环境水样中己烯雌酚与双烯雌酚的离子液体分散液-液微萃取/高效液相色谱法测定

以离子液体([Omim][PF6])为萃取剂,采用冷诱导分散液-液微萃取对环境水样中的己烯雌酚和双烯雌酚残留进行富集.优化后的萃取条件:在pH 3.0的条件下,以50 μL离子液体为萃取剂,0.8 mL甲醇为分散剂,采用反相 Extend-C18柱(5 μm, 250 mm×4.6 mm),流动相为水-甲醇(体积比40 ∶ 60),流速:1.0 mL/min,柱温:35 ℃,检测波长:245 nm.在优化的萃取条件下,己烯雌酚和双烯雌酚的线性范围均为2.5 ～200 μg/L,检出限(S/N=3)为80 ng/L.应用于环境水样中己烯雌酚和双烯雌酚的检测,加标回收率为93% ～98%,相对标准偏差为3.0% ～5.4%,建立的方法简单、环保.     

A numerical analysis of heat transfer in an evacuated flexible multilayer insulation material

In this article, the theoretical heat transfer of flexible multilayer insulation material which can be used in high (<433 K) and low temperature (>123 K) environments has been analyzed. A mathematical model has been developed to describe the heat flux through flexible multilayer insulation material, where the heat transfer consists of thermal radiation, solid spacers and gas heat transfer. The equations for heat transfer model have been solved by iterative method combining with dichotomy method using Matlab. Comparison between the experimental results and the calculated values which are obtained from the model shows that the model is feasible to be applied in practical estimation. The investigation on the flexible multilayer thermal insulation material will present active instruction to improve the performance and accomplish optimum design of the material.     

n维单位球面上的Toeplitz符号演算

探讨了C^n中单位球面S上Berezin变换和Toeplitz算子的性质，证明了由{Tφ,φ∈L^∞ （S）}所生成的C^＊-代数中算子T的符号恰好为单位球B上函数T（称为T的Berezin变换）的非切向边界值．此外，本文还得到了经典Toeplitz符号演算的有趣推广．     

Existence and uniqueness of periodic solutions for forced Liénard-type equations

By using topological degree theory and some analysis skill,some sufficient conditions for the existence and uniqueness of periodic solutions for a class of forced Liénard-type equations are obtained.     

New results on almost periodic solutions for a class of nonlinear Duffing equations with a deviating argument

In this work a class of nonlinear Duffing equations with a deviating argument are considered. Some sufficient conditions for the existence of almost periodic solutions are established, which are new and complement previously known results.     

Palladium-catalyzed hydroalkylation of methylenecyclopropanes with simple hydrazones

A palladium-catalyzed hydroalkylation reaction of methylenecyclopropanes via highly selective C–C σ-bond scission was achieved under mild conditions, in which simple hydrazones served as carbanion equivalents. This method featured good functional group compatibility, affording high yields of C-alkylated terminal alkenes.

A palladium-catalyzed hydroalkylation of methylenecyclopropanes via selective C–C σ-bond scission was achieved, in which simple hydrazones served as carbanion equivalents. This method affords high yields of C-alkylated terminal alkenes with good functional group compatibility.     

Metal-free photo-induced radical C-P and C-S bond formation for the synthesis of 2-phosphoryl benzothiazoles

We reveal here a visible-light promoted phosphorylation of 2-isocyanoaryl thioethers for the first time with concomitant C(sp³)-S bond cleavage and imidoyl C–S formation. Additionally, this method features the use of 3 mol% organic dye Rose Bengal as the photocatalyst without external transition-metal or peroxide oxidants, and provides a novel and environmentally friendly approach for the preparation of a variety of 2-phosphoryl benzothiazoles in moderate to good yields.     

双色场中氦离子高次谐波的保结构算法研究及应用

 通过数值求解含时Schr ö dinger方程,研究了氦离子在不同双色场下的高次谐波。结果显示,尽管倍频光强度仅为基频光的1/10,高次谐波辐射却发生了极大变化。虽然谐波级次推进不多,但效率大大提高了,平台区平均提高103倍,高倍频光对应的高次谐波产生效率提高104~105倍。氦离子在添加倍频光的双色场作用下高次谐波产生效率极大提高的原因是：倍频光极大地加快了电子电离到连续态及返回基态这一过程,使辐射出的高次谐波光子数大大增加,该初步阐释可为高次谐波真正应用到实际中提供一些理论启示。     

Time-dependent plane Poiseuille flow of a Johnson–Segalman fluid

We numerically solve the time-dependent planar Poiseuille flow of a Johnson–Segalman fluid with added Newtonian viscosity. We consider the case where the shear stress/shear rate curve exhibits a maximum and a minimum at steady state. Beyond a critical volumetric flow rate, there exist infinite piecewise smooth solutions, in addition to the standard smooth one for the velocity. The corresponding stress components are characterized by jump discontinuities, the number of which may be more than one. Beyond a second critical volumetric flow rate, no smooth solutions exist. In agreement with linear stability analysis, the numerical calculations show that the steady-state solutions are unstable only if a part of the velocity profile corresponds to the negative-slope regime of the standard steady-state shear stress/shear rate curve. The time-dependent solutions are always bounded and converge to different stable steady states, depending on the initial perturbation. The asymptotic steady-state velocity solution obtained in start-up flow is smooth for volumetric flow rates less than the second critical value and piecewise smooth with only one kink otherwise. No selection mechanism was observed either for the final shear stress at the wall or for the location of the kink. No periodic solutions have been found for values of the dimensionless solvent viscosity as low as 0.01.