012; Reimer, Olaf/A-3117-2013; OI Thompson, David/0000-0001-5217-9135; Reimer, Olaf/0000-0001-6953-1385; Dingus, Brenda/0000-0001-8451-7450 NR 20 TC 64 Z9 64 U1 0 U2 2 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0067-0049 J9 ASTROPHYS J SUPPL S JI Astrophys. J. Suppl. Ser. PD JUL PY 1999 VL 123 IS 1 BP 203 EP 217 DI 10.1086/313227 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219QN UT WOS:000081618400005 ER PT J AU Polissar, AV Hopke, PK Paatero, P Kaufmann, YJ Hall, DK Bodhaine, BA Dutton, EG Harris, JM AF Polissar, AV Hopke, PK Paatero, P Kaufmann, YJ Hall, DK Bodhaine, BA Dutton, EG Harris, JM TI The aerosol at Barrow, Alaska: long-term trends and source locations SO ATMOSPHERIC ENVIRONMENT LA English DT Article DE atmospheric aerosol; arctic haze; factor analysis; trends; potential source contribution function ID ARCTIC AIR-POLLUTION; SEA-ICE; ATMOSPHERIC AEROSOL; METEOROLOGICAL DATA; TRAJECTORY MODELS; FLOW PATTERNS; SOUTH-POLE; SULFUR; HAZE; DECREASE AB Aerosol data consisting of condensation nuclei (CN) counts, black carbon (BC) mass, aerosol light scattering (SC), and aerosol optical depth (AOD) measured at Barrow, Alaska from 1977 to 1994 have been analyzed by three-way positive matrix factorization (PMF3) by pooling all of the different data into one large three-way array. The PMF3 analysis identified four factors that indicate four different combinations of aerosol sources active throughout the year in Alaska. Two of the factors (F1, F2) represent Arctic haze, The first Arctic hate have factor F1 is dominant in January-February while the second factor F2 is dominant in March-April. They appear to be material that is generally ascribed to long-range transported anthropogenic particles. A lower ratio of condensation nuclei to scattering coefficient loadings is obtained for F2 indicating larger particles. Factor F3 is related to condensation nuclei. It has an annual cycle with two maxima, March and July-August indicating some involvement of marine biogenic sources. The fourth factor F4 represents the contribution to the stratospheric aerosol from the eruptions of El Chichon and Mt. Pinatubo. No significant long-term trend for F1 was detected while F2 shows a negative trend over the period from 1982 to 1994 but not over the whole measurement period. A positive trend of F3 over the whole period has been observed. This trend may be related to increased biogenic sulfur production caused by reductions in the sea-ice cover in the Arctic and/or an air temperature increase in the vicinity of Barrow. Potential source contribution function (PSCF) analysis showed that in winter and spring during 1989 to 1993 regions in Eurasia and North America are the sources of particles measured at barrow. In contrast to this, large areas in the North Pacific Ocean and the Arctic Ocean was contributed to observed high concentrations of CN in the summer season. Three-way positive matrix factorization was an effective method to extract time-series information contained in the measured quantities. PSCF was useful for the identification possible source areas and the potential pathways for the Barrow aerosol. The effects of long-distance transport, photochemical aerosol production, emissions from biogenic activities in the ocean, volcanic eruptions on the aerosol measurements made at Barrow were extracted using this combined methodology. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Clarkson Univ, Dept Chem, Potsdam, NY 13699 USA. Univ Helsinki, Dept Phys, FIN-00014 Helsinki, Finland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NOAA, Climate Monitoring & Diagnost Lab, RECGI, Boulder, CO 80303 USA. RP Hopke, PK (reprint author), Clarkson Univ, Dept Chem, Potsdam, NY 13699 USA. RI Hall, Dorothy/D-5562-2012; Hopke, Philip/C-6020-2008 OI Hopke, Philip/0000-0003-2367-9661 NR 76 TC 115 Z9 127 U1 8 U2 44 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 1352-2310 J9 ATMOS ENVIRON JI Atmos. Environ. PD JUL PY 1999 VL 33 IS 16 BP 2441 EP 2458 DI 10.1016/S1352-2310(98)00423-3 PG 18 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 191MW UT WOS:000080027000001 ER PT J AU Baker, MB Blyth, AM Christian, HJ Latham, J Miller, KL Gadian, AM AF Baker, MB Blyth, AM Christian, HJ Latham, J Miller, KL Gadian, AM TI Relationships between lightning activity and various thundercloud parameters: satellite and modelling studies SO ATMOSPHERIC RESEARCH LA English DT Article DE lightning; satellites; ice crystals; thunderstorm activity ID ELECTRIFICATION; PRECIPITATION; ICE; THUNDERSTORMS AB The lightning frequency model developed by Baker et al. [Baker, M.B., Christian, H.J., Latham, J., 1995. A computational study of the relationships linking lightning frequency and other thundercloud parameters, Q. J. R. Meteorol. Sec., 121, 1525-1548] has been refined and extended, in an effort to provide a more realistic framework from which to examine computationally the relationships that might exist between lightning frequency f (which is now being routinely measured from a satellite, using the NASA/MSFC Optical Transient Detector (OTD)) and a variety of cloud physical parameters. Specifically, superior or more comprehensive representations were utilised of: (1) glaciation via the Hallett-Mossop (H-M) process; (2) the updraught structure of the model cloud; (3) the liquid-water-content structure of the model cloud; (4) the role of the reversal temperature T-rev in influencing lightning characteristics; (5) the critical breakdown field for lightning initiation; and (6) the electrical characteristics of the ice crystal anvil of the model cloud. Although our extended studies yielded some new insights into the problem, the basic pattern of relationships between f and the other parameters was very close to that reported by Baker et al. (1995). The more elaborate treatment of T-rev restricted somewhat the range of conditions under which reverse-polarity lightning could be produced if the cloud glaciated via H-M, but confirmed the earlier conclusion that such lightning would not occur if the glaciation was of the Fletcher type. The computations yielded preliminary support for the hypothesis that satellite measurements of f might be used to determine values of the ice-content of cumulonimbus anvils: a parameter of climatological importance. The successful launch and continuing satisfactory functioning of the OTD [Christian, H.J., Goodman, S., 1992. Global observations of lightning from space, Proc. 9th Int. Conf. on Atmospheric Electricity, St. Petersburg, pp. 316-321; Christian, H.J., Blakesee, R.J., Goodman, S.J., 1992. Lightning imaging sensor (LIS) for the earth observing system. NASA Tech. Memorandum, 4350] make it possible-with a high degree of precision-to measure lightning location, occurrence time and frequency f over extensive areas of the Earth's surface. Measured global distributions of lightning and associated lightning stroke radiance demonstrate that: lightning activity is particularly pronounced over the tropics, much greater over land than over the oceans, and exhibits great seasonal variability; lightning radiance tends to be greater over the oceans, less when lightning activity is high, and greater in the Northern Hemisphere winter than summer. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ Washington, Seattle, WA 98195 USA. New Mexico Inst Min & Technol, Dept Phys, Socorro, NM 87801 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Manchester, Inst Sci & Technol, Dept Phys, Manchester M60 1QD, Lancs, England. RP Latham, J (reprint author), Natl Ctr Atmospher Res, Dept Phys, MMM Div, POB 3000, Boulder, CO 80307 USA. NR 21 TC 44 Z9 47 U1 0 U2 13 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD JUL PY 1999 VL 51 IS 3-4 BP 221 EP 236 DI 10.1016/S0169-8095(99)00009-5 PG 16 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221QE UT WOS:000081737100004 ER PT J AU Williams, E Boldi, B Matlin, A Weber, M Hodanish, S Sharp, D Goodman, S Raghavan, R Buechler, D AF Williams, E Boldi, B Matlin, A Weber, M Hodanish, S Sharp, D Goodman, S Raghavan, R Buechler, D TI The behavior of total lightning activity in severe Florida thunderstorms SO ATMOSPHERIC RESEARCH LA English DT Article DE total lightning activity; thunderstorms; Florida ID CHARGE; ELECTRIFICATION; THUNDERCLOUDS; CLOUDS; RADAR; STATE AB The development of a new observational system called LISDAD (Lightning Imaging Sensor Demonstration and Display) has enabled a study of severe weather in central Florida. The total flash rates for storms verified to be severe are found to exceed 60 fpm, with some values reaching 500 fpm. Similar to earlier results for thunderstorm microbursts, the peak flash rate precedes the severe weather at the ground by 5-20 min. A distinguishing feature of severe storms is the presence of lightning 'jumps' - abrupt increases in flash rate in advance of the maximum rate for the storm. The systematic total lightning precursor to severe weather of all kinds - wind, hail, tornadoes - is interpreted in terms of the updraft that sows the seeds aloft for severe weather at the surface and simultaneously stimulates the ice microphysics that drives the intracloud lightning activity. (C) 1999 Elsevier Science B.V. All rights reserved. C1 MIT, Ralph M Parsons Lab, Cambridge, MA 02139 USA. MIT, Lincoln Lab, Lexington, MA 02420 USA. Natl Weather Serv, Melbourne, FL 32935 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35806 USA. RP Williams, E (reprint author), MIT, Ralph M Parsons Lab, 77 Massachusetts Ave, Cambridge, MA 02139 USA. NR 42 TC 114 Z9 128 U1 4 U2 14 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD JUL PY 1999 VL 51 IS 3-4 BP 245 EP 265 DI 10.1016/S0169-8095(99)00011-3 PG 21 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221QE UT WOS:000081737100006 ER PT J AU Bateman, MG Eack, KB Rust, WD Marshall, TC AF Bateman, MG Eack, KB Rust, WD Marshall, TC TI Electrical current along balloon rigging line inside thunderstorms SO ATMOSPHERIC RESEARCH LA English DT Article DE electrical current; balloon; rigging line; thunderstorm ID PRECIPITATION; FIELD AB We have designed a new instrument to measure the current flowing along balloon rigging line during flights through thunderstorms. This instrument was tested in a high voltage facility and used to collect line current data during one balloon flight into a thunderstorm. Using these data, worst-case calculations are made; as such, we claim that they are the upper limits of any alteration (to the measured electric field or particle charge) that may occur, and the real number is Likely much less. It is postulated the rigging-line current could have two separate effects on the measured electric field: (1) reduction of the field due to emission of corona ions, and (2) enhancement of the field due to the insertion of a long thin 'conductor.' Even with current as high as 1 IJ A (the largest measured was around 50-100 nA), these two effects were found to be about -1% and +1%, respectively. Also, the calculated worst-case alteration to charged precipitation measurements is about 0.1 pC. Thus, with proper efforts to make the rigging Line as poor a conductor as possible, it seems that we are justified in stating that these effects are negligible. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Langmuir Lab Atmospher Res, Socorro, NM USA. Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, Los Alamos, NM USA. Natl Severe Storms Lab, Norman, OK 73069 USA. Univ Mississippi, Dept Phys & Astron, University, MS 38677 USA. RP Bateman, MG (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, 977 Explorer Blvd, Huntsville, AL 35806 USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0169-8095 J9 ATMOS RES JI Atmos. Res. PD JUL PY 1999 VL 51 IS 3-4 BP 323 EP 335 DI 10.1016/S0169-8095(99)00017-4 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221QE UT WOS:000081737100012 ER PT J AU Bellan, J Harstad, K AF Bellan, J Harstad, K TI High-energy-density fuel blending strategies and drop dispersion for fuel cost reduction and soot propensity control SO ATOMIZATION AND SPRAYS LA English DT Article AB High-energy-density (HED) liquid fuels have high soot propensity and are expensive. The idea of mitigating these characteristics by adding a less expensive, low soot propensity liquid fuel to the HED is tested through numerical simulations. The model represents an axisymmetric, polydisperse, dense cluster of binary-fuel (solvent/solute) spherical drops embedded into a vortex. Since soot propensity depends on the partial density of the evaporated fuel, this partial density is compared for uncharged and electrostatically charged drops; charging is used here as an effective way to increase dispersion and reduce sooting propensity. Results from the simulations show that while the solvent soot propensity indeed decreases with drop charging contrary to simplistic expectations, addition of HED as a solute increases sooting propensity of the solute with increased drop dispersion. This is due to the additional dispersion maintaining the slip velocity at the drop surface and preferentially evaporating the solute. These counterintuitive but correct physical effects are independent of the initial solvent/solute mass ratio, and the soot propensity decreases with decreasing solute volatility. Based on these results, blending strategies are suggested for minimizing sooting propensity and decreasing fuel costs. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Bellan, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 13 TC 3 Z9 3 U1 0 U2 0 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 JUL-AUG PY 1999 VL 9 IS 4 BP 371 EP 383 PG 13 WC Engineering, Multidisciplinary; Engineering, Chemical; Engineering, Mechanical; Materials Science, Multidisciplinary; Physics, Applied SC Engineering; Materials Science; Physics GA 230JZ UT WOS:000082249200004 ER PT J AU Bishop, PA Lee, SMC Conza, NE Clapp, LL Moore, AD Williams, WJ Guilliams, ME Greenisen, MC AF Bishop, PA Lee, SMC Conza, NE Clapp, LL Moore, AD Williams, WJ Guilliams, ME Greenisen, MC TI Carbon dioxide accumulation, walking performance, and metabolic cost in the NASA launch and entry suit SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE carbon dioxide; CO2; spaceflight; human performance; protective clothing; fight helmets; anti-gravity suits; G-suits; egress ID SUBMAXIMAL EXERCISE; SPACEFLIGHT; CAPACITY; HUMANS; MUSCLE AB Background: In the event of an emergency on landing, Space Shuttle crewmembers while wearing the Launch and Entry Suit (LES) must stand, move to the hatch, exit the spacecraft with the helmet visor closed breathing 100% O-2,O- and walk or run unassisted to a distance of 380 m upwind from the vehicle. The purpose of this study was to characterize the inspired CO2 and metabolic requirements during a simulated unaided egress from the Space Shuttle in healthy subjects wearing the LES. Methods: As a simulation of a Shuttle landing with an unaided egress, 12 male subjects completed a 6-min seated pre-breathe with 100% O-2 followed by a 2-min stand and 5-min walking at 1.56 m . s(-1) (5.6 km . h(-1), 3.5 mph) with the helmet visor closed. During walks with four different G-suit pressures (0.0, 0.5, 1.0, 1.5 psi; 3.4, 6.9, 10.3 kPa), inspired CO2 and walking time were measured. After a 10-min seated recovery, subjects repeated the 5-min walk with the same G-suit pressure and the helmet visor open for the measurement of metabolic rate ((V) over dot O-2). Results: When G-suit inflation levels were 1.0 or 1.5 psi, only one-third of our subjects were able to complete the 5-min visor-closed walk after a 6-min pre-breathe. Inspired CO2 levels measured at the mouth were routinely greater than 4% (30 mmHg) during walking. The metabolic cost at the 1.5 psi G-suit inflation was over 135% of the metabolic cost at 0.0 psi inflation. Conclusion: During unaided egress, G-suit inflation pressures of 1.0 and 1.5 psi resulted in elevated CO2 in the LES helmet and increased metabolic cost of walking, both of which may impact unaided egress performance. Neither the LES, the LES helmet, nor the G-suit were designed for ambulation. Data from this investigation suggests that adapting fight equipment for uses other than those for which it was originally designed can result in unforeseen problems. C1 NASA, Johnson Space Ctr, Exercise Counterness Project, Houston, TX 77058 USA. Univ Alabama, Human Performance Lab, Tuscaloosa, AL USA. Wyle Labs, Life Sci Syst & Serv Div, Houston, TX USA. Swiss Fed Inst Technol, Zurich, Switzerland. RP Greenisen, MC (reprint author), NASA, Johnson Space Ctr, Exercise Counterness Project, Mail Code SD3, Houston, TX 77058 USA. NR 24 TC 17 Z9 17 U1 1 U2 2 PU AEROSPACE MEDICAL ASSOC PI ALEXANDRIA PA 320 S HENRY ST, ALEXANDRIA, VA 22314-3579 USA SN 0095-6562 J9 AVIAT SPACE ENVIR MD JI Aviat. Space Environ. Med. PD JUL PY 1999 VL 70 IS 7 BP 656 EP 665 PG 10 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 211AL UT WOS:000081137700004 PM 10417001 ER PT J AU Putcha, L Berens, KL Marshburn, TH Ortega, HJ Billica, RD AF Putcha, L Berens, KL Marshburn, TH Ortega, HJ Billica, RD TI Pharmaceutical use by US astronauts on space shuttle missions SO AVIATION SPACE AND ENVIRONMENTAL MEDICINE LA English DT Article DE microgravity; drug administration; countermeasures ID IN-SPACE; FLIGHT AB We evaluated in-flight use of medications from astronaut debriefings after 79 U.S. Space Shuttle missions. From the 219 records obtained (each representing one person-flight), 94% included some medication being taken during flight; of that number, 47% were for space motion sickness, 45% for sleep disturbances, and smaller percentages for headache, backache, and sinus congestion. Drugs were taken most often orally, followed in decreasing order of frequency by intranasal, intramuscular, and rectal routes. Drugs for space motion sickness were taken mostly during the first 2 d of flight, drugs for pain during the first 4 d, and drugs fur sleeplessness and sinus congestion were taken consistently for 9 flight days. About 85% of all doses had no reported side effects, and most of the side effects that were reported happened during the first mission day. About 80% of the drug-dose events were perceived effective by the recipients; most of the reports of ineffectiveness occurred during the first mission day. Promethazine, the only drug given by three different routes (orally, intramuscularly, and rectally), was most effective and had minimal side effects when taken intramuscularly. This information, although useful, should be expanded to include objective measures of effectiveness so that therapeutic efficacy can be assessed during flight. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Pharmacol Lab, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Med Operat Branch, Houston, TX 77058 USA. Wyle Labs, Houston, TX USA. RP Putcha, L (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Pharmacol Lab, Mail Code SD3, Houston, TX 77058 USA. NR 13 TC 36 Z9 43 U1 0 U2 5 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 JUL PY 1999 VL 70 IS 7 BP 705 EP 708 PG 4 WC Public, Environmental & Occupational Health; Medicine, General & Internal; Sport Sciences SC Public, Environmental & Occupational Health; General & Internal Medicine; Sport Sciences GA 211AL UT WOS:000081137700012 PM 10417009 ER PT J AU Potter, CS Klooster, SA AF Potter, CS Klooster, SA TI Detecting a terrestrial biosphere sink for carbon dioxide: Interannual ecosystem modeling for the mid-1980s SO CLIMATIC CHANGE LA English DT Article ID NDVI DATA SET; CLIMATE VARIABILITY; GLOBAL-SCALE; VEGETATION; SATELLITE; EXCHANGE AB There is considerable uncertainty as to whether interannual variability in climate and terrestrial ecosystem production is sufficient to explain observed variation in atmospheric carbon content over the past 20-30 years. In this paper, we investigated the response of net CO2 exchange in terrestrial ecosystems to interannual climate variability (1983 to 1988) using global satellite observations as drivers for the NASA-CASA (Carnegie-Ames-Stanford Approach) simulation model. This computer model of net ecosystem production (NEP) is calibrated for interannual simulations driven by monthly satellite vegetation index data (NDVI) from the NOAA Advanced Very High Resolution Radiometer (AVHRR) at 1 degree spatial resolution. Major results from NASA-CASA simulations suggest that from 1985 to 1988, the northern middle-latitude zone (between 30 and 60 degrees N) was the principal region driving progressive annual increases in global net primary production (NPP; i.e., the terrestrial biosphere sink for carbon). The average annual increase in NPP over this predominantly northern forest zone was on the order of +0.4 Pg (10(15) g) C per year. This increase resulted mainly from notable expansion of the growing season for plant carbon fixation toward the zonal latitude extremes, a pattern uniquely demonstrated in our regional visualization results. A net biosphere source flux of CO2 in 1983-1984, coinciding with an El Nino event, was followed by a major recovery of global NEP in 1985 which lasted through 1987 as a net carbon sink of between 0.4 and 2.6 Pg C per year. Analysis of model controls on NPP and soil heterotrophic CO2 fluxes (R-h) suggests that regional warming in northern forests can enhance ecosystem production significantly. In seasonally dry tropical zones, periodic drought and temperature drying effects may carry over with at least a two-year lag time to adversely impact ecosystem production. These yearly patterns in our model-predicted NEP are consistent in magnitude with the estimated exchange of CO2 by the terrestrial biosphere with the atmosphere, as determined by previous isotopic (delta(13)C) deconvolution analysis. Ecosystem simulation results can help further target locations where net carbon sink fluxes have occurred in the past or may be verified in subsequent field studies. C1 NASA, Ames Res Ctr, Ecosyst Sci, Moffett Field, CA 94035 USA. Calif State Univ Monterey Bay, Seaside, CA 93955 USA. RP Potter, CS (reprint author), NASA, Ames Res Ctr, Ecosyst Sci, Mail Stop 242-4, Moffett Field, CA 94035 USA. NR 29 TC 29 Z9 31 U1 1 U2 11 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0165-0009 J9 CLIMATIC CHANGE JI Clim. Change PD JUL PY 1999 VL 42 IS 3 BP 489 EP 503 DI 10.1023/A:1005449017059 PG 15 WC Environmental Sciences; Meteorology & Atmospheric Sciences SC Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 213PN UT WOS:000081282600001 ER PT J AU Wolfson, O Sistla, AP Chamberlain, S Yesha, Y AF Wolfson, O Sistla, AP Chamberlain, S Yesha, Y TI Updating and querying databases that track mobile units SO DISTRIBUTED AND PARALLEL DATABASES LA English DT Article AB In this paper, we consider databases representing information about moving objects (e.g., vehicles), particularly their location. We address the problems of updating and querying such databases. Specifically, the update problem is to determine when the location of a moving object in the database (namely its database location) should be updated. We answer this question by proposing an information cost model that captures uncertainty, deviation, and communication. Then we analyze dead-reckoning policies, namely policies that update the database location whenever the distance between the actual location and the database location exceeds a given threshold, x. Dead-reckoning is the prevalent approach in military applications, and our cost model enables us to determine the threshold x. We propose several dead-reckoning policies and we compare their performance by simulation. Then we consider the problem of processing range queries in the database. An example of a range query is 'retrieve the objects that are currently inside a given polygon P'. We propose a probabilistic approach to solve the problem. Namely, the DBMS will answer such a query with a set of objects, each of which is associated with a probability that the object is inside P. C1 Univ Illinois, Dept Elect Engn & Comp Sci, Chicago, IL 60607 USA. USA, Res Lab, Aberdeen Proving Ground, MD USA. NASA, Goddard Space Flight Ctr, Ctr Excellence Space Data & Informat Sci, Greenbelt, MD USA. RP Wolfson, O (reprint author), Univ Illinois, Dept Elect Engn & Comp Sci, Chicago, IL 60607 USA. NR 24 TC 158 Z9 176 U1 0 U2 7 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0926-8782 J9 DISTRIB PARALLEL DAT JI Distrib. Parallel Databases PD JUL PY 1999 VL 7 IS 3 BP 257 EP 287 DI 10.1023/A:1008782710752 PG 31 WC Computer Science, Information Systems; Computer Science, Theory & Methods SC Computer Science GA 229FQ UT WOS:000082183200002 ER PT J AU Warn-Varnas, A Sellschopp, J Haley, PJ Leslie, WG Lozano, CJ AF Warn-Varnas, A Sellschopp, J Haley, PJ Leslie, WG Lozano, CJ TI Strait of Sicily water masses SO DYNAMICS OF ATMOSPHERES AND OCEANS LA English DT Article; Proceedings Paper CT Symposium in Honor of Professor Robinson, at the AGU/ASLO Ocean Sciences Meeting CY FEB, 1998 CL SAN DIEGO, CALIFORNIA DE water mass model; salinity distributions; Strait of Sicily ID IONIAN SEA; CIRCULATION AB We have derived a water mass model for the Strait of Sicily, based on 1994 and 1995 cruise data. The model consists of seven water masses, suggested by the measured shapes of the vertical temperature and salinity distributions. The core of the Atlantic water is distributed below the surface as a shallow layer, in a depth range of 40 to 100 m, with a salinity minimum. It is capped by upper and surface layers above and a mixed region below. At the bottom, Levantine water is present with a transition region above. Between the mixed and transition region there is, on occasion, a fresher water layer. The structure and statistics of water masses is analyzed over the Strait of Sicily region in terms of their temperature, salinity, and depth values, Objective analysis of the temperature, salinity, and depth parameters is performed in latitude and longitude. The water masses are tracked in terms of their parameter signatures. Changes in temperature and salinity distributions are interpreted. 2-D ellipses that represent the water masses, in terms of means and standard deviation, are derived in a space of temperature, salinity, and depth. Their awes are the standard deviations of parameter space ranges. The areas of the ellipses are compared against the temperature and salinity data distribution. The water mass composition ratios are computed and analyzed. Hypotheses and mechanisms for the origin and mixing of water masses are suggested. Published by Elsevier Science B.V. C1 USN, Res Lab, Stennis Space Ctr, Stennis Space Ctr, MS 39529 USA. SACLANT Undersea Res Ctr, La Spezia, Italy. Harvard Univ, Div Appl Sci, Dept Earth & Planetary Sci, Cambridge, MA 02138 USA. RP Warn-Varnas, A (reprint author), USN, Res Lab, Stennis Space Ctr, Code 7322, Stennis Space Ctr, MS 39529 USA. NR 12 TC 15 Z9 15 U1 0 U2 1 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 JUL PY 1999 VL 29 IS 2-4 BP 437 EP 469 DI 10.1016/S0377-0265(99)00014-7 PG 33 WC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Oceanography SC Geochemistry & Geophysics; Meteorology & Atmospheric Sciences; Oceanography GA 233VQ UT WOS:000082448200013 ER PT J AU Gullerud, AS Dodds, RH Hampton, RW Dawicke, DS AF Gullerud, AS Dodds, RH Hampton, RW Dawicke, DS TI Three-dimensional modeling of ductile crack growth in thin sheet metals: computational aspects and validation SO ENGINEERING FRACTURE MECHANICS LA English DT Article DE stable crack growth; CTOA; 2024-T3 aluminum; 3D finite element analysis; out-of-plane bending AB This work describes the development of two types of three-dimensional (3D) finite element models to predict stable, Mode I crack growth in thin, ductile aluminum alloys, The two presented models extend the standard 2D form of the Crack Tip Opening Angle (CTOA) methodology, which determines crack extension based on obtaining a critical angle at the crack tip. The more general 3D model evaluates the CTOA at each node along the crack front which enables the development of tunneled profiles. The alternative, constant front approach, enforces uniform growth along the crack front, thereby growing the crack in a self-similar manner. For the constant front approach, evaluation of the CTOA occurs at a specified distance behind the crack front which decouples CTOA evaluation from mesh refinement. Both CTOA-based models include adaptive load control strategies to minimize the effects of discrete Load increments on the growth response, Example analyses demonstrate that the more general 3D approach requires cube-shaped elements on the crack plane to eliminate a bias in growth directions, To evaluate the effectiveness of the constant front approach, this work also describes a validation study using loadcrack extension data from 2.3 mm thick Al 2024-T3 specimens tested at NASA-Langley. The test matrix includes C(T) and M(T) specimens, with varying widths (50-600 mm), a/W ratios, and levels of mechanical restraint to suppress out-of-plane bending, Comparisons of load-crack extension curves from experiments and analyses of a 150 mm C(T) specimen, with out-of-plane bending prevented, provide a calibrated (critical) CTOA value of 5.1 degrees, Analyses using the calibrated CTOA value and the constant front approach provide predictions of peak load for constrained and unconstrained specimens in good agreement with the experimental values, (C) 1999 Elsevier Science Ltd, All rights reserved. C1 Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Dodds, RH (reprint author), Univ Illinois, Dept Civil Engn, Urbana, IL 61801 USA. EM r-dodds@uiuc.edu NR 26 TC 56 Z9 57 U1 1 U2 13 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0013-7944 EI 1873-7315 J9 ENG FRACT MECH JI Eng. Fract. Mech. PD JUL PY 1999 VL 63 IS 4 BP 347 EP 374 DI 10.1016/S0013-7944(99)00034-X PG 28 WC Mechanics SC Mechanics GA 217NL UT WOS:000081505800001 ER PT J AU Salem, JA Jenkins, MG AF Salem, JA Jenkins, MG TI A test apparatus for measuring the biaxial strength of brittle materials SO EXPERIMENTAL TECHNIQUES LA English DT Article C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Univ Washington, Seattle, WA 98195 USA. RP Salem, JA (reprint author), NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. NR 15 TC 1 Z9 1 U1 0 U2 1 PU SOC EXPERIMENTAL MECHANICS PI BETHEL PA 7 SCHOOL STREET, BETHEL, CT 06801 USA SN 0732-8818 J9 EXP TECHNIQUES JI Exp. Tech. PD JUL-AUG PY 1999 VL 23 IS 4 BP 19 EP 23 DI 10.1111/j.1747-1567.1999.tb01504.x PG 5 WC Engineering, Mechanical; Mechanics; Materials Science, Characterization & Testing SC Engineering; Mechanics; Materials Science GA 222WR UT WOS:000081808800004 ER PT J AU DeMartini, EE Lau, BB AF DeMartini, EE Lau, BB TI Morphometric criteria for estimating sexual maturity in two snappers, Etelis carbunculus and Pristipomoides sieboldii SO FISHERY BULLETIN LA English DT Article ID SOLEA-SOLEA L; REPRODUCTIVE-CYCLE; DISCRIMINANT-ANALYSIS; LOGISTIC REGRESSION; OVARIAN DEVELOPMENT; FECUNDITY; FISHES; INDEX; MATURATION; GROWTH AB A gross measure of reproductive condition (ovary weight adjusted for body size and oocyte volume) is developed and evaluated as an alternative to commonly used gonad indices, for classifying the maturity status of individual ehu (Etelis carbunculus) and kalekale (Pristipomoides sieboldii), two species of eteline snappers (Lutjanidae) that contribute to the deep-slope hand-line fishery in Hawaii. Discriminant analysis and logistic regression, based on body length, ovary weight, and oocyte volume, were used to classify fish as either immature or mature. Discriminant analysis correctly classified the maturity of about 98% of both ehu and kalekale, with histological criteria as the standard for comparison. Logistic regression correctly classified maturity of 97% of the ehu and 100% of the kalekale. Misclassification errors increased by 3.75-5% (discriminant analysis) or 0-5% (logistic regression) if oocyte volume was excluded and only body length and ovary weight were used as predictors of maturity. For kalekale, estimates of lengths at which 50% are sexually mature (L-50) were identical (29.0 +/- 1.8 [SE] cm fork length, FL; r(2)-=0.92), when maturity was classified histologically or by logistic regression on body, ovary, and oocyte metrics. For ehu, L-50 estimates were similar (r(2)-approximate to 0.96) for maturity assignments based on histology(27.9 +/- 2.4 cm FL) and on logistic regression using gross metrics (27.8 +/- 2.3 cm FL). We conclude that gross morphometrics can provide adequate proxies for histological evidence when categorizing sexual maturity in asynchronous, multiple-spawning fishes like eteline lutjanids. The potential benefits of using gross metrics for assessing sexual maturity in other serial spawners are briefly discussed. C1 NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, Honolulu, HI 96822 USA. RP DeMartini, EE (reprint author), NOAA, Natl Marine Fisheries Serv, SW Fisheries Sci Ctr, Honolulu Lab, 2570 Dole St, Honolulu, HI 96822 USA. NR 51 TC 21 Z9 25 U1 1 U2 3 PU NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE PI SEATTLE PA 7600 SAND POINT WAY NE BIN C15700, SEATTLE, WA 98115 USA SN 0090-0656 J9 FISH B-NOAA JI Fish. Bull. PD JUL PY 1999 VL 97 IS 3 BP 449 EP 458 PG 10 WC Fisheries SC Fisheries GA 216GH UT WOS:000081432700004 ER PT J AU Sanderson, TR Lario, D Maksimovic, M Marsden, RG Tranquille, C Balogh, A Forsyth, RJ Goldstein, BE AF Sanderson, TR Lario, D Maksimovic, M Marsden, RG Tranquille, C Balogh, A Forsyth, RJ Goldstein, BE TI Current sheet control of recurrent particle increases at 4-5 AU SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID INTERACTION REGIONS; ULYSSES AB We examine the relation between the current sheet as derived from observations of the Sun's neutral line, and recurrent particle increases associated with co-rotating interactions regions (CIR) at 4 to 5 AU radial distance as observed by the Ulysses spacecraft during its first out-of-ecliptic orbit around the Sun. We compare observations during the ascent to high southern latitudes, close to solar maximum, with observations during the return to the ecliptic from high northern latitudes, close to solar minimum, when the spacecraft was passing from the streamer belt to high-speed solar wind flow or vice-versa every solar rotation, and when regular recurrent particle increases were observed. Although conditions are very different, we show that the position of the Sun's neutral line, propagated out to the position of the spacecraft, can be used to explain the recurrence of the particle increases observed at 4-5 AU at Ulysses. C1 Estec, ESA, Dept Space Sci, Noordwijk, Netherlands. Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England. CALTECH, Jet Prop Lab, Pasadena, CA USA. RP Sanderson, TR (reprint author), Estec, ESA, Dept Space Sci, Noordwijk, Netherlands. RI Lario, David/D-9318-2016 OI Lario, David/0000-0002-3176-8704 NR 7 TC 13 Z9 13 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 1 PY 1999 VL 26 IS 13 BP 1785 EP 1788 DI 10.1029/1999GL900348 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000001 ER PT J AU Satoh, T Connerney, JEP AF Satoh, T Connerney, JEP TI Spatial and temporal variations of Jupiter's H-3(+) emission deduced from image analysis SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID JOVIAN H-3(+); THERMOSPHERE; IONOSPHERE; MODEL AB Intensity distribution of H-3(+) emission across Jupiter's disk has been analyzed using 3.4-mu m IRTF/ ProtoCAM images acquired in 1992. The apparent disk emission is approximated using a mathematical function, of which parameters characterize (i) the dependence on the solar illumination angle, (ii) limb brightening consistent with the line-of-sight effect, and (iii) the latitudinal variation. A simple atmospheric model reproduces the disk emission (corrected for the line-of-sight effect) well, with H-3(+) emission peak in an altitude range 700-750 km above P = 600 mb level. C1 Sci Univ Tokyo, Frontier Res Ctr Computat Sci, Noda, Chiba 2788510, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Satoh, T (reprint author), Sci Univ Tokyo, Frontier Res Ctr Computat Sci, 2641 Yamazaki, Noda, Chiba 2788510, Japan. RI connerney, john/I-5127-2013 NR 11 TC 7 Z9 7 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 JUL 1 PY 1999 VL 26 IS 13 BP 1789 EP 1792 DI 10.1029/1999GL900372 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000002 ER PT J AU Woo, R Habbal, SR AF Woo, R Habbal, SR TI Radial evolution of density structure in the solar corona SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PHYSICAL-PROPERTIES; SCALE STRUCTURES; WIND; MINIMUM; SLOW AB White-light measurements made by the SOHO coronagraphs (LASCO for Large Angle Spectrometric Coronagraph) and the HAO Mauna Loa Mk III K-coronameter are combined to follow the evolution of path-integrated density structure in the solar corona overlying both coronal hole and quiet Sun regions from 1.15 to 5.5 R-o. The global imaging provided by these two instruments confirms and strengthens earlier results discovered by spacecraft radio ranging measurements [Woo and Habbal, 1999], that the imprint of density structure at the Sun - as manifested in the background latitudinal density profile closest to the Sun at 1.15 R-o - is carried essentially radially into interplanetary space with the same density gradient. The only exceptions are coronal streamers that evolve into the heliospheric current sheet within a few solar radii of the Sun. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Harvard Smithsonian Ctr Astrophys, Belmont, MA 02178 USA. RP Woo, R (reprint author), CALTECH, Jet Prop Lab, MS 238-725,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 22 TC 24 Z9 24 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 JUL 1 PY 1999 VL 26 IS 13 BP 1793 EP 1796 DI 10.1029/1999GL900366 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000003 ER PT J AU Smith, JP Thomsen, MF Borovsky, JE Collier, M AF Smith, JP Thomsen, MF Borovsky, JE Collier, M TI Solar wind density as a driver for the ring current in mild storms SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PLASMA SHEET; POPULATION AB Using the methods of multi- and partial-linear-correlation, we demonstrate that both the solar wind density and the solar wind electric field make significant and independent contributions to the strength of the ring current, as measured by the Dst* index, during mild storms. The solar wind data were obtained from WIND, and the Dst data from OmniWeb. After appropriate cleaning of the data, 55 events from the Wind-era with Dst* excursions below -50 were obtained. Correlations with Dst* were performed with independent, variable time lags for the density and for the electric field,:and the optimal time lags are found to be approximately 5 hours for density and less than one hour for the electric field (in addition to the time shift to Earth). C1 Univ Texas, Inst Fus Studies, Austin, TX 78712 USA. Univ Calif Los Alamos Natl Lab, Space & Atmospher Sci Grp, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Smith, JP (reprint author), Univ Texas, Inst Fus Studies, Austin, TX 78712 USA. 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 SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 1 PY 1999 VL 26 IS 13 BP 1797 EP 1800 DI 10.1029/1999GL900341 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000004 ER PT J AU Takalo, J Timonen, J Klimas, A Valdivia, J Vassiliadis, D AF Takalo, J Timonen, J Klimas, A Valdivia, J Vassiliadis, D TI Nonlinear energy dissipation in a cellular automaton magnetotail field model SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID CRITICALITY; AVALANCHES; SYSTEMS AB A magnetic field model of the magnetotail current sheet based on cellular automaton (CA) is presented. The present isotropic model is a continuously driven, two-dimensional running CA. The model has a physical interpretation in terms of magnetohydrodynamic (MHD) equations, and features self-organized critical (SOC) behavior with power-law scalings both in durations and sizes of instabilities (avalanches). The model has nonlinear energy dissipation, and shows avalanches with and without an external trigger. Thus the model reproduces some of the statistical features recently observed in the magnetotail. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Jyvaskyla, Dept Phys, SF-40351 Jyvaskyla, Finland. RP Takalo, J (reprint author), NASA, Goddard Space Flight Ctr, Code 690-2, Greenbelt, MD 20771 USA. EM jouni@roselott.gsfc.nasa.gov; timonen@snafu.phys.jyu.fi; alex@bokeh.gsfc.nasa.gov; alejo@roselott.gsfc.nasa.gov; vassi@kassandra.gsfc.nasa.gov RI Valdivia, Juan/A-3631-2008 OI Valdivia, Juan/0000-0003-3381-9904 NR 21 TC 48 Z9 48 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 EI 1944-8007 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 1 PY 1999 VL 26 IS 13 BP 1813 EP 1816 DI 10.1029/1999GL900429 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000008 ER PT J AU Minnis, P Schumann, U Doelling, DR Gierens, KM Fahey, DW AF Minnis, P Schumann, U Doelling, DR Gierens, KM Fahey, DW TI Global distribution of contrail radiative forcing SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID AIRCRAFT EXHAUST; CIRRUS CLOUDS; EMISSIONS AB The global distribution of radiative forcing by persistent linear contrails has been estimated for 1992 and 2050 using global contrail cover computed for aircraft fuel consumption scenarios for the two periods, a detailed prescription of the radiative properties of the Earth's surface and the cloudy atmosphere, and flux computations with an established radiative transfer model. The computed global mean radiative forcing by line-shaped contrails is similar to 0.02 Wm(-2) in 1992 and similar to 0.1 Wm(-2) in 2050. At northern mid-latitudes, the zonal mean forcing is five times larger than the global mean. Diffuse contrails and indirect effects of aircraft emissions on natural cirrus are not included in this study. Thus, the results are considered a minimum estimate of contrail effects. C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. DLR Oberfaffenhofen, Inst Phys Atmosphare, D-82230 Wessling, Germany. NASA, Langley Res Ctr, Analyt & Mat Inc, Hampton, VA 23666 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. RP Minnis, P (reprint author), NASA, Langley Res Ctr, MS 420, Hampton, VA 23681 USA. RI Fahey, David/G-4499-2013; Minnis, Patrick/G-1902-2010; OI Fahey, David/0000-0003-1720-0634; Minnis, Patrick/0000-0002-4733-6148; Schumann, Ulrich/0000-0001-5255-6869 NR 26 TC 86 Z9 86 U1 1 U2 7 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUL 1 PY 1999 VL 26 IS 13 BP 1853 EP 1856 DI 10.1029/1999GL900358 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000018 ER PT J AU Greene, AM Broecker, WS Rind, D AF Greene, AM Broecker, WS Rind, D TI Swiss glacier recession since the little ice age: Reconciliation with climate records SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PRECIPITATION; SOUTHERN; NORWAY AB Since the culmination of the Little Ice Age, Alpine glaciers have been in a state of general retreat. The present study, focusing on the Swiss Alps between 1850 and 1973, seeks to relate the concomitant rise in equilibrium-line altitudes (ELAs) to recorded climate shifts. The approach taken involves the development of a regression model, but differs from most other studies in that the relationship of (midlatitude) ELAs to climate is examined at a resolution such that regional values are treated as individual data-points. Although such a treatment implies loss of resolution at small scales, a coherent relationship between climate and ELA is nonetheless obtained, due in large part to the primary control exercised by temperature, as well as the relatively wide range of ELAs included in the regression dataset. The derived relationship is applied to observed Swiss climate shifts, and is found to predict a secular rise in ELA somewhat greater than that observed. It is hypothesized that the difference represents climate change that had not yet been expressed by changes in glacier morphology. C1 Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Greene, AM (reprint author), Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA. EM amg@ldeo.columbia.edu NR 22 TC 15 Z9 17 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 JUL 1 PY 1999 VL 26 IS 13 BP 1909 EP 1912 DI 10.1029/1999GL900380 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 213TU UT WOS:000081290000032 ER PT J AU Murchie, S Robinson, M Hawkins, SE Harch, A Helfenstein, P Thomas, P Peacock, K Owen, W Heyler, G Murphy, P Darlington, EH Keeney, A Gold, R Clark, B Izenberg, N Bell, JF Merline, W Veverka, J AF Murchie, S Robinson, M Hawkins, SE Harch, A Helfenstein, P Thomas, P Peacock, K Owen, W Heyler, G Murphy, P Darlington, EH Keeney, A Gold, R Clark, B Izenberg, N Bell, JF Merline, W Veverka, J TI Inflight calibration of the NEAR multispectral imager SO ICARUS LA English DT Article DE asteroids; instrumentation; surfaces, asteroids; Mathilde; NEAR ID ASTEROID RENDEZVOUS MISSION; NEAR-INFRARED SPECTROMETER; ORIENTALE; FLYBY AB The multispectral imager on the Near-Earth Asteroid Rendezvous spacecraft has been subjected to a comprehensive series of inflight tests to validate its radiometric characteristics measured onground and to characterize instrument stability, pointing, geometric distortion, coalignment with other instruments, and light-scattering characteristics under flight conditions. The results of these tests, described herein, support the conversion of images of 253 Mathilde and 433 Eros into scientifically valid products with known geometric and radiometric characteristics. Key results include stability of dark current during cruise to within 1 data number; stability of the flat field to within the limits of inflight detectability; absolute radiometric accuracy of similar to 5%, with no evident systematic change with time; validation of the focal length with an inflight measurement of 166.85 mm, compared to 167.0 +/- 0.2 mm derived onground; measurement of coalignment with the near-infrared spectrometer under flight conditions; and quantification of the intensity and distribution of scattered light. (C) 1999 Academic Press. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. Northwestern Univ, Dept Geol Sci, Evanston, IL 60208 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. SW Res Inst, Boulder, CO 80302 USA. RP Murchie, S (reprint author), Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI Murchie, Scott/E-8030-2015; Izenberg, Noam/F-3952-2015 OI Murchie, Scott/0000-0002-1616-8751; Izenberg, Noam/0000-0003-1629-6478 NR 24 TC 27 Z9 27 U1 0 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUL PY 1999 VL 140 IS 1 BP 66 EP 91 DI 10.1006/icar.1999.6118 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226KW UT WOS:000082020000008 ER PT J AU Black, GJ Nicholson, PD Bottke, WF Burns, JA Harris, AW AF Black, GJ Nicholson, PD Bottke, WF Burns, JA Harris, AW TI On a possible rotation state of (433) Eros SO ICARUS LA English DT Article DE Eros; rotation asteroids; rotation ID DISTRIBUTIONS; ASTEROIDS; DYNAMICS AB Due to its extremely prolate figure, Asteroid (433) Eros may exhibit an unusual nonprincipal axis rotation state. As a result of a relatively small difference between the maximum and intermediate moments of inertia, a small perturbation such as the gravitational torques experienced during a close planetary encounter could have induced a rather large amplitude libration about the longest axis. Observation of such a state will permit measurement of the moment of inertia ratios; this task may be possible once the NEAR spacecraft enters orbit around Eros in early 2000 to begin an extensive study of its composition and structure. (C) 1999 Academic Press. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Black, GJ (reprint author), Natl Radio Astron Observ, POB 2, Green Bank, WV 24944 USA. NR 15 TC 16 Z9 16 U1 1 U2 1 PU ACADEMIC PRESS INC PI SAN DIEGO PA 525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA SN 0019-1035 J9 ICARUS JI Icarus PD JUL PY 1999 VL 140 IS 1 BP 239 EP 242 DI 10.1006/icar.1999.6126 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 226KW UT WOS:000082020000020 ER PT J AU Guice, J AF Guice, J TI Talking nets: An oral history of neural networks SO IEEE ANNALS OF THE HISTORY OF COMPUTING LA English DT Book Review C1 Caelum Res Corp, Ames Res Ctr, NASA, Stanford, CA 94305 USA. RP Guice, J (reprint author), Caelum Res Corp, Ames Res Ctr, NASA, MS 269-2, Stanford, CA 94305 USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1058-6180 J9 IEEE ANN HIST COMPUT JI IEEE Ann. Hist. Comput. PD JUL-SEP PY 1999 VL 21 IS 3 BP 75 EP 75 DI 10.1109/MAHC.1999.778990 PG 1 WC Computer Science, Theory & Methods; History & Philosophy Of Science SC Computer Science; History & Philosophy of Science GA 216XQ UT WOS:000081470100020 ER PT J AU Ivancic, WD Brooks, D Frantz, B Hoder, D Shell, D Beering, D AF Ivancic, WD Brooks, D Frantz, B Hoder, D Shell, D Beering, D TI NASA's broadband satellite networking research SO IEEE COMMUNICATIONS MAGAZINE LA English DT Article AB ATM is currently considered the primary WAN technology with Internet protocols providing the routing and transport requirements. Another WAN technology being considered is packet over SONET. Using the Advanced Communication Technology Satellite, NASA has demonstrated and is experimenting with these technologies. This article summarizes some of the major completed and ongoing experiments and demonstrations performed using commercial standard protocols such as ATM and TCP/IP over broadband satellite networks. C1 NASA, Washington, DC 20546 USA. Sterling Software, Palo Alto, CA USA. Cisco Syst, San Jose, CA USA. Infinite Global Infrastruct LLC, Chicago, IL USA. RP Ivancic, WD (reprint author), NASA, Washington, DC 20546 USA. NR 5 TC 14 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 0163-6804 J9 IEEE COMMUN MAG JI IEEE Commun. Mag. PD JUL PY 1999 VL 37 IS 7 BP 40 EP 47 DI 10.1109/35.774879 PG 8 WC Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 213LB UT WOS:000081273200007 ER PT J AU Li, R Cai, SJ Wong, L Chen, Y Wang, KL Smith, RP Martin, SC Boutros, KS Redwing, JM AF Li, R Cai, SJ Wong, L Chen, Y Wang, KL Smith, RP Martin, SC Boutros, KS Redwing, JM TI An Al0.3Ga0.7N/GaN undoped channel heterostructure field effect transistor with F-max of 107 GHz SO IEEE ELECTRON DEVICE LETTERS LA English DT Article DE GaN; microwave; transistor ID ALGAN/GAN HETEROSTRUCTURES; MICROWAVE PERFORMANCE; HFETS; POWER AB An Al0.3Ga0.7N/GaN heterostructure field effect transistor (HFET) grown on semi-insulating SiC with an 0.2-mu m gate length is reported. A source-drain ohmic contact resistance of 0.15-Ohm-mm was achieved through the use of high Al content and high n-type doping (1E19 cm(-3)) in the AlGaN donor layer and optimized metallization procedures. We obtained a maximum transconductance of 260 mS/mm, a saturated current density of 1.2 A/mm, and a maximum oscillation frequency in excess of 107 GHz in the devices, The results are one of the best achieved up to now, and they will open up the potential for the applications of AlGaN/GaN HFET's in high-power microwave radar, remote sensing, and communications. C1 Univ Calif Los Angeles, Dept Elect Engn, Device Res Lab, Los Angeles, CA 90095 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Epitron ATMI, Danbury, CT 06810 USA. RP Li, R (reprint author), Univ Calif Los Angeles, Dept Elect Engn, Device Res Lab, Los Angeles, CA 90095 USA. NR 16 TC 57 Z9 59 U1 1 U2 5 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0741-3106 J9 IEEE ELECTR DEVICE L JI IEEE Electron Device Lett. PD JUL PY 1999 VL 20 IS 7 BP 323 EP 325 DI 10.1109/55.772364 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 211FZ UT WOS:000081151400004 ER PT J AU Filman, R AF Filman, R TI Desperately seeking SO IEEE INTERNET COMPUTING LA English DT Editorial Material AB The Spider looks at the other side of search engines: getting them to notice your site. He also goes searching for the Lightweight Directory Access Protocol to find out what all the LDAP buzz is about. C1 NASA, Ames Res Ctr, Caelum Corp, Moffett Field, CA 94035 USA. RP Filman, R (reprint author), NASA, Ames Res Ctr, Caelum Corp, Moffett Field, CA 94035 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE COMPUTER SOC PI LOS ALAMITOS PA 10662 LOS VAQUEROS CIRCLE, PO BOX 3014, LOS ALAMITOS, CA 90720-1314 USA SN 1089-7801 J9 IEEE INTERNET COMPUT JI IEEE Internet Comput. PD JUL-AUG PY 1999 VL 3 IS 4 BP 82 EP + PG 4 WC Computer Science, Software Engineering SC Computer Science GA 222AY UT WOS:000081761100017 ER PT J AU Craeye, C Sobieski, PW Bliven, LF Guissard, A AF Craeye, C Sobieski, PW Bliven, LF Guissard, A TI Ring-waves generated by water drops impacting on water surfaces at rest SO IEEE JOURNAL OF OCEANIC ENGINEERING LA English DT Article DE circular surface waves; rain; wave energy ID RAIN; SCATTERING; RADAR AB Radar observations of the ocean surface can be affected by impacting raindrops. Ring-wave measurements are presented for drops of 2.2 and 2.8 mm in diameter impacting on fresh and salt water surfaces initially at rest. They are based on the observation of the mirror image of a sharp edge on the perturbed surface. The retrieved wave profiles show a rather stable characteristic wavenumber (0.2 mm(-1)) and very small wave amplitudes: the fraction of the incident kinetic energy converted into ring-waves is of the order of 1%. C1 Univ Catholique Louvain, B-1348 Louvain, Belgium. NASA, Goddard Space Flight Ctr, WFF, Lab Hydrospher Proc, Wallops Island, VA 23337 USA. RP Craeye, C (reprint author), Univ Catholique Louvain, B-1348 Louvain, Belgium. RI bliven, francis/E-1450-2012 NR 21 TC 16 Z9 17 U1 1 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0364-9059 J9 IEEE J OCEANIC ENG JI IEEE J. Ocean. Eng. PD JUL PY 1999 VL 24 IS 3 BP 323 EP 332 DI 10.1109/48.775294 PG 10 WC Engineering, Civil; Engineering, Ocean; Engineering, Electrical & Electronic; Oceanography SC Engineering; Oceanography GA 219HW UT WOS:000081602700006 ER PT J AU Barnes, NP Walsh, BM AF Barnes, NP Walsh, BM TI Amplified spontaneous emission-application to Nd : YAG lasers (vol 35, pg 101, 1999) SO IEEE JOURNAL OF QUANTUM ELECTRONICS LA English DT Correction C1 NASA, Langley Res Ctr, Hampton, VA 23681 USA. Boston Coll, Chestnut Hill, MA 02167 USA. RP Barnes, NP (reprint author), NASA, Langley Res Ctr, Hampton, VA 23681 USA. NR 1 TC 3 Z9 3 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 0018-9197 J9 IEEE J QUANTUM ELECT JI IEEE J. Quantum Electron. PD JUL PY 1999 VL 35 IS 7 BP 1100 EP 1100 DI 10.1109/JQE.1999.772183 PG 1 WC Engineering, Electrical & Electronic; Optics; Physics, Applied SC Engineering; Optics; Physics GA 211NK UT WOS:000081167000016 ER PT J AU Weinreb, S Gaier, T Lai, R Barsky, M Leong, YC Samoska, L AF Weinreb, S Gaier, T Lai, R Barsky, M Leong, YC Samoska, L TI High-gain 150-215-GHz MMIC amplifier with integral waveguide transitions SO IEEE MICROWAVE AND GUIDED WAVE LETTERS LA English DT Article DE InP; millimeter-wave; transistor amplifier; wave-guide transition AB The design and measured results of a six-stage InP monolithic microwave integrated circuit (MMIC) amplifier with 20 +/- 6 dB gain from 150 to 215 GHz is reported. The MMIC has integral probes for direct coupling to 140-220 GHz WR-5 waveguide without bond wires or external transitions, This is the first amplifier operating above 140 GHz with sufficient gain to be useful as a single-chip amplifier and demonstrates the practicality of MMIC-based systems in this frequency range for use in radiometry, compact radars, and communication systems. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Massachusetts, Dept Phys & Astron, Amherst, MA 01003 USA. TRW Co Inc, Redondo Beach, CA 90277 USA. Univ Massachusetts, Dept Elect Engn, Amherst, MA 01003 USA. RP Weinreb, S (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Weinreb, Steven/K-8747-2012 NR 7 TC 54 Z9 55 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 1051-8207 J9 IEEE MICROW GUIDED W JI IEEE Microw. Guided Wave Lett. PD JUL PY 1999 VL 9 IS 7 BP 282 EP 284 DI 10.1109/75.774148 PG 3 WC Engineering, Electrical & Electronic SC Engineering GA 215MQ UT WOS:000081385800007 ER PT J AU Cruz-Neira, C Lutz, RR AF Cruz-Neira, C Lutz, RR TI Using immersive virtual environments for certification SO IEEE SOFTWARE LA English DT Article AB Designers, researchers, and developers are already using virtual environments in many ways and in many domains. The technology has matured enough so that now VEs are beginning to be used to certify the systems they simulate. C1 Iowa State Univ, Dept Elect & Comp Engn, Ames, IA 50011 USA. Iowa State Univ, Virtual Real Applicat Ctr, Ames, IA 50011 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Cruz-Neira, C (reprint author), Iowa State Univ, Dept Elect & Comp Engn, Ames, IA 50011 USA. NR 14 TC 2 Z9 2 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 0740-7459 J9 IEEE SOFTWARE JI IEEE Softw. PD JUL-AUG PY 1999 VL 16 IS 4 BP 26 EP 30 DI 10.1109/52.776945 PG 5 WC Computer Science, Software Engineering SC Computer Science GA 215ML UT WOS:000081385400013 ER PT J AU Oberg, J AF Oberg, J TI The US-Russian space relationship: symbolism at any cost? SO IEEE SPECTRUM LA English DT Article C1 ABC News, New York, NY 10023 USA. NASA Mission Controls, Houston, TX USA. RP Oberg, J (reprint author), ABC News, New York, NY 10023 USA. NR 3 TC 0 Z9 0 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 0018-9235 J9 IEEE SPECTRUM JI IEEE Spectr. PD JUL PY 1999 VL 36 IS 7 BP 74 EP 81 PG 8 WC Engineering, Electrical & Electronic SC Engineering GA 211ZF UT WOS:000081191200019 ER PT J AU Oshman, Y Markley, FL AF Oshman, Y Markley, FL TI Spacecraft attitude/rate estimation using vector-aided GPS observations SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article ID GLOBAL POSITIONING SYSTEM AB A sequential filtering algorithm is presented for spacecraft attitude and attitude-rate estimation from Global Positioning System (GPS) differential carrier phase measurements. A third-order, minimal-parameter method for solving the attitude matrix kinematic equation is used to parameterize the state of the filter, which renders the resulting estimator computationally efficient. Borrowing from tracking theory concepts, the angular acceleration is modeled as an exponentially autocorrelated stochastic process, thus avoiding the use of the uncertain spacecraft dynamic model. The new formulation facilitates the use of aiding vector observations in a unified filtering algorithm, which can enhance the robustness and accuracy of the method. Numerical examples are used to demonstrate the performance of the method. C1 Technion Israel Inst Technol, Dept Aerosp Engn, IL-32000 Haifa, Israel. NASA, Goddard Space Flight Ctr, Navigat & Control Ctr, Greenbelt, MD 20771 USA. RP Oshman, Y (reprint author), Technion Israel Inst Technol, Dept Aerosp Engn, IL-32000 Haifa, Israel. NR 17 TC 8 Z9 10 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 0018-9251 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD JUL PY 1999 VL 35 IS 3 BP 1019 EP 1032 DI 10.1109/7.784071 PG 14 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 227YC UT WOS:000082106700022 ER PT J AU Ortiz, J Chen, GR AF Ortiz, J Chen, GR TI Intelligent control of a planning system for astronaut training SO IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS LA English DT Article ID DISCRETE-EVENT SYSTEMS; SUPERVISORY CONTROL AB This work intends to design, analyze and solve, from the systems control perspective, a complex, dynamic, and multiconstrained planning system for generating training plans for crew members of the NASA-led International Space Station. Various intelligent planning systems have been developed within the framework of artificial intelligence. These planning systems generally lack a rigorous mathematical formalism to allow a reliable and flexible methodology for their design, modeling, and performance analysis in a dynamical, time-critical, and multiconstrained environment. Formulating the planning problem in the domain of discrete-event systems under a unified framework such that it can be modeled, designed, and analyzed as a control system will provide a sep-contained theory for such planning systems. This will also provide a means to certify various planning systems for operations in the dynamical and complex environments in space. The work presented here completes the design, development, and analysis of an intricate, large-scale, and representative mathematical formulation for intelligent control of a real planning system for Space Station crew training. This planning system has been tested and used at NASA-Johnson Space Center. C1 Lyndon B Johnson Space Ctr, Mission Operat Directorate, Houston, TX 77058 USA. Univ Houston, Dept Elect & Comp Engn, Houston, TX 77204 USA. RP Ortiz, J (reprint author), Lyndon B Johnson Space Ctr, Mission Operat Directorate, DD2, Houston, TX 77058 USA. NR 21 TC 1 Z9 1 U1 0 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI PISCATAWAY PA 445 HOES LANE, PISCATAWAY, NJ 08855-4141 USA SN 0018-9251 EI 1557-9603 J9 IEEE T AERO ELEC SYS JI IEEE Trans. Aerosp. Electron. Syst. PD JUL PY 1999 VL 35 IS 3 BP 1055 EP 1070 DI 10.1109/7.784074 PG 16 WC Engineering, Aerospace; Engineering, Electrical & Electronic; Telecommunications SC Engineering; Telecommunications GA 227YC UT WOS:000082106700025 PM 12192682 ER PT J AU Way, J McGuire, J AF Way, J McGuire, J TI Introduction to KidSat Special Section SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Editorial Material C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Pacific Union Sch, Arcata, CA USA. RP Way, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1999 VL 37 IS 4 BP 1751 EP 1752 PG 2 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 217VP UT WOS:000081519900001 ER PT J AU Way, J Baker, JD Andres, P McGuire, J Galindo, M Fox, J Stork, EJ AF Way, J Baker, JD Andres, P McGuire, J Galindo, M Fox, J Stork, EJ TI The KidSat Project SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article AB Imagine viewing our world from space; a world astronauts have described as "bright and vivid" with "no borders or boundaries." Then consider how much can be learned by studying Earth from this unique vantage point. The National Aeronautics and Space Administration (NASA) began a three-year pilot program in 1995 designed by a team of scientists, educators, engineers, and high school and college students to share astronauts' unique view of Earth with middle school students, This pilot program was called KidSat. KidSat's primary objective was to merge real-time professional space flight with middle school education by providing students with equal access and direct contribution to the United States space program for the exploration of the Earth. KidSat's long-term intent was to produce higher student achievement and increased competence in science, math, technology, and geography, and to promote an interactive understanding of Earth as an integrated system. Similar to the regular duties of astronauts, scientists, and engineers, students around the nation planned observations and captured images to study Earth's dynamic, fragile environment, using a remotely operated high-resolution color digital camera onboard the Space Shuttle, custom flight software, the Internet, NASA's infrastructure, and a mission operations infrastructure that linked middle schools to the Shuttle through a student-built Mission Control Gateway, Using accompanying curriculum students determined which areas of Earth they wanted to explore and photograph along the Shuttle's flight path. Orbiting communications satellites and the Internet transmitted commands, telemetry and images to and from the classrooms, Via the Shuttle cargo bay video camera, NASA TV carried video of the mission and the Earth for simultaneous viewing in classrooms. The KidSat pilot program was conceived in November 1993 and ended in December 1997, This paper summarizes the results of this program. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Pacific Union Sch, Arcata, CA 95521 USA. Buist Acad, Charleston, SC 29403 USA. Johns Hopkins Univ, Inst Acad Adv Youth, Baltimore, MD 21218 USA. RP Way, J (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1999 VL 37 IS 4 BP 1753 EP 1767 DI 10.1109/36.774689 PG 15 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 217VP UT WOS:000081519900002 ER PT J AU Baker, JD Woodring, J Leach, A Lane, J Spohr, R AF Baker, JD Woodring, J Leach, A Lane, J Spohr, R TI The KidSat Project flight system SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article AB This paper mas witten to discuss the technical aspects of granting students in classrooms the ability to explore and study earth sciences from a unique view of our planet. A high-resolution digital imaging system mounted in the space shuttle cabin window made it possible, in part, to provide realtime student interaction with the space program, This access provided an individual ownership of research and interest in our environment and earth sciences, The other project technical elements, also key to the program success and real-time student interaction, were the University of California, San Diego (UCSD) web-based mission operations system and the Jet Propulsion Laboratory (JPL) ground data system. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. La Canada High Sch, La Canada, CA 91011 USA. NASA, Lyndon B Johnson Space Ctr, Lockeheed Martin, Houston, TX 77058 USA. RP Baker, JD (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 4 TC 0 Z9 0 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1999 VL 37 IS 4 BP 1768 EP 1774 DI 10.1109/36.774690 PG 7 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 217VP UT WOS:000081519900003 ER PT J AU Andres, PM Amy, L Steinwand, D Lawson, J Moffitt, RA AF Andres, PM Amy, L Steinwand, D Lawson, J Moffitt, RA TI Making sense of space-based earth image data: The KidSat data system SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE educational technology; image processing; Internet; remote sensing; user interfaces; visualization AB The KidSat data system provided near real-time access to digital images taken from the space shuttle. The images were made available to middle school students and teachers across the country and overseas through the World Wide Web. The KidSat Project was one of the first NASA programs to attempt to use the web as a means of distributing image data within minutes of the time they were captured in space. After the first hurdle, getting the image data online in a timely manner, was cleared, it became the goal of the data system to present that data in an understandable context. The development of the system was a collaborative effort. Members of the data system team conferred continually with teachers, students, and other members of the KidSat Project. Modifications to the data system were made as often as was possible, while attempting to avoid confusing the users. The goal was to create an online system that presented the KidSat images in a manner that allowed the students to better understand and interpret these images. In short, that goal was reached, but whether the users agreed with this judgment may be directly related to the speed with which they could connect to the Internet, Many lessons were learned along the may, and strategies for future similar projects were devised, For the three KidSat missions, over 1500 images were captured and made available on the data system. Additionally, metadata describing the shuttle location and orientation, satellite weather data (captured at or near the time of the KidSat image), and digital maps of the area directly surrounding the KidSat image were made available. How these various data sets were assembled and how effectively design and operational goals were met is discussed in detail. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Calif State Polytech Univ Pomona, Pomona, CA 91768 USA. Harvey Mudd Coll, Claremont, CA 91711 USA. La Canada High Sch, La Canada, CA 91011 USA. RP Andres, PM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 11 TC 0 Z9 0 U1 0 U2 1 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1999 VL 37 IS 4 BP 1785 EP 1800 DI 10.1109/36.774692 PG 16 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 217VP UT WOS:000081519900005 ER PT J AU Galantowicz, JF Entekhabi, D Njoku, EG AF Galantowicz, JF Entekhabi, D Njoku, EG TI Tests of sequential data assimilation for retrieving profile soil moisture and temperature from observed L-band radiobrightness SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE data assimilation; Kalman filter; microwave radiometry; soil coupled heat and moisture models; soil moisture ID MICROWAVE AB Sequential data assimilation (Kalman filter optimal estimation) techniques are applied to the problem of retrieving near-surface soil moisture and temperature state from periodic terrestrial radiobrightness observations that update soil heat and moisture diffusion models. The retrieval procedure uses a time-explicit numerical model to continuously propagate the soil state profile, its error of estimation, and its interdepth covariances through time, The model's coupled soil moisture and heat fluxes are constrained by micrometeorology boundary conditions drawn from observations or atmospheric modeling. When radiometer data are available, the Kalman filter updates the state profile estimate by weighing the propagated state, error, and covariance estimates against an a priori estimate of radiometric measurement error. The Kalman filter compares predicted and observed radiobrightnesses directly, so no inverse algorithm relating brightness to physical parameters is required. We demonstrate Kalman filter model effectiveness using field observations and a simulation study. An observed 1 m soil state profile is recovered over an eight-day period from daily L-band observations following an intentionally poor initial state estimate. In a four-month simulation study, we gauge the longer term behavior of the soil state retrieval and Kalman gain through multiple rain events, soil dry-downs, and updates from radiobrightnesses. C1 MIT, Dept Civil & Environm Engn, Ralph M Parsons Lab, Cambridge, MA 02139 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Galantowicz, JF (reprint author), Atmospher & Environm Res Inc, 840 Mem Dr, Cambridge, MA 02139 USA. NR 13 TC 92 Z9 107 U1 2 U2 14 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1999 VL 37 IS 4 BP 1860 EP 1870 DI 10.1109/36.774699 PG 11 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 217VP UT WOS:000081519900012 ER PT J AU McDonald, KC Zimmermann, R Way, J Chun, W AF McDonald, KC Zimmermann, R Way, J Chun, W TI Automated instrumentation for continuous monitoring of the dielectric properties of woody vegetation: System design, implementation, and selected in situ measurements SO IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING LA English DT Article DE BOREAS; dielectric behavior; dielectric constant; dielectric monitoring system; vegetation; vegetation physiology ID WALNUT ORCHARD; IMAGING RADAR; WATER; FORESTS; BACKSCATTER; SCATTERING; MODEL; SAR; FLOODPLAIN; ALASKA AB The design and implementation of a system for the automated and continuous irt situ monitoring of the dielectric constant of woody vegetation tissue are presented. The implementation of both single-channel and multichannel systems is discussed. These systems permit unsupervised continuous and long-term monitoring of vegetation canopy dielectric behavior in remote field sites. Utilizing open-ended coaxial lines, the real and imaginary parts of the microwave dielectric constant of woody plant tissue are inferred from direct measurement of the magnitude and phase of the microwave reflection coefficient. Samples of in situ data from forests in contrasting ecological environments are presented. Measurements obtained with our systems allow new insight into the dielectric behavior of vegetation with respect to the physiological and hydraulic function of trees. The observations provide a significant advance in our ability to link canopy physiological and hydraulic behavior to radar remote-sensing observations. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Bayreuth, Dept Plant Ecol, Forest Ecol & Remote Sensing Grp, D-95440 Bayreuth, Germany. RP McDonald, KC (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 51 TC 12 Z9 12 U1 1 U2 2 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 0196-2892 J9 IEEE T GEOSCI REMOTE JI IEEE Trans. Geosci. Remote Sensing PD JUL PY 1999 VL 37 IS 4 BP 1880 EP 1894 DI 10.1109/36.774701 PG 15 WC Geochemistry & Geophysics; Engineering, Electrical & Electronic; Remote Sensing; Imaging Science & Photographic Technology SC Geochemistry & Geophysics; Engineering; Remote Sensing; Imaging Science & Photographic Technology GA 217VP UT WOS:000081519900014 ER PT J AU Descombes, X Morris, RD Zerubia, J Berthod, M AF Descombes, X Morris, RD Zerubia, J Berthod, M TI Estimation of Markov random field prior parameters using Markov chain Monte Carlo maximum likelihood SO IEEE TRANSACTIONS ON IMAGE PROCESSING LA English DT Article DE Chien model; estimation; hierarchical model; image restoration; image segmentation; maximum likelihood; Potts model ID STOCHASTIC RELAXATION; IMAGES; RESTORATION AB Recent developments in statistics now allow maximum likelihood estimators for the parameters of Markov random fields (MRF's) to be constructed. We detail the theory required, and present an algorithm that is easily implemented and practical in terms of computation time. We demonstrate this algorithm on three MRF models-the standard Potts model, an inhomogeneous variation of the Potts model, and a long-range interaction model, better adapted to modeling real world images. We estimate the parameters from a synthetic and a real image, and then resynthesize the models to demonstrate which features of the image have been captured by the model. Segmentations are computed based on the estimated parameters and conclusions drawn. C1 INRIA, F-06902 Sophia Antipolis, France. NASA, Ames Res Ctr, RIACS, Computat Sci Div, Moffett Field, CA 94035 USA. RP Descombes, X (reprint author), INRIA, F-06902 Sophia Antipolis, France. NR 21 TC 48 Z9 55 U1 0 U2 0 PU IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017-2394 USA SN 1057-7149 J9 IEEE T IMAGE PROCESS JI IEEE Trans. Image Process. PD JUL PY 1999 VL 8 IS 7 BP 954 EP 963 DI 10.1109/83.772239 PG 10 WC Computer Science, Artificial Intelligence; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 211GA UT WOS:000081151500008 PM 18267508 ER PT J AU Vatan, F Roychowdhury, VP Anantram, MP AF Vatan, F Roychowdhury, VP Anantram, MP TI Spatially correlated qubit errors and burst-correcting quantum codes SO IEEE TRANSACTIONS ON INFORMATION THEORY LA English DT Article DE additive codes; burst errors; cyclic codes; Gilbert-Varshamov bound; quantum error-correcting code AB We explore the design of quantum error-correcting codes for cases where the decoherence events of qubits are correlated. In particular, we consider the case where only spatially contiguous qubits decohere, which is analogous to the case of burst errors in classical coding theory. We present several different efficient schemes for constructing families of such codes. For example, one can find one-dimensional quantum codes of length n = 13 and 15 that correct burst errors of width b less than or equal to 3; as a comparison, a random-error correcting quantum code that corrects t = 3 errors must have length n greater than or equal to 17. In general, we show that it is possible to build quantum burst-correcting codes that have near optimal dimension. For example, we show that for any constant b, there exist b-burst-correcting quantum codes with length n, and dimension k = n - log n - O(1); as a comparison, the Hamming bound for the case with t (constant) random errors yields k less than or equal to n - t log n + O(1). C1 Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Vatan, F (reprint author), Univ Calif Los Angeles, Dept Elect Engn, Los Angeles, CA 90095 USA. NR 20 TC 8 Z9 9 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 0018-9448 J9 IEEE T INFORM THEORY JI IEEE Trans. Inf. Theory PD JUL PY 1999 VL 45 IS 5 BP 1703 EP 1708 DI 10.1109/18.771250 PG 6 WC Computer Science, Information Systems; Engineering, Electrical & Electronic SC Computer Science; Engineering GA 209TL UT WOS:000081064900038 ER PT J AU Pogorzelski, RJ Maccarini, PF York, RA AF Pogorzelski, RJ Maccarini, PF York, RA TI Continuum modeling of the dynamics of externally injection-locked coupled oscillator arrays (vol 47, pg 471, 1999) SO IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES LA English DT Correction C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Calif Santa Barbara, Dept Elect Engn, Santa Barbara, CA 93106 USA. RP Pogorzelski, RJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 1 TC 1 Z9 1 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 JUL PY 1999 VL 47 IS 7 BP 1147 EP 1147 PN 1 PG 1 WC Engineering, Electrical & Electronic SC Engineering GA 216YX UT WOS:000081473000027 ER PT J AU Alouini, MS Simon, MK AF Alouini, MS Simon, MK TI Performance of coherent receivers with hybrid SC/MRC over Nakagami-m fading channels SO IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY LA English DT Article DE diversity combining; Nakagami fading channels ID DIVERSITY; SIGNALS; SYSTEMS; DPSK AB A performance analysis of two hybrid selective combining/maximal ratio combining (SC/MRC) diversity receivers over Nakagami-m fading channels with a flat multipath intensity profile is presented and numerically compared with that of the conventional SC and MRC schemes. Numerical results for particular cases of interest show that the bit error rate (BER) degradation arising from the use of hybrid SC/MRC instead of MRC is independent of the average signal-to-noise ratio (SNR) regardless of the severity of the fading and that MRC provides a higher rate of improvement than the hybrid SC/MRC as the severity of fading decreases. C1 CALTECH, Dept Elect Engn, Commun Grp, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Alouini, MS (reprint author), Univ Minnesota, Dept Elect & Comp Engn, Minneapolis, MN 55455 USA. NR 24 TC 99 Z9 99 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 0018-9545 J9 IEEE T VEH TECHNOL JI IEEE Trans. Veh. Technol. PD JUL PY 1999 VL 48 IS 4 BP 1155 EP 1164 DI 10.1109/25.775365 PG 10 WC Engineering, Electrical & Electronic; Telecommunications; Transportation Science & Technology SC Engineering; Telecommunications; Transportation GA 217ZT UT WOS:000081529400015 ER PT J AU Lu, YN Nerurkar, VR Aguirre, AA Work, TM Balazs, GH Yanagihara, R AF Lu, YN Nerurkar, VR Aguirre, AA Work, TM Balazs, GH Yanagihara, R TI Establishment and characterization of 13 cell lines from a green turtle (Chelonia mydas) with fibropapillomas SO IN VITRO CELLULAR & DEVELOPMENTAL BIOLOGY-ANIMAL LA English DT Article DE green turtle fibropapilloma; primary culture; cell line; tumor; turtle virus ID HAWAIIAN AB Thirteen cell lines were established and characterized from brain, kidney, lung, spleen, heart, liver. gall bladder urinary bladder, pancreas, testis, skin, and periorbital and tumor tissues of an immature male green turtle (Chelonia mydas) with fibropapillomas. Cell lines were optimally maintained at 30 degrees C in RPMI 1640 medium supplemented with 10% fetal bovine serum. Propagation of the turtle cell lines was serum dependent, and plating efficiencies ranged from 13 to 37%. The cell lines, which have been subcultivated more than 20 times, had a doubling time of approximately 30 to 36 h. When tested for their sensitivity to several fish viruses, most of the cell lines were susceptible to a rhabdovirus, spring viremia carp virus. but refractory; to channel catfish virus (a herpesvirus), infectious pancreatic necrosis virus (a birnavirus), and two other fish rhabdoviruses, infectious hematopoietic necrosis virus and viral hemorrhagic septicemia virus. During in vitro subcultivation: tumor-like cell aggregates appeared in cell lines derived from lungs, testis, and periorbital and tumor tissues, and small, naked intranuclear virus particles were detected by thin-section electron microscopy. These cell lines are currently being used in attempts to isolate the putative etiologic virus of green turtle fibropapilloma. C1 Univ Hawaii, Pacific Biomed Res Ctr, Retrovirol Res Lab, Leahi Hosp, Honolulu, HI 96816 USA. Natl Wildlife Hlth Ctr, Inst Marine & Atmospher Res, Honolulu, HI USA. Natl Marine Fisheries Serv, Honolulu, HI USA. RP Lu, YN (reprint author), Univ Hawaii, Pacific Biomed Res Ctr, Retrovirol Res Lab, Leahi Hosp, 3675 Kilauea Ave, Honolulu, HI 96816 USA. RI Work, Thierry/F-1550-2015 OI Work, Thierry/0000-0002-4426-9090 FU NCRR NIH HHS [G12RR/AI-03061] NR 27 TC 34 Z9 34 U1 1 U2 6 PU SOC IN VITRO BIOLOGY PI LARGO PA 9315 LARGO DR WEST, STE 25, LARGO, MD 20774 USA SN 1071-2690 J9 IN VITRO CELL DEV-AN JI In Vitro Cell. Dev. Biol.-Anim. PD JUL-AUG PY 1999 VL 35 IS 7 BP 389 EP 393 PG 5 WC Cell Biology; Developmental Biology SC Cell Biology; Developmental Biology GA 224QG UT WOS:000081909300006 PM 10462202 ER PT J AU Webster, L Chen, JG Tan, SS Watson, C de Korvin, A AF Webster, L Chen, JG Tan, SS Watson, C de Korvin, A TI Vadidation of authentic reasoning expert systems SO INFORMATION SCIENCES LA English DT Article ID ROUGH SETS AB This paper outlines an approach for validating the expert system's performance by comparing the expert system to the consensus results of the experts (i.e., using several experts to solve the same problem that the authentic reasoning expert system solved). We also discuss a mathematical process that includes the use of rough set theory as a means of capturing and quantifying the reasoning factors and reasoning processes of the experts. Additionally, a generalized entropy criterion for measuring consensus effectiveness based on Dempster-Shafer's theory of mathematical evidence is used in conjunction with rough set and fuzzy set theories. This is used for ascertaining whether or not the behavior of the expert system is evident in the behavior of the experts which is an essential task in validating authentic reasoning expert systems. Published by Elsevier Science Inc. C1 NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Houston, TX 77058 USA. Univ Houston, Dept Ind Engn, Houston, TX 77004 USA. Lockheed Engn & Sci Co, Houston, TX 77058 USA. Univ Houston Downtown, Houston, TX 77002 USA. RP Webster, L (reprint author), NASA, Lyndon B Johnson Space Ctr, Life Sci Res Labs, Mail Stop SD3, Houston, TX 77058 USA. NR 19 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE INC PI NEW YORK PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA SN 0020-0255 J9 INFORM SCIENCES JI Inf. Sci. PD JUL PY 1999 VL 117 IS 1-2 BP 19 EP 46 DI 10.1016/S0020-0255(99)00005-5 PG 28 WC Computer Science, Information Systems SC Computer Science GA 216YH UT WOS:000081471700002 ER PT J AU Raj, SV Whittenberger, JD Zeumer, B Sauthoff, G AF Raj, SV Whittenberger, JD Zeumer, B Sauthoff, G TI Elevated temperature deformation of Cr3Si alloyed with Mo SO INTERMETALLICS LA English DT Article DE silicides, various; mechanical properties at high temperatures ID MODIFIED CR3SI/CR5SI3 INTERMETALLICS; MECHANICAL-BEHAVIOR; SILICON; OXYGEN AB Four-point bend, constant load compressive creep and constant engineering strain rate tests were conducted on are-melted and powder-metallurgy (PM) processed Cr40Mo30Si30 specimens in the temperature range 1400-1700 K. This is a two-phase alloy consisting of (Cr,Mo)(3)Si and (Cr,Mo)(5)Si-3 phases. The PM specimens, which were substantially weaker than the are-melted materials, exhibited a stress exponent, n, of about 2 and an apparent activation energy for creep, Q(a), of 485 kJ/mol. The mechanism in these specimens appeared to be controlled by creep of a glassy phase. In the case of are-melted specimens for which n ' 3 and Q(a) ' 430 kJ/ mol, the rate-controlling creep mechanism appeared to be that dominant in the (Cr,Mo)(5)Si-3 phase. In this case, it is suggested that the Nabarro creep mechanism, where dislocation climb is controlled by Bardeen-Herring vacancy sources, is the dominant creep mechanism. Finally, an analysis of the present and literature data on Cr3Si alloyed with Mo appeared to suggest that the creep rate decreases sharply with an increase in the Mo/Si ratio. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. Max Planck Inst Eisenforsch GmbH, D-40074 Dusseldorf, Germany. RP Raj, SV (reprint author), NASA, Lewis Res Ctr, MS 24-1, Cleveland, OH 44135 USA. NR 20 TC 31 Z9 36 U1 1 U2 6 PU ELSEVIER SCI LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND SN 0966-9795 J9 INTERMETALLICS JI Intermetallics PD JUL PY 1999 VL 7 IS 7 BP 743 EP 755 DI 10.1016/S0966-9795(98)00095-8 PG 13 WC Chemistry, Physical; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Chemistry; Materials Science; Metallurgy & Metallurgical Engineering GA 201TE UT WOS:000080611000001 ER PT J AU Skarda, JRL McCaughan, FE AF Skarda, JRL McCaughan, FE TI Exact solution to stationary onset of convection due to surface tension variation in a multicomponent fluid layer with interfacial deformation SO INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER LA English DT Article ID HORIZONTAL LIQUID LAYER; DRIVEN INSTABILITY; STABILITY; MARANGONI AB Stationary onset of convection due to surface tension variation in an unbounded multicomponent fluid layer is considered. Surface deformation is included and general flux boundary conditions are imposed on the stratifying agencies (temperature/composition) disturbance equations. Exact solutions are obtained to the general N-component problem for both finite and infinitesimal wavenumbers. Long wavelength instability may coexist with a finite wavelength instability for certain sets of parameter values, often referred to as frontier points. For an impermeable/insulted upper boundary and a permeable/conductive lower boundary, frontier boundaries are computed in the space of Bond number, Bo, vs Crispation number, Cr, over the range 5 x 10(-7) less than or equal to Bo less than or equal to 1. The loci of frontier points in (Bo, Cr) space for different values of N, diffusivity ratios, and Marangoni numbers collapsed to a single curve in (Bo, (D) over tilde Cr) space,where (D) over tilde is a Marangoni number weighted diffusivity ratio. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 NASA, Lewis Res Ctr, Micrograv Sci Div, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. Case Western Reserve Univ, Dept Mech & Aerosp Engn, Cleveland, OH 44135 USA. RP Skarda, JRL (reprint author), NASA, Lewis Res Ctr, Micrograv Sci Div, Micrograv Fluid Phys Branch, Cleveland, OH 44135 USA. NR 28 TC 11 Z9 11 U1 0 U2 1 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0017-9310 J9 INT J HEAT MASS TRAN JI Int. J. Heat Mass Transf. PD JUL PY 1999 VL 42 IS 13 BP 2387 EP 2398 DI 10.1016/S0017-9310(98)00309-3 PG 12 WC Thermodynamics; Engineering, Mechanical; Mechanics SC Thermodynamics; Engineering; Mechanics GA 169TK UT WOS:000078764500008 ER PT J AU Volpe, R AF Volpe, R TI Navigation results from desert field tests of the Rocky 7 Mars rover prototype SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article DE field robotics; planetary rovers; mobile robot navigation; localization ID PATHFINDER AB Upcoming missions to the surface of Mars will use mobile robots to traverse long distances from the landing site. To prepare for these missions, the prototype revel; Rocky 7, has been tested in desert field trials conducted with a team of planetary scientists. While several new capabilities have been demonstrated, foremost among these was sun-sensor-based traversal of natural terrain totaling a distance of 1 km. This paper describes navigation results obtained in the field tests, where cross-track error was only 6% of the distance traveled. Comparison with previous results of other planetary rover systems shows this to be a significant improvement. Methods for further improvement are also discussed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Volpe, R (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 26 TC 17 Z9 17 U1 0 U2 0 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 0278-3649 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD JUL PY 1999 VL 18 IS 7 BP 669 EP 683 DI 10.1177/02783649922066493 PG 15 WC Robotics SC Robotics GA 209LD UT WOS:000081048600004 ER PT J AU Prassler, E Scholz, J Fiorini, P AF Prassler, E Scholz, J Fiorini, P TI Navigating a robotic wheelchair in a railway station during rush hour SO INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH LA English DT Article ID MOVING OBSTACLES; MOTION AB This paper describes the hardware design, control and navigation system of and some preliminary experiments with the robotic wheelchair Mobility Aid for elderly and disabled people (MAid). MAid's general task is to transport people with severely impaired motion skills. The authors did not set out to reinvent and redevelop the set of standard skills of so-called intelligent wheelchairs, such as FollowWall, FollowCorridor; PassDoorway which are commonly described in the literature. These maneuvers require motion control skills that disabled people, in spite of their disabilities, are eager to learn and quire good at using. Instead, this work focused on generalizing the approach to fine motion control by considering those maneuvers identified as very burdensome due to their duration and required concentration. One of these functions is deliberative locomotion in rapidly changing, large-scale environments, such as shopping malls, entry halls of theaters, and concourses of airports or railway stations, where tens or hundreds of people and objects move around MAid's performance was tested in the central station of Ulm during rush hour and in the exhibition halls of the Hannover Messe '98, the largest industrial fair in the world. Altogether MAid has survived more than 36 h of testing in public, crowded environments with heavy passenger traffic. C1 Res Inst Appl Knowledge Proc FAW, D-89010 Ulm, Germany. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Res Inst Appl Knowledge Proc FAW, D-89010 Ulm, Germany. EM prassler@faw.uni-ulm.de; scholz@faw.uni-ulm.de; fiorini@jpl.nasa.gov RI Fiorini, Paolo/A-2603-2012 NR 24 TC 44 Z9 45 U1 1 U2 10 PU SAGE PUBLICATIONS LTD PI LONDON PA 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND SN 0278-3649 EI 1741-3176 J9 INT J ROBOT RES JI Int. J. Robot. Res. PD JUL PY 1999 VL 18 IS 7 BP 711 EP 727 DI 10.1177/02783649922066529 PG 17 WC Robotics SC Robotics GA 209LD UT WOS:000081048600007 ER PT J AU Blair, JB Rabine, DL Hofton, MA AF Blair, JB Rabine, DL Hofton, MA TI The Laser Vegetation Imaging Sensor: a medium-altitude, digitisation-only, airborne laser altimeter for mapping vegetation and topography SO ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING LA English DT Article DE laser altimetry; vegetation height; topography; lidar AB The Laser Vegetation imaging Sensor (LVIS) is an airborne, scanning laser altimeter, designed and developed at NASA's Goddard Space Flight Center (GSFC). LVIS operates at altitudes up to 10 km above ground, and is capable of producing a data swath up to 1000 m wide nominally with 25-m wide footprints. The entire time history of the outgoing and return pulses is digitised, allowing unambiguous determination of range and return pulse structure. Combined with aircraft position and attitude knowledge, this instrument produces topographic maps with dm accuracy and vertical height and structure measurements of vegetation. The laser transmitter is a diode-pumped Nd:YAG oscillator producing 1064 nm, 10 ns, 5 mi pulses at repetition rates up to 500 Hz. LVIS has recently demonstrated its ability to determine topography (including sub-canopy) and vegetation height and structure on flight missions to various forested regions in the US and Central America. The LVIS system is the airborne simulator for the Vegetation Canopy Lidar (VCL) mission (a NASA Earth remote sensing satellite due far launch in year 2000), providing simulated data sets and a platform for instrument proof-of-concept studies. The topography maps and return waveforms produced by LVIS provide Earth scientists with a unique data set allowing studies of topography, hydrology, and vegetation with unmatched accuracy and coverage. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Terr Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Syst & Applicat, Lanham, MD 20706 USA. Univ Maryland, Dept Geog, College Pk, MD 20742 USA. RP Blair, JB (reprint author), NASA, Terr Phys Lab, Goddard Space Flight Ctr, Code 924, Greenbelt, MD 20771 USA. RI Rabine, David/C-9626-2013; Blair, James/D-3881-2013; Beckley, Matthew/D-4547-2013 NR 10 TC 254 Z9 266 U1 10 U2 42 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0924-2716 J9 ISPRS J PHOTOGRAMM JI ISPRS-J. Photogramm. Remote Sens. PD JUL PY 1999 VL 54 IS 2-3 BP 115 EP 122 DI 10.1016/S0924-2716(99)00002-7 PG 8 WC Geography, Physical; Geosciences, Multidisciplinary; Remote Sensing; Imaging Science & Photographic Technology SC Physical Geography; Geology; Remote Sensing; Imaging Science & Photographic Technology GA 220PG UT WOS:000081673900007 ER PT J AU Karpova, EA Kubareva, EA Shabarova, ZA AF Karpova, EA Kubareva, EA Shabarova, ZA TI A model of EcoRII restriction endonuclease action: The active complex is most likely formed by one protein subunit and one DNA recognition site SO IUBMB LIFE LA English DT Article DE EcoRII restriction endonuclease; enzyme-substrate complexes; mechanism of enzyme action; modified DNA substrates; nondenaturing polyacrylamide gel assay ID REFRACTORY DNA; OLIGONUCLEOTIDE DUPLEXES; STIMULATE CLEAVAGE; BINDING; MECHANISM; ENZYMES; BASES AB To elucidate the mechanism of interaction of restriction endonuclease EcoRII with DNA, we studied by native gel electrophoresis the binding of this endonuclease to a set of synthetic DNA-duplexes containing the modified or canonical recognition sequence 5'-d(CCA/TGG)-3', All binding substrate or substrate analogues tested could be divided into two major groups: (i) duplexes that, at the interaction with endonuclease EcoRII, form two types of stable complexes on native gel in the absence of Mg2+ cofactor; (ii) duplexes that form only one type of complex, observed both in the presence and absence of Mg2+, Unlike the latter, duplexes under the first group can be hydrolyzed by endonuclease, Data obtained suggest that the active complex is most likely formed by one protein subunit and one DNA recognition sequence. A model of EcoRII endonuclease action is presented. C1 Russian Acad Sci, Inst Biochem & Physiol Microorganisms, Moscow 142292, Russia. Moscow MV Lomonosov State Univ, AN Belozersky Inst Phys & Chem Biol, Moscow 119899, Russia. RP Karpova, EA (reprint author), NASA, George C Marshall Space Flight Ctr, Biophys ES76, Huntsville, AL 35812 USA. RI Karpova, Elena/C-8776-2012; Kubareva, Elena/I-3184-2012 NR 18 TC 4 Z9 4 U1 0 U2 1 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 1521-6543 J9 IUBMB LIFE JI IUBMB Life PD JUL PY 1999 VL 48 IS 1 BP 91 EP 98 DI 10.1080/713803460 PG 8 WC Biochemistry & Molecular Biology; Cell Biology SC Biochemistry & Molecular Biology; Cell Biology GA 263DF UT WOS:000084107000016 PM 10791921 ER PT J AU Hulcher, AB Marchello, JM Hinkley, JA AF Hulcher, AB Marchello, JM Hinkley, JA TI Wedge peel testing for automated fiber placement SO JOURNAL OF ADVANCED MATERIALS LA English DT Article ID CONSOLIDATION AB The success of the automated manufacture of composites is generally measured by the interlaminar bond quality. The objective of this study is to establish a correlation between the simple wedge peel test and the DCB test for interlaminar fracture toughness. The demonstration of such a relationship will lend validity to the wedge peel test, and enable the development of optimal placement parameters more efficiently. Unidirectional composite specimens of both wedge peel and DCB configurations were fiber placed at various processing conditions using the NASA Langley Automated Fiber Placement Facility. The DCB interlaminar fracture toughness and the wedge peel strength were determined for each set of processing conditions. A clear trend in the data from the two test methods is shown. A rise in both the peel strength and the fracture toughness occurs with increasing processing temperature due to increasing resin flow. Peaks in both the wedge peel strength and DCB fracture toughness data are seen to occur at very similar processing conditions. Similarly, both peel strength and fracture toughness decrease with increasing processing temperatures beyond those which provide peak strength data. This decrease is due to possible thermal degradation of the resin. In view of these findings, it is suggested that the wedge peel test can be used for fast and efficient characterization/qualification of interlaminar bond quality. C1 Old Dominion Univ, Norfolk, VA 23508 USA. NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Hulcher, AB (reprint author), Old Dominion Univ, Norfolk, VA 23508 USA. NR 13 TC 2 Z9 2 U1 1 U2 3 PU SAMPE PUBLISHERS PI COVINA PA 1161 PARKVIEW DRIVE, COVINA, CA 91722 USA SN 1070-9789 J9 J ADV MATER-COVINA JI J. Adv. Mater. PD JUL PY 1999 VL 31 IS 3 BP 37 EP 43 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA 245VK UT WOS:000083128700007 ER PT J AU Shen, JY Human, M Sharpe, L Wang, JTS AF Shen, JY Human, M Sharpe, L Wang, JTS TI Alleviation of deformation of cylindrical shell using piezoelectric rings SO JOURNAL OF AEROSPACE ENGINEERING LA English DT Article AB A methodology for alleviating the deformation of cylindrical shells has been developed. The basic idea is to use piezoelectric ring stiffeners bonded to the surface of the shell to stiffen and counteract the deformation caused by external lends such as gravity, internal pressure, and temperature change. The function of the piezoelectric ring stiffeners may be realized by their stiffening effects and, more importantly, through their electrically induced strains causing pressure on the surface of the shell. These strains can, at desirable locations, produce adjustable deformations in the opposite direction of the deformations caused by external lending. Conventional differential equations governing displacements of linearly elastic cylindrical shells are used. For computer simulation, a simply supported thin cylindrical shell having 18 piezoelectric ring stiffeners bonded to its outer surface along the length of the shell is considered. Deformations along two generatrices of the shell are computed to demonstrate the effect of alleviation Since the deformation produced by an individual ring stiffener depends on the magnitude and polarity of the applied voltage, it is possible to counteract deformations caused by any other type of loading. The simulated results for illustration show that the deformation of cylindrical shells can be effectively alleviated. C1 N Carolina Agr & Technol State Univ, NASA, Ctr Aerosp Res, Coll Engn, Greensboro, NC 27411 USA. Georgia Inst Technol, Sch Civil & Environm Engn, Atlanta, GA 30332 USA. RP Shen, JY (reprint author), N Carolina Agr & Technol State Univ, NASA, Ctr Aerosp Res, Coll Engn, Greensboro, NC 27411 USA. NR 5 TC 0 Z9 0 U1 1 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 JUL PY 1999 VL 12 IS 3 BP 92 EP 97 DI 10.1061/(ASCE)0893-1321(1999)12:3(92) PG 6 WC Engineering, Aerospace; Engineering, Civil SC Engineering GA 214WL UT WOS:000081350500002 ER PT J AU Drake, A Kennelly, RA AF Drake, A Kennelly, RA TI In-flight skin friction measurements using oil film interferometry SO JOURNAL OF AIRCRAFT LA English DT Article C1 Washington State Univ, Dept Mech Engn, Richland, WA 99352 USA. NASA, Ames Res Ctr, High Speed Aerodynam Branch, Moffett Field, CA 94035 USA. RP Drake, A (reprint author), Raytheon Aircraft Co, Wichita, KS 67201 USA. NR 8 TC 7 Z9 7 U1 0 U2 5 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 JUL-AUG PY 1999 VL 36 IS 4 BP 723 EP 725 DI 10.2514/2.2498 PG 3 WC Engineering, Aerospace SC Engineering GA 226EN UT WOS:000082007500016 ER PT J AU Laing, AG Fritsch, JM Negri, AJ AF Laing, AG Fritsch, JM Negri, AJ TI Contribution of mesoscale convective complexes to rainfall in Sahelian Africa: estimates from geostationary infrared and passive microwave data SO JOURNAL OF APPLIED METEOROLOGY LA English DT Article ID UNITED-STATES; WEATHER SYSTEMS; PRECIPITATION; RETRIEVAL; LINES AB The contribution of mesoscale convective complexes to the July-September rainfall in Sahelian Africa is assessed using passive microwave data from the Special Sensor Microwave Image and infrared (IR) data from the European Geostationary Meteorological Satellite (Meteosat). A simple precipitation-estimation procedure, which takes advantage of the good time resolution of the IR and the strong relationship between the microwave radiance and rainfall, is developed and applied. The microwave technique uses the 37- and 86-GHz brightness temperatures to define the rain areas and the 86-GHz ice scattering signal to determine the rainfall intensity. The IR cloud shield areas are defined by the 219 K threshold. Regression analyses are used to relate the microwave-derived precipitation characteristics of the system and the IR data closest to the time of the SSM/I observation. These relationships are used to compute the precipitation characteristics of the total set of systems and to determine their monthly rainfall contribution. Results indicate that these systems have precipitation characteristics, such as rain area and volume, which are of the same order of magnitude as systems in the United States. In addition, they provide a significant fraction of the rainfall in Sahelian Africa. C1 Colorado State Univ, Cooperat Inst Res Atmosphere, Ft Collins, CO 80523 USA. Penn State Univ, Dept Meteorol, University Pk, PA 16802 USA. NASA, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Laing, AG (reprint author), Univ S Florida, Dept Geog, 4202 E Fowler Ave,SOC 107, Tampa, FL 33620 USA. NR 36 TC 34 Z9 35 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8763 J9 J APPL METEOROL JI J. Appl. Meteorol. PD JUL PY 1999 VL 38 IS 7 BP 957 EP 964 DI 10.1175/1520-0450(1999)038<0957:COMCCT>2.0.CO;2 PG 8 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 219LE UT WOS:000081608100010 ER PT J AU Koster, RD Suarez, MJ AF Koster, RD Suarez, MJ TI A simple framework for examining the interannual variability of land surface moisture fluxes SO JOURNAL OF CLIMATE LA English DT Article ID ANNUAL WATER-BALANCE; SOIL-WATER; CLIMATE; STORAGE; MODELS AB An equation that describes the partitioning of annual mean precipitation into annual mean evaporation and runoff, developed decades ago by Budyko, is used to derive a second equation that relates the interannual variability of evaporation to gross characteristics of the atmospheric forcing. Both Budyko's original equation and the new variability equation perform well when tested against results from a 20-yr GCM simulation. In these tests, using knowledge of the climatological mean precipitation and net radiation alone, the authors predict the ratio of annual evaporation to annual precipitation with a standard error of 0.10 in nondesert regions, and they predict the ratio of the standard deviation of annual evaporation to that of annual precipitation there with a standard error of 0.14. In analogy with Budyko's conclusion for the mean hydrological cycle, water and energy availability appear to be the critical factors controlling the interannual variability of surface moisture fluxes. The derived equations suggest, and the GCM results confirm, that the ratio of an evaporation anomaly to the corresponding precipitation anomaly tends to be significantly less than the ratio of mean evaporation to mean precipitation. C1 NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Processes, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Atmospheres Lab, Greenbelt, MD 20771 USA. RP Koster, RD (reprint author), NASA, Goddard Space Flight Ctr, Hydrol Sci Branch, Lab Hydrospher Processes, Code 974, Greenbelt, MD 20771 USA. RI Koster, Randal/F-5881-2012 OI Koster, Randal/0000-0001-6418-6383 NR 14 TC 148 Z9 159 U1 1 U2 21 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0894-8755 J9 J CLIMATE JI J. Clim. PD JUL PY 1999 VL 12 IS 7 BP 1911 EP 1917 DI 10.1175/1520-0442(1999)012<1911:ASFFET>2.0.CO;2 PG 7 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 214WN UT WOS:000081350700004 ER PT J AU Wu, MLC Schubert, S Huang, NE AF Wu, MLC Schubert, S Huang, NE TI The development of the South Asian summer monsoon and the intraseasonal oscillation SO JOURNAL OF CLIMATE LA English DT Article ID NORTHERN-HEMISPHERE SUMMER; LONGWAVE RADIATION DATA; INTERANNUAL VARIABILITY; TIBETAN PLATEAU; INDIAN-OCEAN; GLOBAL-SCALE; EL-NINO; CIRCULATION; ONSET; RAINFALL AB Fourteen years (1980-93) of National Aeronautics and Space Administration reanalysis data are used to document and study the variability in the development of the South Asian summer monsoon associated with the Intraseasonal Oscillation (ISO). The focus is on the coupling of the large-scale upper-level divergent circulation with the low-level southwesterlies and the associated developing regions of moisture convergence and precipitation, which serve to define the onset times of the various regions of the South Asian monsoon. The impact of the ISO on the development of the low-level southwesterlies is both local and remote, and depends on the strength and phasing of the ISO with the seasonal cycle. Of the 14 yr examined here, 6 showed a strong contribution to the northeastward progression and onset of the monsoon rains over India. In these cases, the ISO is initially (about 2 weeks prior to onset of rains over India) out of phase with, and therefore suppresses, the seasonal development of the regions of large-scale rising and sinking motion. As the ISO moves to the northeast, the rising branch enters the Indian Ocean and acts to enhance the latent heating in the region of the emerging Somali jet. At low levels the response rakes the form of an anticyclonic circulation anomaly over the Arabian Sea, and a cyclonic circulation anomaly to the south, which nets to inhibit the eastward progression of the Somali jet. As the ISO moves in phase with and enhances the seasonal mean upper-level divergent circulation, there is an abrupt and intense development of the southwesterly winds leading to an unusually rapid northeast shift and intensification of the monsoon rains over India and the Bay of Bengal. The general northeast progression of the anomalies may be viewed a!, an initial suppression and then acceleration of the "normal" seasonal cycle of the monsoon. C1 NASA, Goddard Space Flight Ctr, Data Assimilat Off, Goddard Lab Atmospheres, Greenbelt, MD 20771 USA. Goddard Lab Hydrospher Proc, Oceans & Ice Branch, Greenbelt, MD USA. RP Wu, MLC (reprint author), NASA, Goddard Space Flight Ctr, Data Assimilat Off, Goddard Lab Atmospheres, Code 910-3, Greenbelt, MD 20771 USA. NR 50 TC 36 Z9 39 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 JUL PY 1999 VL 12 IS 7 BP 2054 EP 2075 DI 10.1175/1520-0442(1999)012<2054:TDOTSA>2.0.CO;2 PG 22 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 214WN UT WOS:000081350700012 ER PT J AU Bowles, KJ AF Bowles, KJ TI Durability of graphite-fiber-reinforced PMR-15 composites aged at elevated temperatures SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE composites; polymer matrix; carbon fiber; durability; compression properties; thermal aging AB Earlier work that reported relationships between compression properties and elevated-temperature aging duration and weight losses also pointed out the apparent influence of surface layer formation and growth on the retention of compression properties during extended aging times. Since that time, further studies have focused on evaluating the growth of the surface layer. The composition and features of this layer were found to change as the aging temperature changed. Microcracks and small voids initiated and advanced inward at all temperatures. Visible oxidation at the surface occurred only at temperatures above 260 degrees C. Relationships between layer thickness, aging time, and temperature were evaluated and empirically formulated. Then, the compression properties were graphically related to the surface layer thickness with excellent correlation. C1 NASA, Lewis Res Ctr, Div Mat, Polymers Branch, Cleveland, OH 44135 USA. RP Bowles, KJ (reprint author), NASA, Lewis Res Ctr, Div Mat, Polymers Branch, Cleveland, OH 44135 USA. NR 6 TC 11 Z9 11 U1 0 U2 1 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 JUL PY 1999 VL 21 IS 3 BP 127 EP 132 PG 6 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA 218MX UT WOS:000081557300001 ER PT J AU Brady, RP Kulkarni, MR Chu, TCP Russell, S AF Brady, RP Kulkarni, MR Chu, TCP Russell, S TI Thermal image analysis for the in-situ NDE of composites SO JOURNAL OF COMPOSITES TECHNOLOGY & RESEARCH LA English DT Article DE nondestructive evaluation; thermography; thermoanalysis ID DIFFUSIVITY AB Thermal image analysis is an emerging nondestructive evaluation (NDE) technique that shows promise as a potential on-line monitoring and inspection method for composites. The method is rapid, user-friendly, and can determine two-dimensional material property distributions as well as quantitatively characterize delaminations. In this paper, the theoretical background of the method and fundamental apparatus are described. Results of the analysis applied to defect-free and delaminated carbon-carbon composite plates are discussed. Two-dimensional distributions of thermal diffusivity were obtained and verified with values obtained by the ASTM standard laser flash diffusivity method. Global specific heat and thermal conductivities were also found and compared to baseline values. In all cases the thermal image analysis results were found to provide reasonable engineering accuracy. Additionally, delaminated plates were tested in order to quantitatively characterize defect location and size. The thermal image analysis results for the delaminated plates were comparable, if not more precise, than observations using ultrasonic C-scan. C1 So Illinois Univ, Dept Mech Engn & Energy Proc, Carbondale, IL 62901 USA. NASA, George C Marshall Space Flight Ctr, Nondestruct Evaluat Branch, Div Engn Phys, Greenbelt, MD 20771 USA. RP Brady, RP (reprint author), So Illinois Univ, Dept Mech Engn & Energy Proc, Carbondale, IL 62901 USA. RI Chu, Tsuchin/F-3445-2013 OI Chu, Tsuchin/0000-0002-6939-9924 NR 14 TC 10 Z9 10 U1 0 U2 1 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 JUL PY 1999 VL 21 IS 3 BP 141 EP 146 PG 6 WC Materials Science, Composites; Polymer Science SC Materials Science; Polymer Science GA 218MX UT WOS:000081557300003 ER PT J AU Su, CH Feth, S Hirschfeld, D Smith, TM Wang, LJ Volz, MP Lehoczky, SL AF Su, CH Feth, S Hirschfeld, D Smith, TM Wang, LJ Volz, MP Lehoczky, SL TI Point defect distributions in ZnSe crystals: effects of gravity vector orientation during physical vapor transport growth SO JOURNAL OF CRYSTAL GROWTH LA English DT Article ID SELENIDE SINGLE-CRYSTALS; ZINC SELENIDE; HIGH-PURITY; PHOTOLUMINESCENCE SPECTRA; MICROGRAVITY CONDITIONS; OPTICAL-PROPERTIES; DOPED ZNSE; DONOR; CDTE; LUMINESCENCE AB ZnSe crystals were grown by the physical vapor transport technique under horizontal and vertical (stabilized and destabilized) configurations. Secondary ion mass spectroscopy and photoluminescence measurements were performed on the grown ZnSe samples to map the distributions of [Si], [Fe], [Cu], [Al] and [Li or Na] impurities as well as Zn vacancy, [V-Zn]. Annealings of ZnSe under controlled Zn pressures were studied to correlate the measured photoluminescence emission intensity to the equilibrium Zn partial pressure. In the horizontal grown crystals the segregations of [Si], [Fe], [Al] and [V-Zn] were observed along the gravity vector direction whereas in the vertically stabilized grown crystal the segregation of these point defects was radially symmetrical. No apparent pattern was observed on the measured distributions in the vertically destabilized grown crystal. The observed segregations in the three growth configurations were interpreted based on the possible buoyancy-driven convection in the vapor phase. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Sci Directorate, Micrograv Sci & Applicat Dept, Huntsville, AL 35812 USA. New Mexico Inst Min & Technol, Dept Mat & Met Engn, Socorro, NM 87801 USA. Univ Tennessee, Dept Phys Geol & Astron, Chattanooga, TN 37403 USA. RP Su, CH (reprint author), NASA, George C Marshall Space Flight Ctr, Sci Directorate, Micrograv Sci & Applicat Dept, Huntsville, AL 35812 USA. EM ching.hua.su@msfc.nasa.gov RI Feth, Shari/F-6302-2013 OI Feth, Shari/0000-0003-3545-5649 NR 37 TC 9 Z9 9 U1 1 U2 3 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 JUL PY 1999 VL 204 IS 1-2 BP 41 EP 51 DI 10.1016/S0022-0248(99)00187-6 PG 11 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 214RZ UT WOS:000081342500007 ER PT J AU Aggarwal, MD Choi, J Wang, WS Bhat, K Lal, RB Shields, AD Penn, BG Frazier, DO AF Aggarwal, MD Choi, J Wang, WS Bhat, K Lal, RB Shields, AD Penn, BG Frazier, DO TI Solution growth of a novel nonlinear optical material: L-histidine tetrafluoroborate SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE solution growth; L-histidine tetrafluoroborate; L-HFB; solubility curve; morphology ID 2ND-HARMONIC GENERATION; CRYSTALS AB Single crystals of L-histidine tetrafluoroborate (L-HFB), a semiorganic nonlinear optical (NLO) material have been successfully grown by the temperature lowering and evaporation methods in our laboratory. Solubility curves of L-HFB have been determined in different solvents, such as water, ethanol and acetone. The solubility of L-HFB is very low in acetone and ethanol, therefore, it is not feasible to grow L-HFB single crystals using these solvents. Good quality single crystals of a novel nonlinear optical material L-HFB have been grown from aqueous solution. Effects of seed orientation on morphologies of L-HFB crystals were studied. The advantages and disadvantages of both the evaporation and the temperature lowering techniques are compared. The single crystals in size 20 x 20 x 10 mm(3) were grown with the deionized water as solvent in two weeks with an approximate growth rate of 1.4 mm/d. The transmission range for these crystals has been found to be from 250 to 1500 nm. (C) 1999 Elsevier Science B.V. All rights reserved.Single crystals of L-histidine tetrafluoroborate (L-HFB), a semiorganic nonlinear optical (NLO) material have been successfully grown by the temperature lowering and evaporation methods in our laboratory. Solubility curves of L-HFB have been determined in different solvents, such as water, ethanol and acetone. The solubility of L-HFB is very low in acetone and ethanol, therefore, it is not feasible to grow L-HFB single crystals using these solvents. Good quality single crystals of a novel nonlinear optical material L-HFB have been grown from aqueous solution. Effects of seed orientation on morphologies of L-HFB crystals were studied. The advantages and disadvantages of both the evaporation and the temperature lowering techniques are compared. The single crystals in size 20 x 20 x 10 mm(3) were grown with the deionized water as solvent in two weeks with an approximate growth rate of 1.4 mm/d. The transmission range for these crystals has been found to be from 250 to 1500 nm. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Aggarwal, MD (reprint author), Alabama A&M Univ, Dept Phys, Normal, AL 35762 USA. NR 6 TC 98 Z9 98 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 JUL PY 1999 VL 204 IS 1-2 BP 179 EP 182 DI 10.1016/S0022-0248(99)00200-6 PG 4 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 214RZ UT WOS:000081342500025 ER PT J AU Sen, S Juretzko, F Stefanescu, DM Dhindaw, BK Curreri, PA AF Sen, S Juretzko, F Stefanescu, DM Dhindaw, BK Curreri, PA TI In situ observations of interaction between particulate agglomerates and an advancing planar solid liquid interface: microgravity experiments SO JOURNAL OF CRYSTAL GROWTH LA English DT Article DE microgravity experiments; s l interface; agglomerates ID PARTICLE ENGULFMENT; SOLIDIFYING INTERFACES; BEHAVIOR AB Results are reported of directional solidification experiments on particulate agglomerate pushing and engulfment by a planar solid/liquid (s/l) interface. These experiments were conducted on the Space Shuttle Columbia during the United States Microgravity Payload 4 (USMP-4) Mission. It was found that the pushing to engulfment transition velocity, V(cr), for agglomerates depends not only on their effective size but also their orientation with respect to the s/l interface. The analytical model for predicting V(er) of a single particle was subsequently enhanced to predict V(er), of the agglomerates by considering their shape factor and orientation. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. Univ Alabama, Solidificat Lab, Tuscaloosa, AL 35758 USA. Indian Inst Technol Khargpur, Khargpur, India. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Sen, S (reprint author), NASA, George C Marshall Space Flight Ctr, Univ Space Res Assoc, Huntsville, AL 35812 USA. RI Stefanescu, Doru/G-8101-2012; OI Dhindaw, Brij Kumar/0000-0001-6991-9793; Stefanescu, Doru M./0000-0001-5544-8396 NR 9 TC 19 Z9 19 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 JUL PY 1999 VL 204 IS 1-2 BP 238 EP 242 DI 10.1016/S0022-0248(99)00198-0 PG 5 WC Crystallography; Materials Science, Multidisciplinary; Physics, Applied SC Crystallography; Materials Science; Physics GA 214RZ UT WOS:000081342500033 ER PT J AU Owen, AK Daugherty, A Garrard, D Reynolds, HC Wright, RD AF Owen, AK Daugherty, A Garrard, D Reynolds, HC Wright, RD TI A parametric starting study of an axial-centrifugal gas turbine engine using a one-dimensional dynamic engine model and comparisons to experimental results: Part I - Model development and facility description SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1998 CL STOCKHOLM, SWEDEN AB A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics, and, thus, quantify potential starting improvements for the next generation of gas turbine engines. This paper discusses the model development and describes the test facilities used to obtain the calibration data. The test matrix for the ground level testing is also presented. A companion paper presents the model calibration results and the results of the trade-off study. C1 NASA, USA, Vehicle Prop Directorate, Lewis Res Ctr, Cleveland, OH 44135 USA. Sverdrup Technol Inc, AEDC Grp, Arnold AFB, TN 37389 USA. GE, Lynn, MA 01910 USA. RP Owen, AK (reprint author), NASA, USA, Vehicle Prop Directorate, Lewis Res Ctr, MS 77-6,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 9 TC 0 Z9 2 U1 1 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD JUL PY 1999 VL 121 IS 3 BP 377 EP 383 DI 10.1115/1.2818484 PG 7 WC Engineering, Mechanical SC Engineering GA 220AB UT WOS:000081640500001 ER PT J AU Owen, AK Daugherty, A Garrard, D Reynolds, HC Wright, RD AF Owen, AK Daugherty, A Garrard, D Reynolds, HC Wright, RD TI A parametric starting study of an axial-centrifugal gas turbine engine using a one-dimensional dynamic engine model and comparisons to experimental results: Part II - Simulation calibration and trade-off study SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1998 CL STOCKHOLM, SWEDEN AB A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six-kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper presents the model calibration results and the results of the trade-off study. A companion paper discusses the model development and describes the test facilities used to obtain the calibration data. C1 NASA, USA, Vehicle Prop Directorate, Lewis Res Ctr, Cleveland, OH 44135 USA. Sverdrup Technol Inc, AEDC Grp, Arnold AFB, TN 37389 USA. GE, Lynn, MA 01910 USA. RP Owen, AK (reprint author), NASA, USA, Vehicle Prop Directorate, Lewis Res Ctr, MS 77-6,21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 4 TC 0 Z9 0 U1 1 U2 4 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD JUL PY 1999 VL 121 IS 3 BP 384 EP 393 DI 10.1115/1.2818485 PG 10 WC Engineering, Mechanical SC Engineering GA 220AB UT WOS:000081640500002 ER PT J AU Holdeman, JD Liscinsky, DS Bain, DB AF Holdeman, JD Liscinsky, DS Bain, DB TI Mixing of multiple jets with a confined subsonic crossflow: Part II - Opposed rows of orifices in rectangular ducts SO JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER-TRANSACTIONS OF THE ASME LA English DT Article; Proceedings Paper CT 42nd International Gas Turbine and Aeroengine Congress and Exhibition CY JUN 02-05, 1997 CL ORLANDO, FLORIDA SP Int Gas Turbine Inst ID FLOW AB This paper summarizes experimental and computational results on the mixing of opposed rows of jets with a confined subsonic crossflow in rectangular ducts. The studies from which these results were excerpted investigated flow and geometric variations typical of the complex three-dimensional flowfield in the combustion chambers in gas turbine engines. The principal observation was that the momentum-flux ratio, J, and the orifice spacing, S/H, were the most significant flow and geometric variables. Jet penetration was critical, and penetration decreased as either momentum-flux ratio or orifice spacing decreased. It also appeared that jet penetration remained similar with variations in orifice size, shape, spacing, and momentum-flux ratio when the orifice spacing was inversely proportional to the square-root of the momentum-flux ratio. It was also seem that planar averages must be considered in context with the distributions. Note also that the mass-flow ratios and the orifices investigated were often very large (jet-to-mainstream mass-flow ratio > 1 and the ratio of orifices-area-to-mainstream-cross-sectional-area up to 0/5, respectively), and the axial planes of interest were often just downstream of the orifice trailing edge. Three-dimensional flow was a key part of efficient mixing and was observed for all configurations. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. United Technol Res Ctr, E Hartford, CT 06108 USA. CFD Res Corp, Huntsville, AL 35805 USA. RP Holdeman, JD (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 57 TC 26 Z9 26 U1 2 U2 7 PU ASME-AMER SOC MECHANICAL ENG PI NEW YORK PA 345 E 47TH ST, NEW YORK, NY 10017 USA SN 0742-4795 J9 J ENG GAS TURB POWER JI J. Eng. Gas. Turbines Power-Trans. ASME PD JUL PY 1999 VL 121 IS 3 BP 551 EP 562 DI 10.1115/1.2818508 PG 12 WC Engineering, Mechanical SC Engineering GA 220AB UT WOS:000081640500025 ER PT J AU Emardson, TR Jarlemark, POJ AF Emardson, TR Jarlemark, POJ TI Atmospheric modelling in GPS analysis and its effect on the estimated geodetic parameters SO JOURNAL OF GEODESY LA English DT Article DE space geodesy; Global Positioning System; Kalman filtering; atmospheric modelling ID GLOBAL POSITIONING SYSTEM; GRADIENTS; DELAY AB Permanently operating Global Positioning System (GPS) receivers are used today, for example, in precise positioning and determination of atmospheric water vapour content. The GPS signals are delayed by various gases when traversing the atmosphere. The delay due to water vapour, the wet delay, is difficult to model using ground surface data and is thus often estimated from the GPS data. In order to obtain the most accurate results from the GPS processing, a modelling of the horizontal distribution of the wet delay may be necessary. Through simulations, three such models are evaluated, one of which is developed in this paper. In the first model the water vapour is assumed to be horizontally stratified, thus the wet delay can be described by only one zenith parameter. The second model gives the wet delay with one zenith and two horizontal gradient parameters. The third model uses the correlation between the wet-delay values in different directions. It is found that for large gradients and strong turbulence the two latter models yield lower errors in the estimated vertical coordinate and wet-delay parameters. For large gradients this improvement is up to 7 mm in the zenith wet-delay parameter, from 9 mm down to 2 and 4 mm for the second and third models, respectively. C1 Chalmers Univ Technol, Onsala Space Observ, S-43900 Onsala, Sweden. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Emardson, TR (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 238-600, Pasadena, CA 91109 USA. NR 17 TC 18 Z9 18 U1 1 U2 1 PU SPRINGER VERLAG PI NEW YORK PA 175 FIFTH AVE, NEW YORK, NY 10010 USA SN 0949-7714 J9 J GEODESY JI J. Geodesy PD JUL PY 1999 VL 73 IS 6 BP 322 EP 331 DI 10.1007/s001900050249 PG 10 WC Geochemistry & Geophysics; Remote Sensing SC Geochemistry & Geophysics; Remote Sensing GA 223GY UT WOS:000081834000004 ER PT J AU Goldstein, ML Roberts, DA Deane, AE Ghosh, S Wong, HK AF Goldstein, ML Roberts, DA Deane, AE Ghosh, S Wong, HK TI Numerical simulation of Alfvenic turbulence in the solar wind SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article; Proceedings Paper CT Meeting on the Interrelationship Between Plasma Experiments in the Laboratory and in Space CY 1997 CL MAUI, HI ID FLUX-CORRECTED TRANSPORT; MEAN MAGNETIC-FIELD; MHD TURBULENCE; MAGNETOHYDRODYNAMIC TURBULENCE; RADIAL EVOLUTION; CROSS-HELICITY; FLUCTUATIONS; WAVES; ANISOTROPY; SPECTRA AB Low-frequency fluctuations in the solar wind magnetic field and plasma velocity are often highly correlated, so much so that the fluctuations can be thought of as nearly perfect Alfven waves. Evidence from the Hellos and Ulysses spacecraft suggest strongly that these fluctuations emanate from the solar corona with high correlation and flat power spectra (similar to f(-1)) These fluctuations constitute a source of free energy for a turbulent cascade of magnetic and kinetic energy to high wave numbers, a cascade that evolves most rapidly in the vicinity of velocity shears and the heliospheric current sheet. Numerical solutions of both the compressible and incompressible equations of magnetohydrodynamics (MHD) in Cartesian geometry showed that sharp gradients in velocity would decrease substantially the Alfvenicity of initially pure Alfvenic fluctuations; however, the effects of solar wind expansion on this turbulent evolution is, as yet, undetermined. We demonstrate that as was the case in Cartesian geometry, in an expanding volume, velocity shears and pressure-balanced flux tubes still reduce the Alfvenicity of parallel propagating wave packets. These three-dimensional spherically expanding simulations include velocity shears separating fast and slow flows, pressure-balanced flux tubes, and a central current sheet which is the site of magnetic reconnection. Two-dimensional spectra constructed in the r - theta plane resemble closely those resulting from similar initial conditions in Cartesian geometry. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. SM&A Corp, Largo, MD USA. RP NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 692, Greenbelt, MD 20771 USA. RI Roberts, Dana/D-4625-2012; Goldstein, Melvyn/B-1724-2008 NR 61 TC 36 Z9 36 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9380 EI 2169-9402 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1999 VL 104 IS A7 BP 14437 EP 14451 DI 10.1029/1998JA900128 PG 15 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211WW UT WOS:000081185700005 ER PT J AU Fok, MC Moore, TE Delcourt, DC AF Fok, MC Moore, TE Delcourt, DC TI Modeling of inner plasma sheet and ring current during substorms SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID TAIL CURRENT DISRUPTION; GEOSYNCHRONOUS ORBIT; INJECTION BOUNDARY; ION ENERGIZATION; POLAR WIND; FIELD; PHASE; SIMULATION; EXPANSION; STORM AB The evolution of the inner plasma sheet and the ring current during substorm dipolarizations is simulated. A substorm cycle is treated by stretching and dipolarizing the magnetosphere according to the Tsyganenko 89 model. In order to clarify the relative influences of steady convection and induction electric field on ring current development, the inductive electric field is superposed on two baseline convective states: a nonstorm state using a weak electric field, and a storm-time state using a stronger electric field, Ion distributions on the nightside at 12 Earth radii (RE) during these two substorms are obtained using our single-particle code to trace particle trajectories backward in time to source regions assumed to have steady characteristics. The subsequent acceleration and transport of these boundary ions into the inner magnetosphere is modeled by our kinetic model of the ring current. The simulation generates many frequently observed features of substorm injections, including the sudden appearance of hot plasma tailward of a sharply defined "injection boundary," the earthward motion of an "injection front" the azimuthal and tailward expansion of this enhanced region, and the creation of characteristic ion dispersion patterns near geosynchronous orbit. Comparison of the nonstorm and storm cases suggests that substorms occurring without a convection enhancement produce mainly an enhancement of the cross-tail current but little change in the ring current. With strong convection, the role of substorms is to enable the convection enhancement to create robust ring current in the inner magnetosphere. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Interplanetary Phys Branch, Greenbelt, MD 20771 USA. Ctr Etud Environm Terrestre & Planetaires, CNRS, F-94107 St Maur Des Fosses, France. RP Fok, MC (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Mail Code 692, Greenbelt, MD 20771 USA. RI Moore, Thomas/D-4675-2012; Fok, Mei-Ching/D-1626-2012 OI Moore, Thomas/0000-0002-3150-1137; NR 41 TC 87 Z9 87 U1 0 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1999 VL 104 IS A7 BP 14557 EP 14569 DI 10.1029/1999JA900014 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211WW UT WOS:000081185700012 ER PT J AU Smets, R Delcourt, D Sauvaud, JA Koperski, P AF Smets, R Delcourt, D Sauvaud, JA Koperski, P TI Electron pitch angle distributions following the dipolarization phase of a substorm: Interball-Tail observations and modeling SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SINGLE-PARTICLE ORBITS; MAGNETIC-FIELD; CURRENT SHEET; PLASMA SHEET; ION-ACCELERATION; MAGNETOTAIL; PRECIPITATION; MAGNETOSPHERE; CONVECTION; DYNAMICS AB We investigate Interball-Tail observations of electron pitch angle distributions after the dipolarization phase of a substorm, For 10 keV electrons we observe beamlike, coniclike, and perpendicularly peaked distributions at L similar to 11, L similar to 9, and L similar to 7, respectively. We examine the efficiency of betatron heating and Fermi acceleration associated with adiabatic transport of the electrons during the substorm dipolarization phase. This dipolarization phase was modeled using transition between different K-p, levels within a realistic magnetic field model, The calculations reproduce well the evolution of the high-energy electron flux in the parallel and perpendicular directions. They also reproduce well the pitch angle distribution observed by Interball-Tail at 10 keV, after the dipolarization phase, It is shown that Fermi acceleration is the leading process, compared to betatron heating. The production of the coniclike distributions is narrowly linked to the existence of a transition region between dipolelike and taillike magnetic fields, at about L similar to 9. C1 Ctr Etud Environm Terrestre & Planetaires, CNRS, F-94107 St Maur Des Fosses, France. Polish Acad Sci, Ctr Space Res, PL-00716 Warsaw, Poland. Ctr Etud Spatiale Rayonnements, CNRS, F-31029 Toulouse, France. RP Smets, R (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Code 692,Bldg 2,Room W124, Greenbelt, MD 20771 USA. NR 31 TC 26 Z9 27 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1999 VL 104 IS A7 BP 14571 EP 14581 DI 10.1029/1998JA900162 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211WW UT WOS:000081185700013 ER PT J AU Baker, DN Pulkkinen, TI Buchner, J Klimas, AJ AF Baker, DN Pulkkinen, TI Buchner, J Klimas, AJ TI Substorms: A global instability of the magnetosphere-ionosphere system SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID SOLAR-WIND; GEOTAIL OBSERVATIONS; PLASMA SHEET; GROWTH-PHASE; MODEL; MAGNETOTAIL; DYNAMICS; ONSET; RECONNECTION; SIMULATIONS AB Observational and numerical modeling evidence demonstrates that substorms are a global, coherent set of processes within the magnetosphere and ionosphere. This supports the view that substorms are a configurational instability of the coupled system since the entire magnetosphere changes during the expansion phase onset. It is shown that the magnetosphere progresses through a specific sequence of energy-loading and stress-developing states until the entire system collapses. This energy loading-unloading sequence is the essential basis of the Faraday Loop non-linear linear dynamics model which has been quite successful in describing the fundamental behavior of substorms without invoking detailed treatments of the internal substorm instability mechanism. Present-day MHD models also are seen to produce substorm like global instabilities despite the fact that they do not treat realistically the extremely thin current sheets that play such an essential role in the near-tail dynamics prior to substorm onset. This paper discusses three-dimensional kinetic simulations that have recently shown a variety of initial plasma kinetic instability modes which all evolve quickly to a similar, globally unstable reconnection configuration. Continuing research concerning the substorm onset location and mechanisms addresses important questions of when and exactly how the substorm expansion develops. However, the loaded magnetosphere almost always progresses rapidly to the same basic reconnection configuration irrespective of the detailed localized initiation mechanism. This is likened to the catastrophic collapse of a sand dune that has reached a highly unstable configuration: Any small local perturbation can cause a complete and large-scale collapse irrespective of the perturbation details. It is concluded that the global magnetospheric substorm problem has now largely been solved and that future work should be directed toward understanding the detailed plasma physical processes that occur during substorms. C1 Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. Max Planck Inst Aeron, Katlenberg Lindau, Germany. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Baker, DN (reprint author), Univ Colorado, Atmospher & Space Phys Lab, 1234 Innovat Dr, Boulder, CO 80309 USA. RI Buechner, Joerg/B-1213-2009; Pulkkinen, Tuija/D-8403-2012 OI Pulkkinen, Tuija/0000-0002-6317-381X NR 42 TC 62 Z9 62 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 JUL 1 PY 1999 VL 104 IS A7 BP 14601 EP 14611 DI 10.1029/1999JA900162 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211WW UT WOS:000081185700015 ER PT J AU Parhi, S Suess, ST Sulkanen, M AF Parhi, S Suess, ST Sulkanen, M TI Can Kelvin-Helmholtz instabilities of jet-like structures and plumes cause solar wind fluctuations at 1 AU? SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID RADIATIVELY COOLING JETS; RADIAL IMF COMPONENT; SPATIAL STABILITY; SLAB JET; LATITUDINAL DEPENDENCE; ULYSSES OBSERVATIONS; CORONAL HOLES; IMPRINT; MODELS AB The long high-latitude sampling of Ulysses provides the opportunity to study fine structures. At latitudes poleward of similar to -60 degrees the solar wind had fluctuations in velocity gradients which were attributed to "microstreams." The data also suggested fluctuations characterized by magnetic plus thermal pressure balance structures ('PBS'). At higher frequencies, MHD turbulence was observed and found to be less evolved than it is in the ecliptic but essentially independent of heliographic latitude. It is argued here that microstreams, PBS, and MHD turbulence could all be the remnants of mixing due to sheer instabilities associated with plumes and other filamentary structures ("jets") in coronal holes. To show this, we simulate a plume-like jet in the presence of an ambient magnetic field. We find that the presence of the ambient field reduces the growth rate of the instability, but the shear between a jet and its ambient still becomes unstable to the MHD Kelvin-Helmholtz instability when the shear speed is larger than the largest local magnetosonic speed, a condition probably satisfied for plumes. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. RP Parhi, S (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Mail Stop ES 82, Huntsville, AL 35812 USA. NR 20 TC 19 Z9 19 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-SPACE JI J. Geophys. Res-Space Phys. PD JUL 1 PY 1999 VL 104 IS A7 BP 14781 EP 14787 DI 10.1029/1999JA900041 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211WW UT WOS:000081185700030 ER PT J AU Wu, ST Guo, WP Michels, DJ Burlaga, LF AF Wu, ST Guo, WP Michels, DJ Burlaga, LF TI MHD description of the dynamical relationships between a flux rope, streamer, coronal mass ejection, and magnetic cloud: An analysis of the January 1997 Sun-Earth connection event SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS LA English DT Article ID BOUNDARY-CONDITIONS; HELMET STREAMER; SOLAR CORONA; 1 AU; PROPAGATION; EVOLUTION; HELICITY; PROMINENCES; SIMULATION; GEOMETRY AB We investigate the dynamical relationships between a coronal flux rope, a streamer, a coronal mass ejection (CME), and a magnetic cloud by using observations from the satellites of the International Solar-Terrestrial Physics observatories together with a streamer and flux rope interaction model [Wu and Guo, 1997a]. This is the first physical description of the evolution of a CME related to a flux rope in a streamer near the Sun to a magnetic cloud at 1 AU, The distinctive physical configuration of the model is based on a theoretical suggestion [Low, 1994] and observations [Hundhausen, 1993] that the magnetic structure of a streamer with an embedded cavity provides favorable condition for launch of a CME. We explore this physical scenario by identifying a flux rope as the cavity and using a fully self-consistent numerical simulation to illustrate the dynamical process of evolution of the flux rope/CME into a magnetic cloud. The simulation results are then compared to solar and interplanetary data from the well-observed Sun-Earth connection event of January 6-12, 1997. The data used for this analysis were collected chiefly by the Solar and Heliospheric Observatory (SOHO) Large-Angle and Spectrometric Coronagraph Experiment coronagraph and the solar wind particle and field sensors on the Wind spacecraft, but ground-based solar data were used as well. Because we have detailed observations of the same disturbance both at the Sun (SOHO) and at 1 AU (Wind), this event gives us an unusual opportunity to test the magnetohydrodynamic methodology and to learn about the physical processes of the Sun-Earth connection. In this study we show that when the flux rope rises (owing to increasing axial current, as assumed here, or to some other mechanism), it disrupts the streamer-flux rope system, thus launching a coronal mass ejection. The flux rope then escapes from the streamer and evolves to become a magnetic cloud, as expected, in interplanetary space. The CME is a visible feature moving ahead of the flux rope. The model also predicts a fast-mode shock in front of the magnetic cloud, as observed. C1 Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. Univ Alabama, Dept Mech & Aerosp Engn, Huntsville, AL 35899 USA. USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Wu, ST (reprint author), Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA. NR 50 TC 122 Z9 126 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 JUL 1 PY 1999 VL 104 IS A7 BP 14789 EP 14801 DI 10.1029/1999JA900099 PG 13 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211WW UT WOS:000081185700031 ER PT J AU Melody, JW Neat, GW AF Melody, JW Neat, GW TI Validation of an integrated modeling methodology's closed-loop performance prediction capability SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Article AB This paper validates the integrated modeling methodology used for design and performance evaluation of complex optomechanical systems, particularly spaceborne interferometers, The methodology integrates structural modeling, optical modeling, and control system modeling and design into a common environment, the Integrated Modeling of Optical Systems software package. The validation uses the Micro-Precision Interferometer testbed, a ground-based, full-scale hardware model of a spaceborne interferometer. Parallel development of the testbed and a corresponding integrated model enabled a unique opportunity to validate the modeling methodology with actual testbed measurements, This paper assesses the ability of the integrated modeling methodology to predict performance in a closed-loop configuration, namely with high-bandwidth optical control loops operational, The assessment is a comparison of integrated model closed-loop predictions with testbed closed-loop measurements, indicating that the integrated modeling methodology is accurate to within a factor of two. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Melody, JW (reprint author), Univ Illinois, Coordinated Sci Lab, 1101 W Springfield Ave, Urbana, IL 61801 USA. NR 16 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 JUL-AUG PY 1999 VL 22 IS 4 BP 566 EP 572 DI 10.2514/2.4434 PG 7 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 218DN UT WOS:000081538100009 ER PT J AU Boyle, DP Chamitoff, GE AF Boyle, DP Chamitoff, GE TI Autonomous maneuver tracking for self-piloted vehicles (vol 22, pg 58, 1999) SO JOURNAL OF GUIDANCE CONTROL AND DYNAMICS LA English DT Correction C1 Univ Sydney, Sydney, NSW 2006, Australia. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Boyle, DP (reprint author), Univ Sydney, Sydney, NSW 2006, Australia. NR 1 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 JUL-AUG PY 1999 VL 22 IS 4 BP 624 EP 624 PG 1 WC Engineering, Aerospace; Instruments & Instrumentation SC Engineering; Instruments & Instrumentation GA 218DN UT WOS:000081538100019 ER PT J AU Klemme, BJ Adriaans, MJ Day, PK Sergatskov, DA Aselage, TL Duncan, RV AF Klemme, BJ Adriaans, MJ Day, PK Sergatskov, DA Aselage, TL Duncan, RV TI PdMn and PdFe: New materials for temperature measurement near 2 K SO JOURNAL OF LOW TEMPERATURE PHYSICS LA English DT Article ID CRITICAL-DYNAMICS; GIANT-MOMENT; ALLOYS; FERROMAGNETISM; PALLADIUM; MICROGRAVITY; THERMOMETER; BEHAVIOR; RANGE; IRON AB Interest in the critical dynamics of superfluid He-4 in microgravity conditions has motivated the development of new high resolution thermometry technology for use in space experiments near 2 K. We have developed a magnetic thermometer using dilute magnetic alloys of Mn or Fe dissolved in a pure Pd matrix, similar to previous thermometers used at ultra-low temperatures. These metallic thermometers are easy to fabricate, chemically inert, and can have a low thermal resistance to the stage to be measured Also, the Curie temperature can be varied by changing the concentration of Fe of Mn, making them available for use in a wide temperature range. The derivative of the magnetic susceptibility was measured for PdMn and PdFe between 1.5 K and 4 K using a SQUID magnetometer. These measurements, as well as preliminary noise and drift measurements, show them to have sub-nK resolution with a drift of less than 10(-13) K/s. C1 Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Sandia Natl Labs, Albuquerque, NM 87185 USA. RP Klemme, BJ (reprint author), Univ New Mexico, Dept Phys & Astron, Albuquerque, NM 87131 USA. NR 22 TC 32 Z9 32 U1 1 U2 8 PU KLUWER ACADEMIC/PLENUM PUBL 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 JUL PY 1999 VL 116 IS 1-2 BP 133 EP 146 DI 10.1023/A:1021883011172 PG 14 WC Physics, Applied; Physics, Condensed Matter SC Physics GA 216JF UT WOS:000081438400007 ER PT J AU Sathish, S Madhukar, MS Cantrell, JH Yost, WT AF Sathish, S Madhukar, MS Cantrell, JH Yost, WT TI Assessment of single-fiber fragmentation using scanning acoustic microscopy SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID EMISSION TECHNIQUE AB Scanning acoustic microscopy (SAM) was used to obtain the critical fragmentation length of a 7-mu m-diameter carbon fiber embedded in an optically transparent epoxy matrix and was subjected to a standard fiber fragmentation test. The SAM-assessed critical fragmentation length of 356 +/- 59.5 mu m compared favorably with the value 341 +/- 52.3 mu m obtained independently from commonly used photoelastic techniques. Additionally, the SAM images allowed an assessment of regions of fiber-matrix debond, including the measurement of an average debond of 61.0 +/- 11.8 mu m along the fiber from the fragment ends, which could not be obtained with photoelastic methods. The application of SAM to the assessment of optically opaque composite materials is explained in this paper. C1 Univ Dayton, Res Inst, Dayton, OH 45469 USA. Univ Tennessee, Dept Mech & Aerosp Engn & Engn Sci, Knoxville, TN 37996 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Sathish, S (reprint author), Univ Dayton, Res Inst, 300 Coll Pk, Dayton, OH 45469 USA. RI Madhukar, Madhu/P-4365-2015 NR 15 TC 0 Z9 0 U1 0 U2 0 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUL PY 1999 VL 14 IS 7 BP 2881 EP 2887 DI 10.1557/JMR.1999.0384 PG 7 WC Materials Science, Multidisciplinary SC Materials Science GA 235PF UT WOS:000082550700025 ER PT J AU Southward, RE Bagdassarian, CK Sudol, CJ Wasyk, JL Sproul, SH Broadwater, ST Scott, JL Thompson, DW AF Southward, RE Bagdassarian, CK Sudol, CJ Wasyk, JL Sproul, SH Broadwater, ST Scott, JL Thompson, DW TI Synthesis of surface-metallized polymeric films by in situ reduction of (4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato) silver(I) in a polyimide matrix SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID SINGLE-CRYSTAL; PMDA-ODA; ADHESION; DIFFUSION AB Thermal curing of the (4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato)silver(I)- containing poly(amic acid) formed from 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) and 4,4'-oxydianiline (4,4'-ODA) in dimethylacetamide gives both polyimide films via cyclodehydration and reduction of silver(I) to the native metal. Silver(0) migrates to the surface resulting in surface metallized composite films, which can have excellent reflectivity, but do not exhibit surface electrical conductivity. The films retain mechanical and thermal properties similar to those of the parent polyimide. X-ray diffraction shows crystalline face-centered-cubic silver in the films after thermal curing. Microscopy data show that the surface particle sizes are in the range of approximately 50-100 nm. Significant silver remains in the bulk of the polyimide film with varying particles sizes generally less than approximately 15 nm. The interior of the metallized films is not electrically conducting. Films were characterized by x-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and mechanical measurements. C1 NASA, Langley Res Ctr, Div Mat, Hampton, VA 23665 USA. Coll William & Mary, Dept Chem, Williamsburg, VA 23187 USA. Coll William & Mary, Dept Biol, Williamsburg, VA 23187 USA. RP Southward, RE (reprint author), NASA, Langley Res Ctr, Div Mat, Hampton, VA 23665 USA. NR 40 TC 6 Z9 8 U1 0 U2 1 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUL PY 1999 VL 14 IS 7 BP 2897 EP 2904 DI 10.1557/JMR.1999.0387 PG 8 WC Materials Science, Multidisciplinary SC Materials Science GA 235PF UT WOS:000082550700028 ER PT J AU Qian, ML Wu, XM Yin, QR Zhang, BY Cantrell, JH AF Qian, ML Wu, XM Yin, QR Zhang, BY Cantrell, JH TI Scanning electron acoustic microscopy of electric domains in ferroelectric materials SO JOURNAL OF MATERIALS RESEARCH LA English DT Article ID FORCE MICROSCOPY; FILMS AB Electric domains in single-crystal and polycrystalline barium titanate (BaTiO3) have been observed by use of scanning electron acoustic microscopy (SEAM). A model is presented of the SEAM signal generation, spatial resolution, and contrast mechanism associated with the imaging of electric domains in ferroelectric materials. The SEAM signal is found to depend directly on the sum of the piezoelectric coupling coefficient and spontaneous polarization of the domain, on the charge density of the electron beam interaction volume, and inversely on both the permittivity and the elastic constants of the material. Application of the model to BaTiO3 yields a contrast of roughly 3.5% from 90 degrees domain structures and 6.8% from 180 degrees domain structures. C1 Tongji Univ, Inst Acoust, Shanghai 200092, Peoples R China. Chinese Acad Sci, Shanghai Inst Ceram, Shanghai 200050, Peoples R China. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Qian, ML (reprint author), Tongji Univ, Inst Acoust, Shanghai 200092, Peoples R China. NR 14 TC 8 Z9 11 U1 0 U2 2 PU MATERIALS RESEARCH SOCIETY PI WARRENDALE PA 506 KEYSTONE DR, WARRENDALE, PA 15086 USA SN 0884-2914 J9 J MATER RES JI J. Mater. Res. PD JUL PY 1999 VL 14 IS 7 BP 3096 EP 3101 DI 10.1557/JMR.1999.0415 PG 6 WC Materials Science, Multidisciplinary SC Materials Science GA 235PF UT WOS:000082550700056 ER PT J AU Halpern, D Freilich, MH Weller, RA AF Halpern, D Freilich, MH Weller, RA TI ECMWF and ERS-1 surface winds over the Arabian Sea during July 1995 SO JOURNAL OF PHYSICAL OCEANOGRAPHY LA English DT Article ID OCEAN; SCATTEROMETER AB The European Centre for Medium-Range Weather Forecasts (ECMWF) and Institut Francais Pour la Recherche et l'Exploitation de ia Mer European Remote-Sensing Satellite, named IFR2, surface wind velocity data products are compared during July 1995 over the Arabian Sea. Substantial differences were found. The central positions of the maximum isotach were separated by 450 km, and the ECMWF maximum isotach was 2 m s(-1) higher than that of IFR2. IFR2 wind components contained about 10 times more variance than ECMWF winds for horizontal distances from 50 to 250 km. Along the 8.5 degrees N southern boundary of the Arabian Sea, ECMWF southward Ekman transport was higher than that of IFR2 by an amount that could be observed with current measurements. The ECMWF and IFR2 difference in upward transport of water into the Ekman layer, computed from wind stress curl, was large enough to measure. C1 CALTECH, Jet Prop Lab, Div Earth & Space Sci, Pasadena, CA 91109 USA. Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA. Woods Hole Oceanog Inst, Dept Phys Oceanog, Woods Hole, MA 02543 USA. RP Halpern, D (reprint author), CALTECH, Jet Prop Lab, Div Earth & Space Sci, MS 300-323,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 11 Z9 12 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-3670 J9 J PHYS OCEANOGR JI J. Phys. Oceanogr. PD JUL PY 1999 VL 29 IS 7 BP 1619 EP 1623 DI 10.1175/1520-0485(1999)029<1619:EAESWO>2.0.CO;2 PG 5 WC Oceanography SC Oceanography GA 221RB UT WOS:000081739100015 ER PT J AU Gitzendanner, RL Marsh, C Marsh, RA Puglia, F Vukson, S Surampudi, R AF Gitzendanner, RL Marsh, C Marsh, RA Puglia, F Vukson, S Surampudi, R TI Lithium-ion cells for aerospace applications SO JOURNAL OF POWER SOURCES LA English DT Article C1 Yardney Tech Prod Inc, Pawcatuck, CT 06379 USA. USAF, Res Lab, Propuls Directorate, Battery Branch, Wright Patterson AFB, OH 45433 USA. NASA, Jet Propuls Lab, Washington, DC 20546 USA. RP Marsh, C (reprint author), Yardney Tech Prod Inc, 82 Mech St, Pawcatuck, CT 06379 USA. NR 0 TC 1 Z9 2 U1 0 U2 2 PU ELSEVIER SCIENCE SA PI LAUSANNE PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND SN 0378-7753 J9 J POWER SOURCES JI J. Power Sources PD JUL-AUG PY 1999 VL 80 IS 1-2 BP 272 EP 272 PG 1 WC Chemistry, Physical; Electrochemistry; Energy & Fuels; Materials Science, Multidisciplinary SC Chemistry; Electrochemistry; Energy & Fuels; Materials Science GA 207MJ UT WOS:000080940400046 ER PT J AU Mankbadi, RR AF Mankbadi, RR TI Review of computational aeroacoustics in propulsion systems SO JOURNAL OF PROPULSION AND POWER LA English DT Review ID RADIATION BOUNDARY-CONDITIONS; FINITE-DIFFERENCE SCHEMES; PERFECTLY MATCHED LAYER; SUPERSONIC JET NOISE; COHERENT STRUCTURES; HYPERBOLIC SYSTEMS; AERODYNAMIC SOUND; INSTABILITY WAVES; EXCITED JETS; SUBSONIC JET AB Recent efforts focusing on computational aeroacoustics in propulsion systems are review ed. Difficulties associated with a finite difference solution of the time-dependent governing equations and boundary treatments are briefly discussed. Success and limitations of the large-eddy-simulation (LES) approach in which the sound source and the radiation field are simultaneously obtained are presented. It is suggested that LES be limited to the near field, and that other techniques be used to extend the near field to the far field. Several extension techniques are given, Approximate techniques for fast prediction of the source regime are reviewed. This is followed by discussing the coupling between the engine internal flow and the jet plume noise. C1 NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. Univ Cincinnati, Cincinnati, OH 45221 USA. RP Mankbadi, RR (reprint author), Inst Computat Mech Propuls, Computat Aerocoust Grp, Cincinnati, OH 45221 USA. NR 131 TC 8 Z9 8 U1 0 U2 2 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 JUL-AUG PY 1999 VL 15 IS 4 BP 504 EP 512 DI 10.2514/2.5472 PG 9 WC Engineering, Aerospace SC Engineering GA 217QY UT WOS:000081511500003 ER PT J AU Dong, TZ Mankbadi, RR AF Dong, TZ Mankbadi, RR TI Simulation of unsteady flow in nozzle-ejector mixer SO JOURNAL OF PROPULSION AND POWER LA English DT Article; Proceedings Paper CT AIAA/CEAS 2nd Joint Aeroacoustics Conference CY MAY 06-08, 1996 CL STATE COLL, PENNSYLVANIA SP AIAA, CEAS ID FINITE-DIFFERENCE SCHEMES; BOUNDARY-CONDITIONS AB A numerical-simulation capability is developed with emphasis on capturing the flow and acoustic disturbances in internal flows. The configuration considered is that of a circular ejector with single element primary nozzle. The Favre-filtered Navier-Stokes equations with a subgrid model are used to simulate the large scale structure. The high-order dispersion relation-preserving scheme is used to minimize dispersion and dissipation errors. Special boundary treatments are adopted for inflow, outflow, and solid walls to eliminate nonphysical reflections. Results show the growth of the disturbances, the formation of weak shock-cell structures, and the propagation of acoustic waves. C1 NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. RP Dong, TZ (reprint author), NASA, John H Glenn Res Ctr Lewis Field, Cleveland, OH 44135 USA. NR 27 TC 0 Z9 0 U1 0 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0748-4658 J9 J PROPUL POWER JI J. Propul. Power PD JUL-AUG PY 1999 VL 15 IS 4 BP 539 EP 543 DI 10.2514/2.5476 PG 5 WC Engineering, Aerospace SC Engineering GA 217QY UT WOS:000081511500007 ER PT J AU Pine, AS Rinsland, CP AF Pine, AS Rinsland, CP TI The role of torsional hot bands in modeling atmospheric ethane SO JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER LA English DT Article DE hot bands; molecular-beam spectroscopy; torsional mode ID INFRARED SPECTROSCOPIC MEASUREMENTS; TOTAL COLUMN ABUNDANCE; 3000 CM-1 REGION; C2H6; SPECTRUM; SPLITTINGS; CH3CH3 AB The strong and sharp (P)Q(3) subbranch of the v(7) band of ethane near 2976.8 cm(-1) is relatively free of interfering lines of methane, water and ozone and has been utilized as the signature of ethane for atmospheric monitoring. This subbranch is unresolvable at the Doppler limit, even at low temperature. However, the rotational structure and torsional splittings have been obtained by subDoppler molecular-beam spectroscopy, along with the air-broadening coefficients and their temperature dependence, so that the fundamental band subbranch can be well characterized, apart from minor perturbations evident at high J. This still leaves a significant fraction of the observed structure and intensity in this region unassigned. The strong temperature dependence of this extraneous structure enables us to attribute it to torsional hot bands, which improves the quantitative estimates of atmospheric ethane. We also discuss various approximations to the ethane partition function, accounting for the highly anharmonic torsional mode, needed for the accurate scaling of the intensities over the wide range of atmospheric temperatures. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Alpine Technol, Germantown, MD 20874 USA. NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. RP Pine, AS (reprint author), Alpine Technol, 14401 Poplar Hill Rd, Germantown, MD 20874 USA. NR 23 TC 10 Z9 10 U1 0 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 JUL PY 1999 VL 62 IS 4 BP 445 EP 458 DI 10.1016/S0022-4073(98)00114-9 PG 14 WC Optics; Spectroscopy SC Optics; Spectroscopy GA 188GT UT WOS:000079839000005 ER PT J AU Sutharshana, S Chang, JB Lou, MC AF Sutharshana, S Chang, JB Lou, MC TI Fracture control of space flight structures and pressure vessels SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB The fracture control requirements and their implementation for the design and operation of NASA and U.S. Air Force space Right hardware are reviewed, with the focus on two categories of spaceflight hardware: 1) Space Shuttle payloads that include significant portions of the international space station under development and 2) Right pressure vessels. NASA and the U.S. Air Force have developed detailed fracture control requirements for Space Shuttle payloads and pressure vessels. Understanding these fracture control requirements and incorporating them early in the design phases of a program are important to cost effectively implement fracture control for space Right hardware. C1 Angeles Crest Engn Inc, Pasadena, CA 91103 USA. Aerospace Corp, Struct Dept, El Segundo, CA 90009 USA. CALTECH, Jet Prop Lab, Sci & Technol Dev Sect, Pasadena, CA 91109 USA. RP Sutharshana, S (reprint author), Angeles Crest Engn Inc, Pasadena, CA 91103 USA. NR 7 TC 1 Z9 3 U1 1 U2 1 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1999 VL 36 IS 4 BP 538 EP 542 PG 5 WC Engineering, Aerospace SC Engineering GA 226GQ UT WOS:000082012400008 ER PT J AU Galofaro, JT Doreswamy, CV Vayner, BV Snyder, DB Ferguson, DC AF Galofaro, JT Doreswamy, CV Vayner, BV Snyder, DB Ferguson, DC TI Electrical breakdown of anodized coatings in low-density plasmas SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article AB A comprehensive set of investigations has been performed involving arcing on a negatively biased anodized aluminum plate immersed in a low-density argon plasma at low pressures (P-0 approximate to 7.5 x 10(-5) torr), These arcing experiments were designed to simulate electrical breakdown of anodized coatings in a low Earth orbital environment. When electrical breakdown of an anodized layer occurs, an are strikes, and there is a sudden flux of electrons accelerated into the ambient plasma, This event is directly followed by ejection of a quasineutral plasma cloud consisting of ejected material bf own out of the anodized layer. Statistical analysis of plasma cloud expansion velocities has yielded a mean propagation velocity, v = 19.4 +/- 3.5 km/s, As the plasma cloud expands into the ambient plasma, energy in the form of electrical noise is generated. The radiated electromagnetic noise is detected by means of an insulated antenna immersed in the ambient plasma. The purpose of the investigations is 1) to observe and record the electromagnetic radiation spectrum resulting from the arcing process, 2) to make estimates of the travel time of the quasineutral plasma cloud based on fluctuations to several Langmuir probes mounted in the ambient plasma, and 3) to study induced arcing between two anodized aluminum structures in close proximity. C1 NASA, Lewis Res Ctr, Photovoltaic & Space Environm Branch, Cleveland, OH 44135 USA. Tuskegee Univ, Tuskegee, AL 36088 USA. Ohio Aerosp Inst, Cleveland, OH 44135 USA. RP Galofaro, JT (reprint author), NASA, Lewis Res Ctr, Photovoltaic & Space Environm Branch, Cleveland, OH 44135 USA. NR 11 TC 3 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 0022-4650 J9 J SPACECRAFT ROCKETS JI J. Spacecr. Rockets PD JUL-AUG PY 1999 VL 36 IS 4 BP 579 EP 585 PG 7 WC Engineering, Aerospace SC Engineering GA 226GQ UT WOS:000082012400014 ER PT J AU Hachkowski, MR Peterson, LD Lake, MS AF Hachkowski, MR Peterson, LD Lake, MS TI Friction model of a revolute joint for a precision deployable spacecraft structure SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article; Proceedings Paper CT AIAA/ASME/ASCE/AHS/ASC 37th Structures, Structural Dynamics, and Materials Conference CY APR 15-17, 1996 CL SALT LAKE CITY, UTAH SP Amer Inst Aeronaut & Astronaut, ASME, ASCE, AHS, ASC AB An analytical model is presented for predicting breakaway friction torque in a precision deployable spacecraft structure joint incorporating preloaded angular contact bearings, The model is based on the Todd/Johnson tribological friction model of friction within ball bearings (Todd, M. J., and Johnson, K. L.,"A Model for Coulomb Torque Hysteresis in Ball Bearings," International Journal of Mechanical Science, Vol, 29, 1987, pp, 339-354) and includes the effects of Coulombic microslippage between the bearing components and material hysteretic damping. A new nondimensional parameter is developed to quantify the effects of bearing preload, geometry, and material properties. It is analytically shown that bearing friction can be minimized for a specific bearing contact angle considering both rolling and sliding friction components. Additionally, steady-state bearing friction is calculated to vary nonlinearly with assembly preload. Analytical prediction of bearing friction is correlated with measured data. C1 Raytheon Opt Syst, Space Program, Danbury, CT 06810 USA. Raytheon Opt Syst, Strateg Program, Danbury, CT 06810 USA. Univ Colorado, Dept Aerosp Engn Sci, Ctr Aerosp Struct, Boulder, CO 80309 USA. NASA, Langley Res Ctr, Struct Mech Branch, Hampton, VA 23681 USA. RP Hachkowski, MR (reprint author), Raytheon Opt Syst, Space Program, Danbury, CT 06810 USA. NR 25 TC 2 Z9 4 U1 3 U2 7 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 JUL-AUG PY 1999 VL 36 IS 4 BP 591 EP 598 PG 8 WC Engineering, Aerospace SC Engineering GA 226GQ UT WOS:000082012400016 ER PT J AU Boltz, FW AF Boltz, FW TI Mini/micro shuttles with hypergolic noncryogenic liquid rocket bipropellant SO JOURNAL OF SPACECRAFT AND ROCKETS LA English DT Article C1 NASA, Ames Res Ctr, Aeronaut Div, Moffett Field, CA 94035 USA. RP Boltz, FW (reprint author), NASA, Ames Res Ctr, Aeronaut Div, Moffett Field, CA 94035 USA. NR 6 TC 1 Z9 1 U1 1 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 JUL-AUG PY 1999 VL 36 IS 4 BP 605 EP 608 PG 4 WC Engineering, Aerospace SC Engineering GA 226GQ UT WOS:000082012400019 ER PT J AU Robinson, RC Smialek, JL AF Robinson, RC Smialek, JL TI SiC recession caused by SiO2 scale volatility under combustion conditions: I, experimental results and empirical model SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID WATER-VAPOR; OXIDATION AB A high-pressure burner rig was developed to evaluate the response of chemical-vapor-deposited SiC material during exposure to simulated gas turbine combustor conditions. Linear weight loss and surface recession rates of SiC were observed in both fuel-lean and fuel-rich gas mixtures. This response was shown to result from SiO2 scale volatility. Arrhenius-type temperature dependence was demonstrated. In addition, the effects of pressure and gas velocity were defined in terms of a gaseous-diffusion-controlled process for volatile reaction products (such as SiO, Si(ON)(4), and SiO(OH)(x)). Accordingly, multiple linear regression was used to develop empirical recession relationships of the form exp(-Delta Q/RT)P(x)v(y) for both lean and rich combustion conditions. Part II of this paper discusses the thermodynamics and gaseous-diffusion model of this recession. The empirical models discussed here enable prediction of SIC recession for any combination of T, P, and v in turbine environments. For typical combustion conditions, recession of 0.2-2 mu m/h was predicted at 1200 degrees-1400 degrees C. Thus, longterm, high-temperature, high-velocity exposure may degrade silicon-based or SiO2-forming material by recession in combustion gas environments. C1 NYMA Inc, Brookpark, OH 44142 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 23 TC 138 Z9 141 U1 1 U2 15 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 JUL PY 1999 VL 82 IS 7 BP 1817 EP 1825 PG 9 WC Materials Science, Ceramics SC Materials Science GA 215ZY UT WOS:000081416900023 ER PT J AU Opila, EJ Smialek, JL Robinson, RC Fox, DS Jacobson, NS AF Opila, EJ Smialek, JL Robinson, RC Fox, DS Jacobson, NS TI SiC recession caused by SiO2 scale volatility under combustion conditions: II, thermodynamics and gaseous-diffusion model SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY LA English DT Article ID DEPOSITED SILICON-CARBIDE; WATER-VAPOR; THERMOCHEMISTRY; OXIDATION; SIO(OH)(2); MOLECULES AB In combustion environments, volatilization of SiO2 to Si-O-H(g) species is a critical issue, Available thermochemical data for Si-O-H(g) species were used in the present study to calculate boundary-layer-controlled fluxes from SiO2. Calculated fluxes were compared to volatilization rates of SiO2 scales grown on SLC, which,were measured in a high-pressure burner rig, as reported in Part I of this paper. Calculated volatilization rates also were compared to those measured in synthetic combustion gas furnace tests. Probable vapor species were identified in both fuel-lean and fuel-rich combustion environments, based on the observed pressure, temperature, and velocity dependencies, as well as on the magnitude of the volatility rate. Water vapor was: responsible for the degradation of SiO2 in the fuel-lean environment. SiO2 volatility in fuel-lean combustion environments was attributed primarily to the formation of Si(OH)(4)(g), with a small contribution of SiO(OH)(2)(g), Reducing gases such as H-2 and/or CO, in combination with water vapor, contributed to the degradation of SiO2 in the fuel-rich environment. The model to describe SiO2 volatility in a fuel-rich combustion environment gave a less satisfactory fit to the observed results. Nevertheless, it was concluded-given the known thermochemical data-that SiO2 volatility in a fuel-rich combustion environment is best described by the formation of SiO(g) at 1 atm total pressure and the formation of Si(OH)(4)(g), SiO(OH)(2)(g), and SiO(OH)(g) at higher pressures. Other Si-O-H(g) species, such as Si-2(OH)(6), may contribute to the volatility of SiO2 under fuel-rich conditions; however, complete thermochemical data are unavailable at this time. C1 Cleveland State Univ, Dept Chem Engn, Cleveland, OH 44115 USA. NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Dynacs Engn, Brookpark, OH 44142 USA. RP Opila, EJ (reprint author), Cleveland State Univ, Dept Chem Engn, Cleveland, OH 44115 USA. RI Jacobson, Nathan/A-9411-2009 NR 24 TC 151 Z9 156 U1 4 U2 29 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 JUL PY 1999 VL 82 IS 7 BP 1826 EP 1834 PG 9 WC Materials Science, Ceramics SC Materials Science GA 215ZY UT WOS:000081416900024 ER PT J AU Huston, RJ AF Huston, RJ TI The future of vertical lift - 18th Annual Alexander A. Nikolsky lecture SO JOURNAL OF THE AMERICAN HELICOPTER SOCIETY LA English DT Article; Proceedings Paper CT American-Helicopter-Society 54th Annual Forum CY MAY 22-24, 1998 CL WASHINGTON, D.C. SP Amer Helicopter Soc AB The 1998 Alexander A. Nikolsky Lecture is a challenge to the vertical flight industry to develop night systems for personal use. The argument is offered that the relevant technology and infrastructure for semiautomatic and automatic flight of vertical lift aircraft is either available today or is currently under development. The remaining issue appears to be that of gaining sufficient individual aircraft and system reliability to meet a public standard of safety at an affordable cost. Vehicle cost will be affordable when the market requires mass production. The market will exist when the industry demonstrates quiet, reliable vertical-flight vehicles as a less costly and time consuming alternative to the current congested short-haul air-transport system. C1 NASA, Langley Res Ctr, Hampton, VA 23665 USA. RP Huston, RJ (reprint author), NASA, Langley Res Ctr, Hampton, VA 23665 USA. NR 44 TC 0 Z9 0 U1 0 U2 2 PU AMER HELICOPTER SOC INC PI ALEXANDRIA PA 217 N WASHINGTON ST, ALEXANDRIA, VA 22314 USA SN 0002-8711 J9 J AM HELICOPTER SOC JI J. Am. Helicopter Soc. PD JUL PY 1999 VL 44 IS 3 BP 159 EP 171 PG 13 WC Engineering, Aerospace SC Engineering GA 233VB UT WOS:000082447000001 ER PT J AU Ely, TA Crossley, WA Williams, EA AF Ely, TA Crossley, WA Williams, EA TI Satellite constellation design for zonal coverage using genetic algorithms SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT AAS/AIAA Space Flight Mechanics Meeting CY FEB 09-11, 1998 CL MONTEREY, CALIFORNIA SP AAS, AIAA AB The problem of constellation design presents many difficulties in the form of multiple, competing objectives and a complex design space. Past approaches to solving this problem have been to limit the number of objectives and/or simplify the geometry (such as restricting the design procedure to using only circular orbits) so that a tractable solution is obtainable. The genetic algorithm (GA) has been used in many design problems, but has seen limited application to the problem of constellation design. The GA has the ability to handle objectives of mixed (continuous and discrete) type and complex design spaces that do not have convenient analytical representations. With these capabilities, it becomes possible to consider the use of eccentric, inclined orbits for designing constellations efficiently. A method to evaluate coverage associated with ellipitical orbits via a streets-of-coverage approach was derived for this effort. This paper describes a method for applying a GA in a gaming approach for multiobjective design of satellite constellations for zonal coverage. The algorithm is applied to a northern hemisphere coverage problem, a CONUS-like coverage problem, and an ELLIPSO(TM)-like coverage problem. Results are presented that suggest elliptic orbits may be beneficial to reduce the number of satellites needed for certain coverage problems. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Purdue Univ, Sch Aeronaut & Astronaut, W Lafayette, IN 47907 USA. RP Ely, TA (reprint author), CALTECH, Jet Prop Lab, Mail Stop 301-125L,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 17 TC 17 Z9 19 U1 1 U2 2 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-DEC PY 1999 VL 47 IS 3-4 BP 207 EP 228 PG 22 WC Engineering, Aerospace SC Engineering GA 360KZ UT WOS:000089668000004 ER PT J AU Seywald, H Lim, KB Kumar, RR Anthony, TC AF Seywald, H Lim, KB Kumar, RR Anthony, TC TI Stability analysis for constrained principal axis slew maneuvers SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article; Proceedings Paper CT 35th Aerospace Science Meeting CY JAN 06-10, 1997 CL RENO, NEVADA SP Aerosp Sci ID SPACECRAFT REORIENTATION AB This paper addresses the problem of reorientating a rigid spacecraft from arbitrary initial conditions to prescribed final conditions with zero angular velocity. The control law analyzed is based on quaternion feedback and leaves the user to choose two gains as functions of position, angular rate, and time. For arbitrary initial states, conditions on the controller gains are identified that guarantee global asymptotic stability. For the special case of rest-to-rest reorientations, the control law reduces to earlier results involving a principal axis rotation. The paper also addresses slew rate constraints, both, in terms of the two-norm and infinity-norm. C1 Analyt Mech Associates Inc, Hampton, VA 23666 USA. NASA, Langley Res Ctr, Guidance & Control Branch, Flight Dynam & Control Div, Hampton, VA 23666 USA. Orbital Sci Corp, Loudon, VA USA. RP Seywald, H (reprint author), Analyt Mech Associates Inc, Hampton, VA 23666 USA. NR 19 TC 3 Z9 4 U1 0 U2 1 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-DEC PY 1999 VL 47 IS 3-4 BP 239 EP 258 PG 20 WC Engineering, Aerospace SC Engineering GA 360KZ UT WOS:000089668000006 ER PT J AU Beard, RW Hadaegh, FY AF Beard, RW Hadaegh, FY TI Fuel optimization for unconstrained rotation of spacecraft formations SO JOURNAL OF THE ASTRONAUTICAL SCIENCES LA English DT Article ID CONSTELLATION AB This paper considers the problem of rotating a formation of spacecraft from one orientation to another, using an optimal amount of fuel. The formation is constrained to have the same shape at the beginning and end of a maneuver. However, the shape is unconstrained throughout the maneuver. This implies that to optimize fuel, each spacecraft travels in a straight line, from its beginning to end position. A cost function, motivated by the entropy function from information theory, is used to trade off fuel minimization verses equalizing the fuel across the constellation to avoid fuel starvation. C1 Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84602 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Beard, RW (reprint author), Brigham Young Univ, Dept Elect & Comp Engn, Provo, UT 84602 USA. NR 26 TC 4 Z9 5 U1 0 U2 0 PU AMER ASTRONAUTICAL SOC PI SPRINGFIELD PA 6352 ROLLING MILL PLACE SUITE 102, SPRINGFIELD, VA 22152 USA SN 0021-9142 J9 J ASTRONAUT SCI JI J. Astronaut. Sci. PD JUL-DEC PY 1999 VL 47 IS 3-4 BP 259 EP 273 PG 15 WC Engineering, Aerospace SC Engineering GA 360KZ UT WOS:000089668000007 ER PT J AU Chen, TC Weng, SP Schubert, S AF Chen, TC Weng, SP Schubert, S TI Maintenance of austral summertime upper-tropospheric circulation over tropical South America: The Bolivian high-Nordeste low system SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID RAINFALL ANOMALIES; STATIONARY EDDIES; NORTHERN SUMMER; LINEAR RESPONSE; ATMOSPHERE; OSCILLATION; HEAT; CONVECTION; FEATURES; PATTERNS AB Using the NASA/GEOS reanalysis data for 1980-95, the austral-summer stationary eddies in the tropical-subtropical Southern Hemisphere are examined in two wave regimes: long and short wave (wave 1 and waves 2-6, respectively). The basic structure of the Bolivian high-Nordeste low (BH-NL) system is formed by a shortwave train across South America but modulated by the long-wave regime. The short-wave train exhibits a monsoonlike vertical phase reversal in the midtroposphere and a quarter-wave phase shift relative to the divergent circulation. As inferred from (a) the spatial relationship between the streamfunction and velocity potential and (b) the structure of the divergent circulation, the short-wave train forming the BH-NL system is maintained by South American local heating and remote African heating, while the long-wave regime is maintained by western tropical Pacific heating. The maintenance of the stationary waves in the two wave regimes is further illustrated by a simple diagnostic scheme that includes the velocity-potential maintenance equation (which links velocity potential and diabatic heating) and the streamfunction budget (which is the inverse Laplacian transform of the vorticity equation). Some simple relationships between streamfunction and velocity potential for both wave regimes are established to substantiate the links between diabatic heating and streamfunction; of particular interest is a Sverdrup balance in the short-wave regime. This simplified vorticity equation explains the vertical structure of the short-wave train associated with the BH-NL system and its spatial relationship with the divergent circulation. Based upon the diagnostic analysis of its maintenance a simple forced barotropic model is adopted to simulate the BH-NL system with idealized forcings, which imitates the real 200-mb divergence centers over South America, Africa, and the tropical Pacific. Numerical simulations demonstrate that the formation of the BH-NL system is affected not only by the African remote forcing, but also by the tropical Pacific forcing. C1 Iowa State Univ Sci & Technol, Dept Geol & Atmospher Sci, Atmospher Sci Program, Ames, IA 50011 USA. NASA, Data Assimilat Off, Atmospheres Lab, Goddard Space Flight Ctr, Greenbelt, MD USA. RP Chen, TC (reprint author), Iowa State Univ Sci & Technol, Dept Geol & Atmospher Sci, Atmospher Sci Program, 3010 Agron Hall, Ames, IA 50011 USA. NR 28 TC 25 Z9 25 U1 0 U2 2 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 JUL 1 PY 1999 VL 56 IS 13 BP 2081 EP 2100 DI 10.1175/1520-0469(1999)056<2081:MOASUT>2.0.CO;2 PG 20 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 213DG UT WOS:000081256400003 ER PT J AU Sherwood, SC AF Sherwood, SC TI Feedbacks in a simple prognostic tropical climate model SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID SEA-SURFACE TEMPERATURE; GENERAL-CIRCULATION MODEL; TROPOSPHERIC WATER-VAPOR; LARGE-SCALE DYNAMICS; DEEP CONVECTION; EL-NINO; GREENHOUSE; BUDGET; CLOUDS; CONVERGENCE AB A simple four-cell model of the tropical atmosphere in equilibrium with its boundaries is introduced. which can support a variable diabatic circulation and prognostic temperature and humidity profiles. The model is used to predict atmospheric perturbations away from the observed base state. Prognostic variables include radiation, surface fluxes, and dynamic transports, with temperature and water vapor levels determined by conservation constraints. The model includes a specially developed water vapor scheme that performs favorably compared with observations. The model is used to simulate the local and nonlocal sensitivity of the tropical maritime atmosphere to changes in surface temperature and other boundary conditions at very large horizontal scales. The main findings are as follows. (i) The sensitivity of boundary layer convergence to sea surface temperature (SST) variations depends on the behavior of convective heating over cooler regions and may be overestimated by heuristic models that ignore or oversimplify thermodynamic and radiative constraints. (ii) The maintenance of humidity equilibrium over weakly convective areas is modulated by local radiative feedback, (iii) Evaporation feedbacks on SST may be overestimated by heuristic arguments that do not carefully treat atmospheric water transport. An explanation for the constant-relative humidity behavior of general circulation models under climate changes is also offered based an the results. C1 Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA. RP Sherwood, SC (reprint author), NASA, Univ Space Res Assoc, Goddard Space Flight Ctr, Mailcode 916, Greenbelt, MD 20771 USA. RI Sherwood, Steven/B-5673-2008 OI Sherwood, Steven/0000-0001-7420-8216 NR 57 TC 4 Z9 4 U1 0 U2 1 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUL 1 PY 1999 VL 56 IS 13 BP 2178 EP 2200 DI 10.1175/1520-0469(1999)056<2178:FIASPT>2.0.CO;2 PG 23 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 213DG UT WOS:000081256400008 ER PT J AU Bose, D Govindan, TR Meyyappan, M AF Bose, D Govindan, TR Meyyappan, M TI A continuum model for the inductively coupled plasma reactor in semiconductor processing SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY LA English DT Article ID HIGH-DENSITY PLASMA; MULTICOMPONENT PLASMAS; AMBIPOLAR DIFFUSION; SIMULATION; DYNAMICS AB A comprehensive continuum model is presented for the analysis of high-density plasma reactors widely used in semiconductor processing. The model couples plasma transport, neutral species dynamics, gas flow, heat transfer, and plasma power coupling from an external source. The governing transport equations are served along with Maxwell's equations for a multicomponent, multitemperature system with inductively coupled power deposition. The model and code are applied to a nitrogen discharge in an inductively coupled plasma reactor, and the predictions agree well with the experimental data. The effect of self-consistent modeling of gas flow and gas heat transfer is systematically examined and it is found to affect plasma density and uniformity at low pressures. (C) 1999 The Electrochemical Society. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Thermosci Inst, Moffett Field, CA 94035 USA. RP Bose, D (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 17 TC 24 Z9 24 U1 3 U2 6 PU ELECTROCHEMICAL SOC INC PI PENNINGTON PA 65 SOUTH MAIN STREET, PENNINGTON, NJ 08534 USA SN 0013-4651 J9 J ELECTROCHEM SOC JI J. Electrochem. Soc. PD JUL PY 1999 VL 146 IS 7 BP 2705 EP 2711 DI 10.1149/1.1391996 PG 7 WC Electrochemistry; Materials Science, Coatings & Films SC Electrochemistry; Materials Science GA 220EZ UT WOS:000081652700054 ER PT J AU Chang, KY Scharton, TD AF Chang, KY Scharton, TD TI Force-limited vibration testing of the Cassini spacecraft SO JOURNAL OF THE IEST LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Chang, KY (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 2 TC 0 Z9 0 U1 0 U2 0 PU INST ENVIRONMENTAL SCI TECHNOLOGY PI MT PROSPECT PA 940 E NORTHWEST HIGHWAY, MT PROSPECT, IL 60056 USA SN 1052-2883 J9 J IEST JI J. IEST PD JUL-AUG PY 1999 VL 42 IS 4 BP 14 EP 15 PG 2 WC Engineering, Environmental; Environmental Sciences; Instruments & Instrumentation SC Engineering; Environmental Sciences & Ecology; Instruments & Instrumentation GA 228NA UT WOS:000082141500004 ER PT J AU Siegel, R AF Siegel, R TI Transient thermal analysis for heating a translucent wall with opaque radiation barriers SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article ID FLUX BOUNDARY-CONDITION; TEMPERATURE DISTRIBUTION; COMBINED CONDUCTION; COMPOSITE; LAYERS AB The transient analysis of thermal behavior in translucent media including radiative transfer becomes computationally complex for a multiple-layer composite. A convenient method is developed here for analyzing combined radiation and conduction in a composite wall of translucent and opaque layers. The translucent layers transfer radiation by combined transmission, absorption, emission, and scattering. Metal layers can be required for strength of the composite or to protect ceramic surfaces from a reactive environment. Opaque layers within a translucent ceramic can be used to decrease radiant transmission that may degrade the ceramic insulating ability. The two-flux method is used to determine the local heat source produced by radiation in the translucent layers. The differential equation for the radiative flux in the two flux method is solved with Green's functions that include the opaque or translucent boundary conditions of each translucent layer. Finite difference relations are derived for the transient energy equation, such that the calculated temperature distributions provide good accuracy for energy conservation during the transient. The solution technique is applied to illustrate radiation effects in a composite with one or two translucent layers, with and without opaque layers at the outer boundaries, or between the translucent layers. C1 NASA, John H Glenn Res Ctr Lewis Field, Res & Technol Directorate, Cleveland, OH 44135 USA. RP Siegel, R (reprint author), NASA, John H Glenn Res Ctr Lewis Field, Res & Technol Directorate, 21000 Brookpk Rd, Cleveland, OH 44135 USA. NR 10 TC 5 Z9 7 U1 0 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 JUL-SEP PY 1999 VL 13 IS 3 BP 277 EP 284 DI 10.2514/2.6442 PG 8 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 216VA UT WOS:000081464100001 ER PT J AU Kaya, T Hoang, TT AF Kaya, T Hoang, TT TI Mathematical modeling of loop heat pipes and experimental validation SO JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER LA English DT Article AB A mathematical model to calculate the steady-state performance of a loop heat pipe (LHP) is presented. The mathematical model is based on the steady state energy conservation equations and the pressure drop calculations along the fluid path in the LHP. The LHP operating temperature is calculated as a function of the applied power at a given LHP condition. The heat exchange between each component of the LHP and the surroundings is taken into account. Both convection and radiation environments are modeled. Experimental validation of the model is attempted by using two different LHP designs. The validity of the mathematical model is investigated for different sink temperatures and elevations. The comparison of the calculations and experimental results showed good agreement (within 5%). The proposed method proved to be a useful tool for reliable prediction of the steady state performance characteristics of the LHP. C1 NASA, Goddard Space Flight Ctr, Natl Res Council, Greenbelt, MD 20771 USA. TTH Res Inc, Clifton, VA 20124 USA. RP Kaya, T (reprint author), NASA, Goddard Space Flight Ctr, Natl Res Council, Code 661, Greenbelt, MD 20771 USA. RI Kaya, Tarik/C-1215-2008 NR 24 TC 55 Z9 56 U1 4 U2 17 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 JUL-SEP PY 1999 VL 13 IS 3 BP 314 EP 320 DI 10.2514/2.6461 PG 7 WC Thermodynamics; Engineering, Mechanical SC Thermodynamics; Engineering GA 216VA UT WOS:000081464100007 ER PT J AU Dawson, DL Putnam, AT Light, JT Ihnat, DM Kissinger, DP Rasmussen, TE Bradley, DV AF Dawson, DL Putnam, AT Light, JT Ihnat, DM Kissinger, DP Rasmussen, TE Bradley, DV TI Temporary arterial shunts to maintain limb perfusion after arterial injury: An animal study SO JOURNAL OF TRAUMA-INJURY INFECTION AND CRITICAL CARE LA English DT Article DE shunt; ischemia; arteries; multiple injury; thrombosis; surgery; wounds and injuries; disease models; vascular patency ID INTRALUMINAL SHUNTS; VASCULAR INJURIES; DAMAGE CONTROL; TRAUMA; MANAGEMENT AB Background: Temporary shunt placement can quickly restore perfusion after extremity arterial injury. This study examined the adequacy of limb blood flow with shunt use, non-heparin-bonded shunt patency over prolonged periods, and the safety of this technique. Methods: Common iliac arteries were divided and 4.0-mm Silastic Sundt shunts placed in 16 anesthetized pigs, Eight (group I) had shunts placed immediately; eight others (group II) mere shunted after an hour of limb ischemia and hemorrhagic shock. Physiologic parameters and femoral artery blood flow in both hindlimbs were continuously monitored. Limb lactic acid generation, oxygen utilization, and hematologic and metabolic effects were serially evaluated for 24 hours. Results: Shunts remained patent in 13 of 16 pigs, Shunts thrombosed in two group I animals because of technical errors, but functioned well after thrombectomy and repositioning. Patency could not be maintained in one animal that died from shock. Flow in group I shunted limbs was 57 (+/-11 SD) % of control. For group II animals in shock, shunted limb flow initially averaged 46 +/- 15% of control, but 4 hours after shunt placement, the mean limb blood flow was the same as in group I. Increased oxygen extraction compensated for the lower flow. Lactic acid production mas not increased in comparison to cont ol limbs. Conclusion: Shunts provided adequate flow in this model of extremity trauma. Correctly placed shunts stayed patent for 24 hours, without anticoagulation, if shunt placement followed resuscitation. C1 Wilford Hall USAF Med Ctr, Dept Gen Surg, Lackland AFB, TX 78236 USA. Wilford Hall USAF Med Ctr, Dept Surg Res, Lackland AFB, TX 78236 USA. RP Dawson, DL (reprint author), USAF, Lyndon B Johnson Space Ctr, Div Med Sci, NASA,MC,FS, Mail Code SD,2101 NASA Rd 1, Houston, TX 77058 USA. NR 20 TC 28 Z9 28 U1 0 U2 0 PU LIPPINCOTT WILLIAMS & WILKINS PI PHILADELPHIA PA 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA SN 1079-6061 J9 J TRAUMA JI J. Trauma-Injury Infect. Crit. Care PD JUL PY 1999 VL 47 IS 1 BP 64 EP 71 DI 10.1097/00005373-199907000-00016 PG 8 WC Critical Care Medicine; Surgery SC General & Internal Medicine; Surgery GA 216ZQ UT WOS:000081474700013 PM 10421189 ER PT J AU Wadia, AR Szucs, PN Gundy-Burlet, KL AF Wadia, AR Szucs, PN Gundy-Burlet, KL TI Design and testing of swept and leaned outlet guide vanes to reduce stator-strut-splitter aerodynamic flow interactions (98-GT-70) SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article AB Large circumferentially varying pressure levels produced by aerodynamic flow interactions between downstream stators and struts present a potential noise and stability margin liability in a compression component. These interactions are presently controlled by tailoring the camber and/or stagger angles of vanes neighboring the fan frame struts. This paper reports on the design and testing of a unique set of swept and learned fan outlet guide vanes (OGVs) that do not require this local tailoring even though the OGVs are closely coupled with the fan frame struts and splitter to reduce engine length The swept and leaned OGVs not only reduce core-duct diffusion, but they also reduce the potential flow, interaction between the stator and the strut relative to that produced by conventional radial OGVs. First, the design of the outlet guide vanes using a single blade row three-dimensional viscous flow analysis is outlined. Next, a two-dimensional potential flow analysis was used for the coupled OGV-frame system to obtain a circumferentially nonuniform stator stagger angle distribution to reduce the upstream static pressure disturbance further Recognizing the limitations of the two-dimensional potential flow analysis for this highly three-dimensional set of leaned OGVs, as a final evaluation of the OGV-strut system design, a full three-dimensional viscous analysis of a periodic circumferential sector of the OGVs, including the fan frame struts and splitter was performed The computer model was derived from a NASA-developed code used in simulating the flow field for external aerodynamic applications with complex geometries. The three-dimensional coupled OGV-frame analysis included the uniformly staggered OGV configuration and the variably staggered OGV configuration determined by the two-dimensional potential flow analysis. Contrary to the two-dimensional calculations, the three-dimensional analysis revealed significant flow problems with the variably staggered OGV configuration and showed less upstream flow nonuniformity with the uniformly staggered OGV configuration, The flow redistribution in both the radial and tangential directions, captured fully only in the three-dimensional analysis, was identified as the prime contributor to the lower flow nonuniformity with the uniformly staggered OGV configuration. The coupled three-dimensional analysis was also used to validate the design at off-design conditions. Engine rest performance and stability measurements with both uniformly and variably staggered OGV configurations with and without the presence of inlet distortion confirmed the conclusions from the three-dimensional analysis. C1 GE Aircraft Engines, Cincinnati, OH 45215 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Wadia, AR (reprint author), GE Aircraft Engines, Cincinnati, OH 45215 USA. NR 28 TC 3 Z9 3 U1 0 U2 0 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 JUL PY 1999 VL 121 IS 3 BP 416 EP 427 PG 12 WC Engineering, Mechanical SC Engineering GA 220DN UT WOS:000081649400005 ER PT J AU Dhadwal, HS Kurkov, AP AF Dhadwal, HS Kurkov, AP TI Dual-laser probe measurement of blade-tip clearance SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article AB This paper describes two dual-laser probe integrated fiber optic systems for measuring blade tip clearance in rotating turbomachinery. The probes are nearly flush with the casing inner lining, resulting in minimal flow disturbance. The two probes are closely spaced in a circumferential plane and are slanted at an angle relative to each other so that the blade tip traverse time of the space between the two laser beams varies with the tip radius, allowing determination of the tip clearance at the rotor operating conditions. The tip clearance can be obtained for all the blades in a rotor with a single system, provided there are no synchronous vibrations present at a particular operating condition. These probes were installed in two holders; one provided an included angle between the probes of 20 deg, and the other provided an included angle of 40 deg. The two configurations were calibrated in a vacuum spin rig facility that is capable of reproducing realistic blade tip speeds. C1 Integrated Fiber Opt Syst Inc, Stony Brook, NY 11790 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Dhadwal, HS (reprint author), Integrated Fiber Opt Syst Inc, 25 E Loop Rd, Stony Brook, NY 11790 USA. NR 3 TC 19 Z9 21 U1 0 U2 0 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 JUL PY 1999 VL 121 IS 3 BP 481 EP 485 PG 5 WC Engineering, Mechanical SC Engineering GA 220DN UT WOS:000081649400011 ER PT J AU Khalid, SA Khalsa, AS Waitz, IA Tan, CS Greitzer, EM Cumpsty, NA Adamczyk, JJ Marble, FE AF Khalid, SA Khalsa, AS Waitz, IA Tan, CS Greitzer, EM Cumpsty, NA Adamczyk, JJ Marble, FE TI Endwall blockage in axial compressors SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID CASING TREATMENT; FLOW PHENOMENA AB This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low-speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity, and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10 percent. More importantly, however, the method provides physical insight into, and thus guidance for control of the flow features and phenomena responsible for compressor endwall blockage generation. C1 Allison Adv Dev Co, Indianapolis, IN 46206 USA. Khalsa Int Ind & Trades, Espanola, NM 87532 USA. MIT, Gas Turbine Lab, Cambridge, MA 02139 USA. Univ Cambridge, Whittle Lab, Cambridge, England. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. CALTECH, Pasadena, CA 91125 USA. RP Khalid, SA (reprint author), Allison Adv Dev Co, Indianapolis, IN 46206 USA. NR 21 TC 84 Z9 95 U1 1 U2 12 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 JUL PY 1999 VL 121 IS 3 BP 499 EP 509 PG 11 WC Engineering, Mechanical SC Engineering GA 220DN UT WOS:000081649400015 ER PT J AU Spakovszky, ZS Weigl, HJ Paduano, JD van Schalkwyk, CM Suder, KL Bright, MM AF Spakovszky, ZS Weigl, HJ Paduano, JD van Schalkwyk, CM Suder, KL Bright, MM TI Rotating stall control in a high-speed stage with inlet distortion: Part I - Radial distortion SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID ROBUST-CONTROL AB This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An annular array of 12 jet-injectors located upstream of the rotor tip Was used for forced response testing and to extend the compressor stable operating range. Results for radial distortion are reported in this paper. First, the effects of radial distortion an the compressor performance and the dynamic behavior were investigated. Control laws were designed using empirical transfer function estimates determined from forced response results. The transfer functions indicated that the compressor dynamics are decoupled with radial inlet distortion, as they are for the case of undistorted inlet flow. Single-input-single-output (SISO) control strategies were therefore used for the radial distortion controller designs. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a reduction in stalling mass flow of 9.7 percent relative to the case with inlet distortion and no injection. Use of a robust H-alpha controller with unsteady nonaxisymmetric injection achieved a further reduction in stalling mass flow of 7.5 percent, resulting in a total reduction of 17.2 percent. C1 MIT, Dept Aeronaut & Astronaut, Gas Turbine Lab, Cambridge, MA 02139 USA. Sci Syst Co Inc, Woburn, MA 01801 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Spakovszky, ZS (reprint author), MIT, Dept Aeronaut & Astronaut, Gas Turbine Lab, Cambridge, MA 02139 USA. NR 19 TC 36 Z9 41 U1 3 U2 8 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 JUL PY 1999 VL 121 IS 3 BP 510 EP 516 PG 7 WC Engineering, Mechanical SC Engineering GA 220DN UT WOS:000081649400016 ER PT J AU Spakovszky, ZS van Schalkwyk, CM Weigl, HJ Paduano, JD Suder, KL Bright, MM AF Spakovszky, ZS van Schalkwyk, CM Weigl, HJ Paduano, JD Suder, KL Bright, MM TI Rotating stall control in a high-speed stage with inlet distortion: Part II - Circumferential distortion SO JOURNAL OF TURBOMACHINERY-TRANSACTIONS OF THE ASME LA English DT Article ID AXIAL COMPRESSOR AB This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. Art array of 12 jet injectors located upstream of the compressor was used for forced response testing and feedback stabilization. Results for a circumferential total pressure distortion of about one dynamic head and a 120 deg extent (DC(60) = 0.61) are reported in this paper. part I (Spakovszky et al., 1999) reports results for radial distortion. Control laws were designed using empirical transfer function estimates determined from forced response results. Distortion introduces coupling between the harmonics of circumferential pressure perturbations, requiring multivariable identification and control design techniques. The compressor response displayed a strong first spatial harmonic, dominated by the well-known incompressible Moore-Greitzer mode. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a 6.2 percent reduction of stalling mass flow. Constant gain feedback, using unsteady asymmetric injection yielded a further range extension of 9 percent. A more sophisticated robust H-infinity controller allowed a reduction in stalling mass flow of 10.2 percent relative to steady injection, yielding a total reduction in stalling mass flow of 16.4 percent. C1 MIT, Dept Aeronaut & Astronaut, Gas Turbine Lab, Cambridge, MA 02139 USA. Sci Syst Co Inc, Woburn, MA 01801 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. RP Spakovszky, ZS (reprint author), MIT, Dept Aeronaut & Astronaut, Gas Turbine Lab, Cambridge, MA 02139 USA. NR 21 TC 15 Z9 19 U1 2 U2 9 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 JUL PY 1999 VL 121 IS 3 BP 517 EP 524 PG 8 WC Engineering, Mechanical SC Engineering GA 220DN UT WOS:000081649400017 ER PT J AU Yamada, T AF Yamada, T TI Substrate effects on electronic properties of atomic chains SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article; Proceedings Paper CT 45th International Symposium of the American-Vacuum-Society CY NOV 02-06, 1998 CL BALTIMORE, MARYLAND SP Amer Vacuum Soc ID SCANNING TUNNELING MICROSCOPE; SURFACE; STM; SCALE; WIRES AB A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form;atomically precise device components, is studied theoretically. The substrate has to serve as a two-dimensional template for adatom mounting with a reasonable confinement barrier and also provide electronic isolation, preventing unwanted coupling between independent adatom chains. For excellent structural stability, we demand chemical bonding between the adatoms and substrate atoms to secure the positions (chemical bonding scheme), but then good electronic isolation is not always guaranteed and necessary conditions are clarified. The substrate influences fundamental chain properties through chemical bonds. A chain with group IV adatoms having two chemical bonds each, or a chain with group III adatoms having one chemical bond each, is semiconducting. Charge transfer from or to the substrate across the chemical bonds brings about unintentional doping for semiconducting chains. The electronic properties have to be considered for the combination of the adatom and substrate systems in this scheme, even though the adatom modes are well localized in the adatom chains. (C) 1999 American Vacuum Society. [S0734-2101(99)01304-4]. C1 NASA, Ames Res Ctr, MRJ, Moffett Field, CA 94035 USA. RP Yamada, T (reprint author), NASA, Ames Res Ctr, MRJ, T27A-1, Moffett Field, CA 94035 USA. RI Yamada, Toshishige/E-7834-2012 OI Yamada, Toshishige/0000-0001-7145-9212 NR 30 TC 2 Z9 2 U1 0 U2 0 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD JUL-AUG PY 1999 VL 17 IS 4 BP 1463 EP 1468 DI 10.1116/1.581837 PN 1 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 217DX UT WOS:000081485700070 ER PT J AU Vargo, SE Muntz, EP Shiflett, GR Tang, WC AF Vargo, SE Muntz, EP Shiflett, GR Tang, WC TI Knudsen compressor as a micro- and macroscale vacuum pump without moving parts or fluids SO JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS LA English DT Article; Proceedings Paper CT 45th National Symposium of the American-Vacuum-Society CY NOV 02-06, 1998 CL BALTMORE, MARYLAND SP Amer Vacuum soc AB Applications of Knudsen compressors as both microscale and macroscale vacuum pumps have been investigated. The study is based on a cascade analysis incorporating available transitional thermal transpiration and Poiseuille flow results for slender channels. It was found that the Knudsen compressor is an attractive possibility for microscale pumps down to a pressure of about 1 mTorr and for macroscale pumps to about 0.1 mTorr. A microscale pump for a micromass spectrometer providing a molecule flow rate of 5 x 10(14) molecules/s results in the following pump characteristics: energy use of 2.4 W, pump volume of 13.9 ml at an inlet pressure of 1 mTorr and an energy use of 28.5 inW, and pump volume of 0.16 ml at an inlet pressure of 10 mTorr. A macroscale pump providing a pumping speed of 10(3) l/s results in a pump with an energy use of 1786 W, and pump volume of 1695 l at an inlet pressure of 0.1 mTorr. Several; Knudsen compressor characteristics such as pressure rise, pumping speed, volume, energy use and mass flow are presented (C) 1999 American Vacuum Society. [S0734-2101(99)05904-7]. C1 Univ So Calif, Dept Aeronaut & Mech Engn, Los Angeles, CA 90089 USA. CALTECH, Jet Prop Lab, Microdevices Lab, Pasadena, CA 91109 USA. RP Vargo, SE (reprint author), Univ So Calif, Dept Aeronaut & Mech Engn, Los Angeles, CA 90089 USA. NR 17 TC 58 Z9 59 U1 0 U2 7 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0734-2101 J9 J VAC SCI TECHNOL A JI J. Vac. Sci. Technol. A-Vac. Surf. Films PD JUL-AUG PY 1999 VL 17 IS 4 BP 2308 EP 2313 DI 10.1116/1.581765 PN 2 PG 6 WC Materials Science, Coatings & Films; Physics, Applied SC Materials Science; Physics GA 217DY UT WOS:000081485800095 ER PT J AU Lin, YJ Lee, T Choi, B Saravanos, D AF Lin, YJ Lee, T Choi, B Saravanos, D TI An application of smart-structure technology to rotor blade tip vibration control SO JOURNAL OF VIBRATION AND CONTROL LA English DT Article DE smart structure; rotor blade; vibration control AB This paper presents the experimental development of a simple and effective vibration control scheme by employing smart-structure technology. Due to high accuracy and high slew rate requirements for lightweight structures, vibration control becomes a challenging task. In this paper, it is proposed to actively control rotor blade tip vibration with collocated piezoceramic sensors and actuators. To include the flexible characteristics of rotor blades in the analysis, a flexible cantilever beam is used to simulate the dynamic behavior of the blade subjected to external disturbances, generated by a magnetic shaker. The shaker was installed near the tip of the simulated rotor blade to maximize the external excitations. PZT-4 piezoceramic sensor and actuator were used and considered as elements of the smart structure. Based on the derived dynamic model, a proportional gain feedback controller was implemented to compensate for the vibratory deflections of the underlying structure. The results of the work show that the proposed control methodology along with the smart structure can suppress 85% of the measured structural vibration, which is considered satisfactory. C1 Univ Akron, Dept Mech Engn, Akron, OH 44325 USA. NASA, Lewis Res Ctr, Struct Dynam Branch, Cleveland, OH 44135 USA. RP Lin, YJ (reprint author), Univ Akron, Dept Mech Engn, Akron, OH 44325 USA. NR 21 TC 3 Z9 3 U1 2 U2 3 PU SAGE PUBLICATIONS INC PI THOUSAND OAKS PA 2455 TELLER RD, THOUSAND OAKS, CA 91320 USA SN 1077-5463 J9 J VIB CONTROL JI J. Vib. Control PD JUL PY 1999 VL 5 IS 4 BP 639 EP 658 DI 10.1177/107754639900500408 PG 20 WC Acoustics; Engineering, Mechanical; Mechanics SC Acoustics; Engineering; Mechanics GA 207JL UT WOS:000080933700008 ER PT J AU Chan, PK Stolfo, SJ Wolpert, D AF Chan, PK Stolfo, SJ Wolpert, D TI Guest editors' introduction SO MACHINE LEARNING LA English DT Editorial Material C1 Florida Inst Technol, Melbourne, FL 32901 USA. Columbia Univ, Dept Comp Sci, New York, NY 10027 USA. NASA, Ames Res Ctr, Automated Learning Grp, Moffett Field, CA 94035 USA. RP Chan, PK (reprint author), Florida Inst Technol, Melbourne, FL 32901 USA. NR 13 TC 5 Z9 5 U1 0 U2 0 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0885-6125 J9 MACH LEARN JI Mach. Learn. PD JUL PY 1999 VL 36 IS 1-2 BP 5 EP 7 DI 10.1023/A:1007551004514 PG 3 WC Computer Science, Artificial Intelligence SC Computer Science GA 215PC UT WOS:000081389200001 ER PT J AU Smyth, P Wolpert, D AF Smyth, P Wolpert, D TI Linearly combining density estimators via stacking SO MACHINE LEARNING LA English DT Article; Proceedings Paper CT AAAI 1996 Workshop on Integrating Multiple Learned Models for Improving and Scaling Machine Learning Algorithms CY AUG 05, 1996 CL PORTLAND, OREGON DE density estimation; stacking; kernel densities; cross-validation; mixture models ID MODEL UNCERTAINTY; CLASSIFICATION; REGRESSION; SELECTION; MIXTURES AB This paper presents experimental results with both real and artificial data combining unsupervised learning algorithms using stacking. Specifically, stacking is used to form a linear combination of finite mixture model and kernel density estimators for non-parametric multivariate density estimation. The method outperforms other strategies such as choosing the single best model based on cross-validation, combining with uniform weights, and even using the single best model chosen by "Cheating" and examining the test set. We also investigate (1) how the utility of stacking changes when one of the models being combined is the model that generated the data, (2) how the stacking coefficients of the models compare to the relative frequencies with which cross-validation chooses among the models, (3) visualization of combined "effective" kernels, and (4) the sensitivity of stacking to overfitting as model complexity increases. C1 Univ Calif Irvine, Irvine, CA 92697 USA. CALTECH, Jet Prop Lab 525 3660, Pasadena, CA 91109 USA. NASA, Ames Res Ctr, Caelum Res, Moffett Field, CA 94035 USA. RP Smyth, P (reprint author), Univ Calif Irvine, Irvine, CA 92697 USA. NR 39 TC 15 Z9 15 U1 0 U2 1 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0885-6125 J9 MACH LEARN JI Mach. Learn. PD JUL PY 1999 VL 36 IS 1-2 BP 59 EP 83 DI 10.1023/A:1007511322260 PG 25 WC Computer Science, Artificial Intelligence SC Computer Science GA 215PC UT WOS:000081389200004 ER PT J AU Eberhardt, LL Garrott, RA Becker, BL AF Eberhardt, LL Garrott, RA Becker, BL TI Using trend indices for endangered species SO MARINE MAMMAL SCIENCE LA English DT Article DE auxiliary variables; beach counts; bootstrapping; Hawaiian monk seals; grizzly bears; manatees; transformations; trend indices ID YELLOWSTONE GRIZZLY BEAR; POPULATION-DYNAMICS; CONSERVATION; REGRESSION; POLICIES; SURVIVAL AB Initial appraisals of the status of endangered large-mammal populations may have to depend on indices of population trend. Such indices may possibly be improved by using auxiliary variables. Various models were studied for populations of the Florida manatee (Trichechus manatus latirostris), Yellowstone grizzly bear (Ursus arctos horribilis), and Hawaiian monk seal (Monachus schauinslandi). Several criteria for checking validity of the fitted models were considered, and the simple R-2 criterion appears to provide useful comparisons. Multiple regression models overestimated the rate of change of the East Coast manatee population as determined from three other sources (a covariance model, a non-linear model, and the rate estimated from reproductive and survival data). A multiple regression model for grizzly bears using three auxiliary variables exhibited a fairly high R-2 (0.84)and appeared to provide a better fit than did a non-linear model. A beach count index for Hawaiian monk seals seemed to be unreliable for year-to-year comparisons in contrast to total population counts and estimates from a capture-recapture method. The use of auxiliary variables for checking and improving trend index data appears feasible and well worthwhile. C1 Montana State Univ, Dept Biol, Bozeman, MT 59717 USA. NOAA, Natl Marine Fisheries Serv, Honolulu, HI 96822 USA. RP Eberhardt, LL (reprint author), 2528 W Klamath Ave, Kennewick, WA 99336 USA. NR 32 TC 14 Z9 14 U1 1 U2 4 PU SOC MARINE MAMMALOGY PI LAWRENCE PA 1041 NEW HAMPSHIRE ST, LAWRENCE, KS 66044 USA SN 0824-0469 J9 MAR MAMMAL SCI JI Mar. Mamm. Sci. PD JUL PY 1999 VL 15 IS 3 BP 766 EP 785 DI 10.1111/j.1748-7692.1999.tb00842.x PG 20 WC Marine & Freshwater Biology; Zoology SC Marine & Freshwater Biology; Zoology GA 206EE UT WOS:000080863700010 ER PT J AU Craig, MP Ragen, TJ AF Craig, MP Ragen, TJ TI Body size, survival, and decline of juvenile Hawaiian monk seals, Monachus schauinslandi SO MARINE MAMMAL SCIENCE LA English DT Article DE Hawaiian monk seal; Monachus schauinslandii; demography; conservation biology ID MULTIVARIATE-ANALYSIS; VARIANCE; MORTALITY; BIOLOGY; ECOLOGY; POWER; MASS AB In the mid 1980s half of the entire Hawaiian monk seal species was located at French Frigate Shoals, and this colony may have reached environmental carrying capacity. Since 1989 this colony has declined by 55%, primarily from poor juvenile survival. Only 8%-25% of weaned pups have survived to age 2 during this period, compared to at least 80% between 1984 and 1987. We characterize (1) this drop in survival, (2) a strong, but variable, correlation between survival and size at weaning, (3) interisland differences in size from weaning to age 2 in 1991 through 1993, and (4) decadal-scale changes in mean measures of size at weaning. We. compare observations at French Frigate Shoals with the colony at Laysan Island where abundance is well below historical levels and was therefore expected to be below carrying capacity. At Laysan Island juvenile survival has also been poor (30%-70%), and the size Of weaned pups has decreased during the past decade; Our hypothesis is that poor survival may be due to reduced prey availability at both sites, but particularly at French Frigate Shoals. Evidence to support this hypothesis includes a large increase in total abundance at French Frigate Shoals; reduced size of weaned pups; decreased survival, emaciation, and slower growth rates of juvenile seals; and declining primary productivity. Regardless of cause, the immediate consequences at French Frigate Shoals and Laysan Island, and for the species overall, will likely be poor recruitment and productivity. Because the decline is still in progress, the ultimate consequences for the species' viability are of great concern in light of its already low abundance. C1 Univ Hawaii, Joint Inst Marine & Atmospher Res, Honolulu, HI 96822 USA. NOAA, Natl Marine Fisheries Serv, Honolulu, HI 96822 USA. RP Craig, MP (reprint author), NOAA, Natl Marine Fisheries Serv, 2570 Dole St, Honolulu, HI 96822 USA. NR 57 TC 59 Z9 64 U1 4 U2 37 PU SOC MARINE MAMMALOGY PI LAWRENCE PA 1041 NEW HAMPSHIRE ST, LAWRENCE, KS 66044 USA SN 0824-0469 J9 MAR MAMMAL SCI JI Mar. Mamm. Sci. PD JUL PY 1999 VL 15 IS 3 BP 786 EP 809 DI 10.1111/j.1748-7692.1999.tb00843.x PG 24 WC Marine & Freshwater Biology; Zoology SC Marine & Freshwater Biology; Zoology GA 206EE UT WOS:000080863700011 ER PT J AU Irvine, GV Mann, DH Short, JW AF Irvine, GV Mann, DH Short, JW TI Multi-year persistence of oil mousse on high energy beaches distant from the Exxon Valdez spill origin SO MARINE POLLUTION BULLETIN LA English DT Article ID FATE; TRANSPORT; SEDIMENTS AB For at least 5 yr after the Exxon Valdez spill, relatively unweathered oil mousse has persisted on the exposed rocky shores of Shelikof Strait 500 km from Prince William Sound, Alaska. Previously it was thought that oil would be rapidly removed from such geomorphic settings by wave action. Oil mousse persists at sites in Katmai National Park and Preserve (NP&P) where it was stranded high in the intertidal zone under a lag of large boulders, These boulders armor the beach, preventing waves from disturbing the substrate and its included oil. Weathering of this stranded mousse has been slight mousse sampled in 1989, 1992 and 1994 show negligible changes in polynuclear aromatic hydrocarbons compared to 11-day old Exxon Valdez crude. The preservation of this oil is due to its transport as mousse bob whose interiors largely escape weathering, followed by its sheltering in the interstices of boulder-armored beaches. The transport of mousse may allow for the long distance dispersal of less weathered, and hence still toxic oil. Our findings suggest that the low ecological sensitivity ratings previously applied to exposed, rocky shorelines need to be modified. The biological threat posed by oil stranded on the Katmai NP&P coast probably is slight because of its small amount and sequestered state. However, it still possesses the ability to be chemically toxic and could be released through disturbance of the armoring boulders by unusually high wave events. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Natl Pk Serv, Alaska Reg Off, Anchorage, AK 99503 USA. Univ Alaska, Inst Arctic Biol, Fairbanks, AK 99775 USA. Natl Marine Fisheries Serv, NOAA, Auke Bay Fisheries Lab, Juneau, AK 99801 USA. RP US Geol Survey, Alaska Biol Sci Ctr, 1011 E Tudor Rd, Anchorage, AK 99503 USA. NR 41 TC 25 Z9 27 U1 1 U2 9 PU PERGAMON-ELSEVIER SCIENCE LTD PI OXFORD PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND SN 0025-326X EI 1879-3363 J9 MAR POLLUT BULL JI Mar. Pollut. Bull. PD JUL PY 1999 VL 38 IS 7 BP 572 EP 584 DI 10.1016/S0025-326X(98)00115-5 PG 13 WC Environmental Sciences; Marine & Freshwater Biology SC Environmental Sciences & Ecology; Marine & Freshwater Biology GA 229MK UT WOS:000082198200016 ER PT J AU Weitz, CM Rutherford, MJ Head, JW McKay, DS AF Weitz, CM Rutherford, MJ Head, JW McKay, DS TI Ascent and eruption of a lunar high-titanium magma as inferred from the petrology of the 74001/2 drill core SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID MARE GLASSES; ORIGIN; APOLLO-17; GREEN; MOON AB An analysis of the orange grasses and crystallized beads from the 68 cm deep 74001/2 core has been conducted to understand the processes occurring during ascent and eruption of the Apollo 17 orange glass magma. Equilibrium between melt and metal blebs (Fe85Ni14Co1) within the core, along with Cr contents in olivine phenocrysts, suggest there was an oxidation of C and a reduction of the melt at an O fugacity of IW-1.3 and 1320 degrees C to form CO gas at 200 bars or similar to 4 lan depth. This was followed by development of more oxidized conditions during ascent. Also during ascent, there was formation of euhedral, homogeneous Fo(81) olivine crystals and spinel crystals with higher Al and Mg contents than the smaller spinels in the crystallized beads. Both the metal blebs and Al-rich spinels were trapped inside the Fo(81) olivine phenocrysts as they grew prior to eruption. The composition of the orange glasses are homogeneous throughout the core, except for a few distinct glasses at the top that appear to have been mixed in by micrometeorite reworking. A few glassy melt inclusions of orange glass composition trapped in the Fo(81) phenocrysts contain 600 +/- 100 ppm S and similar to 50 ppm CI compared to the 200 ppm S and 50 ppm Cl in the orange glass melt when quenched. These inclusions therefore document the addition of 400 ppm S to the GO-rich volcanic gas during the eruption. The size and distribution of different volcanic beads in the Apollo 17 deposit indicate a mode of eruption in which the orange glasses and partially crystallized beads formed further away from the volcanic vent where cooling rates were faster. Progressively larger and more numerous crystals in the black beads reflect slower cooling rates at higher optical densities in the volcanic plume. The development of a brown texture in the orange glasses at the bottom of the core, where the black beads dominate, is interpreted to result from devitrification by subsolidus heating either as the orange glasses fell back through the hot plume or after deposition on the surface. The change from domination by orange glasses to black beads in the core probably reflects a decrease in gas content over time, which consequently would increase the plume optical density and favor slower cooling rates. C1 Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Weitz, CM (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 45 TC 33 Z9 33 U1 0 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 JUL PY 1999 VL 34 IS 4 BP 527 EP 540 PG 14 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 222FD UT WOS:000081772000002 ER PT J AU Wentworth, SJ Keller, LP McKay, DS Morris, RV AF Wentworth, SJ Keller, LP McKay, DS Morris, RV TI Space weathering on the Moon: Patina on Apollo 17 samples 75075 and 76015 SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID INTERPLANETARY DUST PARTICLES AB We studied patinas on lunar rocks 75075 and 76015 from the Apollo collection using a multidisciplinary approach, including scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS), transmission electron microscopy (TEM), wavelength-dispersive x-ray (WDS) mapping, Mossbauer spectroscopy, spectral reflectance, and microspectrophotometry. Based on SEM petrography, we have defined three textural types of patina: glazed, fragmental, and classic (cratered). The presence of classic patina is diagnostic of lunar samples that have been exposed directly to the space weathering environment. It is characterized by the presence of microcraters and glass pancakes and is the patina type studied by earlier workers. Classic patina is found on 76015 but not on 75075. Glazed patina is found on both 76015 and 75075, whereas fragmental patina is found only on 75075. The glazed and fragmental patinas on 75075 were probably formed as a result of relatively large nearby impacts; and although these two types of patina are not strictly the result of direct exposure to the space weathering environment, they are important because they affect the optical properties of the rocks. Field emission gun SEM (FE-SEM) of classic patina on 76015 shows evidence of possible solar wind sputtering erosion. Transmission electron microscope studies of 76015 reveal the presence of impact-generated deposits and solar flare particle tracks which, like microcraters and pancakes, are diagnostic of direct exposure to space weathering processes. The outermost surface of the 76015 patina consists of an amorphous rim very much like the rims found on individual lunar soil grains; this amorphous patina rim probably formed by similar processes of impact-generated vapor condensation and possible sputter deposition. Wavelength-dispersive x-ray element maps of polished thin sections of 75075 and 76015 indicate that patina compositions are poor indicators of the compositions and mineralogies of the rocks underlying them. On average, the reflectance spectra of patinas on both samples are slightly darker than those of their unweathered equivalents. Microreflectance measurements show that a thick patina can dramatically alter the optical properties of the rock on which it forms. The backscatter Mossbauer (BaMS) spectrum of a patina-covered surface of 76015 is very similar to that of an unweathered surface, indicating that the Mossbauer signal is generated from beneath the patina. Because BaMS "sees" through surface space-weathering effects to the underlying rock, this technique has great potential for use in robotic missions to other planetary bodies. C1 Lockheed Martin, Houston, TX 77058 USA. MVA Inc, Norcross, GA 30093 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Wentworth, SJ (reprint author), Lockheed Martin, C23,2400 NASA Rd 1, Houston, TX 77058 USA. NR 32 TC 38 Z9 41 U1 0 U2 9 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 JUL PY 1999 VL 34 IS 4 BP 593 EP 603 PG 11 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 222FD UT WOS:000081772000007 ER PT J AU Cintala, MJ Berthoud, L Horz, F AF Cintala, MJ Berthoud, L Horz, F TI Ejection-velocity distributions from impacts into coarse-grained sand SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID COLLISIONAL DISRUPTION; HYPERVELOCITY IMPACT; CRATER DIMENSIONS; SCALING LAWS; FRAGMENTS; METEORITES; TARGETS AB Velocities of ejecta from seven impacts of aluminum projectiles into coarse-grained sand have been measured with a laser-based apparatus that produces stroboscopic photographs of individual grains in ballistic flight. Speeds and angles of the majority of the ejecta can then be measured very precisely. There appears to be little effect of impact velocity on the functional relationship between the scaled, radial launch position and either the speed or angle of ejection; the seven experiments covered a range of impact velocities from 0.8 to 1.9 km s(-1) The measured ejection speeds follow power-law distributions, as predicted by dimensional analysis, but the angle of ejection is not constant throughout a given event as predicted. Indeed, the angle of ejection declines gradually with increasing radial distance from the impact point, but there are indications that the angle increases again as the position of the final crater's rim is approached. The exponents determined from scaled crater dimensions and ejection-speed distributions are substantially different. Although this might imply that assumptions used in the dimensional analysis are not valid, it is also possible that the coarse sand, whose component grains were comparable in dimension to the diameter of the impactors, instead presented a target that was more of an inhomogeneous aggregate of large fragments than a uniform, continuous medium. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Matra Marconi Space, Filton BS12 7YB, England. RP Cintala, MJ (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN2, Houston, TX 77058 USA. NR 28 TC 78 Z9 80 U1 0 U2 3 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 JUL PY 1999 VL 34 IS 4 BP 605 EP 623 PG 19 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 222FD UT WOS:000081772000008 ER PT J AU Shih, CY Nyquist, LE Wiesmann, H AF Shih, CY Nyquist, LE Wiesmann, H TI Samarium-neodymium and rubidium-strontium systematics of nakhlite Governador Valadares SO METEORITICS & PLANETARY SCIENCE LA English DT Article ID ANGRA-DOS-REIS; SM-ND; SNC METEORITES; RB-SR; EARLY DIFFERENTIATION; ISOTOPIC EVIDENCE; RAPID ACCRETION; ND-142 ND-144; MARS; AGE AB The Sm-Nd systematics of whole-rock and mineral separate samples from nakhlite Governador Valadares define a good Sm-147-Nd-143 mineral isochron age of 1.37 +/- 0.02 Ga. This age is in excellent agreement with the Ar-39-Ar-40 and Rb-Sr ages obtained previously for this meteorite. However, the Rb-Sr isotopic data for our sample show that the isotopic system is disturbed. The lack of isotopic equilibrium is probably caused by the weathering of the sample as indicated by the presence of secondary alteration phases. The whole-rock and acid-washed mineral data yield a Rb-Sr age of 1.20 +/- 0.05 Ga, which probably represents a lower limit to the crystallization age of the rock. The petrographic evidence indicates that this meteorite is a clinopyroxene cumulate that probably crystallized in a subsurface sill (McSween, 1994). Thus, the Sm-Nd isotopic age probably represents the age of such a magmatic event. The initial epsilon(143)Nd value determined for the rock at 1.37 Ga is +17 +/- 1, indicating that the parent magma of the rock came from a light-rare-earth-element-depleted source of Sm-147/Nd-144 = similar to 0.237 based on a simple two-stage evolution model. Results of the same model calculation for the initial Sr-87/Sr-86 ratio of the rock suggest that its source material was depleted in Rb-87/Sr-86 by similar to 50% relative to the estimated martian value at 1.37 Ga. Both the high Sm/Nd and low Rb/Sr values support a clinopyroxene-rich cumulate source for the genesis of the nakhlite Governador Valadares. Furthermore, our Sm-Nd age and epsilon(143)Nd data and the previously published epsilon(142)Nd datum for the rock (Harper et al., 1995) are consistent with early differentiation of the parent planet, formation of cumulate sources similar to 4.56 Ga ago, and late melting of the sources and formation of the rock similar to 1.37 Ga ago. The good agreement of isotopic ages and petrographic features among Governador Valadares, Nakhla, and Lafayette strongly suggests that all three nakhlites have undergone similar evolutionary histories. The nakhlite age data suggest that isotopic heterogeneity in the martian mantle sources existed up to similar to 1.37 Ga ago and early mantle structures probably have not been disturbed for a significant portion of martian history. C1 Lockheed Martin Space Mission Syst & Serv Co, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Lockheed Martin Space Mission Syst & Serv Co, Mail Code C23,2400 NASA Rd 1, Houston, TX 77058 USA. EM chi-yu.shih1@jsc.nasa.gov NR 54 TC 41 Z9 41 U1 0 U2 5 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 EI 1945-5100 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 IS 4 BP 647 EP 655 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 222FD UT WOS:000081772000011 ER PT J AU Paque, JM Connolly, HC Lofgren, GE AF Paque, JM Connolly, HC Lofgren, GE TI On the lower limit of chondrule cooling rates: The significance of iron loss in dynamic crystallization experiments - Comment SO METEORITICS & PLANETARY SCIENCE LA English DT Editorial Material C1 NASA, Ames Res Ctr, SETI Inst, Moffett Field, CA 94035 USA. CALTECH, Pasadena, CA 91125 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. RP Paque, JM (reprint author), NASA, Ames Res Ctr, SETI Inst, MS 245-3, Moffett Field, CA 94035 USA. NR 0 TC 1 Z9 1 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 IS 4 BP 671 EP 673 PG 3 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 222FD UT WOS:000081772000014 ER PT J AU Bell, MS Thomas-Keprta, KL Wentworth, SJ McKay, DS AF Bell, MS Thomas-Keprta, KL Wentworth, SJ McKay, DS TI Microanalysis of pyroxene, feldspar, and silica glass in Allan Hills 84001. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ALH84001 C1 Univ Houston, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 8 TC 3 Z9 3 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A10 EP A11 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400012 ER PT J AU Buchanan, PC Lindstrom, DJ Reimold, WU Koeberl, C AF Buchanan, PC Lindstrom, DJ Reimold, WU Koeberl, C TI The South African polymict eucrite Macibini. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Witwatersrand, Dept Geol, ZA-2050 Wits, South Africa. Univ Vienna, A-1090 Vienna, Austria. NR 4 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A20 EP A21 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400033 ER PT J AU Delaney, JS Jones, JH Sutton, SR Simon, S Grossman, L AF Delaney, JS Jones, JH Sutton, SR Simon, S Grossman, L TI In situ microanalysis of vanadium, chromium, and iron oxidation states in extraterrestrial samples by synchrotron microXANES (SmX) spectroscopy. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID ABSORPTION C1 Rutgers State Univ, Dept Geol Sci, Piscataway, NJ 08854 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA. NR 7 TC 6 Z9 6 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A32 EP A32 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400056 ER PT J AU Funaki, M Wasilewski, P AF Funaki, M Wasilewski, P TI A relation of magnetization and sulfidization in the parent body of the Allende (CV3) carbonaceous chondrite. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Natl Inst Polar Res, Tokyo 173, Japan. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 4 TC 4 Z9 4 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A39 EP A39 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400070 ER PT J AU Garvin, JB Schnetzler, CC Frawley, JJ Sakimoto, SEH AF Garvin, JB Schnetzler, CC Frawley, JJ Sakimoto, SEH TI Global geometric characteristics of fresh impact craters on Mars: A new perspective from the Mars Orbiter Laser Altimeter (MOLA). SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Goddard Space Flight Ctr, Terr Phys Lab, Greenbelt, MD 20771 USA. NR 3 TC 1 Z9 1 U1 1 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A41 EP A41 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400074 ER PT J AU Hashimoto, M McKay, G Le, L Schwandt, C Mikouchi, T AF Hashimoto, M McKay, G Le, L Schwandt, C Mikouchi, T TI Experimental crystallization of a revised Shergotty bulk composition. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Kyushu Univ, Dept Earth & Planetary Sci, Fukuoka 812, Japan. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin, Houston, TX 77058 USA. Univ Tokyo, Inst Mineral, Tokyo 113, Japan. NR 4 TC 2 Z9 2 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A51 EP A52 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400094 ER PT J AU Lyon, IC Saxton, JM Sears, DWG Symes, S Turner, G AF Lyon, IC Saxton, JM Sears, DWG Symes, S Turner, G TI Possible mass-independent oxygen-isotopic fractionation in the mesostasis of a Semarkona group A1 chondrule. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID CHONDRITES C1 Univ Manchester, Dept Earth Sci, Manchester M13 9PL, Lancs, England. Univ Arkansas, Dept Biochem & Chem, Cosmochem Grp, Fayetteville, AR 72701 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. NR 8 TC 2 Z9 2 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A76 EP A77 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400140 ER PT J AU Meibom, A Krot, AN Petaev, MI Wilson, L Reisener, R Goldstein, JI Norman, M Campbell, AJ Bennett, V Nuth, J Wasilewski, P Bland, P Hough, RM Trimby, P Keil, K AF Meibom, A Krot, AN Petaev, MI Wilson, L Reisener, R Goldstein, JI Norman, M Campbell, AJ Bennett, V Nuth, J Wasilewski, P Bland, P Hough, RM Trimby, P Keil, K TI Metal condensates in CH and Bencubbin-like chondrites: Evidence for localized nebula heating events and variations in gas composition. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Univ Hawaii, Sch Ocean & Earth Sci & Technol, Hawaii Inst Geophys, Honolulu, HI 96822 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. Univ Lancaster, Inst Environm & Nat Sci, Lancaster, England. Univ Massachusetts, Dept Geosci, Amherst, MA 01003 USA. Univ Massachusetts, Dept Mech & Ind Engn, Amherst, MA 01003 USA. Univ Tasmania, Ctr Ore Deposit Res, Hobart, Tas 7001, Australia. Univ Chicago, Dept Geophys Sci, Chicago, IL 60637 USA. Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 2600, Australia. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Museum Nat Hist, London, England. Open Univ, Milton Keynes MK7 6AA, Bucks, England. Univ Utrecht, Dept Geol, Utrecht, Netherlands. RI Nuth, Joseph/E-7085-2012 NR 3 TC 2 Z9 2 U1 0 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 JUL PY 1999 VL 34 SU S BP A80 EP A81 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400148 ER PT J AU Mikouchi, T Miyamoto, M McKay, GA AF Mikouchi, T Miyamoto, M McKay, GA TI Cooling rates of olivine in the martian meteorites Dar al Gani 476 and elephant moraine 79001. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Planetary Sci Branch, Houston, TX 77058 USA. Univ Tokyo, Inst Mineral, Grad Sch Sci, Tokyo 1130033, Japan. NR 6 TC 5 Z9 5 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A81 EP A82 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400151 ER PT J AU Nyquist, LE Reese, YD Wiesmann, H Shih, CY AF Nyquist, LE Reese, YD Wiesmann, H Shih, CY TI Two ages for ibitira: A record of crystallization and recrystallization? SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract ID METEORITES; NEODYMIUM; EUCRITES C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Lockheed Martin Space Mission Syst & Serv Co, Houston, TX 77058 USA. EM 1.nyquist@jsc.nasa.gov NR 7 TC 5 Z9 5 U1 1 U2 1 PU WILEY-BLACKWELL PI HOBOKEN PA 111 RIVER ST, HOBOKEN 07030-5774, NJ USA SN 1086-9379 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A87 EP A88 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400163 ER PT J AU Owen, T Bar-Nun, A Mahaffy, P Atreya, S Donahue, T Niemann, H AF Owen, T Bar-Nun, A Mahaffy, P Atreya, S Donahue, T Niemann, H TI Icy planetesimals and the formation of planets. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Univ Hawaii, Astron Inst, Honolulu, HI 96822 USA. Tel Aviv Univ, Dept Geophys & Planetary Sci, IL-69978 Tel Aviv, Israel. NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A88 EP A88 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400164 ER PT J AU Schnetzler, CC Fiske, PS Garvin, JB Frawley, JJ AF Schnetzler, CC Fiske, PS Garvin, JB Frawley, JJ TI Recent developments in the search for the site of the 780,000-year-old southeast Asia impact. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Greenbelt, MD 20771 USA. Univ Calif Lawrence Livermore Natl Lab, Phys & Space Technol Directorate, Livermore, CA 94550 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Herring Bay Geophys, Greenbelt, MD 20771 USA. NR 7 TC 1 Z9 1 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A102 EP A103 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400191 ER PT J AU Sipiera, PP Jerman, GA Hoover, RB AF Sipiera, PP Jerman, GA Hoover, RB TI Classification of two new chondritic meteorites from the Sahara Desert, Libya. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 Harper Coll, Schmitt Meteorite Res Grp, Palatine, IL 60067 USA. NASA, George C Marshall Space Flight Ctr, Mat Proc Lab, Huntsville, AL 35812 USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. NR 1 TC 1 Z9 1 U1 0 U2 0 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A109 EP A110 PG 2 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400204 ER PT J AU Zolensky, ME Bodnar, RJ Rubin, AE AF Zolensky, ME Bodnar, RJ Rubin, AE TI Asteroidal water within fluid-inclusion-bearing halite in ordinary chondrites. SO METEORITICS & PLANETARY SCIENCE LA English DT Meeting Abstract C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Virginia Polytech Inst & State Univ, Dept Geol Sci, Blacksburg, VA 24061 USA. Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90095 USA. RI Bodnar, Robert/A-1916-2009 NR 3 TC 11 Z9 11 U1 0 U2 1 PU METEORITICAL SOC PI FAYETTEVILLE PA DEPT CHEMISTRY/BIOCHEMISTRY, UNIV ARKANSAS, FAYETTEVILLE, AR 72701 USA SN 0026-1114 J9 METEORIT PLANET SCI JI Meteorit. Planet. Sci. PD JUL PY 1999 VL 34 SU S BP A124 EP A124 PG 1 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 223EA UT WOS:000081826400232 ER PT J AU Alexander, GD Weinman, JA Karyampudi, VM Olson, WS Lee, ACL AF Alexander, GD Weinman, JA Karyampudi, VM Olson, WS Lee, ACL TI The effect of assimilating rain rates derived from satellites and lightning on forecasts of the 1993 superstorm SO MONTHLY WEATHER REVIEW LA English DT Article ID 12-14 MARCH 1993; UPPER BOUNDARY-CONDITION; PRECIPITABLE WATER; MESOSCALE MODEL; SYNOPTIC-SCALE; CYCLONE; SSM/I; CLOUD; PARAMETERIZATION; RETRIEVALS AB Inadequate specification of divergence and moisture in the initial conditions of numerical models results in the well-documented "spinup" problem. Observational studies indicate that latent heat release can be a key ingredient in the intensification of extratropical cyclones. As a result, the assimilation of rain rates during the early stages of a numerical simulation result, in improved forecasts of the intensity and precipitation patterns associated with extratropical cyclones. It is challenging, however, particularly over data-sparse regions, to obtain complete and tellable estimates of instantaneous rain rate. Here, a technique is described in which data from a variety of sources-passive microwave sensors, infrared sensors, and lightning hash observations-along with a classic image processing technique (digital image morphing) are combined to yield a continuous time series of rain rates, which may their be assimilated into a mesoscale model. The technique is tested on simulations of the notorious 1993 Superstorm. In this case, a fortuitous confluence of several factors-rapid cyclogenesis over an oceanic region, the occurrence of this cyclogenesis at a time inconveniently placed in between Special Sensor Microwave/Imager overpasses, intense lightning during this time, and a poor forecast in thp control simulation-leads to a dramatic improvement in forecasts of precipitation patterns, sea level pressure fields, and geopotential height fields when information from all of the sources is combined to determine the rain rates. Lightning data, in particular: has a greater positive impact on the forecasts than the other data sources. C1 NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Microwave Sensors Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Sci Syst & Applicat Inc, Mesoscale Atmospher Proc Branch, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Caelum Res Corp, Greenbelt, MD 20771 USA. UK Meteorol Off, Remote Sensing Instruments Branch, Farnborough, Hants, England. RP Weinman, JA (reprint author), NASA, Goddard Space Flight Ctr, Univ Space Res Assoc, Code 975, Greenbelt, MD 20771 USA. NR 49 TC 59 Z9 67 U1 0 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 JUL PY 1999 VL 127 IS 7 BP 1433 EP 1457 DI 10.1175/1520-0493(1999)127<1433:TEOARR>2.0.CO;2 PG 25 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221VZ UT WOS:000081748900003 ER PT J AU Grivet-Talocia, S Einaudi, F Clark, WL Dennett, RD Nastrom, GD VanZandt, TE AF Grivet-Talocia, S Einaudi, F Clark, WL Dennett, RD Nastrom, GD VanZandt, TE TI A 4-yr climatology of pressure disturbances using a barometer network in central Illinois SO MONTHLY WEATHER REVIEW LA English DT Article ID DOPPLER-SPREAD PARAMETERIZATION; MESOSCALE WAVE DISTURBANCES; ATMOSPHERIC GRAVITY-WAVES; NUMERICAL SPECTRAL MODEL; 15 DECEMBER 1987; MIDDLE ATMOSPHERE; LOWER STRATOSPHERE; EQUATORIAL OSCILLATIONS; MOMENTUM DEPOSITION; CONVECTIVE STORMS AB This paper presents a climatology of coherent disturbances detected during 1991-95 by a network of barometers with a diameter of about 50 km located in a very Aat terrain centered on the Flatland Atmospheric Observatory in east-central Illinois. An automatic, wavelet-based adaptive filter is used to extract the waveforms of all disturbance events with amplitudes larger than a frequency-dependent threshold. The extracted events cover characteristic temporal scales from about 30 min to 6 h. that is, the range that includes mesoscale disturbances that affect the weather and the forecasts. The analysis resulted in two classes of events. One class, called coherent events, or CEs, consists of disturbances that propagated coherently through the barograph network and for which the phase propagation velocity, dominant period, and horizontal wavelength could be estimated with good accuracy. The propagation direction of 97% of the CEs were between 0 degrees and 180 degrees (i.e., had an eastward component) and the speeds of 96% were between 10 and 50 m s(-1) with a mode at 25-30 m s(-1). The other class, called incoherent events, or IEs, consists of disturbances that had significant amplitudes but that did not propagate coherently across the network, so that the propagation velocity could not be estimated. This class consists of localized disturbances and wave packets with short periods and/or wavelengths, or with pressure signatures that were too different at the network stations. The extracted events are attributed to gravity waves. wave packers, gravity currents, pressure jumps, solitary waves, bores, etc. The rate of occurrence of events had a strong seasonal dependence, with a maximum in fall and winter and a minimum in summer. The CEs occurred about 20%-21% of the total time in fall and winter and 12% in summer, while all events occurred 34% in both fail and winter and 23% in summer. The seasonal dependence of events confirms the strong relation of these disturbances to the baroclinicity of the atmosphere. Concurrent vertical velocity fluctuations observed by the 50-MHz radar at the Flatland Atmospheric Observatory showed that many of the large-amplitude events extended up to at least 7 km. the highest altitude reliably observed by the radar. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NOAA, Aeron Lab, Boulder, CO 80303 USA. St Cloud State Univ, Dept Earth Sci, St Cloud, MN 56301 USA. RP Grivet-Talocia, S (reprint author), Politecn Torino, C Duca Abruzzi 24, I-10129 Turin, Italy. EM grivet@polito.it RI Grivet-Talocia, Stefano/M-1480-2015 OI Grivet-Talocia, Stefano/0000-0002-5463-3810 NR 56 TC 13 Z9 13 U1 1 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 JUL PY 1999 VL 127 IS 7 BP 1613 EP 1629 DI 10.1175/1520-0493(1999)127<1613:AYCOPD>2.0.CO;2 PG 17 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221VZ UT WOS:000081748900013 ER PT J AU Chang, ATC Chiu, LS AF Chang, ATC Chiu, LS TI Nonsystematic errors of monthly oceanic rainfall derived from SSM/1 SO MONTHLY WEATHER REVIEW LA English DT Article ID STOCHASTIC-MODEL; PRECIPITATION AB About 10 yr (July 1987-December 1997 with December 1987 missing) of oceanic monthly rainfall based on data taken by the Special Sensor Microwave/Imager (SSM/I) on board the Defense Meteorological Satellite Program satellites have been computed. The technique, based on the work of Wilheit ct al., includes improved parameterization of the beam-filling correction, a refined Iand mask and sea ice filter. Monthly means are calculated for both 5 degrees and 2.5 degrees latitude-longitude boxes. Monthly means over the latitude band of 50 degrees N-50 degrees S and error statistics are presented. The time-averaged rain rate is 3.09 mm day(-1) (std dev of 0.15 mm day(-1)) with an error of 38.0% (std dev of 3.0%) fur the 5 degrees monthly means over the 10-yr period. These statistics compare favorably with 3.00 mm day(-1) (std dev of 0.19 mm day(-1)) and 46.7% (std dev of 3.4%) computed from the 2.5 degrees monthly means for the period January 1992-December 1994. Examination of the different rain rate categories shows no distinct discontinuity, except for months with a large number of missing SSM/I data. An independent estimate of the error using observations from two satellite, shows an error of 31% (std dev of 2.7%), consistent with the 38% estimated using (A.M.. and P.M.) data from one satellite alone. Error estimates (31%) based on the 5 degrees means by averaging four neighboring 2.5 degrees boxes are larger than those (23%) estimated by assuming the means for these neighboring boxes are independent, thus suggesting spatial dependence of the 2.5 degrees means. Multiple regression analyses show that the error varies inversely as the square root of the number of samples but exhibits a somewhat weaker dependence on the mean rain rate. Regression analyses show a power law dependence of -0.255 to -0.265 on the rain rate for the 2.5 degrees monthly means using data from a single satellite and a dependence of -0.366 for the 5 degrees monthly means and -0.337 for the 2.5 degrees monthly means based on two satellite measurements. The latter estimate is consistent with that obtained by Bell et al, using a different rainfall retrieval technique. C1 NASA, Goddard Space Flight Ctr, Lab Hydrospher Proc, Hydrol Sci Branch, Greenbelt, MD 20771 USA. RP Chang, ATC (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Hydrol Sci Branch, Code 974, Greenbelt, MD 20771 USA. NR 17 TC 18 Z9 18 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 JUL PY 1999 VL 127 IS 7 BP 1630 EP 1638 DI 10.1175/1520-0493(1999)127<1630:NEOMOR>2.0.CO;2 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221VZ UT WOS:000081748900014 ER PT J AU Pielke, RA Walko, RL Steyaert, LT Vidale, PL Liston, GE Lyons, WA Chase, TN AF Pielke, RA Walko, RL Steyaert, LT Vidale, PL Liston, GE Lyons, WA Chase, TN TI The influence of anthropogenic landscape changes on weather in south Florida SO MONTHLY WEATHER REVIEW LA English DT Article ID MESOSCALE CIRCULATIONS; VEGETATION; PRECIPITATION; CONVECTION; GENERATION; MODELS; FLUXES; CLOUDS; SOIL AB Using identical observed meteorology for lateral boundary conditions, the Regional Atmospheric Modeling System was integrated for July-August 1973 for south Florida. Three experiments were performed-one using the observed 1973 Landscape, another the 1993 landscape, and the third the 1900 landscape, when the region was close to its natural state. Over the 2-month period, there was a 9% decrease in rainfall averaged over south Florida with the 1973 landscape and an 11% decrease with the 1993 landscape, as compared with the model results when the 1900 landscape is used. The limited available observations of trends in summer rainfall over this region are consistent with these trends. C1 Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. NASA, Goddard Space Flight Ctr, US Geol Survey, EROS Data Ctr, Greenbelt, MD 20771 USA. FMA Res Inc, Yucca Ridge Field Stn, Ft Collins, CO USA. Colorado State Univ, Grad Degree Program Ecol, Ft Collins, CO 80523 USA. RP Pielke, RA (reprint author), Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA. EM dallas@hercules.atmos.colostate.edu RI Pielke, Roger/A-5015-2009; OI Vidale, Pier Luigi/0000-0002-1800-8460 NR 50 TC 111 Z9 118 U1 0 U2 8 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 JUL PY 1999 VL 127 IS 7 BP 1663 EP 1673 DI 10.1175/1520-0493(1999)127<1663:TIOALC>2.0.CO;2 PG 11 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 221VZ UT WOS:000081748900017 ER PT J AU Balschi, JA Renugopalakrishan, V Collette, TW Dobbs, JC Carreira, LA Pattabiraman, N Langridge, R Sorensen, KR Huang, SG MacElroy, RD AF Balschi, JA Renugopalakrishan, V Collette, TW Dobbs, JC Carreira, LA Pattabiraman, N Langridge, R Sorensen, KR Huang, SG MacElroy, RD TI Molecular conformations of dermorphin: A unique non-nervous tissue mu-agonist SO NEUROSCIENCE RESEARCH COMMUNICATIONS LA English DT Article DE dermorphin; mu-agonist; FT-IR; H-1 NMR; Raman; molecular mechanics and modeling ID PEPTIDE ENKEPHALIN; SELECTIVE DERMORPHIN; DYNAMICS SIMULATIONS; H-1-NMR SPECTROSCOPY; ENERGY MINIMIZATION; MAGNETIC-RESONANCE; AQUEOUS-SOLUTION; NMR; PROTEINS; ANALOGS AB The molecular conformations of dermorphin, Tyr(1)-D-Ala(2) - Phe(3) - Gly(4) - Tyr(5) - Pro(6) - Ser(7)-NH2, are derived from FT-IR, Raman, CD, and 2D NMR spectroscopic studies in aqueous solution. Segawa et al. (1994,1995) have recently reported NMR studies of dermorphin in aqueous solution from which a folded conformation has been postulated. The folded conformation of dermorphin suggested by this study is characterized by a stacking of the aromatic side chains of Tyr(1) and Phe(3). This appears to be critical to the pharmacological profile of dermorphin. The experimentally derived conformation bears partial resemblance to the low energy conformations predicted by molecular mechanics calculations. The proposed conformational model and its possible relevance to the mu-agonist activity of dermorphin are discussed. C1 Brigham & Womens Hosp, NMR Lab Physiol Chem, Boston, MA 02115 USA. Harvard Univ, Sch Med, Dept Orthoped Surg, Lab Study Skeletal Disorders & Rehabil, Boston, MA 02115 USA. Childrens Hosp, Boston, MA 02115 USA. Univ Nacl Autonoma Mexico, Inst Quim, Mexico City 04510, DF, Mexico. Univ Georgia, Dept Chem, Athens, GA 30602 USA. Univ Calif San Francisco, Sch Pharm, Dept Pharmaceut Chem, San Francisco, CA 94143 USA. Harvard Univ, Dept Chem, Cambridge, MA 02138 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Balschi, JA (reprint author), Brigham & Womens Hosp, NMR Lab Physiol Chem, 221 Longwood Ave, Boston, MA 02115 USA. NR 39 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0893-6609 J9 NEUROSCI RES COMMUN JI Neurosci. Res. Commun. PD JUL-AUG PY 1999 VL 25 IS 1 BP 13 EP 24 PG 12 WC Neurosciences SC Neurosciences & Neurology GA 226RE UT WOS:000082034600002 ER PT J AU Goolish, EM Okutake, K Lesure, S AF Goolish, EM Okutake, K Lesure, S TI Growth and survivorship of larval zebrafish Danio rerio on processed diets SO NORTH AMERICAN JOURNAL OF AQUACULTURE LA English DT Article ID VERTEBRATE; BIOLOGY; MODEL AB Within the past decade the zebrafish or zebra danio Danio rerio has become a major vertebrate model for the study of developmental biology, neurobiology, and molecular genetics. Most research universities now include large zebrafish colonies where considerable resources are expended for their feeding and maintenance. Larvae are particularly labor intensive because they are commonly fed a live diet such as paramecia Paramecium sp. and brine shrimp Artemia sp. We evaluated 10 processed (i.e., nonliving) diets as alternatives to a live diet using the criteria of survivorship and growth during the 2-3 weeks following hatching. The test diets included commercial diets, two experimental diets, and freeze-dried brine shrimp. The control diet consisted of live paramecia and brine shrimp. Four experiments that varied in water exchange rate, aeration, and in the timing and method of diet delivery were conducted. No processed diet performed as well as the live-diet control when both larval survivorship and growth rate were considered. Furthermore, differences in water exchange rate and method of diet delivery were equally important in determining survivorship and growth as were differences among individual test diets. Under conditions when larval growth rate was similar to the live-diet control (hi,oh water exchange rate), survivorship was approximately 50% of the control value. Under conditions where larval survivorship was high (low water exchange rate), growth rate was 14-37% of the control value. Although no single test diet performed appreciably better than the others, the following general diet characteristics appeared to increase performance; resistance to breakdown, 200-400-mu m particle size, and a high residence time in the water column. Overall results suggest that processed diets for zebrafish larvae can be substituted for a live diet only if a decrease in either growth rate or survivorship is acceptable. C1 NASA, Ames Res Ctr, Lockheed Martin Space Mission Syst & Serv, Space Stn Biol Res Project, Moffett Field, CA 94035 USA. RP Goolish, EM (reprint author), NASA, Ames Res Ctr, Lockheed Martin Space Mission Syst & Serv, Space Stn Biol Res Project, T20G, Moffett Field, CA 94035 USA. RI Perez , Claudio Alejandro/F-8310-2010 OI Perez , Claudio Alejandro/0000-0001-9688-184X NR 12 TC 32 Z9 32 U1 0 U2 19 PU AMER FISHERIES SOC PI BETHESDA PA 5410 GROSVENOR LANE SUITE 110, BETHESDA, MD 20814-2199 USA SN 1522-2055 J9 N AM J AQUACULT JI N. Am. J. Aqualcult. PD JUL PY 1999 VL 61 IS 3 BP 189 EP 198 DI 10.1577/1548-8454(1999)061<0189:GASOLZ>2.0.CO;2 PG 10 WC Fisheries SC Fisheries GA 351ZK UT WOS:000089189900003 ER PT J AU Klaasen, KP Breneman, HH Cunningham, WF Kaufman, JM Klemaszewski, JE Magee, KP McEwen, AS Mortensen, HB Pappalardo, RT Senske, DA Sullivan, RJ Vasavada, AR AF Klaasen, KP Breneman, HH Cunningham, WF Kaufman, JM Klemaszewski, JE Magee, KP McEwen, AS Mortensen, HB Pappalardo, RT Senske, DA Sullivan, RJ Vasavada, AR TI Calibration and performance of the Galileo solid-state imaging system in Jupiter orbit SO OPTICAL ENGINEERING LA English DT Article DE charge-coupled device camera; calibration; digital imaging; remote sensing; space instrumentation; astronomy; data compression ID IMAGES; CAMERA AB The solid-state imaging subsystem (SSI) on the National Aeronautics and Space Administration's (NASA's) Galileo Jupiter orbiter spacecraft has successfully completed its 2-yr primary mission exploring the Jovian system. The SSI has remained in remarkably stable calibration during the 8-yr flight, and the quality of the returned images is exceptional. Absolute spectral radiometric calibration has been determined to 4 to 6% across its eight spectral filters. Software and calibration files are available to enable radiometric, geometric, modulation transfer function (MIF), and scattered light image calibration. The charge-coupled device (CCD) detector endured the harsh radiation environment at Jupiter without significant damage and exhibited transient image noise effects at about the expected levels. A lossy integer cosine transform (ICT) data compressor proved essential to achieving the SSI science objectives given the low data transmission rate available from Jupiter due to a communication antenna failure. The ICT compressor does introduce certain artifacts in the images that must be controlled to acceptable levels by judicious choice of compression control parameter settings. The SSI team's expertise in using the compressor improved throughout the orbital operations phase and, coupled with a strategy using multiple playback passes of the spacecraft tape recorder, resulted in the successful return of 1645 unique images of Jupiter and its satellites. (C) 1999 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(99)02007-3]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. Sterling Software, Pasadena, CA 91117 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Brown Univ, Dept Geol Sci, Providence, RI 02912 USA. Cornell Univ, Ctr Radiophys & Space Res, Ithaca, NY 14853 USA. CALTECH, Pasadena, CA 91125 USA. RP Klaasen, KP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 14 TC 9 Z9 9 U1 1 U2 3 PU SPIE-INT SOCIETY OPTICAL ENGINEERING PI BELLINGHAM PA 1000 20TH ST, BELLINGHAM, WA 98225 USA SN 0091-3286 J9 OPT ENG JI Opt. Eng. PD JUL PY 1999 VL 38 IS 7 BP 1178 EP 1199 DI 10.1117/1.602168 PG 22 WC Optics SC Optics GA 216GB UT WOS:000081432100015 ER PT J AU Heusser, CJ Heusser, LE Peteet, DM AF Heusser, CJ Heusser, LE Peteet, DM TI Humptulips revisited: a revised interpretation of Quaternary vegetation and climate of western Washington, USA SO PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY LA English DT Article DE Quaternary glaciation; interglaciation; vegetation; climate; Washington ID OLYMPIC PENINSULA; NORTH PACIFIC; COAST; HOLOCENE; AMERICA; RECORD; LAKE AB New pollen data from a 770-cm core of a mire at Humptulips on the southwestern Olympic Peninsula (47 degrees 17'00"N, 123 degrees 54'40"W) and from a nearby deposit regarded as interglacial in age on the West Fork of the Humptulips River provide evidence for a reinterpretation of previous accounts of the Quaternary vegetation and climate. Using a new age model, the highly variable record at Humptulips is here correlated with marine oxygen-isotope stages (OIS) 1-5a. Vegetation during OIS 5a was pine-dominated, mixed woodland and tundra. In OIS 4, 3, and 2, oscillations in pollen assemblages imply repeated intervals of mountain hemlock parkland and tundra. Pine, as an indicator of openness, is also abundant in these stages. Interstadial fluctuations in OIS 3 reflect episodes of lowland western hemlock communities. The earliest of the episodes is of infinite radiocarbon age and the latest dates to approximately 30,000 C-14 yr B.P Parkland in OIS 2, occurring after 24,600 until at least 18,440 C-14 yr B.P., was replaced by transitional pine-alder in OIS 1 (Holocene), which, unlike any of the earlier stages, conveys the development of modem lowland forest dominated by western hemlock. Pollen assemblages over the length of record imply that temperature and humidity at no time were as high as at present; only in OIS 3 do conditions approach those occurring in OIS 1. During OIS 2, 3, and 4, when tree line apparently stood at the location of the site, climate was colder and drier. Temperatures were depressed an estimated greater than or equal to 5 degrees C with precipitation close to 1000 mm compared with 2000-3000 mm at present. Atmospheric circulation during OIS 2 appears to have been much controlled by the location of the Laurentide ice sheet in the continental interior, whereas under the current climatic regime beginning in the early Holocene, westerly air flow has dominated, regulated by interplay between the North Pacific high in summer and the wintertime Aleutian low. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Heusser, CJ (reprint author), 100 Clinton Rd, Tuxedo Park, NY 10987 USA. NR 42 TC 14 Z9 14 U1 1 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0031-0182 J9 PALAEOGEOGR PALAEOCL JI Paleogeogr. Paleoclimatol. Paleoecol. PD JUL 1 PY 1999 VL 150 IS 3-4 BP 191 EP + DI 10.1016/S0031-0182(98)00225-9 PG 27 WC Geography, Physical; Geosciences, Multidisciplinary; Paleontology SC Physical Geography; Geology; Paleontology GA 210WB UT WOS:000081126700003 ER PT J AU Rakoto, H Respaud, M Broto, JM Arushanaov, E Caillat, T AF Rakoto, H Respaud, M Broto, JM Arushanaov, E Caillat, T TI The valence band parameters of CoSb3 determined by Shubnikov-de Haas effect SO PHYSICA B LA English DT Article DE CoSb3; band parameters; Shubnikov-de Haas oscillations ID LIGHTLY DOPED COSB3; TRANSPORT-PROPERTIES; SINGLE-CRYSTALS AB The results of Shubnikov-de Haas (SdH) oscillation measurements on p-CoSb3 single crystals are presented. The values of the cyclotron effective mass were determined. It was found that the effective mass increases from 0.11 m(0), to 0.15 m(0) with increasing hole concentration, indicating a non-parabolicity of the valence band of CoSb3. Using the two-band Kane model a band-edge effective mass of m(n)/m(0) = 0.050 +/- 0.002 and an energy gap E-g = 35 +/- 2 meV were estimated. (C) 1999 Elsevier Science B.V. All rights reserved. C1 INSA, SNCMP, F-31077 Toulouse, France. CSIC, ICMAB, Bellaterra 08193, Spain. Moldavian Acad Sci, Inst Appl Phys, Kishinev 277028, Moldova. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Rakoto, H (reprint author), INSA, SNCMP, Complexe Sci Rangueil, F-31077 Toulouse, France. NR 13 TC 7 Z9 7 U1 2 U2 7 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0921-4526 J9 PHYSICA B JI Physica B PD JUL PY 1999 VL 269 IS 1 BP 13 EP 16 DI 10.1016/S0921-4526(99)00094-0 PG 4 WC Physics, Condensed Matter SC Physics GA 200KG UT WOS:000080538400002 ER PT J AU Huo, WM Brown, D AF Huo, WM Brown, D TI Finite-element Z-matrix method: Application to electron-molecule collisions SO PHYSICAL REVIEW A LA English DT Article ID KOHN VARIATIONAL PRINCIPLE; LOG DERIVATIVE VERSION; IMPACT EXCITATION; B3-SIGMA-U+ STATE; MULTICHANNEL SCATTERING; HYDROGEN SCATTERING; QUANTUM SCATTERING; CROSS-SECTIONS; H-2; RESONANCES AB The Z-matrix formulation of Brown and Light [J. Chem. Phys. 101, 3723 (1994)], based on a Kohn variational principle for a general class of finite-range scattering functionals, is applied to electron-molecule collisions employing a mixed basis of Gaussians and finite-element interpolation polynomials (times spherical harmonics). The local nature of the finite elements is particularly well suited for finite-range calculations, and all integrals involved are energy independent. The implementation of the method is designed to make use of sophisticated target functions. Numerical examples for both elastic collision of H and inelastic collision of H-2 illustrate the applicability of this approach. The results are compared with data obtained using other theoretical methods as well as experimental data. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NASA, Goddard Space Flight Ctr, Inst Space Studies, New York, NY 10025 USA. RP Huo, WM (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. NR 51 TC 5 Z9 5 U1 0 U2 2 PU AMER 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 JUL PY 1999 VL 60 IS 1 BP 295 EP 305 DI 10.1103/PhysRevA.60.295 PG 11 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 212ZF UT WOS:000081247000045 ER PT J AU Beam, DA Yeh, NC Vasquez, RP AF Beam, DA Yeh, NC Vasquez, RP TI Vortex-state complex Hall conductivity of superconducting YBa2Cu3O7-delta epitaxial films at radio frequencies SO PHYSICAL REVIEW B LA English DT Article ID HIGH-TEMPERATURE SUPERCONDUCTORS; QUASI-PARTICLE SCATTERING; T-C SUPERCONDUCTORS; SINGLE-CRYSTALS; TRANSPORT-PROPERTIES; II SUPERCONDUCTORS; DYNAMICS; BI2SR2CACU2O8+DELTA; UNIVERSALITY; PSEUDOGAP AB The vortex-state complex Hall conductivity (sigma(xy)) of superconducting YBa2Cu3O7 epitaxial films is investigated from de to radio frequencies (up to7 x 10(6)Hz), using a direct transport measurement technique. The experimental results are analyzed in terms of a model generalized from that for the de Hall conductivity. This generalized model assumes that (1) the occurrence of sign revers;cll in the de vortex-state Hall conductivity is the result of different carrier densities within and Ear away from the vortex core; (2) the Drude approximation is applicable; and (3) the anomalous sign reversal occurs in the Aux-flow limit. We. find that the temperature and frequency dependencies of our compiler Hall conductivity data are in good agreement with our phenomenological model. In addition, when extended to higher frequencies, the same model provides consistent description for the complex Hall conductivity data at 100-800 GHz. Moreover, the magnetic-field (B) dependence of the complex Hall conductivity data reveals that both vortices (sigma(xy)(upsilon)) and quasiparticles (sigma(xy)(q)) contribute to the vortex-state Hall conduction, where sigma(xy)(upsilon)proportional to B-1 and sigma(xy)(q)proportional to B, in agreement with the model. The magnitude of the real part, sigma(xy)', is also consistent with the theoretical estimate, while the magnitude of the imaginary part, sigma(xy)" is significantly larger than the theoretical prediction, This discrepancy may be attributed to the unconventional electronic structures in vortices of cuprate: superconductors with d-wave or mixed-pairing symmetries. [S0163-1829(99)05225-X]. C1 CALTECH, Dept Phys, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Ctr Space Microelect Technol, Pasadena, CA 91109 USA. RP Yeh, NC (reprint author), CALTECH, Dept Phys, Pasadena, CA 91125 USA. EM ncyeh@caltech.edu NR 44 TC 2 Z9 2 U1 0 U2 1 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD JUL 1 PY 1999 VL 60 IS 1 BP 601 EP 609 DI 10.1103/PhysRevB.60.601 PG 9 WC Physics, Condensed Matter SC Physics GA 218KE UT WOS:000081551100084 ER PT J AU Han, D Kim, YS Noz, ME AF Han, D Kim, YS Noz, ME TI Wigner rotations and Iwasawa decompositions in polarization optics SO PHYSICAL REVIEW E LA English DT Article ID GROUP BERRY PHASES; LORENTZ-GROUP; STATES; LIGHT; FORMALISM AB Wigner rotations and Iwasawa decompositions are manifestations of the internal space-time symmetries of massive and massless particles, respectively. It is shown to be possible to produce combinations of optical filters which exhibit transformations corresponding to Wigner rotations and Iwasawa decompositions. This is possible because the combined effects of rotation, phase-shift, and attenuation filters lead to transformation matrices of the six-parameter Lorentz,group applicable to Jones vectors and Stokes parameters for polarized light waves. The symmetry transformations in special relativity lead to a set of experiments which can be performed in optics laboratories. [S1063-651X(99)08907-2]. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NYU, Dept Radiol, New York, NY 10016 USA. RP Han, D (reprint author), NASA, Goddard Space Flight Ctr, Code 935, Greenbelt, MD 20771 USA. NR 20 TC 24 Z9 25 U1 1 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 JUL PY 1999 VL 60 IS 1 BP 1036 EP 1041 DI 10.1103/PhysRevE.60.1036 PG 6 WC Physics, Fluids & Plasmas; Physics, Mathematical SC Physics GA 218KC UT WOS:000081550900128 PM 11969850 ER PT J AU Golombek, MP AF Golombek, MP TI Mars shows it stripes SO PHYSICS WORLD LA English DT Article C1 CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. RP Golombek, MP (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91125 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-8585 J9 PHYS WORLD JI Phys. World PD JUL PY 1999 VL 12 IS 7 BP 23 EP 24 PG 2 WC Physics, Multidisciplinary SC Physics GA 215MD UT WOS:000081384700026 ER PT J AU Moran, EC Filippenko, AV Ho, LC Shields, JC Belloni, T Comastri, A Snowden, SL Sramek, RA AF Moran, EC Filippenko, AV Ho, LC Shields, JC Belloni, T Comastri, A Snowden, SL Sramek, RA TI The nuclear spectral energy distribution of NGC 4395, the least luminous type 1 Seyfert galaxy SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID ULTRAVIOLET AB We present X-ray (ROSAT), infrared, and radio observations of NGC 4395, which harbors the optically least luminous type 1 Seyfert nucleus discovered thus far. In combination with published optical and ultraviolet spectra, we have used these data to assemble the broadband spectral energy distribution (SED) of the galaxy's nucleus. Interestingly, the SED of NGC 4395 differs markedly from the SEDs of both quasars and typical low-luminosity active galactic nuclei, which may be a manifestation of the different physical conditions (i.e., black hole masses, accretion rates, and/or accretion modes) that exist in these objects. The nuclear X-ray source in NGC 4395 is variable and has an observed luminosity of just similar to 10(38) ergs s(-1). Although this emission could plausibly be associated with either weak Seyfert activity or a bright stellar-mass binary system, the galaxy's optical and ultraviolet emission-line properties strongly suggest that the X-rays arise from a classical active galactic nucleus. C1 Univ Calif Berkeley, Dept Astron, Berkeley, CA 94720 USA. Observ Carnegie Inst Washington, Pasadena, CA 91101 USA. Ohio Univ, Dept Phys & Astron, Athens, OH 45701 USA. Univ Amsterdam, NL-1098 Amsterdam, Netherlands. Osservatorio Astron Bologna, I-40126 Bologna, Italy. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Natl Radio Astron Observ, Socorro, NM 87801 USA. RP Moran, EC (reprint author), Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA. EM edhead@jester.berkeley.edu RI Comastri, Andrea/O-9543-2015 OI Comastri, Andrea/0000-0003-3451-9970 NR 33 TC 46 Z9 46 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 1427 E 60TH ST, CHICAGO, IL 60637-2954 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD JUL PY 1999 VL 111 IS 761 BP 801 EP 808 DI 10.1086/316394 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219MW UT WOS:000081611900003 ER PT J AU Corbet, RHD AF Corbet, RHD TI The use of gamma-ray bursts as direction and time markers in SETI strategies SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC LA English DT Article ID NEUTRINO BURST; SIGNALS; SN1987A; SEARCH AB When transmitting a signal over a large distance, it is more efficient to send a brief beamed signal than a continuous omnidirectional transmission, but this requires that the receiver knows where and when to look for the transmission. For SETI, the use of various natural phenomena has previously been suggested to achieve the desired synchronization. Here it is proposed that gamma-ray bursts may well be the best "synchronizers" of all currently known phenomena because of their large intrinsic luminosities, high occurrence rate, isotropic sky distribution, large distance from the Galaxy, short duration, and easy detectability. For targeted searches, precise positions for gamma-ray bursts are required together with precise distance measurements to a target star. The required burst position determinations are now starting to be obtained, aided in large part by the discovery of optical afterglows. Good distance measurements are currently available from Hipparcos, and even better measurements should be provided by spacecraft now being developed. For nontargeted searches, positional accuracies simply better than a detector's field of view may suffice, but the time delay between the detection of a gamma-ray burst and the reception of the transmitted signal cannot be predicted in an obvious way. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Univ Space Res Assoc, Greenbelt, MD 20771 USA. RP Corbet, RHD (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Univ Space Res Assoc, Greenbelt, MD 20771 USA. NR 36 TC 4 Z9 4 U1 0 U2 0 PU ASTRONOMICAL SOC PACIFIC PI SAN FRANCISCO PA 390 ASHTON AVE, SAN FRANCISCO, CA 94112 USA SN 0004-6280 J9 PUBL ASTRON SOC PAC JI Publ. Astron. Soc. Pac. PD JUL PY 1999 VL 111 IS 761 BP 881 EP 885 DI 10.1086/316395 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 219MW UT WOS:000081611900012 ER PT J AU Marshak, A Wiscombe, W Davis, A Oreopoulos, L Cahalan, R AF Marshak, A Wiscombe, W Davis, A Oreopoulos, L Cahalan, R TI On the removal of the effect of horizontal fluxes in two-aircraft measurements of cloud absorption SO QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY LA English DT Article DE aircraft observations; short-wave radiation ID INDEPENDENT PIXEL APPROXIMATION; STRATOCUMULUS CLOUDS; SOLAR ABSORPTION; RADIATION AB Cloud absorption inferred from the difference between the net fluxes measured by stacked aircraft below and above clouds is strongly affected by the uncertainties due to cloud horizontal inhomogeneity. The simplest way to get rid of these uncertainties is to perform grand averages over flight legs; if flight legs are long enough, grand averaging may lead to a reliable estimate of cloud absorption. However, the amount of information on 'true' cloud absorption returned from such an expensive measurement program will be very limited-often one number per flight leg. This paper contains a discussion on how to enhance the harvest of true absorption data using two related methods: (a) subtraction and (b) conditional sampling. Both methods assume that, simultaneously with broadband measurements, some narrow non-absorbing-band net flux measurements are also available. Both methods are related to Ackerman-Cox type corrections, where subtracting fluxes in a transparent spectral band from those in an absorbing band partially removes the radiative effects of horizontal inhomogeneity and allows the recovery of spatially resolved cloud absorption. The output of the two methods is different: while the subtraction method provides a contiguous record of recovered cloud absorption, the conditional sampling method yields a discrete set of data points where the vertical net flux divergence reliably estimates true cloud absorption. C1 Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87544 USA. RP Marshak, A (reprint author), Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, 1000 Hilltop Circle, Baltimore, MD 21250 USA. RI Oreopoulos, Lazaros/E-5868-2012; Cahalan, Robert/E-3462-2012; Wiscombe, Warren/D-4665-2012; Marshak, Alexander/D-5671-2012 OI Oreopoulos, Lazaros/0000-0001-6061-6905; Cahalan, Robert/0000-0001-9724-1270; Wiscombe, Warren/0000-0001-6844-9849; NR 26 TC 14 Z9 14 U1 0 U2 0 PU ROYAL METEOROLOGICAL SOC PI READING PA 104 OXFORD ROAD, READING, BERKS, ENGLAND RG1 7LJ SN 0035-9009 J9 Q J ROY METEOR SOC JI Q. J. R. Meteorol. Soc. PD JUL PY 1999 VL 125 IS 558 BP 2153 EP 2170 DI 10.1002/qj.49712555811 PN B PG 18 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 230MK UT WOS:000082254800010 ER PT J AU Cucinotta, FA Nikjoo, H Goodhead, DT AF Cucinotta, FA Nikjoo, H Goodhead, DT TI Applications of amorphous track models in radiation biology SO RADIATION AND ENVIRONMENTAL BIOPHYSICS LA English DT Review ID ACCELERATED HEAVY-IONS; INITIATION-PROMOTION MODEL; ALPHA-PARTICLE IRRADIATION; SMALL CYLINDRICAL TARGETS; DOUBLE-STRAND BREAKS; ULTRASOFT X-RAYS; MAMMALIAN-CELLS; MUTATION-INDUCTION; CHROMOSOMAL INSTABILITY; IONIZING-RADIATION AB The average or amorphous track model uses the response of a system to gamma-rays and the radial distribution of dose about an ion's path to describe survival and other cellular endpoints from proton, heavy ion, and neutron irradiation. This model has been used for over 30 years to successfully fit many radiobiology data sets. We review several extensions of this approach that address objections to the original model, and consider applications of interest in radiobiology and space radiation risk assessment. In the light of present views of important cellular targets, the role of target size as manifested through the relative contributions from ion-kill (intra-track) and gamma-kill tinter-track) remains a critical question in understanding the success of the amorphous track model. Several variations of the amorphous model are discussed, including ones that consider the radial distribution of event-sizes rather than average electron dose, damage clusters rather than multiple targets, and a role for repair or damage processing. C1 NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. MRC, Radiat & Genome Stabil Unit, Didcot OX11 0RD, Oxon, England. RP Cucinotta, FA (reprint author), NASA, Lyndon B Johnson Space Ctr, Mail Code SN, Houston, TX 77058 USA. EM Fcucinot@ems.jsc.nasa.gov NR 77 TC 64 Z9 64 U1 0 U2 3 PU SPRINGER PI NEW YORK PA 233 SPRING ST, NEW YORK, NY 10013 USA SN 0301-634X J9 RADIAT ENVIRON BIOPH JI Radiat. Environ. Biophys. PD JUL PY 1999 VL 38 IS 2 BP 81 EP 92 DI 10.1007/s004110050142 PG 12 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 223ND UT WOS:000081846400002 PM 10461753 ER PT J AU Hoegy, WR Brace, LH AF Hoegy, WR Brace, LH TI Use of Langmuir probes in non-Maxwellian space plasmas SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID ELECTRON-TEMPERATURE; ANISOTROPY; VENUS AB Disturbance of the Maxwellian plasma may occur in the vicinity of a spacecraft due to photoemission, interactions between the spacecraft and thermospheric gases, or electron emissions from other devices on the spacecraft. Significant non-Maxwellian plasma distributions may also occur in nature as a mixture of ionospheric and magnetospheric plasmas or secondaries produced by photoionization in the thermosphere or auroral precipitation. The general formulas for current collection (volt-ampere curves) by planar, cylindrical, and spherical Langmuir probes in isotropic and anisotropic non-Maxwellian plasmas are examined. Examples are given of how one may identify and remove the non-Maxwellian components in the Langmuir probe current to permit the ionospheric parameters to be determined. Theoretical volt-ampere curves presented for typical examples of non-Maxwellian distributions include: two-temperature plasmas and a thermal plasma with an energetic electron beam. If the nonionospheric electrons are Maxwellian at a temperature distinct from that of the ionosphere electrons, the volt-ampere curves can be fitted directly to obtain the temperatures and densities of both electron components without resorting to techniques that attempt to derive the plasma distribution from the current by taking derivatives. For an arbitrary isotropic distribution, the current for retarded particles is shown to be identical for the three geometries. For anisotropic distributions, the three probe geometries are not equally suited for measuring the ionospheric electron temperature and density or for determining the distribution function in the presence of non-Maxwellian background electrons. (C) 1999 American Institute of Physics. [S0034-6748(99)02807-5]. C1 NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. Univ Michigan, Space Phys Res Lab, Ann Arbor, MI 48109 USA. RP Hoegy, WR (reprint author), NASA, Goddard Space Flight Ctr, Atmospheres Lab, Greenbelt, MD 20771 USA. NR 16 TC 11 Z9 11 U1 2 U2 3 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUL PY 1999 VL 70 IS 7 BP 3015 EP 3024 DI 10.1063/1.1149862 PG 10 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 210AC UT WOS:000081082100020 ER PT J AU Tabib-Azar, M Akinwande, D Ponchak, GE LeClair, SR AF Tabib-Azar, M Akinwande, D Ponchak, GE LeClair, SR TI Evanescent microwave probes on high-resistivity silicon and its application in characterization of semiconductors SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID COPLANAR WAVE-GUIDE; MICROSTRIP AB In this article we report the design, fabrication, and characterization of very high quality factor 10 GHz microstrip resonators on high-resistivity (high-rho) silicon substrates. Our experiments show that an external quality factor of over 13 000 can be achieved on microstripline resonators on high-rho silicon substrates. Such a high Q factor enables integration of arrays of previously reported evanescent microwave probe (EMP) on silicon cantilever beams. We also demonstrate that electron-hole pair recombination and generation lifetimes of silicon can be conveniently measured by illuminating the resonator using a pulsed light. Alternatively, the EMP was also used to nondestructively monitor excess carrier generation and recombination process in a semiconductor placed near the two-dimensional resonator. (C) 1999 American Institute of Physics. [S0034-6748(99)00807-2]. C1 Case Western Reserve Univ, Cleveland, OH 44106 USA. NASA, Lewis Res Ctr, Cleveland, OH 44135 USA. USAF, Res Lab, Mat & Mfg Directorate, Wright Patterson AFB, OH 45433 USA. RP Tabib-Azar, M (reprint author), Case Western Reserve Univ, Cleveland, OH 44106 USA. NR 14 TC 22 Z9 22 U1 1 U2 2 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUL PY 1999 VL 70 IS 7 BP 3083 EP 3086 DI 10.1063/1.1149871 PG 4 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 210AC UT WOS:000081082100031 ER PT J AU Keller, JW Chornay, DJ Hunsaker, FH Ogilvie, KW Coplan, MA AF Keller, JW Chornay, DJ Hunsaker, FH Ogilvie, KW Coplan, MA TI Gated time-of-flight plasma composition analyzer for space physics research SO REVIEW OF SCIENTIFIC INSTRUMENTS LA English DT Article ID ELECTROSTATIC ANALYZER; DESIGN AB We have constructed and tested a prototype instrument for space plasma physics research. The instrument is capable of measuring total ion velocity distribution functions as well as velocity distribution functions for individual mass-per-charge (m/q) species. The instrument consists of a deflection system, a toroidal energy-per-charge (E/q) analyzer, and a hemispherical condenser that serves either as the second stage of E/q analysis or as a gated time-of-flight velocity filter. The deflection system subtends a full 360 degrees in azimuth and allows one to select ions for analysis in the toroidal section according to their elevation angle with respect to the axis of the instrument. The hemispherical condenser accepts a fraction of the ions transmitted by the toroidal analyzer through an electronic shutter at its entrance plane. With the shutter open, total ion distribution functions are measured. By appropriately gating the shutter and measuring the time of flight of ions introduced into the hemisphere, ion velocities are measured and m/q determined. The dimensions of the instrument have been chosen for measurements of the interplanetary solar wind at distances of 4-20 solar radii (R-sun) from the surface of the sun, consistent with the requirements of a solar probe mission. It can also be adapted to make measurements at 1 a.u. (C) 1999 American Institute of Physics. [S0034-6748(99)04907-2]. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Univ Maryland, Inst Phys Sci & Technol, College Pk, MD 20742 USA. RP Keller, JW (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Keller, John/I-5097-2013 NR 10 TC 1 Z9 1 U1 0 U2 7 PU AMER INST PHYSICS PI WOODBURY PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999 USA SN 0034-6748 J9 REV SCI INSTRUM JI Rev. Sci. Instrum. PD JUL PY 1999 VL 70 IS 7 BP 3167 EP 3172 DI 10.1063/1.1149881 PG 6 WC Instruments & Instrumentation; Physics, Applied SC Instruments & Instrumentation; Physics GA 210AC UT WOS:000081082100044 ER PT J AU Bernstein, MP Sandford, SA Allamandola, LJ AF Bernstein, MP Sandford, SA Allamandola, LJ TI Life's far-flung raw materials SO SCIENTIFIC AMERICAN LA English DT Article C1 NASA, Ames Res Ctr, Astrochem Lab, Moffett Field, CA 94035 USA. RP Bernstein, MP (reprint author), NASA, Ames Res Ctr, Astrochem Lab, Moffett Field, CA 94035 USA. NR 4 TC 35 Z9 36 U1 0 U2 4 PU SCI AMERICAN INC PI NEW YORK PA 415 MADISON AVE, NEW YORK, NY 10017 USA SN 0036-8733 J9 SCI AM JI Sci.Am. PD JUL PY 1999 VL 281 IS 1 BP 42 EP 49 PG 8 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 208AE UT WOS:000080967400022 PM 11536904 ER PT J AU Handy, BN Acton, LW Kankelborg, CC Wolfson, CJ Akin, DJ Bruner, ME Caravalho, R Catura, RC Chevalier, R Duncan, DW Edwards, CG Feinstein, CN Freeland, SL Friedlaender, FM Hoffmann, CH Hurlburt, NE Jurcevich, BK Katz, NL Kelly, GA Lemen, JR Levay, M Lindgren, RW Mathur, DP Meyer, SB Morrison, SJ Morrison, MD Nightingale, RW Pope, TP Rehse, RA Schrijver, CJ Shine, RA Shing, L Strong, KT Tarbell, TD Title, AM Torgerson, DD Golub, L Bookbinder, JA Caldwell, D Cheimets, PN Davis, WN Deluca, EE McMullen, RA Warren, HP Amato, D Fisher, R Maldonado, H Parkinson, C AF Handy, BN Acton, LW Kankelborg, CC Wolfson, CJ Akin, DJ Bruner, ME Caravalho, R Catura, RC Chevalier, R Duncan, DW Edwards, CG Feinstein, CN Freeland, SL Friedlaender, FM Hoffmann, CH Hurlburt, NE Jurcevich, BK Katz, NL Kelly, GA Lemen, JR Levay, M Lindgren, RW Mathur, DP Meyer, SB Morrison, SJ Morrison, MD Nightingale, RW Pope, TP Rehse, RA Schrijver, CJ Shine, RA Shing, L Strong, KT Tarbell, TD Title, AM Torgerson, DD Golub, L Bookbinder, JA Caldwell, D Cheimets, PN Davis, WN Deluca, EE McMullen, RA Warren, HP Amato, D Fisher, R Maldonado, H Parkinson, C TI The transition region and coronal explorer SO SOLAR PHYSICS LA English DT Article ID SOLAR TELESCOPE ARRAY; SOHO MISSION AB The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The similar to 700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5 x 8.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min. C1 Montana State Univ, Dept Phys, Bozeman, MT 59717 USA. Lockheed Martin Palo Alto Adv Technol Ctr, Palo Alto, CA 94304 USA. Smithsonian Astrophys Observ, Cambridge, MA 02138 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Handy, BN (reprint author), Montana State Univ, Dept Phys, POB 173840, Bozeman, MT 59717 USA. RI DeLuca, Edward/L-7534-2013; OI DeLuca, Edward/0000-0001-7416-2895; Golub, Leon/0000-0001-9638-3082 NR 30 TC 886 Z9 898 U1 2 U2 16 PU KLUWER ACADEMIC PUBL PI DORDRECHT PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS SN 0038-0938 J9 SOL PHYS JI Sol. Phys. PD JUL PY 1999 VL 187 IS 2 BP 229 EP 260 DI 10.1023/A:1005166902804 PG 32 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 240JB UT WOS:000082821200001 ER PT J AU Das, NC Monroy, C Robinson, D Jhabvala, M AF Das, NC Monroy, C Robinson, D Jhabvala, M TI Design and fabrication of low power polysilicon sources SO SOLID-STATE ELECTRONICS LA English DT Article ID RESISTORS AB Large area polysilicon infrared (IR) sources have been designed and fabricated using micromachining technology for space flight project. Boron implant dose was varied to obtain different resistances of the polysilicon sources. It is found that there exists a resistance value for which power requirement for light emission is minimum. A linear relationship between input and output power is observed for the emission temperature range of 600 to 900 K. Theoretical expressions of I-V characteristics are derived by taking into account the effect of change in resistance due to self-heating of the polysilicon resistor. Good agreement between theoretical and experimental I-V characteristics is observed within the limit of experimental errors. (C) 1999 Elsevier Science Ltd. All rights reserved. C1 Raytheon STX, Lanham, MD 20706 USA. Orbital Sci Corp, Greenbelt, MD 20770 USA. NASA, Goddard Space Flight Ctr, Solid State Device Branch, Greenbelt, MD 20771 USA. RP Das, NC (reprint author), Raytheon STX, 4400 Forbes Blvd, Lanham, MD 20706 USA. NR 12 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 0038-1101 J9 SOLID STATE ELECTRON JI Solid-State Electron. PD JUL PY 1999 VL 43 IS 7 BP 1239 EP 1244 DI 10.1016/S0038-1101(98)00339-6 PG 6 WC Engineering, Electrical & Electronic; Physics, Applied; Physics, Condensed Matter SC Engineering; Physics GA 219BZ UT WOS:000081589200011 ER PT J AU Launius, RD AF Launius, RD TI History of aerodynamics and its impact on flying machines. SO TECHNOLOGY AND CULTURE LA English DT Book Review C1 NASA, Washington, DC 20546 USA. RP Launius, RD (reprint author), NASA, Washington, DC 20546 USA. NR 1 TC 0 Z9 0 U1 0 U2 1 PU JOHNS HOPKINS UNIV PRESS PI BALTIMORE PA JOURNALS PUBLISHING DIVISION, 2715 NORTH CHARLES ST, BALTIMORE, MD 21218-4319 USA SN 0040-165X J9 TECHNOL CULT JI Technol. Cult. PD JUL PY 1999 VL 40 IS 3 BP 688 EP 690 PG 3 WC History & Philosophy Of Science SC History & Philosophy of Science GA 221FA UT WOS:000081712300033 ER PT J AU Elfouhaily, T Thompson, DR Vandemark, D Chapron, B AF Elfouhaily, T Thompson, DR Vandemark, D Chapron, B TI A new bistatic model for electromagnetic scattering from perfectly conducting random surfaces SO WAVES IN RANDOM MEDIA LA English DT Article ID SMALL-SLOPE APPROXIMATION; WAVE SCATTERING; ROUGH; EXPANSION AB In this paper, we extend the Kirchhoff approach, which is widely used for near-nadir backscattering calculations, to include the proper polarization sensitivity for general bistatic scattering from gently sloping, perfectly conducting surfaces. Previously, Holliday has shown how the inclusion of terms from the second iteration of the surface-current integral equation is required to obtain agreement with the small perturbation method for backscattering conditions. Here we employ a similar approach by retaining all terms in this iterative expansion through first order in the surface slope to derive expressions for the standard Kirchhoff held as well as for a supplementary field that contains the polarization sensitivity. A polarization vector notation is introduced to simplify the inclusion of tilting effects from larger-scale features on the scattering surface. In connection with this latter development, we provide a clarification of the earlier work by Valenzuela on this topic together with an extension to the bistatic problem. These extensions to the standard Kirchhoff approach form the basis for our composite bistatic scattering model which should provide a convenient and powerful tool for calculations involving passive as well as active microwave scattering from random surfaces. C1 Johns Hopkins Univ, Appl Phys Lab, Laurel, MD 20723 USA. NASA, Goddard Space Flight Ctr, Wallops Isl, VA USA. IFREMER, Brest, France. RP Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA. RI Chapron, Bertrand/O-6527-2015 NR 12 TC 53 Z9 54 U1 2 U2 3 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0959-7174 J9 WAVE RANDOM MEDIA JI Waves Random Media PD JUL PY 1999 VL 9 IS 3 BP 281 EP 294 DI 10.1088/0959-7174/9/3/301 PG 14 WC Physics, Multidisciplinary SC Physics GA 220WW UT WOS:000081692100001 ER PT J AU Phillips, J Rajagopalan, B Cane, M Rosenzweig, C AF Phillips, J Rajagopalan, B Cane, M Rosenzweig, C TI The role of ENSO in determining climate and maize yield variability in the US cornbelt SO INTERNATIONAL JOURNAL OF CLIMATOLOGY LA English DT Article DE ENSO; US cornbelt; maize yield; regression analysis; crop simulation ID NINO SOUTHERN OSCILLATION; UNITED-STATES; PREDICTION; AUSTRALIA AB Recent advances in understanding the role of the El Nino- Southern Oscillation (ENSO) in climate variability present opportunities for improving efficiency in agricultural production. We investigated the relationships between ENSO, climate and maize yields in the U.S. cornbelt, using both observed data and crop simulations. Using a time-series of sea-surface temperature anomalies (SSTA) from the NINO3 region of the Pacific Ocean and historical records of temperature and precipitation spatially averaged across 51 mid-western climate divisions from 1950 to 1995, we ran linear correlation tests at three different lags. Northern hemisphere wintertime SSTAs were significantly correlated with air temperature at the 95% level of confidence in both the previous (r = -0.32) and following (r = 0.41) summer, but had opposite signs. Correlations with precipitation were significant only in the summer preceding the ENSO event (r = 0.31). Detrended maize yield for the same area and time period was also significantly related to SSTAs in the winter after harvest, with a correlation coefficient of 0.39, indicating that ENSO accounts for approximate to 15% of interannual maize yield variability in the cornbelt. Crop growth simulations at seven sites across the region suggest that water stress in July and August is the primary cause of lowered corn yield in La Nina years, but shortened grainfill period due to higher temperatures is also important. The benefits of El Nino-related rainfall and cooler temperatures are less pronounced than the negative impacts of warmer and dryer La Ninas. However, advance warning of both ENSO phases may present opportunities for improved crop management in the cornbelt. Copyright (C) 1999 Royal Meteorological Society. C1 Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Lamont Doherty Geol Observ, Palisades, NY 10964 USA. RP Phillips, J (reprint author), Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. RI Cane, Mark/I-8086-2012; Rajagopalan, Balaji/A-5383-2013 OI Rajagopalan, Balaji/0000-0002-6883-7240 NR 19 TC 40 Z9 41 U1 1 U2 7 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0899-8418 J9 INT J CLIMATOL JI Int. J. Climatol. PD JUN 30 PY 1999 VL 19 IS 8 BP 877 EP 888 DI 10.1002/(SICI)1097-0088(19990630)19:8<877::AID-JOC406>3.0.CO;2-Q PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 215FY UT WOS:000081372300005 ER PT J AU Draper, SL Aikin, BJM AF Draper, SL Aikin, BJM TI Effect of composite fabrication on the strength of single crystal Al2O3 fibers in two Fe-base alloy composites SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING LA English DT Article DE Al2O3 fibers; metal matrix composites; tensile strength; acoustic emission ID METAL-MATRIX COMPOSITES; INTERFACIAL BONDING STRENGTH; TENSILE-STRENGTH; BEHAVIOR AB Continuous single-crystal Al2O3 fibers have been incorporated into a variety of metal and intermetallic matrices and the results have consistently indicated that the fiber strength had been reduced by 32-50% during processing [1-4]. Two iron-based alloys, FeNiCoCrAl and FeAlVCMn, were chosen as matrices for Al2O3 fiber reinforced metal matrix composites (MMC) with the goal of maintaining Al2O3 fiber strength after composite processing. The feasibility of Al2O3/FeNiCoCrAl and Al2O3/FeAlVCMn composite systems for high temperature applications were assessed in terms of fiber-matrix chemical compatibility, interfacial bond strength, and composite tensile properties. The strength of etched-out fibers was significantly improved by choosing matrices containing less reactive elements. The ultimate tensile strength (UTS) values of the composites could generally be predicted with existing models using the strength of etched-out fibers. However, the UTS of the composites were less than desired due to low fiber Weibull moduli. Acoustic emission analysis during tensile testing was a useful tool for determining the efficiency of the fibers in the composite and for determining the failure mechanism of the composites. (C) 1999 Elsevier Science S.A. All rights reserved. C1 NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. Case Western Reserve Univ, Cleveland, OH 44106 USA. RP Draper, SL (reprint author), NASA, Glenn Res Ctr, Cleveland, OH 44135 USA. NR 23 TC 7 Z9 7 U1 1 U2 6 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 JUN 30 PY 1999 VL 266 IS 1-2 BP 18 EP 29 DI 10.1016/S0921-5093(99)00033-7 PG 12 WC Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Metallurgy & Metallurgical Engineering SC Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering GA 204GZ UT WOS:000080757000003 ER PT J AU Trajmar, S Kanik, I Khakoo, MA LeClair, LR Bray, I Fursa, D Csanak, G AF Trajmar, S Kanik, I Khakoo, MA LeClair, LR Bray, I Fursa, D Csanak, G TI Elastic electron scattering by laser-excited Ba-138(...6s6p P-1(1)) atoms SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS LA English DT Article ID TRANSITION-PROBABILITIES; NEUTRAL BARIUM; CROSS-SECTIONS; SODIUM ATOMS; EXCITATION; IMPACT; ALIGNMENT; PARAMETERS; BA; ORIENTATION AB The results of a joint experimental and theoretical study concerning elastic electron scattering by laser-excited Ba-138(...6s6p P-1(1)) atoms are described. These studies demonstrate several important aspects of elastic electron collisions with coherently excited atoms, and are the first such studies. From the measurements, collision and coherence parameters, as well as cross sections associated with an atomic ensemble prepared with an arbitrary in-plane laser geometry and linear polarization (with respect to the collision frame), or equivalently with any magnetic sublevel superposition, have been obtained at 20 eV impact energy and at 10 degrees, 15 degrees and 20 degrees scattering angles. The convergent close-coupling (CCC) method was used within the non-relativistic LS-coupling framework to calculate the magnetic sublevel scattering amplitudes. From these amplitudes all the parameters and cross sections at 20 eV impact energy were extracted in the full angular range in 1 degrees steps. The experimental and theoretical results were found to be in good agreement, indicating that the CCC method can be reliably applied to elastic scattering by Ba-138(...6s6p P-1(1)) atoms, and possibly to other heavy elements when spin-orbit coupling effects are negligible. Small but significant asymmetry was observed in the cross sections for scattering to the left and to the right. It was also found that elastic electron scattering by the initially isotropic atomic ensemble resulted in the creation of significant alignment. As a byproduct of the present studies, elastic scattering cross sections for metastable Ba-138 atoms were also obtained. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CALTECH, Div Chem & Chem Engn, Pasadena, CA 91109 USA. Calif State Univ Fullerton, Dept Phys, Fullerton, CA 92834 USA. Flinders Univ S Australia, Elect Struct Mat Ctr, Adelaide, SA 5001, Australia. Los Alamos Natl Lab, Los Alamos, NM 87544 USA. RP Trajmar, S (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. RI Fursa, Dmitry/C-2301-2009; Bray, Igor/B-8586-2009 OI Fursa, Dmitry/0000-0002-3951-9016; Bray, Igor/0000-0001-7554-8044 NR 49 TC 8 Z9 8 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND SN 0953-4075 J9 J PHYS B-AT MOL OPT JI J. Phys. B-At. Mol. Opt. Phys. PD JUN 28 PY 1999 VL 32 IS 12 BP 2801 EP 2829 DI 10.1088/0953-4075/32/12/302 PG 29 WC Optics; Physics, Atomic, Molecular & Chemical SC Optics; Physics GA 214CK UT WOS:000081309900007 ER PT J AU Zimmerli, GA Wilkinson, RA Ferrell, RA Moldover, MR AF Zimmerli, GA Wilkinson, RA Ferrell, RA Moldover, MR TI Electrostriction of near-critical SF6 in microgravity SO PHYSICAL REVIEW LETTERS LA English DT Article ID LIQUID CRITICAL-POINT; DIELECTRIC-CONSTANT AB We used interferometry to measure the electric-field-induced (i.e., "electrostrictive") increase of the density of sulfur hexafluoride near its critical point. The results at the temperatures T-c + 5 mK, T-c + 10 mK, and T-c + 30 mK, with T-c = 319 K, agree with a calculation based on the Clausius-Mossotti relation and the restricted cubic model equation of state. These measurements were performed in microgravity so that the electrostrictive density changes (less than or equal to 3.5% in this work) would not be complicated by stratification of the fluid's density induced by the Earth's gravity. C1 Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. NASA, Lewis Res Ctr, Micrograv Sci Div, Cleveland, OH 44135 USA. Univ Maryland, Dept Phys, College Pk, MD 20742 USA. NIST, Phys & Chem Properties Div, Bethesda, MD 20892 USA. RP Zimmerli, GA (reprint author), Natl Ctr Micrograv Res, Cleveland, OH 44135 USA. RI Moldover, Michael/E-6384-2013 NR 16 TC 8 Z9 8 U1 0 U2 1 PU AMERICAN PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 0031-9007 J9 PHYS REV LETT JI Phys. Rev. Lett. PD JUN 28 PY 1999 VL 82 IS 26 BP 5253 EP 5256 DI 10.1103/PhysRevLett.82.5253 PG 4 WC Physics, Multidisciplinary SC Physics GA 211GN UT WOS:000081152700019 ER PT J AU Pawson, S Naujokat, B AF Pawson, S Naujokat, B TI The cold winters of the middle 1990s in the northern lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID 1995-96 ARCTIC WINTER; QUASI-BIENNIAL OSCILLATION; GENERAL-CIRCULATION MODEL; POLAR VORTEX CONDITIONS; INTERANNUAL VARIABILITY; TEMPERATURE TRENDS; OZONE DEPLETION; HEMISPHERE WINTER; MLS OBSERVATIONS; METEOROLOGY AB Lower stratospheric temperatures in the northern winters of 1994/1995, 1995/1996, and 1996/1997 were low enough to support polar stratospheric cloud (PSC) formation for prolonged periods. While the seasonal evolution of each winter was quite different, there are some common characteristics: notably, the occurrence of extremely cold periods of long duration and the coldness of the late winter in each gear. Comparison with observations over more than three decades indicate the stratosphere was atypically cold in these three years, with the largest anomalies occurring in the late winter and spring, In January and February the coldness seems to Let determined by the interannual variability of the circulation, while in March the persistence of the polar vortex dominated the circulation in these three years. This may be related to the lack of major midwinter warmings in those years. Comparison with other winters shows that although the persistence of the polar vortex well into the spring is not unprecedented, this did not occur frequently in the previous two decades. Further, there is a general temperature decrease in the northern lower stratosphere which contributed to the coldness of the three winters. Comparison of the late winter and spring of 1997 with 1967, both of which were forced only weakly by dynamics, supports the idea that this is due to a change in the radiative balance (with equilibrium at a lower temperature), although there are many caveats to this conclusion. C1 NASA, Goddard Space Flight Ctr, USRA, Greenbelt, MD 20771 USA. Free Univ Berlin, Inst Meteorol, D-12165 Berlin, Germany. RP Pawson, S (reprint author), NASA, Goddard Space Flight Ctr, USRA, Code 910-3, Greenbelt, MD 20771 USA. EM spawson@dao.gsfc.nasa.gov; naujokat@strat01.met.fu-berlin.de RI Pawson, Steven/I-1865-2014 OI Pawson, Steven/0000-0003-0200-717X NR 39 TC 102 Z9 105 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 27 PY 1999 VL 104 IS D12 BP 14209 EP 14222 DI 10.1029/1999JD900211 PG 14 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 211XW UT WOS:000081188000003 ER PT J AU Cole, JE Rind, D Webb, RS Jouzel, J Healy, R AF Cole, JE Rind, D Webb, RS Jouzel, J Healy, R TI Climatic controls on interannual variability of precipitation delta O-18: Simulated influence of temperature, precipitation amount, and vapor source region SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID GENERAL-CIRCULATION MODEL; ISOTOPE COMPOSITION; WATER ISOTOPES; AMAZON BASIN; ICE CORES; GREENLAND; CYCLES; TRENDS; SNOW; HDO AB We use an atmospheric GCM that incorporates stable isotopes and regional vapor source tracers in the hydrologic cycle to explore the relationship between interannual variability in climate and precipitation delta(18)O globally. On the basis of a 12-year simulation forced by observed sea surface temperatures (SSTs), we identify changes in the amount of precipitation and in the contributions of local and nearby vapor sources as the most important determinants of simulated interannual isotopic changes. The model simulates weak positive correlation between temperature and isotopic variability only in certain continental regions, mostly in the extratropics. Comparison with long observed records of isotopes and climate indicates that the model simulates realistic patterns of temperature-isotope correlation but may overestimate the isotopic influence of precipitation amount. perturbations in circulation patterns that alter the transport and mixing of air masses at a site also change the relative contributions of vapor from different source regions. Simulated changes in vapor source regions are large, reaching +/- 10-15% of the total precipitation, and cause significant isotopic variability in nearly all grid cells. Our results suggest that shifts among vapor sources may provide an important control on the interannual isotopic variability observed in modern precipitation and paleoclimatic records. The isotopic variability simulated in this experiment results from the interaction of several aspects of climate. Interannual temperature variability generally involves circulation changes that alter air mass transport, vapor source regions, and condensation history; this advective mechanism may explain the relative weakness of temperature-isotope correlations in both the model and the observations. C1 Univ Colorado, Boulder, CO 80309 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. NOAA, NGDC Paleoclimatol, Boulder, CO 80303 USA. CEA Saclay, CEA, UMR CNRS 1572, Lab Sci Climat & Environm, F-91191 Gif Sur Yvette, France. Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA. RP Cole, JE (reprint author), Univ Colorado, Campus Box 450, Boulder, CO 80309 USA. EM coleje@spot.colorado.edu; drind@giss.nasa.gov; rsw@ngdc.noaa.gov; jouzel@obelix.saclay.cea.fr; rhealy@whoi.edu RI Healy, Richard/J-9214-2015 OI Healy, Richard/0000-0002-5098-8921 NR 47 TC 72 Z9 74 U1 2 U2 14 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 27 PY 1999 VL 104 IS D12 BP 14223 EP 14235 DI 10.1029/1999JD900182 PG 13 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 211XW UT WOS:000081188000004 ER PT J AU Holmes, RL Dimonte, G Fryxell, B Gittings, ML Grove, JW Schneider, M Sharp, DH Velikovich, AL Weaver, RP Zhang, Q AF Holmes, RL Dimonte, G Fryxell, B Gittings, ML Grove, JW Schneider, M Sharp, DH Velikovich, AL Weaver, RP Zhang, Q TI Richtmyer-Meshkov instability growth: experiment, simulation and theory SO JOURNAL OF FLUID MECHANICS LA English DT Article ID RAYLEIGH-TAYLOR; NUMERICAL-SIMULATION; NONLINEAR-THEORY; FRONT TRACKING; GAS-DYNAMICS; NOVA LASER; SHOCK-WAVE; DRIVEN; INTERFACE; FLOW AB Richtmyer-Meshkov instability is investigated for negative Atwood number and two-dimensional sinusoidal perturbations by comparing experiments, numerical simulations and analytic theories. The experiments were conducted on the NOVA laser with strong radiatively driven shocks with Mach numbers greater than 10. Three different hydrodynamics codes (RAGE, PROMETHEUS and FroriTier) reproduce the amplitude evolution and the gross features in the experiment while the fine-scale features differ in the different numerical techniques. Linearized theories correctly calculate the growth rates at small amplitude and early time, but fail at large amplitude and late time. A nonlinear theory using asymptotic matching between the linear theory and a potential flow model shows much better agreement with the late-time and large-amplitude growth rates found in the experiments and simulations. We vary the incident shock strength and initial perturbation amplitude to study the behaviour of the simulations and theory and to study the effects of compression and nonlinearity. C1 Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. Univ Calif Lawrence Livermore Natl Lab, Livermore, CA 94551 USA. Drexel Univ, Dept Phys & Atmospher Sci, Philadelphia, PA 19104 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Sci Applicat Int Corp, San Diego, CA 92121 USA. SUNY Stony Brook, Dept Appl Math & Stat, Stony Brook, NY 11794 USA. Berkeley Res Associates, Springfield, VA USA. RP Holmes, RL (reprint author), Univ Calif Los Alamos Natl Lab, POB 1663, Los Alamos, NM 87545 USA. RI Velikovich, Alexander/B-1113-2009; OI ZHANG, Qiang /0000-0002-8659-5396 NR 49 TC 138 Z9 142 U1 8 U2 26 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 JUN 25 PY 1999 VL 389 BP 55 EP 79 DI 10.1017/S0022112099004838 PG 25 WC Mechanics; Physics, Fluids & Plasmas SC Mechanics; Physics GA 219FH UT WOS:000081596900003 ER PT J AU Farrell, WM Desch, MD Zarka, P AF Farrell, WM Desch, MD Zarka, P TI On the possibility of coherent cyclotron emission from extrasolar planets SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID TERRESTRIAL KILOMETRIC RADIATION; SOLAR-WIND CONTROL; RADIO-EMISSION; MAGNETISM; NEPTUNE; URANUS; LAW AB A model of the coherent cyclotron emission from extrasolar planets is presented. Scaling laws known to operate in our solar system (including scaling laws of planetary magnetic fields and the radiometric Bode's law of radio power generation) are applied to the extrasolar systems. We consider the possibility that each of the extrasolar planets possesses a substantial planetary magnetic field which is in quasi-continuous interaction with the local stellar wind. Cyclotron emission from extrasolar planets is then driven by the stellar wind/magnetospheric interaction, much like the coherent cyclotron radio emission processes associated with planets in our solar system. Based on the model results, the best candidate for solar-wind-driven cyclotron emission is Tau Bootes, with an expected median amplitude of about 2 janskys (1 Jy = 10(-26) W m(-2) Hz(-1)) at 28 MHz, an intensity level of about a factor of 100 below the current limit of detectability. However, variations in the local stellar medium could conceivably increase power levels by a factor of 100 for short periods of time. Like the solar planets, the extrasolar planets should radiate episodically, with emission reoccurring at the planetary rotation period. Thus spectral integration techniques could also be applied to improve the likelihood of detectability. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Observ Paris, CNRS, DESPA, URA 264, F-92195 Meudon, France. RP Farrell, WM (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Mailstop 695-0, Greenbelt, MD 20771 USA. RI Farrell, William/I-4865-2013 NR 32 TC 85 Z9 85 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 JUN 25 PY 1999 VL 104 IS E6 BP 14025 EP 14032 DI 10.1029/1998JE900050 PG 8 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 211DE UT WOS:000081144000001 ER PT J AU Harmon, JK Arvidson, RE Guinness, EA Campbell, BA Slade, MA AF Harmon, JK Arvidson, RE Guinness, EA Campbell, BA Slade, MA TI Mars mapping with delay-Doppler radar SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID POLAR ANOMALIES; MERCURY RADAR; ICE; GANYMEDE; CALLISTO; IMAGES; REGION; BACKSCATTER; TOPOGRAPHY; SATELLITES AB Mars radar imaging results from Arecibo 12.6-cm observations are presented. The images were derived from delay-Doppler mapping using a coded-long-pulse technique to mitigate the effects of echo overspreading. Images of the depolarized echo are used to identify regions of high decimeter-scale roughness. Some of the strongest echo features are located on the major shield volcanoes or on relatively young off-shield flows such as the Olympus and Pavonis lava aprons. The shields themselves have highly irregular radar signatures suggesting complex volcanic histories. Some Mars radar features have twice the depolarized brightness of the roughest terrestrial lava flows, apparently due to higher levels of multiple scattering from surfaces of spectacular roughness or from volume scattering. Low-brightness (smooth) areas are associated with older surfaces such as fractured and highland terra, as well as with terrain interpreted to be debris lobes, ash flows, and aureoles; in particular, a close connection was found between the 12.6-cm counterpart of the "Stealth" feature and the Medusae Fossae Formation (postulated to be deep ignimbrite deposits). Marte Vallis is anomalous in being the only outflow channel showing strongly enhanced echoes, which supports the idea that this channel and the Elysium Basin that it drained are filled with lava flows. A weak radar feature was found for the south polar residual ice cap. Comparisons with Goldstone 3.5-cm data show that the south polar enhancement is much weaker at 12.6 cm than at 3.5 cm, indicating that the southern ice cap becomes optically thin at the longer wavelength. A north polar enhancement has also been found, which is comparable in strength to the 12.6-cm south polar feature. C1 Natl Astron & Ionosphere Ctr, Arecibo Observ, Arecibo, PR 00612 USA. Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA. Smithsonian Inst, Natl Air & Space Museum, Washington, DC 20560 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Harmon, JK (reprint author), Natl Astron & Ionosphere Ctr, Arecibo Observ, HC3 Box 53995, Arecibo, PR 00612 USA. NR 53 TC 41 Z9 42 U1 1 U2 3 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUN 25 PY 1999 VL 104 IS E6 BP 14065 EP 14089 DI 10.1029/1998JE900042 PG 25 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 211DE UT WOS:000081144000004 ER PT J AU Lane, MD AF Lane, MD TI Midinfrared optical constants of calcite and their relationship to particle size effects in thermal emission spectra of granular calcite SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID BIDIRECTIONAL REFLECTANCE SPECTROSCOPY; PARTICULATE PLANETARY SURFACES; ENERGY-TRANSFER; MINERALS; MODEL; SCATTERING; EMITTANCE; REGOLITHS; CONTRAST; QUARTZ AB Application of dispersion theory and the Fresnel reflection equations in this midinfrared (2000-400 cm(-1)) emission study of calcite enables 11 oscillators and their band parameters to be described. Of the 11, two have not been defined previously in the literature: one for the ordinary ray (at 891 cm(-1)) and one for the extraordinary ray (at 848 cm(-1)). Updated optical constants (n and k) of calcite are presented as well. Emissivity spectra of a suite of calcite particulate samples are also shown. The variations in the spectral shape of the fundamental and transparency bands that are influenced by particle size are related to the new optical constants. Type I, II, and III band behaviors are discussed as they relate to the optical and physical properties of the calcite particle size fractions. It is shown here that for Type II band behavior, the spectral bands that invert with decreased particle size shift to the position of maximum k for that band rather than to "lower frequencies," as has been concluded in previous studies. C1 Arizona State Univ, Dept Geol, Tempe, AZ 85287 USA. RP Lane, MD (reprint author), NASA, Lyndon B Johnson Space Ctr, Code SN3, Houston, TX 77058 USA. NR 53 TC 46 Z9 48 U1 2 U2 12 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 JUN 25 PY 1999 VL 104 IS E6 BP 14099 EP 14108 DI 10.1029/1999JE900025 PG 10 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 211DE UT WOS:000081144000006 ER PT J AU Cummer, SA Farrell, AM AF Cummer, SA Farrell, AM TI Radio atmospheric propagation on Mars and potential remote sensing applications SO JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS LA English DT Article ID IONOSPHERE WAVE-GUIDE; MODE AB We theoretically analyze the propagation of very low frequency (VLF) and extremely low frequency (ELF) electromagnetic energy in the spherical waveguide formed by the ground and ionosphere of Mars to investigate the possibility of using such signals to remotely sense Martian ground conductivity and ionospheric parameters. This energy is presumed to be radiated from an electrical discharge in a Martian dust storm. Using a synthesis of observed and modeled Martian ionospheric and ground parameters and assuming a discharge current similar to that in a terrestrial lightning discharge, we calculate radio atmospheric spectra and waveforms for a variety of discharge orientations and observed electromagnetic field components. A number of characteristics of the modeled Martian radio atmospherics (sferics) are found to be significantly different from those of terrestrial sferics, and we discuss how these features could provide information regarding the Martian ionosphere. We also show that measurements of VLF and ELF attenuation rates could provide a measurement of large-scale ground conductivity to a depth of a few kilometers or more, thereby providing a technique for probing large-scale subsurface geological features which affect bulk conductivity, such as areas containing ice or water. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RP Cummer, SA (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. RI Cummer, Steven/A-6118-2008 OI Cummer, Steven/0000-0002-0002-0613 NR 29 TC 23 Z9 24 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0148-0227 J9 J GEOPHYS RES-PLANET JI J. Geophys. Res.-Planets PD JUN 25 PY 1999 VL 104 IS E6 BP 14149 EP 14157 DI 10.1029/1998JE000622 PG 9 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 211DE UT WOS:000081144000009 ER PT J AU Terashima, Y Kunieda, H Misaki, K AF Terashima, Y Kunieda, H Misaki, K TI ASCA observation of the low-luminosity Seyfert 1.5 galaxy NGC 5033 SO PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN LA English DT Article DE galaxies : active; galaxies : individual (NGC 5033); galaxies : Seyfert; X-rays : spectra ID ACTIVE GALACTIC NUCLEI; IRON K-EMISSION; X-RAY-SPECTRA; GAS IMAGING SPECTROMETER; ALPHA EMISSION; BOARD ASCA; VARIABILITY; LINE; SEARCH; DISK AB We present the results of an ASCA observation of the low-luminosity Seyfert 1.5 galaxy NGC 5033. A point-like X-ray source with a luminosity of 2.3 x 10(41) erg s(-1) in the 2-10 keV band (at 18.7 Mpc; Tully 1988, AAA 045.002.054) was detected at the nucleus. The X-ray light curve shows variability on a timescale of similar to 10(4) s With an amplitude of similar to 20%. The X-ray continuum is represented by a weakly absorbed (N-H approximate to 9 x 10(20) cm(-2)) power-law with a photon index of 1.72 +/- 0.04, which is quite similar to Seyfert 1 galaxies with higher luminosities. An Fe K alpha emission line is detected at 6.40(-0.06)(+0.08) keV (redshift corrected) and the equivalent width is 290 +/- 100 eV. The line width is unresolved. The narrower line width and larger equivalent width compared to Seyfert Is imply that fluorescent Fe K alpha emission from matter further out from the center than the accretion disk significantly contributes to the observed Fe K alpha line. We suggest that fluorescent Fe K alpha emission from the putative torus contributes to the observed Fe K alpha line. C1 Nagoya Univ, Dept Phys, Chikusa Ku, Nagoya, Aichi 4648602, Japan. RP NASA, Goddard Space Flight Ctr, Code 662, Greenbelt, MD 20771 USA. NR 47 TC 14 Z9 14 U1 0 U2 4 PU OXFORD UNIV PRESS PI OXFORD PA GREAT CLARENDON ST, OXFORD OX2 6DP, ENGLAND SN 0004-6264 EI 2053-051X J9 PUBL ASTRON SOC JPN JI Publ. Astron. Soc. Jpn. PD JUN 25 PY 1999 VL 51 IS 3 BP 277 EP 283 DI 10.1093/pasj/51.3.277 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211UP UT WOS:000081180500002 ER PT J AU Muller, HSP Cohen, EA Christen, D AF Muller, HSP Cohen, EA Christen, D TI The rotational spectrum of chloryl chloride, ClClO2, in its ground vibrational state SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID DIPOLE-MOMENT; CRYOGENIC MATRICES; SELF-REACTION; LINE CATALOG; 3 ISOMERS; DIOXIDE; CL2O2; PHOTOCHEMISTRY; SUBMILLIMETER; MILLIMETER AB Rotational spectra of the four main isotopomers of ClClO2 which together span the quantum numbers 10 less than or equal to J less than or equal to 77 and 0 less than or equal to K(a)less than or equal to 34 have been studied in selected regions between 10 and 417 GHz. The in situ syntheses using reactions between FClO2 and either HCl or BCl3 are described. Rotational and centrifugal distortion constants have been derived and used for structure and harmonic force field calculations. The quadrupole coupling constants for both Cl nuclei have been determined and the molecular dipole moment has been derived from low field Stark effect measurements in the submillimeter region. The results are discussed in relationship to published results from a matrix-isolation study, from theoretical calculations, and from studies of related molecules. (C) 1999 American Institute of Physics. [S0021-9606(99)02024-3]. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Tubingen, Inst Phys & Theoret Chem, D-72076 Tubingen, Germany. RP Muller, HSP (reprint author), Univ Cologne, Inst Phys 1, Zulpicher Str 77, D-50937 Cologne, Germany. OI Mueller, Holger/0000-0002-0183-8927 NR 46 TC 22 Z9 22 U1 0 U2 2 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 JUN 22 PY 1999 VL 110 IS 24 BP 11865 EP 11875 PG 11 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 204CN UT WOS:000080745500025 ER PT J AU Liao, XZ Zou, J Cockayne, DJH Leon, R Lobo, C AF Liao, XZ Zou, J Cockayne, DJH Leon, R Lobo, C TI Indium segregation and enrichment in coherent InxGa1-xAs/GaAs quantum dots SO PHYSICAL REVIEW LETTERS LA English DT Article ID TRANSMISSION-ELECTRON-MICROSCOPY; ISLANDS; LUMINESCENCE; EQUILIBRIUM; SPECTRA; STATE; SHAPE; SI AB Significant differences in the image features of InxGa1-xAs quantum dots (QDs) grown on (001) and vicinal (001) GaAs were seen in [001] on-zone bright-held transmission electron microscope images. Simulated images were obtained by modeling the strain field distribution of the QDs with finite element analysis and then using this model in dynamical electron diffraction contrast simulations. Comparison of the experimental images and the simulated images shows that (i) In segregation exists in the QDs and (ii) the average In content of the QDs is higher than the average In content of the film. C1 Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Australian Natl Univ, Dept Elect Mat Engn, Canberra, ACT 0200, Australia. RP Liao, XZ (reprint author), Univ Sydney, Australian Key Ctr Microscopy & Microanal, Sydney, NSW 2006, Australia. RI Liao, Xiaozhou/B-3168-2009; Zou, Jin/B-3183-2009; Lobo, Charlene/B-3977-2013; Lobo, Charlene/G-5003-2011 OI Liao, Xiaozhou/0000-0001-8565-1758; Zou, Jin/0000-0001-9435-8043; Lobo, Charlene/0000-0002-2746-1363; Lobo, Charlene/0000-0002-2746-1363 NR 20 TC 83 Z9 85 U1 2 U2 12 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 JUN 21 PY 1999 VL 82 IS 25 BP 5148 EP 5151 DI 10.1103/PhysRevLett.82.5148 PG 4 WC Physics, Multidisciplinary SC Physics GA 207XP UT WOS:000080961300050 ER PT J AU Ricca, A Musgrave, CB AF Ricca, A Musgrave, CB TI Theoretical study of the Cl-passivated Si(111) surface SO SURFACE SCIENCE LA English DT Article DE abstraction reactions; binding energy; clusters; density functional theory; gas-surface interactions; infrared spectra ID GAUSSIAN-BASIS SETS; CORRELATED MOLECULAR CALCULATIONS; COUPLED-CLUSTER THEORY; PLUS ADSORBED BR; ELECTRON CORRELATION; WAVE-FUNCTIONS; HYDROGEN; ENERGIES; EXTRACTION; KINETICS AB The Cl-passivated Si(111) surface is studied using density functional theory, in conjunction with the B3LYP functional and the cluster model. We compute the Si-Cl frequency and the Si-Cl bond energy for R(3)SiCl, and the abstraction barrier for the reaction R(3)SiCl + H --> R(3)Si + HCl using the B3LYP approach. We calibrate the B3LYP bond energy and the abstraction barriers using the values obtained using the G2MP2, G2 and CCSD(T) approaches. Our computed B3LYP Si-Cl frequency of 555 cm(-1) is in good agreement with the experimental value of 588 cm(-1). The shift in the Si-Cl frequency as surface chlorine is added to the cluster agrees with experimental observations. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA. Stanford Univ, Dept Mat Sci, Stanford, CA 94305 USA. RP Ricca, A (reprint author), NASA, Ames Res Ctr, Thermosci Inst, Moffett Field, CA 94035 USA. EM ricca@pegasus.arc.nasa.gov NR 29 TC 8 Z9 8 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD JUN 21 PY 1999 VL 430 IS 1-3 BP 116 EP 125 DI 10.1016/S0039-6028(99)00407-0 PG 10 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 217GQ UT WOS:000081492000019 ER PT J AU Dobson, CC AF Dobson, CC TI Laser-induced fluorescence measurements of translational temperature and relative cycle number by use of optically pumped trace-sodium vapor SO APPLIED OPTICS LA English DT Article ID RESONANCE AB Sodium fluorescence induced by a narrow-bandwidth tunable laser has been used to measure temperature, pressure, axial velocity, and species concentrations in wind tunnels, rocket engine exhausts, and the upper atmosphere. Optical pumping of the ground states of the sodium, however, can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating such measurements. Here a straightforward extension of rate equations originally proposed to account for the features of the pumped spectrum is used to make temperature measurements from spectra taken in pumped vapor. Also determined from the spectrum is the relative fluorescence cycle number, which has application to measurement of diffusion rate and transverse flow velocity. The accuracy of both the temperature and the cycle-number measurements is comparable with that of temperature measurements made in the absence of pumping. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Dobson, CC (reprint author), NASA, George C Marshall Space Flight Ctr, MS EP63, Huntsville, AL 35812 USA. EM chris.dobson@msfc.nasa.gov NR 14 TC 1 Z9 1 U1 0 U2 0 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 1559-128X EI 2155-3165 J9 APPL OPTICS JI Appl. Optics PD JUN 20 PY 1999 VL 38 IS 18 BP 3924 EP 3930 DI 10.1364/AO.38.003924 PG 7 WC Optics SC Optics GA 208FA UT WOS:000080978900011 PM 18320000 ER PT J AU Wells, JD Moiseev, A Ormes, JF AF Wells, JD Moiseev, A Ormes, JF TI Illuminating dark matter and primordial black holes with interstellar antiprotons SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; elementary particles ID COSMIC-RAY ANTIPROTONS; GAMMA-RAYS; SOLAR MINIMUM; GALACTIC ANTIPROTONS; HALO; ANNIHILATIONS; MODULATION; PARTICLES; RADIATION; MASS AB Interstellar antiproton fluxes can arise from dark matter annihilating or decaying into quarks or gluons that subsequently fragment into antiprotons. Evaporation of primordial black holes can also produce a significant antiproton cosmic-ray flux. Since the background of secondary antiprotons from spallation has an interstellar energy spectrum that peaks at similar to 2 GeV and falls rapidly for energies below this, low-energy measurements of cosmic antiprotons are useful in the search for exotic antiproton sources. However, measurement of the flux near the Earth is challenged by significant uncertainties arising from the effects of the solar wind. We suggest evading this problem and more effectively probing dark matter signals by placing an antiproton spectrometer aboard an interstellar probe currently under discussion. We address the experimental challenges of a light, low-power-consuming detector, and present an initial design of such an instrument. This experimental effort could significantly increase our ability to detect, and have confidence in, a signal from exotic, nonstandard antiproton sources. Furthermore, solar modulation effects in the heliosphere could be better quantified and understood by comparing results to inverse modulated data derived from existing balloon and space-based detectors near the Earth. C1 CERN, Div Theory, CH-1211 Geneva 23, Switzerland. Stanford Univ, Stanford Linear Accelerator Ctr, Stanford, CA 94309 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Wells, JD (reprint author), CERN, Div Theory, CH-1211 Geneva 23, Switzerland. NR 52 TC 12 Z9 12 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP 570 EP 575 DI 10.1086/307325 PN 1 PG 6 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211KA UT WOS:000081158700004 ER PT J AU Dickins, JE Irvine, WM AF Dickins, JE Irvine, WM TI The formaldehyde ortho para ratio as a probe of dark cloud chemistry and evolution SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : abundances; ISM : clouds; ISM : molecules ID MOLECULAR CLOUDS; DENSE CORES; METHYL CYANIDE; TMC-1; MULTITRANSITION; OUTFLOW AB We present measurements of the H2CO ortho/para ratio toward four star-forming cores, L723, L1228, L1527, and L43, and one quiescent core, L1498. Combining these data with earlier results by Minh et al., three quiescent cores are found to have ortho/para ratios near 3, the ratio of statistical weights expected for gas-phase formation processes. In contrast, ortho/para ratios are 1.5-2.1 in five star-forming cores, suggesting thermalization at a kinetic temperature of 10 K. We attribute modification of the ortho/para ratio in the latter cores to formation and/or equilibration of H2CO on grains with subsequent release back into the gas phase due to the increased energy inputs from the forming star and outflow. We see accompanying enhancements in the H2CO abundance relative to H-2 to support this idea. The results suggest that the formaldehyde ortho/para ratio can differentiate between quiescent cores and those in which low-mass star formation has occurred. C1 Univ Massachusetts, Five Coll Radio Astron Observ, Dept Phys & Astron, Amherst, MA 01003 USA. RP Dickins, JE (reprint author), CALTECH, Jet Prop Lab, MS 169-506,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 27 TC 37 Z9 38 U1 1 U2 4 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP 733 EP 739 DI 10.1086/307317 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211KA UT WOS:000081158700017 PM 11543064 ER PT J AU Meier, DL AF Meier, DL TI Multidimensional astrophysical structural and dynamical analysis. I. Development of a nonlinear finite element approach SO ASTROPHYSICAL JOURNAL LA English DT Article DE hydrodynamics; methods : numerical; MHD; relativity; stars : rotation ID NUMERICAL-METHOD; STARS; HYDRODYNAMICS; COLLAPSE AB A new held of numerical astrophysics is introduced that addresses the solution of large multidimensional structural or slowly evolving problems (rotating stars, interacting binaries, thick advective accretion disks, four-dimensional spacetimes, etc.), as well as rapidly evolving systems. The technique employed is the finite element method (FEM), which has been used to solve engineering structural problems for more than three decades. The approach developed here has the following key features: 1. The computational mesh can extend into the time dimension, as well as space-generally, only a few cells deep for most (flat-space) astrophysical problems, but throughout spacetime for solving Einstein's field equations. 2. When time is treated as a mesh dimension, virtually all equations describing the astrophysics of continuous media, including the held equations, can be written in a compact form similar to that routinely solved by most engineering finite element codes (albeit for nonlinear equations in a four-dimensional spacetime instead of linear ones in two or three space dimensions): the divergence of a generalized stress tensor equals a generalized body-force vector, both of which are functions only of position, the state variables, and their gradients. 3. The transformations that occur naturally in the four-dimensional FEM possess both coordinate and boost features, such that: (A) although the computational mesh may have a complex, nonanalytic, curvilinear structure, and may be adapted to the geometry of the problem, the physical equations still can be written in a simple coordinate system that is independent of the mesh structure; and (B) if the mesh has a complex how velocity with respect to coordinate space, the transformations will form the proper advective derivatives, automatically converting the equations to arbitrary Lagrangian-Eulerian. 4. Only relatively simple differential equations need to be encoded. The complex difference equations on the arbitrary curvilinear grid are generated automatically by the FEM integrals. A different integration method must be used for equations of odd and even orders. This first paper concentrates on developing a robust and widely applicable set of techniques using the nonlinear FEM, and presents some examples. The second paper in this series will deal with making the method fast and efficient, so that large, astrophysically interesting computational meshes can be employed. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 36 TC 9 Z9 9 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP 788 EP 813 DI 10.1086/307292 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211KA UT WOS:000081158700024 ER PT J AU Norris, JP Bonnell, JT Watanabe, K AF Norris, JP Bonnell, JT Watanabe, K TI Constraints on association of single-pulse gamma-ray bursts and supernovae SO ASTROPHYSICAL JOURNAL LA English DT Article DE gamma rays : bursts; methods : statistical; supernovae : general ID 25 APRIL 1998 AB We explore the hypothesis, similar to one recently suggested by Bloom and colleagues, that some nearby supernovae are associated with smooth, single-pulse gamma-ray bursts, possibly having no emission above similar to 300 keV. We examine BATSE bursts with durations longer than 2 s, fitting those which can be visually characterized as single-pulse events with a lognormal pulse model. The fraction of events that can be reliably ascertained to be temporally and spectrally similar to the exemplar, GRB 980425-possibly associated with SN 1998bw-is 4/1573 or 0.25%. This fraction could be as high as 8/1573 (0.5%) if the dimmest bursts are included. Approximately 1.5% of bursts are morphologically similar to GRB 980425 but have emission above similar to 300 keV. A search of supernova catalogs containing 630 detections during BATSE's lifetime reveals only one burst (GRB 980425) within a 3 month time window and within the total 3 sigma BATSE error radius that could be associated with a Type Ib/c supernova. Thus, we find no further evidence to support a single-pulse GRB and SN Ib/c connection. We also find no tendency for any set of single-pulse GRBs to fall near the supergalactic plane, whereas SNe of Type Ib/c do show this tendency-evidence that the two phenomena are not related. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. RP Norris, JP (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 26 TC 18 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 JUN 20 PY 1999 VL 518 IS 2 BP 901 EP 908 DI 10.1086/307299 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211KA UT WOS:000081158700033 ER PT J AU Mandzhavidze, N Ramaty, R Kozlovsky, B AF Mandzhavidze, N Ramaty, R Kozlovsky, B TI Determination of the abundances of subcoronal He-4 and of solar flare-accelerated He-3 and He-4 from gamma-ray spectroscopy SO ASTROPHYSICAL JOURNAL LA English DT Article DE solar wind; Sun : abundances; Sun : atmosphere; Sun : flares; Sun : particle emission; Sun : X-rays, gamma rays ID HELIUM; PARTICLES; PROTON AB A series of narrow gamma-ray lines at 0.339, 0.429, 0.478, 0.937, 1.00, 1.04, 1.05, and 1.08 result almost exclusively from the bombardment of ambient He, O, and Fe by accelerated alpha-particles and He-3 nuclei. Study of these lines, combined with the Fe-56 line at 0.847 MeV and the O-16 line at 6.129 MeV, allows the determination of the abundances of alpha-particles and He-3 accelerated in solar flares and of the ambient He in the gamma-ray production region in the solar atmosphere. Using the Solar Maximum Mission/GRS and Compton Gamma Ray Observatory/OSSE data for 20 flares, we find that with significance not exceeding about 2.5 sigma there are Bares that exhibit alpha-particle abundance enhancements (alpha/p > 0.1), show evidence for the presence of accelerated He-3, and indicate ambient He abundance enhancements. In some cases the accelerated H-3/He-4 similar to 1, and for essentially all of the flares He-3/He-4 could be 0.1, consistent with our earlier conclusion that in both impulsive and gradual flares that particles that interact and produce gamma rays are always accelerated by the same mechanism that operates in impulsive flares, namely, stochastic acceleration through gyroresonant wave-particle interactions. The ambient He abundance enhancements suggest that there are chromospheric regions where He/O exceeds its photospheric value, a result that could have important implications for solar atmospheric dynamics. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Greenbelt, MD 20771 USA. Tel Aviv Univ, Sch Phys & Astron, Ramat Aviv, Israel. RP Mandzhavidze, N (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 30 TC 48 Z9 49 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP 918 EP 925 DI 10.1086/307321 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211KA UT WOS:000081158700035 ER PT J AU Ragot, BR AF Ragot, BR TI Nongyroresonant pitch angle scattering SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; plasmas; scattering; solar wind; turbulence; waves ID COSMIC-RAY TRANSPORT; QUASI-LINEAR THEORY; ENERGETIC PARTICLES; ACCELERATION; WAVES; COEFFICIENTS; DIFFUSION; SPECTRUM; FIELDS AB The spatial transport of charged particles, in a turbulence of slab Alfven waves and isotropic fast magnetosonic waves, is determined by the pitch angle scattering of these particles. For pitch ankle cosines mu larger than the Alfven speed over the particle speed, this pitch angle scattering is provided by either gyroresonance with the Alfven waves or transit-time damping (TTD) with the fast-mode component of the spectrum. For smaller pitch angle cosines, however, there is no TTD, and if the particle rigidity is less than 1 GV, in the solar wind there is no gyroresonance possible either. A new nonresonant process is presented here that very efficiently scatters the particles through mu = 0 and is due to waves that cannot be in gyroresonance with the particles. The contributions to the particles' mean free path, of this nonresonant scattering process as well as of the TTD and gyroresonant ones, are calculated. The application to low-energy cosmic rays in the solar wind leads to the following conclusions. Below 10(2)-10(3) MV, the nonresonant process dominates the gyroresonant one at large pitch angles. Below 0.1-1 MV, the slowest scattering does not occur any longer at large pitch angles but at small ones, via TTD, with a relatively high and flat curve of mean free path versus rigidity. The resulting mean free path, between 10(-2) and 10(5) MV, gives very reasonable fits for the observational data, which diversity could be explained by slight modifications of the turbulence parameters. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Ragot, BR (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 24 TC 18 Z9 18 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP 974 EP 984 DI 10.1086/307315 PN 1 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211KA UT WOS:000081158700041 ER PT J AU Canuto, VM AF Canuto, VM TI Overshooting in massive stars: Conceptual problems and suggested solution SO ASTROPHYSICAL JOURNAL LA English DT Article DE convection; stars : evolution; stars : interiors ID DYNAMICAL MODEL; TURBULENT CONVECTION AB Overshooting (OV) in massive stars faces a basic difficulty: what theoretical models offer is not what stellar structure studies need. The former use del(mu) = 0 and define the OV where the negative convective flux J vanishes, while the latter need to know where the concentration flux J(c) vanishes. We suggest that J may be dynamically irrelevant and derive the new dynamic equations for J(c). A new feature emerges: for large concentration gradients del C, J(c) is no longer proportional to del C, as always assumed. 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 18 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 JUN 20 PY 1999 VL 518 IS 2 BP L119 EP L122 DI 10.1086/312082 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211MA UT WOS:000081163800015 ER PT J AU Macomb, DJ Finger, MH Harmon, BA Lamb, RC Prince, TA AF Macomb, DJ Finger, MH Harmon, BA Lamb, RC Prince, TA TI Discovery of pulsed X-ray emission from the small magellanic cloud transient RX J0117.6-7330 SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; stars : individual (RX J0117.6-7330); X-rays : general ID GAMMA-RAY; PULSARS; SMC AB We report on the detection of pulsed, broadband, X-ray emission from the transient source RX J0117.6-7330. The pulse period of 22 s is detected by the ROSAT/PSPC instrument in a 1992 September 30-October 2 observation and by the Compton Gamma-Ray Obselvatory/BATSE instrument during the same epoch. Hard X-ray pulsations are detectable by BATSE for approximately 100 days surrounding the ROSAT observation (1992 August 28-December 8). The total directly measured X-ray luminosity during the ROSAT observation is 1.0 x 10(38) (d/60 kpc)(2) ergs s(-1). The pulse frequency increases rapidly during the outburst, with a peak spin-up rate of 1.2 x 10(-10) Hz s(-1) and a total frequency change of 1.8%. The pulsed percentage is 11.3% from 0.1-2.5 keV, increasing to at least 78% in the 20-70 keV band. These results establish RX J0117.6-7330 as a transient Be binary system. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Astrophys Program, Greenbelt, MD USA. NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. CALTECH, Space Radiat Lab, Pasadena, CA 91125 USA. RP Macomb, DJ (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. NR 14 TC 22 Z9 22 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP L99 EP L102 DI 10.1086/312074 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211MA UT WOS:000081163800010 ER PT J AU Sahai, R Bujarrabal, V Zijlstra, A AF Sahai, R Bujarrabal, V Zijlstra, A TI A highly collimated bipolar outflow in a proto-planetary nebula: Hubble Space Telescope imaging of Hen 401 SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; planetary nebulae : general; stars : AGB and post-AGB; stars : mass loss ID MASS-LOSS; PROTOPLANETARY; EMISSION; EVOLUTION; OBJECTS; IMAGES; STARS; JETS; DUST; CO AB We have obtained high-resolution wide- and narrowband images of the bipolar proto-planetary nebula Hen 401 with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. Two very long (14." 5), cylindrical-shaped bipolar outflow lobes are seen in reflected light, each with a length/width ratio of approximate to 7, probably the largest seen in a proto-planetary nebula so far. The lobes are limb-brightened, indicating that they are optically thin to scattering. The central star, resolved for the first time from the surrounding nebulosity, is girdled by an equatorial torus and a bipolar skirtlike structure, both of which are coaxial with the lobes. A faint halo around the lobes marks the presence of an asymptotic giant branch (AGB) circumstellar envelope. We find H alpha emission from photoionized gas in the vicinity of the central star, and we tentatively detect two small shock-emitting blobs located along the nebular axis about +/-6." 2 from the central star. A comparison of the lobe morphology with theoretical models indicates that the highly collimated lobes of Hen 401 result from the momentum-driven shock interaction of a high-velocity bipolar jet with the circumstellar envelope of the progenitor AGB star. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Observ Astron Nacl, Alcala De Henares 28800, Spain. Univ Manchester, Inst Sci & Technol, Dept Phys, Manchester M60 1QD, Lancs, England. RP Sahai, R (reprint author), CALTECH, Jet Prop Lab, MS 183-900,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 32 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 JUN 20 PY 1999 VL 518 IS 2 BP L115 EP L118 DI 10.1086/312084 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211MA UT WOS:000081163800014 ER PT J AU Titarchuk, L Osherovich, V AF Titarchuk, L Osherovich, V TI Correlations between kilohertz quasi-periodic oscillations and low-frequency features attributed to radial oscillations and diffusive propagation in the viscous boundary layer around a neutron star SO ASTROPHYSICAL JOURNAL LA English DT Article DE accretion, accretion disks; diffusion; stars : individual (4U 1728-34; Scorpius X-1); stars : neutron; waves; X-rays : stars AB We present a dimensional analysis of two characteristic timescales in the boundary layer where the disk adjusts to the rotating neutron star (NS). The boundary layer is treated as a transition region between the NS surface and the first Keplerian orbit. The radial transport of the angular momentum in this layer is controlled by a viscous force defined by the Reynolds number, which in turn is related to the mass accretion rate. We show that the observed low-Lorentzian frequency is associated with radial oscillations in the boundary layer, where the observed break frequency is determined by the characteristic diffusion time of the inward motion of the matter in the accretion flow. Predictions of our model regarding relations between those two frequencies and the frequencies of kilohertz quasi-periodic oscillations (kHz QPOs) compare favorably with recent observations of the source 4U 1728-34. This Letter contains a theoretical classification of kHz QPOs in NS binaries and the related low-frequency features. Thus, results concerning the relationship between the low-lorentzian frequency of viscous oscillations and the break frequency are presented in the framework of our model of kHz QPOs viewed as Keplerian oscillations in a rotating frame of reference. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. George Mason Univ, Inst Computat Sci & Informat, Fairfax, VA 22030 USA. Raytheon Co, Informat Technol Serv, Lanham, MD 20706 USA. Raytheon Co, Sci Serv, Lanham, MD 20706 USA. RP Titarchuk, L (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 13 TC 91 Z9 91 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 JUN 20 PY 1999 VL 518 IS 2 BP L95 EP L98 DI 10.1086/312083 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211MA UT WOS:000081163800009 ER PT J AU Woods, PM Kouveliotou, C van Paradijs, J Finger, MH Thompson, C AF Woods, PM Kouveliotou, C van Paradijs, J Finger, MH Thompson, C TI BeppoSAX observations of SGR 1900+14 in quiescence and during an active period SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : general; stars : individual (SGR 1900+14); stars : neutron; X-rays : bursts ID MAGNETIZED NEUTRON-STARS; X-RAY PULSAR; SOFT GAMMA-REPEATERS; BURST; SGR-1900+14; TRANSIENT; DISCOVERY AB We present results from two BeppoSAX Narrow-Field Instrument observations of SGR 1900+14 made during a quiescent and an active period of the source. We detect pulsations in the 1997 May 12-13 observation (quiescence) at 5.157190(7) s and the 1998 September 15-16 observation (active period) at 5.160261(12) s. Using results recently reported by Hurley et al., we establish a long-term spin-down rate during quiescence of 5.82(2) x 10(-11) s s(-1), which implies a dipole magnetic field of similar to 5.5 x 10(14) G. We confirm deviations from a constant spin-down rate during the active period. We also find spectral similarities between SGR 1900+14 in quiescence and anomalous X-ray pulsars. C1 Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. Univ Space Res Assoc, Greenbelt, MD USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Univ Amsterdam, Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Univ N Carolina, Dept Phys & Astron, Chapel Hill, NC 27599 USA. RP Woods, PM (reprint author), Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. NR 38 TC 49 Z9 49 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 20 PY 1999 VL 518 IS 2 BP L103 EP L106 DI 10.1086/312085 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211MA UT WOS:000081163800011 ER PT J AU Grenfell, JL Harrison, RM Allen, AG Shi, JP Penkett, SA O'Dowd, CD Smith, MH Hill, MK Robertson, L Hewitt, CN Davison, B Lewis, AC Creasey, DJ Heard, DE Hebestreit, K Alicke, B James, J AF Grenfell, JL Harrison, RM Allen, AG Shi, JP Penkett, SA O'Dowd, CD Smith, MH Hill, MK Robertson, L Hewitt, CN Davison, B Lewis, AC Creasey, DJ Heard, DE Hebestreit, K Alicke, B James, J TI An analysis of rapid increases in condensation nuclei concentrations at a remote coastal site in western Ireland SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID PARTICLE FORMATION; DIMETHYL SULFIDE; ATMOSPHERIC SULFUR; SEASONAL-VARIATIONS; BOUNDARY-LAYER; UNITED-KINGDOM; MACE HEAD; AEROSOLS; ATLANTIC; TROPOSPHERE AB Massive "bursts" in condensation nuclei (CN) concentration were recorded at a remote site on the west Irish coast during campaigns in summer 1996 and spring/summer 1997. Number concentrations of 3-7 nm diameter CN were observed to rise daily from 10(2)-10(3) UP to similar to 10(5) /cm(3) for 1-3 hours. Data were collected as part of the Atmospheric Chemistry Studies in the Oceanic Environment program. In a previous paper the burst phenomenon was linked to the movement of the tide, and it was suggested that enhanced biogenic emissions occurred near low tide with concomitant rapid homogeneous gas phase CN formation. In this paper possible chemical mechanisms for the burst phenomenon are investigated. Two approaches are adopted. First, by assuming a 20:80 sulfate:water molar composition and calculating the number distribution using data from condensation particle counters, the total mass of CN formed during a burst is evaluated. This is compared with that mass of sulfate produced by OH-initiated dimethyl sulfide (DMS) oxidation, The procedure is termed "mass balance." Second, a variety of chemical species are coplotted with tidal height. DMS oxidation is not believed to play a major role in CN formation at this site because (1) the mass balance calculations imply ambient DMS concentrations higher than those observed, and (2) gas phase HCl, HNO3, SO2, and NH3 did not exhibit any discernible correlation with tidal height. Further, none of the suite of observed nonmethane hydrocarbons or DMS showed a tidal relation. No mechanism has to date been convincingly identified for the burst phenomenon. C1 Univ Birmingham, Inst Publ & Environm Hlth, Birmingham B15 2TT, W Midlands, England. Univ E Anglia, Sch Environm Sci, Norwich NR4 7TJ, Norfolk, England. Univ Sunderland, Sch Environm, Ctr Marine & Atmospher Sci, Sunderland SR2 7BW, England. Univ Lancaster, Inst Environm & Nat Sci, Lancaster LA1 4YQ, England. Univ Leeds, Ctr Environm, Leeds LS2 9JT, W Yorkshire, England. Univ Leeds, Sch Chem, Leeds LS2 9JT, W Yorkshire, England. Heidelberg Univ, Inst Umweltphys, D-69120 Heidelberg, Germany. RP Grenfell, JL (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Harrison, Roy/A-2256-2008; Lewis, Alastair/A-6721-2008; Hewitt, Charles Nicholas/B-1219-2009; OI Harrison, Roy/0000-0002-2684-5226; Lewis, Alastair/0000-0002-4075-3651; Hewitt, Charles Nicholas/0000-0001-7973-2666; Heard, Dwayne/0000-0002-0357-6238 NR 56 TC 35 Z9 36 U1 0 U2 5 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1999 VL 104 IS D11 BP 13771 EP 13780 DI 10.1029/1999JD900096 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 207BL UT WOS:000080915400005 ER PT J AU Adams, PJ Seinfeld, JH Koch, DM AF Adams, PJ Seinfeld, JH Koch, DM TI Global concentrations of tropospheric sulfate, nitrate, and ammonium aerosol simulated in a general circulation model SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Review ID ATMOSPHERIC EQUILIBRIUM-MODEL; NORTH-ATLANTIC OCEAN; ANTHROPOGENIC SULFATE; SULFUR CYCLE; THERMODYNAMIC MODEL; GREENHOUSE GASES; PACIFIC-OCEAN; NITRIC-ACID; CHEMICAL CHARACTERIZATION; 3-DIMENSIONAL MODEL AB Global sulfate aerosol composition is simulated online in the Goddard Institute for Space Studies general circulation model II' (GISS GCM II-prime). Four sulfur species, hydrogen peroxide, gas phase ammonia, and particulate ammonium are the prognostic tracer species, the emissions, transport, and deposition of which are explicitly simulated. Nitric acid fields are prescribed based on a global chemical transport model. An online thermodynamic equilibrium calculation determines the partitioning of ammonia and nitrate between gas and aerosol phases, and the quantity of aerosol water based on the temperature, relative humidity, and sulfate concentration in each GCM grid cell. The total global burden of sulfate, nitrate, ammonium, and aerosol water is 7.5 Tg and is most sensitive to changes in sulfur emissions. Tropospheric lifetimes for ammonium and ammonia are 4.2 and 0.9 days, respectively; the tropospheric ammonium burden is 0.30 Tg N, compared with 0.14 Tg N for ammonia. Simulated ammonium concentrations are generally within a factor of 2 of observations. Subgrid variability in measured concentrations hinders comparison of observations to predictions. Ammonium nitrate aerosol plays an important role in determining total aerosol mass in polluted continental areas. In the upper troposphere and near the poles, cold temperatures allow unneutralized nitric acid to condense into the aerosol phase. Acidic aerosol species tend to be neutralized by ammonia to a greater degree over continents than over oceans. The aerosol is most basic and gas phase ammonia concentrations are highest over India. Water uptake per mole of sulfate aerosol varies by two orders of magnitude because of changes in relative humidity and aerosol composition. Spatial variations in aerosol composition and water uptake have implications for direct and indirect aerosol radiative forcing. C1 CALTECH, Dept Chem Engn, Pasadena, CA 91125 USA. NASA, Goddard Inst Space Studies, New York, NY 10025 USA. RP Adams, PJ (reprint author), CALTECH, Dept Chem Engn, 1200 E Calif Blvd, Pasadena, CA 91125 USA. EM petera@cco.caltech.edu; seinfeld@cco.caltech.edu; koch@hess.geology.yale.edu RI Adams, Peter/D-7134-2013 OI Adams, Peter/0000-0003-0041-058X NR 117 TC 174 Z9 179 U1 2 U2 45 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1999 VL 104 IS D11 BP 13791 EP 13823 DI 10.1029/1999JD900083 PG 33 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 207BL UT WOS:000080915400007 ER PT J AU Lingenfelser, GS Grose, WL Remsberg, EE Fairlie, TD Pierce, RB AF Lingenfelser, GS Grose, WL Remsberg, EE Fairlie, TD Pierce, RB TI Comparison of satellite and in situ ozone measurements in the lower stratosphere SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID HALOGEN OCCULTATION EXPERIMENT; ATMOSPHERE RESEARCH SATELLITE; ASHOE/MAESA; PHOTOMETER; UARS AB An air parcel trajectory model with chemistry initialized using data obtained by the Halogen Occultation Experiment (HALOE) has been demonstrated to be an effective tool for studying chemical and transport processes in the lower stratosphere. One of the sources of the differences between the trajectory calculations and the in situ observations from instruments aboard the NASA ER-2 aircraft is the uncertainty in the initial HALOE data. We compared HALOE ozone (O-3) With near-coincident O-3 Obtained by the NOAA dual-beam UV-absorption photometer during the 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft campaign in a previous study. We have extended this study to obtain a more reliable evaluation of the differences in the remote and in situ O-3 data by increasing the statistical base and using a revised version of HALOE data. In the present study we have extended the comparisons of O-3 data to encompass four separate ER-2 airborne campaigns that have occurred since HALOE became operational in 1991. By extending the previous study to encompass the time span from 1991 through 1996, a broader range of latitude in both hemispheres, and a variety of seasons, we believe the conclusions resulting from the comparisons to be more robust and reliable. Statistical analyses show that the best agreement between HALOE and ER-2 O-3 occurs in the 50-70 mbar region, where the difference of the means and RMS differences between the data sets are less than 7% and 28%, respectively, and where the HALOE data have an estimated error greater than 18% but less than 30%. Differences are larger in the 70-100 mbar region, where the maximum mean and RMS differences are 20% and 50%, respectively. These differences are somewhat less than those determined in the previous study. C1 Sci Applicat Int Corp, NASA LaRC, Hampton, VA 23681 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. Sci & Technol Corp, NASA LaRC, Hampton, VA 23681 USA. RP Lingenfelser, GS (reprint author), Sci Applicat Int Corp, NASA LaRC, MS 401B, Hampton, VA 23681 USA. EM g.s.lingenfelser@larc.nasa.gov RI Pierce, Robert Bradley/F-5609-2010 OI Pierce, Robert Bradley/0000-0002-2767-1643 NR 12 TC 3 Z9 3 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1999 VL 104 IS D11 BP 13971 EP 13979 DI 10.1029/1999JD900179 PG 9 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 207BL UT WOS:000080915400019 ER PT J AU Dessler, AE Wu, J Santee, ML Schoeberl, MR AF Dessler, AE Wu, J Santee, ML Schoeberl, MR TI Satellite observations of temporary and irreversible denitrification SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES LA English DT Article ID POLAR STRATOSPHERIC CLOUDS; ATMOSPHERE RESEARCH SATELLITE; NITRIC-ACID TRIHYDRATE; REACTIVE NITROGEN; OZONE DEPLETION; 1-D MODEL; VORTEX; HNO3; AEROSOLS; WINTER AB We have investigated temporary and irreversible denitrification in the polar regions. We find that the formation of type I polar stratospheric clouds (PSCs) in both hemispheres is best described by a supercooled ternary solution model. Considering the uncertainties in the analysis, our results are also consistent with a nitric acid dihydrate composition for type I PSCs, but not a nitric acid trihydrate composition. In the Northern Hemisphere, we observe that an upper limit of 17% of HNO3 is irreversibly lost each time the temperature of an air mass drops below similar to 190 K. It seems likely that in order to remove a significant fraction of the HNO3 from an air mass in the Northern Hemisphere, one must expose it to low temperatures multiple times. C1 Univ Maryland, Dept Meteorol, College Pk, MD 20742 USA. Univ Maryland, Earth Syst Sci Interdisciplinary Ctr, College Pk, MD 20742 USA. NASA, Jet Prop Lab, Pasadena, CA 91109 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 47 TC 20 Z9 19 U1 0 U2 0 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-897X J9 J GEOPHYS RES-ATMOS JI J. Geophys. Res.-Atmos. PD JUN 20 PY 1999 VL 104 IS D11 BP 13993 EP 14002 DI 10.1029/1999JD900133 PG 10 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 207BL UT WOS:000080915400021 ER PT J AU Sternberg, R Szopa, C Coscia, D Zubrzycki, S Raulin, F Vidal-Madjar, C Niemann, H Israel, G AF Sternberg, R Szopa, C Coscia, D Zubrzycki, S Raulin, F Vidal-Madjar, C Niemann, H Israel, G TI Gas chromatography in space exploration - Capillary and micropacked columns for in situ analysis of Titan's atmosphere SO JOURNAL OF CHROMATOGRAPHY A LA English DT Article; Proceedings Paper CT 22nd International Symposium on Chromatography CY SEP 13-18, 1998 CL ROME, ITALY DE capillary columns; stationary phases; GC; Titan's atmosphere; hydrocarbons; nitriles ID MOLECULAR-WEIGHT HYDROCARBONS; PERMANENT GASES; ORGANIC-CHEMISTRY; LOW-TEMPERATURE; NITRILES; HUYGENS AB The gas chromatography-mass spectrometry (GC-MS) experiment using capillary and micropacked columns is one of the main instruments of the Huygens probe of the Cassini-Huygens mission launched in October 1997 for the in situ analysis of Titan's atmosphere. Because of its composition and density the study of the atmosphere of Titan is of primary interest for understanding the prebiotic chemistry in the primitive Earth's environment. We describe here the GC subsystem of the GC-MS instrument with a particular emphasis on its exobiological implications. The GC subsystem includes three columns which operate in parallel: a carbon molecular sieve micropacked column is used for the separation of CO, N-2 and other permanent gases; a capillary column will separate the light hydrocarbons up to C-3; a second capillary column with a cyanopropyl dimethyl polysiloxane stationary phase will analyze the C-4-C-8 hydrocarbons and the low-molecular mass nitriles up to C-4. These heavier compounds will mainly result from the pyrolysis of the aerosols present in the atmosphere of Titan by using the aerosol collector pyrolyser instrument. (C) 1999 Published by Elsevier Science B.V. All rights reserved. C1 Univ Paris 07, LISA, F-94010 Creteil, France. Univ Paris 12, CNRS UMR 7583, F-94010 Creteil, France. CNRS UMR 7581, Lab Rech Polymeres, F-94320 Thiais, France. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. CNRS, Serv Aeron, F-91371 Verrieres Buisson, France. RP Sternberg, R (reprint author), Univ Paris 07, LISA, F-94010 Creteil, France. RI szopa, cyril/C-6865-2015 OI szopa, cyril/0000-0002-0090-4056 NR 23 TC 25 Z9 25 U1 0 U2 8 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0021-9673 J9 J CHROMATOGR A JI J. Chromatogr. A PD JUN 18 PY 1999 VL 846 IS 1-2 BP 307 EP 315 DI 10.1016/S0021-9673(99)00254-X PG 9 WC Biochemical Research Methods; Chemistry, Analytical SC Biochemistry & Molecular Biology; Chemistry GA 210PM UT WOS:000081113900037 ER PT J AU DiSanti, MA Mumma, MJ Dello Russo, N Magee-Sauer, K Novak, R Rettig, TW AF DiSanti, MA Mumma, MJ Dello Russo, N Magee-Sauer, K Novak, R Rettig, TW TI Identification of two sources of carbon monoxide in comet Hale-Bopp SO NATURE LA English DT Article ID PLANETARY-ATMOSPHERES; HALLEY; P/HALLEY; MODEL; GAS; CO; EVOLUTION; TIME; DUST AB The composition of ices in comets may reflect that of the molecular cloud in which the Sun formed, or it may show evidence of chemical processing in the pre-planetary accretion disk around the proto-Sun. As carbon monoxide (CO) is ubiquitous in molecular clouds(1,2), its abundance with respect to water could help to determine the degree to which pre-cometary material was processed, although variations in CO abundance may also be influenced by the distance from the Sun at which comets formed(3-5). Observations have not hitherto provided an unambiguous measure of CO in the cometary ice (native CO). Evidence for an extended source of CO associated with comet Halley was provided by the Giotto spacecraft(6-9), but alternative interpretations exist(10). Here we report observations of comet Hale-Bopp which show that about half of the CO in the comet comes directly from ice stored in the nucleus. The abundance of this CO with respect to water (12 per cent) is smaller than in quiescent regions of molecular clouds, but is consistent with that measured in proto-stellar envelopes(11), suggesting that the ices underwent some processing before their inclusion into Hale-Bopp. The remaining CO arises in the coma, probably through thermal destruction of more complex molecules. C1 Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Rowan Univ, Dept Chem & Phys, Glassboro, NJ 08028 USA. Iona Coll, Dept Phys, New Rochelle, NY 10801 USA. Univ Notre Dame, Dept Phys & Astron, Notre Dame, IN 46556 USA. RP DiSanti, MA (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. 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 32 TC 75 Z9 75 U1 0 U2 1 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUN 17 PY 1999 VL 399 IS 6737 BP 662 EP 665 DI 10.1038/21378 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 207JB UT WOS:000080932800051 PM 10385117 ER PT J AU Frey, H Sakimoto, SEH Roark, JH AF Frey, H Sakimoto, SEH Roark, JH TI Discovery of a 450 km diameter, multi-ring basin on Mars through analysis of MOLA topographic data SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID IMPACT BASINS AB Mars Orbiter Laser Altimeter (MOLA) topographic data have revealed a previously unknown, 450 km wide, 2 km deep basin centered at 30N, 312W near the Phison Rupes. This basin, as large as and deeper than the obvious Cassini impact basin located 1000 km to the SW, is not apparent in the existing but good quality Viking imagery. Gridded MOLA data show the feature as a dosed depression. Based on analysis of slope breaks readily visible in two MOLA profiles, we suggest this Phison Rupes Basin has three topographic rings with diameters approximately 350, 455 and 670 km. These rings outline a region of lower impact crater density and smoother inter-crater plains. Similar previously unknown features may exist elsewhere on Mars, and MOLA topographic data may be able to locate them. C1 NASA, Goddard Space Flight Ctr, Geodynam Branch, USRA, Greenbelt, MD 20771 USA. NASA, Goddard Space Flight Ctr, Geodynam Branch, SSAI, Greenbelt, MD 20771 USA. RP Frey, H (reprint author), NASA, Goddard Space Flight Ctr, Geodynam Branch, USRA, Greenbelt, MD 20771 USA. NR 16 TC 15 Z9 15 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUN 15 PY 1999 VL 26 IS 12 BP 1657 EP 1660 DI 10.1029/1999GL900357 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 207DT UT WOS:000080920700004 ER PT J AU Burton, SP Thomason, LW Sasano, Y Hayashida, S AF Burton, SP Thomason, LW Sasano, Y Hayashida, S TI Comparison of aerosol extinction measurement by ILAS and SAGE II SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Seventy-three pairs of nearly coincident profiles of aerosol extinction at visible wavelengths from the Improved Limb Atmospheric Spectrometer (Version 3.1) and the Stratospheric Aerosol and Gas Experiment (SAGE) II (Version 5.931) are compared for a week in January and February 1997. The comparisons require an interpolation of SAGE Il multi-wavelength aerosol extinction profiles to compensate for the difference between the measurement wavelengths of the two instruments. The profiles are shown to agree within ten percent for the altitude range from approximately 15 to 24 km, with a small systematic bias that requires further study. C1 NASA, Langley Res Ctr, Div Atmospher Sci, Hampton, VA 23681 USA. Sci Applicat Int Corp, Hampton, VA USA. Natl Inst Environm Studies, Tsukuba, Ibaraki, Japan. Nara Womens Univ, Fac Sci, Nara 6308506, Japan. RP Burton, SP (reprint author), NASA, Langley Res Ctr, Div Atmospher Sci, Mail Stop 475, Hampton, VA 23681 USA. EM s.p.burton@larc.nasa.gov; l.w.thomason@larc.nasa.gov; sasano@nies.go.jp; sachiko@ics.nara-wu.ac.jp RI Sasano, Yasuhiro/C-2927-2009; OI Sasano, Yasuhiro/0000-0001-7470-5642; Thomason, Larry/0000-0002-1902-0840 NR 6 TC 10 Z9 11 U1 1 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUN 15 PY 1999 VL 26 IS 12 BP 1719 EP 1722 DI 10.1029/1999GL900359 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 207DT UT WOS:000080920700020 ER PT J AU Bergstrom, RM Russell, PB AF Bergstrom, RM Russell, PB TI Estimation of aerosol direct radiative effects over the mid-latitude North Atlantic from satellite and in situ measurements SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID OPTICAL-THICKNESS; SULFATE AEROSOLS; BLACK CARBON; MODEL AB We estimate solar radiative flux changes due to aerosols over the mid-latitude North Atlantic by combining optical depths from AVHRR measurements with aerosol properties from the recent TARFOX program. Results show that, over the ocean, the aerosol decreases the net radiative flux at the tropopause and therefore has a cooling effect. Cloud-free, 24-hour average flux changes range from -9 W/m(2) near the eastern US coast in summer to -1 W/m(2) in the mid-Atlantic during winter. Cloud-free North Atlantic regional averages range from -5.1 W/m(2) in summer to -1.7 W/m(2) in winter, with an annual average of -3.5 W/m(2). Cloud effects, estimated from ISCCP data, reduce the regional annual average to -0.8 W/m(2). All values are for the moderately absorbing TARFOX aerosol (omega(0.55 mu m) = 0.9); values for a nonabsorbing aerosol are similar to 30% more negative. We compare our results to a variety of other calculations of aerosol radiative effects. C1 Bay Area Environm Res Inst, San Francisco, CA 94122 USA. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Bergstrom, RM (reprint author), Bay Area Environm Res Inst, 3430 Noriega, San Francisco, CA 94122 USA. NR 25 TC 20 Z9 23 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 JUN 15 PY 1999 VL 26 IS 12 BP 1731 EP 1734 DI 10.1029/1999GL900330 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 207DT UT WOS:000080920700023 ER PT J AU Lau, KM Wu, HT AF Lau, KM Wu, HT TI Assessment of the impacts of the 1997-98 El Nino on the Asian-Australia monsoon SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article AB Singular Value Decomposition (SVD) analyses of rainfall and sea surface temperature (SST) are carried out globally over the entire tropics and regionally over the Asia-Australian (AA)-monsoon domain. Contributions to monsoon rainfall predictability by basin-scale SST forcing and regional SST coupling are evaluated from cumulative anomaly correlation with dominant regional SVD modes. The observed 1997-98 AA-monsoon anomalies are found to be very complex with approximately 34% of the anomalies of the Asian (boreal) summer monsoon and 74% of the Australia (austral) monsoon attributable to basin-scale SST influence associated with El Nino. For the boreal and austral monsoon respectively, regional coupled processes contribute an additional 19% and 10%, leaving about 47% and 16% due to other factors including high frequency transients. Results suggest that in order to improve seasonal-to-interannual predictability of the AA-monsoon, we need to investigate and exploit not only monsoon-Fl Nino relationship, but also intrinsic monsoon regional coupled processes. C1 NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Greenbelt, MD 20771 USA. RP Lau, KM (reprint author), NASA, Goddard Space Flight Ctr, Climate & Radiat Branch, Code 661, Greenbelt, MD 20771 USA. NR 6 TC 28 Z9 31 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 JUN 15 PY 1999 VL 26 IS 12 BP 1747 EP 1750 DI 10.1029/1999GL900307 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 207DT UT WOS:000080920700027 ER PT J AU Wright, R Rothery, DA Blake, S Harris, AJL Pieri, DC AF Wright, R Rothery, DA Blake, S Harris, AJL Pieri, DC TI Simulating the response of the EOS Terra ASTER sensor to high-temperature volcanic targets SO GEOPHYSICAL RESEARCH LETTERS LA English DT Article ID PREFLIGHT AB Infrared satellite data provide information regarding the thermal state and nature of activity at active volcanoes. Such radiometry has been hampered, however, by the tendency of many currently operational sensors to saturate over high-radiance targets. Here the simulated response of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to high-temperature volcanic features is presented and compared to that of the Landsat Thematic Mapper (TM), which has provided the bulk of useful data since the mid 1980's. We find that ASTER's improved spectral resolution and increased dynamic range will markedly reduce the problem of sensor saturation common in TM-based studies, thus providing valuable data previously unavailable. Saturation will still occur however, when the fractional area of high-temperature (similar to 1000 degrees C) material approaches similar to 1% (similar to 9 m(2)) of ASTER's 30-m short-wave infrared pixels. C1 Open Univ, Dept Earth Sci, Milton Keynes MK7 6AA, Bucks, England. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Univ Hawaii, SOEST, HIGP, Honolulu, HI 96822 USA. RP Wright, R (reprint author), Open Univ, Dept Earth Sci, Walton Hall, Milton Keynes MK7 6AA, Bucks, England. NR 9 TC 17 Z9 19 U1 0 U2 2 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 0094-8276 J9 GEOPHYS RES LETT JI Geophys. Res. Lett. PD JUN 15 PY 1999 VL 26 IS 12 BP 1773 EP 1776 DI 10.1029/1999GL900360 PG 4 WC Geosciences, Multidisciplinary SC Geology GA 207DT UT WOS:000080920700034 ER PT J AU Smelyanskiy, VN Dykman, MI Rabitz, H Vugmeister, BE Bernasek, SL Bocarsly, AB AF Smelyanskiy, VN Dykman, MI Rabitz, H Vugmeister, BE Bernasek, SL Bocarsly, AB TI Nucleation in periodically driven electrochemical systems SO JOURNAL OF CHEMICAL PHYSICS LA English DT Article ID DISSIPATIVE DYNAMICAL-SYSTEMS; FOKKER-PLANCK MODELS; WEAK-NOISE LIMIT; LARGE FLUCTUATIONS; TRANSIENT NUCLEATION; SINGULAR FEATURES; GROWTH; TIME; DEPOSITION; BEHAVIOR AB We calculate both the exponent and the prefactor in the nucleation rate of a periodically driven system. Nucleation dynamics is described by the Fokker-Planck equation for the probability distribution of the nuclei over their size. This distribution is found using the concept of the most probable (optimal) nucleation path. The results apply in a broad range of driving force amplitudes, from weak to moderately strong forces where the nucleation rate is changed exponentially strongly, and also in the broad range of the driving frequencies, from low-frequency driving, where the system follows the force adiabatically, to high-frequency nonadiabatic driving. For strong driving forces, the time dependence of the nucleation rate changes from strongly nonsinusoidal to a weak with the increasing frequency of driving. The response of the nucleation rate to the driving force is described in terms of logarithmic susceptibility (LS), which can be obtained from the optimal nucleation path in the absence of the driving. LS is a smooth function of frequency, and therefore even a driving force with comparatively high frequency can change the modulation rate exponentially strongly. LS and the Faraday current are calculated for simple models of electrochemical systems, where the ac driving is produced by modulation of the electrode potential. We also suggest how to find LS from measurements of the average nucleation rate. (C) 1999 American Institute of Physics. [S0021-9606(99)50121-9]. C1 NASA, Caelum Res Corp, Ames Res Ctr, Moffett Field, CA 94035 USA. Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA. Princeton Univ, Dept Chem, Princeton, NJ 08544 USA. RP Smelyanskiy, VN (reprint author), NASA, Caelum Res Corp, Ames Res Ctr, MS 269-2, Moffett Field, CA 94035 USA. NR 48 TC 21 Z9 21 U1 2 U2 2 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 JUN 15 PY 1999 VL 110 IS 23 BP 11488 EP 11504 DI 10.1063/1.479090 PG 17 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 200CH UT WOS:000080521200044 ER PT J AU Li, XJ Chang, P AF Li, XJ Chang, P TI Mixing induced by the Atlantic equatorial wave activity in an eddy-resolving OGCM SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID NORTH BRAZIL CURRENT; CIRCULATION; MODEL; OCEAN; PROPAGATION; VARIABILITY; SIMULATION; TRANSPORT; PACIFIC AB The variability of equatorial circulation in the middepth Atlantic Ocean from an eddy-resolving ocean general circulation model (OGCM) was analyzed. Four types of equatorially trapped waves were identified which dominate the variability of the circulation: an annual Rossby wave, a semiannual Rossby wave, a group of 40- to 60-day short Rossby waves, and a group of 30-day Yanai waves. In particular, the 40- to 60-day short Rossby waves were found near the western boundary to the north of the equator, which may be related to nonlinear instability processes associated with the north Brazil current (NBC) retroflection. The wave-induced stirring and transport along the equator was investigated by calculating the trajectories of a large ensemble of particles in the middepth equatorial Atlantic Ocean from the eddy-resolving, model-simulated velocity field. The distribution of finite-time Lyapunov exponents derived from the simulated velocity at a depth of similar to 2000 m bears a close resemblence to the observed CFC tongue, suggesting that the wave-induced chaotic stirring and transport may contribute to the formation of the observed CFC tongue in the middepth equatorial Atlantic Ocean along the equator. C1 Texas A&M Univ, Dept Oceanog, College Stn, TX 77843 USA. RP Li, XJ (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,MS 300-323, Pasadena, CA 91109 USA. RI Chang, Ping /A-1642-2013 OI Chang, Ping /0000-0002-9085-0759 NR 38 TC 4 Z9 4 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 JUN 15 PY 1999 VL 104 IS C6 BP 13303 EP 13315 DI 10.1029/1999JC900069 PG 13 WC Oceanography SC Oceanography GA 207BF UT WOS:000080914900004 ER PT J AU Shulman, I Lewis, JK Mayer, JG AF Shulman, I Lewis, JK Mayer, JG TI Local data assimilation in the estimation of barotropic and baroclinic open boundary conditions SO JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS LA English DT Article ID OPEN-OCEAN FLOWS; MODEL; DYNAMICS AB The problem of data assimilation in the specification of open boundary conditions for limited area models is addressed in this paper. Optimization approaches are detailed, which are based on combining available data on an open boundary with the physics of the hydrodynamical model. In our case the physics is in terms of the flux of energy through the open boundary. These optimized boundary conditions, for both barotropic and baroclinic situations, interpreted physically as special Linearizations of the Bernoulli equation for each normal mode. Because of the complexity of decomposing variables into normal modes for open boundaries with varying bathymetry, we present two alter native approaches. The first is a simplification of the optimized baroclinic boundary condition based on normal modes. The second makes use of empirical orthogonal functions instead of normal modes. The results of testing and comparisons of these approaches are presented for coupling coarse- and fine-resolution models. In this case our approach is in assimilating values and variables from a large-scale model. (along the open boundaries of a limited area model). In the proposed coupling schemes the energy fluxes are estimated either from coarse or from fine-grid model results. With the progress of oceanographic observing systems we would like to explore ways of combining model outputs with the oceanographic measurements in order to estimate energy fluxes used in optimized open boundary conditions. C1 Univ So Mississippi, Inst Marine Sci, Stennis Space Ctr, Hattiesburg, MS 39406 USA. Ocean Phys Res & Dev, Long Beach, MI USA. Univ So Mississippi, Dept Comp Sci, Hattiesburg, MS 39406 USA. RP Shulman, I (reprint author), Univ So Mississippi, Inst Marine Sci, Stennis Space Ctr, Bldg 1103,Room 249, Hattiesburg, MS 39406 USA. NR 30 TC 7 Z9 7 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 JUN 15 PY 1999 VL 104 IS C6 BP 13667 EP 13680 DI 10.1029/1999JC900022 PG 14 WC Oceanography SC Oceanography GA 207BF UT WOS:000080914900028 ER PT J AU Shindell, DT Rind, D Balachandran, N AF Shindell, DT Rind, D Balachandran, N TI Interannual variability of the Antarctic ozone hole in a GCM. Part II: A comparison of unforced and QBO-induced variability SO JOURNAL OF THE ATMOSPHERIC SCIENCES LA English DT Article ID QUASI-BIENNIAL OSCILLATION; NORTHERN-HEMISPHERE WINTER; GROUND-BASED OBSERVATIONS; MIDDLE ATMOSPHERE MODEL; PLANETARY-WAVES; CLIMATE-CHANGE; CIRCULATION; DEPLETION; STRATOSPHERE; MODULATION AB Simulations were performed with the Goddard Institute for Space Studies GCM including a prescribed quasibiennial oscillation (QBO), applied at a constant maximum value, and a physically realistic parameterization of the heterogeneous chemistry responsible for severe polar ozone loss. While the QBO is primarily a stratospheric phenomenon, in this model the QBO modulates the amount and propagation of planetary wave energy in the troposphere as well as in the stratosphere. Dynamical activity is greater in the easterly than in the unforced case. while westerly years are dynamically more quiescent. By altering zonal winds and potential vorticity, the QBO forcing changes the refraction of planetary waves beginning in midwinter, causing the lower-stratospheric zonal average temperatures at Southern Hemisphere high latitudes to be similar to 3-5 K warmer in the easterly phase than in the westerly during the late winter and early spring. Ozone loss varies nonlinearly with temperature, due to the sharp threshold for formation of heterogeneous chemistry surfaces, so that the mean daily total mass of ozone depleted in this region during September was 8.7 X 10(10) kg in the QBO easterly maximum, as compared with 12.0 X 10(10) kg; in the westerly maximum and 10.3 x 10(10) kp in the unforced case. Through this mechanism, the midwinter divergence of the Eliassen-Palm flux is well correlated with the subsequent springtime total ozone loss (R-2: = 0.6). The chemical ozone loss differences are much larger than QBO-induced transport differences in our model. Inclusion of the QBO forcing also increased the maximum variability in total ozone loss from the similar to 20% value found in the unforced runs to similar to 50%. These large variations in ozone depletion are very similar in size to the largest observed variations in the severity of the ozone hole. The results suggest that both random variability and periodic QBO forcing are important components, perhaps explaining some of the difficulties encountered in previous attempts to correlate the severity of the ozone hole with the QBO phase. C1 Columbia Univ, NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. RP Shindell, DT (reprint author), Columbia Univ, NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Shindell, Drew/D-4636-2012 NR 30 TC 8 Z9 8 U1 0 U2 0 PU AMER METEOROLOGICAL SOC PI BOSTON PA 45 BEACON ST, BOSTON, MA 02108-3693 USA SN 0022-4928 J9 J ATMOS SCI JI J. Atmos. Sci. PD JUN 15 PY 1999 VL 56 IS 12 BP 1873 EP 1884 DI 10.1175/1520-0469(1999)056<1873:IVOTAO>2.0.CO;2 PG 12 WC Meteorology & Atmospheric Sciences SC Meteorology & Atmospheric Sciences GA 210ZR UT WOS:000081135900007 ER PT J AU Collins, SD Smith, RL Gonzalez, C Stewart, KP Hagopian, JG Sirota, JM AF Collins, SD Smith, RL Gonzalez, C Stewart, KP Hagopian, JG Sirota, JM TI Fourier-transform optical microsystems SO OPTICS LETTERS LA English DT Article ID FIBEROPTIC SWITCH; MICROJOINERY AB The design, fabrication, and initial characterization of a miniature single-pass Fourier-transform spectrometer (FTS) that has an optical bench that measures 1 cm x 5 cm x 10 cm is presented. The FTS is predicated on the classic Michelson interferometer design with a moving mirror. Precision translation of the mirror is accomplished by microfabrication of dovetailed bearing surfaces along single-crystal planes in silicon. Although it is miniaturized, the FTS maintains a relatively high spectral resolution, 0.1 cm(-1), with adequate optical throughput. (C) 1999 Optical Society of America. C1 Univ Calif Davis, Dept Elect & Comp Engn, Microinstruments & Syst Lab, Davis, CA 95616 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Maryland Baltimore Cty, Joint Ctr Earth Syst Technol, Baltimore, MD 21250 USA. RP Collins, SD (reprint author), Univ Calif Davis, Dept Elect & Comp Engn, Microinstruments & Syst Lab, Davis, CA 95616 USA. RI Smith, Rosemary/H-7359-2015; Collins, Scott/A-5806-2016 OI Smith, Rosemary/0000-0001-8483-6777; Collins, Scott/0000-0003-0204-5109 NR 8 TC 50 Z9 51 U1 1 U2 4 PU OPTICAL SOC AMER PI WASHINGTON PA 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA SN 0146-9592 J9 OPT LETT JI Opt. Lett. PD JUN 15 PY 1999 VL 24 IS 12 BP 844 EP 846 DI 10.1364/OL.24.000844 PG 3 WC Optics SC Optics GA 208FK UT WOS:000080980000018 PM 11543549 ER PT J AU Yamada, T Bauschlicher, CW Partridge, H AF Yamada, T Bauschlicher, CW Partridge, H TI Substrate for atomic chain electronics SO PHYSICAL REVIEW B LA English DT Article ID SCANNING TUNNELING MICROSCOPE; SURFACE; STM; SCALE; WIRES AB A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studies theoretically. Since the van der Waals force turns out inappropriately weak, adatoms have to be secured with chemical bonding to the substrate atoms, but then electronic isolation between the adatom and substrate systems is not always guaranteed. A chain model shows that good isolation is expected on an s-p crossing substrate such as Si, Ge, or GaAs through surface localization, reflecting the bulk nature of the substrate. Isolation is better if adatoms are electronically similar to the substrate atoms, and can be manipulated by hydrogenation. Chain structures with group IV adatoms with two chemical bonds, or group III adatoms with one chemical bond, are semiconducting, reflecting the surface nature of the substrate. These structures are unintentionally doped due to the charge transfer across the chemical bonds. Physical properties of adatom chains have to be considered for the unified adatom and substrate systems. C1 NASA, Ames Res Ctr, MRJ, Moffett Field, CA 94035 USA. NASA, Ames Res Ctr, STC 2303, Moffett Field, CA 94035 USA. RP Yamada, T (reprint author), NASA, Ames Res Ctr, MRJ, T27A-1, Moffett Field, CA 94035 USA. EM yamada@nas.nasa.gov RI Yamada, Toshishige/E-7834-2012 OI Yamada, Toshishige/0000-0001-7145-9212 NR 34 TC 11 Z9 11 U1 0 U2 1 PU AMER PHYSICAL SOC PI COLLEGE PK PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA SN 1098-0121 EI 1550-235X J9 PHYS REV B JI Phys. Rev. B PD JUN 15 PY 1999 VL 59 IS 23 BP 15430 EP 15436 DI 10.1103/PhysRevB.59.15430 PG 7 WC Physics, Condensed Matter SC Physics GA 210ZB UT WOS:000081134500085 ER PT J AU Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M De Marzo, C Grimani, C Finetti, N Papini, P Piccardi, S Spillantini, P Ricci, M Castolino, M De Pascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ AF Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M De Marzo, C Grimani, C Finetti, N Papini, P Piccardi, S Spillantini, P Ricci, M Castolino, M De Pascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ TI New measurement of the flux of atmospheric muons SO PHYSICAL REVIEW LETTERS LA English DT Article ID CAPRICE-RICH DETECTOR; COSMIC-RAY; NEUTRINO; PERFORMANCE; SPECTROMETER AB We report a new measurement of the momentum spectra of both positive and negative muons as a function of atmospheric depth in the momentum range 0.3-2 and 0.3-40 GeV/c, respectively. The measured flux values have been compared with the spectra obtained from simulations, which were carried out to interpret the atmospheric neutrino data. We find that our data disagree with the results from the simulations. The ratio of the flux of muons derived from simulations to that measured is at largest 1.8 and varies with atmospheric depth and muon momentum. C1 Royal Inst Technol, KTH, S-10405 Stockholm, Sweden. Ctr Rech Nucl, F-67037 Strasbourg, France. Univ Gesamthsch Siegen, D-57068 Siegen, Germany. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Univ Bari, Dipartmento Fis, I-70126 Bari, Italy. Ist Nazl Fis Nucl, Sez Bari, I-70126 Bari, Italy. Univ Urbino, Dipartimento Fis, I-60129 Urbino, Italy. Univ Florence, Dipartimento Fis, I-50125 Florence, Italy. Ist Nazl Fis Nucl, Sez Firenze, I-50125 Florence, Italy. Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy. Univ Rome, Dipartimento Fis, I-00133 Rome, Italy. Ist Nazl Fis Nucl, Sez Roma, I-00133 Rome, Italy. Univ Trieste, Dipartimento Fis, I-34147 Trieste, Italy. Ist Nazl Fis Nucl, Sez Trieste, I-34147 Trieste, Italy. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. RP Boezio, M (reprint author), Royal Inst Technol, KTH, S-10405 Stockholm, Sweden. RI Cafagna, Francesco/A-9299-2010; Morselli, Aldo/G-6769-2011; Castellano, Marcello/J-3428-2012; Vacchi, Andrea/C-1291-2010; OI Cafagna, Francesco/0000-0002-7450-4784; Morselli, Aldo/0000-0002-7704-9553; Castellano, Marcello/0000-0002-4211-2903; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981 NR 33 TC 33 Z9 33 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 JUN 14 PY 1999 VL 82 IS 24 BP 4757 EP 4760 DI 10.1103/PhysRevLett.82.4757 PG 4 WC Physics, Multidisciplinary SC Physics GA 205CT UT WOS:000080804300006 ER PT J AU Thayumanavan, S Mendez, J Marder, SR AF Thayumanavan, S Mendez, J Marder, SR TI Synthesis of functionalized organic second-order nonlinear optical chromophores for electrooptic applications SO JOURNAL OF ORGANIC CHEMISTRY LA English DT Article ID BOND-LENGTH ALTERNATION; SIDE-CHAIN POLYIMIDES; DONOR-ACCEPTOR POLYENES; THERMAL STABILITIES; AROMATIC POLYIMIDES; 2ND-HARMONIC GENERATION; POLED POLYMER; DESIGN; FILMS; HYPERPOLARIZABILITIES AB The design and syntheses of functionalized second-order nonlinear optical chromophores, suitable for covalent incorporation into functionalized high-performance polymers, are described. The chromophores with hydroxy alkyl functionality have diarylamino groups as the donor moiety and a styryl thiophene moiety as the conjugated bridge. The triarylamine parts of the molecules were synthesized using palladium-catalyzed C-N bond forming reactions. The conjugated bridge was assembled using the Wittig reaction. The acceptor groups were installed in the last steps of the syntheses. C1 CALTECH, Beckman Inst, Pasadena, CA 91125 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91125 USA. Univ Arizona, Dept Chem, Tucson, AZ 85721 USA. RP Marder, SR (reprint author), CALTECH, Beckman Inst, 139-74, Pasadena, CA 91125 USA. OI Thayumanavan, S/0000-0002-6475-6726 NR 58 TC 50 Z9 51 U1 1 U2 7 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0022-3263 J9 J ORG CHEM JI J. Org. Chem. PD JUN 11 PY 1999 VL 64 IS 12 BP 4289 EP 4297 DI 10.1021/jo981707v PG 9 WC Chemistry, Organic SC Chemistry GA 205YQ UT WOS:000080849000013 ER PT J AU Loewenstein, M White, RE AF Loewenstein, M White, RE TI Prevalence and properties of dark matter in elliptical galaxies SO ASTROPHYSICAL JOURNAL LA English DT Article DE dark matter; galaxies : elliptical and lenticular, cD ID X-RAY-EMISSION; LUMINOSITY FUNCTION; REDSHIFT SURVEY; MASS; EVOLUTION; CLUSTERS; HALOS; ABUNDANCES; NGC-4472; SAMPLE AB Given the recently deduced relationship between X-ray temperatures and stellar velocity dispersions (the T-sigma relation) in an optically complete sample of elliptical galaxies (see recent work of Davis & White), we demonstrate that L > L-* elliptical galaxies contain substantial amounts of dark matter in general. We present constraints on the dark matter scale length and on the dark-to-luminous mass ratio within the optical half-light radius and within the entire galaxy. For example, we find that minimum values of dark matter core radii scale as r(dm) > 4(L-V/3L(*))(3/4) h(80)(-1) kpc and that the minimum dark matter mass fraction is greater than or similar to 20% within one optical effective radius r(e) and is greater than or similar to 39%-85% within 6r(e), depending on the stellar density profile and observed value of beta(spec). We also confirm the prediction of Davis & White that the dark matter is characterized by velocity dispersions that are greater than those of the luminous stars: sigma(dm)(2) approximate to 1.4-2 sigma(*)(2). The T-sigma relation implies a nearly constant mass-to-light ratio within six half-light radii: M/L-V approximate to 25 h(80) M./L-V.. This conflicts with the simplest extension of cold dark matter theories of large-scale structure formation to galactic scales; we consider several modifications that can better account for the observed T-sigma relation. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, 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, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 38 TC 73 Z9 73 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 JUN 10 PY 1999 VL 518 IS 1 BP 50 EP 63 DI 10.1086/307256 PN 1 PG 14 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211JZ UT WOS:000081158600005 ER PT J AU Haiman, Z Spaans, M AF Haiman, Z Spaans, M TI Models for dusty Ly alpha emitters at high redshift SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : evolution; galaxies : ISM; galaxies : stellar content; stars : formation; ultraviolet : galaxies ID RESONANCE-LINE RADIATION; STAR-FORMING GALAXIES; GUNN-PETERSON TROUGH; PRIMEVAL GALAXIES; COSMOLOGICAL CONSTANT; INTERGALACTIC MEDIUM; DISK GALAXIES; REIONIZATION; EMISSION; UNIVERSE AB Models are presented for the Ly alpha emission of dusty high-redshift galaxies by combining the Press-Schechter formalism with a treatment of the inhomogeneous dust distribution inside galaxies. It is found that the amount of Ly alpha radiation escaping from the galaxies strongly depends on the time over which the dust is produced through stellar activity and on the ambient inhomogeneity of the H II regions that surround the ionizing OB stars. Good agreement is found with recent observations, as well as with previous nondetections. Although a detailed determination of the individual model parameters is precluded by uncertainties, we find that (1) the dust content in primordial galaxies builds up in no more than similar to 5 x 10(8) yr, (2) the galactic H II regions are inhomogeneous with a cloud-covering factor of order unity, and (3) the overall star formation efficiency is at least similar to 5%. It is predicted that future observations can detect these Ly alpha galaxies up to redshifts of similar to 8. If the universe is reionized at z(r) less than or similar to 8, the corresponding decline in the number of Ly alpha emitters at z greater than or similar to z(r) could prove to be a useful probe of the reionization epoch. C1 NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA. RP Haiman, Z (reprint author), NASA, Fermilab Astrophys Grp, Fermi Natl Accelerator Lab, Batavia, IL 60510 USA. NR 59 TC 108 Z9 108 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 JUN 10 PY 1999 VL 518 IS 1 BP 138 EP 144 DI 10.1086/307276 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211JZ UT WOS:000081158600012 ER PT J AU Evans, AS Scoville, NZ Dinshaw, N Armus, L Soifer, BT Neugebauer, G Rieke, M AF Evans, AS Scoville, NZ Dinshaw, N Armus, L Soifer, BT Neugebauer, G Rieke, M TI Hubble Space Telescope NICMOS observations of rest-frame optical continuum and H alpha+[N I] emission in FSC 10214+4724 SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : distances and redshifts; galaxies : individual (IRAS FSC 10214+4724); gravitational lensing; infrared : galaxies ID IRAS SOURCE FSC-10214+4724; GRAVITATIONAL LENS; GALAXY; F10214+4724; LUMINOSITY; QUASAR; RADIO AB High-resolution 1.10, 2.05, 2.12, and 2.15 mu m imaging of the gravitationally lensed system FSC 10214+4724 are presented. These data extend Hubble Space Telescope (HST) observations of the lens system to redder wavelengths, thus providing the highest resolution images to date of the rest-frame optical and narrow-line (i.e., H alpha + [N II]) regions of the background quasar. The length of the are in the wide-band continuum images increases with increasing wavelength, and the H alpha + [N II] emission has a length in between that of the 1.10 and 2.05 mu m emission. The structure of the are changes from having an eastern and western peak at 1.10 mu m to having a single peak in the center at 2.05 mu m. The changing structure and length of the are can be understood in terms of a model in which the background quasar consists of a region of scattered active galactic nucleus (AGN) light that dominates at 1.10 mu m (rest frame 3300 Angstrom), surrounded by a more extended narrow-line region. An even more extended red stellar population would thus contribute light at 2.05 mu m (rest frame 6200 Angstrom). In addition, the H alpha + [N II] emission has structural features similar to the 1.10 mu m emission normalized by the (predominantly stellar) 2.05 mu m emission, possibly confirming that the 1.10 mu m emission is a superposition of the sources associated with the line emission (AGNs/massive stars) and the red stellar component that dominates the 2.05 mu m emission. The counterimage of the lensed quasar is detected in the 1.10 and 2.05 mu m images, and the rest frame 3300 and 6200 Angstrom magnifications of the lensed quasar are calculated to be 50 +/- 11 and 25 +/- 6, respectively, which translates into a rest-frame optical luminosity for the quasar of similar to 6 x 10(9) L.. These magnification values are lower than the previously measured magnification of similar to 100 at rest frame 2400 Angstrom. If the dust in the primary lensing galaxy is not affecting the measurement of the counterimage flux at 2400 and 3300 Angstrom, the magnification of the quasar appears to decrease with increasing wavelength. Flux measurements of the primary lensing galaxy fit the spectral energy distribution of an unevolving elliptical galaxy at a redshift of 0.9, consistent with previous determinations of the redshift. C1 CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064 USA. CALTECH, Jet Prop Lab, SIRTF Sci Ctr, Pasadena, CA 91125 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RP Evans, AS (reprint author), CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. NR 23 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 JUN 10 PY 1999 VL 518 IS 1 BP 145 EP 152 DI 10.1086/307279 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211JZ UT WOS:000081158600013 ER PT J AU Points, SD Chu, YH Kim, S Smith, RC Snowden, SL Brandner, W Gruendl, RA AF Points, SD Chu, YH Kim, S Smith, RC Snowden, SL Brandner, W Gruendl, RA TI The supergiant shell LMC 2. I. The kinematics and physical structure SO ASTROPHYSICAL JOURNAL LA English DT Article DE ISM : bubbles; ISM : individual(LIVIC 2); ISM : kinematics and dynamics; Magellanic Clouds ID LARGE MAGELLANIC CLOUD; VIOLENT INTERSTELLAR-MEDIUM; NEUTRAL ATOMIC-HYDROGEN; STELLAR ASSOCIATIONS; IRREGULAR GALAXIES; STAR-CLUSTERS; IONIZED-GAS; LINE SURVEY; EMISSION; REGION AB LMC 2 has the brightest, most coherent filamentary structure of all known supergiant shells in the Large Magellanic Cloud. The optical emission-line images show active star formation regions along the western edge and long filaments to the east. ROSAT PSPC and HRI images show bright X-ray emission from within the shell boundary, indicating the presence of hot gas. Counterintuitively, neither high-resolution echelle spectra in the Hot line nor aperture synthesis H I 21 cm emission-line observations show LMC 2 to have the kinematics expected of an expanding shell. Rather, LMC 2 appears to consist of hot gas confined between H I sheets. The interior surfaces of these sheets are ionized by the UV flux of massive stars in the star formation regions along the periphery of LMC 2, while the heating is provided by outflows of hot gas from the star formation regions and by SNRs interior to LMC 2. We have compared LMC 2 to other supergiant shells in the LMC and in more distant galaxies. When the spatial resolution of our data are degraded, we find that LMC 2 resembles supergiant shells observed at a distance of 4 Mpc that have previously been interpreted as expanding shells. Therefore, great caution should be exercised in the analysis and interpretation of the kinematics of distant supergiant shells to prevent overestimates of their velocities and total kinetic energies. C1 Univ Illinois, Dept Astron, Urbana, IL 61801 USA. Australian Natl Univ, Mt Stromlo & Siding Spring Observ, Weston, ACT 2611, Australia. Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. CALTECH, Jet Prop Lab, IPAC, Pasadena, CA 91125 USA. Univ Illinois, Dept Astron, Lab Astron Imaging, Urbana, IL 61801 USA. RP Points, SD (reprint author), Univ Illinois, Dept Astron, 1002 W Green St, Urbana, IL 61801 USA. RI Snowden, Steven/D-5292-2012 NR 70 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 JUN 10 PY 1999 VL 518 IS 1 BP 298 EP 323 DI 10.1086/307249 PN 1 PG 26 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211JZ UT WOS:000081158600026 ER PT J AU Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M De Marzo, C Finetti, N Papini, P Piccardi, S Spillantini, P Ricci, M Casolino, M De Pascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ AF Boezio, M Carlson, P Francke, T Weber, N Suffert, M Hof, M Menn, W Simon, M Stephens, SA Bellotti, R Cafagna, F Castellano, M Circella, M De Marzo, C Finetti, N Papini, P Piccardi, S Spillantini, P Ricci, M Casolino, M De Pascale, MP Morselli, A Picozza, P Sparvoli, R Barbiellini, G Bravar, U Schiavon, P Vacchi, A Zampa, N Mitchell, JW Ormes, JF Streitmatter, RE Golden, RL Stochaj, SJ TI The cosmic-ray proton and helium spectra between 0.4 and 200 GV SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmic rays; elementary particles ID CAPRICE-RICH DETECTOR; SOLAR MINIMUM; ANTIPROTONS; FLUX; SPECTROMETER; PERFORMANCE; ATMOSPHERE; RADIATION; ENERGIES; NUCLEI AB We report on the hydrogen nuclei (protons and deuterons) spectrum from 0.15 to 200 GeV and on the helium nuclei spectrum over the energy range from 0.2 to 100 GeV nucleon(-1) at the top of the atmosphere measured by the balloon-borne experiment Cosmic Antiparticle Ring-Imaging Cerenkov Experiment (CAPRICE), which was flown from Lynn Lake, Manitoba, Canada, on 1994 August 8-9. We also report on the proton spectrum over the energy range from 0.15 to 4.2 GeV. The experiment used the NMSU-WiZard/CAPRICE balloon-borne magnet spectrometer equipped with a solid radiator Ring-Imaging Cerenkov (RICH) detector and a silicon-tungsten calorimeter for particle identification. This was the first time a RICH was used together with an imaging calorimeter in a balloon-borne experiment. These detectors allowed for clear particle identification, as well as excellent control of the detector efficiencies. The data were collected during 18 hr at a residual mean atmospheric depth of 3.9 g cm(-2). With this apparatus 516,463 hydrogen and 32,457 helium nuclei were identified in the rigidity range 0.4 to 200 GV and 1.2 to 200 GV, respectively. The observed energy spectrum at the top of the atmosphere can be represented by (1.1 +/- 0.1) x 10(4) E-2.73+/-0.06 particles (m(2) GeV sr s)(-1) for hydrogen (E in GeV) between 20 and 200 GeV and (4.3 +/- 0.9) x 10(2) E-2.65+/-0.07 particles (m2 GeV nucleon(-1) sr s)(-1) for helium nuclei (E in GeV nucleon-l) between 10 and 100 GeV nucleon(-1). These spectra are in good agreement with other recent measurements above 10 GeV. The observed spectra flatten below 10 GeV due to solar modulation and are consistent with earlier measurements when solar modulation is taken into account. Between 5 and 200 GV the hydrogen to helium ratio as a function of rigidity was found to be approximately constant at 6.1 +/- 0.1. C1 Royal Inst Technol KTH, S-10405 Stockholm, Sweden. Ctr Rech Nucl, F-67037 Strasbourg, France. Univ Siegen, D-57068 Siegen, Germany. Tata Inst Fundamental Res, Bombay 400005, Maharashtra, India. Univ Bari, Dipartmento Fis, I-70126 Bari, Italy. Sez INFN Bari, I-70126 Bari, Italy. Univ Florence, Dipartimento Fis, I-50125 Florence, Italy. Sez INFN Firenze, I-50125 Florence, Italy. Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy. Univ Roma Tor Vergata, Dipartimento Fis, I-00133 Rome, Italy. Ist Nazl Fis Nucl, Sez Roma, I-00133 Rome, Italy. Univ Trieste, Dipartimento Fis, I-34147 Trieste, Italy. Ist Nazl Fis Nucl, Sez Trieste, I-34147 Trieste, Italy. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. New Mexico State Univ, Las Cruces, NM 88003 USA. RP Boezio, M (reprint author), Royal Inst Technol KTH, S-10405 Stockholm, Sweden. RI Cafagna, Francesco/A-9299-2010; Morselli, Aldo/G-6769-2011; Castellano, Marcello/J-3428-2012; Vacchi, Andrea/C-1291-2010; OI Cafagna, Francesco/0000-0002-7450-4784; Morselli, Aldo/0000-0002-7704-9553; Castellano, Marcello/0000-0002-4211-2903; Vacchi, Andrea/0000-0003-3855-5856; Bellotti, Roberto/0000-0003-3198-2708; casolino, marco/0000-0001-6067-5104; Sparvoli, Roberta/0000-0002-6314-6117; Picozza, Piergiorgio/0000-0002-7986-3321; Papini, Paolo/0000-0003-4718-2895; Boezio, Mirko/0000-0002-8015-2981 NR 38 TC 149 Z9 151 U1 0 U2 5 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1999 VL 518 IS 1 BP 457 EP 472 DI 10.1086/307251 PN 1 PG 16 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211JZ UT WOS:000081158600039 ER PT J AU Reames, DV AF Reames, DV TI Quiet-time spectra and abundances of energetic particles during the 1996 solar minimum SO ASTROPHYSICAL JOURNAL LA English DT Article DE acceleration of particles; cosmic rays; interplanetary medium; ISM : abundances; shock waves ID ANOMALOUS COSMIC-RAYS; TERMINATION SHOCK; HELIOSPHERE; WIND; IONS; ACCELERATION; COMPONENT; NITROGEN; OXYGEN; GEOTAIL AB We report the energy spectra and abundances of ions with atomic number, Z, in the interval 2 less than or equal to Z less than or equal to 36 and energies similar to 3-20 MeV amu(-1) for solar and interplanetary quiet periods between 1994 November and 1998 April, as measured by the large-geometry Low-Energy Matrix Telescope on the Wind spacecraft near Earth. The energy spectra show the presence of galactic and "anomalous" cosmic-ray components (GCR and ACR, respectively), depending on the element. ACR components are reported for Mg and Si for the first time at 1 AU, and the previous observation of S and Ar is confirmed. However, only GCR components are clearly apparent for the elements Ca, Ti, Cr, Fe, as well as for C. New limits are placed on a possible ACR contribution for other elements, including Kr. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Reames, DV (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 31 TC 35 Z9 35 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1999 VL 518 IS 1 BP 473 EP 479 DI 10.1086/307255 PN 1 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211JZ UT WOS:000081158600040 ER PT J AU Kazanas, D Mastichiadis, A AF Kazanas, D Mastichiadis, A TI Relativistic electrons in blazars: A hadronic origin? SO ASTROPHYSICAL JOURNAL LA English DT Article DE galaxies : active; galaxies : jets; gamma rays : theory; radiation mechanisms : nonthermal ID ACTIVE GALACTIC NUCLEI AB Recent observations of blazars have established that their gamma-ray emission is associated, as a rule, with very fast variability (as short as similar to 15 minutes for the TeV photons of Mrk 421); as such, these observations push the theoretical models for the production of the required relativistic electrons to their limits. Herein we investigate the possibility that "blobs" loaded with relativistic protons could produce such an activity. We show that, if the proton number density in a blob exceeds a certain critical value, then reflection of its own synchrotron produced photons on some external "mirror" such as a line-emitting cloud, can initiate a feedback process in which the protons can lose most of their energy content in a blob crossing time, resulting in a flare of the same duration. By performing a dimensional analysis, we find the necessary conditions for such an instability to occur, and we show that the conditions required are consistent with those usually assumed to prevail within the relativistic jets of this class of active galactic nuclei. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Athens, Dept Astron, GR-15784 Athens, Greece. RP Kazanas, D (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 661, Greenbelt, MD 20771 USA. NR 9 TC 16 Z9 16 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 JUN 10 PY 1999 VL 518 IS 1 BP L17 EP L20 DI 10.1086/312056 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211LZ UT WOS:000081163700005 ER PT J AU Konopelko, AK Kirk, JG Stecker, FW Mastichiadis, A AF Konopelko, AK Kirk, JG Stecker, FW Mastichiadis, A TI Evidence for intergalactic absorption in the TeV gamma-ray spectrum of Markarian 501 SO ASTROPHYSICAL JOURNAL LA English DT Article DE BL Lacertae objects : individual (Markarian 501); galaxies : active; gamma rays : theory ID SELF-COMPTON MODEL; INFRARED RADIATION; EMISSION; BLAZARS; VARIABILITY; ORIGIN; STATE; JETS AB The recent High-Energy Gamma-Ray Array (HEGRA) observations of the blazar Mrk 501 show strong curvature in the very high energy gamma-ray spectrum. Applying the gamma-ray opacity derived from an empirically based model of the intergalactic infrared background radiation field to these observations, we find that the intrinsic spectrum of this source is consistent with a power law: dN(gamma)/dE proportional to E-alpha, with alpha = 2.00 +/- 0.03 over the range 500 GeV-20 TeV. Within current synchrotron self-Compton scenarios, the fact that the TeV spectral energy distribution of Mrk 501 does not vary with luminosity, combined with the correlated, spectrally variable emission in X-rays as observed by the BeppoSAX and Rossi X-Ray Timing Explorer instruments, also independently implies that the intrinsic spectrum must be close to alpha = 2. Thus, the observed curvature in the spectrum is most easily understood as resulting from intergalactic absorption. C1 Max Planck Inst Kernphys, D-69029 Heidelberg, Germany. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Univ Athens, Dept Phys, GR-15783 Zografos, Greece. RP Konopelko, AK (reprint author), Max Planck Inst Kernphys, D-69029 Heidelberg, Germany. RI Stecker, Floyd/D-3169-2012; Kirk, John/A-8901-2013 OI Kirk, John/0000-0002-9859-0496 NR 40 TC 31 Z9 31 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 10 PY 1999 VL 518 IS 1 BP L13 EP L15 DI 10.1086/312062 PN 2 PG 3 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 211LZ UT WOS:000081163700004 ER PT J AU Kaneko, H Padilla, PA AF Kaneko, H Padilla, PA TI A note on the finite element method with singular basis functions SO INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING LA English DT Article DE finite element method with singular basis functions; the collocation method; singular interpolation elements ID SHAPE FUNCTIONS AB In this note, we make a few comments concerning the paper of Hughes and Akin (Int. J. Numer. Meth. Engng., 15, 733-751 (1980)). Our primary goal is to demonstrate that the rate of convergence of numerical solutions of the finite element method with singular basis functions depends upon the location of additional collocation points associated with the singular elements. Copyright (C) 1999 John Wiley & Sons, Ltd. C1 Old Dominion Univ, Dept Math & Stat, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Flight Dynam & Control Div, Crew Vehicle Integrat Branch, Hampton, VA 23681 USA. RP Kaneko, H (reprint author), Old Dominion Univ, Dept Math & Stat, Norfolk, VA 23529 USA. NR 8 TC 0 Z9 0 U1 0 U2 0 PU JOHN WILEY & SONS LTD PI W SUSSEX PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND SN 0029-5981 J9 INT J NUMER METH ENG JI Int. J. Numer. Methods Eng. PD JUN 10 PY 1999 VL 45 IS 4 BP 491 EP 495 DI 10.1002/(SICI)1097-0207(19990610)45:4<491::AID-NME597>3.0.CO;2-Y PG 5 WC Engineering, Multidisciplinary; Mathematics, Interdisciplinary Applications SC Engineering; Mathematics GA 197ND UT WOS:000080370500005 ER PT J AU Celaya, MA Wahr, JM Bryan, FO AF Celaya, MA Wahr, JM Bryan, FO TI Climate-driven polar motion SO JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH LA English DT Article ID SYSTEM-MODEL; CHANDLER-WOBBLE; EARTHS WOBBLE; EXCITATION; ROTATION; FLUCTUATIONS; SIGNALS; LENGTH AB The output of a coupled climate system model provides a synthetic climate record with temporal and spatial coverage not attainable with observational data, allowing evaluation of climatic excitation of polar motion on timescales of months to decades. Analysis df the geodetically inferred Chandler excitation power shows that it has fluctuated by up to 90% since 1900 and that it has characteristics representative of a stationary Gaussian process. Our model-predicted climate excitation of the Chandler wobble also exhibits variable power comparable to the observed. Ocean currents and bottom pressure shifts acting together can alone drive the 14-month wobble. The same is true of the excitation generated by the combined effects of barometric pressure and winds. The oceanic and atmospheric contributions are this large because of a relatively high degree of constructive interference between seafloor pressure and currents and between atmospheric pressure and winds. In contrast, excitation by the redistribution of water on land appears largely insignificant. Not surprisingly, the full climate effect is even more capable of driving the wobble than the effects of the oceans or atmosphere alone are. Our match to the observed annual excitation is also improved, by about 17%, over previous estimates made with historical climate data. Efforts to explain the 30-year Markowitz wobble meet with less success. Even so, at periods ranging from months to decades, excitation generated by a model of a, coupled climate system makes a close approximation to the amplitude of what is geodetically observed. C1 Natl Ctr Atmospher Res, Boulder, CO 80307 USA. Univ Colorado, Dept Phys, Boulder, CO 80302 USA. Univ Colorado, Cooperat Inst Res Environm Sci, Boulder, CO 80302 USA. RP Celaya, MA (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 238-332, Pasadena, CA 91109 USA. EM mcelaya@pop.jpl.nasa.gov; wahr@lemond.colorado.edu; bryan@cgd.ucar.edu RI Bryan, Frank/I-1309-2016 OI Bryan, Frank/0000-0003-1672-8330 NR 42 TC 31 Z9 36 U1 0 U2 1 PU AMER GEOPHYSICAL UNION PI WASHINGTON PA 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA SN 2169-9313 EI 2169-9356 J9 J GEOPHYS RES-SOL EA JI J. Geophys. Res.-Solid Earth PD JUN 10 PY 1999 VL 104 IS B6 BP 12813 EP 12829 DI 10.1029/1999JB900016 PG 17 WC Geochemistry & Geophysics SC Geochemistry & Geophysics GA 205GM UT WOS:000080813000006 ER PT J AU Nesbitt, FL Thorn, RP Payne, WA Tardy, DC AF Nesbitt, FL Thorn, RP Payne, WA Tardy, DC TI Absolute rate constant and product branching fractions for the reaction between F and C2H4 at T=202-298 K SO JOURNAL OF PHYSICAL CHEMISTRY A LA English DT Article ID CN RADICAL REACTIONS; TEMPERATURE-DEPENDENCE; HYDROGEN ABSTRACTION; ATOMIC-HYDROGEN; FLUORINE-ATOMS; DIODE-LASER; T=298 K; MOLECULES; KINETICS; HYDROCARBONS AB The discharge-flow kinetic technique coupled to mass-spectrometric detection has been used to determine the variable-temperature dependence of the rate constant and product branching fractions for the reaction between F(P-2) and C2H4 at P = 1 Torr nominal pressure (He). The reaction was studied at T = 202 and 236 K by monitoring the decay of C2H4 in the presence of a large excess of F(P-2). The overall rate coefficients were determined to be k(1)(202 K) = (1.7 +/- 0.4) x 10(-10) cm(3) molecule(-1) s(-1) and k(1)(236 K) = (2. 1 +/- 0.5) x 10(-10) cm(3) molecule(-1) s(-1) with the quoted uncertainty representing total errors. Further, the branching fractions for the two observed reaction channels F + C2H4 --> C2H3 + HF (1a) and F + C2H4 --> C2H3F + H (1b) were determined by quantitatively measuring the yield of C2H3F under conditions of excess C2H4. The stabilized adduct, C2H4F, was not detected at T = 202 K. The derived branching fractions were Gamma(1a)(202 K) = 0.25 +/- 0.09, Gamma(1b) (202 K) = 0.75 +/- 0.16, and Gamma(1a)(236 K) = 0.27 +/- 0.13, and Gamma(1b) (236 K) = 0.73 +/- 0.20, where the quoted uncertainty represents total errors. By inclusion of k(1)(298 K) = (3.0 +/- 0.8) x 10(-10) cm(3) molecule(-1) s(-1), a revised value that used data from our previous study and Gamma(1a)(298 K) = 0.35 +/- 0.04 and Gamma(1b) (298 K) s = 0.65 +/- 0.04 from a laser photolysis/photoionization mass spectrometry study, we obtain the Arrhenius expressions k(1a)(T) = (7.5 +/- 4.0) x 10(-10) exp[(-1.2 +/- 0.3)/(RT)] and k(1b)(T) = (5.2 +/- 1.0) x 10(-10) exp[(-0.6 +/- 0.1)/(RT)] in units of cm(3) molecule(-1) s(-1) for k and in units of kcal mol(-1) for activation energy. The quoted uncertainty represents total errors at 1 sigma precision errors plus 15% systematic errors. RRKM calculations have shown that the critical energy for H addition to C2H3F is less than 6 kcal mol(-1) larger than that for the addition of F to C2H4 and that the competitive decomposition of chemically activated C2H4F radicals favor C-H bond rupture by a factor greater than 1000 over that for C-F bond rupture. C1 NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. Coppin State Coll, Dept Nat Sci, Baltimore, MD 21216 USA. Univ Iowa, Dept Chem, Iowa City, IA 52242 USA. RP Thorn, RP (reprint author), NASA, Goddard Space Flight Ctr, Extraterr Phys Lab, Greenbelt, MD 20771 USA. NR 63 TC 4 Z9 4 U1 1 U2 1 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 1089-5639 J9 J PHYS CHEM A JI J. Phys. Chem. A PD JUN 10 PY 1999 VL 103 IS 23 BP 4470 EP 4479 DI 10.1021/jp9901747 PG 10 WC Chemistry, Physical; Physics, Atomic, Molecular & Chemical SC Chemistry; Physics GA 206YH UT WOS:000080907800007 ER PT J AU Ricca, A Bauschlicher, CW Kang, JK Musgrave, CB AF Ricca, A Bauschlicher, CW Kang, JK Musgrave, CB TI Hydrogen abstraction from a diamond(111) surface in a uniform electric field SO SURFACE SCIENCE LA English DT Article DE C; clusters; density functional theory; field effect; H; low index single crystal AB Bond breaking in a strong electric field is shown to arise from a crossing of the ionic and covalent asymptotes. The specific example of hydrogen abstraction from a diamond(111) surface is studied using a cluster model. The addition of nearby atoms in both the parallel and perpendicular direction to the electric field are found to have an effect. It is also shown that the barrier is not solely related to the position of the ionic and covalent asymptotes. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. Stanford Univ, Dept Chem Engn & Mat Sci, Stanford, CA 94305 USA. RP Ricca, A (reprint author), NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RI Kang, Jeung ku/C-1610-2011 NR 11 TC 7 Z9 7 U1 0 U2 1 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0039-6028 J9 SURF SCI JI Surf. Sci. PD JUN 10 PY 1999 VL 429 IS 1-3 BP 199 EP 205 DI 10.1016/S0039-6028(99)00377-5 PG 7 WC Chemistry, Physical; Physics, Condensed Matter SC Chemistry; Physics GA 209FH UT WOS:000081037200030 ER PT J AU Bolotnikov, A Ramsey, B AF Bolotnikov, A Ramsey, B TI Studies of light and charge produced by alpha-particles in high-pressure xenon SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT LA English DT Article DE scintillation light; luminescence signal; high-pressure gas ID LIQUID XENON; RECOMBINATION LUMINESCENCE; GASEOUS XENON; FLUID XENON; ION-PAIR; IONIZATION; ARGON; CHAMBER; KRYPTON; XE AB The results of measurements of scintillation light induced by alpha-particles in high-pressure Xe are presented. The ratio of N-ex/N-i, and the intensity and time characteristics of the luminescence signal have been measured for different densities up to 0.74 g/cm(3). The role and mechanisms of the electron-ion recombination in high-pressure gas have been investigated. The existence of clusters and self-trapped excitons above 0.6 g/cm(3) has been observed and discussed. This work is a part of a development program of high-pressure Xe detectors for low-energy gamma rays. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Bolotnikov, A (reprint author), CALTECH, 220-47, Pasadena, CA 91125 USA. NR 36 TC 26 Z9 26 U1 0 U2 2 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0168-9002 J9 NUCL INSTRUM METH A JI Nucl. Instrum. Methods Phys. Res. Sect. A-Accel. Spectrom. Dect. Assoc. Equip. PD JUN 4 PY 1999 VL 428 IS 2-3 BP 391 EP 402 DI 10.1016/S0168-9002(99)00173-4 PG 12 WC Instruments & Instrumentation; Nuclear Science & Technology; Physics, Nuclear; Physics, Particles & Fields SC Instruments & Instrumentation; Nuclear Science & Technology; Physics GA 206QK UT WOS:000080890400015 ER PT J AU Margot, JL Campbell, DB Jurgens, RF Slade, MA AF Margot, JL Campbell, DB Jurgens, RF Slade, MA TI Topography of the lunar poles from radar interferometry: A survey of cold trap locations SO SCIENCE LA English DT Article ID POLAR ANOMALIES; MERCURY; ICE; MOON; CLEMENTINE; STABILITY; IMAGES; REGION AB Detailed topographic maps of the lunar poles have been obtained by Earth-based radar-interferometry with the 3.5-centimeter wavelength Goldstone Solar System Radar. The interferometer provided maps 300 kilometers by 1000 kilometers of both polar regions at 150-meter spatial resolution and 50-meter height resolution. Using ray tracing, these digital elevation models were used to locate regions that are in permanent shadow from solar illumination and may harbor ice-deposits. Estimates of the total extent of shadowed areas poleward of 87.5 degrees latitude are 1030 and 2550 square kilometers for the north and south poles, respectively. C1 Cornell Univ, Dept Astron, Ithaca, NY 14853 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. RP Campbell, DB (reprint author), Arecibo Observ, HC3 Box 53995, Arecibo, PR 00612 USA. RI Margot, Jean-Luc/A-6154-2012 OI Margot, Jean-Luc/0000-0001-9798-1797 NR 26 TC 77 Z9 84 U1 1 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 JUN 4 PY 1999 VL 284 IS 5420 BP 1658 EP 1660 DI 10.1126/science.284.5420.1658 PG 3 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 202TM UT WOS:000080668300041 PM 10356393 ER PT J AU Shindell, DT Miller, RL Schmidt, GA Pandolfo, L AF Shindell, DT Miller, RL Schmidt, GA Pandolfo, L TI Simulation of recent northern winter climate trends by greenhouse-gas forcing SO NATURE LA English DT Article ID SURFACE AIR-TEMPERATURE; STRATOSPHERIC CIRCULATION; INTERANNUAL VARIABILITY; GEOPOTENTIAL HEIGHT; MIDDLE ATMOSPHERE; HEMISPHERE; MODEL; OZONE; TROPOSPHERE; GCM AB The temperature of air at the Earth's surface has risen during the past century(1), but the fraction of the warming that can be attributed to anthropogenic greenhouse gases remains controversial. The strongest warming bends have been over Northern Hemisphere land masses during winter, and are closely related to changes in atmospheric circulation. These circulation changes are manifested by a gradual reduction in high-latitude sea-level pressure, and an increase in mid-latitude sea-level pressure associated with one phase of the Arctic Oscillation (a hemisphere-scale version of the North Atlantic Oscillation)(2). Here we use several different climate-model versions to demonstrate that the observed sea-level-pressure trends, including their magnitude, can be simulated by realistic increases in greenhouse-gas concentrations, Thus, although the warming appears through a naturally occurring mode of atmospheric variability, it may be anthropogenically induced and may continue to rise. The Arctic Oscillation trend is captured only in climate models that include a realistic representation of the stratosphere, while changes in ozone concentrations are not necessary to simulate the observed climate trends. The proper representation of stratospheric dynamics appears to be important to the attribution of climate change, at least on a broad regional scale. C1 NASA, Goddard Inst Space Studies, New York, NY 10025 USA. Columbia Univ, Ctr Climate Syst Res, New York, NY 10025 USA. Columbia Univ, Dept Appl Phys, New York, NY 10027 USA. Univ British Columbia, Dept Earth & Ocean Sci, Vancouver, BC V6T 1Z4, Canada. RP Shindell, DT (reprint author), NASA, Goddard Inst Space Studies, 2880 Broadway, New York, NY 10025 USA. RI Shindell, Drew/D-4636-2012; Schmidt, Gavin/D-4427-2012; Miller, Ron/E-1902-2012 OI Schmidt, Gavin/0000-0002-2258-0486; NR 30 TC 374 Z9 390 U1 1 U2 32 PU MACMILLAN MAGAZINES LTD PI LONDON PA PORTERS SOUTH, 4 CRINAN ST, LONDON N1 9XW, ENGLAND SN 0028-0836 J9 NATURE JI Nature PD JUN 3 PY 1999 VL 399 IS 6735 BP 452 EP 455 DI 10.1038/20905 PG 4 WC Multidisciplinary Sciences SC Science & Technology - Other Topics GA 202TH UT WOS:000080667900044 ER PT J AU Fonda, M Petach, M Rogers, CF Huntington, J Stratton, D Nishioka, K Tipo, M AF Fonda, M Petach, M Rogers, CF Huntington, J Stratton, D Nishioka, K Tipo, M TI Resuspension of particles by aerodynamic deagglomeration SO AEROSOL SCIENCE AND TECHNOLOGY LA English DT Article AB A deagglomerator system was developed, characterized by laboratory tests, and flown under low-gravity (low-g) microgravity conditions. Requirements for a dry powder deagglomeration system were generated by university and National Aeronautics and Space Administration (NASA) scientists from diverse fields of interest including exobiology, planetary sciences, and atmospheric sciences, Existing deagglomeration methods and devices are reviewed, An aerosol generation method suitable for dry powders over a large range of particle sizes and types at high concentrations with consistent deagglomeration efficiency are evaluated. Development of a pulsed-flow laboratory device and experimental approaches to meet the requirements without being g-dependent are described. Results of laboratory one-g quantitative characterization on one type of dry powder particle generator is discussed, Data from NASA low-g tests are summarized. C1 NASA, Ames Res Ctr, Hernandez Engn Inc, Moffett Field, CA 94035 USA. TRW Co Inc, Space & Elect Grp, Appl Technol Grp, Redondo Beach, CA 90278 USA. Univ Nevada, Desert Res Inst, Reno, NV 89506 USA. Seti Inst, Mt View, CA 94043 USA. RP Fonda, M (reprint author), NASA, Ames Res Ctr, Hernandez Engn Inc, MS 239-4, Moffett Field, CA 94035 USA. RI Fonda, Mark/A-7983-2013 NR 12 TC 5 Z9 5 U1 0 U2 5 PU TAYLOR & FRANCIS INC PI PHILADELPHIA PA 325 CHESTNUT ST, SUITE 800, PHILADELPHIA, PA 19106 USA SN 0278-6826 J9 AEROSOL SCI TECH JI Aerosol Sci. Technol. PD JUN PY 1999 VL 30 IS 6 BP 509 EP 529 DI 10.1080/027868299304381 PG 21 WC Engineering, Chemical; Engineering, Mechanical; Environmental Sciences; Meteorology & Atmospheric Sciences SC Engineering; Environmental Sciences & Ecology; Meteorology & Atmospheric Sciences GA 208DP UT WOS:000080975200001 ER PT J AU King, MK AF King, MK TI Microgravity studies offer insights into combustion SO AEROSPACE AMERICA LA English DT News Item C1 NASA Headquarters, Micrograv Combust Program, Washington, DC 20546 USA. RP King, MK (reprint author), NASA Headquarters, Micrograv Combust Program, Washington, DC 20546 USA. NR 0 TC 0 Z9 0 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0740-722X J9 AEROSPACE AM JI Aerosp. Am. PD JUN PY 1999 VL 37 IS 6 BP 20 EP 23 PG 4 WC Engineering, Aerospace SC Engineering GA 204VK UT WOS:000080785200006 ER PT J AU Whitmore, SA Petersen, BJ AF Whitmore, SA Petersen, BJ TI Dynamic response of pressure sensing systems in slip-flow with temperature gradients SO AIAA JOURNAL LA English DT Article C1 NASA, Dryden Flight Res Ctr, Aerodynam Branch, Aerodynam Grp, Edwards, CA 93523 USA. Boeing Co, Douglas Aircraft Div, Long Beach, CA 90013 USA. RP Whitmore, SA (reprint author), NASA, Dryden Flight Res Ctr, Aerodynam Branch, Aerodynam Grp, Edwards, CA 93523 USA. NR 16 TC 5 Z9 5 U1 0 U2 0 PU AMER INST AERONAUT ASTRONAUT PI RESTON PA 1801 ALEXANDER BELL DRIVE, STE 500, RESTON, VA 22091 USA SN 0001-1452 J9 AIAA J JI AIAA J. PD JUN PY 1999 VL 37 IS 6 BP 772 EP 774 DI 10.2514/2.789 PG 3 WC Engineering, Aerospace SC Engineering GA 201DA UT WOS:000080578400019 ER PT J AU Stein, TP Leskiw, RJ Schluter, MD Hoyt, RW Lane, KW Gretebeck, RE LeBlanc, AD AF Stein, TP Leskiw, RJ Schluter, MD Hoyt, RW Lane, KW Gretebeck, RE LeBlanc, AD TI Energy expenditure and balance during spaceflight on the space shuttle SO AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY LA English DT Article DE astronauts; nitrogen balance; bed rest ID SKELETAL-MUSCLE; BED REST; CALORIC REQUIREMENTS; RESISTANCE EXERCISE; PROTEIN; REAPPRAISAL; TURNOVER; FLIGHT; RATS AB The objectives of this study were as follows: 1) to measure human energy expenditure (EE) during spaceflight on a shuttle mission by using the doubly labeled water (DLW) method; 2) to determine whether the astronauts were in negative energy balance during spaceflight; 3) to use the comparison of change in body fat as measured by the intake DLW EE, O-18 dilution, and dual energy X-ray absorptiometry (DEXA) to validate the DLW method for spaceflight; and 4) to compare EE during spaceflight against that found with bed rest. Two experiments were conducted: a flight experiment (n = 4) on the 16-day 1996 Life and microgravity sciences shuttle mission and a 6 degrees head-down tilt bed rest study with controlled dietary intake (n = 8). The bed rest study was designed to simulate the flight experiment and included exercise. Two EE determinations were done before flight (bed rest), during flight (bed rest), and after flight (recovery). Energy intake and N balance were monitored for the entire period. Results were that body weight, water, fat, and energy balance were unchanged with bed rest. For the flight experiment, decreases in weight (2.6 +/- 0.4 kg, P < 0.05) and N retention (-2.37 +/- 0.45 g N/day, P ( 0.05) were found. Dietary intake for the four astronauts was reduced in flight (3,025 +/- 180 vs. 1,943 +/- 179 kcal/day, P < 0.05). EE in flight was 3,320 +/- 155 kcal/day, resulting in a negative energy balance of 1,355 +/- 80 kcal/day (-15.7 +/- 1.0 kcal.kg(-1).day(-1), P < 0.05). This corresponded to a loss of 2.1 +/- 0.4 kg body fat, which was within experimental error of the fat loss determined by O-18 dilution (-1.4 +/- 0.5 kg) and DEXA (-2.4 +/- 0.4 kg. All three methods showed no change in body fat with bed rest. in conclusion, 1) the DLW method for measuring EE during spaceflight is valid, 2) the astronauts were in severe negative energy balance and oxidized body fat, and 3) in-flight energy (E) requirements can be predicted from the equation: E = 1.40 x resting metabolic rate + exercise. C1 Univ Med & Dent New Jersey, Sch Osteopath Med, Dept Surg, Stratford, NJ 08084 USA. USA, Environm Med Res Inst, Natick, MA 01760 USA. NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA. Baylor Coll Med, Dept Radiol, Houston, TX 77030 USA. Purdue Univ, Dept Foods & Nutr, W Lafayette, IN 47907 USA. RP Stein, TP (reprint author), Univ Med & Dent New Jersey, Sch Osteopath Med, Dept Surg, 2 Med Ctr Dr, Stratford, NJ 08084 USA. EM tpstein@umdnj.edu NR 30 TC 86 Z9 87 U1 1 U2 3 PU AMER PHYSIOLOGICAL SOC PI BETHESDA PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814 USA SN 0363-6119 EI 1522-1490 J9 AM J PHYSIOL-REG I JI Am. J. Physiol.-Regul. Integr. Comp. Physiol. PD JUN PY 1999 VL 276 IS 6 BP R1739 EP R1748 PG 10 WC Physiology SC Physiology GA 203EP UT WOS:000080695000025 PM 10362755 ER PT J AU Socki, RA Romanek, CS Gibson, EK AF Socki, RA Romanek, CS Gibson, EK TI On line technique for measuring stable oxygen and hydrogen isotopes from microliter quantities of water SO ANALYTICAL CHEMISTRY LA English DT Article ID O-18 AB Detailed here is a method for extracting and analyzing oxygen and hydrogen isotopes from 10 mu L-sized water samples. Based on the traditional CO2-H2O equilibration technique, the oxygen isotope exchange reaction is done exclusively in sealed 6-mm (o.d.) Pyrex tubes at 25 degrees C, with full isotope exchange completed in at least 28 h. Using the same water sample employed in the O-18 equilibration, D/H extractions are done in separate sealed 6-mm (o.d.) Pyrex tubes by reaction with Zn at 450 degrees C to form H-2(g). Provided that a correction factor is applied to O-18 analyses, accuracy and precision for both O-18 and D/H are comparable to standard techniques using much larger samples. C1 NASA, Houston, TX 77058 USA. Univ Georgia, Savannah River Ecol Lab, Aiken, SC 29802 USA. NASA, Johnson Space Ctr, Houston, TX 77058 USA. RP Socki, RA (reprint author), NASA, C-23 Lockheed Martin,2400 Rd, Houston, TX 77058 USA. NR 15 TC 20 Z9 20 U1 0 U2 3 PU AMER CHEMICAL SOC PI WASHINGTON PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA SN 0003-2700 J9 ANAL CHEM JI Anal. Chem. PD JUN 1 PY 1999 VL 71 IS 11 BP 2250 EP 2253 DI 10.1021/ac981140i PG 4 WC Chemistry, Analytical SC Chemistry GA 200RL UT WOS:000080553800042 PM 10366895 ER PT J AU Aust, JF Cooper, JB Wise, KL Jensen, BJ AF Aust, JF Cooper, JB Wise, KL Jensen, BJ TI In situ analysis of a high-temperature cure reaction in real time using modulated fiber-optic FT-Raman spectroscopy SO APPLIED SPECTROSCOPY LA English DT Article DE fiber optics; FT-Raman; polymer curing; high temperature ID FOURIER-TRANSFORM RAMAN; ND-YAG LASER; PROBE AB The vibrational spectrum of a high-temperature (330 degrees C) polymerization reaction was successfully monitored in real time with the use of a modulated fiber-optic Fourier transform (FT)-Raman spectrometer, A phenylethynyl-terminated monomer was cured, and spectral evidence for two different reaction products was acquired. The products are a conjugated polyene chain and a cyclized trimer, This is the first report describing the use of FT-Raman spectroscopy to monitor a high temperature (>250 degrees C) reaction in real time. C1 Old Dominion Univ, Dept Biochem & Chem, Norfolk, VA 23529 USA. NASA, Langley Res Ctr, Hampton, VA 23681 USA. RP Cooper, JB (reprint author), Old Dominion Univ, Dept Biochem & Chem, Norfolk, VA 23529 USA. NR 19 TC 7 Z9 7 U1 0 U2 0 PU SOC APPLIED SPECTROSCOPY PI FREDERICK PA 201B BROADWAY ST, FREDERICK, MD 21701 USA SN 0003-7028 J9 APPL SPECTROSC JI Appl. Spectrosc. PD JUN PY 1999 VL 53 IS 6 BP 682 EP 686 DI 10.1366/0003702991947333 PG 5 WC Instruments & Instrumentation; Spectroscopy SC Instruments & Instrumentation; Spectroscopy GA 210PD UT WOS:000081113100013 ER PT J AU Bryant, PM Scoville, NZ AF Bryant, PM Scoville, NZ TI High-resolution CO observations of luminous infrared galaxies SO ASTRONOMICAL JOURNAL LA English DT Review DE galaxies : interactions; galaxies : ISM; galaxies : nuclei; galaxies : Seyfert; galaxies : starburst; ISM : molecules ID SEYFERT 2 GALAXIES; MOLECULAR GAS; MERGING GALAXIES; SPIRAL GALAXIES; INTERACTING GALAXIES; STAR FORMATION; IRAS GALAXIES; STARBURST GALAXIES; MARKARIAN GALAXIES; APERTURE SYNTHESIS AB We have performed a high-resolution imaging survey of the CO J = 1 --> 0 emission in seven galaxies with infrared (IR) luminosities exceeding 3 x 10(11) L.-five of which are mergers. The resultant maps show that the molecular gas is very highly concentrated towards the cores of the mergers, with gas surface densities approaching or exceeding 10(4) Mo pc(-2) within 300-400 pc of the nuclei in three cases. This result supports earlier findings based on data from a smaller sample of luminous mergers. In the two mergers that show closely spaced double IR (stellar) nuclei, CO emission peaks between the nuclei and shows an extent roughly equal to the nuclear separation The gas cores of the individual merging galaxies appear to be coalescing, while the stellar cores remain distinct. In the three single nucleus mergers, the CO peaks are coincident with the stellar nuclei, consistent with the hypothesis that these are relatively evolved merger remnants. In two of the three mergers with the most compact CO emission (Mrk 231 and NGC 6240), the empirical Galactic conversion factor from CO luminosity to molecular gas mass appears to overestimate the nuclear gas mass by a factor of more than 2 (3.6 in the case of Mrk 231). For Mrk 231, the high brightness temperature of the CO emission (T-b > 34 K) is the likeliest explanation for this overestimate. In the third such merger (NGC 2623, however, the geometry and kinematics suggest that the molecular gas mass is within a factor of 2 of the value given by using the Galactic conversion factor. Nonetheless, in all three of these objects, the molecular gas probably dominates the nuclear gravitational potential. We suggest that the molecular gas in objects with such high gas mass surface densities (similar to 10(4) M. (-2)) is distributed in nuclear disks. These disks must be thin because of their self-gravity, with a full width of 30-40 pc (compared to radii of 300-400 pc) for a vertical velocity dispersion of 90 km s(-1). The mean volume density of molecular hydrogen in such disks must be over 104 cm(-3). The trend of increasing L-FIR/L-CO with increasing CO surface brightness is confirmed. The high concentrations of molecular gas thus appear intimately related to the high luminosities of these systems and probably serve as the fuel. C1 Univ Hawaii, NASA, Infrared Telescope Facil, Inst Astron, Honolulu, HI 96822 USA. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. RP Univ Hawaii, NASA, Infrared Telescope Facil, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA. NR 109 TC 173 Z9 173 U1 0 U2 1 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-6256 EI 1538-3881 J9 ASTRON J JI Astron. J. PD JUN PY 1999 VL 117 IS 6 BP 2632 EP 2655 DI 10.1086/300879 PG 24 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 214VU UT WOS:000081348900008 ER PT J AU Devine, D Bally, J Reipurth, B Shepherd, D Watson, A AF Devine, D Bally, J Reipurth, B Shepherd, D Watson, A TI A giant Herbig-Haro flow from a massive young star in G192.16-3.82 SO ASTRONOMICAL JOURNAL LA English DT Article DE HII regions; ISM : Herbig-Haro objects; ISM : individual (HH 396, HH 397); ISM : jets and outflows; stars : formation ID DR-21 OUTFLOW SOURCE; MOLECULAR OUTFLOWS; STELLAR OBJECTS; LINE EMISSION; CEPHEUS-A; EVOLUTION; REGIONS; JETS; CO; KINEMATICS AB We report the discovery of a 10 pc-long Herbig-Haro (HH) flow powered by a moderately massive young star associated with the compact H II region G192.16-3.82. At a distance of 2 kpc, the luminosity of G192.16-3.82 is about 3000 L-.. The I-II-I 396/397 complex consists of a network of filamentary emission-line objects tracing a pair of collimated and limb-brightened outflow lobes that emerge from an opaque cloud core. The H alpha- and [S II]-bright nebulosity has a large area covering factor, extending well beyond the mapped extent of the associated high-velocity molecular outflow. The HH 396/397 complex contains some shocks with a surface brightness comparable to III-I 168 in Cepheus A, placing these among the brightest known HH objects. Furthermore, a large fraction of a 1' by 18' region surrounding G192.16-3.82 is laced with lower surface brightness emission-line features, making I-II-I 396/397 one of the most spatially extended HH complexes studied so far. The dynamical age of this outflow is in the range 10(4) to 10(5) yr. We discuss plausible evolutionary scenarios for outflows powered by high-mass protostars and argue that the G192.16-3.82 outflow complex is relatively evolved. Despite being very elongated, this HH flow is most likely powered by a moderately collimated wind, rather than a highly collimated jet. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. CALTECH, Div Phys Math & Astron, Pasadena, CA 91125 USA. Univ Nacl Autonoma Mexico, Inst Astron, Morelia 58090, Michoacan, Mexico. RP Devine, D (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 49 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 0004-6256 J9 ASTRON J JI Astron. J. PD JUN PY 1999 VL 117 IS 6 BP 2919 EP 2930 DI 10.1086/300871 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 214VU UT WOS:000081348900028 ER PT J AU Devine, D Reipurth, B Bally, J Balonek, TJ AF Devine, D Reipurth, B Bally, J Balonek, TJ TI A giant Herbig-Haro flow from Haro 6-10 SO ASTRONOMICAL JOURNAL LA English DT Article DE ISM : clouds; ISM : jets and outflows; stars : formation; stars : pre-main-sequence ID T-TAURI STARS; AURIGA MOLECULAR CLOUD; EMBEDDED YOUNG STARS; OPTICAL SPECTROSCOPY; INFRARED COMPANIONS; STELLAR OBJECTS; EXCITING STARS; JETS; OUTFLOWS; IMAGES AB We report the discovery of a parsec-scale Herbig-Haro flow emanating from the young binary system Hare 6-10 in Taurus. The how extends for about 39' (1.6 pc) at a position angle of about 222 degrees and contains part of the previously known HH 184. The apparent ends of the flow are defined by the newly discovered III-I 410 and HH 411, which are located 24' southwest and 15' northeast, respectively, from Hare 6-10. We suggest that the giant HH flow is most likely driven by the infrared companion to the T-Tauri primary in Hare 6-10; however, the T-Tauri component also appears to be driving a relatively weak and much smaller outflow with a north-south orientation. The two flows appear to undergo synchronized episodes of increased mass ejection, which may be due to enhanced gravitational interactions between the binary components during periastron. We also report the discovery of a new I-II-I jet, III-I 414, which is driven by IRAS 04264+2433. HH 414 points directly toward an associated bow shock, HH 413; the HH 413/414 flow crosses the axis of the III-I 410/411 how at a large angle. C1 NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Greenbelt, MD 20771 USA. Univ Colorado, Ctr Astrophys & Space Astron, Boulder, CO 80309 USA. Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA. Colgate Univ, Dept Phys & Astron, Hamilton, NY 13346 USA. RP Devine, D (reprint author), NASA, Goddard Space Flight Ctr, Astron & Solar Phys Lab, Code 681, Greenbelt, MD 20771 USA. NR 37 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 0004-6256 J9 ASTRON J JI Astron. J. PD JUN PY 1999 VL 117 IS 6 BP 2931 EP 2940 DI 10.1086/300886 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 214VU UT WOS:000081348900029 ER PT J AU Dobbie, PD Barstow, MA Burleigh, MR Hubeny, I AF Dobbie, PD Barstow, MA Burleigh, MR Hubeny, I TI Opacities along the line of sight to and in the atmosphere of the white dwarf in the close detached DAO plus dM binary RE J0720-318 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : abundances; stars : atmospheres; stars : binaries : close; stars : individual : RE J0720-318 ID PRE-CATACLYSMIC BINARY; EPSILON-CANIS-MAJORIS; ALL-SKY SURVEY; EXTREME-ULTRAVIOLET; RADIATIVE LEVITATION; INTERSTELLAR-MEDIUM; TEMPERATURE SCALE; MASS-DISTRIBUTION; HEAVY-ELEMENTS; V471 TAURI AB We present the results from a multi-wavelength study of the mixed H+He composition DAO white dwarf RE J0720-318. A detailed analysis of UV and EW spectroscopic data with state-of-the-art non-LTE photospheric models demonstrates that the observed opacity to EUV radiation probably results from a more complex structure than a simple H+He, chemically layered atmosphere. Instead, EUV photometry and phase resolved EUV spectroscopy indicate a likely spatial nonuniformity in the surface distribution of helium, which is consistent with a model in which material is accreted from the wind of the dM secondary. The rotational modulation of the spatially inhomogeneous EUV opacity allows us to estimate the rotation period of the white dwarf (0.463 +/- 0.004 days). We have also reviewed two plausible origins proposed by Burleigh et al. (1997) and Dupuis et al. (1997a) to account for the unusual N(HI)/N(HeI)similar to 1 along this fine of sight. We conclude that it is probably due to the presence of a cloud of ionized gas along this line of sight, rather than a circumbinary disk. The cloud, residing between 123-170 pc distant in the direction of the CMa ISM tunnel, may be greater than or similar to 40 pc in length. C1 Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. RP Dobbie, PD (reprint author), Univ Leicester, Dept Phys & Astron, Univ Rd, Leicester LE1 7RH, Leics, England. EM pdd@star.le.ac.uk NR 67 TC 12 Z9 12 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN PY 1999 VL 346 IS 1 BP 163 EP 174 PG 12 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 203FK UT WOS:000080697300022 ER PT J AU Guirado, JC Jones, DL Lara, L Marcaide, JM Preston, RA Rao, AP Sherwood, WA AF Guirado, JC Jones, DL Lara, L Marcaide, JM Preston, RA Rao, AP Sherwood, WA TI Dual-frequency VLBI observations of the gravitational lens system PKS 1830-211 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE cosmology : gravitational lensing; galaxies : quasars : individual : PKS 1830-211 ID RING PKS-1830-211; EINSTEIN RING; RADIO-SOURCE; PKS1830-211; IMAGES AB From simultaneous 8.4 and 2.3 GHz VLBA observations we have studied the morphology and properties of the compact components of the gravitational lens PKS 1830-211. We have found that the size of the southwest component increases as lambda(2), most probably due to scattering by interstellar plasma. while the size of the northeast component does not increase with such wavelength dependence, The small separation between both lensed components, compared with the typical size of scattering clumps in our Galaxy, suggests that the scattering material is located in the lensing galaxy, rather than in the Milky Way. Within the uncertainties, the flux-density ratios of the brightest feature in the two compact components for the two frequency bands agree with each other, as expected for images of the same background feature. C1 Univ Valencia, Dept Astron, E-46100 Burjassot, Valencia, Spain. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain. Tata Inst, Natl Ctr Radio Astrophys, Poona 411007, Maharashtra, India. Max Planck Inst Radioastron, D-53121 Bonn, Germany. RP Guirado, JC (reprint author), Univ Valencia, Dept Astron, E-46100 Burjassot, Valencia, Spain. EM jcg@vlbi.uv.es NR 21 TC 17 Z9 17 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN PY 1999 VL 346 IS 2 BP 392 EP 396 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 212PK UT WOS:000081225300011 ER PT J AU De Moortel, I Hood, AW Ireland, J Arber, TD AF De Moortel, I Hood, AW Ireland, J Arber, TD TI Phase mixing of Alfven waves in a stratified and open atmosphere SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE magnetohydrodynamics (MHD); waves; Sun : corona ID SOLAR CORONAL HOLES AB Phase mixing was introduced by Heyvaerts and Priest (1983) as a mechanism for heating the plasma in the open magnetic field regions of coronal holes. Here the basic process is modified to include a stratified atmosphere in which the density decreases with height. We present an analytical solution in the case of zero dissipation and use a numerical code in the non-zero dissipation case to describe the effect of strati fication on phase mixing. The exponential damping behaviour derived by Heyvaerts and Priest is largely confirmed in the non stratified limit. However, it is shown that the decrease in density lengthens the oscillation wavelengths and thereby reduces the generation of transverse gradients. Furthermore we found that in a stratified atmosphere the perturbed magnetic field and velocity behave quite differently depending on whether we consider resistivity or viscosity. Ohmic heating is spread out over a greater height range in a stratified medium whereas viscous heating is not strongly influenced by the stratification. C1 Univ St Andrews, Sch Math & Computat Sci, St Andrews KY16 9SS, Fife, Scotland. NASA, Goddard Space Flight Ctr, Greenbelt, MD 20711 USA. RP De Moortel, I (reprint author), Univ St Andrews, Sch Math & Computat Sci, N Haugh, St Andrews KY16 9SS, Fife, Scotland. EM ineke@mcs.st-and.ac.uk NR 16 TC 42 Z9 42 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN PY 1999 VL 346 IS 2 BP 641 EP 651 PG 11 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 212PK UT WOS:000081225300040 ER PT J AU Israel, GL Oosterbroek, T Angelini, L Campana, S Mereghetti, S Parmar, AN Segreto, A Stella, L van Paradijs, J White, NE AF Israel, GL Oosterbroek, T Angelini, L Campana, S Mereghetti, S Parmar, AN Segreto, A Stella, L van Paradijs, J White, NE TI BeppoSAX monitoring of the "anomalous" X-ray pulsar 4U 0142+61 SO ASTRONOMY & ASTROPHYSICS LA English DT Article DE stars : evolution; stars : neutron; stars : pulsars : individual : 4U 0142+61; X-rays : stars ID DISCOVERY; SPECTRUM; PULSATIONS; 4U-0142+61; EMISSION AB The 8.7 s X-ray pulsar 4U0142+61 was monitored by BeppoSAX between January 1997 and February 1998. This source belongs to the rapidly growing class of "anomalous" X-ray pulsars (AXPs) which have pulse periods in the 6-12 s range and no plausible optical, infrared or radio counterparts. The BeppoSAX periods measurements show that 4U0142+61 continues its spin-down at a nearly constant rate of P similar to 2 x 10(-12) s s(-1). The 0.5-10 keV pulse shape is double peaked. The phase-averaged spectrum can be described by a steep absorbed power-law (Gamma similar to 4) plus a blackbody with kT similar to 0.4 keV. 4U0142+61 was also detected serendipitously in a March 1996 RXTE observation pointed towards the nearby 1455 s Xray pulsar RX J0146.9+6121. The timing analysis results are reported for this observation and the spin history of 4U 0142+61 since 1979 is discussed. C1 Osservatorio Astron Roma, I-00040 Monte Porzio Catone, Roma, Italy. European Space Agcy, Estec, Dept Space Sci, Div Astrophys, NL-2200 AG Noordwijk, Netherlands. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Osservatorio Astrofis Brera, I-23807 Merate, Lecco, Italy. CNR, Ist Fis Cosm G Occhialini, I-20133 Milan, Italy. CNR, Ist Fis Cosm & Applicaz Informat, I-90146 Palermo, Italy. Astron Inst Anton Pannekoek, NL-1098 SJ Amsterdam, Netherlands. Ctr High Energy Astrophys, NL-1098 SJ Amsterdam, Netherlands. UAH, Dept Phys, Huntsville, AL 35899 USA. RP Israel, GL (reprint author), Osservatorio Astron Roma, Via Frascati 33, I-00040 Monte Porzio Catone, Roma, Italy. EM israel@coma.mporzio.astro.it RI White, Nicholas/B-6428-2012; OI White, Nicholas/0000-0003-3853-3462; Campana, Sergio/0000-0001-6278-1576; Segreto, Alberto/0000-0001-7341-6603; Israel, GianLuca/0000-0001-5480-6438 NR 32 TC 35 Z9 35 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN PY 1999 VL 346 IS 3 BP 929 EP 935 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 212FT UT WOS:000081207200032 ER PT J AU Moehler, S Sweigart, AV Landsman, WB Heber, U Catelan, M AF Moehler, S Sweigart, AV Landsman, WB Heber, U Catelan, M TI Physical parameters of hot horizontal-branch stars in NGC 6752: deep mixing and radiative levitation SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE stars : early-type; stars : fundamental parameters; stars : horizontal-branch; Galaxy : globular clusters : individual : NGC 6752 ID GLOBULAR-CLUSTERS; NGC-6752; GIANTS AB Atmospheric parameters (T-eff, log g and log n(He)/n(H)) are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC 6752. For 19 stars Mg II and Fe II lines are detected indicating an iron enrichment by a factor 50 on average with respect to the cluster abundance whereas the magnesium abundances are consistent with the cluster metallicity. This finding adds to the growing evidence that radiative levitation plays a significant role in determining the physical parameters of blue KB stars. Indeed, we find that iron enrichment can explain part,; but not all, of the problem of anomalously low gravities along the blue HE. Thus the physical parameters of horizontal branch stars hotter than about 11,500 K in NGC 6752, as derived in this paper, are best explained by a combination of helium mixing and radiative levitation effects. C1 Univ Erlangen Nurnberg, Astron Inst, Dr Remeis Sternwarte, D-96049 Bamberg, Germany. NASA, Goddard Space Flight Ctr, Raytheon ITSS, Greenbelt, MD 20771 USA. RP Moehler, S (reprint author), Univ Erlangen Nurnberg, Astron Inst, Dr Remeis Sternwarte, Sternwartstr 7, D-96049 Bamberg, Germany. EM moehler@sternwarte.uni-erlangen.de; sweigart@bach.gsfc.nasa.gov; landsman@mpb.gsfc.nasa.gov; heber@sternwarte.uni-erlangen.de; catelan@stars.gsfc.nasa.gov RI Heber, Ulrich/G-3306-2013 OI Heber, Ulrich/0000-0001-7798-6769 NR 13 TC 36 Z9 36 U1 0 U2 0 PU EDP SCIENCES S A PI LES ULIS CEDEX A PA 17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE SN 0004-6361 J9 ASTRON ASTROPHYS JI Astron. Astrophys. PD JUN PY 1999 VL 346 IS 1 BP L1 EP L4 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 203FK UT WOS:000080697300001 ER PT J AU Vandenbussche, B Ehrenfreund, P Boogert, ACA van Dishoeck, EF Schutte, WA Gerakines, PA Chiar, J Tielens, AGGM Keane, J Whittet, DCB Breitfellner, M Burgdorf, M AF Vandenbussche, B Ehrenfreund, P Boogert, ACA van Dishoeck, EF Schutte, WA Gerakines, PA Chiar, J Tielens, AGGM Keane, J Whittet, DCB Breitfellner, M Burgdorf, M TI Constraints on the abundance of solid O-2 in dense clouds from ISO-SWS and ground-based observations SO ASTRONOMY & ASTROPHYSICS LA English DT Letter DE ISM : abundances; ISM : molecules; ISM : dust, extinction; infrared : ISM : lines and bands ID INFRARED-SPECTROSCOPY; ICE ANALOGS; INTERSTELLAR; N-2; CO; ABSORPTION; MANTLES; OXYGEN; DUST; H2O AB The Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) has been used to search for solid O-2 in cold dense clouds at 6.45 mu m. Additional constraints on the O-2 abundance are obtained from analysis of the 4.67 mu m solid CO absorption profile observed from the ground. We derive upper limits of 50% and 100% of solid O-2 relative to solid CO toward the protostellar sources R CrA IRS2 and NGC 7538 IRS9 respectively, corresponding to abundances of 30 x 10(-6) and 15 x 10(-6) relative to n(H). These results indicate that the abundance of solid O-2 in dense clouds accounts for less than 6% of the total oxygen budget in the interstellar medium. The reservoirs of oxygen in dense clouds are discussed, taking into account recent measurements of oxygen-bearing species. C1 Katholieke Univ Leuven, Inst Sterrenkunde, B-3001 Heverlee, Belgium. Leiden Observ, Raymond & Beverly Sackler Lab Astrophys, NL-2300 RA Leiden, Netherlands. Kapteyn Astron Inst, NL-9700 AV Groningen, Netherlands. Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA. ESA, Dept Space Sci, Div Astrophys, ISO Data Ctr, E-28080 Madrid, Spain. NASA, Ames Res Ctr, Moffett Field, CA 94035 USA. RP Vandenbussche, B (reprint author), Katholieke Univ Leuven, Inst Sterrenkunde, Celestijnenlaan 200B, B-3001 Heverlee, Belgium. RI Gerakines, Perry/B-9705-2009; Gerakines, Perry/D-2226-2012 OI Gerakines, Perry/0000-0002-9667-5904 NR 26 TC 55 Z9 55 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 JUN PY 1999 VL 346 IS 3 BP L57 EP L60 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 212FT UT WOS:000081207200006 ER PT J AU Bautista, MA AF Bautista, MA TI Atomic data from the Iron Project XXXIX. Photoionization cross sections and oscillator strengths for NiII SO ASTRONOMY & ASTROPHYSICS SUPPLEMENT SERIES LA English DT Article DE atomic data; atomic processes; line : formation; ISM : abundances; ultraviolet : general; infrared : ISM : lines and bands ID IONS AB We present calculations of energy levels, photoionization cross sections and dipole allowed transition probabilities for singly ionized nickel. The computations were carried out in the close coupling approximation using the R-matrix method including 49 LS terms with multiplicity (2S + 1) = 1, 3, and 5 of the target ion Ni III. We calculated 836 LS states, 561 of which are bound, with principal quantum number n less than or equal to 10 and angular momentum L less than or equal to 7. The results also include dipole oscillator strengths for 23 738 LS transitions, and photoionization cross sections with detailed resonance structures for all bound states. The f-values and radiative lifetimes agree well with available experimental measurements. However, the present f-values disagree considerably from previous computations by Kurucz and coworkers which are currently used in Ni II abundance determination of the ISM. In particular, the Kurucz f-values for transitions from the Ni II ground state seem to be overestimated by factors of two to three thus, nickel may be less depleted in ISM than previously estimated. The photoionization cross section for the 3d(9) D-2 ground state of Ni II exhibits near threshold packs of resonances that rise over the background cross section by several orders of magnitude. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Bautista, MA (reprint author), NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Code 662, Greenbelt, MD 20771 USA. NR 19 TC 15 Z9 15 U1 0 U2 0 PU E D P SCIENCES PI LES ULIS CEDEXA PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES ULIS CEDEXA, FRANCE SN 0365-0138 J9 ASTRON ASTROPHYS SUP JI Astron. Astrophys. Suppl. Ser. PD JUN PY 1999 VL 137 IS 3 BP 529 EP 535 PG 7 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 222MJ UT WOS:000081789100010 ER PT J AU Kazanas, D Mastichiadis, A AF Kazanas, D Mastichiadis, A TI The origin of TeV electrons in blazars SO ASTROPARTICLE PHYSICS LA English DT Article DE accretion; black hole physics; radiation mechanisms : Compton and inverse Compton; active galaxies : blazars AB There is increasing observational evidence that relativistic particles of energies similar to 1 TeV provide a significant pressure component of the plasma which powers at least some of the relativistic jets associated with AGN. Furthermore, observations of flares with duration similar to 15 min at TeV energies indicate that the associated electrons are accelerated to the required energies on these or shorter time scales, which are comparable to the synchrotron loss time for the values of the magnetic fields thought present in these jets. As such, they push the potential acceleration mechanisms to their limits and prompt us to examine the conditions under which it may be possible for hadronic processes to provide the electrons of the requisite energies. Relativistic hadrons could presumably exist within the flow, having been accelerated efficiently near the compact object and then transported along with it, releasing their energy by an instability due to p-gamma reactions once a well-defined threshold is reached. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, LHEA, Greenbelt, MD 20771 USA. Univ Athens, Dept Astron, GR-15784 Athens, Greece. RP Kazanas, D (reprint author), NASA, Goddard Space Flight Ctr, LHEA, Greenbelt, MD 20771 USA. NR 4 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 41 EP 44 DI 10.1016/S0927-6505(99)00022-5 PG 4 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300007 ER PT J AU Lister, ML Marscher, AP AF Lister, ML Marscher, AP TI Predictions of ECS and SSC models for flux-limited samples of gamma-ray blazars SO ASTROPARTICLE PHYSICS LA English DT Article ID EMISSION; JET AB The external Compton scattering (ECS) and synchrotron self-Compton (SSC) models make distinct predictions for the amount of Doppler boosting of high-energy gamma-rays emitted by blazars. We examine how these differences affect the predicted properties of AGN samples selected on the basis of gamma-ray emission. We create simulated flux-limited samples based on the ECS and SSC models, and compare their properties to those of identified EGRET blazars. We find that for small gamma-ray-selected samples, the two models make very similar predictions, and cannot be reliably distinguished. This is primarily due to the fact that not only the Doppler factor, but also the cosmological distance and intrinsic luminosity play a role in determining whether an AGN is included in a flux-limited gamma-ray sample. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Boston Univ, Dept Astron, Boston, MA 02215 USA. RP Lister, ML (reprint author), CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 10 TC 15 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 65 EP 67 DI 10.1016/S0927-6505(99)00027-4 PG 3 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300012 ER PT J AU Ghosh, KK Ramsey, BD Sivaram, C AF Ghosh, KK Ramsey, BD Sivaram, C TI Origin of MeV gamma-ray emissions from blazars SO ASTROPARTICLE PHYSICS LA English DT Article ID COMPTEL AB We have developed a model for MeV emission from blazars that involves the production of MeV gamma-rays through Inverse Compton (IC) scattering of electrons in the blob of a jet, with the UV photons of the accretion disk. The OSSE and the COMPTEL spectra of PKS 0528 + 134 have been fitted with the computed MeV gamma-ray fluxes of the above model. A good fit was obtained with electrons of Lorentz factor of 10(1.5) to 10(3) and a jet with viewing angle of less than or equal to 15 degrees and an accretion disk temperature in the range of 2.0 to 6.0 x 10(5) K. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Space Sci Lab, Huntsville, AL 35812 USA. Indian Inst Astrophys, Bangalore 560034, Karnataka, India. RP Ghosh, KK (reprint author), NASA, George C Marshall Space Flight Ctr, Space Sci Lab, ES84, Huntsville, AL 35812 USA. NR 13 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 69 EP 71 DI 10.1016/S0927-6505(99)00028-6 PG 3 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300013 ER PT J AU Stecker, FW AF Stecker, FW TI Intergalactic extinction of high energy gamma-rays SO ASTROPARTICLE PHYSICS LA English DT Article DE gamma-rays; BL Lac objects; gamma-ray bursts; background radiation; infrared ID DAMPED LYMAN-ALPHA; VERY-HIGH-ENERGY; INFRARED RADIATION; HIGH REDSHIFTS; ABSORPTION; GALAXIES; CONSTRAINTS; BURST; MARKARIAN-501; EVOLUTION AB We discuss the determination of the intergalactic pair-production absorption coefficient as derived by Stecker and De Jager by making use of a new empirically based calculation of the spectral energy distribution of the intergalactic infrared radiation field as given by Malkan and Stecker. We show that the results of the Malkan and Stecker calculation agree well with recent data on the infrared background. We then show that previous spectral data from observations of Mrk 421 and Mrk 501 are consistent with the amount of intergalactic absorption predicted by Stecker and De Jager and that the new HEGRA observations of the flaring spectrum of Mrk 501 presented at this conference actually appear to show the amount of intergalactic absorption which we predict. As a further test for intergalactic absorption, we give a predicted spectrum, with absorption included, for PKS 2155-304. This XBL lies at a redshift of 0.12, the highest redshift source yet observed at an energy above 0.3 TeV. This source should have its spectrum steepened by similar to 1 in its spectral index between similar to 0.3 and similar to 3 TeV and should show an absorption cutoff above similar to 6 TeV. We also discuss the determination of the gamma-ray opacity at higher redshifts (out to z = 3), following the treatment of Salamon and Stecker. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. RP NASA, Goddard Space Flight Ctr, High Energy Phys Lab, Greenbelt, MD 20771 USA. RI Stecker, Floyd/D-3169-2012 NR 55 TC 22 Z9 22 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 EI 1873-2852 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 83 EP 91 DI 10.1016/S0927-6505(99)00030-4 PG 9 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300015 ER PT J AU Kataoka, J Mattox, JR Quinn, J Kubo, H Makino, F Takahashi, T Inoue, S Hartman, RC Madejski, GM Sreekumar, P Wagner, SJ AF Kataoka, J Mattox, JR Quinn, J Kubo, H Makino, F Takahashi, T Inoue, S Hartman, RC Madejski, GM Sreekumar, P Wagner, SJ TI Multiwavelength observations of the TeV blazar Mrk 501 in March 1996. The first report of the detection by EGRET SO ASTROPARTICLE PHYSICS LA English DT Article AB We present the results of a multiwavelength campaign for Mrk 501 performed in March 1996 with ASCA, EGRET, Whipple, and optical telescopes. We report here for the first time the detection of a GeV gamma-ray flux from Mrk 501 with EGRET with 3.5 sigma significance (E > 100 MeV). A higher flux was also observed in April/May 1996, with 4.0 sigma significance for E > 100 MeV, and 5.2 sigma significance for E > 500 MeV. We find that the multiband spectrum in March 1996 is consistent with that calculated from a one-zone SSC model, except for the extremely 'flat' TeV spectrum. We show that the discrepancy cannot be explained by either second order Comptonization or the contribution of the 'seed' IR photons from the host galaxy. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Inst Space & Astronaut Sci, Boston, MA USA. Boston Univ, Dept Astron, Boston, MA 02215 USA. Fred Lawrence Whipple Observ, Amado, AZ USA. Tokyo Inst Technol, Tokyo 152, Japan. Tokyo Metropolitan Univ, Dept Phys, Tokyo, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Landessternwarte Heidelberg, Heidelberg, Germany. RP Kataoka, J (reprint author), Inst Space & Astronaut Sci, Boston, MA USA. NR 10 TC 14 Z9 15 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 149 EP 151 DI 10.1016/S0927-6505(99)00040-7 PG 3 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300026 ER PT J AU Carson, M McKernan, B Yaqoob, T Fegan, D AF Carson, M McKernan, B Yaqoob, T Fegan, D TI A search for short time scale TeV variability in Mkn501 SO ASTROPARTICLE PHYSICS LA English DT Article ID COMPTON AB We analyse Whipple TeV gamma-ray data from active states of Mkn501 for short time scale variability using the new Excess Pair Fraction (EPF) method. No evidence is found for significant variability on time scales less than 10 minutes. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Natl Univ Ireland Univ Coll Dublin, Dept Phys, Dublin 4, Ireland. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Carson, M (reprint author), Natl Univ Ireland Univ Coll Dublin, Dept Phys, Dublin 4, Ireland. OI Carson, Michael/0000-0003-0400-7819 NR 5 TC 1 Z9 1 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 153 EP 154 DI 10.1016/S0927-6505(99)00041-9 PG 2 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300027 ER PT J AU Wehrle, AE AF Wehrle, AE TI Multiwavelength observations of GeV blazars SO ASTROPARTICLE PHYSICS LA English DT Article ID BL LAC OBJECTS; RADIO; MILLIMETER; RADIATION; COMPTEL; 3C-279 AB Multiwavelength observations of GeV blazers have been used to constrain physical models of the relativistic jets. Using the EGRET and COMPTEL instruments on the Compton Observatory, in concert with other spacecraft and ground-based telescopes, we can form complete spectral energy distributions from 10(9) to 10(22) Hz. Such "snapshots" of the spectral energy distribution, especially during flares, show changes attributable to varying conditions in the jet. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Ctr Infrared Proc & Anal, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Pasadena, CA 91125 USA. RP Wehrle, AE (reprint author), Ctr Infrared Proc & Anal, Jet Prop Lab, MS 100-22, Pasadena, CA 91125 USA. NR 26 TC 6 Z9 6 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 169 EP 176 DI 10.1016/S0927-6505(99)00044-4 PG 8 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300030 ER PT J AU Takahashi, T Madejski, G Kubo, H AF Takahashi, T Madejski, G Kubo, H TI X-ray observations of TeV blazars and multi-frequency analysis SO ASTROPARTICLE PHYSICS LA English DT Article DE galaxies : active; galaxies : jet; BL Lacertae objects : general; BL Lacertae objects : individual (Markarian 421); quasars : general; gamma-rays : theory ID LACERTAE OBJECT MARKARIAN-421; ACTIVE GALAXY MARKARIAN-421; SPECTRUM RADIO QUASARS; RELATIVISTIC JETS; GAMMA-RAYS; MULTIWAVELENGTH OBSERVATIONS; EGRET OBSERVATIONS; VARIABILITY; EMISSION; FLARE AB The nonthermal spectra of blazars, observed from radio to GeV/TeV gamma-rays, reveal two pronounced components, both produced by radiation by energetic particles. One peaks in the IR-to-soft X-ray band, radiating via the synchrotron process; the other, peaking in the high-energy gamma-rays, is produced by the Compton process. These spectra - and, in particular, the ASCA data - suggest that the origin of the seed photons for Comptonization is diverse. In the High-energy peaked BL Lac objects (HBLs), the dominant seed photons for Comptonization appear to be the synchrotron photons internal to the jet (SSC process). In the quasar-hosted blazars (QHBs), on the other hand, the X-ray band emission is still dominated by the SSC process, while the MeV to GeV range is produced by Comptonization of external photons such as the emission line light. In the context of this three-component model, we derive the magnetic field of 0.1-1 Gauss for all classes of blazars. Lorentz factors gamma(peak) of electrons radiating at each peak of the nu F(nu) spectra are estimated to be similar to 10(5) for HBLs; this is much higher than similar to 10(3) for QHBs. This difference is consistent with the fact that the four sources that are known to emit TeV gamma-rays (TeV blazars) are all classified as HBLs. Among the TeV blazars, Mkn 421 is one of the brightest and most variable emitters from ultraviolet (eV) to hard gamma-ray (TeV) energies, and its correlated inter-band variability suggests that both keV and TeV spectral regimes are produced by the same, most energetic end of the electron population radiating via the synchrotron process in the keV, and the SSC process in TeV band. The multi-frequency observations including TeV energy band provide the best opportunity to understand high-energy emission from blazar jets. In this paper, we discuss results of multi-frequency analysis and review the results of intensive campaigns for Mkn 421 from 1994 to 1998. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. Tokyo Inst Technol, Dept Phys, Meguro Ku, Tokyo 1528551, Japan. RP Takahashi, T (reprint author), Inst Space & Astronaut Sci, Kanagawa 2298510, Japan. NR 49 TC 33 Z9 33 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 JUN PY 1999 VL 11 IS 1-2 BP 177 EP 187 DI 10.1016/S0927-6505(99)00045-6 PG 11 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300031 ER PT J AU Vestrand, WT Sreekumar, P AF Vestrand, WT Sreekumar, P TI RXTE observations of PKS 2155-304 during the November 1997 gamma-ray outburst SO ASTROPARTICLE PHYSICS LA English DT Article DE X-rays; gamma-rays; BL Lacertae objects; PKS 2155-304 AB We present X-ray observations of the nearby BL Lac PKS 2155-304 taken when it was undergoing a GeV/TeV gamma-ray outburst. During the outburst we measured X-ray fluxes in the 2-10 keV band that are the largest ever observed for PKS 2155-304, Comparison of these November 1997 measurements and other X-ray observations made contemporaneously with GeV or TeV gamma-ray observations indicate that X-ray and gamma-ray emissions are correlated. Measurements with X-ray all-sky monitors such as the ASM/RXTE and MOXE can therefore signal the presence of outbursts at gamma-ray energies from PKS 2155-304. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. Univ Calif Los Alamos Natl Lab, Los Alamos, NM 87545 USA. NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Vestrand, WT (reprint author), Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA. NR 9 TC 12 Z9 12 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 197 EP 199 PG 3 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300034 ER PT J AU Bloom, SD AF Bloom, SD TI Prospects for detecting and identifying high Galactic latitude EGRET sources at E > 50 GeV SO ASTROPARTICLE PHYSICS LA English DT Article ID BL LACERTAE; SKY SURVEY; IDENTIFICATIONS AB The majority of EGRET sources remain unidentified with counterparts at any other wavelength. However, a subset of sources at high Galactic latitude are very like to be associated with extragalactic radio sources, and either are blazars or are very similar to them. With the source localization of VERITAS, identification with these radio sources will be much firmer, should they be detected in gamma rays. I will discuss their chances for being detected at E > 50 GeV based on the multiwavelength data from representative radio sources which are considered to be good matches to EGRET unidentified objects. I will also discuss implications for the physics and classification of the sources. (C) 1999 Elsevier Science B.V. All rights reserved. C1 Ctr Infrared Proc & Anal, Jet Prop Lab, Pasadena, CA 91125 USA. CALTECH, Pasadena, CA 91125 USA. RP Ctr Infrared Proc & Anal, Jet Prop Lab, MS 100-22, Pasadena, CA 91125 USA. NR 18 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 EI 1873-2852 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 209 EP 212 DI 10.1016/S0927-6505(99)00051-1 PG 4 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300037 ER PT J AU Sreekumar, P Bertsch, DL Hartman, RC Nolan, PL Thompson, DJ AF Sreekumar, P Bertsch, DL Hartman, RC Nolan, PL Thompson, DJ TI GeV emission from the nearby radio galaxy Centaurus A SO ASTROPARTICLE PHYSICS LA English DT Article DE radio galaxy; Centaurus A; gamma-rays ID GAMMA-RAY EMISSION; EGRET OBSERVATIONS; NUCLEUS; COMPTON AB EGRET has detected 67 sources associated with active galactic nuclei. With the exception of radio galaxy Cen A, all are classified as belonging to the blazar class of active galactic nuclei. The cumulative exposure from multiple EGRET observations has provided the first clear detection of Centaurus A. Unlike the gamma-ray blazars seen by EGRET which are believed to exhibit near-alignment of the central jet along the line-of-sight, Cen A provides the first evidence for >100 MeV emission from a source with a confirmed large-inclination jet. Although the high-energy emission represents a lower luminosity than most EGRET blazars, with the advent of new more sensitive instruments such as GLAST and VERITAS, the detection of off-axis high-energy emission from more distant radio galaxies (space density of radio galaxies being similar to 10(3) times the blazar density) is an exciting possibility. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Univ Space Res Assoc, Washington, DC USA. Stanford Univ, WW Hansen Labs Phys, Stanford, CA 94305 USA. RP Sreekumar, P (reprint author), NASA, Goddard Space Flight Ctr, Code 661, Greenbelt, MD 20771 USA. RI Nolan, Patrick/A-5582-2009; Thompson, David/D-2939-2012 OI Thompson, David/0000-0001-5217-9135 NR 20 TC 72 Z9 72 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 221 EP 223 DI 10.1016/S0927-6505(99)00054-7 PG 3 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300040 ER PT J AU Connaughton, V VERITAS Collaboration AF Connaughton, V VERITAS Collaboration TI Gamma-ray bursts at VERITAS energies SO ASTROPARTICLE PHYSICS LA English DT Article DE gamma-ray bursts ID 28 FEBRUARY 1997; TIME DILATION; BATSE; REDSHIFT; PHOTONS AB Many of the recent contributions to the field of gamma-ray bursts (GRBs) have come from the discovery and observations of counterparts at wavelengths other than those traditionally associated with GRBs. Searches for VHE counterparts suffer two problems: slew time and, more severely, large GRB location error boxes. VERITAS provides a chance to overcome or compensate for these obstacles with fast slew times, large sky coverage, and a low energy threshold. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. RP Connaughton, V (reprint author), NASA, George C Marshall Space Flight Ctr, ES 84, Huntsville, AL 35812 USA. NR 22 TC 0 Z9 0 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 255 EP 257 DI 10.1016/S0927-6505(99)00060-2 PG 3 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300046 ER PT J AU Gehrels, N Michelson, P AF Gehrels, N Michelson, P TI GLAST: the next-generation high energy gamma-ray astronomy mission SO ASTROPARTICLE PHYSICS LA English DT Article DE gamma-ray astronomy; space astrophysics; future missions ID SUPERNOVA-REMNANTS; EGRET SOURCES; PULSARS; RADIATION AB The Gamma Ray Large Area Space Telescope (GLAST) is a high energy (20-300 GeV) gamma-ray astronomy mission planned for launch in 2005. The overarching scientific theme of the mission is studying sites of particle acceleration in the Universe. Topics of interest include active galactic nuclei and their jets, extragalactic and galactic diffuse emissions, dark matter, supernova remnants, pulsars, and the unidentified high energy gamma-ray sources. The sensitivity is 2 x 10(-9) photons cm(-2) s(-1) (>100 MeV) for a 2 year all-sky survey, which is a factor of >30 better than CGRO/EGRET. The GLAST program is currently in a high level of mission development activity. (C) 1999 Elsevier Science B.V. All rights reserved. C1 NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. Stanford Univ, Stanford, CA 94305 USA. RP Gehrels, N (reprint author), NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA. NR 26 TC 215 Z9 215 U1 0 U2 0 PU ELSEVIER SCIENCE BV PI AMSTERDAM PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS SN 0927-6505 J9 ASTROPART PHYS JI Astropart Phys. PD JUN PY 1999 VL 11 IS 1-2 BP 277 EP 282 PG 6 WC Astronomy & Astrophysics; Physics, Particles & Fields SC Astronomy & Astrophysics; Physics GA 212PW UT WOS:000081226300052 ER PT J AU Scoccimarro, R Couchman, HMP Frieman, JA AF Scoccimarro, R Couchman, HMP Frieman, JA TI The bispectrum as a signature of gravitational instability in redshift space SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; large-scale structure of universe; methods : numerical; methods : statistical ID GALAXY CORRELATION-FUNCTIONS; LARGE-SCALE BIAS; POWER SPECTRUM; REAL; FLUCTUATIONS; EVOLUTION; DISTORTIONS; SIMULATIONS; UNIVERSE; 3-POINT AB The bispectrum provides a characteristic signature of gravitational instability that can be used to probe the Gaussianity of the initial conditions and the bias of the galaxy distribution. We study how this signature is affected by redshift distortions using perturbation theory and high-resolution numerical simulations. We obtain perturbative results for the multipole expansion of the redshift-space bispectrum that provide a natural way to break the degeneracy between bias and Omega present in measurements of the redshift-space power spectrum. We propose a phenomenological model that incorporates the perturbative results and also describes the bispectrum in the transition to the nonlinear regime. We stress the importance of nonlinear effects and show that inaccurate treatment of these can lead to significant discrepancies in the determination of bias from galaxy redshift surveys. At small scales we find that the bispectrum monopole exhibits a strong configuration dependence that reflects the velocity dispersion of clusters. Therefore the hierarchical model for the three-point function does not hold in redshift space. C1 CITA, McLennan Phys Labs, Toronto, ON M5S 3H8, Canada. Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada. Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Univ Chicago, Dept Astron & Astrophys, Chicago, IL 60637 USA. RP Scoccimarro, R (reprint author), CITA, McLennan Phys Labs, 60 St George St, Toronto, ON M5S 3H8, Canada. NR 35 TC 101 Z9 102 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 JUN 1 PY 1999 VL 517 IS 2 BP 531 EP 540 DI 10.1086/307220 PN 1 PG 10 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700001 ER PT J AU Hui, L Rutledge, RE AF Hui, L Rutledge, RE TI The b distribution and the velocity structure of absorption peaks in the Ly alpha forest SO ASTROPHYSICAL JOURNAL LA English DT Article DE cosmology : theory; intergalactic medium; quasars : absorption lines ID PHOTOIONIZED INTERGALACTIC MEDIUM; GRAVITATIONAL COLLAPSE; MODEL; STATISTICS; EVOLUTION; CLOUDS AB A theory is developed that relates the observed b parameter of a Ly alpha absorption line to the velocity curvature of the corresponding peak in the optical depth fluctuation. Its relation to the traditional interpretation of b as the thermal broadening width is discussed. It is demonstrated that, independent of the details of the cosmological model, the differential b distribution has a high-b asymptote of dN/db proportional to b(-m), where m greater than or equal to 5, when we make the reasonable assumption that low-curvature fluctuations are statistically favored over high-curvature ones. There in general always exist lines much broader than the thermal width. We develop a linear perturbative analysis of the optical depth fluctuation, which yields a single-parameter prediction for the full b distribution. In addition to exhibiting the high-velocity tail, it qualitatively explains the observed sharp low-b cutoff-a simple reflection of the fact that high-curvature fluctuations are relatively rare. Although the existence of the high-b asymptote, which is independent of the validity of the linear expansion, is consistent with the observed b distribution, a detailed comparison of the linear prediction with six observational data sets indicates that higher order corrections are not negligible. The perturbative analysis nonetheless offers valuable insights into the dependence of the b distribution on cosmological parameters such as Omega and the power spectrum. A key parameter is the effective smoothing scale of the optical depth fluctuation, which is in turn determined by three scales: the thermal broadening width, the baryon smoothing scale (approximately the Jeans scale), and the observation/simulation resolution. The first two are determined by reionization history, but are comparable in general, whereas the third varies by about an order of magnitude in current hydrodynamic simulations. Studies with non-resolution-dominated b distributions can be used to probe the reionization history of the universe. C1 Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, Batavia, IL 60510 USA. Max Planck Inst Extraterr Phys, D-85740 Garching, Germany. RP Hui, L (reprint author), Fermi Natl Accelerator Lab, NASA, Fermilab Astrophys Ctr, POB 500, Batavia, IL 60510 USA. NR 27 TC 36 Z9 37 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 JUN 1 PY 1999 VL 517 IS 2 BP 541 EP 548 DI 10.1086/307202 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700002 ER PT J AU Holberg, JB Barstow, MA Bruhweiler, FC Hubeny, I Green, EM AF Holberg, JB Barstow, MA Bruhweiler, FC Hubeny, I Green, EM TI Far-ultraviolet Space Telescope Imaging spectrograph spectra of the white dwarf REJ 1032+532. II. Stellar spectrum SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : abundances; stars : individual (REJ 1032+532); ultraviolet : stars; white dwarfs ID ALL-SKY SURVEY; MASS-DISTRIBUTION; HOT; SPECTROSCOPY; ATMOSPHERES; RICH; EUV AB We discuss the Nubble Space Telescope Space Telescope Imaging Spectrograph UV echelle spectrum of the hot DA white dwarf REJ 1032+532. The interstellar data from this spectrum are presented by Holberg and coworkers. In this paper we discuss a number of strong photospheric features due to C, N, and Si that are present in the REJ 1032+532 spectrum. While the inferred heavy element content of REJ 1032+532 roughly matches the predictions of radiative levitation for carbon and silicon, the observed nitrogen abundance greatly exceeds predictions by a factor of 50. The observed shapes of the N v lines provide the first evidence, at UV wavelengths, of heavy element stratification in a hot DA while dwarf. Homogeneous models are unable to reproduce the shape of the REJ 1032+532 N v lines, nor can they account for the relatively low degree of EUV opacity in the star. We present a simple stratified nitrogen model that resolves these problems. The high degree of stratification in REJ 1032+532 is the signature of ongoing mass loss in this star. The radial velocity of REJ 1032+532 obtained with Space Telescope Imaging Spectrograph differs by 44 km s(-1) from that obtained from the Balmer H I lines with the Multiple Mirror Telescope. This suggests that REJ 1032+532 is likely a member of a binary system containing either a late M star or another white dwarf. C1 Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England. Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA. NASA, Goddard Space Flight Ctr, AURA, NOAO, Greenbelt, MD 20771 USA. Univ Arizona, Steward Observ, Tucson, AZ 85721 USA. RP Holberg, JB (reprint author), Univ Arizona, Lunar & Planetary Lab, Gould Simpson Blvd, Tucson, AZ 85721 USA. EM holberg@argus.lpl.arizona.edu; mab@star.le.ac.uk; fredb@iacs.gsfc.nasa.gov; hubeny@tlusty.gsfc.nasa.gov; bgreen@as.arizona.edu NR 28 TC 22 Z9 22 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 JUN 1 PY 1999 VL 517 IS 2 BP 850 EP 858 DI 10.1086/307238 PN 1 PG 9 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700025 ER PT J AU Smith, MA Robinson, RD AF Smith, MA Robinson, RD TI A multiwavelength campaign on gamma Cassiopeiae. III. The case for magnetically controlled circumstellar kinematics SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; stars : activity; stars : emission-line, Be; stars : individual (gamma Cassiopeiae); stars : rotation ID FAR-UV; X-RAY; STARS; DISKS; MODEL; VARIABILITY; INSTABILITY; ATMOSPHERES; SYSTEM AB In two previous papers, we have discussed simultaneous Rossi X-Ray Timing Explorer (RXTE) and Hubble Space Telescope GHRS observations made of gamma Cas (B0.5e) over a full day on 1996 March 14-15. The light curves generated from these data show features that anticorrelate and led us to conclude that the star has multiple surface activity centers that: rotate into view every rotational cycle of 1.123 days. In a second paper we found that dips in the UV continuum (UVC) light curve are probably caused by the passage of cool, co-orbiting clouds that are suspended above surface X-ray-active centers. In this paper we use difference spectra from our >21 hr GHRS time series to investigate less than or equal to 2% spectral variations within the photospheric Si IV 1394-1403 Angstrom lines as well as smaller variations from features in neighboring wavelengths at 1382-1386 and 1404-1417 Angstrom. Several difficulties arise in interpreting these variations as signatures of surface inhomogeneities, so we have studied both types of variations in the context of the kinematics of occulting circumstellar (CS) structures. By means of model-atmospheres codes and up-to-date line lists, we computed a grid of cloud opacity for various temperatures in our spectral range. Using these synthetic spectra, we are able to identify features as optically thick absorptions due to Fe II, Cr II, and C I lines from "cool" (T < 10,000 K) plasma, of Si IV, Si III, S IV, and Ni II lines from "warm" plasma (similar to 10,000-18,000 K), and of Si Iv and Fe v lines from hot plasma (greater than or equal to 30,000 K). The variations of the cool- and hot-plasma lines are in phase with the UVC light curve while the warm-plasma line curves lead these curves by 3-4 hr. The cool- and warm-plasma lines participate in the blue-to-red deceleration and appear to be analogues of the "migrating subfeature" pattern found in optical lines by previous observers. The velocity range for these lines is consistent with limits of +/-V sin i, suggesting that they are formed in corotating cloudlets that are distinct from the cool clouds we studied in a previous pager. In contrast, warm and hot-plasma lines are "ultrasharp features" ("USFs") that maintain a constant velocity for several hours. The USFs are visible over a wide velocity range, in some cases having a velocity of at least +1500 km s(-1). Both cooling and heating of circumstellar plasma is consistent with the existence of strong nonradiative processes operating in some regions above gamma Gas. Additionally, the migrating subfeatures find a ready explanation in circumstellar cloudlets forced by magnetic forces into corotation, as was also inferred from the UVC light curve in Smith, Robinson, & Hatzes. The existence of the stationary ultrasharp absorption features, particularly at large positive velocities, is difficult to explain unless one invokes interactions between magnetic loops from the star and a putative field in the circumstellar disc. This picture holds the potential of explaining the hot, flaring character of this star's X-rays and predicts the existence of other X-ray-emitting gamma Cas analogues as magnetic Be stars having dense CS discs. 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 20771 USA. RP Smith, MA (reprint author), Space Telescope Sci Inst, STScI, CSC, 3700 San Martin Dr, Baltimore, MD 21218 USA. EM msmith@stsci.edu NR 39 TC 35 Z9 35 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 JUN 1 PY 1999 VL 517 IS 2 BP 866 EP 882 DI 10.1086/307216 PN 1 PG 17 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700027 ER PT J AU Brooke, TY Sellgren, K Geballe, TR AF Brooke, TY Sellgren, K Geballe, TR TI New 3 micron spectra of Young stellar objects with H2O ice bands SO ASTROPHYSICAL JOURNAL LA English DT Article DE circumstellar matter; infrared : stars; stars : pre-main-sequence ID INFRARED-SPECTROSCOPY; MU-M; ABSORPTION FEATURES; MOLECULAR CLOUD; MONOCEROS R2/IRS-3; PROTOSTAR GL-2136; METHANOL; TAURUS; STARS; DUST AB We present new ground-based 3 mu m spectra of 14 young stellar objects with H2O ice absorption bands. The broad absorption feature at 3.47 mu m was detected toward all objects, and its optical depth is correlated with the optical depth of H2O ice, strengthening an earlier finding. The broad absorption feature at 3.25 mu m was detected toward two more sources, and an upper limit is given for a third source. The optical depths of the 3.25 mu m feature obtained to date are better correlated with the optical depth of the refractory silicate dust than with that of H2O ice. If this trend is confirmed, this would support our proposed identification of the feature as the C-H stretch of aromatic hydrocarbons at low temperature. An absorption feature at 3.53 mu m due to solid methanol was detected for the first time toward Mon R2/IRS 2, as well as toward W33A and GL 2136. The wavelengths of the CH3OH features toward W33A, GL 2136, and NGC 7538/IRS 9 can be fitted by CH3OH-rich ices, whereas the wavelength of the feature toward Mon R2/IRS 2 suggests an H2O-rich ice environment. Solid methanol abundances toward GL 2136, NGC 7538/IRS 9, and Mon R2/IRS 2 are 3%-5% relative to H2O ice. There is an additional narrow absorption feature near 3.47 mu m toward W33A. For the object W51/IRS 2, spatially resolved spectra from 2 to 4 mu m indicate that the H2O ice is located predominantly in front of the eastern component and that the H2O ice extinction is much deeper than previously estimated. For the object RNO 91, spectra from 2 to 4 mu m reveal stellar (or circumstellar) CO gas absorption and deeper H2O ice extinction than previously estimated. C1 CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. Ohio State Univ, Dept Astron, Columbus, OH 43210 USA. Joint Astron Ctr, Hilo, HI 96720 USA. RP Brooke, TY (reprint author), CALTECH, Jet Prop Lab, MS 169-237,4800 Oak Grove Dr, Pasadena, CA 91109 USA. NR 48 TC 106 Z9 108 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 JUN 1 PY 1999 VL 517 IS 2 BP 883 EP 900 DI 10.1086/307237 PN 1 PG 18 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700028 ER PT J AU McCollough, ML Robinson, CR Zhang, SN Harmon, BA Hjellming, RM Waltman, EB Foster, RS Ghigo, FD Briggs, MS Pendleton, GN Johnston, KJ AF McCollough, ML Robinson, CR Zhang, SN Harmon, BA Hjellming, RM Waltman, EB Foster, RS Ghigo, FD Briggs, MS Pendleton, GN Johnston, KJ TI Discovery of correlated behavior between the hard X-ray and the radio bands in Cygnus X-3 SO ASTROPHYSICAL JOURNAL LA English DT Article DE radio continuum : stars; stars : individual (Cygnus X-3); X-rays : stars ID VLBI OBSERVATIONS; GRO J1655-40; SPACED DATA; 8.3 GHZ; OUTBURST; EMISSION; JET AB Using Compton Gamma Ray Observatory BATSE hard X-ray (HXR) data and GHz radio monitoring data from the Green Bank Interferometer, we have performed a long-term study (similar to 1800 days) of the unusual X-ray binary Cyg X-3, resulting in the discovery of a remarkable relationship between these two wavelength bands. We find that during quiescent radio states, the radio flux is strongly anticorrelated with the intensity of the HXR emission. The relationship switches to a correlation with the onset of major radio flaring activity. During major radio flaring activity, the HXR drops to a very low intensity during quenching in the radio and recovers during the radio flare. Injection of plasma into the radio jets of Cyg X-3 occurs during changes in the HXR emission and suggests that disk-related and jet-related components are responsible for the high energy emission. C1 Univ Space Res Assoc, Huntsville, AL 35805 USA. NASA, George C Marshall Space Flight Ctr, Huntsville, AL 35812 USA. Natl Radio Astron Observ, Socorro, NM 87801 USA. USN, Res Lab, Washington, DC 20375 USA. Natl Radio Astron Observ, Green Bank, WV 24944 USA. Univ Alabama, Dept Phys, Huntsville, AL 35899 USA. USN Observ, Washington, DC 20392 USA. RP McCollough, ML (reprint author), Univ Space Res Assoc, Huntsville, AL 35805 USA. NR 32 TC 50 Z9 50 U1 0 U2 1 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1999 VL 517 IS 2 BP 951 EP 955 DI 10.1086/307241 PN 1 PG 5 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700034 ER PT J AU Corbet, RHD Marshall, FE Peele, AG Takeshima, T AF Corbet, RHD Marshall, FE Peele, AG Takeshima, T TI Rossi X-Ray Timing Explorer observations of the X-ray pulsar XTE J1855-026: A possible new supergiant system SO ASTROPHYSICAL JOURNAL LA English DT Article DE pulsars : individual (XTE J1855-026); stars : individual (XTE J1855-026) stars : neutron; stars : winds, outflows; supergiants; X-rays : stars ID VELA X-1; PERFORMANCE; BINARY; LINE AB A new X-ray source, XTE J1855-026, was discovered during Rossi X-Ray Timing Explorer (RXTE) scans along the Galactic plane. The source shows pulsations at a period of 361 s and also modulation at a period of 6.1 days, which we interpret as the orbital period of the system. The X-ray spectrum above similar to 3 keV can be fitted with an absorbed power-law model with a high-energy cutoff and an iron emission line at approximately 6.4 keV. We interpret these results as indicating that XTE J1855-026 is likely to consist of a neutron star accreting from the wind of an O or B supergiant primary. A less likely interpretation is that XTE J1855-026 is instead a Be/neutron star binary, in which case it would have the shortest known orbital period for such a system. C1 NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA. RP Corbet, RHD (reprint author), Univ Space Res Assoc, Greenbelt, MD USA. NR 27 TC 29 Z9 30 U1 0 U2 0 PU IOP PUBLISHING LTD PI BRISTOL PA TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND SN 0004-637X EI 1538-4357 J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1999 VL 517 IS 2 BP 956 EP 963 DI 10.1086/307235 PN 1 PG 8 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700035 ER PT J AU Wooden, DH Harker, DE Woodward, CE Butner, HM Koike, C Witteborn, FC McMurtry, CW AF Wooden, DH Harker, DE Woodward, CE Butner, HM Koike, C Witteborn, FC McMurtry, CW TI Silicate mineralogy of the dust in the inner coma of comet C/1995 01 (Hale-Bopp) pre- and post-perihelion SO ASTROPHYSICAL JOURNAL LA English DT Review DE comets : individual (Hale-Bopp 1995 O1); dust, extinction; infrared : solar system; interplanetary medium ID INTERPLANETARY DUST; INTERSTELLAR DUST; SOLAR NEBULA; INFRARED OBSERVATIONS; OPTICAL-PROPERTIES; IRRADIATED GRAINS; FAYALITIC OLIVINE; BETA-PICTORIS; SPECTRA; MODEL AB We present 7.5-13.4 mu m infrared (IR) spectrophotometry (R similar or equal to 180-360) of the 10 mu m silicate emission from dust in the inner coma (i.e., within a diameter of 3") of comet C/1995 O1 (Hale-Bopp) at four temporal epochs from 1996 October through 1997 June during Hale-Bopp's approach to, arrival at, and recession from perihelion. Hale-Bopp's silicate feature is the strongest observed from any comet to date: the flux-to-continuum ratio at 10.0 mu m is 2.5 at 2.8 AU preperihelion, increases to 3.0 at 0.93 AU, and then decreases to 2.4 at 1.7 AU postperihelion, dropping more rapidly in strength than expected from preperihelion spectra and indicating a diminishment in the relative abundance of submicron sized grains by perihelion passage. The silicate feature also evolves with heliocentric distance. When far from perihelion, at similar to 2.8 AU, the High Efficiency Faint Object Grating Spectrometer (HIFOGS) 10 mu m silicate feature contains a 9.3 mu m shoulder attributable to amorphous pyroxene, broad emission from amorphous olivine (9.7 mu m), and the 11.2 mu m peak associated with crystalline olivine. Concurrent with the HIFOGS spectra at 2.8 AU, the Infrared Space Observatory (ISO) Short Wavelength Spectrometer (SWS) spectrum also shows the strong far-IR peaks of crystalline olivine at 18 mu m, 23 mu m, and 33 mu m. When close to perihelion the HIFOGS spectra include a newly discovered 9.3 mu m peak, identifiable as Mg-rich crystalline pyroxene. We hypothesize that the crystalline pyroxenes are cooler than the other silicates, too cool to be detected at 9.3 mu m at 2.8 AU but warm enough to be detected at 1.2 AU. The best-fit empirical model for the temporal evolution of Hale-Bopp's silicate feature constrains the Mg-rich crystalline pyroxenes to be dominated by ortho-pyroxene rather than clino-pyroxene. The crystalline pyroxenes have a color temperature that is 0.6 times cooler than and an abundance that is about 9 times greater than the other silicates at all epochs, assuming equivalent particle size distributions for all components. Comparing crystalline ortho-pyroxene and crystalline olivine in radiative equilibrium, both with Mg number 09,the ortho-pyroxene crystals are cooler because they are less absorbing at visible acid near-IR wavelengths. Thus, it is the high Mg content of the crystalline pyroxenes that accounts for their cooler temperature. The dominance of Mg-rich pyroxenes among Hale-Bopp's cometary silicates is consistent with PUMA-I mass spectrometer measurements of comet P/Halley 1986 III and with cometary interplanetary dust particles. The high Mg content of the pyroxenes in comet Hale-Bopp implies that they are either pristine solar nebula condensates or presolar grains such as the Mg-rich crystals recently discovered by ISO around asymptotic giant branch stars. C1 NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. Univ Wyoming, Dept Phys & Astron, Wyoming Infrared Observ, Laramie, WY 82071 USA. Univ Arizona, Submillimeter Telescope Observ, Tucson, AZ 85721 USA. Carnegie Inst Washington, Dept Terr Magnetism, Washington, DC 20005 USA. Kyoto Pharmaceut Univ, Kyoto 607, Japan. RP Wooden, DH (reprint author), NASA, Ames Res Ctr, Div Space Sci, Moffett Field, CA 94035 USA. OI Harker, David/0000-0001-6397-9082; Butner, Harold/0000-0003-4899-2064 NR 117 TC 187 Z9 189 U1 0 U2 4 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 JUN 1 PY 1999 VL 517 IS 2 BP 1034 EP 1058 DI 10.1086/307206 PN 1 PG 25 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VC UT WOS:000081011700041 ER PT J AU Leggett, SK Toomey, DW Geballe, TR Brown, RH AF Leggett, SK Toomey, DW Geballe, TR Brown, RH TI Revised fluxes for Gliese 229B SO ASTROPHYSICAL JOURNAL LA English DT Article DE stars : individual (Gliese 229B); stars : low-mass, brown dwarfs ID COOL BROWN DWARF; COCO AB We have used the coronagraphic instrument CoCo with the Infrared Telescope Facility's camera, NSFCAM, to obtain improved photometry at JHKL' of the giant planet/brown dwarf Gliese 229B. We have recalibrated the published spectra for this object and recalculated its luminosity. Our L' value and our flux calibration of the spectra at JHK are significantly different from those previously published. Our results show good agreement at all bands except H with evolutionary models by Burrows et al. which include grain condensation. The model comparison implies that Gliese 229B is likely to be a 0.5 Gyr old 25M(J) object with T-eff similar to 900 K. C1 Joint Astron Ctr, Hilo, HI 96720 USA. NASA, IRTF, Hilo, HI 96720 USA. Gemini N Observ, Hilo, HI 96720 USA. Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA. RP Leggett, SK (reprint author), Joint Astron Ctr, 660 N Aoboku Pl, Hilo, HI 96720 USA. OI Leggett, Sandy/0000-0002-3681-2989 NR 14 TC 65 Z9 65 U1 0 U2 0 PU UNIV CHICAGO PRESS PI CHICAGO PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA SN 0004-637X J9 ASTROPHYS J JI Astrophys. J. PD JUN 1 PY 1999 VL 517 IS 2 BP L139 EP L142 DI 10.1086/312049 PN 2 PG 4 WC Astronomy & Astrophysics SC Astronomy & Astrophysics GA 208VF UT WOS:000081012000017 ER EF