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  • 1
    Electronic Resource
    Electronic Resource
    Photodegradation of polyethylene films formulated with a titanium-based photosensitizer and titanium dioxide pigment (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 847-856 
    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: This work reports on the photodegradation of low-density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow-extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530702
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  • 2
    Electronic Resource
    Electronic Resource
    Theory of hydrogen bonding in supercritical fluids (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1243-1253 
    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: The degree of hydrogen bonding and macroscopic thermodynamic properties for pure and mixed fluids are predicted with the hydrogen bonding lattice fluid (LFHB) equation of state over a wide range in density encompassing the gas, liquid and supercritical states. The model is successful for molecules forming complex self-associated networks, in this case pure methanol, ethanol, and water, and the mixture 1-hexanol-SF6. In supercritical water, significant hydrogen bonding is still present despite all the thermal energy and is highly pressure- and temperature-dependent. A fundamental description of pressure and temperature effects on hydrogen bonding is presented for a well-defined case, the formation of a complex between a donor and acceptor in an inert solvent, where no self-association is present. The partial molar enthalpy and volume change on complexation both become pronounced near the critical point, where the density is highly variable with temperature and pressure.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380811
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetic study of the synthesis of n-octyl octanoate using cobalt chloride as catalyst (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 210-215 
    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 kinetics of the pseudohomogeneous liquid phase synthesis of a high molecular weight ester in a stirred tank reactor using cobalt chloride as catalyst has been studied at various temperatures, catalyst concentrations, and acid/alcohol molar ratios. A kinetic model has been determined that predicts the experimental results quite well.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170310
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  • 4
    Electronic Resource
    Electronic Resource
    Design and evalution of control strategies for high cell density fermentations (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 293-304 
    Details
    ISSN: 0006-3592
    Keywords: control ; fermentation ; baker's yeast ; high cell density ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A methodology for the design and evalution of bioprocess control strategies is presented. The strategies manage nutrient supply with demand and vary with the metabolic condition and phase of fermentation operation. Six carbon source addition strategies are based on different combinations of available measurements; they are described and evaluated under different operating conditions for yeast cultivation. It is concluded that a single control strategy is not the most appropriate under all possible operating conditions. An oxygen uptake rate-based control strategy performs better with a mean respiratory quotient (RQ) value less than 1.1 during an oxygen limitation than an ethanol control strategy which had a mean RQ of 14. The designed strategies and an approach of applying the strategy that best matches fermentation conditions consistently enables achievement of high cell densities 78.7 g DCW/L and yields 0.50 g DCW/g glucose as the mean values for three fermentations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390307
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  • 5
    Electronic Resource
    Electronic Resource
    Albumin denaturation during ultrafiltration: Effects of operating conditions and consequences on membrane fouling (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 528-534 
    Details
    ISSN: 0006-3592
    Keywords: albumin denaturation ; ultrafiltration ; protein denaturation ; membrane fouling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ultrafiltration of high-purity grade bovine serum albumin has been carried out under various temperature between 5 and 30°C and at various cross-flow velocities, pressures, and concentrations with the aim of studying protein denaturation and its consequences on the process. Three different pump heads have been tested. Denaturation of proteins in solution has been monitored by laser light scattering and size exclusion chromatography. The rate of protein denaturation increases with temperature, cross-flow, and time. It is observed that membrane fouling is different whether denaturation has occurred or not. Under high-concentration polarization, denaturation can occur in the boundary layer if the wall concentration exceeds 400 g/L. It is shown how the residence time, operating temperature, and pressure play an important part in membrane fouling. This can provide guidelines for process design and control.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260380511
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  • 6
    Electronic Resource
    Electronic Resource
    Tensorial resolution: A direct trilinear decomposition (1990)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 4 (1990), S. 29-45 
    Details
    ISSN: 0886-9383
    Keywords: Tensor ; Superdiagonalization ; GRAM ; Three-way ; Multilinear ; Trilinear ; PARAFAC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Modern instrumentation in chemistry routinely generates two-dimensional (second-order) arrays of data. Considering that most analyses need to compare several samples, the analyst ends up with a three-dimensional (third-order) array which is difficult to visualize or interpret with the conventional statistical tools.Some of these data arrays follow the so-called trilinear model, \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm R}_{ijk} = \sum\limits_{r = 1}^N {{\rm X}_{ir} {\rm Y}_{jr} {\rm Z}_{kr} + {\rm Error}_{ijk} } $$\end{document} These trilinear arrays of data are known to have unique factor analysis decompositions which correspond to the true physical factors that form the data, i.e. given the array ∝, a unique solution can be found in many cases for each order X, Y and Z. This is in contrast to the well-known second-order bilinear data factor analysis, where the abstract solutions obtained are not unique and at best cannot be easily compared with the underlying physical factors owing to a rotational ambiguity.Trilinear decompositions have had the disadvantage, however, that a non-linear optimization with many parameters is necessary to reach a least-squares solution. This paper will introduce a method for reducing the problem to a rectangular generalized eigenvalue-eigenvector equation where the eigenvectors are the contravariant form (pseudo-inverse) of the actual factors. It is shown that the method works well when the factors are linearly independent in at least two orders (e.g. Xir and Yjr are full rank matrices).Finally, it is shown how trilinear decompositions relate to multicomponent calibration, curve resolution and chemical analysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180040105
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  • 7
    Electronic Resource
    Electronic Resource
    Dependence between fusion temperatures and chemical components of a certain type of coal using classical, non-parametric and bootstrap techniques (1990)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 4 (1990), S. 429-439 
    Details
    ISSN: 0886-9383
    Keywords: Principal components ; Multiple and stepwise regression ; Non-parametric density and regression estimation ; Bootstrap inference ; Canonical correlation ; PLS regression ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A statistical study of the dependence between various critical fusion temperatures of a certain kind of coal and its chemical components is carried out. As well as using classical dependence techniques (multiple, stepwise and PLS regression, principal components, canonical correlation, etc.) together with the corresponding inference on the parameters of interest, non-parametric regression and bootstrap inference are also performed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180040606
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of poly(vinyl alcohol) derivatives containing amidoxime groups (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 183-196 
    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: Poly(vinylalkohol) (PVAL) wurde mit Acrylnitril in alkalischem Medium modifiziert. Die Struktur der so hergestellten Polymeren wurde mit IR-, 1H-NMR und 13C-NMR-Spektroskopie bestimmt. Der Einfluß der Zusammensetzung des Reaktionsgemisches, der Temperatur und des Katalysators wurde ermittelt. 13C NMR-Spektroskopie wurde zur Bestimmung der Sequenzverteilung von cyanethyliertem PVAL (das als Vinylalkohol-(VAL)-2-Cyanethyl-vinylether-(VCE)-Copolymeres angesehen werden kann) eingesetzt. Die 13C NMR-Spektren der Methylen-C-Atome der Hauptkette zeigen drei gesplittete Peaks, deren Intensitäten sich mit der Copolymerzusammensetzung ändern und die den drei Diadensequenzen zugeordnet werden können. Die Ergebnisse zeigen, daß die VCE-Einheiten im Copolymeren überwiegend alternierend angeordnet sind. Nitrilgruppen in cyanoethyliertem PVAL wurden mit Hydroxylamin in einer Reaktion zweiter Ordnung in Amidoximgruppen umgewandelt; die Aktivierungsenergie betrug 51,6 kJ/mol. Lösliche Polymerchelate zwischen PVAL mit Amidoxim-gruppen und Cu2+ -1onen wurden hergestellt, wobei nicht alle Amidoximgruppen an der Bindung der Kupferionen beteiligt sind.
    Notes: The modification reaction of poly(vinyl alcohol) (PVAL) with acrylonitrile in alkaline medium was studied. The structure of the resulting polymers was determined by means of IR, 1H and 13C NMR spectroscopy. The influence of solvent composition, catalyst and temperature was evaluated. 13C NMR spectroscopy was used for the determination of the sequence distribution of cyanoethylated PVAL (considered as a vinyl alcohol (VAL)-(2-cyanoethyl) vinyl ether (VCE) copolymer). The 13C NMR spectra of the methylene carbons in the main chain show three split peaks, the intensities of which change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that VCE units have an alternating tendency in the copolymer. Nitrile groups in cyanoethylated PVAL were converted to amidoxime groups by reaction with hydroxylamine. The reaction showed second order kinetics. The activation energy was found to be 51.6 kJ/mol. Soluble polymeric chelates between amidoximated PVAL and cupric ions have been prepared. It is noteworthy that not all the amidoxime groups participate in binding cupric ions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052180114
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  • 9
    Electronic Resource
    Electronic Resource
    Dextran functionalized by cyclic carbonate groups as supports of bioactive compounds (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 206 (1993), S. 77-85 
    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: Es werden Aspekte der Reaktion von Dextran mit Ethyl-chlorformiat und Triethylamin als Katalysator behandelt. Mittels 1H- und 13C NMR-Spektroskopie wurden in den gebildeten modifizierten Dextranen cyclische und acyclische Carbonatgruppen nachgewiesen. Vorversuche zeigten, daß die Reaktion cyclischer Carbonatgrupen mit verschiedenen Amin-Modellverbindungen stark vom Basencharakter des Amins abhängt. Phenethylamin und Tyramin wurden quantitativ an aktiviertes Dextran mit cyclischen Carbonatgruppen gebunden. Die Dextran-Phenethylamin- und Dextran-Tyramin-Addukte werden unter den angewendeten Bedingungen (pH 1,0 oder 9,1 bei 37°C) nicht heterogen hydrolysiert.
    Notes: This work deals with some features of the reaction of dextran with ethyl chloroformate using triethylamine as catalyst. The presence of cyclic and acyclic carbonate groups in the resulting modified dextrans was demonstrated by IR, 1H and 13C NMR spectroscopy. Preliminary experiments have shown that the reaction of cyclic carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino type drugs (Phenethylamine and tyramine) were quantitatively bound to activated dextran with cyclic carbonate groups. The heterogeneous hydrolysis of dextran-phenethylamine or dextran-tyramine adducts showed that no hydrolysis takes place under the applied conditions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052060108
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  • 10
    Electronic Resource
    Electronic Resource
    Functionalization of dextran: Incorporation of carboxy groups by O-succinoylation (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 194 (1992), S. 79-89 
    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: Die Modifizierung von Dextran rnit Bernsteinsaureanhydrid unter Verwendung von Pyridin als Katalysator und DMF/LiCl als Liisungsmittel wurde untersucht und die Struktur der gebildeten Polymeren IH- und 13C-NMR-spektroskopisch bestimmt. Es wurde eine lineare Abhangigkeit zwischen der Reaktionsgeschwindigkeit und der Bernsteinsaureanhydrid-Konzentration gefunden, wobei die Reaktion beziiglich Pyridin erster und beziiglich des Polymeren zweiter Ordnung war. Die Aktivierungsenergie betrug 69,O kUmol. Die I3C-NMR-Spektren von teilweise, d. h. rnit nur einer SuccinatGruppe pro Anhydroglucose-Einheit modifiziertem Dextran wurden untersucht, um die Selektivitat der Reaktion von Dextran rnit Bernsteinsaureanhydrid in homogener Phase abzuschatzen. Die Analyse der Ring-Kohlenstoffatome der Anhydroglucose-Einheit zeigte, dal3 die Reaktivitat der einzelnen Hydroxy-Gruppen in der Reihenfolge C-2 3 C-3 〉 C-4 abnimmt; Proben rnit einem hoheren Substitutionsgrad, d. h. rnit mehr als einer Succinat-Gruppe pro Anhydroglucose-Einheit, zeigten die umgekehrte Reihenfolge C-4 〉 C-3 〉 C-2. Dieses Ergebnis ist vermutlich auf intramolekulare Wasserstoffbriicken Bindungen in Verbindung rnit sterischen Effekten zuriickzufiihren.
    Notes: The modification reaction of dextran with succinic anhydride using pyridine as catalyst and N,N-dimethylformamide/lithiumchloride system as solvent was studied. The structure of the resulting polymers was determined by means of 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on succinic anhydride concentration was found. The orders with respect to pyridine and polymer concentrations were 1 and 2, respectively. The activation energy was found to be 69.0 kJ/mol. 13C NMR spectra at 75.4 MHz of partially modified dextran with monosuccinate groups were studied in order to evaluate the selectivity of the reaction of dextran with succinic anhydride in the homogeneous phase. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of individual hydroxy groups decreases in the order C-2 ∽ C-3 〉 C-4. For samples with higher degree of substitution the order is C-4 〉 C-3 〉 C-2. The results were explained by considering the formation of intramolecular hydrogen bonds as well as by steric considerations.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051940107
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