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Comparative studies on the concerted and two-step mechanism of ketene-methylenimine cycloaddition

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Chinese Journal of Chemistry 1996年第2期14卷 97-104页

作者： Fang, dc Fu, XY BEIJING NORMAL UNIV DEPT CHEMBEIJING 100875PEOPLES R CHINA

The concerted reaction mechansim of the ketene-methylenimine cycloaddition reaction was reconfirmed by IRC calculation at HF/6-31G* level. Other possible reaction schemes were also studied. The cis and gauch intermediate cannot be found on the potential energy surface, and the trans intermediate can only lead to a 6-membered ring product. Therefore, a two step mechanism to form p-lactam is excluded for the title reaction.

关键词： ketene methylenimine cycloaddition mechanism

Isomeric structures, isomerization and decomposition of silylenoids H2SiMX(MX=KF,KCl LiBr,NaBr and KBr)

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Chinese Journal of Chemistry 1995年第6期13卷 481-486页

作者： Feng, dc Feng, SY Deng, CH SHANDONG UNIV INST THEORET CHEMSHANDONG 250100PEOPLES R CHINA

The isomeric structures, isomerization and decomposition of silylenoids H(2)SiMX (MX=KF, KCl, LiBr, NaBr and KBr) have been investigated by ab initio molecular orbital theory. These silylenoids have four kinds of very similar equilibrium structures. The three-membered ring and p-complex structures should be stable and experimentally detectable. The lifetime of sigma-complex and tetrahedral structures would be very short and experimentally undetectable.

关键词： silylenoids H(2)SiMX isomeric structures isomerization decomposition

Random walk terminally attached to wall on different lattices

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Chinese Science Bulletin 1997年第5期42卷 433-437页

作者： Wu, dc Liao, Q Light Industry and Textile College Sichuan Union University Chengdu China

SINCE the concept of random walks (RW) was propounded formally by Pearson in 1905, there has been extensive research in mathematics. Then it expanded to many areas such as physics, chemistry, biology, engineering, commerce and social studies. The study of confined RW is interesting because of the practical applications. An RW terminally attached to an impene-

关键词： random walks lattice model absorbing wall tail chain.

EFFECT　OF　ANNEALING　ON　MICROSTRUCTURE　OF　AROMATIC　LIQUID　CRYSTALLINE　COPOLYESTERS

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Chinese Chemical Letters 1996年第1期7卷 73-74页

作者： Wang, Y Wu, dc Li, RX SICHUAN UNION UNIV COLL TEXTCHENGDU 610065PEOPLES R CHINA

The effects of thermal treatment on microstructure of the Polyesters were studied. Annealing below Tc-n, physical diffusion PrOCesses dominate to yield an increasing crystallinity along with increased molecular weight transesterification reactions are limited to the end groups and the microstructure had not changed Annealing near Tc-n, chemical processes dominate and simultaneously make the microdomains ordered more perfectly. Analysis by 13C NMR Proved that interchain transesterification had occurred.

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Synthesis and Properties of Cerium Oxide Nanometer Powders by Pyrolysis of Amorphous Citrate

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Journal of Materials Science & Technology 1997年第2期13卷 113-116页

作者： Dong, XT Hong, GY Yu, dc Yu, DS CHINESE ACAD SCI CHANGCHUN INST APPL CHEMCHANGCHUN 130022PEOPLES R CHINA

CeO2 nanometer powders of different sizes were prepared at low temperature by pyrolysis of amorphous citrate. XRD patterns show that CeO2 is cubic in structure, space group O-h(5)-F-M3M. TEM indicates that the prepared CeO2 is spherical in shape, and the particle size distribution is in narrow range. It was found that calcination temperature is a more important factor affecting the crystallite size of CeO2 than calcining time, the smaller the particle, the bigger the crystal lattice distortion, the worse the crystal growth. Solubility test of CeO2 in nitric acid reveals that the surface activity of CeO2 decreases with the increasing particle sizes. IR spectra analysis shows that the absorption of Ce-O bond is shifted to higher energy with the decrease of CeO2 particle sizes.

关键词： Cerium compounds

Protective effect of early enteral feeding on postburn impairment of liver function and its mechanism in rats

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World Journal of Gastroenterology 2000年第1期6卷 79-83页

作者： Zhu L Yang ZC Li A Cheng dc Institute of Burn Research Southwest HospitalThird Military Medical UniversityChongqing 400038China Critical Care Department Peking Union Medical College Hospital(PUMCH)Chinese Academy of Medical science(CAMS)Beijing 100730China

AIM To study the protective effect of earlyenteral feeding(EEF)on the postburnimpairment of liver function and its *** Wistar rats with 30% of total bodysurface area(TBSA)full-thickness burn *** effects of EEF on the postburnchanges of gastric intramucosal pH,endotoxinlevels in portal vein,water contents of hepatictissue,blood concentrations of tumor necrosisfactor(TNF-α),plasma activities of alanineaminotransferase(ALT)and asparateaminotransferase(AST),as well as the bloodcontents of total(TB)and direct bilirubin(DB),total protein(TP)and albumin(ALB)wereserially determined within 48h *** EEF could significantly improvegastric mucosal acidosis,reduce portal veinendotoxin level and water content of hepatictissue,as well as plasma concentrations of TNF-α at all timepoints after severe burns(P<0.01);postburn elevation of the plasma activities ofALT,AST and the contents of TB,DB wereeffectively prevented,whereas the plasmaconcentrations of TP and ALB were markedlyincreased 24 h and 48 h posturn in EEF groupcompared with that of the burn without EEFgroup(P<0.01).CONCLUSION EEF has significant beneficialeffects on the improvement of hepatic function in rats after severe burn,and is probably relatedwith an increase in splanchnic blood flow,reduction of the absorption of gut-originendotoxin and the consequent release ofinflammatory mediators.

关键词： Subject headings early enteral feeding liver postburn impairments

Synthesis of Novel Molecular Receptors from Estradiol Dimer

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Chinese Chemical Letters 1997年第6期8卷 483-486页

作者： Li, DH Shi, dc Chen, SH Zhao, HM SICHUAN UNIV FAC SCIDEPT CHEMCHENGDU 610064PEOPLES R CHINA

A novel type of estrogen-based receptor has been synthesized. These receptor compounds 3a-d have been characterized by mass spectra, H-1 NMR spectra, IR spectra and elemental analyses.

关键词： ACID

Role of Alloying Elements P, Cu in Liquid Phase Sintering of Short Cast Iron Fiber

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Journal of Materials Science & Technology 1995年第2期11卷 122-126页

作者： YU, DL HE, JL TIAN, YJ CHEN, SZ LI, dc Hanshan Univ Qinhuangdao China

The effects of alloying elements P and Cu on the sintering process and mechanical properties of short cast iron fiber compact have been studied. The experimental results show that the sintering can be enhanced obviously by addition of phosphorus. The radial crush strength of sintered compacts increases with P content up to 0.15%, but when P content is over 0.15%, eutectics formed at the interfaces of fibers cause the decrease in strength and quasi-cleavage fracture of the sintered compact. Addition of Cu could not only reduce the volume shrinkage effectively, but also increase the strength and hardness of the sintered compact.

关键词： Fibers

CD4 and CD8 T cells mediate distinct lethal meningoencephalitis in mice challenged with Tacaribe arenavirus

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Cellular & Molecular Immunology 2017年第1期14卷 90-106页

作者： Derek dc Ireland Cecilia Tami Joao Pedras-Vasconcelos Daniela Verthelyi Division of Biologics Review and Research-III Office of Biotechnology Center for Drug Evaluation and Research Food and Drug Administration Silver Spring MD 20993 USA

Neonates are at increased risk of viral encephalopathies that can result in neurological dysfunction, seizures, permanent disability and even death. The neurological damage results from the combined effect of the virus and the immune response it elicits, thus finding tools to facilitate viral clearance from central nervous system （CNS） while minimizing neuron damage remains a critical challenge. Neonatal mice inoculated intraperitoneally with Tacaribe virus （TCRV） develop seizures, hindlimb paralysis and death within 15 days of inoculation. TCRV localizes to the CNS within days of challenge, primarily infecting astrocytes in the cerebellum and brain stem. We show that infection leads to inflammation, T cell and monocyte infiltration into the cerebellar parenchyma, apoptosis of astrocytes, neuronal degeneration and loss of Purkinje cells. Infiltrating antigen-specific T cells fail to clear the virus but drive the disease, as T-cell-deficient CD3ε KO mice survive TCRV infection with minimal inflammation or clinical manifestations despite no difference in CNS viral loads in comparison with T-cell sufficient mice. CD8＋ T cells drive the pathology, which even in the absence of CD4＋ T-cell help, infiltrate the parenchyma and mediate the apoptotic loss of cerebellar astrocytes, neurodegeneration and loss of Purkinje cells resulting in loss of balance, paralysis and death. CD4＋ T cells are also pathogenic inducing gliosis and inflammation in the cerebellum and cerebrum that are associated with wasting and death several weeks after CD4＋ T-cell transfer. These data demonstrate distinct pathogenic effects of CD4＋ and CD8＋ T cells and identify them as possible therapeutic targets.

关键词： Astrocytes CD4 T cells CD8 T cells encephalitis Purkinje cells virus