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  • 1
    ISSN: 1040-0397
    Keywords: XPS analysis ; Fluoride ; Ion selective electrode ; Surface analysis ; Hydroxide interference ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lanthanum fluoride and cerium fluoride single crystals, used as the sensing membranes of the fluoride ion-selective electrode (F-ISE), were investigated for their hydroxide interference and surface reactions with OH- in high pH conditions. While these membranes show fast response and excellent Nernstian behavior over a wide concertration range in buffered F- solutions, they deviate from the theoretical slope at high pH. CeF3, in particular, exhibits a much larger deviation from the Nernstian slope and a substantially slower response to a F- activity change compared to LaF3. This larger deviation is due to more extensive and faster formation of hydroxo-complexes, with the release of a greater amount of the fluoride ion into the hydrated gel layer. The slower response of the CeF3 membrane after contact with OH- is due to the formation of CeIV oxide on the surface, which acts as a blocking layer to the exchange of F-.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 36 (1997), S. 516-521 
    ISSN: 0021-9304
    Keywords: porous-coated ; titanium ; PLA-PGA ; protein release ; degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue ingrowth into porous-coated orthopedic and dental implants is commonly used as a means to achieve long-term fixation of these prostheses. However, the degree of tissue ingrowth is often inadequate and inconsistent. If the pores of these implants are impregnated with a controlled drug release system delivering relevant growth factors, then it might be possible to stimulate more tissue ingrowth. The present study introduces such a system based on biodegradable polymers and investigates its protein release profile and polymer degradation characteristics. Porous coated titanium implants were impregnated with a mixture of a 50%-50% polylactic acid-polyglycolic acid copolymer and a model protein, soybean trypsin inhibitor. Control implants contained only the polymer and no protein. The implants were subjected to hydrolytic degradation in phosphate buffered saline at 37°C for periods of 3, 6, and 11 weeks. The protein release and the mass and molecular weight of the polymer were monitored. The results indicate that the protein is released in three distinct phases and the polymer loses almost all its mass and molecular weight by 11 weeks. There was a significant difference in the polymer degradation characteristics between the control and test implants, which might be the result of some complex polymer-protein interactions. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 36, 516-521, 1997.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 2179-2188 
    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 kinetics of methyl methacrylate (MMA) polymerization, and of its copolymerization with various acrylates, at high conversions in the presence of a chain transfer agent, are investigated with a dilatometer over the entire course of reaction. The displacement to higher conversions of the onset of the gel effect in the MMA homopolymerization, in the presence of a chain transfer agent, was determined. Similar information is also provided for the MMA-acrylate copolymerization systems. An increase in polymerization temperature slightly delays the onset of the gel effect in the MMA-acrylate copolymerization, but considerably increases the final conversion. The final conversion in copolymerization for a constant concentration of the chain transfer agent is independent of the initiator concentration, but is a function of the polymerization temperature. The reaction time for reaching the limiting conversion in copolymerization is increased with an increasing amount of the second monomer, as well as with an increasing number of carbon atoms in the acrylate used as the second monomer. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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