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STUDY ON PYROLYSIS OF POLYPHENYLSILSESQUIOXANE

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chinese Journal of Polymer Science 2002年第6期20卷 573-577页

作者： Jun Ma Liang-he shi Jian-min Zhang Bai-yu Li De-yan Shen Jian Xu State Key Laboratory of Polymer Physics & chemistry Center for Molecular Science, institute of chemistry,chinese academy of sciences, beijing 100080 china chinese Acad Sci Inst Chem State Key Lab Polymer Phys & Chem Ctr Mol Sci Beijing 100080 Peoples R China

X-ray photoelectron spectroscopy and Raman spectroscopy were' used to determine the chemical change of polyphenylsilsesquioxane (PPSQ) during pyrolysis in flowing nitrogen. Two temperature ranges were found for pyrolysed PPSQ below and above 600degreesC, respectively. The former is related to the rearrangement of PPSQ backbone and the latter reflects that most of backbone structure of PPSQ might be broken down and unorganized. Carbon formed in carbonization of PPSQ sample pyrolysed at 900degreesC should be sp(3) bonded carbon with crystallite size effects or defects.

关键词： pyrolysis polyphenylsilsesquioxane

Boundedness of Solutions in Asymmetric Oscillations via the Twist Theorem

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Acta Mathematica Sinica,English Series 2001年第2期17卷 313-318页

作者： Yi Qian WANG institute of Mathematics. academy of Mathematics and Systems sciences. chinese academy of Science, beijing 100080 P. R. china institute of Mathematics Academy of Mathematics and Systems Sciences Chinese Academy of Science Beijing 100080 P. R. China

In this paper we consider the boundedness of all the solutions for the equation x'+ax^+ -bx^-=f(t). where f(t) is a smooth 2π-periodic function, a and b are positive constants (a≠b).

关键词： Boundedness Asymmetric Canonical transformation Twist theorem

Difference discrete connection and curvature on cubic lattice

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Science china Mathematics 2006年第11期49卷 1458-1476页

作者： WU Ke, ZHAO Weizhong & GUO Hanying Department of Mathematics, Capital Normal University, beijing 100037, china institute of Theoretical Physics, chinese academy of sciences, beijing 100080, china 1. Department of Mathematics Capital Normal University Beijing 100037 China 2. institute of Theoretical Physics Chinese Academy of Sciences Beijing 100080 China

In a way similar to the continuous case formally, we define in different but equivalent manners the difference discrete connection and curvature on discrete vector bundle over the regular lattice as base space. We deal with the difference operators as the discrete counterparts of the derivatives based upon the differential calculus on the lattice. One of the definitions can be extended to the case over the random lattice. We also discuss the relation between our approach and the lattice gauge theory and apply to the discrete integrable systems.

关键词： discrete connection, discrete curvature, noncommutative calculus, lattice gauge theory, discrete Lax pair.

Photoconductivity of fullerene derivatives

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chinese Science Bulletin 1998年第24期43卷 2071-2074页

作者： LI Fengying, XU Juhua, LI Yuliang, FAN Louzhen, REN Deyuan and ZHU Daoben institute of chemistry, chinese academy of sciences, beijing 100080, china institute of chemistry Chinese Academy of Sciences Beijing China

Two fullerene derivatives (compounds 1 and 2) have been synthesized. Their redox properties have been measured by cyclic voltammetry. The photoconductivities of poly(N_vinylcarbazo_le) (PVK) doped with fullerene and with their derivatives have been studied to explore the possible relationship between the reductibility of fullerenes and the photoconductivity of fullerenes_doped PVK. The charge generation efficiencies of PVK doped with fullerene and with its derivatives have changed remarkably: the diversity of charge generation efficiency is obvious in different doping systems. The result indicates that there is charge transfer between fullerenes and PVK.

关键词： C 60 derivatives PVK reductibility photoconductivity.

Pressure Effect on the Local Composition SurroundingEthyl Acetoacetate in Supercritical CO_2 - Ethanol Mixture

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chinese Chemical Letters 1998年第2期9卷 191-196页

作者： Jie LU Guan Ying YANG Ling ZHAO Bu Xing HAN and Hai Ke YAN(institute of chemistry, chinese academy of sciences, beijing 100080) chinese Acad Sci Inst Chem Beijing 100080 Peoples R China

The keto-enol tautomerization of ethyl acetoacetate (EAA) in supercritical CO2-ethanol mixture has been investigated at 308.15 K and at different pressures using UV-Visspectroscopy. A method for calculating the local composition about EAA has been developed based on the relationship between the equilibrium constant and dielectric property of the mixing solvent. The results indicate that the local concentration of ethanol surrounding EAA is much higher than that in the bulk.

关键词： supercritical CO_2 ethanol cosolvent cluster local density enhancement

Lattice Boltzmann simulation for the spiral waves in the excitable medium

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Communications in Nonlinear Science and Numerical Simulation 2000年第4期5卷 147-150页

作者： Guangwu YAN and Li YUAN (institute of Computational Mathematics, academy of Mathamatics and System sciences, chinese academy of sciences, beijing 100080, china e-mail: lyuan＠*** Department of Mathematics, Jilin University, Chanychun 130023, Ch Inst. of Computational Mathematics Acad. of Math. and System Sciences Chinese Academy of Sciences Beijing 100080 China Department of Mathematics Jilin University Changchun 130023 China

We propose lattice Boltzmann method for the spiral waves. Using Chapman-Enskog expansion and multiscales technique, we obtain equilibrium distribution functions of the model. As an example, we simulate the Selkov rea... 详细信息

关键词： lattice Boltzmann method excitable medium Selkov system spiral waveL

Studies on BEPC upgrade from pretzel to double-ring

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Science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2084-2089页

作者： ZHANG Chuang institute of High Energy Physics,chinese academy of sciences,beijing 100049,china 1. institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China

Physics opportunity in the charm and τ energy region calls for higher luminosity of the beijing Electron-Positron Collider (BEPC).The BEPC has experienced continuous improvement since its completion in ***,as a major upgrading project of the BEPC,aims at enhancing its luminosity of factor 30–100,following the principle of "one machine,two purposes" as adopted in BEPC,so that both high energy physics and synchrotron radiation experiments can be carried out with *** the BEPC to BEPCII,the double-ring scheme with multi-bunch e +-e-collision in the large crossing angle was studied in comparison with the single-ring pretzel *** the dedicated synchrotron radiation operation,artful "bridges" are designed to connect two halves of the outer ring in both the southern and the northern crossing *** paper reviews the studies on the BEPC upgrade from pretzel to double-ring structure of BEPCII.

关键词： collider storage ring high energy physics synchrotron radiation

Expression pattern of a β_2 tubulin gene in zebrafish embryos identified by whole mount in situ hybridization

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chinese Science Bulletin 1998年第22期43卷 1894-1898页

作者： LI Shuhong, GUO Shaodong and SUN Fangzhen institute of Developmental Biology, chinese academy of sciences, beijing 100080, china institute of Developmental Biology Chinese Academy of Sciences Beijing China

Zebrafish is a good vertebrate model for development studies. Research on gene expression and regulation during zebrafish embryonic development plays an important role in revealing the molecular mechanism of morphogenesis in vertebrate. Tubulin locates the cytoplasmic determinants in eggs, organizes the formation of basic cytoskeleton and controls various cell movements. There are several types of tubulin, each of which has specific expression regions and functions. In this study, the full_length cDNA of a Xenopus β 2 tubulin was used as template to generate Dig_labeled antisense RNA which was used as a probe to carry out in situ hybridization on whole mount zebrafish embryos. Under the experimental conditions, the tubulin transcript was first detected in a group of cells in embryos at the midblastula stage. With the development of the embryo, this transcript was gradually restricted to the nervous system. These results demonstrate that the expression of this β 2 tubulin gene in zebrafish embryos is neural specific.

关键词： tubulin gene whole mount in situ hybridization zebrafish.

Some problems on the studies of the late Pleistocene human evolution and formation of modern human populations

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Progress in Natural Science:Materials International 2006年第12期16卷 1233-1241页

作者： LIU Wu(institute of Vertebrate Paleontology and Paleoanthropology, chinese academy of sciences, beijing 100044, china) [a]institute of Vertebrate Paleontology and Paleoanthropology Chinese Academy of Sciences Beijing China

For the past two decades, studies and debates on the modern human origins around the world have attracted attentions to the late Pleistocene human evolution and formation of modern human populations, and some controversial hypotheses and problems have been proposed. In the present paper, some problems on the late Pleistocene human evolution, and the formation and differentiations of modern human populations in china are studied with a brief description and comments on the research advances in this field.

关键词： late Pleistocene human evolution formation and differentiation of modern human population paleoanthropology.