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Theoretical study on thermal decomposition of azoisobutyronitrile in ground state

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Science China chemistry 2004年第5期47卷 373-380页

作者： SUN Chengke1.2. ZHAO Hongmei1.& LI Zonghe1.1. {1. of {1., {2. Normal university, {2. 1.0875, China 2. department of chemistry, Qujing Normal College, Qujing 655000, China 1. department of {1. Beijing Normal University 100875 Beijing China 2. department of chemistry Qujing Normal College 655000 Qujing China

The thermal decomposition mechanisms of azoisobutyronitrile (AIBN) in the ground state have been investigated systematically. Based on the potential energy surfaces (PES) of various possible dissociation paths obtained using the semiempirical AM1.method with partial optimization, the density function theory B3LYP/6-31.G* method was employed to optimize the geometric parameters of the reactants, the intermediates, the products and the transition states, which were further confirmed by the vibrational analysis. The obtained results show that the re- action process of the two-bond (three-body) simultaneous cleavage Me2.CN)C─ N=N─ C(CN)Me2. 2.e2.CN)C?+N2.is much more favorable than the reaction process of the two one- bond asynchronous cleavage Me2.CN)CN=N─C(CN)Me2.? Me2.CN)CN=N?+ Me2.CN)C?? Me2.CN)C?+ N2. It was suggested that the electron shrinking effect of double bond (─N=N─) in AIBN and the stabilities of the Me2.CN)C?radical as well as N2.molecule are main factors of leading to the reaction proceeding in the former pathway. The calculation results were consistent with all the experimental facts.

关键词： azoisobutyronitrile, radicals, thermal decomposition, density function theory (DFT).

Study on the two and three-parameter working stability regions of 3Y-TZP suspension

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Science China(Technological Sciences) 2006年第5期49卷 547-568页

作者： CHEN Youqiang1. 2. ZHANG Xinni3, CHEN Sha’ou3 & QI Ping3 1. {1. of {1., Qingdao {2., Qingdao 2.6071. China 2. department of chemistry, tsinghua university, beijing 1.0084, China 3. {1. of Physics, Qingdao {2., Qingdao 2.6071. China 1. department of {1. Qingdao University Qingdao 266071 China 2. department of chemistry Tsinghua University Beijing 100084 China 3. department of Physics Qingdao University Qingdao 266071 China

We determined the variation tendency of viscosity (η) at various solids load- ing (α) for 3Y-TZP suspension as a function of dispersant concentration (Cw) using vis- cosity measurement, measured the diameter of particles as a function of Cw in very dilute suspension using light scattering method, and obtained the surface features of the sedi- ment of suspension with different Cw using SEM. We also discussed the influence of the microstructure of adsorbed polymer layers on particles and their interactions in the dis- persing medium on the stability of suspension. Then two different stable states and two different unstable states for 3Y-TZP suspension were given. Accordingly, the (Cw, η), (Cw, α), and (α, η) two-parameter, and (Cw, α, η) three-parameter stability maps were con- structed. Based on the DLVO theory calculations, the dispersant concentration, particle distance (r), and interparticle potential energy (VT) maps with various solids loading for 3Y-TZP aqueous suspension were also constructed. In (Cw, r) two-parameter coordinate system, the stable motion region map for particles was established. The Cw, α, and VT,max (the highest potential energy) surface of the potential barrier map was obtained through calculation and simulation on the basis of the surfaces of Cw, r, VT maps introduced above. The (Cw, α) two-parameter stability map was then obtained from the Cw, α, VT,max map. The results showed that this theoretical map can qualitatively prove the experimentally obtained results—the existence of different dispersed states of particles in suspension system and the variation tendency of suspension stability with changing each parame- ter—were reasonable.

关键词： 3Y-TZP, suspension, stability, DLVO theory, interparticle potential energy.

Theoretical study on the reaction mechanism of (CH3)3CO(.) radical with NO

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Science China chemistry 2004年第4期47卷 289-294页

作者： ZHAO Hongmei1.2. LIU Kun1. SUN Chengke1.& LI Zonghe1.1. {1. of {1., {2. Normal university, {2. 1.0875, China 2. department of chemistry, Beihua university, Jilin 1.2.1., China 1. department of {1. Beijing Normal University 100875 Beijing China 2. department of chemistry Beihua University 132013 Jilin China

The reaction mechanism of (CH3)3CO? radical with NO is theoretically investigated at the B3LYP/6-31.* level. The results show that the reaction is multi-channel in the single state and triplet state. The potential energy surfaces of reaction paths in the single state are lower than that in the triple state. The balance reaction: (CH3)3CONO(CH3)3CO?+NO, whose potential energy surface is the lowest in all the reaction paths, makes the probability of measuring (CH3)3CO? radical increase. So NO may be considered as a stabilizing reagent for the (CH3)3CO? radical.

关键词： (CH3)3CO. radical DFT reaction mechanism NO

Parameter estimation for whole-body kinetic model of FDG metabolism

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Progress in Natural Science:Materials International 2006年第11期16卷 1164-1170页

作者： CUI Yunfeng~1. BAI Jing~1.*, CHEN Yingmao~2.and TIAN Jiahe~2.1. department of Biomedical Engineering,{1.,{2., China 2. department of Nuclear Medicine, General Hospital of PLA, beijing 1.0853, China) [a]department of Biomedical Engineering Tsinghua University Beijing China [b]department of Nuclear Medicine General Hospital of PLA Beijing China

Based on the radioactive tracer [ ~ 1. F]2.fluoro-2.deoxy-D-glucose （FDG）, positron emission tomography （PET）, and compartment model, the tracer kinetic study has become an important method to investigate the glucose metabolic kinetics in human body. In this work, the kinetic parameters of three-compartment and four-parameter model for the FDG metabolism in the tissues of myocardium, lung, liver, stomach, spleen, pancreas, and marrow were estimated through some dynamic FDG-PET experiments. Together with published brain and skeletal muscle parameters, a relatively complete whole-body model was presented. In the liver model, the dual blood supply from the hepatic artery and the portal vein to the liver was considered for parameter estimation, and the more accurate results were obtained using the dual-input rather than the single arterial-input. The established whole-body model provides the functional information of FDG metabolism in human body. It can be used to further investigate the glucose metabolism, and also be used for the simulation and visualization of FDG metabolic process in human body.

关键词： compartment model FDG PET parameter estimation.

A new orthogonality relationship for orthotropic thin plate theory and its variational principle

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Science China(Physics,Mechanics & Astronomy) 2005年第3期48卷 371-380页

作者： LUO Jianhui 1., LONG Yuqiu 2.& LIU Guangdong 1.1. College of Civil Engineering, Hunan {1., Changsha 41.082. China 2. {1. of Civil Engineering,{2., beijing 1.0084, China 1. College of Civil Engineering Hunan University 410082 Changsha China 2. {1. of Civil Engineering Tsinghua University 100084 Beijing China

The thought how dual vectors are constructed in a new orthogonality relationship for theory of elasticity is generalized into orthotropic thin plate bending problems by using the analogy theory between plane elasticity problems and plate bending problems. Dual differential equations are directly obtained by using a mixed variables method. A dual differential matrix to be derived possesses a peculiarity of which principal diagonal sub-matrixes are zero matrixes. Two independently and symmetrically orthogonality sub-relationships are discovered. By using the integral form for elastic bending theory of orthotropic thin plate the orthogonality relationship is demonstrated. By selecting felicitous dual vectors a new orthogonality relationship for theory of elasticity can be generalized into elastic bending theory of orthotropic thin plate. By using the integral form a variational principle which is relative to differential form and a whole function expression are proposed.

关键词： theory of elasticity, thin plate theory, dual vectors, orthogonality relationship, orthotropic, variational principle.

Electric-stimulus rate encoding algorithm of Mandarin tonal information in cochlear implant

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Progress in Natural Science:Materials International 2006年第12期16卷 1315-1321页

作者： GUAN Tian~1. GONG Qin~1.and YE Datian~2.*(1. {1. of Biomedical Engineering,{1.,{2., China 2. Research Center of Biomedical Engineering, Graduate School at Shenzhen,{1., Shenzhen 51.055, China) [a]department of Biomedical Engineering Tsinghua University Beijing China [b]Research Center of Biomedical Engineering Graduate School at Shenzhen Tsinghua University Shenzhen China

The modern multi-channel cochlear implants usually extract and encode the temporal envelope cues. This kind of algorithms can hardly satisfy the users who speak tonal languages, such as Mandarin. Many studies have tried to enhance the recognition ability of Mandarin through encoding tonal information and made suggestions to frequency-modulate the fixed pulse-rate carrier with the extracted tonal information based on the rate-pitch theory in electric hearing. However, how to encode and deliver the tonal information such as F_0by changing electric-stimulus rate has not got further study in clinical electric-stimulus mode. The present paper focuses on this matter by piecewise calculating the appreciable electric-stimulus rates. Then an electric-stimulus encoding algorithm of Mandarin tone is brought forward and testified through acoustic simulations. Such conclusion can be drawn that this algorithm of electric-stimulus rate could convey tonal information well and help to enhance the Mandarin speech recognition ability.

关键词： cochlear implant tone fundamental frequency electric-stimulus rate.

Surface effects of monolayer-protected gold nanoparticles on the redox reactions between ferricyanide and thiosulfate

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Science China chemistry 2005年第5期48卷 424-430页

作者： LI Di1. SUN Chunyan1. HUANG Yunjie1. LI Jinghong1.2.& CHEN Shaowei3 1. State Key Laboratory of Electroanalytical {1., Changchun Institute of Applied {1., Chinese Academy of Sciences, Changchun 1.002., China {2., tsinghua university, beijing 1.0084, China 3. department of {1., university of California, Santa Cruz, Santa Cruz, CA 95064, USA 1. State Key Laboratory of Electroanalytical chemistry Changchun Institute of Applied chemistry Chinese Academy of Sciences 130022 Changchun China 2. department of chemistry Tsinghua University 100084 Beijing China 3. department of {1. University of California 95064 Santa Cruz Santa Cruz CA USA

Electron transfer through the self-assembled monolayers (SAMs) on gold nanopar-ticles is investigated by using the monolayer protected gold nanoclusters (MPCs) as elec-tron-transfer mediators. 3-Mercaptopropionic acid (MPA) and 1.-meraptoundecanoic acid (MUA) MPCs were employed to catalyze the redox reaction between potassium ferricyanide and sodium thiosulfate. The catalytic mechanism was proposed that the MPCs act as diffusing elec-tron-mediators and electron transfers to and from the MPCs surface. Therefore the electron transfer rate through the capping layers would be proportional to the MPCs catalyzed reaction rate, which was monitored by the UV absorbance of ferricyanide. The calculated apparent rate constant was orders of magnitude smaller than that of the maximum of tunneling current, which was attributed to the splited energy level of the nanoscale particles.

关键词： electron transfer, three-dimensional self-assembled monolayers, redox reaction, electron transfer mediator, surface effect.

Distribution of actinomycetes in oil contaminated ultisols of the Niger Delta(Nigeria)

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Journal of Environmental Sciences 2000年第3期12卷 296-302页

作者： J.P. Essien 1. E. D. Udosen 2.(1. {1. of Microbiology, {1. of Uyo, Nigeria {2. and Biochemistry, {1. of Uyo,Nigeria) department of Microbiology University of Uyo Nigeria department of {1. and Bio{1. University of Uyo Nigeria

The distribution of actinomycetes in oil contaminated sandy loam ultisols of the Niger Delta region of Nigeria was studied to aid in understanding the effect of hydrocarbons on indigenous microbial population in tropical soils. The average total counts of actinomycetes in all the oil samples analysed was 1. 3 cfu/g. Higher counts of actinomycetes were observed during the dry season than during the wet season. The counts of hydrocarbonoclastic actinomycetes correlated positively with the total count of actinomycetes. The actinomycetes were generally restricted to the top soil(0—1. cm soil depth) although a seemingly deeper(down to 40 cm soil depth) distribution was noticed in the dry season. The isolates included oil degrading species of Actinoplanes, Norcadia, Streptomyces and Streptosporangium. Their high oil utilization ability indicates their positive potential and role in the bioremediation of oil spilled soils.

关键词： actinomycetes oil contaminated ultisols

Preparation of MWNTs/Al_2._3 composites and their mechanical and electrical properties

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Science China(Technological Sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1.2. ZHAO Daqing1.2. XU Zening1.2.& WU Minsheng1.2.1. department of Mechanical Engineering,{1.,{2., China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology,{1.,{2., China 1. department of Mechanical Engineering Tsinghua University 100084 Beijing China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2.3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1.2. which is 80% higher than that of pure Al2.3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2.t% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1.2. Furthermore, the electrical resistivity is as low as 8.4×1.?3 ?·m, decreasing by 1. orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.