INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al....INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al.,2024).Currently,travel time tomography is the most commonly used method for velocity modeling based on ocean bottom seismometer(OBS)data(Zhang et al.,2023;Sambolian et al.,2021).This method usually assumes that the sub-seafloor structure is layered,and therefore faces challenges in high-precision modeling with strong lateral discontinuities.展开更多
Three-dimensional(3D)covalent organic frameworks(COFs)have attracted extensive attention as photocatalysts for CO_(2)reduction reactions.Introducing metal atoms is essential for enhancing activity,but previous metal s...Three-dimensional(3D)covalent organic frameworks(COFs)have attracted extensive attention as photocatalysts for CO_(2)reduction reactions.Introducing metal atoms is essential for enhancing activity,but previous metal sites in 3D COFs predominantly exhibit symmetrical coordination,making them unsuitable for CO_(2)activation.Here,we design a 3D COF with 2,2'-pyridine linked around tetra-(4-anilyl)methane(TCM-Bpy-COF),where Co^(2+)is asymmetrically coordinated by bipyridine and acetates(TCMBpy-COF-CoAc).The TCM-Bpy-COF-CoAc exhibits outstanding photocatalytic CO_(2)reduction performance under weak visible light,achieving a CO evolution rate of 26,650μmol g^(-1)h^(-1)under 5 W of lightemitting-diode(LED)lamp and high apparent quantum efficiency.The performance far exceeds that of symmetrically coordinated bipyridine-Co-bipyridine TCM-Bpy-COF and surpasses most reported COF-based photocatalysts.In-situ spectral characterizations and theoretical calculations show that asymmetric N,O-coordination around the Co^(2+)center polarizes electron density and lowers reaction energy barriers of^(*)COOH intermediates,enhancing the conversion of CO_(2)to CO.This work inspires the design of 3D COF-based photocatalysts with highly catalytic efficiency.展开更多
The microstructure of twinning as well as the phase boundary between 1:5 H and 2:17 R phase in Fe-rich Sm_(2)Co_(17)-type magnets was characterized at atomic scale using nanobeam diffraction and highresolution STEM-HA...The microstructure of twinning as well as the phase boundary between 1:5 H and 2:17 R phase in Fe-rich Sm_(2)Co_(17)-type magnets was characterized at atomic scale using nanobeam diffraction and highresolution STEM-HAADF imaging,and the reason for the dramatic increase of coercivity during slow cooling was investigated based on the microchemistry analysis.The twinning relationship in the 2:17 R phase originates from ordered substitution of Sm atoms by Co-Co atomic pairs on every three(3033)and(3033)planes,leading to formation of two corresponding equivalent twin variants.The basal plane of the 2:17 R phase,the 1:3 R platelet phase across the 2:17 R cell and the 1:5 H cell boundary phase between two adjacent 2:17 R cells all can act as effective twin boundary.The cell boundary phase is precipitated along the pyramidal habit plane,and a fully coherent phase boundary(PB)is formed between the 1:5 H and 2:17 R phases with the orientation relationship to be PB//(1121)1:5 H//(1011)_(2):17 R.The phase boundary may either be parallel to or intersect with the pyramidal planes occupied by Co-Co atomic pairs.The substantial increase of coercivity during slow cooling is ascribed to the development of large gradient of the elements concentration within the cell boundary phase,resulting in large gradient of domain wall energy,and thus the pinning strength of the cell boundary phase against magnetic domain wall motion is significantly enhanced.展开更多
Though oxygen defects are associated with deteriorated structures and aggravated cycling performance in traditional layered cathodes,the role of oxygen defects is still ambiguous in Li-rich layered oxides due to the i...Though oxygen defects are associated with deteriorated structures and aggravated cycling performance in traditional layered cathodes,the role of oxygen defects is still ambiguous in Li-rich layered oxides due to the involvement of oxygen redox.Herein,a Co-free Li-rich layered oxide Li_(1.286)Ni_(0.071)Mn_(0.643)O_(2)has been prepared by a co-precipitation method to systematically investigate the undefined effects of the oxygen defects.A significant O_(2)release and the propagation of oxygen vacancies were detected by operando differential electrochemical mass spectroscopy(DEMS)and electron energy loss spectroscopy(EELS),respectively.Scanning transmission electron microscopy-high angle annular dark field(STEMHAADF)reveals the oxygen vacancies fusing to nanovoids and monitors a stepwise electrochemical activation process of the large Li_(2)MnO_(3)domain upon cycling.Combined with the quantitative analysis conducted by the energy dispersive spectrometer(EDS),existed nano-scale oxygen defects actually expose more surface to the electrolyte for facilitating the electrochemical activation and subsequently increasing available capacity.Overall,this work persuasively elucidates the function of oxygen defects on oxygen redox in Co-free Li-rich layered oxides.展开更多
Boron nitride nanotubes(BNNTs)were treated as brittle materials and could be used to enhance the composite mechanical properties.Many approaches were used to verify the theoretical prediction experimentally,but how to...Boron nitride nanotubes(BNNTs)were treated as brittle materials and could be used to enhance the composite mechanical properties.Many approaches were used to verify the theoretical prediction experimentally,but how to in situ real-time characterize nanomechanical properties of BNNTs was still interested to the researchers.An in situ transmission electron microscopy(TEM)equipped with a force transducer holder had been used to study the structure evolution behavior of BNNTs with axial compression.Real-time video and the force transducer had been used synchronously to record the whole force loading process where the mechanical deformation of BNNT began,buckled and ended with fracture.An in dividual ultrathin BNNT was employed to con duct the loading test.The results showed that the elastic deformation happened on the BNNT.Young's modulus?1.05-1.37 Tpa and elasticity coefficient?198.7-255.9 N/m of BNNT were calculated by Euler formula and Hooker's law,respectively.展开更多
The undesirable capacity loss after first cycle is universal among layered cathode materials,which results in the capacity and energy decay.The key to resolving this obstacle lies in understanding the effect and origi...The undesirable capacity loss after first cycle is universal among layered cathode materials,which results in the capacity and energy decay.The key to resolving this obstacle lies in understanding the effect and origin of specific active Li sites during discharge process.In this study,focusing on Ah-level pouch cells for reliability,an ultrahigh initial Coulombic efficiency(96.1%)is achieved in an archetypical Li-rich layered oxide material.Combining the structure and electrochemistry analysis,we demonstrate that the achievement of high-capacity reversibility is a kinetic effect,primarily related to the sluggish Li mobility during oxygen reduction.Activating oxygen reduction through small density would induce the oxygen framework contraction,which,according to Pauli repulsion,imposes a great repulsive force to hinder the transport of tetrahedral Li.The tetrahedral Li storage upon deep oxygen reduction is experimentally visualized and,more importantly,contributes to 6%Coulombic efficiency enhancement as well as 10%energy density improvement for pouch cells,which shows great potentials breaking through the capacity and energy limitation imposed by intercalation chemistry.展开更多
Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon...Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith(LR),specifically through the reaction FeO/Fe2O3+H/Fe+H2O.This process is demonstrated using LR samples brought back by the Chang’E-5 mission.FeO and Fe2O3 are lunar minerals containing Fe oxides.Hydrogen(H)retained in lunar minerals from the solar wind can be used to produce water.The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K.This amount is10,000 times the naturally occurring OH and H2O on the Moon.Among the five primary minerals in LR returned by the Chang’E-5 mission,FeTiO3 ilmenite contains the highest amount of H,owing to its unique lattice structure with sub-nanometer tunnels.For the first time,in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles.Electron irradiation promotes the endogenous redox reaction,which is helpful for understanding the distribution of OH on the Moon.Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon,which is helpful for establishing a scientific research station on the Moon.展开更多
Helium-3(3He)is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy.It is thought that the lunar regolith contains large amounts of helium,but i...Helium-3(3He)is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy.It is thought that the lunar regolith contains large amounts of helium,but it is challenging to extract because most helium atoms are reserved in defects of crystals or as solid solutions.Here,we find large amounts of helium bubbles in the glassy surface layer of ilmenite particles that were brought back by the Chang’E-5 mission.The special disordered atomic packing structure of glasses should be the critical factor for capturing the noble helium gas.The reserves in bubbles do not require heating to high temperatures to be extracted.Mechanical methods at ambient temperatures can easily break the bubbles.Our results provide insights into the mechanism of helium gathering on the moon and offer guidance on future in situ extraction.展开更多
The self-attraction of nanowires(NWs)would lead to NWs bunching up together when fabricated in high density and the short circuit of NW-based devices during service.However,the underlying mechanism of the self-attract...The self-attraction of nanowires(NWs)would lead to NWs bunching up together when fabricated in high density and the short circuit of NW-based devices during service.However,the underlying mechanism of the self-attraction of NWs remains debatable due to the lack of in situ characterization of the attraction.In this study,a versatile method of in situ investigating the self-attraction of NWs was developed.The attractive force between two NWs and their distance can be determined quantitatively in the process of attraction under an optical microscope,eliminating the influence of electron beam in electron microscopes.With this approach,the self-attraction of SiC NWs was investigated and a two-stage mechanism for the self-attraction was proposed.The electrostatic force between two individual SiC NWs increased as their distance decreased,and acted as the initial driving force for the attraction of NWs.SiC NWs remained in contact under van der Waals force until they separated when external force exceeded van der Waals force.The charge density and the Hamaker constant of SiC NWs were determined to be 1.9×10^(-4)C·m^(-2)and 1.56×10^(-19)J,which played an important role in the attraction of NWs.The results shed light on the mechanism of selfattraction among NWs and provide new insights into fabricating high-quality NWs and developing high-performance NW-based devices.展开更多
Risk assessment is critical in preventing aortic dissection(AD).This study aims to evaluate the wall stress(WS)distribution,especially at the locations of proximal tears in patient-specific type-B aortic dissection(TB...Risk assessment is critical in preventing aortic dissection(AD).This study aims to evaluate the wall stress(WS)distribution,especially at the locations of proximal tears in patient-specific type-B aortic dissection(TBAD)to explore the pathogenesis of dissection.In addition,the shape of the aortas were assessed and associated with TBAD risk.In this paper,30 three-dimensional models were reconstructed based on patient-specific CT angiography images,and finite element analysis(FEA)was used to analyze the admission blood pressure.In addition,the anatomic variables including the head vessel angles,the aorta diameters,curvatures and torturosity ware measured.Tears occurred at either local high WS or low WS region,and these acute TBAD patients can be classified into three groups based on the location of initial intimal tears.In addition,the WS values at tear sites of each group showed significant difference(P<0.001).Moreover,the angles of the left subclavian and brachiocephalic arteries were statistical different among three groups.Increased wall stress or decreased wall strength both contribute to the pathogenesis of aortic dissections.In addition,abnormal head vessel angles may be monitored as an important risk factor for aortic dissection,and its specific features may further help to determine the potential tear location.展开更多
Surface-enhanced Raman scattering(SERS)has been applied in many fields due to its advantages of fast and nondestructive detection.For semiconductors,the large-scale electron-hole pair separation of heterojunction is c...Surface-enhanced Raman scattering(SERS)has been applied in many fields due to its advantages of fast and nondestructive detection.For semiconductors,the large-scale electron-hole pair separation of heterojunction is conducive to efficient charge transfer,which is a promising SERS substrate.Here,we designed a Fe_(2)O_(3)@CeO_(2) heterojunction substrate by hydrothermal method and explored its enhancement mechanism in detail.α-Fe_(2)O_(3) is a promising semiconductor with a narrow bandgap,and CeO_(2) has adequate oxygen vacancies on the surface.Combingα-Fe_(2)O_(3) and CeO_(2) into a shell-core structure,Fe_(2)O_(3)@CeO_(2) heterojunction presents higher SERS performance than pure Fe_(2)O_(3) and CeO_(2) for methyl orange(MO)molecule with a limit of detection(LOD)of 5×10^(-8) mol/L.Under the excitation of 514 nm,Fe_(2)O_(3) can produce an effective exciton resonance due to its narrow bandgap(2.01 eV).The oxygen vacancy in CeO_(2) acts as the active site to promote the adsorption of molecules and facilitate the photo-induced charge transfer(PICT)between the substrate and MO molecules.Therefore,the high SERS performance of Fe_(2)O_(3)@CeO_(2) heterojunction is achieved due to the coupling effect of excitons resonance,molecular resonance,and PICT resonance.It is found that Fe_(2)O_(3)@CeO_(2) has good SERS performance and stability to organic pesticides,especially metamitron(LOD=5×10^(-9) mol/L).This work combines the advantages of Fe_(2)O_(3) being prone to producing photoelectrons and abundant oxygen vacancies of CeO_(2),providing a reference for designing semiconductor SERS.展开更多
基金financially supported by the National Key R&D Program of China(No.2023YFF0803404)the Zhejiang Provincial Natural Science Foundation(No.LY23D040001)+4 种基金the Open Research Fund of Key Laboratory of Engineering Geophysical Prospecting and Detection of Chinese Geophysical Society(No.CJ2021GB01)the Open Re-search Fund of Changjiang River Scientific Research Institute(No.CKWV20221011/KY)the ZhouShan Science and Technology Project(No.2023C81010)the National Natural Science Foundation of China(No.41904100)supported by Chinese Natural Science Foundation Open Research Cruise(Cruise No.NORC2019–08)。
文摘INTRODUCTION.Crustal velocity model is crucial for describing the subsurface composition and structure,and has significant implications in offshore oil and gas exploration and marine geophysical engineering(Xie et al.,2024).Currently,travel time tomography is the most commonly used method for velocity modeling based on ocean bottom seismometer(OBS)data(Zhang et al.,2023;Sambolian et al.,2021).This method usually assumes that the sub-seafloor structure is layered,and therefore faces challenges in high-precision modeling with strong lateral discontinuities.
基金financial support from the National Natural Science Foundation of China(No.22072183)the Natural Science Foundation of Hunan Province,China(No.2022JJ30690)supported in part by the High Performance Computing Center of Central South University。
文摘Three-dimensional(3D)covalent organic frameworks(COFs)have attracted extensive attention as photocatalysts for CO_(2)reduction reactions.Introducing metal atoms is essential for enhancing activity,but previous metal sites in 3D COFs predominantly exhibit symmetrical coordination,making them unsuitable for CO_(2)activation.Here,we design a 3D COF with 2,2'-pyridine linked around tetra-(4-anilyl)methane(TCM-Bpy-COF),where Co^(2+)is asymmetrically coordinated by bipyridine and acetates(TCMBpy-COF-CoAc).The TCM-Bpy-COF-CoAc exhibits outstanding photocatalytic CO_(2)reduction performance under weak visible light,achieving a CO evolution rate of 26,650μmol g^(-1)h^(-1)under 5 W of lightemitting-diode(LED)lamp and high apparent quantum efficiency.The performance far exceeds that of symmetrically coordinated bipyridine-Co-bipyridine TCM-Bpy-COF and surpasses most reported COF-based photocatalysts.In-situ spectral characterizations and theoretical calculations show that asymmetric N,O-coordination around the Co^(2+)center polarizes electron density and lowers reaction energy barriers of^(*)COOH intermediates,enhancing the conversion of CO_(2)to CO.This work inspires the design of 3D COF-based photocatalysts with highly catalytic efficiency.
基金Project supported by Zhejiang Province Public Welfare Technology Application Research Project(LGC20E010002)National Natural Science Foundation of China(51877094)。
文摘The microstructure of twinning as well as the phase boundary between 1:5 H and 2:17 R phase in Fe-rich Sm_(2)Co_(17)-type magnets was characterized at atomic scale using nanobeam diffraction and highresolution STEM-HAADF imaging,and the reason for the dramatic increase of coercivity during slow cooling was investigated based on the microchemistry analysis.The twinning relationship in the 2:17 R phase originates from ordered substitution of Sm atoms by Co-Co atomic pairs on every three(3033)and(3033)planes,leading to formation of two corresponding equivalent twin variants.The basal plane of the 2:17 R phase,the 1:3 R platelet phase across the 2:17 R cell and the 1:5 H cell boundary phase between two adjacent 2:17 R cells all can act as effective twin boundary.The cell boundary phase is precipitated along the pyramidal habit plane,and a fully coherent phase boundary(PB)is formed between the 1:5 H and 2:17 R phases with the orientation relationship to be PB//(1121)1:5 H//(1011)_(2):17 R.The phase boundary may either be parallel to or intersect with the pyramidal planes occupied by Co-Co atomic pairs.The substantial increase of coercivity during slow cooling is ascribed to the development of large gradient of the elements concentration within the cell boundary phase,resulting in large gradient of domain wall energy,and thus the pinning strength of the cell boundary phase against magnetic domain wall motion is significantly enhanced.
基金supported by the National Natural Science Foundation of China(52272253)the"Lingyan"Research and Development Plan of Zhejiang Province(2022C01071)+2 种基金the S&T Innovation 2025 Major Special Programme of Ningbo(2018B10081)the Natural Science Foundation of Ningbo(202003N4030)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022299)。
文摘Though oxygen defects are associated with deteriorated structures and aggravated cycling performance in traditional layered cathodes,the role of oxygen defects is still ambiguous in Li-rich layered oxides due to the involvement of oxygen redox.Herein,a Co-free Li-rich layered oxide Li_(1.286)Ni_(0.071)Mn_(0.643)O_(2)has been prepared by a co-precipitation method to systematically investigate the undefined effects of the oxygen defects.A significant O_(2)release and the propagation of oxygen vacancies were detected by operando differential electrochemical mass spectroscopy(DEMS)and electron energy loss spectroscopy(EELS),respectively.Scanning transmission electron microscopy-high angle annular dark field(STEMHAADF)reveals the oxygen vacancies fusing to nanovoids and monitors a stepwise electrochemical activation process of the large Li_(2)MnO_(3)domain upon cycling.Combined with the quantitative analysis conducted by the energy dispersive spectrometer(EDS),existed nano-scale oxygen defects actually expose more surface to the electrolyte for facilitating the electrochemical activation and subsequently increasing available capacity.Overall,this work persuasively elucidates the function of oxygen defects on oxygen redox in Co-free Li-rich layered oxides.
基金supported by the National Natural Science Foundation of China(Nos. 51573201, 21773205, 51501209 and 201675165)Key R&D Program of Yunnan Province(No. 2018BA068)+7 种基金NSFC-Zhejiang Joint Fund for the Integration of Industrialization and Informatization(No. U1709205)National Key R&D Program of China(No. 2017YFB0406000)the Project of the Chinese Academy of Sciences(Nos. YZ201640 and KFZD-SW409)Public Welfare Project of Zhejiang Province (No. 2016C31026)Science and Technology Major Project of Ningbo (Nos.2016B10038 and 2016S1002)International S&T Cooperation Program of Ningbo(No. 2017D10016)the 3315 Program of Ningbo for financial supportthe financial support by the Science and Technology Major Project of Ningbo (No. 2015S1001)
文摘Boron nitride nanotubes(BNNTs)were treated as brittle materials and could be used to enhance the composite mechanical properties.Many approaches were used to verify the theoretical prediction experimentally,but how to in situ real-time characterize nanomechanical properties of BNNTs was still interested to the researchers.An in situ transmission electron microscopy(TEM)equipped with a force transducer holder had been used to study the structure evolution behavior of BNNTs with axial compression.Real-time video and the force transducer had been used synchronously to record the whole force loading process where the mechanical deformation of BNNT began,buckled and ended with fracture.An in dividual ultrathin BNNT was employed to con duct the loading test.The results showed that the elastic deformation happened on the BNNT.Young's modulus?1.05-1.37 Tpa and elasticity coefficient?198.7-255.9 N/m of BNNT were calculated by Euler formula and Hooker's law,respectively.
基金financially supported by the National Natural Science Foundation of China(Grant No.52272253)“Lingyan”Research and Development Plan of Zhejiang Province(Grant No.2022C01071)+2 种基金Low Cost Cathode Material(Grant No.TC220H06P)the Natural Science Foundation of Ningbo(Grant No.202003N4030)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2022299)
文摘The undesirable capacity loss after first cycle is universal among layered cathode materials,which results in the capacity and energy decay.The key to resolving this obstacle lies in understanding the effect and origin of specific active Li sites during discharge process.In this study,focusing on Ah-level pouch cells for reliability,an ultrahigh initial Coulombic efficiency(96.1%)is achieved in an archetypical Li-rich layered oxide material.Combining the structure and electrochemistry analysis,we demonstrate that the achievement of high-capacity reversibility is a kinetic effect,primarily related to the sluggish Li mobility during oxygen reduction.Activating oxygen reduction through small density would induce the oxygen framework contraction,which,according to Pauli repulsion,imposes a great repulsive force to hinder the transport of tetrahedral Li.The tetrahedral Li storage upon deep oxygen reduction is experimentally visualized and,more importantly,contributes to 6%Coulombic efficiency enhancement as well as 10%energy density improvement for pouch cells,which shows great potentials breaking through the capacity and energy limitation imposed by intercalation chemistry.
基金Financial support from the National Key R&D Program of China(2018YFA0703600)the National Natural Science Foundation of China(NSFC 52222105,51922102,92163108,61888102,and 51827801)+2 种基金the Youth Innovation Promotion Association CAS(2019296)the Zhejiang Provincial Natural Science Foundation of China(LZ22A030001 and LR22E010004)the Ningbo 2025 Science and Technology Innovation Project is acknowledged.
文摘Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith(LR),specifically through the reaction FeO/Fe2O3+H/Fe+H2O.This process is demonstrated using LR samples brought back by the Chang’E-5 mission.FeO and Fe2O3 are lunar minerals containing Fe oxides.Hydrogen(H)retained in lunar minerals from the solar wind can be used to produce water.The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K.This amount is10,000 times the naturally occurring OH and H2O on the Moon.Among the five primary minerals in LR returned by the Chang’E-5 mission,FeTiO3 ilmenite contains the highest amount of H,owing to its unique lattice structure with sub-nanometer tunnels.For the first time,in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles.Electron irradiation promotes the endogenous redox reaction,which is helpful for understanding the distribution of OH on the Moon.Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon,which is helpful for establishing a scientific research station on the Moon.
基金financial support from National Natural Science Foundation of China(NSFC 51922102,92163108,61888102,11790291)Youth Innovation Promotion Association CAS(2019296)+1 种基金Zhejiang Provincial Natural Science Foundation of China(LZ22A030001,LR22E010004)Ningbo 2025 Science and Technology Innovation Project(2022Z033)are acknowledged.
文摘Helium-3(3He)is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy.It is thought that the lunar regolith contains large amounts of helium,but it is challenging to extract because most helium atoms are reserved in defects of crystals or as solid solutions.Here,we find large amounts of helium bubbles in the glassy surface layer of ilmenite particles that were brought back by the Chang’E-5 mission.The special disordered atomic packing structure of glasses should be the critical factor for capturing the noble helium gas.The reserves in bubbles do not require heating to high temperatures to be extracted.Mechanical methods at ambient temperatures can easily break the bubbles.Our results provide insights into the mechanism of helium gathering on the moon and offer guidance on future in situ extraction.
基金The authors acknowledge the financial supports from the Youth Innovation Promotion Association CAS(No.2019295)the Science and Technology Major Project of Ningbo(No.2018B10046)+2 种基金the National Key R&D Program of China(No.2018YFA0703400)the National Natural Science Foundation of China(Nos.51573201 and 52142501)Changjiang Scholars Program of Chinese Ministry of Education,the Xinghai Science Funds for Distinguished Young Scholars at Dalian University of Technology,and the Collaborative Innovation Center of Major Machine Manufacturing in Liaoning。
文摘The self-attraction of nanowires(NWs)would lead to NWs bunching up together when fabricated in high density and the short circuit of NW-based devices during service.However,the underlying mechanism of the self-attraction of NWs remains debatable due to the lack of in situ characterization of the attraction.In this study,a versatile method of in situ investigating the self-attraction of NWs was developed.The attractive force between two NWs and their distance can be determined quantitatively in the process of attraction under an optical microscope,eliminating the influence of electron beam in electron microscopes.With this approach,the self-attraction of SiC NWs was investigated and a two-stage mechanism for the self-attraction was proposed.The electrostatic force between two individual SiC NWs increased as their distance decreased,and acted as the initial driving force for the attraction of NWs.SiC NWs remained in contact under van der Waals force until they separated when external force exceeded van der Waals force.The charge density and the Hamaker constant of SiC NWs were determined to be 1.9×10^(-4)C·m^(-2)and 1.56×10^(-19)J,which played an important role in the attraction of NWs.The results shed light on the mechanism of selfattraction among NWs and provide new insights into fabricating high-quality NWs and developing high-performance NW-based devices.
基金This work was supported by grants from National Natural Science Foundation of China(81770471,12072214,1802253)Sichuan Provincial Department of Science and Technology Application Basic Project(2018YYJC,2019YJ0026).
文摘Risk assessment is critical in preventing aortic dissection(AD).This study aims to evaluate the wall stress(WS)distribution,especially at the locations of proximal tears in patient-specific type-B aortic dissection(TBAD)to explore the pathogenesis of dissection.In addition,the shape of the aortas were assessed and associated with TBAD risk.In this paper,30 three-dimensional models were reconstructed based on patient-specific CT angiography images,and finite element analysis(FEA)was used to analyze the admission blood pressure.In addition,the anatomic variables including the head vessel angles,the aorta diameters,curvatures and torturosity ware measured.Tears occurred at either local high WS or low WS region,and these acute TBAD patients can be classified into three groups based on the location of initial intimal tears.In addition,the WS values at tear sites of each group showed significant difference(P<0.001).Moreover,the angles of the left subclavian and brachiocephalic arteries were statistical different among three groups.Increased wall stress or decreased wall strength both contribute to the pathogenesis of aortic dissections.In addition,abnormal head vessel angles may be monitored as an important risk factor for aortic dissection,and its specific features may further help to determine the potential tear location.
基金supported by the National Natural Science Foundation of China(Nos.12274018,52022006,32025021,52222602,12374390),Ningbo 3315 Innovative Teams Program(No.2019A-14-C)the Member of Youth Innovation Promotion Association Foundation of CAS(No.2023310)+2 种基金Key Scientific and Technological Special Project of Ningbo City(Nos.2023Z209,2023Z189)Beijing Nova Program(No.20220484170),Fundamental Research Funds for the Central Universities(No.FRF-TP-22-001C1)Jiangxi Provincial Natural Science Foundation(No.20232BAB213027).
文摘Surface-enhanced Raman scattering(SERS)has been applied in many fields due to its advantages of fast and nondestructive detection.For semiconductors,the large-scale electron-hole pair separation of heterojunction is conducive to efficient charge transfer,which is a promising SERS substrate.Here,we designed a Fe_(2)O_(3)@CeO_(2) heterojunction substrate by hydrothermal method and explored its enhancement mechanism in detail.α-Fe_(2)O_(3) is a promising semiconductor with a narrow bandgap,and CeO_(2) has adequate oxygen vacancies on the surface.Combingα-Fe_(2)O_(3) and CeO_(2) into a shell-core structure,Fe_(2)O_(3)@CeO_(2) heterojunction presents higher SERS performance than pure Fe_(2)O_(3) and CeO_(2) for methyl orange(MO)molecule with a limit of detection(LOD)of 5×10^(-8) mol/L.Under the excitation of 514 nm,Fe_(2)O_(3) can produce an effective exciton resonance due to its narrow bandgap(2.01 eV).The oxygen vacancy in CeO_(2) acts as the active site to promote the adsorption of molecules and facilitate the photo-induced charge transfer(PICT)between the substrate and MO molecules.Therefore,the high SERS performance of Fe_(2)O_(3)@CeO_(2) heterojunction is achieved due to the coupling effect of excitons resonance,molecular resonance,and PICT resonance.It is found that Fe_(2)O_(3)@CeO_(2) has good SERS performance and stability to organic pesticides,especially metamitron(LOD=5×10^(-9) mol/L).This work combines the advantages of Fe_(2)O_(3) being prone to producing photoelectrons and abundant oxygen vacancies of CeO_(2),providing a reference for designing semiconductor SERS.
