流动注射化学发光检测盐酸异丙嗪

在碱性介质中,盐酸异丙嗪对luminol-KMnO4发光体系有显著的增强作用.基于此增强作用,建立了一种FI-CL检测盐酸异丙嗪的新方法.在最优化的实验条件下,盐酸异丙嗪的ΔICL强度与其浓度在7.0×10-9~9.0×10-7 mol/L浓度范围内有较好的线性关系.线性方程为ΔICL=35.19+1.19×10-10 c,相关系数r=0.998 4,检出限为4.9×10-9 mol/L.对7.0×10-9 mol/L的盐酸氯丙嗪标准溶液进行11次平行测定,其RSD为2.4%.盐酸异丙嗪加标回收率在89.1%~96.1%之间.     

吡啶/喹啉单亚胺镍(Ⅱ)配合物的合成及液体聚丁二烯的制备

金属配合物中引入侧臂软电子给体膦或硫是提高配合物催化性能的有效途径。本文合成了一系列吡啶/喹啉单亚胺NNP三齿Ni(Ⅱ)配合物(2a~2d),采用傅里叶变换红外光谱、元素分析及单晶衍射对配合物进行了表征。配合物2a为方形锥体构型,配合物2d为三角双锥构型。该系列配合物在倍半乙基氯化铝(EASC)活化下,催化合成了数均相对分子质量为4200~7700、顺-1,4结构的摩尔分数在74.5%~79.9%的液体聚丁二烯。催化活性随着聚合温度的升高而提高。在90℃时,催化体系仍有很高的聚合活性,聚丁二烯的收率达到85.9%,表明其具有高的热稳定性。     

应用于活性负离子聚合的高真空实验技术研究与改进

高真空实验技术在装置设计、加工制作以及操作实施方面需要实验人员具备熟练的玻璃烧接技术;细颈的制作及反应装置的退火处理是较为关键的操作;考虑到聚合反应装置的体积较大,对火封操作进行了设计改进,使其能够应用于位置固定的装置;对操作中频繁采用的易碎封口安瓿进行了设计改进,使实验操作更为便利;针对已封闭装置预留的细颈部位,设计...     

Improved high-efficiency organic solar cells via incorporation of a conjugated polyelectrolyte interlayer

The power conversion efficiencies of bulk heterojunction (BHJ) solar cells can be increased from 5 to 6.5% by incorporating an ultrathin conjugated polyelectrolyte (CPE) layer between the active layer and the metal cathode. Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C(71) butyric acid methyl ester (PC(71)BM) were chosen for the photoactive layer. CPEs with cationic polythiophenes, in both homopolymer and block copolymer configurations, were used to improve the electronic characteristics. The significant improvement in device performance and the simplicity of fabrication by solution processing suggest a promising and practical pathway for improving polymer solar cells with high efficiencies.     

A myelin-specific contrast agent for magnetic resonance imaging of myelination

Myelination is one of the most fundamental biological processes in the development of vertebrate nervous systems. Abnormal or disrupted myelination occurs in many acquired or inherited neurodegenerative diseases, including multiple sclerosis (MS) and various leukodystrophies. To date, magnetic resonance imaging (MRI) has been the primary tool for diagnosing and monitoring the progression of MS and related diseases; however, any change in signal intensity of conventional MRI reflects a change only in tissue water content, which is a nonspecific measure of the overall changes in macroscopic tissue injury. Thus, the use of MRI as a primary measure of disease activity was shown to be disassociated from the clinical outcome due to the lack of specificity for myelination. In order to increase the MRI specificity for myelin pathologies, we designed and synthesized the first Gd-based T(1) MR contrast agent (MIC) that binds to myelin with high specificity. In this Communication, we demonstrate that MIC localizes in brain regions in proportion to the extent of myelination. In addition, MIC possesses promising MR contrast properties, which allow for direct detection of myelin distribution through T(1) mapping in the mouse brain.     

新教材应谋求教学内容与课时设置的有机统一--从"探究形变与弹力的关系"的教学设计谈起

新课程倡导的教学理念是“用教材”而不是“教教材”．在这一指导思想编写的新教材的特点是既“浅”又“活”，其重要变化就是减少了显性知识点，但内涵更加丰富，给教师留有更大的创作空间．但有一个遗憾就是这一特点没能充分在课时设置上体现出来．以新版《高中物理实验教材(必修1)》(广东教育出版社，2004年版．以下简称实验教材)为例，     

Chemical bonding, electron-phonon coupling, and structural transformations in high-pressure phases of Si

The nature of chemical bonding of the stable phases of Si at high pressure was analyzed. The effect of pressure is to promote sp electrons into the d orbitals, thus increasing the metallic character and reducing the dimensionality of covalent bonding. Localized covalent bonds, however, persist up to approximately 40 GPa (Si-VI, Cmca) and help to stabilize directional framework structures. At high pressures, Si becomes a metal, and the usual dense packed structures prevail. The existence of conducting and localized electrons gives rise to a combination of "steep and flat bands" near the Fermi level in Si-V. This peculiar electron topology in conjunction with low-frequency vibrations contributes to the relatively high superconducting temperature in Si-V and VI.     

Valence band x-ray emission spectra of compressed germanium

We report measurements of the valence band width in compressed Ge determined from x-ray emission spectra below the Ge K edge. The width of the valence band does not show any pressure dependence in the semiconducting diamond-type structure of Ge below 10 GPa. On the other hand, in the metallic beta-Sn phase above 10 GPa the valence band width increases under compression. Density-functional calculations show an increasing valence band width under compression both in the semiconducting phase (contrary to experiment) and in the metallic beta-Sn phase of Ge (in agreement with observed pressure-induced broadening). The pressure-independent valence band width in the semiconducting phase of Ge appears to require theoretical advances beyond the density-functional theory or the GW approximation.     

ChemInform Abstract: Predicted Lithium—Boron Compounds under High Pressure.

The existence of Li₃B₂, Li₂B, Li₄B, and Li₆B that might be experimentally synthesizable over a wide range of pressures is predicted by an unbiased structure search method based on particle‐swarm optimization algorithms in combination with DFT calculations.     

Remarks on the length of conjugacy classes of finite groups

Let G be a finite group. The question of how certain arithmetical conditions on the lengths of the conjugacy classes of G influence the group structure has been studied by several authors. In this paper we study restrictions on the structure of a finite group in which the lengths of conjugacy classes are not divisible by p ² for some prime p. We generalise and provide simplified proofs for some earlier results.