Synthesis of Star-Shaped Polystyrenes with Glucose in the Chain-End and Core

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) was reacted with 4-ethylphenyl 2,3,4,6-tetra-O-acetyl-β-D -glucopyranoside using tert-butyl hydroperoxide and cobalt(II)acetate tetrahydrate in acetonitrile. The reaction provided 4-[1′-(2″,2″,6″,6″-tetramethyl-1″-piperidinyloxy)-ethyl]phenyl 2,3,4,6-tetra-O-acetyl-β-D -glucopyranoside, glycoconjugated initiator. Star-shaped polystyrene architectures in which glucose was covalently bonded in the core and chain-end were successfully prepared from the glycoconjugated initiator, styrene, and 1,4-divinylbenzene as starting materials.     

Properties of Star-Branched Polymer Chains Near a Surface

We considered two model systems of star-branched polymers near an impenetrable surface. The model chains were constructed on a simple cubic lattice. Each star polymer consisted of f = 3 arms of equal length and the total number of segments was up to 799. The excluded volume effect was included into these models only and therefore the system was studied at good solvent conditions. In the first model system polymer chain was terminally attached with one arm to the surface. The grafted arm could slide along the surface. In the second system the star-branched chain was adsorbed on the surface and the strength of adsorption was were varied. The simulations were performed using the dynamic Monte Carlo method with local changes of chain conformations. The internal and local structures of a polymer layer were determined. The lateral diffusion and internal mobility of star-branched chains were studied as a function of strength of adsorption and the chain length. The lateral diffusion and internal mobility of star-branched chains were studied as a function of strength of adsorption and the chain length. It was shown that the behavior of grafted and weakly adsorbed chains was similar to that of a free three-dimensional polymer, while the strongly adsorbed chains behave as a two-dimensional system.     

Span‐Length Distributions of Star‐Branched Polymers

Many relations between the physical, rheological or mechanical properties of linear polymers and their molar mass are well known. For disperse polymers, parameters that express these relations are typically related to (a combination of) the moments of the molar‐mass distribution. Properties of branched, nonlinear polymers have been far more difficult to describe in the form of general relations. Monodisperse star polymers or regular stars, with a distinct number of arms and equal arm length, are the simplest member of the family of branched polymers and have served as model compounds in many studies. For these regular stars, the relation between zero shear viscosity and arm or span length has been determined. To establish equivalent relations for disperse star‐branched polymers, it is important to assess the span‐length distribution and its moments; these parameters can be calculated when the distribution of the molar mass of the arms of a star‐branched polymer is known, for instance, for a known polymerization mechanism.

Span‐length probability functions of star‐branched polycondensates with x_n = 100: f = 1 (•), f = 2 (○), f = 3 (▪), f = 5 (□), and f = 10 (+).     

Synthesis and Characterization of Uncharged Water‐Soluble Star Polymers Containing a Porphyrin Core

Uncharged water‐soluble porphyrins were prepared by reaction between tetrakis(p‐hydroxyphenyl)porphyrin and chlorinated poly(ethylene glycol) methyl ethers of different molecular weights. Water‐solubility was achieved by binding four poly(ethylene glycol) branches to a porphyrin core to give star polymers with molecular weights in the range 2000–21 000 Da. Structural characterization of these star polymers was performed by means of gel permeation chromatography, NMR spectroscopy, and MALDI‐TOF analysis.     

图的星边染色综述

重图G的星色指数是指对G的边进行正常染色使得没有长为4的路或圈是双色的所需的最小颜色数,记作x'st(G).本文对图的星色指数的结果做了一个总结,给出了一些有趣的证明和技巧,并收集了一些公开问题和猜想.     

关于非负正定矩阵的L(o)der序和预偏序的一个注记

指出对于非负正定矩阵的平方阵的减序,矩阵的非负正定性可以减弱为Hermmite矩阵,同时利用矩阵的组合关系,给出Hermmite矩阵的平方矩阵的*序的等价刻画.     

星形聚氧乙烯及星形杂臂氧化乙烯-苯乙烯共聚物的合成

以原子转移自由基偶联法合成了多臂星形聚合物S-PEO和星形杂臂共聚物PEO-PS。以傅立叶红外光谱(FT-IR)和核磁共振(1H NMR)分析方法确定了产物的结构。以GPC分析测试了产物的分子量和分子量分布。GPC分析结果表明所得聚合物分子量增大,分子量分布窄,偶联反应效率可高达99%以上。     

s+r星单辐照模型与对流模型参数的对比研究

将解释s r星元素丰度的单辐照和对流2种参数化模型的最佳拟合参数进行了对比,找出了这些参量的分布规律以及各参量之间的关系,得到了s-过程和r-过程核合成相关信息,进一步确定了s r星的主要形成机制.还对文献[13]做了有益的补充,给出了单辐照模型r-过程分量系数与s-过程分量系数之间的关系图.     

几何校正在大区域地理影像数据处理中的应用

遥感资料的准备和处理是遥感技术在实际应用中的核心工作,几何校正是利用地面控制点(GCP)对遥感影像进行的几何纠正。文章用多种RS软件对卫星数据进行几何校正,并对相关模型参数设置、控制点输入和几何校正作了探讨。     

流夸克质量对混合星性质的影响

利用强子物质的相对论平均场理论和夸克物质的有效质量口袋模型, 研究流夸克质量的选取对混合星性质的影响. 结果表明, 随着流夸克质量的增大, 强子\|夸克相变使密度变大, 超子种类变多, 混合相区域的状态方程变硬, 中子星的最大质量及半径变大. 当奇异流夸克质量由90 MeV增到200 MeV时, 混合星最大质量由1.4 M⊙增至1.63 M⊙（M⊙=1.99×1030kg为太阳质量）, 半径由10.24 km增至11.64 km. 