Hyperforatone A(1),the 1,8-seco rearranged polycyclic polyprenylated acylphloroglucinol,possessed an unusual bicyclo[5.4.0]undecane skeleton bearing a 5/7/6/5 ring system,and two known biosynthetically related precurs...Hyperforatone A(1),the 1,8-seco rearranged polycyclic polyprenylated acylphloroglucinol,possessed an unusual bicyclo[5.4.0]undecane skeleton bearing a 5/7/6/5 ring system,and two known biosynthetically related precursors(2 and 3)were isolated from Hypericum perforatum(St.John's wort).The structure and absolute configuration were unambiguously confirmed by a combination of comprehensive spectroscopic data,computational methods including residual dipolar couplings(RDCs),and X-ray crystallography.Density functional theory(DFT)calculations revealed that the cationic cyclization reaction was key to proposed formation mechanism for hyperforatone A.Furthermore,in vitro and in vivo experiments demonstrated that compound 1 was a potential anti-neuroinfiammatory agent.展开更多
The electrochemical CO_(2)reduction reaction(CO_(2)RR)is considered a promising technology for converting atmospheric CO_(2)into valuable chemicals.It is a significant way to mitigate the shortage of fossil energy and...The electrochemical CO_(2)reduction reaction(CO_(2)RR)is considered a promising technology for converting atmospheric CO_(2)into valuable chemicals.It is a significant way to mitigate the shortage of fossil energy and store excessive renewable electricity in fuels to maintain carbon neutrality.Considering the substantially reduced cost of clean electricity,C1 molecule unitization has emerged as a competitive strategy for room-temperature electrolysis.However,the practical implementation of CO_(2)RR has been hindered by low desired product selectivity,high overpotential,and undesirable hydrogen evolution reactions(HER).Consequently,it is imperative to execute a timely assessment of advanced strategies in CO_(2)RR,with emphasis on catalytic design strategies,understanding of structure–activity relationships,and deactivation of catalysts.In this context,it is imperative to investigate the intrinsic active sites and reaction mechanisms.This review focuses on the design of novel catalysts and their active sites via operando techniques.The combination of advanced characterization techniques and theoretical calculations provides a high-throughput way to obtain a deeper understanding of the reaction mechanism.Furthermore,optimization of the interplay between the catalyst surface and reaction intermediate disturbs the linear correlation between the adsorption energies of the intermediates,resulting in a convoluted cascade system.The appropriate strategies for CO_(2)RR,challenges,and future approaches are projected in this review to stimulate major innovations.Moreover,the plausible research directions are discussed for producing C_(1)chemicals via electrochemical CO_(2)RR at room temperature.展开更多
Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate ...Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate due to carbon deposition or sintering.Single-atom Ni/CeO_(2)catalysts with suitable metalsupport interactions may provide a new strategy for developing highly active and coking-resistant nickel-based catalysts.In this work,we investigated the properties of the catalytic models of singleatom Ni loaded on CeO_(2)(111),CeO_(2)(110)and CeO_(2)(100),as well as their catalytic DRM performance with the density functional theory method(DFT).The interaction of CeO_(2)with different low-index crystal planes and single-atom Ni can be explained by the anchoring effect of surface O ions on Ni.Adsorption energies,growth patterns of Ni clusters,and migration studies of Ni atoms all indicate that the CeO_(2)(100)surface has the strongest anchoring effect on isolated Ni atoms,followed by the CeO_(2)(110)surface,with the CeO_(2)(111)surface being the weakest,Methane activation studies have shown that the activation ability of Ni_(1)/CeO_(2)(110)for methane strongly depends on the coordination environment of Ni,By contrast,methane activation by Ni on Ni_(1)/CeO_(2)(111)exhibits better activity and stability.Moreover,the Ni—CeO_(2)interaction correlates well with the DRM reaction performance.Interactions that are too strong anchor Ni atoms well but are not optimal for DRM activity.Ni_(1)/CeO_(2)(110)has relatively moderate interactions,promotes the^(*)CH_(4)→^(*)CH process,and has good resistance to carbon deposition.The metalsupport interaction-DRM reactivity(or stability)relationship is vital for the design of"super"highactivity and high-stability DRM catalysts.展开更多
In this paper,the mechanical response of a one-dimensional(1D)hexagonal piezoelectric quasicrystal(PQC)thin film is analyzed under electric and temperature loads.Based on the Euler-Bernoulli beam theory,a theoretical ...In this paper,the mechanical response of a one-dimensional(1D)hexagonal piezoelectric quasicrystal(PQC)thin film is analyzed under electric and temperature loads.Based on the Euler-Bernoulli beam theory,a theoretical model is proposed,resulting in coupled governing integral equations that account for interfacial normal and shear stresses.To numerically solve these integral equations,an expansion method using orthogonal Chebyshev polynomials is employed.The results provide insights into the interfacial stresses,axial force,as well as axial and vertical deformations of the PQC film.Additionally,fracture criteria,including stress intensity factors,mode angles,and the J-integral,are evaluated.The solution is compared with the membrane theory,neglecting the normal stress and bending deformation.Finally,the effects of stiffness and aspect ratio on the PQC film are thoroughly discussed.This study serves as a valuable guide for controlling the mechanical response and conducting safety assessments of PQC film systems.展开更多
We study the geometries, stabilities, electronic and magnetic properties of （MgO）n （n=2-10） clusters doped with a single Mn atom using the density functional theory with the gener- alized gradient approximation. T...We study the geometries, stabilities, electronic and magnetic properties of （MgO）n （n=2-10） clusters doped with a single Mn atom using the density functional theory with the gener- alized gradient approximation. The optimized geometries show that the impurity Mn atom prefers to replace the Mg atom which has low coordination number in all the lowest-energy MnMgn-1On （n=2-10） structures. The stability analysis clearly represents that the average binding energies of the doped clusters are larger than those of the corresponding pure （MgO）n clusters. Maximum peaks of the second order energy differences are observed for MnMg~_1On clusters at n=6, 9, implying that these clusters exhibit higher stability than their neighboring clusters. In addition, all the Mn-doped Mg clusters exhibit high total magnetic moments with the exception of MnMgO2 which has 3.00μB. Their magnetic behavior is attributed to the impurity Mn atom, the charge transfer modes, and the size of MnMgn- 1On clusters.展开更多
This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are obs...This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first ＂shell＂ in geometric structure while the larger clusters are generated based on this fundamental unit.展开更多
A theory of （1＋1）-dimensional gravity is constructed on the basis of the teleparallel equivalent of general relativity. The fundamental field variables are the tetrad fields ei^μ and the gravity is attributed to t...A theory of （1＋1）-dimensional gravity is constructed on the basis of the teleparallel equivalent of general relativity. The fundamental field variables are the tetrad fields ei^μ and the gravity is attributed to the torsion. A dilatonic spherically symmetric exact solution of the gravitational field equations characterized by two parameters M and Q is derived. The energy associated with this solution is calculated using the two-dimensional gravitational energy- momentum formula.展开更多
Thioredoxin reductase 1(TrxR1)is over activity in tumor cell to maintain their redox balance.Although gold clusters have great potential in antitumor drug as they could well inhibit TrxR1,the molecular mechanism has n...Thioredoxin reductase 1(TrxR1)is over activity in tumor cell to maintain their redox balance.Although gold clusters have great potential in antitumor drug as they could well inhibit TrxR1,the molecular mechanism has not been disclosed yet.In this work,we revealed gold clusters can well inhibit the activity of TrxR1 in lung tumor cells and further disclosed the inhibition mechanism by using computational simulation methods.We firstly inferred the binding sites of gold in the hydrophobic cavities on TrxR1.The simulation results show that the gold ion(released from Au cluster)interact with–SH of Cys189 in TrxR1,this greatly increase the distance between the C-terminal redox center of TrxR1 and the Trx redox center,thereby destroy the electron transfer pathway between them.Our electron transfer destroying mechanism is different from the previous hypothesis that gold binds to the Sec498 of TrxR1 which has never been proved by experimental and theory studies.This work provides a new understanding of the gold clusters to inhibit TrxR1 activity.展开更多
The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid...The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.展开更多
An Ethereum blockchain based on proof of stake ( PoS) consensus mechanism is used to achieve the data sharing within the civil aviation service platform for both airport group management and passengers. Considering th...An Ethereum blockchain based on proof of stake ( PoS) consensus mechanism is used to achieve the data sharing within the civil aviation service platform for both airport group management and passengers. Considering the Gas consumption of Ethereum, the dynamic batch-service capacity constraint by the Block Gas Limit and the priority mechanism depending on the different Gas Price of transactions, M/ G/1 queuing theory with batch-service is used to construct the service model of transactions confirmation process in the proposed blockchain system, where the effects of transactions arrival rate, block capacity, service rate and number of nodes on the average confirmation time of transactions with different priority are analyzed, and eventually a performance analysis model of blockchain for civil aviation business data is proposed. The simulation results prove the usability and accuracy of the model, which can provide both theoretical basis for data sharing of civil aviation using Ethereum blockchain and the further optimization of transactions confirmation time.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.22077102,32201249)the Science and Technology Program of Gansu Province(No.22YF7GA046)。
文摘Hyperforatone A(1),the 1,8-seco rearranged polycyclic polyprenylated acylphloroglucinol,possessed an unusual bicyclo[5.4.0]undecane skeleton bearing a 5/7/6/5 ring system,and two known biosynthetically related precursors(2 and 3)were isolated from Hypericum perforatum(St.John's wort).The structure and absolute configuration were unambiguously confirmed by a combination of comprehensive spectroscopic data,computational methods including residual dipolar couplings(RDCs),and X-ray crystallography.Density functional theory(DFT)calculations revealed that the cationic cyclization reaction was key to proposed formation mechanism for hyperforatone A.Furthermore,in vitro and in vivo experiments demonstrated that compound 1 was a potential anti-neuroinfiammatory agent.
基金funded by a National Research Council of Science&Technology grant from the Ministry of Science and ICT(MSIT),Republic of Korea(No.CAP21012-100)the Korea Institute of Energy Technology Evaluation and Planning(KETEP)under the Ministry of Trade,Industry&Energy(MOTIE),Republic of Korea(No.20224C10300010)。
文摘The electrochemical CO_(2)reduction reaction(CO_(2)RR)is considered a promising technology for converting atmospheric CO_(2)into valuable chemicals.It is a significant way to mitigate the shortage of fossil energy and store excessive renewable electricity in fuels to maintain carbon neutrality.Considering the substantially reduced cost of clean electricity,C1 molecule unitization has emerged as a competitive strategy for room-temperature electrolysis.However,the practical implementation of CO_(2)RR has been hindered by low desired product selectivity,high overpotential,and undesirable hydrogen evolution reactions(HER).Consequently,it is imperative to execute a timely assessment of advanced strategies in CO_(2)RR,with emphasis on catalytic design strategies,understanding of structure–activity relationships,and deactivation of catalysts.In this context,it is imperative to investigate the intrinsic active sites and reaction mechanisms.This review focuses on the design of novel catalysts and their active sites via operando techniques.The combination of advanced characterization techniques and theoretical calculations provides a high-throughput way to obtain a deeper understanding of the reaction mechanism.Furthermore,optimization of the interplay between the catalyst surface and reaction intermediate disturbs the linear correlation between the adsorption energies of the intermediates,resulting in a convoluted cascade system.The appropriate strategies for CO_(2)RR,challenges,and future approaches are projected in this review to stimulate major innovations.Moreover,the plausible research directions are discussed for producing C_(1)chemicals via electrochemical CO_(2)RR at room temperature.
基金Project supported by the Major Science and Technology Projects in Yunnan Province(202302AG050005)。
文摘Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate due to carbon deposition or sintering.Single-atom Ni/CeO_(2)catalysts with suitable metalsupport interactions may provide a new strategy for developing highly active and coking-resistant nickel-based catalysts.In this work,we investigated the properties of the catalytic models of singleatom Ni loaded on CeO_(2)(111),CeO_(2)(110)and CeO_(2)(100),as well as their catalytic DRM performance with the density functional theory method(DFT).The interaction of CeO_(2)with different low-index crystal planes and single-atom Ni can be explained by the anchoring effect of surface O ions on Ni.Adsorption energies,growth patterns of Ni clusters,and migration studies of Ni atoms all indicate that the CeO_(2)(100)surface has the strongest anchoring effect on isolated Ni atoms,followed by the CeO_(2)(110)surface,with the CeO_(2)(111)surface being the weakest,Methane activation studies have shown that the activation ability of Ni_(1)/CeO_(2)(110)for methane strongly depends on the coordination environment of Ni,By contrast,methane activation by Ni on Ni_(1)/CeO_(2)(111)exhibits better activity and stability.Moreover,the Ni—CeO_(2)interaction correlates well with the DRM reaction performance.Interactions that are too strong anchor Ni atoms well but are not optimal for DRM activity.Ni_(1)/CeO_(2)(110)has relatively moderate interactions,promotes the^(*)CH_(4)→^(*)CH process,and has good resistance to carbon deposition.The metalsupport interaction-DRM reactivity(or stability)relationship is vital for the design of"super"highactivity and high-stability DRM catalysts.
基金Supported by the National Natural Science Foundation of China (Nos. 11902293 and 12272353)。
文摘In this paper,the mechanical response of a one-dimensional(1D)hexagonal piezoelectric quasicrystal(PQC)thin film is analyzed under electric and temperature loads.Based on the Euler-Bernoulli beam theory,a theoretical model is proposed,resulting in coupled governing integral equations that account for interfacial normal and shear stresses.To numerically solve these integral equations,an expansion method using orthogonal Chebyshev polynomials is employed.The results provide insights into the interfacial stresses,axial force,as well as axial and vertical deformations of the PQC film.Additionally,fracture criteria,including stress intensity factors,mode angles,and the J-integral,are evaluated.The solution is compared with the membrane theory,neglecting the normal stress and bending deformation.Finally,the effects of stiffness and aspect ratio on the PQC film are thoroughly discussed.This study serves as a valuable guide for controlling the mechanical response and conducting safety assessments of PQC film systems.
文摘We study the geometries, stabilities, electronic and magnetic properties of （MgO）n （n=2-10） clusters doped with a single Mn atom using the density functional theory with the gener- alized gradient approximation. The optimized geometries show that the impurity Mn atom prefers to replace the Mg atom which has low coordination number in all the lowest-energy MnMgn-1On （n=2-10） structures. The stability analysis clearly represents that the average binding energies of the doped clusters are larger than those of the corresponding pure （MgO）n clusters. Maximum peaks of the second order energy differences are observed for MnMg~_1On clusters at n=6, 9, implying that these clusters exhibit higher stability than their neighboring clusters. In addition, all the Mn-doped Mg clusters exhibit high total magnetic moments with the exception of MnMgO2 which has 3.00μB. Their magnetic behavior is attributed to the impurity Mn atom, the charge transfer modes, and the size of MnMgn- 1On clusters.
文摘This paper studies supersonic jet-cooled 1-fluoronaphthalene （1FN） clusters by ultraviolet （UV） laser ionization at 281 nm in a time-of-flight mass spectrometer. The （1FN）＋ （n=1-3） series cluster ions are observed where the signal intensity decreases with increasing cluster size. The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured. Using density functional theory calculations, it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds. The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first ＂shell＂ in geometric structure while the larger clusters are generated based on this fundamental unit.
文摘A theory of （1＋1）-dimensional gravity is constructed on the basis of the teleparallel equivalent of general relativity. The fundamental field variables are the tetrad fields ei^μ and the gravity is attributed to the torsion. A dilatonic spherically symmetric exact solution of the gravitational field equations characterized by two parameters M and Q is derived. The energy associated with this solution is calculated using the two-dimensional gravitational energy- momentum formula.
基金financially supported by the National Science Foundation of China(Nos.21727817,U2067214,11621505,31971311)the National Key Basic Research Program of China(No.2020YFA0710700)。
文摘Thioredoxin reductase 1(TrxR1)is over activity in tumor cell to maintain their redox balance.Although gold clusters have great potential in antitumor drug as they could well inhibit TrxR1,the molecular mechanism has not been disclosed yet.In this work,we revealed gold clusters can well inhibit the activity of TrxR1 in lung tumor cells and further disclosed the inhibition mechanism by using computational simulation methods.We firstly inferred the binding sites of gold in the hydrophobic cavities on TrxR1.The simulation results show that the gold ion(released from Au cluster)interact with–SH of Cys189 in TrxR1,this greatly increase the distance between the C-terminal redox center of TrxR1 and the Trx redox center,thereby destroy the electron transfer pathway between them.Our electron transfer destroying mechanism is different from the previous hypothesis that gold binds to the Sec498 of TrxR1 which has never been proved by experimental and theory studies.This work provides a new understanding of the gold clusters to inhibit TrxR1 activity.
基金supported by the Science and Technology Foundation of Jiangsu Province(BK20151237)the Special Nano-technology of Suzhou(ZXG2013004)+2 种基金USTC-NSRL Association Fundingthe Collaborative Innovation Centre of Suzhou Nano Science and Technologythe Supercomputation Center of USTC
文摘The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.
基金the Open Foundation of Key Laboratory of Airports Cluster Intelligent Operation(No.KLACIO201900006124)National Natural Science Foundation of China(No.61901011)+1 种基金Foundation of Beijing Municipal Commission of Education(No.KM202010005017,KM202110005021)Beijing Natural Science Foundation(No.L192002).
文摘An Ethereum blockchain based on proof of stake ( PoS) consensus mechanism is used to achieve the data sharing within the civil aviation service platform for both airport group management and passengers. Considering the Gas consumption of Ethereum, the dynamic batch-service capacity constraint by the Block Gas Limit and the priority mechanism depending on the different Gas Price of transactions, M/ G/1 queuing theory with batch-service is used to construct the service model of transactions confirmation process in the proposed blockchain system, where the effects of transactions arrival rate, block capacity, service rate and number of nodes on the average confirmation time of transactions with different priority are analyzed, and eventually a performance analysis model of blockchain for civil aviation business data is proposed. The simulation results prove the usability and accuracy of the model, which can provide both theoretical basis for data sharing of civil aviation using Ethereum blockchain and the further optimization of transactions confirmation time.
