As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding...As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.展开更多
The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling....The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.展开更多
Chiral pyridyl alcohols are a type of synthetically versatile building block for natural products,functional materials and bioactive molecules.Herein,a highly efficient Ir/f-amphox-catalyzed asymmetric hydrogenation o...Chiral pyridyl alcohols are a type of synthetically versatile building block for natural products,functional materials and bioactive molecules.Herein,a highly efficient Ir/f-amphox-catalyzed asymmetric hydrogenation of 1-(pyridin-2-yl)ketone derivatives to access chiral pyridyl alcohols was reported.The reaction proceeds smoothly under mild conditions,delivering excellent yields and enantioselectivities(up to>99%ee,turnover number(TON)up to 2000).A broad range of pyridyl alkyl and aryl ketones were successfully transformed,demonstrating the generality and synthetic utility of this methodology.展开更多
Chiral carbonyl compounds frequently occur in natural products and pharmaceuticals. Additionally, they serve as important intermediates in organic synthesis. Transition metal-catalyzed asymmetric carbonylative cross-c...Chiral carbonyl compounds frequently occur in natural products and pharmaceuticals. Additionally, they serve as important intermediates in organic synthesis. Transition metal-catalyzed asymmetric carbonylative cross-coupling reactions are among the most straightforward and effective methods for synthesizing chiral carbonyl compounds, including esters, amides, and ketones. The advances in asymmetric carbonylative cross-coupling reactions using various O-, N-, C-, and S-containing nucleophiles or electrophiles over the past decade are summarized.展开更多
The catalytic enantioselective electrophilic amination reaction has emerged as a highly efficient method for synthesizing diverse nitrogen-containing chiral molecules,with the development of various asymmetric catalys...The catalytic enantioselective electrophilic amination reaction has emerged as a highly efficient method for synthesizing diverse nitrogen-containing chiral molecules,with the development of various asymmetric catalysis systems.Chiral phosphoric acids(CPA)have been widely acknowledged as versatile chiral organocatalysts since it was first discovered in 2004,finding application in catalyzing diverse asymmetric reactions.A comprehensive overview of recent advances in CPA-catalyzed asymmetric electrophilic amination reactions using different N-electrophilic reagents,including azo reagents,aryldiazonium salts,and imine derivatives,is presented.Furthermore,insights into future developments in this field are offered.展开更多
Asymmetric allylic C—H functionalization is a valuable and challenging research area. Different from the conventional direct allylic C—H cleavage strategy, transition metal-catalyzed migratory allylic substitution o...Asymmetric allylic C—H functionalization is a valuable and challenging research area. Different from the conventional direct allylic C—H cleavage strategy, transition metal-catalyzed migratory allylic substitution of remote dienes has emerged as a new route to achieve allylic C—H functionalization enantioselectively. This review provides a detailed summary of the development and advance of this strategy, introduces the related mechanistic processes, and discusses the area based on the types of catalysts and products.展开更多
Herein,we report the first asymmetric synthesis of illihenin A,an antiviral sesquiterpenoid bearing a cage-like tricyclo[6.2.2.01,5]dodecane skeleton.Starting from an abundant feedstock(-)-α-cedrene,this19-step synth...Herein,we report the first asymmetric synthesis of illihenin A,an antiviral sesquiterpenoid bearing a cage-like tricyclo[6.2.2.01,5]dodecane skeleton.Starting from an abundant feedstock(-)-α-cedrene,this19-step synthesis approach features a novel ring-reorganization strategy that includes early stage C7-hydroxylation of the cedrane skeleton and a later-stage ring disassembly-reassembly procedure,affording the desired product with high synthetic efficiency and minimal chiral manipulation.The key transformations include the following:(i)a hydroxy group-directed SmI2-mediated reductive coupling to construct the congested tertiary 7-OH cedrane,(ii)aβ-fragmentation triggered by an alkoxy radical to release a spiro[4.5]decane,and(iii)an intramolecular Aldol reaction,concomitant withα-epimerization,to furnish the tricyclic framework.In addition,preliminary investigation of antiviral activity against CVB3 revealed that illihenin A can significantly inhibit ROS production and apoptosis.展开更多
The chemo-,regio-,and enantio-controlled synthesis of P-chiral phosphines in a general and efficient manner remains a significant synthetic challenge.In this study,a Pd-catalyzed hydrofunctionalization is developed fo...The chemo-,regio-,and enantio-controlled synthesis of P-chiral phosphines in a general and efficient manner remains a significant synthetic challenge.In this study,a Pd-catalyzed hydrofunctionalization is developed for the highly selective synthesis of P-stereogenic alkenylphosphinates and alkenylphosphine oxides via conjugate addition of enynes.Notably,this methodology is suitable for both phosphine oxide and phosphinate nucleophiles,providing a versatile approach for the construction of diverse P-chiral organophosphosphorus compound.展开更多
An enantioselective catalytic method for the direct [4 + 1] annulation of yne–allylic acetates with pyrazolones has been realized by a copper-catalyzed remote strategy. A variety of enantioenriched spiropyrazolones a...An enantioselective catalytic method for the direct [4 + 1] annulation of yne–allylic acetates with pyrazolones has been realized by a copper-catalyzed remote strategy. A variety of enantioenriched spiropyrazolones are rapidly accessed in high yields with moderate to good enantiocontrol. The facile follow-up transformations highlight its potential utility in the synthesis of diverse spiropyrazolones building blocks.展开更多
The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the...The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the use of chiral Br?nsted acids as catalysts.Here,we report a copper-catalyzed asymmetric cascade cyclization/Meinwald rearrangement reaction,allowing the practical and atom-economic synthesis of a range of chiral tricyclic pyrroles bearing a chiral oxa-quaternary carbon stereocenter in high yields and enantioselectivities.Thus,this protocol not only represents the first transition-metal-catalyzed enantioselective Meinwald rearrangement,but also constitutes the first example of asymmetric formal monocarbon insertion into C-O bond of ester.Moreover,theoretical calculations provide further evidence for this multiple cascade cyclization and elucidate the origin of enantioselectivity.展开更多
Presently,financial portfolio managers lack a solid basis for building a reliable risk management strategy for green debt instrument investments due to the lack of compelling growth and resilience data.Therefore,this ...Presently,financial portfolio managers lack a solid basis for building a reliable risk management strategy for green debt instrument investments due to the lack of compelling growth and resilience data.Therefore,this study assesses the role of green bonds in financial markets by assessing and correlating their complex scaling behaviors across multiple periods with those of key benchmark assets(e.g.,conventional bonds,high-yield bonds,Euro-Dollar exchange,Dow Jones Industrial Index,Bitcoin,and Gold).Specifically,we explore linear and nonlinear correlation patterns using crosscorrelation tests and the dynamic conditional correlation model,focusing on bond interactions under various degrees of freedom.Our analysis reveals that although most assets exhibit nonlinear correlations,Bitcoin uniquely aligns linearly with U.S.bonds under certain conditions.Green bonds,however,display nonlinear correlations with Bitcoin and stand out for their distinct upward financial persistence.We find also that green bonds are primary drivers in the financial domain,highlighted by their pronounced interactions and the consistent cross-correlation with the Euro-Dollar exchange rate.Moreover,green bonds have the lowest multifractality,showing persistent upward trends and antipersistent downward trends,rendering them quite resilient during periods of high volatility.These results imply that green bonds may be advantageous to portfolio risk management strategies,especially during crises when diversification and hedging tactics are needed.展开更多
The concept of non-Hermitian mechanics introduces new dimensions to metamaterial research,yet current studies have primarily focused on wave manipulation,neglecting the vibration transmittance characteristics of finit...The concept of non-Hermitian mechanics introduces new dimensions to metamaterial research,yet current studies have primarily focused on wave manipulation,neglecting the vibration transmittance characteristics of finite-size metamaterials with boundary reflections.This paper explores the asymmetric vibration transmittance characteristics of a simply supported NonHermitian Metamaterial Panel(NHMP)with two lossy resonators,under the impact of supersonic aerodynamic forces.By examining the non-Hermiticity of a non-aerodynamically loaded NHMP and a host panel aeroelastic system separately,we demonstrate that the NHMP subjected to supersonic aerodynamic force is a complex non-Hermitian system,exhibiting asymmetric vibration transmittance driven by both the fluid-structure interaction effect and lossy resonators.We theoretically and numerically clarify that an ideal aeroelastic system,such as a host panel aeroelastic system,functions as a non-Hermitian mechanical system due to the fluid-structure interaction effect,with the critical flutter point aligning with the Exceptional Point(EP).The results of this study indicate that at low dynamic pressures,the lossy resonators primarily govern asymmetric vibration transmittance,whereas at high dynamic pressures,the fluid-structure interaction effect becomes the dominant factor.Notably,at the EP,asymmetric vibration transmittance is unaffected by the mass ratio of lossy resonators,which is attributed to the invariance of the operational deflection shapes of the NHMP at the EP.This study offers a novel perspective on panel aeroelastic systems and nonHermitian metamaterials,advancing the field through its comprehensive analyses.展开更多
Electrocatalytic oxidation of surplus ethylene glycol(EG)to high-value glycolic acid(GA)represents a promising approach for sustainable resource utilization,though critical challenges persist in developing durable ele...Electrocatalytic oxidation of surplus ethylene glycol(EG)to high-value glycolic acid(GA)represents a promising approach for sustainable resource utilization,though critical challenges persist in developing durable electrocatalysts and achieving effective recovery of the free acid product from its salt derivatives in alkaline electrolytes.In this work,a PdNi/NF catalyst was rationally synthesized via a one-step electrodeposition method.Systematic characterization revealed that the electron transfer from Ni to Pd modulates *OH adsorption to accelerate EG oxidation reaction(EGOR)while preventing Pd deactivation through oxidation.The optimized system demonstrated exceptional alkaline performance with a glycolic acid Faraday efficiencyof 95%and a current density of 666 mA·cm^(-2).When implemented in an asymmetric EGOR||HER flowcell configuration where only the cathodic electrolyte contains alkaline,the system demonstrated exceptional operational stability by sustaining 70 mA·cm^(-2) current density at a low cell voltage of 0.9 V in neutral media for over 100 h,with product glycolic acid requiring no further acidification.This investigation provides a practical framework for designing efficientelectrocatalytic systems that simplifiesproduct separation steps.展开更多
The dynamic kinetic resolution(DKR)process remains a highly efficacious approach for constructing chiral amino alcohols via the catalytic asymmetric hydrogenation ofα-amino ketones.We report herein a highly efficient...The dynamic kinetic resolution(DKR)process remains a highly efficacious approach for constructing chiral amino alcohols via the catalytic asymmetric hydrogenation ofα-amino ketones.We report herein a highly efficient and enantioselective anti-selective dynamic kinetic asymmetric hydrogenation ofα-amino ketones catalyzed by Ir-(S)-f-phamidol system,providing various chiral amino alcohols and chiral oxazolidin-2-ones divergently with high diastereo-and enantioselectivity(up to 99%yield,up to 99%ee and up to 99:1 dr).In addition,the reaction could be performed on the gram-scale,and the resulting chiral amino alcohols are key intermediates of norephedrine and metaraminol.展开更多
The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters.Contrary to the extensive investigation of the stereochemistry resulting from ep...The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters.Contrary to the extensive investigation of the stereochemistry resulting from epoxide building block,the chirality from anhydride and the configurational match with epoxide remain elusive.Herein,we discover that the bimetallic chromium catalysts have led to an obvious enhancement in terms of reactivity and enantioselectivity for the asymmetric copolymerization of meso-epoxide with various non-symmetric chiral anhydrides.Up to 97%ee was obtained during the asymmetric copolymerization of cyclohexene oxide(CHO)with(R)-methylsuccinic anhydride(R-MSA),and three-or four-carbon chiral centers were simultaneously installed in the aliphatic polyester backbone.In particular,the different combinations of stereochemistry in epoxide and anhydride building blocks considerably affect the thermal properties and crystalline behaviors of the resulting polyesters.This study uncovers an interesting method for regulating polymer crystallinity via matching the chirality of different monomers.展开更多
The low ductility and strong mechanical anisotropy of wrought magnesium alloys have hindered their further processing and application.In this study,AZ31 magnesium alloy sheet was prepared by a new asymmetrical angular...The low ductility and strong mechanical anisotropy of wrought magnesium alloys have hindered their further processing and application.In this study,AZ31 magnesium alloy sheet was prepared by a new asymmetrical angular rolling(AAR)process,compared with conventional symmetrical rolling(SR)process and asymmetrical rolling(ASR)process.The effects of three rolling processes on the microstructure,texture and mechanical properties of the alloy sheets were systematically studied.The results show that the AAR sheet exhibits excellent mechanical properties compared to other two rolling processes.It not only achieves the highest ductility of 17.9%,17.9%,and 18.5% in the three directions,but also has the lowest mechanical anisotropy values for yield strength,ultimate tensile strength and elongation.The AAR process significantly reduces the anisotropy of the material by achieving the smallest average grain size of 4.93μm and the most homogeneous grain size distribution.Introduced bi-directional asymmetric shear stresses randomizes grain orientation and activates the non-basal slip system,which also significantly reduces the anisotropy.In addition,the tensile twinning mechanism dominates during the AAR process,which contributes to texture weakening and the activation of the non-basal slip system.Through the synergy of these mechanisms,the AAR sheet is characterized by high ductility and low anisotropy.展开更多
The edge crack behavior of copper foil in asymmetrical micro-rolling was studied.The effects of the speed ratio between rolls,grain size and stress state in the deformation zone on edge cracks of the rolled piece in a...The edge crack behavior of copper foil in asymmetrical micro-rolling was studied.The effects of the speed ratio between rolls,grain size and stress state in the deformation zone on edge cracks of the rolled piece in asymmetrical rolling were analyzed.Low plasticity,uneven deformation and longitudinal secondary tensile stress generated in the edge area of the rolled piece during the rolling process are the main causes of edge cracks.The larger the grain size of the rolled piece,the smaller the number of edge cracks and the deeper the expansion depth,and the larger the spacing between cracks under the same rolling reduction.Asymmetrical rolling can effectively increase the rolling reduction at when the copper foil fist shows edge cracks compared to symmetrical rolling.This enhancement is attributed to the shearing stress induced by asymmetrical rolling,which reduces the rolling force and longitudinal secondary tensile stress,and increases the residual compressive stress on the surface of the rolled piece.The edge crack defects of copper foil can be effectively reduced by increasing the speed ratio between the rolls in asymmetrical rolling.展开更多
Due to insufficient energy density,supercapacitors(SCs)with preeminent-power and long cycle stability cannot be implemented in some practical applications.Exploring hybrid materials with redox activity to emerge high ...Due to insufficient energy density,supercapacitors(SCs)with preeminent-power and long cycle stability cannot be implemented in some practical applications.Exploring hybrid materials with redox activity to emerge high specific capacitance in ionic liquid(IL)electrolytes can solve this problem.Herein,we report a redox-organic molecule 2,6-diaminoanthraquinone(DAAQ)modified MXene(Ti3C2Tx)/Graphene(DAAQ-M/G)composite material.With the assist of graphene oxide(GO),MXene and graphene fabricate a three-dimensional(3D)interconnected structure as a conductive framework,which inhibits self-stacking of MXene monolayers and ensures high electronic conductivity.Meanwhile,DAAQ is loaded onto the M/G framework through covalent/non-covalent functionalization.The DAAQ as a spacer effectively enlarges the interlayer spacing of MXene nanosheets,and meanwhile produces reversible redox reactions during charge/discharge processes to provide additional Faradaic contribution to capacity.Therefore,the specific capacitance(capacity)of the DAAQ-M/G as the negative electrode material reaches to 226 F g^(-1)(306 C g^(-1))at 1 A g^(-1)in 1-ethyl-3-methylimidazolium tetrafluoroborate(EmimBF4)electrolyte.Furthermore,an asymmetric supercapacitor(ASC)is assembled using DAAQ-M/G as the negative electrode and self-prepared organic molecule hydroquinone modified reduced graphene oxide(HQ-RGO)material as the positive electrode,with a high energy density of 43 Wh kg^(-1)at high power density of 1669 Wkg^(-1).The ASC can maintain 80%of initial specific capacitance after 9000 cycles.This research can provide better support to develop advanced organic molecules-modified MXene composite materials for ionic liquid-based SCs.展开更多
We present work on a cavity-driven QED system combining an asymmetrical Fabry–Perot cavity and N two-level atoms(TLAs)and show the convenience of simplifying from distinguishable atoms to undistinguishable bosons whe...We present work on a cavity-driven QED system combining an asymmetrical Fabry–Perot cavity and N two-level atoms(TLAs)and show the convenience of simplifying from distinguishable atoms to undistinguishable bosons when the atoms are prepared in the same initial state.Such simplification is valid even when the atoms are not prepared in the inphase condition,since any partial in-phase initial state will evolve into the ground state through a relaxation process.Thus,we get a reduced group of differential equations by introducing the Dicke states,and the under-zero Lyapunov exponents verify its stability.We also work out the collective unconventional photon blockade(UCPB)and get two kinds of giant nonreciprocal UCPBs(NUCPBs)in the weak-driving approximation.Results show that we can employ N noninteracting bosonic atoms to generate a collective UCPB instead of a monoatomic UCPB as the UCPB conditions do not vary with the number of atoms.Furthermore,the forward giant NUCPB only occurring for N larger than a certain number as well as the backward giant NUCPB are controllable by the cavity asymmetry and by the number of atoms.Our findings suggest a prospective approach to the generation of quantum nonreciprocity by N identical atoms.展开更多
Mitochondria are crucial organelles responsible for maintaining cell growth,and their homeostasis is closely linked to p H regulation.Physiologically,mitochondria exhibit a weakly alkaline state(pH~8.0).However,when s...Mitochondria are crucial organelles responsible for maintaining cell growth,and their homeostasis is closely linked to p H regulation.Physiologically,mitochondria exhibit a weakly alkaline state(pH~8.0).However,when subjected to stress stimuli that cause damage,cells initiate the process of mitophagy,resulting in mitochondrial acidification.Therefore,monitoring changes in mitochondrial p H to comprehend the physiological processes associated with mitophagy is essential.In this study,we developed an asymmetric pentamethine cyanine dye Cy5.5-H-Cy N as a probe for continuous monitoring of mitophagy in living cells.By incorporating an azaindole structure into the dye molecule,a ratiometric fluorescence response was achieved that is specifically responsive to p H variations while preserving its ability to target mitochondria and emit near-infrared fluorescence.Through various methods inducing mitophagy,Cy5.5-H-Cy N was employed to determine mitochondrial p H quantitatively,demonstrating its suitability as an ideal probe for continuous monitoring of mitophagy in living cells.展开更多
文摘As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.
文摘The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.
文摘Chiral pyridyl alcohols are a type of synthetically versatile building block for natural products,functional materials and bioactive molecules.Herein,a highly efficient Ir/f-amphox-catalyzed asymmetric hydrogenation of 1-(pyridin-2-yl)ketone derivatives to access chiral pyridyl alcohols was reported.The reaction proceeds smoothly under mild conditions,delivering excellent yields and enantioselectivities(up to>99%ee,turnover number(TON)up to 2000).A broad range of pyridyl alkyl and aryl ketones were successfully transformed,demonstrating the generality and synthetic utility of this methodology.
文摘Chiral carbonyl compounds frequently occur in natural products and pharmaceuticals. Additionally, they serve as important intermediates in organic synthesis. Transition metal-catalyzed asymmetric carbonylative cross-coupling reactions are among the most straightforward and effective methods for synthesizing chiral carbonyl compounds, including esters, amides, and ketones. The advances in asymmetric carbonylative cross-coupling reactions using various O-, N-, C-, and S-containing nucleophiles or electrophiles over the past decade are summarized.
文摘The catalytic enantioselective electrophilic amination reaction has emerged as a highly efficient method for synthesizing diverse nitrogen-containing chiral molecules,with the development of various asymmetric catalysis systems.Chiral phosphoric acids(CPA)have been widely acknowledged as versatile chiral organocatalysts since it was first discovered in 2004,finding application in catalyzing diverse asymmetric reactions.A comprehensive overview of recent advances in CPA-catalyzed asymmetric electrophilic amination reactions using different N-electrophilic reagents,including azo reagents,aryldiazonium salts,and imine derivatives,is presented.Furthermore,insights into future developments in this field are offered.
文摘Asymmetric allylic C—H functionalization is a valuable and challenging research area. Different from the conventional direct allylic C—H cleavage strategy, transition metal-catalyzed migratory allylic substitution of remote dienes has emerged as a new route to achieve allylic C—H functionalization enantioselectively. This review provides a detailed summary of the development and advance of this strategy, introduces the related mechanistic processes, and discusses the area based on the types of catalysts and products.
基金financially supported by the National Natural Science Foundation of China(No.22177135)the CAMS Innovation Fund for Medical Sciences(CIFMS)(No.2023-I2M-2-006)。
文摘Herein,we report the first asymmetric synthesis of illihenin A,an antiviral sesquiterpenoid bearing a cage-like tricyclo[6.2.2.01,5]dodecane skeleton.Starting from an abundant feedstock(-)-α-cedrene,this19-step synthesis approach features a novel ring-reorganization strategy that includes early stage C7-hydroxylation of the cedrane skeleton and a later-stage ring disassembly-reassembly procedure,affording the desired product with high synthetic efficiency and minimal chiral manipulation.The key transformations include the following:(i)a hydroxy group-directed SmI2-mediated reductive coupling to construct the congested tertiary 7-OH cedrane,(ii)aβ-fragmentation triggered by an alkoxy radical to release a spiro[4.5]decane,and(iii)an intramolecular Aldol reaction,concomitant withα-epimerization,to furnish the tricyclic framework.In addition,preliminary investigation of antiviral activity against CVB3 revealed that illihenin A can significantly inhibit ROS production and apoptosis.
基金the National Natural Science Foundation of China(NSFC,No.22271241),Yunnan Key Laboratory of Chiral Functional Substance Research and Application(No.202402AN360010)Research Grants Council of Hong Kong(GRF,No.12303422)HKBU KRPS grant for financial support.
文摘The chemo-,regio-,and enantio-controlled synthesis of P-chiral phosphines in a general and efficient manner remains a significant synthetic challenge.In this study,a Pd-catalyzed hydrofunctionalization is developed for the highly selective synthesis of P-stereogenic alkenylphosphinates and alkenylphosphine oxides via conjugate addition of enynes.Notably,this methodology is suitable for both phosphine oxide and phosphinate nucleophiles,providing a versatile approach for the construction of diverse P-chiral organophosphosphorus compound.
基金financial support from the National Natural Science Foundation of China (Nos. 21801087 and 22201089)。
文摘An enantioselective catalytic method for the direct [4 + 1] annulation of yne–allylic acetates with pyrazolones has been realized by a copper-catalyzed remote strategy. A variety of enantioenriched spiropyrazolones are rapidly accessed in high yields with moderate to good enantiocontrol. The facile follow-up transformations highlight its potential utility in the synthesis of diverse spiropyrazolones building blocks.
基金financial support from the National Natural Science Foundation of China(Nos.22125108,22101238,22331004 and 22121001)Yunnan Fundamental Research Project(No.202401CF070024)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK20211059)the Project of Science and Technology of Xuzhou Government(No.KC22080)NFFTBS(No.J1310024)。
文摘The Meinwald rearrangement has proven to be one of the most useful tools in organic synthesis.However,examples of asymmetric Meinwald rearrangements are quite scarce,and these reactions have so far been limited to the use of chiral Br?nsted acids as catalysts.Here,we report a copper-catalyzed asymmetric cascade cyclization/Meinwald rearrangement reaction,allowing the practical and atom-economic synthesis of a range of chiral tricyclic pyrroles bearing a chiral oxa-quaternary carbon stereocenter in high yields and enantioselectivities.Thus,this protocol not only represents the first transition-metal-catalyzed enantioselective Meinwald rearrangement,but also constitutes the first example of asymmetric formal monocarbon insertion into C-O bond of ester.Moreover,theoretical calculations provide further evidence for this multiple cascade cyclization and elucidate the origin of enantioselectivity.
基金Benjamin M.Tabak(Grant no.305485/2022-9)gratefully acknowledges financial support from the CNPq foundation and CAPES Foundation。
文摘Presently,financial portfolio managers lack a solid basis for building a reliable risk management strategy for green debt instrument investments due to the lack of compelling growth and resilience data.Therefore,this study assesses the role of green bonds in financial markets by assessing and correlating their complex scaling behaviors across multiple periods with those of key benchmark assets(e.g.,conventional bonds,high-yield bonds,Euro-Dollar exchange,Dow Jones Industrial Index,Bitcoin,and Gold).Specifically,we explore linear and nonlinear correlation patterns using crosscorrelation tests and the dynamic conditional correlation model,focusing on bond interactions under various degrees of freedom.Our analysis reveals that although most assets exhibit nonlinear correlations,Bitcoin uniquely aligns linearly with U.S.bonds under certain conditions.Green bonds,however,display nonlinear correlations with Bitcoin and stand out for their distinct upward financial persistence.We find also that green bonds are primary drivers in the financial domain,highlighted by their pronounced interactions and the consistent cross-correlation with the Euro-Dollar exchange rate.Moreover,green bonds have the lowest multifractality,showing persistent upward trends and antipersistent downward trends,rendering them quite resilient during periods of high volatility.These results imply that green bonds may be advantageous to portfolio risk management strategies,especially during crises when diversification and hedging tactics are needed.
基金co-supported by the National Natural Science Foundation of China(Nos.12372170,12402104 and 12072276)the National Science Basic Research Program of Shaanxi Province,China(No.2022JM-047)the 111 Project of China(No.BP0719007)。
文摘The concept of non-Hermitian mechanics introduces new dimensions to metamaterial research,yet current studies have primarily focused on wave manipulation,neglecting the vibration transmittance characteristics of finite-size metamaterials with boundary reflections.This paper explores the asymmetric vibration transmittance characteristics of a simply supported NonHermitian Metamaterial Panel(NHMP)with two lossy resonators,under the impact of supersonic aerodynamic forces.By examining the non-Hermiticity of a non-aerodynamically loaded NHMP and a host panel aeroelastic system separately,we demonstrate that the NHMP subjected to supersonic aerodynamic force is a complex non-Hermitian system,exhibiting asymmetric vibration transmittance driven by both the fluid-structure interaction effect and lossy resonators.We theoretically and numerically clarify that an ideal aeroelastic system,such as a host panel aeroelastic system,functions as a non-Hermitian mechanical system due to the fluid-structure interaction effect,with the critical flutter point aligning with the Exceptional Point(EP).The results of this study indicate that at low dynamic pressures,the lossy resonators primarily govern asymmetric vibration transmittance,whereas at high dynamic pressures,the fluid-structure interaction effect becomes the dominant factor.Notably,at the EP,asymmetric vibration transmittance is unaffected by the mass ratio of lossy resonators,which is attributed to the invariance of the operational deflection shapes of the NHMP at the EP.This study offers a novel perspective on panel aeroelastic systems and nonHermitian metamaterials,advancing the field through its comprehensive analyses.
基金financially supported by the National Key Research and Development Program of China(2022YFA1504200)the National Natural Science Foundation of China(22178033 and 22090030)the Fundamental Research Funds for the Central Universities(2024CDJXY010).
文摘Electrocatalytic oxidation of surplus ethylene glycol(EG)to high-value glycolic acid(GA)represents a promising approach for sustainable resource utilization,though critical challenges persist in developing durable electrocatalysts and achieving effective recovery of the free acid product from its salt derivatives in alkaline electrolytes.In this work,a PdNi/NF catalyst was rationally synthesized via a one-step electrodeposition method.Systematic characterization revealed that the electron transfer from Ni to Pd modulates *OH adsorption to accelerate EG oxidation reaction(EGOR)while preventing Pd deactivation through oxidation.The optimized system demonstrated exceptional alkaline performance with a glycolic acid Faraday efficiencyof 95%and a current density of 666 mA·cm^(-2).When implemented in an asymmetric EGOR||HER flowcell configuration where only the cathodic electrolyte contains alkaline,the system demonstrated exceptional operational stability by sustaining 70 mA·cm^(-2) current density at a low cell voltage of 0.9 V in neutral media for over 100 h,with product glycolic acid requiring no further acidification.This investigation provides a practical framework for designing efficientelectrocatalytic systems that simplifiesproduct separation steps.
基金the National Key R&D Program of China(No.2021YFA1500201)Shenzhen Science and Technology Innovation Committee(No.KQTD20150717103157174)+6 种基金Stable Support Plan Program of Shenzhen Natural Science Fund(No.20200925161222002)Key-Area Research and Development Program of Guangdong Province(No.2020B010188001)Innovative Team of Universities in Guangdong Province(No.2020KCXTD016)National Natural Science Foundation of China(No.21991113)the National Natural Science Foundation of China(Nos.21901107 and 22171129)the Guangdong Basic and Applied Basic Research Foundation(2022B1515020055)Shenzhen Science and Technology Innovation Committee(No.JCYJ20210324104202007)for financial support。
文摘The dynamic kinetic resolution(DKR)process remains a highly efficacious approach for constructing chiral amino alcohols via the catalytic asymmetric hydrogenation ofα-amino ketones.We report herein a highly efficient and enantioselective anti-selective dynamic kinetic asymmetric hydrogenation ofα-amino ketones catalyzed by Ir-(S)-f-phamidol system,providing various chiral amino alcohols and chiral oxazolidin-2-ones divergently with high diastereo-and enantioselectivity(up to 99%yield,up to 99%ee and up to 99:1 dr).In addition,the reaction could be performed on the gram-scale,and the resulting chiral amino alcohols are key intermediates of norephedrine and metaraminol.
基金financially supported by the National Natural Science Foundation of China(Nos.22071016 and 21920102006)。
文摘The asymmetric alternating copolymerization of meso-epoxide and cyclic anhydrides provides an efficient access to enantiopure polyesters.Contrary to the extensive investigation of the stereochemistry resulting from epoxide building block,the chirality from anhydride and the configurational match with epoxide remain elusive.Herein,we discover that the bimetallic chromium catalysts have led to an obvious enhancement in terms of reactivity and enantioselectivity for the asymmetric copolymerization of meso-epoxide with various non-symmetric chiral anhydrides.Up to 97%ee was obtained during the asymmetric copolymerization of cyclohexene oxide(CHO)with(R)-methylsuccinic anhydride(R-MSA),and three-or four-carbon chiral centers were simultaneously installed in the aliphatic polyester backbone.In particular,the different combinations of stereochemistry in epoxide and anhydride building blocks considerably affect the thermal properties and crystalline behaviors of the resulting polyesters.This study uncovers an interesting method for regulating polymer crystallinity via matching the chirality of different monomers.
基金financially supported by Fund Program for Research Project Supported by Shanxi Scholarship Council of China(No.20230007)(jie bang guashuai)‘Open Competition’project:Preparation technology and product development of key new materials for 5G communication(No.20231207)+3 种基金Projects of the Patent Conversion Program in Shanxi Province(No.20241140)Research and Innovation Projects in Shanxi Province(No.2023KY633)Graduate Education Innovation Project at Taiyuan University of Science and Technology(No.BY2023003)Basic Research Plan Free Exploration of General Program in Shanxi Province(No.202303021221143).
文摘The low ductility and strong mechanical anisotropy of wrought magnesium alloys have hindered their further processing and application.In this study,AZ31 magnesium alloy sheet was prepared by a new asymmetrical angular rolling(AAR)process,compared with conventional symmetrical rolling(SR)process and asymmetrical rolling(ASR)process.The effects of three rolling processes on the microstructure,texture and mechanical properties of the alloy sheets were systematically studied.The results show that the AAR sheet exhibits excellent mechanical properties compared to other two rolling processes.It not only achieves the highest ductility of 17.9%,17.9%,and 18.5% in the three directions,but also has the lowest mechanical anisotropy values for yield strength,ultimate tensile strength and elongation.The AAR process significantly reduces the anisotropy of the material by achieving the smallest average grain size of 4.93μm and the most homogeneous grain size distribution.Introduced bi-directional asymmetric shear stresses randomizes grain orientation and activates the non-basal slip system,which also significantly reduces the anisotropy.In addition,the tensile twinning mechanism dominates during the AAR process,which contributes to texture weakening and the activation of the non-basal slip system.Through the synergy of these mechanisms,the AAR sheet is characterized by high ductility and low anisotropy.
基金supported by the National Natural Science Foundation of China(Nos.52204401,52005432)Hebei Natural Science Foundation of China(No.E2021203179),Excellent Young Talents Program of University of Anhui Province,China(No.gxyq2022093)Excellent Youth Research Projects in Universities of Anhui Province,China(No.2022AH030153).
文摘The edge crack behavior of copper foil in asymmetrical micro-rolling was studied.The effects of the speed ratio between rolls,grain size and stress state in the deformation zone on edge cracks of the rolled piece in asymmetrical rolling were analyzed.Low plasticity,uneven deformation and longitudinal secondary tensile stress generated in the edge area of the rolled piece during the rolling process are the main causes of edge cracks.The larger the grain size of the rolled piece,the smaller the number of edge cracks and the deeper the expansion depth,and the larger the spacing between cracks under the same rolling reduction.Asymmetrical rolling can effectively increase the rolling reduction at when the copper foil fist shows edge cracks compared to symmetrical rolling.This enhancement is attributed to the shearing stress induced by asymmetrical rolling,which reduces the rolling force and longitudinal secondary tensile stress,and increases the residual compressive stress on the surface of the rolled piece.The edge crack defects of copper foil can be effectively reduced by increasing the speed ratio between the rolls in asymmetrical rolling.
基金supported by the National Natural Science Foundation of China(Nos.22173028,21873026).
文摘Due to insufficient energy density,supercapacitors(SCs)with preeminent-power and long cycle stability cannot be implemented in some practical applications.Exploring hybrid materials with redox activity to emerge high specific capacitance in ionic liquid(IL)electrolytes can solve this problem.Herein,we report a redox-organic molecule 2,6-diaminoanthraquinone(DAAQ)modified MXene(Ti3C2Tx)/Graphene(DAAQ-M/G)composite material.With the assist of graphene oxide(GO),MXene and graphene fabricate a three-dimensional(3D)interconnected structure as a conductive framework,which inhibits self-stacking of MXene monolayers and ensures high electronic conductivity.Meanwhile,DAAQ is loaded onto the M/G framework through covalent/non-covalent functionalization.The DAAQ as a spacer effectively enlarges the interlayer spacing of MXene nanosheets,and meanwhile produces reversible redox reactions during charge/discharge processes to provide additional Faradaic contribution to capacity.Therefore,the specific capacitance(capacity)of the DAAQ-M/G as the negative electrode material reaches to 226 F g^(-1)(306 C g^(-1))at 1 A g^(-1)in 1-ethyl-3-methylimidazolium tetrafluoroborate(EmimBF4)electrolyte.Furthermore,an asymmetric supercapacitor(ASC)is assembled using DAAQ-M/G as the negative electrode and self-prepared organic molecule hydroquinone modified reduced graphene oxide(HQ-RGO)material as the positive electrode,with a high energy density of 43 Wh kg^(-1)at high power density of 1669 Wkg^(-1).The ASC can maintain 80%of initial specific capacitance after 9000 cycles.This research can provide better support to develop advanced organic molecules-modified MXene composite materials for ionic liquid-based SCs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12164022 and 12174288)Natural Science Foundation of Jiangxi Province of China(Grant No.20232BAB201044)+1 种基金Scientific Research Foundation of the Education Department of Jiangxi Province of China(Grant No.GJJ211039)China Postdoctoral Science Foundation(Grant No.2023M732028)。
文摘We present work on a cavity-driven QED system combining an asymmetrical Fabry–Perot cavity and N two-level atoms(TLAs)and show the convenience of simplifying from distinguishable atoms to undistinguishable bosons when the atoms are prepared in the same initial state.Such simplification is valid even when the atoms are not prepared in the inphase condition,since any partial in-phase initial state will evolve into the ground state through a relaxation process.Thus,we get a reduced group of differential equations by introducing the Dicke states,and the under-zero Lyapunov exponents verify its stability.We also work out the collective unconventional photon blockade(UCPB)and get two kinds of giant nonreciprocal UCPBs(NUCPBs)in the weak-driving approximation.Results show that we can employ N noninteracting bosonic atoms to generate a collective UCPB instead of a monoatomic UCPB as the UCPB conditions do not vary with the number of atoms.Furthermore,the forward giant NUCPB only occurring for N larger than a certain number as well as the backward giant NUCPB are controllable by the cavity asymmetry and by the number of atoms.Our findings suggest a prospective approach to the generation of quantum nonreciprocity by N identical atoms.
基金supported by the Fundamental Research Funds for the Central Universities(Nos.DUT23YG137 and DUT22LAB601)Liaoning Binhai Laboratory(No.LBLB-202303)+1 种基金Liaoning Province Science and Technology Joint Fund(Nos.2023JH2/101800039 and 2023JH2/101800037)National Natural Science Foundation of China(Nos.21925802,22090011,and 21878039)。
文摘Mitochondria are crucial organelles responsible for maintaining cell growth,and their homeostasis is closely linked to p H regulation.Physiologically,mitochondria exhibit a weakly alkaline state(pH~8.0).However,when subjected to stress stimuli that cause damage,cells initiate the process of mitophagy,resulting in mitochondrial acidification.Therefore,monitoring changes in mitochondrial p H to comprehend the physiological processes associated with mitophagy is essential.In this study,we developed an asymmetric pentamethine cyanine dye Cy5.5-H-Cy N as a probe for continuous monitoring of mitophagy in living cells.By incorporating an azaindole structure into the dye molecule,a ratiometric fluorescence response was achieved that is specifically responsive to p H variations while preserving its ability to target mitochondria and emit near-infrared fluorescence.Through various methods inducing mitophagy,Cy5.5-H-Cy N was employed to determine mitochondrial p H quantitatively,demonstrating its suitability as an ideal probe for continuous monitoring of mitophagy in living cells.
