基于第一性原理的单层WS2热输运特性研究

二维WS₂是一种层状过渡金属硫化物，因其具有特殊的层状结构、可调带隙及稳定的物理化学性质而备受关注。结合玻尔兹曼输运方程(BTE)和密度泛函理论(DFT),利用第一性原理研究了单层WS₂声子的输运特性，分析了声子的谐性效应和非谐性效应对WS₂晶格热导率的影响机理，计算了其声子的临界平均自由程，提出通过调整阻断频率的方法来调控WS₂的晶格热导率。研究结果表明：单层WS₂在300 K时的本征晶格热导率为149.12 W/(m·K),且随温度的升高而降低；从各声子支对总热导率的贡献来看，声学声子支起主要作用，特别是纵向声学(longitudinal acoustic, LA)声子支对单层WS₂热导率的贡献百分比最大(44.28%);单层WS₂声学声子支和光学声子支之间的较大带隙(声光学声子支之间无散射)导致其具有较高的晶格热导率。本文研究可为基于单层WS₂纳米电子器件的设计和改进提供借鉴和理论指导。     

Slater Sum in Cylindrically Symmetric Inhomogeneous Electron Liquids: Towards A Differential Equation for the Stark Effect in Hydrogen Atom

Abstract

Attention is focussed here on a variety of cylindrically symmetric inhomogeneous electron liquids. These include separable potentials in which a general variation along the (z) axis of cylindrical symmetry is combined with isotropic harmonic confinement in the (x, y) plane. in this case, an explicit differential equation is derived for the Slater sum along the z axis by projecting out of the (off-diagonal) canonical density matrix the states with zero angular momentum about the axis of symmetry. Some attention is then given to the calculation of the Slater sum for a hydrogen-like atom in a uniform electric field of arbitrary strength. the model of a separable potential with harmonic confinement, though no longer exact, is shown to lead directly to a (now approximate) equation for the Slater sum along the z axis for the Stark effect in hydrogen. Finally some further progress is shown to be possible in the extreme high field limit.     

Use of 2, 3-Butanedione Monoxime for Homogeneous Precipitation of Nickel (II)

Abstract

The solid monoxime of 2, 3-butanedione is a more convenient material than liquid dione for the homogenous generation of DMG. 2, 3-butanedione dioxime. Determinations of Ni in steels and in pure Ni(II) solutions have shown the optimum pH and order of adding reagents. Gravimetric and/or an EDTA titrimetric finish are possible for a method of reliability within ± 0.2 mg of Ni in 50–150 mg Ni. The solid has the same character and filterability as that from the 1960 dione method of Salesin and Gordon¹.     

Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.     

Sequential-dissociation kinetics of non-covalent complexes of DNA with multiple proteins in separation-based approach: General theory and its application

Binding of multiple proteins to DNA is crucial in many regulatory cellular processes. The kinetics of assembly and disassembly of DNA–multiple protein complexes is very difficult to study in detail due to the lack of suitable experimental approaches. A separation-based approach has been recently proposed to resolve disassembly kinetics of such complexes. While conceptually simple, the separation-based approach generates experimental data with very complex patterns. The analysis of these patterns is a challenging problem on its own. Here we report on a mathematical approach that can extract a solution for the experimental data obtained in separation-based analysis of sequential dissociation of a DNA complex with multiple proteins. This case describes the dissociation of proteins one-by-one from the complex. Generally speaking, a mathematical solution of such problems requires calculations of multiple integrals. Our approach reduces this procedure to taking double integrals and constructing their superposition. We tested this approach with the experimental data obtained for three-step sequential dissociation of complexes of DNA with two protein copies.     

Development of GC–MS/MS method with programmable temperature vaporization large volume injection for monitoring of 17β-estradiol and 2-methoxyestradiol in plasma

Monitoring of estradiol and its metabolites in biological samples is essential for the accurate diagnosis of a number of endocrine diseases. In this study, a sensitive, precise and specific GC–MS/MS method for the quantification of 17β-estradiol (17-BE) and its main metabolite, 2-methoxyestradiol (2-MEOE), in plasma was developed and validated. Plasma concentrations of these steroids are currently investigated as diagnostic markers for pre-eclampsia, a systematic disorder of pregnancy and a leading cause of maternal and fetal morbidity and mortality worldwide.     

Fluorimetric Analysis of Aluminum in Diluted Hemodialysis Solutions by Using a Novel Schiff Base

A spectrofluorimetric method has been developed for trace amount of aluminum(III) by using a novel Schiff base, N,N′-bis(salicylidene)-1,4-diaminobuthane (BUTAS), and 4-methyl-2-aminophenol (OAP). Since the aluminum complexes are generally fluorescent, aluminum(III) increases the fluorescence intensity of BUTAS-OAP by formation of Al-BUTAS-OAP complex. The fluorescence of the complex is measured at an excitation wavelength of 410 nm with an emission at 526 nm. Aluminum(III) can be detected within a concentration limit of 0.11–1.62 ppb and the lowest detection limit being 0.07 ppb. The proposed method was applied to diluted hemodialysis solution and spectrofluorimetric data was compared with data of standard pharmacopoeia method.     

Corrosion inhibition of ammonium molybdate for AA6061 alloy in NaCl solution and its synergistic effect with calcium gluconate

The corrosion inhibition of ammonium heltamolybdate (AH) and calcium gluconate (CG) for AA6061 alloy in 3% NaCl solution was investigated by the electrochemical measurements. It indicates that AH inhibits the corrosion of AA6061 alloy and acts as an anodic inhibitor. Maximum inhibition efficiency reaches 74.3% at the concentration of 1 × 10^?4 mol.l^?1 AH. The results of the electrochemical studies reveal AH is physically adsorbed on the AA6061 alloy surface and the adsorption follows Langmuir isotherm. The combination of AH and CG enhances the inhibition efficiency to 95.9%. The enhanced inhibition is attributed to the promotion of AH adsorption by CG. The mixture of AH and CG is a mixed‐type inhibitor and renders the corrosion potential to more positive values. Copyright © 2011 John Wiley & Sons, Ltd.     

A Sensitive Spectrophotometric Method for the Determination of Some Imidazoline Derivatives by 2,6-Dichlorophenol-Indophenol

Abstract

A new and highly sensitive method is presented for the spectrophotometric determination of four imidazoline derivatives: antazoline hydrochloride, tolazoline hydrochloride, xylometazoline hydrochloride and naphazoline nitrate. The method is based on the reaction of the corresponding drug base with 2,6 - dichlorophenol -indophenol (DGPIP) in chloroform to give a blue chromogen exhibiting a maximum at 588 - 603nm. The method could be applied for the quantitative determination of the above drugs either pure or in their pharmaceutical preparations (tablets and nasal drops). The results obtained are accurate and have good reproducibility.