水煤气变换反应的微观动力学分析──Cu基催化剂上H_2S中毒失活原因的 Monte Carlo 模拟研究

用ＢＯＣＭＰ方法及ＭｏｎｔｅＣａｒｌｏ模拟技术，对Ｈ２Ｓ导致Ｃｕ基催化剂失活的原因进行了计算分析。研究结果表明，当原料气中存在Ｈ２Ｓ时，ＷＧＳ反应的活化能明显高于无Ｈ２Ｓ时的活化能，随着表面Ｈ２Ｓ浓度的增大（θ＝０，０．１０，０．２５），反应的活化能也逐渐变大（其大小比为１∶１．３４∶３．３），究其原因可归结为Ｈ２Ｓ的存在使得反应物分子的吸附热减小，从而使Ｈ２Ｏ的解离吸附（ＷＧＳ反应的速控步骤）活化能增大。     

Ab initio studies on reaction H2C=C(OH)Li+CH3 + (CH3 -)

The possible structures and isomerizations of H₂C=C(OH)Li are studied theoretically by the gradient analytical method at RHF/6-31+G level. According to these results, reactions of H₂C=C(OH)Li with CH₃ ⁺ and CH ₃ ^- are investigated thoroughly. When H₂C=C(OH)Li reacts with CH ₃ ⁺ , H_zC=C(OH)Li firstly changes from structure1 to structure4, and then combines with CH₃ ⁺. In this reaction, the configuration of central carbon is retained. When H₂C=C(OH)Li reacts with CH ₃ ^- , structure1 firstly breaks its C-O bond to give contact ion-pair. Then through transition state16 which is similar to structure2, the attack of CH ₃ ^- from the opposite side of^-OH replaces^-OH group and inverts the configuration of carbenoid carbon atom. All the results show that the ambident reactivity of carbenoid has close relationship with the stability of special structures. Project supported by the National Natural Science Foundation of China (Grant No. 29773025).     

A Restudy of Direct Chelatometric Titration of Vanadium(IV) with N-Benzoyl-N-phenylhydroxylamine as Indicator

This paper restudies the method of direct chelatometric titration of V(IV) with N-benzoyl-N-phenylhydroxylamine (BPHA) as indicator. The indicator functions entirely differently from indicators hitherto used in chelatometry. The solution contains two independent systems – the indicator and the titrand-titrant system – without any color changing species. The BPHA-V(V) chelate once formed as the result of aerial oxidation constitutes the indicator system and does not react with EDTA. Its color therefore remains unchanged throughout titration. It is not a metallochromic indicator. Its function is that of color-screening. The color of the titrant system deepens during titration, but does not change. The end-point is indicated by one color completely covering up the other. Hence, this method is of purely empirical nature.Received July 5, 2002; accepted February 11, 2003 Published online July 16, 2003     

The Role of Carnitine Acyltransferases in the Maintenance of Cell Function

Summary. Carnitine acyltransferases catalyse equilibria between acyl-CoA esters and the respective acylcarnitines. Therefore, they act not only as pathway enzymes, but also as modulators of acyl-CoA concentrations within individual sub-cellular compartments. Because acyl-CoA esters are potent biologically active metabolites, carnitine acyltransferase activities are potentially able to affect a diverse range of physiological processes, ranging from insulin secretion, to appetite control, and insulin sensitivity of tissues. The distinctive subcellular distributions of the different types of carnitine acyltransferases also enables them to participate in the transfer of acyl moieties across intracellular membranes, and of particular acylcarnitine esters across the plasma membrane and into the plasma. Pharmacological strategies that make use of these properties to improve cell function are discussed.     

Syntheses and Properties of Two Heterocyclically Substituted Hypericin Derivatives: 10,11-Dibenzothiazolyl-10,11-didemethylhypericin and 10,11-Dibenzoxazolyl-10,11-didemethylhypericin

Summary. The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1).     

反相微乳液法制备棒状羟基磷灰石纳米粒子

在(Tritonx-100 Tween 80)，环己烷，(正己醇 正丁醇)，0．5mol／L Ca(NO3)2水溶液反相微乳液体系中，采用滴加0．3mol／L(NH4)2HPO4水溶液的加料方式成功制备出直径在20～25nm，长度在28～64nm的棒状羟基磷灰石纳米粒子。通过对(Triton X-100 Tween 80)，环己烷，(正己醇 正丁醇)／0．5mol／L Ca(NO3)2水溶液三元相图及水溶液反应机理的分析，确定了最佳反相微乳液组成；研究了HLB值和表面活性剂用量对羟基磷灰石颗粒大小的影响。实验结果表明，最佳反相微乳液组成为：47．6(wt)％的环己烷、37．4(wt)％的表面活性剂和助表面活性剂、15(wt)％0．5mol／L的Ca(NO3)2水溶液。     

Investigation of the species-specific degradation behaviour of methylmercury and ethylmercury under microwave irradiation

The degradation behaviour of methylmercury (MeHg) under microwave irradiation is investigated, as is the (different) degradation behaviour of ethylmercury (EtHg) under similar irradiation. A simple and highly sensitive SPME-GC-pyrolysis-AFS system was used to analyse the aqueous MeHg and EtHg standard solutions after derivatization with sodium tetraphenylborate (NaBPh₄). Samples were irradiated in a microwave digester at microwave powers ranging from 20 to 160 W for durations of 2 to 10 min. The different tolerances towards microwave treatment of the two organomercury species were evident. Practically no degradation was experienced for MeHg for up to 8 minutes of irradiation at 120 W or for up to 4 minutes at 160 W. Significant analyte loss was observed for EtHg after 2 minutes at 40 W of microwave power. Awarded a Poster Prize on the occasion of the European Winter Conference on Plasma Spectrochemistry, February 2005, Budapest, Hungary     

Electrochromic and structural characteristics of mesoporous WO<Subscript>3</Subscript> films prepared by a sol-gel method

The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tungstic hexaethoxide precursors with the addition of an organic stabiliser via a sol-gel method is reported. These films have been structurally characterised and both the film morphology and crystalline composition of the films were found to be significantly dependent on the temperature at which the films were annealed and upon the choice of precursor. Films annealed at lower temperatures consisted of amorphous and hexagonal tungsten trioxide, whereas films annealed above 500 °C comprised solely of monoclinic WO₃. The electrochromic activity of the films was found to be equally dependent on method of preparation, and both the composition and the structure of the WO₃ films were shown to clearly influence the colouration efficiency of the films.Dedicated to Zbigniew Galus on the occasion of his 70^th birthday.     

Neighboring amide group participation in ester aminolysis in aprotic solvents

The piperidinolysis of 8-quinolyl-, p-nitrophenyl-, o-, and p-piperidinocarbonylphenyl acetates in acetonitrile and in chlorobenzene was studied at 25°C. The strictly second order kinetic behaviour and the weaks solvent-dependence of the rate of the reaction of o-piperidinocarbonylphenyl acetate indicate anchimeric assistance by the o-amide group, and support the suggestion that amide groups of hydrophobic enzyme active sites may act as general base catalysts.

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Improved selectivity and detection limit of the carbonate-selective electrode

The properties of the carbonate neutral carrier 4-( n-hexadecyl)-3-nitro-1-trifluoroacetylbenzene were compared with those of a similar carrier, without a nitro group, studied previously. In spite of differences in the Hammett constant of the carbonyl group responsible for interaction with the analyte, the analytical characteristics of both carriers, measured under the same conditions, were comparable. Special care was taken to avoid the presence of an excessive carbon dioxide level in the diffusion layer at the membrane-solution interface. The internal reference solution was prepared without carbonate components; the external solution was protected from contact with atmospheric carbon dioxide. Under such conditions the detection limit of both electrodes was extended to 10(-11 )mol L(-1), and the selectivity towards salicylate, chloride, and acetate was significantly improved.