Visible-light-induced,autopromoted nickel-catalyzed three-component arylsulfonation of 1,3-enynes and mechanistic insights

Science China Chemistry - A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported. This methodology exhibited mild conditions,...     

Nickel-Catalyzed Cross-Coupling of Ethyl Chlorofluoroacetate with Aryl Bromides

A combinatorial nickel-catalyzed monofluoroalkylation of aryl bromides with the industrial raw regent ethyl chlorofluoroacetate has been developed. The two key factors to successful conversion are the combination of nickel with readily available nitrogen and phosphine ligands and the using of a mixture of different solvents. Mechanistic investigations indicated a new zinc regent might generated in situ and be involved in the reaction process.     

流动肥皂膜气体界面及其在柱状汇聚激波作用下演化的实验研究

在Richtmyer-Meshkov(RM)不稳定性实验研究中,形成两种不同密度流体的初始扰动界面是前提和关健.本文提出了一种流动肥皂膜气体界面生成方法,其工作原理是由细丝构成的导流框从激波管实验段穿过,肥皂液从导流框的上端注入并在重力作用下在导流框中形成流动肥皂膜,膜的两测可以分别充入不同密度的气体从而形成稳定的气体...     

Electrochemical preparation and magnetic properties of submicron Co x Pb1−x dendrites

Magnetic dendrites of Co _x Pb_1−x were fabricated through potentiostatic electrochemical deposition on Cu substrates in boric acid solution at room temperature. The as-deposited dendrites were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), electrodeposition (ED), and energy dispersive X-ray spectroscopy (EDS). SEM results indicate that the Co _x Pb_1−x dendrites are highly symmetrical in structures. The diameters of the branches are about 50 ~ 200 nm, and the backbones are continuous with lengths up to about 10 μm. XRD patterns show that the as-deposited dendrites are solid solutions. The annealing treatment can result in the recrystallization of these metastable alloys into two separate phases. TEM, ED, and EDS results also reveal that the backbones and the branches of the dendrites are composed of different amounts of cobalt. Magnetic measurements confirm that the as-deposited Co _x Pb_1−x dendrites have a softly ferromagnetic behavior, and a small coercive force (about 80 Oe). Also the saturation magnetizations of the Co _x Pb_1−x dendrites decrease rapidly with the temperature increasing.     

Jet formation in shock-heavy gas bubble interaction

The influences of the acoustic impedance and shock strength on the jet formation in shock-heavy gas bubble interaction are numerically studied in this work. The process of a shock interacting with a krypton or a SF 6 bubble is studied by the numerical method VAS2D. As a validation, the experiments of a SF 6 bubble accelerated by a planar shock were performed. The results indicate that, due to the mismatch of acoustic impedance, the way of jet formation in heavy gas bubble with different species is diversified under the same initial condition. With respect to the same bubble, the manner of jet formation is also distinctly different under different shock strengths. The disparities of the acoustic impedance result in different effects of shock focusing in the bubble, and different behaviors of shock wave inside and outside the bubble. The analyses of the wave pattern and the pressure variation indicate that the jet formation is closely associated with the pressure perturbation. Moreover, the analysis of the vorticity deposition, and comparisons of circulation and baroclinic torque show that the baroclinic vorticity also contributes to the jet formation. It is concluded that the pressure perturbation and baroclinic vorticity deposition are the two dominant factors for the jet formation in shock-heavy gas bubble interaction.     

LIPS技术探测CH4/空气火焰中的OH自由基

论述了激光诱导偏振光谱技术的基本原理,实验方法及其对燃烧场的测量结果.利用光谱扫描方法获得了A2∑ -X2Ⅱ(0,0)跃迁带系列吸收谱线及P1(2)谱线的线型轮廓.测量了CH4/空气预混火焰不同化学配比、不同空间位置OH自由基的相对分布.实验中通过设计精密旋转调节装置有效提高了信噪比.     

Terminal C(sp3)H alkylation of internal alkenes via Ni/H-catalyzed isomerization

An efficient nickel-catalyzed reductive relay cross-coupling of internal alkenes with alkyl (or aryl) halides has been developed. This method has demonstrated broad substrate scope, mild reaction conditions and excellent terminal-selectivity. Moreover, this efficient strategy could be applied to the terminal-selective alkylation of isomeric mixtures of internal alkenes.     

Induction of a High-Yield Lovastatin Mutant of Aspergillus terreus by 12C6+ Heavy-Ion Beam Irradiation and the Influence of Culture Conditions on Lovastatin Production Under Submerged Fermentation

Heavy-ion beams, possessing a wide mutation spectrum and increased mutation frequency, have been used effectively as a breeding method. In this study, the heavy-ion beams generated by the Heavy-Ion Research Facility in Lanzhou were used to mutagenize Aspergillus terreus CA99 for screening high-yield lovastatin strains. Furthermore, the main growth conditions as well as the influences of carbon and nitrogen sources on the growth and the lovastatin production of the mutant and the original strains were investigated comparatively. The spores of A. terreus CA99 were irradiated by 15, 20, 25, and 30 Gy of 80 MeV/u (12)C(6+) heavy-ion beams. Based on the lovastatin contents in the fermentation broth, a strain designated as A. terreus Z15-7 has been selected from the clone irradiated by the heavy-ion beam. When compared with the original strain, the content of lovastatin in the fermentation broth of A. terreus Z15-7 increased 4-fold. Moreover, A. terreus Z15-7 efficiently used the carbon and nitrogen sources for the growth and production of lovastatin when compared to the original strain. The maximum yield of lovastatin, 916.7 μg/ml, was obtained as A. terreus Z15-7 was submerged cultured in the chemically defined medium supplemented with 3% glycerol as a carbon source, 1% corn meal as an organic nitrogen source, and 0.2% sodium nitrate as an inorganic nitrogen source at 30 °C in the shake flask. The result shows that heavy-ion beam irradiation is an effective method for the mutation breeding of lovastatin production of A. terreus.     

Consensus of second-order and high-order discrete-time multi-agent systems with random networks

This paper studies the convergence and convergence speed for the second-order and the high-order discrete-time multi-agent systems with random networks and arbitrary weights. Random networks mean that the existence of any edge is probabilistic and independent of any other edge. By introducing the agreement set, velocity control gain and high-order state control gain, some consensus protocols are provided for the discrete-time random networks. Moreover, the per-step and asymptotic convergence factors are proposed to measure the convergence and convergence speed. Some examples and simulation results are given to illustrate the effectiveness of the obtained theoretical results.     

纳米板钛矿基TiO2的晶粒尺寸效应

借助精确的X射线衍射测量,结合独立衍射峰对不同晶粒度纳米板钛矿基TiO-2样品中板钛矿和金红石相的微结构参量进行了较细致的研究,给出了标征物相、晶面指数(hk1)和晶面间距d-{hkl}值,详细分析结果的系列XRD谱,并得到晶面间距、晶格常数、轴比、晶胞体积等参数数值及其相对常规粗晶的变化情况,从而初步揭示出其晶粒微结构的尺寸效应.作者首次发现,纳米板钛矿基TiO-2样品中板钛矿和金红石相晶粒均存在着非单调的各向异性晶格畸变.