Synthesis and Electrochemical Studies of Spinel LiNi1−xMnxVO4

Spinel compound LiNi_1−xMn_xVO₄ (0≤x≤0.4) had been prepared by using the moist chemical method. X-ray diffraction spectra showed that the lattice constant increased with x in the LiNi_1−xMn_xVO₄, XPS spectra indicating that Li1s had a chemical shift towards lesser binding energy, and manganese in LiNi_1−xMn_xVO₄ existing as the mixed valence of Mn²⁺ and Mn³⁺. The electrochemical charge and discharge testing at a current density of 0.1 mA/cm² between the potentials of 4.0 and 3.0 V vs Li/Li⁺ in 1 mol/dm³ LiPF₆/EC+DEC (1:1 by volume) at 25°C showed that LiNi_1−xMn_xVO₄ cell has a better rechargeability, but a lower cell voltage of 4.0 V vs Li/Li⁺ than that without the doping sample, and the capacity and the cycle efficiency of the Li/LiNi_1−xMn_xVO₄ cells increased with x in the LiNi_1−xMn_xVO₄.     

Effect of enzyme concentration on the dynamic behavior of a membrane-bound enzyme system

The dynamic behavior of the reaction-diffusion system, composed of glucose oxidase (EC 1.1.3.4) immobilized at a uniform concentration in a membrane, used as a glucose electrode is represented by a diffusion equation with a nonlinear reaction-term in one-dimensional space. The mathematical model is analyzed by computer simulation, that is, numerical integration of the equation under various initial and boundary conditions, to examine the effect of enzyme concentration on the response characteristics (responsiveness and linearity in response) of the electrode. The analysis of the responses of the system to stepwise changes in the boundary value (glucose concentration in simple solution) infers that the enzyme concentration governs the patterns of the spatial distributions of the substrates (glucose and dissolved oxygen) in steady states and transient responses. It is also revealed that the response characteristics of the electrode are optimized with concentration of immobilized enzyme and that the system establishes the steady states at the same spatial distributions of the substrates, regardless of the boundary value. The diffusion of the substrates and the oxygen concentration also have significant effects on the response characteristics of the electrode.     

Effects of fluorine atoms on the optical nonlinear response of stilbene derivatives

The effect of fluorine atoms on the second-order optical nonlinear response of 4-nitro-4′-methoxy-trans-stilbene and polyene derivatives containing up to three double bonds (n=1, 2, 3) has been investigated within a semiempirical context (PM3 Hamiltonian). Experimental data reported in literature indicate a β_vec(SHG) value of 34, 47 and 76 (×10⁻³⁰ esu) for n=1, 2, 3, respectively, at 0.65 eV in CHCl₃ solutions. Our calculations show that fluorinating the nitrophenyl group the β_vec(SHG) is doubled. Further increase in the second-order nonlinear response can be obtained fluorinating the CC bond linkers between the aromatic moieties.Besides, the effect of different donor-acceptor pairs has been studied and the results interpreted in the two-state model context.Some results concerning the third-harmonic generation (THG), γ (THG), are presented, and a possible interpretation proposed.     

Study of the bandwidth characteristic of a non-reflection-type gyrotron TWA

With a set of equations for the self-consistent large-signal interaction derived in this paper, the bandwidth characteristics of a non-reflection-type gyrotron-TWA using a tapered waveguide and tapered magnetic field system have been analysed. Numerical calculations indicate that under defined conditions an instantaneous bandwidth of nearly 10 % at a center frequency of 35 GHz with a length of the order of only8 cm of the rf interaction region could be achieved.     

基于小波变换的循环伏安弱信号特征信息提取

本研究采用连续小波变换(continuous wavelet transform，CWT)技术处理循环伏安弱信号，通过研究苯酚、对苯二酚和对硝基苯酚的共存体系循环伏安弱信号，表明CWT可以成功地识别出极弱信号中的指纹特征信息，并且经处理得到的对应的小波系数峰比原始信号更窄，更高，由此可以成功地确定弱峰的数目和位置。由循环伏安信号所得的结果，有力地证实CWT是循环伏安弱信号识别的有力工具，对于理解弱响应体系电化学机理具有重要作用。     

Development of a systems analysis approach for resolving the structure of biodegrading soil systems

An experimental and mathematical method is developed for the microbial systems analysis of polyaromatic hydrocarbon (PAH)-degrading mixed cultures in PAH-contaminated “town gas” soil systems. Frequency response is the primary experimental and data analysis tool used to probe the structure of these complicated systems. The objective is to provide a fundamental protocol for evaluating the performance of specific mixed microbial cultures on specific soil systems by elucidating the salient system variables and their interactions. Two well-described reactor systems, a constant volume stirred tank reactor (CSTR) and a plug flow differential volume reactor, are used in order to remove performance effects that are related to reactor type as opposed to system structure. These two reactor systems are well-defined systems that can be described mathematically and represent the two extremes of one potentially important system variable, macroscopic mass transfer. The experimental and mathematical structure of the protocol is described, experimental data is presented, and data analysis is demonstrated for the stripping, sorption, and biodegradation of napththalene.     

Analysis of polynuclear aromatic hydrocarbons by glass capillary gas chromatography using simultaneous flame ionization and electron capture detection

The possibility of simultaneous application of an electron capture (ECD) and a flame ionization detector (FID) connected to a glass capillary column for analyzing polynuclear aromatic hydrocarbons (PNA) has been investigated. The ECD/FID ratio is determined for 46 PNA compounds. The ratios vary from 0.02 to 117 with relative standard deviations better than 20 percent determined from 10 replicate analyses. The results suggest that the method may be used for obtaining additional evidence in identifying PNA in environmental samples. Impurities and transformation products in the standard were identified by computerized glass capillary gas chromatography/mass spectrometry. Quinones and diones are responsible for the high EC-response determined in some trace components in the standard. An application of the method is shown for PNA from particulates in urban atmospheres.     

有机官能化MSU-x孔分子筛的界面特征

MSU- x是自 M41S系列介孔分子筛问世以来所合成的另一类新型介孔分子筛材料 ,它具有三维立体交叉排列的 " worm- like"孔道结构特征及采用中性模板剂、廉价无毒等诸多合成优点 [1～ 4],有着潜在的应用价值 .为了改善纯硅的介孔材料的表面和孔道性质 ,扩大其应用领域 ,除了在骨架引入金属离子或在其孔道中负载催化活性物质外 ,对介孔材料进行有机官能化制备无机-有机杂化材料改善其骨架和孔道性质是当前研究的热点之一 [5].正是由于活性有机基团的存在 ,使得这些材料可直接用于催化反应 ,或作为中间介质成为其它络合离子的主体 .由于有机基…     

药物不良反应的特点与预防

药物不良反应已成为全社会关注的热点，及时了解有关不良反应的情况并采取必要的预防措施，以保证患者用药安全，维护患者身体健康是医务工作者刻不容缓的任务。     

侧链对聚对苯撑乙炔溶解性和光谱性能的影响

利用钯催化反应合成了一类侧链含不同烷氧取代基(甲氧基，辛烷氧基，十二烷氧基)的聚时苯撑乙炔，讨论了侧链烷氧取代基对聚对苯撑乙炔的分子量和溶解性的影响，比较了聚合物的紫外吸收光谱和荧光光谱特征。