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The Synthesis of 1-Aryl-5-Fluorouracil

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Chinese Chemical Letters 2000年第10期11卷 865-866页

作者： Jin Zong YOU Shao yuan chen Omar ISHRUD Yan Guang WANG Yao Zu chen Department of Chemistry Zhejiang UniversityHangzhou 310027 National Laboratory of Applied Organic Chemistry Lanzhou UniversityLanzhou 730000

A series of new type substituted 5-fluorouracil derivatives, 1-aryl-5-fluorouracil (4a-4f), were synthesized via diaryliodonium salts and the structure of the title compound was finally confirmed by IR, UV. H-1-NMR. M... 详细信息

关键词： synthesis 1-aryl-5-fluorouracil

A Factor-GARCH Model for High Dimensional Volatilities

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Acta Mathematicae Applicatae Sinica 2022年第3期38卷 635-663页

作者： Xiao-ling LI yuan LI Jia-zhu PAN Xing-fa zhang School of Economics and Statistics Guangzhou UnversityGuangzhou 510006China College of Mathematics and Informatics South China Agricultural UniversityGuangzhou 510642China Department of Mathematics&Statistics University of StrathclydeGlasgow G11XHUK

This paper proposes a method for modelling volatilities(conditional covariance matrices)of high dimensional dynamic *** combine the ideas of approximate factor models for dimension reduction and multivariate GARCH models to establish a model to describe the dynamics of high dimensional *** condition and thresholding technique are applied to the estimation of the error covariance matrices,and quasi maximum likelihood estimation(QMLE)method is used to estimate the parameters of the common factor conditional covariance *** theories are developed for the proposed *** Carlo simulation studies and real data examples are presented to support the methodology.

关键词： approximate factor models conditional variance-covariance matrix multivariate GARCH sparse estimation thresholding

Structure of human lysine methyltransferase Smyd2 reveals insights into the substrate divergence in Smyd proteins

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Journal of Molecular Cell Biology 2011年第5期3卷 293-300页

作者： Shutong Xu chen Zhong Tianlong zhang Jianping Ding State Key Laboratory of Molecular Biology and Research Center for Structural Biology Institute of Biochemistry and Cell BiologyShanghai Institutes for Biological SciencesChinese Academy of SciencesShanghai 200031China Graduate School of Chinese Academy of Sciences 320 YueYang RoadShanghai 200031China

The SET-and myeloid-Nervy-DEAF-1(MYND)-domain containing(Smyd)lysine methyltransferases 1–3 share relatively high sequence similarity but exhibit divergence in the substrate *** we report the crystal structure of the full-length human Smyd2 in complex with S-adenosyl-L-homocysteine(AdoHcy).Although the Smyd1–3 enzymes are similar in the overall structure,detailed comparisons demonstrate that they differ substantially in the potential substrate-binding *** binding site of Smyd3 consists mainly of a deep and narrow pocket,while those of Smyd1 and Smyd2 consist of a comparable pocket and a long *** addition,Smyd2,which has lysine methyltransferase activity on histone H3-lysine 36,exhibits substantial differences in the wall of the substrate-binding pocket compared with those of Smyd1 and Smyd3 which have activity specifically on histone H3-lysine *** differences in the substrate-binding site might account for the observed divergence in the specificity and methylation state of the *** modeling study of Smyd2 in complex with a p53 peptide indicates that mono-methylation of p53-Lys372 might result in steric conflict of the methyl group with the surrounding residues of Smyd2,providing a structural explanation for the inhibitory effect of the SET7/9-mediated mono-methylation of p53-Lys372 on the Smyd2-mediated methylation of p53-Lys370.

关键词： Smyd2 Smyd proteins SET family histone lysine methyltransferase epigenetics

Synthesis of nano-CaCO_3 composite particles and their application

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Journal of University of Science and Technology Beijing 2008年第1期15卷 67-73页

作者： Wei Wu Xueqin zhang Jianfeng chen Shuling Shen Key Lab of the Ministry of Education of China for Nanomaterials Beijing University of Chemical Technology Beijing 100029 China Research Center of the Ministry of Education of China for High Gravity Engineering and Technology Beijing University of Chemical Technology Beijing 100029 China

Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO3-ABS （acrylonitrile-butadiene-styrene copolymer） composite material were studied. It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate （BA） and styrene （St）. The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO3 surface treatment. 2008 University of Science and Technology Beijing. All rights reserved.

关键词： nano-calcium carbonate composite particles soapless emulsion polymerization composite material mechanical properties mechanism

Metal-organic framework loaded manganese oxides as efficient catalysts for low-temperature selective catalytic reduction of NO with NH3

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Frontiers of Chemical Science and Engineering 2017年第4期11卷 594-602页

作者： zhang, Minhua Huang, Baojuan Jiang, Haoxi chen, Yifei Key Laboratory for Green Chemical Technology of Ministry of Education R&D Center for Petrochemical Technology Tianjin University Tianjin China Collaborative Innovation Center of Chemical Science and Engineering Tianjin China

A mild in-situ deposition method was used to fabricate Mn-based catalysts on a UiO-66 carder for the selective catalytic reduction of NO by NH3 （NH3-SCR）. The catalyst with 8.5 wt-% MnOx loading had the highest catalytic activity for NH3-SCR with a wide temperature window （100-290 C） for 90% NO conversion. Char- acterization of the prepared MnOx/UiO-66 catalysts showed that the catalysts had the crystal structure and porosity of the UiO-66 carrier and that the manganese particles were well-distributed on the surface of the catalyst. X-ray photoelectron spectroscopy analysis showed that there are strong interactions between the MnOx and the Zr oxide secondary building units of the UiO-66 which has a positive effect on the catalytic activity. The 8.5 wt-% MnOx catalyst maintained excellent activity during a 24-h stability test and exhibited good resistance to SO2 poisoning.

关键词： metal-organic framework selective catalyticreduction manganese oxides deNOx SO2 resistance

Epitaxial quasi-2D/3D hybrid perovskite heterojunctions for photodetector with enhanced detectivity and stability

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Nano Research 2024年第7期17卷 6594-6602页

作者： Yifu chen Lin zhang Xinxin Peng Weiran Qin Shiqing Li Yingwei Wang Zhihui chen Si Xiao Bin Yang Biao Liu Junliang Yang Han Huang Yun Lin Jun He Liming Ding Yongbo yuan Hunan Key Laboratory of Super Microstructure and Ultrafast Process School of PhysicsCentral South UniversityChangsha 410083China Hunan Key Laboratory of Nanophotonics and Devices School of PhysicsCentral South UniversityChangsha 410083China College of Materials Science and Engineering Hunan UniversityChangsha 410082China Department of Photoelectric Information School of PhysicsCentral South UniversityChangsha 410083China Center for Excellence in Nanoscience Key Laboratory of Nanosystem and Hierarchical FabricationNational Center for Nanoscience and TechnologyChinese Academy of ScienceBeijing 100190China

Although numerous metal halide perovskite materials have been investigated in the field of optoelectronic,the development of perovskite heterojunctions with exotic structures is still ***,we report the epitaxial growth of quasi-two-dimensional(Q-2D)perovskites on methylammonium lead iodide(MAPbI_(3))single crystals to form perovskite heterojunctions with interfacial *** MAPbI_(3)adjacent to epitaxial Q-2D perovskite shows blue shifted photoluminescence with shortened lifetime,which becomes significant with the reduced layer number of the Q-2D *** findings suggest the presence of an interfacial strain gradient leading to enhanced photocarrier ***,compared to the MAPbI_(3)single crystal detector,the BA_(2)MAPb_(2)I_(7)/MAPbI_(3)(BA:n-butylamine)heterojunction-based photodetector demonstrates a bandpass detecting property and exhibits 5 times enhanced external quantum efficiency and 83 times enhanced specific detectivity(D*=3.26×10^(11)Jones).Remarkably,the unencapsulated BA_(2)MAPb_(2)I_(7)/MAPbI_(3)heterojunction is stable in ambient condition for>300 *** Q-2D/3D heterojunction shows suppressed ion inter-diffusion due to the presence of Q-2D phase.

关键词： epitaxial growth interfacial strain quasi-two-dimensional/three-dimensional(Q-2D/3D)heterojunctions ion inter-diffusion

Genetic structure of the invasive Colorado potato beetle Leptinotarsa decemlineata populations in China

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Journal of Integrative Agriculture 2020年第2期19卷 350-359页

作者： YANG Fang-yuan GUO Jian-jun LIU Ning zhang Run-zhi Institute of Entomology Guizhou UniversityGuiyang 550025P.R.China Institute of Zoology Chinese Academy of SciencesBeijing 100101P.R.China University of Chinese Academy of Sciences Beijing 100049P.R.China

The Colorado potato beetle(CPB),Leptinotarsa decemlineata Say,is an infamous invasive species *** was first found in Xinjiang Uygur Autonomous Region of China in 1993 and spread to Northeast China in *** better understand the genetic structure and the diffusion path of their populations in China,we used nine polymorphic microsatellite loci to elucidate the genetic diversity,genetic structure and gene flow among nine CPB populations across Xinjiang and Northeast *** results show that:(1)Two genetically separated clusters were identified by phylogenetic tree,principal coordinate analysis(PCoA)and Bayesian cluster *** one contained populations from Xinjiang,*** two contained populations from Northeast China.A genetic differentiation existed between the two clusters.(2)Three populations in Northeast China hold an obvious genetic differentiation according to the phylogenetic tree and PCoA,indicating that multiple introductions may occur in Northeast China.(3)The Altay population in Xinjiang showed a closer genetic relationship with the populations in Northeast China which may be due to the fact that they collectively originated in neighboring Russia.(4)Among all populations,Mulei and Wusu had obvious gene migrations from Tacheng,indicating that the inland populations are most likely to originate from Tacheng,Xinjiang.

关键词： Colorado potato beetle genetic variation alien invasive species microsatellite marker

Geomagnetic Shielding Property and Mechanism of Fe–Ni Laminated Composite

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Acta Metallurgica Sinica(English Letters) 2014年第5期27卷 918-923页

作者： Xiangyu Ma Qiang zhang Xiang chen Gaohui Wu School of Material Science and Engineering Harbin Institute of Technology Department of Applied Science and Technology Politecnico di Torino

Ni layers were deposited on the two sides of pure Fe substrate by using electroplating to form Ni/Fe/Ni diffusion couple. After diffusion heat treatment, Fe-Ni laminated composite was obtained with Fe-Ni alloy/Fe/Fe-Ni alloy structure. The results indicate that the Fe-Ni layers combine well with the substrate and the Fe-Ni/Fe interface presents an interlocking microstructure with small-size grains. The concentration of element Ni in the Fe-Ni layer decreases from surface to interior exhibiting a gradient distribution. Geomagnetic shielding factor （SF） of Fe-Ni laminated composite can reach as high as 22.6, which is about seven times of that of pure Fe substrate. Mathematical equation of SF for laminated structure was derived according to magnetic circuit and resistance theory. The theoretical expression reveals that parameters such as the thickness and magnetic permeability of the shield material play an important role in the magnetic shielding behavior and the theoretical calculation results of SF coincide well with our experimental values.

关键词： Fe-Ni laminated composite Initial permeability Magnetic shield Shielding factor

Modeling of a space flexible probe–cone docking system based on the Kane method

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Chinese Journal of Aeronautics 2014年第2期27卷 248-258页

作者： zhang Xiang Huang Yiyong chen Xiaoqian Han Wei College of Aerospace Science and Engineering National University of Defense Technology

Recent developments in micro- and nano-satellites have attracted the interest of the research community worldwide. Many colleges and corporations have launched their satellites in space. Meanwhile, the space flexible probe-cone docking system for micro- and nano-satellites has become an attractive topic. In this paper, a dynamic model of a space flexible probe-cone dock- ing system, in which the flexible beam technology is applied, is built based on the Kane method. The curves of impact force versus time are obtained by the Lagrange model, the Kane model, and the experimental method. The Lagrange model was presented in the reference and verified by both finite element simulation and experiment. The results of the three methods show good agreements on the condition that the beam flexibility and the initial relative velocity change. It is worth mentioning that the introduction of vectorial mechanics and analytical mechanics in the Kane method leads to a large reduction of differential operations and makes the modeling process much easier than that of the Lagrange method. Moreover, the influences of the beam flexibility and the initial relative velocity are discussed. It is concluded that the initial relative velocity of space docking operation should be controlled to a certain value in order to protect the docking system.

关键词： Dynamic models Flexible structures Impact testing Kane method Space probe-cone docking