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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 32 (1975), S. 235-244 
    ISSN: 1432-0533
    Keywords: Glioma ; Autoradiography ; Cell Kinetics ; Tissue Culture ; Labeling Index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The kinetics of monolayer cell cultures, derived from brain tumors which had been labeled with3H-thymidine just prior to surgical removal, have been investigated. Analysis of autoradiographs indicates that: 1. the distribution of cell types in primary cultures is similar to that of the viable areas of the parent tumorin vivo; 2. the first week of culture constitutes a lag phase; and 3. vigorous proliferation commences during the second week of culture. Double labeling of the tritiated cultures with14C-thymidine indicates that the pulse labeling index (PLI)* of primary cultures during the first week is lower than that of the parent tumor and that the PLI of the culture increases during the second week. In contrast, we found that long-term established cultures in our laboratory have a high PLI during the first few days after passage, quickly reach a maximum, and then drop precipitously 1 week after passage. These latter variations in PLI correspond to the following growth pattern: 1. exponential growth; 2. a stationary phase due to medium exhaustion; or 3. a plateau due to overcrowding. There are indications that some cell types, which have the capacity to divide in the parent tumor, lose this ability after transfer to tissue culture.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 6 (1989), S. 193-209 
    ISSN: 0887-3585
    Keywords: protein folding ; simulated annealing ; empirical potentials ; Monte Carlo dynamics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The current work describes a simplified representation of protein structure with uses in the simulation of protein folding. The model assumes that a protein can be represented by a freely rotating rigid chain with a single atom approximately the effect of each side chains. Potentials describing the attraction or repulsion between different types of amino acids are determined directly from the distribution of amino acids in the database of known protein structures. The optimization technique of simulated annealinghas been used to dynamically sample the conformations available to this sample model, allowing the protein to evolve from an extended, random coil into a compact globular structure. Many characteristics expected of true proteins, such as the sequence-dependent formation of secondary structure, the partitioning of hydrophobic residues, and specific disulfide, suggestion the model may accurately simulate the folding process.
    Additional Material: 8 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 11 (1967), S. 1509-1527 
    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: Some of the problems encountered in adhesive bonding of plastic attachments to human tooth surfaces were investigated. Acrylic adhesives based on poly(methyl methacrylate)-methyl methacrylate monomer mixtures with benzoyl peroxide initiation and N,N-dimethylaniline acceleration were utilized. Both homopolymers and copolymers were investigated. Recently extracted upper central incisors were employed in the bonding experiments. Bond strengths were improved by pretreating the tooth surfaces with mineral acids such as H3PO4. Surface wetting by the liquid adhesive was shown to be improved by the acid treatment. The molecular weight of polymer or copolymer employed in the liquid adhesive had an important effect on bond strengths. The optimum molecular weight for obtaining maximum bond strengths was around 20,000 g./mole. Water immersion of the bonded specimens at 37°C. for periods up to 6 weeks had a deleterious effect on bond strengths. Nevertheless, it was shown that some of the adhesives formed reasonably strong bonds for periods exceeding 6 months even with water immersion.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 61 (1962), S. 403-411 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of molecular magnetic anisotropy upon the broadline NMR spectrum of a bulk polymer have been recognized and measured for the first time. The F19 NMR absorption spectra in polytetrafluoroethylen (PTFE) show a line-shape asymmetry over a broad range of temperatures which can be explained by the magnetic anisotropy of C-F bonds. Nuclear magnetic resonance studies of PTFE samples whose crystalline regions are aligned by cold drawing have made possible an estimate of the anisotropy of C-F bonds in this material: Δσ, the magnetic anisotropy of the screening constant, is found to be 171 ± 15 ppm; the screening of each F19 nucleus is paramagnetic, being maximum when the direction of its C-F bond is perpendicular to the large static magnetic field and minimum (probably zero) when parallel. Static magnetic susceptibility measurements of PTFE show the predicted diamagnetism, and only a small (〈5%) static magnetic anisotropy of the molecular crystals is found.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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