Film electrode for the kinetic study of irreversible solid-to-solid reactions

Journal of Solid State Electrochemistry - In the last twenty years, direct electro-reduction of solid oxides in molten salt has been investigated extensively. Compared with thermodynamics, kinetics...     

Synthesis of Atomically Thin Boron Films on Copper Foils

Two‐dimensional boron materials have recently attracted extensive theoretical interest because of their exceptional structural complexity and remarkable physical and chemical properties. However, such 2D boron monolayers have still not been synthesized. In this report, the synthesis of atomically thin 2D γ‐boron films on copper foils is achieved by chemical vapor deposition using a mixture of pure boron and boron oxide powders as the boron source and hydrogen gas as the carrier gas. Strikingly, the optical band gap of the boron film was measured to be around 2.25 eV, which is close to the value (2.07 eV) determined by first‐principles calculations, suggesting that the γ‐B₂₈ monolayer is a fascinating direct band gap semiconductor. Furthermore, a strong photoluminescence emission band was observed at approximately 626 nm, which is again due to the direct band gap. This study could pave the way for applications of two‐dimensional boron materials in electronic and photonic devices.     

Protection against DNA damage and inhibition of lipid peroxidation by flavones from Eremosparton songoricum (Litv) Vass

Seven flavonoids were isolated from Eremosparton songoricum (Litv) Vass and their antioxidation actions were examined. To investigate protective ability against DNA damage induced by H₂O₂, human peripheral blood mononuclear cells (PBMCs) were incubated with 5-hydroxy-7,4′-dimethoxyflavone,5,7-dihydroxy-3′,4′-dimethoxyflavone, acacetin, chrysoeriol, pedalitin, flavogadorinin and 5,7,4′-trihydroxy-3′-methoxyflavone-4′-O-D-glucoside separately and then treated by H₂O₂. The percentage of damaged cells were determined by single-cell gel electrophoresis. To examine their inhibition of lipid peroxidation, the compounds were incubated with rat microsomes and the reaction was initiated by Fe²⁺/Vc. The lipid peroxidation product thiobarbituric acid reactive substances (TBARS) was determined. The result showed most of flavonoids had concentration-dependent antioxdative activities. The relationship of antioxidation and the structure is discussed.     

一类包含多元Logistic分布的多元分布

采用 Ali 等人的方法模拟了一类包含第Ⅰ型多元 Logistic 分布的多元分布。考虑了这类多元分布的一些分布特征,尤其是解决了这类分布函数的识别性问题。     

The extraction of trivalent actinides and lanthanides by a novel unsymmetrical diglycolamide

Journal of Radioanalytical and Nuclear Chemistry - N,N′-dioctyl-N,N′-di-dodecyl-3-oxapentane-1,5-diamide ((DdO)2DGA) is a novel unsymmetrical diglycolamide. Herein, we analyzed the...     

Development of a strategy and process parameters for a green process in counter-current chromatography: purification of tanshinone IIA and cryptotanshinone from Salvia miltiorrhiza Bunge as a case study

A strategy for the development of a green process using counter-current chromatography technology is presented in this paper. The strategy began with solvent system selection, followed by linear scale-up from an analytical to a preparative process with optimized operating parameters. A two-stage separation using a multi-injection method was performed with a solvent system of hexane-dichloromethane-methanol-water (4:0.75:4:1) for the 1st stage and a hexane-ethanol-water (4:2:2) for the 2nd stage. A 191.8 mg of tanshinone IIA was purified, with a 97% purity and 34.4% recovery and a 276.7 mg of cryptotanshinone was separated, with a 95% purity and 31.8% recovery from 2.1g of crude extract. Process parameters (throughput, efficiency, environmental risk factor and general process evaluation) and mass factors (mass intensity, separation mass efficiency and greenness) of a target were developed for monitoring of the counter-current chromatography process.     

Sonochemistry-assisted microwave synthesis and optical study of single-crystalline CdS nanoflowers

Well-defined flower-like CdS nanostructures have been synthesized by applying ultrasound and microwave simultaneously, which consist of hexagonal nanopyramids and/or nanoplates depending on different sulfur sources. It is shown that the synergistic effect of microwave and sonochemistry is the main mechanism for the formation of the nanoflowers. Optical characterization of the nanoflowers shows a large blue-shift up to 100 nm in comparing with simple low-dimensional CdS nanostructures. This structure induced shift in optical properties may have potential applications in optoelectronics devices, catalysis, and solar cells.     

A new method for stress analysis of a cyclically symmetric structure

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混合分布的识别性及其应用

设(Y_1,Y_2)是非负的二维随机变量,有联合分布函数F(y_1,y_2),设Z=min(Y_1,Y_2),定义随机变量I=1;2;3,分别对应于Y_1Y_2;Y_1=Y_2时.记p_i=P(I=i),f_i(·)为给定I=i时Z的条件密度(i=1;2;3).给定可识最小值(Z,I)的联合密度函数P_iJ_i(·)(i=1;2;3),得到F(·,·)是混合分布时,F(·,·)用P_if_i(·)来表示的一个显式表达式.对三维及以上情形,得到类似的结果.特别,把识别基本定理应用于多元Marshall-Olkin型指数分布的参数估计,得到了基于观察值(Z_jI_j)(j=1,2,…,n)的参数的极大似然估计及矩估计,并且证明了极大似然估计具有联合完备充分的,渐近无偏的,均方误差一致的,及渐近正态性特性,修正估计恰好是Arnold估计,它是唯一的一致最小方差无偏估计,且同时是渐近有效估计,本文还指出了矩估计方法的不唯一性.     

单细胞水平的分析方法研究及进展

本文评述了近年来单细胞分析的应用及进展，介绍了超微电极电化学分析法和微柱分离法两大类方法在单细胞分析中应用的机理、必要的技术、有关研究内容和最新进展及其发展方向。