光活性[1]1-联萘酚(BINOL)的不对称合成

由于 1 ,1 -联萘酚 ( BINOL)可作为手性配体或手性催化剂的前体 ,在不对称合成反应中具有广泛的应用 [1,2 ] ,所以如何得到光学纯的 BINOL的研究吸引了许多化学家的注意 .制备光学活性的 BINOL的方法较多 ,但一般效果较好的是用拆分的方法[3,4] .通过 2 -萘酚不对称氧化偶联直接得到 BINOL的方法也有许多报道 [5 ,6 ] ,但结果都不理想 .近来 ,Kocovsky等 [7]用鹰爪金碱作为手性诱导试剂 ,在Cu Cl2 存在下 ,2 -萘酚偶联得 BINOL,其 ee值为 1 0 0 % ,但产率只有 1 4% ,且由于鹰爪金碱价格昂贵 ,限制了该法的应用 .在此基础上 ,我…     

基于纯方位的浅海距离特征量解算分析

目标辐射噪声的LOFAR图中的干涉条纹包含了目标的运动参数和环境信息。当LOFAR图中的干涉条纹模糊或缺失时,其中的目标距离信息将无法提取。对于匀速直线运动的声源目标,仅利用方位信息,通过构造距离特征量和目标方位的关系模型,给出了一种浅海估计距离特征量的补充方法。浅海数值仿真和实验验证表明了该方法的可行性和有效性。     

Lewis碱改性氧化锆基质色谱固定相的研究进展

综述了Lewis碱改性氧化锆(或其复合氧化物)基质高效液相色谱填料的研究进展,涉及的改性剂包括氟离子、磷酸盐、有机膦酸、羧酸、酚类化合物、蛋白质和环糊精衍生物等。简要介绍了Lewis碱改性氧化锆固定相在毛细管电色谱中的应用。 引用文献51篇。     

光声喇曼光谱的理论分析

对光声喇曼光谱(PARS)作了系统的理论分析,分别导出固体和液体介质中的光声喇曼光谱的信号表达式,并进行了数值估算。 关键词：     

Solvent and concentration effects on the properties of electrospun poly(ethylene terephthalate) nanofiber mats

This study describes the preparation and characterization of nanofibrous mats obtained by electrospinning poly(ethylene terephthalate) (PET) solutions in trifluoroacetic acid/dichloromethane (TFA/DCM). Special attention was paid to the effect of polymer concentration and solvent properties on the morphology, structure, and mechanical and thermal properties of the electrospun nonwovens. The results show that the spinnable concentration of PET solution in TFA/DCM solvents is above 10 wt %. Mats have nanofibrous morphology with fibers having an average diameter in the range of 200–700 nm (depending on polymer concentration and solvent composition) and an interconnected pore structure. Higher solution concentration favors the formation of uniform fibers without beads and with higher diameter. Morphology and fiber assembly changed with the solvent properties. Solvent mixtures rich in TFA, i.e., those with higher dielectric constant and lower surface tension, originated fibers with small diameter. However, due to the lower volatility, those solvent mixtures also produced more branched and crosslinking fibers, with less morphologic uniformity. Mechanical properties (Young's modulus, ultimate strength, and elongation at break) and thermal properties (glass transition, crystallization, and melting) have been studied for the PET electrospun nanomats and compared with those of the original polymer. Solvent effect on fiber crystallinity was not significant, but a complex effect was observed on the mechanical properties of the electrospun mats, as a consequence of the different structural organization of the fibers within the mat network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 460–471, 2008     

十二烯基丁二酸改性氧化锆色谱固定相性能研究

本文用十二烯基丁二酸（DSA）改性氧化锆得到一种新的锆基质色谱固定相。改性前后的红外光谱的差异表明，DSA以两个羧基与氧化锆结合，由于多位点结合方式提高了固定相的稳定性，因此固定相可以在碱性（pH8．5）条件下稳定使用。锆基质色谱固定相具有较强的疏水性，用于中性及碱性化合物的分离取得了满意的结果。     

龙爪芦荟和库拉索芦荟中微量锗的测定与红外光谱区别

采用吸光光度法对龙爪芦荟和库拉索芦荟中的微量锗进行了测定,并探讨了两种芦荟的红外光谱的区别。结果表明,龙爪芦荟中含锗量在26.1～28.6μg·g-1,回收率为91.6%～97 5%。库拉索芦荟中含锗量在16.8～20.0μg·g-1,回收率为87.1%～94.5%。两种芦荟的FT IR光谱图在2100cm-1处有明显差异,由此可区别两种芦荟。     

QuEChERS-液相色谱-串联质谱法测定植物性食品中30种氨基甲酸酯类农药残留

基于欧洲标准化委员会标准方法(EN 15662)对食品基质的分类,选择6种代表性植物性食品作为基质,系统优化了QuEChERS样品前处理方法;在此基础上,建立了30种氨基甲酸酯类农药的液相色谱-串联质谱分析方法。实验结果表明,除涕灭威砜的线性范围为2~100 μg/kg,其他29种氨基甲酸酯类农药的线性范围均为1~100 μg/kg;6种样品基质在3个添加水平(5、20、100 μg/kg)下的回收率为56.13%~127.6%,相对标准偏差为0.47%~16%;以信噪比(S/N)≥10计,30种农药的定量限(LOQ)为0.041~1.9 μg/kg。本文方法灵敏、有效,适用于植物性食品基质中30种氨基甲酸酯类农药残留的测定。     

On Mixed Pressure-Velocity Regularity Criteria to the Navier-stokes Equations in Lorentz Spaces,Part Ⅱ:The Non-slip Boundary Value Problem

This paper is a continuation of the authors recent work [Beir?o da Veiga, H.and Yang, J., On mixed pressure-velocity regularity criteria to the Navier-Stokes equations in Lorentz spaces, Chin. Ann. Math., 42(1), 2021, 1–16], in which mixed pressure-velocity criteria in Lorentz spaces for Leray-Hopf weak solutions of the three-dimensional NavierStokes equations, in the whole space R~3 and in the periodic torus T~3, are established. The purpose of the present work is to extend the result of mentio...     

A new proposal for the discretization of the Griffin—Wheeler—Hartree—Fock equations

A polynomial expansion is proposed as a new way to discretize the Griffin-Wheeler-Hartree-Fock equations of the Generator Coordinate Hartree-Fock method. The implementation of the polynomial expansion in the Generator Coordinate Hartree-Fock method discretizes the Griffin-Wheeler-Hartree-Fock equations through a numerical mesh which is not equally spaced. This procedure makes the optimization of Gaussian exponents in the Generator Coordinate Hartree-Fock method more flexible and more efficient. The results obtained with the polynomial expansion for atomic Hartree-Fock energies show this technique is very powerful when employed in the design of compact and high accurate Gaussian basis sets used in ab initio non-relativistic (Hartree-Fock) and relativistic (Dirac-Fock) calculations.