Determination and Differentiation of Two Seemingly Identical Medicinal Herbs by Capillary Electrophoresis with Electrochemical Detection

A high-performance capillary electrophoresis with electrochemical detection (CE-ED) method has been employed for the determination of six bioactive ingredients in traditional Chinese herbs, Herba cepbalanoplosis segeti and Herba cirsii japonici. The effects of several factors such as the acidity and concentration of running buffer, the separation voltage, the applied potential and the injection time on CE-ED were investigated. Under the optimum conditions, the six analytes could be well separated within 21 min in a 75 cm length capillary at the separation voltage of 15 kV in a 50 mmol L^–1 borax running buffer (pH 8.4). A 300 m diameter carbon disk electrode was used as the working electrode positioned carefully opposite the outlet of the capillary in a wall-jet configuration at potential of +950 mV (vs. SCE). Good linear relationship was established between peak current and concentration of analytes over two orders of magnitude with detection limits (S/N=3) ranged from 1.5×10^–7 to 6.0×10^–7 g mL^–1 for all six analytes. This proposed method has been successfully applied for the analysis of traditional Chinese herbs after a relatively simple extraction procedure, further on, for the differentiation of these above two seemingly identical herbs based on their electropherograms or characteristic electrochemical profiles.     

A new insight into the adsorption of bovine serum albumin onto porous polyethylene membrane by zeta potential measurements, FTIR analyses, and AFM observations

The mode of adsorption of bovine serum albumin (BSA) on porous polyethylene (PE) membrane was studied as a function of time and concentration, which may contribute to the surface coverage. An improved physical model for adsorption is initiated based on the results of the adsorptional and desorptional measurements, FTIR analysis, and AFM observations as well as streaming potential measurements. The results obtained indicate that the adsorptional mode depend on both time and concentration. It is shown that a critical concentration (about 1000 ppm here) exists in the adsorptional process. Below this concentration, the adsorption seems to be conducted in a normal side-on way but time elapse gives rise to greater conformational change than concentration increase; above this concentration, the aggregation of protein molecular plays a decisive role and the adsorption is in an aggregation way, which is similar to end-on, but a relative large gap between the adsorbed molecules exists due to aggregation. This conclusion is general and can be expected to apply in other globular protein-hydrophobic porous surface systems.     

Interesting fluorescence properties of C60-centered dendritic adduct with twelve symmetrically attached pyrenes

A C60-centered dendritic adduct with 12 symmetrically attached pyrene species was synthesized and found to have relatively simple fluorescence emission kinetics, in particular, the mono-exponential decay of the significant pyrene excimer emission.     

K-Mo基催化剂的表面酸性与其合成醇选择性

对500℃和800℃焙烧制得的氧化态K－MoO3／γ－AlO3，K－MoO3／SiO2及非负载K－Mo催化剂进行硫化后，测试其合成醇活性．结果表明500℃焙烧制得的负载型催化剂显示较高的合成低碳烃活性和较低的合成低磷醇选择性，经800℃焙烧后，合成低磷醇的选择性大幅度提高．500℃焙烧的非负载K－Mo催化剂显示较高的合成醇选择性，经800℃焙烧后，促碳醇的选择性保持不变．用氨的吸附及TPD方法测定了各样品的酸性，并与催化剂活性对照，发现催化剂酸性越强，酸量越大，则其合成醇选择性越低．催化剂上的乙醇分解实验证实，催化剂的酸量大小与它的醇分解活性成正变关系，这些结果说明催化剂酸性对其合成醇性能有直接的影响．     

Effects of antimony on the surface tension of molten silicon

The effect of antimony concentration (C(Sb)/mass%) on the surface tension of molten silicon has been determined with the sessile drop method in the temperature range from 1693 to 1773 K and in the range of the oxygen partial pressure, Po(2), in an Ar atmosphere from 10(-23) to 10(-21) MPa. The results show that the surface tension of molten silicon decreases with increasing Sb concentration in the range of C(Sb)<0.9 mass%, which indicates positive adsorption of Sb in molten silicon and can be fairly described with the Szyszkowski's equation. The maximum decrease rate of surface tension is about 65 mN m(-1) (mass% C(Sb))(-1), and the temperature coefficient of surface tension, (partial differential sigma/ partial differential T)C(Sb), increases with increasing C(Sb). The evaporation of the systems was only observed between the melting points of antimony (904 K) and silicon (1683 K), and the surface tension presents no dependence on measuring time above the melting point of silicon.     

Metal/oxide interfacial reactions: Oxidation of metals on SrTiO3 (100) and TiO2 (110)

We studied chemical reactions between ultrathin metal films (Al, Cr, Fe, Mo) and single-crystal oxides (SrTiO3 (100), TiO2 (110)) with X-ray photoelectron spectroscopy (XPS). The work function of the metal and the electron density in the oxide strongly influence the reaction onset temperature (T(RO)), where metal oxidation is first observed, and the rate of metal oxidation at the metal/oxide interfaces. The Fermi levels of the two contacting phases affect both the space charges formed at the interfaces and the diffusion of ionic defects across the interfaces. These processes, which determine metal oxidation kinetics at relatively low temperatures, can be understood in the framework of the Cabrera-Mott theory. The results suggest that the interfacial reactivity is tunable by modifying the Fermi level (E(F)) of both contacting phases. This effect is of great technological importance for a variety of devices with heterophase boundaries.     

稀土电解槽的研究现状及发展趋势

综述了国内外稀土电解槽的类型和特点,国内在稀土电解槽的电场、磁场、流场、熔盐性质、工艺条件、电阻常数以及电解槽的热平衡和电极材料等方面的研究现状。提出了槽电压与结构参数之间的关系以及结构参数的优化设计方法,根据槽容量进行优化设计可显著降低槽电压,达到节能降耗的目的。     

一类新的毛细管气相色谱固定液—侧链液晶冠醚聚硅氧烷的研究

合成了一种新的毛细管气相色谱用固定液——侧链含冠醚液晶的聚硅氧烷,这种固定液易于涂渍在弹性石英毛细管柱上,柱效高,热稳定性好,极性中等,它具有高分子液晶和高分子冠醚固定液的双重保留性能,适于分离多种异构体。     

甲基丙烯酸三苯墓甲酯和甲基丙烯酸酯类的共聚物在溶液中的螺旋诱导和解旋作用

甲基丙烯酸三苯墓甲酯和甲基丙烯酸酯类的共聚物在溶液中的螺旋诱导和解旋作用陈传福，刘卫宏，陈永明，任长玉，习复（中国科学院化学研究所北京１０００８０）关键词甲基丙烯酸三苯基甲酯，甲基丙烯酸甲酯，光学活性，螺旋诱导，解旋在手性阴离子复合引发剂存在下，甲基...     

A denitrogenative palladium-catalyzed cascade for regioselective synthesis of fluorenes

We herein report a denitrogenative palladium-catalyzed cascade for the modular and regioselective synthesis of polysubstituted fluorenes. Hydrazone facilitates the Pd(ii) to Pd(iv) oxidative addition in a Catellani pathway and is also the methylene synthon in the proposed reaction. Aryl iodides and 2-bromoarylaldehyde hydrazones undergo a norbornene-controlled tandem reaction sequence to give a broad scope of fluorenes in the presence of a palladium catalyst. The method described is scalable and adaptable to a three-component reaction with in situ generation of the hydrazone group. Preliminary mechanistic investigations have been conducted.

Hydrazone assists Pd(ii)/(iv) oxidative addition and is the methylene synthon in a palladium-catalyzed, norbornene-mediated regioselective synthesis of fluorenes.