大科学装置同步辐射光源在生命分析化学中的应用

大科学装置的建设和水平是一个国家科技发展程度的标志. 同步辐射装置是一种先进的多学科交叉的高端大科学研究设施, 作为独特的宽光谱高亮度光源, 同步辐射光源提供了其他光源所无法比拟的优势. 我国迄今已建成的最大的大科学装置—— 上海光源的建立和应用是新中国成立60年来的重大成就之一, 标志着我国在建设国际先进水平的大型科学实验装置方面具备了高水平的技术和集成与创新的能力, 已进入国际先进行列. 本文侧重介绍同步辐射光源在生命分析化学领域中的巨大作用, 并以上海光源为例介绍同步辐射光源装置的发展和应用状况, 旨在唤起和推动我国分析化学家的高度重视, 并充分利用我国这一先进的大型科学装置, 将生命分析化学的研究推进到一个崭新的、更高的层次.     

Large-scale preparation of five polar polyphenols including three isomers from Phyllanthus emblica Linn. by preparative high-speed counter-current chromatography

The separation of polar compounds is challenging work due to poor retention and insufficient selectivity. In the present study, an efficient strategy for large-scale preparation of five polar polyphenols including three isomers from Phyllanthus emblica Linn has been established by preparative high-speed counter-current chromatography. Macroporous resin column chromatography was used for the enrichment of the polar polyphenols. However, sugar and other ultra-polar impurities were co-washed out with the targets. Liquid-liquid extraction with ethyl acetate/water (1/1, v/v) solvent system was developed to remove the ultra-polar impurities with a clearance rate of 95%. Finally, the targets were introduced to preparative high-speed counter-current chromatography for separation using ethyl acetate/n-butanol/acetic acid/water (2/7/1/10, v/v/v/v) solvent system. As a result, 191 mg of Mucic acid 1,4-lactone 5-O-gallate, 370 mg of β-Glucogallin, 301 mg of Gallic acid, 195 mg of Mucic acid 1,4-lactone 3-O-gallate and 176 mg of Mucic acid 1,4-lactone 2-O-gallate with purity higher than 98% were obtained from 1.5 g of sample. Mucic acid 1,4-lactone 3-O-gallate, Mucic acid 1,4-lactone 3-O-gallate, and Mucic acid 1,4-lactone 2-O-gallate are isomers. The results showed that high-speed counter-current chromatography could be well developed for the separation of polar compounds from natural products.     

Liquid Crystals: A Bibliography for 1975

Abstract

The static dielectric constants of biphenyl-4-p-n-alkoxybenzoates have been measured as functions of temperature. The dielectric anisotropy (δ?) for the successive homologues (hexyl to undecyl) shows an alternation similar to that exhibited by the nematic-isotropic transition temperature (T _NI). The dispersion of ?_∥ in the frequency range of 0.1-15 MHz has been studied for four successive members of biphenyl-4-p-n-alkoxybenzoates (heptyl to decyl derivatives) as well as of trans-p-n-alkoxy-α-methyl-p'-cyanophenyl cinnamates (eighth to eleventh members). For both series the relaxation frequency (f _R) and the frequency of dielectric isotropy (f _o) evaluated at a common relative temperature show an alternation similar to T _NI. For any given compound the Arrhenius plots for f _R and f _o give the same value of the activation energy (W). In the case of the biphenyl esters the vaue of W is the same for the seventh and eighth members, but increases for the higher members which exhibit a smectic phase at lower temperatures. On the contrary for cinnamic acid esters W is found to be the same for all homologues irrespective of whether the nematic phase is preceded by a smectic phase or not.     

Multi-direction-based Nelder–Mead method

The original Nelder–Mead (NM) method tends to be used to optimize low-dimensional functions. This article provides a modified NM that has the capability of large-scale optimization. The modification of NM is characterized by (a) working with a population of points, (b) mining multiple search directions through two strategies – point-grouping and variable-centroid multi-direction (VCMD), thus giving rise to VCMD plus grouping (VCMD_g) and (c) introducing random coefficients into NM and performing mutation on best-points, producing a random NM (NM_r). The combination of NM_r and VCMD_g, NM_r-VCMD_g, is just the modified NM in this work.     

Two hybrid nonlinear conjugate gradient methods based on a modified secant equation

In order to take advantage of the attractive features of the Hestenes–Stiefel and Dai–Yuan conjugate gradient (CG) methods, we suggest two hybridizations of these methods based on Andrei's approach of hybridizing the CG parameters convexly and Powell's approach of nonnegative restriction of the CG parameters. The hybridization parameter in our methods is computed from a modified secant equation obtained based on the search direction of the Hager–Zhang nonlinear CG method. We show that if the line search fulfils the Wolfe conditions, then one of our methods is globally convergent for uniformly convex functions and the other is globally convergent for general functions. We report some numerical results demonstrating the efficiency of our methods in the sense of the performance profile introduced by Dolan and Moré.     

Numerical Simulation of a Turbulent Thermal

Ascent of a large-scale thermal in a standard atmosphere is calculated with the use of the Reynolds equations and the k model of turbulence, which takes into account temperature inhomogeneity and vorticity of the flow, and the Euler equations. Results of numerical calculations of a flow examined experimentally are presented. Gas-dynamic and turbulent flow parameters obtained in calculations and experiments are compared.     

An investigation of interior-point and block pivoting algorithms for large-scale symmetric monotone linear complementarity problems

In this paper we describe a computational study of block principal pivoting (BP) and interior-point predictor-corrector (PC) algorithms for the solution of large-scale linear complementarity problems (LCP) with symmetric positive definite matrices. This study shows that these algorithms are in general quite appropriate for this type of LCPs. The BP algorithm does not seem to be sensitive to bad scaling and degeneracy of the unique solution of the LCP, while these aspects have some effect on the performance of the PC algorithm. On the other hand, the BP method has not performed well in two LCPs with ill-conditioned matrices for which the PC algorithm has behaved quite well.A hybrid algorithm combining these two techniques is also introduced and seems to be the most robust procedure for the solution of large-scale LCPs with symmetric positive definite matrices.Support of this work has been provided by the Instituto de Telecomunicações.     

二级高压驱动阵列弹珠同步弹射微型爆源的研制

针对当前大当量地下爆炸真空室模拟试验中爆源起爆方式高度依赖火药制品等问题,基于地下爆炸相似理论和二级气炮原理,自主研制了二级高压驱动阵列弹珠同步弹射微型爆源装置。装置利用二级高压气体驱动弹珠同步击碎玻璃球壳,释放球内高压气体,以模拟真实爆炸气体生成物的推出。整套爆源装置的发射参数：高压气室充气压力4 MPa,玻璃球壳内残余稳态气体压力约为3 kPa,能够用于0~20 kt当量地下爆炸成坑效应的真空室模拟。爆源适用性试验验证表明,该爆源装置的爆破机制和爆破效果满足大当量地下抛掷爆炸真空室模拟试验的功能需求,且具有较高的安全性、可控性和可操作性,为开展相关模拟试验提供了新的技术方法。

     

大型结构变形及形貌摄像测量技术研究进展

船体、机翼、工程建筑等大型结构的变形与形貌的精确测量是实验力学的基本任务之一。摄像测量具有测量精度高、范围大、非接触、可动态测量等优点,是结构形貌与运动测量的重要手段。本文介绍了作者及其所在科研团队近年来利用摄像测量技术在大型结构变形、形貌测量等方面的研究成果和典型应用范例,主要包括：提出折线光路像机链摄像测量方法与技术,用于船体等大型结构,不稳定平台的静态基准转换,以及地下工程、边坡等的多点变形长期动态监测;采用多摄像机联合组网,用于机翼、风电叶片等大型结构形貌与变形的高精度测量;在投影轮廓线辅助下进行多部像机组网,用于对大型堆场三维形貌、料堆体积和高程等的高精度测量等。     

High-effciency improved symmetric successive over-relaxation preconditioned conjugate gradient method for solving large-scale finite element linear equations

Fast solving large-scale linear equations in the finite element analysis is a classical subject in computational mechanics. It is a key technique in computer aided engineering (CAE) and computer aided ...