Formation of sol-gel nanostructured mullite by additions of fluoride ion

Summary The subject of this study was to investigate the effect of fluoride ions addition on the temperature of sol gel mullite formation based on the hypotheses that the presence of fluoride ions can decrease the temperature of mullite formation (in respect to common 980°C, in sol-gel processing). Polymeric sols were prepared by mixing TEOS and aluminum nitrate nanohydrate and by adding fluoride ions (from 2 to 5 mass%). DTA, TG, XRD and SEM were used for characterisation of mullite gel and crystalline mullite. The experimental results confirmed that the addition of fluoride ions decrease the temperature of mullite formation up to 890°C for the fluorine concentration of 3.5 mass%. Experimental results showed that the temperature of mullite formation is not a simple function of the fluoride ion content. The mechanism of fluorine effect was discussed in terms of the gelling process, gel structure and the phase separation before the mullite formation.     

Some non conventional devices with temperature control design and application

The development of a temperature control system based on semiconductor thermobatteries has been used in a set of devices for studying the martensitic transformation. The devices range from a simple stage for an optical microscope to a more elaborated system as a differential scanning calorimeter [1]. Here the attention is placed in this last system. The general problems of the temperature scanning calorimetry are reviewed from the signal theory point of view and the solutions applied to our system discussed. Some measurements are shown as an example of its application.     

Structural Features of Solid Phases and Topology of Phase Diagrams

The paper considers model phase diagrams of binary and ternary systems involving transformations (transitions) of phase equilibria. The relationship between the type of structural solidstate transformation and the type of phase diagram is shown. Topological series of phase diagrams of systems with continuous and limited types of solid solutions are considered, including phase diagrams with polymorphic transitions between intermediate solid phases of variable composition.     

Introducing Bt Gene Into Maize With Ovary Injection

It is reported here that Bt toxin gene has been successfully transferred into maize inbred line by ovary injection for the first time both at home and abroad. One transgenic plant (To) has been confirmed by Southern blotting and PCR test, and 71 progenies (T1) from T0 have been obtained through self-pollination. Of these 71 progenies, seven plants demonstrated positive results in the PCR test; four were used to feed Asian corn borer, and certain effect of insect-resistance was observed. The experiments on the ovary injection in Hainan Province have also been repeated, thus providing new chance to the application of genetic engineering to the maize improvement.     

Investigation of eutectic transformation of Zn−Al alloy by DTA

The paper discusses the investigation of crystallization of metals and alloys by differential thermal analysis (DTA). It was assumed that this method allows determination of the mechanism and kinetics of volumetric crystallization underiso conditions (e.g. anisothermal) on the basis of the parameters of the equation expressing an integral form of the DTA curve. From DTA, a course of eutectic transformation was determined for a technical Zn?Al alloy containing 4wt% Al. Investigations were carried out under continuous cooling at various rates and the kinetics parameters were determined with the KEKAM equation:-ln(1-x)=kl _n     

Room Temperature Solid State Reaction Involving Structural Transformation of Covalent Oxide Network

An interesting structural transformation from a two dimensional (2d) covalent oxide network with a layered structure to a three-dimensional (3d) network with a tunnel structure was found at room temperature in the mixture of hydrated alkali-metal molybdenum bronze and amorphous alkali-metal molybdate. From various experimental results it was concluded that the transformation was due to a room temperature solid state reaction.     

手性环丙烷类衍生物双水解转换的研究

具有四个新手性中心的螺环／环丙烷类化合物4在丙酮－12％HCl溶液中50℃下 发生双手性辅基－双水解转换反应，得到了手性环丙烷／双半缩醛类化合物，螺 [1-溴－4－羟基－5－氧杂－6－氧代双环[3.1.0]己烷－2，2′-(3′-亲核氧基－ 4′－羟基丁内酯）]（5），化学产率65％－79％，光学纯度ee≥98。通过元素分 析，[a]D^20,UV,IR,^1H NMR,^13C NMR,MS以及X射线四圆衍射测定，确认了它们的 化学结构、立体化学和绝对构型。该双半缩醛类化合物的合成方法学研究可为官能 团的转换，为某些复杂结构的手性化合物提供新的合成方法和途径。     

Dilatation transformation and sum rules for general potentials including self-consistent field potentials

The eigenfunctions and energies of general dilated Hamiltonians are expanded in powers of the dilatation parameter. These expansions, augmented by stationarity and stability conditions, are used to derive exact sum rules for bound and resonance states. Particular attention is paid to Hamiltonians with potentials which depend on external parameters, such as the nuclear coordinates in molecules, and to self-consistent potentials. The sum rules can be employed in practical computations to improve the quality of the results and may also serve in analyzing the results from approximate calculations.     

Reactions of isoquinoline derivatives with pyridinium salts yielding 4-naphthylpyridines

Regiospecific introduction of the 2-naphthyl residue into position 4 of the pyridine ring occurs in the reactions of isoquinolinium salts with 4-methylpyridinium salts through the intermolecular transformation of the isoquinoline bicyclic system involving the methyl group of the pyridinium salt. The reaction occurs under the action of methylammonium sulfite in an aqueous medium on heating. This method provides ring transformation not only for isoquinolinium salts but even for unsubstituted isoquinoline.     

单晶电极表面研究中的超高真空技术

阐述了超高真空和电化学联合技术的性能,这种技术是获取电极-溶液界面微观信息的一种手段.给出了有关样品制备和表面分析技术在实验中的方方面面,并选取了一些单晶电极表面研究的最近成果--电化学池中重构的Au(100)-hex和Pt(100)-hex单晶电极的相转变以及Pt在Ru(0001)和Ru(1010)表面,RuO2(100)在Ru(0001)上外延生长的结构研究.