银催化的苄位C—H键氟化反应

正含氟化合物由于其独特的性质,被广泛使用于医药、农药、材料科学以及用于正电子发射计算机断层显像中的显像剂.二氟甲基官能团作为羟基的电子等排体,引起了研究者的广泛关注,但芳基二氟甲基化合物的合成方法相对较少,目前主要通过过渡金属的偶联反应来实现.最近,南开大学元素有机化学国家重点实验室汤平平课题组发     

可离去和/或可修饰导向基团辅助的C—H键官能化反应研究进展

过渡金属催化的导向基团辅助的C—H键官能团化反应是当前有机化学的研究热点之一.近年来,利用可离去和/或可修饰导向基团进行C—H键官能团化反应正受到化学家的特别关注并且发展迅速.借助可离去或可修饰导向基团,不但能够大大扩展可利用的碳氢底物,而且对于快速构建分子多样性具有重要作用.作者按不同杂原子(氮、氧、硫、硅等)导向基团进行分类,全面综述了近年来关于可离去和/或可修饰导向基团辅助的各种C—H键官能团化反应的研究进展及合成应用.最后,对该领域所存在的问题和局限性进行了总结,并对今后的发展方向作了展望.     

新型咔唑类衍生物的合成、光谱性质及其与Ct-DNA作用的研究

以咔唑为原料,经CuBr·SMe2催化C—N键形成、硝化、还原以及Pd金属催化C—N键偶联等反应合成了一系列新型咔唑衍生物.研究了它们自身在不同溶剂中的紫外吸收和荧光发射光谱以及化合物2的盐酸盐和Ct-DNA相互作用的光谱行为.结果表明,这一系列化合物具有明显的溶致变色效应,其中化合物4最为显著.Ct-DNA结合实验表明化合物2盐酸盐的荧光随着Ct-DNA的滴加而线性增强.Ct-DNA的小沟槽为该分子的主要结合位点,两者的结合能处于104 L·mol-1级别,属中等强度结合.     

混料模型D—最优试验设计的改进DE算法研究

差分进化算法(Differential Evolution Algorithm)有较强的全局收敛能力和稳健性,应用该算法可解决工程学、计算机科学等领域的一些复杂优化问题。本文介绍一个改进DE算法,该算法适用于混料模型的近似最优设计问题,对于具有附加约束试验域的混料问题也可高效求解。最后,本文给出应用改进DE算法求解混料模型D-最优试验设计的例子。     

RETRACTED ARTICLE: A uniqueness lemma with applications to regularization and incompressible fluid mechanics

In this paper,we extend our previous result from Lévy(2016).We prove that transport equations with rough coefficients do possess a uniqueness property,even in the presence of viscosity.Our method relies strongly on duality and bears a strong resemblance to the well-known DiPerna-Lions theory first developed by DiPerna and Lions(1989).This uniqueness result allows us to reprove the celebrated theorem of Serrin(1962)in a novel way.As a byproduct of the techniques,we derive an L¹ bound for the vorticity in terms of a critical Lebesgue norm of the velocity field.We also show that the zero solution is unique for the 2D Euler equations on the torus under a mild integrability assumption.     

Negative differential resistance in a molecular junction of carbon nanotube and benzene

We propose a novel molecular junction with single-walled carbon nanotubes as electrodes bridged by a benzene molecule, in which the electrodes are saturated by different terminations (C-, H- and N-). It is found that the different terminations at the carbon nanotube ends strongly affect the electronic transport properties of the junction. The current-voltage (I-V) curve of the N-terminated carbon nanotube junction shows a more striking nonlinear feature than that of the C- and H-terminated junctions at smal...     

A method based on magnetic moment measurement to identify the structural transition of quenched Fe1 -xGax (x = 0.15ben 0.30) alloys

A method based on the measurement of Fe average atomic magnetic moment to identify the structural transition caused by the increase of Ga content in quenched Fe_{1 - x}Ga_x alloys (0.15 ≤ x ≤ 0.30) is proposed. The quenched Fe_{1 - x}Ga_x alloys show a change of the Fe average atomic magnetic moment from 2.25 μ_B to 1.78 μ_B and then to 1.58 μ_B, which corresponds to the structural transition from A2 to D0₃ and then to B2. The relationship between the structure and the magnetostriction is clarified, and the maximum magnetostriction appears in the A2 phase. The variation tendency of the magnetostriction is well characterized, which also reflects the structural transition.     

利用辛空间上子空间构作(d,r;z]-disjunct矩阵

一个(d,r;z]-disjunct矩阵在许多领域有着极为广泛的应用.利用辛空间上m维(m,s)型子空间的性质构作了(d,r;z]-disjunct矩阵,并利用子空间的计数定理计算了它的参数.     

Property (ω′) and Its Perturbation

In this note we define the property (ω′), a variant of Weyl’s theorem, and establish for a bounded linear operator defined on a Hilbert space the necessary and sufficient conditions for which property (ω′) holds by means of the variant of the essential approximate point spectrum σ1(·) and the spectrum defined in view of the property of consistency in Fredholm and index. In addition, the perturbation of property (ω′) is discussed.     

具无穷时滞退化中立型微分系统的周期解(英文)

In this paper,we discuss the periodic solutions of the nonlinear singular neutral differential systems with infinite delay.By using matrix measure and Krasnoselskii＇s fixed point theorem,we obtained the suffcient conditions of the existence of periodic solutions.