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  • 1
    ISSN: 0039-9140
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 58 (1997), S. 408 -414 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrochemical reduction of 2,6-dimethyl-3-ethyl-4-oxo-4H-pyrido[l,2-a]pyrimidine (base and HCl salt) was investigated by polarography and controlled potential electrolysis in aqueous buffered solutions at different pH values on a dropping mercury electrode and a mercury pool cathode. Controlled potential electrolyses performed in methanolic borate buffer solution (pH=9, 10) at the first polarographic wave (1.45 V vs SCE) gave a stable C-8-coupled hydrodimer (III) in a one-electron process with a product yield of 52%. Reduction performed in alkaline methanolic solution (pH=13.4), at the second polarographic wave (− 1.86 V vs SCE) showed a dihydromonomer (IV) formation with a product yield of 87%, in a two-electron process. The structures of the reduction products were demonstrated by1H and13C NMR spectroscopy as well as by mass spectrometric (MS) data. Two different routes were suggested for the reduction mechanism; a one-electron process involving a neutral radical intermediate formation accompanied by a rapid dimerization and one involving the primarily-formed neutral radical by a second electron uptake and protonation to give the dihydroderivative.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 605-622 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxygen transfer coefficient has been investigated in S. noursci and S. lavendulae fermentation broths obtained from fermentors of different operating volumes (61., 30001., 20,0001.). Fermentors had KLas values ranging from 1.0 to 17.0 min-1, calculated from sulphite oxidation rates. The dynamic measurement of the volumetric oxygen transfer coefficient. (KLa) has been performed in the different fermenting systems. As the fermentation progressed, especially in the first stages, KLa values have decreased in both fermentations and in each system of fermentors. In order to characterise the whole fermenting system an average KLas was calculated from the obtained KLa values. The average KLa grew with increasing KLas values and ranged from 0.03 to 3.72 min-l. Some factors possibly having an influence on the, change of KLa have been studied.The oxygen transfer coefficients of the broths have been measured in falling films and ranged from 0.05 to 0.4 cm min-1. The flow conditions have been characterized by Reynolds numbers of broths varying between 1.0 and 60.0. The average thickness of the falling films have been measured and plotted against Reynolds number. The Re+ which is the breaking-point of the plot increased as the fermentation proceeded. In the region of Re+ the values of the oxygen transfer coefficient increased rapidly. An approximate correlation could be established between the Re+ and the physical properties of fermentation broth.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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