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
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
A prior observational study indicated an asymmetric link between sea surface temperature(SST)in the Tasman Sea and ENSO during austral summer.Specifically,El Niño is associated with a dipolar SST anomaly pattern,...A prior observational study indicated an asymmetric link between sea surface temperature(SST)in the Tasman Sea and ENSO during austral summer.Specifically,El Niño is associated with a dipolar SST anomaly pattern,featuring warming in the northwest and cooling in the southeast,whereas La Niña corresponds to basin-scale warming.This study employs the experiments of coupled models from the sixth phase of the Coupled Model Intercomparison Project(CMIP6)to assess ENSO’s impact on Tasman Sea SST.While all 15 models capture the observed dipolar SST anomalies(SSTAs)in the Tasman Sea during El Niño years,only 7 models capture the basin-scale warmth in the Tasman Sea during La Niña years.Consequently,the models are bifurcated into two groups:group-one models yield one physically reasonable asymmetric connection as observed,including the asymmetry of oceanic heat transport,especially the Ekman meridional transport anomalies induced by zonal wind stress driven by the asymmetric atmospheric circulation over the Tasman Sea.However,due to abnormal responses to ENSO and systematic biases in model simulations,including jet and storm tracks,oceanic heat fluxes,ocean currents,and SST,the group-two models fail to reproduce the asymmetric connection between the Tasman Sea and ENSO.This study not only validates the observational asymmetric connection of SSTAs in the Tasman Sea with respect to the two opposite ENSO phases,but also provides evidence and clues to reduce the bias in group-two models.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
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
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
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
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
Lithium-sulfur(Li-S)batteries are regarded as the most formidable competitor to lithium-ion batteries due to their superior theoretical capacity.However,the negative impact of soluble lithium polysulfide(LiPSs)and slo...Lithium-sulfur(Li-S)batteries are regarded as the most formidable competitor to lithium-ion batteries due to their superior theoretical capacity.However,the negative impact of soluble lithium polysulfide(LiPSs)and slow redox reaction kinetics seriously hamper the commercialization of Li-S batteries.In this study,a defect-rich single-atom catalyst with an oversaturated asymmetric Fe-N_(5)coordination structure anchored in defective g-C_(3)N_(4)(C_(3)N_(4)-Fe@rGO)is designed via an absorption-pyrolysis strategy.The two-dimensional(2D)conducting C_(3)N_(4)@graphene structure with abundant defect sites accelerates the trans-fer and transportation of lithium ions and electrons.The oversaturated asymmetric Fe-N_(5)coordination structure effectively improves the adsorbility of LiPSs and accelerates the redox kinetics of sulfur species.Hence,the Li-S cell with a C_(3)N_(4)-Fe@rGO modified separator reveals a high initial capacity(1197.1 mAh g^(-1) at 0.2 C)and a low capacity decay rate(0.037%per cycle after 900 cycles at 1 C).Even at high sulfur loading and extreme temperatures of 0℃,it also shows good cycling performance.This work creates ideas for synthesizing oversaturated single-atom coordination environments and an efficient route to the practical realization of the Li-S batteries.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
Disrupting the symmetric electron distribution of porphyrin-like Fe singleatom catalysts has been considered as an effective way to harvest high intrinsic activity.Understanding the catalytic performance governed by g...Disrupting the symmetric electron distribution of porphyrin-like Fe singleatom catalysts has been considered as an effective way to harvest high intrinsic activity.Understanding the catalytic performance governed by geometric microstrains is highly desirable for further optimization of such efficient sites.Here,we decipher the crucial role of local microstrain in boosting intrinsic activity and durability of asymmetric Fe single-atom catalysts(Fe-N_(3)S_(1))by replacing one N atom with S atom.The high-curvature hollow carbon nanosphere substrate introduces 1.3%local compressive strain to Fe-N bonds and 1.5%tensile strain to Fe-S bonds,downshifting the d-band center and accelerating the kinetics of*OH reduction.Consequently,highly curved Fe-N_(3)S_(1)sites anchored on hollow carbon nanosphere(FeNS-HNS-20)exhibit negligible current loss,a high half-wave potential of 0.922 V vs.RHE and turnover frequency of 6.2 e^(−1)s^(−1)site−1,which are 53 mV more positive and 1.7 times that of flat Fe-N-S counterpart,respectively.More importantly,multiple operando spectroscopies monitored the dynamic optimization of strained Fe-N_(3)S_(1)sites into Fe-N_(3)sites,further mitigating the overadsorption of*OH intermediates.This work not only sheds new light on local microstrain-induced catalytic enhancement,but also provides a plausible direction for optimizing efficient asymmetric sites via geometric configurations.展开更多
We present a theoretical scheme to realize two-dimensional(2D)asymmetric diffraction grating in a five-level inverted Y-type asymmetric double semiconductor quantum wells(SQWs)structure with resonant tunneling.The SQW...We present a theoretical scheme to realize two-dimensional(2D)asymmetric diffraction grating in a five-level inverted Y-type asymmetric double semiconductor quantum wells(SQWs)structure with resonant tunneling.The SQW structure interacts with a weak probe laser field,a spatially independent 2D standing-wave(SW)field,and a Laguerre–Gaussian(LG)vortex field,respectively.The results indicate that the diffraction patterns are highly sensitive to amplitude modulation and phase modulation.Because of the existence of vortex light,it is possible to realize asymmetric high-order diffraction in the SQW structure,and then a 2D asymmetric grating is established.By adjusting the detunings of the probe field,vortex field,and SW field,as well as the interaction length,diffraction intensity,and direction of the 2D asymmetric electromagnetically induced grating(EIG)can be controlled effectively.In addition,the number of orbital angular momenta(OAM)and beam waist parameter can be used to modulate the diffraction intensity and energy transfer of the probe light in different regions.High-order diffraction intensity is enhanced and high-efficiency 2D asymmetric diffraction grating with different diffraction patterns is obtained in the scheme.Such 2D asymmetric diffraction grating may be beneficial to the research of optical communication and innovative semiconductor quantum devices.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 dynamic behaviors of a large-scale ring neural network with a triangular coupling structure are investigated.The characteristic equation of the high-dimensional system using Coate’s flow graph method is calculate...The dynamic behaviors of a large-scale ring neural network with a triangular coupling structure are investigated.The characteristic equation of the high-dimensional system using Coate’s flow graph method is calculated.Time delay is selected as the bifurcation parameter,and sufficient conditions for stability and Hopf bifurcation are derived.It is found that the connection coefficient and time delay play a crucial role in the dynamic behaviors of the model.Furthermore,a phase diagram of multiple equilibrium points with one saddle point and two stable nodes is presented.Finally,the effectiveness of the theory is verified through simulation results.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
Low ionic conductivity is a major obstacle for polymer solid-state electrolytes.In response to this issue,a design concept of enhanced regional electric potential difference(EREPD)is proposed to modulate the interacti...Low ionic conductivity is a major obstacle for polymer solid-state electrolytes.In response to this issue,a design concept of enhanced regional electric potential difference(EREPD)is proposed to modulate the interaction of nanofillers with other components in the composite polymer solid-state electrolytes(CPSEs).While ensuring the periodic structure of the graphdiyne(GDY)backbone,methoxysubstituted GDY(OGDY)is prepared by an asymmetric substitution strategy,which increases the electric potential differences within each repeating unit of GDY.The staggered distributed electron-rich regions and electron-deficient regions on the two-dimensional plane of OGDY increase the free Li^(+)concentration through Lewis acid-base pair interaction.The adjacent ERRs and EDRs form uniformly distributed EREPDs,creating a continuous potential gradient that synergistically facilitates the efficient migration of Li^(+).Impressively,the OGDY/poly(ethylene oxide)(PEO)exhibits a high ionic conductivity(1.1×10^(-3)S cm^(−1))and ion mobility number(0.71).In addition,the accelerated Li^(+)migration promotes the formation of uniform and dense SEI layers and inhibits the growth of lithium dendrites.As a proof of concept,Li||Li symmetric cell and Li||LiFePO_(4)full cell and pouch cell assembled with OGDY/PEO exhibit good performance,highlighting the effectiveness of our EREPD design strategy for improving CPSEs performance.展开更多
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.
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supported by the National Key Research and Development Program of China(Grant No.2023YFF0805101)the National Natural Science Founda-tion of China(Grant Nos.42376250 and 42405068).
文摘A prior observational study indicated an asymmetric link between sea surface temperature(SST)in the Tasman Sea and ENSO during austral summer.Specifically,El Niño is associated with a dipolar SST anomaly pattern,featuring warming in the northwest and cooling in the southeast,whereas La Niña corresponds to basin-scale warming.This study employs the experiments of coupled models from the sixth phase of the Coupled Model Intercomparison Project(CMIP6)to assess ENSO’s impact on Tasman Sea SST.While all 15 models capture the observed dipolar SST anomalies(SSTAs)in the Tasman Sea during El Niño years,only 7 models capture the basin-scale warmth in the Tasman Sea during La Niña years.Consequently,the models are bifurcated into two groups:group-one models yield one physically reasonable asymmetric connection as observed,including the asymmetry of oceanic heat transport,especially the Ekman meridional transport anomalies induced by zonal wind stress driven by the asymmetric atmospheric circulation over the Tasman Sea.However,due to abnormal responses to ENSO and systematic biases in model simulations,including jet and storm tracks,oceanic heat fluxes,ocean currents,and SST,the group-two models fail to reproduce the asymmetric connection between the Tasman Sea and ENSO.This study not only validates the observational asymmetric connection of SSTAs in the Tasman Sea with respect to the two opposite ENSO phases,but also provides evidence and clues to reduce the bias in group-two models.
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 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.
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supported by the National Natural Science Foundation of China(Nos.U21A2060 and 22178116)the Natural Science Foundation of Shanghai(No.22ZR1417400)the Fundamental Research Funds for the Central Universities(Nos.222201817001,50321041918013,JKA01221601,JKD01241701).
文摘Lithium-sulfur(Li-S)batteries are regarded as the most formidable competitor to lithium-ion batteries due to their superior theoretical capacity.However,the negative impact of soluble lithium polysulfide(LiPSs)and slow redox reaction kinetics seriously hamper the commercialization of Li-S batteries.In this study,a defect-rich single-atom catalyst with an oversaturated asymmetric Fe-N_(5)coordination structure anchored in defective g-C_(3)N_(4)(C_(3)N_(4)-Fe@rGO)is designed via an absorption-pyrolysis strategy.The two-dimensional(2D)conducting C_(3)N_(4)@graphene structure with abundant defect sites accelerates the trans-fer and transportation of lithium ions and electrons.The oversaturated asymmetric Fe-N_(5)coordination structure effectively improves the adsorbility of LiPSs and accelerates the redox kinetics of sulfur species.Hence,the Li-S cell with a C_(3)N_(4)-Fe@rGO modified separator reveals a high initial capacity(1197.1 mAh g^(-1) at 0.2 C)and a low capacity decay rate(0.037%per cycle after 900 cycles at 1 C).Even at high sulfur loading and extreme temperatures of 0℃,it also shows good cycling performance.This work creates ideas for synthesizing oversaturated single-atom coordination environments and an efficient route to the practical realization of the Li-S batteries.
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supported by the Natural Science Foundation of Shandong Province (ZR2024JQ004)the National Natural Science Foundation of China (22108306, 22478432)Taishan Scholars Program of Shandong Province
文摘Disrupting the symmetric electron distribution of porphyrin-like Fe singleatom catalysts has been considered as an effective way to harvest high intrinsic activity.Understanding the catalytic performance governed by geometric microstrains is highly desirable for further optimization of such efficient sites.Here,we decipher the crucial role of local microstrain in boosting intrinsic activity and durability of asymmetric Fe single-atom catalysts(Fe-N_(3)S_(1))by replacing one N atom with S atom.The high-curvature hollow carbon nanosphere substrate introduces 1.3%local compressive strain to Fe-N bonds and 1.5%tensile strain to Fe-S bonds,downshifting the d-band center and accelerating the kinetics of*OH reduction.Consequently,highly curved Fe-N_(3)S_(1)sites anchored on hollow carbon nanosphere(FeNS-HNS-20)exhibit negligible current loss,a high half-wave potential of 0.922 V vs.RHE and turnover frequency of 6.2 e^(−1)s^(−1)site−1,which are 53 mV more positive and 1.7 times that of flat Fe-N-S counterpart,respectively.More importantly,multiple operando spectroscopies monitored the dynamic optimization of strained Fe-N_(3)S_(1)sites into Fe-N_(3)sites,further mitigating the overadsorption of*OH intermediates.This work not only sheds new light on local microstrain-induced catalytic enhancement,but also provides a plausible direction for optimizing efficient asymmetric sites via geometric configurations.
基金supported by the National Natural Science Foundation of China(Grant No.12105210)the Knowledge Innovation Program of Wuhan-Basi Research(Grant No.2023010201010149)。
文摘We present a theoretical scheme to realize two-dimensional(2D)asymmetric diffraction grating in a five-level inverted Y-type asymmetric double semiconductor quantum wells(SQWs)structure with resonant tunneling.The SQW structure interacts with a weak probe laser field,a spatially independent 2D standing-wave(SW)field,and a Laguerre–Gaussian(LG)vortex field,respectively.The results indicate that the diffraction patterns are highly sensitive to amplitude modulation and phase modulation.Because of the existence of vortex light,it is possible to realize asymmetric high-order diffraction in the SQW structure,and then a 2D asymmetric grating is established.By adjusting the detunings of the probe field,vortex field,and SW field,as well as the interaction length,diffraction intensity,and direction of the 2D asymmetric electromagnetically induced grating(EIG)can be controlled effectively.In addition,the number of orbital angular momenta(OAM)and beam waist parameter can be used to modulate the diffraction intensity and energy transfer of the probe light in different regions.High-order diffraction intensity is enhanced and high-efficiency 2D asymmetric diffraction grating with different diffraction patterns is obtained in the scheme.Such 2D asymmetric diffraction grating may be beneficial to the research of optical communication and innovative semiconductor quantum devices.
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Supported by Natural Science Foundation of Shandong Province of China(Grant Nos.ZR2020MF080 and ZR2020MF065).
文摘The dynamic behaviors of a large-scale ring neural network with a triangular coupling structure are investigated.The characteristic equation of the high-dimensional system using Coate’s flow graph method is calculated.Time delay is selected as the bifurcation parameter,and sufficient conditions for stability and Hopf bifurcation are derived.It is found that the connection coefficient and time delay play a crucial role in the dynamic behaviors of the model.Furthermore,a phase diagram of multiple equilibrium points with one saddle point and two stable nodes is presented.Finally,the effectiveness of the theory is verified through simulation results.
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supported by the National Key Research and Development Project of China(2022YFA1204500,2022YFA1204503,2018YFA0703501)the National Natural Science Foundation of China(22275115,21875274,11704024)+4 种基金the Natural Science Foundation of Shandong Province(ZR2024ZD02)Natural Science Foundation of Hebei Province(B2020201006)Hebei Province Innovation Capability Enhancement Plan Project(22567620H)Young Scholarship Funding of Shandong University.Post-graduate Innovation Fund Project of Open Laboratory Project Fund of Hebei University(HBU2025SS010)Basic Research Project of Shandong University-Xin’an Group Silicon-Based High-End New Materials Institute.
文摘Low ionic conductivity is a major obstacle for polymer solid-state electrolytes.In response to this issue,a design concept of enhanced regional electric potential difference(EREPD)is proposed to modulate the interaction of nanofillers with other components in the composite polymer solid-state electrolytes(CPSEs).While ensuring the periodic structure of the graphdiyne(GDY)backbone,methoxysubstituted GDY(OGDY)is prepared by an asymmetric substitution strategy,which increases the electric potential differences within each repeating unit of GDY.The staggered distributed electron-rich regions and electron-deficient regions on the two-dimensional plane of OGDY increase the free Li^(+)concentration through Lewis acid-base pair interaction.The adjacent ERRs and EDRs form uniformly distributed EREPDs,creating a continuous potential gradient that synergistically facilitates the efficient migration of Li^(+).Impressively,the OGDY/poly(ethylene oxide)(PEO)exhibits a high ionic conductivity(1.1×10^(-3)S cm^(−1))and ion mobility number(0.71).In addition,the accelerated Li^(+)migration promotes the formation of uniform and dense SEI layers and inhibits the growth of lithium dendrites.As a proof of concept,Li||Li symmetric cell and Li||LiFePO_(4)full cell and pouch cell assembled with OGDY/PEO exhibit good performance,highlighting the effectiveness of our EREPD design strategy for improving CPSEs performance.
