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Synthesis and Stereochemistry of New cyclic Phosphate-phosphonates

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chinese chemical Letters 1997年第1期8卷 11-12页

作者： Zhou, j chen, RY NANKAI UNIV NATL KEY LAB ELEMENTOORGAN CHEMINST ELEMENTOORGAN CHEMTIANJIN 300071PEOPLES R CHINA

The novel cyclic phosphate-phosphqnates,cis/trans-2-phosp dimethyl-1,3,2-dioxaphosphorinane 2-sulfides(selenides) (7a-f),were synthesized by a one-pot reaction using tris(diethviamino)phosphine activated by iodine as the phosphorylating and ring-closing reagent in good overall yields. The geometric stereoisomers were isolated and characterized. A cis-configuration and a chair preferred conformation of one isomer of 7b were established by X-ray diffraction analysis.

关键词： Synthesis and Stereochemistry of New cyclic Phosphate-phosphonates

Methylation status of p16 gene in colorectal carcinoma and normal colonic mucosa

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World journal of Gastroenterology 1999年第5期5卷 451-454页

作者： Zhang j Lai MD chen j Hangzhou Railway cent Hosp Dept Clin Pathol Hangzhou 310000 Zhejiang Provin Peoples R China Zhejiang Univ Sch Med Dept Pathol Hangzhou 310006 Zhejiang Provin Peoples R China

INTRODUcTIONp16 gene (also known as MTS-1, INK4a, cDKN2A), located on chromosome 9p21, is a G1-specific cell-cycle regulatory gene. It is composed of three exons, which encode 156 amino acids[1]. The gene is frequently inactivated in many human cancers. Unlike other tumor-suppressor genes that are commonly inactivated by point mutations, small homozygous deletions and methylation of the promoter represent the major mechanism of p16 gene inactivation[2,3]. In the Western countries, colorectal carcinoma ranks first among malignant tumors. The mortality from colorectal carcinoma has been rapidly growing in china in the last two to three decades. The genetic alterations involved in this tumor are still unclear. Rare mutation and infrequent deletion of p16 gene in primary colorectal carcinoma has been widely reported[4]. There were a few papers on p16 gene methylation in colorectal carcinoma, but the results were contradictory[5,6]. In this study, we have examined a total of 60 samples of colorectal carcinoma and paired 60 samples of the normal colonic mucosa for methylation by means of PcR-based methylation assay. There is infrequent methylation in the promoter of p16 gene both in colorectal carcinoma and normal colonic mucosa. The methylation status in 5′ cpG island of p16 gene in colorectal carcinoma is not related to the clinical pathologic parameters of these tumors.

关键词： colonic mucosa colorectal neoplasms p16 gene methylation

Hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect neurons from cardiac arrest-induced pyroptosis

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Neural Regeneration Research 2025年第4期20卷 1103-1123页

作者： Xiahong Tang Nan Zheng Qingming Lin Yan You Zheng Gong Yangping Zhuang jiali Wu Yu Wang Hanlin Huang jun Ke Feng chen Shengli clinical Medical college of Fujian Medical University Fujian Medical UniversityFuzhouFujian ProvinceChina Department of Emergency Fujian Provincial HospitalFuzhouFujian ProvinceChina Fujian Provincial Key Laboratory of Emergency Medicine FuzhouFujian ProvinceChina The Second Department of Intensive care Unit Fujian Provincial Hospital South BranchFuzhouFujian ProvinceChina

cardiac arrest can lead to severe neurological impairment as a result of inflammation,mitochondrial dysfunction,and post-cardiopulmonary resuscitation neurological *** preconditioning has been shown to improve migration and survival of bone marrow–derived mesenchymal stem cells and reduce pyroptosis after cardiac arrest,but the specific mechanisms by which hypoxia-preconditioned bone marrow–derived mesenchymal stem cells protect against brain injury after cardiac arrest are *** this end,we established an in vitro co-culture model of bone marrow–derived mesenchymal stem cells and oxygen–glucose deprived primary neurons and found that hypoxic preconditioning enhanced the protective effect of bone marrow stromal stem cells against neuronal pyroptosis,possibly through inhibition of the MAPK and nuclear factor κB ***,we transplanted hypoxia-preconditioned bone marrow–derived mesenchymal stem cells into the lateral ventricle after the return of spontaneous circulation in an 8-minute cardiac arrest rat model induced by *** results showed that hypoxia-preconditioned bone marrow–derived mesenchymal stem cells significantly reduced cardiac arrest–induced neuronal pyroptosis,oxidative stress,and mitochondrial damage,whereas knockdown of the liver isoform of phosphofructokinase in bone marrow–derived mesenchymal stem cells inhibited these *** conclude,hypoxia-preconditioned bone marrow–derived mesenchymal stem cells offer a promising therapeutic approach for neuronal injury following cardiac arrest,and their beneficial effects are potentially associated with increased expression of the liver isoform of phosphofructokinase following hypoxic preconditioning.

关键词： bone marrow–derived mesenchymal stem cells cardiac arrest cardiac resuscitation hypoxic preconditioning liver isoform of phosphofructokinase mitochondria neuroinflammation oxidative stress pyroptosis reactive oxygen species

The Method of Fundamental Solutions for Solving Exterior Axisymmetric Helmholtz Problems with High Wave-Number

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Advances in Applied Mathematics and Mechanics 2013年第4期5卷 477-493页

作者： Wen chen ji Lin c.S.chen college of Engineering Mechanics Hohai UniversityNanjing 210098JiangsuChina Department of Mathematics University of Southern MississippiHattiesburgMS 39406USA

In this paper,we investigate the method of fundamental solutions(MFS)for solving exterior Helmholtz problems with high wave-number in axisymmetric *** the coefficientmatrix in the linear system resulting fromtheMFS approximation has a block circulant structure,it can be solved by the matrix decomposition algorithm and fast Fourier transform for the fast computation of large-scale problems and meanwhile saving computer memory *** numerical examples are provided to demonstrate its applicability and efficacy in two and three dimensional domains.

关键词： Method of fundamental solutions exterior Helmholtz problem circulant matrix fast Fourier transform axisymmetric domain

FORMATION OF GRADIENT cOATING OF Fe-BASED ALLOY WITH RARE EARTHS BY PLASMA SURFAcING

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 713-718页

作者： L.j.Shang A.Q.Sun j.F.chen c.M.Zhang Q.K.cai collegeofMaterialsScienceandEngineering ShenyangPolytechnicUniversityShenyang110023China SchoolofMaterialsandMetallurgy NortheasternUniversityShenyang110004China

A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), differential thermal analyzer(DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7c3, Fe3c, cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases cr7c3 and cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wt% RE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-c eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc. Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.

关键词： rare earth plasma surfacing Fe-base alloy microstructure graded coating

INFLUENcE OF SILIcON IN STEELS ON GALVANIZED cOATINGS

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Acta Metallurgica Sinica(English Letters) 2006年第2期19卷 85-90页

作者： c.S. che j.T. Lu G. Kong Q.Y. Xu j.H. chen college of Materials Science and Engineering South China University of Technology Guangzhou 510640 China

After steel sheets （0.37wt%Si） pre-electroplated with a thin layer of pure Fe were immersed in molten zinc for various time, the change in the microstructure of the galvanized coating on the steel and the change of α-Fe/Г interface were studied. The EDS （energy dispersive sepectroscopy） resuits show that excessive silicon accumulates on the surface of the steel substrate due to the low solubility of silicon in the Г layer after the Fe layer is depleted by the increasing growth of the compound layers. With the movement of α-Fe/Г interface towards the substrate by the Fe/Zn reaction, silicon-rich α-Fe peels off from the substrate and breaks into particles. The particles, much like an inert marker in a Kirkendall effect experiment, move towards the δ layer through the Г layer because silicon-rich α-Fe can not be adsorbed in the Г layer. On reaching the 8/F interface, the particles quickly dissolve in the δ layer, and accelerate its growth, resulting in the gradual disappearance of the Г layer. At the same time, the normal coating is quickly changed into coatings typical of reactive steels as silicon dissolved in the δ layer soon diffuses toward the ζ layer. A similar process may happen in the initial stage of galvanizing reactive steels on a small scale, although it is hard to be observed.

关键词： Zn coating intermetallics steel electrodeposition

3-D FINITE ELEMENT ANALYSIS OF THE EFFEcT OF WELDING RESIDUAL STRESS ON HYDROGEN DIFFUSION IN HYDROGEN cONTAINED ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 2007年第5期20卷 347-354页

作者： W.c. jiang j.M. Gong j.Q. Tang H. chen S.T. Tu college of Mechanical and Power Engineering Nanjing University of Technology Nanjing 210009 China

The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method （ FEM）. The effect of welding residual stress on hydrogen diffusion has been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. The hydrogen diffusion coefficient in weld metal, the heat affected zone （HAZ）, and the base metal of the 16MnR steel weldment were measured using the electrochemical permeation technique. The hydrogen diffusion without the effect of stress was also calculated and compared. Owing to the existence of welding residual stress, the hydrogen concentration was obviously increased and the hydrogen wouM diffuse and accumulate in the higher stress region.

关键词： 16MnR steel hydrogen diffusion welding residual stress finite element analysis

Effect of compressibility on the hypervelocity penetration

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Acta Mechanica Sinica 2018年第1期34卷 82-98页

作者： W.j.Song X.W.chen P.chen Department of Mechanics and Engineering Science College of Engineering Peking University Advanced Research Institute for Multidisciplinary Science Beijing Institute of Technology The State Key Lab of Explosion Science and Technology Beijing Institute of Technology centre for Applied Physics and Technology (cAPT) Peking University

We further consider the effect of rod strength by employing the compressible penetration model to study the effect of compressibility on hypervelocity ***, we define different instances of penetration efficiency in various modified models and compare these penetration efficiencies to identify the effects of different factors in the compressible model. To systematically discuss the effect of compressibility in different metallic rod-target combinations, we construct three cases, i.e., the penetrations by the more compressible rod into the less compressible target, rod into the analogously compressible target, and the less compressible rod into the more compressible target. The effects of volumetric strain, internal energy, and strength on the penetration efficiency are analyzed simultaneously. It indicates that the compressibility of the rod and target increases the pressure at the rod/target interface. The more compressible rod/target has larger volumetric strain and higher internal energy. Both the larger volumetric strain and higher strength enhance the penetration or anti-penetration ability. On the other hand, the higher internal energy weakens the penetration or anti-penetration ability. The two trends conflict, but the volumetric strain dominates in the variation of the penetration efficiency, which would not approach the hydrodynamic limit if the rod and target are not analogously compressible. However, if the compressibility of the rod and target is analogous, it has little effect on the penetration efficiency.

关键词： compressibility Hypervelocity penetration Equation of state(EOS) Shockwave Bernoulli equation

Nanocrystal Model for Liquid Metals and Amorphous Metals

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journal of Materials Science & Technology 2010年第1期26卷 69-74页

作者： X.L. Tian, c.W. Zhan, j.X. Hou, X.c. chen and j.j. Sun Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, jinan 250061, china [a] Key Laboratory of Liquid Structure and Heredity of Materials Ministry of Education Shandong University jinan 250061 china

A nanocrystal model for liquid metals and amorphous metals has been developed. With the nanocrystal model, the broadening peak profiles （BPPs） of cu, Al, Al65cu20Fe15 alloy, cu7oNi30 alloy and Fe50Si50 alloy were gained by broadening the X-ray diffraction （XRD） peaks of a crystal lattice. By comparing the BPPs with the XRD intensity curves measured on the liquid metals, it is found that the BPPs are closely in agreement with the XRD intensity curves, respectively, except the FesoSiso alloy. Therefore, the nanocrystal model can be used to determine if the atomic cluster structure of the liquid metal is similar to the structure of its crystal lattice.

关键词： Liquid metal Atomic cluster Structure crystal lattice