DIELS-ALDER REACTIONS OF FURAN WITH DIENOPHILES CATALYZED BY YbCl3

The yield and stereoselectivity of the Diels-Alder reactions between furan(or 2-methylfuran)and different dienophiles are markedly enhanced by the catalysis of anhydrous YbCl₃.     

利用特征为2域上伪辛几何中1维非迷向子空间构作PBIB设计

关于结合方案和PBIB设计的定义及所用的有关符号见文献[1].设F_q为特征为2的有限域,q=2~r.熟知F_q上的对称矩阵合同于以下三种形式的矩阵(见[1]p.24).     

抗坏血酸同顺磁离子Mn~(2+)、Gd~(3+)络会的~(13)C NMR研究

该文用顺磁离子对其近邻~(13)C核的NMR吸收增宽效应,系统地研究了抗坏血酸在不同溶剂中对金属离子Mn~(2+)、Gd~(3+)的配合行为.在水溶液中,抗坏血酸可通过两种配合方式与Mn~(2+)作用,但与Gd~(3+)的作用只有一种稳定的结构.在水中抗坏血酸对金属的配位活性部位分别是1位羟基氧,3位离解的羟基氧和6位羟基氧.在DMSO中,3位羟基由于H~+对该基团的静电遮蔽而变得对金属离子Mn~(2+)表现为配位惰性,同时6位羟基配位活性较大增强.对Gd~(3+)来说,此时没有优势配位活性部位存在.文章还讨论了抗坏血酸在H_2O-DMSO混合溶剂中的~(13)C NMR谱及在DMSO中NaOH对其~(13)C NMR谱及其与金属络合结构的影响.     

A flow tube study of methyl iodine uptake on soot surface

The black carbon aerosols are now recognized for their potential impact on climate and the halogenated compounds are thought to be very important in atmospheric chemistry. However, there are very few studies on the interactions between soot aerosols and halogenated compounds. We report the measurement of the uptake of CH₃I on soot. The measured uptake coefficient is 0.0103 ± 0.0015 at a total pressure of 2–4 Torr and 298 K. The results suggest that the uptake of CH₃I occurs efficiently on soot particles. The present work suggests that heterogeneous loss of CH₃I on soot may influence the concentration of CH₃I throughout the atmosphere.     

重金属Pb2+对玉米苗生长的影响

以水栽培的玉米幼苗为材料，用不同浓度的醋酸铅溶液处理后，分别在第10天、第20天、第30天对玉米苗的根、茎、叶分别进行Pb^2＋含量测定。分析结果：Pb^2＋在玉米体内的分布表现为根〉叶〉茎；玉米中的叶绿素含量均降低；随着Pb^2＋浓度的增大，玉米细胞的膜透性表现根〉叶〉茎依次升高；Pb^2＋对玉米的伤害率的大小表现为根〉叶〉茎。该实验为进一步研究农作物对重金属Pb^2＋的耐性和重金属Pb^2＋在农作物体内的分布提供了可参考的数据。     

纯锆上离子注入钇和镧后的表面分析

用金属蒸汽真空弧源，以40kV加速电压对纯锆样品分别进行了10¹⁶—10¹⁷/cm²的钇、镧离子注入，注入温度约为130℃.然后对注入样品进行表面分析.x射线光电子能谱分析表明，注入的钇以Y₂O₃形式存在，镧以La₂O₃形式存在.俄歇电子能谱表明，纯锆基体表面的氧化膜厚度随着离子注入剂量的增加而增加，当离子注入剂量达到10¹⁷/cm²时，氧化膜的厚度达到了最大值.卢瑟福背散射显示镧层的厚度约为30nm，同时直接观察到当离子注入剂量为(La+Y)10¹⁷/cm²时，纯锆样品表面发生了严重的溅射. 关键词： 纯锆 钇和镧离子共注入 卢瑟福背散射 x射线光电子能谱     

Large second-order optical nonlinearities of s-triazine derivatives: View from micro molecules to macro crystals

Organic nonlinear optics (NLO) is also called mo-lecular nonlinear optics. In recent years organic mate-rials have been intensively studied because of their large NLO coefficients and structural diversities[1―3]. Second harmonic generation (SHG) is a bas…     

In situ Synthesis of Oligonucleotides on Plasma Treated Polypropylene Microporous Membrane

Polypropylene microporous membranes were treated with plasma in a mixture of N2 and H2 (1:2 in volume). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and ultra-violet (UV) spectra demonstrated the success of grafting amino groups. The density of the polar amino groups on the membrane surface is about 0.59 μmol/cm^2. The as-treated membranes were successively applied to the in situ synthesis of oligonucleotides and an average coupling yield was more than 98%. The surface feature of the treated membrane is suggested to be responsible for its advantage over a glass slide.     

具有一对零态射的Morita Context环(II)

设$(A,B,V,W,\psi,\phi)$是一个Morita Context,具有一对零态射$\psi=0$, $\phi=0$, $C =\left ( \begin{array} {cc}A & V \\W & B \end{array}\right)$是对应的Morita Context环.本文给出了$C$与$A,B,V,W$之间关于环的$\pi$-正则性、semiclean性、Mophic性和环的Exchgange性、Potent性、GM性的关系.