Studies on the Middle-phase Microemulsion of Lauric-N-methylglucamide

The phase behaviour of the middle-phase microemulsion for the quaternary system lauric-N-methylglucamide （MEGA-12）/n-butanollalkane/water has been studied with Winsor type, δ-γ, fishlike and novel ε-β fishlike phase diagrams. A series of phase inversions Winsor I （2）→Ⅲ（3）→Ⅱ （ 2 ） were observed for the three kinds of phase diagrams. The phase types, the phase volumes and the range of alcohol concentrations from the beginning to the end of the middle-phase microemulsion were obtained from Winsor phase diagram. From δ-γ, fishlike phase diagram, the physicochemical parameters, such as the mass fraction of n-butanol in the hydrophile-lipophile balanced inteffacial layer, A^s, the coordinates of the start and end points of the middle-phase microemulsion, and the solubilities of MEGA-12 and n-butanol in alkane phase were calculated. The novel ε-β fishlike phase diagram was also presented. From this kind of diagram, the above experimental phenomena were observed and the physicochemical parameters were calculated precisely. The novel fishlike phase diagram has advantages over the Winsor and δ-γ fishlike phase diagrams in the evaluation of the solubilization power of the microemulsion and calculation of the related physicochemical parameters.     

轴对称压—弯下圆板中圆脱层的后屈曲扩展

本文分析了周边承受轴对称压一弯载荷的圆板中薄圆脱层的后屈曲扩展.运用基于四阶龙格-库塔积分公式的打靶法得到无量纲形式Von Karman非线性方程组的单参数解族.利用与路径无关的M积分导出能量释放率表达式并给出相应的数值解.文中还探讨了分叉、跳跃及扩展的可能性.     

Trimeric liquid crystals containing lateral alkyl chains

Abstract

The first twelve members of the n-alkyl 2,5-bis-(4′-cyanobiphenyloxybutyloxy)-benozates have been prepared. The compounds are nematogenic; in addition the first three members exhibit a smectic A phase. The nematic-isotropic transition temperatures decrease with little or no alternation on increasing the number of methylene groups in the lateral chain; this is analogous to the behaviour found in monomeric and polymeric mesogens possessing lateral alkyl chains.     

Microwave heating of ceramic composites

The microwave heating of a ceramic composite is modelled andanalysed. The composite consists of many small ceramic particlesembedded in a ceramic cement. The composite is assumed to bewell insulated, and each particle is assumed to be in imperfectthermal contact with the surrounding cement. Based on thesetwo assumptions an asymptotic theory exploiting the small Biotnumber and small non-dimensional contact conductance is developed.Our asymptotic theory yields a set of nonlinear partial differentialequations which govern the temperature in the composite. Theseare reduced to a set of coupled nonlinear ordinary differentialequations in which the surface area of each particle entersas a parameter. Recent experiments with such composites haveshown that the steady-state temperature of the composite isstrongly dependent upon the radii of the embedded particles.Our model captures this effect. In fact, our analysis showsthat the assumption of imperfect thermal contact between theparticles and the ceramic cement is essential for this trendto be established.     

在接枝微粒PS/SiO2上固载季铵盐及初步应用

采用"grafting from"的方式在溶液聚合体系中将苯乙烯(St)接枝聚合在微米级硅胶表面,制备了接枝微粒PS/SiO2;使用新型氯甲基化试剂1,4-二氯甲氧基丁烷,对接枝的聚苯乙烯进行了氯甲基化反应,制得了接枝有氯甲基聚苯乙烯(CMPS)的接枝微粒CMPS/SiO2;使用叔胺试剂对CMPS大分子链上的苄氯基团实施了季铵化反应,最终制得了固载有季铵盐(Quaternary salt)的复合型功能微粒QPS/SiO2.用红外光谱(FTIR)与化学分析法对功能微粒QPS/SiO2的化学结构与组成进行了表征;研究了各种因素对CMPS/SiO2季铵化反应的影响规律;初步考察了QPS/SiO2对大肠杆菌的(E.coil)抗菌性能.研究结果表明,接枝微粒CMPS/SiO2的季铵化反应比较容易进行;溶剂性质、叔胺试剂的种类及温度对CMPS/SiO2的季铵化反应均有影响.使用CMPS的良溶剂和用位阻小的叔胺试剂,所得产物的季铵化度均较高.QPS/SiO2具有很强的抗菌活性.使用很小的剂量(10 g/L)、在很短的接触时间内(3 min)抗菌率即可达100%,是一种优良的水不溶抗菌材料;QPS/SiO2的季铵化度越高,其抗菌活性越高;使用碳氢链较长的三丁胺制备的QPS/SiO2,其抗菌性能明显优于使用三乙胺制备的QPS/SiO2.     

Pre-transitional behaviour in the isotropic phase of nematogenic mixtures: An NMR investigation

Deuterium NMR spectroscopy has been used to study the pre-transitional behaviour in the isotropic phase of a nematogenic mixture for both the homogeneous system and the biphasic region. The field-induced order of the solute, p-xylene-d₁₀, exhibits the expected divergence with temperature in the homogeneous system but is found to remain constant in the isotropic component of the biphasic region. The field-induced ordering matrix is determined for the solute and the variation of its components explained.     

Molecular dynamics study of the effect of atomic roughness on the slip length at the fluid-solid boundary during shear flow

A systematic study into the effect of solid roughness on the slip boundary condition during shear flow is presented. Atomic roughness is modeled by varying the size and spacing between solid atoms at constant packing fraction while the interaction parameters and the thermodynamic state of the fluid are kept constant. It is shown that the fluid structure as manifest in the amplitude of the density oscillations increases with increasing smoothness of the surfaces. The fluid-solid slip length is shown to exhibit nonmonotonic behavior as the solid structure is varied from smooth to rough. Slip occurs for both smooth and rough surfaces, and stick occurs only for surfaces commensurate with the fluid.     

Efficient Hydrolysis of RNA by a PNA - Diethylenetriamine Adduct

The introduction of a urea bond linking a protected diethylenetriamine (DETA) unit and the terminal amino group of a resin-bound peptide nucleic acid (PNA) decamer gave access to a PNA - DETA adduct (shown here), which hydrolyzed the target 25-mer RNA rapidly and sequence specifically.     

The influence of anions and kink structure on the enantioselective electro-oxidation of glucose

The electro-oxidation of glucose in sulfuric acid using well-defined chiral platinum single crystal electrodes has been demonstrated previously to be an enantioselective reaction with the degree of enantioselectivity being dependent on the surface density of kink sites. The chirality of the surface originates from the microstructure of the kink site whereby the sequence of the three fundamental adsorption sites [111], [100] and [110] constituting the kink may be viewed from the electrolyte phase either in a clockwise (R-enantiomer) or anti-clockwise (S-enantiomer) fashion. In the present study, this work is extended to examine the role of both kink structure and specifically adsorbed anions on the mechanism of chiral discrimination. Kinked surfaces based on [111] terraces (Pt[976],Pt[643] and Pt[531]),[100] terraces (Pt[721]) and [110] terraces (Pt[11,7,1] and Pt[841]) have been investigated and both the magnitude and potential dependence of the enantioselective electro-oxidation of glucose characterised. Additionally, the changes engendered by interchanging the character of the two steps whose confluence form the kink whilst maintaining the symmetry of the terrace has also been examined via a comparison of Pt[643] and Pt[431]. Low energy electron diffraction (LEED) was used to confirm that all surfaces when clean and thermally annealed were in their (1 x 1) state. Cyclic voltammetry (CV) confirmed this finding for flame-annealed electrodes after cooling in hydrogen. Three general points emerge from the electro-oxidation studies: (i) The highest degree of enantioselectivity is exhibited by kink sites adjacent to [111] and [110] terraces in sulfuric acid. (ii) The adsorption of specifically adsorbed anions like bisulfate/sulfate influences strongly the chiral discriminatory behaviour of all surfaces. (iii) No electro-oxidation takes place at [110] sites, as evidenced by complete overlap of the [110] step hydrogen underpotential deposition (UPD) charge in glucose and glucose-free solutions. Nonetheless it is deduced that [110] sites must play some part in the initial orienting of the glucose molecule prior to reaction. Ideas based on these findings are developed in order to rationalise in particular the influence of anion adsorption on the initial enantioselective interaction of the glucose molecule with the chiral surface.