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  • 11
    Electronic Resource
    Electronic Resource
    Radiative transfer in photocatalytic systems (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 532-537 
    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: Radiation absorption at the surface of catalytic particles is the initial step of photocatalytic oxidation reactions currently considered for their potential effectiveness in the treatment of polluted water with traces of highly toxic organics. Owing to the presence of catalyst particles within the fluid phase, the radiation field within a photocatalytic reactor results from the absorption and scattering within the participating medium. An annular reactor with a coaxial central lamp was considered, and the resulting 2-D radiation field was analyzed using a Monte Carlo technique to solve the radiative transfer equation. Results are discussed based on the relevant optical parameters, and a heuristic is derived for the design and rating of a photocatalytic reactor. To exploit the reaction volume effectively, the order of magnitude of the optical thickness should be close to unity, and for a given value of the absorption coefficient the catalyst with the lowest albedo should be selected; however, a precise evaluation of the phase function is not crucial to a relable representation of the radiation field.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420222
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  • 12
    Electronic Resource
    Electronic Resource
    An investigation of the physico-chemical basis of foaming in fungal fermentations (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 801-807 
    Details
    ISSN: 0006-3592
    Keywords: foaming ; fermentations ; biochemical basis ; biosurfactants ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A detailed physico-chemical analysis of two foaming fungal fermentations was carried out to identify that key groups of compounds responsible for foam formation. Fermentations were carried out on a 20-L scale in a stirred aerated tank, over 7 days, using a commercial, defined medium. The organisms investigated were Penicillium herqueii, a hyphomycete, and an unidentified Ingoldian fungus. Samples of broth and, where possible, foam were analyzed to determine which groups of compounds were concentrated into generated foams. Surface tension, bulk viscosity, and antifoam A concentration were additionally determined in broth samples. To date the cause of foaming in fermentations has been attributed to the surfactant properties of extracellular proteins. This assumption was tested and found to be incomplete as many additional groups of biochemicals were found to be enriched into the foam. The results of the investigation revealed the presence of proteins, carbohydrates, α-keto acids, and lipophilic biosurfactants, particularly extracellular pigments, enriched within stable foams. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440705
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  • 13
    Electronic Resource
    Electronic Resource
    Rapid screening for metabolite overproduction in fermentor broths, using pyrolysis mass spectrometry with multivariate calibration and artificial neural networks (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1205-1216 
    Details
    ISSN: 0006-3592
    Keywords: pyrolysis mass spectrometry ; artificial neural networks ; fermentor broths ; regression analysis ; chemometrics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Binary mixtures of model systems consisting of the antibiotic ampicillin with either Escherichia coli or Staphylococcus auresu were subjected to pyrolysis mass spectrometry (PyMS). To deconvolute the pyrolysis mass spectra, so as to obtain quantitative information on the concentration of ampicilin in the mixtures, partial least squares regression (PLS), principal components regression (PCR), and fully interconnected feedforward artificial neural networks (ANNs) were studied. In the latter case, the weights were modified using the standard backpropagation algorithm, and the nodes used a sigmoidal squsahing funciton. It was found that each of the methods could be used to provide calibration models which gave excellent predictions for the concentrations of ampicillin in samples on which they had not been trained. Furthermore, ANNs trained to predict the amount of ampicilin in E. coli were able to generalise so as to predict the concentration of ampicillin in a S. aureus background, illustrating the robustness of ANNs to rather substantial variations in the biological background. The PyMS of the complex mixture of ampicilin in bacteria could not be expressed simply in terms of additive combinations of the spectra describing the pure components of the mixtures and their relative concentrations. Intermolecular reactions took place in the pyrolysate, leading to a lack of superposition of the spectral components and to a dependence of the normalized mass spectrum on sample size. Samples from fermentations of a single organism in a complex production medium were also analyzed quantitatively for a drug of commercial interest. The drug could also be quantified in a variety of mutant-producing strains cultivated in the same medium. The combination of PyMS and ANNs constitutes a novel, rapid, and convenient method for exploitation in strain improvement screening programs. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260441008
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  • 14
    Electronic Resource
    Electronic Resource
    Viscosity of polyethylenes: Dependence on molecular weight and temperaturePresented in part before the Polymer Division of the American Chemical Society, Atlantic City, N. J., Sept., 1959. (1960)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 3 (1960), S. 194-199 
    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: Existing viscosity data on polyethylenes were studied as a function of temperature and molecular weight. New measurements were made on low density polyethylenes which had molecular weights useful for the test of theory. Viscosities of normal alkanes, considered as a lower extension of polyethylenes, were also correlated. The equation, log η = A log (M) - B (where η is absolute viscosity, M is molecular weight, and A and B are constants), is applicable over a wide range of Newtonian viscosities. Bueche's theory postulates that A approaches unity for chain lengths up to a critical molecular weight, Mc, where molecular entanglement abruptly becomes important. Above Mc, the theory requires A to be 3.4. Values of A for normal alkanes are shown to approach unity below Mc. The entanglement point, Mc, is temperature dependent and occurs at relatively low molecular weights. Above Mc, A for linear polyethylenes is near 3.4. However, certain polyethylene data give higher values for A. Activation energies for viscous flow, ΔE*, were obtained for polyethylenes and normal alkanes. They were found to be internally consistent and to vary as a linear function of the log of molecular weight. The change of ΔE* with less general functions of molecular weights shows a maximum curvature near Mc. Results are considered in terms of flow theory.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1960.070030808
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  • 15
    Electronic Resource
    Electronic Resource
    Viscosity of polyethylenes: Dependence on molecular weight at high shearPresented in part before the Polymer Division of the American Chemical Society, Atlantic City, N. J., Sept., 1959. (1960)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 3 (1960), S. 200-205 
    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 high shear, concentric cylinder viscometer was used to study polyethylene samples which differed in molecular weight. Viscosities were measured at several temperatures in laminar flow at shear rates up to 2.5 × 105 sec.-1. Five high molecular weight normal alkanes were also studied in evaluating shear dependent flow. Viscosities of the normal alkanes and polyethylenes with molecular weights up to about 3300 were Newtonian over the shear range studied. Polyethylenes with higher molecular weights showed large and reversible decreases in viscosity with increasing shear. Viscosity results at high shear were compared with available theory. Previous concepts based on molecular orientation apparently cannot account for the abrupt onset of non-Newtonian flow with increasing molecular weight. An alternate explanation of non-Newtonian flow is offered in terms of molecular disentanglements. This concept permits a qualitative prediction of the magnitude of non-Newtonian flow, as well as the molecular weights for which it will become important.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1960.070030809
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  • 16
    Electronic Resource
    Electronic Resource
    Column fractionation of polymers. IV. Large-scale polyester column fractionationBased on a paper presented before the Polymer Division of the 145th National Meeting of the American Chemical Society, New York, September 1963. (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 2963-2969 
    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 small-scale fractionation of 9 g. and a large-scale fractionation of 90 g. of a polyester were carried out. The polymer was prepared by condensation of isophthalic acid, maleic anhydride, and propylene glycol in the mole ratio 1:2:3. Results from the two fractionations were in good agreement despite different fractionation conditions. By proton magnetic resonance measurements the fractions were found to have nearly constant chemical compositions. The Huggins' constant and the Staudinger relation for this polyester were determined from data on fractions in chloroform at 30°C. Integral and differential molecular weight distributions as well as various molecular weight averages for the polyester were obtained by a computer program. The fractionation data were applied to several popular distribution correlations. The experimental distribution was found to be in good agreement with that expected from the theory of polycondensation kinetics.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080638
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  • 17
    Electronic Resource
    Electronic Resource
    Interfacial polymerization of n-alkyl α-cyanoacrylate homologs (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1617-1623 
    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 n-alkyl α-cyanoacrylates from methyl through n-octyl exhibit a reverse order of polymerization rate on biological substrates compared to that on water. On water, the lower homologs spread and polymerize rapidly, whereas the higher homologs spread but polymerize slowly. On biological substrates, the lower homologs do not spread or spread slightly and the higher homologs exhibit large spreadabilities and very rapid polymerization rates. Determination of the spreading coefficients for these systems by using the monomers or model compounds confirm the observed spreadabilities. It is proposed that the increased rate of polymerization of the higher homologs on biological substrates may be due to increased catalyst concentrations on these surfaces or to the solubilization of the higher homologs at the interface, making the catalyst sites more available to the monomer. The suggestion is made that if the liquid monomers spread and orient on the substrate and subsequently polymerize, the polymers will maintain the orientation. If such is the case, a technique is available for preparing stereospecific vinyl polymers which may have different spatial configurations depending on the polarity of the liquid substrate upon which they have been allowed to spread and polymerize.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1966.070101101
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  • 18
    Electronic Resource
    Electronic Resource
    Polymer degradation. V. Changes in molecular weight distributions during sonic irradiation of polyisobuteneProd. No. 1470 (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 335-340 
    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: Gel permeation chromatography was used to follow changes in the molecular weight distribution of a polyisobutene, initial Mv = 466,000, during degradation induced by sonic irradiation. Seven samples taken at times of 200-163,500 sec. were studied. In general, a steady decrease in molecular weight was observed, although a bimodal distribution was present after 20,000 sec. irradiation. Various measures of inhomogeneity, Mw/Mn, U, etc., were examined. The function, σn/Mw, where σn is the standard deviation of the number distribution, is considered as a measure of the relative distribution. It is shown to be almost constant throughout the degradation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070110302
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  • 19
    Electronic Resource
    Electronic Resource
    Characterization of polybutenesPresented in part before the 145th National Meeting of the American Chemical Society, New York, September 1963. (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 1371-1378 
    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: To characterize butene polymers, rapid and precise small- and large-scale column fractionation techniques have been developed for low molecular weight pure polyisobutenes and for mixed butene polymers. Fractionation results have been used to determine molecular weight distribution curves of typical commercial butene polymers. Narrow distribution fractions obtained from fractionation have been used to investigate viscosity-molecular weight correlations for both pure polyisobutenes and for mixed butene polymers. Molecular weights were predominantly determined with the relatively new technique of vapor pressure osmometry. Molecular weights and distributions were also checked with cryoscopic and light scattering molecular weights. The chemical composition of several fractions was determined by high resolution nuclear magnetic resonance. The Huggins' constant was measured for several bulk polymers and established for low molecular weight butene polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080327
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  • 20
    Electronic Resource
    Electronic Resource
    Ion-exchange and affinity chromatography costs in α-galactosidase purification (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 717-724 
    Details
    ISSN: 0006-3592
    Keywords: Chromatography costs ; cost equations ; α-galactosidase ; enzyme purification ; affinity chromatography ; ion-exchange chromatography ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The purification of α-galactosidase from soybean seeds is a five to six-step procedure consisting of cryoprecipitation, acid precipitation and ammonium sulfate fractionation followed by two or three chromatography steps. The procedures, while not optimized, were carried out in a manner that resulted in 414-515-fold purification, as reported previously. The costs of two purification sequences were compared. In the best case, the preparative-scale costs of stationary phase, reagents, and hardware were $790 per million enzyme units, excluding labor. Stationary phase costs predominated over extraction, chromatography reagent, and eluent costs when the stationary phase is replaced after 10-40 cycles of use. However, if stationary phase life exceeds 50-200 cycles, stationary phase costs become similar in magnitude to eluent and reagent costs. Labor costs, which are process-specific and difficult to estimate, exceed all other costs by a factor of 10-50 at a small scale of operation and constitute a major cost, regardless of scale. This case study provides equations and a frame-work for carrying out a first comparison of costs for multistep purification sequences. Column life, throughput, and scale of operation were found to determine not only the magnitude, but also the relative contributions, of the different components that make up purification costs. This analysis shows that there are major opportunities for reducing purification costs through the development of less expensive stationary phases and the implementation of intelligent process control and automation for process scale chromatography.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390704
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