In this article, we consider the global chaotic synchronization of general cou- pled neural networks, in which subsystems have both discrete and distributed delays. Stochastic perturbations between subsystems are also...In this article, we consider the global chaotic synchronization of general cou- pled neural networks, in which subsystems have both discrete and distributed delays. Stochastic perturbations between subsystems are also considered. On the basis of two sim- ple adaptive pinning feedback control schemes, Lyapunov functional method, and stochas- tic analysis approach, several sufficient conditions are developed to guarantee global syn- chronization of the coupled neural networks with two kinds of delay couplings, even if only partial states of the nodes are coupled. The outer-coupling matrices may be symmetric or asymmetric. Unlike existing results that an isolate node is introduced as the pinning target, we pin to help the network realizing synchronization without introducing any iso- late node when the network is not synchronized. As a by product, sufficient conditions under which the network realizes synchronization without control are derived. Numerical simulations confirm the effectiveness of the obtained results.展开更多
Cu-based electrocatalysts can have excellent activity for the generation of C_(2+)products from a CO_(2)reduction reaction(CO_(2)RR).Cuδ+species is crucial in tuning the performance of the catalysts.Herein,we discove...Cu-based electrocatalysts can have excellent activity for the generation of C_(2+)products from a CO_(2)reduction reaction(CO_(2)RR).Cuδ+species is crucial in tuning the performance of the catalysts.Herein,we discovered that Si-doped Cu catalysts had excellent performance for electrochemical CO_(2)to C_(2+)products.A high Faradaic efficiency(FE)of 84.7%was achieved with a current density of 289mA cm^(−2)in the flow-cell system.In situ experimental results showed that the significant reconstruction occurred during the electrolysis,resulting in the formation of the asymmetric Cu sites(Cu^(0)-Cu^(+)).The ratio of Cu^(0)and Cu^(+)could be tuned by changing Si content.Controlled experiments and theoretical calculations demonstrated that the asymmetric Cu sites caused by the appropriate Si doping promoted CO_(2)activation and strengthened the adsorption of^(*)CO intermediate.This was beneficial to the subsequent^(*)CO–^(*)CO dimerization step,and thus,accounted for the enhancement of C_(2+)selectivity.展开更多
Plan asymmetric buildings are very susceptible to earthquake induced damage due to lateral torsional coupling, and the corners of these systems suffer heavy damage during earthquakes. Therefore, it is important to inv...Plan asymmetric buildings are very susceptible to earthquake induced damage due to lateral torsional coupling, and the corners of these systems suffer heavy damage during earthquakes. Therefore, it is important to investigate the seismic behavior of an asymmetric plan building with MR dampers. In this study, the effectiveness of MR damper-based control systems has been investigated for seismic hazard mitigation of a plan asymmetric building. Furthermore, the infl uence of the building parameters and damper command voltage on the control performance is examined through parametric study. The building parameters chosen are eccentricity ratio and frequency ratio. The results show that the MR damper-based control systems are effective for plan asymmetric systems.展开更多
An efficient catalytic asymmetric dearomatizing amination of 2-naphthols and phenols catalyzed by N,N′-dioxide-copper(I)complex as a chiral catalyst was presented.A variety of optically activeβ-naphthalenone compoun...An efficient catalytic asymmetric dearomatizing amination of 2-naphthols and phenols catalyzed by N,N′-dioxide-copper(I)complex as a chiral catalyst was presented.A variety of optically activeβ-naphthalenone compounds with a nitrogen-containing quaternary carbon stereocenter were obtained with high yield and enantioselectivity under mild reaction conditions.Mechanistic studies indicated that this Csp^(2)–N dearomatizing coupling proceeds via 1,3-reductive elimination of phenolate-Cu~Ⅲ-amino intermediate in five-membered ring transition states.The origin of enantioselectivity has also been elucidated based on density functional theory calculations.展开更多
Comprehensive Summary An asymmetric synthesis of dihydrospirotryprostatin B was achieved in 15 steps(8 purifications)from L-tryptophan.The main feature of our synthetic strategy is the efficient construction of spiroc...Comprehensive Summary An asymmetric synthesis of dihydrospirotryprostatin B was achieved in 15 steps(8 purifications)from L-tryptophan.The main feature of our synthetic strategy is the efficient construction of spirocyclic oxindole intermediate containing a chiral quaternary carbon center,involving the silica gel-mediated cyclization of tryptamine-ynamide and oxidation under neat conditions.展开更多
Natural product elansolid A belongs to one type of polyketide macrolactone with promising antibiotic activity.Pre-viously,the first total synthesis of elansolid A in 28 longest linear sequence(LLS)and 41 steps in tota...Natural product elansolid A belongs to one type of polyketide macrolactone with promising antibiotic activity.Pre-viously,the first total synthesis of elansolid A in 28 longest linear sequence(LLS)and 41 steps in total has been achieved.Herein,the simplified analog of elansolid A,featured with a cyclohexyl-fused 19-memebered macrolactone,was proposed,and its asymmetric total synthesis based on a convergent strategy and key reactions exemplified by desymmetric alcoholysis of anhydride,Pd-catalyzed Stille coupling,Suzuki-Miyaura coupling as well as Mukaiyama macrolactonization was finished.展开更多
The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHS...The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.展开更多
基金supported by the National Natural Science Foundation of China under Grant No. 60874088 and No. 11072059the Scientific Research Fund of Yunnan Province under Grant No. 2010ZC150the Scientific Research Fund of Yunnan Provincial Education Department under Grant No. 07Y10085
文摘In this article, we consider the global chaotic synchronization of general cou- pled neural networks, in which subsystems have both discrete and distributed delays. Stochastic perturbations between subsystems are also considered. On the basis of two sim- ple adaptive pinning feedback control schemes, Lyapunov functional method, and stochas- tic analysis approach, several sufficient conditions are developed to guarantee global syn- chronization of the coupled neural networks with two kinds of delay couplings, even if only partial states of the nodes are coupled. The outer-coupling matrices may be symmetric or asymmetric. Unlike existing results that an isolate node is introduced as the pinning target, we pin to help the network realizing synchronization without introducing any iso- late node when the network is not synchronized. As a by product, sufficient conditions under which the network realizes synchronization without control are derived. Numerical simulations confirm the effectiveness of the obtained results.
基金the National Natural Science Foundation of China(grant nos.22203050,22002172,22293015,22033009,and 22121002)Natural Scientific Foundation of Shandong(grant no.ZR2022QB002)+1 种基金Beijing Natural Science Foundation(grant no.J210020)Photon Science Center for Carbon Neutrality,and CAS Project for Young Scientists in Basic Research(YSBR-050).
文摘Cu-based electrocatalysts can have excellent activity for the generation of C_(2+)products from a CO_(2)reduction reaction(CO_(2)RR).Cuδ+species is crucial in tuning the performance of the catalysts.Herein,we discovered that Si-doped Cu catalysts had excellent performance for electrochemical CO_(2)to C_(2+)products.A high Faradaic efficiency(FE)of 84.7%was achieved with a current density of 289mA cm^(−2)in the flow-cell system.In situ experimental results showed that the significant reconstruction occurred during the electrolysis,resulting in the formation of the asymmetric Cu sites(Cu^(0)-Cu^(+)).The ratio of Cu^(0)and Cu^(+)could be tuned by changing Si content.Controlled experiments and theoretical calculations demonstrated that the asymmetric Cu sites caused by the appropriate Si doping promoted CO_(2)activation and strengthened the adsorption of^(*)CO intermediate.This was beneficial to the subsequent^(*)CO–^(*)CO dimerization step,and thus,accounted for the enhancement of C_(2+)selectivity.
文摘Plan asymmetric buildings are very susceptible to earthquake induced damage due to lateral torsional coupling, and the corners of these systems suffer heavy damage during earthquakes. Therefore, it is important to investigate the seismic behavior of an asymmetric plan building with MR dampers. In this study, the effectiveness of MR damper-based control systems has been investigated for seismic hazard mitigation of a plan asymmetric building. Furthermore, the infl uence of the building parameters and damper command voltage on the control performance is examined through parametric study. The building parameters chosen are eccentricity ratio and frequency ratio. The results show that the MR damper-based control systems are effective for plan asymmetric systems.
基金supported by the National Natural Science Foundation of China(22188101)Sichuan Science and Technology Program(2021YJ0561)。
文摘An efficient catalytic asymmetric dearomatizing amination of 2-naphthols and phenols catalyzed by N,N′-dioxide-copper(I)complex as a chiral catalyst was presented.A variety of optically activeβ-naphthalenone compounds with a nitrogen-containing quaternary carbon stereocenter were obtained with high yield and enantioselectivity under mild reaction conditions.Mechanistic studies indicated that this Csp^(2)–N dearomatizing coupling proceeds via 1,3-reductive elimination of phenolate-Cu~Ⅲ-amino intermediate in five-membered ring transition states.The origin of enantioselectivity has also been elucidated based on density functional theory calculations.
基金the National Natural Science Foundation of China(22277082)Liaoning Province Education Administration of China(LJKQz2022236)+1 种基金Liaoning Provincial Foundation of Natural Science(2022-MS-245)China Postdoctoral Science Foundation(2022MD723807)for financial support.
文摘Comprehensive Summary An asymmetric synthesis of dihydrospirotryprostatin B was achieved in 15 steps(8 purifications)from L-tryptophan.The main feature of our synthetic strategy is the efficient construction of spirocyclic oxindole intermediate containing a chiral quaternary carbon center,involving the silica gel-mediated cyclization of tryptamine-ynamide and oxidation under neat conditions.
基金Project supported by the High-Level Talent Program of Yunnan Province(No.Y93D321261)the Regional Development Program for Young Scholars,Chinese Academy of Sciences(CAS)(No.E323521311)the Science and Technology Department of Yunan Province(Nos.202305AH34005,202401AS070096)。
文摘Natural product elansolid A belongs to one type of polyketide macrolactone with promising antibiotic activity.Pre-viously,the first total synthesis of elansolid A in 28 longest linear sequence(LLS)and 41 steps in total has been achieved.Herein,the simplified analog of elansolid A,featured with a cyclohexyl-fused 19-memebered macrolactone,was proposed,and its asymmetric total synthesis based on a convergent strategy and key reactions exemplified by desymmetric alcoholysis of anhydride,Pd-catalyzed Stille coupling,Suzuki-Miyaura coupling as well as Mukaiyama macrolactonization was finished.
基金Supported by National Natural Science Foundation of China（60474029 60774045 60634020 61075065） the Graduate Degree Thesis Innovation Foundation of Central South University
基金supported by the National Key Research and Development Program of China (2023YFB4604100, and 2023YFB4604800)the National Natural Science Foundation of China (92163123, 12304492, and 52250191)+1 种基金Zhejiang Provincial Natural Science Foundation of China (LZ24A050002)the China Postdoctoral Science Foundation (2023M733120)。
文摘The paradigm shift of Hermitian systems into the non-Hermitian regime profoundly modifies inherent property of the topological systems, leading to various unprecedented effects such as the nonHermitian skin effect(NHSE). In the past decade, the NHSE has been demonstrated in quantum, optical and acoustic systems. Beside those wave systems, the NHSE in diffusive systems has not yet been observed, despite recent abundant advances in the study of topological thermal diffusion. In this work,we design a thermal diffusion lattice based on a modified Su-Schrieffer-Heeger model and demonstrate the diffusive NHSE. In the proposed model, the asymmetric temperature field coupling inside each unit cell can be judiciously realized by appropriate configurations of structural parameters. We find that the temperature fields trend to concentrate toward the target boundary which is robust against initial excitation conditions. We thus experimentally demonstrated the NHSE in thermal diffusion and verified its robustness against various defects. Our work provides a platform for exploration of non-Hermitian physics in the diffusive systems, which has important applications in efficient heat collection, highly sensitive thermal sensing and others.
