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991.
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Horst Bergmann 《Mathematische Annalen》1976,221(1):81-94
Ohne Zusammenfassung 相似文献
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Horst Kutsch 《Fresenius' Journal of Analytical Chemistry》1987,328(7):572-576
Summary A new method is presented derived from the systematic changes occurring in the UV/VIS absorption (400 and 600 nm) of humic substances in dimethyl sulfoxide during a multiple temperature-gradient cycle (16 ° C 85 ° C 16 ° C). The thermo-optical analysis is made possible because of specific and reproducible interaction between molecule components of the humic substances, on the one hand, and dimethyl sulfoxide as reagent, on the other hand. It was possible to demonstrate a thermally dependent change in some physico-chemical properties (electrical conductivity, UV/VIS, IR and ESR spectra) of fulvic and humic acids. Further, it should be possible to apply the results of the observations on the model system p,o-chloranil in dimethyl sulfoxide to humic substances. After correction for expansion-dependent hypochromism, the thermo-optograms are evaluated according to the appearance of hyperchromism with respect to the first absorption recorded at 16 ° C (400 and 600 nm). Humic substances were investigated from mineral soils, peats and composts.
Thermo-optische Analyse von Huminstoffen — Ein neues Verfahren mit Dimethylsulfoxid als Reagens相似文献
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Rainer Traber Ekehardt Vogelmann Siegfried Schreiner Tilmann Werner Horst E. A. Kramer† 《Photochemistry and photobiology》1981,33(1):41-48
Abstract— Quenching of the excited states of lumiflavin and 3-methyl-5-deazalumiflavin by methyl-and methoxy-substituted benzenes and naphthalenes in methanol was investigated. The observed difference in the reactivity of acid and neutral lumiflavin triplets is explained thermodynamically by applying the Michaelis cycle, as being due to the higher reduction potential of the acid triplet. In this connection the p K values of lumiflavin triplet (p K M = 6.5) and semiquinone (p K M = 11.3) have also been determined in methanol. The difference in the reactivity between the singlet and triplet states of lumiflavin is found to be greater as predicted by the difference in excitation energy. The reactivities of the excited states of flavin and 5-deazaflavin differ only slightly in contrast to the marked difference in the ground state reactivities of electron transfer reactions. This is explained in terms of the model of Rehm and Weller. The pH dependence of the electron transfer quenching of 5-deazaflavin triplet was investigated in water, yielding a triplet p K of 2.5. In contrast to the flavin, this triplet p K does not significantly differ from the p K of the 5-deazaflavin ground state. From this, different sites of protonation are deduced for the photoexcited triplet states of flavin and 5-deazaflavin. 相似文献
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