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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1217-1227 
    ISSN: 0006-3592
    Keywords: acetophenone ; phenethyl alcohol ; Saccharomyces cerevisiae ; diffusion coefficient ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intrabead diffusion coefficients of acetophenone and phenethyl alcohol were measured at 30°C in the triphasic immobilized yeast-water-hexane system. Saccharomyces cerevisiae cells were deactivated with hydrochloric acid and entrapped in calcium-alginate beads. Measurements of dry cell loss during deactivation, shrinkage of the beads during deactivation and the final porosity of the beads were made for various cell loadings. Final concentrations of wet cells in the beads ranged from approximately 0.25 to 0.30 g/mL. Mass transfer in the hexane phase, external to the beads, was eliminated experimentally. The estimated error of 5% to 10% in the diffusion coefficients is within the experimental error associated with the bead method. The effect of significant sampling volumes on the diffusivities was estimated theoretically and accounted for experimentally. The intrabead concentration of acetophenone and phenethyl alcohol was 150 to 800 ppm. The deactivated cells were shown to be impervious to acetophenone so that the measured diffusivities are extracellular parameters. The cell volume fraction in the beads ranged from 0.70 to 0.90, significantly higher than previously reported data. The effective diffusion coefficients conform to the random pore model. No diffusional interaction between acetophenone and phenethyl alcohol was observed. The addition of 2 vol% ethanol or methanol slightly increased the diffusivities. The thermodynamic partition coefficients were measured in the bead-free water-organic system and found to be an order of magnitude lower than the values calculated from the analysis of the diffusion data for the organic-bead system, suggesting that bead-free equilibrium data cannot be used in triphasic systems. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 182-190 
    ISSN: 0006-3592
    Keywords: dechlorination ; bioremediation ; PCBs ; sediments ; anaerobic granules ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A polychlorinated biphenyl (PCB)-dechlorinating anaerobic microbial consortium, developed in a granular form, demonstrated extensive dechlorination of PCBs present in Raisin River sediments at room (20° to 22°C) and at a relatively low (12°C) temperature. Highly chlorinated PCB congeners were dechlorinated and less chlorinated compounds were produced. The homolog comparison showed that tri-, tetra-, penta-, hexa-, and heptachlorobiphenyl compounds decreased significantly, and mono- and dichlorobiphenyl compounds increased. After 32 weeks of incubation at 12°C, the predominant less chlorinated products included 2-, 4-, 2-2/26-, 24-, 2-4-, 24-2-, 26-2-, and 26-4-CB. Among these, 24- and 24-2-CB did not accumulate at room temperature, suggesting a further dechlorination of these congeners. Predominantly meta dechlorination (i.e., pattern M) was catalyzed by the microbial consortium in the granules. Dechlorination in the control studies without granules was not extensive. This study is the first demonstration of enhanced reductive dechlorination of sediment PCBs by an exogenous anaerobic microbial consortium. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 182-190, 1997.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 10 (1972), S. 2397-2407 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyethylene single crystals deformed on copper and NaCl single-crystal substrates by the method of Gleiter and Argon were examined in transmission electron microscopy attached to carbon film carriers constraining them to their deformed state and also after they have been removed from the deformed substrates and were allowed to relax. It was observed that the imposed shear strains can be accommodated by the polyethylene crystals by a combination of debonding from the substrate, elastic flexing, extensive inplane twinning and martensitic shear transformations, buckling, and tearing. No contrast effects suggestive of slip lines could be observed in dark field studies, and the gold droplet decoration technique failed to detect any unambiguous slip lines. From this it is concluded that the critical shear stress for slip is always higher than that for twinning and martensitic shear transformations, and that crystals will deform preferentially by these latter modes.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1993-1996 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1671-1683 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermodynamic treatment of crystallization phenomena in a prestretched rubber was undertaken. Emphasis was put on defining conditions for the thermodynamic stability of the extendedor folded-chain crystal structure. The extended-chain structure is found to be stable thermodynamically at temperatures higher than the isotropic melting point of un-cross-linked polymer Tm0 in the stretched state, while the folded chain one is not. Below Tm0, the stretch ratio of the network structure determines which crystal structure is more stable. The relation among the critical stretch ratio for the extended/folded crystalline structure transition, temperature, and molecular weight is also discussed. The crystallinity predicted by this work becomes zero at a temperature of Tmi, the isotropic melting point of a cross-linked system. The value of Tmi decreases with increasing cross-link density, and this is consistent with the experimental data reported in the literature.
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 19-34 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Experiments were performed to determine the effects of strain rate, temperature, and pressure on the flow stress of polyethylene and Lexan polycarbonate deformed in shear. The results were analyzed to determine the activation enthalpy and the shear and dilatation activation volumes of the rate-limiting mechanism of the deformation process. Results show that the activation event involves a volume containing several monomer units and that this volume must dilate by as much as 7% during the activation event. The activation enthalpy was approximately 2.5 × 10-12 erg for polyethylene and 1.1 × 10-12 erg for polycarbonate. The rate-limiting mechanism for polyethylene seemed to be unchanged by plastic strains of up to 250%.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 155-162 
    ISSN: 0887-6266
    Keywords: polyimides ; reflectivity ; moisture absorption ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Water absorption in thin films (〈1000 Å) of a commercial polyimide was evaluated by monitoring dimensional changes induced by a humid environment. Film thickness was measured using x-ray reflectivity, which is a nondestructive technique offering angstrom resolution in the measurements of thin film or multilayer thickness. The effect of several variables on the absorption of moisture were monitored in polyimide films adhered to polished silicon substrates, including total dry film thickness, exposure time, and the contribution of a coupling agent. The percentage increase in film thickness due to moisture uptake is found to be a weak function of dry film thickness, decreasing as dry film thickness increases, and to be somewhat affected by the use of an interfacial coupling agent. The observed behavior points to the polymer/substrate interface as a strong factor controlling the absorption of moisture in the polyimide/silicon system, and is believed to reflect the presence of a highly moisture-saturated interfacial layer. A bilayer model is proposed, and the feasibility of using this model to describe the observed behavior is considered. Published 1998 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America. J Polym Sci B: Polym Phys 36: 155-162, 1998
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 2199-2208 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Lexan polycarbonate specimens in the form of tubes were deformed in torsion. The deformation occurs by the nucleation and growth of discrete shear bands. Shear bands are initially formed at the upper yield point. Development of the bands is accompanied by a drop in the stress to a lower yield point. At the lower yield point the strain inside the bands is approximately 70% and remains constant thereafter. Further deformation occurs by growth of the bands until they cover the entire sample. When the direction of twisting is reversed after the shear bands are formed, the deformed material untwists uniformly, without deformation in the previously undeformed material, and the stress required for untwisting the deformed material is lower than the stress required to propagate the band into undeformed material.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 751-765 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: High-strength/high-modulus polyethylene (PE) fibers have been obtained from linear polymers by melt-spinning the polyethylene followed by hot-drawing the spun filaments. Fibers with different tensile properties were made by changing the extrusion, solidification, and drawing conditions and by use of different types of polyethylene. Potential correlations of fiber strength with morphological parameters such as crystallite dimensions, and crystalline and amorphous orientation were examined. The integrated meridional small-angle x-ray scattering intensity is the only morphological parameter which was found to correlate well with the strength of fibers prepared under different conditions and from different polymer types. Implications with respect to the molecular mechanism of PE fiber drawing are also discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 1659-1661 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
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