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  • Articles  (2,883)
  • Polymer and Materials Science  (1,840)
  • Chemical Engineering  (505)
  • Life and Medical Sciences  (412)
  • Engineering  (126)
  • 1980-1984  (1,972)
  • 1965-1969  (872)
  • 1940-1944  (39)
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  • Articles  (2,883)
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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependence of photoelastic properties of crosslinked amorphous polyethylenes (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 1183-1202 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crosslinked samples of polyethylene were prepared by electron irradiation of both high- and low-density polymers in the crystalline state. A further crosslinked sample was obtained by curing a high-density polyethylene by reaction with dicumyl peroxide at 180°C. The stress-strain-birefringenece relations were obtained on specimens cut from these samples at temperatures between 130 and 250°C. All samples showed a substantial decrease in stress-optical coefficient with increasing degree of crosslinking and with increasing temperature. The stress-optical properties at each temperature were extrapolated to zero degree of crosslinking to give quantities characteristic of the Gaussian network. Comparison of these properties with the theory of networks of rotational isomeric chains with both independent and interdependent rotation allows estimates to be obtained for (1) the trans-gauche energy differences in rotation around skeletal bonds and (2) the difference in principal optical polarizabilities for the CH2 group in the elastomeric state. This latter quantity is shown to be more nearly given by Denbigh's than by Bunn and Daubeny's bond polarizability values.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1968.160060611
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  • 2
    Electronic Resource
    Electronic Resource
    The numerical solution of boundary-layer problems (1965)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 11 (1965), S. 733-739 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method for numerical solution of boundary-layer problems has greater applicability as well as greater speed and accuracy than the several previously proposed methods. The method uses the Goertler-transformed equations and a nonlinear finite-difference procedure. In most earlier work on difference methods the equations have been linearized at each step parallel to the boundary. The method of treatment of the boundary conditions on the equation of change for energy or mass transfer is shown to have an important influence on accuracy, and a new, more accurate method of treating boundary conditions involving the normal derivative is presented.Typical complete solutions are compared with the several methods. The solutions include both similar and more general flows up to separation, as well as coupling between the momentum and energy-balance equations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690110432
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  • 3
    Electronic Resource
    Electronic Resource
    Deterioration of plastic films under soil burial conditionsIssued as N.R.C.C. # 18807. (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 509-519 
    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: The deterioration of polyolefin, poly(ethylene terephthalate), and polyamide films under soil burial conditions extending up to 32 months has been investigated. Based on changes in their elongation at break, the films can be ranked in order of increasing sensitivity to degradation: Polyester ≃ polypropylene 〈 low-density polyethylene ≃ high-density polyethylene 〈 nylon 6.6. The degraded nylon 6.6 and polyethylene films were characterized by infrared and luminescence spectroscopy and scanning electron microscopy, as well as by wet analysis for hydroperoxides. From a comparison with the well-known oxidative sensitivity of nylon 6.6 in oxygenated water at slightly elevated temperatures, the rapid deterioration of nylon 6.6 film during soil burial was also concluded to be an oxidative process. The somewhat smaller, but significant, embrittlement of the polyethylenes studied could not be simply explained by thermal oxidation (with only trace oxidation products detectable) or microbiological attack (deterioration being unaffected by surface activation to enhance wettability).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260211
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  • 4
    Electronic Resource
    Electronic Resource
    Fracture of porous polyethylene-bone composite (1983)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 17 (1983), S. 59-70 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Porous high-density polyethylene specimens were implanted in the femurs of mongrel canines. At the end of the residency period (3 or 6 months), the animals were sacrificed and the implants were retrieved. The work-of-fracture of the implant specimens was then determined using the technique of Tattersall and Tappin. The work required to fracture a specimen in three-point bending by controlled crack propagation through a triangular cross section was obtained directly from the load-deflection curve. The area of the resulting fracture surface was measured by macro-photographic techniques, and the work-of-fracture was calculated as work per unit area. The implants were subsequently sectioned and examined microradiographically to determine the extent of bone ingrowth. Bone specimens adjacent to the implants and porous high-density polyethylene controls (no ingrowth) were also tested to determine their work-of-fracture. The results showed that bone adjacent to the implant specimens had a higher work-of-fracture than normal medial, canine femoral bone and was not appreciably different from the composite. The work-of-fracture of porous high-density polyethylene was not significantly increased by an increase in bone infiltration, and this anomalous behavior was attributed to a degradation of the polyethylene during implant residence. Control studies supported this hypothesis.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820170106
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  • 5
    Electronic Resource
    Electronic Resource
    Correlations between blood compatibility and heparin adsorptivity for an impermeable isotropic pyrolytic carbon (1969)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 3 (1969), S. 497-528 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The influences of conditioning treatments and surface topography on the heparin adsorptivity and the thromboresistance of a high-strength, impermeable, isotropic, pyrolytic carbon were investigated. The results of the adsorption studies indicate that the adsorption of heparin on such carbon surfaces is near the amount required for monolayer formation. The adsorbed heparin is rapidly elutriated in plasma. The heparin adsorption is not enhanced by a pretreatment with benzalkonium chloride. There was no relationship between the amount of heparin adsorbed on these materials and their compatibility with blood. Polishing, for example, which reduced heparin adsorption, enhanced the tromboresistance of these carbons, and while chemisorption of oxygen markedly reduced their thromboresistance, it did not influence the amount of heparin that could be adsorbed. In vivo tests showed that polished and outgassed, impermeable isotropic carbons deposited at low temperatures were significantly thromboresistant without the exogenous application of heparin. Examples of applications of these new materials in experimental valves are presented.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820030311
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  • 6
    Electronic Resource
    Electronic Resource
    Blood-materials interactions: The minimum interfacial free energy and the optimum polar/apolar ratio hypotheses (1982)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 16 (1982), S. 381-398 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Numerous hypotheses exist to explain observed blood-materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer-coated tubes; centrifugal force platelet adhesion on polymer-coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer-coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood-materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypotheses can explain the apparent conflict between the platelet adhesion data and the coagulation time data.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820160407
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  • 7
    Electronic Resource
    Electronic Resource
    Perturbation of the switch-on of transcriptase activity in intermediate subviral particles from reovirus (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 112 (1982), S. 10-18 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Intermediate subviral particles (ISVP) derived from reovirus represent a simple model system for the switch-on of transcriptase function. In such particles the endogenous transcriptase is present in a switched-off form, one step removed from the switched-on state. Switch-on of transcriptase function is an active process in this system and can be triggered by K+ ions. A variety of agents which affect gene expression in cells were tested for an effect on switch-on in ISVP. Marked effects on switch-on in ISVP were observed with a diverse group of test agents, including DMSO and other solvents, BUdR, TdR, caffeine, theophylline, and temperature. The correlation in response between ISVP and cells suggests that the ISVP system may be useful as a model for studying the biochemical mechanisms underlying the perturbative effects of such agents on gene expression in cells.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041120104
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  • 8
    Electronic Resource
    Electronic Resource
    Mean free path for inelastic scattering of 1.2 kev electrons in thin poly(methylmethacrylate) films (1980)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 2 (1980), S. 5-10 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mean free paths for inelastic scattering (λ) of low energy electrons in poly(methylmethacrylate) (PMMA) have been determined by measuring Al Kα excited C 1s and Si 2s photoelectron signal intensities as a function of ellipsometrically determined thicknesses of PMMA overlayers on silicon substrates. The λ values obtained are 29 ± 4 Å for 1196 eV electrons and 33 ± 5 Å for 1328 eV electrons. These data are necessary for the quantitative analysis of the surface region of PMMA and similar polymers by X-ray photoelectron spectroscopy (XPS). The magnitude of the λ values determined indicates that XPS measurements can provide chemical information about the surface region of polymers, such as PMMA, in the depth range of ∼6 to 100 Å. The results of this study are compared and discussed with respect to λ values determined for other organic compounds.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740020103
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  • 9
    Electronic Resource
    Electronic Resource
    Inhibition of the metabolism of ram spermatozoa by derivatives of α-chlorohydrin (1981)
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 203-217 
    Details
    ISSN: 0148-7280
    Keywords: α-chlorohydrin ; antifertility agent ; ram ; sperm metabolism ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects of the male antifertility agent, α-chlorohydrin, six of its derivatives, and glycidol were studied on the metabolism of washed ram spermatozoa in vitro with fructose as substrate. The α-chlorohydrin derivatives were the amino, the phosphorylated, and four glycol-bridge (ketal) compounds. All compounds except glycidol, in a concentration between 0.1 and 100 mM, reduced the aerobic glycolsis and/or oxidation of fructose. However, there was not a high correlation between the ability of these compounds to inhibit the metabolism of ram spermatozoa in vitro and their antifertility activity when administered to male rats. Other factors are clearly involved in their antifertility activity, eg, the concentration of the compounds in the epididymis and their conversion of either more or less spermicidal compounds in the body.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120040305
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  • 10
    Electronic Resource
    Electronic Resource
    Morphological and ultrastructural characterization of mammalian spermatozoa processed for flow cytometric DNA analyses (1984)
    New York, NY : Wiley-Blackwell
    Gamete Research 10 (1984), S. 339-351 
    Details
    ISSN: 0148-7280
    Keywords: spermatozoa ; flow cytometry ; DNA staining ; nuclear morphology ; ultrastructure ; mammals ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The morphological and ultrastructural changes that occur during preparation of porcine, bovine, and murine spermatozoa for flow cytometric quantification of the relative DNA content of the X- and Y-chromosome-bearing sperm populations were examined. Ejaculated spermatozoa from the boar and bull were washed using a series of dimethyl sulfoxide (DMSO) solutions prior to fixation, whereas the epididymal mouse spermatozoa were washed only in phosphate-buffered saline (PBS). Spermatozoa from all three species were then fixed in ethanol and processed for fluorochrome staining by a treatment regimen consisting of sulfhydryl reduction and proteolysis. The processed sperm nuclei were stained for DNA with the fluorochrome, 4′-6-diamidino-2-phenylindole (DAPI) before quantification by flow cytometry. Scanning and transmission electron micrographs of sperm heads taken at various steps of the preparation and staining procedures show 1) that the rigorous washing procedure disrupted the plasma and outer acrosomal membranes, 2) that ethanol fixation resulted in removal of the outer membranes and disintegration of the nuclear envelope, and 3) that thiol and proteolysis treatment removed the remaining cellular organelles including the tail and rapidly induced partial decondensation of the tightly packed chromatin. Sequential micrographs showed that the nuclear matrix of all three species increased in thickness about twofold during the preparation and staining. Consequently, the harsh procedures currently used for quantitative staining of DNA for high-resolution flow cytometric analyses destroy most cellular organelles and thereby prevent simultaneous characterization of DNA content and other sperm cell constituents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120100402
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