Charge ordering modulations in a Bi_0.4Ca_0.6MnO₃ film with a thickness of 110 nm

The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi 0.4 Ca 0.6 MnO 3 film with a thickness of 110 nm at 103 K.Six different types of superlattice structures are observed using the selected-area electron diffraction(SAED) technique,while three of them match well with the modulation stripes in high-resolution transmission electron microscopy(HRTEM) images.It is found that the modulation periodicity and direction are completely different in the region close to the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface from those in the region a little further from the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface,and the possible reasons for this are discussed.Based on the experimental results,structural models are proposed for these localized modulated structures.     

Effect of C doping on the structural and electronic properties of LiFePO₄:A first-principles investigation

Using first-principles calculations within the generalized gradient approximation (GGA) +U framework, we investigate the effect of C doping on the structural and electronic properties of LiFePO 4 . The calculated formation energies indicate that C doped at O sites is energetically favoured, and that C dopants prefer to occupy O 3 sites. The band gap of the C doped material is much narrow than that of the undoped one, indicating better electro- conductive properties. To maintain charge balance, the valence of the Fe nearest to C appears as Fe 3+ , and it will be helpful to the hopping of electrons.     

Nd薄膜靶表面氧化过程研究

用Ａｕｇｅｒ电子能谱（ＡＥＳ）对Ｘ光激光实验使用的Ｎｄ薄膜靶的表面氧化进行了分析，结合Ａｒ离子束刻蚀进行元素的深度分布剖析，得到了表面氧化层厚度，所得结果与Ｒｕｔｈｅｒ－ｆｏｒｄ背散射（ＲＢＳ）方法测量的结果相吻合。实验表明，样品暴露在空气中２０至３０ｍｉｎ，氧化即基本达到饱和，相应的氧化层厚度约为２０ｎｍ。     

核磁共振碳谱的研究:烷烃分子的化学位移δ与原子距边矢量μ

系统研究了核磁共振碳谱及其化学位移规律性。并提出了一种新的分子图论参数：原子距离－边数矢量（μ矢量），并发现它与烷烃的１３－ＣＮＭＲ有良好的相关性。     

Potentiometric study of end-point detection in the coulometric determination of carbon dioxide

The coulometric determination of carbon dioxide is based on the alkalimetric titration of the product of absorption of carbon dioxide in an organic solution of monoethanolamine. The processes occurring in various solvents have been investigated and optimized for analytical application. The protolytic reactions of 2-hydroxyethylcarbamic acid have been investigated in 2-propanol + 2, 5 and 10% water, dimethylformamide + 2% water, dimethylsulphoxide +5, 10 and 20% water. In coulometric generation of the base, 0.1M solutions of tetraethylammonium bromide in these solvents were used. The course of the titration was followed potentiometrically with glass and antimony indicator electrodes. From the titration curves the autoprotolysis constants of the mixed solvents and protonation constants of monoethanolamine in them were calculated. These constants and the concentration of monoethanolamine influence the size of the end-point break for the titrations. On this basis, optimal conditions for analysis have been selected and the total carbon content in samples of natural waters has been determined.     

碳笼化合物的高效液相色谱研究

采用化学键合固定相（ＤＮＡＰ－ＳＰ）及二元混合流动相（５０％苯－正已烷），对碳笼化合物Ｃ６０与Ｃ７０的高效液相色谱（ＨＰＬＣ）分析及分离进行了研究。比较了多种流动相对Ｃ６０、Ｃ７０分离效果的影响，苯／正已烷混合体系是最好的流动相。     

神经网络与紫外光谱法同时测定芳香类化合物

测定了苯酚、苯胺、α萘胺、间二硝基苯及对氧基苯甲醛混合体系的紫外光谱，用神经网络法直接对混合体系紫外光谱数据进行处理，成功地测定了混合体系各组分含量，结果良好     

Plastic analysis of the crack problem in two-dimensional decagonal Al-Ni-Co quasicrystalline materials of point group 10,■

The fundamental plastic nature of the quasicrystalline materials remains an open problem due to its essential complicacy.By developing the proposed generalized cohesive force model,the plastic deformation of crack in point group 10,10 decagonal quasicrystals is analysed strictly and systematically.The crack tip opening displacement(CTOD) and the size of the plastic zone around the crack tip are determined exactly.The quantity of the crack tip opening displacement can be used as a parameter of nonlinear fracture mechanics of quasicrystalline material.In addition,the present work may provide a way for the plastic analysis of quasicrystals.     

Optical biosensors based on Prussian Blue films

Optical biosensing schemes based on enzymatically modified inorganic/organic transparent films predominately composed of Prussian Blue are demonstrated. The composite film, which is non-electrochemically deposited on a non-conducting support. is used as an optical transducer for flow-through biosensors based on hydrolases and oxidases. Urease and glucose oxidase are utilized as model enzymes. Action of the urea biosensor is based on optical pH sensitivity of Prussian Blue indicator. The glucose biosensor is acting as first-generation optical biosensor based on in situ generated Prussian White transducer for hydrogen peroxide. These simple, single-pass transmission optical biosensors exhibit sensitivity in the millimolar range of concentration. The biosensors are very stable owing to presence of a poly(pyrrolylbenzoic acid) network in the composite material. This organic polymer plays a dual role as a binding agent for inorganic material and as a functionalized support for strong covalent immobilization of enzyme molecules.     

Coulometric titrations in microscale study of ionic equilibria

Summary Coulometric titration, a well established technique in research and in routine analysis, can successfully be applied to the study of ionic equilibria in solution. Processes, where either lyate or lyonium ions serve as titrants, for determination of acids and bases, respectively, were investigated. Among the systems studied are: autoprotolytic equilibria of various amphiprotic solvents, acid-base equilibria in water, organic and mixed solvents and complexation reactions. In all these examples the titration was followed by a potentiometric pH-indicator electrode. In nonaqueous solvents coulometry overcame the limited solubility of electrolytes, the difficulty of standardization on solutions and the necessity of working in isolated systems to avoid contamination of the sample with water vapour or with carbon dioxide.Because volumes below 1 ml and concentrations in the order of 0.001 mol/l can be used, this technique can be successfully applied to the investigation of micromole amounts of compounds, when protolytic properties of substances available in minute quantities should be evaluated. Furthermore this technique was applied to the evaluation of protonation constants of biologically important buffers and the stability constants of their calcium complexes.