Construction d'un Atlas 3D numérique de la cornée humaine par recalage d'images

Nous proposons de construire un atlas numérique 3D contenant les caractéristiques moyennes et les variabilités de la morphologie d’un organe. Nos travaux seront appliqués particulièrement à la construction d'un atlas numérique 3D de la totalité de la cornée humaine incluant la surface antérieure et postérieure à partir des cartes topographiques fournies par le topographe Orbscan II. Nous procédons tout d'abord par normalisation de toute une population de cornées. Dans cette étape, nous nous sommes basés sur l'algorithme de recalage ICP (iterative closest point) pour aligner simultanément les surfaces antérieures et postérieures d'une population de cornée vers les surfaces antérieure et postérieure d'une cornée de référence. En effet, nous avons élaboré une variante de l'algorithme ICP adapté aux images (cartes) de cornées qui tient compte de changement d'échelle pendant le recalage et qui se base sur la recherche par voisinage via la distance euclidienne pour établir la correspondance entre les points. Après, nous avons procédé pour la construction de l'atlas cornéen par le calcul des moyennes des élévations de surfaces antérieures et postérieures recalées et leurs écarts-types associés. Une population de 100 cornées saines a été utilisée pour construire l'atlas cornéen normal. Pour visualiser l’atlas, on a eu recours à des cartes topographiques couleurs similairement à ce qu’offrent déjà les systèmes topographiques actuels. Enfin, des observations ont été réalisées sur l'atlas cornéen reflétant sa précision et permettant de développer une meilleure connaissance de l’anatomie cornéenne.

The great asymmetry : America's closest allies in times of war

This dissertation focuses on military cooperation between the United States and its special allies. It argues that alliance expectations determine the level of military cooperation, while two intervening variables - the level of government cohesion and military capabilities - determine its implementation. This study also shows how secondary states deploy strategies to overcome power asymmetries through bilateral concessions, international organizations and by appealing to principle. The focus of the research is on special allies, as they have the most to gain or lose by going along with American plans. My contention is that secondary allies can rarely influence the dominant ally decisively, but they can act autonomously and resist to pressures exerted by the stronger alliance partner. The argument builds on three central claims. First, power asymmetries between allies translate into different assessments of international threats. Second, when disagreements over threats arise, the outcome of intra-alliance bargaining is not necessarily dictated by the preferences of the stronger power. Third, secondary states, as opposed to the dominant partner, face unique constraints when facing major foreign policy decisions, i.e. they face a trade-off between establishing a credible reputation as an alliance partner in a politically feasible way while minimizing domestic audience costs. To examine the theoretical puzzle presented by asymmetric military cooperation, I introduce a causal explanation that builds on neoclassical realism, to zone in on the interaction between systemic and domestic variables. My research makes a contribution to alliance theory and foreign policy decision-making by studying how special allies respond to American decisions in times of threat and how systemic constraints are channeled through state-level variables. To investigate the causal link between threat perception, alliance expectations and domestic constraints, this study relies on the method of structured focused comparison with three detailed case studies. The focus is on the initial decision made by special allies regarding whether or not to participle in joint mobilization with the United States. The decision-making process is presented from the perspective of secondary allied states and measures the explanatory factors that motivated the decision on military cooperation. The case studies are the UK, Canada and Australia’s response to the war in Afghanistan and the war in Iraq during the period of 2001 to 2003.