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  • Articles: DFG German National Licenses  (32)
  • Physics  (24)
  • Biochemistry and Biotechnology  (6)
  • 08B25  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Algebra universalis 24 (1987), S. 169-185 
    ISSN: 1420-8911
    Keywords: Contravariant left adjunction ; variety of algebras ; epimorphs and dominions of initial objects ; reduced product of a family of algebras with respect to a filter ; Primary: 18A40 ; 18C05 ; Secondary: 06E15 ; 08A65 ; 08B25 ; 18A20 ; 18A32 ; 18A35 ; 18B35 ; 18G15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is shown that any pair of contravariant mutually left adjoint functors between varieties of algebrasC andD factors through the retractions of these categories onto the complete lattices of epimorphs of their respective initial objects, and is thus fairly degenerate. However, some interesting contravariant left adjoint functors do exist between categories of finitely generated (or otherwise restricted) algebras.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Algebra universalis 28 (1991), S. 153-187 
    ISSN: 1420-8911
    Keywords: action of a Boolean ring on a set, sheaf of sets on the spectrum of a Boolean ring, commuting rectangular band operations ; bounded Boolean power of a set or algebra ; least nontrivial hypervariety of algebras ; Primary: 06E15 ; 06E20 ; 18F20 ; secondary: 08A05 ; 08B25 ; 18C10 ; 20M50 ; 54H10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract LetB be a Boolean ring (with 1),S a sheaf of sets on the Stone space Spec(B), andS the set of global sections of S. For everya εB ands, t εS, leta(s, t) denote the element ofS which agrees withs on the support ofa, and witht elsewhere. We set down identities satisfied by this ternary operationB×S×S→S (involving also the Boolean operations ofB). For a fixed Boolean ringB, we call a setS given with a ternary operation satisfying these identities aBset. The above construction is shown to give a functorial equivalence between sheaves of setsS on Spec(B) with nonempty sets of global sections, and nonemptyB-setsS. For any setA, the bounded Boolean powerA[B]* is the freeB-set onA. The varieties ofB-sets, asB ranges over all Boolean rings, constitute (together with one trivial variety) the least nontrivial hypervariety of algebras, in the sense of W. Taylor.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 11 (1973), S. 2909-2926 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A free radical initiator, poly(bisphenol A 4,4′-azobis-4-cyanopentanoate) (BPA), containing more than one azo group per molecule, was used to polymerize styrene in N,N-dimethylformamide (DMF) at 60°C. Polymerization rates were measured gravimetrically or dilatometrically, and the molecular weights of the isolated polystyrenes were determined viscometrically, both before and after hydrolysis. BPA has a relatively low initiator efficiency of 0.28. The activation energy and velocity constant at 60°C for decomposition of BPA per azo group in DMF were found spectroscopically to be 105.9 kJ/mole and 2.08 × 10-5 sec-1, respectively. The molecular weights of unhydrolysed polystyrenes increased with increasing conversion and a theory is developed to explain these results.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 13 (1975), S. 1049-1070 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of vinylferrocene in benzene at 60°C in the presence of 2,2′-azobisisobutyronitrile has been studied. Densities and apparent densities were determined and rates of polymerization measured dilatometrically. The results show that vinylferrocene does not obey normal vinyl polymerization kinetics. Thus the rate of polymerization is proportional to the mean monomer and mean initiator concentrations both raised to a power of 1.1, and the degree of polymerization is independent of the initiator concentration. The polymerization reaction also has a high overall activation energy of 139 kJ/mole. The unusual kinetics are due to a monomolecular termination of the polyvinylferrocene chain radical which is also intermolecular with respect to the chain radical. Termination occurs by an intramolecular electron transfer reaction from a ferrocene nucleus to the growing chain radical which deactivates the chain radical and produces a polymer molecule containing a high spin Fe (III) complex. The presence of this species has been confirmed by Möussbauer and ESR spectroscopy. The rate constant for termination is between 3 and 60 sec-1. Intramolecular electron transfer has not been previously observed in vinyl polymerizations. The term “intralectran” is suggested to describe this new type of termination. Vinylferrocene readily undergoes transfer to monomer (with a transfer constant equal to about 8 × 10-3) and to polymer, but not to benzene.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 533-537 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nylon 66 [poly(hexamethylene adipamide)] and Nomex [poly(m-phenylene isophthalamide)] were metalated by using solutions of sodium in liquid ammonia. Metalation of the Nomex polymer was also carried out by using sodium naphthalene in tetrahydrofuran. The metalated polymers were then reacted with acrylonitrile monomer to yield the corresponding anionic graft copolymers. The heterogeneous nature of these reactions is discussed in relation to the structure of the graft copolymers.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 57-64 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A relatively high-molecular-weight polyurethane based on MDI and ethylene glycol was prepared and characterized. This polymer was metalated with sodium hydride in N,N-dimethylformamide (DMF) at about 0°C. Metalation was confirmed principally by spectroscopic identification of the N-methyl derivative obtained by coupling the metalated polymer with methyl iodide. Under appropriate reaction conditions the metalated polyurethane was used for the anionic graft polymerization of the reactive monomers acrylonitrile and ethylene and propylene sulfides. Attempted anionic graft polymerizations with other monomers, including styrene and ethylene and propylene oxides, were unsuccessful. The polyurethane grafted with acrylonitrile was separated by fractionation from accompanying small amounts of polyacrylonitrile, a low-molecular-weight homopolymer. One sample of polyurethane grafted with acrylonitrile was identified by microanalysis, IR, NMR, and increase in weight and was also characterized by differential thermal analysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 2879-2885 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relatively high-molecular-weight segmented polyurethanes based on methylene bis(4-phenyl-iso-cyanate), poly(propylene glycol), butane-1,4 diol, and cis-2-butene-1,4 diol have been synthesized and characterized. These unsaturated polyurethanes were successfully grafted using N-vinyl pyrrolidone as monomer and 2,2′-azobisisobutyronitrile as free-radical initiator. However, grafting experiments involving benzoyl peroxide as initiator were unsuccessful. The graft copolymers were isolated from the ungrafted polyurethane and poly(N-vinyl pyrrolidone) by selective solvent extraction. Elemental microanalysis, IR, NMR, thermogravimetric analysis, and equilibrium water sorption measurements were used to characterize the graft copolymers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 1141-1151 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fire- and heat-resistant polymer was obtained by the thermal polymerization of bismaleimido-substituted 2,2-bis(anilino)-4,4,6,6-tetrakis-(4-Aminophenoxy)-cyclotriphosphazene. The thermal stabilities of the polymer were evaluated in nitrogen and in air by thermogravimetric analysis. This polymer was stable to 345°C and had char yields of 78% at 800°C in nitrogen and of 71% at 700°C in air. The structures of cyclotriphosphazene precursors and the polymer were characterized using Fourier-transform infrared and proton nuclear magnetic resonance spectroscopy.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 2779-2788 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bulk and suspension polymerizations of vinyl chloride have been carried out in the presence of small known amounts of added oxygen at 54°C in the presence of peroxide initiators. The concentrations of oxygen were in the range 0-1240 ppm for 1-gal bulk polymerization systems and 0-400 ppm for 15-gal suspension polymerization systems. The thermal stabilities of the polymers prepared in the presence of oxygen were lower than those prepared under corresponding oxygen-free conditions. The average molecular weights of bulk polymers isolated at relatively low conversions were reduced in the presence of oxygen, and the infrared spectra of the polymers were altered. The significance of the decreased thermal stabilities of the polymers prepared in the presence of oxygen is discussed briefly in relation to the possible sites of initiation of dehydrochlorination.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 13 (1975), S. 2005-2017 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Styrene has been polymerized thermally at 60.5°C, without added initiator, in the presence of ferrocene. An increase in the rate of polymerization was observed, but the degree of polymerization remained constant. Evidence of ferrocene-styrene interaction is presented, and a kinetic scheme involving propagation with styrene in such an interaction state is proposed to account for these findings. Various kinetic parameters defined by this scheme have been evaluated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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