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  • Chemistry  (11)
  • Conducting polymers
  • 1980-1984  (8)
  • 1850-1859  (3)
  • 1
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Cold Compaction Molding and Sintering of Ultra High Molecular Weight Polyethylene (UHMWPE) has been examined as a function of particle size, sintering time and temperature, and cooling rate. Properties nearly equivalent to those obtained by compression molding can be obtained from samples with a fibrous particle morphology, sintered just above the melting point, with further improvement possible by control of particle size and addition of fine particles of normal molecular weight linear polyethylene. UHMWPE with a nodular particle morphology sintered poorly.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 74 (1850), S. 262-277 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0275-3723
    Keywords: cell growth ; nutrients ; growth factors ; transformation ; cloning ; kinetic analysis ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The principles of enzyme kinetic analysis were applied to quantitate the relationships among serum-derived growth factors, nutrients, and the rate of survival and multiplication of human fibroblasts in culture. The survival or multiplication rate of a population of cells plotted against an increasing concentration of a growth factor or nutrient in the medium exhibited a hyperbolic pattern that is characteristic of a dissociable, saturable interaction between cells and the ligands. Parameters equivalent to the Km and Vmax of enzyme kinetics were assigned to nutrients and growth factors. When all nutrient concentrations were optimized and in steady state, serum factors accelerated the rate of multiplication of a normal cell population. The same set of nutrients that supported a maximal rate of multiplication in the presence of serum factors supported the maintenance of non-proliferating cells in the absence of serum factors. Therefore, under this condition, serum factors are required for cell division and play a purely regulatory iole in multiplication of the cell population. The quantitative requirement for 18 nutrients of 29 that were examined was significantly higher (P 〈 0.001) for cell multiplication in the presence of serum factors than for cell maintenance in the absence of serum factors. This indicated specific nutrients that may be quantitatively important in cell division processes as well as in cell maintenance. The quantitative requirement for Ca2+, Mg2+, K+, Pi, and 2-oxocarboxylic acid for cell multiplication was modified by serum factors and other purified growth factors. The requirement for over 30 other nutrients could not clearly be related to the level of serum factors in the medium. Serum factors also determined the Ca2+, K+, and 2-oxocarboxylic acid requirement for maintenance of non-proliferating cells. Therefore, when either Ca2+, K+, or 2-oxocarboxylic acid concentration was limiting, factors in serum played a role as cell “survival or maintenance” factors in addition to their role in cell division as “growth regulatory” factors. However, with equivalent levels of serum factors in the medium, the requirement for Ca2+, K+, and 2-oxocarboxylic acids was still much higher for multiplication than for maintenance. Kinetic analysis revealed that the concentrations of individual nutrients modify the quantitative requirement for others for cell multiplication in a specific pattern. Thus, specific quantitative relationships among different nutrients in the medium are important in the control of the multiplication rate of the cell population. When all nutrient concentrations were optimal for multiplication of normal cells, the multiplication response of SV40-virus-transformed cells to serum factors was similar to that of normal cells. When serum factors were held constant, transformed cells required significantly less (P 〈 0.001) of 12 of the 26 nutrients examined. Therefore, the transformed cells only have a growth advantage when the external concentration of specific nutrients limits the multiplication rate of normal cells. Taken together, the results suggest that the control of cell multiplication is intimately related to external concentrations of nutrients. Specific growth regulatory factors may stimulate cell proliferation by modification of the response of normal cells to nutrients. Transforming agents may confer a selective growth advantage on cells by a constitutive alteration of their response to extracellular nutrients.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0275-3723
    Keywords: spectrin ; erythrocyte ; cytoskeleton ; oligomers ; tetramer ; associations ; Chemistry ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Spectrin reversibly self-associates to high molecular weight oligomers through a concentration-driven process characterized by association constants of about 105 mol-1. This association is prominent under physiological conditions of pH, ionic strength, and temperature. It is disrupted by urea, but not Triton X-100. The process of spectrin association appears mathematically to resemble that for tropomyosin, although the mechanism is probably different. Spectrin association is weak compared to other prominent protein-protein associations in the red cell membrane skeleton. The linkage of these weak and strong associations suggests a process whereby the membrane skelton spontaneously assembles. Such affinity-modulated assembly involving weak associations is likely to be the focus of numerous membrane control mechanisms.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural abundance proton-coupled 15N NMR spectra have been observed for pyridine and a series of mono- and disubstituted pyridines using polarization transfer achieved by the selective population transfer method. The magnitudes and signs of the 15N—1H spin-spin coupling constants between the ring-nitrogen and ring-protons are determined from complete iterative spectral analysis and/or selective population transfer experiments. Substituent effects on the 15N—1H coupling constants are discussed and compared with those for 13C—1H couplings in substituted benzenes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 19 (1982), S. 31-34 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of the antileukemic ansa macrolide maytansine and eight naturally occurring homologues were recorded. Signals were assigned to specific carbon atoms of the ansa macrolide ring and C-3 ester side chain using data from off-resonance decoupling, single frequency decoupling, and 180°-τ-907° double pulse experiments. The assignment of each carbon is discussed for maytansine and tabulated for the other eight maytansinoids.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 397-402 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gramicidin A exists in distinctly different conformations in phospholipid vesicles and in organic solvents. These different folding motifs are also reflected in crystals of gramicidin formed in the presence and absence of lipid molecules.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1793-1811 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A well-known nucleation-growth model, used extensively to describe the crystallization of synthetic polymers, has been applied to collagen. The model gives (1) a general representation of the effect of temperature on the rate of collagen fibril formation, (2) a semi-quantitative description of the effect of collagen concentration on growth rate, and (3) an estimate of fibril diameter that is in agreement with observations made by electron microscopy. The mechanism described is apparently that of the early stages of fibril growth, in which microfibrils are formed. An important parameter required in this approach is the free energy of fibril formation. The free energy was approximated by use of an expression derived by Flory for rodlike polymers. Flory's equation plus experimental data on collagen solubility permitted calculation of the free energy over a range of temperature. The resultant expression was of the same form as one commonly used in describing crystallization of synthetic polymers.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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