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  • Cell & Developmental Biology  (1,374)
  • ASTROPHYSICS  (1,224)
  • GEOPHYSICS  (762)
  • 1995-1999
  • 1990-1994  (3,131)
  • 1935-1939  (229)
  • 1990  (3,131)
  • 1938  (125)
  • 1937  (104)
Collection
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  • 1995-1999
  • 1990-1994  (3,131)
  • 1935-1939  (229)
Year
  • 1
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    Accurate GPS measurement of the location and orientation of a floating platform (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: This article describes the design and initial tests of the GPS portion of a system for making seafloor geodesy measurements. In the planned system, GPS antennas on a floating platform will be used to measure the location of an acoustic transducer, attached below the platform, which interrogates an array of transponders on the seafloor. Since the GPS antennas are necessarily some distance above the transducer, a short-baseline GPS interferometer consisting of three antennas is used to measure the platform's orientation. A preliminary test of several crucial elements of the system was performed. The test involved a fixed antenna on the pier and a second antenna floating on a buoy about 80 m away. GPS measurements of the vertical component of this baseline, analyzed independently by two groups using different software, agree with each other and with an independent measurement within a centimeter. The first test of an integrated GPS/acoustic system took place in the Santa Cruz Basin off the coast of southern California in May 1990. In this test a much larger buoy, designed and built at SIO, was equipped with three GPS antennas and an acoustic transducer that interrogated a transponder on the ocean floor. Preliminary analysis indicates that the horizontal position of the transponder can be determined with a precision of about a centimeter.
    Keywords: GEOPHYSICS
    Type: Marine Geodesy (ISSN 0149-0419); p. 255-264.
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  • 2
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    AVHRR imagery reveals Antarctic ice dynamics (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A portion of AVHRR data taken on December 5, 1987 at 06:15 GMT over a part of Antarctica is used here to show that many of the most significant dynamic features of ice sheets can be identified by a careful examination of AVHRR imagery. The relatively low resolution of this instrument makes it ideal for obtaining a broad view of the ice sheets, while its wide swath allows coverage of areas beyond the reach of high-resolution imagers either currently in orbit or planned. An interpretation is given of the present data, which cover the area of ice streams that drain the interior of the West Antarctic ice sheet into the Ross Ice Shelf.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 741
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  • 3
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    Earth Radiation Budget Experiment - Preliminary seasonal results (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Data from the Earth Radiation Budget Satellite (ERBS) and from the operational NOAA-9 satellite being placed in the archive of the earth Radiation Budget Experiment (ERBE) are discussed. The results of the ERBE data validation effort are reviewed along with ERBE solar constant observations and earth-viewing results. The latter include monthly average results for July 1985, annual average clear-sky fluxes, and annual average, zonal, and global results.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 297
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  • 4
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    Error analysis for earth orientation recovery from GPS data (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The use of GPS navigation satellites to study earth-orientation parameters in real-time is examined analytically with simulations of network geometries. The Orbit Analysis covariance-analysis program is employed to simulate the block-II constellation of 18 GPS satellites, and attention is given to the budget for tracking errors. Simultaneous solutions are derived for earth orientation given specific satellite orbits, ground clocks, and station positions with tropospheric scaling at each station. Media effects and measurement noise are found to be the main causes of uncertainty in earth-orientation determination. A program similar to the Polaris network using single-difference carrier-phase observations can provide earth-orientation parameters with accuracies similar to those for the VLBI program. The GPS concept offers faster data turnaround and lower costs in addition to more accurate determinations of UT1 and pole position.
    Keywords: GEOPHYSICS
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  • 5
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    Geomagnetic sudden impulses and storm sudden commencements - A note on terminology (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The definitions of and distinctions between storm sudden commencements (SSCs) and geomagnetic sudden impulses (SIs) are examined and present definitions of SIs and SSCs are modernized. Quantitative definitions of the two terms are recommended.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 1808
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  • 6
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    A model of the 8-25 micron point source infrared sky (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A model is developed that permits the representation of the Galactic disk and bulge, the molecular ring, extragalactic sky, and other Galactic structures in terms of the IR point-source sky. Full characterization is achieved for up to 87 types of Galactic sources in terms of scale heights and absolute magnitudes, and the model is guided by a parallel Monte Carlo simulation of the Galaxy at 12 microns. The model predicts differential and cumulative IR source counts for all bandpasses in the IRAS ranges and can therefore be employed to predict the character of the point-source sky related to IR space observations.
    Keywords: ASTROPHYSICS
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  • 7
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    The nature of interstellar/pre-cometary dust (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: During the past 15 years considerable progress in observational techniques has been achieved in the middle-infrared region (5000-500/cm, 2-20 microns), the region where most diagnostic molecular vibrations occur. Spectra of many different astronomical infrared sources, some deeply embedded in dark molecular clouds and others obscured only by dust in the diffuse interstellar medium are now available. These spectra provide a powerful probe, not only for the identification of interstellar molecules in both the gas and solid phases, but also of the physical and chemical conditions which prevail in these two very different domains. By comparing these spectra with laboratory spectra one can determine the composition and abundance of the icy material frozen on the cold (- 10K) dust in the dark interior of molecular clouds and of the hydrocarbon component of dust in the diffuse interstellar medium. As these are the building blocks of comets, the work described here also gives insight into the nature of comets.
    Keywords: ASTROPHYSICS
    Type: ; : Optical Pattern Re
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  • 8
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    GPS measurements of regional deformation in southern California - Some constraints on performance (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Results from the first major survey of southern California with GPS equipment are presented along with some limited results from late experiments assessing GPS performance by analysis of day-to-day and longer-term repeatability, as well as comparisons with VLBI. GPS performance on longer (50-500 km or longer) baselines, a length range useful for measurement of regional deformation and fault block velocities, is emphasized. The implications of this level of performance for meeting longer-term scientific objectives is addressed. It is concluded that GPS techniques and yield results comparable to those achieved with mobile VLBI techniques in California, assuming that appropriate network design and analysis techniques are used. GPS can thus provide important constraints on regional deformation in California with five yrs or less of measurements.
    Keywords: GEOPHYSICS
    Type: EOS (ISSN 0096-3941); 71; 1051-105
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  • 9
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    Interannual and decade fluctuations in the earth's rotation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The main findings of a study of earth rotation changes on the longer interannual and decade range of time scales are summarized. The earth rotation data provide important constraints on models of the internal structure and dynamics of the core and lower mantle. Torques at the core-mantle interface are due to time varying fluid motions in the core. A torque of about 0.2 Hadley units is found in the axial component during the 1980 period.
    Keywords: GEOPHYSICS
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  • 10
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    Study of the crust and mantle using magnetic surveys by Magsat and other satellites (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This article summarizes some of the methodology and results for studies of the earth's mantle and crust. Mantle conductivity studies can be made either by studying signals impressed on the earth from outside, e.g., the ionosphere or magnetosphere, or by studing signals originating in the core and transmitted through the mantle. Crustal field studies begin with a careful selection of the data and subsequent removal of core and external fields by some sort of filtering. Average maps from different local times sometimes differ, presumably due to the remaining presence of fields of external origin. Several techniques for further filtering are discussed. Where large-area aeromagnetic maps are available, crustal maps derived from satellite data can be compared with upward continued data. In general, the comparisons show agreement, with some differences, particularly in and near the auroral belts. The satellite data are further reduced by various methods of inverse and forward modeling, sometimes including reduction to the pole. These techniques are generally unstable at the equator. Common methods of stabilizing the inversions include principle components analysis and ridge regression. Because of the presence of the core field, the entire crustal contribution from the field is not known. Also, there is a basic nonuniqueness to the inverse solutions. Nevertheless, magnetizations that are interpretable can be derived.
    Keywords: GEOPHYSICS
    Type: (ISSN 0253-4126); 99; 581-618
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  • 11
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    Differential absorption lidar detection of ozone in the troposphere and lower stratosphere (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The DIAL technique for deriving O3 profiles from lidar measurements is discussed. Examples of a variety of O3 and aerosol measurements are presented from studies of (1) photochemically produced O3 in the summertime over the eastern United States and in biomass burning plumes during the dry season over the Amazon Basin of Brazil; (2) vertical O3 transport from the mixed layer into the free troposphere via cloud dynamics and from the stratosphere into the troposphere via tropopause fold events; and (3) O3 depletion in the O3 hole over Antarctica. The NASA airborne DIAL system is considered to be an advanced field system.
    Keywords: GEOPHYSICS
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  • 12
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    Short wavelength striations on expanding plasma clouds (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The present evaluation of current understanding of the growth and evolution of less-than-1 ion gyroradius 'flute modes' on a plasma as it expands across and ambient magnetic field notes that the mechanism by which the instability is generated, and its approximate linear theory (encompassing nonlocal, finite-beta, and collisional effects), have reached a satisfactory degree of development. AMPTE Ba releases have been the bases of most of the observational studies. Substantial progress is also noted in the development of a nonlinear mode-coupling theory which can resolve remaining differences between theory and observation.
    Keywords: GEOPHYSICS
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  • 13
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    Turbulence in astrophysics (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Some of the astrophysical scenarios in which turbulence plays an important role are discussed in view of the comparative advantages of currently available models of turbulence phenomena; attention is given to a specific model that has undergone continuous refinement since 1985. The desideratum in this inquiry is a turbulence model which incorporates the best features of an a priori deterministic model, as well as a redundant set of results from full numerical simulations for a wide variety of turbulent flows; there should also be a simplification of the former, and an enlargement of the complexities of the latter.
    Keywords: ASTROPHYSICS
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  • 14
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    Recent advances in magnetospheric substorm research (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: More than two decades of magnetospheric exploration have led to a reasonably clear morphological picture of geomagnetic substorms, which is often summarized in terms of the near-earth neutral line model of substorms. Although this qualitative theory is quite comprehensive and explains a great many observations, it is hard pressed to explain both recent observations of consistently earthward flow within 19 RE and also the prompt onset of magnetic turbulence at 8 RE at the time of substorm onset. Other theories have recently been proposed which tend to be more quantitative, but which explain a more limited number of substorm observations. The challenge seems to be to understand the esential physics of these various quantitative theories and integrate them into a larger structure such as provided by the near-earth neutral line model.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric and Terrestrial Physics (ISSN 0021-9169); 52; 1155-116
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  • 15
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    Cosmic impacts, cosmic catastrophes. II (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The role of extraterrestrial impacts in shaping the earth's history is discussed, arguing that cosmic impacts represent just one example of a general shift in thinking that has made the idea of catastrophes respectable in science. The origins of this view are presented and current catastrophic theory is discussed in the context of modern debate on the geological formation of the earth. Various conflicting theories are reviewed and prominent participants in the ongoing scientific controversy concerning catastrophism are introduced.
    Keywords: ASTROPHYSICS
    Type: Mercury (ISSN 0047-6773); 19; 21-25
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  • 16
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    The AMPTE lithium releases in the solar wind - A possible trigger for geomagnetic pulsations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Shortly after the AMPTE/IRM satellite had released Lithium ions into the solar wind, magnetometers on the ground and in the frontside magnetosphere observed deflections of a type similar to those associated with solar wind pressure pulses. Since the natural solar wind was very stable during this event and did not exhibit pressure changes, the magnetic deflections have likely been caused by the artificially injected Lithium cloud when it hit the magnetosphere. Order of magnitude estimates show that 300 g of Lithium vapor released in the solar wind are indeed able to produce a 300 nT magnetic deflection on the ground under favorable conditions.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2301-230
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  • 17
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    Hydrocarbon emission features in the IR spectra of warm supergiants (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations in the 3-13 micron range are presented for two objects possessing the unidentified 21-micron feature, IRAS 22272 and IRAS 07134, which were obtained in the course of search for circumstellar aromatic hydrocarbon (PAH) emission bands. The 3.3 and 6.2 micron bands are attributed to circumstellar PAH molecules, and the 6-9 micron plateau and the 12- and 6.9-micron lines are attributed to larger, aromatic hydrocarbon clusters. These are the coolest stars known to exhibit the IR emission bands. The 21-micron feature is conjectured to also originate in a carbonaceous carrier.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 365; L23-L26
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  • 18
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    The absence of circumstellar dust debris around G giants (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The IRAS data base has been searched for evidence for circumstellar dust around luminosity class III G giants, stars whose progenitors are mostly main-sequence A stars. While 20 percent of all main-sequence A dwarfs have dust which absorbs at least 5 x 10 to the -6th of the light from the star, less than 3 percent of all G giants have such clouds. One possible explanation for the absence of detectable dust debris around the G giants is that the Poynting-Robertson effect leads to the decay of the dust around the main-sequence A stars, and that the supply of these grains is not renewed indefinitely. In this case, the derived upper limit to the grain radius of about 0.2 cm for the bulk of the grains emitting the far-infrared emission is consistent with data derived from ground-based submillimeter observations. Another possible explanation for the lack of grains around at least some G giants is that the dust around the original A dwarf is mainly composed of relatively volatile material like water ice which thermally evaporates in a relatively short time during the giant phase of higher luminosity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 365; 317-320
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  • 19
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    CO(J = 2 - 1) study of molecular clouds in the southwest arm of M31 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first map of M31 in the CO(J = 2 - 1) transition, covering a 3 arcmin by 3 arcmin section of the SW arm-interarm region, is presented. The CO spectra in the arm region defined by H II regions are characterized by strong, narrow features which are interpreted here to be giant molecular clouds with masses of a few 100,000 solar masses. The interarm emission is interpreted as an ensemble of small clouds with masses of a few 10,000 solar masses. On the arm about 70 percent of the emission comes from large clouds, while off the arm essentially all of it comes from small clouds. The mass surface density on this section of M31 is about that of a comparable section of the Scutum arm of the Galaxy. The velocities of the giant clouds in the arm are shifted with respect to the rest of the molecular and atomic gas by about 15 km/s. This may be due to cloud response to passage through the spiral arm potential.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 365; 195-207
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  • 20
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    Lidar observations of ozone changes induced by subpolar air mass motion over Table Mountain, California (34.4 deg N) (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Between October 15 and November 8, 1988, the Goddard Space Flight Center mobile stratospheric lidar was in place at the (JPL) Table Mountain Facility (located at 34.4 deg N, 117.7 deg W) for the purpose of intercomparing with the JPL lidar permanently stationed at the observatory. During the course of the intercomparison both lidar systems detected a significant change in the vertical profile of ozone lasting for several days. An analysis of meteorological data available from the National Meteorological Center has shown this change to be dynamical in origin due to the transport of subpolar air over Table Mountain.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 20527-20
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  • 21
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    Magnetically controlled circumstellar matter in the helium-strong stars (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper reports the observation and interpretation of the ultraviolet spectrum variations of nine helium-strong stars: HD 36485, 37017, 37479, 37776, 58260, 60344, 64740, 96446, and 133518. A unified model is developed to account for the observed correlation among three stellar properties: the line profile characteristics of the C IV and Si IV resonance doublets, the variations in the strength of these lines, and the inferred magnetic field geometry. It is proposed that circumstellar plasma is trapped in the stellar magnetosphere near the magnetic equator or is channeled to form jetlike outflows from the magnetic polar regions. These results, together with those of a previous study of the helium-weak sn stars, show that both helium-weak and helium-strong stars can possess magnetospherically trapped plasma, notwithstanding their different photospheric properties. New results for radii and temperatures of the helium-strong stars in Ori OB 1 and for HD 64740 from low-dispersion IUE spectra are also presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 365; 665-676
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  • 22
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    Comment on 'A new method of spectral analysis and its application to the earth's free oscillations - The 'Sompi' method' by S. Hori et al (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 19789
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  • 23
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    First images of water vapor masers in the galaxy M33 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first successful VLBI observations of 10 extragalactic H2O masers in the M33 galaxy are reported. A spectral-line VLBI synthesis map is constructed, the first of any extragalactic H2O maser sources. The map has the lowest noise of any K-band spectral line VLBI map yet produced. The maser emission extends over about 300 milliarcseconds and is divided into 14 distinct spatial components, the strongest of which has a correlated flux density of about 0.7 Jy. The relative positions of some of these components are determined accurately enough to provide first-epoch measurements for proper motion studies. The characteristics of the maser are similar to those of the most powerful maser in the Galaxy, W49N. A compact H II region is found close to the maser which is 1 pc in diameter and whose emission measure is about 6 x 10 to the 7th pc/cm exp 6. This region is the compact component of a more extended H II complex that extends over about 100 pc.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 364; 513-526
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  • 24
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    Gamma-ray burster counterparts - Archival data (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper reports on the results of a search for optical transient images associated with gamma-ray bursters based on the collection of archival photographs at the Harvard College Observatory. This study searched through over 32,000 plates showing 16 gamma-ray burst error regions. The primary result is the identification of three optical transient images. The recurrence time scale for optical events with a gamma-ray to optical fluence ratio of less than 1000 is estimated to be 1.3 yr (with a 99-percent confidence interval of between 0.41 and 4.8 yr). A control study was simultaneously made where regions of the sky with no bursters were examined. The control region was 15.6 times larger than the burst search region, yet no optical transients were found. This paper describes in detail the methodology and the statistical results. Close attention is paid to a detailed analysis of the three optical transient images.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 364; 590-600
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  • 25
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    Laboratory measurements of NO2 line parameters near 1600/cm for the interpretation of stratospheric spectra (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Tunable diode laser laboratory measurements of infrared spectral parameters of selected NO2 lines near 1600/cm have been made to assess the contribution of uncertainties in these parameters to stratospheric measurements of NO2 made using the Balloon-Borne Laser In-Situ Sensor (BLISS) tunable diode laser spectrometer. Relative line intensities are measured to accuracies of better than 2 percent, with a root-sum-squared uncertainty in the absolute linestrengths of 4.5 percent. Air-broadening coefficients have been determined from measurements at total pressures in the range 20-100 Torr, at temperatures of 293 K and 214 K. These results are also discussed in the light of the discrepancies between infrared instruments flown in the 1982 and 1983 Balloon Intercomparison Campaigns.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 2157-216
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  • 26
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    Intrusive and extrusive growth of the Mount St Helens lava dome (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: High-resolution, digital topographic maps of the Mount St. Helens dome derived from aerial photographs are used here to make a quantitative assessment of the partitioning of magma into endogenous intrusion and exogenous lobes. The endogenous growth is found to be predictable, which shows that the cooling dome controls its own development independently of such deep-seated factors as magma overpressure and extrusion rate. The observed regular decrease in exogenous growth rate also allows volume prediction. Knowledge of the volume can be used to determine when an ongoing eruptive event should end. Finally, the observed transition from predominantly exogenous to predominantly endogenous growth reflects the increase in crust thickness, which in turn seems to depend on long repose periods rather than some fundamental change in the character of the dome.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 348; 435-437
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  • 27
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    Meteoritic silicon carbide - Pristine material from carbon stars (1990)
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    Publication Date: 2011-08-19
    Description: All five gases in interstellar silicon carbide grains have grossly nonsolar isotopic and elemental abundances that vary with grain size but are strikingly similar to calculated values for the helium-burning shell of low-mass carbon stars. Apparently these grains formed in carbon-star envelopes, and were impregnated with noble gas ions from a stellar wind. Meteoritic SiC provides a detailed record of nuclear and chemical processes in carbon stars.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 348; 293-298
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  • 28
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    Pc1 pulsations observed by AMPTE/CCE in the earth's outer magnetosphere (1990)
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    Publication Date: 2011-08-19
    Description: Electromagnetic ion-cyclotron waves in the Pc1-2 frequency range (0.1-5 Hz) have been observed in earth's equatorial magnetosphere over the range L = 3 to 9 by the AMPTE/CCE magnetic-field experiment. Detailed analysis of data from two orbits together with preliminary occurrence statistics from 31 days are reported. One example occurred during disturbed geomagnetic conditions (maximum AE greater than 1000 nT) and exhibited intense Pc1 from L = 5 to the magnetopause (L = about 7.5). The second example occurred during moderate to quiet conditions (average AE = about 300 nT) and displayed Pc1 in two distinct L ranges: low (L = about 4) and high (L greater than 7.5). Statistical results show that Pc1 are about 4 times more common for L greater than 7 than for L less than 6 and occur primarily in the afternoon. The discovery of a statistically dominant outer-magnetospheric source region implies that ring-current interaction with the plasmasphere is not the primary source of Pc1 excitation, but suggests that plasma sheet ions may be a significant energy source for Pc1. This result is consistent with the strong dependence of the linear convective growth rate on magnetic-field strength.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 1853-185
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  • 29
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    Quasinormal modes of Reissner-Nordstrom black holes (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A matrix-eigenvalue algorithm is presented for accurately computing the quasi-normal frequencies and modes of charged static blackholes. The method is then refined through the introduction of a continued-fraction step. The approach should generalize to a variety of nonseparable wave equations, including the Kerr-Newman case of charged rotating blackholes.
    Keywords: ASTROPHYSICS
    Type: Physical Review D - Particles and Fields, 3rd Series (ISSN 0556-2821); 41; 2986-299
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    The mechanics of the South Iceland Seismic Zone (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The mechanics of the South Iceland Seismic Zone is examined by means of boundary element modeling. The differences between the observed geometry of the major tectonically active features and that of a geometrically orthogonal ridge-transform system (which assumes that the upper part of the earth's crust is an elastic plate containing vertical cuts) are examined. It is suggested that north-south faults can accommodate transform deformation only if the faults are longer or more numerous than those observed so far. This is considered reasonable because earthquake surface rupture lengths are commonly less than the inferred fault length at depth. The South Iceland Seismic Zone is subject to sequences of large earthquake every 45-112 years. In comparing the seismic moment release derived from earthquake magnitudes with that predicted by the models, it is confirmed that the system of north-south faults can act as a transform fault.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 17339-17
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    Electron-positron pairs, Compton reflection, and the X-ray spectra of active galactic nuclei (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is shown here that reprocessing of radiation fron nonthermal pair cascades by cold material in the central parts of active galactic nuclei (AGN) gives rise to X-ray and gamma-ray spectra that satisfy current observational constraints. An average 1-30 keV X-ray spectral index alpha(x) of about 0.7 in the compact range 30-300 is obtained for a wide range of Lorentz factors of the injected electrons. The gamma-ray spectra are steep, with alpha(gamma) about two, and satisfy the observational constraints. Radiation from pair cascades exhibits steep power law decreases in soft X-rays similar to those observed in AGN. The overall picture is consistent with AGN having an accretion disk which intercepts and reprocesses a substantial fraction of the nonthermal continuum incident upon it from above and below.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 363; L1-L4
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  • 32
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    Analysis of the COS B data for evidence of linear polarization of Vela pulsar gamma rays (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The COS B spark chamber telescope observations of the Vela pulsar were analyzed for gamma-ray polarization. No significant quadrupole moment is found in the azimuthal distribution of the electron-positron pair production planes. However, analysis of the sensitivity indicates that even 100-percent polarization would not be detected. Therefore, the null result does not constrain the polarization of the Vela pulsar gamma-ray emission. This result contradicts the report of Caraveo et al. (1988) of possible evidence for polarization of the Vela pulsar gamma rays.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 363; 270-273
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    Gas release in comet nuclei (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Processes taking place during the evolution of a comet nucleus are examined, taking into account the release of gas on crystallization and the gas flow through the porous nucleus. In particular, the stresses caused by the gas pressure, the contribution of gas flow to the heat transfer, and the rate of gas emission by the comet along its orbit were determined using a model of spherically symmetric comet nucleus made of porous amorphous ice, with 10 percent CO gas trapped in it. Several values of density and pore size are considered, and for each combination of parameters, the model is evolved for 20-30 revolutions in Comet P/Halley's orbit. It is shown that a model of 0.2 g/cu cm density reproduces well many of the light-curve and activity characteristics of Comet P/Halley.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 363; 274-282
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    Images in the rocket ultraviolet - Young clusters in H II regions of M83 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: UV images of M83 at 1540 and 2360 A reveal 18 compact sources that are associated with H II regions. E(B - V) values were estimated individually from the observed UV and optical colors and the Galactic UV extinction curve, using theoretical flux distributions. The dereddened colors are consistent with ages up to 3 x 10 to the 6th yr. A maximum possible age of 6.5 x 10 to the 6th yr is obtained assuming foreground reddening only. The distribution of observed colors is consistent with the Galactic reddening curve but not with enhanced far-UV extinction, as in the LMC 30 Dor curve. The H-alpha fluxes suggest either that dust within the H II regions absorbs up to 70 percent of the Lyman continuum radiation or that a similar fraction of the H-alpha flux is below the surface brightness detection limit. Cluster mass estimates depend on the range of stellar masses present but are probably in the range 10,000-100,000 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 363; 154-158
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  • 35
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    Dynamical instabilities in axisymmetric stellar systems. I - Oblate E6 models (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The stability of a set of models based on isothermal oblate E6 elliptical galaxies is studied using N-body techniques. The only stable models are those that are near the isotropic model and have nearly equal number of stars in retrograde and prograde orbits. Fast rotators are unstable to modes that appear to be analogous to the classical streaming instability seen in many disk systems. Systems with a large velocity dispersion in the direction of the cylindrical radius are unstable to modes that appear to be similar to the radial orbit instability observed in some spherical systems. However, evidence is presented that these two instabilities may be related, and an instability criterion that applies to both is constructed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 363; 66-78
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    Carbon monoxide over the Amazon Basin during the wet season (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the distribution of carbon monoxide in the lower atmosphere (150-5000 m) over the Amazon region of Brazil during the wet season, taken in conjunction with the 1987 NASA Global Tropospheric Experiment/Amazon Boundary Layer Experiment (ABLE 2B), are analyzed. About 100 hr of airborne, in situ CO measurements were obtained using a tunable diode laser system, providing insights into factors influencing the basin-scale distribution of CO in the Amazonian troposphere during wet season conditions. Distribution of CO over the altitudes 0.15-4.5 km was influenced by such factors as surface emissions from biological sources and long-range transport of pollutants from Northern Hemisphere sources. It is noted that the disruption of mixed layer growth and decay processes has a particularly important influence on CO concentration in the daytime lower troposphere and that the correlation of CO with O3 was positive under conditions influenced by Northern Hemisphere air and negative under all other conditions observed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 16927-16
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  • 37
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    Comparisons of SiO maser and long-period variable positions in the R Aquarii and Omicron Ceti binary systems (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It has been determined that the absolute position of the centroid of SiO maser-emitting spots toward both R Aqr and Omicron Cet are coincident with the position of the long-period variables (LPVs) in these binary systems to within the errors of measurement. The SiO positions were determined with the Hat Creek interferometer, while the LPV positions were determined with the 8-in transit circle of the US Naval Observatory. These results contradict an earlier report of a circumbinary SiO maser far removed from the LPV in the R Aqr binary system; statistical reasons for the discrepancy are suggested. High-resolution spectra of both sources are presented and possible models are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 663-666
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  • 38
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    Giotto IMS measurements of the production rate of hydrogen cyanide in the coma of Comet Halley (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The ion composition measurements in the ionosphere of Comet Halley by the ion mass spectrometer (IMS) experiment on the Giotto spacecraft are used to estimate the relative abundance of HCN. From a comparison of the normalized number density of ions with mass-to-charge (M/q) ratio of 28 AMU/e with steady-state photochemical models, it can be determined that the production rate of HCN directly from the central nucleus is Q(HCN) is less than about 0.0002 Q(H2O) at the time of Giotto encounter. The related photochemical- model calculations also indicate that Q(NH3)/Q(H2O) at the time of Giotto encounter. The related photo-chemical model calculations also indicate that Q(HN3)/Q(H2O) equals about 0.005, in agreement with recent determination from ground-based observations. The estimated value of Q(HCN) is lower than the relative abundance of Q(HCN)/Q(H2O) of about 0.001, as derived from radio observations of the 88.6 GHz emission of the J = 1 - 0 transition of HCN. The difference may be the result of time variations of the coma composition and dynamics, as well as other model-dependent effects.
    Keywords: ASTROPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 8; 319-325
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  • 39
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    Exosat observations of Cygnus X-2 continuum and line spectrum (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An analysis of five Exosat observations of Cyg X-2, taken around a full binary orbit is presented. The data were obtained using all instrumentation (1000 lines/mm Transmission Grating Spectrometer, Channel Multiplier Array + filters, Medium-Energy experiment, and Gas Scintillation Proportional Counter) simultaneously, and span the full energy range 0.5-20 keV. No clear evidence was found for a correlation of any of the source characteristics with orbital phase. During two of the observations, significant iron K emission at 6.7 keV was detected, the relative strength of which seems to correlate with total X-ray intensity during two sharp intensity dips. The previous detection of discrete emission features in the 12-19 A band with the Einstein grating is confirmed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 596-606
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  • 40
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    Thermal structure of neutral winds from young stellar objects (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The physical processes that control the thermal structure of lightly ionized winds from cool protostars are discussed. Attention is concentrated on the hydrogen gas, and the heating, cooling, and chemical processes that affect the neutral and ionic species of atomic and molecular hydrogen are examined. Warm silicate dust may condense out of the cooling wind and may heat the gas through collisions. Singly ionized sodium atoms, which do not recombine for the mass-loss rates considered, set a lower limit to the ionization fraction in the wind. Magnetic fields, which are presumed to accelerate the wind, couple directly to the ionic component of the gas and transfer momentum and energy to the neutral component through collisions. This process of ambipolar diffusion is found to be the dominant source of heat input to the gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 546-569
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  • 41
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    Multiple ground-based and satellite observations of global Pi 2 magnetic pulsations (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Four Pi 2 events are examined using data obtained concurrently at the Syowa-Iceland conjugate stations, the EISCAT-Magnetometer Cross, low-latitude stations HER on the nightside and KAK on the dayside, and at AMPTE/CCE in the outer magnetosphere during the period from 2300 UT on May 22 to 0300 UT on May 23, 1985. Several characteristics of Pi 2 are established on the basis of high time resolution magnetic field data. First of all, horizontal components, H and D, of the Pi 2 oscillate nearly antiphase and in-phase, respectively, between the high- and low-altitude stations in the midnight southern hemisphere. Both H and D components of the Pi 2 have nearly in-phase relationships between the nightside and the dayside stations at low altitude. The Pi 2 amplitude is larger at the high-latitude station and decreases toward low latitudes. The dominant periods of the Pi 2 are nearly identical at all stations.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 15175-15
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    The ice-core record - Climate sensitivity and future greenhouse warming (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The prediction of future greenhouse-gas-warming depends critically on the sensitivity of earth's climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial-interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the role of greenhouse gases in explaining past global climate change, and the validity of models predicting the effect of increasing concentrations of such gases in the atmosphere.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 347; 139-145
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    Chaotic, subduction-like downflows in a spherical model of convection in the earth's mantle (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Model calculations are described for a compressible fluid in a three-dimensional spherical shell with 80 percent of the surface heat flow generated within the model mantle. The numerical solutions are strongly chaotic, with surface planforms dominated by long curvilinear downflows reminiscent of the descending slabs in the earth's mantle. The results suggest that descending slabs play an important part in driving mantle convection, and that their chaotic evolution may influence the spatial and temporal behavior of plates and thus the dispersal and aggregation of continents.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 347; 274-277
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    The circumstellar dust envelopes of red giant stars. I - M giant stars with the 10-micron silicate emission band (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Spherical dust envelope models of red giant stars are constructed by solving the radiative transfer equations of the generalized two-stream Eddington approximation. The IRAS observations of M giant stars which show the 10-micron silicate emission band in IRAS LRS spectra are explained by the models with the dirty silicate grains with K proportional to lambda exp -1.5 for lambda greather than 28 microns. Under the assumption of steady mass flow in the envelope, this model analysis gives the following conclusions: (1) the strength of the silicate emission peak at 10 microns is a good indicator of the mass loss rate of the star, (2) no stars with the 10-microns silicate emission feature are observed in the range of mass loss rate smaller than 7 x 10 to the -8th solar mass/yr, and (3) the characteristic time of the mass loss process of M stars does not exceed a few 10,000 years.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 227; 2, Ja
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    WRA 751, a candidate for a new luminous blue variable (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are presened on spectroscopic observations (carried out with the ESO 1.52-m telescope at La Silla, Chile) and measurements made by the Infrared Astronomical Satellite on the star WRA 751. It is estimated that the T(eff) of this star is 30,000 K and its E(B-V) is 1.8 mag. Comparison with evolutionary tracks of Maeder and Meynet (1980) indicates that WRA 751 is located in the region of luminous blue variables at a lower limit of the initial mass of about 50 solar masses. Its other physical characteristics, such as the light variability, strong Fe II lines, and the extinction-free spectral energy distribution, suggest that WRA 751 is a candidate for a new luminous blue variable.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 227; 1, Ja
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  • 46
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    The mixing length parameter alpha (1990)
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    Publication Date: 2011-08-19
    Description: The standard mixing length theory, MLT, treats turbulent eddies as if they were isotropic, while the largest eddies that carry most of the flux are highly anisotropic. Recently, an anisotropic MLT was constructed, and the relevant equations derived. It is shown that these new equations can actually be cast in a form that is formally identical to that of the standard isotropic MLT, provided the mixing length parameter, derived from stellar structure calculations, is interpreted as an intermediate, auxiliary function alpha(x), where x, the degree of anisotropy is given as a function of the thermodynamic variables of the problem. The relation between alpha(x) and the physically relevant alpha(l = Hp) is also given. Once the value alpha is deduced, it is found to be a function of the local thermodynamic quantities, as expected.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 227; 1, Ja
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  • 47
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    Extensional reactivation of an abandoned thrust - A bound on shallowing in the brittle regime (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Shallow dip angles (not greater than 45 deg) suggested by field observations of continental extensional faults are not predicted by classical isotropic Mohr-Coulomb-Anderson theory. Earthquake data indicate that normal faults exist in the upper crust with dip angles commonly as shallow as 30 deg. One explanation of the apparent conflict between theory and structural/seismic observations is that intrinsically weak, shallow-dipping pre-existing faults are preferentially reactivated. An analytical treatment clarifies the roles of geometry, intact/preexisting fault strengths and fluid pore pressures. Frictional strength ratios of 3 or greater could account for extremely shallow normal faults (dips 10-20 deg) without consideration of pore pressures in excess of the least principal stress or of principal stress systems rotated away from the gravity vector. Moderate reduction in friction (3/4) with respect to wall rock can reduce the dip to 30 deg and can account for shallow normal-slip earthquakes.
    Keywords: GEOPHYSICS
    Type: Journal of Structural Geology (ISSN 0191-8141); 12; 3, 19
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    Calibration correction of an active scattering spectrometer probe to account for refractive index of stratospheric aerosols (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The use of the active scattering spectrometer probe (ASAS-X) to measure sulfuric acid aerosols on U-2 and ER-2 research aircraft has yielded results that are at times ambiguous due to the dependence of particles' optical signatures on refractive index as well as physical dimensions. The calibration correction of the ASAS-X optical spectrometer probe for stratospheric aerosol studies is validated through an independent and simultaneous sampling of the particles with impactors; sizing and counting of particles on SEM images yields total particle areas and volumes. Upon correction of calibration in light of these data, spectrometer results averaged over four size distributions are found to agree with similarly averaged impactor results to within a few percent: indicating that the optical properties or chemical composition of the sample aerosol must be known in order to achieve accurate optical aerosol spectrometer size analysis.
    Keywords: GEOPHYSICS
    Type: Aerosol Science and Technology (ISSN 0278-6826); 12; 992-1002
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    Far-infrared spectroscopy of the DR 21 star formation region (1990)
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    Publication Date: 2011-08-19
    Description: Far-IR line and continuum observations of the DR 21 star formation region are presented. It is shown that the extended emission in the 63 micron forbidden O I, 35 micron forbidden Si II, and 158 micron forbidden C II lines is most likely produced in dense, warm photodissociation regions on the surfaces of atomic and molecular clumps of size smaller than 0.6 pc. The gas temperatures in these photoelectrically heated, predominantly atomic layers are 250-500 K and are maintained by FUV fluxes 10,000 or more times the average interstellar radiation field. Gas densities in the surface layers are in the range 10,000-50,000/cu cm. The gas phase abundance of Si(+) is inferred to be about 5 x 10 to the -6th relative to hydrogen, or about 0.15 of its solar abundance. The mass of atomic gas is at least 200 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 132-144
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    An extremely carbon-poor planetary nebula in the Small Magellanic Cloud (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An optical and ultraviolet study is presented of object 28 of Sanduleak et al. (1978) in the SMC. This object is an extreme type of I PN which apparently has undergone all three stages of nuclear dredge-up together with an appreciable amount of convective envelope burning. Optical and UV data are well-represented by a model in which the central star has a temperature of 180,000 K and a radius of 0.09 solar radius. A nebular mass of 0.71 solar mass and a central star mass of 0.65-0.71 solar mass are inferred. The object apparently evolved from a massive progenitor with main-sequence mass greater than five solar masses, which underwent both second and third nuclear dredge-up and very efficient hot bottom burning.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 361; 101-106
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    Improved line parameters for ozone bands in the 10-micron spectral region (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A complete update of spectroscopic line parameters for the 10-micron bands of ozone is reported. The listing contains calculated positions, intensities, lower state energies, and air- and self-broadened halfwidths of more than 53,000 lines. The results have been generated using improved spectroscopic parameters obtained in a number of recent high resolution laboratory studies. A total of eighteen bands of (O-16)3 (sixteen hot bands plus the nu(1) and nu(3) fundamentals) are included along with the nu(1) and nu(3) fundamentals of both (O-16)(O-16)(O-18) and (O-16)(O-18)(O-16). As shown by comparisons of line-by-line simulations with 0.003/cm resolution balloon-borne stratospheric solar spectra, the new parameters greatly improve the accuracy of atmospheric calculations in the 10-micron region, especially for the isotopic (O-16)(O-16)(O-18) and (O-16)(O-18)(O-16) lines.
    Keywords: GEOPHYSICS
    Type: Applied Optics (ISSN 0003-6935); 29; 3667-367
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    The volume- and surface-binding energies of ice systems containing CO, CO2, and H2O (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Laboratory-measured, temperature-dependent sticking efficiencies are presently used to derive the surface-binding energies of CO and CO2 on H2O-rich ices, with a view to determining the condensation and vaporization properties of these systems as well as to the measured energies' implications for both cometary behavior and the evolution of interstellar ices. The molecular volume and the surface binding energies are not found to be necessarily related on the basis of simple nearest-neighbor scaling in surface and bulk sites; this may be due to the physical constraints associated with matrix structure-associated physical constraints, which sometimes dominate the volume-binding energies.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 87; 188-192
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    Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. I - Theory (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method is presented for determining the optical thickness and effective particle radius of stratiform cloud layers from reflected solar radiation measurements. A detailed study is presented which shows that the cloud optical thickness (tau c) and effective particle radius (r/e/) of water clouds can be determined solely from reflection function measurements at 0.75 micron and 2.16 microns, provided tau c is not less than 4 and r(e) is not less than 6 microns. For optically thin clouds, the retrieval becomes ambiguous, resulting in two possible solutions for the effective radius and optical thickness. Adding a third channel near 1.65 micron does not improve the situation noticeably, whereas the addition of a channel near 3.70 microns reduces the ambiguity in deriving the effective radius. The effective radius determined by the above procedure corresponds to the droplet radius at some optical depth within the cloud layer.
    Keywords: GEOPHYSICS
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 47; 1878-189
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    The anomalous 3.43 and 3.53 micron emission features toward HD 97048 and Elias 1 - C-C vibrational modes of polycyclic aromatic hydrocarbons? (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The 5-8 micron spectra obtained toward the two protostellar sources, HD 97048 and Elias 1 exhibit strong anomalous emission features at 3.43 and 3.53 microns. Combining these results with earlier data established that the emission in the general IR features is extended on at least a 20-arcsec scale. In view of the high energy density in the emission zone, as well as the apparent correspondence of the anomalous 3.43 and 3.53 micron features with weak emission shoulders associated with the general family of IR emission bands, an explanation for these observations in terms of C-C overtones and combination tones of large or dehydrogenated polycyclic aromatic hydrocarbons is judged to be provisionally suitable.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 360; 577-589
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    The structure and evolution of radiatively cooling jets (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The two-dimensional simulations presently used to characterize the structure and evolution of radiatively cooling supersonic jets reveal that cooling jet morphologies resemble those of adiabatic outflows, but with the fundamental difference that a dense, cold shell will condense out of the shocked gas at the head of the jet when the cooling distance behind either of the two principal shocks is smaller than the jet radius. For very high cooling rates, the material that accumulates at the head of the jet forms an extended plug of cold gas resembling the 'nose cone' observed in numerical simulations of strongly magnetized adiabatic jets. An investigation is made of the dependence of jet properties on the density ratio between the beam and the ambient medium, as well as on the strength of radiative cooling.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 360; 370-386
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    Studies in astronomical time series analysis. IV - Modeling chaotic and random processes with linear filters (1990)
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    Publication Date: 2011-08-19
    Description: While chaos arises only in nonlinear systems, standard linear time series models are nevertheless useful for analyzing data from chaotic processes. This paper introduces such a model, the chaotic moving average. This time-domain model is based on the theorem that any chaotic process can be represented as the convolution of a linear filter with an uncorrelated process called the chaotic innovation. A technique, minimum phase-volume deconvolution, is introduced to estimate the filter and innovation. The algorithm measures the quality of a model using the volume covered by the phase-portrait of the innovation process. Experiments on synthetic data demonstrate that the algorithm accurately recovers the parameters of simple chaotic processes. Though tailored for chaos, the algorithm can detect both chaos and randomness, distinguish them from each other, and separate them if both are present. It can also recover nonminimum-delay pulse shapes in non-Gaussian processes, both random and chaotic.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 359; 469-482
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    Comment on 'Solar sources of interplanetary southward B(z) events responsible for major magnetic storms (1978-1979)' by F. Tang, B. T. Tsurutani, W. D. Gonzalez, S. I. Akasof, and E. J. Smith (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 12301-12
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    Solar maximum-minimum extremes in the summer noontime polar cap F region ion composition - The measurements (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 12269-12
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    CDAW 7 revisited - Further evidence for the creation of a near-earth substorm neutral line (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Eastman et al. (1988) have interpreted the CDAW 7 substorm of April 24, 1979, previously taken as unambiguously supporting the near-earth neutral line model of magnetospheric substorms, in terms of spatial movements of a preexisting plasma-sheet boundary layer (PSBL) and its associated current sheets across the observing ISEE 1 and 2 spacercraft. It is presently noted that, by contrast, a reinvestigation of ISEE 1 and 2 energetic particle measurements around substorm onset on short time-scales shows the observed flux pattern to require the formation of a particle source eastward of the ISEE spacecraft, well within the plasma sheet, associated with the substorm onset. Strong flows were absent prior to substorm onset, indicating the temporal nature of the event, as opposed to an encounter with a preexisting PSBL containing large flows.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 12045-12
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  • 60
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    Low-latitude coronal hole as the only possible explanation for the November 25, 1978, geomagnetic storm - Comment on 'Solar sources of interplanetary southward Bz events responsible for major magnetic storms (1978-1979)' by F. Tang et al (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10717-10
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    Aircraft measurements of NO(x) over the eastern Pacific and continental United States and implications for ozone production (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are reported from airborne measurements of NO, NO2, O3, and CO obtained in the free troposphere (FT) and boundary layer (BL) over the western U.S. and eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The aircraft instrumentation and the CITE 2 flight protocols are described, and the results are presented in extensive tables and graphs. Over the ocean the median mixing ratios for NO and NO2 were found to be 4.0 and 10.4 parts per trillion by volume (pptv), respectively, in the BL and 12.4 and 18.0 pptv in the FT; the corresponding values over land were 34.5 and 75.0 pptv in the BL and 13.0 and 36.0 pptv in the FT. in continental air masses. NO(x) is shown to be positively correlated with O3 and CO and negatively correlated with dewpoint over the ocean, whereas over land NO(x) was positively correlated with O3, CO, and dewpoint.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10205-10
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    Peroxyacetyl nitrate measurements during CITE 2 - Atmospheric distribution and precursor relationships (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results are reported from airborne PAN measurements obtained at altitudes 0-6 km over the continental U.S. and the eastern Pacific during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) in summer 1986. The CITE 2 flights and instrumentation are described, and the results are presented in extensive graphs and characterized in detail. It is shown that PAN is an important reactive N-containing species in the troposphere. Although the PAN mixing ratios were highly variable, in general high mixing ratios of 100-300 parts per trillion by volume (pptv) were found at 4-6 km, and very low ratios (5-20 pptv) were detected in the marine boundary layer. Good correlation was seen between the CITE 2 PAN values and those for O3, NO(y), NO(x), HNO3, C2H6, CO, and CFCl3.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10163-10
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    Kinetic instability associated with spherical shell distribution of cometary pickup ions (1990)
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    Publication Date: 2011-08-19
    Description: The stability of ion shell distribution is an interesting and important issue in view of the fact that it is stable under perturbations propagating parallel to the ambient magnetic field, despite large amount of free energy it contains. It was found, however, that if the shell distribution of ions has a sufficient amount of drift speed with respect to the solar wind hydromagnetic waves, it can become unstable. The obliquely propagating hydromagnetic instability associated with the ion shell distribution was recently discovered. This letter presents the unified stability analysis of the ion shell distribution, under what condition the drift-induced instability of the type first discussed by Gary and Sinha (1989), and the oblique hydromagnetic instability discussed by Wu and Yoon (1990) are excited, and how the two types of instabilities are related.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 1033-103
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  • 64
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    Imaging and two-dimensional spectra of the IR-bright galaxy NGC 2146 - A recent low-energy merger? (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: New data are presented on the IR-luminous galaxy NGC 2146 from several sources: direct imaging in B, R, and H-alpha; IR imaging in the J, H, and K bands; long-slit spectroscopy at optical and IR wavelengths; and scanning etalon observations in H-alpha. The results allow measurement of the interstellar extinction in the dust lane, and estimation of the true luminosity of the galaxy and nuclear regions. The spectra indicate that there is no active nucleus, and measure the changing ratio of forbidden to permitted lines across the galaxy. IR images and colors indicate the existence of a significant population of hot young stars in the central regions of the system. The H-alpha velocity maps show the full radial-velocity pattern, and suggest that the system consists of a disturbed disk and a merging or interacting arm which connects to the inner dust and radio structures. Outer H-alpha and H I structures appear to be the earlier remnants of this spiraling merger.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 100; 60-69
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    The fuelling of active galactic nuclei (1990)
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    Publication Date: 2011-08-19
    Description: Accretion mechanisms for powering the central engines of active galactic nuclei (AGN) and possible sources of fuel are reviewed. It is a argued that the interstellar matter in the main body of the host galaxy is channeled toward the center, and the problem of angular momentum transport is addressed. Thin accretion disks are not a viable means of delivering fuel to luminous AGN on scales much larger than a parsec because of the long inflow time and effects of self-gravity. There are also serious obstacles to maintaining and regulating geometrically thick, hot accretion flows. The role of nonaxisymmetric perturbations of the gravitational potential on galactic scales and their triggers is emphasized. A unified model is outlined for fueling AGN, in which the inflow on large scales is driven by gravitational torques, and on small scales forms a mildly self-gravitating disk of clouds with inflow driven by magnetic torques or cloud-cloud collisions.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 679-686
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    A 5.75-millisecond pulsar in the globular cluster 47 Tucanae (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A pulsar with a period of 5.75 ms and a dispersion measure of 25/cu cm pc has been found in the direction of 47 Tucanae. Despite its probable origin as a member of a binary system, timing measurements show that the pulsar is now single. The observed dispersion measure is consistent with the pulsar lying outside the Galactic electron layer and within 47 Tucanae, but it is very different from the value of 67/cu cm pc for the pulsars that were reported recently as being in this globular cluster. It is suggested that the latter pulsars probably do not in fact lie within 47 Tucanae.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 598-600
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    Calibration of the C-14 timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Uranium-thorium ages obtained by mass spectrometry from corals raised off the island of Barbados confirm the high precision of this technique over at least the past 30,000 years. Comparison of the U-Th ages with C-14 ages obtained on the Holocene samples shows that the U-Th ages are accurate, because they accord with the dendrochronological calibration. Before 9,000 yr BP, the C-14 ages are systematically younger than the U-Th ages, with a maximum difference of about 3500 yr at about 20,000 yr BP. The U-Th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 405-410
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    Heterogeneous reactions on nitric acid trihydrate (1990)
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    Publication Date: 2011-08-19
    Description: The first direct measurements are reported of the reaction probabilities at stratospheric temperatures for two important heterogeneous reactions on nitric acid trihydrate (NAT), the compound which makes up the predominant, type I form of polar stratospheric cloud (PSC). Sticking coefficients and solubilities of HCl and NAT, which are important in modeling physicochemical processes in the stratosphere, are also reported. The results show that the conversion of the chlorine reservoir species in the stratosphere to photochemically active forms can occur within a few days of the first appearance of type I PSCs during the polar winter.
    Keywords: GEOPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 333-335
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    Flat-spectrum radio sources - Cosmic conspiracy or relativistic neutrons? (1990)
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    Publication Date: 2011-08-19
    Description: The intensity spectrum of the core of radio-loud AGN varies smoothly from 10 exp 8.5 to 10 to the 16th Hz, and is flat between 10 to the 9th and 10 to the 10th Hz, implying that a single emission mechanism is responsible. It is proposed here that energy is transported from the central source by relativistic neutrons which travel freely over a large volume and decay into relativistic protons. The protons produce secondary electrons which generate the observed radiation. The photon spectra thus produced are largely model-independent and flat.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 319-322
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    Evolution and detectability of comet clouds during post-main-sequence stellar evolution (1990)
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    Publication Date: 2011-08-19
    Description: The destruction of volatile-rich comet disks and Oort-type clouds around luminous post-main-sequence stars is modeled. The models are in agreement with several aspects of existing observations of water and complex molecules in the envelopes of giant and supergiant stars. If confirmed, these results would establish the common existence of Oort-type clouds around other stars and would constitute indirect evidence for sites of past planetary formation.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 305-308
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    Apparent orbit of the spectroscopic binary Beta Arietis with the time Mark III Stellar Interferometer (1990)
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    Publication Date: 2011-08-19
    Description: The spectroscopic binary Beta Ari has been directly resolved with the Mark III Stellar Interferometer. Observations in 1988 were analyzed to determine the visual orbit of the system with the following results: eccentricity = 0.903 +/- 0.012, semimajor axis = 0.0361 +/- 0.0003 arcsec, inclination = 44.7 +/- 1.3 deg, longitude of periastron = 209.1 deg +/- 1.2 deg, position angle of ascending node = 79.1 deg +/- 0.8 deg. The measured magnitude difference between two components, Delta m = 2.63 +/- 0.22 at 800 nm, yields individual visual magnitudes of m(v1) = 2.70 +/- 0.02 and m(v2) = 5.80 +/- 0.20. Combined with data from spectroscopic observations, masses M1 = (2.34 +/- 0.10) solar masses, M2 = (1.34 +/- 0.07) solar masses, and geometrical parallax pi = 0.053 arcsec +/- 0.002 arcsec are derived. These results demonstrate that both components of Beta Ari agree well with the empirical mass-luminosity relation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 641-645
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    A model of the pre-Sedov expansion phase of supernova remnant-ambient plasma coupling and X-ray emission from SN 1987A (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper examines the mechanism responsible for coupling supernova (SN) remnant to the ambient medium during the pre-Sedov or the so-called free expansion phase, immediately following the progenitor explosion. A theory is developed for the interaction of an SN piston with the ambient medium during the pre-Sedov phase. The possibility of X-ray production by the high-speed portion of the piston during this phase is investigated. The relevant observations of high-energy emissions from the SN 1987A, including the X-ray spectrum, luminosity, and temporal development, are considered. It is shown that the commonly assumed snowplow model for SNR evolution is valid, because of the action of a variety of collisionless two-stream instabilities that permit the coupling of the ambient plasma with SNR.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 549-571
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    A test of the association of infrared activity with bars (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The hypothesis that high FIR luminosities in noninteracting galaxies are dependent on material fed into their nuclei or into circumnuclear rings along bars can be tested by NIR imaging. A sample of 22 galaxies was selected from the Revised Shapley-Ames Catalog, that have FIR luminosities greater than 10 to the 10th lunar luminosities and hot colors between 60 and 100 microns, indicative of possible nuclear starbursts, but are not interacting or classified as Seyfert galaxies. Fifteen galaxies of the sample of 16 that are not clearly barred from optical data and are isolated were imaged at 1.6 micron and 2.2 microns. In an evaluation of the IR images, at least eight of these galaxies do not appear to have bars. Strong bars therefore do not appear to be an absolute requirement for high IR luminosity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 416-429
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    Stellar dynamics of powerful radio galaxies (1990)
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    Publication Date: 2011-08-19
    Description: New data on the stellar dynamics of 20 powerful radio galaxies (PRGs) were collected with the KPNO 4 m using the RC spectrograph and a TI CCD and were combined with similar data in the literature to generate a total sample of 47 PRGs. A detailed investigation of the various PRG subgroups (normal/peculiar optical morphology, and presence/absence of optical emission lines) revealed important distinctions among these groups as well as distinctions between some PRGs and normal elliptical galaxies. It is found that PRGs with peculiar optical morphologies are dynamically peculiar as well: their stellar velocity dispersions are lower than those of both elliptical galaxies and PRGs with normal optical morphologies, and they show evidence for more rotational support. Results suggest that some of the PRGs are the product of a merger of two galaxies, at least one of which was a disk system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 399-415
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    Comment on 'Local generation of electrostatic bursts at Comet Giacobini-Zinner: Modulation by steepened magnetosonic waves' by A. L. Brinca et al (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 8287-828
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    The distortion of the magnetotail equilibrium structure by a net cross-tail magnetic field (1990)
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    Publication Date: 2011-08-19
    Description: Explicit solutions are presented for quiet, quasi-static magnetotail configurations in the presence of a net cross-tail magnetic field component in addition to field components associated with tail flaring. The solutions are derived using the general three-dimensional equilibrium theory of Birn (1987). It is found that the net By(N) field varies only weakly along field lines and across the tail. The presence of the net By(N) in the neutral sheet implies that a part of the cross-tail current becomes field-aligned, flowing from the southern to the northern hemisphere for By(N) larger than zero and from north to south for By(n) less than zero. The deformations of magnetic flux surfaces suggest that there may be a class of field lines extending from the earth into the magnetosheath region through the low-latitude flanks of the tail. A topological connection is found of the low-latitude region near the magnetopause with the plasma sheet boundary layer, separating closed plasma sheet and open lobe field lines.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 8019-802
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    New bound on neutrino dipole moments from globular-cluster stars (1990)
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    Publication Date: 2011-08-19
    Description: Neutrino dipole moments mu(nu) would increase the core mass of red giants at the helium flash by delta(Mc) = 0.015 solar mass x mu(nu)/10 to the -12th muB (where muB is the Bohr magneton) because of enhanced neutrino losses. Existing measurements of the bolometric magnitudes of the brightest red giants in 26 globular clusters, number counts of horizontal-branch stars and red giants in 15 globular clusters, and statistical parallax determinations of field RR Lyr luminosities yield delta(Mc) = 0.009 + or - 0.012 solar mass, so that conservatively mu(nu) is less than 3 x 10 to the -12th muB.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 64; 2856-285
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    Studies of H I and D I in the local interstellar medium (1990)
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    Publication Date: 2011-08-19
    Description: High-dispersion IUE spectra are presented of the hydrogen Ly-alpha chromospheric emission line of two nearby late-type stars, Capella and Lambda And. Both interstellar H I and D I Ly-alpha absorption can be seen against the chromospheric line, and the density, velocity dispersion, and bulk velocity of the gas in those lines of sight are derived. Limits are placed on the D/H ratio. The results are consistent with the current picture of the local interstellar medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 223-228
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    Efficient star formation in the spiral arms of M51 (1990)
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    Publication Date: 2011-08-19
    Description: The molecular, neutral, and ionized hydrogen distributions in the Sbc galaxy M51 (NGC 5194) are compared. To estimate H2 surface densities observations of the CO (J = 1 - 0) transition were made in 60 positions out to a radius of 155 arcsec. Extinction-corrected H-alpha intensities were used to compute the detailed massive star formation rates (MSFRs) in the disk. Estimates of the gas surface density, the MSFR, and the ratio of these quantities, MSFR/sigma(p), were then examined. The spiral arms were found to exhibit an excess gas density, measuring between 1.4 and 1.6 times the interarm values at 45 arcsec resolution. The total (arm and interarm) gas content and massive star formation rates in concentric annuli in the disk of M51 were computed. The two quantities fall off together with radius, yielding a relatively constant MSFR/sigma(p) with radius. This behavior is not explained by current models of star formation in galactic disks.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 135-148
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    The ephemeris of X 1822 - 371 (1990)
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    Publication Date: 2011-08-19
    Description: From the analysis of eclipses observed with the HEAO-1, Einstein, Exosat and Ginga satellites, it is shown that the orbital period of X1822 - 371 is increasing on a time-scale of 2.9 million yr. The period change, one of only three determined amongst the LMXBs, is in the opposite sense to the expected evolutionary trend, but in the same sense as the period change of Cyg X-3. The observation of an eclipse simultaneously in the X-ray and optical bands shows that the optical eclipse is asymmetric and has a minimum 3 min later than that of the X-ray eclipse, reflecting a pronounced asymmetry in the optically emitting disk structure.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 244; 39P-43P
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    Signatures of aging silicate dust (1990)
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    Publication Date: 2011-08-19
    Description: A self-consistent explanation for the width, strength, and position of spectral features which may be diagnostic of the structure and composition of circumstellar and interstellar silicate grains is presented based on a long series of laboratory experiments using simple oxide analogs. The ratio of the integrated absorption strength of the grains near 10 mu to that near 20 mu is shown to decrease monotonically with increased processing. This ratio may be diagnostic of the relative age of the silicate. The oxidation state of iron in the grains is directly related to both the near-IR grain opacity and enhanced absorption in the UV. The oxidation state of both iron and silicon is directly related to the rate of nucleation, growth, and processing in a circumstellar outflow, as well as to the processing history of the grain after it reaches the interstellar medium. Other diagnostic indicators of the average silicon oxidation state, degree of structural polymerization, and dispersion in the average degree of structural polymerization are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 163; 1, Ja
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    Outgoing long-wave radiation computed from HIRS2/MSU soundings (1990)
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    Publication Date: 2011-08-19
    Description: Fields of outgoing long-wave radiation (OLR) have been computed using geophysical parameters retrieved from analysis of HIRS2/MSU sounding data as input to a modified version of the Wu-Kaplan radiation code used in the Goddard Laboratory for Atmospheres fourth-order general circulation model. Monthly mean results for 1979 agree with monthly mean OLR fields measured by the Nimbus 7 earth radiation budget (ERB) broadband narrow field of view instrument within standard deviations of 6.3 W/sq m but with a global mean bias of 8.0 W/sq m. Results are shown for July 1979. The areas of disagreement between high-resolution infrared radiation sounder OLR and ERB OLR are small but spatially coherent with patterns which may be related to sampling differences. The difference patterns are much less extensive than those between OLR derived from advanced very high resolution radiometer 11-micron observations and ERB OLR.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7579-760
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    Measuring tropospheric HNO3 - Problems and prospects for Nylon filter and mist chamber techniques (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A series of laboratory and field measurements was performed to evaluate the mist chamber technique for determining tropospheric HNO3 concentrations. Both the mist chamber and standard Nylon filter techniques exhibit high collection efficiency and excellent agreement measuring HNO3 vapors from a permeation source. When simultaneously sampling ambient air in eastern Virginia, the Nylon filter measured an average of 70 percent higher HNO3 concentration than the mist chamber technique. The results indicate that O3 causes a low-level positive artifact interference in HNO3 measurements performed with the filter technique. This O3-induced error is small, however, compared to the large difference between atmospheric HNO3 concentrations determined with the two techniques. It is hypothesized that unidentified (organic?) nitrogen species in the atmosphere react for form NO3(-) on the filter and this phenomenon may interfere with Nylon filter measurements of HNO3 vapor. These potential interferences did not appear to affect measurements of HNO3 with the mist chamber method.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7553-756
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  • 84
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    Effect of solar proton events on the middle atmosphere during the past two solar cycles as computed using a two-dimensional model (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper investigates the effects of solar proton events (SPEs) on the middle atmosphere during the past two solar cycles (1963-1984), by examining changes in the production of odd nitrogen, NO(y), and ozone and using a proton energy degradation scheme to derive ion pair production rates. These calculations show that NO(y) is not substantially changed over a solar cycle by SPEs; significant SPEs last only 1-5 days, tend to occur near solar maximum, and are typically months to years apart, preventing a build up of SPE-produced NO(y). Fractional ozone changes are even smaller than the fractional NO(y) changes and are significant only for the August 1972 SPE. Ozone, like NO(y), returns to its ambient levels on time scales of several months to a year.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7417-742
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  • 85
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    Analysis of the eight-year trend in ozone depletion from empirical models of solar backscattered ultraviolet instrument degradation (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Arguments are presented showing that the basic empirical model of the solar backscatter UV (SBUV) instrument degradation used by Cebula et al. (1988) in their analysis of the SBUV data is likely to lead to an incorrect estimate of the ozone trend. A correction factor is given as a function of time and altitude that brings the SBUV data into approximate agreement with the SAGE, SME, and Dobson network ozone trends. It is suggested that the currently archived SBUV ozone data should be used with caution for periods of analysis exceeding 1 yr, since it is likely that the yearly decreases contained in the archived data are too large.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 7403-741
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  • 86
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    Orbital periods of recurrent novae (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The class of recurrent novae (RN) with thermonuclear runaways contains only three systems (T Pyx, U Sco, and V394 CrA), for which no orbital periods are known. This paper presents a series of photometric observations where the orbital periods for all three systems are discovered. T Pyx is found to have sinusoidal modulation with an amplitude of 0.08 mag and a period of 2.3783 h (with a possible alias of 2.6403 h). U Sco is found to be an eclipsing system with an eclipse amplitude of roughly 1.5 mag and an orbital period of 1.2344 days. V394 CrA is found to have sinusoidal modulation with an amplitude of 0.5 mag and a period of 0.7577 days. Thus two out of three RN with thermonuclear runaways (or five out of six for all RN) have evolved companions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 355; L39-L42
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  • 87
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    The effect of catastrophic collisional fragmentation and diffuse medium accretion on a computational interstellar dust system (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The effects of catastrophic collisional fragmentation and diffuse medium accretion on a the interstellar dust system are computed using a Monte Carlo computer model. The Monte Carlo code has as its basis an analytic solution of the bulk chemical evolution of a two-phase interstellar medium, described by Liffman and Clayton (1989). The model is subjected to numerous different interstellar processes as it transfers from one interstellar phase to another. Collisional fragmentation was found to be the dominant physical process that shapes the size spectrum of interstellar dust. It was found that, in the diffuse cloud phase, 90 percent of the refractory material is locked up in the dust grains, primarily due to accretion in the molecular medium. This result is consistent with the observed depletions of silicon. Depletions were found to be affected only slightly by diffuse cloud accretion.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 355; 518-535
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  • 88
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    Optical environments of radio quasars (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: CCD images of 36 radio-loud quasars in the redshift range 0.1-0.75 are discussed. The objects were chosen to represent the full range of radio structure found with VLA A-configuration observations. Measured quantities are compared and correlated from both radio and optical observations. At least 70 percent of the quasars show evidence for current or recent interaction. Consideration is given to host galaxy sizes and luminosities, states of tidal interaction and numbers of companions, radio morphology, and luminosity.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 99; 1715-172
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  • 89
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    Balloon Intercomparison Campaigns - Results of remote sensing measurements of HCl (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The balloon-borne instruments used in the two Balloon Intercomparison Campaigns in 1982 and 1983 to measure stratospheric HCl included five different IR spectrometers, three of which operated in the solar absorption mode and two in emission mode (at distinctly different wavelengths). This paper describes the instruments and the data reduction and analysis procedures used in each case, together with the sources and estimated magnitudes of associated errors. Comparisons are made between different techniques (absorption vs emission) used on the same gondola, as well as between the same technique used on different gondolas. The final results yield a mean profile of HCl concentration between 18 and 40 km altitude. The absolute accuracy of the final profile is estimated to be no worse than 10 percent.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 237-272
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  • 90
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    Intercomparison of measurements of stratospheric hydrogen fluoride (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of the vertical profile of hydrogen fluoride (HF) vapor in the stratosphere and of the vertical column amounts of HF above certain altitudes were made using a variety of spectroscopic instruments in the 1982 and 1983 Balloon Intercomparison Campaigns. Both emission instruments working in the far-infrared spectral region and absorption instruments using solar occultation in the 2.5-micron region were employed. No systematic differences were seen in results from the two spectral regions. A mean profile from 20 - 45 km is presented, with uncertainties ranging from 20 to 50 percent. Total columns measured from ground and from 12 km are consistent with the profile if the mixing ratio for HF is small in the troposphere and low stratosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 219-236
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  • 91
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    Ozone measurements from the Balloon Intercomparison Campaign (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the Balloon Intercomparison Campaign (BIC), conducted during fall, 1982 (BIC-1) and summer, 1983 (BIC-2), are reported. Results of five remote and two in situ techniques agree (with a few exceptions) within 95-percent confidence level uncertainties and generally within 15 percent above 20 km. Weighted mean profiles, which best represent conditions during the campaign, are used as a comparison standard. Accuracies of experiments indicated by BIC generally confirm estimated uncertainties for ECC sondes, UV photometry, and microwave emission experiments, are somewhat better for far-IR emission and IR absorption experiments, and are somewhat worse for IR emission and solar UV absorption experiments. The large collection of BIC measurements confirms a problem reported earlier with current theoretical modeling of ozone near 40 km.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 181-218
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  • 92
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    Intercomparison of remote measurements of stratospheric NO and NO2 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: During the 1982 and 1983 Balloon Intercomparison Campaigns, the vertical profile of stratospheric NO2 was measured remotely by nine instruments and that of NO by two. Total overhead columns were measured by two more instruments. Between 30 and 35 km, where measurements overlapped, agreement between NO profiles was within + or - 30 percent, which is better than the accuracies claimed by the experimenters. Between 35 and 40 km, there was similarly good agreement between NO2 profiles, but below 30 km, differences of greater than a factor of 3 were found. In the second campaign, NO2 values from most instruments agreed within their quoted errors, except that the Oxford radiometer gave much lower values; the first campaign and the column measurements show a more uniform spread of results.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 111-144
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  • 93
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    Analysis of the origins and implications of the O-18 content of stratospheric water vapor (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Factors influencing the O-18 content of stratospheric H2O are reviewed in order to provide a theoretical framework for the interpretation of measurements of this quantity, which are now becoming available. Depletions in O-18 of 5-10 percent in stratospheric H2O are expected based on the known correlation between that of D and O-18 in tropospheric H2O and observed measurements of large (typically 50 percent) depletions of D in stratosphere H2O. H2O formed in the stratosphere as a result of oxidation of CH4 can be expected to reflect primarily the O-18 content of stratospheric O2, which is the same as that of tropospheric O2 (slightly enhanced with respect to standard mean ocean water). Thus, a reduction in the O-18 depletion is expected with increasing altitude, but not a large enhancement in O-18 in upper stratospheric H2O as found in recent far infrared measurements. The observed large enhancement of O-18 in stratospheric O3 is not expected to be reflected in stratospheric H2O. Necessary laboratory data for the improved quantification of these effects are reviewed.
    Keywords: GEOPHYSICS
    Type: Journal of Atmospheric Chemistry (ISSN 0167-7764); 10; 39-57
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  • 94
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    Observations of 40-70 micron bands of ice in IRAS 09371 + 1212 and other stars (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: IRAS 09371 + 1212 is still an absolutely unique object. This M giant star, with circumstellar CO and a spectacular bipolar nebula, displays unique IRAS FIR colors which had been attributed to strong emission in the 40-70-micron bands of ice, as subsequently supported by the observation of a strong 3.1-micron absorption band. The results of the KAO observations have confirmed its unusual nature: the far-infrared bands of ice are by far the strongest known. Its dust temperature, 50 K or less, is by far the lowest known for a late-type circumstellar envelope.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 355; L27-L30
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  • 95
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    The physical and infrared spectral properties of CO2 in astrophysical ice analogs (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Results of measurements of the infrared spectroscopic and condensation-vaporization properties of CO2 in pure and mixed ices are presented. Detailed examination of five infrared CO2 bands, 2.20, 2.78, 4.27, 15.2, and 4.39 microns, shows that the peak position, FWHM, and profile of the bands provide important information about the composition, formation, and subsequent thermal history of the ices. Absorption coefficients and their temperature dependence for all five CO2 bands are determined. The temperature dependence variation is found to be less than 15 percent from 10 to 150 K, i.e., the temperature at which H2O ice sublimes. The number of parameters associated with the physical behavior of CO2 in CO2- and H2O-rich ices, including surface binding energies, and condensation and sublimation temperatures, are determined under experimental conditions. The implications of the data obtained for cometary models are considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 355; 357-372
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  • 96
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    Heating and melting of small icy satellites by the decay of Al-26 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The effect of radiogenic heating due to Al-26 on the thermal evolution of small icy satellites is studied. The object is to find the extent of internal melting as a function of the satellite radius and of the initial Al-26 abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of about 10 to the 6th yr (comparable with the lifetime of Al-26. The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of K-40, Th-232, U-235, and U-238, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10 to the 9th yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. The main conclusion is that the initial Al-26 abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, about 7 x 10 to the -7th by mass).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 355; 281-286
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  • 97
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    Shocked forbidden O I 63 micron line emission from the supernova remnant IC 443 (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of the fine-structure emission from the forbidden O I 63 micron line in the SNR IC 443 are presented. It is shown that the emission correlates well with the distribution of line emission from shock-excited molecular hydrogen, which leads to the conclusion that the line is shock-excited. X-ray heating as well as UV-heating from a photodissociation region is ruled out as a possible excitation mechanism for the emission. It is shown that the forbidden O I 63 micron line is an important contributor to the total emission in the IRAS 60 micron band, estimated as approximately 40-75 percent of the total band flux. An attempt to shock model the line emission from IC 443 is made; however, to match the observational evidence, it has to be assumed that the shock is J-type, and that the oxygen chemistry is suppressed so that oxygen remains in atomic form and does not get converted into H2O. However, no theoretical rationale for these assumptions can be provided.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 355; 197-209
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  • 98
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    Forbidden-line emission and infrared excesses in T Tauri stars - Evidence for accretion-driven mass loss? (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is suggested that disk accretion provides the requisite external source to power the winds of T Tauri stars. As a test of this hypothesis, a potential accretion diagnostic for a representative sample of stars is compared to diagnostics of the wind strength. The luminosity of H-alpha, formed in the inner wind, and the luminosity of the forbidden emission lines, formed in the outer wind, are used as wind diagnostics, while the excess infrared luminosity is used as a potential accretion diagnostic. It is found that forbidden-line O I 6300 A and H-alpha line luminosities are correlated with each other over two orders of magnitude; this is interpreted as the indication of a wide range of mass-loss rates among the given sample of T Tauri stars. The luminosity of each of these lines is also found to be correlated with excess infrared luminosity. However, neither the forbidden nor the H-alpha luminosity is well correlated with the photospheric luminosity, leading to a conclusion that it is the disk, not the star, which primarily determines the strength of wind indicators in T Tauri stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 354; 687-700
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  • 99
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    Hydrogen constituents of the mesosphere inferred from positive ions - H2O, CH4, H2CO, H2O2, and HCN (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The concentrations in the mesosphere of H2O, CH4, H2CO, H2O2, and HCN were inferred from data on positive ion compositions, obtained from one mid-latitude and four high-latitude rocket flights. The inferred concentrations were found to agree only partially with the ground-based microwave measurements and/or model prediction by Garcia and Solomon (1985). The CH4 concentration was found to vary between 70 and 4 ppb in daytime and 900 and 100 ppbv at night, respectively. Unexpectedly high H2CO concentrations were obtained, with H2CO/H2O ratios between 0.0006 and 0.1, and a mean HCN volume mixing ratio of 6 x 10 to the -10th was inferred.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 5613-563
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  • 100
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    Heterodyne spectrophotometry of ozone in the 9.6-micron band using a tunable diode laser (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Tunable diode laser heterodyne spectrophotometry (TDLHS) has been used to make extremely high resolution (0.0003/cm) solar spectra in the 9.6-micron ozone band. Observations have shown that a signal-to-noise ratio of 120:1 (about 30 percent of theoretical) for an integration time of 1/8 s can be achieved at a resolution of 0.0013 wave numbers. The spectral data have been inverted to yield a total column amount of ozone, in good agreement with that measured at the nearby NOAA ozone monitoring facility in Boulder, Colorado. Line positions for several ozone lines in the spectral region 996-997/cm are reported. Recent improvements have produced a signal-to-noise ratio of 95:1 (about 40 percent of theoretical) at 0.0003/cm and extended the range of wavelengths which can be observed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 5567-557
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