胶束电动力学毛细管色谱法测定尿中核苷

用胶束电动力学毛细管色谱法测定尿中核苷.通过苯基硼酸亲和色谱柱对尿中核苷进行纯化,以十二烷基磺酸钠(SDS)-十水合四硼酸钠-磷酸二氢钠为缓冲液(pH=6.96),在未涂层石英毛细管上,于7kV恒压,29℃下进行电泳分离,检测波长为254nm.此方法用于28个正常人尿中14种核苷的测定,确定了正常成年人(汉族)尿中核苷的排放范围.     

普通有机分子或药物热分解稳定性的理论预测

采用密度泛函理论方法, 在B3LYP/6-31+G(d,p)水平上, 对任意选定的32个有机化合物或药物进行最低能量构象优化和结构参数理论计算. 建立了四极矩参数Q_ii与半数摩尔热分解函数Y_d(1/2)的相关方程, 其定量构性关系(QSPR)方程为Y_d(1/2)=-8.65747-3.8954Q_ii, 相关系数为r²=-0.99297, 交叉验证相关系数为XV-r²=0.99188, F检验结果为4237.343321. 训练集化合物的半数分解温度T_d(1/2)的平均绝对预测误差(AVEDEV)为14.70 K. 进一步利用该方程对测试集中43个分子进行预测验证, T_d(1/2)的预测值与实验值的相关系数为0.92304, Y_d的预测值与实验值的相关系数为0.99345, 证实了所建立方法的可靠性. 结构差异性分析表明, 训练集和测试集中的化合物均较均匀地分布在结构参数的3D空间中, 化合物结构具有较好的多样性和差异性.     

A variational principle for gradient flows

We verify – after appropriate modifications – an old conjecture of Brezis-Ekeland ([3], [4]) concerning the feasibility of a global variational approach to the problems of existence and uniqueness of gradient flows for convex energy functionals. Our approach is based on a concept of self-duality inherent in many parabolic evolution equations, and motivated by Bolza-type problems in the classical calculus of variations. The modified principle allows to identify the extremal value –which was the missing ingredient in [3]– and so it can now be used to give variational proofs for the existence and uniqueness of solutions for the heat equation (of course) but also for quasi-linear parabolic equations, porous media, fast diffusion and more general dissipative evolution equations.Both authors were partially supported by a grant from the Natural Science and Engineering Research Council of Canada.This paper is part of this authors Masters thesis under the supervision of the first named author.Revised version: 31 March 2004     

Identification of a Connection from Cauchy Data on a Riemann Surface with Boundary

We consider a connection ?^X{\nabla^X} on a complex line bundle over a Riemann surface with boundary M ₀, with connection 1-form X. We show that the Cauchy data space of the connection Laplacian (also called magnetic Laplacian) L : = ?^X*?^X + q{L := \nabla^X{^*\nabla^X} + q} , with q a complex-valued potential, uniquely determines the connection up to gauge isomorphism, and the potential q.     

Rail-end bolt hole fatigue crack in three dimensions

This work is concerned with subcritical crack growth in rail-end bolt hole caused by fatigue. Included in the analysis are the mechanical wheel loads and thermal fluctuations experienced by the rail. The interaction of cyclic loading with the rail geometry is considered to be essential. Finite element stress analysis is coupled with the strain energy density criterion for determining the subcritical crack growth steps. The crack can grow and follow any arbitrary surface in the three-dimensional space depending on the symmetry or antisymmetry conditions of the load and geometry. Results on crack shapes and growth rates compare favorably with those observed experimentally.     

自由溶液和筛分介质条件下芯片DNA瞬间等速电泳预浓缩的比较

利用芯片电泳方法考察瞬间等速电泳-筛分电泳偶联分析的结果,比较了自由溶液和筛分介质中DNA瞬间等速电泳的预浓缩效果.结果显示,相比较于筛分介质条件,自由溶液瞬间等速电泳有利于改善预浓缩和后续筛分电泳分离效果.对此结果的解释是:自由溶液条件下DNA迁移速度的提高可以延长瞬间等速电泳持续时间,有利于提高预浓缩效率.此外,样品压缩区带在自由溶液-筛分介质界面的二次富集也是预浓缩效果得到改善的原因之一.     

Simultaneous determination of p-phenylenediamines and aminophenols in hair dye products: interlaboratory study

An isocratic HPLC method routinely used in the National Laboratory for Food and Drug Analysis of Taiwan was validated for the simultaneous determination of six aminophenols and phenylenediamines in commercial hair dyes. After extraction of the commercial hair dye product, the dye intermediates were determined by HPLC. Recoveries from the extraction were between 91.6 and 96.5%. The method was then evaluated in an interlaboratory collaborative study according to AOAC guidelines. Five laboratories in Taiwan participated in the study that analyzed the test product, which was preanalyzed by two laboratories to ensure acceptable homogeneity. The RSD(r) and RSD(R) values of the measurements obtained for the dye intermediates in the product were < or = 3.75 and < or = 5.95%, respectively. The method demonstrated acceptable reproducibility, as evidenced by HorRat values of 0.82- 0.97. The applicability of the method to the determination of oxidative hair dye components was further demonstrated in analyses of two different products. The method is thus proposed to be used by manufacturers and laboratories to evaluate the quality of commercial hair dyes containing the six aminophenols and phenylenediamines.     

拓扑半金属材料的单晶生长研究进展

拓扑半金属已经成为凝聚态物理研究的一个热点领域,这类材料的单晶生长是研究其物理性质的基础.目前,对于拓扑材料的研究已经形成了以理论计算为指引,对潜在的拓扑材料进行单晶制备,并结合物性测量对理论预言加以验证的科研合作方式.在这种科研团队合作中,单晶生长起衔接作用.本文介绍了近年来拓扑半金属材料单晶生长方法,涵盖了拓扑Dirac半金属、Weyl半金属、Node-Line半金属以及其他打破常规分类的拓扑绝缘体及拓扑半金属材料等,并针对各个材料,详细总结了其生长方法.