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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 3 (1987), S. 107-111 
    ISSN: 1432-0789
    Keywords: Oniscus asellus ; Leaf litter ; Acer negundo ; A. saccharum ; Fagus grandifolia ; Picea rubens ; Tsuga canadensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Feeding by the isopod, Oniscus asellus, produced changes in the sulfur constituents of leaf litter substrates (Acer negundo, A. saccharum, Fagus grandifolia, Picea rubens, and Tsuga canadensis). Isopod consumption of leaf litter generally accelerated the mineralization of carbon-bonded S and increased the formation of ester sulfate in all substrates. After the isopod egestion of A. negundo leaves, fecal decomposition over 6 weeks increased total S concentration from 68 to 120 μmol S/g due to the catabolism of organic carbon. During the same period sulfate decreased from 34 to 20 μmol S/g and carbon-bonded S increased from 34 to 100 μmol S/g. Thus the total S pool in aged feces became enriched with organic S (83% of total S). Macroinvertebrate consumption accelerated the transformation of S constituents and the carbon-bonded S concentration approached that of the Oa organic horizon of a northern hardwood forest.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 1543-1543 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photosensitized crosslinking of polyenes with polythiols has been demonstrated to be a free-radical chain reaction whose apparent quantum yield is in the range of 2 × 102-4 × 102 mole/einstein. Initiation occurs by abstraction of a hydrogen atom from the thiol group by the excited n,π* triplet of the ketonic photosensitizer. Kinetic studies of model systems have shown that electron-donating substituents attached or close to the double bond accelerate the thiol addition while electron-withdrawing groups decrease the rate. With a given olefin, slight differences in reaction rates are observed depending on the structure of the thiol. Mercaptopropionate esters are more reactive than mercaptoacetates which, in turn, are more reactive than alkane thiols. Cure rates for polyene-polythiol systems are in accord with results found for the model systems. Aromatic carbonyl compounds are the most effective sensitizers for this reaction. To a first approximation, the effectiveness of the sensitizer depends only upon the absorbance. No correlation was found between photoactivity and the triplet energies or lifetimes of the sensitizers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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