Single-Molecule single crystals of isotactic polystyrene

Single-molecule single crystals were grown from amorphous droplets of fractionated isotactic polystyrene. The crystals were analyzed by electron microscopy and electron diffraction. The molecular mass distribution could be matched with a statistical analysis of single-molecule particles (amorphous and crystals). Proof was brought that single molecules of isotactic polystyrene do not reach equilibrium dimensions on crystallization, rather assume the lamellar morphology with chain-folded macroconformation, also known from crystallization of polymolecular crystals. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America. US Government contract No. DE-AC05-840R-21400.

     

ANN原子参数法预报合金相晶型及晶格常数

运用人工神经网络方法，以二元合金组成元素的电子结构为基本特征，对二元合金相晶型作了区分，进一步对其晶格常数作了预报，结果令人满意。     

环境和生物样品中铂族金属的分析研究进展

评述了近年来环境和生物样品中痕量铂族金属的分析研究进展，重点介绍了样品的预处理和分离富集技术以及检测手段等。     

Conformation dependence of electronic structures of poly(ethylene oxide)

The electronic structure of pure poly(ethylene oxide) (PEO) for four different polymeric chain conformations has been studied by Hartree-Fock (HF) and density functional theory (DFT) through the analysis of their valence band photoelectron spectroscopy (VB-PES), X-ray emission spectroscopy (XES), and resonant inelastic X-ray scattering (RIXS). It is shown that the valence band of PEO presents specific conformation dependence, which can be used as a fingerprint of the polymeric structures. The calculated spectra have been compared with experimental results for PEO powder.     

Investigation of radical cation in electrophilic fluorination by ESI-MS

Reaction solutions of selectfluor (1) with triphenylethylene (4a) and tetraphenylethylene (4b) were monitored by ESI-MS and ESI-MS/MS. Detection and characterization of the key radical cationic intermediates 5a.+ and 5b.+) fully supports the SET mechanism in electrophilic fluorination as depicted above. [reaction: see text]     

PPC/SBR并用弹性体的配方选择

利用正交法对丁苯橡胶（SBR）／聚丙撑碳酸酯（PPC）共混弹性体进行配方设计，得到了一个具有良好综合性能的配方。并通过方差分析得出PPC含量和马来酸酐（MA）用量是影响弹性体拉伸性能的最显著因素。     

一类酶反应底物的光化学荧光研究

研究了对位取代酚类酶反应底物的光化学荧光反应机理，指出光子不仅可以取代过氧化物酶，而且可以取代氧化剂（Ｈ_２Ｏ_２）。用于测定多种酶反应底物，结果满意。     

镉—溴化物—罗丹明B高灵敏显色反应的研究：离心光度法测定镉

本研究了一个高灵敏的测定镉的方法，离心光度法，该体系络合物λｍａｘ＝５６０ｎｍ，表观摩尔吸系数ε５６０＝５．０６×１０＾８Ｌ．ｍｏｌ＾－１．ｃｍ＾－１，Ｃｄ＾２＋浓度０．１０×１０＾－２－１．０×１０＾－２μｇ／１０ｍＬ呈线性关系，本法已用于血清和水中痕量镉的测定，探讨了高灵敏的显色反应机理。     

N－取代硫代磷酰胺二乙酯合成新方法的研究

以ＰＥＧ作相转移催化剂，在无机碱（Ｋ＿２ＣＯ＿３或Ｎａ＿２ＣＯ＿３）存在下，用乙基氯化物（Ｏ，Ｏ－二乙基硫代磷酰氯）与不同的胺反应，合成了六种Ｎ－取代硫代磷酰胺二乙酯，其结构经ＩＲ、ＮＭＲ和元素分析证实。     

Carbon nanotube assisted synthesis of CeO2 nanotubes

CeO₂ nanotubes have been synthesized facilely using carbon nanotubes (CNTs) as templates by a liquid phase deposition method. The properties of the CeO₂ nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS) as well as thermogravimetry and differential thermal analysis (TG-DTA). The obtained CeO₂ nanotubes with a polycrystalline face-centered cubic phase have a uniform diameter ranging from 40 to 50 nm. The CeO₂ nanotubes are composed of many tiny interconnected nanocrystallites of about 10 nm in size. The pretreatment of CNTs and calcination temperature were confirmed to be the crucial factors determining the formation of CeO₂ nanotubes. A possible formation mechanism has been suggested to explain the formation of CeO₂ nanotubes.