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  • Chemistry  (35)
  • Physics  (14)
  • 1990-1994  (20)
  • 1980-1984  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1817-1827 
    ISSN: 0887-624X
    Keywords: polymer blends ; hydrogen bonding ; miscibility ; phase behavior ; equilibrium constants ; hexafluoroisopropanol groups ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dimensionless equilibrium constants describing the self-association of the hexafluoro-2-alkyl-2-propanol group have been determined from infrared spectroscopic data. Corresponding values of these equilibrium constants for a fully modified polyisoprene containing the hexafluoroisopropanol group (PHFPI) were calculated by taking into account differences in the molar volume of the model and the specific repeat unit of the polymer. Equilibrium constants describing the inter-association of PHFPI with methacrylate, acrylate, and acetoxy type carbonyl groups were obtained from spectroscopic studies of miscible PHFPI blends with poly(n-butyl methacrylate), poly(methyl acrylate), and an ethylene-co-vinyl acetate copolymer containing 70 wt% vinyl acetate. The set of equilibrium constant values were then used to calculate theoretical miscibility windows for the complete range of PHFPI blends with poly(n-alkyl methacrylate)s and four copolymers, ethylene-co-methyl methacrylate, styrene-co-methyl acrylate, ethylene-co-methyl acrylate, and ethylene-co-vinyl acetate. Experimental infrared studies confirm the general validity of the predicted miscibility windows. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1189-1193 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 2039-2056 
    ISSN: 0887-624X
    Keywords: blends ; hydrogen bonding ; miscibility ; phase behavior ; equilibrium constants ; fluoropolymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical calculations of miscibility windows for binary polymer blends in which one component is an essentially alternating copolymer of tetrafluoroethylene and vinyl alcohol (FVOH) are reported. FVOH has an inherently low solubility parameter [≈ 6.2 (cal. cm-3)0.5] that is outside the range commonly encountered in miscible polymer blends and thus represents a stringent test of the predictive capabilities of an association model we have used in previous work. The application of this model requires that we determine dimensionless equilibrium constants describing the self-association of a model compound 3,4-pentafluorobutan-2-ol (PFB) at 25°C from infrared spectroscopic data. Analogous equilibrium constants for FVOH were scaled from those of PFB by taking into account differences in the molar volume of the model and the specific repeat of the copolymer (see M. M. Coleman, J. F. Graf, and P. C. Painter: Specific Interactions and the Miscibility of Polymer Blends, Technomic, Lancaster, PA, 1991). Equilibrium constants describing the inter-association of FVOH with ester type carbonyl groups were obtained from spectroscopic studies of miscible blends with poly(ethyl methacrylate). These equilibrium constant values were then used to calculate theoretical miscibility windows for the complete range of blends of FVOH with polymethacrylates, ethylene-co-methyl acrylate, styrene-co-methyl acrylate, and ethylene-co-vinyl acetate copolymers. Experimental results performed in our laboratories confirm the general validity of the predicted miscibility windows. © 1993 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 24 (1982), S. 1773-1788 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alcohol dehydrogenase has been covalently attached to the surfaces of nylon stir rods. Several rod types have been evaluated in terms of their mixing efficiency and enzyme loading. Fluorometric monitoring of the rate of conversion of NAD to NADH serves as a measure of the reaction rate under varying conditions. The rate of reaction of the enzyme stir rods has been evaluated in terms of RPM, buffer concentration, NAD reagent concentration, and pH. The rate of reaction is seen to reach a plateau at higher stir rates, indicating a lack of diffusional hindrances. The reaction rate also begins to level off at phosphate buffer concentration of 0.1M to 0.15M. Saturating conditions are reached at an NAD concentration of 2.5mM. The optimum pH is found to be 9.0. The Stability of the covalent bond between the enzyme and the nylon has been assessed by comparing the bond strength to the energies of various disruptive forces to which the enzyme is exposed. Centrifugal, drag, and shear forces are shown to be insufficient to cause rupture of the bond. The stability to the immobilized enzyme preparation has been investigated under varying conditions of immobilization and use. No effect on activity loss was found for rotation rate or for continuous versus intermittent use. It was found that enhanced stability occurred for hydrolytic cleavage of the nylon, using nitric acid, as compared to nonhydrolytic cleavage. Hydrolytic cleavage also led to some degree of adsorption of the enzyme to the surface of the nylon. Thus, the possibility of increased stability to multipoint attachment of the enzyme is discussed. Possible cause of activity loss are discussed, as well as the extension of the enzyme stir rod to use in scale model reactor studies.
    Additional Material: 7 Ill.
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 316-322 
    ISSN: 0899-0042
    Keywords: chiral LC ; drug enantiomers ; modelling ; central composite desire ; optimization ; β-cyclodextrin ; response surface ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of a central composite design to the enantiomeric separation of the antifungal drug tioconazole is investigated. The design involves application of a mathematical model to the data to model the response in regions of the factor space not investigated in the experimental design. The significance of the variable terms in the model is assessed statistically and those terms declared not significant are removed from the model. The statistical adequacy of these reduced models is discussed, together with an examination of the prediction errors of the models. Three-dimensional predicted response surfaces for the complete models are presented and the predictive performance assessed. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 500-509 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Methods are presented for the construction of optimal and suboptimal estimators for inferential control systems. Optimal estimators are constructed with the aid of Kalman filtering techniques applied to linear systems driven by integrated white noise disturbances. The description of the disturbances as integrated white noise leads to optimal dynamic estimators which reduce to optimal static estimators for sustained disturbances. Suboptimal estimators are constructed by prespecifying the structure of the estimator and choosing estimator parameters so as to minimize the mean square error in estimation.Optimal and suboptimal estimators are compared by using them in an inferential control system which attempts to control the product composition of a simulated multicomponent distillation column. There is little difference in performance between optimal and suboptimal estimators which use temperature and flow measurements to estimate product composition. However, the inferential control system using a simple suboptimal estimator is significantly superior to the policy of maintaining a selected tray temperature constant through a standard feedback control system. The inferential control system is also superior to composition feedback control systems where the measurement delay is greater than 5 min.
    Additional Material: 9 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 485-492 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Methods are presented for the design of a static estimator which infers unmeasurable product qualities from secondary measurements. The secondary measurements are selected so as to minimize the number of such measurements required to obtain an accurate estimate which is insensitive to modeling errors. Unlike previous work, the number of secondary measurements can be fewer than the number of unmeasured disturbances. If the statistics of the disturbances and/or measurement noise are available, this information can be incorporated into the design procedure to obtain an optimal static estimator.The design procedure is illustrated by application to a simulated industrial debutanizer. Data for the simulation were supplied by the Marathon Oil Company. Deviations in bottoms product quality are compared for the current control policy (maintenance of a stage temperature at its set point) and the inferential control system with the column subjected to representative feed composition disturbances. Results show that inferential control based on four, five, or six tray temperature measurements improves the steady state control performance by as much as 400%.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 492-500 
    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 static estimator of part I is incorporated into a dynamic control system. The system structure minimizes output feedback and thereby achieves stability even in the event of significant modeling errors. This inherent stability permits the use of simple and economical lead-lag compensation for the estimator and controller portions of the system. The overall system response to disturbances is similar to that of feed-forward control systems.The proposed control system structure is used to infer and control the overhead and bottoms product compositions of a simulated multicomponent distillation. Product compositions are inferred from selected stage temperature and process flow measurements. Inferential control system response to various disturbances is comparable or superior to that of a tuned composition feedback control system for both single product control and for simultaneus overhead and bottoms product control.
    Additional Material: 11 Ill.
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interactions between mononucleoside and dinucleoside phosphates containing adenine and/or cytosine and L-tryptophan have been studied at low pD by proton magnetic resonance (pmr) spectroscopy. The results of those studies indicate that, despite extensive protonation of ring positions, and resulting electrostatic repulsion, ring stacking does occur between both like and unlike molecules. Geometries for stacked complexes are proposed and the extent of complex formation between L-tryptophan and adenosine or cytidine in 3′ or 5′ esterified positions is discussed qualitatively.
    Additional Material: 6 Ill.
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