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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1290-1295 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The electrical impedance of the culture medium shows complex changes during the growth and fermentation process of yeast, and this prevents its possible application for the monitoring of certain yeast activities. Clarification of the mechanism of such changes is thus essential for practical use. As a first step toward this aim, the impedance, yeast concentration, and pH of a batch culture medium were measured using special cells with two compartments and also the usual type of cell with one compartment. In the special cells, the yeast was cultured in one compartment only. Conducting ions and nonconducting substances diffused through an intermediate porous membrane sandwiched between the two compartments. The impedances of the two compartments were measured simultaneously by the four-electrode method. The main mechanism responsible for increasing the impedance was the conducting ions produced by the yeast extract added as a nutrient to the culture broth by certain nonconducting substances during the process of growth. The increase in the yeast concentration was also a minor factor increasing the impedance. These increases surpassed the impedance decrease caused by the increase of H+ ions produced by some accumulated acidic substances, and the impedance thus increased.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 1651-1665 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chemical structure of the plasma-polymerized pyridine film produced on a glass reactor wall by means of the plasma technique in which the pyridine vapor was electronically excited by high-frequency power under a reduced pressure was elucidated. The polymer was highly hydrophilic and was soluble to some of the polar organic solvents so that nitrogen-containing polar functional groups were predicted to participate in the chemical structure of the polymer molecules. 1H-NMR, 13C-NMR, and IR spectroscopies, high-resolution mass spectral data, and number-average molecular weight determination with some aid of microelemental analysis revealed the presence of various functional groups such as imine, nitrile, amine, pyridine ring, its N-oxide, and even amide. The oxygen atoms involved in the last two groups were supposedly introduced by contact with ambient air after the plasma process. The hydrophilic nature of the polymer which was essential for preparing reverse osmosis membrane was therefore due to the overall hydration effect of these polar functional groups.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 16 (1990), S. 397-398 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The temperature-dependent Raman spectra of crystalline uranyl nitrate hexahydrate, UO2(NO3)2 · 6H2O, are reported in the temperature range 15-290 K. A group theoretically consistent assignment of the bands in terms of UO22+, NO3- and H2O vibrations is proposed. The temperature-dependent studies of thermosensitive bands associated with these entities were used to study the previously reported phase transition at 140 ± 5 K and to detect another phase transition at 190 ± 5 K. The latter transition shows up prominently in the temperature-dependent fluorescence studies and is also accompanied by a sharp increase in the Rayleigh scattering. The transition at 190 ± 5 K is triggered by the dynamics of H2O-II and UO22+ whereas that at 140 ± 5 K is associated with the dynamics of H2O-II/NO3-. Both the transitions are of second order.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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