Mechanochemical synthesis of the nanocrystalline semiconductors in an industrial mill

Nanocrystalline semiconductor particles MeS (Me = Pb, Zn, Cd, Cu) were successfully synthesized by the mechanochemical route from the corresponding metal acetates and sodium sulphide in an industrial eccentric vibratory mill. Structure properties of the as-prepared products were characterized by X-ray powder diffraction which reveals the crystalline nature of MeS nanoparticles. The methods of TEM, particle size analysis and low temperature nitrogen sorption were used to analyze particle morphology and surface area measurement. The average sizes of MeS particles at 4-18 nm were estimated by Scherrer's formula. The main advantage of the application of an industrial mill is that it is a “quantity” process permitting kilograms of material to be produced in an ambient temperature in a very short processing time.     

A numerical study of wave propagation and run-up in water channels

It is important to understand how water waves propagate through water channels in order to reduce inundation damages induced by surges and/or tsunami run-up. For this purpose, a two-dimensional numerical model is developed based on Nonlinear Shallow Water Equations. In order to appropriately describe the strongly nonlinear hydrodynamics, a high-order TVD scheme is implemented. Model capabilities are confirmed through comparison with existing analytical studies including the dam-break problems, run-up and back-wash on a sloping bathymetry. The model is then applied to the study on the inundation of bore propagating in a channel of parabolic cross-section from a side breach.

     

A study of mechanochemical reduction of lead sulphide by elemental iron on the surface by X-ray photoelectron spectroscopy

The mechanochemical reduction of lead sulphide with elemental iron in a high-energy mill was studied. X-ray photoelectron spectroscopy was used for characterization of obtained products of reduction. Elemental lead as well as its divalent forms were identified in the surface layer of products of mechanochemical reduction. The mechanochemical reduction of lead sulphide with elemental iron on the surface is a complicated reaction and the identification of compounds formed in the surface layer is not unambiguous.However, only 23% of elemental lead on the surface is produced. The degree of mechanochemical transformation in the surface layer is not very high under chosen conditions. Higher power input is needed for further progress of the reaction.     

Electron microscopy of actin rods and bundles in Dictyostelium discoideum by high-pressure freezing

A new type of actin rods comprising actin tubules appears in dormant spores of Dictyostelium discoideum. Occasionally, the rods in the nucleus were observed in an amorphous state using a combination of high-pressure freezing and freeze-substitutions. Also in the case of actin bundles formed in the nudeus of vegetative cells exposed to dimethyl sulphoxide, actin filaments seemed to be embedded in matrices. The karyoplasm of spores fixed by the above method appeared to be denser than that obtained by other methods. As soluble materials may be efficiently retained in the nucleus, actin tubules or actin filaments embedded in those materials may result in hazy images of actin rods and bundles.     

The role of lipids in heme synthesis

The effect of lipids on protoheme ferrolyase, which combines ferrous iron with protoporphyrin, was investigated. The enzyme extracted with 1% Na cholate from acetone-dried powder of chicken erythrocyte stroma showed high enzymic activity, while that extracted with 0.4 M KCl showed little activity. The former contained lipids, the main components of which were lecithin and phosphatidylethanolamine, whereas the latter contained little lipid. Crude lipids of several sources restored the enzyme activity of 0.4 M KCl extracts. The activating effects of purified lipids, especially phospholipids which showed the strongest activation, were further examined. Phospholipids were divided into three groups: the choline-containing group, lecithin and sphingomyelin, was inhibitory or slightly accelerative on heme synthesis; the acidic phospholipids, namely phosphatidylethanolamine, cardiolipin, phosphatidic acid and phosphatidylinositol, were strong activators and the intensity of activation was in the order of the acidity of the phospholipids; and the lysophospholipids, namely lysolecithin, lysophosphatidylethanolamine and sphingosylphosphorylcholine, activated the heme synthesis most effectively. In the presence of cholate, choline-containing lipids were highly effective, while acidic phospholipids were inhibitory and lysophospholipids were neutral. Palmitic acid showed slight stimulative effect. Tripalmitin was neutral or inhibitory. Anionic, cationic and neutral synthetic detergents were slightly stimulative in low concentration and inhibitory in high concentration. An activation mechanism of phospholipids was proposed in which the hydrophilic anionic part of lipid in the lipoprotein enzyme molecule attracts ferrous iron. After being stripped of solvation water, the ferrous iron is transferred to the hydrophobic part of the enzyme molecule to be inserted into porphyrin.     

电化学沉积生物陶瓷新方法

在钛基板上电沉积了致密的、结合良好的磷酸钙生产陶瓷膜。在55℃下使用含钙离子0．01mol/dm^3。磷酸根离子0.006mol/dm^3,NaCl浓度为0.145mol/dm^3的溶液，考察了添加H2O2的影响，无论使用H2O2与否，所得的沉积物均为羟基磷灰石（hydroxyapatite,AHp)，但是在使用H2O2时，阴极电位约为-0.2V(vsSCE)即开始有阴有电流，而且没有氢气析出。与此形成对照的是在不使用H2O2时，需要极化到－1．4V(vsSCE)才有阴极电流，并且伴随着大量氢气析出。H2O2显著增强了膜的结合。     

Qualitative reasoning with imprecise probabilities

This paper investigates the possibility of performing automated reasoning in probabilistic knowledge bases when probabilities are expressed by means of linguistic quantifiers. Data are expressed in terms of ill-known conditional probabilities represented by linguistic terms. Each linguistic term is expressed as a prescribed interval of proportions. Then instead of propagating numbers, qualitative terms are propagated in accordance with the numerical interpretation of these terms. The quantified syllogism, modeling the chaining of probabilistic rules, is studied in this context. It is shown that a qualitative counterpart of this syllogism makes sense and is fairly independent of the thresholds defining the linguistically meaningful intervals, provided that these threshold values remain in accordance with the intuition. The inference power is less than a full-fledged probabilistic constraint propagation device but corresponds better to what could be thought of as commonsense probabilistic reasoning. Suggestions that may improve the inferencing power in the qualitative setting are proposed.This paper is an extended and revised version of a paper entitled A Symbolic Approach to Reasoning with Linguistic Quantifiers inProc. 8th Conf. Uncertainty in Artificial Intelligence Dubois, D., Wellman, M.P., D'Ambrosio, B., and Smets, Ph. (Eds.), Morgan Kaufmann, pp. 74–82, 1992.     

Electrochemical studies of the reaction between titanium metal and titanium ions in the KCl-NaCl molten salt system at 973 K

The reaction between titanium metal and titanium ions in the KCl?NaCl molten salt system was investigated by means of electrochemical and physical methods at 973 K in an inert gas atmosphere (argon). It was found that the reaction between titanium metal and Ti³⁺ in the molten salts with TiCl₃ followed a simple reaction (I). However, in the case of the concentration of K₂ TiF₆ being higher than 2.7 mol % the reaction was (II); in the case of it being less than 0.8 mol %, reactions (III) and (III′) were followed. $$\begin{gathered} 2Ti^{3 + } + Ti = 3Ti^{2 + } (I) \hfill \\ 3Ti^{4 + } + Ti = 4Ti^{3 + } (II) \hfill \\ Ti^{4 + } + Ti = 2Ti^{2 + } (III) \hfill \\ 3Ti^{2 + } = Ti + 2Ti^{3 + } (III')(on cooling) \hfill \\ \end{gathered} $$ It was also found that these reactions were controlled by charge transfer and diffusion simultaneously.     

NaBH_4的水性还原法制备纳米铜颗粒(英文)

在碱性溶液中用NaBH4还原Cu2+制备纳米铜颗粒,研究NaBH4浓度和滴加速率对Cu纳米颗粒制备的影响。反应的最佳条件是:0.2mol/LCu2+,溶液pH12,温度313K,1%明胶作为分散剂,将0.4mol/LNaBH4溶液以50mL/min的速率加入CuSO4溶液中。氨水是最佳的络合剂。采用一系列实验研究不同时间点的反应进程。