聚丙烯腈热处理的反应机理

本文作者将聚丙烧腈样品分别在200°,250℃……的真空和空气中,以及在180°, 200℃……的氨气中,以逐步升温的方式进行热处理。在每一阶段处理的前后,对样品和产物的红外光谱、重量、它们在浓硫酸和冰醋酸中的溶解度、在浓硫酸中的紫外光谱、以及它们在冰醋酸回流抽提后所余残渣的红外光谱都进行了测量。提出了足以解释所有主要现象的反应机理,其中包括三个重要步骤的反应:(1)特征基团的产生,(2)分子内部的环化,(3)较高温度下的脱氨反应。从每个步骤反应的分析可以看出,热处理所得产物只能是含多核呲啶骈环不长、结构杂乱的高聚物。由于过去学者提出的反应机理只是根据部分实验结果考虑了分子内部环化的发生,而不可能发现到环化的必然中断,因此有些作者根据这机理所作关于产物的半导体电磁性能的解释是值得进一步研究的。     

有机小分子发光材料与聚合物发光材料在大气存放条件下的稳定性对比研究

分别采用紫外光电子能谱（UPS）、X光电子能谱（XPS）、原子力显微镜（AFM）、以及光致发光光谱（PL）等方法对在大气存放条件下的8－羟基喹啉铝（Alq)薄膜和聚（9,9－二辛烷基芴）（PFO）薄膜的电子结构、表面形 及发光特性进行了对比。研究结果表明,PFO的电子结构、表面形貌以及发光特性受外界气氛影响极小,是一种非常稳定的聚合物发光材料。这为聚合物发光器件的稳定性提供了有利的条件。     

A NEW SILENT MUTATION FOUND IN THE CHINESE PAH LOCUS AND ITS ROLE IN THE PRENATAL DIAGNOSIS OF PHENYLKETONURIA

A silent mutation or sequence polymorphism, A to T substitution at codon 399 in exon11 of the PAH gene from a Chinese PKU patient, was found by sequence analysis. The fre-quencies of this new mutation in normal and abnormal (PKU) genes were 0.005 and 0.09,respectively, based on the analyses of 100 normal individuals and 39 PKU patients usingDNA amplification with polymerase chain reaction (PCR) and oligonucleotide hybridizationmethods. This silent mutation can be used as a "genetic marker" for PKU prenatal diagno-sis. Recently, a fetus at risk for PKU, who could not be completely predicted by RFLPslinkage analysis, was prenatally diagnosed with this genetic marker.     

烯烃聚合高性能FI催化剂的进展

FI催化剂系一近几年发展起来的烯烃聚合高性能催化剂。以它的极高的活性、聚合物分子结构的可控性、多重活性聚合等特性而引人注目。本评述首先进行该催化剂的化学描述,然后分别介绍该催化剂的主要特征、活性中心结构、聚合机理和应用,重点介绍该催化剂的五大特征。     

用电发光法测量碳化硅少数载流子寿命的若干问题

本文介绍一种测量碳化硅半导体少数载流子寿命的方法,叙述有关的原理和测试设备,并就对测试结果有极大影响的谐振干扰、点接触的电学性质和电发光特性等问题进行了试验。提出了若干可以避兔谐振干扰、防止触点旁路并控制整流比的有效措施。推荐采用焊铟方法制备低阻接触。指出,为了保证实验结果的可靠性,测试前必须了解样品的发光特性。采用这种方法测定了若干碳化硅单晶的少数载流子寿命,测得值一般低于4.2×10^-9秒。     

Synthesis,Crystal Structure and Theoretical Calculations of N-Benzyl-1-(5-(3-chlorophenyl)-1,3,4-oxadiazol-2-yl)cyclopentanamine

N-benzyl-1-(5-(3-chlorophenyl)-1,3,4-oxadiazol-2-yl)cyclopentanamine was synthesized via one-pot reaction of appropriate benzylamine, cyclopentanone,(N-isocyanimino)triphenylphosphorane and m-chlorobenzoic acid. The quantum theoretical calculations for crystal structure were performed by density functional theory(DFT/B3LYP/6-311+G*). From the optimized structure, geometric parameters were obtained and experimental measurements were compared with the calculated data. Frontier molecular orbitals(FMOs), total density of states(DOS), molecular electrostatic potential(MEP), molecular properties, natural charges, NMR parameters and NBO analysis for the product were investigated by theoretical calculations.     

Theory of the nucleation of protein macromolecular ions

Protein molecules are amphoteric and exist in aqueous solution as macromolecular ions that carry a charge which depends upon temperature and pH. Despite the repulsive Coulomb forces acting between them, protein macromolecular ions can form crystals in pH buffered solutions of strong electrolytes. It is proposed that the first step in the mechanism of crystallization is the formation of crystal nuclei made from partially discharged macromolecular ions that have exchanged H⁺ with the buffer. We suggest that the strength of the bare Coulomb repulsive force is weakened by the Debye-Hückel plasma screening provided by the inert electrolyte. This screening causes the rate of nucleus formation to increase with increasing ionic strength. Extending classic nucleation theory to account for these various charge effects, the results are applied to the case of lysozyme and a calculation is made of the dependence of the steady state nucleation rate upon temperature, pH, ionic strength, and protein supersaturation. It is found that the nucleation rate increases with increasing temperature and increasing ionic strength. Under condition of fixed temperature, supersaturation, and inionic strength, the nucleation rate has local maxima at low pH, where individual lysozyme macro ions are highly charged, and at pH ? 11, where they have zero average net charge. At both pH values, the nucleus that determines the rate has minimum size. In contrast to standard nucleation theory, which ignores charge, it is found that the size of the nucleus that controls the rate is different from the size of the nucleus that has the lowest concentration. All other conditions being the same, it is predicted that lysozyme crystals should nucleate most rapidly near pH = 2 and near pH = 11.     

氢原子在金属表面的吸附理论

本文在相关基函数理论框架下,利用巨分子模型,建立了氢原子在简单金属表面的吸附理论模型。通过对吸附平衡位置参量的变分数值计算,我们得到了关于氢原子在金属Al(r_s=2.07),Mg(r_s=2.66),Li(r_s=3.28)和Na(r_s=3.99)表面上的吸附能,吸附体系的电子密度以及平衡位置。对于传统的密度泛函方法得到的结果,本文作了比较。 关键词：