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  • Chemistry  (101)
  • Computational Chemistry and Molecular Modeling  (31)
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  • 1
    Electronic Resource
    Electronic Resource
    Studies of mold filling and curing in the reaction injection molding process (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 250-260 
    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 model is developed for pressure rise, extent of reaction and temperature changes during filling and curing in thin rectangular molds for the reaction injection molding (RIM) process. The predictions of the model are shown to be in good agreement with experimental results obtained for several intrumented molds using polyurethane RIM chemical systems. The relevant dimensionless groups are identified. Criteria for good mold filling are developed.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690280213
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  • 2
    Electronic Resource
    Electronic Resource
    Laminar tube flow with a thermosetting polymerization (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 973-980 
    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: Two models describing the laminar flow of a polymerizing liquid through a tube have been developed and tested experimentally. One model is a full finite difference solution of the balance equations. The other is an approximate analytical solution which assumes that flow ceases after viscosity increases about tenfold. The models are compared to two experimental cases: (1) the pressure rise needed to keep the flow rate through the tube constant and (2) the flow rate decrease when pressure at the tube entrance is held constant. The finite difference model is more accurate in the early stages of polymerization while the approximate analytical model is more accurate at long times. The models have application to runner flow in reaction injection molding, to nozzles in thermoset molding, to thermoset dispensing equipment and to continuous reactive polymer processes in general.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690280612
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  • 3
    Electronic Resource
    Electronic Resource
    Optical resolution of two isomeric naphthylalanines by immobilized enyzmes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 170-173 
    Details
    ISSN: 0899-0042
    Keywords: β-(1-naphthyl)alanine ; β-(2-naphthyl)alanine ; alumina ; α-chymotrypsin ; subtilisin ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical resolution of β-(1-naphthyl)alanine and β-(2-naphthyl)alanine have been efficiently carried out through enzymatic hydrolysis of their methyl ester and/or N-acetyl ester derivatives by immobilized enzymes. Difficulties related to the lipophilic character of these amino acids were overcome by using emulsions of n-butyl acetate-water as reaction medium. The use of an automatic recirculating apparatus allowed reproducible and repetitive use of the immobilized biocatalysts.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030305
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  • 4
    Electronic Resource
    Electronic Resource
    Estimation of dispersion coefficients in packed beds (1992)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 15 (1992), S. 168-181 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design and performance of fixed beds are greatly influenced by fluid dispersion. Unfortunately, the existing design data do not provide an accurate picture of this phenomenon. This paper presents an attempt to characterize the dispersive features of packed beds by obtaining reliable estimates of the associated coefficients in the axial (DL) and radial (DR) directions. Such an objective is achieved by developing a representative two-dimensional pseudo-continuous dispersed flow model which is subsequently employed to compute the desired coefficients using data obtained from a refined experimental approach. The established values have been correlated to allow such coefficients to be reliably predicted under a variety of physical and operating conditions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270150305
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  • 5
    Electronic Resource
    Electronic Resource
    The influence of impeller type in pilot scale Xanthan fermentations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 95-108 
    Details
    ISSN: 0006-3592
    Keywords: Xanthan fermentation ; impeller type ; power consumption ; mixing ; oxygen transfer ; Xanthan productivity ; product quality ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rheological complexity of Xanthan fermentations presents an interesting problem from a mixing viewpoint, because the phenomena of poor bulk blending and low oxygen mass transfer rates inherent in highly viscous fermentations (and their consequences) can be systematically investigated, even at the pilot plant scale. This study in a 150 L fermentor compares the physical and biological performance of four pairs of impellers: a standard Rushton turbine, a large diameter Rushton turbine, a Prochem Maxflo T, and a Scaba 6SRGT. Accurate in-fermentor power measurements, essential for the comparison of impellers in relation to operating costs are also reported. It is demonstrated that the agitator performance in Xanthan fermentations is very specific and the choice of which impeller to use in bioreactors to obtain enhanced performance is dependant on the applied criterion. None of the criterion favored the use of the standard Rushton turbine, therefore suggesting that there are strong grounds for retrofitting these impellers with either large diameter impellers of similar design or with novel agitators. In addition, fluid dynamic modeling of cavern formation has clearly highlighted the importance of a well mixed and oxygenated region for providing the capacity for high microbial oxygen uptake rates which govern Xanthan productivity and quality. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 95-108, 1998.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of diffusion limitation on immobilized nitrifying microorganisms at low temperatures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 1-9 
    Details
    ISSN: 0006-3592
    Keywords: nitrification ; immobilized cells ; activation energy ; diffusion limitation ; temperature ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Activation energies of suspended and immobilized nitrifying bacteria were determined and compared to determine if diffusion limitation results in decreased sensitivity for temperature. The activation energy for the respiration activity of suspended Nitrosomonas europaea and Nitrobacter agilis was found to be 86.4 and 58.4 kJ mol-1, respectively. The activation energy for oxygen diffusion in the support material, κ-carrageenan, determined from the effect of temperature on the effective diffusion coefficient (D), was 17.2 kJ mol-1. Consequently, the apparent actvation energy of diffusion limited cells should be lower. It was indeed shown that due to the effect of diffusion limitation and to temperature effects on the Monod constant Ks, the immobilized-cell activity was less sensitive to temperature. The apparent activation energy for immobilized Ns. europaea was between 28.6 and 94.2 kJ mol-1 and for immobilized Nb. agilis between 1.4 and 72.9 kJ mol-1, depending on the oxygen concentration and temperature. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450102
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  • 7
    Electronic Resource
    Electronic Resource
    Extraction of equine chorionic gonadotrophin from pregnant mare plasma by direct adsorption on chromatographic media (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 22-25 
    Details
    ISSN: 0006-3592
    Keywords: eCG ; pregnant mare serum gonadotrophin ; batch sorption ; hormone purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equine chorionic gonadotrophin (eCG) is a hormone of practical value in veterinary medicine and animal production. Here we report a novel preparation procedure based on its direct adsorption onto anionic-exchange resins in a batch-wise mode. The active plasma is previously conditioned to reduce pH and ionic strength to required levels. After the adsorption stage, a 90% recovery of the initial eCG is achieved, with a concentration factor of about 50 and an enrichment factor around 500, with high preservation of biological activity. Further purification is carried out by cation-exchange column chromatography. The recovery for the whole process is higher than 70%, and the final potency of the preparation is close to 4000 IU/mg. The process is well suited for its application to the industrial scale. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 22-25, 1998.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Matrix-assisted laser desorption/ionization of high-mass molecules by Fourier-transform mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 239-241 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Following the first demonstrations of high-mass analysis using time-of-flight matriz-assisted laser desorption/ionization (MALDI) techniques by Hillenkamp,1,2 Tanaka3 and their co-workers, there have been significant efforts in a number of laboratories to adapt the new methodology to Fourier-transform mass Spectrometry (FTMS). The motivation fsor this research is obvious. Namely, it would be desirable to couple the unparalleled high mass resolution of FTMS4 with the extended mass range proveded by MALDI, paricularly for analysis of polymers and biomolecules. Unfortuanately, Prior to the presnt work, attempts to mate FTMS and MALDI have met with limited success. The highest mass matrix-assisted laser-desorption-FTMS result previously obtained appears to be the unpublished low resolution spectrum of bovine insulin recently reported by russell co-workers.5 We,6 Campana and co-workes,7 and Hettich and Buchanan8,9 have had some sucess with MALDI-FTMS of biomolecules with masses lower than 3000 Da.9 Fruthermore, with single exception of Campana's report of obtaining mass resolutiojn of 5000 for the moleculer ion of melittin,7 such spectra have not displayed high resolution. Here, we report successful development of MALDI-FTMS, demonstrated with spectra obtained from a variety of high-mass polymer and biomolecule samples, using 355nm radiation from an excimer-pumped dye laser for desorption/ionization and sinapinic acid as matrix, Some of these spectra are of much higher mass resolution than is possible with current time-of flight mass spectrometers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290060403
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  • 9
    Electronic Resource
    Electronic Resource
    The oxidation of Fe—Nb alloys in 1 atm of pure oxygen at 600-800°CDedicated to Professor Dr. H. J. Grabke on the occasion of his 60th birthday (1995)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 46 (1995), S. 223-231 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Die Oxidation von Fe—Nb—Legierungen in 1 atm reinen Sauerstoffs bei 600-800°CDie Korrosion von zwei Fe-Nb-Legierungen mit 15 bzw. 30 Gewichts-% Nb ist bei 600-800 °C unter 1 atm reinen Sauerstoffs untersucht worden. Die Reaktion folgte im wesentlichen dem parabolischen Geschwindigkeitsgesetz mit Geschwindigkeitskonstanten, die erheblich niedriger lagen als für die Oxidation von reinem Eisen. Interne Oxidation und eine Verringerung an Niob in der Legierung sind in keinem Fall beobachtet worden. Der externe Zunder besteht aus einer Matrix aus Fe2O3, die eine Dispersion aus zweifachem Fe-Nb-Oxid enthält, während FeO und Fe3O4 nicht gefunden wurden. Das Oxidationsverhalten dieser Legierungen wird interpretiert in Bezug auf ein angepaßtes Phasendiagramm für das ternäre System Fe—Nb—O, wobei die Effekte der geringen Löslichkeit des Niobs im Grundmetall und die Anwesenheit von zwei Metallphasen in der Legierung berücksichtigt werden.
    Notes: The corrosion of two Fe-Nb alloys containing 15 and 30 wt% Nb has been studied at 600-800°C under 1 atm of pure oxygen. The reaction followed the parabolic rate law to a reasonable approximation with rate constants much lower than for the oxidation of pure iron under the same conditions. Internal oxidation and depletion of niobium in the alloy have never been observed. The external scales were composed of a matrix of Fe2O3 containing a dispersion of double Fe-Nb oxide, while FeO and Fe3O4 were not observed. The oxidation behavior of these alloys is interpreted with reference to an approximate phase diagram of the ternary system Fe—Nb—O, taking into account the effects of the low solubility of niobium in the base metals and of the presence of two metal phases in the alloy.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19950460406
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  • 10
    Electronic Resource
    Electronic Resource
    Pronase in amino acid technology: Optical resolution of nonproteinogenic α-amino acids (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 472-478 
    Details
    ISSN: 0899-0042
    Keywords: nonproteinogenic α-amino acid ; pronase ; optical resolution ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a practical method to produce pure enantiomers of non-proteinogenic α-amino acids by pronase-catalyzed hydrolysis of their methyl esters. Each of the two pure enantiomers was obtained in high yield, while the reaction conditions were optimized with a view to large scale production. Part of this work was devoted to conceiving an analytical procedure especially designed to monitor the steric course of enzymatic reactions. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060605
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