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     

Quantum chemical definition and calculation of oxidation number

A new quantum chemical definition of oxidation number is proposed, in the present paper, as a direct generalization of the corresponding classical definition. According to the proposed general definition, the oxidation number can be calculated by use of molecular orbital data and a population analysis method or by use of other quantum chemical methods. For the practical calculation, we present a corresponding concrete calculation procedure within the framework of the maximum overlap population principle, which is very simple and very easy to use. The calculated numerical results are, on the whole, in good agreement with chemists' intuitive concepts of chemical bonding.     

CLIMATIC CHANGE SINCE LITTLE ICE AGE RECORDED BY DUNDE ICE CAP

The climatic change since the Little Ice Age recorded in the Dunde Ice Cap is presentedin this paper. There have been three cold periods and three warm periods since 1400AD.Among them, the coldest one was in the 17th century. Many evidences verified the three coldand warm variations recorded in the Dundc Ice Cap. But it was found from the comparison between the Dunde Icc Cap climatic record and thewinter temperature record in Shanghai that there was a temporal dfference in climatic changebetween East China and West China. The general trend is that the cooling and warmingprocesses in West China were earlier than that in East China. In the Dunde Ice Cap, it isnow in an anomalous warm period, while it is not as warm as in Dunde Ice Cap recordaccording to the winter temperature in Shanghai. In addition to the possible cause of temporaldifference in climatic change between West China and East China, another possible cause isthat the greenhouse effect of CO_2 may already be recognizable in the Dunde Ice Cap a     

聚酰亚胺光控取向膜的研究现状

用线性偏振紫外光照射聚酰亚胺膜可以诱导液晶取向。本文对四种聚酰亚胺光控取向膜进行了详细的概述，并简述了这种光控取向膜的机理及未来应用。     

Synthesis and Luminescent Properties of an Acetylide-Bridged Dinuclear Platinum(II) Terpyridyl Complex

Introduction Luminescent coordinatively unsaturated platinum(II) complexes are appealing from photochemical and pho-tophysical perspective.1,2 In particular, platinum(II) ter-pyridyl complexes have attracted considerable attention due to their rich spectroscopic2a-d and biological proper-ties.2a,e-g However, the development of the photochem-istry of these complexes is limited by their short-lived MLCT excited state in solution at room temperature. The lack of emission originates from low-l…     

Structural Characterization of the Chiral Skeleton Cluster RuCoMo (Co)_8(μ_3-Se ) C_5H_4C (O) C_6H_4C (O)OCH_3

1INTRoDUCTIoNIntenseinterestintransition-metalclusterscontinuesbecausetheyrepresentpos-sibleconceptualbridgesbetweenhomogeneousandheterogeneouscatalystsmoreoveralsobecausetheyrepresentsyntheticchallenges.TheuseofelementsofGroup16ofthePeriodicTableassingleatomligandsforclustergrowthandstabilizationofthemetalcorearenowwellestablished[1i.ThereisanincreasinginterestintheuseofSe-bridgrdclusters,manyofthereactionsofSe2Fe2(CO),andSe2Fe,(CO),havebeenreported"';however,therehasbeenverylittlewor…     

位阻型金属卟啉的合成

用平衡法合成了ｍｅｓｏ－四（２，３，５，６－四甲苯基）卟啉及其铁，锰，钴，锌金属配合物。     

Two New Pyrrolizidines from Ligularia lankongensis

Two new pyrrolizidines named lankongensisine A (1), B (2) were isolated from the roots of Ligularia lankongensis collected in Lijiang, Yunnan, and their structures were established by spectroscopic analysis.     

Enhancive Synthesis of ‐lβ, 11‐Diol‐4‐en‐eudesmol

An enhancive synthesis of ?1β, 11‐diol‐4‐en‐eudesmol, starting from 2‐chloroacrylonitrile, is described. The effect of temperature on the Diels‐Alder reaction of 2‐chloroacrylonitrile with 2‐methylfuran and the condition of cationic cyclization of diene were discussed in detail.     

粉煤灰与复合添加剂的固相反应过程分析

煤灰分中主要矿物质之间的反应对灰分特性有着重要影响。本文在具有温控的小型高温反应器中对粉煤灰和复合添加剂所组成的混合灰样进行了静态煅烧试验，并对煅烧后的灰样进行了X射线衍射分析（XRD），着重讨论了温度和时间以及复合添加剂量对灰分矿相组成特性的影响。试验结果表明：当温度低于1200℃时，灰色中主要是游离态的氧化物和部分新生成的矿物如钙黄长石，硅酸二钙；当温度在1200℃-1300℃时，灰分中的主要矿物是钙黄长石，当温度在1320℃－1350℃时，灰分主要矿物是硅酸二钙，同时存在一定量的硅酸三钙、铝酸三钙、铁铝酸四钙以及硫铝酸钙。随着灰分中氧化钙的含量增加，高碱性矿物含量逐渐增大，同时高温下加热持续时间过长，部分新生成的矿物将发生分解。