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Catalytic asymmetric silicon-carbon bond-forming transformations based on Si–H functionalization

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Science China Chemistry 2023年第6期66卷 1654-1687页

作者： li li Wei-Sheng Huang Zheng xu li-wen xu China Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education Key Laboratory of Organosilicon Material Technology of Zhejiang ProvinceCollege of MaterialChemistry and Chemical EngineeringHangzhou Normal UniversityHangzhou 311121China State Key Laboratory for Oxo Synthesis and Selective Oxidation Suzhou Research InstituteLanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

In view of the exciting advancement on silicon–carbon bond-forming transformations achieved in the past decade,this review intends to show a unified illustration of the recent findings on enantioselective Si–H bond functionalization aided by asymmetric ***,this review describes the enantioselective silicon–carbon bond-forming Si–H bond functionalization,focusing on the reactivity and stereoselectivity in catalytic asymmetric hydrosilylation,carbene Si–H insertion,C–H silylation,and Si–C bond-forming cross-coupling reactions that were achieved with high enantioselectivity in the presence of transitionmetal catalyst *** review highlights recent and representative examples of the enantioselective Si–H bond functionalization,discusses the origins of silicon-involving stereoselectivities,and evaluates the substrate scopes and limitations in these catalytic asymmetric Si–H bond functionalization reactions due to the special reactivity of different hydrosilanes.

关键词： Si-H functionalization hydrosilylation C-H silylation carbene Si-H insertion asymmetric catalysis

The Minimax Estimator of Stochastic Regression Coefficients and Parameters in the Class of All Estimators

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Acta Mathematica Sinica,English Series 2007年第3期23卷 497-506页

作者： li wen xu Song Gui WANG Department of Mathematics Tsinghua University Beijing 100084 P. R. China College of Applied Sciences Beijing University of Technology Beijing 100022 P. R. China College of Applied Sciences Beijing University of Technology Beijing 100022. P. R. China

In this paper, the authors address the problem of the minimax estimator of linear combinations of stochastic regression coefficients and parameters in the general normal linear model with random effects. Under a quadratic loss function, the minimax property of linear estimators is investigated. In the class of all estimators, the minimax estimator of estimable functions, which is unique with probability 1, is obtained under a multivariate normal distribution.

关键词： minimax estimator stochastic regression coefficients quadratic loss function normal linear model

High Pressure Raman Study of Phase Transitions on Solid Benzene Using Raman Notch Filter Set

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Chinese Physics Letters 1996年第4期13卷 293-296页

作者： xu li-wen WANG Ru-ju CHEN liang-chen Institute of Physics Chinese Academy of SciencesBeijing 100080

A high-throughput Haman notch filter set has been manufactured and used to collect the Raman scattering signals of pressure-hiduced phase transitions of solid benzene in a diamond anvil cell up to 15 GPa at room *** changes in the profiles as well as the frequencies of Raman scattering spectra are observed and enable us to determine the phase transition.

关键词： temperature. transition. Transition

Consistent Nonnegative Estimates of Variance Components

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Acta Mathematicae Applicatae Sinica 2010年第2期26卷 177-186页

作者： li-wen xu Song-gui Wang Jian-hong Shi College of Sciences North China University of Technology Beijing 100144 China College of Applied Sciences Beijing University of Technology Beijing 100022 China School of Mathematics and Computer Sciences Shanxi Normal University Linfen 041004 China

In this paper, the estimation of variance components in the linear mixed model with two random effects is investigated. The class of combination estimates based on the quadratic invariant statistics and consistent nonnegative estimates are obtained. Furthermore, it is shown that the consistent nonnegative estimate dominates ANOVA estimate under some conditions.

关键词： linear mixed models invariant statistics consistency nonnegative estimate

Silicon-mediated enantioselective synthesis of structurally diverseα-amino acid derivatives

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Science China Chemistry 2020年第8期63卷 1082-1090页

作者： Jun-Han Ma li li Yu-li Sun Zheng xu Xing-Feng Bai Ke-Fang Yang Jian Cao Yu-Ming Cui Guan-Wu Yin li-wen xu Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education and Key Laboratory of Organosilicon Material Technology of Zhejiang ProvinceHangzhou Normal UniversityHangzhou 311121China State Key Laboratory for Oxo Synthesis and Selective Oxidation Suzhou Research Institute(SRI)and Lanzhou Institute of Chemical Physics(LICP)University of Chinese Academy of Sciences(UCAS)Lanzhou 730000China

The catalytic asymmetric synthesis of novel and chiral amino acid derivatives with unconventional chemo-,diastereo-,and enantio-selectivity remains a paramount *** we reported a novel protocol for the use of highly enantioselective copper-catalyzed cycloaddition ofα,β-unsaturated acylsilanes as a springboard reaction for the facile synthesis of structurally diversified pyrrolidines and complicatedα-amino esters by *** newly developed process could provide a wide range of synthetically useful acylsilane-substituted pyrrolidines(ASiP)in high yields and excellent diastereo-and enantioselectivities with Cu/(R)-XylBINAP complex as the *** the downstream desilylation transformation enables to expand the potntial applications of 1,3-dipolar cycloaddition in the construction of structurally unique amino acid derivatives,in which an unprecedented and concerted fluoride anion-promoted C–X(X=H,Si,N,C)bond cleavage occurred to the enantioselective construction of aldehyde-substituted pyrrolidines,linear cinnamaldehyde or alkene-substituted amino esters in high ee values.

关键词： (3+2)cycloaddition asymmetric catalysis acylsilane pyrrolidine amino aldehyde amino acids

A NEW APPROACH OF SIMULTANEOUS FAULTS DIAGNOSIS BASED ON RANDOM SETS AND DSMT

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Journal of Electronics(China) 2009年第1期26卷 24-30页

作者： li Zhiliang xu Xiaobin wen Chenglin Institute of Information and Control Hangzhou Dianzi University Hangzhou 310018 China

Simultaneous faults often occur in running equipments, in order to solve the problems of the simultaneous faults, a new approach based on random sets and Dezert-Smarandache Theory (DSmT) is proposed in this paper. Firstly, the simultaneous faults' model is built based on the generalized frame of discernment in DSmT. Secondly, according to the unified description of combination rules in evidence reasoning based on random sets, a new combination rule for simultaneous faults diagnosis is proposed. Thirdly, according to the working characteristics and environment of the sensors used to acquire fault characteristic information, a new method to construct basic probability assignment function is pro- posed based on membership. Finally, diagnosis result is obtained by use of the new combination rule combined with decision rules. A case pertaining to the fault diagnosis for a multi-function rotor test-bed is given, and the result shows that the proposed diagnosis approach is feasible and efficient.

关键词： Random sets Dezert-Smarandache Theory (DSmT) Basic probability assignment Simultaneous fault Diagnosis

Measurement of R line Fluorescence in Ruby Using the Diamond Anvil Cell at Low Temperature

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Chinese Physics Letters 2000年第8期17卷 555-557页

作者： xu li-wen CHE Rong-Zheng JIN Chang-Qing Institute of Physics and Center for Condensed Matter Chinese Academy of SciencesBeijing 100080

Using our custom-built high-pressure cryostat we have performed the measurements of the R line fluorescence of ruby in the diamond anvil cell from room temperature down to *** maximum pressure was 11.1 *** computer curve fitting,different equations have been found for functions of wavenumber versus temperature between ambient pressure and 2.7 *** changes of the shape and linewidth of R lines were observed.

关键词： Diamond Fluorescence ambient

Palladium-catalyzed hydrosilylation of ynones to access siliconstereogenic silylenones by stereospecific aromatic interactionassisted Si–H activation

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Science China Chemistry 2021年第5期64卷 761-769页

作者： Jia-Le Xie Zheng xu Han-Qi Zhou Yi-xue Nie Jian Cao Guan-Wu Yin Jean-Philippe Bouillon li-wen xu Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education Key Laboratory of Organosilicon Material Technology of Zhejiang ProvinceHangzhou Normal UniversityHangzhou 311121China State Key Laboratory for Oxo Synthesis and Selective Oxidation Suzhou Research Institute(SRI)Lanzhou Institute of Chemical Physics(LICP)University of the Chinese Academy of Sciences(UCAS)Lanzhou 730000China Normandie University INSA RouenUNIROUENCNRSCOBRA(UMR 6014)Rouen 76000France

Hydrosilylation is one of the most important reactions in synthetic chemistry and ranks as a fundamental method to access organosilicon compounds in industrial and academic ***,the enantioselective construction of chiral-at-silicon compounds via catalytic asymmetric hydrosilylation remained limited and *** we report a highly enantioselective hydrosilylation of ynones,a type of carbonyl-activated alkynes,using a palladium catalyst with a chiral binaphthyl phosphoramidite *** stereospecific hydrosilylation of ynones affords a series of silicon-stereogenic silylenones with up to 94%yield,>20:1 regioselectivity and 98:2 *** density functional theory(DFT)calculations were conducted to elucidate the reaction mechanism and origin of high degree of stereoselectivity,in which the powerful potential of aromatic interaction in this reaction is highlighted by the multiple C–H-πinteraction and aromatic cavity-oriented enantioselectivitydetermining step during desymmetric functionalization of Si–H bond.

关键词： asymmetric catalysis DFT calculations hydrosilylation silicon-stereogenic vinylsilanes aromatic interaction

PSD95 Gene Specific siRNAs Attenuate Neuropathic Pain through Modulating Neuron Sensibility and Postsynaptic CaMKIIα Phosphorylation

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Chinese Medical Sciences Journal 2011年第4期26卷 201-207页

作者： Le Shen xu li wen Chen li xu Wei liu xue-rong Yu Yu-guang Huang Department of Anesthesiology Peking Union Medical College Hospital Chinese Academy of Medical Sciences ＆ Peking Union Medical College Beijing 100730 China

Objective To observe the effects of PSD95 gene specific siRNAs on neuropathic pain relief, neuron viability, and postsynaptic calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) phosphorylation in vitro and in vivo. Methods Gene-specific siRNAs of rat PSD95 were synthesized chemically for transfection. Adult male Sprague-Dawley (SD) rats were randomly divided into 3 groups: nave group (n=6), sham group (n=6), and sciatic nerve chronic constriction injury (CCI) group (n=24). The CCI group was further divided into 4 groups (n=6 in each group), which were pretreated with normal saline, transfection vehicle, negative control siRNAs, and PSD95 gene specific siRNAs respectively. All the subgroups received corresponding agents intrathecally for 3 days, started one day before the CCI of sciatic nerve. Both mechanical allodynia and thermal hyperalgesia were measured on post-operative day 3 and 7. PSD95 gene silenced NG108-15 cells were further stimulated by glutamate, with the cell viability and the expression/phosphorylation of CaMKIIα measured by MTT cell proliferation assay and Western blot, respectively. Results The siRNAs decreased PSD95 mRNA level significantly both in vivo and in vitro. Neuropathic pain rats pretreated with PSD95 gene specific siRNAs exhibited significant elevation in the mechanical withdrawal threshold and paw withdrawal thermal latency, without affecting the baseline nociception. PSD95 gene silencing enhanced neuronal tolerance against the glutamate excitotoxicity, meanwhile the phosphorylation of CaMKIIα Thr286 was attenuated. Conclusion Pre-emptive administration of PSD95 gene specific siRNAs may attenuate the central sensitization CaMKIIα-related signaling cascades, leading to the relief of neuropathic pain.

关键词： PSD95 siRNAs neuropathic pain glutamate excitotoxicity calcium/calmodulin- dependent protein kinase IItt