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991.
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993.
Experimental investigation of the LiAlSi2O6‐MgSiO3 and LiAlSi2O6‐CaMgSi2O6 isopleths at 1 atm 下载免费PDF全文
The phase diagrams of the LiAlSi2O6‐MgSiO3 and LiAlSi2O6‐CaMgSi2O6 isopleths were experimentally investigated at 1 atm using the quenching method and differential scanning calorimetry and the phases produced were characterized with the help of X‐ray diffraction and electron probe microanalysis. With the help of thermodynamic optimization, the phase diagrams of both systems were more accurately reported. No detectable solubility of Li2O in diopside and enstatite was found. However, both systems are not simple binary eutectic systems because their phase equilibria are somewhat complex due to the presence of some β‐spodumene solid solution. In the β‐spodumene solid solution, no notable solubility of MgO and CaO was detected; evidence of significant solubility of SiO2 was confirmed. 相似文献
994.
Regioselectivity and fatty acid specificity of crude lipase extracts from Pseudozyma tsukubaensis,Geotrichum candidum,and Candida rugosa 下载免费PDF全文
995.
Resveratrol formulated with a natural deep eutectic solvent inhibits active matrix metalloprotease‐9 in hormetic conditions 下载免费PDF全文
996.
AbstractThe article explores the suburban infrastructure reality at a global scale. It does so by acknowledging both the wide diversity of suburban forms across the world and the existence of common features that warrant the apprehension of suburbs as a unified object of study. Due to their rapid growth rate and an insufficient infrastructure development response, suburbs are perceived as more severely afflicted by infrastructure tensions than other urban sectors. They thus provide an ideal object of study to identify urban infrastructure shortcomings in the present age. At the same time, by virtue of their infrastructure difficulties and ongoing expansion, suburbs can be seen as a foremost source of infrastructure innovation. 相似文献
997.
Pierre Hansen Marcus V. Poggi de Aragão Celso C. Ribeiro 《Annals of Mathematics and Artificial Intelligence》1990,1(1-4):97-109
An intelligent front-end or logic assistant is an interactive program devised to assist the users of an information retrieval system in the formulation of their queries. In order to provide knowledge usable in such a program, we study a problem of query optimization with an average efficiency criterion. We formulate it as a new combinatorial optimization problem, which we call 0-1 hyperbolic sum, and provide an exact branch-and-bound algorithm and two heuristics (of simulated annealing and tabu search type) to solve it. Computational experience illustrating the effectiveness of the tabu search technique is reported.This research was done in part during a visit of the first author to the Pontifical Catholic University of Rio de Janeiro in July and August 1987, sponsored by CNPq. It was also supported in part by grants 0271 and 0066 of AFOSR to Rutgers University. 相似文献
998.
Homogeneous and Heterogeneous Hydrogenation of Nitriles in a Liquid Phase: Chemical, Mechanistic, and Catalytic Aspects 总被引:2,自引:0,他引:2
Primary or alkylated amines are important chemicals and intermedi-ates. N-Alkylamines are used without further transformation as surface-active agents. Aliphatic primary diamines polymerize with aliphatic diacids to give linear polyamides which have conquered a large place in textile and mechanical industry [11. Mono- and polyamines are produced by catalytic hydrogenation of the corresponding nitriles [2]. In particular this pathway to hexamethylenediamine has been made easier since the synthesis of adi-ponitrile by hydrocyanation of butadiene was made possible [3]. The spec-ifications for production of amines are often very drastic from the point of view of purity, in particular for the diamines used in the textile industry. Thus the stress is put on selectivity of the reaction and most of industrial processes have a yield approaching stoichiometry. It exists few reviews on reduction of nitriles [4, 51, the literature dealing with this type of reaction being mostly published in patents [6-91, and practical knowledge is at the state of “know-how” [lo]. Up to now, two types of processes have been used industrially for the 相似文献
999.
EtOH/ETBE azeotropic mixture was separated by pervaporation through films of polyurethaneimides (PUI), i. e., alternating block copolymers varying in their structure only by their oligomeric soft blocks. Pervaporation performances strongly depend on the flexible segments: fluxes on the molecular weight and selectivity towards ethanol on the chemical structure in the decreasing order: PEG, PCL, PCD, PTMG, PPG. In order to correlate selectivity with segment polarity, a new solvatochromic polarity probe that was well soluble in PUI was synthesized. Using 13 solvents covering a wide polarity range, Vis λmax of the photochromic indicator open form was linearly correlated with the ET(30) polarity scale. By illumination of the dissolved dye, PUI polarity was investigated in relation to soft segment nature and size. The very high PUI polarity values and their splitting for highest size segments were assigned to preferential probe solvation by interblock urethane junctions combined with phase segregation. Polarity values consistent with the chemical structure of the flexible segments were provided by similar measurements on suitably end-capped precursors of these segments and were then linearly correlated with the related PUI pervaporation selectivity. © 1995 John Wiley & Sons, Inc. 相似文献
1000.
Isabelle Henry Jean‐Pierre Pascault Mohamed Taha Grard Vigier Jean‐Jacques Flat 《应用聚合物科学杂志》2002,83(2):225-233
Precursors of polyurethane acrylate based on hydroxy‐terminated polybutadiene (HTPB) soft segments, different diisocyanate and hydroxy ethyl acrylate (HEA) as hard units, were synthesized in bulk or in solution in methyl methacrylate. During precursor synthesis (in bulk), microphase separation was observed by small‐angle X‐ray scattering (SAXS). Diffusing particles are around 50 Å in size and are assumed to be assembling of hard segments. From these morphologies, it can be deduced that some isocyanate groups were trapped/or buried in hard domains. At a larger scale, around millimeters, hard segment crystallites were observed. Properties such as molar masses, melting and glass‐transition temperatures, and viscosities were correlated with precursor structure and morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 225–233, 2002 相似文献