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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen transfer from 9,10-dihydrophenanthrene to anthracene (1989)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 21 (1989), S. 375-386 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic studies of the transfer of hydrogen from 9,10-dihydrophenanthrene to anthracene were done at 350°C in the liquid phase. Principal products were phenanthrene and 9,10-dihydroanthracene. Autocatalysis occurred at low extents of reaction, where H-transfer from 9,10-dihydroanthracene to anthracene caused an increase in free radical concentrations. At higher extents of reaction, 9,10-dihydroanthracene inhibited rates by diverting intermediate 9-hydrophenanthryl radicals back to reactants. A quantitative kinetic model based on literature rate and thermodynamic data fits the observations well. A key net reaction is the transfer of an H-atom from a radical (9-hydrophenanthryl) to a molecule (anthracene). It is shown that this process does not involve a free H-atom intermediate. The derived rate constant for this exothermic process (7.5 × 103 M-1 s-1) is considerably greater than that for the related, but thermoneutral H-transfer between anthracene moieties (120 M-1 s-1).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550210602
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Rate constants for hydrogen abstraction by resonance stabilized radicals in high temperature liquids (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 19 (1987), S. 943-957 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Benzylic H-atom abstraction rates by diphenylmethyl radicals from a series of donors were determined in nonpolar liquids at elevated temperatures. Relative rates were converted to absolute rates via available equilibrium constant data for the dimerization of diphenylmethyl radicals. Abstraction by diphenylmethyl from 1, 2, 3, 4-tetrahydronaphthalene (tetralin) was studied over the temperature range 489-573 K. Its Arrhenius expression is 109.9±0.3 exp{-(10183 ± 373)/T} M-1 s-1. Abstraction from other donors was studied at 548 K. Rate constant values ranged from a low of 3.6 M-1 s-1 for toluene to a high of 3000 M-1 s-1 for 9, 10-dihydroanthracene. Similar reactions with the fluorenyl radical were also studied. In this case, relative rates were converted to absolute rates with an equilibrium constant for fluorenyl dimerization determined from the observed homolysis rate of the dimer and an assumed recombination rate. In addition, forward and reverse rate measurements yielded the equilibrium constant for hydrogen transfer between fluorenyl and diphenylmethyl. At 548 K, fluorenyl is favored by a factor of 13 over diphenylmethyl.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550191006
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  • 3
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    Are supernovae radio sources - A search for radio emission from young supernova remnants (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A search has been conducted for radio emission at 11 and 3.7 cm from 46 recent supernovae having accurately determined positions and ages of a few months to 79 years. None of these supernovae was detected at a flux density greater than 5-10 mJy. These negative results cannot be explained by internal absorption and are thus due to intrinsically weak synchrotron emission in young supernova remnants. There are two possibilities: either (1) relativistic particles are accelerated not by the supernova outburst but by processes occurring much later (at least about 75 years) in the remnant or (2) the magnetic field in the young remnants evolves very slowly, in proportion to the inverse square root of time, so that its value in the remnants observed was no more than about 0.002 gauss. The constraints the observations place on these possibilities and on the energy in cosmic rays in young remnants are discussed. Gamma-ray observations at times of no more than about 1 year following an outburst will allow one to discriminate between the two alternative explanations of the radio results.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 220
    Format: text
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  • 4
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    Star formation in the inner galaxy: A far-infrared and radio study of two H2 regions (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy H II regions G30.8-0.0 (in the W43 complex) and G25.4-02., along with radio and molecular line measurements at selected positions. An effort is made to understand far infrared wavelingths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. For G25.4-0.2, the radio recombination line and CO line data permit resolution of the distance ambiguity for this source. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright H II regions. Using revised distances of 4.3 kpc for G26.4SE and 12 kpc for G25.4NW, that the latter, which is apparently the fainter of the two sources, is actually the more luminous. Though it is not seen on the Palomar Sky Survey, G25.4SE is easily visible in the 9532A line of S III and is mapped in this line. The ratio of total luminosity to ionizing luminosity is very similar to that of H II regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated.
    Keywords: ASTRONOMY
    Type: NASA-TM-88184 , REPT-86008 , NAS 1.15:88184 , PREPRINT-38
    Format: application/pdf
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  • 5
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    The discovery of an X-ray bright BL Lacertae object - 0414 + 009 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: X-ray, optical, and radio observations have been made of an X-ray source originally discovered by Ulmer et al. (1980) in a survey of Abell clusters of galaxies. The relatively flat radio spectrum, the featureless optical spectrum, and the shape of the X-ray spectrum lead to the classification of the source as a BL Lacertae object. The source has one of the highest X-ray flux density ratios to both the optical and radio flux densities, and its strength at all these wavelengths warrants further multiwavelength studies. The radio, optical, and X-ray flux densities for the observations were 100 mJy, V = 16.4 (1 mJy), and 1 UFU (1.6 micro Jy). The X-ray flux varied by a factor of 2 over a 1 year period, but no 100 s time scale variations were seen. A search of the Harvard plate stacks did not reveal any optical variations. A model for the source is presented, and the implications of this object with respect to X-ray surveys are briefly discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 270; July 1
    Format: text
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  • 6
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    Star formation in the inner galaxy: A far-infrared and radio study of two H2 regions (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy HII regions G30.8-0.0 (in the W43 complex) and G25.4-0.2, along with radio and molecular line measurements at selected positions. The purpose of this study is an effort to understand star formation in the molecular ring at 5 kpc in galactic radius. Measurements at several far infrared wavelengths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. Using radio recombination line and CO line data for G25.4-0.2, the distance ambiguity for this source is resolved. The large distance previously ascribed to the entire complex is found to apply to only one of the two main components. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright HII regions. Using the revised distances of 4.3 kpc for G25.4SE and 12 kpc for G25.4NW, it is found that the latter, which is apparently the fainter of the two sources, is actually the more luminous. The ratio of total luminosity to ionizing luminosity is very similar to that of HII regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated.
    Keywords: ASTRONOMY
    Type: NASA-TM-86720 , REPT-85221 , NAS 1.15:86720
    Format: application/pdf
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  • 7
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    Carbon recombination line observations of the sharpless 140 region (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Carbon recombination-line emission has been detected at two frequencies from a dark cloud contiguous with the small H II region Sharpless 140. The observations show the dark cloud to be of unusually low temperature and to have a markedly inhomogeneous density distribution, with localized region of high density surrounding one or more embedded stars. The carbon is probably ionized by photons from both the exciting star of S140 and the embedded stars. The dark cloud and S140 apparently represent two stages of star formation which have occurred over a period of at least 500,000 years in adjacent regions of the same dark cloud.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 204; Mar. 15
    Format: text
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  • 8
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    Further joint X-ray, infrared and radio observations of Cygnus X-3 (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Observations of Cygnus X-3 were carried out at 2.5 - 7.5 keV, 2.2 micron, 8.1 GHz and 2.7 GHz over a two week period. The X-ray data show the periodic structure which is typical of Cyg X-3. At times the X-ray and infrared measurements show very similar periodic structure, both in phase and shape, while at other times the infrared data show no periodic variability. The radio fluxes were usually low during the period of observation; both the daily average radio flux levels and spectral index remained nearly constant.
    Keywords: ASTRONOMY
    Type: NASA-CR-143536
    Format: application/pdf
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  • 9
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    CO observations of the expanding envelope of IRC plus 10216 (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: High-sensitivity emission profiles were observed for the transition of C12O16 and C13O16 towards IRC + or - 10216. It appears that the spherically symmetric uniform mass-outflow model proposed by Morris is necessary to describe the line profiles. The outflow appears to be slightly accelerated, having a velocity of 15 km/sec at the edges of the CO cloud, compared with 12 km/sec for the more centrally confined molecules.
    Keywords: ASTRONOMY
    Type: NASA-CR-119157 , AD-A011098 , REPT-1975-8
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  • 10
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    CO observations of galactic reflection nebulae (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Carbon monoxide emission has been observed toward about 35 galactic reflection nebulae. The peaking of CO temperatures near the hotter stars indicates substantial local heating of the gas and dust by the embedded stars. Wide low-level emission wings are seen on several of the (C-12)O line profiles; these are most plausibly interpreted as due to cloud material accelerated by such processes as radiation pressure from the newborn stars.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 214
    Format: text
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