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  • Chemistry  (433)
  • Polymer and Materials Science  (87)
  • Life and Medical Sciences  (13)
  • ASTROPHYSICS  (11)
  • Fisheries
  • 1980-1984  (464)
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Publisher
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Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1038-1044 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Pyridylhydrazones as Carbonyl Derivatives to induce Fragmentation in Mass SpectrometryIt was found that the 2-pyridylhydrazone is a derivative of the carbonyl group, which is able to induce fragmentation of an alicyclic skeleton with an efficiency comparable to that of the tertiary amino group and the ethylene acetal group.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 255-260 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stereoselectivity in the Photosensitized [2 + 2] Cycloaddition Reaction of Dichlorovinylene Carbonate to PhenanthreneIn the [2 + 2] cycloaddition reaction of dichlorovinylene carbonate (2) to phenanthrene (1) only one product 3 is selectively isolated. Its exo-configuration is proved by single crystal X-ray structure analysis. 3 is a masked α-diketone. Hydrolysis or ammonolysis lead after a benzilic acid rearrangement to an α-hydroxycyclopropanecarboxylic acid system 6 and 8.
    Notes: Bei der sensibilisierten [2 + 2]-Photocycloaddition von Dichlorvinylencarbonat (2) an Phenanthren (1) wird selektiv nur ein Produkt isoliert, dessen exo-Konfiguration 3 eine Röntgenstruktur-analyse beweist. 3 ist ein maskiertes α-Diketon, dessen Hydrolyse bzw. Ammonolyse über eine Benzilsäure-Umlagerung zum α-Hydroxycyclopropancarbonsäure-System 6 und 8 führt.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2011-08-17
    Description: The paper presents HEAO 1 low-energy X-ray observations of 59 known or suspected RS CVn systems cited in the lists of Hall (1976), Eggen (1978), and the circulars of the Working Group on RS CVn systems of IAU Commission 42. The data are used to argue against the validity of the minimum flux coronal models. A coronal loop model is used to derive expressions for the loop parameters in terms of observable quantities, and find acceptable solutions for RS CVn systems. It is concluded that the difference between solar activity and that observed in RS CVn systems may be merely a matter of scale.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 236
    Format: text
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  • 4
    Publication Date: 2019-06-28
    Description: The results of a study of five X-ray discovered weak emission pre-main-sequence stars in the Taurus-Auriga star formation complex are presented. All are of spectral type K7-M0, and about 1-2 mag above the main sequence. One is a double-lined spectroscopic binary, the first spectroscopic binary PMS star to be confirmed. The ages, masses, and radii of these stars as determined by photometry and spectroscopy are discussed. The difference in emission strength between these and the T Tauri stars is investigated, and it is concluded that these 'post-T Tauri' stars do indeed appear more evolved than the T Tauri stars, although there is no evidence of any significant difference in ages.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
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  • 5
    Publication Date: 2019-06-28
    Description: In connection with the present investigation, X-ray, radio, and ultraviolet observations of AR Lacertae over one orbital cycle have been obtained. The X-ray light curve shows a deep primary minimum and a broad, shallow secondary minimum. The quiescent corona of the G2 IV component is small and asymmetric. This corona extends some 0.02 stellar radii above the photosphere; the leading, spotted hemisphere is brighter in X-rays than the trailing hemisphere. The K0 IV component has two coronal components. The extended, presumably hotter component extends to one stellar radius above the photosphere and exhibits a brighter leading hemisphere. There is an inner coronal component which is small relative to the stellar radius, but the lack of coverage past mid-eclipse severely limits the possibility to deduce the nature of this component. The UV observations also imply a nonuniform surface distribution of plage regions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 267; April 15
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  • 6
    Publication Date: 2019-06-27
    Description: It is shown that Cyg X-6 and Cyg X-7 are part of a large X-ray ring, 13 degrees in diameter. At a distance of 2 kpc, this X-ray source lies behind the Great Rift of Cygnus, and as such has radiation from its central region absorbed. The diameter of the emitting region is 450 pc. The X-ray source is associated with a ring of elongated H-alpha filaments which enclose the Cygnus X radio source. At the center of this region lies the highly luminous Cygnus OB2 association.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 238
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  • 7
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: Einstein IPC observations of 10 fields containing pre-main-sequence stars are presented. The detection of significant soft X-ray flux from eight cataloged T Tauri stars plus the optical identification of two new T Tauri-like stars associated with X-ray sources are reported. It is demonstrated than an inverse correlation between the H-alpha equivalent width and the detection of X-ray flux exists. This is interpreted in terms of a model wherein the X-ray emission arises in a corona similar to that of active late-type stars, which is small compared to the extent of the circumstellar envelope. It is postulated that the lack of correlation of X-ray flux (or H-alpha) with A(v) is due to a lack of grains in the envelopes of the more active T Tauri stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 250
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  • 8
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    In:  Other Sources
    Publication Date: 2019-06-28
    Description: Follow-up Einstein X-ray observations of four fields containing pre-main-sequence stars are presented. A search has been made for evidence of variability on time scales of hours and of 1 year. A large, slow flare in AS 205, and the X-ray disappearance of AA Tau are reported. Otherwise, T Tauri stars appear no more variable in X-rays than do active solar-like stars. An attempt has been made to determine spectral parameters for a number of the brighter sources. X-ray absorption column densities are consistent with those inferred from A(v), and T(x) of about 10-million K, in all cases. The importance of these observations for models of T Tauri stars and their coronae is considered.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 194-201
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  • 9
    Publication Date: 2019-06-28
    Description: Absorption dips which recur with a period of 2985 s have been observed from the X-ray burst source 4U 1915-05. It is suggested that the dips are caused by obscuration of the X-ray source by material at the point where the gas stream from the companion meets the accretion disk, and that the 2985 s periodicity is the orbital period of the binary system. These observations represent the first direct evidence of the binary nature of X-ray burst sources. In addition, a new optical identification of 4U 1915-05 is suggested: a 22 magnitude candidate observed in a CCD image of the optical field at the arcsec-accurate HRI X-ray position.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 253
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  • 10
    Publication Date: 2019-06-28
    Description: X-ray observations of 14 early F dwarfs are reported and these stars are used, together with a complete sample from the literature, to examine how the characteristics of coronal X-ray emission vary from dwarfs of spectral type A through G. Evidence for a rotation-activity relation in stars redder than B - V = 0.45 is found. Stellar duplicity and age, except insofar as they influence the rotation rate, do not appear to be important in determining the coronal X-ray flux level in F dwarfs. It is suggested that the appearance of a relation between rotation and activity at B - V = 0.45 indicates the turn-on of a solar-like dynamo. The high X-ray surface fluxes and small variance thereof for dwarfs with B - V = 0.3-0.45 are also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 794-800
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