Cross-Polarisation Applied to the Study of Liquid Crsytalline Ordering

Summary.  Cross polarisation is extensively used in solid state NMR for enhancing signals of nuclei with low gyromagnetic ratio. However, the use of the method for providing quantitative structural and dynamics information is limited. This arises due to the fact that the mechanism which is responsible for cross polarisation namely, the dipolar interaction, has a long range and is also anisotropic. In nematic liquid crystals these limitations are easily overcome since molecules orient in a magnetic field. The uniaxial ordering of the molecules essentially removes problems associated with the angular dependence of the interactions encountered in powdered solids. The molecular motion averages out intermolecular dipolar interaction, while retaining partially averaged intramolecular interaction. In this article the use of cross polarisation for obtaining heteronuclear dipolar couplings and hence the order parameters of liquid crystals is presented. Several modifications to the basic experiment were considered and their utility illustrated. A method for obtaining proton–proton dipolar couplings, by utilizing cross polarisation from the dipolar reservoir, is also presented. Corresponding author. E-mail: kvr@sif.iisc.ernet.in Received May 28, 2002; accepted June 19, 2002     

Short-Range Ordering in Liquid Bicyclohexyl by X-Ray Diffraction

Abstract

The paper reports results of the X-ray diffraction structural studies of liquid bicyclohexyl, C₆H₁₁—C₆H₁₁ at room temperature, using CuK _α radiation. Angular distribution of X-ray scattered intensity was measured, and the electron-density radial-distribution function was calculated. Computer techniques were used to minimize the effects of experimental errors, uncertainties in the scattering factors, and termination errors. Good agreement between the theoretical and experimental functions was obtained on assuming the statistically most probable model of this molecule. The structural data obtainable by X-ray analysis for liquid bicyclohexyl were discussed. The mean distances between the neighbouring molecules and the radii of coordination spheres were found. The maxima in the differential radial distribution function were at: r ₁ = 4.68, r ₂ = 5.57, r ₃ = 6.62, r ₄ = 8.05 Å. X-ray structural analysis was applied to determine the packing coefficient of bicyclohexyl molecules. A simple model of short-range arrangement of the molecules in liquid bicyclohexyl was proposed.     

Ionic Liquid Ordering at an Oxide Surface

The interaction of the ionic liquid [C₄C₁Im][BF₄] with anatase TiO₂, a model photoanode material, has been studied using a combination of synchrotron radiation photoelectron spectroscopy and near‐edge X‐ray absorption fine structure spectroscopy. The system is of interest as a model for fundamental electrolyte–electrode and dye‐sensitized solar cells. The initial interaction involves degradation of the [BF₄]^? anion, resulting in incorporation of F into O vacancies in the anatase surface. At low coverages, [C₄C₁Im][BF₄] is found to order at the anatase(101) surface via electrostatic attraction, with the imidazolium ring oriented 32±4° from the anatase TiO₂ surface. As the coverage of ionic liquid increases, the influence of the oxide surface on the topmost layers is reduced and the ordering is lost.     

Double Pore Silica Gel Monolith Applied to Liquid Chromatography

Silica gels retaining double pore structure in the size ranges of micrometer and nanometer have been applied to the rod-shaped monolithic column for liquid chromatography. The macropore structure was designed by controlling the phase separation process induced by the hydrolysis and polycondensation of alkoxysilane, whereas the mesopore structure was tailored by the solvent exchange treatments on wet gels. The size exclusion chromatograms on polystyrene standards exhibited almost similar features for octadecyl-modified rod and conventional packed beads columns. The dependence of plate height on the velocity of mobile phase determined for amylbenzene was by far weaker in the rod column than in the packed beads column, suggesting that additional geometrical factors should be considered in describing the separation mechanism in the rod column.     

小角X射线散射表征AOT/水层状溶致液晶的有序性

用小角X射线散射研究了AOT/水层状溶致液晶的有序性. 通过对散射曲线的解析, 讨论了表面活性剂浓度、温度和助表面活性剂等三个方面对溶致液晶层状相结构有序性的影响. 在一定的范围内, 提高温度, 改变表面活性剂浓度和加入少量助表面活性剂可使碳氢链排列由稀疏转变为密实, 层状相也相应地由“柔性双层”过渡到更加有序化的“平面双层”. 基于形状因子和体系内分子间作用力, 提出了层状相形成与有序化的机理, 同时采用分子模拟的方法展现了不同浓度下的液晶结构.     

Water-Induced Breaking of the Coulombic Ordering in a Room-Temperature Ionic Liquid Metal Complex

Control of ion arrangements in ionic liquids represents a major challenge owing to the presence of the predominant coulombic interactions between cationic and anionic ion species that forms the coulombic ordering. Here, water-induced ion rearrangement in a room-temperature ionic liquid (RT-IL) metal complex, (1-ethyl-3-methylimidazolium)₂[MnN(CN)₄], is demonstrated through coordinative interactions between anions. Solidification occurred, which was associated with the formation of a “separated” structure consisting of cation columns and anionic cyanide-bridged one-dimensional coordination polymers. The energy diagram is in accord with the resultant RT-IL incorporating mononuclear [MnN(CN)₄]²⁻ molecules being a kinetic phase stabilized by inter-ion repulsions of the anionic divalent metal complex moieties. Water acts to decrease the coulombic interactions, including repulsion, giving rise to breaking of the coulombic ordering arising from coordination bond formation in the IL phase.     

Spatial Ordering of Conduction Electrons in Metals from Liquid Phase Diffraction

Abstract

Egelstaff, March and McGill proposed the idea that electron-electron correlation functions for conduction electrons in liquid metals could be extracted from experiment by combining X-ray, neutron and electron diffraction studies. Though electron diffraction studies are still only in early stages of development, evidence has nevertheless gathered that conduction electrons have a significant degree of ordering near the melting point of liquid metals. In the latter part of the review, this conclusion is brought into contact with current ideas on strongly correlated electronic ground states in crystalline metals. In both areas, resonating bonds proposed by Pauling seem an essential ingredient in understanding the electronic behavior.     

微量热法研究过氧化氢酶反应

利用微量热法和热动力学方程研究了过氢化氢酶反应.该反应遵循Michaelis-Menten动力学,298.15K和pH7.0时,其米氏常数、酶转换数以及摩尔反应焓分别为2.36×10^-2mol/L、1.20×10⁴s^-1和-83.67kJ·mol^-1.过氧化氢酶反应后期对底物是一级反应,其总反应速度常数和一级速度常数分别为k_o=6.31×10⁵L·mol^-1·s^-1和k₁=6.31×10⁵/[E_o]s^-1.该反应服从Ogura机理,其酶-底物三元复合物的分解速度常数为6.00×10³s^-1.     

Supported Liquid Membrane Enrichment Studies of Natural Water Samples Applied to Liquid Chromatographic Determination of Triazine Herbicides

Abstract

A method for sample work-up and enrichment using Supported Liquid Membrane (SLM) and liquid chromatographic determination of triazine herbicides in natural waters was investigated. A porous PTFE membrane was impregnated with a water immiscible organic solvent, forming a barrier between two aqueous phases. With a flowing donor and a stagnant acceptor solution, an enrichment of the triazines was obtained. The various factors that influence the extraction efficiency and selectivity of the extraction procedure were experimentally studied. The obtained results were in good agreement with the developed theoretical model. The pH of the acceptor solution was found to be the critical limiting factor in obtaining higher extraction efficiencies and led to an extraction efficiency decrease with an increase in enrichment time. By increasing both the trapping capacity of the acceptor solution and the donor flow rate, the method detection limit of the triazines ranged from 0.03 to 0.16 μgL^?1 in natural waters with 20 minutes extraction time.     

Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance

The electronic performance of conjugated polymers depends on the microstructure of the polymer films. A percolated network morphology with high crystallinity, ordered intermolecular packing and long‐range order is beneficial for charge transport. In recent reports, some conjugated polymers have been shown to exhibit liquid crystallinity. The appearance of liquid crystalline ordering provides a new solution to solve the difficulties in microstructure manipulation. In this review, we summarize how liquid crystallinity can assist molecular arrangement and guide long‐range orientation during film processing, leading to high charge mobility. We expect that this article could draw more attention to the liquid crystallinity of conjugated polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1572–1591     

液相等电聚焦结合双向凝胶电泳分离碱性蛋白

在蛋白组学研究中, 经典的双向凝胶电泳法(2-DE)对碱性蛋白及低丰度蛋白的分离存在技术障碍, 但预分离技术的应用可弥补其缺陷. 液相等电聚焦可有效地分离富集复杂蛋白样品. 碱性胶条用于2-DE可极大地提高蛋白上样量和凝胶分辨率. 将上述两种技术相结合用于碱性蛋白质和低丰度蛋白质的分离鉴定, 可使碱端区域双向凝胶图谱质量显著提高, 蛋白点更清晰且点数增多, 质谱鉴定确信度提高, 碱性蛋白和低丰度蛋白质谱鉴定成功率提高, 对于蛋白组学研究具有一定的意义.     

液相色谱和质谱联用技术结合化学计量学应用于代谢组学的研究进展

代谢组学作为系统生物学的重要组成部分,已经成为继基因组学、转录组学、蛋白质组学之后兴起的一个新的组学研究热点。准确全面的检测生物体液中浓度较低的代谢物变化是进行代谢组学研究的基础。液相色谱和质谱联用(LC/MS)技术结合化学计量学很好地实现了对大量样品和微量代谢物的快速定性、定量分析,极大地推动了代谢组学的相关研究。本文综述了LC/MS与化学计量学相结合用于代谢组学研究的现状,并对后续的研究进行了展望。     

TEM Orientation Mapping Applied to the Study of Shear Band Formation

The formation of brass-type shear bands (SBs) in twinned microstructures of oriented copper single crystals, has been investigated after channel-die deformation at 77K. Setting up a system for making high-resolution orientation maps using transmission electron microscopy (TEM) has opened new advantageous circumstances for the analysis of orientation changes within SBs. This method with spatial resolution higher than 10nm allows an examination of microstructure images composed of nanoscale sub-cells forming SBs structure. The early stages of SBs formation are the result of equally effective operation of two slip systems operating on the {111} slip planes which could be represented by a resultant super-system of type. This process leads to the lattice rotation about axis and to the rise of Goss orientation within the band. A minor group of components is observed near , arising from the near primary matrix orientation. For well-developed SBs, a second rotation about direction is observed. This tendency, resulting from the type slip systems operation, is usually accompanied by activation of new slip systems. Hence the process of SBs formation is regarded as a strictly crystallographic one.     

糖尿病人微量元素谱的多元分析

胜多元分析了糖尿病患者样品中微量元素，了解微量元素与糖尿病的关系，并提出了新见解。用ＩＣＰ－ＡＥＳ测定糖尿病患者血、发中１８种微量和宏量元素 ；结果经多元分析处理，找到血、发共有的相关链：Ｍｎ－Ｎｉ－Ｃｕ－ＳｒＴｉ，它与患者年龄、性别、样品无关，看来它提供了机体的特殊信息。     

参锗精口服液临床40例验证报告

用参锗精治疗老年病，经４０例临床验证，治疗组总有效率达９０％。     

Specific Features of Reversed-Phase High-Performance Liquid Chromatography as Applied to Determining the Distribution Coefficients of Pesticides in the Hexane-Acetonitrile System

The suitability of reversed-phase high-performance liquid chromatography for determining the distribution coefficients of organic compounds in the hexane-acetonitrile system was considered. A version of the necessary additional step in the sample preparation procedure was proposed, namely, changing from nonpolar hexane to a solvent unlimitedly miscible with the eluent. The distribution coefficients were determined for 20 pesticides by the proposed method and compared with those determined by gas chromatography.     

A Magnetic Ionic Liquid Based on Tetrachloroferrate Exhibits Three‐Dimensional Magnetic Ordering: A Combined Experimental and Theoretical Study of the Magnetic Interaction Mechanism

A new magnetic ionic liquid (MIL) with 3D antiferromagnetic ordering has been synthetized and characterized. The information obtained from magnetic characterization was supplemented by analysis of DFT calculations and the magneto‐structural correlations. The result gives no evidence for direct iron‐iron interactions, corroborating that the 3D magnetic ordering in MILs takes place via super‐exchange coupling containing two diamagnetic atoms intermediaries.     

Size‐Dependent Ordering of Liquid Crystals Observed in Polymeric Capsules with Micrometer and Smaller Diameters

Made to order : Aqueous dispersions of polymer‐encapsulated liquid crystal (LC) droplets were synthesized with precise interfacial chemistry and sizes in the micrometer‐to‐sub‐micrometer range. Size‐dependent changes in LC ordering could be observed. Study of the competition between size and interfacial chemistry on LC ordering enables size‐dependent properties of LC droplets to be exploited in applications such as photonics and sensing.

     

Artificial Neural Networks Applied to the Quantitative Structure-Activity Relationship Study of Para-substituted Phenols

The artificial neural network (ANN) model with back-propagation of error is used to study the quantitative structure-activity relationship of para-substituted phenol derivatives between the biological activity and the physicochemical property parameters. Network parameters are optimized, and an empirical rule for dynamically adjusting the network's learning rate is proposed to improve the network's performance. The results showthat the three-layer ANN model gives satisfactory performance, with f(x)=1/(1+exp(-x)) as the network node's input-output transformation function and the number of hidden nodes 10. The network gives the mean square error (rose) of 0.036 when predicting the biological activity of 26 para-substituted phenol derivatives. This result compares favourably with that obtained by the conventional methods.