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  • ASTROPHYSICS  (1,880)
  • LUNAR AND PLANETARY EXPLORATION  (1,552)
  • ASTRONOMY  (834)
  • METEOROLOGY AND CLIMATOLOGY  (788)
  • Chemical Engineering  (675)
  • ENERGY PRODUCTION AND CONVERSION  (558)
  • 1990-1994  (2,925)
  • 1980-1984  (3,362)
Collection
Keywords
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Years
Year
  • 1
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    Gamma-ray observations of NGC 253 and M82 with OSSE (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Gamma-ray observations of the nearby starburst galaxies NGC 253 and M82 over the energy range (0.05-10) MeV have been obtained with the Oriented Scintillation Spectrometer Experiment (OSSE) spectrometer on the Compton Gamma-Ray Observatory (CGRO). The priority of these galaxies as OSSE targets had been established on the grounds that the average supernova rate may be high in starbursts as indicated by infrared and radio observations, and at distances of approximately 3 Mpc a significant chance of supernova gamm-ray line detection exists. NGC 253 was detected in continuum emission up to 165 keV with a total significance of 4.4 sigma and an estimated luminosity of 3 x 10(exp 40) ergs/s. The spectrum is best fit by a power law of photon index approximately 2.5. We consider the possible contribution of different emission mechanisms, including inverse Compton scattering, bremsstrahlung, discrete sources, and Type Ia/Ib supernova continuum to the measured flux. No significant continuum flux was observed from M82. A search for the gamma-ray line from the decay of the most abundant radioactive element produced in supernovae (Ni-56 yields Co-56 yields Fe-56) yielded no significant detection: the 3 sigma upper limits to the line fluxes at 0.158, 0.812, 0.847, and 1.238 MeV for both galaxies are obtained.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 437; 1; p. 173-178
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  • 2
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    Apollo 12 ropy glasses revisited (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We analyzed ropy glasses from Apollo 12 soils 12032 and 12033 by a variety of techniques including SEM/EDX, electron microprobe analysis, INAA, and Ar-39-Ar-40 age dating. The ropy glasses have potassium rare earth elements phosphorous (KREEP)-like compositions different from those of local Apollo 12 mare soils; it is likely that the ropy glasses are of exotic origin. Mixing calculations indicate that the ropy glasses formed from a liquid enriched in KREEP and that the ropy glass liquid also contained a significant amount of mare material. The presence of solar Ar and a trace of regolith-derived glass within the ropy glasses are evidence that the ropy glasses contain a small regolith component. Anorthosite and crystalline breccia (KREEP) clasts occur in some ropy glasses. We also found within these glasses clasts of felsite (fine-grained granitic fragments) very similar in texture and composition to the larger Apollo 12 felsites, which have a Ar-39-Ar-40 degassing age of 800 +/- 15 Ma. Measurements of 39-Ar-40-Ar in 12032 ropy glass indicate that it was degassed at the same time as the large felsite although the ropy glass was not completely degassed. The ropy glasses and felsites, therefore, probably came from the same source. Most early investigators suggested that the Apollo 12 ropy glasses were part of the ejecta deposited at the Apollo 12 site from the Copernicus impact. Our new data reinforce this model. If these ropy glasses are from Copernicus, they provide new clues to the nature of the target material at the Copernicus site, a part of the Moon that has not been sampled directly.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 29; 3; p. 323-333
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  • 3
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    Megawatt solar power systems for lunar surface operations (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The work presented here shows that a solar power system can provide power on the order of one megawatt to a lunar base with a fairly high specific power. The main drawback to using solar power is still the high mass, and therefore, cost of supplying energy storage through the solar night. The use of cryogenic reactant storage in a fuel cell system, however, greatly reduces the total system mass over conventional energy storage schemes.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: USRA, Proceedings of the 6th Annual Summer Conference: NASA(USRA University Advanced Design Program; p 229-239
    Format: application/pdf
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  • 4
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    An unusually strong Einstein ring in the radio source PKS1830 - 211 (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: High-resolution radio images of PKS1830 - 211 are obtained to study the possibility that the double structure is a gravitationally lensed object. The VLBI observations, taken from interferometric radiotelescope networks, reveal an elliptical ring that connects two bright spots of similar composition. Because the lens and the lensed object are closely aligned, and because of the structure of the two spots, the source is concluded to be a radio Einstein ring. The source is found to be close to the galactic plane, and the lens and the lensed object are extragalactic. The source is also found to be unusually bright, suggesting that it is aligned with a bright background source or amplified by some mechanism related to a source that is not so bright.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 352; 132-134
    Format: text
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  • 5
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    Oriented Scintillation Spectrometer Experiment observations of Co-57 in SN 1987A (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory has observed SN 1987A for two 2 week periods during the first 9 months of the mission. Evidence for gamma-ray line and continuum emission from Co-57 is observed with an intensity of about 10 exp -4 gamma/sq cm/s. This photon flux between 50 and 136 keV is demonstrated by Monte Carlo calculations to be independent of the radial distribution of Co-57 for models of low optical depth, viz., models having photoelectric absorption losses of 122 keV photons no greater than several percent. For such models the observed Co-57 flux indicates that the ratio Ni-57/Ni-56 produced in the explosion was about 1.5 times the solar system ratio of Fe-57/Fe-56. When compared with nearly contemporaneous bolometric estimates of the luminosity for SN 1987A, our observations imply that Co-57 radioactivity does not account for most of the current luminosity of the supernova remnant in low optical depth models. We suggest alternatives, including a large optical depth model that is able to provide the SN 1987A luminosity and is consistent with the OSSE flux. It requires a 57/56 production ratio about twice solar.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 399; 2; p. L137-L140.
    Format: text
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  • 6
    Electronic Resource
    Electronic Resource
    Letters to the editor (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 791-799 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370517
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  • 7
    Electronic Resource
    Electronic Resource
    J-R curve calculation with the normalization method for toughened polymers (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 128-134 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The method of normalization is used to develop the J-R curve fracture toughness characterization for polymeric materials. This method can develop J-R curves directly from load vs. displacement records without a need for an on-line crack monitoring system. It was used previously to develop J-R curves for metallic materials and is applied here for the first time to polymer materials. Single edge notched bend specimens of rubber toughened nylon 6/6 and rubber toughened amorphous nylon are used in this study. The J-R curves from the method of normalization are compared with the results obtained from the multiple specimen method of ASTM Standard E813. The results show that the method of normalization gives reasonable J-R curves; both methods show agreement over the early J-R curve region. In addition the JIc values are determined for each method and compared. Based on this work it is suggested that the method of normalization could be used as a general test method to develop J-R curves for polymeric materials.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760340209
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  • 8
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    Pulsed high-energy gamma-rays from the radio pulsar PSR1706-44 (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Gamma radiation above 100 MeV in energy has been detected from the radio pulsar PSR1706-44. The gamma emission forms a single broad peak within the pulsar period of 102 ms, in contrast to the two narrow peaks seen in the other three known high-energy gamma-ray pulsars. The emission mechanism in all cases is probably the same, the differences arising from the geometry of the magnetic and rotation axes and the line of sight. Gamma-ray emission accounts for as much as 1 percent of the total neutron star spindown energy in these pulsars, much more than emerges at optical or radio frequencies. Thus, study of this emission is important in understanding pulsar emission and evolution.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 359; 6396; p. 615, 616.
    Format: text
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  • 9
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    Cosmogenic nuclides in core samples of the Chico L6 chondrite - Evidence for irradiation under high shielding (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Results are presented from an analysis of core samples obtained from different depths of the Chico (New Mexico) L6 chondrite for various cosmogenic nuclides (Be-10, Al-26, and stable isotopes of He, Ne, and Ar). The relationships between the measured abundances of cosmogenic nuclides and cosmogenic Ne-22/Ne-21 ratio were compared with predictions of recent semiempirical models of Graf et al. (1990) and Reedy (1991), and it was found that both models closely reproduce the observed trends and absolute values of the data obtained. Noble gas data indicate that Chico experienced shielding similar to that of Jilin and greater than those of the Knyahinya or the Keyes chondrites. The exposure history for Chico is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 27; 4; p. 371-381.
    Format: text
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  • 10
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    (Ar-39)-(Ar-40) dating of mesosiderites - Evidence for major parent body disruption less than 4 Ga ago (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The (Ar-39) (Ar-40) chronologies were determined for 14 different mesosiderites representing the full range of classification according to recrystallization, and these chronologies were compared with analogous data for other meteorite types and for lunar highland rocks. Results of Ar-Ar chronologies indicate the history of a degassing of Ar due to a major thermal event that occurred less than 3.9 Ga ago; this event is not the metal-silicate mixing event, which is known to have occurred earlier than 4.4 Ga ago. It is suggested that a major collisional disruption-reassembly event less than 3.9 Ga ago took place, leaving the metal-silicate breccias buried under tens of kilometers of rubble, where they cooled slowly through the Ar closure temperatures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 54; 2549-256
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