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  • 1
    Electronic Resource
    Electronic Resource
    Cross-flow ultrafiltration of proteins through asymmetric polysulfonic membranes: I. Retention curves and pore size distributions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 617-625 
    Details
    ISSN: 0006-3592
    Keywords: cross-flow ultrafiltration ; polysulfonic membranes ; proteins ; concentration-polarization ; pore size distributions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flux and retention of 0.1%w/w aqueous solutions of several proteins [lysozyme, pepsin, bovine serum albumin (BSA), lipase, and γ-globulin] with molecular weights of 14.6, 36, 67, 801 and 150 kDa are studied when they are tangentially filtered, with transmembrane pressure differences until 1 MPa and circulation velocities in the re-tentate loop from 0.04 to 1.98 m/s (laminar regime), through two asymmetric polysulfone commercial membranes (E-100 with a nominal pore size of 0.01 μm and E-500 with a nominal pore size of 0.04 μm). Results are analyzed with the film theory for the concentration-polarization phenomenon, obtaining the mass transfer coefficient along with the apparent and true retention coefficients for the cell used, as a function of the feed circulation velocity and the molecular weight of the solute. The standard retention curves lead to pore size distributions differing from the nominal ones. These differences can be attributed to the modifications of the membranes when they are in operational conditions, probably due to protein adsorption. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470602
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  • 2
    Electronic Resource
    Electronic Resource
    Retention of proteins in cross-flow UF through asymmetric inorganic membranes (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1901-1910 
    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: The flow and retention of 0.1% w/w aqueous solutions of pepsin, bovine serum albumin (BSA), lipase, γ-globulin, and invertase with molecular weights of 36,000, 67,000, 80,000, 150,000, and 270,000 dalton (g/mol) are studied when they are tangentially filtered through an inorganic microporous membrane with a nominal pore size of 0.02 × 10-6 m made by Anopore, with transmembrane pressure differences up to 100 kPa. The data were analyzed within the frame of the film layer theory for the concentration polarization phenomenon. This allows the mass-transfer coefficient to be obtained for the cell used as a function of the feed circulation speed and the molecular weight of the solute. Apparent and true retention curves obtained lead to a size exclusion radius smaller than the nominal one but very similar to that obtained from scanning electronic photographs.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690401114
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  • 3
    Electronic Resource
    Electronic Resource
    Carbon paste electrodes with electrolytic binder: Influence of the preparation method (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 184-188 
    Details
    ISSN: 1040-0397
    Keywords: Carbon paste ; Electrolytic binder ; Sulfuric acid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the construction of carbon paste electrodes (CPE) is described. Here ferrocene is used as the insoluble electroactive species, graphite powder as conductor and sulfuric acid as binder. The CPE thus prepared prevents ferrocenium ions from diffusing towards the bulk solutions. Voltammetric, chronopotentiometric and chronoamperometric experiments performed with these CPEs show that the different preparation methods yield different electrochemical parameters for the ferrocene-ferrocenium system.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070215
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  • 4
    Electronic Resource
    Electronic Resource
    The participation of aromatic neighboring groups in gas-phase elimination reactions (1978)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 10 (1978), S. 923-929 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase pyrolysis of 2-chloroethylbenzene and p-methoxy-2-chloroethylbenzene was studied in a static system over the temperature range of 411°-471°C and a pressure range of 39-202 mm Hg. The reactions in seasoned vessels, with the propene inhibitor always present, were homogeneous, first-order, and unimolecular. The rate constants are given by the Arrhenius equation for 2-chloroethylbenzene: \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k(\sec ^{- 1}) = (13.07 \pm 0.35) - (220.9 \pm 4.6){\rm kJ/mol/2}{\rm .303}RT $$\end{document} and for p-methoxy-2-chloroethylbenzene: \documentclass{article}\pagestyle{empty}\begin{document}$$ \log k(\sec ^{- 1}) = (13.81 \pm 0.34) - (228.4 \pm 4.6){\rm kJ/mol/2}{\rm .303}RT $$\end{document} The presence of phenyl substituents in the β position of ethyl chloride has been found to provide anchimeric assistance in these elimination reactions.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550100903
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  • 5
    Electronic Resource
    Electronic Resource
    Steric influence in the direction of elimination of gas-phase pyrolyses of several highly branched secondary acetates (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 57-67 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients for the gas-phase pyrolyses of a series of structurally related secondary acetates have been measured in a static system over the temperature range of 289.1-359.5°C and the pressure range 50.0-203.0 torr. The temperature dependence of the rate coefficients is given by the following Arrhenius equations: for 3-hexyl acetate, log k1 (s-) = (12.12 ± 0.33) - (176.1 ± 3.9)kJ/mol/2.203RT; for 5-methyl-3-hexyl acetate, log k1 (s-) = (13.17 ± 0.20) - (186.2 ± 2.3)kJ/mol/2.303RT; and for 5,5-dimethyl-3-hexyl acetate, log k1 (s-) = (12.70 ± 0.19) - (177.4 ± 2.2)kJ/mol/2.303RT. The direction of elimination of these esters has shown from the invariability of olefin distributions at different temperatures and percentages of decomposition that steric hindrance is a determining factor in the eclipsed cis conformation. Moreover, a more detailed analysis indicates that the greater the alkyl-alkyl interaction, the less favored the elimination tends to be. Otherwise, an increase of alkyl-hydrogen interaction caused steric acceleration to be the determining factor.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550160108
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  • 6
    Electronic Resource
    Electronic Resource
    Gas-phase elimination kinetics of 1-substituted ethyl acetates. Effect of polar substituents at the α carbon of secondary acetates (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 205-218 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase elimination of several polar substituents at the α carbon of ethyl acetates has been studied in a static system over the temperature range of 310-410°C and the pressure range of 39-313 torr. These reactions are homogeneous in both clean and seasoned vessels, follow a first-order rate law, and are unimolecular. The temperature dependence of the rate coefficients is given by the following Arrhenius equations: 2-acetoxypropionitrile, log k1 (s-1) = (12.88 ± 0.29) - (203.3 ± 2.6) kJ/mol (2.303RT)-1; for 3-acetoxy-2-butanone, log ±1(s-1) = (13.40 ± 0.20) - (202.8 ± 2.4) kJ/mol (2.303RT)-1; for 1,1,1-trichloro-2-acetoxypropane, log ℜ1 (s-1) = (12.12 ± 0.50) - (193.7 ± 6.0) kJ/mol (2.303RT)-; for methyl 2-acetoxypropionate, log ℜ1 (s-1) = (13.45 ± 0.05) - (209.5 ± 0.5) kJ/mol (2.303RT)-1; for 1-chloro-2-acetoxypropane, log ℜ1 (s-1) = (12.95 ± 0.15) - (197.5 ± 1.8) kJ/mol (2.303RT)-1; for 1-fluoro-2-acetoxypropane, log ℜ1 (s-1) = (12.83 ± 0.15)- (197.8 ± 1.8) kJ/mol (2.303RT)-1; for 1-dimethylamino-2-acetoxypropane, log ℜ1 (s-1) = (12.66 ± 0.22) -(185.9 ± 2.5) kJ/mol (2.303RT)-1; for 1-phenyl-2-acetoxypropane, log ℜ1 (s-1) = (12.53 ± 0.20) - (180.1 ± 2.3) kJ/mol (2.303RT)-1; and for 1-phenyl-3-acetoxybutane, log ℜ1 (s-1) = (12.33 ± 0.25) - (179.8 ± 2.9) kJ/mol (2.303RT)-1. The Cα—O bond polarization appears to be the rate-determining process in the transmition state of these pyrolysis reactions. Linear correlations of electron-releasing and electron-withdrawing groups along strong σ bonds have been projected and discussed. The present work may provide a general view on the effect of alkyl and polar substituents at the Cα—O bond in the gas-phase elimination of secondary acetates.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.550150302
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