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  • Articles  (21)
  • Chemistry  (21)
  • Wiley-Blackwell  (21)
  • American Physical Society
  • Springer
  • 2005-2009
  • 1990-1994  (9)
  • 1985-1989  (10)
  • 1970-1974  (2)
  • 1920-1924
  • 1905-1909
  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of tri-N-acetylated heparin pentasaccharide 2 is described. It was assembled from five suitably blocked monosaccharide units (3-7). Glucuronic-acid building block 4 was prepared from glucose by direct Jones oxidation of the 6-O-trityl derivative 18. The resulting acid 16 was esterified to 17 in large mounts using methyl chloroformate/base. Trimethylsilyl bromide proved to be an excellent reagent for the hydrolysis of a prop-1-enyl glycoside (19 →21). The pentasaccharide 29 was obtained by a [2 + 2] + 1 synthesis, the glycosylation reactions furnished good to very good yields. The identity of protected oligosaccharides was confirmed by 1H-NMR spectroscopy. Sequential deblocking of the pentasaccharide, O-sulfation, and N-acetylation gave 2 which was shown to exhibit ca. 600 times lower anticoagulant activity than pentasaccharide 1.
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird über den Beginn einer Untersuchung zur Kristallisationskinetik von Polycaprolacton (Poly(1-oxy-6-oxohexamethylene) (1)) berichtet. Die primäre Keimbildung und das primäre Sphärolith-Wachstum aus der Polymerschmelze werden bei hinreichend hohen Temperaturen verfolgt, wodurch sichergestellt ist, daß das Wachstum der Kristallite durch Keimbildung bestimmt ist. Die kinetischen Daten werden weitgehend mit Hilfe des Avrami-Modells interpretiert, welches sich gut auf die Kristallisation von 1 anwenden ließ.
    Notes: A kinetic crystallization study of polycaprolactone (poly(1-oxy-6-oxohexamethylene) (1)) has been initiated to investigate the primary nucleation and primary spherulitic growth from a polymer melt at temperatures that are high enough to insure nucleation-limited crystallite growth. The analysis of the kinetic data is largely made on the basis of an Avrami model which proved to be well suited for the interpretation of the crystallization of 1.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 391-407 
    ISSN: 0886-9383
    Keywords: Neural networks ; Non-linear multivariate regression ; Pattern classification ; Kalman filter ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Finding methods for the optimization of weights in feedforward neural networks has become an ongoing developmental process in connectionist research. The current focus on finding new methods for the optimization of weights is mostly the result of the slow and unreliable convergence properties of the gradient descent optimization used in the original back-propagation algorithm. More accurate and computationally expensive second-order gradient methods have displaced earlier first-order gradient optimization of the network connection weights. The global, extended Kalman filter is among the most accurate and computationally expensive of these second-order weight optimization methods. The iterative, second-order nature of the filter results in a large number of calculations for each sweep of the training set. This can increase the training time dramatically when training is conducted with data sets that contain large numbers of training patterns. In this paper an adaptive variant of the global, extended Kalman filter that exhibits substantially improved convergence properties is presented and discussed. The adaptive mechanism permits more rapid convergence of network training by identifying data that contain redundant information and avoiding calculations based on this redundant information.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 377-393 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general mathematical model of the chemostat system is developed in order to define an experimental program of dynamic testing. A glucose-limited culture ofSaccharomyces cerevisiae was grown in a chemostat using chemically defined medium. The chemostat was perturbed from an initial steady state by changes in input glucose concentration, dilution rate, pH, and temperature. Dynamic responses of cell mass, glucose, cell number, RNA, and protein concentrations were measured. A number of simulation techniques were used in developing a dynamic mathematical model and in comparing the developed model with experimental data as well as the Monod model. The resulting model was found to be quantitatively accurate and superior to the Monod model. The developed model was interpreted in the light of cell physiology. Adjustment of intracellular RNA fraction was found to be rate limiting in acceleration of cell specific growth rate.
    Additional Material: 14 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 281-284 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Time-switched detectors ; UV detection ; Fluorimetric detection ; Vitamin A ; Vitamin E ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An HPLC method utilizing a UV and a fluorimetric detector linked in series is described. By use of a simple integrator-controlled time-switched relay, analysis of serum vitamin A and E is accomplished on the same chromatogram and at optimum sensitivity for each detector. A single internal standard (retinyl acetate) monitored only by the UV detector permits measurement of both vitamins over a wide linear range. Precision of the assays is satisfactory, both on a within-day and on a day-to-day basis. Recoveries of both vitamins are virtually 100% whilst sensitivity is 2 μg/L (retinol) and 0.05 mg/L (α-tocopherol).
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1783-1788 
    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 procedure is described for preparing fairly uniform spheres of three different nylon polymers by phase separation. The mean diameter and polydisperse index were 5 μm and 1.056 for Griltex nylon, 5.7 μm and 1.046 for nylon 6/6, and 12.9 μm and 1.016 for nylon 6. The phase separation is done by taking a 1 wt % solution in a theta solvent above the theta temperature and cooling it rapidly. The spheres of the three nylons have various degrees of roughness. Formation of highly uniform particles during phase separation is discussed in a preliminary way. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 7
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composition of Mixtures of Hydrocarbons after BIRCH-Reduction of Substituted Benzenes and Acid Catalyzed Addition of Alcohols to Alkylsubstituted Cyclohexenes and Cyclohexa-1,4-dienes.10 different benzene hydrocarbons 1, indane, tetraline, anisol and phenol are reduced by sodium in liquid ammonia in the presence of methanol to the BIRCH products 2. The product mixture compositions are determined through capillary GLC. On storage at + 6°C some rearomatization of the 1,4-cyclohexadienes 2 occurs. Data of the 1H- and 13C-n.m.r. spectra and also mass spectra of the BIRCH 1,4-dienes 2 are given. For comparison 4-alkoxycyclohexenes 4 and 1-alkoxy-1-methylcyclohexanes 8 are prepared and spectroscopically characterized. Acid-catalyzed addition of alcohols to the 1,4-cyclohexadiene systems is a slow process and gives the 4-alkoxy-4-alkylcyclohex-1-enes (4) only in moderate yields up to 30 %. Most of the products are dimers 5 and also oligomers 6 of the parent hydrocarbons 2.
    Additional Material: 1 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 333 (1991), S. 447-453 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three Component Reactions. XX. Methoxymercuration of Cyclohexa-1,4-dienes.The methoxymercuration of several cyclohexa-1,4-dienes leads to insoluble mixtures of mono- and bismercuricompounds 2-4 and 5-7. After reduction with NaBH4/NaOH mixtures of methoxycyclohexenes and bismethoxycyclohexanes result. The result of capillary gaschromatographic analyses and n.m.r. spectra allow a semiquantitative evaluation of the reaction pathways.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 1088-1092 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H.-N.M.R. Spectroscopic Evidence for the Complex Formation of Strontium Ions by Amido Podands
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 97 (1985), S. 745-760 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es ist schon sehr lange bekannt, daß sich manche Übergangsmetallsulfide in wäßrigem Ammoniumpolysulfid lösen. Obwohl anzunehmen war, daß sich dabei Metallpolysulfide bilden, hat man sich diesem Verbindungstyp erst in den letzten Jahren intensiver zugewandt. Dabei konnte eine Fülle neuer Komplexe mit Polysulfido-Chelatliganden Sn2- (n=2,3,4…) isoliert und charakterisiert werden. Die Komplexe interessieren bezüglich ihrer Struktur und Reaktivität, aber auch im Hinblick auf mögliche Anwendungen; mit ihnen können Schwefelringe definierter Größe gezielt hergestellt werden, und es deutet sich an, daß sie auch in der Katalyse Verwendung finden könnten.
    Additional Material: 26 Ill.
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