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961.
Hengzhao Li Bin Zhang Yanhong Dong Ting Liu Yuntong Zhang Haiyu Nie Ruoyan Yang Xiaodong Ma Yun Ling Jie An 《Tetrahedron letters》2017,58(28):2757-2760
A new single electron transfer reaction for the reductive deuteration of activated alkenes has been developed for the selective synthesis of α,β-dideuterio compounds. A cheap, stable and commercially-available sodium dispersion with high specific surface area is employed as the electron donor to replace the traditionally used sodium/liquid ammonium system. Deuterium source is provided by EtOD-d1. Excellent yields and deuterium incorporations were obtained across a broad range of activated alkenes with good functional group tolerance. This method provided a cheap, efficient and operationally-simple method for the synthesis of deuterium labeled compounds. 相似文献
962.
Measurement of the heavy neutral MSSM Higgs bosons H and A production in the process γγ → A/H → b
at the Photon Linear Collider [1,2] has been considered in two independent analyses for the parameter range corresponding
to the so-called ‘LHC wedge’. Significantly different conclusions were obtained; signal-to-background ratio 36 vs. 2. Here
assumptions and results of these two analyses are compared. We have found that differences in the final results are mainly
due to different assumptions on γγ-luminosity spectra, jet definitions and selection cuts.
相似文献
963.
Evidence for visible quantum cutting involving the emission of two visible photons for each vacuum-ultraviolet (VUV) photon absorbed is demonstrated in SrAl(12)O(19):Pr,Cr using synchrotron radiation as one of the excitation sources. Upon VUV excitation of the 4f5d states of Pr(3+), quantum cutting could occur by a two-step energy transfer from Pr(3+) to Cr(3+) by cross relaxation and sequential transfer of the remaining excitation energy. A theoretical visible quantum efficiency of 147% is estimated in SrAl(12)O(19):2% Pr,5% Cr, suggesting the possibility of a VUV phosphor with visible quantum efficiency higher than 100% based on Pr(3+)-Cr(3+) pair in oxide materials. 相似文献
964.
Highly Enantioselective Nickel‐Catalyzed Intramolecular Reductive Cyclization of Alkynones 下载免费PDF全文
Wenzhen Fu Ming Nie Aizhen Wang Ziping Cao Prof. Dr. Wenjun Tang 《Angewandte Chemie (International ed. in English)》2015,54(8):2520-2524
The first asymmetric nickel‐catalyzed intramolecular reductive cyclization of alkynones is reported. A P‐chiral monophosphine and triethylsilane were used as the ligand and the reducing reagent, respectively, to form a series of tertiary allylic alcohols bearing furan/pyran rings in excellent yields and enantioselectivities. This reaction has a broad substrate scope and enabled the efficient synthesis of dehydroxycubebin and chiral dibenzocyclooctadiene skeletons. 相似文献
965.
Rui Ning Hao Zhou Shi-Xin Nie Dr. Yu-Fei Ao Prof. Dr. De-Xian Wang Prof. Dr. Qi-Qiang Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10986-10990
The tight binding enabled by tailor-made macrocycles can be manipulated for tuning the catalysis process. In parallel to well-developed crown ether-based cation-binding catalysis, a macrocycle-enabled counteranion trapping strategy is presented for boosting highly efficient and enantioselective catalysis. A set of bis-diarylthiourea macrocycles containing two BINOL moieties were designed and synthesized. They possess a well-confined chiral cavity and strong binding affinities towards disulfonate anions. Caused by the tight binding, just 1 mol % macrocycle in combination with 1 mol % ethanedisulfonic acid can promote excellent conversion and up to 99 % ee in the Friedel–Crafts reaction of indoles with imines. The acid or the macrocycle alone do not afford any reactivity. The high catalytic efficiency and excellent stereocontrol was ascribed to large, complexation-induced acidity enhancement and tight ion-pairing facilitated by cave-like macrocyclic cavity. 相似文献
966.
We study the electrically forced thickness-shear and thickness-twist vibrations of stepped thickness piezoelectric plate mesa resonators made of polarized ceramics or 6-ram class crystals. A theoretical analysis based on the theory of piezoelectricity is performed, and an analytical solution is obtained using the trigonometric series. The electrical admittance, resonant frequencies, and mode shapes are calculated, and strong energy trapping of the modes is observed. Their dependence on the geometric parameters of the resonator is also examined. 相似文献
967.
Xiaohui Guo a Jianzhong Lin a b Deming Nie a a Institute of Fluid Mechanics China Jiliang University Hangzhou China b State Key Laboratory of Fluid Power Transmission Control Zhejiang University Hangzhou China 《中国颗粒学报》2011,9(2)
The drag force on a cylindrical particle is calculated using lattice Boltzmann method.The results show that the drag coefficient of a particle with different orientation angles decreases with increasing Reynolds number.When the principal axis of the particle is parallel to flow,the drag coefficient is much larger than that of others and decreases fastest with increasing Reynolds number,which becomes more obvious with increasing particle aspect ratio.When the principal axis of the particle is inclined to flo... 相似文献
968.
甲基环己烷燃烧反应特性的光谱研究 总被引:1,自引:0,他引:1
利用激波管实验装置由反射激波点火,在点火温度1 164~1 566 K,点火压力1.03~1.99 atm,燃料浓度为1.0%,当量比为1.0的条件下,用光谱单色仪、光电倍增管、压力传感器和示波器等组成测试系统,测量了甲基环己烷燃烧过程中主要中间产物OH,CH和C2自由基特征光辐射随时间的连续变化,并测得了甲基环己烷/氧气/氩气的点火延迟时间。通过对测量结果的分析,初步认识了甲基环己烷燃烧反应中几个主要中间产物的光辐射特性及其反映出的甲基环己烷燃烧反应特性。实验所测点火延迟时间与已报道的实验结果和燃烧反应机理预测结果符合较好。本文实验结果为构建和验证甲基环己烷燃烧反应机理提供了实验依据。 相似文献
969.
Zhou X Xiong C Xu G Liu H Tang Y Zhu Z Chen R Qiao H Tseng YH Peng WP Nie Z Chen Y 《Journal of the American Society for Mass Spectrometry》2011,22(2):386-398
The potential distribution in the curved quadrupole is exactly characterized by the Laplace equation, and an approximate solution to the Laplace equation is calculated. We represent the Laplace equation under the coordinates named minimal rotation frame (MRF) and derive an expression on the hexapole and octopole superposition. Our conclusion is in agreement with the results by the numerical (SIMION) method. Based on the Poincare-Lighthill-Kuo (PLK) method reported in our previous work, the nonlinear effects of ion motion are investigated in detail. The frequency shift of ion motion can be well eliminated by coupling the hexapole component with a positive octopole component, and the transmission efficiency of ions is found to decrease dramatically with the increase of the ionic kinetic energy in the z-direction. Furthermore, the transmission characteristics of ions are discussed with regards to the phase-space theory. The results show that the centrifugally introduced axis shift is mainly responsible for the ion losses. A modified direct current (dc) voltage supply pattern is hence proposed to compensate for this effect. 相似文献