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  • Polymer and Materials Science  (9)
  • Cell & Developmental Biology  (3)
  • Life and Medical Sciences  (3)
  • Wiley-Blackwell  (12)
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  • Wiley-Blackwell  (12)
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  • 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: 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: Polypyrrole (PPY) films having high conductivity were synthesized electrochemically in acetonitrile at low temperature and low current density. Pristine, deprotonated, and ozone-pretreated PPY films were subjected to either thermally induced or near-UV-light-induced graft copolymerization with acrylic acid (AAc), or sodium salt of 4-styrenesulfonic acid (NaSS). Surface structures and redox states of the pristine, deprotonated, reprotonated, and surface-modified polypyrrole films were studied by angle-dependent X-ray photoelectron spectroscopy (XPS). The morphology of the PPY surface after modification by graft co-polymerization was revealed by atomic force microscopy (AFM). The results showed that the density of surface grafting decreased with ozone pretreatment. Surface grafting of the two polymeric acids also gave rise to a self-protonated surface structure. A substantial proportion of the grafted protonic acid groups at the surface remained free for further surface functionalization. The surface characteristics, in particular the charge-transfer interactions and the changes in the intrinsic redox states of the substrate films, associated with the external protonation and surface self-protonation processes were also discussed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 3
    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: A series of rosin-based rigid polyurethane foams of different composition were synthesized directly from chemically modified gum rosin. The effect of the composition of these rosin-based rigid polyurethane foams on their thermal stability and compression strength was measured. It was shown that the onset temperature of weight loss and the dimensional stability at high temperature increased with increase of the molar ratio of NCO/OH. The TGA data further confirmed that the second stage weight loss in the two-stage weight loss process of these polyurethane foams was governed by thermal degradation of the isocyanate component. Although density had no significant influence on the TGA curves of the rosin-based rigid polyurethane foams, it had great influence on the dimensional stability at high temperature and compression strength of the foams. It has been shown that the inclusion of rosin in rigid polyurethane foams increases the strength and thermal stability compared with that of polyether-based ones. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Surface modification of polypyrrole (PPY), polyaniline (PAN) and poly(3-alkylthiophene) films by ozone was studied by angle-resolved x-ray photoelectron spectroscopy (XPS). In the case of the N-containing polymers, oxidation occurs readily and mainly at the carbon atoms, resulting in the formation of CνO, CξO, COOH and even OνCOOH (especially for PAN) species. The carbon atoms of doped PPY and PAN films are significantly more resistant to ozone oxidation, but the samples suffer some loss of the dopant in the surface region. Ozone treatment does not involve the direct oxidation of the nitrogen heteroatoms to form theνNOx species, even at high extent of carbon oxidation. In addition, a substantial decrease in the intrinsic oxidation state ([ξNν]/[νNHν] ratio) was observed in the 25% deprotonated PPY (DP-PPY) base, the 50% intrinsically oxidized emeraldine (EM) base and the 75% intrinsically oxidized nigraniline (NA) base after ozone treatment and subsequent atmospheric exposure. In the case of the S-containing polymers, ozone treatment results predominantly in the oxidation of sulphur heteroatoms to give rise to the sulphone and peroxide species. The oxidized sulphur species, however, are readily reduced or consumed in a photochemical reaction.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0148-7280
    Keywords: gonadotropins ; oocytes ; maturation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The present study examined the effects of gonadotropins and ovarian steroids during in vitro meiotic maturation of rat oocytes on their ability to undergo in vitro fertilization. Fully grown oocytes were isolated from antral follicles of immature rats and cultured as oocyte-cumulus cell complexes (OCC) under conditions in which completion of meiotic maturation occurs spontaneously. They were then exposed to spermatozoa under conditions in which oocytes matured in vivo exhibit high fertilization rates. Compared with oocytes from pregnant mare's serum gonadotropin (PMSG) or follicle-stimulating hormone (FSH)-treated rats, a simiiar proportion of the oocytes (〉80%) from untreated rats underwent germinal vesicle breakdown, but such oocytes had a lower rate of fertilization (70% vs. 20%). The presence of FSH during in vitro maturation restored the fertilization rate for oocytes from untreated rats, while a cytochrome P450 inhibitor, aminoglutethimide phosphate abolished this beneficial effect of FSH. The addition of progesterone during the in vitro maturation period duplicated the beneficial effect of FSH on fertilization rate of oocytes from untreated rats; oestradiol-17β was less effective in this regard, and 5α-dihydrotestosterone was ineffective. These findings indicate that FSH and progesterone, although having no apparent effect on nuclear maturation of the oocyte, play an important role during oocyte maturation in enabling normal fertilization to occur.
    Additional Material: 4 Ill.
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  • 6
    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.
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  • 7
    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.
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  • 8
    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.
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  • 9
    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: A series of hydroxyl-terminated maleopimaric acid esters (HTMAEs) and rigid polyurethane (PU) foams based on these HTMAEs were synthesized using chemically modified natural gum rosin and its derivative maleopimaric acid as raw materials. Thermal stability of these polyols and their corresponding rigid PU foams was studied by a thermogravimetric method and a dimensional stability measurement. It was shown that the thermal stability of the final foams was strongly dependent on the structure of their corresponding polyols. The thermogravimetric analysis curves of these rosin-based rigid PU foams displayed two distinct regions of weight loss. It has been shown that at the initial stage of weight loss the process was dominated by polyol component degradation; the second stage was governed by isocyanate component degradation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 10
    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.
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