Littérature scientifique sur le sujet « Curvature driven migration »

This paper discusses a coupled mechanics–phase-field model that can predict microstructure evolution in metallic polycrystals and in particular evolution of lattice orientation due to either deformation or grain boundary migration. The modeling framework relies on the link between lattice curvature and geometrically necessary dislocations and connects a micropolar or Cosserat theory with an orientation phase-field model. Some focus is placed on the underlying theory and in particular the theory of dislocations within a continuum single crystal plasticity setting. The model is finally applied to the triple junction problem for which there is an analytic solution if the grain boundary energies are known. The attention is drawn on the evolution of skew–symmetric stresses inside the grain boundary during migration.

Domain migration is observed on the surface of ternary giant unilamellar vesicles held in a temperature gradient in conditions where they exhibit coexistence of two liquid phases. The migration localizes domains to the hot side of the vesicle, regardless of whether the domain is composed of the more ordered or disordered phase and regardless of the proximity to chamber boundaries. The distribution of domains is explored for domains that coarsen and for those held apart due to long-range repulsions. After considering several potential mechanisms for the migration, including the temperature preferences for each lipid, the favored curvature for each phase, and the thermophoretic flow around the vesicle, we show that observations are consistent with the general process of minimizing the system’s line tension energy, because of the lowering of line interface energy closer to mixing. DNA strands, attached to the lipid bilayer with cholesterol anchors, act as an exemplar “cargo,” demonstrating that the directed motion of domains toward higher temperatures provides a route to relocate species that preferentially reside in the domains.

In silicon steels, interaction of grain boundaries with particles occurs in a selective way. Currently, it is very difficult to include this preferential interaction directly in the classical simulation models. A new approach of grain growth simulation based on the concept of curvature-driven migration of the grain boundaries in the presence of particles has been used to study the abnormal grain growth (AGG) in Fe-3%Si alloy.

On étudie la dynamique et la rhéologie d'une suspension de vésicules (un modèle pour les globules rouges) dans la limite de faibles nombres de Reynolds en utilisant des simulations numériques, basées sur les méthodes des intégrales au bord et du champ de phase. L'attention est mise sur le lien entre la dynamique microscopique des particules et le comportement d'ensemble de la suspension (c. à d. La rhéologie). On analyse une suspension diluée de vésicules dans un écoulement de cisaillement linéaire et on décrit en détail l'influence des paramètres qui en gouvernent la dynamique. On explique le comportement complexe des grandeurs rhéologiques (viscosité effective et différence des contraintes normales) et on détail le rôle de la membrane de la vésicule. On examine l'influence de la courbure des lignes d'écoulement sur la dynamique des vésicules, et on reporte une migration non-négligeable dans la direction de concavité. L'interprétation donnée reste valable pour la plupart des fluides complexes, comme les émulsions et les suspensions de polymères. De plus, on a investigué le comportement d'une suspension de vésicules dans un apparat de Taylor-Couette microscopique, et une transition vers des états ordonnés a été mise en évidence à des fractions volumiques très faibles. On étudie aussi le comportement d'ensembles de vésicules dans un écoulement parabolique, une situation qui imite les globules rouges dans les capillaires sanguins. Les vésicules, soumises aux seules forces hydrodynamiques, forment des agrégats de taille finie, un fait qui pourrait être d'importance physiologique. La transposition des résultats ci-dessus aux globules rouges est discutée
The dynamics and the rheology of a suspension of vesicles (a model for red blood cells) in the limit of small Reynolds number are studied by means of two-dimensional numerical simulations, based on the boundary integral and phase field methods. The focus is on the link between the microscopic dynamics of the particles and the overall behavior of the suspension (i. E. Rheology). A dilute suspension of vesicles in a linear shear flow is analyzed in detail and the influence of the three parameters governing the dynamics of a single vesicle (reduced volume; viscosity contrast; capillary number) is extensively described. The nontrivial behavior of the rheological quantities (effective viscosity and normal stress difference) is explained and the role of the membrane of the vesicle detailed. The influence of the curvature of the flow lines on the dynamics of the vesicles is investigated for the first time, and consistent inward migration is reported. The suggested interpretation remains valid for the flow of the majority of complex fluids, like emulsions and polymer suspensions, and is thus expected to have an impact in other fields. Moreover, the behavior of a suspension of vesicles in a microscopic Taylor-Couette cell is investigated, and a transition to ordered states is reported at very low volume fraction. The behavior of sets of vesicles in a parabolic flow, a setup that mimics red blood cells in the microvasculature, is presented. Vesicles submitted to sole hydrodynamical interactions are found to form aggregates of finite size, a fact that may prove of physiological interest. Finally, the transposition to red blood cells of the results above is discussed

Contemporary empirical studies on identity question and political identity reveal that numerous political challenges revolve around the questions of identity. Identity thesis engenders a landscape of tremendous diversity and variation, which poses political problems when there is too much or too little of it. It manifests itself when there is a shift towards cultural diversity, largely due to upswing in migration and globalization. Given the multi-ethnic configuration of Nigeria characterized by heightened identity politics, a scenario of acute crisis of identity is inexorable. This study, therefore, examines why societies are today increasingly characterized by ethnic, racial, and religious diversity, which creates room for various forms of identity. Drawing upon extensive contemporary research and literature on diversity and identity politics, the study adopts qualitative descriptive methodology with content analysis curvature. Findings reveal that Nigerian political behavior, socio-economic relationship, and governance are driven by identity politics and ethnic solidarity.