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1.
Measurement of integrated luminosities at BESIII for data samples at center-of-mass energies between 4.0 and 4.6 GeV 下载免费PDF全文
《中国物理C(英文版)》2022,46(11):113002-113002-11
The integrated luminosities of data samples collected in the BESIII experiment in 2016–2017 at center-of-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events. The integrated luminosities of old datasets collected in 2010–2014 are updated by considering corrections related to detector performance, offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter, which can haphazardly occur. 相似文献
2.
Dr. A. Suresh Kumar Dr. Guguloth Thirupathi G. Surendra Reddy Prof. Dr. Dhevalapally B. Ramachary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(5):1177-1183
An ideal stereoselective insertion of in situ generated benzynes into lawsones through domino formal [2+2]-cycloaddition followed by rearrangement is disclosed. The reaction allowed for the preparation of biologically important benzannulated bicyclo[3.3.0]octanes in good yields and with excellent selectivities by using simple substrates and conditions. 相似文献
3.
4.
The electrochemical behavior of austenitic stainless steel (Type 304) in 3 M sulfuric acid with 3.5% recrystallized sodium chloride at specific concentrations of butan-1-ol was investigated with the aid of potentiodynamic polarization, open circuit measurement and weight loss technique. Butan-1-ol effectively inhibited the steel corrosion with a maximum inhibition efficiency of 78.7% from weight-loss analysis and 80.9% from potentiodynamic polarization test at highest concentration studied. Adsorption of the compound obeyed the Freundlich isotherm. Thermodynamic calculations reveal physiochemical interactions and spontaneous adsorption mechanism. Surface characterizations showed the absence of corrosion products and topographic modifications of the steel. Statistical analysis depicts the overwhelming influence and statistical significance of inhibitor concentration on the inhibition performance. 相似文献
5.
An accurate potential energy surface for the ground electronic state of SH3 system has been constructed with 41,882 high level ab initio energy points and the neural network fitting method. The time-dependent wave packet method has been used to calculate the first state-to-state differential cross sections for the title reaction up to 1.2 eV in full dimensions, based on the reactant–product decoupling scheme. It is found that the majority of H2S are produced in the ground vibrational state, with a large fraction of available energy for the reaction ending up as product translational motion. The differential cross sections at the threshold energy are dominated by a very narrow peak in the backward direction. With the increase of collision energy, the width of the angular distribution increases considerably, which is a typical feature of a direct reaction via abstract mechanism, similar to the H2 + OH → H2O + H reaction. © 2018 Wiley Periodicals, Inc. 相似文献
6.
A new synthetic application of N-sulfonyl-1,2,3-triazoles acting as a 1-aza-[4C] synthon via the 1,2-shift reaction of an α-imine rhodium carbene was developed for the synthesis of fused pyrimidine derivatives. The high reactivity of the strained three-membered 2H-azirine ring facilitated the unusual cyclization of electron-deficient dienes with electron-deficient dienophiles. The compatibility was good with common functionalities tolerated. Excellent chemoselectivity was observed, and no reactions occurred between the rhodium carbene and 2H-azirine. The products could be converted into seven-membered multi-functionalized 1H-1,4-diazepine derivatives, illustrating the potential application of the protocol in medium-sized N-heterocycle synthesis. 相似文献
7.
Evgeny M. Buev Anastasia A. Smorodina Vladimir S. Moshkin Vyacheslav Y. Sosnovskikh 《Tetrahedron letters》2019,60(9):649-652
Nonstabilized azomethine ylides react with 4-arylidene-2-phenyloxazol-5(4H)-ones to form diazaspiro[4.4]nonenes, which were hydrolyzed to aryl cucurbitine derivatives in 35–67% overall yield. 相似文献
8.
Changgui Zhao Daniel A. Glazier Daoshan Yang Dan Yin IIia A. Guzei Michael M. Aristov Peng Liu Weiping Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(3):897-901
We have developed the first intermolecular hetero‐[5+2] cycloaddition reaction between oxidopyrylium ylides and cyclic imines with excellent control of regio‐ and stereoselectivity. Surprisingly, divergent stereochemistry was observed depending on the substitution pattern of the oxidopyrylium ylide. This new reaction provides quick access to highly substituted nitrogen‐containing seven‐membered rings—azepanes. Notably, a broad range of oxidopyrylium ylides and cyclic imines participate in this novel hetero‐[5+2] cycloaddition reaction and the cycloadducts can be readily transformed into the core skeletons of bioactive natural products. DFT calculations revealed that the cycloaddition proceeds through a stepwise pathway and the imine nitrogen atom serves as the nucleophile to initiate the cycloaddition. 相似文献
9.
Hydrogenation of acetophenone over nano‐Cu/SiO2 catalysts was investigated. The catalysts, prepared by a liquid precipitation method using various precipitating agents, were characterized using low‐temperature nitrogen adsorption, X‐ray diffraction, temperature‐programmed desorption of ammonia, hydrogen temperature‐programmed reduction, transmission electron microscopy and X‐ray photoelectron spectroscopy. It was found that the catalysts prepared by a homogeneous precipitation method had better activity and stability than those prepared by a co‐precipitation method. The catalyst prepared using urea as precipitating agent had well‐dispersed copper species, high surface area and abundant pore structure. The catalytic performance and mechanism of the Cu/SiO2 catalysts were further studied. It was found that the activity and stability of the catalysts could be improved by adjusting the proportion of Cu+/(Cu+ + Cu0). The sample prepared using urea as precipitating agent presented higher activity and selectivity. Also, the catalyst prepared using urea maintained a high catalytic performance while being continuously used for 150 h under the optimal reaction conditions. 相似文献
10.
Enas Aljuhani Amnah M. A. Alsuhaibani A. M. El-Didamony N. Hassan Sameh Abo Taleb Moamen S. Refat 《光谱学与光谱分析》2019,39(7):2316-2324
A new six intraperitoneal injection insulin-mimetic vanadyl(Ⅱ) compounds [(VD-13)(VO+2)(AA-1n)] (where (n=1~6); AA1=isoleucine, AA2=threonine, AA3=proline, AA4=phenylalanine, AA5=lysine and AA6=glutamine) were synthesized by the chemical reactions between vitamin D3 (VD3), VOSO4 and amino acids (AAn) with equal molar ratio 1∶1∶1 in neutralized media. The structures of these complexes were elucidated by spectroscopic methods like, infrared and solid reflectance spectroscopes. Magnetic moments and electronic spectra reveal square pyramid geometrical structure of the complexes. The infrared spectra assignments of these complexes revealed that the chelation towards vanadyl(Ⅳ) ions existed via deprotonation of the hydroxyl group of VD3 drug ligand and so amino acids act as bidentate ligand via N-amino and O-carboxylate groups. The anti-diabetic efficiency of these complexes were evaluated against streptozotocin induced diabetic male albino rats. 相似文献