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  • Chemistry  (31)
  • Polymer and Materials Science  (20)
  • 1990-1994  (31)
  • 1975-1979
  • 1960-1964
  • 1991  (31)
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis, dielectric and X-ray powder diffraction studies of Fe(III), Co(II) and Ni(II) chelate polymers with 5,8-dihydroxy-1,4-naphthoquinone (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 177-189 
    Details
    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: Koordinationspolymere von 5,8-Dihydroxy-1,4-naphthochinon mit Fe(III), Co(II) and Ni(II) wurden hergestellt und durch Elementaranalyse, DSC, IR-Spektroskopie und Messung der magnetischen Momente charakterisiert. Aus den DSC-Daten wurden die Reaktionsordnungen und die Aktivierungsenergien des thermischen Abbaus der Polymeren berechnet. Die elektrischen Eigenschaften wie Dielektrizitätskonstante und Wechselstromleitfähigkeit wurden gemessen. Aus Röntgen-Pulverdiagrammen wurden die Elementarzellenparameter berechnet und die Kristallsymmetrie bestimmt.
    Notes: Coordination polymers of Fe(III), Co(II) and Ni(II) with 5,8-dihydroxy-1,4-naphthoquinone have been synthesized and characterized by elemental analysis, IR and magnetic moment studies. From DSC data, the order of the decomposition reaction and the activation energy for the decomposition of the different polymers have been evaluated. Electrical properties like the dielectric constant and the dc conductivity of the polymers have been measured. From x-ray powder diffractograms cell parameters were calculated, the pattern indexed, and the symmetry determined.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910112
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, and evaluation of poly[n-alkyl(oxy)-n-hexyl acrylates] (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 935-945 
    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: Oxoalkyl acrylates of long-chain 7-oxo alcohols were synthesized as intermediate monomers for the preparation of poly[n-alkyl (oxy) -n-hexyl acrylates] for the first time. These polymers have wide applications as fluidity improvers (pour point depressants) for petroleum crude oils. Characterization of all the intermediate monomers was done by IR, 1H-NMR, and MS, and that of polymers by IR, 1H-NMR, and GPC. These polymers were systematically investigated for their efficacy as pour point depressants on three types of high waxy Bombay High (Indian) crudes. In addition to establishing the pour points, relevant rheological parameters of the untreated and the additive-treated crude oils were determined in the laboratory with a rotational viscometer. Results of the crude oils that were pre- and posttreated with these new polymers have shown enhanced activity of flow properties as compared to the crudes that were treated with poly(n-alkyl acrylate) flow improver.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420407
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  • 3
    Electronic Resource
    Electronic Resource
    Thermally stimulated depolarization currents in poly(acrylamide) films (1991)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 379-383 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Mechanismus der Ladungsspeicherung in Poly(acrylamid)-Filmen wurde mit der Methode der thermisch stimulierten Depolarisationsströme (TSDC) untersucht. Die TSDC wurden in Abhängigkeit von der Feldstärke, der Temperatur und der Dauer der Polarisation bei verschiedenen Aufheizgeschwindigkeiten gemessen. Bei niedrigen Polarisationstemperaturen wurde in den TSDC-Spektren nur ein Peak gefunden, bei höheren Polarisationstemperaturen traten zwei Peaks auf. Der erste Peak wurde der Dipolorientierung, der zweite der Raumladungspolarisation zugeordnet.
    Notes: The charge storage mechanism in poly(acrylamide) films was studied by means of the technique of thermally stimulated depolarization currents (TSDC). The TSDC were measured as a function of field strength, temperature and time of polarization in dependence on the heating rate. One peak was observed on the TSDC spectra at low polarizing temperatures, while two peaks occurred for higher polarizing temperatures. The first peak was attributed to dipole orientation and the second one to space charge polarization.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1991.010420809
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical conduction in pure and doped poly(acrylamide) films (1991)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 465-469 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die stationäre elektrische Leitung in aus der Lösung erhaltenen Poly(acrylamid)-Filmen wurde im Temperaturbereich von 303 bis 450 K bei unterschiedlichen Feldstärken untersucht. Es wurde festgestellt, daß die Richardson-Schottky- und Poole-Frenkel-Mechanismen gleichzeitig auftreten. In mit Eosin bzw. Rhodamin B dotierten Filmen wurde die elektrische Leitung der Bildung von Charge-Transfer-Komplexen zugeschrieben.
    Notes: The steady state electrical conduction in solution grown poly(acrylamide) films was investigated in the temperature range 303 to 450 K at different field strengths. It was found that the Richardson-Schottky and Poole-Frenkel mechanisms operate simultaneously. In films doped with cosin and rhodamine B, respectively, the electrical conduction was attributed to the formation of charge transfer complexes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1991.010420915
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  • 5
    Electronic Resource
    Electronic Resource
    Copolymerization reactivity ratios of N,N-dimethyl acrylamide and isopropyl methacrylate determined by 1H-NMR spectroscopy (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 51-55 
    Details
    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: N,N-Dimethylacrylamid (DMA) und Isopropylmethacrylat (IPM) wurden in Dimethylformamid mit Azoisobutyronitril als Initiator copolymerisiert. Die Copolymerzusammensetzung wurde 1H-NMR-spektroskopisch ermittelt. Die Copolymerisationsparameter (rDMA = 0,58, rIPM = 2,76) wurden nach Kelen-Tüdős berechnet.
    Notes: Copolymers of N,N-dimethyl acrylamide (DMA) and isopropylmethacrylate (IPM) were prepared in dimethyl formamide using azoisobutyronitrile as initiator. The composition of copolymers was determined by 1H-NMR analysis. Reactivity ratios (rDMA = 0.58, rIPM = 2.76) were calculated from these values by using the Kelen-Tüdős differential linear equation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920104
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  • 6
    Electronic Resource
    Electronic Resource
    Polyimides derived from ether ketone diamines (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1025-1032 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyimides were prepared from the reaction of two aromatic dianhydrides with two diamines containing carbonyl and ether connecting groups between the aromatic rings. The diamines were prepared from the reaction of 4-aminophenol or (3-aminophenol) with an activated aromatic difluoro compound (4,4′-difluorobenzophenone) in the presence of potassium carbonate. Some of these polyimides were shown to be semicrystalline as evidenced by wide-angle X-ray diffraction. Glass transition temperatures were observed between 203 and 242°C. All polyimides were found to be thermally stable up to 400-450°C with a char yield of about 50-60% at 900°C. The effect of the structure on the properties of polyimides, such as crystallinity, glass transition temperature and thermal behaviour, is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920501
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  • 7
    Electronic Resource
    Electronic Resource
    Utility of culture redox potential for identifying metabolic state changes in Amino acid fermentation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1034-1040 
    Details
    ISSN: 0006-3592
    Keywords: amino acid fermentation ; culture redox potential ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We investigated the relationship of dissolved oxygen and culture redox potential (CRP) on amino acid production. Corynebacterium glutamicum ATCC 14296 was used for all experiments. The fermentation can be divided into a growth phase and a production phase. Our results indicate that in order to get higher amino acid production, a lower oxygen supply during the exponential phase is favored. A higher oxygen supply rate appears to be necessary during the production phase. Culture redox potential (CRP) was used to monitor the fermentation. CRP readings were observed to drop to a characteristic minimum value as the metabolic state changed from a growth to production phase. This was evidenced by the commencement of amino acid production and a simultaneous uptake of lactate. Upon lactate exhaustion, the CRP increased abruptly. At the same time, maximal amino acid yields were observed. By the use of minimum CRP as an indication of metabolic phase changes, the agitation rate was changed to increase oxygen supply during the production phase. This significantly increased amino acid production. These results show that culture redox potential measurements can be used to monitor and optimize amino acid production by process manipulation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380912
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  • 8
    Electronic Resource
    Electronic Resource
    Axial mixing in a reciprocating plate column with very small density gradients (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1019-1026 
    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: Axial dispersion coefficients have been measured in single-phase flow conditions in a 5.08-cm-dia. reciprocating plate extraction column. The measurements were done under steady-state conditions by analyzing temperature profiles (for hot and cold water mixing) and concentration profiles (for mixing of water and salt solutions). The results confirm previous published data of Holmes et al. (1991) in showing that axial dispersion is increased strongly in the unstable situation, where liquid density increases with height. The earlier work is extended to the condition where buoyant energy dissipation is exceeded by mechanical energy dissipation by four orders of magnitude. Even in this case, axial mixing is increased significantly by density gradient-induced instability. Results have been correlated by a simple equation based on a mixing length model.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370707
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  • 9
    Electronic Resource
    Electronic Resource
    Solvent effects on biocatalysis in organic systems: Equilibrium position and rates of lipase catalyzed esterification (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1137-1143 
    Details
    ISSN: 0006-3592
    Keywords: organic-phase biocatalysis ; equillibrium ; reaction rates ; log P ; solvent choice ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Porcine pancreatic lipase immobilized on celite particles has been employed as a catalyst for the esterification of dodecanol and decanoic acid in a predominantly organic system. Solvent influence on the equilibrium position and on the catalyst activity has been studied using 20 solvents, including aliphatic and aromatic hydrocarbons, ethers, ketones, nitro- and halogenated hydrocarbons, and esters. The equilibrium constant for esterification correlates well with the solubility of water in the organic solvent, which in turn shows a good relationship with a function of Guttman's donor number and the electron pair acceptance index number of the solvent. This may be rationalized in terms of the requirements for solvation of water and of the reactants. The catalyst activity, measured as the initial rate of the esterification reaction, is best correlated as a function of both n-octanol-water partition coefficient (log P) and either the electron pair acceptance index or the polarizability.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260381004
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  • 10
    Electronic Resource
    Electronic Resource
    Letter to the editors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 441-441 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030604
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