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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1110-1121 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The dielectric behavior of glassy thermoplastic polymer in the microwave frequency range was investigated. Specifically, the relationship between energy absorption and temperature for several thermoplastic systems was examined to test the theoretical basis for heating under microwave irradiation. Irradiation under traveling and standing wave conditions were explored. The heating rate versus temperature data at a frequency of 2.45 GHz yielded a microwave calorimetry procedure for examination of the dielectric and relaxation behaviors. Correlations were drawn between (a) the apparent activation energy and the critical temperature, and (b) the shape of the dielectric spectra at 2.45 GHz and its shape in the kHz region. WLF relationships were examined for glassy thermoplastics to show the difference in changing activation energy with temperature.
    Additional Material: 17 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1092-1109 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The objective of this effort has been to investigate the relationship between polymer structure and microwave absorptivity. Dielectric loss factor, ε″, loss tangent, tan δ, and oscillator strength, (εS -- ε∞), were used to evaluate potential material processability under applied microwave radiation. Numerous polymeric materials varying in chemical and physical structures were irradiated in a low power (≤ 100W) electric field at 2.45 GHz. Electromagnetic radiation was applied as either traveling or resonant wave modes in cylindrical and rectangular waveguides. In general, heatability was found to be a direct function of the dielectric loss dispersion dependence on temperature and frequency. The dielectric loss factor obtained at low frequency measurements was found to be directly proportional to the heatability of polymers. A WLF plot was used to predict the shift of dielectric loss maxima into or out of the microwave frequency range.
    Additional Material: 19 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1122-1131 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: The overall objective of these studies was to investigate the relationship between polymer structure and microwave absorptivity. In this paper, the microwave processing of semicrystalline polymers such as poly(ether ether ketone) (PEEK), nylons, and poly(ethylene terephthalate) (PET), via a cylindrical resonance wave cavity and a rectangular standing wave applicator is described. These polymeric materials were irradiated in low power (〈 50W) electric fields at 2.45 GHz. Silicone flexible molds were necessary for improved processing of nylons and PEEK at temperatures below their Tc Rapid heating rates were observed between the glass transition temperature, Tg, and the melting temperature, Tm, for all these polymers provided that Tc was exceeded. Both dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA) spectra were utilized to predict the heating phenomena between amorphous and semicrystalline materials and to explain the rapid crystallizing rate of PEEK. above its glass transition temperature. Correlations were drawn between (a) the apparent activation energy and the critical temperature (Tc) and (b) the shape of the dielectric spectra at 2.45 GHz and its shape in kHz region.
    Additional Material: 15 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 269-272 
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An isotope dilution mass spectrometry method is described for determining chenodeoxycholic acid pool size in children. The stable isotopically labeled tracer. (11,12-2H2) chenodeoxycholic acid, was administered orally to children, and the enrichment of bile was measured by selected ion monitoring gas chromatography mass spectrometry. The level of (11,12-2H2) chenodeoxycholic acid enrichment found in the patient samples was in the range of 0.5 to 5%. Data are presented illustrating the duplication of this method in two independent laboratories using standard quadrupole mass spectrometers. This procedure provides the clinician with a non-radioactive method for determining chenodeoxycholic acid pool size which is especially beneficial in studies involving children and pregnant women.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 23 (1991), S. 197-202 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have performed a product and kinetic study of the hydrolysis of 3,4-diphenyl-1,2,5-thiadiazole-1,1-dioxide in aqueous solution. Benzil and sulfamide are the only products of hydrolysis and are formed in equimolar yields.The kinetic results indicate that a first order law is followed up to 90% conversion. The observed rate constant is independent of substrate concentration.Ionic strength and buffer concentration do not affect the rate constant, but the reaction is acid-base catalyzed. The rate-pH profile has been determined and a mechanism that fits the experimental data satisfactorily is proposed. Corresponding rate constants and equilibrium constants for the protonation of the substrate are reported.
    Additional Material: 1 Ill.
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  • 6
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular theories of rubberlike elasticity are surveyed, starting with the earliest attempts carried out in the 1930's and ending with work still very much in progress. The models are variously based on phenomenological arguments, affinely-deforming networks, phantom networks, constrained junctions, constrained chains, slip-links, molecular tubes, van der Waals concepts, or rotational isomeric chains. Most of the theories are analytical, but some involve computer simulations based on Monte Carlo methods. The theories are generally for networks of Gaussian chains, but there have been significant advances for non-Gaussian networks as well, and these are particularly important with regard to a better understanding of ultimate properties. The major outstanding problem on the theory side, however, seems to be a quantitative treatment of chain entanglements.There have also been numerous advances on the experimental side. These include preparation of model networks of known structure, accumulation of elasticity data for deformations other than the much-studied simple elongation, development of new characterization techniques (such as fluorescence polarization, and X-ray and neutron scattering), investigation of the phenomenon of gel collapse, borrowing of ideas from the area of bioelastomers, and preparation of novel reinforcing fillers.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1899-1908 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A microscope capable of measuring the CD of intact single eukaryotic cells, DNA microcrystals, and other microscopic structures has been constructed and tested. It can measure the CD spectra in the 200- and 800-nm wavelength range and consists of a modification to a standard Cary 60 CD machine in combination with a Zeiss uv microspectrometer. Preliminary CD spectra of red blood cells and lymphocytes are presented.
    Additional Material: 4 Ill.
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  • 8
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aggregation of filipin in aqueous medium and filipin-induced changes in cholesterol micelles have been studied using intensity and dynamic light scattering. The dependencies of filipin aggregate dimensions on concentration, solvent, and temperature were studied, and revealed that the aggregates do not have a well-defined geometry, i.e., a critical micelle concentration cannot be detected and stable structures are not formed. The aggregates are of size Rg ≈ 110 nm and Rh ≈ 63 nm, referring to the radius of gyration and hydrodynamic radius, respectively. In the concentration range studied (1 μM 〈 C 〈 30 μM), a low molecular weight species (monomer/dimer) is always present together with the aggregates. In ethanol/ water mixtures, large (Rg ≈ 500 nm), narrow distribution aggregates are formed in the water volume fraction range 0.45 〈 ΦH2O 〈 0.65. Aggregation also occurs on changing the temperature; In the range 7-37°C, smaller aggregates (10-30 nm) form and the process is only partially reversible.No pronounced effect of filipin on the structure of the cholesterol micelles was observed (a small increase in Rg and Rh is noted). These results rule out any “specificity” for the filipin interactions with cholesterol, which has been considered a key event in the filipin biochemical mode of action. A reevaluatiori Of this question is suggested and some alternatives are advanced. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 24 (1990), S. V 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1372-1378 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Polymer coatings are widely used to protect glass from indentation damage. A model for the strength degradation that occurs when a sharp indenter penetrates through the coating is developed by accounting for the indentation load shared by the coating and substrate. This model accounts for the additional load supported by the coating due to the pile-up of coating material underneath the indenter. The model predicts the strength degradation as a function of indentation load, coating and substrate hardnesses, and coating thickness. Comparison of the model to experimental data for a wide range of polymer coatings (two epoxies, epoxy acrylate, and urethane acrylate) on soda-lime glass substrates shows good agreement.
    Additional Material: 10 Ill.
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