芳硒化铯与炔硒醚反应合成(Z)-1,2-二芳硒基烯

芳硒化钠与炔硒醚在室温不反应．但是，在室温、氮气保护下芳硒化铯与炔硒醚能有效的进行反应，立体选择生成(Z)-1，2-二芳硒基烯，产率在88％～95％．这表明ArSeCs中ArSe^-具有较强的亲核性．本方法具有反应条件温和、产率高、不需无水条件、实验操作简单．这一方法为(Z)-1，2-二芳硒基烯的合成提供了一条新的有效的途径．     

氢氧化铯催化下三甲硅基乙炔与二芳基二硒醚反应研究

氢氧化铯催化下,以THF作溶剂,在低温(-20℃)、空气中,三甲硅基乙炔与二芳基二硒醚反应20 h,给出摩尔比为70∶30的二苯硒基乙炔和三苯硒基乙烯的混合物,产率为96%;而在室温进行,反应速度大大加快,仅需1 h,得到摩尔比为5∶55∶45的二苯硒基乙炔、三苯硒基乙烯和(Z)-1,2-二苯硒基乙烯的混合物,产率为92%;在氮气保护及室温下反应1 h,以95%的产率生成唯一的产物(Z)-1,2-二苯硒基乙烯.溶剂对反应速度和反应结果也有较大的影响.以DMF作溶剂,即使在-20℃,也能使反应有效发生,高产率的生成唯一的产物(Z)-1,2-二苯硒基乙烯.讨论了反应机理.     

碳酸铯催化下烷基芳醚的制备

研究了碳酸铯催化酚与卤代烃反应制备烷基芳醚．以碳酸铯作催化剂,氢氧化钾作碱,DMF作溶剂,室温下,在分子筛存在下,苯酚、萘酚、3,5-二叔丁基苯酚及4-[二(4 -叔丁基苯基)苯基甲基]苯酚与溴乙烷、溴丁烷及苄溴等反应形成相应的烷基芳醚,收率为90%～96%．结果表明,碳酸铯可有效地催化酚与卤代烃反应．     

二甲戊灵(Pendimethalin)市场分析报告

(接10月16日版)2.5主要的工艺情况简介从二甲戊灵的结构式(图1)来看,该化合物的苯环上有烷基、硝基、胺基等官能团,故其合成主要涉及硝化、还原烷基化和亲核取代等反应。     

原核生物硒蛋白的生物合成

硒是包括哺乳动物在内许多生物的必需微量元素,与人类健康密切相关。硒分布的不平衡导致所在地食物中硒含量差异较大,且高硒地区的人易发生硒中毒,而低硒地区的人易硒缺乏。胞内硒酸盐经还原及硒磷酸合成酶的活化,在硒代半胱氨酸合酶(SelA)催化下利用Ser-tRNAUGAsec合成硒代半胱氨酸(selenocysteine,Sec),Sec经tRNAUGAsec特异性的类EF-TU延伸因子SelB整合入蛋白质形成硒蛋白。文中主要概述了原核生物硒酸盐的还原代谢和硒代半胱氨酸的插入机制,并提出了利用硒蛋白的合成机制作为检测硒酸盐含量的思路。     

工业副产物硒的氧化

在化学反应中，二氧化硒作为温和的氧化剂，可以将羟基、甲基等基团氧化为醛基，而本身被还原为硒，成为废弃物。以合成反应中生成的硒为原料，用浓硝酸和浓硫酸的混合物进行氧化反应，使其氧化为可以重复使用的二氧化硒，反应收率为94％，并用滴定法测定其含量为96％，符合工业化生产的要求。     

DCC缩合酯化法合成水杨酸壳寡糖酯

[目的]研究高效、广谱、安全杀菌抗菌剂水杨酸壳寡糖酯的制备方法。[方法]以二环己基碳二亚胺（DCC）作脱水剂,壳寡糖经氨基保护后与水杨酸进行DCC缩合酯化反应,制备水杨酸壳寡糖酯。[结果]经DCC缩合酯化反应,得到了水杨酸壳寡糖酯,在适宜的条件下,其酯化度可达120.0%,酯化收率可达71.8%。[结论]该方法反应条件比较温和,且所得水杨酸壳寡糖酯产率较高。     

氢氧化铯催化二芳基二硫醚与端炔反应研究

以3-甲氧基丙炔与二苯基二硫醚的反应作为模型.探讨反应条件对反应结果的影响.实验表明以THF作溶荆,在0℃以下,不论是在空气氛中或在氮气氛中反应,都产生3-甲氧基丙炔基苯基硫醚与(Z)-1,2-二苯硫基烯的混合物,总收率约40%.在室温、空气氛中反应得上述两种生成物的混合物,总收率约80%.而在氮气保护下进行反应,则仅产生(Z)-1,2-苯硫基烯.探讨了反应机理.在氮气保护下,进行了其他端炔与二芳基二硫醚反应,高立体选择的合成了6种(Z)-1,2-芳硫基烯.本方法为(Z)-1,2-芳硫基烯的合成提供了一条简便途径.     

NiSe2的合成制备及其电化学性能

采用溶剂热法在一缩二乙二醇(C_4H_(10)O_3)中一步合成二硒化镍纳米材料,反应中添加十六烷基三甲基溴化铵(CTAB)和聚乙烯吡咯烷酮(PVP)为表面活性剂.利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、能谱仪(EDS)和拉曼光谱对产物进行了表征,利用电化学工作站对其电化学性能进行测试.结果表明,形貌规则的多面体和树枝状的产物被成功合成制备.通过控制镍硒比(n(Ni)∶n(Se))、反应时间和反应温度以合成不同形貌的二硒化镍.     

不同供硒水平对水稻生长的影响及水稻对硒的富集作用

通过盆栽土培与水培相结合,以亚硒酸钠的形式供给不同水平的硒,研究了水稻对硒元素的富集作用以及硒对水稻生长的影响,结果表明：用硒作微肥,适量施用,能增强根系还原能力,促进分蘖,增加产量,提高籽粒含硒量;水稻耐受硒的程度与其生长期和土壤的持硒能力有关。高硒环境在水稻生育前期对水稻生长有抑制作用。     

改革求生存 创新谋发展——浅析地市级农业科学院(所)发展之路

地市级农业科学院(所)近年来,进行了一系列的科技体制改革,文章在论述以往改革的做法和成效的基础上,找出了改革中存在的几个影响发展的瓶颈问题,并进一步提出解决问题的对策。     

Hemagglutination by fava bean extract inhibited by simple sugars

Hemagglutination by extract of fava bean was inhibited by 5-percent d-glucose, d-fructose, or maltose, but not by 5-percent d-galactose or lactose. Failure to inhibit seems to reflect the presence of a hydroxyl group at the carbon No. 4 position. Hemagglutination was enhanced by dextran of high molecular weight, but not by dextran of low molecular weight. The finding supports the hypothesis that large molecular size explains the enhancement by gum acacia of hemagglutination by fava bean.     

Transformation by v-sis occurs by an internal autoactivation mechanism

Transformation by the v-sis oncogene appears to require an interaction of its protein product, p28v-sis, with the receptor for the platelet-derived growth factor (PDGF). However, this interaction may not occur at the cell surface as predicted by the autocrine hypothesis because phenotypic transformation was not reversed by incubation of SSV-NRK cells with antisera to PDGF and because morphological transformation did not occur when nontransformed NRK cells were cultured continuously with p28v-sis. A mutant of the wild-type v-sis gene was constructed that encodes a v-sis protein targeted for retention within the endoplasmic reticulum and Golgi. NRK cells expressing the mutant v-sis gene did not secrete any detectable v-sis protein but were as fully transformed as wild-type v-sis transfectants. The results support a mechanism of transformation by v-sis in which internal activation of the PDGF receptor occurs before expression of either p28v-sis or the PDGF receptor at the cell surface.     

依法治校与以德治校的思考

依法治校与以德治校是学校管理科学化、规范化的必须和标志。文章以实际工作中存在的一些问题为背景，就如何坚持依法治校与以德治校提出处理好若干关系的建议，指出依法治校是学校管理的保障和前提，以德治校是学校发展的灵魂和动力。     

Language discrimination by human newborns and by cotton-top tamarin monkeys

Humans, but no other animal, make meaningful use of spoken language. What is unclear, however, is whether this capacity depends on a unique constellation of perceptual and neurobiological mechanisms or whether a subset of such mechanisms is shared with other organisms. To explore this problem, parallel experiments were conducted on human newborns and cotton-top tamarin monkeys to assess their ability to discriminate unfamiliar languages. A habituation-dishabituation procedure was used to show that human newborns and tamarins can discriminate sentences from Dutch and Japanese but not if the sentences are played backward. Moreover, the cues for discrimination are not present in backward speech. This suggests that the human newborns' tuning to certain properties of speech relies on general processes of the primate auditory system.     

Hardening by annealing and softening by deformation in nanostructured metals

We observe that a nanostructured metal can be hardened by annealing and softened when subsequently deformed, which is in contrast to the typical behavior of a metal. Microstructural investigation points to an effect of the structural scale on fundamental mechanisms of dislocation-dislocation and dislocation-interface reactions, such that heat treatment reduces the generation and interaction of dislocations, leading to an increase in strength and a reduction in ductility. A subsequent deformation step may restore the dislocation structure and facilitate the yielding process when the metal is stressed. As a consequence, the strength decreases and the ductility increases. These observations suggest that for materials such as the nanostructured aluminum studied here, deformation should be used as an optimizing procedure instead of annealing.     

Ionization of liquids by radiation: measurement by charge scavenging

Pulse radiolysis of dilute solutions of triphenylcarbinol in saturated hydrocarbon gives spectra of the triphenylmethyl free radical, (C(6)H(5))(3)C., and cation, (C(6)H(5))(5)C(+). The yield of the ion is independent of the carbinol concentration, and is thought to measure the yield of free ions generated in the solvent. The relative yields of ions thus found in cyclohexane and 2,2,4-trimethylpentane agree with measurements made by the clearing-field method.     

Interferon: production by chick erythrocytes activated by cell fusion

In the presence of Sendai virus inactivated with ultraviolet light, nucleated chick erythrocytes can be fused with several types of human cells to form heterokaryons. Although chick erythrocytes alone cannot be stimulated by Sendai virus to produce interferon, fusion with a human cell (AH-1) which itself may produce human interferon results in heterokaryons in which the erythrocyte genome is activated and chick interferon is produced. When nucleated chick erythrocytes are fused with another type of human cell (HeLa clone S-3) which does not produce human interferon when stimulated, no chick interferon is detectable, despite morphologic changes suggestive of activation of the erythrocyte nuclei.