FLAPW方法研究δ-钚单层表面几何和电子结构

采用全势线性缀加平面波（FLAPW）方法, 在广义梯度近似（GGA）下研究了单层δ-钚（100）和（111）面的几何和电子结构. 结果表明,自旋-轨道耦合对平衡几何结构的影响强于自旋极化,与体相相比,表面晶格常数显著收缩,实验上可选择晶格常数相对较小的物质作为δ-钚薄膜的沉积基体. 表面原子由于近邻原子数目的减少,5f电子波函数重叠几率的降低,更多地表现出局域化特征,（100）面5f电子的局域化程度强于（111）面.     

Studies on Synthesis and Electrochemical Performance of Li1+δNi1-xCoxO2-yFy Cathode Materials for Lithium-ion Rechargeable Batteries

It is a technological problem of LiNiO2 cathode material for lithium-ion secondary batteries because of the difficult preparation and hard purification, instable performance, remarkable capacity fading at initial discharge, worse thermal stability and safety of Ni-series cathode materials,and it is also the key factor of hindering LiNiO2 cathode material from practical applications.Recently, by doping some metal cations such as Co, Mn, Mg, Al, Cr and so on[1-5] into LiNiO2, the preparation difficulty and the purification hardness can be obviously improved, and the initial irreversible discharge capacity can be reduced, and the ratio of the initial discharge to charge capacity can be enhanced. But the cyclic stability, thermal stability and safety of LiNiO2 are not enough to satisfy the demand of commercial use.At present, the synthesis of LiNiO2 cathode material must be sintered under oxygen atmosphere in most cases, and the improved effect of fluoride doping on the electrochemical properties of LiNiO2 has seldom been reported in the literatures.In this paper, the cobalt cation and fluorine anion co-doping cathode materials Li1+δNi1-xCoxO2-yFy( 0≤δ≤0.2, 0≤x≤0.5, 0≤y≤0.1 ) were synthesized by solid state reaction method at 650℃ ～750℃ under air atmosphere, and characterized by XRD、 SEM、 TEM、 BET、 laser particle-size distribution measurement and electrochemical performance testing, the effect of different nickel sources on the properties of as-synthesized cathode materials was investigated. The results demonstrated that the cobalt and fluorine ions co-doping cathode materials Li1+δNi1-xCoxO2-yFy have complete layered structure, uniform surface morphology and better particle-size distribution as well as excellent electrochemical performances. At 20～25℃, 0.15～0.25mA charge and discharge current,4.25～2.70V cut-off voltage, 0.2～0.5C charge and discharge rate and 0.2～0.5 mA/cm2 current density,LiNi0.8Co0.2O1.95F0.05 cathode material has higher initial charge and discharge capacity and better cyclic properties which can be mainly attributed to the doping of the higher electronegativity fluorine which improves the structural stability and the synergistic reaction of cobalt and fluorine ions co-doping on the cathode materials. Under the above conditions, the initial charge and discharge capacity of LiNi0.8Co0.2O1.95F0.05 is 165.70mAh/g and 146.10mAh/g, respectively. After 50 cycles, it has more than 140mAh/g of discharge capacity and displays preliminary application possibility in the future.     

Spectrophotometric Determination of δ4 -3-Ketosteroids Using Oxalyldihydrazide

Abstract

A novel spectrophotometric method for the assay of δ⁴ -3-Ketosteroids in formulations is presented. Oxalyldihydrazide in methanol reacts selectively with δ⁴-3-Ketosteroids at pH 2 forming stable hydrazones which exhibit intense absorption specta at 300 nm. and high molar absorpitivities ranging from 14480–18750 for most steroids studied. Methyltestosterone showed exception ally high sensitivity where its molar absorpitivity was 21630. As little as 5–30 μg steroid were determined with 99.28 ± 0.65–100.16 ± 0.94% accuracy. The method was applied successfully to the micro-determination of cortisone, hydrocortisone, hydrocortisone acetate, norethisterone, norethisterone acetate, norgestrel and methyltestosterone in substance as well as in different pharmaceutical dosage forms. The precision of assay was compareble with existing spectrometric methods for ketosteroid drugs. The method is simple, accurate mean - while selective and more sensitive than the INH-method.     

Facile transformation of glutamic acid into proline residue inside a tripeptide backbone

In this Letter we present a simple reaction pathway which allows the conversion of the glutamic acid residue of a tripeptide into a proline residue. The reaction was performed by using Boc-Val-Glu-Phe-NH₂ as a starting material and is based on a NaH-induced intraresidue alkylation under reaction conditions analogous to that adopted during the Freidinger lactams formation.     

水溶性聚苯胺/SmBaCu0.7Mn0.3O5+δ材料的制备与氨敏性能研究

采用化学氧化法制备了水溶性聚苯胺（PANI）,用溶胶-凝胶法制备了 SmBaCu1-yMnyO5+δ（y=0, 0.1, 0.2, 0.3,0.4, 0.5, 0.6）（SBCM）粉体,用微粒填充法制备了 PANI / SBCM 复合材料。利用 FT-IR、XRD、TEM 多种手段对产物进行表征,并制成气敏元件,在室温操作温度下测试其对氨气的灵敏度。结果表明,在相同条件下,在 PANI元件、SBCM 元件及 PANI / SBCM 元件气敏测试中,PANI/SmBaCu0.7Mn0.3O5+δ（PANI/SBC70M30） 元件对氨气的气敏性能最优,对体积分数为 100×10–6的 NH3灵敏度在室温条件下达到最大值为 4.66,同时还具有较好的选择性、响应-恢复特性与稳定性,响应时间和恢复时间分别为 16 和 121 s。     

Nonemptiness of Approximate Subdifferentials of Midpoint δ-Convex Functions

ABSTRACT

For some given positive δ, a function f:D ? X → ? is called midpoint δ-convex if it satisfies the Jensen inequality f[(x ₀ + x ₁)/2] ≤ [f(x ₀) + f(x ₁)]/2 for all x ₀, x ₁ ∈ D satisfying ‖x ₁ ? x ₀‖ ≥ δ (Hu, Klee, and Larman, SIAM J. Control Optimiz. Vol. 27, 1989). In this paper, we show that, under some assumptions, the approximate subdifferentials of midpoint δ-convex functions are nonempty.     

A two-particle exchange interaction model

The magnetisation reversal of two interacting particles was investigated within a simple model describing exchange coupling of magnetically uniaxial single-domain particles. Depending on the interaction strength W, the reversal may be cooperative or non-cooperative. A non-collinear reversal mode is obtained even for two particles with parallel easy axes. The model yields different phenomena as observed in spring magnets such as recoil hysteresis in the second quadrant of the field-magnetisation-plane, caused by exchange bias, as well as the mentioned reversal-rotation mode. The Wohlfarth’s remanence analysis performed on aggregations of such pairs of interacting particles shows that the deviation δM(H_m) usually being considered as a hallmark of magnetic interaction vanishes for all maximum applied fields H_m not only at W=0, but also for sufficiently large values of W. Furthermore, this so-called δM-plot depends on whether the sample is ac-field or thermally demagnetised.     

Attainment and (sub)differentiability of the infimal convolution of a function and the square of the norm

Let X be a Banach space whose norm is simultaneously LUR and Gateaux (Fréchet) smooth. Under some assumptions, it is shown that the infimal convolution of a fairly general function on X and the square of the norm is generically strongly attained and hence is Gateaux (Fréchet) differentiable. This contains a result of S. Dutta on distance functions.     

Oxygen-permeable membranes based on partially B-site substituted BaFe1−yMyO3−δ (M=Cu or Ni)

We carried out the partial substitution of the B-site in BaFeO_3−δ perovskite with divalent cations to develop novel oxygen-permeable materials. We demonstrated that the partial substitution of Cu or Ni by more than 10% resulted in the stabilization of the cubic perovskite structure even at room temperature in a highly oxygen-permeable phase, as revealed by the X-ray diffraction (XRD) analysis. The Cu substitution was more effective for the stabilization, because the introduction of Cu in the lattice more effectively made the Goldschmidt tolerance factor (t) close to 1.0. Ni- and Cu-substituted BaFeO_3−δ membranes showed higher oxygen permeabilities than their parent BaFeO_3−δ membranes particularly at lower temperatures around 600-700 °C owing to the stabilization of the cubic phase. Among the fabricated membranes, a BaFe_0.85Cu_0.15O_3−δ membrane (1.0 mm thickness) showed the highest oxygen permeation flux (1.8 cm³ min⁻¹ cm⁻² at 930 °C) under an air/He gradient. The results indicated that Cu-substituted BaFeO_3-δ is promising as a material for Co-free membranes with high oxygen permeabilities.