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  • 11
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A series of studies were performed using S35-labeled heparin to determine the amount and the permanancy of heparin grafted onto nonthrombogenic surfaces. The calculated thicknesses of the heparin layers (based on geometrical areas) ranged from 100 to 1500 A. It was shown that the surface having a 100-A layer of attached heparin was nonthrombogenic. The stability of the heparin attached to polypropylene, silicone rubber, hydrin rubber, and graphite-benzalkonium-heparin (GBH) surfaces in distilled water, isotonic saline, and human plasma was measured. The results showed that after exposure to water and saline, the first three surfaces retained most of the attached heparin (〉90%) in contrast to the GBH surface which retained only 31%. After contact with human plasma for 3 hr at 37°C, polypropylene retained 32% and GBH surfaces 19% of the heparin which was initially present. In another series of experiments, the adsorption of P32-labeled proteins onto unheparinized, quaternary ammonium, and heparinized surfaces was measured. The results indicated that the amounts of albumin, Hageman factor, thrombin, and γ-globulin adsorbed onto heparinized surfaces were equal to or greater than the amounts adsorbed onto unheparinized surfaces. The implications of this in terms of the nonthrombogenicity of the heparinized surfaces are discussed.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The biocompatibility of nine different materials, including positive and negative references, 4 polyurethane based and 3 latex based materials was investigated by (1) cytotoxic assay using V79 Chinese hamster cells, (2) the thickness of inflammatory layer at 3 and 7 days after intramuscular implantation test, and (3) the course of the blood flow in tissue reaction around subcutaneously implanted materials using Laser Doppler Flowmetry (LDF) over 14 days following implantation. In addition, for some materials, different modes of sterilization were compared. Although the three methods explore different reactive systems, the material ranking obtained was highly similar for the three methods, suggesting a relative accuracy between them. For one latex however, an absence of cytotoxic effect in culture and a highly intense response by LDF investigation of the same order of magnitude as for the positive reference implant suggest that bioincompatibility may result from the material itself and cannot be exclusively investigated by the leaching of toxic components.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 1383-1389 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The formation of carboxylic acid groups (carboxyl + ester groups) was found in a threephase reaction of crosslinked poly(chloromethylstyrene) beads with an excess amount of sodium nitrite in immiscible solvents of benzene and water with tetrabutylammonium bromide as a phase transfer catalyst (PTC), and the dependence of carboxylic acid yield on the experimental conditions was studied. The product contains hydroxyl groups and ester bonds besides carboxyl groups. It was tentatively considered that the carboxyl groups are produced by direct oxidation of chloromethylstyrene groups by nitrous anions. Nitrous anions do not only act as a nucleophile but also as an oxidative reagent in this case.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 2 (1964), S. 129-131 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 2 (1964), S. 2749-2758 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Styrene, methyl methacrylate, ethyl acrylate, and octyl acrylate were each copolymerized with tetraethylene glycol dimethacrylate (TEGDM) over the complete range of copolymer compositions. Modulus-temperature curves of these polymers were constructed and compared. The equation of state for rubber elasticity was applied to the rubbery plateau regions of these polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 1 (1963), S. 483-489 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rheology of polytetrafluoroethylene above its melting point was studied by the technique of stress relaxation. The temperature shift for the maximum relaxation time at various temperatures fits the WLF equation, if the value of Tg is taken to be 110°C. Degradation of the polymer becomes appreciable above 380°C. Master stress relaxation curves were constructed from the data between 336 and 380°C. The continuous distribution of relaxation times was obtained, and also the discrete distribution of relaxation times by procedure X. The contribution of the maximum relaxation time to the total flow viscosity indicates that the molecular weight distribution of the sample used was narrow.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A: General Papers 1 (1963), S. 1472-1472 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 46 (1995), S. 267-270 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Biaxial extensional flow behavior of monodisperse polystyrene melts has been investigated by using a lubricated squeezing flow method at constant strain rates. Master curves for the biaxial stress growth coefficient ηB+ are obtained by applying the time-temperature superposition principle. The coefficient ηB+ deviates from a linear viscoelastic curve at very small strain such as 0.1, and then approaches a quasi steady state. The quasi-steady-state viscosity ηB,qs decreases with the strain rate ηB. At very small strain rates, the coefficient ηB+ increases again after the quasi steady state and becomes much larger than the linear viscoelastic curve. The strain rate dependence curves of ηB,qs obtained for different molecular weight samples can be superposed to give a super master curve using the weight-average relaxation time η0 as a reducing parameter. It is found that the biaxial viscosity ηB,qs begins to decrease at much smaller reduced strain rate (∊Bτ0=0.01) compared with the shear viscosity, which begins to decrease at reduced strain rate of about 1.0.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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