Gradient-dependent plasticity is introduced into the phenomenological Johnson-Cook model to study the effects of strainhardening, strain rate sensitivity, thermal-softening, and microstructure. The microstructural eff...Gradient-dependent plasticity is introduced into the phenomenological Johnson-Cook model to study the effects of strainhardening, strain rate sensitivity, thermal-softening, and microstructure. The microstructural effect （interactions and interplay among microstructures） due to heterogeneity of texture plays an important role in the process of development or evolution of an adiabatic shear band with a certain thickness depending on the grain diameter. The distributed plastic shear strain and deformation in the shear band are derived and depend on the critical plastic shear strain corresponding to the peak flow shear stress, the coordinate or position, the internal length parameter, and the average plastic shear strain or the flow shear stress. The critical plastic shear strain, the distributed plastic shear strain, and deformation in the shear band are numerically predicted for a kind of steel deformed at a constant shear strain rate. Beyond the peak shear stress, the local plastic shear strain in the shear band is highly nonuniform and the local plastic shear deformation in the band is highly nonlinear. Shear localization is more apparent with the increase of the average plastic shear strain. The calculated distributions of the local plastic shear strain and deformation agree with the previous numerical and experimental results.展开更多
Fault rockburst is treated as a strain localization problem under dynamicloading condition considering strain gradient and strain rate. As a kind of dynamic fracturephenomena, rockburst has characteristics of strain l...Fault rockburst is treated as a strain localization problem under dynamicloading condition considering strain gradient and strain rate. As a kind of dynamic fracturephenomena, rockburst has characteristics of strain localization, which is considered as aone-dimensional shear problem subjected to normal compressive stress and tangential shear stress.The constitutive relation of rock material is bilinear (elastic and strain softening) and sensitiveto shear strain rate. The solutions proposed based on gradient-dependent plasticity show thatintense plastic strain is concentrated in fault band and the thickness of the band depends on thecharacteristic length of rock material. The post-peak stiffness of the fault band was determinedaccording to the constitutive parameters of rock material and shear strain rate. Fault bandundergoing strain softening and elastic rock mass outside the band constitute a system and theinstability criterion of the system was proposed based on energy theory. The criterion depends onthe constitutive relation of rock material, the structural size and the strain rate. The staticresult regardless of the strain rate is the special case of the present analytical solution. Highstrain rate can lead to instability of the system.展开更多
The capacity of energy absorption by fault bands after rock burst wascalculated quantitatively according to shear stress-shear deformation curves considering theinteractions and interplaying among microstructures due ...The capacity of energy absorption by fault bands after rock burst wascalculated quantitatively according to shear stress-shear deformation curves considering theinteractions and interplaying among microstructures due to the heterogeneity of strain softeningrock materials. The post-peak stiffness of rock specimens subjected to direct shear was derivedstrictly based on gradient-dependent plasticity, which can not be obtained from the classicalelastoplastic theory. Analytical solutions for the dissipated energy of rock burst were proposedwhether the slope of the post-peak shear stress-shear deformation curve is positive or not. Theanalytical solutions show that shear stress level, confining pressure, shear strength, brittleness,strain rate and heterogeneity of rock materials have important influence on the dissipated energy.The larger value of the dissipated energy means that the capacity of energy dissipation in the formof shear bands is superior and a lower magnitude of rock burst is expected under the condition ofthe same work done by external shear force. The possibility of rock burst is reduced for a lowersoftening modulus or a larger thickness of shear bands.展开更多
A method for calculation of temperature distribution in adiabatic shear band is proposed in terms of gradient-dependent plasticity where the characteristic length describes the interactions and interplaying among micr...A method for calculation of temperature distribution in adiabatic shear band is proposed in terms of gradient-dependent plasticity where the characteristic length describes the interactions and interplaying among microstructures. First, the increment of the plastic shear strain distribution in adiabatic shear band is obtained based on gradient-dependent plasticity. Then, the plastic work distribution is derived according to the current flow shear stress and the obtained increment of plastic shear strain distribution. In the light of the well-known assumption that 90% of plastic work is converted into the heat resulting in increase in temperature in adiabatic shear band, the increment of the temperature distribution is presented. Next, the average temperature increment in the shear band is calculated to compute the change in flow shear stress due to the thermal softening effect. After the actual flow shear stress considering the thermal softening effect is obtained according to the Johnson-Cook constitutive relation, the increment of the plastic shear strain distribution, the plastic work and the temperature in the next time step are recalculated until the total time is consumed. Summing the temperature distribution leads to rise in the total temperature distribution. The present calculated maximum temperature in adiabatic shear band in titanium agrees with the experimental observations. Moreover, the temperature profiles for different flow shear stresses are qualitatively consistent with experimental and numerical results. Effects of some related parameters on the temperature distribution are also predicted.展开更多
Shear localization in linear strain softening heterogeneous material under simple shear was investigated analytically. The closed-form solutions obtained based on gradient plasticity theory considering interactions an...Shear localization in linear strain softening heterogeneous material under simple shear was investigated analytically. The closed-form solutions obtained based on gradient plasticity theory considering interactions and interplaying among microstructures due to heterogeneity of metal material show that in the normal direction of shear band, elastic shear displacement is linear; while plastic and total shear displacement are non-linear. Elastic shear strain in the band is uniform and the non-uniformity of total shear displacement stems from localized plastic shear displacement. In the center of the band, plastic and total shear displacement all reach their maximum values. In strain-softening process, elastic displacement decreases as flow shear stress decreases. Contrarily, plastic and total shear displacement increase and manifest shear localization occurs progressively. Under the same shear stress level, plastic and total shear displacement increase as strain softening modulus and elastic shear modulus decrease. The present analytical solutions were compared with many experimental results and the agreement is good.展开更多
The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmiss...The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation mechanisms.These findings were discussed with the local strain measurements via digital image correlation.The results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of yielding.The small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier effect.The volume fraction of RA gradually decreased from 26.8%to 8.2%prior to fracture.In the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.展开更多
Brain plasticity-A universal tool with many variations:The study of brain plasticity has been gaining interest since almost a century and has now reached a huge amount of information(>80,000 results in PubMed).Over...Brain plasticity-A universal tool with many variations:The study of brain plasticity has been gaining interest since almost a century and has now reached a huge amount of information(>80,000 results in PubMed).Overall,different types of plasticity,including stem cell-driven genesis of new neurons(adult neurogenesis),cells in arrested maturation(dormant neurons),neuro-glial and synaptic plasticity,can coexist and contribute to grant plastic changes in the brain,from a cellular to system level(Benedetti and Couillard-Despres,2022;Bonfanti et al.,2023).展开更多
Cells,tissues,and organs are constantly subjected to the action of mechanical forces from the extracellular environment-and the nervous system is no exception.Cell-intrinsic properties such as membrane lipid compositi...Cells,tissues,and organs are constantly subjected to the action of mechanical forces from the extracellular environment-and the nervous system is no exception.Cell-intrinsic properties such as membrane lipid composition,abundance of mechanosensors,and cytoskeletal dynamics make cells more or less likely to sense these forces.Intrinsic and extrinsic cues are integrated by cells and this combined information determines the rate and dynamics of membrane protrusion growth or retraction(Yamada and Sixt,2019).Cell protrusions are extensions of the plasma membrane that play crucial roles in diverse contexts such as cell migration and neuronal synapse formation.In the nervous system,neurons are highly dynamic cells that can change the size and number of their pre-and postsynaptic elements(called synaptic boutons and dendritic spines,respectively),in response to changes in the levels of synaptic activity through a process called plasticity.Synaptic plasticity is a hallmark of the nervous system and is present throughout our lives,being required for functions like memory formation or the learning of new motor skills(Minegishi et al.,2023;Pillai and Franze,2024).展开更多
Adult neurogenesis persists after birth in the subventricular zone, with new neurons migrating to the granule cell layer and glomerular layers of the olfactory bulb, where they integrate into existing circuitry as inh...Adult neurogenesis persists after birth in the subventricular zone, with new neurons migrating to the granule cell layer and glomerular layers of the olfactory bulb, where they integrate into existing circuitry as inhibitory interneurons. The generation of these new neurons in the olfactory bulb supports both structural and functional plasticity, aiding in circuit remodeling triggered by memory and learning processes. However, the presence of these neurons, coupled with the cellular diversity within the olfactory bulb, presents an ongoing challenge in understanding its network organization and function. Moreover,the continuous integration of new neurons in the olfactory bulb plays a pivotal role in regulating olfactory information processing. This adaptive process responds to changes in epithelial composition and contributes to the formation of olfactory memories by modulating cellular connectivity within the olfactory bulb and interacting intricately with higher-order brain regions. The role of adult neurogenesis in olfactory bulb functions remains a topic of debate. Nevertheless, the functionality of the olfactory bulb is intricately linked to the organization of granule cells around mitral and tufted cells. This organizational pattern significantly impacts output, network behavior, and synaptic plasticity, which are crucial for olfactory perception and memory. Additionally, this organization is further shaped by axon terminals originating from cortical and subcortical regions. Despite the crucial role of olfactory bulb in brain functions and behaviors related to olfaction, these complex and highly interconnected processes have not been comprehensively studied as a whole. Therefore, this manuscript aims to discuss our current understanding and explore how neural plasticity and olfactory neurogenesis contribute to enhancing the adaptability of the olfactory system. These mechanisms are thought to support olfactory learning and memory, potentially through increased complexity and restructuring of neural network structures, as well as the addition of new granule granule cells that aid in olfactory adaptation. Additionally, the manuscript underscores the importance of employing precise methodologies to elucidate the specific roles of adult neurogenesis amidst conflicting data and varying experimental paradigms. Understanding these processes is essential for gaining insights into the complexities of olfactory function and behavior.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
Strength and plasticity of metallic structural materials are the fundamental indicators of the service reliability[1].However,as is well known,a general trade-offrelationship exists between strength and plasticity of ...Strength and plasticity of metallic structural materials are the fundamental indicators of the service reliability[1].However,as is well known,a general trade-offrelationship exists between strength and plasticity of metallic materials,making it difficult to improve both of them synchronously[2].At present,only few of the successful cases[3-8],achieved via nano-particles[7],heterogeneous microstructures[8],etc.are mostly limited to some specific materials or processes.展开更多
Neuronal plasticity,the brain's ability to adapt structurally and functionally,is essential for learning,memory,and recovery from injuries.In neurodegenerative diseases such as Alzheimer's disease and Parkinso...Neuronal plasticity,the brain's ability to adapt structurally and functionally,is essential for learning,memory,and recovery from injuries.In neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease,this plasticity is disrupted,leading to cognitive and motor deficits.This review explores the mechanisms of neuronal plasticity and its effect on Alzheimer's disease and Parkinson's disease.Alzheimer's disease features amyloid-beta plaques and tau tangles that impair synaptic function,while Parkinson's disease involves the loss of dopaminergic neurons affecting motor control.Enhancing neuronal plasticity offers therapeutic potential for these diseases.A systematic literature review was conducted using databases such as PubMed,Scopus,and Google Scholar,focusing on studies of neuronal plasticity in Alzheimer's disease and Parkinson's disease.Data synthesis identified key themes such as synaptic mechanisms,neurogenesis,and therapeutic strategies,linking molecular insights to clinical applications.Results highlight that targeting synaptic plasticity mechanisms,such as long-term potentiation and long-term depression,shows promise.Neurotrophic factors,advanced imaging techniques,and molecular tools(e.g.,clustered regularly interspaced short palindromic repeats and optogenetics)are crucial in understanding and enhancing plasticity.Current therapies,including dopamine replacement,deep brain stimulation,and lifestyle interventions,demonstrate the potential to alleviate symptoms and improve outcomes.In conclusion,enhancing neuronal plasticity through targeted therapies holds significant promise for treating neurodegenerative diseases.Future research should integrate multidisciplinary approaches to fully harness the therapeutic potential of neuronal plasticity in Alzheimer's disease and Parkinson's disease.展开更多
Extracellular vesicles(EVs)are cell-derived,lipid membrane-enclosed vesicles carrying a broad spectrum of biologically active molecules(including proteins,RNAs,and bioactive lipids)which play important roles in interc...Extracellular vesicles(EVs)are cell-derived,lipid membrane-enclosed vesicles carrying a broad spectrum of biologically active molecules(including proteins,RNAs,and bioactive lipids)which play important roles in intercellular communication.EVs crucially control neuronal energy metabolism under physiological conditions,constrain oxidative stress a nd brain inflammatory responses,and promote neuronal survival and plasticity upon brain damage.展开更多
The effects of potassium(K)doping on the incipient plasticity of tungsten(W)under nanoindentation were investigated using a combination of experiments and mesoscale defects dynamic simulations.The transmission electro...The effects of potassium(K)doping on the incipient plasticity of tungsten(W)under nanoindentation were investigated using a combination of experiments and mesoscale defects dynamic simulations.The transmission electron microscopy study reveal that nanometer-sized bubbles were formed through the vaporization of K in specimens prepared by spark plasma sintering.In order to investigate the mechanical properties of the K-doped W specimens,nano-characterization experiments and defect dynamics simula-tions were conducted,comparing with those in pure W.Nanoindentation tests reveal that the maximum shear yield stress approaches the theoretical strength in annealed pure W,while K-doped W samples exhibit significant yield drop accompanied with stochastic variations.A newly developed mesoscale defect dynamics model to concurrently couple dislocation dynamics with finite element method has been also employed to investigate micro-mechanisms of plasticity under nanoindentation and the effects of K-bubbles on the plastic deformation.The simulations revealed that the localized stress concentration induced by the K-bubbles promoted dislocation nucleation and enhanced plastic deformation,thereby reducing the yield stress,showing good agreement with the experiment.展开更多
The mechanical anisotropy on extruded AZ31 magnesium alloy bar has been investigated by combining experimental measurement and crystal plasticity modeling.Monotonic tension and compression are conducted in four loadin...The mechanical anisotropy on extruded AZ31 magnesium alloy bar has been investigated by combining experimental measurement and crystal plasticity modeling.Monotonic tension and compression are conducted in four loading directions with the oblique angleϕof 0°,30°,60°and 90°from extrusion radial direction to extrusion direction,and are also simulated by visco-plastic self-consistent model with considering twinning and detwinning scheme at the first time.The simulation results are well in agreement with the corresponding experimental data.Combined with the Schmid factor(SF),the anisotropic mechanical behaviors including yield strength,ultimate strength and strain hardening rate are interpreted with the predicted relative activities of deformation modes,texture evolution and twin volume fraction.With the loading angle varying from 0°to 90°,it is found that prismatic slip becomes the primary deformation mode with the decreasing relative activities of basal slip and extension twinning in tension.While the deformation mechanism is more complex in compression:Extension twinning gets great activation at the beginning of the deformation,especially under compression along 90°;basal slip and pyramidal<c+a>slip dominate the late deformation of compression along 0°and 30°,while basal slip and prismatic slip are dominated modes in compression along 60°and 90°.Additionally,different {10 1 2}twinning behaviors with two or three and one or two pairs of twin variants being activated in tension along 30°and compression along 90°,respectively,have a close correlation with the texture evolution to coordinate plastic deformation.The activation of{10 1 2}twinning,which varies with the loading angleϕ,results in the increased trend of strain hardening rate.Following the exhausting of twinning,non-basal slips with the highest SF become the primary deformation mode subsequently,contributing to the decreasing trend in hardening behavior and the anisotropy of ultimate strength.展开更多
In this paper,the author follows the trail of C.Malabou,Q.Meillassoux,and G.Deleuze and tries to test three philosophical concepts that seem to be particularly threatened in the era of automatic digital reproduction.T...In this paper,the author follows the trail of C.Malabou,Q.Meillassoux,and G.Deleuze and tries to test three philosophical concepts that seem to be particularly threatened in the era of automatic digital reproduction.These three concepts are plasticity(defended for many years by C.Malabou),contingency(reconstructed by Q.Meillassoux),and virtuality(developed by G.Deleuze).The main task of the text will be to reflect on which of these three concepts better protects our thinking against automation and stays faithful to the ideal of creativity.In what sense are plasticity,contingency,and the possibility of virtualization the a priori condition of any transformation,physical or intellectual,affective or conceptual metamorphosis?In what sense are these three concepts the only conditions for the survival of every living being?Would a being without contingency,plasticity,and disposition to virtualization simply be a dead being?展开更多
The nanoindentation pop-in behaviors of 13 grains with diverse crystallographic orientations were analysed using a coarse-grained Mg-2 wt.% Gd alloy.Within nanoscale stressed volumes within all grains,the converted sh...The nanoindentation pop-in behaviors of 13 grains with diverse crystallographic orientations were analysed using a coarse-grained Mg-2 wt.% Gd alloy.Within nanoscale stressed volumes within all grains,the converted shear stresses for the first pop-in,calculated using the indentation Schmid factor,ranged from 1 to 1.3 GPa,consistent with theoretical predictions for dislocation nucleation in Mg.The estimated activation volume of the first pop-in was approximately 27–40 A3(involving about ~2 atoms),aligning with reported atomistic simulations of the surface dislocation semi-loop nucleation.While indented near the -axis,grains exhibit higher first pop-in loads and successive pop-ins,implying the possibility of a cross-slip nucleation mechanism to accommodate -axis deformation.展开更多
The visual cortex is an essential part of the brain for processing visual information.It exhibits structural and functional plasticity,which is crucial for adapting to complex visual environments.The quintessential ma...The visual cortex is an essential part of the brain for processing visual information.It exhibits structural and functional plasticity,which is crucial for adapting to complex visual environments.The quintessential manifestation of visual cortical plasticity is ocular dominance plasticity during the critical period,which involves numerous cellular and molecular events.While previous studies have emphasized the role of visual cortical neurons and their associated functional molecules in visual plasticity,recent findings have revealed that structural factors such as the extracellular matrix and glia are also involved.Investigating how these molecules interact to form a complex network that facilitates plasticity in the visual cortex is crucial to our understanding of the development of the visual system and the advancement of therapeutic strategies for visual disorders like amblyopia.展开更多
Animal adaptation to environmental challenges is a complex process involving intricate interactions between the host genotype and gut microbiome composition.The gut microbiome,highly responsive to external environment...Animal adaptation to environmental challenges is a complex process involving intricate interactions between the host genotype and gut microbiome composition.The gut microbiome,highly responsive to external environmental factors,plays a crucial role in host adaptability and may facilitate local adaptation within species.Concurrently,the genetic background of host populations influences gut microbiome composition,highlighting the bidirectional relationship between host and microbiome.Despite this,our understanding of gut microbiome plasticity and its role in host adaptability remains limited,particularly in reptiles.To clarify this issue,we conducted a reciprocal translocation experiment with gravid females of the Qinghai toad-headed lizards(Phrynocephalus vlangalii)between high-altitude(2?600 m a.s.l.)and superhigh-altitude(3?600 m a.s.l.)environments on Dangjin Mountain of the Qinghai-Xizang Plateau,China.One year later,we assessed the phenotypes and gut microbiomes of their offspring.Results revealed significant plasticity in gut microbiome diversity and structure in response to contrasting elevations.Highaltitude conditions increased diversity,and maternal effects appeared to enable high-altitude lizards to maintain elevated diversity when exposed to superhigh-altitude environments.Additionally,superhigh-altitude lizards displayed distinct gut microbiome structures with notable host specificity,potentially linked to their lower growth rates.Overall,these findings underscore the importance of the gut microbiome in facilitating reptilian adaptation to rapid environmental changes across altitudinal gradients.Furthermore,this study provides critical insights into microbial mechanisms underpinning local adaptation and adaptative plasticity,offering a foundation for future research on host-microbiome interactions in evolutionary and ecological contexts.展开更多
Epilepsy is a chronic neurological disorder affecting~65 million individuals worldwide.Abnormal synaptic plasticity is one of the most important pathological features of this condition.We investigated how ubiquitin-sp...Epilepsy is a chronic neurological disorder affecting~65 million individuals worldwide.Abnormal synaptic plasticity is one of the most important pathological features of this condition.We investigated how ubiquitin-specific peptidase 47(USP47)influences synaptic plasticity and its link to epilepsy.We found that USP47 enhanced excitatory postsynaptic transmission and increased the density of total dendritic spines and the proportion of mature dendritic spines.Furthermore,USP47 inhibited the degradation of the ubiquitinatedα-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor(AMPAR)subunit glutamate receptor 1(GluR1),which is associated with synaptic plasticity.In addition,elevated levels of USP47 were found in epileptic mice,and USP47 knockdown reduced the frequency and duration of seizure-like events and alleviated epileptic seizures.To summarize,we present a new mechanism whereby USP47 regulates excitatory postsynaptic plasticity through the inhibition of ubiquitinated GluR1 degradation.Modulating USP47 may offer a potential approach for controlling seizures and modifying disease progression in future therapeutic strategies.展开更多
基金This work was financially supported by the Educational Department of Liaoning Province (No.2004F052) and the National Natural Science Foundation of China (No. 50309004).
文摘Gradient-dependent plasticity is introduced into the phenomenological Johnson-Cook model to study the effects of strainhardening, strain rate sensitivity, thermal-softening, and microstructure. The microstructural effect （interactions and interplay among microstructures） due to heterogeneity of texture plays an important role in the process of development or evolution of an adiabatic shear band with a certain thickness depending on the grain diameter. The distributed plastic shear strain and deformation in the shear band are derived and depend on the critical plastic shear strain corresponding to the peak flow shear stress, the coordinate or position, the internal length parameter, and the average plastic shear strain or the flow shear stress. The critical plastic shear strain, the distributed plastic shear strain, and deformation in the shear band are numerically predicted for a kind of steel deformed at a constant shear strain rate. Beyond the peak shear stress, the local plastic shear strain in the shear band is highly nonuniform and the local plastic shear deformation in the band is highly nonlinear. Shear localization is more apparent with the increase of the average plastic shear strain. The calculated distributions of the local plastic shear strain and deformation agree with the previous numerical and experimental results.
基金This work was financially supported by the National Natural Science Foundation of China (No.50309004) Liaoning Technical University (No. 02-38).
文摘Fault rockburst is treated as a strain localization problem under dynamicloading condition considering strain gradient and strain rate. As a kind of dynamic fracturephenomena, rockburst has characteristics of strain localization, which is considered as aone-dimensional shear problem subjected to normal compressive stress and tangential shear stress.The constitutive relation of rock material is bilinear (elastic and strain softening) and sensitiveto shear strain rate. The solutions proposed based on gradient-dependent plasticity show thatintense plastic strain is concentrated in fault band and the thickness of the band depends on thecharacteristic length of rock material. The post-peak stiffness of the fault band was determinedaccording to the constitutive parameters of rock material and shear strain rate. Fault bandundergoing strain softening and elastic rock mass outside the band constitute a system and theinstability criterion of the system was proposed based on energy theory. The criterion depends onthe constitutive relation of rock material, the structural size and the strain rate. The staticresult regardless of the strain rate is the special case of the present analytical solution. Highstrain rate can lead to instability of the system.
基金This work was financially supported by the National Natural Science Foundation of China (No.50309004).
文摘The capacity of energy absorption by fault bands after rock burst wascalculated quantitatively according to shear stress-shear deformation curves considering theinteractions and interplaying among microstructures due to the heterogeneity of strain softeningrock materials. The post-peak stiffness of rock specimens subjected to direct shear was derivedstrictly based on gradient-dependent plasticity, which can not be obtained from the classicalelastoplastic theory. Analytical solutions for the dissipated energy of rock burst were proposedwhether the slope of the post-peak shear stress-shear deformation curve is positive or not. Theanalytical solutions show that shear stress level, confining pressure, shear strength, brittleness,strain rate and heterogeneity of rock materials have important influence on the dissipated energy.The larger value of the dissipated energy means that the capacity of energy dissipation in the formof shear bands is superior and a lower magnitude of rock burst is expected under the condition ofthe same work done by external shear force. The possibility of rock burst is reduced for a lowersoftening modulus or a larger thickness of shear bands.
文摘A method for calculation of temperature distribution in adiabatic shear band is proposed in terms of gradient-dependent plasticity where the characteristic length describes the interactions and interplaying among microstructures. First, the increment of the plastic shear strain distribution in adiabatic shear band is obtained based on gradient-dependent plasticity. Then, the plastic work distribution is derived according to the current flow shear stress and the obtained increment of plastic shear strain distribution. In the light of the well-known assumption that 90% of plastic work is converted into the heat resulting in increase in temperature in adiabatic shear band, the increment of the temperature distribution is presented. Next, the average temperature increment in the shear band is calculated to compute the change in flow shear stress due to the thermal softening effect. After the actual flow shear stress considering the thermal softening effect is obtained according to the Johnson-Cook constitutive relation, the increment of the plastic shear strain distribution, the plastic work and the temperature in the next time step are recalculated until the total time is consumed. Summing the temperature distribution leads to rise in the total temperature distribution. The present calculated maximum temperature in adiabatic shear band in titanium agrees with the experimental observations. Moreover, the temperature profiles for different flow shear stresses are qualitatively consistent with experimental and numerical results. Effects of some related parameters on the temperature distribution are also predicted.
文摘Shear localization in linear strain softening heterogeneous material under simple shear was investigated analytically. The closed-form solutions obtained based on gradient plasticity theory considering interactions and interplaying among microstructures due to heterogeneity of metal material show that in the normal direction of shear band, elastic shear displacement is linear; while plastic and total shear displacement are non-linear. Elastic shear strain in the band is uniform and the non-uniformity of total shear displacement stems from localized plastic shear displacement. In the center of the band, plastic and total shear displacement all reach their maximum values. In strain-softening process, elastic displacement decreases as flow shear stress decreases. Contrarily, plastic and total shear displacement increase and manifest shear localization occurs progressively. Under the same shear stress level, plastic and total shear displacement increase as strain softening modulus and elastic shear modulus decrease. The present analytical solutions were compared with many experimental results and the agreement is good.
基金supported by the National Key R&D Program of China(No.2017YFB0304402)。
文摘The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile testing.In-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation mechanisms.These findings were discussed with the local strain measurements via digital image correlation.The results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of yielding.The small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier effect.The volume fraction of RA gradually decreased from 26.8%to 8.2%prior to fracture.In the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.
基金supported by Progetto Trapezio,Compagnia di San Paolo(67935-2021.2174)to LB,Fondazione CRT(Cassa di Risparmio di Torino,RF=2022.0618)to LB。
文摘Brain plasticity-A universal tool with many variations:The study of brain plasticity has been gaining interest since almost a century and has now reached a huge amount of information(>80,000 results in PubMed).Overall,different types of plasticity,including stem cell-driven genesis of new neurons(adult neurogenesis),cells in arrested maturation(dormant neurons),neuro-glial and synaptic plasticity,can coexist and contribute to grant plastic changes in the brain,from a cellular to system level(Benedetti and Couillard-Despres,2022;Bonfanti et al.,2023).
基金supported by PTDC-01778/2022-NeuroDev3D,iNOVA4Health(UIDB/04462/2020 and UIDP/04462/2020)LS4FUTURE(LA/P/0087/2020)。
文摘Cells,tissues,and organs are constantly subjected to the action of mechanical forces from the extracellular environment-and the nervous system is no exception.Cell-intrinsic properties such as membrane lipid composition,abundance of mechanosensors,and cytoskeletal dynamics make cells more or less likely to sense these forces.Intrinsic and extrinsic cues are integrated by cells and this combined information determines the rate and dynamics of membrane protrusion growth or retraction(Yamada and Sixt,2019).Cell protrusions are extensions of the plasma membrane that play crucial roles in diverse contexts such as cell migration and neuronal synapse formation.In the nervous system,neurons are highly dynamic cells that can change the size and number of their pre-and postsynaptic elements(called synaptic boutons and dendritic spines,respectively),in response to changes in the levels of synaptic activity through a process called plasticity.Synaptic plasticity is a hallmark of the nervous system and is present throughout our lives,being required for functions like memory formation or the learning of new motor skills(Minegishi et al.,2023;Pillai and Franze,2024).
文摘Adult neurogenesis persists after birth in the subventricular zone, with new neurons migrating to the granule cell layer and glomerular layers of the olfactory bulb, where they integrate into existing circuitry as inhibitory interneurons. The generation of these new neurons in the olfactory bulb supports both structural and functional plasticity, aiding in circuit remodeling triggered by memory and learning processes. However, the presence of these neurons, coupled with the cellular diversity within the olfactory bulb, presents an ongoing challenge in understanding its network organization and function. Moreover,the continuous integration of new neurons in the olfactory bulb plays a pivotal role in regulating olfactory information processing. This adaptive process responds to changes in epithelial composition and contributes to the formation of olfactory memories by modulating cellular connectivity within the olfactory bulb and interacting intricately with higher-order brain regions. The role of adult neurogenesis in olfactory bulb functions remains a topic of debate. Nevertheless, the functionality of the olfactory bulb is intricately linked to the organization of granule cells around mitral and tufted cells. This organizational pattern significantly impacts output, network behavior, and synaptic plasticity, which are crucial for olfactory perception and memory. Additionally, this organization is further shaped by axon terminals originating from cortical and subcortical regions. Despite the crucial role of olfactory bulb in brain functions and behaviors related to olfaction, these complex and highly interconnected processes have not been comprehensively studied as a whole. Therefore, this manuscript aims to discuss our current understanding and explore how neural plasticity and olfactory neurogenesis contribute to enhancing the adaptability of the olfactory system. These mechanisms are thought to support olfactory learning and memory, potentially through increased complexity and restructuring of neural network structures, as well as the addition of new granule granule cells that aid in olfactory adaptation. Additionally, the manuscript underscores the importance of employing precise methodologies to elucidate the specific roles of adult neurogenesis amidst conflicting data and varying experimental paradigms. Understanding these processes is essential for gaining insights into the complexities of olfactory function and behavior.
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.
基金financially supported by the National Natural Science Foundation of China(NSFC)(Nos.52371084,52301177,52322105,52130002,and 52321001)the Youth Innovation Promotion Association CAS(No.2021192)+1 种基金the IMR Innovation Fund(No.2023-ZD01)the Fund of Science and Technology on Surface Physics and Chemistry Laboratory(No.XKFZ202303).
文摘Strength and plasticity of metallic structural materials are the fundamental indicators of the service reliability[1].However,as is well known,a general trade-offrelationship exists between strength and plasticity of metallic materials,making it difficult to improve both of them synchronously[2].At present,only few of the successful cases[3-8],achieved via nano-particles[7],heterogeneous microstructures[8],etc.are mostly limited to some specific materials or processes.
基金financially supported by King Abdulaziz University,Deanship of Scientific Research(DSR)。
文摘Neuronal plasticity,the brain's ability to adapt structurally and functionally,is essential for learning,memory,and recovery from injuries.In neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease,this plasticity is disrupted,leading to cognitive and motor deficits.This review explores the mechanisms of neuronal plasticity and its effect on Alzheimer's disease and Parkinson's disease.Alzheimer's disease features amyloid-beta plaques and tau tangles that impair synaptic function,while Parkinson's disease involves the loss of dopaminergic neurons affecting motor control.Enhancing neuronal plasticity offers therapeutic potential for these diseases.A systematic literature review was conducted using databases such as PubMed,Scopus,and Google Scholar,focusing on studies of neuronal plasticity in Alzheimer's disease and Parkinson's disease.Data synthesis identified key themes such as synaptic mechanisms,neurogenesis,and therapeutic strategies,linking molecular insights to clinical applications.Results highlight that targeting synaptic plasticity mechanisms,such as long-term potentiation and long-term depression,shows promise.Neurotrophic factors,advanced imaging techniques,and molecular tools(e.g.,clustered regularly interspaced short palindromic repeats and optogenetics)are crucial in understanding and enhancing plasticity.Current therapies,including dopamine replacement,deep brain stimulation,and lifestyle interventions,demonstrate the potential to alleviate symptoms and improve outcomes.In conclusion,enhancing neuronal plasticity through targeted therapies holds significant promise for treating neurodegenerative diseases.Future research should integrate multidisciplinary approaches to fully harness the therapeutic potential of neuronal plasticity in Alzheimer's disease and Parkinson's disease.
基金supported by the German Research Foundation(grants 514990328,389030878,405358801/428817542(within FOR2879)and 449437943(within TRR332,project C06)German Federal Ministry of Education and Science(3DOS,grant 161L0278B)(to DMH)。
文摘Extracellular vesicles(EVs)are cell-derived,lipid membrane-enclosed vesicles carrying a broad spectrum of biologically active molecules(including proteins,RNAs,and bioactive lipids)which play important roles in intercellular communication.EVs crucially control neuronal energy metabolism under physiological conditions,constrain oxidative stress a nd brain inflammatory responses,and promote neuronal survival and plasticity upon brain damage.
基金supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(No.RS-2024-00445448)the National Research Foundation of Korea(NRF)funded by the Ministry of Science(No.NRF-2021R1A2C3005096)the ITER Technology R&D Program.
文摘The effects of potassium(K)doping on the incipient plasticity of tungsten(W)under nanoindentation were investigated using a combination of experiments and mesoscale defects dynamic simulations.The transmission electron microscopy study reveal that nanometer-sized bubbles were formed through the vaporization of K in specimens prepared by spark plasma sintering.In order to investigate the mechanical properties of the K-doped W specimens,nano-characterization experiments and defect dynamics simula-tions were conducted,comparing with those in pure W.Nanoindentation tests reveal that the maximum shear yield stress approaches the theoretical strength in annealed pure W,while K-doped W samples exhibit significant yield drop accompanied with stochastic variations.A newly developed mesoscale defect dynamics model to concurrently couple dislocation dynamics with finite element method has been also employed to investigate micro-mechanisms of plasticity under nanoindentation and the effects of K-bubbles on the plastic deformation.The simulations revealed that the localized stress concentration induced by the K-bubbles promoted dislocation nucleation and enhanced plastic deformation,thereby reducing the yield stress,showing good agreement with the experiment.
基金supported by the National Natural Science Foundation of China(Nos.52271123,52101154)the Basic Research Program of Jiangsu(No.BK20231496)+2 种基金the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No.23KJA130001)the Graduate Innovation Program of China University of Mining and Technology(No.2024WLJCRCZL048)the Postgraduate Research and Practice Innovation Program of Jiangsu Province(No.KYCX24_2700).
文摘The mechanical anisotropy on extruded AZ31 magnesium alloy bar has been investigated by combining experimental measurement and crystal plasticity modeling.Monotonic tension and compression are conducted in four loading directions with the oblique angleϕof 0°,30°,60°and 90°from extrusion radial direction to extrusion direction,and are also simulated by visco-plastic self-consistent model with considering twinning and detwinning scheme at the first time.The simulation results are well in agreement with the corresponding experimental data.Combined with the Schmid factor(SF),the anisotropic mechanical behaviors including yield strength,ultimate strength and strain hardening rate are interpreted with the predicted relative activities of deformation modes,texture evolution and twin volume fraction.With the loading angle varying from 0°to 90°,it is found that prismatic slip becomes the primary deformation mode with the decreasing relative activities of basal slip and extension twinning in tension.While the deformation mechanism is more complex in compression:Extension twinning gets great activation at the beginning of the deformation,especially under compression along 90°;basal slip and pyramidal<c+a>slip dominate the late deformation of compression along 0°and 30°,while basal slip and prismatic slip are dominated modes in compression along 60°and 90°.Additionally,different {10 1 2}twinning behaviors with two or three and one or two pairs of twin variants being activated in tension along 30°and compression along 90°,respectively,have a close correlation with the texture evolution to coordinate plastic deformation.The activation of{10 1 2}twinning,which varies with the loading angleϕ,results in the increased trend of strain hardening rate.Following the exhausting of twinning,non-basal slips with the highest SF become the primary deformation mode subsequently,contributing to the decreasing trend in hardening behavior and the anisotropy of ultimate strength.
文摘In this paper,the author follows the trail of C.Malabou,Q.Meillassoux,and G.Deleuze and tries to test three philosophical concepts that seem to be particularly threatened in the era of automatic digital reproduction.These three concepts are plasticity(defended for many years by C.Malabou),contingency(reconstructed by Q.Meillassoux),and virtuality(developed by G.Deleuze).The main task of the text will be to reflect on which of these three concepts better protects our thinking against automation and stays faithful to the ideal of creativity.In what sense are plasticity,contingency,and the possibility of virtualization the a priori condition of any transformation,physical or intellectual,affective or conceptual metamorphosis?In what sense are these three concepts the only conditions for the survival of every living being?Would a being without contingency,plasticity,and disposition to virtualization simply be a dead being?
基金financial support of NSERC Discovery Grant (RGPIN-2019–05882) and Canada Research Chair program (CRC-2021–00512)。
文摘The nanoindentation pop-in behaviors of 13 grains with diverse crystallographic orientations were analysed using a coarse-grained Mg-2 wt.% Gd alloy.Within nanoscale stressed volumes within all grains,the converted shear stresses for the first pop-in,calculated using the indentation Schmid factor,ranged from 1 to 1.3 GPa,consistent with theoretical predictions for dislocation nucleation in Mg.The estimated activation volume of the first pop-in was approximately 27–40 A3(involving about ~2 atoms),aligning with reported atomistic simulations of the surface dislocation semi-loop nucleation.While indented near the -axis,grains exhibit higher first pop-in loads and successive pop-ins,implying the possibility of a cross-slip nucleation mechanism to accommodate -axis deformation.
基金supported by the National Natural Science Foundation of China(81770956,81371049,32471055 and 82171090)Project of Tianjin 131 Innovative Talent Team(201936)+4 种基金the Science and Technology Planning Project of Tianjin(21JCYBJC00780)the Science and Technology Fund for Health of Tianjin(TJWJ2023ZD008)Shanghai Municipal Science and Technology Major Project(2018SHZDZX01)ZJLab,Shanghai Center for Brain Science and Brain-Inspired Technology,the Lingang Laboratory(LG-QS-202203-12)Tianjin Key Medical Discipline(Specialty)Construction Project(TJYXZDXK‑016A).
文摘The visual cortex is an essential part of the brain for processing visual information.It exhibits structural and functional plasticity,which is crucial for adapting to complex visual environments.The quintessential manifestation of visual cortical plasticity is ocular dominance plasticity during the critical period,which involves numerous cellular and molecular events.While previous studies have emphasized the role of visual cortical neurons and their associated functional molecules in visual plasticity,recent findings have revealed that structural factors such as the extracellular matrix and glia are also involved.Investigating how these molecules interact to form a complex network that facilitates plasticity in the visual cortex is crucial to our understanding of the development of the visual system and the advancement of therapeutic strategies for visual disorders like amblyopia.
基金supported by the National Natural Science Foundation of China (31861143023,31872252)Strategic Priority Research Program of the Chinese Academy of Sciences (XDA20050201)。
文摘Animal adaptation to environmental challenges is a complex process involving intricate interactions between the host genotype and gut microbiome composition.The gut microbiome,highly responsive to external environmental factors,plays a crucial role in host adaptability and may facilitate local adaptation within species.Concurrently,the genetic background of host populations influences gut microbiome composition,highlighting the bidirectional relationship between host and microbiome.Despite this,our understanding of gut microbiome plasticity and its role in host adaptability remains limited,particularly in reptiles.To clarify this issue,we conducted a reciprocal translocation experiment with gravid females of the Qinghai toad-headed lizards(Phrynocephalus vlangalii)between high-altitude(2?600 m a.s.l.)and superhigh-altitude(3?600 m a.s.l.)environments on Dangjin Mountain of the Qinghai-Xizang Plateau,China.One year later,we assessed the phenotypes and gut microbiomes of their offspring.Results revealed significant plasticity in gut microbiome diversity and structure in response to contrasting elevations.Highaltitude conditions increased diversity,and maternal effects appeared to enable high-altitude lizards to maintain elevated diversity when exposed to superhigh-altitude environments.Additionally,superhigh-altitude lizards displayed distinct gut microbiome structures with notable host specificity,potentially linked to their lower growth rates.Overall,these findings underscore the importance of the gut microbiome in facilitating reptilian adaptation to rapid environmental changes across altitudinal gradients.Furthermore,this study provides critical insights into microbial mechanisms underpinning local adaptation and adaptative plasticity,offering a foundation for future research on host-microbiome interactions in evolutionary and ecological contexts.
基金supported by grants from the National Natural Science Foundation of China(82071458 and 32160190)the United Foundation of Zunyi Municipality(Zunshikehe HZ Zi(2021)14)+3 种基金the Science and Technology Project of Guizhou Provincial Health Commission(gzwkj2021-020)the Guizhou Epilepsy Basic and Clinical Research Scientific,Technological Innovation Talent Team Project(CXTD[2022]013)the Excellent Young Talents Training Program of the Affiliated Hospital of Zunyi Medical University(rc220220906)the Guizhou Provincial Hundred Level Innovative Talents Funds(GCC-2022-038-1).
文摘Epilepsy is a chronic neurological disorder affecting~65 million individuals worldwide.Abnormal synaptic plasticity is one of the most important pathological features of this condition.We investigated how ubiquitin-specific peptidase 47(USP47)influences synaptic plasticity and its link to epilepsy.We found that USP47 enhanced excitatory postsynaptic transmission and increased the density of total dendritic spines and the proportion of mature dendritic spines.Furthermore,USP47 inhibited the degradation of the ubiquitinatedα-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor(AMPAR)subunit glutamate receptor 1(GluR1),which is associated with synaptic plasticity.In addition,elevated levels of USP47 were found in epileptic mice,and USP47 knockdown reduced the frequency and duration of seizure-like events and alleviated epileptic seizures.To summarize,we present a new mechanism whereby USP47 regulates excitatory postsynaptic plasticity through the inhibition of ubiquitinated GluR1 degradation.Modulating USP47 may offer a potential approach for controlling seizures and modifying disease progression in future therapeutic strategies.
