Size and purity of gold nanoparticles changes with different types of thiolate ligands

Gold nanoparticles (Au-NPs) were prepared by a surfactant-free single-phase reduction of hydrogen tetrachloroaurate(III) hydrate in the presence of different organic thiol ligands. Sizes, size distributions, and crystallinity of the Au-NPs were determined by high-resolution transmission electron microscopy and powder X-ray diffraction, whereas thermogravimetric analysis provided information on the organic ligand-to-gold ratios as well as amounts of contaminants. A systematic decrease in size with increasing conical bulk of the thiolate ligand is observed but large size distributions and contamination of the generated Au-NPs prohibit detailed mechanistic studies. A first-generation Fréchet dendron thiol produced the smallest and cleanest Au-NPs of the narrowest size distribution.     

New conversion of Friendl(a)nder reaction of 3-amino-lH-benzo[f]chromene-2-carbonitriles with cyclohexanone

Two different skeletons of heterocyclic compounds, quinoline and quinazolinone analogs could be obtained by a novel one-potsynthesis from substituted 3-amino-lH-benzo[f]chromene-2-carbonitrile derivatives and cyclohexanone in DMF in the catalyst ofanhydrous zinc chloride under reflux. A plausible mechanism was proposed.     

具有共轭结构的导电聚合物及其应用

具有共轭结构的导电聚合物在微电子学和光电子领域有着广泛的应用前景。文章简要介绍了这类聚合物材料的主要合成方法、导电机理及其应用概况，并对目前该领域的研究进展作了扼要评述。     

On the distribution of αp modulo one (II)

Suppose that α is an irrational number and β is a real number. It is proved that there are infinitely many prime numbers p such that ‖ αp-β‖ <p ^-9/28.     

气相色谱-质谱法分析橡苔浸膏中的挥发性化学成分

用挥发油提取器提取橡苔浸膏中的挥发油 ,利用气相色谱 -质谱法 ( GC- MS)分析了其中的化学成分 ,采用GC峰面积归一化法定量 ,鉴定出 2 4种化合物 ,共占挥发油总量的 83%以上     

一般梯图的亏格分布

本文求出了-些曲面集的亏格分布的显式表达式.在联树的基础上,通过运用曲面分类法把一般梯图的亏格分布转化为这些曲面集的线性组合,从而可求出它们的显式表达式.     

合约决策条件下的一种二层报童问题模型

考虑到顾客需求和市场价格具有高度的不确定性，供应商和零售商为了回避风险而达到最大的期望利润，双方通常可以采用签订合约的方式来进行决策。为此，我们建立了以供应商为领导层、零售商为从属层的具有合约决策的一个二层报童模型。供应商和零售商可以依据该模型的最优解通过谈判协商确定合约决策变量值以获取较高的期望利润。     

A convergence analysis of the inexact Rayleigh quotient iteration and simplified Jacobi-Davidson method for the large Hermitian matrix eigenproblem

The inexact Rayleigh quotient iteration (RQI) is used for computing the smallest eigenpair of a large Hermitian matrix. Under certain condition, the method was proved to converge quadratically in literature. However, it is shown in this paper that under the original given condition the inexact RQI may not quadratically converge to the desired eigenpair and even may misconverge to some other undesired eigenpair. A new condition, called the uniform positiveness condition, is given that can fix misconvergence problem and ensure the quadratic convergence of the inexact RQI. An alternative to the inexact RQI is the Jacobi-Davidson (JD) method without subspace acceleration. A new proof of its linear convergence is presented and a sharper bound is established in the paper. All the results are verified and analyzed by numerical experiments. This work was supported by the National Natural Science Foundation of China (Grant Nos. 10471074, 10771116) and the Doctoral Program of the Ministry of Education of China (Grant No. 20060003003)