离子辐照对聚苯乙烯低温导电特性的影响

室温下用 3MeV的硅离子对聚苯乙烯 (PS)进行辐照 ,对辐照后的样品在室温至液氮温度范围的导电特性进行了测量 .结果表明 ,当辐照剂量在 1× 10 1 2 cm- 2 附近 ,PS的室温电阻发生突变 .随着温度的降低 ,PS电阻增大 ,在低辐照剂量下 ,电阻在 15 5K附近急剧增加 .对于高辐射剂量样品 ,在较高的温度下呈现热激活导电 ,在低温下电子通过隧穿传导 .分析认为 ,PS电阻随温度的变化是由于不同剂量辐照离子在聚合物中形成的对电子传导有贡献的导电中心密度不同 .通过拟合样品的渗流临界特性 ,分析了样品电阻随辐照剂量的变化

Rotamers of m-aminophenol cation studied by mass analyzed threshold ionization spectroscopy and theoretical calculations

The vibrationally resolved spectra of selected rotamers of m-aminophenol have been recorded by mass analyzed threshold ionization spectroscopy in connection with two-color resonant two-photon excitation scheme. The adiabatic ionization energies of the cis and trans rotamers are 61460 +/- 5 and 61734 +/- 5 cm(-1), respectively. The frequencies of modes 1 (breathing) and 18a (in-plane CH bending) are measured to be 744 and 1097 cm(-1) for the cis, and 736 and 1104 cm(-1) for the trans rotamer, respectively. This indicates that different orientation of the OH with respect to the NH2 substituent only slightly influences these two modes. (C) 2004 Elsevier B.V. All rights reserved.

不同时间尺度径流对植被变化的响应

植被覆盖对陆地生态系统的水分循环起着重要作用。径流对植被变化在不同时间尺度的响应研究,对区域生态环境建设及水资源管理具有重要的参考价值。该文介绍基于对比流域法,在多年平均、年际、季节等不同时间尺度径流对植被变化响应的研究结果。多年平均尺度上,由植被类型更替引起的径流绝对变化量,湿润区较干旱区大,其相对变化量在干旱区严重;年际尺度上,因植被变化,径流从一种平衡状态到另一种平衡状态的响应时间因抚育措施和地区不同而不同,造林情况下,湿润地区一般需要15~20 a,干旱地区约需25 a甚至更长,森林自然恢复情况下则需要上百年;季节尺度上,径流对植被变化的响应在季风影响区较四季湿润地区强烈。流量历时曲线研究表明,干旱地区造林,其基流无论在量或发生概率的变化上均较湿润区强烈。

A novel alcohol dehydrogenase biosensor based on solid-state electrogenerated chemiluminescence by assembling dehydrogenase to Ru(bpy)(3)(2+)-Au nanoparticles aggregates

Based on electrogenerated chemiluminescence (ECL), a novel method for fabrication of alcohol dehydrogenase (ADH) biosensor by self-assembling ADH to Ru(bpy)(3)(2+) -AuNPs aggregates (Ru-AuNPs) on indium tin oxide (ITO) electrode surface has been developed. Positively charged Ru(bpy)(3)(2+) could be immobilized stably on the electrode surface with negatively charged AuNPs in the form of aggregate via electrostatic interaction. On the other hand, AuNPs are favourable candidates for the immobilization of enzymes because amine groups and cysteine residues in the enzymes are known to bind strongly with AuNPs. Moreover, AuNPs can act as tiny conduction centers to facilitate the transfer of electrons. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate, and it displayed wide linear range, high sensitivity and good stability.

稀土铽离子对辣根过氧化物酶活力指数的影响

The effect of Tb3+ ion on the Activity Index (RZ=A403/A275) of HRP was investigated by a combination of ultraviolet-visible, FT-infrared and X-ray photoelectron spectroscopic techniques. It was found that Tb3+ ion could bond to the O and/or N group of the amides in the polypeptide chains of HRP, leading to a decrease in the enzymatic activity index of HRP.

Organic white-light-emitting devices based on a multimode resonant microcavity

Organic white-light-emitting devices ( OLEDs) based on a multimode resonant microcavity defined by a pair of dielectric mirrors and metal mirrors were presented. By selective effects of the quarter-wave dielectric stack mirror on mode, white light emission containing three individual narrow peaks of red, green and blue was achieved, and showed weak dependence on the viewing angle. The Commission Internationale De L'Eclairage ( CIE) chromaticity coordinates changed from ( 0.29, 0.37) at 0 degrees to ( 0.31, 0.33) at 40 degrees. Furthermore, the brightness and electroluminescence efficiency of the microcavity OLEDs were enhanced compared with noncavity OLEDs. The maximum brightness reached 1940 cd m(-2) at a current density of 200 mA cm(-2), and the maximum current efficiency and power efficiency are 1.6 cd A(-1) at a current density of 12 mA cm(-2) and 0.41 1m W-1 at a current density of 1.6 mA cm(-2), which are over 1.6 times higher than that of a noncavity OLED.

Electrocatalytic oxidation of ascorbic acid by ferrocene in lipid film cast on a glassy carbon electrode

A ferrocene-dimyristoyl phosphatidylcholine (DMPC) film electrode was prepared by casting the solution of ferrocene and DMPC in chloroform onto a glassy carbon electrode surface. Ferrocene retained in the biological membrane gave a couple of irreversible peaks of cyclic voltammogram. The electrode exhibited good electrocatalytic activity for the oxidation of ascorbic acid (H(2)A) in phosphate buffer (pH 6.64) with an anodic peak potential of +340 mV (vs. Ag/AgCl). The anodic current was directly proportional to the square root of the scan rate below 150 mV s(-1). The influence of the pH value was investigated and it was observed that pH 6.64 was the suitable value to the anodic peak potential and current. The thickness of the film and the interference of uric acid were also studied. The electrode can be used to determine H(2)A in the presence of equimolar uric acid. The catalytic peak current increased linearly with the concentration of H(2)A in the range of 1 X 10(-4)-5 X 10(-3) mol L-1.

探测束偏转光谱电化学

评述了探测束偏转光谱与电化学手段相结合作为一种现场的光谱电化学技术在研究电极／电解质界面上的应用。分别从实验装置、偏转原理、影响因素及其应用等方面加以论述。

醋酸纤维素为母体的稀土离子选择性电极的研制

醋酸纤维素为母体的稀土离子选择电极,制备容易,使用方便,可以测定混合稀土,电极的线性范围为1.2×10~(-1)～1×10~(-5)mol/L,适宜的pH范围较宽,测定结果令人满意。

红外光谱法研究离聚体中离子聚集状态

红外光谱法研究离聚体中离子聚集状态冯克，高洪涛，李卓美，阎荣江（中山大学高分子研究所，广州，５１０２７５）（中国科学院长春应用化学研究所）关键词离聚体，红外光谱，离子聚集离聚体是指含有１５ｍｏｌ％以下离子基团的聚合物，依离子含量高低，离子聚集状态分为...

用NMR方法研究稀土离子对DPPC脂质体构象的影响

随着稀土元素在工农业中的广泛应用,稀土进入机体内的作用机理是人们日益关心的问题.而稀土对生物体的作用,首先是通过生物膜.因此研究稀土与生物膜的作用是阐明其生理过程的重要环节.生物膜的结构比较复杂,而磷脂脂质体却能表现出生物膜膜脂结构的许

Close coupling between phytoplankton growth and microzooplankton grazing in the western South China Sea

We conducted 28 dilution experiments during August-September 2007 to investigate the coupling of growth and microzooplankton grazing rates among ultraphytoplankton populations and the phytoplankton community and their responses to habitat variability (open-ocean oligotrophy, eddy-induced upwelling, and the Mekong River plume) in the western South China Sea. At the community level, standing stocks, growth, and grazing rates were strongly and positively correlated, and were related to the higher abundance of larger phytoplankton cells (diatoms) at stations with elevated chlorophyll concentration. Phytoplankton growth rates were highest (> 2 d(-1)) within an eastward offshore jet at 13 degrees N and at a station influenced by the river plume. Among ultraphytoplankton populations, Prochlorococcus dominated the more oceanic and oligotrophic stations characterized by generally lower biomass and phytoplankton community growth, whereas Synechococcus became more important in mesotrophic areas (eddies, offshore jet, and river plume). The shift to Synechococcus dominance reflected, in part, its higher growth rates (0.87 +/- 0.45 d(-1)) compared to Prochlorococcus (0.65 +/- 0.29 d(-1)) or picophytoeukaryotes (0.54 +/- 0.50 d(-1)). However, close coupling of microbial mortality rates via common predators is seen to play a major role in driving the dominance transition as a replacement of Prochlorococcus, rather than an overprinting of its steady-state standing stock.

青海海北地区高山嵩草草甸植物群落生物量动态及能量分配

对青海海北地区高山草甸主要植物群落小嵩草(K obresia pygmaea) 草甸、矮嵩草(K. humilis) 草甸、藏嵩草(K. tibetica) 沼泽化草甸地上生物量动态和能量分配的研究结果表明, 不同植物群落年地上净生产量及其年际动态和主要植物类群生物量季节动态具明显的差异, 其生物量季节动态可由如下模型表示: W i = Ki/(1 + exp (A i - B it) ) 　　植物群落地上、地下生物量的垂直分布呈典型的金字塔和倒金字塔模式。小嵩草草甸、矮嵩草草甸和藏嵩草沼泽化草甸的地上净生产量依次为368.4g·m – 2·a- 1、418.5 g·m – 2·a- 1和518.4 g·m – 2·a- 1, 所固定的太阳能值依次为6655.16kJ·m – 2·a- 1、7610.09 kJ·m – 2·a- 1、9488.77 kJ·m – 2·a- 1。光能利用率分别为0.1097%、0.1256%、0.1568%。