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  • 1
    Electronic Resource
    Electronic Resource
    Effects of pH and temperature on cardioactive polypeptides from sea anemones: A 1H-nmr study (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1143-1157 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of pH and temperature on the 300-MHz 1H-nmr spectra of three cardioactive polypeptides from sea anemones, anthopleurin-A from Anthopleura xanthogrammica (AP-A) and Anemonia sulcata toxins I and II (ATX I and II), are described. AP-A and ATX II exhibit major spectral heterogeneity. Evidence from the pH and temperature studies and from high performance liquid chromatography indicates that this heterogeneity is conformational rather than chemical in origin. By contrast, purified isotoxins of ATX I show no evidence of conformational heterogeneity. The pKa values of most of the ionizable groups in these polypeptides are not strongly perturbed by interactions in the tertiary structure, with the exception of one of the Asp carboxylates, which has a pKa of ≲ 2 in AP-A and ATX II and 3.0 in ATX I. Protonation of this carboxylate, suggested to be Asp-9, leads to a conformational change in all three molecules. All three polypeptides are thermally stable, showing some conformational changes but not major unfolding at elevated temperatures.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270708
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and structure of Cp3U=CHPMe3: A compound with a U=C multiple bond (1988)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 121 (1988), S. 417-420 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Struktur von Cp3U=CHPMe3: Eine Verbindung mit U=C-MehrfachbindungGrünes, kristallines Cp3U=CHPMe3 wurde durch Umsetzung von Cp3UCl mit Li[CH2]2PMe2 oder H2C=PMe3 dargestellt. Seine Kristallstruktur wurde durch Röntgenbeugungsanalyse an Einkristallen bestimmt. Der kurze U=CH-Abstand von 2.274(8) Å und der große Winkel U—C—P von 143.5(5)° deuten Uran-Kohlenstoff-Mehrfachbindungscharakter an. Die 1J (13C1H)-Kopplungskonstanten in den CH-Gruppen zwischen Uran und Phosphor von Cp3U=CHPMe3 (95 Hz), Cp3U=CHPMe2Ph (100 Hz) und Cp3U=CHPPh2Me (113 Hz) sind auffallend klein. Den Strukturdaten kann aber keine agostische UCHP-Wechselwirkung entnommen werden.
    Notes: Green, crystalline Cp3U=CHPMe3 has been synthesized by the reaction of Cp3UCl with Li[CH2]2PMe2 or CH2=PMe3. Its crystal structure has been determined by single crystal X-ray diffraction. The short U=CH bond distance, 2.274(8) Å, and large U—C—P angle, 143.5(5)°, indicate uranium-carbon multiple bond character. The 1J(13C1H) coupling constants within the CH group between uranium and phosphorus in Cp3U=CHPPh2Me (95 Hz), Cp3U=CHPMe2Ph (100 Hz), and Cp3U=CHPPh2Me (113 Hz) are surprisingly small, but no agostic interaction UCHP can be derived from the structural data.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19881210306
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  • 3
    Electronic Resource
    Electronic Resource
    The modification of polysulfone by metalation (1988)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 26 (1988), S. 123-127 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1988.140260211
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  • 4
    Electronic Resource
    Electronic Resource
    Electrochemical measurement of effective diffusivity in Hall-Heroult electrolyte (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1649-1655 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Forced-convection mass transfer at the metal/bath interface during aluminum reduction from cryolitic melts was studied under reproducible convective conditions. A film of molten aluminum on a rotating molybdenum cylinder was the cathode. Concentration overpotential measured as a function of rotation rate, current density, and bath composition was converted to concentration differences between the bulk and the metal surface. Chosen as the basis for calculation of a mass transfer coefficient was the concentration of aluminum fluoride given by: \documentclass{article}\pagestyle{empty}\begin{document}$$ C_{{\rm AlF}_{\rm 3} } = \frac{{2\rho (100 - Al_2 {\rm O}_3 \% - {\rm CaF}_2 \% - IMP\%)}}{{100M_{{\rm AlF}_3} (CR + 2)}} $$\end{document} where the amounts of indicated compounds are in weight percent, IMP designates impurities, M is molecular weight, ρ is the density of the melt, and CR is the cryolite ratio, the ratio of moles NaF to moles AlF3. Agreement with a correlation for mass transfer to a rotating cylinder allowed the calculation of effective diffusivities for aluminum fluoride species, in alumina-saturated melts, of: 11.1 ± 1.1 × 10-5 cm2/s at 1.8 CR; 11.4 ± 1.7 × 10-5 cm2/s at 2.3 CR; 5.4 ± 0.8 × 10-5 cm2/s at 3.0 CR; and 4.4 ± 0.9 × 10-5 cm2/s at 4.0 CR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690341008
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  • 5
    Electronic Resource
    Electronic Resource
    On-line optimizing control of a packed-bed immobilized-cell reactor (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 626-632 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line optimizing control has been used to find and track the economically optimal operating conditions of a packed-bed reactor. The continuous reactor under study converts the ammonium salt of fumaric acid to aspartic acid using whole cells immobilizing in K-carrageenan beads. The on-line optimizing control was performed using a leastsquares recursive estimation algorithm with a variable forgetting factor to estimate the parameters in a linear discrete-time model. A Newton optimization procedure used these parameters to calculate the direction and distance to the optimal conditions. Features found to enhance the speed and stability of the algorithm included the use of a variable forgetting factor algorithm, both low- and high-pass filtering of the data, outlier rejection, and linearizing input-outupt transformations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690340412
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  • 6
    Electronic Resource
    Electronic Resource
    Miniemulsion copolymerization of vinyl acetate and butyl acrylate. II. Mathematical model for the monomer transport (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1495-1517 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A mathematical model is presented to describe the monomer transport between monomer droplets, aqueous phase, and polymer particles during the course of an emulsion polymerization. The model was used to investigate the role of the cosurfactant (hexadecane) in the miniemulsion copolymerization of 50:50 molar ratio vinyl acetate-butyl acrylate monomer mixture, as well as the effect of the different components and process variables on the rate of copolymerization, monomer distribution between phases, and composition of the copolymer.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260712
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  • 7
    Electronic Resource
    Electronic Resource
    Secondary electron emission characteristics of oxidized beryllium cathodes (1988)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 11 (1988), S. 389-397 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Oxidized beryllium surfaces are used in a number of microwave crossed-field amplifier (CFA) tubes as secondary electron emission cold cathodes. During operation the cathode surface is subjected to electron and ion bombardment in a complex process which produces both erosion and replenishment of the oxide surface, in addition to a significant build-up of amorphous carbon. The result is a general degradation of tube performance. Special techniques were developed to opoen an evacuated tub and transfer the cathode to a UHV surface analysis system with minimal contamination from the atmosphere. Three CFA tubes with various histories of operation were examined and measurements from made of the secondary electron emission (delta), first crossover, voltage at delta maximum, and the surface chemical composition by AES at several points on each cathode. Significant differences were found which reflected their number of hour of operation, as well as variations in manufacturing procedures. A generalized linear cofrrelation between secondary electron emission and the surface carbon atomic fraction was obtained when the data for all the tubes was combined and analyzed. The deleterious effects of carbon in operated CFA tubes were confirmed and suggest that reduction of potential sources of carbon contamination in the tube during manufacture, processing, and operation should improve overall performance.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740110620
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