反应原料组成对单分散苯乙烯微球粒径及其分布的影响

采用分散聚合工艺制备微米级单分散聚苯乙烯微球，并对分散聚合反应的内部影响因素(分散稳定剂、助稳定剂、单体、引发剂)进行了研究．结果表明，随着分散稳定剂和助稳定剂用量的增加，聚苯乙烯微球的粒径减小；随着单体和引发剂用量的增加，聚苯乙烯微球的粒径增大．分散稳定剂和单体用量是影响聚苯乙烯微球粒径分布的两个主要内部因素．     

Theoretical Study on the Reaction Mechanism of Ketene CH2CO with Isocyanate NCO Radical

The bimolecular single collision reaction potential energy surface of an isocyanate NCO radical with a ketene CH2CO molecule was investigated by means of B3LYP and QCISD（T） methods. The computed results indicate that two possible reaction channels exist on the surface. One is an addition-elimination reaction process, in which the CH2CO molecule is attacked by the nitrogen atom at its methylene carbon atom to lead to the formation of the intermediate OCNCH2CO followed by a C-C rupture channel to the products CH2NCO＋CO. The other is a direct hydrogen abstraction channel from CHzCO by the NCO radical to afford the products HCCO＋HNCO. Because of a higher barrier in the hydrogen abstraction reaction than in the addition-elimination reaction, the direct hydrogen abstraction pathway can only be considered as a secondary reaction channel in the reaction kinetics of NCO＋ CH2CO. The predicted results are in good agreement with previous experimental and theoretical investigations.     

炭气凝胶及其有机气凝胶前驱体的研究进展

介绍了炭气凝胶及其有机气凝胶前驱体的发展概况，着重总结了制备工艺条件(如催化剂及其浓度、反应物总浓度、反应物配比、溶剂、反应温度及时间、超临界干燥工艺条件和炭化工艺条件等)对有机气凝胶及其相应炭气凝胶中孔网络结构的影响，综述了中孔网络结构改性研究的进展．     

季铵盐固相催化使聚氯乙烯脱HCl

通过将季铵盐与聚氯乙烯(PVC)混溶成膜,使其在固相脱HCl,研究了催化剂对PVC脱HCl反应速度和产物结构的影响以及固相反应与温度、时间的关系.发现在催化性能上下基铵盐比乙基铵盐好得多,根据实验结果提出了季铵盐通过分解成叔胺实现催化的机理.     

Fe（acac）3-Al（i-Bu）3-α，α＇-联吡啶催化丙烯腈与苯乙烯共聚合

研究了Fe（acac）3-Al（i-Bu）3-α，α＇-联吡啶（acac=乙酰丙酮）催化体系催化丙烯腈（AN）与苯乙烯共聚合，用元素分析和核磁共振研究了共聚物的结构，在单体比为1：1时共聚物中丙烯腈／苯乙烯含量分别为49．3％和50．7％．用凝胶渗透色谱研究了聚合物分子量和分子量分布，共聚物分子量分布较窄．动力学研究表明共聚合反应对单体浓度呈一级关系，表观活化能为57．8kJ／mol．     

Study on thermal stability of poled non-linear optical polymers

A logarithmic expression is proposed to describe relaxation of the polar order in side chain polymers,together with a new way of plotting temperature dependent relaxation data.This results in a straight line extending even below the glass transition temperature in the case of poled nonlinear optics (NLO) side chain polymers.A simple procedure to determine the rotational diffusion constant Dr is given and Dr values of several polymer systems have been evaluated and compared with each other.It appears that,starting from the conventional and well known poled polymer system currently applied,a further lowering of Dr by about 3 orders of magnitude is necessary in order to reach an acceptable orientational stability or lifetime of poled polymers for practical applications.Attempts have been made to introduce electron push-pull substituents into high thermostable molecular frameworks and results of preliminary measurements are reported.     

EPR Study on the complex formed by charge-transfer process between ground-state acceptor chloranil and nine donors

EPR study showed that the semi-quinone radical anion of chloranil (TCQ) was formed in a charge-transfer process between ground state chloranil as acceptor and each one of the following ground state donors,i.e.,N,N'-diethyl aniline (DEA),phenothiazine (PTZ),carbazole (CBZ),pyrene (PY),ferrocene (FRO),triphenylphosphine (TPP),triethylamine (TEA),anthracene (AN) and N,N-diethyl-3-aminophenyl ester of palmitic acid (DPP).Our results indicate that there is a tunneling effect for the ground-state charge-transfer process between chloranil and the donor.     

气色相谱-质谱法测定化妆品中的氯霉素

氯霉素是一种广谱抗生素,化妆品卫生规范规定氯霉素等抗生素为禁用物质.关于氯霉素的检测多采用高效液相色谱(HPLC)[1]和高效液相色谱-质谱(HPLC-MS)[2] 测定,或者经N,O-双三甲基硅烷基-三氟乙酰胺(BSTFA)、三甲基氯硅烷(TMCS)等硅烷化[3-4]后进行气相色谱(GC)、GC-MS测定.本文建立了采用较为普通的乙酸酐试剂进行衍生化,然后用GC-MS测定的方法.将该法应用于化妆品中氯霉素的检测,取得了较好的效果.     

A Tail Measure With Variable Risk Tolerance: Application in Dynamic Portfolio Insurance Strategy

Methodology and Computing in Applied Probability - Risk measures for tail risk have an important application in the dynamic portfolio insurance strategies. We propose a new risk measure called...     

Hopf bifurcation of a tumor immune model with time delay

In this paper, a tumor immune model with time delay is studied. First, the stability of nonnegative equilibria is analyzed. Then the time delay τ is selected as a bifurcation parameter and the existence of Hopf bifurcation is proved. Finally, by using the canonical method and the central manifold theory, the criteria for judging the direction and stability of Hopf bifurcation are given.