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Gamma-ray observations of NGC 253 and M82 with OSSE (1994)

Kurfess, J. D. ; Jung, G. V. ; Bhattacharya, D. ; [weitere]

In: Other Sources

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Publikationsdatum: 2019-08-28

Beschreibung: 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.

Schlagwort(e): ASTRONOMY

Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 437; 1; p. 173-178

Format: text

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2

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Megawatt solar power systems for lunar surface operations (1990)

Alhadeff, S. ; Cook, D. ; Gillespie, D. ; [weitere]

In: CASI

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Publikationsdatum: 2013-08-31

Beschreibung: 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.

Schlagwort(e): ENERGY PRODUCTION AND CONVERSION

Materialart: USRA, Proceedings of the 6th Annual Summer Conference: NASA(USRA University Advanced Design Program; p 229-239

Format: application/pdf

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3

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Landau damping of auroral hiss (1994)

Gurnett, D. A. ; Menietti, J. D. ; Morgan, D. D. ; [weitere]

In: Other Sources

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Publikationsdatum: 2019-07-13

Beschreibung: Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit omega/k(sub parallel) to values of 3.4 x 10(exp 4) km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, omega/k(sub parallel) is limited to values greater than 6.8 x 10(exp 4) km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that omega/k(sub parallel) corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities.

Schlagwort(e): GEOPHYSICS

Materialart: Journal of Geophysical Research (ISSN 0148-0227); 99; A2; p. 2471-2488

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4

Digitale Medien

D2-m-carborane-siloxanes. III. Preparation and properties of trifluoropropyl-modified polymers (1977)

Peters, E. N. ; Stewart, D. D. ; Bohan, J. J. ; [weitere]

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 973-981

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Linear D2-m-carborane-siloxanes with one, two, and three trifluoropropyl moieties per repeat unit were prepared by the condensation reaction between bisureidosilanes and carborane disilanol. Molecular weights between 100,000 and 220,000 were obtained. Compared to fluorosilicones, the trifluoropropyl-modified carborane-siloxanes exhibited greater thermal and oxidative stability and in certain cases comparable solvent resistance. The swelling index for carborane-siloxane elastomers decreased with increasing trifluoropropyl content, although this fluorocarbon moiety did compromise the thermal stability of the carborane system.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1977.170150418

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5

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Electroinitiated polymerization of arylvinyl monomers (1979)

Smith, J. D. B. ; Phillips, D. Colin ; Davies, D. H.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 1411-1418

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The electroinitiated polymerizations of styrene, 2-vinylnaphthalene, and 9-vinylanthracene were compared in sulfolane and acetone solvents in the presence of ZnCl2. The relative orders of polymerization rates and polymerization efficiencies, in both solvents, were 9-vinylanthracene 〉 2-vinylnaphthalene 〉 styrene, with faster rates and higher efficiencies occurring in sulfolane. Data obtained from viscosity and gel permeation chromatography (GPC) studies indicate that the molecular weights of the polymers produced in these systems are extremely low, 〈5000. Chemical composition and infrared (IR) spectral data suggest that abnormal transfer reactions (possibly from solvent) may be occurring in the electroinitiated 9-vinylanthracene polymerizations. The polymerization mechanism appears to be cationic in these monomer-solvent systems with ZnCl2.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1979.170170515

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6

Digitale Medien

Aromatic polyamides. II. Thermal degradation of some aromatic polyamides and their model diamides (1981)

Khanna, Y. P. ; Pearce, E. M. ; Smith, J. S. ; [weitere]

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2817-2834

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Thermal degradation behavior of poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) was investigated with the aid of some appropriate model compounds. The pyrolysis products of these materials were identified by gas chromatography (GC), gas chromatography/Fourier transform infrared spectroscopy (GC/FT-IR), and gas chromatography/mass spectrometry (GC/MS). The residual chars were characterized by IR spectroscopy. Thermogravimetric analysis (TGA) was applied to study the effect of end-group concentration on the degradation characteristics of the two polyamides. Kinetic parameters that describe the thermal degradation of the polyamides were also evaluated by TGA. The results of this investigation suggest that the thermal decomposition of these aromatic polyamides involves homolytic as well as hydrolytic cleavages of the amide units.

Zusätzliches Material: 13 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1981.170191115

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7

Digitale Medien

ESCA investigation of the electronic structure of polyhexafluorobut-2-yneThis is considered as Part X of Reactions Involving Fluoride Ion and Part VI of Applications of ESCA to Structure and Bonding in Polymers. A preliminary account of this work has been presented at the Faraday Discussion Meeting No. 54 on the photoelectron spectroscopy of molecules, Sussex University, 1972. (1974)

Chambers, R. D. ; Clark, D. T. ; Kilcast, D. ; [weitere]

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 1647-1652

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Polyperfluorobut-2-yne is prepared by a fluoride ion-induced polymerization of hexafluorobut-2-yne. The mass spectrum indicates a regular fragmentation pattern but the ESCA spectrum establishes the structure as a polyene, rather than a crosslinked system, and the occurrence of a shake-up peak assists in this assignment.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1974.170120805

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8

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Photoinitiation and electroinitiation in the polymerization of 2-vinylnaphthalene (1977)

Davies, D. H. ; Phillips, D. C. ; Smith, J. D. B.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2673-2684

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The zinc chloride-catalyzed polymerization of 2-vinylnaphthalene (VN) with both photoinitiation and electronitiation methods was examined. Good yields were obtained with both methods, the electroinitiated process being somewhat faster. The mechanism for polymerization initiation was investigated through a detailed comparison of the kinetics. Both initiation methods show a similar response to increasing input energy and to change in salt to monomer mole ratio. Both methods indicate formation of a ZnCl2-(2-VN)2 complex as intermediate with the formation of the species being rate-determining. These results, together with other similar investigations, are then used to deduce a mechanism that involves the formation of an electronically excited donor-acceptor complex. It is argued that in certain salt-stabilized, electron-delocalized, aromatic systems, such excitation is possible in electroinitiation.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1977.170151112

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9

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Spectroscopic studies of solutions, suspensions, and precipitates of poly(1,6-di-p-toluene sulfonyloxy-2,4-hexadiyne) (1981)

Bloor, D. ; Batchelder, D. N. ; Ando, D. J. ; [weitere]

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 321-334

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ISSN: 0098-1273

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Optical-absorption, fluorescence, and Raman spectra for solutions, suspensions, and precipitates of poly(1,6-di-p-toluene sulfonoxy-2,4-hexadiyne) in and from nitrobenzene, acetone, and chloroform are presented. These are interpreted in terms of the occurrence of two forms of the polymer chain; a quasicrystalline form with properties close to those of single crystal polymer and a chain-extended form occurring in solution and colloidal particles, with an absorption energy of about 2.5 eV (20,000 cm-1). No evidence is found for the presence of very short polymer chains in partially polymerized monomer at low conversion. The relationship of these results to those for deformed single crystals is briefly discussed.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1981.180190212

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10

Digitale Medien

Electroinitiated polymerization of 2-vinylnaphthalene (1977)

Phillips, D. Colin ; Davies, D. H. ; Smith, J. D. B. ; [weitere]

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 1563-1571

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: As part of a program to extend the range of donor-acceptor-initiated polymerization processes, the electroinitiation of 2-vinylnaphthalene in a zinc chloride-sulfolane solution has been studied. Good conversion yields of well-characterized (NMR, IR, GPC, elemental analysis) poly(vinylnaphthalene) were obtained with the process showing several mechanistic similarities to other donor-acceptor salt electropolymerization systems.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1977.170150704

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