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Structure and properties of low-dielectric-constant poly(acetoxystyrene-co-octavinyl-polyhedral oligomeric silsesquioxane) hybrid nanocomposite

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Chinese Chemical Letters 2010年第4期21卷 488-491页

作者： Zhang, Chao xu, hong Yao Zhao, Xian Donghua Univ State Key Lab Modificat Chem Fibers & Polymer Mat Shanghai 201620 Peoples R China Donghua Univ Coll Mat Sci & Engn Shanghai 201620 Peoples R China Shandong Univ State Key Lab Crystal Mat Jinan 250100 Peoples R China

Low-dielectric-constant poly(acetoxystyrenezhi-co-octavinyl-polyhedral oligomeric silsesquioxane)(PAS-POSS) organicinorganic hybrid nanocomposite was successfully synthesized via one-step free radical polymerization and characterized by FTIR,high-resolution ~1H NMR,^(29)Si NMR,DSC,TGA,AFM,spectroscopic elhpsometry and dielectric constants measurements. The results show T_g and T_(dec) were elevated dramatically due to the incorporation of inorganic POSS *** ellipsometry and dielectric consta...

关键词： Low-dielectric-constant Hybrid nanocomposite POSS

Numerical simulation on the rheo-diecasting of the semi-solid A356 aluminum alloy

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International Journal of Minerals,Metallurgy and Materials 2009年第4期16卷 422-426页

作者： Yue-long Bai Jun xu Zhi-feng Zhang Wei-min Mao hong xu General Research Institute for Non-ferrous Metals Beijing 100088 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Research Center for Foundry Engineering North University of China Taiyuan 030051 China

The effect of injection pressure, piston velocity, and the forming temperature of semisolid slurry on the filling behavior of the semi-solid A356 aluminum alloy was investigated by simulation methods. The simulation results show that these processing parameters have an important effect on the filling behavior of the semi-solid A356 aluminum alloy. The slurry flows steadily in the cavity when the injection pressure, the piston velocity, and the forming temperature are low, but it is prone to turbulent flow when the injection pressure, the piston velocity, and the forming temperature are much higher. Therefore it is necessary to determine the appropriate processing parameters to get a steady flow of the slurry in the cavity.

关键词： semi-solid A356 aluminum alloy rheo-diecasting mould filling numerical simulation

Alisol B acetate induces apoptosis of SGC7901 cells via mitochondrial and phosphatidylinositol 3-kinases/Akt signaling pathways

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World Journal of Gastroenterology 2009年第23期15卷 2870-2877页

作者： Yong-hong xu Li-Jie Zhao Yan Li Department of DigestiveDiseases Shengjing Hospital of China Medical UniversityShenyang 110004 Liaoning Province China

AIM： To examine the effect of alisol B acetate on the growth of human gastric cancer cell line SGC7901 and its possible mechanism of action.METHODS： The cytotoxic effect of alisol B acetate on SGC7901 cells was measured by 3-（4,5-dimethylthiazol- 2-yl）-2,5-diphenyltetrazolium bromide （MI-I-） assay. Phase-contrast and electron microscopy were used to observe the morphological changes. Cell cycle and mitochondrial transmembrane potential （A^Pm） were determined by flow cytometry. Western blotting was used to detect the expression of apoptosis-regulated gene Bcl-2, Bax, Apaf-1, caspase-3, caspase-9, Akt, P-Akt and phosphatidylinositol 3-kinases （PI3K）.RESULTS： Alisol B acetate inhibited the proliferation of SGC7901 cell line in a time- and dose-dependent manner. PI staining showed that alisol B acetate can change the cell cycle distribution of SGC7901, increase the proportion of cells in G0-G1 phase and decrease the proportion of S phase cells and G2-M phase cells. Alisol B acetate at a concentration of 30 pmol/L induced apoptosis after 24, 48 and 72 h incubation, with occurrence rates of apoptotic cells of 4.36%, 14.42% and 21.16%, respectively. Phase-contrast and electron microscopy revealed that the nuclear fragmentation and chromosomal condensed, cells shrank and attachment loss appeared in the SGC7901 treated with alisol B acetate. Apoptosis of SGC7901 cells was associated with cell cycle arrest, caspase-3 and caspase-9 activation, loss of mitochondrial membrane potential and up-regulation of the ratio of Bax/Bcl-2 and inhibition of the PI3K/Akt.CONCLUSION： Alisol B acetate exhibits an antiproliferative effect in SGC7901 cells by inducing apoptosis. Apoptosis of SGC7901 cells involves mitochondria-caspase and PI3K/Akt dependent pathways.

关键词： Alisol B acetate Apoptosis Mitochondria Phosphatidylinositol 3-kinases/Akt SGC7901 cells

Electrochemical studies of 1,5-dihydroxynaphthalene as substrate for voltammetric enzyme immunoassay

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Science China Chemistry 2004年第3期47卷 184-191页

作者： JIAO Kui YAO hong xu Jin ZHANG Shusheng College of Chemistry and Molecular Engineering Qingdao University of Science and Technology Qingdao 266042 China College of Chemistry and Molecular Engineering Qingdao University of Science and Technology Qingdao 266042 China College of Chemistry and Molecular Engineering Qingdao University of Science and Technology Qingdao 266042 China College of Chemistry and Molecular Engineering Qingdao University of Science and Technology Qingdao 266042 China

A sensitive voltammetric enzyme immunoanalytical method is described for assay of horseradish peroxidase (HRP), labelled-HRP and antigen:antibody:labelled-HRP conjugate (Ag︰AB︰IgG-HRP) using 1,5-dihydroxynaphthalene (1,5-DHN) as substrate. 1,5-DHN is an electrochemical inactive substance, but it may be oxidized by O2 in air to 5-hydroxy-1,4-naphtho- quinone in basic solution, which produces a well-defined voltammetric reduction peak. After adding H2O2 and HRP, HRP catalyzes H2O2 oxidizing 5-hydroxy-1,4-naphthoquinone to 3-hydroxyphthalic acid, leading to the decrease of the voltammetric reduction peak, with which the activity of HRP and the labelled-HRP, further the antigen and antibody may be determined. The mechanism of this voltammetric enzyme-linked immunoassay system is different from the previous reports, in which there are no voltammetric reduction peaks before the addition of H2O2 and HRP, and the reduction peaks appear after the addition of H2O2 and HRP. The height of the voltammetric peak is directly proportional to the concentration of HRP in the previous systems, while the decrease of the voltammetric peak is linear with the concentration of HRP in this system. This new electrochemical method is combined with an indirect enzyme immunoassay using di-rect antigen-coating format for the detection of the purified tobacco mosaic virus (TMV) with a linear range from 25.0 to 340.0 ng/mL, and a detection limit 25.0 ng/mL.

关键词： 1,5-dihydroxynaphthalene, tobacco mosaic virus, horseradish peroxidase, enzyme immunoassay, voltammetry.

Molecular Biological and Biochemical Studies Reveal New Pathways Important for Cotton Fiber Development

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Journal of Integrative Plant Biology 2007年第1期49卷 69-74页

作者： Yu xu hong-Bin Li Yu-Xian Zhu National Laboratory of Protein Engineering and Plant Genetic Engineering Peking University Beijing 100871 China

As one of the longest single-celled seed trichomes, fibers provide an excellent model for studying fundamental biological processes such as cell differentiation, cell expansion, and cell wall biosynthesis. In this review, we summarize recent progress in cotton functional genomic studies that characterize the dynamic changes in the transcriptomes of fiber cells. Extensive expression profilings of cotton fiber transcriptomes have provided comprehensive information, as quite a number of transcription factors and enzyme-coding genes have been shown to express preferentially during the fiber elongation period. Biosynthesis of the plant hormone ethylene is found significantly upregulated during the fiber growth period as revealed by both microarray analysis and by biochemical and physiological studies. It is suggested that genetic engineering of the ethylene pathway may improve the quality and the productivity of cotton lint. Many metabolic pathways, such as biosynthesis of cellulose and matrix polysaccharides are preferentially expressed in actively growing fiber cells. Five gene families, including proline-rich proteins （PRP）, arabinogalactan proteins （AGP）, expansins, tubulins and lipid transfer proteins （LTP） are activated during early fiber development, indicating that they may also be needed for cell elongation. In conclusion, we identify a few areas of future research for cotton functional genomic studies.

关键词： cotton fiber functional genomics plant hormone transcriptome transcription factors

Synthesis and characterization of poly(methyl methacrylate-co-polyhedral oligomeric silsesquioxane)hybrid nanocomposites

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Chinese Chemical Letters 2007年第8期18卷 960-962页

作者： Ben hong Yang hong Yao xu Cun Li Shan Yi Guang School of Chemistry and Chemical Engineering Anhui University Hefei 230039 China College of Material Science and Engineering ＆ State Key Laboratory of Chemical Fibers and Polymeric Materials Donghua University Shanghai 200051 China Department of Chemical and Material Engineering Hefei University Hefei 230022 China

A novel poly（methyl methacrylate-co-polyhedral oligomeric silsesquioxane） hybrid nanocomposite was synthesized by free radical polymerization and characterized by 1H NMR, 29Si NMR, and TGA technologies. Compared wit... 详细信息

关键词： Poly(methyl methacrylate) Polyhedral silsesquioxane Nanoeomposite

Rigidity of closed submanifolds in a locally symmetric Riemannian manifold

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Applied Mathematics(A Journal of Chinese Universities) 2016年第2期31卷 237-252页

作者： GU Juan-ru LENG Yan xu hong-wei Department of Applied Mathematics Zhejiang University of Technology Hangzhou 310023 China Center of Mathematical Sciences Zhejiang University Hangzhou 310027 China

Let Mn（n ≥ 4） be an oriented closed submanifold with parallel mean curvature in an （n ＋ p）-dimensional locally symmetric Riemannian manifold Nn＋p. We prove that if the sectional curvature of N is positively pinched in [5, 1], and the Ricci curvature of M satisfies a pinching condition, then M is either a totally umbilical submanifold, or δ= 1, and N is of constant curvature. This result generalizes the geometric rigidity theorem due to xu and Gu [15].

关键词： Submanifold Ejiri rigidity theorem Ricci curvature Mean curvature.

Finite element modeling of consolidation process of Si C fiber-reinforced titanium matrix composites via matrix-coated fiber method

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Rare Metals 2015年第12期34卷 844-850页

作者： Xiang-hong xu Yan-Qing Yang Xian Luo Lin Qin Ju-hong Lou Qing Sun Shazhou Polytechnic Institute of Technology State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The consolidation process of SiCf/Ti-6Al-4V composites by matrix-coated fiber (MCF) method via hot pressing was investigated using finite element modeling (FEM). By analyzing the elastic–plastic contact deformation of the representative aligned coated fibers, the consolidation maps delineating the time–temperature–pressure relationship for full densification were constructed. Both the flow coefficient and the contact area coefficient used to describe the contact deformation were calculated according to the model. In addition, the effect of fiber content on matrix stress distribution was analyzed. The results show that fiber content is a significant factor that influences the densification process. Higher fiber content will lower the consolidation rate.

关键词： Titanium matrix composites Consolidation Finite element modeling Matrix-coated fiber

Tubes with coated and sintered porous surface for highly efficient heat exchangers

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Frontiers of Chemical Science and Engineering 2018年第3期12卷 367-375页

作者： hong xu Yulin Dai honghai Cao Jinglei Liu Li Zhang Mingjie xu Jun Cao Peng xu Jianshu Liu State Key Laboratory of Chemical Engineering East China University of Science and Technology Shanghai 200237 China Wuxi Chemical Equipment Co. Ltd Wuxi 214131 China Department of Material Science and Engineering University of California in Irvin CA 92697 USA

Surface modification is a direct and effective way to enhance the efficiency of heat exchangers. Surface modification by forming a microporous coated layer can greatly enhance the boiling heat transfer and thus achieve a high performance. In this paper, we systematically investigate the boiling behavior on a plain surface with/ without sintered microporous coatings of copper powder. The results demonstrated that the sintered surface has a better performance in nucleate boiling due to the increased nucleation sites. The superheat degree is lower and the bubble departure diameter is larger for the sintered surface than for the plain surface, so the heat can be carried away more efficiently on the sintered surface. In addition, the heat transfer capacity on the sintered surface depends on both the powder size and the coating thickness for a high flux tube. The optimum heat transfer capacity can be obtained when the thickness of the microporous coating layer is 3-5 times of the sintered powder diameter. As a result, the heat transfer coefficient tube can be up to 3 times higher for the tube with a sintered surface than that with a plain surface, showing a pronounced enhancement in heat transfer and a high potential in chemical engineering industry application.

关键词： microporous coating layer surface modification boiling enhancement sintering