Numerical method of non-isothermal curve analysis by means of electrical resistance measurement during cooling

The temperature-dependence of the electrical resistance of Al-Zn 78 wt.% was measured during linear cooling of the samples in the range of eutectoidal decomposition. The resulting resistancevs. temperature curves were analysed by:

deriving the temperature-dependence of the volume fractionx(T) of theη precipitate;

fitting the theoretical functionx(T)=x _h (T)+x _c (T) following from numerical integration of the reaction rate equations for the simultaneously occurring homogeneous (H) and cellular (C) precipitation processes.

As a result, the activation energiesE _h andE _c , the JMA exponentsn _h andn _c , the rate constantsk _h andk _c , and the critical temperaturesT _o of the two processes were estimated.     

呼出气体酒精含量探测器检定的注意事项

介绍呼出气体酒精含量探测器的工作原理和国家标准对使用探测器的要求,为确保探测器有效准确的量值溯源,采用呼出气体酒精含量探测器自动检测系统进行检定。该系统能够解决标准气体不易保存和定值容易发生改变的难题,同时控制吹气压力,保证探测器采样的一致性,并列举了检定操作时应注意的问题和细节。     

复合酶酶解假酸浆黄酮苷抗氧化性研究

本文研究了复合酶酶解前后假酸浆提取物的抗氧化活性能力,并采用薄层色谱法(TLC)对酶解产物中总黄酮进行了分离,利用高效液相色谱-质谱联用技术对其鉴定分析。通过对DPPH自由基、羟自由基及超氧阴离子自由基清除能力实验,酶解液抗氧化性能显著高于假酸浆提取液;酶解液的薄层及HPLC-MS法初步鉴定出假酸浆中含有桑色素、二氢槲皮素和儿茶素三种黄酮。     

Immobilized cobalt/rhodium heterobimetallic nanoparticle-catalyzed silylcarbocylization and carbonylative silylcarbocyclization of 1,6-enynes

Reaction of 1,6-enynes with a hydrosilane in the presence of immobilized cobalt/rhodium bimetallic nanoparticles gives 2-methyl-1-silylmethylidene-2-cyclopentanes in the absence of carbon monoxide and 2-formylmethyl-1-silylmethylidene-2-cyclopentanes under 1 atm of carbon monoxide, respectively. [reaction: see text]     

Uniform hierarchical silica film with perpendicular macroporous channels and accessible ordered mesopores for biomolecule separation

Herein, we demonstrate that silica films with perpendicular macroporous channels and accessible ordered mesopores can be conveniently prepared. The hierarchical macroporous–mesoporous silica films are synthesized by using zinc oxide nanorod array as macroporous template and CTAB surfactant as mesoporous template. In basic surfactant-containing solution, ordered mesoporous silica shells homogeneously grow on the zinc oxide nanorod array. The growth of the mesostructures do not require any chemical modification for the zinc oxide nanorod, which opens a new way for preparing hierarchical silica films with perpendicular mesochannels. The prepared hierarchical macroporous–mesoporous silica films possess a uniform thickness of 2 mm, large perpendicular macropores with a length of 1.8 mm and a width of 80 nm, and accessible ordered mesopores. Separation experiment demonstrates that this macroporous–mesoporous film can effectively separate biomolecules with different sizes.     

Synthesis of Anthracene Derivatives with Azaacene-Containing Iptycene Wings and the Utilization as a Dopant for Solution-Processed Organic Light-Emitting Diodes

Substituted acene derivatives are regarded as promising materials for organic electronic devices such as organic light-emitting diodes (OLEDs). In particular, anthracene derivatives are known to exhibit good fluorescence property, with the air stability and solubility in common organic solvents expected to give advantages for solution-processed device fabrication. In this study, a series of bistriisopropylsilyl(TIPS)ethynyl anthracene derivatives with azaacene-containing iptycene wings have been synthesized by using condensation reactions. Effects of size of azaacenes on optical properties and packing structures were investigated. UV/Vis absorption and fluorescence spectra indicate that the π-elongation of iptycene units has small effects on the overall π-system, which is also supported by electrochemical measurements. Secondly, single-crystal X-ray analysis implies that the molecules likely have interactions with the iptycene units of adjacent molecules, while the iptycene wings and TIPSethynyl groups can prevent the central anthracene unit from undesirable non-radiative energy loss. Finally, the most emissive derivative was used as a dopant for solution-processed OLEDs, showing obvious electroluminescence with a luminance of over 920 cd m⁻².     

真空蒸馏预富集-电感耦合等离子体发射光谱法测定铂

建立了真空蒸馏预富集-电感耦合等离子体发射光谱法测定铅试样中微量铂的方法.在真空条件下,利用Pb和Pt在较高温度下蒸汽压的差别进行分离,富集后的铂溶解制成溶液后进行电感耦合等离子体发射光谱检测,实现了真空密闭回收铅.针对试样的特点,对真空蒸馏方法理论上的可行性进行研究.结果表明:在蒸馏温度为1250 K,真空度为30 Pa,蒸馏时间为3 h条件下,铂的富集分离效果最好,可富集至99.01%以上.线性范围为0.023～20 mg/L,检出限(3σ)为0.0069 mg/L,对样品测定的相对标准偏差为1.7%(n=6).用本方法对样品中加入的铂标准溶液进行了测定,回收率为99.8%～103.0%.本方法简便快速、无污染,已应用于废电路板贵金属冶余物料中铂的测定.     

Preparation of MoO3/Pt electrodes by electrodeposition for a direct methanol fuel cell

MoO₃/Pt binary catalysts with various Mo/Pt ratios were prepared by an electrodeposition method for use as the anode in a direct methanol fuel cell. Pt was electrodeposited onto indium tin oxide (ITO) substrate, and then MoO₃ was electrodeposited from an Mo-peroxo electrolyte on the top of Pt with different deposition times. The crystallinity of synthesized films was analyzed by X-ray diffraction (XRD), and the oxidation state of both the platinum and molybdenum were determined by X-ray photoelectron spectroscopy (XPS) analyses. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM/EDS) was employed to investigate the surface morphology and composition. The catalytic activity and stability for methanol oxidation were measured using cyclic voltammetry and chronoamperometry in a mixture of 0.5 M H₂SO₄ and 0.5 M CH₃OH aqueous solution. Electrocatalytic activity for CO oxidation was also evaluated in a 0.5-M H₂SO₄ solution. The addition of a proper amount of MoO₃ was found to significantly improve both the catalytic activity and stability for methanol oxidation.     

水分子通道蛋白的结构与功能

水分子穿越双磷脂生物膜的输运机理是生理学和细胞生物学中一个长期未能解决的重要问题.AQP1水通道蛋白的发现和鉴定使得人们确认出一个新的蛋白质家族--水通道蛋白家族.正是这一蛋白家族的存在,使得水分子可以进行快速的跨膜传输.由晶体学方法解出的哺乳动物AQP1水通道蛋白的原子结构,最终揭示了水通道蛋白只允许水分子快速传输而阻挡其他的小分子和离子(包括质子H+)的筛选输运机理.本文概述了水通道蛋白的发现和其对水分子的筛选传输机理.