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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 149-153 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions for normal phase high performance liquid chromatrography-chemical ionization mass spectrometry of underivatized glycosphingolipids with the use of a moving belt transport interface were investigated. Chromatography was performed on a 2 mm ID × 3 cm column packed with 5 μm spherical silica. A gradient of increasing methanol and water in methylene chloride was used to resolve mono-, di-, tri-, and tetraglycosylceramides and sulfatides in less than 15 min. A polyimide belt was used to transport the sample residues to the mass spectrometer where ammonia chemical ionization mass spectrometry was used to obtain spectra. One to 5 μg of each component was sufficient to obtain full spectral scans. Mono- and dihexosylceramide spectra showed [M + H]+ ions of good abundance, while the higher glycosphingolipids have molecular weights that exceed the range of the mass spectrometer utilized. All glycosphingolipids gave ions characteristic of their ceramide, fatty acid, long chain base and carbohydrate components. Sequence information which reflected the relative position of hexose and N-acetylhexosamine residues was also obtained.
    Additional Material: 8 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1779-1790 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of protein aggregation in salt-induced precipitation processes were studied as a function of salt type, salt concentration, temperature and protein concentration. α-chymotrypsin (αCT) was used as a model protein. Stopped-flow turbidimetry was used to monitor the progress of precipitations. Analysis of the linear portions of the turbidity trajectories indicates that temperature and salt concentration effects are related to protein solubility; the protein concentration dependence is well described by the Smoluchowski collision equation. The aggregation kinetics of partially-inhibited αCT exhibit poisoning behavior, underscoring the importance of dimerization and monomer addition in the precipitation of αCT. Solute particle radius distributions determined via dynamic laser light scattering for low salt and supernatant αCT solutions indicated that significant aggregation does not occur in the absence of supersaturation. A detailed population balance model was proposed that accounted for specific and nonspecific interactions and monomer addition. The model is expected to find general application to protein aggregation phenomena, in particular for proteins that have specific quaternary interactions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1947-1954 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent experimental validation of theoretical and numerical predictions regarding scalar variance decay in a pipe have revealed that the traditional plug-flow reactor picture of pipe flow omits key physical mechanisms. In particular, the far-field decay exhibits a power law rather than exponential decay. These observations are examined by performing a set of experiments where the manner in which the scalar constituents are introduced into the pipe is varied. Significant differences are noted in the behavior of the variance decay until the very far field is reached, where an invariant power-law form emerges.
    Additional Material: 14 Ill.
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  • 4
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microkinetic simulations have been carried out to describe the partial oxidation of methane over silica-supported molybdena and vanadia. The objective of this study was to formulate a physically reasonable reaction network to capture the basic aspects of the surface catalytic chemistry and to use this network to link methane oxidation kinetics with the kinetics observed for the oxidation of subsequent gaseous products, i.e., methanol, formaldehyde, and carbon monoxide. The most abundant reactive intermediates on the catalyst surface are suggested to be oxygen and hydroxyl groups. This reaction network successfully predicts the catalytic activities, selectivities, activation energies, and reaction orders observed over silica-supported molybdena and vanadia; and the microkinetic model also semiquantitatively explains the kinetic trends for related catalyst systems and is consistent with surface bonding energetics reported in the literature over various oxide catalysts. The microkinetic reaction network properly reduces to the more simple macrokinetic model reported previously for methane partial oxidation.
    Additional Material: 12 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1277-1292 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Improvements in bioprocess performance can be achieved by genetic modifications of metabolic control structures. A novel optimization problem helps quantitative understanding and rational metabolic engineering of metabolic reaction pathways. Maximizing the performance of a metabolic reaction pathway is treated as a mixed-integer linear programming formulation to identify changes in regulatory structure and strength and in cellular content of pertinent enzymes which should be implemented to optimize a particular metabolic process. A regulatory superstructure proposed contains all alternative regulatory structures that can be considered for a given pathway. This approach is followed to find the optimal regulatory structure for maximization of phenylalanine selectivity in the microbial aromatic amino acid synthesis pathway. The solution suggests that from the eight feedback inhibitory loops in the original regulatory structure of this pathway, inactivation of at least three loops and overexpression of three enzymes will increase phenylalanine selectivity by 42%. Moreover, novel regulatory structures with only two loops, none of which exists in the original pathway, could result in a selectivity up to 95%.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 994-1002 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Interpenetrating polymer networks (IPNs) of poly(ethylene oxide) (PEO) and a polyether substituted polysiloxane were synthesized containing variations of PEO content (35 and 65% dry network weight) and PEO systematically varied from low to high molecular weight (2,000, 8,000, and 20,000). Biocompatibility was assessed by measureing 111In platelet deposition in a baboon femoral ex vivo shunt. Mass transfer analysis revealed that platelet transport to PEO/polysiloxane surfaces was kinetically limited and correlated with both PEO content and molecular weight. Differences in material performance were noted particularly after the initial 30 min blood contact period. In mid and high PEO molecular weight networks (8,000 and 20,000), reduced platelet deposition was noted with increased PEO content. In materials of high PEO content (65%), mid and high PEO molecular weight samples had significantly lower levels of platelet adsorption than PDMS (60 min; p〈 0.05) or networks of low PEO molecular weight, coded 2K-65 (30 and 60 min; p 〈 0.05). The lowest level of platelet deposition was noted on 20K-65 networks, less than one platelet per 1,000 μm2.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 8 (1962), S. 193-200 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Data on the vapor phase photochlorination of chloroform in flow reactors are interpreted on the basis of reaction mechanisms presented in the literature. In order to estimate the rates of light absorption it is also necessary to interpret the rate data obtained for the uranyl sulfateoxalic acid reaction.The chlorination results are represented quite well by a mechanism in which the most important termination step is a termolecular reaction between trichloromethyl radicals and chlorine. Deviations from this model are observed as the flow of reactants becomes turbulent and as the light intensity increases. The observed decrease in reaction rate under such conditions is attributed to the increased significance of a second termination step, the unimolecular deactivation of chlorine radicals at the reactor wall.
    Additional Material: 9 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 10 (1964), S. 548-550 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 13 (1967), S. 52-60 
    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 unified theory of one-dimensional, adiabatic, separated, two-phase flow is presented. To describe the flow adequately, four mixture specific volumes are defined. They are based on area, momentum, kinetic energy, and velocity averages. Increasing relative velocity between the phases initially lowers all mixture specific volumes except the velocity average. The momentum average specific volume minimizes when the slip ratio equals (Vg/Vf)1/2, while the kinetic energy average specific volume reaches its minimum value at a slip ratio of (Vg/Vf)1/3. Area average specific value does not minimize with slip ratio.Because a higher slip ratio would decrease the entropy of a closed system, (Vg/Vf)1/3 is the maximum slip ratio attainable in two-phase critical flow. Based on the maximum slip ratio and isentropic flow, a new critical flow model was developed and compared with the steam-water critical flow data of four recent investigations. While the predicted flow rates followed well the pressure behavior of the experimental data, they were too low at high qualities and too high at low qualities. The average percentage difference between experimental and predicted critical flow rates was -8.5% (three hundred and seventy-six data points).Differences in the approach to critical flow between a gas and a vapor-liquid stream appear to be caused by the latter's increased frictional and gravitational pressure drops and relative velocity effects.
    Additional Material: 7 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 475-481 
    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 mathematical model has been developed to predict the variations in temperature, velocity, and composition which occur during anionic polymerization in laminar flow in a tubular reactor. It is found that very large radial gradients in all three are to be expected when a solution containing only solvent and monomer is polymerized. Recycle of part of the product or prepolymerization in stirred-tank reactors may be used to reduce greatly the distortion of the radial profiles.
    Additional Material: 8 Ill.
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