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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 697-704 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Depolarization currents were used to study the persistent polarization induced in polystyrene and poly(methyl methacrylate) by cooling with flow under pressure. These studies showed that the charge on electrets made by flow under pressure consists in part of a surface charge which leaks off rapidly in moist air and in part of a charge due to volume polarization which decays more slowly. The volume polymerization produced in poly(methyl methacrylate) by flow under pressure is of the same order as that produced by cooling under a voltage drop, but flow under pressure produces a larger surface charge.
    Additional Material: 3 Ill.
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  • 2
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ability of various polymers to acquire persistent polarization (i.e., to become electrets) was investigated. Polarization was induced in the polymers by two methods: (a) by cooling under a voltage drop and (b) by cooling with flow under pressure. There was found to be an optimum temperature for electret formation by either method. This optimum temperature was roughly 37°C. above Tg when polarization was produced by application of a voltage drop and roughly 57°C. when polarization was produced by flow under pressure. Crystallinity and the nonhomogeneities present in blended polymers were harmful to electret formation, but a small critical amount of ionic impurity was helpful.
    Additional Material: 3 Ill.
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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: Polytetrafluoroethylene surfaces have been treated to reduce thrombogenicity in order to make them suitable for use in prosthetic devices that come in contact with blood. This was done by first etching the surface with potassium in liquid ammonia to produce double bonds and then using these double bonds as sites for grafting on polyacids or as sites for chemical reactions. Tubes so treated were tested for thrombo-genetic activity by implantation in the thoracic aorta or inferior vena cava of dogs. These tests showed that the thrombogenicity of a polytetrafluoroethylene surface can be reduced by attaching negatively charged groups provided the surface concentration of these groups is not too high (order of 1-2 × 10-6 equivalent per cm2 geometric area) and provided the distribution of these groups is uniform. Sulfonic acid groups obtained by chlorosulfonation and carboxyl groups attached by grafting tert-butyl crotonate and hydrolyzing to crotonic acid were effective. Long chains of poly(acrylic acid), poly-(ethylenesulfonic acid), and poly(vinyl alcohol) sulfate were less effective.
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 5 (1961), S. 627-634 
    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: The coagulating and regenerating conditions that are necessary for the formation of a highly durable cellulosic film are described. It is shown that low orientation, low lateral order, low gel swelling, and cellulose with a high DP are primary requisites for best film properties. Experiments demonstrated that the application of a unidirectional stress produced an unbalance of physical properties in the film, and this, in general, had an adverse effect on the durability level of a packaging film. Studies of the rates of loss of water and sodium hydroxide from the viscose during coagulation revealed that thermal and osmotic effects were not as important in determining the rate of coagulation as was the buffering and neutralizing capacity of the bath. A bath with high acid content caused the cellulose to be regenerated prior to collapse of the sheet.
    Additional Material: 13 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 4 (1970), S. 259-268 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The adsorption of radiotagged fibrinogen on modified polytetrafluoroethylene surfaces was measured to shed light on the reason of reduced thrombogenicity. These measurements show that when fibrinogen is adsorbed from a solution in which the molecules are in a coiled, undenatured state, adsorption is greater on sulfonated, etched Teflon - a reduced thrombogenic surface, than on unsulfonated, etched Teflon - a thrombogenic surface. On the other hand, when fibrinogen is picked up from a water-air interface in the form of a monolayer consisting of denatured molecules, the pick-up is independent of the thrombogenicity of the surface.
    Additional Material: 2 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 43 (1998), S. 422-427 
    ISSN: 0021-9304
    Keywords: poly(propylene fumarate) ; poly(lactic-co-glycolic acid) ; injectable polymers ; polymer-cell constructs ; bone flaps ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Traumatic injuries, cancer treatment, and congenital abnormalities are often associated with abnormal bone shape or segmental bone loss. Restoration of normal structure and function in these cases requires replacement of the missing bone that may be accomplished by surgical transfer of natural tissue from an uninjured location elsewhere in the body. However, this procedure is limited by availability, adequate blood supply, and secondary deformities at the donor site. One strategy to overcome these problems is to develop living tissue substitutes based on synthetic biodegradable polymers. Three methods of bone regeneration using biodegradable polymers are being studied in our laboratory: tissue induction, cell transplantation, and fabrication of vascularized bone flaps. Injectable polymers are used for filling skeletal defects and guiding bone tissue growth. Their main advantage is minimizing the surgical intervention or the severity of the surgery. Polymer-cell constructs also hold great promise in the field of tissue engineering. They provide a scaffold on which cells grow and organize themselves. As the cells begin to secrete their own extracellular matrix, the polymer degrades and is eventually eliminated from the body, resulting in completely natural tissue replacement. Bone flaps can be fabricated ectopically into precise shapes and sizes. With an attached vascular supply, these flaps can be transferred into areas deficient in vascularity. This article discusses polymer concepts regarding bone tissue engineering and reviews recent advances of our laboratory on guided bone regeneration using biodegradable polymer scaffolds. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 43: 422-427, 1998
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 56 (1962), S. 203-212 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of acrylonitrile with n-butyllithium in toluene at -78°C. was studied at three monomer concentrations, 5.7, 13, and 27%, and at butyllithium concentrations from 0.5 to 1.5 × 10-2 m./1. With high concentrations of monomer the conversion was reduced by a gel effect. At low monomer concentrations the dependence of polymerization rate on monomer and catalyst concentration was similar to the dependence observed by other workers in the polymerization of styrene with butyllithium at 20-30°C. At -78°C. in toluene there was no evidence for termination of polyacrylonitrile chains by monomer. Cyanoethylation and reactions which produce yellowing at higher temperatures were absent. The initial polymerization was rapid and the initial catalyst efficiency low. Molecular weights were from 250,000 to 1,300,000.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 38 (1959), S. 63-72 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystalline poly(tert-butyl acrylate) was prepared with lithium dispersions, n-butyllithium, and lithium plus n-butyllithium as catalysts. Methyl acrylate, n-, see-, and iso-butyl acrylate gave only amorphous polymer under the conditions that produced crystalline poly(iert-butyl acrylate). Very pure monomer was necessary for the preparation of crystalline poly(tert-butyl acrylate) with lithium dispersions. That the poly(tert-butyl acrylate) was crystalline was shown by x-ray diffraction, observation with the polarizing microscope (preparation of birefringent spherulites) and the electron microscope, study of infrared absorption, softening point, and density, and finally by preparation of crystalline polymethyl acrylate from crystalline poly(tert-butyl acrylate) by ester interchange. The nuclear magnetic resonance spectrum of the crystalline poly(tert-butyl acrylate) showed no evidence of band splitting and the viscosity-slope constant, k′, was the same for crystallizable and noncrystallizable polymer.
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Radiotagged acrylamide was polymerized in a solution containing untagged polyacrylamide in order to study branch formation. Polymerizations were carried out at 50°C. and at 78°C. with a persulfate-bisulfite catalyst. At 78°C., polymer with from one to seven branches was formed, while at 50°C. even with larger amounts of catalyst, the polymer was almost exclusively linear. The intrinsic viscosity of branched polyacrylamide, in water at 30°C., was compared with the predictions of the Zimm and Stockmayer equation for the intrinsic viscosity of trifunctionally branched molecules. This equation gave values which agreed well with measured values of the number of branches.
    Additional Material: 3 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 7 (1969), S. 871-876 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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