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  • ASTROPHYSICS  (119)
  • ENERGY PRODUCTION AND CONVERSION  (96)
  • Physics  (54)
  • 1980-1984  (269)
  • 1981  (269)
  • 1
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    Rapid variability of 10-140 keV X-rays from Cygnus X-1 (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: On five occasions in 1977 and 1978, Cygnus X-1 was observed using the low-energy detectors of the UCSD/MIT Hard X-ray and Low-Energy Gamma Ray experiment on the HEAO 1 satellite. Rapid (times between 0.08 and 1000 sec) variability was found in the 10-140 keV band. The power spectrum was white for frequencies between 0.001 and 0.05 Hz and was proportional to the inverse of the frequency for frequencies between 0.05 and 3 Hz, indicating correlations on all time scales less than approximately 20 s. The shape of the energy spectrum was correlated with intensity; it was harder at higher intensity. If the emission is produced by Comptonization of a soft photon flux in a hot cloud, the heating of the cloud cannot be constant; it must vary on time scales up to approximately 20 s. A variable accretion rate could cause the observed effects.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
    Format: text
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of monomer functional groups on the composition of some three component random phenolic copolymers (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 3005-3012 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some three-component random phenolic copolymers were prepared from three typical phenolic monomers; for example, p-chlorophenol, p-aminophenol, and p-cresol. Several samples of the copolymer were prepared by changing the feed composition and the composition of the copolymers was established by estimating —NH2 and —OH groups by electrometric titration techniques in nonaqueous media. Halogen was estimated by Volhard's method. The average degree of polymerization (DP) of the copolymers was calculated from the features of the electrometric titration curves, and the effects of monomer functional groups on the composition of the copolymers were interpreted in terms of the electron-donating and electron-attracting nature of the substituents present in the monomers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170191132
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    Paper (German National Licenses)
    Fulltext
  • 3
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    A heating mechanism for the chromospheres of M dwarf stars (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The atmospheric structure of the dwarf M-stars which is especially important to the general field of stellar chromospheres and coronae was investigated. The M-dwarf stars constitute a class of objects for which the discrepancy between the predictions of the acoustic wave chromospheric/coronal heating hypothesis and the observations is most vivid. It is assumed that they represent a class of stars where alternative atmospheric heating mechanisms, presumably magnetically related, are most clearly manifested. Ascertainment of the validity of a hypothesis to account for the origin of the chromospheric and transition region line emission in M-dwarf stars is proposed.
    Keywords: ASTROPHYSICS
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 73-79
    Format: text
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  • 4
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    A variable mixing-length ratio for convection theory (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is argued that a natural choice for the local mixing length in the mixing-length theory of convection has a value proportional to the local density scale height of the convective bubbles. The resultant variable mixing-length ratio (the ratio between the mixing length and the pressure scale height) of this theory is enhanced in the superadiabatic region and approaches a constant in deeper layers. Numerical tests comparing the new mixing length successfully eliminate most of the density inversion that typically plagues conventional results. The new approach also seems to indicate the existence of granular motion at the top of the convection zone.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 244
    Format: text
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  • 5
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    Rotation of dwarf star chromospheres in the ultraviolet (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Periodic variations in the ultraviolet fluxes of chromospheric emission line multiplets are investigated for F, G and K stars as evidence of rotational modulation. Vacuum ultraviolet spectra were obtained with the IUE spacecraft for six stars as many as 11 times over the period April 23 to December 3, 1980. Variations in the emission fluxes of the hydrogen Lyman-alpha, Si II and Mg II lines are observed with periods up to 47 days. The periodicity, which is identified with rotational modulation, is found to persist over many rotational cycles, although the periods and time dependences of the fluxes from the different ionic species are not identical, probably due to differential rotation and global distributions. The spread of the UV periods is observed to be within 10%, with one or two peaks per cycle and a ratio of modulated to umodulated flux ranging from 1.1 to 3.0, analogous to solar behavior.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
    Format: text
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  • 6
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    Abundances of argon, sulfur, and neon in six galactic H II regions from infrared forbidden lines (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Airborne measurements of the Ar II (6.99 micron) and S III (18.71 micron) forbidden lines for six compact H II regions are presented, as well as ground-based 2-4 micron and 8-13 micron spectroscopy if not already published. From these data and radio data, lower limits to the elemental abundances of Ar, Ne, and S are deduced. G29.9-0.0, at 5 kpc from the galactic center, is overabundant in all these elements. The other five regions (at distances 6-13 kpc from the center) mainly appear to be consistent with standard abundances, with the exception of G75.84 + 0.4 at 10 kpc from the galactic center, which is overabundant in S. However, preliminary results on G12.8-0.2 at 6 kpc from the galactic center suggest a possible underabundance. A large statistical sample of H II regions is required in order to determine if there is a radial gradient in the heavy element abundances of the Galaxy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 250
    Format: text
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  • 7
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    Li/SO2 Cell for Galileo (1981)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: Some information on the special process controls for lithium sulfur dioxide (Li/SO2) batteries is presented with reference to how those controls affected the Galileo probe program and the instrument test vehicle program. The general considerations that go into any application for basically any type of battery system are discussed. Particular emphasis is given to some of the design tradeoffs which resulted because of the addition of the safety characteristics of the Li/SO2 system.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA. Goddard Space Flight Center The 1980 Goddard Space Flight Center Battery Workshop; p 13-22
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  • 8
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    The Gemini-Monoceros X-ray enhancement - A giant X-ray ring (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A 1.5 deg spatial resolution map of the 1/4 KeV diffuse X-ray background enhancement in the Gemini and Monoceros constellations is found to show a circular ring-shaped emission feature with a diameter of 20 deg. The feature and possible X-ray contributions from the Mon OB1 association and neighboring supernova remnants are discussed. From 300 pc, the region has a radius of 50 pc, with an emitting electron density of 0.01 per cu cm. A shell of expanding neutral hydrogen and nonthermal radio spur is observed outside the ring with the X-ray emitting pulsar PSR 0656 + 14 lying close to the center of the ring. Origins of the ring are discussed, ruling out formation by the association Mon OB1. The ring is considered to be a field supernova remnant formed by the progenitor of the central pulsar, and providing constraints on theories of remnant evolution. This conclusion is found to agree with estimated supernova rates, and the absence of additional examples of this stage of evolution is an observational selection effect.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
    Format: text
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  • 9
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    Supernova remnant revolution in an inhomogeneous medium. I - Numerical models (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The first numerical simulations of supernova remnant evolution in an inhomogeneous gas are presented. Evolution in the lowest density substrate (the intercloud) is assumed to be spherically symmetric with a large intercloud filling factor and many dense regions (clouds) within the remnant; however, mass momentum and energy transfer between cloud and intercloud are included and the position and morphology of individual clouds tracked. Evolution is considered in several different models of the interstellar medium, both those in which the intercloud gas is diffuse (0.001 to 0.01/cu cm) and those in which it is relatively dense (n approximately 0.3/cu cm) under a variety of assumptions about the efficiency of thermal evaporation from the clouds into the intercloud medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 247
    Format: text
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  • 10
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    Short time-scale variability of chromospheric Ca II in late-type stars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The short time-scale variability of singly ionized calcium chromospheric emission has been investigated in a few late-type stars. Emission-line variations with time scales of a few minutes to hours are seen in Alpha Tau (K5 III), Lambda And (G8 III-IV), and Epsilon Eri (K2 V). The existence of substantial chromospheric flux changes (10 to the 30th to 10 to the 32nd ergs) over short periods of time suggests that the calcium emission arises from a few small, coherent regions. Frequencies present in the data are discussed in the context of acoustic wave predictions and estimated acoustic cutoff frequencies for giants and dwarfs.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
    Format: text
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