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  • Wiley-Blackwell  (102)
  • American Chemical Society (ACS)  (59)
  • Molecular Diversity Preservation International (MDPI)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 2 (1956), S. 477-481 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The theoretical-plate concept in chromatography has been treated on the basis of continuous flow of eluent through the plates of the column. A treatment more precise in principle than the previous treatments is presented. General elution and deposition equations have been derived and applied to special cases of practical interest. The derived formulas have the advantage of precision, generality, and simplicity.The theory was found adaptable to the treatment of gradient elution and also to the calculation of the fraction of solute which has been eluted or still-adsorbed on the column during the elution process.A method for the determination of the number of theoretical plates in a chromatographic column is also described.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 2055-2059 
    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: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 5 (1959), S. 69-72 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Part A of this paper is essentially a continuation of a previous paper on the theoretical plate concept in chromatography (4). It deals with some special cases of eluting conditions and zone shapes. A more general equation, which combines both elution and deposition, is derived, and methods for approximating a continuous zone by means of a discontinuous one are discussed.Part B discusses the effect of the finite size of samples and the dead free volume at the bottom of the column on the shape of elution curves. The effect of representative sample volumes is calculated, and the deviation between the experimental and the true elution curves is illustrated.A simple expression for the number of theoretical plates utilizing the ratio between the maximum concentrations at the top and bottom of the column is derived and corrected for the effect of the finite size of samples.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 5 (1959), S. 223-224 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To obtain numerical answers for the concentration distribution of solute on a chromatographic column or in the effluent, tables and charts of the Poisson distribution are used. Their use however is limited to a small number of theoretical plates. The transformation of the Poisson to the normal distribution enables the calculations to be performed for any number of theoretical plates through the use of the normal distribution tables.Equations derived previously for columns containing a large number of plates and employing elaborate mathematical procedures and approximations have been simply deduced by applying a limit property of the Poisson distribution to the exact equations.A relationship between the Poisson and normal distribution is derived, and charts are drawn which allow the rapid evaluation of the Poisson in terms of the normal values.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 4 (1958), S. 290-292 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper lists various properties of the Poisson distribution and related functions which can be derived from elementary principles without reference to theories of probability or statistics. They are intended for use by persons who may have to deal with Poisson distributed variables but not from a satistical point of view. Limit values and sums of the Poisson distribution, the sums of related functions, and different relations between its sums and integrals are given.Differential and difference equations which lead to solutions in the form of a Poisson distribution are discussed. The general elution equation is derived by setting up the differential-difference equation for plate n in a chromatographic column and showing that the Poisson distribution is a solution to this equation. The complete solution is then obtained by applying the boundary conditions of the process.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 746-752 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Competitive liquid-phase hydrodesulfurization of thiophene and hydrogenation of cyclohexene on a monolithic CoMo/γ-Al2O3 catalyst were studied. The flow pattern in the monolithic catalyst reactor was segmented gas-liquid flow (slug flow). The hydrogen pressure and the temperature were varied between 30-40 bar and 509-523 K, respectively. The experimental data are consistent with rate expressions of the Langmuir-Hinshelwood type where the reactions proceed on two different types of active sites. This kinetic model is based on hydrogenation of the thiophene ring prior to sulfur elimination.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 212 (1993), S. 13-18 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die elektrische Leitfähigkeit (σ) von Cellulose-HYPHAN® und seinen Komplexen mit Cr3+, Mn2+, Mo5+ und Hg2+ wurde im Temperaturbereich 25-510°C bestimmt. Die Aktivierungsenergie wurde aus der Abhängigkeit von log σ von der reziproken Temperatur berechnet. Die Ergebnisse zeigen, daß die Leitfähigkeit mit steigender Temperatur zunimmt und dabei zwei Maxima durchläuft. Das erste Maximum läßt sich dem Wassergehalt zuordnen, während das zweite mit dem thermischen Abbau der Cellulose-Kette zusammenhängt. Die Werte der Aktivierungsenergie lassen darauf schlieäen, daß sich beim Erhitzen die Halbleitereigenschaften der Komplexe verbessern.
    Notes: The electrical conductivity, σ, of cellulose HYPHAN® and its complexes with Cr3+, Mn2+, Mo5+ or Hg2+ was measured from room temperature to 510°C. The activation energy, ΔE, of the samples was calculated from log σ against 1/T curves. The results show that the electrical conductivity increases by temperature with two maximum peaks. The first peak is attributed to the moisture content, while the second one is attributed to the thermal degradation of the cellulose chain. The values of the activation energy indicate that the samples change from low semiconductor to high semiconductor property with heating.
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 683-691 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of parameters such as styrene dilution and active site concentration on the polymerization of styrene in the presence of a di-tert-butyl nitroxide adduct (A-T) was examined. It is confirmed that the rate of styrene polymerization is independent of A-T concentration, with no monomer dilution effect. An increase in radical concentration generated in the medium leads to faster propagation, but the molecular weight of the polymers formed is alway controlled by the A-T concentration.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 161 (1994), S. 483-489 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Little is known about the cellular and molecular regulation of the uptake process of the water-soluble vitamin biotin into liver cells, the major site of biotin utilization and metabolism. Such studies are best done using a highly viable and homogeneous cellular system that allows examination of prolonged exposure to an agent(s) or a particular condition(s) on the uptake process. Isolated hepatocytes when maintained in primary culture lose their ability to transport biotin by the specialized carrier system. The aim of the present study was, therefore, to examine the mechanism(s) of biotin uptake by the cultured human-derived liver cells, Hep G2. Uptake to biotin by Hep G2 cells was appreciable and linear for up to 10 min of incubation. The uptake process was Na+ gradient-dependent as indicated by studies of Na+ replacement and pretreatment of cells with gramicidin and ouabain. Biotin uptake was also dependent on both incubation temperature and intracellular energy. Unlabeled biotin and the structural analogs with free carboxyl groups (thioctic acid, desthiobiotin) but not those with blocked carboxyl group (biocytin, biotin methyl ester, and thioctic amide) caused significant inhibition of 3H-biotin uptake at 37°C but not 4°C. Initial rate of biotin uptake was saturable as a function of concentration at 37°C but was lower and linear at 4°C. Pretreatment of Hep G2 cells with sulfhydryl group inhibitors (e.g., p-chloromer-curibenzene sulfonate) led to a significant inhibition in biotin uptake; this inhibition was effectively reversed by reducing agents (e.g., dithiothreitol). Biotin uptake was also inhibited by the membrane transport inhibitors probenecid (noncompetitively), DIDS and furosemide but not by amiloride. Pretreatment of Hep G2 cells with valinomycin did not alter biotin uptake. The stoichiometric ratio of biotin to Na+ uptake in Hep G2 cells was also determined and found to be 1:1. These findings demonstrate that biotin uptake by these cultured liver cells is mediated through a specialized carrier system that is dependent on Na+-gradient, temperature, and energy and transports the vitamin by an electroneutral process. These findings are similar to those seen with native liver tissue preparations and demonstrate the suitability of Hep G2 cells for in-depth investigations of the cellular and molecular regulation of biotin uptake by the liver. © 1994 Wiley-Liss, Inc.This article is a US Government work, and as such, is in the public domain in the United State of America.
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  • 10
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2] Photocycloaddition of 2-(trimethylsilyloxy)-1,3-butadiene to a number of 2-cycloalkenones proved to be quite a general reaction leading to good yields of the cycloadducts (Table). This finding is surprising since dienes, in general, are better known as quenchers of enone triplets rather than as photochemical reactants. Both the high substrate concentrations, which can be employed in these cycloadditions, and the remarkable regio and stereoselectivity of the processes qualify them as valuable for syntheses. In a first application, the photoproducts 1a, b were transformed in three steps into a viable precursor 4 of the pentalenolactone-G and -H antibiotics.
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