Conformational statistics of polymer chain terminally attached to wall (Ⅲ)——NRW model loop chain

When the two end groups of a linear polymer chain are absorbed on a solid surface,the polymer chain forms the "loop" conformation.Investigation has been made on the conformational statistics of a model loop chain by the normal landom walk (NRW) on a lattice confined in the half-infinite space.Based on the conformational distribution function of the NRW model tail chain,it is easy to deduce an analytical formula expressing the conforma-tional number of the model loop chain.It was found that the ratio of the conformational number of the model loop chain to that of the free chain varies with the power function N-2/3 when the chain length N→∞ The same result was obtained by means of the recursion equation.The ratio of the mean square end-to-end distance h2 for the model loop chain to its mean square bond length I2 is 2N/3 Compared with the free chain with the same length N,the mean square end-to-end distance of the model loop chain contracts to a certain extent.The basic relationships deduced were support     

THE COMPARISON OF LANZHOU LOESS PROFILE WITH VOSTOK ICE CORE IN ANTARCTICA OVER THE LAST GLACIATION CYCLE

Loess near Lanzhou in the late Pleistocene is very sensitive to climatic fluctuations. The Beiyuan terrace profile in Linxia City, of which the curve of susceptibility tallies with the trend of isotopic curves of Vostok 2083 m ice core in Antarctica, is 35m thick. There are five layers of paleosols under Malan loess(L_1). Upper three layers (S_(1-a),S(1-b)and S_(1-c) correspond to three warm stages in last interglaciation, Interstadial of Last Glacial (C stage in Antarctic ice core)was clearly recorded in the Beiyuan profile, in which three layers of paleosols and two of loess were formed. The lowest section of the profile belongs to penultimate glaciation, in which fossils of cold-drought-resistant mammal and mollusc have been discovered.     

人类第七大营养素——膳食纤维

膳食纤维被称为人类第七大营养素,本文介绍了膳食纤维的有关化学问题,如其结构特点、理化性质、生理功能和检测方法,以及膳食纤维的应用与开发现状。     

PVP/CHI交联共混水凝胶的pH敏感性研究

制备戊二醛交联的PVP/CH I共混水凝胶,红外光谱佐证了凝胶网络的生成。pH敏感性实验表明,凝胶的溶胀率在pH=1.0的介质中最大,在pH=4.0的介质中次之,在中性或pH=9.0的碱性介质中最低,表明凝胶具有明显的pH敏感性。CH I含量、交联剂用量、CH I脱乙酰度均对凝胶的pH敏感性有影响,CH I含量40%、交联剂用量0.3%、CH I脱乙酰度99%的PVP/CH I凝胶pH敏感性较显著。介质pH值由1.0到7.0变化时,凝胶拉伸强度随着溶胀率的降低而增大。     

Quantum chemical study on the one-carbon unit transfer of imidazolinium

One-carbon unit transfer reaction of folate cofactor model compound, 1-acetyl-2-methyl-imidazolinium, with 1,2-diaminobenzene has been studied theoretically with ONIOM method. The result shows that there are two pathways to complete this reaction because the imidazolinium ring has two breaking patterns. Both the two pathways have six steps. They are combination of two reactants, proton migration, break of five-membered ring, formation of benzimidazole derivate, another proton migration, and formation of final products. In each of the above pathways, the two proton migration steps have higher energy, which illuminate that the reaction is catalyzed by general acid-base. This fact agrees with the experimental results of enzymatic one-carbon unit transfer at oxidation level of formate.     

氢气辅助的水中埋弧法制备小直径碳纳米管

用改进的石墨电弧放电方法制备了小直径、高质量的碳纳米管,以水为打弧介质,氢气为保护气体.该方法具有装置简单,电流小,无催化剂,制备出的多壁碳纳米管直径小于10 nm等优点.     

我国锂资源及其开发技术进展

介绍了我国盐湖锂资源的现状及其开发技术的进展情况,讨论了各种提锂工艺的优缺点,并对现阶段我国盐湖锂资源的开发提出了建议。     

线粒体和亚线粒体体外代谢及漆酶影响的微量热研究

首次将微量热用于亚细胞层次的研究，测定了鲤鱼肝脏线粒体和亚线粒体代谢的热谱及其漆树漆酶的影响，并用ＭＴＤ方程和演化计算技术对它们的代谢热动力学参数进行了全局优化。     

铂-丁二酮肟络合吸附波测定微量铂

铂和丁二酮肟在pH 4.1的HAc~NaAc支持电解质中,形成具有电活性络合物。在单扫示波极谱-0.88 V(vs.SCE)左右出现良好还原波。此波峰高与铂的浓度在1.0×10-8~4.0×10-6mol/L范围内呈线性关系。检出限为2.6×10-9mol/L。并成功的用于贵金属合成样及合金样品中铂量的测定。     

N,N'-二(二乙氧基硫代磷酰基)-1,4-苯二胺的合成、晶体结构及热性能研究

通过二乙氧基硫代磷酰氯与对苯二胺反应生成了标题化合物N,N'-二(二乙氧基硫代磷酰基)-1,4-苯二胺，并应用元素分析, FTIR及¹H NMR对标题化合物进行了表征. 利用X射线单晶衍射测定了其晶体结构, 同时应用TG分析法对其热性能进行了分析. 标题化合物的相对分子质量M_r＝412.42, 为正交晶系, Pbca空间群, 晶胞参数为a＝0.86936(16) nm, b＝1.2787(2) nm, c＝1.8897(3) nm, β＝90°, V＝2.1006(7) nm³, Z＝8, D_c＝1.304 g/cm³, μ(Mo Kα)＝0.425 mm^－1, F(000)＝872, S＝1.052. 最终偏离因子R＝0.0628, wR＝0.1860, 可观测衍射点1852个[I＞2σ(I)]. 该晶体通过对苯二胺连接并以中心对称分布, 并形成层状结构, 且存在弱的分子内氢键N—H…S. TG分析表明该化合物有很好的热稳定性及成炭性, 通过其阻燃聚丙烯腈表明, 该物质是一种高效能的膨胀型阻燃剂.