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  • 1
    Electronic Resource
    Electronic Resource
    Distance limit for a class of model γ -ray burst sources (1978)
    [s.l.] : Nature Publishing Group
    Nature 271 (1978), S. 525-527 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Some of the available spectral burst data3"8 show a significant flux of photons in the 〉 1 MeV range3"5-8. The 27 April 1972, event observed by Apollo 16 (ref. 3) shows at higher energies a power law spectrum with a possible line feature around 4 MeV. However, power law spectra and lines cannot ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/271525a0
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  • 2
    Electronic Resource
    Electronic Resource
    VB calculations with orthogonal basis functions (1978)
    Springer
    Theoretical chemistry accounts 47 (1978), S. 193-203 
    Details
    ISSN: 1432-2234
    Keywords: VB method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract As a first step in the development of a semiempirical VB method,ab initio VB calculations were performed to obtain potential energy curves for the molecules HF and BeH2 and the energy profile of the collinear exchange reaction F + H2 → HF + H. The applicability of the method is discussed with particular emphasis on the calculation of integrals over OAO's, the choice of valence structures to be included in the CI scheme and the interpretation of the wave function in terms of OAO's.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577161
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  • 3
    Electronic Resource
    Electronic Resource
    Anreicherung und Bestimmung von Blei in Boden- und Sedimentaufschlüssen und -extrakten mit der Flammenatomabsorption (1978)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 291 (1978), S. 213-216 
    Details
    ISSN: 1618-2650
    Keywords: Best. von Blei in Boden, Sedimenten ; Spektralphotometrie, Atomabsorption ; Flamme, Reextraktion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In Vorversuchen wurde gezeigt, da\ beim Aufbewahren der organischen APDC/MIBK-Extrakte starke Bleiverluste auftraten. Daher war es notwendig, das Blei mit SalpetersÄure in die wÄ\erige Phase zu reextrahieren. Wiederfindungsversuche bestÄtigten, da\ Extraktion und Reextraktion quantitativ verlaufen. Das Blei wird dabei um den Faktor fünf angereichert. Es werden mittlere Standardabweichungen für vier Konzentrationsbereiche angegeben. Als Nachweisgrenze wurde eine Konzentration von 0,16 mg Pb/l gefunden, die durch die Anreicherung auf ca. 0,03 mg Pb/l gesenkt wird. Arbeitsvorschriften für das Verfahren sind angegeben.
    Notes: Summary Preliminary investigations have shown, that considerable losses of lead occur during storage of the organic APDC/MIBK-extracts. Therefore, it was necessary to reextract lead into the aqueous phase by nitric acid. Investigations of recoveries confirmed, that extraction and reextraction of lead were quantitative. In this way the concentration of lead is increased by a factor of five. Mean standard deviations for four concentration ranges are given. A detection limit of 0.16 mg of Pb/l is obtained, which is lowered by the preceding enrichment to about 0.03 mg of Pb/l. Details of the procedure are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00480692
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  • 4
    Electronic Resource
    Electronic Resource
    Änderungen in der Stickstoffversorgung auf Dauerflächen im Brachland (1978)
    Springer
    Plant ecology 36 (1978), S. 105-113 
    Details
    ISSN: 1573-5052
    Keywords: Nitrogen mineralization ; Old-field vegetation ; Permanent plots ; Soil nutrients ; Vegetation dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Starting in 1968 plant succession and nitrogen status in the top soil of an old field was investigated. The soil is a calcareous loam which was sterilized by heating. In the absence of human influence distinct successional stages with characteristic floristical and physiognomical features were observed. During the first six years vegetational development was characterized by competition between therophytes and hemicryptophytes. Agricultural treatments such as annual ploughing (spring, summer) and cutting (autumn) were found to change the trend of the succession. Five years after starting the experiment total nitrogen content in the top soil of the control area had increased slightly, while the ploughed plots persisted in their low values. A comparison of the nitrogen mineralisation between 1970 and 1974 showed decreasing amounts of mineral nitrogen in the later stage (1970: 67 kg Nmin/ha/30 weeks; 33 kg Nmin/ha/30 weeks). On the other hand, mineral nitrogen supply on the ploughed plots was not significantly different after the five-years-period. It is suggested that in old-field vegetation the external nitrogen cycle of the early therophyte stage changed to an internal one when long-lived hemicryptophytes, rhizome- and root-budding geophytes became dominant. Tables 1 to 4 show the vegetation development under different treatments; the figures represent average cover values per vegetation season using Londo's (1975) scale. Table 5 contains the total nitrogen concentration values in the uppermost of 10 cm of mineral soil, and Table 6 lists the values for soil volume, mean soil temperatures, average water content, and mineral nitrogen supplies for 1970 and 1974.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221837
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