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  • Chemistry  (19)
  • 2005-2009
  • 2000-2004
  • 1995-1999  (19)
  • 1935-1939
  • 1999  (1)
  • 1997  (18)
  • 1
    Electronic Resource
    Electronic Resource
    Resonant microwave power absorption in slabs and cylinders (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 615-624 
    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: Resonant power absorption is an important phenomenon during microwave heating. The resonances that occur when plane electromagnetic waves are incident on infinitely long cylinders and slabs are investigated as a function of sample dimensions. For cylinders two kinds of incident waves are studied: TMz when the electric field is oriented along the axis of the cylinder and TEz when the magnetic field is oriented along the axis. At a resonant condition the overage power absorbed by the sample is a local maximum. Due to attenuation within the sample the resonances decrease in intensity as the sample size increases. Using the dielectric properties of water, resonances are found to be a function of the ratio of the sample dimension to the wavelength of radiation, λs, in the sample. For slabs of thickness L and integer values of n, resonances occurred at L/λs = 0.5n; for cylinders of diameter D, resonances occurred at D/λs = 0.5n - 0.257. The generality of these relations to predict resonances in other food samples are shown using existing dielectric data. Resonances in cylinders for both polarizations occurred at similar radii. However, the radius at which the first resonance occurred for the TMz case was absent in the TEz case.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430307
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  • 2
    Electronic Resource
    Electronic Resource
    Design and characterization of thermosetting polyimide structural adhesive and composite matrix systems (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2943-2954 
    Details
    ISSN: 0887-624X
    Keywords: phenyl ethynyl ether imides ; amorphous or semicrystalline morphology ; volatile free thermosetting matrix ; structural adhesives ; composites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fully cyclized, organo soluble, phenylethynyl-terminated, ether-imide oligomers of 2-10,000 g/mol (Mn) were prepared by the reaction of 2,2′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-propane dianhydride (bisphenol-A dianhydride, BPADA) with a stoichiometric excess of either para, meta, or isomeric mixtures of phenylene diamine and phenylethynylphthalic anhydride (4-PEPA) endcapper. High para-containing oligomers produced semicrystalline powders, but the all meta isomer was completely amorphous. The lower molecular weight oligomers displayed an attractive low viscosity melt and were cured to very high gel content networks at 350-380°C for 30-90 min. The cured 3000 g/mol oligomers showed a (DSC) glass transition temperature (Tg) of 267°C and produced tough, solvent-resistant films. Excellent adhesion to surface-treated titanium alloys was achieved, as judged by single-lap shear measurements. Resin infusion molding was conducted, which permitted low-void, graphite-fabric composite panels to be prepared. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2943-2954, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Catalytic chain transfer for molecular weight control in the emulsion homo- and copolymerizations of methyl methacrylate and butyl methacrylate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 859-878 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of catalytic chain transfer in semi-batch emulsion polymerization has been studied for two monomers, viz, methyl and n-butyl methacrylate. Two different catalytic chain transfer reagents were used with different water solubilities: cobaloxime boron fluoride (COBF), which was found to partition approximately equally between organic and aqueous phases, and tetra-phenyl cobaloxime boron fluoride (COPhBF), which was found to reside predominantly in the organic phase. The difference in hydrophilicity between the two transfer agents was found to affect the polymerization mechanism. COBF exhibited superior transfer behavior in all cases, whereas the restricted mobility of the COPhBF had a deleterious effect on the efficiency of the transfer mechanism. The best results were achieved under monomer flooded conditions using COBF. MALDI-TOF mass spectrometry analysis shows catalytic chain transfer to be the dominant mechanism initiating and stopping chain growth as none of the chains appear to have initiator fragment end groups. Analysis of copolymers by MALDI-TOF mass spectrometry reveals both molecular weight and composition data. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 859-878, 1997
    Additional Material: 21 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of solvent on the homo-propagation rate coefficients of styrene and methyl methacrylate (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 2311-2321 
    Details
    ISSN: 0887-624X
    Keywords: styrene ; methyl methacrylate ; pulsed-laser polymerization ; “living” free radical ; propagation rate coefficient ; solvent effects ; benzyl alcohol ; N-methyl pyrrolidinone ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The free radical propagation rate coefficients of both Methyl Methacrylate (MMA) and Styrene (STY) have been measured using Pulsed-Laser Polymerization. The effect of solvents on the propagation rate coefficient, kp, is reported for several solvents, namely, bromobenzene, chlorobenzene, dimethyl sulphoxide, diethyl malonate, diethyl phthalate, benzonitrile, and benzyl alcohol, at 26.5°C. This preliminary data indicated that benzyl alcohol (BzA) had a large effect on the MMA propagation reaction. As earlier work indicated that N-methyl pyrrolidinone (NMP) would also have a large effect on the kp of MMA, Arrhenius parameters were evaluated for both MMA and STY at two different concentrations of monomer in BzA and NMP. BzA had a significant effect (at 95% confidence) increasing both the activation energy (Ea) and the preexponential factor (A) for MMA and STY. In NMP, a similar trend is observed for MMA polymerization; however, while a solvent effect on STY was observed, the effect on Ea and A was too small to discern with confidence. A series of additional experiments was performed to evaluate the influence of camphorsulfonic acid (CSA) as an additive in STY polymerization. There was no effect of CSA on kp, confirming that the strong effect CSA has on “living” radical polymerization of styrene does not originate from complexation leading to an accelerated propagation step but rather by altering the ratio of active-to-dormant chains in the reaction. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2311-2321, 1997
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Permeation studies on oriented single-crystal ferrierite membranes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 83-90 
    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: Large, high-quality, single crystals of pure-silica ferrierite are synthesized, and the structure is described. Selected individual crystals (approximately 600 μm X 500 μm X 20 μm) are mounted in a membrane configuration so that only the 10-membered-ring channels (5.4 Å X 5.4 Å X 4.2 Å) or the 8-membered-ring channels (4.6 Å X 3.7 Å X 3.0 Å) are accessible for gas-molecule permeation. The first examples of transport exclusively through 8- or 10-membered-ring channel systems are reported and obtained through crystal orientation in the membrane. A series. of adsorption experiments are conducted to help select suitable probe molecules and evaluate the role of adsorption in the permeation process for single-crystal membranes. Methane, n-butane, isobutane and nitrogen probe molecules are used to study intracrystalline sorption and transport effects for different crystal orientations, pressures and temperatures. Both pure-gas selectivities and mixed-gas separation factors are reported. A mixed-gas separation factor of n-butane/isobutane = 116 for the 10-membered-ring orientation of the crystal at 383 K and a transmembrane pressure difference of 1.01 X 105 Pa are found using this technique. In addition, molecular sieving is observed for the 8-membered-ring orientation of the crystal since methane, but not butane, transport is observed for this crystal orientation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430111
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  • 6
    Electronic Resource
    Electronic Resource
    A Novel Sensitive Colorimetric Assay for Visual Detection of Solid-Phase Bound Amines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2787-2791 
    Details
    ISSN: 1434-193X
    Keywords: Solid-phase peptide synthesis ; Disperse Red 1 ; p-Nitrophenyl ester ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new simple and efficient method for the detection of incomplete coupling reactions during solid-phase peptide synthesis is decribed. Using p-nitrophenyl ester 1 (NF31), free amino groups can be visually detected on the resin by direct coloring of the beads. A specific feature of the assay resides in the possibility of detection of sterically hindered primary amines.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Modeling and optimization of a batch process for in vitro RNA production (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 210-220 
    Details
    ISSN: 0006-3592
    Keywords: ribonucleic acids ; transcription ; optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: RNA molecules are commonly produced in vitro by transcription, utilizing a DNA template, an RNA polymerase enzyme, and nucleoside triphosphate substrates (NTPs). In addition to the full-length RNA molecule coded for by the DNA template, significant amounts of shorter RNA molecules are produced. A simplified model of this complex transcription process is presented, with the shorter RNA molecules lumped into a single pool. The rate equations do not depend on the stoichiometry of the RNA molecule of interest, which facilitates application of the model to other RNA molecules. Optimal initial conditions for batch in vitro RNA transcription to produce a dodecamer RNA containing three different nucleotides have been predicted using the model. The predicted optimal values for equimolar NTPs are 10 to 15 mM initial concentration for each NTP and 50 to 60 mM for magnesium acetate, yielding a maximum final dodecamer concentration of 0.8 ± 0.1 mM at the 90% confidence interval. Experimental data agree well with the model results. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 210-220, 1997.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Critically evaluated rate coefficients for free-radical polymerization, 2.Part 1: cf. ref.1. Propagation rate coefficients for methyl methacrylate (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1545-1560 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Pulsed-laser polymerization (PLP) in conjunction with molar mass distribution (MMD) measurement is the method of choice for determining the propagation rate coefficient kp in free-radical polymerizations. The authors, members of the IUPAC Working Party on Modeling of kinetics and processes of polymerization, collate results from using PLP-MMD to determine kp as a function of temperature T for bulk free-radical polymerization of methyl methacrylate at low conversions and ambient pressure. Despite coming from several different laboratories, the values of kp are in excellent agreement and obey consistency checks. These values are therefore recommended as constituting a benchmark data set, one that is best fitted by \documentclass{article}\pagestyle{empty}\begin{document}$ k_p = 10^{6,427} {\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {\frac{{ - 22,36{\rm kJ} \cdot {\rm mol}^{ - 1} }}{{R \cdot T}}} \right) $\end{document}The 95% joint confidence interval for these Arrhenius parameters is also given. In so doing, we describe the most appropriate statistical methods for fitting kp(T) data and then obtaining a joint confidence interval for the fitted Arrhenius parameters. As well, we outline factors which impose slight limitations on the accuracy of the PLP-MMD technique for determining kp, factors which may apply even when this technique is functioning well. At the same time we discuss how such systematic errors in kp can be minimized.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980518
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  • 9
    Electronic Resource
    Electronic Resource
    Electrochemil investigation of the photodecomposition of selected ferrocene derivatives (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 650-652 
    Details
    ISSN: 1040-0397
    Keywords: Photodecomposition ; Ferrocene derivatives ; Cyclic voltmmetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photostability of nine ferrocene derivatives of varying functionality was investigated using cyclic voltammetry. Derivatives with carbonyl groups (aldehyde or ketone) directly attached to the cyclopentadiene ring system were found to decompose in aqueous (pH 7.4) solution over a period of 10 min when exposed to light. The kinetics of the photodecomposition process were investigated and the relative values of the rate constants for the photodecomposition tabulated. The implications for biosensor applications are assessed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140090816
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  • 10
    Electronic Resource
    Electronic Resource
    The Quest For Extra-Large Pore, Crystalline Molecular Sieves (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1745-1750 
    Details
    ISSN: 0947-6539
    Keywords: large-pore materials ; materials science ; molecular sieves ; zeolites ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The definition and reasons for desiring extralarge pore, crystalline molecular sieves are ennumerated. A historical perspective on the development of these materials is presented with emphasis on critical features important for practical application. Based on the known physiochemical properties of extra-large pore materials, several avenues for their synthesis are suggested. Finally, a few issues of concern when dealing with this class of materials are presented.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19970031104
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