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  • Wiley-Blackwell  (478)
  • 1970-1974  (448)
  • 1950-1954  (30)
  • 1973  (448)
  • 1950  (30)
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  • 1970-1974  (448)
  • 1950-1954  (30)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 269-282 
    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: The development of gel permeation chromatography (GPC) has provided a convenient tool for the rapid determination of molecular weight distribution. The question has arisen as to the suitability of the method for specification purposes. The present work, suggested by the Naval Air Systems Command, represents an attempt to assess the precision of the method through a series of tests carried out by a number of laboratories using identical procedures on the same samples. Ten laboratories agreed to take part. Naval Ordnance Station, Indian Head, worked out standard conditions for operation of the chromatograph, for calibration of the columns, and for analysis of the GPC curves. Two samples of polystyrene were used by the various organizations for calibration of their instruments. Number-average molecular weight, heterogeneity index, and cumulative molecular weight distribution curves were determined on four samples of carboxyl-terminated polybutadiene (CTPB) and two samples of hydroxyl-terminated polybutadiene (HTPB), all unidentified except by letter code. All laboratories used identical directions for setting up CTPB and HTPB calibration curves which were based on curves determined from vapor-pressure osmometer molecular weights and GPC count numbers of fractionated material. Variation among the different laboratories was 0.15 in heterogeneity index, and a maximum of 1200 in molecular weight provided one aberrant set of values was eliminated. The six samples had heterogeneity indices from 1.15 to 1.54, while molecular weight varied from approximately 3000 to 6000. The average coefficient of variation of the molecular weight values was 6.2 ± 0.7%, which is quite acceptable. Variation in heterogeneity index was too great for specification purposes when considered among the different laboratories, but may be sufficiently good when measured by any one laboratory.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 1131-1145 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several techniques for investigating the multiplicity and stability of open isothermal enzymatic reactors are discussed and some of the pitfalls in previous thinking pointed out. The example which is used to illustrate these methods exhibits several interesting features. Among these is the existence of a stable oscillatory state which surrounds a unique steady state which is asymptotically stable to certain finite disturbances.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 169 (1973), S. 177-189 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die elektroinitiierte Polymerisation von N-Vinylcarbazol (VCZ) wurde in Aceton bei 25°C mit Zinkbromid als Katalysator unter Verwendung von Platinelektroden eingehend untersucht. Die Polymerisationsgeschwindigkeit erwies sich als direkt abhängig von der Stromstärke, der Zinkbromid-Konzentration und dem anfänglichen Wassergehalt des Solvens.Die Molekulargewichte der entstandenen Polymeren (1000-6000) sind unabhängig von der Stromstärke, der Zinkbromid-Konzentration und dem Umsetzungsgrad des Monomeren zum Polymeren, werden jedoch beeinflußt durch Wasser, die Monomerkonzentration und das Elektrodenmaterial. Die chemische Zusammensetzung der Polymeren ändert sich nicht mit der Stromstärke, der Zinkbromid-Konzentration, dem Umsetzungsgrad und dem Elektrodenmaterial. Sie ändert sich jedoch ein wenig mit dem Wassergehalt des Acetons.
    Notes: The electroinitiated polymerization of N-vinylcarbazole (VCZ) in acetone solvent at 25°C with zinc bromide, as catalyst, and platinum electrodes was investigated in detail. The polymerization rate was found to be directly dependent on current strength, zinc bromide concentration and the initial water content of the solvent.The molecular weights of the formed polymers (1000-6000) are independent of current strength, zinc bromide concentration and degree of conversion of monomer to polymer, but are affected by water, monomer concentration, and by the type of electrodes used. The chemical composition of the polymer is invariant with current strength, zinc bromide concentration, degree of conversion, and electrode material but does vary slightly with the water content of acetone.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 11 (1973), S. 683-688 
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 11 (1973), S. 149-155 
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 647-654 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The primary amine initiated homopolymerization of γ-benzyl-L-glutamate NCA in dioxane at 25°C, 35°C, 50°C, and 65°C has been investigated. The reactions were virtually independent of temperature indicating an activation energy of less than 1 kcal/mole. The entropy of activation was estimated to be -65 entropy units at 300°K. The reaction proceeded in two stages. The first stage was zero-order with respect to monomer, whereas the second was first-order with respect to monomer. Both stages were first-order with respect to initiator. These results were interpreted by assuming that the rate constant for propagation was not independent of the degree of polymerization up to the point where a conformational transition to α-helix occurred.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 1377-1385 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using Wilson's GF-matrix method as modified by Higgs for infinite helical polymers, dispersion curves and the frequency distribution function have been calculated for poly-L-proline II chain. Infrared spectrum is obtained and a Urey-Bradley force field, which provides best fit with the observed frequencies, is evaluated. The result are discussed from the viewpoint of the conformational characteristics of forms I and II.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 5 (1973), S. 459-463 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method of loading axisymmetric finite element models by application of a uniform circumferentially distributed moment is presented herein. Operationally, this is accomplished by changing the radius of curvature of some reference point in the axisymmetric model. The radius change gives rise to hoop strains, which are used in an ‘initial strain’ method to actually load the model. The resulting pure axisymmetric moment is computed by integrating the hoop stresses thus generated over a cross-sectional cut through the axisymmetric model. For non-linear problems, the procedure just described can be performed incrementally. Several numerical examples are presented herein to illustrate the method, such as bending of a curved bar, sharp folding of a thin sheet and bending of a toroidal tube until the cross-section is flattened.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2771-2782 
    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: The exotherm for the polymerization of methyl methacrylate was monitored by a simple thermal technique to gain useful information about the effect of several factors on the polymerization rate and the degree of completion. All reactions were begun at room temperature (24°C) and no external heating was provided. Initiation was by decomposition of benzoyl peroxide (and mixtures with lauroyl peroxide) catalyzed by the accelerator N,N-dimethyl-p-toluidine. Specific factors examined were peroxide and accelerator levels, sample size, peroxide combinations, and crosslinking agents. The results are discussed in terms of the stoichiometry of the initiator system; the balance of heat generation, heat capacity, and heat loss; and the autoacceleration effect.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 359-375 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New methods of crosslinking enzyme molecules inside a matrix with or without an inactive protein are described. Enzyme activity yields range between 30 and 80% of the activity of the untreated preparations. Even fragile enzyme systems, for instance those using mobile cofactors, can be efficiently immobilized. Increased resistance towards heat denaturation and proteolysis results.
    Additional Material: 7 Ill.
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