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  • Polymer and Materials Science  (5)
  • Cell & Developmental Biology  (2)
  • Wiley-Blackwell  (7)
  • 1990-1994  (7)
Collection
Publisher
  • Wiley-Blackwell  (7)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 353-365 
    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: Chitosan was chemically modified by alkylation with N-(2-bromoethyl) phthalimide, N-(3-bromopropyl) phthalimide, and N-(4-bromobutyl) phthalimide. The resulting N-(phthalidimidoalkyl) chitosans were treated with hydrazine to remove the phthalidimido group resulting in the final N-(aminoalkyl) chitosan products. For comparison purposes, poly(vinyl alcohol) (PVA) was alkylated with N-(3-bromopropyl) phthalimide, then treated with hydrazine to give the N-(3-aminopropyl) PVA product. All alkylation products were characterized by solution 1H- and 13C-NMR and by solid-state CP-MAS 13C-NMR. The above synthetic polymer derivatives, as well as chitosan, polyallyl amine, and polyethylen-imine, were used to form membrane coatings around calcium alginate beads in which blue dextran of molecular weight 7.08×104 or 26.6×104 was entrapped. These microcapsules were prepared by extrusion of a solution of blue dextran in sodium alginate into a solution containing calcium chloride and the membrane polymer. Membrane integrity and permeability were assessed by measuring the elution of the blue dextran from the capsules, spectrophotometrically. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In order to obtain quantitative surface compositional information, an earlier crystallographic electron attenuation model has been extended to treat polycrystalline alloys. Simple correction factors are obtained that yield large corrections to elemental Auger intensity ratios. The model has been applied to a binary surface alloy formed by heating cerium overlayers on a polycrystalline rhodium substrate. It is shown that an alloy film is formed whose thickness is proportional to the number of Ce layers initially deposited. The surface alloy is identified as Ce3Rh2, which corresponds to a known bulk phase.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: polymer solution ; light scattering ; poly(isobornyl methacrylate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermodynamic and hydrodynamic properties of dilute solutions of poly (isobornyl methacrylate) (PIMA) in tetrahydrofuran (THF) were characterized by using viscosity, static, and dynamic light scattering measurements. PIMA samples with different molecular weight were obtained by fractional precipitation of PIMA solution. Chain dimension parameters (Rg and RH), together with second virial coefficient A2 and intrinsic viscosity [η], were used to calculate various solution parameters characterizing polymer chains in polymer solutions. The experimental results are compared with calculation, indicating that PIMA behaves as a flexible coil in THF. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: physical aging ; tracer diffusion coefficient ; camphorquinone ; polysulfone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of physical aging on the tracer diffusion coefficient D of camphorquinone in polysulfone is investigated. It is shown that if the sample is sufficiently annealed and physical aging is nearly complete, the temperature dependence of D will reflect the primary α-relaxation process of the host polymer. In the temperature range between Tg (=185°C) and 165°C, D is found to be a function of time, and the time dependence of D is given by D = At-μ, with μ approximately equal to unity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1040-452X
    Keywords: tPA ; Cortical granule reaction ; Sperm penetration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The resumption of meiosis results in synthesis of tissue-type plasminogen activator (tPA) in the rat and mouse oocytes (Haurte et al., Cell 43:551-558, 1985). The present study demonstrates that freshly ovulated rat oocytes released their tPA into the surrounding medium upon in vitro activation by sperm penetration or treatment with a calcium ionophore. The presence of a neutralizing monoclonal anti-tPA antibody during in vitro activation by the calcium ionophore inhibited the activation-induced zona hardening and also preserved the ability of the oocyte to be penetrated by sperm subsequent to activation. Rat oocytes undergo zona hardening during in vitro maturation in the absence of serum, presumably as a result of spontaneous cortical granule release, based on findings in mice and hamsters. In the present study, the anti-tPA antibody prevented the zona hardening and enhanced partition by spermatozoa of rat oocytes that were matured in vitro without serum. Collectively, the observations reported here suggest a possible role of tPA released during the cortical granule reaction in the zona reaction, which contributes to the block to polyspermy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1040-452X
    Keywords: Zonae pellucidae ; Trypsin inhibitor ; β-Mercaptoethanol ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The present study confirms that zonae pellucidae of rat oocytes became resistant to chymotrypsin digestion (zona hardening) after undergoing in vitro maturation (IVM) in a serum-free medium. However, zona hardening and did not occur when empty zonae without oocytes were cultured in the same IVM conditions, suggesting that oocyte-derived factor(s) is responsible for zona hardening in oocytes matured in the serum-free medium. Zona hardening occurred primarily after dictyate oocytes were cultured for 6-8 hours in the IVM medium without serum. Zona hardening could be prevented or alleviated if oocytes were cultured in the IVM medium containing bovine foetal calf serum, a soybean trypsin inhibitor, or β-mercaptoethanol, and in vitro fertilization rates for such oocytes were normal. Possible mechanisms of the phenomenon of zona hardening in oocytes matured in serum-free conditions are discussed in relation to its possible relevance to the cortical reaction and the physiological block to polyspermy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1042-7147
    Keywords: Polymer blends ; Crystallization ; Relaxation behavior ; 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
    Notes: In this paper we focus on miscible blends of two engineering polymers: poly(butylene terephthalate) (PBT) and a polyarylate (PAr). The issue of transesterification in these blends will be addressed, followed by a discussion of the crystallization kinetics of PBT, poly(ethylene terephthalate) and several PBT/PAr blends. The ability to estimate polymer-polymer interaction parameters in blends from melting point depression will also be discussed. The amorphous phase behavior of the PBT/PAr blends has been explored primarily using dielectric spectroscopy. For blends in which PBT has crystallized, we observe two relaxations associated with Tg-like motion, and this behavior is interpreted in light of our recent work on order-disorder interphases in crystalline blends.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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