Nanotwinned polycrystals exhibit an excellent strength-ductility combination due to nanoscale twins and grains. However, nanotwin-assisted grain coarsening under mechanical loading reported in recent experiments may r...Nanotwinned polycrystals exhibit an excellent strength-ductility combination due to nanoscale twins and grains. However, nanotwin-assisted grain coarsening under mechanical loading reported in recent experiments may result in strength drop based on the Hall-Petch law. In this paper, a phase-field model is developed to investigate the effect of coupled evolutions of twin and grain boundaries on nanotwin-assisted grain growth. The simulation result demonstrates that there are three pathways for coupled motions of twin and grain boundaries in a bicrystal under the applied loading, dependent on the amplitude of applied loading and misorientation of the bicrystal. It reveals that a large misorientation angle and a large applied stress promote the twinning-driven grain boundary migration. The resultant twin-assisted grain coarsening is confirmed in the simulations for the microstructural evolutions in twinned and un-twinned polycrystals under a high applied stress.展开更多
Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites.The interface between the current collector and deposited lithium plays a cr...Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites.The interface between the current collector and deposited lithium plays a critical role in preventing dendrite formation by regulating the thermodynamics and kinetics of lithium deposition.In this study,we develop a phase field model to investigate the influence of the current collector’s surface energy on lithium deposition morphology and its effect on the quality of the lithium metal film.It is demonstrated that a higher surface energy of the current collector promotes the growth of lithium metal along the surface of the current collector.Further,our simulation results show that a higher surface energy accelerates the formation of the lithium metal film while simultaneously reducing its surface roughness.By examining different contact angles and applied potentials,we construct a phase diagram of deposition morphology,illustrating that increased surface energy facilitates the dense and uniform deposition of lithium metal by preventing the formation of lithium filaments and voids.These findings provide new insights into the development and application of anode-free lithium metal batteries.展开更多
Development of high-performance phase transformation electrodes in lithium ion batteries requires comprehensive studies on stress-mediated lithiation involving migration of the phase interface. It brings out many coun...Development of high-performance phase transformation electrodes in lithium ion batteries requires comprehensive studies on stress-mediated lithiation involving migration of the phase interface. It brings out many counter-intuitive phenomena, especially in nanoscale electrodes, such as the slowing down migration of phase interface, the vanishing of miscibility gap under high charge rate, and the formation of surface crack during lithiation. However, it is still a challenge to simulate the evolution of stress in arbitrarily-shaped nanoscale electrodes, accompanied with phase transformation and concurrent plastic deformation. This article gives a brief review of our efforts devoted to address these issues by developing phase field model and simulation. We demonstrate that the miscibility gap of two-phase state is affected not only by stress but also by surface reaction rate and particle size. In addition, the migration of phase interface slows down due to stress. It reveals that the plastic deformation generates large radial expansion, which is responsible for the transition from surface hoop compression to surface hoop tension that may induce surface crack during lithiation. We hope our effort can make a contribution to the understanding of stress-coupled kinetics in phase transformation electrodes.展开更多
Super-enhancers(SEs)comprise large clusters of enhancers,which are co-occupied by multiple lineage-specific and master tran-scription factors,and play pivotal roles in regulating gene expression and cell fate determin...Super-enhancers(SEs)comprise large clusters of enhancers,which are co-occupied by multiple lineage-specific and master tran-scription factors,and play pivotal roles in regulating gene expression and cell fate determination.However,it is still largely un-known whether and how SEs are regulated by the noncoding portion of the genome.Here,through genome-wide analysis,wefound that tpng noncoding RNA(IncRNA)genes preferentially lie next to SEs.In mouse embryonic stem cells(mESCs),depletionof$E-associated IlncRNA transcripts dysregulated the activity of their nearby SEs.Specifically,we revealed a critical regulatoryrole of the IncRNA gene Platr22 in modulating the activity of a nearby SE and the expression of the nearby pluripotency regulatorZFP281.Through these regulatory events,Platr22 contributes to pluripotency maintenance and proper differentiation of mESCs.Mechanistically,Platr22 transcripts coat chromatin near the SE region and interact with DDX5 and hnRNP-L.DDX5 further recruitsp300 and other factors related to active transcription.We propose that these factors assemble into a transcription hub,thus pro-moting an open and active epigenetic chromatin state.0ur study highlights an unanticipated role for a class of lncRNAs in epige-netically controlling the activity and vulnerability to perturbation of nearby SEs for cell fate determination.展开更多
Dear Editor, In mammalian genomes, pervasive transcription produces thousands of long non-coding RNA （IncRNA） transcripts （Olebali et al., 2012; Hon et al., 2017）. Compared to protein-coding mRNAs, IncRNAs are le...Dear Editor, In mammalian genomes, pervasive transcription produces thousands of long non-coding RNA （IncRNA） transcripts （Olebali et al., 2012; Hon et al., 2017）. Compared to protein-coding mRNAs, IncRNAs are less conserved, and often exhibit low-level, developmental stage-and tissue-specific expression （Pauli et al., 2011; Hu et al., 2012; Lee, 2012; Ulitsky and Bartel, 2013; Cech and Steitz, 2014; Hon et al., 2017）. Many IncRNAs are strongly correlated with their neighboring mRNA genes in terms of expression and function, and tend to regulate nearby transcription （Orom et al., 2010; Engreitz et al., 2016; Luo etal., 2016）. It has been implicated that IncRNAs play versatile roles in regulating diverse aspects of cell biology through mechanisms at multiple levels （Pauli et al., 2011; Lee.展开更多
基金Project supported by the National Natural Science Foundation of China(No.11672285)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040502)+1 种基金the Collaborative Innovation Center of Suzhou Nano Science and Technologythe Fundamental Research Funds for the Central Universities
文摘Nanotwinned polycrystals exhibit an excellent strength-ductility combination due to nanoscale twins and grains. However, nanotwin-assisted grain coarsening under mechanical loading reported in recent experiments may result in strength drop based on the Hall-Petch law. In this paper, a phase-field model is developed to investigate the effect of coupled evolutions of twin and grain boundaries on nanotwin-assisted grain growth. The simulation result demonstrates that there are three pathways for coupled motions of twin and grain boundaries in a bicrystal under the applied loading, dependent on the amplitude of applied loading and misorientation of the bicrystal. It reveals that a large misorientation angle and a large applied stress promote the twinning-driven grain boundary migration. The resultant twin-assisted grain coarsening is confirmed in the simulations for the microstructural evolutions in twinned and un-twinned polycrystals under a high applied stress.
基金supported by the National Key Research and Development Program of China(2022YFA1203602)the National Natural Science Foundation of China(Grant No.12025206)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0620101)the National Natural Science Foundations of China(Grant No.12202366).
文摘Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites.The interface between the current collector and deposited lithium plays a critical role in preventing dendrite formation by regulating the thermodynamics and kinetics of lithium deposition.In this study,we develop a phase field model to investigate the influence of the current collector’s surface energy on lithium deposition morphology and its effect on the quality of the lithium metal film.It is demonstrated that a higher surface energy of the current collector promotes the growth of lithium metal along the surface of the current collector.Further,our simulation results show that a higher surface energy accelerates the formation of the lithium metal film while simultaneously reducing its surface roughness.By examining different contact angles and applied potentials,we construct a phase diagram of deposition morphology,illustrating that increased surface energy facilitates the dense and uniform deposition of lithium metal by preventing the formation of lithium filaments and voids.These findings provide new insights into the development and application of anode-free lithium metal batteries.
基金supported by the National Natural Science Foundation of China (Grant no. 11472262)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant no. XDB22040502)+1 种基金the Collaborative Innovation Center of Suzhou Nano Science and Technologythe Fundamental Research Funds for the Central Universities
文摘Development of high-performance phase transformation electrodes in lithium ion batteries requires comprehensive studies on stress-mediated lithiation involving migration of the phase interface. It brings out many counter-intuitive phenomena, especially in nanoscale electrodes, such as the slowing down migration of phase interface, the vanishing of miscibility gap under high charge rate, and the formation of surface crack during lithiation. However, it is still a challenge to simulate the evolution of stress in arbitrarily-shaped nanoscale electrodes, accompanied with phase transformation and concurrent plastic deformation. This article gives a brief review of our efforts devoted to address these issues by developing phase field model and simulation. We demonstrate that the miscibility gap of two-phase state is affected not only by stress but also by surface reaction rate and particle size. In addition, the migration of phase interface slows down due to stress. It reveals that the plastic deformation generates large radial expansion, which is responsible for the transition from surface hoop compression to surface hoop tension that may induce surface crack during lithiation. We hope our effort can make a contribution to the understanding of stress-coupled kinetics in phase transformation electrodes.
基金Grant support is from the National Basic Research Program of China(2017YFA050420A and 2018YFA0107604)the National Natural Science Foundation of China(31630095 and 31925015)+1 种基金the Center for Life Science at Tsinghua UniversityWe thank J.Wang,X.Fu,B.Zhou,and Shen laboratory members for insightful discussion and suggestions.
文摘Super-enhancers(SEs)comprise large clusters of enhancers,which are co-occupied by multiple lineage-specific and master tran-scription factors,and play pivotal roles in regulating gene expression and cell fate determination.However,it is still largely un-known whether and how SEs are regulated by the noncoding portion of the genome.Here,through genome-wide analysis,wefound that tpng noncoding RNA(IncRNA)genes preferentially lie next to SEs.In mouse embryonic stem cells(mESCs),depletionof$E-associated IlncRNA transcripts dysregulated the activity of their nearby SEs.Specifically,we revealed a critical regulatoryrole of the IncRNA gene Platr22 in modulating the activity of a nearby SE and the expression of the nearby pluripotency regulatorZFP281.Through these regulatory events,Platr22 contributes to pluripotency maintenance and proper differentiation of mESCs.Mechanistically,Platr22 transcripts coat chromatin near the SE region and interact with DDX5 and hnRNP-L.DDX5 further recruitsp300 and other factors related to active transcription.We propose that these factors assemble into a transcription hub,thus pro-moting an open and active epigenetic chromatin state.0ur study highlights an unanticipated role for a class of lncRNAs in epige-netically controlling the activity and vulnerability to perturbation of nearby SEs for cell fate determination.
文摘Dear Editor, In mammalian genomes, pervasive transcription produces thousands of long non-coding RNA （IncRNA） transcripts （Olebali et al., 2012; Hon et al., 2017）. Compared to protein-coding mRNAs, IncRNAs are less conserved, and often exhibit low-level, developmental stage-and tissue-specific expression （Pauli et al., 2011; Hu et al., 2012; Lee, 2012; Ulitsky and Bartel, 2013; Cech and Steitz, 2014; Hon et al., 2017）. Many IncRNAs are strongly correlated with their neighboring mRNA genes in terms of expression and function, and tend to regulate nearby transcription （Orom et al., 2010; Engreitz et al., 2016; Luo etal., 2016）. It has been implicated that IncRNAs play versatile roles in regulating diverse aspects of cell biology through mechanisms at multiple levels （Pauli et al., 2011; Lee.
