Gamma-convergence et singularités vortex au bord dans des films ferromagnétiques minces avec interaction de Dzyaloshinskii-Moriya

Cette thèse porte sur l'analyse asymptotique d'un modèle variationnel pour les films ferromagnétiques minces. On étudie l'énergie micromagnétique, définie pour des applications d'un ouvert de R^3 à valeurs dans la sphère S^2, appelées aimantations, en prenant en compte l'effet antisymétrique dû à l'interaction de Dzyaloshinskii-Moriya. Dans le premier chapitre de la thèse, on étudie la Gamma-convergence de l'énergie micromagnétique dans un régime de film mince qui favorise l'émergence de vortex au bord de taille epsilon>0, via une pénalisation au bord obtenue dans la Gamma-limite de l'énergie. Cette limite est en fait définie pour des aimantations invariantes dans l'épaisseur du film et à valeurs dans le cercle unité S^1, ce qui signifie que le modèle général en trois dimensions se réduit à un modèle en deux dimensions. On cherche ensuite les minimiseurs locaux de l'énergie Gamma-limite dans le demi-plan supérieur. Pour cela, on étudie d'abord ses points critiques, qui satisfont un problème de Neumann non linéaire similaire au problème de Peierls-Nabarro. On en déduit, sous certaines conditions, l'unicité des minimiseurs locaux de l'énergie au sens de De Giorgi. Ceux-ci correspondent à des applications qui tendent à présenter un vortex de taille epsilon>0 sur le bord du domaine. Dans le second chapitre de la thèse, on considère un autre régime de film mince favorisant les singularités vortex au bord. Grosso modo, ce régime consiste dans l'analyse du modèle précédent lorsque epsilon tend vers 0. On montre que l'étude du modèle général en trois dimensions se ramène ici aussi à l'étude d'un modèle intermédiaire en deux dimensions, mais dans lequel figurent à la fois une pénalisation intérieure (les applications ne sont plus à valeurs dans S^1) et une pénalisation au bord du domaine. D'abord, on étudie ce modèle intermédiaire en deux dimensions. Grâce à la notion de Jacobien global, on obtient des résultats de compacité et un développement asymptotique au second ordre par Gamma-convergence de l'énergie micromagnétique. Le terme d'ordre un montre que les singularités vortex sont localisées au bord du domaine, tandis que le terme d'ordre deux est une énergie renormalisée, semblable à celle rencontrée dans le modèle de Ginzburg-Landau, qui permet d'estimer le coût d'interaction entre les vortex au bord. On calcule explicitement cette énergie renormalisée, influencée par l'interaction de Dzyaloshinskii-Moriya, et on étudie la structure des minimiseurs. Enfin, grâce à ces résultats, nous déduisons la Gamma-convergence à l'ordre deux dans le modèle en trois dimensions.This thesis deals with the asymptotic analysis of a variational model for thin ferromagnetic films. We study the micromagnetic energy for three-dimensional maps with values into the unit sphere S^2, called magnetizations, by taking into account the antisymmetric effect of the Dzyaloshinskii-Moriya interaction. In the first chapter, we study the Gamma-convergence of the micromagnetic energy in a thin-film regime that favors boundary vortices of size epsilon>0, via a boundary penalization in the Gamma-limit energy. This limit is in fact defined for magnetizations that are invariant in the thickness of the film and take values into the unit circle S^1. It means that the general three-dimensional model reduces to a two-dimensional model. We then focus on local minimizers in the upper-half plane of the Gamma-limit energy. To do so, we begin with studying its critical points, that satisfy a nonlinear Neumann boundary value problem, similar to the Peierls-Nabarro problem. We deduce, under certain conditions, the uniqueness of the local minimizers of the energy in the sense of De Giorgi. These minimizers correspond to maps having a vortex of size epsilon>0 on the boundary of the domain. In the second chapter, we consider another thin-film regime for boundary vortices. Roughly speaking, this regime corresponds to the limit epsilon tends to 0 in the previous model. The study of the three-dimensional general model reduces here to an intermediate two-dimensional model for R^2-valued maps (not S^1-valued maps), that combines an interior penalization and a boundary penalization on the domain. First, we study this two-dimensional intermediate model. Using the notion of global Jacobian, we prove compactness results and an asymptotic expansion at the second order by Gamma-convergence for the micromagnetic energy. The first order term indicates that the singularities are located on the boundary of the domain, while the second order term is a renormalized energy, similar to the Ginzburg-Landau model, that measures the interactions between the boundary vortices. We compute explicitely this renormalized energy, that depends on the Dzyaloshinskii-Moriya interaction, and study the structure of its minimizers. Finally, thanks to these results, we deduce the Gamma-convergence at the second order for the general three-dimensional model

People of New York vs. Van Wormer Brothers, Witness Index

https://digitalrepository.trincoll.edu/vanwormers_case/1003/thumbnail.jp

People of New York vs. Van Wormer Brothers, Second Copy, Vol. 1

https://digitalrepository.trincoll.edu/vanwormers_case/1004/thumbnail.jp

People of New York vs. Van Wormer Brothers, Second Copy, Vol. 2

https://digitalrepository.trincoll.edu/vanwormers_case/1005/thumbnail.jp

NorthStar, a support tool for the design and evaluation of quality improvement interventions in healthcare

Background: The Research-Based Education and Quality Improvement (ReBEQI) European partnership aims to establish a framework and provide practical tools for the selection, implementation, and evaluation of quality improvement (QI) interventions. We describe the development and preliminary evaluation of the software tool NorthStar, a major product of the ReBEQI project. Methods: We focused the content of NorthStar on the design and evaluation of QI interventions. A lead individual from the ReBEQI group drafted each section, and at least two other group members reviewed it. The content is based on published literature, as well as material developed by the ReBEQI group. We developed the software in both a Microsoft Windows HTML help system version and a web-based version. In a preliminary evaluation, we surveyed 33 potential users about the acceptability and perceived utility of NorthStar. Results: NorthStar consists of 18 sections covering the design and evaluation of QI interventions. The major focus of the intervention design sections is on how to identify determinants of practice (factors affecting practice patterns), while the major focus of the intervention evaluation sections is on how to design a cluster randomised trial. The two versions of the software can be transferred by email or CD, and are available for download from the internet. The software offers easy navigation and various functions to access the content. Potential users (55% response rate) reported above-moderate levels of confidence in carrying out QI research related tasks if using NorthStar, particularly when developing a protocol for a cluster randomised trial Conclusion: NorthStar is an integrated, accessible, practical, and acceptable tool to assist developers and evaluators of QI interventions

The feasibility of working memory tablet tasks in predicting scholastic skills in classroom settings

Cognitive assessment in natural group settings facilitates data collection but poses threats to the validity. In this study, tablet‐based working memory (WM) tasks, the counting span, and reading span were used in predicting 12‐year‐old children's (N = 837) scholastic skills and fluid intelligence in a classroom with environmental noise. WM tasks had excellent internal consistency, correlated with scholastic skills, and accounted for more of the variance in cognitive performance (grade point average, fluid intelligence, scholastic skills) compared with individually administered (n = 190) digit span task. Furthermore, the multilevel analysis revealed that compared with the classrooms with no noise, when naturally occurring speech or nonspeech types of environmental noises were present during assessment, WM scores or the reliability estimates were not lower. In contrast, when both types of noises were present, the relationships between some of the WM and achievement scores were even stronger. Thus, assessments in natural classroom contexts may promote revealing the individual differences in WM.Peer reviewe

Effect of pre-germination time of brown rice on serum cholesterol levels of hypercholesterolaemic rats.

Background: Brown rice is unpolished rice with immeasurable benefits for human health. Brown rice (BR) and pre-germinated brown rice (PGBR) are known to contain various functional compounds such as gamma-oryzanol, dietary fibre and gamma-aminobutyric acid (GABA). In the present study, the experimental diets containing BR and PGBR (24, 48 h pre-germination) were used to investigate the influence of pre-germination time of brown rice on blood cholesterol in Sprague-Dawley male rats. Result: Hypercholesterolaemia and elevation of LDL-cholesterol were successfully ameliorated by the experimental diets containing BR and PGBR (24 and 48 h pre-germination). As compared to the control sample, the pre-germination time had a significant (P < 0.05) effect on blood cholesterol of Sprague-Dawley male rats. It was also found that the significantly (P < 0.05) better effect on lipid profile of hypercholesterolaemic rats was observed by prolonging the pre-germination time. As compared to non-germinated brown rice, the germinated brown rice showed the higher cardio-protective effect on hypercholesterolaemic Sprague-Dawley male rats. Conclusion: The present study suggests that the changes of blood cholesterol can be mainly modulated by using the PGBR rather than BR. The prolonging of pre-germination time led to an increase in the bioactive components, thereby providing a more efficient functional diet affecting the high blood cholesterol. This study suggests that PGBR can be used instead of BR and polished rice in the human diet