Transition metal-mediated or catalyzed hydrocarboxylation of olefins with CO2

The development of new methods to incorporate carbon dioxide into organic molecules is of special significance and interest as it is an abundantly available and recyclable C1 source. Catalytic hydrocarboxylation of readily available olefins with CO₂ represents a highly atom- and step-economic approach toward transformations of CO₂ into widely-used aliphatic acids. However, due to relatively lower reactivity of them, this goal has been always a formidable challenge. Herein we review relevant progress on transition metal-mediated or catalyzed methodologies toward the desired hydrocarboxylation, with an emphasis on the development of two main pathways, including transition-metal-catalyzed cyclometallation of olefin and CO₂ and direct addition of alkylmetal to CO₂.     

Dehydrogenative etherification homocoupling of heterocyclic N-oxides

A novel approach was developed for the dehydrogenative etherification homocoupling of heterocyclic N-oxides in the presence of silver oxide and PyBroP. Various substrates were well tolerated and the desired products were obtained in moderate to good yields. Generally, this reaction features excellent functional group compatibility, broad substrate scope and good regioselectivity.     

On the reactivity of innercomplex-bonded palladium : A new specific test for cyanides in alkaline solutions

It has been found that the innercomplex salts of palladium with dimethylglyoxime, (benzildioxime and furildioxime), salicylaldoxime and 8-hydroxyquinolinc do not enter into redox reaction with carbon monoxide, cither in solid or in molecular dispersed form.Solutions of palladium-dimethylglyoxime and palladium-salicylaldoxime in alkali hydroxide or ammonia are masked with respect to many reactions of the palladium as well as of the organic components. In alkaline solutions, when adding alkali cyanide, demasking occurs, with the deliberation of the innercomplex forming organic components. For the processes of dissolution and demasking appropriated equations are suggested.The demasking of dimethylglyoximc in alkaline solutions of palladium dimethylglyoxime permits a new sensitive test for cyanide ion. This cyanide test seems to be appropriate for the detection of illuminating gas.Palladium hydroxyquinorate is insoluble in solutions of alkali cyanides, though it is not precipitable from cyanide containing palladium solutions. An explanation for this “false equilibrium” is suggested.     

Numerical and experimental investigations on the band-gap characteristics of metamaterial multi-span beams

A novel metamaterial multi-span beam with periodic simple supports and local resonators is designed and investigated. The frequency responses of the proposed metamaterial multi-span beam are computed by the spectral element method (SEM). The accuracy and feasibility of the SEM are verified by the finite element method (FEM) and the vibration experiments. The results show that the metamaterial multi-span beam could generate both the local resonance band-gaps in the low-frequency ranges and the Bragg band-gaps in the medium and high frequency regions. By adjusting the natural frequencies of the local resonators, the thickness of the base beam and the length of the unit-cell, the local resonance and the Bragg band-gaps can be controlled, respectively. The coupling effects of these two kinds of band-gaps are investigated by the parametrical design, which broadens the band-gaps and consequently improves the vibration reduction performance.     

Iodination of terminal alkynes using KI/CuSO4 – A facile method with potential for radio-iodination

Herein, we report an efficient new method for the iodination of terminal alkynes using stoichiometric KI and CuSO₄ in a mix of acetonitrile and acetate buffer that holds promise for further development into a method for radio-iodination.     

新疆各族大学生ABO血型分布的研究

调查了新疆大学主要三个民族的大学生ABO血型，结果表明：本校学生ABO血型频率依次为O〉B〉A〉AB，在维吾尔族学生中血型频率分布依次为B型（30．23oA）、A型（29．96％）、O型（25．91％）、AB型（13．90oA），基因频率为r（0．4968）〉q（0．2525）〉p（0．2507）．各表型分布的观察值与期望值间均无显著性差异（P〉0．1）；汉族学生中血型频率分布依次为O型（31．02％）、B型（29．77％）、A型（28．22oA）、AB型（10．99oA），基因频率为r（0．5494）〉q（0．2303）〉p（O．2203）．各表型分布的观察值与期望值问无显著性差异（P〉0．1）；哈萨克族学生中血型频率分布以次为O型（36．36oA）、B型（27．27％）、A型（26．09%）、AB型（10．28％），基因频率为r（0．588O）〉q（0．2097））〉p（0．2023），各表型分布的观察值与期望值间均无显著性差异（P〉0．1）．在学科分类来观察大学生ABO血型之间差异显著．     

迎接数字化时代的到来--浅谈大学物理实验教学改革

本简单介绍了数字化、多媒体设备在大学物理实验教学改革中的应用，以提高大学物理实验的教学效果。     

当代大学物理实验教学方法改革探析

在大学物理实验教学过程中应以大学物理实验课程的培养计划和实施素质教育为目标,采取灵活多变的实验教学方法,注重学生的主体作用,引导学生积极思考,重视教学互动,重点培养学生的研究创新能力和实际操作动手能力。同时结合当今科技的最新发展,注重实验的科技性、创新性、实用性,以科研方式组织教学,充分激发学生对科学研究的兴趣,提高学生的综合素质。     

Minimum degree condition for a graph to be knitted

For a positive integer $k$, a graph is $k$-knitted if for each subset $S$ of $k$ vertices, and every partition of $S$ into (disjoint) parts $S_1,\dots ,S_t$ for some $t\ge 1$, one can find disjoint connected subgraphs $C_1,\dots ,C_t$ such that $C_i$ contains $S_i$ for each $i\in \left[t\right]?\{1,2,\dots ,t\}$. In this article, we show that if the minimum degree of an $n$-vertex graph $G$ is at least $n∕2+k∕2?1$ when $n\ge 2k+3$, then $G$ is $k$-knitted. The minimum degree is sharp. As a corollary, we obtain that $k$-contraction-critical graphs are $?\frac{k}{8}?$-connected.     

Bistachybotrysins D and E,one stereoisomeric pair of cytotoxic phenylspirodrimane dimers from Stachybotrys chartarum

Bistachybotrysins D and E (1 and 2), one stereoisomeric pair of phenylspirodrimane dimers, were isolated from Stachybotrys chartarum CGMCC 3.5365. They represent novel phenylspirodrimane dimers with a central [6,5,6]-tricyclic carbon scaffold containing a cyclopentanone core. The structures of 1 and 2 were elucidated through extensive spectroscopic data analysis, and their absolute configurations were characterized by calculated electronic circular dichroism (ECD). Compounds 1 and 2 displayed potent cytotoxic activity against the four human tumor cell lines HCT116, BGC823, Daoy and HepG2 with IC_ (50)values ranging from 6.7 μmol/L to 11.6 μmol/L. Furthermore, a plausible biogenetic pathway for 1 and 2 is proposed.