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  • 1
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Proton magnetic resonance data have been obtained for 6-methyl-2′-deoxyuridine (dT*), its 3′- and 5′-monophosphates, and its 3′,5′-diphosphate, as well as for the corresponding thymine derivatives. The synthesis of the dideoxynucleoside monophosphates - d(TpT), d(T*pT), d(TpT*), and d(T*pT*) - was accomplished, and spectral data were obtained for these four dimers. The data show that the 6-methyluracil base prefers the syn conformation about the N-glycosyl bond at the monomer and dimer levels. The presence of the syn base leads to increases in the cis couplings of the sugar ring, J1′2″ and J2′3′, which indicate a trend towards eclipsing of the substituents on the C1′-C2′ and C2′-C3′ fragments. This trend is discussed in terms of changes in the pseudorotational parameters which describe the pucker of the ring. The syn base destabilizes the g+ conformer about the C4′-C5′ bond, leading to a preference for the t conformer in all dT* residues at the monomer and dimer levels. Preliminary work on the formation of cyclobutane-type photodimers in d(T*pT) and d(T*pT*) is discussed and presented as evidence for the capability of the syn 6-methyluracil base to form base-stacked complexes.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 2
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The geminal and vicinal 13C-31P coupling constants have been monitored, as a function of pH, for a series of uracil and cytosine 3′- and 5′-nucleotides with a ribose, arabinose, or 2′-deoxyribose sugar. Data were also obtained for two 3′,5′-diphosphates in the ribose and arabinose series. The geminal J(C5′-P5′) and J(C3′-P3′) couplings show only a small dependence on the ionization state of the phosphate, decreasing by 〈 0.5 Hz in the pH 5-7 range. For the ribose and arabinose 3′-nucleotides, the vicinal J(C4′-P3′) increase (up to 1.5 Hz) on secondary phosphate ionization in the pH 5-7 range, whereas their J(C2′-P3′) couplings decrease (up to 1.5 Hz) over the same pH range. In contrast for the 2′-deoxyribose molecules, both couplings decrease (∼0.5 Hz) on phosphate ionization. The titration curves provide information about the influence of the sugar on the conformation about the C3′—O3′ bond. Some conformational trends could be rationalized by consideration of the sugar-puckerdependent contact interactions between the 3′-phosphate and the substituents on the furanose ring.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 3
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Kinetic data are reported for the fast polymerization of a thermoplastic polyurethane under conditions similar to that of commercial reaction injection molding (RIM). The components were a 2000 molecular weight polyester polyol, butanediol and 4,4′-diphenylmethane diisocyanate. Three catalysts-dibutyltin dilaurate, phenyl mercuric propionate, and triethylenediamine-as well as uncatalyzed formulations were studied. Kinetic parameters were obtained by numerically fitting adiabatic temperature rise data with both second-order and hyperbolic models. The hyperbolic model gave consistently better fits and is supported by mechanistic studies in the literature. Activation energies compare well to literature values. The uncatalyzed rate was found to be significant. The kinetic parameters obtained by this method are useful measures of catalyst performance in the RIM systems. Moreover, the models provide a conveient way to predict the extent of reaction during the production of parts by the RIM process. The shape of the reaction pathway (extent of reaction time) may be important in the development of physical properties of polymers produced by the RIM process. Physical properties for these samples compare favorably to those for a conventionally produced (batch) polyurethane of the same formulation.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 16 (1970), S. 339-344 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The present state of the theory of nonisothermal tube flow is inadequate to predict the behavior of polymer melts. In addition, relatively few experimental measurements on radial temperature profiles of polymer melts in the tube flow have been reported. For non-Newtonian systems, the separation of viscous losses due to frictional heat generation and those due to the effect of shear rate is a formidable problem which has hampered progress. This paper will describe a method of measuring shear induced heating and present experimental data on radial temperature profiles in tube flow. A novel method of estimating the velocity profile is also described.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 5
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The compatibility of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with random copolymers of ortho- and para-fluorostyrene as well as with ortho- and para-chlorostyrene of various copolymer compositions was examined. The compatibility was studied by DSC and visual observation of film clarity. It was found that copolymers of ortho-fluorostyrene with para-chlorostyrene containing 15-74 mol % p-CIS are compatible with PPO in all proportions. Compatibility of the PPO/poly-(ortho-fluorostyrene-co-ortho-chlorostyrene) system was observed for copolymers containing between 15 and 36 mol % ortho-chlorostyrene. Copolymers of para-fluorostyrene with para-chlorostyrene, as well as copolymers of para-fluorostyrene with ortho-chlorostyrene appear to be incompatible with PPO at 210°C.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 505-509 
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Observable coupling over five formal bonds between the methoxy group protons and the ortho ring proton in 2-methoxypyridine, coupliugs between the methoxy group carbon and ring protons, and methoxy carbon spin-lattice relaxation times are all consistent with a preference for the planar cis conformer, in which conjugation is favoured and repulsions between the methyl group and the ortho hydrogen are reduced. Small-amplitude torsioas about the C-2-O bond may carry the methoxy group away from this orientation, but more distant conformations can probably be excluded. Methyl group rotation is less hindered in the cis than in the trans conformer. Molecular orbital calculations at the STO-3G level, with complete geometry optimization, support the conduskus drawn from experimental evidence.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 20 (1982), S. 97-102 
    ISSN: 0360-6384
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Supramolecular Structure and Cellular Biochemistry 17 (1981), S. 147-152 
    ISSN: 0275-3723
    Schlagwort(e): skeletal muscle ; cell surface ; monospecific antibody ; myogenesis ; Chemistry ; Molecular Cell Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: The differentiation of skeletal muscle is characterized by recognition, alignment, and subsequent fusion of myoblast cells at their surfaces to form large, multinucleated myotubes. Monoclonal antibodies were used to investigate anti-genie changes in the cell surface membrane specific for various stages of myogenesis. Chick embryonic skeletal muscle cells were cultured in vitro to the desired stage of differentiation and then injected into BALB/c mice. Spleen cells from the immunized mice were hybridized with NS-1 or P3 8653 mouse myeloma cells. Hybrid cell clones were selected in HAT medium and screened using an indirect radioimmunoassay for the production of monoclonal antibodies specific to myogenic cell surfaces. Target cells for the radioimmunoassay included three stages of myogenesis (myoblasts, midfusion myoblasts, and myotubes) and chick lung cells as a control for polymorphic antigens. Sixty-one clones were obtained which produced antibodies specific for myogenic cells. Thirty-five of these clones were generated from mice immunized with midfusion myoblast stages of myogenesis and 26 were obtained from mice immunized with the later myotube stage of myogenesis. Quantitative measurements by RIA of myogenic determinants per cell surface area on each target cell type revealed that most of the determinants decrease during myogenesis when midfusion myoblasts are used as the immunogen. When myotube stages are used as the immunogen, more determinants increase with cell differentiation. Therefore, the most common pattern of determinant change is for them to be present at all stages of myogenesis but to vary quantitively through development. There are determinants unique to each stage of myogenesis and marked quantitative differences within a cell stage for each determinant.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 2 (1981), S. 473-480 
    ISSN: 0173-2803
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 3 (1982), S. 269-274 
    ISSN: 0173-2803
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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