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81.
The heterogeneous bulk polymerization of acrylonitrile initiated by AIBN has been studied by means of an improved dilatometric technique and a new method of analysis, where the initial reaction rate (vw)0 results from the intercept of a straight line in a \documentclass{article}\pagestyle{empty}\begin{document}$ \frac {\ln \left( 1 \hbox{---} {\rm U} \right)} {{\rm e}^{{- 0,5} {\rm k}_{\rm s}{\rm t} \hbox{---} 1}}$\end{document} versus t plot. It has been found that the initial reaction rate is proportional to the square root of the initial catalyst concentration S0. The ratio of the rate coefficients of propagation and termination\documentclass{article}\pagestyle{empty}\begin{document}$\frac { {\rm k}_{\rm a} } { {\rm k}_{ {\rm w}^{2} } } $\end{document} could be calculated from the slope of a straight line passing through the origin in a plot of (vw)0 versus \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt { {\rm S}_{0} }$\end{document} and yielded a value of 280 mol 1?1. 相似文献
82.
Dieter Braun Manfred Rtzsch Peter Fiedler Günter Weber Heinz Hofmann Bernd Gutschalk 《大分子材料与工程》1991,187(1):101-121
Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?w = 1.2 ? 390·104 g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?n, M?w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties. 相似文献
83.
84.
High-Strength Zirconia Fibers 总被引:1,自引:0,他引:1
David B. Marshall F. F. Lange Peter D. Morgan 《Journal of the American Ceramic Society》1987,70(8):187-C
Fine-grained polycrystalline zirconia fibers have been formed from an acetate precursor. The fibers contained a Y2 O3 additive, which inhibited grain growth (grain size ≤0.5 μm) and allowed the tetragonal phase to be retained at room temperature. Fibers with diameters in the range 2 to 5 μm had strengths in the range 1.5 to 2.6 GPa. 相似文献
85.
Biosynthesis of the aldehydic sex pheromone components released by females ofHeliothis zea was found to be catalyzed by primary alcohol oxidases residing in the cuticle that covers the glands. Activity, as indicated by conversion of primary alcohol to aldehyde, was as high in cell-free cuticle as it was in intact pheromone glands. Studies indicated that some activity was associated with the surface of the epicuticle and could be removed, into buffer, by sonication. However, the majority of activity lies within the inner epicuticle and exo- and endocuticular layers. The oxidase was not functional in pharate pupae that did not have mature adult cuticle but became functional just prior to adult emergence. The enzyme in individual glands was saturated at alcohol concentrations above 100 n. moles. Nonionic detergents did not affect the activity of the oxidase in the cuticle but treatment with either 7 M urea or 1% SDS resulted in total loss of activity. Studies on the effect of pH indicated an optimum at 6.4; however, activity was high throughout the range of 5–9. The oxidase was functional in both dichloromethane and hexane, suggesting that this enzyme system may have applications for organic synthesis of aldehydes. 相似文献
86.
Peter Kalustian 《Journal of the American Oil Chemists' Society》1985,62(2):431-433
The pharmaceutical and cosmetic industries are large and still growing. New products, astute marketing and sophisticated advertising
have been very effective in these industries. They are more and more exacting and highly complex in their requirements. They
require specification products with specific performance characteristics.
The cosmetic industry and drug or pharmaceutical industries are defined. Information is given about the unique composition
of palm and lauric oils which make them suitable raw materials for use in these applications.
These two base oils are used in the form of triglycerides, whole fatty acids, fractionated fatty acids or fatty chemical derivatives.
Information is given about these various ingredients, their use in specific cosmetic and pharmaceutical products and reasons
for their use.
Particular use is made of palmitic, stearic, myristic and short-chain fatty acids. The derivatives would include glycerine
esters, monostearates, other monoglycerides, propylene glycol esters, polyglycerol esters, sorbitans and sorbitan ethylene
oxide products, isopropyl palmitic and myristate. Specific powdered stearins and cocoa butter substitutes are used in various
formulations.
The production and marketing of ingredients for this industry are natural growths of the developing fatty acid industry in
Malaysia and nearby countries of southeast Asia. 相似文献
87.
Optical microscopy is widely used in the characterization of coals and cokes. This Paper shows that the laser Raman microprobe (MOLE) which combines an optical microscope and a Raman spectrometer can provide useful additional information. Three main areas were investigated: identification of minerals in coal and coke; structural characterization of coals and cokes; and the interaction of inorganic additives and coal. Where possible, the results were compared with conventional optical microscopy measurements whereby it was shown that the optical texture and Raman spectra of cokes are not closely related. The Raman spectra of high temperature cokes were used to estimate the size of microcrystalline regions. 相似文献
88.
子午线轮胎出现不久,就采用钢丝带束层代替了纤维带束层,这对于实现子午线轮胎提高使用寿命和改善操纵性能的潜能是必要的。 相似文献
89.
This paper presents a simplified method for the chemical synthesis of cholest-4-en-3-one, which is a naturally occurring steroid
and a salient intermediate in steroid chemistry. Pyridinium chlorochromate (PCC) in refluxing benzene has been found to be
an effective and convenient reagent for the oxidation and concomitant isomerization of cholest-5-en-3β-ol (cholesterol) to
cholest-4-en-3-one in high yield. Also described are the carbon-13 nuclear magnetic resonance spectral properties of cholest-4-en-3-one
and of the isolated reaction intermediate cholest-5-en-3-one.
Based on a paper presented at the Symposium on Plant and Fungal Sterols: Biosynthesis Metabolism and function held at the
AOCS Annual Meeting, Baltimore, MD, April 1990. 相似文献
90.