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Thomas C. Amu 《Journal of solution chemistry》1981,10(1):69-78
Interdiffusion coefficient have been measured for 1,1,2,2-tetrabromoethane in 21 organic solvents in order to ascertain the influence of shape, size, viscosity, nature and degree of branching, of the solvent molecules on transport properties. None of the existing correlations for diffusion in binary liquid systems appear to fit all the experimental data. Steric effects due to the solvent molecules are shown to be very important in the interpretation of the diffusion process. 相似文献
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D. Giron P. Remy S. Thomas E. Vilette 《Journal of Thermal Analysis and Calorimetry》1997,48(3):465-472
The amorphous state of solids is characterized by a higher chemical and physical reactivity and a hygroscopic behaviour. Furthermore processing of amorphous powders is often difficult, because of the instability. Fast crystallizations, precipitations and milling favour the formation of the amorphous state. Galenical processes like granulation, drying, lyophilization, mixing, may also induce amorphous regions in the drug products.X-ray diffraction techniques can be used for the determination of the amorphicity of drug raw materials or drug products. Unfortunately, 10% is the detection limit, which in normal cases can be attained. Amorphous substances undergo an exothermic crystallization at temperatures above the glass transition point. Water which is a plasticizer decreases the temperature of the glass transition point, allowing the crystallization to occur at lower temperatures. The crystallization energy is measure of by microcalorimetry.Examples show the influence of the choice of the experimental conditions, especially the influence of the amorphicity on the kinetic of the reaction. Critical steps are discussed for three different drug substances. Limits of detection in the magnitude of 1 % are possible using microcalorimetry. 相似文献
109.
The 1D- and 2D-6Li, 6Li-INADEQUATE experiments are described as new tools for the detection of scalar coupled nonequivalent 6Li nuclei in organolithium clusters. Practical applications of these sequences are demonstrated for the 6Li-NMR spectra of (E)-1-lithio-2-(2-lithiophenyl)-1-phenylhex-1-ene ( 1 ) and (E)-2-lithio-1-(2-lithiophenyl)-1-phenylpent-1-ene ( 2 ), where signals due to dimers and monomers can be distinguished. The performance of the 2D-6Li, 6Li-INADEQUATE and the 6Li, 6Li-COSY-45-LR experiment are compared. The 6Li chemical shifts of 1 and 2 are discussed. 相似文献
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This paper describes basic studies of the surface modification of polyimide covered wires for insulation of electrical machines. Drain-off of the impregnating resin during production should be reduced by introduction of surface catalytic groups. 1H NMR kinetic analysis of aminolytic ring opening reaction of low molecular model compounds for polyimides showed very fast modification reactions. The catalytic effect of various functional groups on unsaturated polyester imide, acrylate and epoxy resins was investigated by DSC. Co(II)-catalysts and tertiary aliphatic amines proved highest activity for double bond containing systems and epoxy resins, respectively. Aminolytic treatment of Kapton® slides was followed by ATR-IR spectroscopy. Plate-plate rheometer measurements of epoxy resins employing tertiary amine-treated Kapton® slides proved significantly reduced gelling temperature. 相似文献