A cellular automaton （CA）-based model for the precise two-dimensional simulation of the dendritic morphology of cast aluminum alloys was developed. Compared with previous CA models, the new model considers the solid...A cellular automaton （CA）-based model for the precise two-dimensional simulation of the dendritic morphology of cast aluminum alloys was developed. Compared with previous CA models, the new model considers the solidification process in more detail, solving the solute and heat conservation equations in the modeling domain, including calculation of the solid fraction, the tip velocity, and the solute diffusion process, all of which have significant influence on the dendrite evolution. The rotating grids technique was used in the simulation to avoid anisotropy introduced by the square grid. Dendritic grain profiles for different crystallographic orientations show the existence of a great number of regular and parallel secondary and tertiary arms. The simulation results for the secondary arm spacing and grain size were compared with experimental data and with results reported in the literature. A good agreement was found between the simulated results and the experimental data. It can be concluded that the model can be used to predict the dendritic microstructure of aluminum alloy in a quantitative manner.展开更多
Dendritic spines are small membranous protrusions that receive synaptic inputs from other neurons,enabling the initiation of dendritic N-methyl-D-aspartic(NMDA)spikes and somatic action potentials.During learning and ...Dendritic spines are small membranous protrusions that receive synaptic inputs from other neurons,enabling the initiation of dendritic N-methyl-D-aspartic(NMDA)spikes and somatic action potentials.During learning and memory processes,both the number of spines on a dendrite and the morphology of individual spines are constantly changing.The individual influence of spine number and morphology on dendritic NMDA spikes has already been revealed,but the functional significance of the coregulation of spine number and morphology on NMDA spikes remains elusive.Here,we systematically investigated the initiation of local dendritic NMDA spikes by the dynamic distributions of the spine number and morphology on single dendrites in reconstructed neuron models.Different from the traditional cognition,we found the threshold number of spines required to generate local dendrite NMDA spikes on distal dendrites is fewer than that on proximal ones,because the thinner distal dendrites own higher impedance.As for the spine morphology,the presence of moreα-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid(AMPA)receptors on the spine leads to larger NMDA spikes rather than an increase in the spine dimension alone.Furthermore,we first suggested that a single dendrite containing spines with gradually increasing head diameters away from the soma could generate larger NMDA spikes than that irrational distribution of spine morphology containing spines with decreasing head diameters,which can be compensated by the increasing spine number.Complementarily,the distance-dependent distribution of spine number and morphology co-regulate the intension of dendritic NMDA spikes.These findings about the threshold for NMDA spikes provide novel insights into the role of the irrational dynamic distribution of the spine number and morphology in senescence and disease processes such as Alzheimer’s disease,schizophrenia,and Parkinson’s disease,which causes abnormal neuron firing.展开更多
基金Supported by the National Natural Science Foundation of China (No. 10477010) and the National Key Basic Research and Devel-opment (973) Program of China (No. G2000067208-3)
文摘A cellular automaton （CA）-based model for the precise two-dimensional simulation of the dendritic morphology of cast aluminum alloys was developed. Compared with previous CA models, the new model considers the solidification process in more detail, solving the solute and heat conservation equations in the modeling domain, including calculation of the solid fraction, the tip velocity, and the solute diffusion process, all of which have significant influence on the dendrite evolution. The rotating grids technique was used in the simulation to avoid anisotropy introduced by the square grid. Dendritic grain profiles for different crystallographic orientations show the existence of a great number of regular and parallel secondary and tertiary arms. The simulation results for the secondary arm spacing and grain size were compared with experimental data and with results reported in the literature. A good agreement was found between the simulated results and the experimental data. It can be concluded that the model can be used to predict the dendritic microstructure of aluminum alloy in a quantitative manner.
基金supported by the National Key Research and Development Program of China (Grant No.2019YFA0705400)the Natural Science Foundation of Jiangsu Province (Grant No.BK20212008)+3 种基金the National Natural Science Foundation of China (Grant No.12002158)the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures (Grant Nos.MCMS-I-0421K01,MCMS-I-0422K01)the Fundamental Research Funds for the Central Universities (Grant No.NJ2022002)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Dendritic spines are small membranous protrusions that receive synaptic inputs from other neurons,enabling the initiation of dendritic N-methyl-D-aspartic(NMDA)spikes and somatic action potentials.During learning and memory processes,both the number of spines on a dendrite and the morphology of individual spines are constantly changing.The individual influence of spine number and morphology on dendritic NMDA spikes has already been revealed,but the functional significance of the coregulation of spine number and morphology on NMDA spikes remains elusive.Here,we systematically investigated the initiation of local dendritic NMDA spikes by the dynamic distributions of the spine number and morphology on single dendrites in reconstructed neuron models.Different from the traditional cognition,we found the threshold number of spines required to generate local dendrite NMDA spikes on distal dendrites is fewer than that on proximal ones,because the thinner distal dendrites own higher impedance.As for the spine morphology,the presence of moreα-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid(AMPA)receptors on the spine leads to larger NMDA spikes rather than an increase in the spine dimension alone.Furthermore,we first suggested that a single dendrite containing spines with gradually increasing head diameters away from the soma could generate larger NMDA spikes than that irrational distribution of spine morphology containing spines with decreasing head diameters,which can be compensated by the increasing spine number.Complementarily,the distance-dependent distribution of spine number and morphology co-regulate the intension of dendritic NMDA spikes.These findings about the threshold for NMDA spikes provide novel insights into the role of the irrational dynamic distribution of the spine number and morphology in senescence and disease processes such as Alzheimer’s disease,schizophrenia,and Parkinson’s disease,which causes abnormal neuron firing.
