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  • 1
    Electronic Resource
    Electronic Resource
    The mechanical and magnetic alignment of liquid crystalline epoxy thermosets (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1845-1853 
    Details
    ISSN: 0887-624X
    Keywords: liquid crystalline ; networks ; epoxy ; thermotropic ; thermoset ; smectic ; nematic ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The processing of a new series of liquid crystalline (LC) epoxy networks was evaluated. Above the glass transition temperature, the low crosslink density networks could be mechanically aligned. The mechanically oriented networks readily lost orientation upon heating. Highly anisotropic liquid crystalline (LC) epoxy networks were also prepared by aligning the mesophase of the prepolymer during the curing process under the influence of a magnetic field. Orientation parameters (f) of 0.13 to 0.57 were achieved by these processes as determined by x-ray diffraction analysis. The ability of the magnetically aligned networks to retain their orientation above the glass transition temperature was determined by time-resolved x-ray diffraction. The stability of the alignment of these networks was found to depend on crosslink density. The effect of the anisotropy of these networks was investigated by measuring the coefficient of thermal expansion (CTE). In the aligned networks, there was a substantial reduction in CTE parallel to the direction of the applied field compared to the randomly oriented networks. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300907
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  • 2
    Electronic Resource
    Electronic Resource
    NMR investigations of the possible cross reactions between cyanate and epoxy resins (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2203-2221 
    Details
    ISSN: 0887-624X
    Keywords: cyanate ; epoxy ; mixed resins ; curing ; cross reaction ; 13C-, 15N-, and 1H-NMR ; oxazolidinone ; carbamate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The possible cross reactions indicated by solid-state NMR between cyanate functionalized resin and epoxy functionalized resin have been investigated by using both natural abundance and labeled monofunctional model compounds. These soluble products were isolated and purified by silica gel adsorption chromatography and gel permeation chromatography. They were fully characterized by high resolution 1H-, 13C-, 15N-NMR spectroscopy and by mass spectrometry. The major cross-reaction product is a racemic mixture of enantiomers, which contain an oxazolidinone ring formed by one cyanate molecule and two epoxy molecules. However, epoxy consumption lags cyanate consumption in the overall reaction as triazine formation from the cyanate is much faster than the two competing reactions, the cross reaction between cyanate and epoxy, and the self-polymerization of epoxy, under the conditions investigated. The cross reaction between cyanate and epoxy is limited. Approximately 12% of cross reaction between cyanate and epoxy was found in the overall reaction. In addition to the cross reactions of epoxy and cyanate, the reactions of epoxy and the carbamate, which is the major side product for the curing reaction of cyanate resin in solution, have also been investigated, and the mechanism of these reactions discussed. From the reactions of epoxy and carbamate, several products related to cross reaction between epoxy and cyanate have been isolated and identified. It is suggested that the reaction of epoxy and carbamate is one of the pathways in the overall cross reaction between epoxy and cranate resins. Finally, the mechanism of the overall cross-curing reaction between the diepoxy and dicyanate mixed resins is discussed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321201
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  • 3
    Electronic Resource
    Electronic Resource
    Liquid crystalline epoxy thermosets based on dihydroxymethylstilbene: Synthesis and characterization (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1831-1843 
    Details
    ISSN: 0887-624X
    Keywords: liquid crystalline ; networks ; epoxy ; thermotropic ; thermoset ; smectic ; nematic ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes the synthesis and characterization of a new series of liquid crystalline thermosets. Nematic epoxy-terminated oligoethers based on dihydroxy-α-methylstilbene were synthesized for this study. These prepolymers were crosslinked within the nematic mesophase using methylenedianiline. Depending upon the molecular weight and polydispersity of the oligoether, the crosslinking reaction resulted in networks with either a smectic or nematic molecular organization in contrast to the simple nematic phase of the oligoether. The formation of a smectic-like structure on curing was found to be related to the breadth of the prepolymer molecular weight. In those networks with a low crosslink density a clearing transition could be observed, whereas in the more highly crosslinked networks the molecular organization was frozen in until decomposition. The glass transition temperature of these LC networks rose as the crosslink density was increased, ranging from 35 to 152°C. In agreement with theory, the clearing transition of the networks was found to be dependent on the phase state during curing © 1992 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300906
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  • 4
    Electronic Resource
    Electronic Resource
    Increased oxygen mass transfer rates from single bubbles in microbial systems at low reynolds numbers (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 647-681 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The presence of microorganisms have been shown to increase by over 40% the mass transfer rates from small oxygen bubbles at low Reynolds number flow. This increase was found to be due only to the microbe cells as inert particles disrupting the quasi-static liquid surface film surrounding the gas bubble and thus decreasing the gas-liquid interfacial resistance. The observed increase in oxygen mass transfer rates was not dependent on cell viability, no effect was noted due to cell-liquid interfacial resistance, nor was the phenomenon due to altering the physical properties of the liquid during cell propagation. These results were obtained in a unique plexiglass apparatus designed for observing under a microscope a small (0.4 mm dia.) stationary oxygen bubble collapsing into a flowing fluid. The oxygen bubble was injected by a small hypodermic needle and the fluid was suspensions of the yeast Candida intermedia, the bacterium Pseudomonas ovalis, 0.3μ alumina, as well as base points of cell free broth and pure water. Several well-known chemical inhibitors of oxidative phosphorylation were used to limit cell oxygen uptake. Calculations of oxygen mass transfer rates were compared with the semi-empirical model of Frössling, the circulating sphere model of Levich, and the rigid sphere concentration boundary layer model of Fried-lander, the latter two showing strong Reynolds number dependence that may be due to radial fluid motion.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260110411
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of heat evolution and correlation with oxygen consumption during microbial growthThis paper was presented in part at the 154th Meeting of the American Chemical Society, Chicago, III., Sept. 11, 1967. (1969)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 269-281 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A procedure for measuring the rate of heat production from a fermentation has been developed. The method is based on measuring the rate of temperature rise of the fermentation broth resulting from metabolism, when the temperature controller is turned off. The heat accumulation measured in this manner is then corrected for heat losses and gains. A sensitive thermistor is used to follow the temperature rise with time. This procedure is shown to be as accurate as previous methods but much simpler in execution. Using this technique, the rate of heat production during metabolism was found to correlate with the rate of oxygen consumption. Experiments were performed using bacteria (E. coli and B. subtilis), a yeast (C. intermedia), and a mold (A. niger). The substrates investigated included glucose, molasses, and soy bean meal. The proportionality constant for the correlation is independent of the growth rate, slightly dependent on the substrate, and possibly dependent On the type of organism growth. This correlation has considerable potential for predicting heat evolution from the metabolism of microorganisms on simple or complex substrates and providing quantitative parameters necessary for heat removal calculations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260110302
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  • 6
    Electronic Resource
    Electronic Resource
    Human interferon production with diploid fibroblast cells grown on microcarriers (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 433-442 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A variety of diploid human fibroblast lines have been successfully grown to high densities (〉106 cell/ml) on recently developed microcarriers. Interferon induction using poly I·poly C and a superinduction procedure resulted in yields greater than 10,000 units/ml with one cell line. A direct comparison of microcarrier cultures to roller bottle cultures showed equivalent interferon yields on a per cell basis and some apparent differences relating to optimum inducer concentrations and kinetics of interferon accumulation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260210306
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  • 7
    Electronic Resource
    Electronic Resource
    Enhancing gas-liquid mass transfer rates in non-newtonian fermentations by confining mycelial growth to microbeads in a bubble column (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 2873-2887 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (kLa) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260251206
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  • 8
    Electronic Resource
    Electronic Resource
    A mechanistic analysis of the inoculum requirement for the cultivation of mammalian cells on microcarriers (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 585-595 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the cultivation of mammalian cells on microcarriers a minimum inoculum concentration is required to initiate cell attachment and subsequent cell growth. A critical cell number model has been proposed to elucidate the mechanism of the inoculum requirement. In this model it was hypothesized that after inoculation a critical number of cells per microcarrier is required for normal growth to occur; failure to acquire enough cells will impede cell growth. This critical cell number model was expressed mathematically and used to simulate cell distribution and growth on microcarriers under different cultivation conditions. By comparing the simulated growth kinetics with the experimental results, the actual critical cell number per microcarrier was identified. The critical number could be reduced by employing an improved medium for the cultivation.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260270507
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  • 9
    Electronic Resource
    Electronic Resource
    Fluorescence sensing of fermentation parameters using fiber optics (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 32 (1988), S. 55-63 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method has been developed for measuring fermentation parameters such as dissolved oxygen, pH, and cell density that differs from traditional techniques that require electrodes and off-line samples. Fluorescent indicators, each sensitive to a single variable, are dissolved directly into a fermentation broth. A fiber-optic probe fluorimeter measures the fluorescence intensities that can then be correlated with parameter values. In addition, an integrated scatter scanning technique can be used to monitor cell density in situ. Results have been obtained using simulated baker's yeast broth and during actual baker's yeast fermentations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260320109
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  • 10
    Electronic Resource
    Electronic Resource
    Separation and concentration of amino acids using liquid emulsion membranes (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 32 (1988), S. 604-615 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The separation and concentration of amino acids using liquid emulsion membranes (LEMs) are discussed. Using L- phenylalanines as a model solute, it is experimentally shown using a facilitated transport system that separation and concentration can be simultaneously achieved. The rate of separation, final product concentration, and membrane swell are shown to increase with increasing chloride driving forces in the membrane, These effects are shown to be insensitive to the particular salt used as the driving force. Changes in the carrier concentration are shown to result in higher initial fluxes and higher swell rates. Hydrodynamically induced membrane breakage is minimal for the system under consideration. Experiments indicate that osmotically induced water transport (“swelling”) in the LEM system is mediated by both the carrier and the emulsion-stabilizing surfactant. The data suggest that this swell is a diffusion-limited process. The specificity of the carrier is examined and is found to be directly related to the hydrophobicity of the solute. Strategies for optimizing LEM formulations are discussed. Emphasis is placed on the hydration characteristics of the surfactant and the specificity of the carrier.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260320505
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