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  • American Association for the Advancement of Science  (301)
  • Wiley-Blackwell  (299)
  • Institute of Physics  (244)
  • 2020-2022
  • 1965-1969  (844)
  • 1955-1959
  • 1965  (844)
  • 1
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The alternating copolymerization of bicyclo[2.2.1]hept-2-ene and sulfur dioxide has been found to be quite unusual for a free-radical polymerization: (1) the initiation of copolymerization is spontaneous, even at -40°C.; (2) solution copolymerization is extremely fast, yielding very high molecular weight polymer within a few seconds; (3) conversions are high (up to 93% within a minute); (4) molecular weight during copolymerization increases at essentially constant conversion; (5) the reaction is incapable of being chemically inhibited indefinitely, short of exhausting one of the constituent monomers; (6) at elevated temperatures, the monomers and copolymer appear to be in equilibrium; (7) large concentrations of free radicals have been detected by electron paramagnetic resonance to be associated with the bulk copolymerization; and (8) the copolymerization appears to result in “living” free-radical polymers. A copolymerization mechanism is proposed to explain these observations. Bicycloheptene and sulfur dioxide initially form a 1 : 1 molecular charge transfer complex which rearranges to a biradical; subsequent coupling of biradicals with each other (and possibly also with the molecular complexes themselves) leads to rapid propagation to high molecular weight, alternating copolymer. Speculations that similar mechanisms may be important in other copolymerization reactions are also made.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 1965-09-10
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 1965-03-26
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 3 (1965), S. 609-616 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The melting characteristics of unfractionated yeast s-RNA in neutral aqueous solution have been examined by high-resolution proton magnetic resonance spectroscopy. These studies indicate that the bases of s-RNA become rotationally activated at lower temperatures than their associated ribose units. These observations, as well as the recently determined base sequence of an alanine-specific s-RNA, suggest that base complementarity may not be the primary determinant in the stabilization of the secondary structure of s-RNA. In addition, evidence for exchange of C8-protons of purine bases of s-RNA with D2O was obtained at temperatures above 70°C.
    Additional Material: 4 Ill.
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  • 5
    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: Three methods of measuring thermal oxidative stability of polypropylene have been compared. The oxygen absorption and the sealed tube tests give comparable results. The polymer lifetimes in circulating oven-aging tests differ significantly from those obtained by the first two methods. The oven-aging lifetime is aparently influenced to a large extent by the volatilization of the added stabilizer and of the oxidation products, the former decreases whereas the latter increases the polymer lifetime. The optimum composition of a synergistic stabilizer system was found to vary with the test method.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 1051-1057 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional data generation and analysis procedures used to select a descriptive Hougen-Watson reaction rate model have been reviewed and some statistical objections to these conventional procedures have been presented. In an attempt to assess the practical importance of these objections, a recently published example was analyzed with both conventional techniques and nonlinear least squares procedures, which more closely conform to theoretical weighting requirements. Comparisons were made between the results of the conventional linear least squares analysis of isothermal data and those of nonlinear least squares analyses of both isothermal and nonisothermal data. It was found that the nonlinear least squares procedures were useful for a rational selection of an acceptable model and estimation of its parameters.General observations were made concerning good regions for further experimentation if a discrimination among rival models is desired. Additional well-designed experiments were found to be necessary to allow a reduction of the confidence region of the parameters of the Hougen-Watson models to an acceptable size.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 1026-1032 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Birefringent studies have been carried out on a viscoelastic fluid (polystyrene in Aroclor) flowing in straight, converging, and diverging channels, for the purpose of obtaining point-by-point stress data (the shear stress and the difference in normal stresses). A preliminary analysis in terms of the Coleman-Noll second order theory for viscoelastic fluids shows good agreement.
    Additional Material: 12 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 112-120 
    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 θ method of convergence has been applied to conventional and complex columns at unsteady state operation. A different holdup for each stage may be specified in terms of molal, mass, or volumetric units. Plate efficiencies were used, and the K values and enthalpies were taken to be polynomials in temperature.
    Additional Material: 2 Ill.
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  • 9
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Peak nucleate boiling fluxes for liquid oxygen near 1 atm, have been measured on a 0.75-in.-diameter flat polished horizontal platinum surface located in a known, variable magnetic-field gradient that produced steady acceleration (which could be maintained indefinitely) on the oxygen acting in opposition to the earth's gravitation, gE. Measurements were made under condition ranging from net negative (directed away from the heated surface) accelerations of -0.03gE acting on the bulk liquid to the normal accelerations, 1.0gE. The results indicate that at zero g conditions for the bulk liquid, the peak nucleate boiling flux is ∼0.55 of the value at 1.0gE. For bulk-liquid accelerations ranging from ∼0.25 to 1gE, the experimental results confirm the ¼ power dependence of peak flux on acceleration as predicted by various correlations. However, below 0.25gE the peak flux becomes insensitive to the acceleration, varying approximately in proportion to the 1/14 power of the net acceleration. At bulk-liquid conditions of zero g (±0.005gE) the peak plux breaks sharply and falls by a factor of 10 between zero g and -0.03gE (for this apparatus).
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 866-873 
    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 absorption of ammonia and oxygen in horizontal cocurrent gas-liquid froth flow in a 1-in. I.D. pipe has been investigated. At superficial liquid rates between 2 × 106 and 3.2 × 106 lb./(hr.)(sq.ft.) and superficial gas rates between 5 × 103 and 18 × 103 lb./(hr.)(sq.ft.), the length of a transfer unit in both systems was between 0.5 and 4.0 ft. The effects of distance and temperature were also investigated.With the use of James and Silberman's data on bubble size and distribution in froth flow to estimate average bubble sizes, the gas-phase-controlled ammonia absorption data could be explained by the model of unsteady state transfer from a stagnant sphere. With the use of an interfacial-area estimate from the ammonia results, the liquid-phase-controlled oxygen absorption data were correlated by a Sherwood number characterizing the transfer from the bubbles, a Reynolds number characterizing the turbulence within the system, and the void fraction.
    Additional Material: 7 Ill.
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