检索结果-南通市图书馆

Theoretical study on the hydrolysis mechanism of N,N-dimethyl-N′-(2.,3′-dideoxy-3′-thiacytidine)formamidine

在线全文

学校读者我要写书评

暂无评论

science china {2. 2008年第10期51卷 911-917页

作者： ZHANG Chang1 & XUE Ying2. 1 College of chemistry and Environment Protection engineering, Southwest {2. for Nationalities, Chengdu 610041, china 2.College of chemistry, sichuan {2., Chengdu 610064, china 1. College of chemistry and Environment Protection engineering Southwest University for Nationalities Chengdu 610041 China 2. College of chemistry Sichuan University Chengdu 610064 China

The hydrolysis mechanisms of N,N-dimethyl-N′-(2.,3′-dideoxy-3′-thiacytidine)formamidine (FA-3TC) in the gas phase and in aqueous solution were studied by use of the density functional theory B3LYP/6-31+G(d, p) method. Two possible reaction pathways in the title reaction were considered. In one pathway water attacks the C=N double bond first (path A) while in the other water attacks the C—N single bond first (path B). The calculated results indicate that the first step in both pathways is the rate-limiting process and path A is more favorable than path B in the gas phase. The effect of solvent water on the title reaction was assessed at the B3LYP/6-31+G(d, p) level of theory based on the po-larizable continuum model (CPCM). In water the first mechanism (path A) is also favored.

关键词： N N-dimethyl-N′-(2. 3′-dideoxy-3′-thiacytidine)formamidine hydrolysis solvent effect B3LYP polarizable continuum model

γ-Hydroxy-α,β-acetylenic esters:asymmetric syntheses and applications

在线全文

学校读者我要写书评

暂无评论

science china {2. 2010年第1期53卷 21-35页

作者： GAO Ge1 & PU Lin2.1department of chemistry,{2. university,Chengdu 610064,china 2.0} of chemistry,university of Virginia,Charlottesville,Virginia 2.904-4319,USA 1. department of chemistry Sichuan University Chengdu 610064 China2. Department of Chemistry University of Virginia Charlottesville Virginia 22904-4319 USA

γ-Hydroxy-α,β-acetylenic esters are versatile synthetic precursors to many organic *** paper reviews the synthesis of chiral γ-hydroxy-α,β-acetylenic esters by asymmetric reduction of γ-oxo-α,β-acetylenic esters,enantioselective addition to aldehydes in the presence of chiral catalysts,and diastereoselective addition to chiral *** preparation of racemic γ-hydroxy-α,β-acetylenic esters is also *** are provided for the application of γ-hydroxy-α,β-acetylenic esters in organic synthesis.

关键词： γ-hydroxy-α β-acetylenic ester asymmetric enantioselective diastereoselective

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation in an expanded granular sludge bed reactor

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2003年第3期15卷 423-432页

作者： ZHANG Dai-jun 1,2.(1. department of Environmental science, Chongqing {2., Campus A, Chongqing 400044, china 2. Key Laboratory for the Southwest china Resources Exploitation and Environmental Disaster Control engineering, Ministry of Education, china.) department of Environmental science Chongqing University China

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation(ANAMMOX) was studied in an expanded granular sludge bed(EGSB) reactor in this work. Experimental results from the continuous treatment of wastewater with nitrite and ammonium, which lasted for 107 days, demonstrated that wastewater with high nitrite and ammonium could be anaerobically treated in an expanded granular sludge bed reactor. More than 91% to 97% of COD were removed at up to about 3.9 g COD/(L·d) of COD volumetric loading rate. More than 97% to 100% of nitrite was denitrified at up to about 0.8 g NO -_2.N/(L·d), which is 16 times higher than that in a conventional activated sludge system with nitrification/denitrification(0.05 gN/(L·d)). No dissimilatory reduction of nitrite to ammonium occurred in the process. However, maximum of about 40% ammonium was found to be lost. Batch tests of 15 days with sludge from the reactor showed that 100% of nitrite was denitrified completely, and about 3% of ammonium was removed when only ammonium (34.3 mg/L) and nitrite(34.3 mg/L) were added into the sludge suspension medium. Furthermore, about 15% of ammonium amounts were lost with organic COD addition. It suggested that the methanogenesis in the system could enhance ANAMMOX because of intermediate hydrogen produced during methanogenesis.

关键词： methanogenesis denitrification ANAMMOX EGSB reactor

PRECIPITATION HARDENING IN B2.ORDERED NiAl BY Ni_(2.AlTi COMPOUND

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2001年第5期14卷 313-318页

作者： W.H. Tian, K. Ohishi and M. Nemoto 1)department of Materials Physics and chemistry, {2. of science and Technology Beijing, Beijing 100083, china 2.department of Materials science and engineering, Faculty of engineering 36, Kyushu {2., Fuk Dept. of Mat. Phys. and Eng. Univ. of Sci. and Technol. Beijing Beijing 100083 China

Microstructural variations and correlated hardness changes in B2.ordered NiAl containing fine precipitation of Ni2.lTi have been investigated by means of transmission electron microscopy (TEM) and hardness tests. The amount of age hardening is not large as compared to the large microstructural variations during aging. TEM observations have revealed that the L2.-type Ni2.lTi precipitates keep a lattice coherency with the NiAl matrix at the beginning of aging. By longer periods of aging Ni2.lTi precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. The temperature dependence of the yield strength of precipitate-containing B2.ordered NiAl was investigated by compression tests over the temperature range of 873-12.3 K. The fine precipitation of Ni2.lTi was found to enhance greatly the yield strength and the high-temperature strength is comparable with that of superalloy Mar-M2.0.

关键词： Aluminum Hardening Mechanical properties Nickel Precipitation (chemical)

Polymer-assisted nanoparticulate contrast-enhancing materials

在线全文

学校读者我要写书评

暂无评论

science china {2. 2010年第3期53卷 479-486页

作者： DING Yin1,3,HU Yong2.WU Wei1 & JIANG XiQun1 1Laboratory of Mesoscopic chemistry and department of Polymer {2. and engineering,College of chemistry & Chemical engineering,Nanjing university,Nanjing 2.0093,china 2.ational Laboratory of Solid State Microstructure,department of Material {2. and engineering,Nanjing university,Nanjing 2.0093,china 3Key Laboratory of Analytical chemistry for Life {2.,Ministry of Education,School of chemistry and Chemical engineering,Nanjing university,Nanjing 2.0093,china 1. Laboratory of Mesoscopic chemistry and department of Polymer {2. and engineering College of Chemistry & Chemical Engineering Nanjing University Nanjing 210093 China3. Key Laboratory of Analytical Chemistry for Life Science Ministry of Education School of Chemistry and Chemical Engineering Nanjing University Nanjing 210093 China2. National Laboratory of Solid State Microstructure Department of Material Science and Engineering Nanjing University Nanjing 210093 China

The application of nanotechnology in medicine research has significant potential in modern biomedical research,disease diagnosis and *** fluorophore-based detection techniques have been widely used as imaging and signal transduction tools for the detection of trace levels of *** photosensitivity of the fluorophores,however,limits their application in such complex environments as living bio-systems where degradation or photobleaching *** nanoparticles have unique and stable optical,electrical,magnetic and catalytic properties because of their various shapes,sizes and *** potential of the nanoparticles as novel imaging agents has been studied as a possible solution to this *** modification of inorganic nanoparticles could enhance their biostability in physiological conditions and ability of targeting bioactive molecules.

关键词： contrast agent cell image gold nanoparticles iron oxide nanoparticles carbon nanotubes polymeric-inorganic hybrid nanoparticles

Biological exposure models for oil spill impact analysis

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2000年第4期12卷 482-485页

作者： XIONG De qi 1, Mark Reed 2. Narve Ekrol 2.(1. department of Marine Environmental engineering, Dalian Maritime {2., Dalian 11602., china E mail: deqi@*** 2. department of Environmental engineering, SINTEF Applied chemistry Institut 大连海事大学辽宁大连 1 1 6 0 2 SINTEF Applied chemistry Institute 挪威 Trondheim 70 3 4

The oil spill impact analysis (OSIA) software system has been developed to supply a tool for comprehensive, quantitative environmental impact assessments resulting from oil spills. In the system, a biological component evaluates potential effects on exposed organisms based on results from a physico chemical fates component, including the extent and characteristics of the surface slick, and dissolved and total concentrations of hydrocarbons in the water column. The component includes a particle based exposure model for migratory adult fish populations, a particle based exposure model for spawning planktonic organisms (eggs and larvae), and an exposure model for wildlife species (sea birds or marine mammals). The exposure model for migratory adult fish populations simulates the migration behaviors of fish populations migrating to or staying in their feeding areas, over wintering areas or spawning areas, and determines the acute effects (mortality) and chronic accumulation (body burdens) from the dissolved contaminant. The exposure model for spawning planktonic organisms simulates the release of eggs and larvae, also as particles, from specific spawning areas during the spawning period, and determines their potential exposure to contaminants in the water or sediment. The exposure model for wild species calculates the exposure to surface oil of wildlife (bird and marine mammal) categories inhabiting the contaminated area. Compared with the earlier models in which all kinds of organisms are assumed evenly and randomly distributed, the updated biological exposure models can more realistically estimate potential effects on marine ecological system from oil spill pollution events.

关键词： oil spill biological exposure acute effects chronic accumulation migration of fish spawning of eggs and larvae habitat

“LIVING”/CONTROLLED RADICAL POLYMERIZATION OF ETHYL METHYLACRYLATE WITH 2.2.-AZOBISISOBUTYRONITRILE/FERRIC CHLORIDE/TRIPHENYLPHOSPHINE INITIATION SYSTEM

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer science 2000年第2期18卷 149-153页

作者： Xiao-ping Chen Kun-yuan Qiu department of Polymer science and {2., College of chemistry, Peking university, Beijing 100871, china Peking Univ Coll Chem Dept Polymer Sci & Engn Beijing 100871 Peoples R China

'Living'/controlled radical polymerization of ethyl methacrylate (EMA) was carried out with a 2.2.-azobisisobutyronitrile (AIBN)/ferric chloride (FeCl_3)/triphenylphosphine (PPh_3) initiation system at 85℃. Thc numberaverage molecular weight (M_n) increases linearly with monomer conversion and the rate of polymerization is first order withrespect to monomer concentration. The M_w of PEMA ranges from 3900 to 17600 and the polydispersity indices are quitenarrow (1.09～1.2.). The conversion can reach up to～100% and M_w of the polymers obtained is close to that designed. Thepolymerization mechanism belongs to the reverse atom transfer radical polymerization (ATRP). The polymer was end-functionalized by chlorine atom, which acts as a macroinitiator to proceed extension polymerization in the presence ofCuBr/bipy catalyst system via an ATRP process. The presence of ω-chlorine in the PEMA obtained was identified by ~1H-NMR spectrum.

关键词： 'Living'/controlled radical polymerization Reverse ATRP Ethyl methacrylate AIBN/FeCl_3/PPh_3 Bulk polymerization

Dynamic damage and stress-strain relations of ultra-high performance cementitious composites subjected to repeated impact

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2010年第6期53卷 1520-1525页

作者： LAI JianZhong1 & SUN Wei2.1 department of Materials science and {2.,Nanjing university of science and Technology,Nanjing 2.0094,china 2.College of Materials science and {2.,Southeast university,Nanjing 2.1189,china 1. department of Materials science and {2. Nanjing University of Science and Technology Nanjing 210094 China2. College of Materials Science and Engineering Southeast University Nanjing 211189 China

Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste *** dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity *** show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume *** stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation *** effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were *** show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.

关键词： ultra-high performance cementitious composites (UHPCC) split Hopkinson pressure bar (SHPB) repeated impact damage stress-strain

A computer simulation of nucleation and growth of thin films

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2004年第4期47卷 442-451页

作者： ZHENG Xiaoping1,ZHANG Peifeng2.HE Deyan2.LIU Jun2. MA Jiantai3 1. Key Laboratory of Opto-Electronic Technology and Intelligent Control, Ministry of Education, Lanzhou Jiaotong university, Lanzhou 730070, china 2. School of Physical {2. and Technology, Lanzhou university, Lanzhou 730000, china 3. School of chemistry and chemistry engineering, Lanzhou university, Lanzhou 730000, china 1. Key Laboratory of Opto-Electronic Technology and Intelligent Control Ministry of Education Lanzhou Jiaotong University 730070 Lanzhou China 2. School of Physical science and Technology Lanzhou University 730000 Lanzhou China 3. School of chemistry and chemistry {2. Lanzhou University 730000 Lanzhou China

A three-dimensional kinetic Monte Carlo technique has been developed for simulating the nucleation and growth of thin films. This model involves incident atom attachment, surface diffusion of the atoms on the growing surface and atom detachment from the growing surface. It takes some new effects into account, such as a significant improvement in calculation of activation energy for the atom diffusion, which renders the model more reasonable. In addition three optimum temperatures and the consistency of their dependence on deposition rate have been found out; the dependence of the surface roughness and relative density on the deposition rate has been discussed; and the approximation of freezing neighbour atoms and periodic boundary conditions has been applied.

关键词： Monte Carlo, thin film, nucleation, surface roughness, relative density.