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891.
Bola型阴离子表面活性剂与溴化十二烷基三乙铵混合体系的表面性质与聚集行为 总被引:7,自引:0,他引:7
研究了具有简单结构的bola型阴离子表面活性剂二十酸二钠(C_(20)Na_2)与 阳离子型普通表面活性剂溴化十二烷基三乙铵(C_(12)Et_3)混合体系的表面性质 ,发现混合体系的cmc和γ_(cmc)比C_(12)Et_3单一体系未有显著降低。以负染色 ,FF-TEM,动态光散射(DLS)及粘度方法研究了混合体系的聚集行为,发现混合 体系中同时形成球形囊泡和管状聚集体,提出了产生这种聚集行为的机制。 相似文献
892.
Precise determination of d-spacings and compositional ratio of cellulose Iα and Iβ in various native cellulose samples was successfully carried out by synchrotron-radiated X-ray diffraction and time-of-flight
(TOF) neutron diffraction from quasi-powder specimens. X-ray diffraction peaks were separated by the deconvolution method
using six types of profile function: Gaussian, Lorentzian, intermediate Lorentzian, modified Lorentzian, pseudo-Voigt, and
Pearson VII. In terms of R-factors, the pseudo-Voigt function gave the best fit with the observation, and was used for determination
of d-spacings. The numerical results for Valonia cellulose were: dIα (1 0 0) = 0.613 nm; dIβ (1 1 0) = 0.603 nm; dIβ (1 1 0) = 0.535 nm; dIα (0 1 0) = 0.529 nm; Iα content = 0.65. The differences determined between dIα (1 0 0) and dIβ (1 1 0) and between dIβ (1 1 0) and dIα (0 1 0) were similar to those previously reported. Comparison between unresolved peaks for the two types of cellulose samples
revealed a small but definite difference between dIα (1 1 0) and dIβ (2 0 0). The TOF neutron diffractometry using deuterated samples confirmed this difference.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
893.
M. R. Castellar M. A. Taipa J. M. S. Cabral 《Applied biochemistry and biotechnology》1997,61(3):299-314
A kinetic study ofChromobacterium viscosum lipase was undertaken, and compared withPseudomonas glumae lipase. Optimum operation conditions were pH 9.0 and 50°C for both enzymes. A substrate specificity study was also developed. Both enzymes showed higher activity on triglycerides with a long chain of fatty acid; the specific activity was always higher for C.viscosum lipase. Stability of both enzymes in aqueous medium at 60°C and pH 9.0 was evaluated. C.viscosum lipase was three times more stable than P.glumae lipase, with at 1/2 value of 0.75 h. In addition, the activity of C.viscosum lipase with substrate concentration was studied with a triolein emulsion. A dependence of the intrinsic characteristics of the emulsion was observed. Therefore, stability ofC. viscosum lipase B with reaction products was assayed in a micellar system. Acid products reduced the specific activity of the enzyme. Glycerol and high buffer concentration were stabilizers of enzyme deactivation. Finally, substrate specificity ofC. viscosum lipase B in a micellar system was developed with tributyrin, tricaprylin, and triolein. Only tributyrin showed an apparent Michaelis-Menten kinetic with Vmax app = 958 U/mg and Kma app = 75.5 mM. Tricaprylin and triolein showed diffusion limitations at low substrate concentration and substrate inhibition at high substrate concentration. Diffusion parameters were calculated for both these substrates. Mass transfer coefficients (k1) were 0.314 Å/min and 1.53 Å/min for tricaprylin and triolein, respectively. Effectiveness factors (η) were 0.536 and 0.768 for tricaprylin and triolein, respectively. 相似文献
894.
HU Xiangqian & LI Lemin State Key Laboratory of Rare Earth Materials Applications College of Chemistry Molecular Engineering Peking Universit Beijing China 《中国科学B辑(英文版)》2004,47(6):453-465
The compounds containing transition metals orother heavy elements play important roles in chemistry.They possess diverse properties which have been util-ized in numerous functional materials. Some of theseproperties are also involved in biological processes.However, it is very difficult to study these compoundsdeeply by means of quantum chemical methods, be-cause in these systems usually there are a large amountof electrons, the distribution of the frontier orbitals isdense, the correlation be… 相似文献
895.
The solid-liquid equilibria of the quasi-quaternary system H2O-Zn(NO3)2·6H2O-Cu(NO3)2·3H2O-NH4NO3 were studied at 25°C by using a synthetic method based on conductivity measurements. Three isoplethic sections has been established at 25°C and the stable solid phases which appear are: NH4NO3(IV), Zn(NO3)2·6H2O, anhydrous Cu(NO3)2, Cu(NO3)2·3H2O and metastable Cu(NO3)·2.5H2O. Neither double salts, nor mixed crystals are observed at these temperatures and composition range. 相似文献
896.
This work is a part of the systematic study of the ternary based chalcogenides systems. The aim is to determine the phase
equilibrium, and to determine the limits of the phase area. This is done in view to perfecting knowledge of elaboration conditions
for new materials and to study of their physical properties.
Few works have been devoted to the study of the ternary system Se-Te-Sn, only the cross section SnSe-SnTe has been studied
[1] and [2].
The experimental study by DTA, DSC and X-ray diffraction on powder performed at room temperature, exhibits a miscibility gap
in the liquid state which narrows as it goes through the Sn-Se binary system.
Three cross sections behave as ‘quasi-binary‘ system and six ternary invariants have been exhibited: three ternary eutectics
and three ternary quasi-peritectics.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
897.
稀土萃取分离过程自动控制研究现状及发展趋势 总被引:9,自引:2,他引:9
在简要描述稀土萃取分离生产过程的基础上,综述了目前国内外稀土萃取分离过程中稀土元素成分在线检测的方法、装置及其应用现状;稀土串级萃取分离生产过程的计算机流程模拟以及稀土萃取生产过程的自动控制方法、技术及其应用现状.指出了稀土元素组分含量的软测量方法,以综合生产指标为目标的稀土萃取分离生产过程优化控制方法以及由生产过程管理系统和过程控制系统两层结构组成的稀土萃取分离生产过程综合自动化系统已成为稀土萃取分离生产过程自动化未来发展的方向. 相似文献
898.
The binary system Li2Se-In2Se3 was investigated in the range of 40 to 100 mol% In2Se3 by thermoanalytical and X-ray methods. The system is characterized by two eutectic points. Beside the two binary components
and the known ternary compound LiInSe2 another ternary compound crystallizes in this binary system at 83.3 mol% In2Se3. This compound was identified as LiIn5Se8. In contrast to (Cu, Ag)IB5
IIIC8
VI compounds such as CuIn5S8 [1] it does not crystallize in the spinel structure. LiIn5Se8 shows a stratified structure. The melting point was determined to be at 810°C. Starting from room temperature up to the melting
point no phase transitions were observed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
899.
Xiuhua Hao 《Tetrahedron letters》2005,46(15):2697-2700
In a fluorous biphase system, Hf[N(SO2C8F17)2]4 complex (1 mol %) catalyzes Friedel-Crafts acylation of aromatic compounds such as anisole, toluene and chlorobenzene, and the corresponding aromatic ketones are obtained in satisfactory to high yields. The catalyst is selectively soluble in lower fluorous phase and can be easily recovered by simple phase separation. Furthermore, the catalyst can be reused without decrease of activity in most cases. 相似文献
900.
Oxygen Atom Adsorption and Diffusion on Pd Low-index Surfaces and (311) Stepped Surface 总被引:2,自引:0,他引:2
Introduction Atom adsorption on transition metal surfaces has attracted special attention as a base for understanding the fundamental processes of oxidative catalysis. Particularly interesting is the adsorption and diffusion of oxygen on well-defined metal surfaces. An oxygen covered palladium surface, for example, plays a central role in several important reactions such as oxidation of carbon monoxide and ammonia. In particular, the (100), (111), (110) surfaces and the interactions with oxyge… 相似文献