A series of Al-Ti-B master alloys were prepared by different preparation routes,and the TiB2 particles in the master alloys were extracted and analyzed.It is found that the forming process has significant influence on...A series of Al-Ti-B master alloys were prepared by different preparation routes,and the TiB2 particles in the master alloys were extracted and analyzed.It is found that the forming process has significant influence on the three-dimensional morphology of TiB2 particles.Different preparation routes result in different reaction forms,which accounts for the morphology variation of TiB2 particles.When the Al-Ti-B master alloy is prepared using ＂halide salt＂ route,TiB2 particles exhibit hexagonal platelet morphology and are independent with each other.In addition,the reaction temperature almost does not have influence on the morphology of TiB2 particles.However,TiB2 particles exhibit different morphologies at different reaction temperatures when the master alloys are prepared with Al-3B and Ti sponge.When the master alloy is prepared at 850 ℃,a kind of TiB2 particle agglomeration forms with a size larger than 5 μm.The TiB2 particles change to layered stacking morphology even dendritic morphology with the reaction temperature reaching up to 1200 ℃.展开更多
A three-dimensional （3-D） modified cellular automaton （MCA） method was developed for simulating the dendrite morphology of cubic system alloys. Two-dimensional （2-D） equations of growth velocities of the dendrit...A three-dimensional （3-D） modified cellular automaton （MCA） method was developed for simulating the dendrite morphology of cubic system alloys. Two-dimensional （2-D） equations of growth velocities of the dendrite tip, interface curvature and anisotropy of the surface energy were extended to 3-D system in the model. Therefore, the model was able to describe the morphology evolution of 3-D dendrites. Then, the model was applied to simulate the mechanism of spacing adjustment for 3-D columnar dendrite growth, and the competitive growth of columnar dendrites with different preferred growth orientations under constant temperature gradient and pulling velocity. Directional solidification experiments of NH4Cl-H2O transparent alloy were performed. It was found that the simulated results compared well with the experimental results. Therefore, the model was reliable for simulating the 3-D dendrite growth of cubic system alloys.展开更多
Morphological alterations in dendritic spines have been linked to changes in functional communication between neurons that affect learning and memory.Kinesin-4 KIF21A helps organize the microtubule-actin network at th...Morphological alterations in dendritic spines have been linked to changes in functional communication between neurons that affect learning and memory.Kinesin-4 KIF21A helps organize the microtubule-actin network at the cell cortex by interacting with KANK1;however,whether KIF21A modulates dendritic structure and function in neurons remains unknown.In this study,we found that KIF21A was distributed in a subset of dendritic spines,and that these KIF21A-positive spines were larger and more structurally plastic than KIF21A-negative spines.Furthermore,the interaction between KIF21A and KANK1 was found to be critical for dendritic spine morphogenesis and synaptic plasticity.Knockdown of either KIF21A or KANK1 inhibited dendritic spine morphogenesis and dendritic branching,and these deficits were fully rescued by coexpressing full-length KIF21A or KANK1,but not by proteins with mutations disrupting direct binding between KIF21A and KANK1 or binding between KANK1 and talin1.Knocking down KIF21A in the hippocampus of rats inhibited the amplitudes of long-term potentiation induced by high-frequency stimulation and negatively impacted the animals’cognitive abilities.Taken together,our findings demonstrate the function of KIF21A in modulating spine morphology and provide insight into its role in synaptic function.展开更多
In a sample quenched during equiaxed solidification of an Al-5 wt.% Cu alloy, the multi-scales 3-dimensional morphology of equiaxed dendrite was observed. The slim primary stem and secondary branches constitute the fr...In a sample quenched during equiaxed solidification of an Al-5 wt.% Cu alloy, the multi-scales 3-dimensional morphology of equiaxed dendrite was observed. The slim primary stem and secondary branches constitute the frame of dendrite, and rows of dense tertiary branches further divide the 3-dimensional space. In the divided space, the quartic branches grow further. The dendritic branches,which are perpendicular to each other, can change their growth directions and coalesce into a whole. In the tertiary branches and quartic branches, the formation of double branch structures is induced by competitive growth. The branch that wins in the competitive growth will produce a cabbage-like structure by wrapping the failed branches. In addition, the side branch can also wrap the original parent branch to produce cabbage-like structures. Depending on the historical growth direction, the dendritic arms can form vein-like and spicate structures, and the shapes of single dendritic arm may be the cylinder, plate and trapezoid platform. According to the compositions and etching morphology, the single dendritic arm in the final solidification structures should coalesce from a fine porous structure. The porous structures at different length-scales are principally induced by the preferential growth. Based on 3-dimensional morphology of equiaxed dendrite, a new research object for the investigation of microsegregation was suggested.展开更多
The normal vector of migration direction in the solid-liquid interface of dendrites was used to describe the phase-field governing equation. By using the three angles formed by the normal vector for the migration dire...The normal vector of migration direction in the solid-liquid interface of dendrites was used to describe the phase-field governing equation. By using the three angles formed by the normal vector for the migration direction of the dendritic growth interface and the coordinate axes of the simulation region, the authors expressed the interfacial anisotropy equation, and built a phase-field model for the competitive growth of multiple grains. Taking a Al-2%mole-Cu binary alloy as an example, the competitive growth of multiple grains during isothermal solidification was simulated by applying parallel computing techniques. In addition, the phase field simulation results were verified by the experimental method. The simulation results show that the competitive growth of equiaxed dendrite is divided into two types: the first occurs during the process of competitive growth, the tips of primary dendrite on different grains taking part in the competition stop growing in their optimal growth direction; the second also occurs during competitive growth, the tips of primary dendrite which participate in the competition on different grains never stop growing in their optimal growth direction. The dendritic morphologies of the first competition growth type are divided into two types. Primary dendrites of grains taking part in the competition stop growing in their optimal growth direction and the competition plane enlarges when neither one wins the competition. However, when one wins the competition, the primary dendrites of grains with superiority go through the blocking grains and continue to grow in their optimal growth direction. The primary dendrites of inferior grains stop growing in their optimal growth direction and then instead grow in those areas without obstacles. The dendritic morphology of the second competition-growth type is shown to be the deformation of primary dendrites, which are mainly represented as the deflection and bending observed from different views. Compared with the metallographic picture, the simulation results can show the morphology of the competitive growth in all directions, so this simulation method can better characterize the competitive growth process.展开更多
Three-dimensional morphology of ferrite allotriomorphs nucleated at grain boundary edges in low carbon steel was revealed by means of serial sectioning in conjunction with computer-aided three-dimensional reconstructi...Three-dimensional morphology of ferrite allotriomorphs nucleated at grain boundary edges in low carbon steel was revealed by means of serial sectioning in conjunction with computer-aided three-dimensional reconstruction techniques. The typical morphology of them was of an elongated triangular pyramid. The length, width and thickness of ferrite allotriomorphs were measured on the basis of three-dimensional reconstructed images. The aspect ratio （length/width） of them was 4.5 on an average and scattered from 3 to 6. The measured sizes were smaller than calculated ones, which was probably attributed to solute drag-like effect of manganese in the alloy.展开更多
The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear...The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear-formed fractures are prone to secondary instability,posing a severe threat to deep engineering.Although numerous studies regarding three-dimensional(3D)morphologies of fracture surfaces have been conducted,the understanding of shear-formed fractures under TM coupling conditions is limited.In this study,direct shear tests of intact granite under various TM coupling conditions were conducted,followed by 3D laser scanning tests of shear-formed fractures.Test results demonstrated that the peak shear strength of intact granite is positively correlated with the normal stress,whereas it is negatively correlated with the temperature.The internal friction angle and cohesion of intact granite significantly decrease with an increase in the temperature.The anisotropy,roughness value,and height of the asperities on the fracture surfaces are reduced as the normal stress increases,whereas their variation trends are the opposite as the temperature increases.The macroscopic failure mode of intact granite under TM coupling conditions is dominated by mixed tensileeshear and shear failures.As the normal stress increases,intragranular fractures are developed ranging from a local to a global distribution,and the macroscopic failure mode of intact granite changes from mixed tensileeshear to shear failure.Finally,3D morphological characteristics of the asperities on the shear-formed fracture surfaces were analyzed,and a quadrangular pyramid conceptual model representing these asperities was proposed and sufficiently verified.展开更多
The formation of intragranular ferrite at inclusions was analyzed by SEM-EDX in a vanadium microalloyed steel with an excess amount of sulfur. The precipitation of MnS at aluminum oxides may result in Mn depletion, wh...The formation of intragranular ferrite at inclusions was analyzed by SEM-EDX in a vanadium microalloyed steel with an excess amount of sulfur. The precipitation of MnS at aluminum oxides may result in Mn depletion, which, in turn, promotes the formation of intragranular ferrite. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite is nearly equiaxed whereas it is plate-like at lower temperatures.展开更多
Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional(3D) X-ray micro-computed tomography, Electron Back...Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional(3D) X-ray micro-computed tomography, Electron Back-scattered Diffraction(EBSD) and X-ray Diffraction(XRD). The application of high static axial magnetic field(5T) during directional solidification was found to destabilize the solid/liquid interface and cause the growth direction of dendrite deviate from thermal gradient, leading to irregular solid/liquid interfacial shape and cellular to dendritic morphology transition. The thermoelectric magnetic convection(TEMC) caused by the interaction of thermoelectric effect and magnetic field was supposed to be responsible for the transition. In addition, the EBSD and XRD results confirm that the preferred growth direction of α-Al was found to transform from the traditionally expected <100> to<110>. The dendrite orientation transition(DOT) in Al-10 wt.%Zn alloy can be attributed to the effect of applied magnetic field on the anisotropy of crystal during solidification. The result indicates the potential application of high static magnetic field in altering the morphology and preferred growth direction of dendrite during directional solidification.展开更多
A numerical model based on the cellular automaton method for the three-dimensional simulation of dendritic growth of magnesium alloy was developed. The growth ki- netics was calculated from the complete solution of th...A numerical model based on the cellular automaton method for the three-dimensional simulation of dendritic growth of magnesium alloy was developed. The growth ki- netics was calculated from the complete solution of the transport equations. By con- structing a three-dimensional anisotropy model with the cubic CA cells, simulation of dendritic growth of magnesium alloy with six-fold symmetry in the basal plane was achieved. The model was applied to simulate the equiaxed dendritic growth and columnar dendritic growth under directional solidification, and its capability was addressed by comparing the simulated results to experimental results and those in the previously published works. Meanwhile, the three-dimensional simulated results were also compared with that of in two dimensions, offering a deep insight into the microstructure formation of magnesium alloy during solidification.展开更多
This study aimed to examine the differences in the morphological properties and proliferation of olfactory ensheathing cells in three-dimensional culture on collagen-heparan sulfate biological scaffolds and in two-dim...This study aimed to examine the differences in the morphological properties and proliferation of olfactory ensheathing cells in three-dimensional culture on collagen-heparan sulfate biological scaffolds and in two-dimensional culture on common flat culture plates. The proliferation rate of olfactory ensheathing cells in three-dimensional culture was higher than that in two-dimensional culture, as detected by an M-I-r assay. In addition, more than half of the olfactory ensheathing cells subcultured using the trypsinization method in three-dimensional culture displayed a spindly Schwann cell-like morphology with extremely long processes, while they showed a flat astrocyte-like morphology in two-dimensional culture. Moreover, spindle-shaped olfactory ensheathing cells tended to adopt an elongated bipolar morphology under both culture conditions. Experimental findings indicate that the morphological properties and proliferation of olfactory ensheathing cells in three-dimensional culture on collagen-heparan sulfate biological scaffolds are better than those in two-dimensional culture.展开更多
In this paper,the diversity of complicated dendrite microstructure and its evolution behavior during solidification in different magnesium alloys under various processing conditions were illustrated using synchrotron ...In this paper,the diversity of complicated dendrite microstructure and its evolution behavior during solidification in different magnesium alloys under various processing conditions were illustrated using synchrotron X-ray imaging technique.A variety of dendritic morphologies and branching structures were revealed,i.e.,sixfold plate-like symmetric structure in Mg-Al-based structure,12-branch structure in Mg-Zn-based alloys and 18-branch structure in Mg-Sn-and Mg-Ca-based alloys as well as seaweed like hyper-branched structure in Mg-38wt%Zn alloy.In addition,a dendrite morphology and orientation transition with increasing addition of Zn content were also observed in Mg-Zn alloy,with dendrite growth pattern transform from anisotropy(low Zn addition)with sixfold symmetric snow-flake structure to relative isotropy(intermediate Zn addition)where seaweed morphology presented and then back to anisotropy(high Zn addition)when only 12 branches with preferred<11 2 1>orientations were observed.The phase-field model representing the typical dendritic morphologies and branching structures under various conditions was also depicted and discussed.Further,the two-dimensional(2D)real-time dendrite growth dynamics in different Mg-based alloys captured using synchrotron X-ray radiography for unveiling the originate of theα-Mg dendrite was reviewed.Following this,the four-dimensional(3D+time)synchrotron X-ray tomographic in situ observation of dendritic morphology evolution indicating the formation mechanism of the diverse dendritic morphology during Mg-Sn-and Mg-Zn-based alloys was also summarized.Finally,the future study on exploring the complicated dendritic morphologies and their origination during solidification of Mg-based alloys is prospected.展开更多
The influence of periodic pressure with low and high frequencies on microstructure and dendritic sidebranching was studied by using 3-D phase field method. In both low and high frequency cases, the variation trend of ...The influence of periodic pressure with low and high frequencies on microstructure and dendritic sidebranching was studied by using 3-D phase field method. In both low and high frequency cases, the variation trend of SDAS (secondary dendritic arm spacing) with increasing pressure frequency is opposite to that of sidebranching frequency, while the variation trend of the average length of secondary arms is consistent with that of sidebranching frequency. The high sidebranching frequency indicates that more secondary arms share the whole driving force of dendrite growth, resulting in lower driving force for each one and leading to less developed secondary arms. The smallest SDAS is obtained when perturbed by the periodic pressure with the frequency of 0.157/τ0 (τ0 is the physical unit of time in the dimensionless phase field model) and 2.200/τ0 in low and high frequency cases, respectively. Comparisons of dendritic morphology and secondary arms are made between the low and high frequency cases. Firstly, in the low frequency case, secondary arms are luxuriant especially when pressure frequency is low, with many high-order side branches stretching out. Secondly, the average length of secondary arms in primary dendrite is longer in the low frequency case than that without pressure, and much longer than that in the high frequency case. Thirdly, the dendrite tip without side branches in the high frequency case is much longer than that in the low frequency case. All of the differences in dendritic morphology and sidebranching in the two cases can be attributed to the different modulation mechanism. In the low frequency case, periodic pressure determines tip velocity and then modulates sidebranching directly. While in the high frequency case, periodic pressure cannot determine sidebranching directly, but via modulating tiny protuberances in dendrite tip, part of which evolves into side branch. In this case, the tiny protuberances take part of the whole driving force, leading to less developed secondary arms.展开更多
The interface morphologies and microstruetures of the directionally solidified Ni-5wt-% Cu alloy during dendrite-to-cell transition at high growth rates have been investigated with a newly developed apparatus for unid...The interface morphologies and microstruetures of the directionally solidified Ni-5wt-% Cu alloy during dendrite-to-cell transition at high growth rates have been investigated with a newly developed apparatus for unidirectional solidification with the temperature gradient at the solid/liquid interface higher than 1000 K/cm.The results show that in the vicinity of dendrite-to-cell transition point,the well developed sidebranches become shrivelled with the increase of growth rate and disappear at the dendrite-to-cell transition,and the primary spacing decreases simultaneously.Moreover,the length of mushy zone decreases greatly dur- ing the dendrite-to-cell transition.Cells obtained at high growth rates have very similar morphologies to those at low growth rates,but with much smaller cell spacings and unsmoothed cell walls which may be attributed to the different stability conditions of the cell walls at low and high growth rates respectively.展开更多
The sedimentary bed morphology modulated by the wake flow of a wall-mounted flexible aquatic vegetation blade across various structural aspect ratios(A_(R)=l/b,where l and b are the length and width of the blade,respe...The sedimentary bed morphology modulated by the wake flow of a wall-mounted flexible aquatic vegetation blade across various structural aspect ratios(A_(R)=l/b,where l and b are the length and width of the blade,respectively)and incoming flow velocities was experimentally investigated in a water channel.A surface scanner was implemented to quantify bed topography,and a tomographic particle image velocimetry system was used to characterize the three-dimensional wake flows.The results showed that due to the deflection of incoming flow,the velocity magnitude increased at the lateral sides of the blade,thereby producing distinctive symmetric scour holes in these regions.The normalized morphology profiles of the sedimentary bed,which were extracted along the streamwise direction at the location of the maximum erosion depth,exhibited a self-similar pattern that closely followed a sinusoidal wave profile.The level of velocity magnitude enhancement was highly correlated to the postures of the flexible blade.At a given flow velocity,the blade with lower aspect ratios exhibited less significant deformation,causing more significant near-bed velocity enhancement in the wake deflection zone and therefore leading to higher erosion volumes.Further investigation indicated that when the blade underwent slight deformation,the larger velocity enhancement close to the bed can be attributed to more significant flow deflection effects at the lateral sides of the blade and stronger flow mixing with high momentum flows away from the bed.Supported with measurements,a basic formula was established to quantify the shear stress acting on the sedimentary bed as a function of incoming flow velocity and blade aspect ratio.展开更多
Three-dimensional（3D） histology utilizes tissue clearing techniques to turn intact tissues transparent,allowing rapid interrogation of tissue architecture in three dimensions.In this article,we summarized the availa...Three-dimensional（3D） histology utilizes tissue clearing techniques to turn intact tissues transparent,allowing rapid interrogation of tissue architecture in three dimensions.In this article,we summarized the available tissue clearing methods and classified them according to their physicochemical principles of operation,which provided a framework for one to choose the best techniques for various research settings.Recent attempts in addressing various questions regarding the degenerating and regenerating nervous system have been promising with the use of 3D histological techniques.展开更多
Arc erosion morphologies of Ag/MeO（10） electrical contact materials after 50000 operations under direct current of 19 V and 20 A and resistive load conditions were investigated using scanning electron microscope（SE...Arc erosion morphologies of Ag/MeO（10） electrical contact materials after 50000 operations under direct current of 19 V and 20 A and resistive load conditions were investigated using scanning electron microscope（SEM） and a 3D optical profiler（3DOP）. The results indicated that 3DOP could supply clearer and more detailed arc erosion morphology information. Arc erosion resistance of Ag/SnO_2（10） electrical contact material was the best and that of Ag/CuO（10） was the worst. Arc erosion morphology of Ag/MeO（10） electrical contact materials mainly included three different types. Arc erosion morphologies of Ag/ZnO（10） and Ag/SnO_2（10） electrical contact materials were mainly liquid splash and evaporation, and those of Ag/CuO（10） and Ag/CdO（10） were mainly material transfer from anode to cathode. Arc erosion morphology of Ag/SnO_2（6）In_2O_3（4） electrical contact materials included both liquid splash, evaporation and material transfer. In addition, the formation process and mechanism on arc erosion morphology of Ag/MeO（10） electrical contact materials were discussed.展开更多
The solid-liquid interracial morphology evolution was investigated in directional solidification （DS） of Al-1.5%Cu alloy （mass fraction）. The results show that the solidified microstructural evolution is gradual o...The solid-liquid interracial morphology evolution was investigated in directional solidification （DS） of Al-1.5%Cu alloy （mass fraction）. The results show that the solidified microstructural evolution is gradual other than sharp, and the microstructure patterns are interesting and diversiform at the pulling rate ranging from 30 μm/s to 1500 μm/s. Indeed, dendrite to cell transition follows this sequence： dendrites→→banded cellular dendrites→elongated cells and part of dendrites→main elongated cells and little dendrites. Moreover, the present microstructure is not normal microstructure as we saw before. Further, according to the experimental phenomenon, the dendrite to cell transition was studied theoretically. Dendrite tip shape is an important parameter to characterize the dendrite to cell transition. As the dendrite to cell transition is far from equilibrium solidification, non-equilibrium solidification is taken into consideration in calculation. Finally, it is speculated that the dendrite to cell transition would occur at the minimum tip radius.展开更多
An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, clo...An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.展开更多
Three-dimensional investigation of sulfides is required in order to improve the mechanical properties of steel by controlling the sulfides in the steel.A method including its principles and device is introduced for th...Three-dimensional investigation of sulfides is required in order to improve the mechanical properties of steel by controlling the sulfides in the steel.A method including its principles and device is introduced for the investigation of threedimensional morphology of sulfides.The method is suitable for gear steel,free cutting steel,non-quenched steel,tempered steel(ws≥0.02 wt.%),etc.The influences of current density,time,and temperature on the exposure degree of sulfide inclusions were investigated by using 16MnCrS5 steel.The best parameters of electrolytic etching of sulfur steel,as found by experimentation,are as follows:current density,37.5-52.5 mA/cm2;time,30-35 min;and temperature,—10 to 0℃.Under these conditions,the three-dimensional morphology of sulfide inclusions in sulfur-bearing steel can be exposed effectively.展开更多
基金Project(50625101) supported by the National Science Fund for Distinguished Young Scholars of ChinaProject supported by Graduate Independent Innovation Foundation of Shandong University(GIIFSDU),ChinaProject(51071097) supported by the National Natural Science Foundation of China
文摘A series of Al-Ti-B master alloys were prepared by different preparation routes,and the TiB2 particles in the master alloys were extracted and analyzed.It is found that the forming process has significant influence on the three-dimensional morphology of TiB2 particles.Different preparation routes result in different reaction forms,which accounts for the morphology variation of TiB2 particles.When the Al-Ti-B master alloy is prepared using ＂halide salt＂ route,TiB2 particles exhibit hexagonal platelet morphology and are independent with each other.In addition,the reaction temperature almost does not have influence on the morphology of TiB2 particles.However,TiB2 particles exhibit different morphologies at different reaction temperatures when the master alloys are prepared with Al-3B and Ti sponge.When the master alloy is prepared at 850 ℃,a kind of TiB2 particle agglomeration forms with a size larger than 5 μm.The TiB2 particles change to layered stacking morphology even dendritic morphology with the reaction temperature reaching up to 1200 ℃.
基金Projects (2005CB724105, 2011CB706801) supported by the National Basic Research Program of ChinaProjects (10477010, 51171089) supported by the National Natural Science Foundation of China+1 种基金Project (2007AA04Z141) supported by the High-Tech Research and Development Program of ChinaProjects (2009ZX04006-041-04, 2011ZX04014-052) supported by the Important National Science & Technology Specific
文摘A three-dimensional （3-D） modified cellular automaton （MCA） method was developed for simulating the dendrite morphology of cubic system alloys. Two-dimensional （2-D） equations of growth velocities of the dendrite tip, interface curvature and anisotropy of the surface energy were extended to 3-D system in the model. Therefore, the model was able to describe the morphology evolution of 3-D dendrites. Then, the model was applied to simulate the mechanism of spacing adjustment for 3-D columnar dendrite growth, and the competitive growth of columnar dendrites with different preferred growth orientations under constant temperature gradient and pulling velocity. Directional solidification experiments of NH4Cl-H2O transparent alloy were performed. It was found that the simulated results compared well with the experimental results. Therefore, the model was reliable for simulating the 3-D dendrite growth of cubic system alloys.
基金supported by the National Key Research and Development Program of China,No.2021ZD0202503(to AHT)the National Natural Science Foundation of China,Nos.31872759(to AHT)and 32070707(to CF)+1 种基金Shenzhen Science and Technology Program,No.RCJC20210609104333007(to ZW)Shenzhen-Hong Kong Institute of Brain Science,Shenzhen Fundamental Research Institutions,No.2021SHIBS0002(to ZW).
文摘Morphological alterations in dendritic spines have been linked to changes in functional communication between neurons that affect learning and memory.Kinesin-4 KIF21A helps organize the microtubule-actin network at the cell cortex by interacting with KANK1;however,whether KIF21A modulates dendritic structure and function in neurons remains unknown.In this study,we found that KIF21A was distributed in a subset of dendritic spines,and that these KIF21A-positive spines were larger and more structurally plastic than KIF21A-negative spines.Furthermore,the interaction between KIF21A and KANK1 was found to be critical for dendritic spine morphogenesis and synaptic plasticity.Knockdown of either KIF21A or KANK1 inhibited dendritic spine morphogenesis and dendritic branching,and these deficits were fully rescued by coexpressing full-length KIF21A or KANK1,but not by proteins with mutations disrupting direct binding between KIF21A and KANK1 or binding between KANK1 and talin1.Knocking down KIF21A in the hippocampus of rats inhibited the amplitudes of long-term potentiation induced by high-frequency stimulation and negatively impacted the animals’cognitive abilities.Taken together,our findings demonstrate the function of KIF21A in modulating spine morphology and provide insight into its role in synaptic function.
文摘In a sample quenched during equiaxed solidification of an Al-5 wt.% Cu alloy, the multi-scales 3-dimensional morphology of equiaxed dendrite was observed. The slim primary stem and secondary branches constitute the frame of dendrite, and rows of dense tertiary branches further divide the 3-dimensional space. In the divided space, the quartic branches grow further. The dendritic branches,which are perpendicular to each other, can change their growth directions and coalesce into a whole. In the tertiary branches and quartic branches, the formation of double branch structures is induced by competitive growth. The branch that wins in the competitive growth will produce a cabbage-like structure by wrapping the failed branches. In addition, the side branch can also wrap the original parent branch to produce cabbage-like structures. Depending on the historical growth direction, the dendritic arms can form vein-like and spicate structures, and the shapes of single dendritic arm may be the cylinder, plate and trapezoid platform. According to the compositions and etching morphology, the single dendritic arm in the final solidification structures should coalesce from a fine porous structure. The porous structures at different length-scales are principally induced by the preferential growth. Based on 3-dimensional morphology of equiaxed dendrite, a new research object for the investigation of microsegregation was suggested.
基金funded by the National Natural Science Foundation of China(Grant Numbers:11504149,11364024,51661020)
文摘The normal vector of migration direction in the solid-liquid interface of dendrites was used to describe the phase-field governing equation. By using the three angles formed by the normal vector for the migration direction of the dendritic growth interface and the coordinate axes of the simulation region, the authors expressed the interfacial anisotropy equation, and built a phase-field model for the competitive growth of multiple grains. Taking a Al-2%mole-Cu binary alloy as an example, the competitive growth of multiple grains during isothermal solidification was simulated by applying parallel computing techniques. In addition, the phase field simulation results were verified by the experimental method. The simulation results show that the competitive growth of equiaxed dendrite is divided into two types: the first occurs during the process of competitive growth, the tips of primary dendrite on different grains taking part in the competition stop growing in their optimal growth direction; the second also occurs during competitive growth, the tips of primary dendrite which participate in the competition on different grains never stop growing in their optimal growth direction. The dendritic morphologies of the first competition growth type are divided into two types. Primary dendrites of grains taking part in the competition stop growing in their optimal growth direction and the competition plane enlarges when neither one wins the competition. However, when one wins the competition, the primary dendrites of grains with superiority go through the blocking grains and continue to grow in their optimal growth direction. The primary dendrites of inferior grains stop growing in their optimal growth direction and then instead grow in those areas without obstacles. The dendritic morphology of the second competition-growth type is shown to be the deformation of primary dendrites, which are mainly represented as the deflection and bending observed from different views. Compared with the metallographic picture, the simulation results can show the morphology of the competitive growth in all directions, so this simulation method can better characterize the competitive growth process.
基金Item Sponsored by National Natural Science Foundation of China and Baosteel (50734004)
文摘Three-dimensional morphology of ferrite allotriomorphs nucleated at grain boundary edges in low carbon steel was revealed by means of serial sectioning in conjunction with computer-aided three-dimensional reconstruction techniques. The typical morphology of them was of an elongated triangular pyramid. The length, width and thickness of ferrite allotriomorphs were measured on the basis of three-dimensional reconstructed images. The aspect ratio （length/width） of them was 4.5 on an average and scattered from 3 to 6. The measured sizes were smaller than calculated ones, which was probably attributed to solute drag-like effect of manganese in the alloy.
基金supported by the National Natural Science Foundation of China(Grant No.51974173)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2020QD122).
文摘The shear failure of intact rock under thermo-mechanical(TM)coupling conditions is common,such as in enhanced geothermal mining and deep mine construction.Under the effect of a continuous engineering disturbance,shear-formed fractures are prone to secondary instability,posing a severe threat to deep engineering.Although numerous studies regarding three-dimensional(3D)morphologies of fracture surfaces have been conducted,the understanding of shear-formed fractures under TM coupling conditions is limited.In this study,direct shear tests of intact granite under various TM coupling conditions were conducted,followed by 3D laser scanning tests of shear-formed fractures.Test results demonstrated that the peak shear strength of intact granite is positively correlated with the normal stress,whereas it is negatively correlated with the temperature.The internal friction angle and cohesion of intact granite significantly decrease with an increase in the temperature.The anisotropy,roughness value,and height of the asperities on the fracture surfaces are reduced as the normal stress increases,whereas their variation trends are the opposite as the temperature increases.The macroscopic failure mode of intact granite under TM coupling conditions is dominated by mixed tensileeshear and shear failures.As the normal stress increases,intragranular fractures are developed ranging from a local to a global distribution,and the macroscopic failure mode of intact granite changes from mixed tensileeshear to shear failure.Finally,3D morphological characteristics of the asperities on the shear-formed fracture surfaces were analyzed,and a quadrangular pyramid conceptual model representing these asperities was proposed and sufficiently verified.
基金This project was sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, the Education Ministry of China and by the Scientific Research Fund of the Education Bureau of Hubei Province, China (No.2004Q001).
文摘The formation of intragranular ferrite at inclusions was analyzed by SEM-EDX in a vanadium microalloyed steel with an excess amount of sulfur. The precipitation of MnS at aluminum oxides may result in Mn depletion, which, in turn, promotes the formation of intragranular ferrite. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite is nearly equiaxed whereas it is plate-like at lower temperatures.
基金financially supported by National Natural Science Foundation of China (Grant Nos. 51690162, 51604171 and 51701112)China Postdoctoral Science Foundation (Grant Nos. 2017T100291 and 2017M611530)+1 种基金Shanghai Municipal Science and Technology Commission (No. 17JC1400602)open funding of State Key Laboratory of Solidification Processing in NWPU (SKLSP201602 and SKLSP201706)
文摘Effect of high static magnetic field on the dendritic morphology and growth direction in directionally solidified Al-10 wt.%Zn alloy were studied by three-dimensional(3D) X-ray micro-computed tomography, Electron Back-scattered Diffraction(EBSD) and X-ray Diffraction(XRD). The application of high static axial magnetic field(5T) during directional solidification was found to destabilize the solid/liquid interface and cause the growth direction of dendrite deviate from thermal gradient, leading to irregular solid/liquid interfacial shape and cellular to dendritic morphology transition. The thermoelectric magnetic convection(TEMC) caused by the interaction of thermoelectric effect and magnetic field was supposed to be responsible for the transition. In addition, the EBSD and XRD results confirm that the preferred growth direction of α-Al was found to transform from the traditionally expected <100> to<110>. The dendrite orientation transition(DOT) in Al-10 wt.%Zn alloy can be attributed to the effect of applied magnetic field on the anisotropy of crystal during solidification. The result indicates the potential application of high static magnetic field in altering the morphology and preferred growth direction of dendrite during directional solidification.
基金supported by the Ministry of Science and Technology of China(Nos.2011BAE21B00,2011ZX04001-071 and 2010DFA72760)
文摘A numerical model based on the cellular automaton method for the three-dimensional simulation of dendritic growth of magnesium alloy was developed. The growth ki- netics was calculated from the complete solution of the transport equations. By con- structing a three-dimensional anisotropy model with the cubic CA cells, simulation of dendritic growth of magnesium alloy with six-fold symmetry in the basal plane was achieved. The model was applied to simulate the equiaxed dendritic growth and columnar dendritic growth under directional solidification, and its capability was addressed by comparing the simulated results to experimental results and those in the previously published works. Meanwhile, the three-dimensional simulated results were also compared with that of in two dimensions, offering a deep insight into the microstructure formation of magnesium alloy during solidification.
基金sponsored by the National Natural Science Foundation of China,No. 30570628,30770751 and 81171089
文摘This study aimed to examine the differences in the morphological properties and proliferation of olfactory ensheathing cells in three-dimensional culture on collagen-heparan sulfate biological scaffolds and in two-dimensional culture on common flat culture plates. The proliferation rate of olfactory ensheathing cells in three-dimensional culture was higher than that in two-dimensional culture, as detected by an M-I-r assay. In addition, more than half of the olfactory ensheathing cells subcultured using the trypsinization method in three-dimensional culture displayed a spindly Schwann cell-like morphology with extremely long processes, while they showed a flat astrocyte-like morphology in two-dimensional culture. Moreover, spindle-shaped olfactory ensheathing cells tended to adopt an elongated bipolar morphology under both culture conditions. Experimental findings indicate that the morphological properties and proliferation of olfactory ensheathing cells in three-dimensional culture on collagen-heparan sulfate biological scaffolds are better than those in two-dimensional culture.
基金supported by National Nature Science Foundation of China(No.51701112 and No.51690162)National Key Research and Development Program of China(No.2019YFA0705300)+1 种基金Shanghai Rising-Star Program(20QA1403800 and 21QC1401500)open fund of State Key Laboratory of Solidifi cation Processing in NWPU(Grant No.SKLSP202107)。
文摘In this paper,the diversity of complicated dendrite microstructure and its evolution behavior during solidification in different magnesium alloys under various processing conditions were illustrated using synchrotron X-ray imaging technique.A variety of dendritic morphologies and branching structures were revealed,i.e.,sixfold plate-like symmetric structure in Mg-Al-based structure,12-branch structure in Mg-Zn-based alloys and 18-branch structure in Mg-Sn-and Mg-Ca-based alloys as well as seaweed like hyper-branched structure in Mg-38wt%Zn alloy.In addition,a dendrite morphology and orientation transition with increasing addition of Zn content were also observed in Mg-Zn alloy,with dendrite growth pattern transform from anisotropy(low Zn addition)with sixfold symmetric snow-flake structure to relative isotropy(intermediate Zn addition)where seaweed morphology presented and then back to anisotropy(high Zn addition)when only 12 branches with preferred<11 2 1>orientations were observed.The phase-field model representing the typical dendritic morphologies and branching structures under various conditions was also depicted and discussed.Further,the two-dimensional(2D)real-time dendrite growth dynamics in different Mg-based alloys captured using synchrotron X-ray radiography for unveiling the originate of theα-Mg dendrite was reviewed.Following this,the four-dimensional(3D+time)synchrotron X-ray tomographic in situ observation of dendritic morphology evolution indicating the formation mechanism of the diverse dendritic morphology during Mg-Sn-and Mg-Zn-based alloys was also summarized.Finally,the future study on exploring the complicated dendritic morphologies and their origination during solidification of Mg-based alloys is prospected.
基金This wurk was supputed by lhe Nativual Higl Teeltwlugy Research and Development Program of China(Grant No.2018YF E0204300)Institute Guo Qiang,Tsinghua University(Grant No.2019GQG1010).
文摘The influence of periodic pressure with low and high frequencies on microstructure and dendritic sidebranching was studied by using 3-D phase field method. In both low and high frequency cases, the variation trend of SDAS (secondary dendritic arm spacing) with increasing pressure frequency is opposite to that of sidebranching frequency, while the variation trend of the average length of secondary arms is consistent with that of sidebranching frequency. The high sidebranching frequency indicates that more secondary arms share the whole driving force of dendrite growth, resulting in lower driving force for each one and leading to less developed secondary arms. The smallest SDAS is obtained when perturbed by the periodic pressure with the frequency of 0.157/τ0 (τ0 is the physical unit of time in the dimensionless phase field model) and 2.200/τ0 in low and high frequency cases, respectively. Comparisons of dendritic morphology and secondary arms are made between the low and high frequency cases. Firstly, in the low frequency case, secondary arms are luxuriant especially when pressure frequency is low, with many high-order side branches stretching out. Secondly, the average length of secondary arms in primary dendrite is longer in the low frequency case than that without pressure, and much longer than that in the high frequency case. Thirdly, the dendrite tip without side branches in the high frequency case is much longer than that in the low frequency case. All of the differences in dendritic morphology and sidebranching in the two cases can be attributed to the different modulation mechanism. In the low frequency case, periodic pressure determines tip velocity and then modulates sidebranching directly. While in the high frequency case, periodic pressure cannot determine sidebranching directly, but via modulating tiny protuberances in dendrite tip, part of which evolves into side branch. In this case, the tiny protuberances take part of the whole driving force, leading to less developed secondary arms.
文摘The interface morphologies and microstruetures of the directionally solidified Ni-5wt-% Cu alloy during dendrite-to-cell transition at high growth rates have been investigated with a newly developed apparatus for unidirectional solidification with the temperature gradient at the solid/liquid interface higher than 1000 K/cm.The results show that in the vicinity of dendrite-to-cell transition point,the well developed sidebranches become shrivelled with the increase of growth rate and disappear at the dendrite-to-cell transition,and the primary spacing decreases simultaneously.Moreover,the length of mushy zone decreases greatly dur- ing the dendrite-to-cell transition.Cells obtained at high growth rates have very similar morphologies to those at low growth rates,but with much smaller cell spacings and unsmoothed cell walls which may be attributed to the different stability conditions of the cell walls at low and high growth rates respectively.
基金supported by the National Science Foundation under Grant No.2327916.
文摘The sedimentary bed morphology modulated by the wake flow of a wall-mounted flexible aquatic vegetation blade across various structural aspect ratios(A_(R)=l/b,where l and b are the length and width of the blade,respectively)and incoming flow velocities was experimentally investigated in a water channel.A surface scanner was implemented to quantify bed topography,and a tomographic particle image velocimetry system was used to characterize the three-dimensional wake flows.The results showed that due to the deflection of incoming flow,the velocity magnitude increased at the lateral sides of the blade,thereby producing distinctive symmetric scour holes in these regions.The normalized morphology profiles of the sedimentary bed,which were extracted along the streamwise direction at the location of the maximum erosion depth,exhibited a self-similar pattern that closely followed a sinusoidal wave profile.The level of velocity magnitude enhancement was highly correlated to the postures of the flexible blade.At a given flow velocity,the blade with lower aspect ratios exhibited less significant deformation,causing more significant near-bed velocity enhancement in the wake deflection zone and therefore leading to higher erosion volumes.Further investigation indicated that when the blade underwent slight deformation,the larger velocity enhancement close to the bed can be attributed to more significant flow deflection effects at the lateral sides of the blade and stronger flow mixing with high momentum flows away from the bed.Supported with measurements,a basic formula was established to quantify the shear stress acting on the sedimentary bed as a function of incoming flow velocity and blade aspect ratio.
文摘Three-dimensional（3D） histology utilizes tissue clearing techniques to turn intact tissues transparent,allowing rapid interrogation of tissue architecture in three dimensions.In this article,we summarized the available tissue clearing methods and classified them according to their physicochemical principles of operation,which provided a framework for one to choose the best techniques for various research settings.Recent attempts in addressing various questions regarding the degenerating and regenerating nervous system have been promising with the use of 3D histological techniques.
基金Project(2012QNZT003)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2012M521542)supported by the Postdoctoral Science Foundation of China+1 种基金Project(14JJ3014)supported by the Hunan Provincial Natural Science Foundation of ChinaProject(BSh1202)supported by the Zhejiang Provincial Postdoctoral Scientific Research Foundation of China
文摘Arc erosion morphologies of Ag/MeO（10） electrical contact materials after 50000 operations under direct current of 19 V and 20 A and resistive load conditions were investigated using scanning electron microscope（SEM） and a 3D optical profiler（3DOP）. The results indicated that 3DOP could supply clearer and more detailed arc erosion morphology information. Arc erosion resistance of Ag/SnO_2（10） electrical contact material was the best and that of Ag/CuO（10） was the worst. Arc erosion morphology of Ag/MeO（10） electrical contact materials mainly included three different types. Arc erosion morphologies of Ag/ZnO（10） and Ag/SnO_2（10） electrical contact materials were mainly liquid splash and evaporation, and those of Ag/CuO（10） and Ag/CdO（10） were mainly material transfer from anode to cathode. Arc erosion morphology of Ag/SnO_2（6）In_2O_3（4） electrical contact materials included both liquid splash, evaporation and material transfer. In addition, the formation process and mechanism on arc erosion morphology of Ag/MeO（10） electrical contact materials were discussed.
基金Project(SKLSP201418)supported by the Fund of the State Key Laboratory of Solidification Processing in North China University of Technology,ChinaProjects(51171151,51331005)supported by the National Natural Science Foundation of China
文摘The solid-liquid interracial morphology evolution was investigated in directional solidification （DS） of Al-1.5%Cu alloy （mass fraction）. The results show that the solidified microstructural evolution is gradual other than sharp, and the microstructure patterns are interesting and diversiform at the pulling rate ranging from 30 μm/s to 1500 μm/s. Indeed, dendrite to cell transition follows this sequence： dendrites→→banded cellular dendrites→elongated cells and part of dendrites→main elongated cells and little dendrites. Moreover, the present microstructure is not normal microstructure as we saw before. Further, according to the experimental phenomenon, the dendrite to cell transition was studied theoretically. Dendrite tip shape is an important parameter to characterize the dendrite to cell transition. As the dendrite to cell transition is far from equilibrium solidification, non-equilibrium solidification is taken into consideration in calculation. Finally, it is speculated that the dendrite to cell transition would occur at the minimum tip radius.
基金Project(51274250)supported by the National Natural Science Foundation of ChinaProject(2012BAK09B02-05)supported by the National Key Technology R&D Program during the 12th Five-year Plan of China
文摘An integration processing system of three-dimensional laser scanning information visualization in goaf was developed. It is provided with multiple functions, such as laser scanning information management for goaf, cloud data de-noising optimization, construction, display and operation of three-dimensional model, model editing, profile generation, calculation of goaf volume and roof area, Boolean calculation among models and interaction with the third party soft ware. Concerning this system with a concise interface, plentiful data input/output interfaces, it is featured with high integration, simple and convenient operations of applications. According to practice, in addition to being well-adapted, this system is favorably reliable and stable.
基金National Natural Science Foundation of China(Nos.51671124 and 51474142)State Key Laboratory of Development and Application Technology of Automotive Steel(Baosteel Group).
文摘Three-dimensional investigation of sulfides is required in order to improve the mechanical properties of steel by controlling the sulfides in the steel.A method including its principles and device is introduced for the investigation of threedimensional morphology of sulfides.The method is suitable for gear steel,free cutting steel,non-quenched steel,tempered steel(ws≥0.02 wt.%),etc.The influences of current density,time,and temperature on the exposure degree of sulfide inclusions were investigated by using 16MnCrS5 steel.The best parameters of electrolytic etching of sulfur steel,as found by experimentation,are as follows:current density,37.5-52.5 mA/cm2;time,30-35 min;and temperature,—10 to 0℃.Under these conditions,the three-dimensional morphology of sulfide inclusions in sulfur-bearing steel can be exposed effectively.
