In this study,an inverse design framework was established to find lightweight honeycomb structures(HCSs)with high impact resistance.The hybrid HCS,composed of re-entrant(RE)and elliptical annular re-entrant(EARE)honey...In this study,an inverse design framework was established to find lightweight honeycomb structures(HCSs)with high impact resistance.The hybrid HCS,composed of re-entrant(RE)and elliptical annular re-entrant(EARE)honeycomb cells,was created by constructing arrangement matrices to achieve structural lightweight.The machine learning(ML)framework consisted of a neural network(NN)forward regression model for predicting impact resistance and a multi-objective optimization algorithm for generating high-performance designs.The surrogate of the local design space was initially realized by establishing the NN in the small sample dataset,and the active learning strategy was used to continuously extended the local optimal design until the model converged in the global space.The results indicated that the active learning strategy significantly improved the inference capability of the NN model in unknown design domains.By guiding the iteration direction of the optimization algorithm,lightweight designs with high impact resistance were identified.The energy absorption capacity of the optimal design reached 94.98%of the EARE honeycomb,while the initial peak stress and mass decreased by 28.85%and 19.91%,respectively.Furthermore,Shapley Additive Explanations(SHAP)for global explanation of the NN indicated a strong correlation between the arrangement mode of HCS and its impact resistance.By reducing the stiffness of the cells at the top boundary of the structure,the initial impact damage sustained by the structure can be significantly improved.Overall,this study proposed a general lightweight design method for array structures under impact loads,which is beneficial for the widespread application of honeycomb-based protective structures.展开更多
Understanding the acid resistance mechanism of S.mutans is crucial for preventing dental caries.FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis.Our previou...Understanding the acid resistance mechanism of S.mutans is crucial for preventing dental caries.FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis.Our previous study revealed that the FtsZ in S.mutans(SmFtsZ) has higher self-assembly and GTPase activity under acidic stress,which may be responsible for acid resistance and ca riogenesis of S.mutans.However,the functional structure mechanism of SmFtsZ under low pH conditions is still unclear.Here,we further reported the crystal structure of S.mutans FtsZ,revealing a unique lateral interface.Through protein polymerization and GTPase activity assay,we experimentally demonstrated that the mutation of Arg68 on this lateral interface significantly reduced the functional activity of FtsZ in an acidic environment.The phenotype assay and rat caries model further showed that the mutation of Arg68 effectively inhibited the acid resistance of S.mutans and the occurrence and progress of dental caries in vivo.By employing a molecular dynamics simulation analysis,we conclude that the mutation of Arg68 disrupts the conformation change necessary for SmFtsZ polymerization under acidic conditions.Our study proposes a novel mechanism to maintain FtsZ function in bacteria and could be a potential target for antimicrobial drugs to inhibit the growth of S.mutans in acidic environments.展开更多
This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A tempe...This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.展开更多
We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th_(2)Mo_(2)Ru_(2)Si_(4)C,crystallized in a collapsed 22241-type structure.This structure is characterized by the intergrowth o...We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th_(2)Mo_(2)Ru_(2)Si_(4)C,crystallized in a collapsed 22241-type structure.This structure is characterized by the intergrowth of ThMo_(2)Si_(2)C and ThRu_(2)Si_(2) units interconnected by equivalent Si-Si bonds that enhance inter-sublattice coupling.The refined lattice parameters are a=4.2212(1)Å and c=20.3899(7)Å.Electrical resistivity and magnetic susceptibility measurements of both polycrystalline and single-crystal samples consistently demonstrate bulk superconductivity with a transition temperature T_(c)∼6.0 K significantly higher than those of the constituent compound ThMo_(2)Si_(2)C and its related analogs.Under magnetic fields,the superconducting state exhibits a nearly isotropic behavior,which is attributed to strong covalent interlayer coupling.First-principles calculations reveal a substantial contribution from the Mo-d orbitals near the Fermi level,which exhibit several band-crossing points.The enhancement in T_(c) can be attributed to the synergistic combination of the valence electron concentration and the inter-sublattice self-doping effect between the[Ru_(2)Si_(2)]and[Mo_(2)Si_(2)C]layers.展开更多
Magnesium(Mg)and its alloys,as the lowest density metallic structural alloys,have been widely employed across various industries,including electronic communication,automotive,aircraft,defense,and military.While Mg all...Magnesium(Mg)and its alloys,as the lowest density metallic structural alloys,have been widely employed across various industries,including electronic communication,automotive,aircraft,defense,and military.While Mg alloys are susceptible to issues like pitting or stress corrosion when utilized as key structural components in humid environments,resulting in corrosion fatigue,stress corrosion cracking,or even complete corrosion failure,which impedes their broader applications.To address these disadvantages of Mg alloys,surface selfnanocrystallization(SSNC),involving refining the grain size to create a nanosurface layer,has been proposed to delay or mitigate the initiation and propagation of cracks,thereby significantly enhancing corrosion resistance.The purpose of this paper is to review the effects of various surface self-nanocrystallization techniques,including surface mechanical attrition treatment,high-energy shot peening,ultrasonic surface rolling processing,laser shock peening,and supersonic particle bombardment,on the microstructure and properties of Mg alloys.Additionally,the mechanisms underlying the surface nanocrystallization-induced microstructural evolution in Mg alloys and the factors influencing their corrosion resistance are systematically summarized.Finally,the current challenges and prospects are discussed as well.展开更多
Efficient thermal management is critical to the reliability and performance of nanoscale electronic and photonic devices,particularly those incorporating multilayer structures.In this study,non-equilibrium molecular d...Efficient thermal management is critical to the reliability and performance of nanoscale electronic and photonic devices,particularly those incorporating multilayer structures.In this study,non-equilibrium molecular dynamics simulations were conducted to systematically investigate the effects of temperature,penetration depth,and Si layer thickness on the interfacial thermal resistance(ITR)in nanometer-scale Mo/Si multilayers,widely employed in extreme ultraviolet lithography.The results indicate that:(i)temperature variations exert a negligible influence on the ITR of amorphous Mo/Si interfaces,which remains stable across the range of 200-900 K;(ii)increasing penetration depth enhances the overlap of phonon density of states,thereby significantly reducing ITR;(iii)the ITR decreases with increasing Si thickness up to4.2 nm due to quasi-ballistic phonon transport,but rises again as phonon scattering becomes more pronounced at larger thicknesses.This study provides quantitative insights into heat transfer mechanisms at amorphous interfaces and also offers a feasible strategy for tailoring interfacial thermal transport through structural design.展开更多
The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate.The long-period magnetotelluric(LMT)and broadband magnetotel...The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate.The long-period magnetotelluric(LMT)and broadband magnetotelluric(MT)techniques are both used to study the deep electrical conductivity structure in this region;magnetic and gravity surveys are also performed along the profile.According to the 2-D resistivity model along the Yanyuan-Yongshan profile,a high-conductivity layer(HCL)exists widely in the crust,and a high-resistivity block(HRB)exists widely in the upper mantle in general,as seen by the fact that a large HCL exists from the western Jinpingshan tectonic zone to the eastern Mabian tectonic zone in the crust,while the HRB found in the Panxi tectonic zone is of abnormally high resistivity in that background compared to both sides of Panxi tectonic zone.In addition,the gravity and magnetic field anomalies are of high value.Combined with geological data,the results indicate that there probably exists basic or ultrabasic rock with a large thickness in the lithosphere in the Panxi axial region,which indicates that fracture activity once occurred in the lithosphere.As a result,we can infer that the high-resistivity zone in the Panxi lithosphere is the eruption channel for Permian Emeishan basalt and the accumulation channel for basic and ultrabasic rock.The seismic sources along the profile are counted according to seismic record data.The results indicate that the most violent earthquake sources are located at the binding site of the HRB and the HCL,where the tectonic activity zone is generally acknowledged to be;however,the earthquakes occurring in the HCL are not so violent,which reflects the fact that the HCL is a plastic layer,and the fracture threshold of a plastic layer is low generally,making high stress difficult to accumulate but easy to release in the layer.As a result,a higher number of smaller earthquakes occurred in the HCL at Daliangshan tectonic zone,and violent earthquakes occurred at the binding site of high-and low-resistivity blocks at the Panxi tectonic zone.展开更多
The influence of pore structure difference on rock electrical characteristics of reservoir and oil reservoir was analyzed taking Triassic Chang 6 reservoir in Block Yanwumao in the middle of Ordos Basin as an example....The influence of pore structure difference on rock electrical characteristics of reservoir and oil reservoir was analyzed taking Triassic Chang 6 reservoir in Block Yanwumao in the middle of Ordos Basin as an example. The relationship between the pore structure difference and the low resistivity oil layer was revealed and demonstrated through core observation, lab experiments, geological research, well log interpretation and trial production etc. The results show that there were two kinds of oil layers in Chang 6 oil layer set, normal oil layer and low resistivity oil layer in the region, corresponding to two types of pore structures, pore type mono-medium and micro-fracture-pore type double-medium; the development of micro-fracture changed greatly the micro-pore structure of the reservoir, and the pore structure difference had an important influence on the rock electrical characteristics of the extra-low permeability sandstone reservoir and oil reservoir; the normal oil layers had obvious characteristics of pore-type mono-medium, and were concentrated in Chang 61, Chang 6232 and Chang 62; the low resistivity oil layers had obvious characteristics of micro-fracture-pore type double-medium, which were mainly distributed in Chang 612 and Chang 63. The mud filtrate penetrated deep into the oil layers along the micro-cracks, leading to sharp reduction of resistivity, and thus low resistivity of the oil layer; the low resistivity oil layers had better storage capacity and higher productivity than the normal oil layers.展开更多
To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of...To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of the resistivity log of ultrahigh-pressure（UHP） metamorphic rocks.To check the logs＇ quality,we compared the resistivity log data with the core test data.The two datasets show a good coherence.On the whole,the resistivity of the UHP metamorphic rocks from the CCSD-MH is very high（mostly higher than 1 000 ？？m）.From orthogneiss to paragneiss,amphibolite,retrograded eclogite,rutile eclogite,phengite eclogite,and ultramafic rock,the resistivity decreases gradually.The fracture zone,enrichment of metal minerals,and serpentinization of peridotite can probably cause the decrease of resistivity.Comparing the electrical structure of the crust of Dabie（大别） terrane and Sulu terrane,we can conclude that（1） the electrical structure of the crust of Dabie terrane and Sulu terrane shows a very big difference,（2） the high-resistivity zone of the north Sulu orogen extended to a very great depth（60 km）,but the high-resistivity zone of Dabie orogen is over the depth of 25 km.展开更多
The effect of the Ni/Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi5-xCux series was studied.The value of temperature of phase transition(T_(ph))estimated from temperature...The effect of the Ni/Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi5-xCux series was studied.The value of temperature of phase transition(T_(ph))estimated from temperature dependence of electrical resistance varied non-linearly across copper doping from 32.5 K(x=0.0)to 29.1 K(x=5.0).The value of residual resistivity(ρo)estimated at low temperature range decreased from 27.28μΩcm(x=0.0)to 9.44μΩcm(x=5.0),which was discussed as the influence of microstructure.In order to describe the temperature dependence of resistivityρ(T)a variety of approaches were applied due to different scattering mechanisms occurring at high and low temperature ranges.The change withinρ(T)curvature was evidenced at low temperature range across copper doping.The temperature variation of the resistivity was quite peculiar for Cu-rich compounds(x=4.8,x=5.0),which might be correlated with the incommensurate magnetic structure derived from the weakly negative interaction between the nearest neighbours of Gd.The correlation between microstructure and resistivity was observed.展开更多
A new type of phosphor Sr2ZrO4 with one-dimensional structure was prepared bysolid reaction and its luminescence is seen at room temperature. The excitation and emissionspectra were measured and display broad maximum ...A new type of phosphor Sr2ZrO4 with one-dimensional structure was prepared bysolid reaction and its luminescence is seen at room temperature. The excitation and emissionspectra were measured and display broad maximum at 354 nm and 386 nm respectively. Themechanism of this luminescence is ascribed to charge transfer.展开更多
In this paper, on the basis of the heat conduction equation without consideration of the advection and turbulence effects, one-dimensional model for describing surface sea temperature ( T1), bottom sea temperature ( T...In this paper, on the basis of the heat conduction equation without consideration of the advection and turbulence effects, one-dimensional model for describing surface sea temperature ( T1), bottom sea temperature ( Tt ) and the thickness of the upper homogeneous layer ( h ) is developed in terms of the dimensionless temperature θT and depth η and self-simulation function θT - f(η) of vertical temperature profile by means of historical temperature data.The results of trial prediction with our one-dimensional model on T, Th, h , the thickness and gradient of thermocline are satisfactory to some extent.展开更多
The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, N...The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, Nb leads to a stabilization of the cubic γ-U phase, while it requires much higher Zr concentrations （≥30 at.% Zr）. All U-T splats become superconducting with Tc in the range of 0.61-2.11 K. A good agreement of the experimentally observed specific-heat jump at Tc with that from BCS theory prediction was obtained for U-15 at.% Mo consisting of the γ-U phase with an ideal bcc A2 structure.展开更多
A new one-dimensional polymeric complex [Cd（SCN）2（H2O）]L （L = N,N′-bis（furan- 2-ylmethylene）hydrazine） has been synthesized and characterized by IR, UV spectra, TG-DTA technique and single-crystal X-ray diffr...A new one-dimensional polymeric complex [Cd（SCN）2（H2O）]L （L = N,N′-bis（furan- 2-ylmethylene）hydrazine） has been synthesized and characterized by IR, UV spectra, TG-DTA technique and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, pace group P1^- with a = 5.9268（8）, b = 10.8678（15）, c = 13.3671（19） A, α = 109.295（2）, β = 95.092（2）, γ = 97.8580（10）°, V = 796.70（19）A^3, Z = 2, C12H10CdN4O3S2, Mr = 434.76, μ = 1.648 mm^-1, Dc = 1.812 g/cm^3, F（000） = 428, R = 0.0308 and wR = 0.0769. The crystal structure reveals that the structure of [Cd（SCN）2（H2O）]n features di-μ-1,3-thiocyante bridges and 1D chains. The octahedrally coordinated Cd atom is surrounded by one oxygen atom from water molecule, three S atoms and two N atoms from five di-μ-1,3 thiocyanato bridges. The Cd atoms are connected by two di-μ-1,3 thiocyanato bridges with the Cd（1）…Cd（1A） separation of 4.239（1） A and Cd（1）...Cd（1B） of 5.852（1）/~. In addition, the one-dimensional straight chain structure is further connected by multiform intermolecular N-H…O hydrogen bonds and π-π interactions to form a three-dimensional supramolecular structure.展开更多
A new zinc polymer, {Zn（O2CC12H8CO2）（H2O）}, or {Zn（DPHA）（H2O）}n （O2CC12H8CO2, DPHA = 1,1′ -biphenyl-2,2′-dicarboxylate dianion） has been synthesized under hydrothermal conditions. The crystal is of monocli...A new zinc polymer, {Zn（O2CC12H8CO2）（H2O）}, or {Zn（DPHA）（H2O）}n （O2CC12H8CO2, DPHA = 1,1′ -biphenyl-2,2′-dicarboxylate dianion） has been synthesized under hydrothermal conditions. The crystal is of monoclinic, space group P21/c with a = 12.8418（5）, b = 5.9505（2）, c = 17.2989（5） A, β = 104.020（2）°, V = 1282.52（8） A^3, C14H10O5Zn, Mr= 323.61, Z = 4, Dc = 1.676 g/cm^3,μ = 1.930 mm^-1, F（000） = 656, R = 0.0766 and wR = 0.1871 for 1775 observed reflections （I 〉 2σ（I））. It consists of Zn2（DPHA）2（H2O）2 units, which are further extended into a one-dimensional double helical-chain polymer via Zn-O bonding. The hydrogen bonding interactions extend the helical chains into a two-dimensional layer structure.展开更多
Reaction of (NH_4)_2MoS_4 with AgI in α-MePy gives the title com- pound,an X-ray analysis of which shows that the molecule forms a one-dimensional polymeric chain with continuous metal-metal bonds.
The complexe{[K(DB18-crown-6)]_(2)(CH_(3)CN)}[Pt(SCN)_(4)]was synthesized and characterized by elemental analysis,IR spectrum and X-ray diffraction analysis.The complexe belongs to monoclinic,space group c2/c with cel...The complexe{[K(DB18-crown-6)]_(2)(CH_(3)CN)}[Pt(SCN)_(4)]was synthesized and characterized by elemental analysis,IR spectrum and X-ray diffraction analysis.The complexe belongs to monoclinic,space group c2/c with cell dimensions,a=2.5904(8),6=1.3653(4),c-1.84706(6)nm,β=123.811(4)°,V=5-339(3)nm^(3),Z=4,.Dcalcd=l.577 g/cm^(3),F(000)=2552,R_(1)=0.051 l,wR_(2)=0.1411.The complexe shows one-dimensional chain of{[K(DB18-crown-6)]+complex cation and[Pt(SCN),i]2-complex anion bridged by N atom of CHaCN moleculer between two[K(DB18-crown-6)]_(2)[Pt(SCN)_(4)]groups respectively.展开更多
With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite h...With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.展开更多
In an aqueous solution of the mixtures of γ-amino propyl triethoxy silane and γ-glycidoxy propyl trimethoxy silane, a composite silane conversion coating was developed on galvanized steel. FESEM （field emission sca...In an aqueous solution of the mixtures of γ-amino propyl triethoxy silane and γ-glycidoxy propyl trimethoxy silane, a composite silane conversion coating was developed on galvanized steel. FESEM （field emission scanning electron microscope）, XPS （X-ray photoelectron spectroscopy）, ATR FTIR （attenuated total reflection Flourier transform infrared spectroscopy） and SST （salt spray test） were used to characterize the obtained composite silane conversion coating and also the coating formation process was studied. The result showed that the surface of the composite silane conversion coating was complete, consecutive and compact. The coating could endure a neutral salt spray test for 72 h without corrosion. The result of salt spray test indicated that the composite silane conversion coating can provide a better corrosion inhibition than the coating which was composed of the single silane. Based on observation and analysis, it was proposed that the formation process of the silane coating on zinc should consist of three steps： the hydrolysis of the silane molecules, silane chemical adsorption and silane crosslinking condensation. The crosslinking reactions took place between ~＇-amino propyl triethoxy and ＂/-glycidoxy propyl trimethoxy silane during the forming process of the coating, and a high crosslinked density interpenetrating structure network was obtained, so the composite silane conversion coating could keep the corrosive substances from the zinc more effectively.展开更多
基金the financial supports from National Key R&D Program for Young Scientists of China(Grant No.2022YFC3080900)National Natural Science Foundation of China(Grant No.52374181)+1 种基金BIT Research and Innovation Promoting Project(Grant No.2024YCXZ017)supported by Science and Technology Innovation Program of Beijing institute of technology under Grant No.2022CX01025。
文摘In this study,an inverse design framework was established to find lightweight honeycomb structures(HCSs)with high impact resistance.The hybrid HCS,composed of re-entrant(RE)and elliptical annular re-entrant(EARE)honeycomb cells,was created by constructing arrangement matrices to achieve structural lightweight.The machine learning(ML)framework consisted of a neural network(NN)forward regression model for predicting impact resistance and a multi-objective optimization algorithm for generating high-performance designs.The surrogate of the local design space was initially realized by establishing the NN in the small sample dataset,and the active learning strategy was used to continuously extended the local optimal design until the model converged in the global space.The results indicated that the active learning strategy significantly improved the inference capability of the NN model in unknown design domains.By guiding the iteration direction of the optimization algorithm,lightweight designs with high impact resistance were identified.The energy absorption capacity of the optimal design reached 94.98%of the EARE honeycomb,while the initial peak stress and mass decreased by 28.85%and 19.91%,respectively.Furthermore,Shapley Additive Explanations(SHAP)for global explanation of the NN indicated a strong correlation between the arrangement mode of HCS and its impact resistance.By reducing the stiffness of the cells at the top boundary of the structure,the initial impact damage sustained by the structure can be significantly improved.Overall,this study proposed a general lightweight design method for array structures under impact loads,which is beneficial for the widespread application of honeycomb-based protective structures.
基金supported by the Beijing Natural Science Foundation:7222220National Natural Science Foundation of China (82001039)+2 种基金Research Foundation of Peking University School and Hospital of Stomatology:PKUSS20230117The Fundamental Research Funds for the Central UniversitiesYoung Elite Scientist Sponsorship Program by CAST (No.2019QNRC001 to Y.L.L)。
文摘Understanding the acid resistance mechanism of S.mutans is crucial for preventing dental caries.FtsZ is the core protein for cell division in bacteria that can polymerize into Z-rings and drive cytokinesis.Our previous study revealed that the FtsZ in S.mutans(SmFtsZ) has higher self-assembly and GTPase activity under acidic stress,which may be responsible for acid resistance and ca riogenesis of S.mutans.However,the functional structure mechanism of SmFtsZ under low pH conditions is still unclear.Here,we further reported the crystal structure of S.mutans FtsZ,revealing a unique lateral interface.Through protein polymerization and GTPase activity assay,we experimentally demonstrated that the mutation of Arg68 on this lateral interface significantly reduced the functional activity of FtsZ in an acidic environment.The phenotype assay and rat caries model further showed that the mutation of Arg68 effectively inhibited the acid resistance of S.mutans and the occurrence and progress of dental caries in vivo.By employing a molecular dynamics simulation analysis,we conclude that the mutation of Arg68 disrupts the conformation change necessary for SmFtsZ polymerization under acidic conditions.Our study proposes a novel mechanism to maintain FtsZ function in bacteria and could be a potential target for antimicrobial drugs to inhibit the growth of S.mutans in acidic environments.
文摘This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.
基金supported by the National Key Research and Development Program of China (Grant Nos.2022YFA1403202 and 2023YFA1406101)the CAS Superconducting Research Project (Grant No.SCZX-0101)。
文摘We report the discovery of bulk superconductivity in a new quinary intermetallic compound Th_(2)Mo_(2)Ru_(2)Si_(4)C,crystallized in a collapsed 22241-type structure.This structure is characterized by the intergrowth of ThMo_(2)Si_(2)C and ThRu_(2)Si_(2) units interconnected by equivalent Si-Si bonds that enhance inter-sublattice coupling.The refined lattice parameters are a=4.2212(1)Å and c=20.3899(7)Å.Electrical resistivity and magnetic susceptibility measurements of both polycrystalline and single-crystal samples consistently demonstrate bulk superconductivity with a transition temperature T_(c)∼6.0 K significantly higher than those of the constituent compound ThMo_(2)Si_(2)C and its related analogs.Under magnetic fields,the superconducting state exhibits a nearly isotropic behavior,which is attributed to strong covalent interlayer coupling.First-principles calculations reveal a substantial contribution from the Mo-d orbitals near the Fermi level,which exhibit several band-crossing points.The enhancement in T_(c) can be attributed to the synergistic combination of the valence electron concentration and the inter-sublattice self-doping effect between the[Ru_(2)Si_(2)]and[Mo_(2)Si_(2)C]layers.
基金funded by the National Key R&D Program of China(No.2024YFB3713703,2023YFB3712700,2021YFB3702101)the Fundamental Research Funds for the Central Universities(2024IAIS-ZD004)+1 种基金State Key Laboratory of Mechanical Transmission for Advanced Equipment Open Fund(SKLMT-ZZKT-2024Z04)the support by the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(311021013).
文摘Magnesium(Mg)and its alloys,as the lowest density metallic structural alloys,have been widely employed across various industries,including electronic communication,automotive,aircraft,defense,and military.While Mg alloys are susceptible to issues like pitting or stress corrosion when utilized as key structural components in humid environments,resulting in corrosion fatigue,stress corrosion cracking,or even complete corrosion failure,which impedes their broader applications.To address these disadvantages of Mg alloys,surface selfnanocrystallization(SSNC),involving refining the grain size to create a nanosurface layer,has been proposed to delay or mitigate the initiation and propagation of cracks,thereby significantly enhancing corrosion resistance.The purpose of this paper is to review the effects of various surface self-nanocrystallization techniques,including surface mechanical attrition treatment,high-energy shot peening,ultrasonic surface rolling processing,laser shock peening,and supersonic particle bombardment,on the microstructure and properties of Mg alloys.Additionally,the mechanisms underlying the surface nanocrystallization-induced microstructural evolution in Mg alloys and the factors influencing their corrosion resistance are systematically summarized.Finally,the current challenges and prospects are discussed as well.
基金supported by the National Natural Science Foundation of China(Grant No.52206092)the National Key R&D Program of China(Grant No.2024YFF0508900)+1 种基金the Big Data Computing Center of Southeast Universitythe Center for Fundamental and Interdisciplinary Sciences of Southeast University。
文摘Efficient thermal management is critical to the reliability and performance of nanoscale electronic and photonic devices,particularly those incorporating multilayer structures.In this study,non-equilibrium molecular dynamics simulations were conducted to systematically investigate the effects of temperature,penetration depth,and Si layer thickness on the interfacial thermal resistance(ITR)in nanometer-scale Mo/Si multilayers,widely employed in extreme ultraviolet lithography.The results indicate that:(i)temperature variations exert a negligible influence on the ITR of amorphous Mo/Si interfaces,which remains stable across the range of 200-900 K;(ii)increasing penetration depth enhances the overlap of phonon density of states,thereby significantly reducing ITR;(iii)the ITR decreases with increasing Si thickness up to4.2 nm due to quasi-ballistic phonon transport,but rises again as phonon scattering becomes more pronounced at larger thicknesses.This study provides quantitative insights into heat transfer mechanisms at amorphous interfaces and also offers a feasible strategy for tailoring interfacial thermal transport through structural design.
基金supported by National High-Tech R&D Program of China(Grant 2014AA06A612)the project of the China Geological Survey(Grants 1212011220263,1212010914049 and 1212011121273)
文摘The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate.The long-period magnetotelluric(LMT)and broadband magnetotelluric(MT)techniques are both used to study the deep electrical conductivity structure in this region;magnetic and gravity surveys are also performed along the profile.According to the 2-D resistivity model along the Yanyuan-Yongshan profile,a high-conductivity layer(HCL)exists widely in the crust,and a high-resistivity block(HRB)exists widely in the upper mantle in general,as seen by the fact that a large HCL exists from the western Jinpingshan tectonic zone to the eastern Mabian tectonic zone in the crust,while the HRB found in the Panxi tectonic zone is of abnormally high resistivity in that background compared to both sides of Panxi tectonic zone.In addition,the gravity and magnetic field anomalies are of high value.Combined with geological data,the results indicate that there probably exists basic or ultrabasic rock with a large thickness in the lithosphere in the Panxi axial region,which indicates that fracture activity once occurred in the lithosphere.As a result,we can infer that the high-resistivity zone in the Panxi lithosphere is the eruption channel for Permian Emeishan basalt and the accumulation channel for basic and ultrabasic rock.The seismic sources along the profile are counted according to seismic record data.The results indicate that the most violent earthquake sources are located at the binding site of the HRB and the HCL,where the tectonic activity zone is generally acknowledged to be;however,the earthquakes occurring in the HCL are not so violent,which reflects the fact that the HCL is a plastic layer,and the fracture threshold of a plastic layer is low generally,making high stress difficult to accumulate but easy to release in the layer.As a result,a higher number of smaller earthquakes occurred in the HCL at Daliangshan tectonic zone,and violent earthquakes occurred at the binding site of high-and low-resistivity blocks at the Panxi tectonic zone.
基金Supported by the Natural Science Foundation of Shaanxi Province,China(2010JM5003)
文摘The influence of pore structure difference on rock electrical characteristics of reservoir and oil reservoir was analyzed taking Triassic Chang 6 reservoir in Block Yanwumao in the middle of Ordos Basin as an example. The relationship between the pore structure difference and the low resistivity oil layer was revealed and demonstrated through core observation, lab experiments, geological research, well log interpretation and trial production etc. The results show that there were two kinds of oil layers in Chang 6 oil layer set, normal oil layer and low resistivity oil layer in the region, corresponding to two types of pore structures, pore type mono-medium and micro-fracture-pore type double-medium; the development of micro-fracture changed greatly the micro-pore structure of the reservoir, and the pore structure difference had an important influence on the rock electrical characteristics of the extra-low permeability sandstone reservoir and oil reservoir; the normal oil layers had obvious characteristics of pore-type mono-medium, and were concentrated in Chang 61, Chang 6232 and Chang 62; the low resistivity oil layers had obvious characteristics of micro-fracture-pore type double-medium, which were mainly distributed in Chang 612 and Chang 63. The mud filtrate penetrated deep into the oil layers along the micro-cracks, leading to sharp reduction of resistivity, and thus low resistivity of the oil layer; the low resistivity oil layers had better storage capacity and higher productivity than the normal oil layers.
基金supported by the Fundamental Research Funds for the Central Universities (No. CUG090106)the National Natural Science Foundation of China (No. 41074086)the Ph.D. Programs Foundation of Ministry of Education of China (No. 20100145120006)
文摘To understand the electrical structure of the Sulu（苏鲁） terrane,we analyzed the resis-tivity logs of the Chinese Continental Scientific Drilling main hole（CCSD-MH） and obtained the statis-tical characteristics of the resistivity log of ultrahigh-pressure（UHP） metamorphic rocks.To check the logs＇ quality,we compared the resistivity log data with the core test data.The two datasets show a good coherence.On the whole,the resistivity of the UHP metamorphic rocks from the CCSD-MH is very high（mostly higher than 1 000 ？？m）.From orthogneiss to paragneiss,amphibolite,retrograded eclogite,rutile eclogite,phengite eclogite,and ultramafic rock,the resistivity decreases gradually.The fracture zone,enrichment of metal minerals,and serpentinization of peridotite can probably cause the decrease of resistivity.Comparing the electrical structure of the crust of Dabie（大别） terrane and Sulu terrane,we can conclude that（1） the electrical structure of the crust of Dabie terrane and Sulu terrane shows a very big difference,（2） the high-resistivity zone of the north Sulu orogen extended to a very great depth（60 km）,but the high-resistivity zone of Dabie orogen is over the depth of 25 km.
文摘The effect of the Ni/Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi5-xCux series was studied.The value of temperature of phase transition(T_(ph))estimated from temperature dependence of electrical resistance varied non-linearly across copper doping from 32.5 K(x=0.0)to 29.1 K(x=5.0).The value of residual resistivity(ρo)estimated at low temperature range decreased from 27.28μΩcm(x=0.0)to 9.44μΩcm(x=5.0),which was discussed as the influence of microstructure.In order to describe the temperature dependence of resistivityρ(T)a variety of approaches were applied due to different scattering mechanisms occurring at high and low temperature ranges.The change withinρ(T)curvature was evidenced at low temperature range across copper doping.The temperature variation of the resistivity was quite peculiar for Cu-rich compounds(x=4.8,x=5.0),which might be correlated with the incommensurate magnetic structure derived from the weakly negative interaction between the nearest neighbours of Gd.The correlation between microstructure and resistivity was observed.
文摘A new type of phosphor Sr2ZrO4 with one-dimensional structure was prepared bysolid reaction and its luminescence is seen at room temperature. The excitation and emissionspectra were measured and display broad maximum at 354 nm and 386 nm respectively. Themechanism of this luminescence is ascribed to charge transfer.
文摘In this paper, on the basis of the heat conduction equation without consideration of the advection and turbulence effects, one-dimensional model for describing surface sea temperature ( T1), bottom sea temperature ( Tt ) and the thickness of the upper homogeneous layer ( h ) is developed in terms of the dimensionless temperature θT and depth η and self-simulation function θT - f(η) of vertical temperature profile by means of historical temperature data.The results of trial prediction with our one-dimensional model on T, Th, h , the thickness and gradient of thermocline are satisfactory to some extent.
基金supported by the Czech Science Foundation under the Grant No.15-01100Ssupported within the program of Czech Research Infrastructures(No.LM2011025)+2 种基金supported by the Grant Agency of the Charles University under the Project No.1332314supported by the Czech-Polish cooperation in the scope of Czech-Polish project7AMB14PL036(9004/R14/R15)European Regional Development Fund under the Infrastructure and Environment Programme
文摘The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, Nb leads to a stabilization of the cubic γ-U phase, while it requires much higher Zr concentrations （≥30 at.% Zr）. All U-T splats become superconducting with Tc in the range of 0.61-2.11 K. A good agreement of the experimentally observed specific-heat jump at Tc with that from BCS theory prediction was obtained for U-15 at.% Mo consisting of the γ-U phase with an ideal bcc A2 structure.
基金supported by the Natural Science Foundation of the Ministry of Education of China (No.207068)Henan Province (No.0611023000)the Education Department of Henan Province (No.2007150003,2007150011)
文摘A new one-dimensional polymeric complex [Cd（SCN）2（H2O）]L （L = N,N′-bis（furan- 2-ylmethylene）hydrazine） has been synthesized and characterized by IR, UV spectra, TG-DTA technique and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, pace group P1^- with a = 5.9268（8）, b = 10.8678（15）, c = 13.3671（19） A, α = 109.295（2）, β = 95.092（2）, γ = 97.8580（10）°, V = 796.70（19）A^3, Z = 2, C12H10CdN4O3S2, Mr = 434.76, μ = 1.648 mm^-1, Dc = 1.812 g/cm^3, F（000） = 428, R = 0.0308 and wR = 0.0769. The crystal structure reveals that the structure of [Cd（SCN）2（H2O）]n features di-μ-1,3-thiocyante bridges and 1D chains. The octahedrally coordinated Cd atom is surrounded by one oxygen atom from water molecule, three S atoms and two N atoms from five di-μ-1,3 thiocyanato bridges. The Cd atoms are connected by two di-μ-1,3 thiocyanato bridges with the Cd（1）…Cd（1A） separation of 4.239（1） A and Cd（1）...Cd（1B） of 5.852（1）/~. In addition, the one-dimensional straight chain structure is further connected by multiform intermolecular N-H…O hydrogen bonds and π-π interactions to form a three-dimensional supramolecular structure.
基金This work was financially supported by the NNSF of China (No. 20173063), the State Key Basic Research and Development Plan of China (001CB108906) and the NSF of Fujian Province (E0020001)
文摘A new zinc polymer, {Zn（O2CC12H8CO2）（H2O）}, or {Zn（DPHA）（H2O）}n （O2CC12H8CO2, DPHA = 1,1′ -biphenyl-2,2′-dicarboxylate dianion） has been synthesized under hydrothermal conditions. The crystal is of monoclinic, space group P21/c with a = 12.8418（5）, b = 5.9505（2）, c = 17.2989（5） A, β = 104.020（2）°, V = 1282.52（8） A^3, C14H10O5Zn, Mr= 323.61, Z = 4, Dc = 1.676 g/cm^3,μ = 1.930 mm^-1, F（000） = 656, R = 0.0766 and wR = 0.1871 for 1775 observed reflections （I 〉 2σ（I））. It consists of Zn2（DPHA）2（H2O）2 units, which are further extended into a one-dimensional double helical-chain polymer via Zn-O bonding. The hydrogen bonding interactions extend the helical chains into a two-dimensional layer structure.
文摘Reaction of (NH_4)_2MoS_4 with AgI in α-MePy gives the title com- pound,an X-ray analysis of which shows that the molecule forms a one-dimensional polymeric chain with continuous metal-metal bonds.
文摘SbNb_3(Se_2)_6, Mr=1347.99, tetragonal, P4/mnc,a=b=9.466(2),c=19.075(3) ,V=1709.0(4) ~3, z=4, Dm=5.2(2)g/cm^3, Dc=5.24g/c^3,λ(Moka)=0.71069 ,μ=287.39cm^(-1), F(000)=2328,T=276(1)k,R=5.9％,Rw=6.9％, for 479 unique observed reflections (1>3σ(1)).The structure is composed of [Nb3(Se2)s]∞ chains along the c axis with Sb atoms inserted between them.
文摘The complexe{[K(DB18-crown-6)]_(2)(CH_(3)CN)}[Pt(SCN)_(4)]was synthesized and characterized by elemental analysis,IR spectrum and X-ray diffraction analysis.The complexe belongs to monoclinic,space group c2/c with cell dimensions,a=2.5904(8),6=1.3653(4),c-1.84706(6)nm,β=123.811(4)°,V=5-339(3)nm^(3),Z=4,.Dcalcd=l.577 g/cm^(3),F(000)=2552,R_(1)=0.051 l,wR_(2)=0.1411.The complexe shows one-dimensional chain of{[K(DB18-crown-6)]+complex cation and[Pt(SCN),i]2-complex anion bridged by N atom of CHaCN moleculer between two[K(DB18-crown-6)]_(2)[Pt(SCN)_(4)]groups respectively.
基金sponsored by National Natural Science Foundation of China(No.52302121,No.52203386)Shanghai Sailing Program(No.23YF1454700)+1 种基金Shanghai Natural Science Foundation(No.23ZR1472700)Shanghai Post-doctoral Excellent Program(No.2022664).
文摘With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.
基金Item Sponsored by National High-Tech Research and Development Program(863 Program)of China(2009AA03Z529)
文摘In an aqueous solution of the mixtures of γ-amino propyl triethoxy silane and γ-glycidoxy propyl trimethoxy silane, a composite silane conversion coating was developed on galvanized steel. FESEM （field emission scanning electron microscope）, XPS （X-ray photoelectron spectroscopy）, ATR FTIR （attenuated total reflection Flourier transform infrared spectroscopy） and SST （salt spray test） were used to characterize the obtained composite silane conversion coating and also the coating formation process was studied. The result showed that the surface of the composite silane conversion coating was complete, consecutive and compact. The coating could endure a neutral salt spray test for 72 h without corrosion. The result of salt spray test indicated that the composite silane conversion coating can provide a better corrosion inhibition than the coating which was composed of the single silane. Based on observation and analysis, it was proposed that the formation process of the silane coating on zinc should consist of three steps： the hydrolysis of the silane molecules, silane chemical adsorption and silane crosslinking condensation. The crosslinking reactions took place between ~＇-amino propyl triethoxy and ＂/-glycidoxy propyl trimethoxy silane during the forming process of the coating, and a high crosslinked density interpenetrating structure network was obtained, so the composite silane conversion coating could keep the corrosive substances from the zinc more effectively.
