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 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
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
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
Mode-pairing quantum key distribution(MP-QKD)is an excellent scheme that can exceed the repeaterless ratetransmittance bound without complex phase locking.Nevertheless,MP-QKD usually needs to ensure that the communica...Mode-pairing quantum key distribution(MP-QKD)is an excellent scheme that can exceed the repeaterless ratetransmittance bound without complex phase locking.Nevertheless,MP-QKD usually needs to ensure that the communication distances of the two channels are equal.To address the problem,the asymmetric MP-QKD protocol is proposed.In this paper,we enhance the performance of the asymmetric MP-QKD protocol based on the advantage distillation(AD)method without modifying the quantum process.The simulation results show that the AD method can extend the communication distance by about 70 km in the case of asymmetry.And we observe that as the misalignment error increases,the AD method further increases the expandable communication distance.Our work can further enhance the robustness and promote the practical application of the asymmetric MP-QKD.展开更多
The asymmetric molecular design strategy,with advantages in modulating the molecular dipole moment and intermolecular interactions and achieving more favorable molecular packing and orientation,has been an effective a...The asymmetric molecular design strategy,with advantages in modulating the molecular dipole moment and intermolecular interactions and achieving more favorable molecular packing and orientation,has been an effective approach for designing high-performance nonfullerene acceptors(NFAs).Herein,two asymmetric NFAs,Y-CN-2F and Y-CN-2Cl,were designed and synthesized by introducing a linear alkyl chain terminated with the 4-cyanobiphenyl group,a well-known mesogenic unit,at one of the inner pyrrole positions instead of the normal 2-butyloctyl branched alkyl chain.The difference between Y-CN-2F and Y-CN-2Cl is the terminated IC-groups,which was modified with F and Cl halogens,respectively.Both NFAs displayed strong absorption in the near-infrared to visible-light range,which is complementary to that of typical medium-bandgap donor polymers.After optimization with D18 donor in organic solar cells(OSCs),Y-CN-2F and Y-CN-2Cl provided comparable power conversion efficiencies(PCEs)of 15.33%and 15.88%.While the D18:Y-CN-2F based devices displayed higher fill factors(FFs),those based on D18:Y-CN-2Cl exhibited higher current densities and open-circuit voltages.The Y-CN-2Cl film showed longer light absorption than YCN-2F,which is beneficial for more light harvesting.Moreover,D18:Y-CN-2Cl displayed a lower fluorescence lifetime and faster carrier transfer processes,which could be attributed to its higher mobility.For the D18:Y-CN-2F blended film,a more pronounced fiber network structure and balanced carrier mobility were observed,which contributed to the higher FFs values.This work presents new efforts to develop more asymmetric NFAs with specific functional segments for efficient organic electronics.展开更多
The dynamic processes responsible for the movement of tropical cyclone Khanun(2017)were studied by analyzing data from the mesoscale WRF model simulation.The simulated motion was induced by the ventilation flow of bot...The dynamic processes responsible for the movement of tropical cyclone Khanun(2017)were studied by analyzing data from the mesoscale WRF model simulation.The simulated motion was induced by the ventilation flow of both the environmentaland asymmetric rotational wind averaged over an area within a radius of 200 km from Khanun's center.The results revealed that during Khanun's intensification period,environmental wind barely changed,whereas the speed and direction of asymmetric rotational wind exhibited significant changes as Khanun's southwestward movement switched to a northwestward movement.The streamfunction analysis revealed that the change in the direction of movement was consistent with the ventilation flow of asymmetric rotational wind across Khanun's center associated with the asymmetric circulation rotation.The cyclonic circulation center rotated counterclockwise,moving from the northeast to the north before and during the rapid intensification period,and exhibited wandering behavior during this period.The rotational rate of asymmetric circulation was quantitatively estimated using the formulation based on the budget of asymmetric rotational kinetic energy.This calculation revealed that the rapid counterclockwise rotation resulted from the conversion of environmental to asymmetric rotational kinetic energy and was related to the horizontal advection of environmental tangential flow.The rotation of the asymmetric circulation displayed a wandering behavior when the dissipation term became significant.The dissipation term plus the conversion from symmetric to asymmetric rotational kinetic energy associated with the advection of symmetric tangential wind by the environmental radial wind led to a slow clockwise rotation of the asymmetric cyclonic center to the north.展开更多
The impacts of asymmetric rolling(ASR)and cold rolling(CR)on the creep-aging behavior of AA2219 alloys were revealed by creep deformation experiments,tensile tests,electron backscattered diffraction(EBSD)and transmiss...The impacts of asymmetric rolling(ASR)and cold rolling(CR)on the creep-aging behavior of AA2219 alloys were revealed by creep deformation experiments,tensile tests,electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM).The ASR specimens under creep stress condition of 1.2σ0.2(σ0.2 is the yield strength)displayed a 50%higher creep strain than the CR specimens.At a creep stress of 0.5σ0.2,the ASR specimens demonstrated remarkably mechanical properties,with a tensile strength of 525 MPa,a yield strength of 338 MPa,and an elongation of 15.2%.This enhancement can be ascribed to the effective grain refinement and promotion of recrystallization after ASR.Notably,ASR resulted in the formation of higher cube textures and a denser forest dislocation structure compared with CR.Additionally,ASR specimens demonstrated a higher density of dispersive,smallerθ′precipitates and larger average Taylor factors compared with CR specimens.展开更多
Catalytic asymmetric dearomatization(CADA)has emerged as a powerful strategy for transforming planar aromatic systems into three-dimensional chiral architectures[1].Notably,the Büchner reaction and arene cyclopro...Catalytic asymmetric dearomatization(CADA)has emerged as a powerful strategy for transforming planar aromatic systems into three-dimensional chiral architectures[1].Notably,the Büchner reaction and arene cyclopropanation excel in constructing complex polycyclic frameworks[2].However,current methods predominantly rely on diazo compounds as carbene precursors(Scheme1a),which pose safety risks and limit functional group compatibility.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 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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61505261,62101597,61605248,and 61675235)the National Key Research and Development Program of China(Grant No.2020YFA0309702)+2 种基金the China Postdoctoral Science Foundation(Grant No.2021M691536)the Natural Science Foundation of Henan Province(Grant Nos.202300410534 and 202300410532)the Anhui Initiative in Quantum Information Technologies.
文摘Mode-pairing quantum key distribution(MP-QKD)is an excellent scheme that can exceed the repeaterless ratetransmittance bound without complex phase locking.Nevertheless,MP-QKD usually needs to ensure that the communication distances of the two channels are equal.To address the problem,the asymmetric MP-QKD protocol is proposed.In this paper,we enhance the performance of the asymmetric MP-QKD protocol based on the advantage distillation(AD)method without modifying the quantum process.The simulation results show that the AD method can extend the communication distance by about 70 km in the case of asymmetry.And we observe that as the misalignment error increases,the AD method further increases the expandable communication distance.Our work can further enhance the robustness and promote the practical application of the asymmetric MP-QKD.
基金financially supported by the National Natural Science Foundation of China(Nos.22465018,52163018 and 22405107)of ChinaJiangxi Provincial Department of Science and Technology(Nos.20232BBE50026,jxsq2023102153,20232BAB21302 and 2024SSY05132)Jiangxi Academy of Sciences(Nos.2023YYB07,2022YSBG22031,2022YJC2019,2022YJC2017,2023YSBG21017,2022YYB10,2022YRCS002,2023YJC1001,and 2023YSBG22025)。
文摘The asymmetric molecular design strategy,with advantages in modulating the molecular dipole moment and intermolecular interactions and achieving more favorable molecular packing and orientation,has been an effective approach for designing high-performance nonfullerene acceptors(NFAs).Herein,two asymmetric NFAs,Y-CN-2F and Y-CN-2Cl,were designed and synthesized by introducing a linear alkyl chain terminated with the 4-cyanobiphenyl group,a well-known mesogenic unit,at one of the inner pyrrole positions instead of the normal 2-butyloctyl branched alkyl chain.The difference between Y-CN-2F and Y-CN-2Cl is the terminated IC-groups,which was modified with F and Cl halogens,respectively.Both NFAs displayed strong absorption in the near-infrared to visible-light range,which is complementary to that of typical medium-bandgap donor polymers.After optimization with D18 donor in organic solar cells(OSCs),Y-CN-2F and Y-CN-2Cl provided comparable power conversion efficiencies(PCEs)of 15.33%and 15.88%.While the D18:Y-CN-2F based devices displayed higher fill factors(FFs),those based on D18:Y-CN-2Cl exhibited higher current densities and open-circuit voltages.The Y-CN-2Cl film showed longer light absorption than YCN-2F,which is beneficial for more light harvesting.Moreover,D18:Y-CN-2Cl displayed a lower fluorescence lifetime and faster carrier transfer processes,which could be attributed to its higher mobility.For the D18:Y-CN-2F blended film,a more pronounced fiber network structure and balanced carrier mobility were observed,which contributed to the higher FFs values.This work presents new efforts to develop more asymmetric NFAs with specific functional segments for efficient organic electronics.
基金supported by the National Natural Science Foundation of China(Grant No.41930967)。
文摘The dynamic processes responsible for the movement of tropical cyclone Khanun(2017)were studied by analyzing data from the mesoscale WRF model simulation.The simulated motion was induced by the ventilation flow of both the environmentaland asymmetric rotational wind averaged over an area within a radius of 200 km from Khanun's center.The results revealed that during Khanun's intensification period,environmental wind barely changed,whereas the speed and direction of asymmetric rotational wind exhibited significant changes as Khanun's southwestward movement switched to a northwestward movement.The streamfunction analysis revealed that the change in the direction of movement was consistent with the ventilation flow of asymmetric rotational wind across Khanun's center associated with the asymmetric circulation rotation.The cyclonic circulation center rotated counterclockwise,moving from the northeast to the north before and during the rapid intensification period,and exhibited wandering behavior during this period.The rotational rate of asymmetric circulation was quantitatively estimated using the formulation based on the budget of asymmetric rotational kinetic energy.This calculation revealed that the rapid counterclockwise rotation resulted from the conversion of environmental to asymmetric rotational kinetic energy and was related to the horizontal advection of environmental tangential flow.The rotation of the asymmetric circulation displayed a wandering behavior when the dissipation term became significant.The dissipation term plus the conversion from symmetric to asymmetric rotational kinetic energy associated with the advection of symmetric tangential wind by the environmental radial wind led to a slow clockwise rotation of the asymmetric cyclonic center to the north.
基金financial supports from the National Key Research and Development Program of China(No.2021YFB3400900)the National Natural Science Foundation of China(Nos.U22A20190,U2341273,52205435)+2 种基金the Natural Science Foundation of Hunan Province,China(No.2022JJ40621)the Science and Technology Innovation Program of Hunan Province,China(No.2020RC4001)the Project of State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,China(No.ZZYJKT2022-07)。
文摘The impacts of asymmetric rolling(ASR)and cold rolling(CR)on the creep-aging behavior of AA2219 alloys were revealed by creep deformation experiments,tensile tests,electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM).The ASR specimens under creep stress condition of 1.2σ0.2(σ0.2 is the yield strength)displayed a 50%higher creep strain than the CR specimens.At a creep stress of 0.5σ0.2,the ASR specimens demonstrated remarkably mechanical properties,with a tensile strength of 525 MPa,a yield strength of 338 MPa,and an elongation of 15.2%.This enhancement can be ascribed to the effective grain refinement and promotion of recrystallization after ASR.Notably,ASR resulted in the formation of higher cube textures and a denser forest dislocation structure compared with CR.Additionally,ASR specimens demonstrated a higher density of dispersive,smallerθ′precipitates and larger average Taylor factors compared with CR specimens.
文摘Catalytic asymmetric dearomatization(CADA)has emerged as a powerful strategy for transforming planar aromatic systems into three-dimensional chiral architectures[1].Notably,the Büchner reaction and arene cyclopropanation excel in constructing complex polycyclic frameworks[2].However,current methods predominantly rely on diazo compounds as carbene precursors(Scheme1a),which pose safety risks and limit functional group compatibility.
