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An extension of the Bollobás-Riordan polynomial for vertex partitioned ribbon graphs: definition and universality
No full textInternational audienc
Identification et Étude des Propriétés Modulatrices de l'Interaction des Protéines Anti-apoptotiques Bcl-xL/Bak et Mcl-1/Bid de Polycétides Cycliques Isolés d'Endiandra Kingiana Gamble (Lauraceae); approche vers la synthèse totale des kingianines
No full textThe preliminary screening showed that the bark of Endiandra kingiana Gamble exhibited potency as a modulating agent between Bcl-xL and Bak, which prompted its chemical investigation. Two groups of compounds were isolated and characterized; the endiandric acid series and the kingianin series. Eight new endiandric acid analogues (kingianic acids A-H [120-127]) and three new kingianin analogues (kingianin O-Q [128-130]) were isolated and structurally elucidated. The isolated compounds were evaluated for two bioassays; Bcl-xL/Bak and Mcl-1/Bid of binding affinities and cytotoxic effects against various human tumour cells. The second part describes the progression towards the total synthesis of kingianin analogues. The pentacyclic kingianin skeleton was formed by Diels-Alder reaction between two monomers having a bicyclo[4.2.0]octadiene backbone formed by a stereospecific electrocyclization of polyenes. The research was focusing on construction of bicyclo[4.2.0]octadiene monomer using [2+2] ketene cycloaddition approach at the early stage of the synthesis. One of the main advantages of such a strategy is the rapid assembly of the carbon skeleton of kingianins, thus maximizing the chances for good overall yields of the final products. So far, an efficient synthesis of the bicyclo[4.2.0]octene backbone was successfully achieved. Five approaches to synthesize this backbone starting from [2+2] cycloaddition of the cyclohexadienes to functionalized ketenes followed by functionalization of substituent at C-7 and C-8 positions with the correct relative configuration were described. From these approaches, compounds 280 and 311 were identified as the key intermediates. This key step of the synthesis provided an access to the kingianins skeleton.Un criblage biologique préliminaire a montré que l'extrait des écorces d'Endiandrakingianapossédait une forte affinité pour la protéine anti-apoptotique Bcl-xL, motivant ainsi la réalisationd’une étude chimique complète. Deux groupes de composés ont été isolés et caractérisés: d’une part, huit nouveaux dérivés de l'acide endiandrique (les acides kingianiques A à H [120−127]) et d’autre part, trois nouvelleskingianines (les kingianines O à Q [128−130]). Le potentiel inhibiteur des nouvelles molécules vis-à-vis des interactionsBcl-xL/Bak et Mcl-1/Bida ensuite été évalué, ainsi que leurs propriétés cytotoxiques sur diverses lignées cellulaires tumorales humaines. La seconde partie du manuscrit présente une approche vers la synthèse totale des kingianines et de composés analogues.Le squelette pentacyclique des produits naturels résulte formellement d’une réaction de Diels-Alder entre deux unités bicyclo[4.2.0]octadiène, elles-mêmes issues d’une cascade d’électrocyclisation de tétraènes entièrement conjugués. Une stratégie de construction directe de motifs bicyclo[4.2.0]octadiènespar une cycloaddition [2+2] entre des cycloalcènes et des cétènes convenablement choisisdoit assurer l’obtention des molécules cibles avec de bons rendements globaux. Au total, cinq approches ont été implémentées. Elles débutent par la cycloaddition [2+2] entre des cyclohexadiènes et des cétènes fonctionnalisés et se poursuivent par la fonctionnalisation des positions C7 et C8 en contrôlant la configuration relative de ces centres. Les résultats obtenus ont conduit à identifier les composés 280 et 311 comme des intermédiaires clefs à même d’être convertis en diènes ou en diénophiles, pouvant alors être engagés dans des cycloadditions de Diels-Alder pour accéder à la structure pentacyclique des kingianines
Trois Essais sur les Progrès de la Santé et le Développement Économique en Afrique
No full textThis dissertation aims at opening the black box of African health progress during and followingthe colonial period. It does so by making three contributions to the literature on health policies,health standards and fertility patterns, in the 20th century’s Africa.The first chapter compares the colonial strategies for health policies’ provision and other colonialpolicies in former FrenchWest Africa between 1904 and 1958. Drawing on colonial archivesand existing data, it gathers a unique dataset containing colonial inputs at the colonial districtlevel: medical and educational staff, vaccinations, public work’s expenses and conscription.There was a very general strategy as regards to the provision of colonial services. In this context,the allocation of health inputs was specific in two dimensions only. First, medical staffwas used as a means of colonial “coverage”. Second, there is a long-lasting effect of preventionleading to a “diversification” strategy for all health investments. Away from these specificities,the common factors to all investments have to do with the colonial administration’s preferencefor path dependence, investments’ returns to scale, the diseases’ contagion risk and the demandfor colonial services. This work also suggests that there was no specialization of districtsin one type of investments.The second chapter of this thesis looks at the relationship between adult height and underfivemortality in the context of the “double African Paradox” in West Africa. Africans arerelatively tall in spite of extremely unfavorable income and disease environments. Moreover,their height stature decreased since the 1960’s despite improving health conditions and a fallin under-five mortality rates. This study points to selective mortality, by bringing forward apositive correlation between mothers’ height and mortality in the 1980’s West Africa. It thenestimates a new model of height differential between survivors and deceased. Results implythat selective mortality could be large enough to mask significant height increases in the 1980’sWest Africa. In high mortality contexts, anthropometric studies should discuss mortality levelsand trends. More generally, results imply that the issue of selective mortality is crucial to assessthe long-term impact of most health interventions.The third chapter tackles another specificity of African health: fertility and gender preferences.It develops a new indicator of gender preferences based on birth spacing. Applying it to Africaprovides evidence that son preference is strong and increasing in North Africa, whereas Sub-Saharan African countries display a preference for variety or no preference at all. Traditionalfamily systems accurately predict the nature of gender preferences, while religion does not.Last, the magnitude of preferences is stronger for wealthier and more educated women.Cette thèse a pour ambition d’ouvrir la boîte noire que constituent les progrès de la santé en Afrique auXXème siècle. Ce faisant, elle apporte trois contributions à la littérature portant sur les investissementsde santé, les conditions de santé et la fécondité en Afrique au XXème siècle.Le premier chapitre compare la stratégie de l’administration coloniale en ce qui concerne les politiquesde santé à sa stratégie pour d’autres politiques coloniales dans l’ex-Afrique Occidentale Française entre1904 et 1958. Ce chapitre utilise des archives coloniales et des données existantes pour créer unebase de données inédite sur les investissements au niveau des cercles coloniaux: personnels de santé etd’enseignement, vaccinations, dépenses de travaux publics et conscription. La provision de politiquescoloniales était déterminée par une stratégie très générale et l’allocation des politiques de santé n’estspécifique que selon deux dimensions. Le personnel de santé était mobilisé pour “couvrir” le territoireconquis et l’effet de longue durée de la prévention menait à une stratégie de “diversification” pour tousles investissements de santé. En dehors de ces spécificités, les facteurs communs à tous les investissementscoloniaux sont liés à la préférence de l’administration coloniale pour une dépendance au sentierdes investissements, aux rendements d’échelle des investissements, au risque de transmission de maladieset à la demande pour les services coloniaux. Ce chapitre suggère aussi que l’administration nevisait pas une spécialisation des districts par type d’investissements.Le second chapitre étudie la relation entre la taille à l’âge adulte et la mortalité avant cinq ans en Afriquede l’Ouest, dans le contexte du “double paradoxe Africain”. Les Africains sont relativement grands,malgré un environnement sanitaire dégradé et des revenus relativement bas. De plus, leur taille à l’âgeadulte a diminué depuis 1960, malgré une amélioration des conditions de santé, et une diminution dela mortalité avant cinq ans. Ce travail suggère qu’une partie de ce paradoxe s’explique par la mortalitésélective, en mettant en avant une corrélation positive entre la taille des mères et la mortalité, dansl’Afrique de l’Ouest des années 80. Ce chapitre propose une modélisation inédite du différentiel de tailleentre survivants et décédés. L’estimation de ce modèle indique qu’on ne peut pas exclure qu’en l’absencede sélection par la mortalité, les tailles adultes auraient augmenté, plutôt que stagné, pendant les années80. Dans des contextes de forte mortalité, les études anthropométriques doivent discuter des niveauxet des tendances de mortalité, afin de prendre en compte la mortalité sélective. Plus généralement, les résultats de ce travail impliquent que la question de la sélection par la mortalité est essentielle pourévaluer l’impact de long-terme de la plupart des politiques de santé.Le troisième chapitre traite d’une autre spécificité de la santé en Afrique: le lien entre fécondité etpréférences de genre. Ce chapitre développe un indicateur des préférences de genre fondé sur les intervallesde naissance observés. Cet indicateur est ensuite appliqué au cas de l’Afrique. La préférencepour les garçons est à la fois forte et croissante dans le temps en Afrique du Nord, alors que les paysd’Afrique sub-Saharienne sont caractérisés par une préférence pour la variété, ou par une absence depréférence de genre. Les systèmes familiaux traditionnels prédisent avec précision le type de préférence,ce qui n’est pas le cas de la religion déclarée. Enfin, la magnitude des préférences de genre est plusimportante pour les femmes plus riches et/ou plus éduquées
Arbitrary-detuning asynchronous optical sampling with amplified laser systems
No full textInternational audienceWe demonstrate that Arbitrary-Detuning ASynchronous OPtical Sampling (AD-ASOPS) makes possible multiscale pump-probe spectroscopy with time delays spanning from picosecond to millisecond. The implementation on pre-existing femtosecond amplifiers seeded by independent free-running oscillators is shown to be straightforward. The accuracy of the method is determined by comparison with spectral interferometry, providing a distribution with a standard deviation ranging from 0.31 to 1.7 ps depending on experimental conditions and on the method used to compute the AD-ASOPS delays. (C) 2015 Optical Society of Americ
Steps Towards Quantification of the Cardiological Stress Exam
No full textInternational audienceIn this work we aim to advance the translation of model-based myocardial contractility estimation to the clinical problem of quantitative assessment of the dobutamine stress exam. In particular, we address the question of limited spatial resolution of the observations obtained from cine MRI during the stress test, in which typically only a small number of cine MRI slices are acquired. Due to the relative risk during the dobutamine infusion, a safe acquisition protocol with a healthy volunteer under the infusion of a beta-blocker is applied in order to get a better insight into the contractility estimation using such a type of clinical data. The estimator is compared for three types of observations, namely the processed short axis cine stack contiguously covering the ven-tricles, the short axis stack limited to only 3 slices and the combination of 3 short and 3 long axis slices. A decrease of contractilities in AHA regions under the beta-blocker infusion was estimated for each observation. The corrected model (by using the estimated parameters) was then compared with the displacements extracted from 3D tagged MRI
Discrete Derivatives of Vector Fields on Surfaces – An Operator Approach
No full textInternational audienceVector fields on surfaces are fundamental in various applications in computer graphics and geometry processing. In many cases, in addition to representing vector fields, the need arises to compute their derivatives, for example, for solving partial differential equations on surfaces or for designing vector fields with prescribed smoothness properties. In this work, we consider the problem of computing the Levi-Civita covariant derivative, that is, the tangential component of the standard directional derivative, on triangle meshes. This problem is challenging since, formally, tangent vector fields on polygonal meshes are often viewed as being discontinuous, hence it is not obvious what a good derivative formulation would be. We leverage the relationship between the Levi-Civita covariant derivative of a vector field and the directional derivative of its component functions to provide a simple, easy-to-implement discretization for which we demonstrate experimental convergence. In addition, we introduce two linear operators which provide access to additional constructs in Riemannian geometry that are not easy to discretize otherwise, including the parallel transport operator which can be seen simply as a certain matrix exponential. Finally, we show the applicability of our operator to various tasks, such as fluid simulation on curved surfaces and vector field design, by posing algebraic constraints on the covariant derivative operator. ACM Reference Format: Omri Azencot, Maks Ovsjanikov, Frédéric Chazal, and Mirela Ben-Chen. 2015. Discrete derivatives of vector fields on surfaces – An operator approach
Focused Linear Logic and the λ-calculus
No full textInternational audienceLinear logic enjoys strong symmetries inherited from classical logic while providing a constructive framework comparable to intuitionistic logic. However, the computational interpretation of sequent calculus presentations of linear logic remains problematic, mostly because of the many rule permutations allowed in the sequent calculus. We address this problem by providing a simple interpretation of focused proofs, a complete subclass of linear sequent proofs known to have a much stronger structure than the standard sequent calculus for linear logic. Despite the classical setting, the interpretation relates proofs to a refined linear λ-calculus, and we investigate its properties and relation to other calculi, such as the usual λ-calculus, the λµ-calculus, and their variants based on sequent calculi
Variational Approach to Dynamic Brittle Fracture via Gradient Damage Models
No full textInternational audienceIn this paper we present a family of gradient-enhanced continuum damage models which can be viewed as a regularization of the variational approach to fracture capable of predicting in a unified framework the onset and space-time dynamic propagation (growth, kinking, branching, arrest) of complex cracks in quasi-brittle materials under severe dynamic loading. The dynamic evolution problem for a general class of such damage models is formulated as a variational inequality involving the action integral of a generalized Lagrangian and its physical interpretation is given. Finite-element based implementation is then detailed and mathematical optimization methods are directly used at the structural scale exploiting fully the variational nature of the formulation. Finally, the link with the classical dynamic Griffith theory and with the original quasi-static model as well as various dynamic fracture phenomena are illustrated by representative numerical examples in quantitative accordance with theoretical or experimental results
Boltzmann equation for granular media with thermal force in a weakly inhomogeneous setting
No full textIn this paper, we consider the spatially inhomogeneous diffusively driven inelastic Boltzmann equation in different cases: the restitution coefficient can be constant or can depend on the impact velocity (which is a more physically relevant case), including in particular the case of viscoelastic hard spheres. In the weak thermalization regime, i.e. when the diffusion parameter is sufficiently small, we prove existence of global solutions considering the close-to-equilibrium regime as well as the weakly inhomogeneous regime in the case of a constant restitution coefficient. It is the very first existence theorem of global solution in an inelastic ``collision regime'' (that is excluding \cite{AR} where an existence theorem is proven in a near to the vacuum regime). We also study the long-time behavior of these solutions and prove a convergence to equilibrium with an exponential rate. The basis of the proof is the study of the linearized equation. We obtain a new result on it, we prove existence of a spectral gap in weighted (stretched exponential and polynomial) Sobolev spaces and a result of exponential stability for the semigroup generated by the linearized operator. To do that, we develop a perturbative argument around the spatially inhomogeneous equation for elastic hard spheres and we take advantage of the recent paper \cite{GMM}where this equation has been considered. We then link the linearized theory with the nonlinear one in order to handle the full non-linear problem thanks to new bilinear estimates on the collision operator that we establish. As far as the case of a constant coefficient is concerned, the present paper largely improves similar results obtained in \cite{MM2} in a spatially homogeneous framework. Concerning the case of a non-constant coefficient, this kind of results is new and we use results on steady states of the linearized equation from \cite{AL3}