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Highly Selective Preparation of 3-and 6-Modified Mannose/Altrose Derivatives

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Chemical Research in Chinese Universities 2006年第3期22卷 339-342页

作者： LIU Xiao-hong XIE Dang CHENG Chang-mei WANG Xia-yu GUO Xiao-qiang ZHAO Yu-fen Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology of Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 P.R. China Institute of Polymer Science and Engineering Xiangtan University Xiangtan 411105 P.R. China

A highly efficient method to get 3-and 6-modified mannose/ahrose derivatives for oligosaccharide synthesis is described. All the compounds were obtained exclusively with the combinations of 3-and/or 6-hydroxyl protect... 详细信息

关键词： Mannose Altrose Selective protection Selective deprotection

Expression Optimization and Characterization of the Catalytic Domain of Human MT3-MMP

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Chemical Research in Chinese Universities 2006年第2期22卷 129-133页

作者： SHI Xiu-juan JIN Feng-hai WANG Hui-ling YANG Jin-gang WANG Zhi-yong FANG Xue-xun Key Laboratory of Molecular Enzymology and Engineering the Ministry of Education School of Pharmacy College of Life Science Jilin University Changchun 130021 P. R. China

Matrix metalloproteinases（MMPs） are a family of proteases that are required for many biological processes and are also elevated in many pathological conditions. MMP inhibitors （MMPIs） may therefore be useful as therapeutic agents in treating a number of diseases including cancer, cardiovascular diseases and arthritis. Attempts have been made to develop MMPIs. Recombinant MMPs have been used to screening MMPs in vitro assays. In this work, we report the expression of MMP-16 in E. coli and the characterization of the recombinant MMP-16 with a commonly used MMP substrate DQ-gelatin.

关键词： Matrix metalloproteinase(MMP) Protein expression Catalytic domain MMP-16

Joining of SiC_p/Al composites by insert powder layers

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中国有色金属学会会刊：英文版 2005年第5期15卷 1067-1071页

作者：黄继华董月铃万云张建纲周国安 School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Mixed Al-Si, Al-Si-SiC and Al-Si-W powders were employed as insert layers to reactive diffusion bond SiC_p/6063 MMC. The results show that SiC_p/6063 MMC joints bonded by the insert layer of the mixed Al-Si powder have a dense joining layer with a typical hypoeutectic microstructure. Using mixed Al-Si-SiC powder as insert layer, SiC_p/6063 MMC can be reactive diffusion bonded by a composite joint. Because of the SiC segregations, however, there are a number of porous zones in the joining layer, which results in the low shear strength of the joints, even lower than that of joints reactive diffusion bonded by the insert layer of mixed Al-Si powder. The W added into the insert layer of Al-Si-W nearly all reacts with Al to form intermetallic WAl_ 12 during bonding. The reaction between the W and Al facilitates to form a dense joint of high quality, and the formed intermetallic WAl_ 12 has a reinforcing effect on the joints, which lead to the high shear strength of the joints. In general, under the condition of fixed bonding time (temperature), the shear strengths of the joints increase as the bonding temperature (time) increases, but tend to a maximum at bonding temperature of 600℃(time 90min).

关键词：铝硅焊接工艺复合材料粉末层插入法亚共晶

The Influence of Ion-Acoustic Turbulence on the Electron Acceleration in the Reconnecting Current Sheet

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Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 99-109页

作者： Gui-PingWu Guang-LiHuang Yu-HuaTang DepartmentofPhysics SoutheastUniversityNanjing210096 PurpleMountainObservatory ChineseAcademyofSciencesNanjing210008 DepartmentofAstronomy NanjingUniversityNanjing210093

Through solving the single electron equation of motion and the Fokker Planck equation including the terms of electric field strength and ion-acoustic turbulence, we study the influence of the ion-acoustic wave on the electron acceleration in turbulent reconnecting current sheets. It is shown that the ion-acoustic turbulence which causes plasma heating rather than particle acceleration should be considered. With typical parameter values, the acceleration time scale is around the order of 10-6 s, the accelerated electrons may have approximately a power-law distribution in the energy range 20-100 keV and the spectral index is about 3-10, which is basically consistent with the observed hard X-ray spectra in solar flares.

关键词： turbulence - acceleration of particles - Sun: X-rays gamma rays

Influence of the Choice of Core-Envelope Transition Point on the Binary Merger of Two Main-sequence Components

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Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 65-76页

作者： Xue-FeiChen Zhan-WenHan NationalAstronomicalObservatories YunnanObservatoryChineseAcademyofSciencesKunming650011／／GraduateSchooloftheChineseAcademyofSciencesBeijing100039 NationalAstronomicalObservatories YunnanObservatoryChineseAcademyofSciencesKunming650011

We have studied the influence of different choices of core-envelope transition point on the final merger of contact binaries with two main-sequence components. A binary of 1.00 + 0.90M⊙ with an initial orbital period of 0.35d is examined. The mass fraction of the primary mixed with the matter of the secondary, qmix, determined by the chosen core-envelope transition point, ranges from 0.04 to 1.00 in our analysis. If as qmix 0.71, the larger qmix is, the greater the mixing, hence the longer the blue straggler lifetime, tBS, and also the greater the luminosity. For qmix= 1.00, tBS -8.5×108yr. Estimation by (?)r - (?)a = 0.0 shows that the point at which tBS begins to increase is about qmix= 0.68. In comparison with the homogeneously mixed models, the merger with a helium profile similar to that of the primary is less luminous and has a shorter tBS.

关键词： stars: binaries - stars: evolution - stars: blue stragglers

Two-fluid Dynamics in Clusters of Galaxies

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Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 6-20页

作者： Yu-Qing LouNational Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012Department of Physics & Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing 100084 Department of Astronomy and Astrophysics, The University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 USA National Astronomical Observatories Chinese Academy of Sciences Beijing 100012

We develop a theoretical formulation for the large-scale dynamics of galaxy clusters involving two spherical 'isothermal fluids' coupled by their mutual gravity and derive asymptotic similarity solutions analytically. One of the fluids roughly approximates the massive dark matter halo, while the other describes the hot gas, the relatively small mass contribution from the galaxies being subsumed in the gas. By properly choosing the self-similar variables, it is possible to consistently transform the set of time-dependent two-fluid equations of spherical symmetry with self-gravity into a set of coupled nonlinear ordinary differential equations (ODEs). We focus on the analytical analysis and discuss applications of the solutions to galaxy clusters.

关键词： dark matter - hydrodynamics - ISM: general - galaxies: clusters -outflows winds - shocks

Energetic Coefficient of Restitution for a Planar Two-Body Oblique Collision with Friction

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Tsinghua Science and Technology 2004年第6期9卷 684-687,693页

作者：姚文莉陈滨刘才山 Department of Mechanics and Engineering Science Peking University Beijing 100871 ChinaCollege of Science Shandong University of Science and Technology Taian 271019 China Department of Mechanics and Engineering Science Peking University Beijing 100871 China

Although the coefficient of restitution was originally thought to be only a material property, the coefficient of restitution also depends upon initial conditions as well as on the frictional effect for oblique collisions. The objective of this paper is to demonstrate a method for obtaining the coefficient of restitution for oblique collisions and thereby to provide a theoretical guide for collision experiments. In this paper, we derive expressions for the energetic coefficient of restitution (e*) based on general normal contact deformation law, by which the value of e* can be obtained according to the initial conditions. An example shows that the results calculated by the derived expressions are reasonable.

关键词： oblique collision energetic coefficient of restitution tangential contact modes

Polarization in Gamma-Ray Bursts Produced by Pinch Discharge

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Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 57-64页

作者： MeiWu LiChen Ti-PeiLi KeyLab.ofParticleAstrophys. Inst.ofHighEnergyPhys.ChineseAcademyofSciencesBeijing100039 DepartmentofAstronomy BeijingNormalUniversityBeijing100875 KeyLab.ofParticleAstrophys. Inst.ofHighEnergyPhys.ChineseAcademyofSciencesBeijing100039／／CenterforAstrophysicsTsinghuaUniversityBeijing100084

Large-voltage, high-temperature plasma columns produced by pinch discharge can generate γ-ray flashes with energy spectra and spectral evolution consistent with what are observed in γ-ray bursts (GRBs), and the inverse Compton scattering (ICS) during the discharge process can produce high linear polarization. Our calculation indicates that the observed polarization depends on the angle between the line-of-sight to the GRB and the direction of the pinch discharge, but only weakly depends on observed γ-ray energy.

关键词： gamma-ray bursts radiation mechanism non-thermal polarization

Finite difference time domain method forward simulation of complex geoelectricity ground penetrating radar model

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Journal of Central South University of Technology 2005年第4期12卷 478-482页

作者：戴前伟冯德山何继善 School of Info-physics and Geomatics Engineering Central South University Changsha 410083China School

The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of curl interface underground or “v” figure complex model, it is difficult to realize. So it is important to forward the complex geoelectricity model. This paper takes two Maxwell’s vorticity equations as departure point, makes use of the principles of Yee’s space grid model theory and the basic principle finite difference time domain method, and deduces a GPR forward system of equation of two dimensional spaces. The Mur super absorbed boundary condition is adopted to solve the super strong reflection on the interceptive boundary when there is the forward simulation. And a self-made program is used to process forward simulation to two typical geoelectricity model.

关键词： ground penetrating radar finite difference time domain method forward simulation ideal frequency dispersion relationship