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  • Wiley-Blackwell  (9)
  • Oxford University Press  (6)
  • Springer Nature  (6)
  • American Chemical Society (ACS)
  • 1990-1994  (21)
  • 1990  (21)
  • 1
    Electronic Resource
    Electronic Resource
    Coextrusion of it-polypropylene film (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 455-465 
    Details
    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: it-Polypropylene films were coextruded by using dies of varying extrusion draw ratio (EDR) from 2-10. Among the resulting films, the film coextruded at EDR 9 possesses the most attractive superstructure and the highest modulus. The dynamic modulus at room temperature was 7 GPa and an αc dispersion peak occurred at 100°C in E″-temperature curves, which is higher by about 20°C than that of the multistep zone-drawn and zone-annealed fibers previously reported. Further, to prepare films with higher draw ratio and higher modulus, repetition of the coextrusion was attempted. Consequently, the draw ratio and the E′ at room temperature reached 12 and 13 GPa, respectively. The present paper discusses changes in molecular orientation, crystallinity, uniformity of the superstructure, and dynamic viscoelasticity, with increasing of the used EDR and repeating the coextrusion with some combinations of EDR.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410302
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  • 2
    Electronic Resource
    Electronic Resource
    Interfacial adsorption and crystallization of polycarbonate in carbon fiber composites (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 1873-1885 
    Details
    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 polycarbonate (PC)/carbon fiber (CF) composite system has been examined with regard to interfacial adsorption and crystallization by altering times and temperatures of annealing. Times up to 180 min and temperatures of 245, 275, and 300°C have been investigated. Tranverse tensile, tranverse toughness, and scanning electron microscopy results on unidirectional, continuous-fiber composites indicate improved fiber/matrix adhesion at longer times and higher temperatures of annealing. Improvements in transverse toughness and transverse tensile strength of a factor of two is achieved. The data indicate that primarily adsorption rather than secondary interfacial crystallization is the likely mechanism for increased adhension. Isothermal transverse toughness values have been found to fit well to a Langmuir-type expression. The temperature dependence of adsorption as measured by transverse toughness is described well by an Arrhenius equation. The dependence of transverse toughness on PC molecular weights from Mw = 26,600 to 39,800 was found to be large, with higher molecular weights adsorbing more effectively.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070390905
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  • 3
    Electronic Resource
    Electronic Resource
    Pressure effects in the capillary flow of amorphous polymers (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1355-1356 
    Details
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410543
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  • 4
    Electronic Resource
    Electronic Resource
    Integral kinetics of α-galactosidase purified from Glycine max for simultaneous hydrolysis of stachyose and raffinose (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 15-22 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: α-Galactosidase from soybean (Glycine max) was purified by a five-step procedure. The enzyme's natural substrates, raffinose and stachyose, have Km's of 3. 0 mM and 4. 79 mM, respectively. The products, galactose and sucrose, were measured after separation by liquid chromatography. Galactose is a competitive product inhibitor of stachyose and raffinose hydrolysis with a Ki of 0. 12 mM. We determined these parameters by an integral kinetic approach. Stachyose hydrolysis gives a nearly constant level of raffinose shortly after hydrolysis begins. Thus, cleavage of the first α-(1,6)-bond in the tetrasaccharide is the rate-limiting step. Since the stachyose hydrolysis yields raffinose, soybean α-galactosidase simultaneously hydrolyzes two substrates. We present a novel approach for analyzing simultaneous substrate hydrolysis with competitive product inhibition by a modified integral rate expression. The experimentally found kinetic parameters are confirmed by solving the simultaneous equations which describe the hydrolysis. This technique may be applicable to other hydrolytic enzymes with multiple substrates.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350104
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  • 5
    Electronic Resource
    Electronic Resource
    Novel monoclonal antibodies identify antigenic determinants unique to cellular senescence (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 425-433 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Normal human diploid fibroblasts exhibit a limited lifespan in vitro and are used as a model to study in vivo aging. Monoclonal antibodies were generated against partially purified surface membranes from human diploid fibroblasts at the end of their lifespan (senescent). Three hybridomas were isolated that secreted antibodies reacting to cellular determinants expressed specifically on senescent human fibroblasts of different origin, including neonatal foreskin, embryonic lung, and adult skin punch biopsy, but not expressed on matched young cells. The antibodies did not bind to immortal human cells and normal young cells made reversibly nondividing, indicating the antigens are not expressed in cells that are not senescent. The antibodies identified senescent cells in a mixed cell population and expression of the senescent cell antigens correlated strongly with the cells inability to synthesize DNA at the onset of senescence. The antigens appeared to be cell surface or extracellular matrix associated, and the epitopes were destroyed by mild trypsin treatment. Western analysis indicated all three antibodies reacted with fibronectin. Though the antigenic determinants on the fibronectir molecule were not accessible in the intact young cell, the epitopes were present in fibronectin extracted from both senescent and young cells, as well as purified human plasma fibronectin. These antibodies and the senescent specific expression of the antigens provide powerful tools to investigate the mechanisms leading to in vitro senescence. This may enable us to investigate directly the relationship between cellular aging and aging of the individual.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041420228
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  • 6
    Electronic Resource
    Electronic Resource
    A new approach for processing ultrahigh-molecular weight polyethylene powder: Solid-state rolling followed by hot stretch (roll-draw) (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 2441-2444 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281220
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  • 7
    Electronic Resource
    Electronic Resource
    An optical study of phase transitions of poly (ethylene terephthalate-co-p-hydroxybenzoic acid) liquid crystal (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1677-1684 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The copolyester containing 40 mol % ethylene terephthalate (PET) and 60 mol % p-hydroxybenzoate (HB) units has been reported by several investigators to be biphasic in the solid and the liquid states. The reported thermal transitions in the two phases, however, are in part contradictory, perhaps partly due to different polymerization conditions. The present work is a study of the transitions in each of the two phases of this copolyester by polarized light microscopy and by light transmission measurements. By light transmission measurements, the two phases were found to have two different glass transition temperatures for the onset of segmental motion, consistent with two assignable temperatures (T.). Cold crystallization and melting in each of the two different phases was also detected. The results help clarify the nature of transitions and agree with the results of dynamic mechanical analysis on the same thermotropic liquid crystalline copolyester.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281003
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  • 8
    Electronic Resource
    Electronic Resource
    On the melting behavior of a thermotropic rigid random copolyester based on terephthalic acid and substituted hydroquinones (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1891-1902 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermotropic liquid crystalline random copolyesters, based on terephthalic acid and substituted hydroquinones, display an unusually large heat for the crystal-nematic transition; this phenomenon is related to their highly ordered structures. To modify the structures, annealing was carried out in the solid state at different temperatures over different times. As the annealing time or temperature is increased, the melting peaks shift to higher temperatures, whereas the heat of fusion shows no significant change or is lowered, respectively. An explanation is offered in terms of crystal perfection and a molecular weight increase. No evidence for a random-to-block conversion on annealing is found.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281102
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  • 9
    Electronic Resource
    Electronic Resource
    Anisotropy of the fluorescence from the monomer, five oligomers, and a polymer of epicatechin (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 57-60 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The steady-state fluorescence anisotropy r has been measured at 25°C for dilute solutions of epicatechin units connected by interflavan bonds with 4β → 8 stereochemistry. The molecules studied are monodisperse oligomers from the monomer through the hexamer, and a polydisperse sample with a number-average degree of polymerization xn of 10. The hexamer and smaller oligomers have been removed from the polydisperse sample. All samples have a very small value of r in 1,4-dioxane and in methanol. Higher values of r are seen in ethylene glycol and in glycerol. In the latter two solvents, the monomer has significantly higher r than any species with xn 〉 1. This observation is interpreted as evidence for the presence of excitation migration from one monomer to another in the dimer and species of higher xn.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290109
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  • 10
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    Use of the Escherichia coli ssb Gene to Prevent Bioreactor Takeover by Plasmidless Cells (1990)
    Springer Nature
    Details
    Publication Date: 1990-01-01
    Print ISSN: 0733-222X
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer Nature
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