Ru-catalyzed Asymmetric Hydrogenation of Aryl Ketones Using Tetrazole Derived NH_2-hybrid Ligand

Readily available chiral hybrid NH₂/tetrazole ligand [(S)‐TEA, 1 ] in combination with Ru‐BINAP or Ru‐DIOP complexes catalyzes the asymmetric hydrogenation of a number of simple ketones with moderate enantioselectivity (up to 72% ee). The tetrazole functionality results in reversal of the typically observed chiral‐induction for related systems and allows for hydrogenation to be uncharacteristically conducted in (non‐protic) THF solvent. The observed catalyst performance is sensitive to the reaction conditions employed and the particular compounds involved. The origins of such features are considered to derive from the added functionality provided by the tetrazole moiety in 1 , which due to its modular nature provides a good basis for further development.     

色谱法辅助傅里叶变换红外光谱法用于固定源大气醛酮毒物现场监测

1 引言 1990年美国公布的新空气清洁法中列出了9种重点控制的醛酮污染物:由于FTIR光谱法具有快速、方便等特点,很适合于现场分析,所以美国国家环保局希望FTIR光谱法能成为固定污染源大气毒物现场监测方法。我们曾建立了FTIR光谱自动差减定量软件及醛酮的FTIR标准谱图库,并探讨了将其用于定量的可行性问题。本文将其用于北京第三有机化工厂乙醛车间工艺尾气的现场监测。该厂废气经吸收塔后直接放空。2 实验部分     

复合索赔次数模型与混合索赔次数模型中的若干结果

本文利用完整描述方法研究复合索赔次数模型与混合索赔次数模型中总索赔次数的概率分布 ,得到了十余例典型索赔次数模型的相关结果 ,这些结果推广了文献 [1]、[2 ]、[6 ]的有关结论。     

Positivity of direct images of positively curved volume forms

We discuss Kiselman–Berndtsson’s minimum principle for plurisubharmonic functions in terms of the positivity of direct images of certain positively curved volume forms, and generalize it to holomorphically convex manifolds with compact group actions. With this generalization and other techniques, we establish a minimum principle for positively curved volume forms from the point of view of geometric invariant theory on Stein manifolds. Minimum principle with some noncompact group actions is also considered.     

Solid-phase extraction of sulfonylurea herbicides from water samples with single-walled carbon nanotubes disk

Microchimica Acta - This study presents a new, easily made and practical solid-phase extraction disk, a single-walled carbon nanotubes (SWCNTs) disk. The properties of the disk were evaluated by...     

CO2焊接短路过渡过程的动态分析─短路液桥的动态变化与力学测算

CO₂气体保护焊接是一种高效、节能和低成本的焊接方法,在钢结构焊接生产中得到了广泛的应用。但也存在着诸如:金属飞溅、焊缝成形较差等问题,要解决这些问题,必须首先对CO₂焊接过程的电弧形态以及熔滴变化情况从理论上深入分析研究。本文以高速摄影与光线示波器同步进行拍摄,记录了CO₂悍接短路过渡中熔滴的长大、缩颈、脱落的全过程以及相对应的电流电压波形。利用影片数据分析处理系统对所得影片及记录波形进行了分析处理,得到了熔滴过渡形成金属液桥爆断瞬间的最大电流值及所受合力的大小。从理论上更进一步研究了短路过渡的机理,建立了短路过渡的模型,这对正确调节焊接工艺规范,保证焊接质量具有重大的指导意义,研究结果表明:在常规短路过渡CO₂焊接中,抑制飞溅是提高CO₂焊接质量的关键,利用焊接规范来调节短路频率和短路峰值电流是抑制飞溅的主要途径。     

β-萘甲酰化β-环糊精的分子识别性能研究

最近二十年,外形似“锥简”,腔内疏水,脏外亲水的环糊精（Cyclodextrin,CD包括a,o,7－CD等）,以其特有的结构在模拟酶、分子识别等众多领域内深受广大科学工作者重视［’－‘］．为了获得更有效的模拟酶及分子识别功能体,我们已合成并报道了一系列含有发色基团的CD衍生物卜一句．本文利用基紫外光谱对产一茶甲酸化公CD的分子识别性能作了研究,结果显示3一位修饰CD（3一氧一八茶甲酸基一只CD）1对客体（环己醇）的包结性能是6一位修饰CD（6一氧一界禁甲酸基一八CD）2的4．4倍·结果还显示用环乙烷作客体时与主体正的包结和用…     

Nonisothermal <Emphasis Type="Italic">n</Emphasis>th-order DAEM equation and its parametric study – use in the kinetic analysis of biomass pyrolysis

Nonisothermal nth-order distributed activation energy model (DAEM) was derived. Numerical solutions of the nonisothermal nth-order DAEM equation were performed. The influences of various parameters relevant to biomass pyrolysis on numerical results of the nonisothermal nth-order DAEM equation were also studied. Investigated parameters are heating rate, the mean of activation energy distribution, standard deviation of activation energy distribution, frequency factor and reaction order. The study results can be further responsible for determination of nth-order DAEM kinetic parameters from thermogravimetric analysis data of biomass.