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31.
Structural Chemistry - Rice, well known as the most important staple food source worldwide, is highly susceptible to many infectious diseases, especially rice sheath blight caused by fungus...  相似文献   
32.
A comparison was made to investigate the structures and bonding of nickel complex that carry tetrylone and tetrylene ligands [(CO)2Ni‐{E(PH3)2}] ( Ni1E ) and [(CO)2Ni‐{NHEMe}] ( Ni2E ) (E = C to Pb) using quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP, TZ2P+). The nature of the Ni–E bonds was analyzed with charge‐ and energy decomposition methods. The structures of tetrylone complexes Ni1E exhibit an interesting trend with the ligands E(PH3)2 are bonded in a tilted orientation relative to the fragment Ni(CO)2. In contrast, the calculated equilibrium structures of complexes Ni2E exhibit the NHEMe ligands (E = C to Sn) bonded in a head‐on way to the Ni(CO)2 fragment, while the bending angle gives the strongest side‐on bonded ligand NHPbMe when E = Pb. The interesting trend of the bond dissociation energy (BDE) is observed for the tetrylone, which has the same trend BDEs compared with tetrylene complexes. The EDA‐NOCV results indicate that the tetrylone ligands {E(PH3)2} in complexes are similar to the tetrylene ligands NHEMe as strong σ‐donors and weak π‐acceptors. The BDEs calculated for the Ni–E bonds in Ni1E and Ni2E show that the effect of bulky ligands may obscure the intrinsic Ni–E bond strength. The bonding analysis shows that the tetrylone ligands in Ni1E may act in a similar fashion to the tetrylene ligands in Ni2E . All complexes Ni1E and Ni2E are suitable targets for synthesis.  相似文献   
33.
Direct C–H arylation of unactivated heteroaromatics with aryl halides catalyzed by cobalt porphyrin is reported. The reaction is proposed to go through a homolytic aromatic substitution reaction. The aryl radical is electrophilic and a SOMO–HOMO interaction is predominant in the aryl radical addition process.  相似文献   
34.
We have constructed variations for classes of regular solutions of the degenerate Beltrami equation with constraints of the set-theoretic and integral types for the complex coefficient and, on this basis, proved the variational principles of maximum and other necessary conditions of extremum. Some applications to equations of mathematical physics are given.  相似文献   
35.
The extraction of biologically active substances by carbon dioxide from various plant raw materials (amaranth seeds, Sophora japonica flower buds, Stephania rotunda stems, and Stevia rebaudiana leaves) was studied at sub- and supercritical parameters. A laboratory unit for the extraction of plant raw materials by liquefied gases and supercritical fluids at 5–35 MPa pressures and 285–350 K temperatures was developed. The maximum yield of the extracted substances from plants specified was obtained at temperature and pressure exceeding the critical parameters of CO2 (320–330 K, 28–30 MPa).  相似文献   
36.
Let W (N,d) be the N-parameter Wiener process with values in R d .It is shown that the range of W(N,d) is all of Rd when d<2N, answering a question raised earlier by Orey and Pruitt.  相似文献   
37.
胡平  柳玉启 《应用数学和力学》1996,17(11):1005-1011
本文提出韧性金属弹塑性大变形拟流动角点理论(quasi-flowcornertheory).该理论从塑性变形正交法则出发,将”模量衰减函数”及屈服面的尖点效应引入本构模型,从而实现了由正交法则本构模型向非正交法则本构模型以及从塑性加载向物理弹性却载的光滑过渡,使一般无角点各向异性硬化屈服函数与有角点硬化情形相结合成为可能.用于数值模拟各向异性金属薄板单向拉伸失稳与剪切带分析并与实验结果作比较,表明本文理论的有效性.  相似文献   
38.
Some invariance principles are obtained for the one-sample rank order statistics of a -mixing or strong mixing type time series. The estimation of the center of symmetry of the time series and tests for serial dependence are considered as applications.  相似文献   
39.
40.
13,17,53,57-tetraphenyl-13,17,53,57-tetrathio-3,7-dithia-1,5(1,5)-di(1,5-diaza-3,7-diphosphacyclooctana)-2,4,6,8(1,4)-tetrabenzenacyclooctaphane 2b was obtained by sulfurization of the corresponding macrocyclic tetraphosphine 1b. The structure of the inclusion complex of tetrasulfide 2b with DMF was investigated by the X-ray crystal structure analysis. A novel for this type of cyclophanes and relatively rare conical-like conformation of the macrocycle was found. A methyl group from one of the solvating DMF molecules penetrates the macrocyclic cavity of 2b from the side of the wider rim. According to quantum-chemical simulations, this may be the reason of the unusual conical conformation of 2b because the cavity of the macrocycles of this type is highly flexible. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
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