Poincaré-Cosserat equations for Lighthill three-dimensional dynamic model of a self propelled eel devoted to Robotics

International audienceIn this article, we propose a dynamic model of the three-dimensional eel swim. This model is analytical and suited to the on-line control of eel-like robots. The proposed solution is based on the Large Amplitude Elongated Body Theory of Lighthill and a working frame recently proposed in [1] for the dynamic modeling of hyper-redundant robots. This working frame was named "macro-continuous" since at this macroscopic scale, the robot (or the animal) is considered as a Cosserat beam internally (and continuously) actuated. This article proposes new results in two directions. Firstly, it achieves an extension of the Lighthill theory to the case of a self propelled body swimming in three dimensions, while including a model of the internal control torque. Secondly, this generalization of the Lighthill model is achieved due to a new set of equations which is also derived in this article. These equations generalize the Poincaré equations of a Cosserat beam to the case of an open system containing a fluid stratified around the slender beam

Unification monétaire et soutenabilité : les enseignements de l’histoire canadienne aux Européens

Cet article cherche à étudier l’unification monétaire canadienne qui s’est déroulée de 1841 à 1867 pour fournir des enseignements sur la situation monétaire européenne. L’objectif consiste à montrer que l’établissement de règles monétaires particulières a permis à l’État canadien de mettre en œuvre certaines politiques économiques. Grâce à ces dernières, il a assuré le développement de facteurs de soutenabilité, à savoir développement économique homogène, transferts budgétaires et mobilité du travail. Ainsi, nous pouvons en déduire les éléments nécessaires pour résoudre et financer les déséquilibres au sein de l’Union économique et monétaire. Le développement d’un État fédéral, capable de mettre en œuvre une politique budgétaire expansionniste, nous semble être la condition sine qua non.This article studies the Canadian monetary unification which took place from 1841 to 1867. It provides useful information to the European monetary situation. The goal consists to show how a specific political process to determine monetary rules allow the State to implement economic policies. Because of the latter, it enabled the development of sustainability determinants for the Canadian monetary unification, namely economic convergence and growth, fiscal transfer and labour mobility. Thus, we deduce the key characteristics to resolve and finance the economic and monetary union disequilibrium. The Development of a federal state, able to implement an expansionist fiscal policy, seems to the sine qua non condition

Efficient Linear Programming for Dense CRFs

The fully connected conditional random field (CRF) with Gaussian pairwise potentials has proven popular and effective for multi-class semantic segmentation. While the energy of a dense CRF can be minimized accurately using a linear programming (LP) relaxation, the state-of-the-art algorithm is too slow to be useful in practice. To alleviate this deficiency, we introduce an efficient LP minimization algorithm for dense CRFs. To this end, we develop a proximal minimization framework, where the dual of each proximal problem is optimized via block coordinate descent. We show that each block of variables can be efficiently optimized. Specifically, for one block, the problem decomposes into significantly smaller subproblems, each of which is defined over a single pixel. For the other block, the problem is optimized via conditional gradient descent. This has two advantages: 1) the conditional gradient can be computed in a time linear in the number of pixels and labels; and 2) the optimal step size can be computed analytically. Our experiments on standard datasets provide compelling evidence that our approach outperforms all existing baselines including the previous LP based approach for dense CRFs.Comment: 24 pages, 10 figures and 4 table

Fast Dynamics of a three dimensional eel-like robot: comparisons with Navier-Stokes simulations

International audienceThis article proposes a dynamic model of the swim of elongated ﰣshes suited to the on-line control of bio-mimetic eel-like robots. The approach is analytic and can be considered as an extension of the original reactive "Large-Elongated-Body-Theory" of Lighthill to the three dimensional self propulsion augmented of a resistive empirical model. While all the mathematical fundamentals are detailed in [1], this article essentially focuses on the numerical validation and calibration of the model and the study of swimming gaits. The proposed model is coupled to an algorithm allowing us to compute the motion of the ﰣsh head and the ﰣeld of internal control torque from the knowledge of the imposed internal strain ﰣelds. Based on the Newton-Euler formalism of robots dynamics, this algorithm works faster than real time. As far as precision is concerned, many tests obtained with several planar and three dimensional gaits are reported and compared (in the planar case) with a Navier-Stokes solver, devoted until today to the planar swim. The comparisons obtained are very encouraging since in all the cases we tested, the diﰢerences between our simpliﰣed and reference simulations do not exceed ten per cent

Efficient Relaxations for Dense CRFs with Sparse Higher Order Potentials

Dense conditional random fields (CRFs) have become a popular framework for modelling several problems in computer vision such as stereo correspondence and multi-class semantic segmentation. By modelling long-range interactions, dense CRFs provide a labelling that captures finer detail than their sparse counterparts. Currently, the state-of-the-art algorithm performs mean-field inference using a filter-based method but fails to provide a strong theoretical guarantee on the quality of the solution. A question naturally arises as to whether it is possible to obtain a maximum a posteriori (MAP) estimate of a dense CRF using a principled method. Within this paper, we show that this is indeed possible. We will show that, by using a filter-based method, continuous relaxations of the MAP problem can be optimised efficiently using state-of-the-art algorithms. Specifically, we will solve a quadratic programming (QP) relaxation using the Frank-Wolfe algorithm and a linear programming (LP) relaxation by developing a proximal minimisation framework. By exploiting labelling consistency in the higher-order potentials and utilising the filter-based method, we are able to formulate the above algorithms such that each iteration has a complexity linear in the number of classes and random variables. The presented algorithms can be applied to any labelling problem using a dense CRF with sparse higher-order potentials. In this paper, we use semantic segmentation as an example application as it demonstrates the ability of the algorithm to scale to dense CRFs with large dimensions. We perform experiments on the Pascal dataset to indicate that the presented algorithms are able to attain lower energies than the mean-field inference method

Composing Multiple Variability Artifacts to Assemble Coherent Workflows

International audienceThe development of scientific workflows is evolving towards the system- atic use of service oriented architectures, enabling the composition of dedicated and highly parameterized software services into processing pipelines. Building consistent workflows then becomes a cumbersome and error-prone activity as users cannot man- age such large scale variability. This paper presents a rigorous and tooled approach in which techniques from Software Product Line (SPL) engineering are reused and ex- tended to manage variability in service and workflow descriptions. Composition can be facilitated while ensuring consistency. Services are organized in a rich catalog which is organized as a SPL and structured according to the common and variable concerns captured for all services. By relying on sound merging techniques on the feature mod- els that make up the catalog, reasoning about the compatibility between connected services is made possible. Moreover, an entire workflow is then seen as a multiple SPL (i.e., a composition of several SPLs). When services are configured within, the prop- agation of variability choices is then automated with appropriate techniques and the user is assisted in obtaining a consistent workflow. The approach proposed is com- pletely supported by a combination of dedicated tools and languages. Illustrations and experimental validations are provided using medical imaging pipelines, which are rep- resentative of current scientific workflows in many domains

Increased Muscle Stress-Sensitivity Induced by Selenoprotein N Inactivation in Mouse: A Mammalian Model for SEPN1-Related Myopathy

Selenium is an essential trace element and selenoprotein N (SelN) was the first selenium-containing protein shown to be directly involved in human inherited diseases. Mutations in the SEPN1 gene, encoding SelN, cause a group of muscular disorders characterized by predominant affection of axial muscles. SelN has been shown to participate in calcium and redox homeostasis, but its pathophysiological role in skeletal muscle remains largely unknown. To address SelN function in vivo, we generated a Sepn1-null mouse model by gene targeting. The Sepn1−/− mice had normal growth and lifespan, and were macroscopically indistinguishable from wild-type littermates. Only minor defects were observed in muscle morphology and contractile properties in SelN-deficient mice in basal conditions. However, when subjected to challenging physical exercise and stress conditions (forced swimming test), Sepn1−/− mice developed an obvious phenotype, characterized by limited motility and body rigidity during the swimming session, as well as a progressive curvature of the spine and predominant alteration of paravertebral muscles. This induced phenotype recapitulates the distribution of muscle involvement in patients with SEPN1-Related Myopathy, hence positioning this new animal model as a valuable tool to dissect the role of SelN in muscle function and to characterize the pathophysiological process

Les politiques des sciences. Séminaire alternatif

Michel Agier, Mathieu Arnoux, Alban Bensa, Alain Blum, Simona Cerutti, Francis Chateauraynaud, Robert Descimon, Nicolas Dodier, Jean-Claude Galey, Nancy L. Green, Christian Jouhaud, Christian Topalov, directeurs d’étudesIsabelle Backouche, Juliette Cadiot, Fanny Cosandey, Sophie Desrosiers, André Gunthert, Liora Israël, Cyril Lemieux, Mary Picone, Sylvain Piron, maîtres de conférencesIrène Bellier, directrice de recherche au CNRSMichel Barthélémy, Elie Haddad, Cédric Lomba, Birgit Müller, Sop..

Functional study of the skin microbial community by metagenomics

La peau l’un des plus grands organes du corps humain avec une superficie moyenne de 1,5m2 à 2m2 est à l’interface avec le monde extérieur et régule les échanges entre les deux milieux. Avec ses nombreuses invaginations et des apports nutritifs constants cet écosystème favorise la colonisation par des microorganismes. Les études taxonomiques basées sur le séquençage du gène rrs après amplification PCR à partir de l’ADN extrait ont permis de découvrir la diversité des différentes populations microbiennes qui colonisent la peau humaine dont peu sont cultivables in vitro. A côté des espèces communes à tous les individus une certaine spécificité individuelle a été trouvée de même qu’il a été montré que la surface du corps humain se différencie en régions avec des spécificités physico-chimiques propres pour lesquelles des correspondances taxonomiques du microbiote ont été détectées. Ce travail de thèse, réalisé dans le cadre d’un contrat CIFRE avec la société LibraGen a eu pour but d’aborder le volet fonctionnel du microbiote cutané grâce à l’application de l’approche séquençage haut débit de l’ADN metagénomique bactérien extrait de la peau humaine. Cet objectif a nécessité le développement d’une méthode de prélèvement‐extraction de l’ADN afin de remédier aux contraintes spécifiques de l’écosystème étudié, une faible densité microbienne et la putative présence de contamination par l’ADN humain. Les données de séquence obtenues nous ont permis de caractériser le potentiel fonctionnel du microbiote cutané des différents sites cutanés et, par comparaisons inter-environnementales de déterminer les fonctions spécifiquement rencontrées dans ce microbiote lié à l’homme. Les applications de ces travaux sont importantes comme par exemple la démonstration d’un effet sur le microbiote d’une application quotidienne d’onctions qui modifie tant la diversité taxonomique que le potentiel fonctionnel du microbiote cutané.Skin is one of the largest human organs, with an average surface of 1.8 m2. At the interface between the human body and its external environment, skin is continually exposed to chemical and biological aggression and provides efficient protection of the human body. Its appearance is a good indicator of internal health, as skin reacts very rapidly to any change. Historically, skin microbiology was limited to the study of microorganisms isolated from skin pathologies, including those that provoke the pathological state and those that result from the pathology. However, the presence of skin microorganisms extends far beyond these pathological aspects, as non-pathological bacteria are detected everywhere on the skin, with up to 107 bacterial cells by cm2 in some areas. Skin is not a sterile human organ, but acts as an ecological niche for commensal microor- ganisms whose presence participates in protection against pathogens by preventing their colonization. Skin microbiology had been studied long before consid- ering the commensal skin bacteria, the majority of which could not be cultivated in vitro and the role of which was neglected until these new approaches, based on amplification and sequencing of DNA directly extracted from skin, were applied. Metagenomics revolutionized the study of microbiology in numerous environments where most bacteria are difficult to isolate. The first result of this approach was a more accurate estimation of microbial diversity, which had been underestimated by traditional approaches. However, interest in metagenomics exceeds a simple inventory of bacteria by providing information on their activity, function and interrelationship with other organisms.Our objective in this work realized in a CIFRE collaboration with Libragen company, was to study the functional profiles of the human skin microbiome with the application of metagenomic tools. This approach required first developing a method for the sampling and the dna extraction in order to overcome the constraints specific to this microbiome. Then, the sequencing data allowed characterizing the functional potential of the skin microorganisms in comparison to other environmental metagenome, and to find specificities of their local adaptations among three different skin sites. Applications of this work can be very important and one application tried in this thesis was the demonstration of the effect of several cutaneous cosmetic applications that modified the microflora at the taxonomic level and at the functional potential level

Monnaie, pouvoir et Etats : le régime politique de la monnaie européenne

Source : ABES [http://www.idref.fr/033702462/id] - theses.fr, 27/01/2022This dissertation intends to analyze the political regime of the European money. This concept refers to the expressions of power pertaining to money according to three modalities, namely (i) the construction of issue, circulation and distribution rules, (ii) the implementation of economic and fiscal policies and (iii) the crisis. The Canadian monetary unification (1841-1867) will serve as a case to show key characteristics in the European monetary unification and provide relevance to the proposed concept. Intergovernmental negotiations from 1989 to 1992 correspond to a period of time which highlights power relationships between the French and German executive. These relationships determined a set of parameters: exchange rate regime (external and internal), the regulation of capital and labour, product and services mobility (external and internal), the existence of a centralized State, indebtedness arrangements for States, central bank organization, and fiscal transfers which stabilized in a socio-political compromise. That resulted in a fiscal policy framework that, by its interaction with the previous parameters, require the State to establish specific economic policies. Competitive disinflation and procyclical policies interrogate the reproduction of economic order, which consists of capital accumulation to pay back debts issued in the previous period. This non-sustainability of the political regime of the European money provokes a crisis, which will be resolved according the institutional context built by the socio-political compromise. Due to the lack of a European State, modifying these compromise characteristics is almost impossible thus, jeopardizing this regime.Cette thèse se propose d’analyser le régime politique de la monnaie européenne. Ce concept fait référence aux manifestations du pouvoir au sein de la monnaie selon trois modalités, à savoir (i) la construction des règles d’émission, de circulation et de distribution, (ii) la réalisation des politiques budgétaires et économiques et (iii) la crise. Nous mobiliserons le cas de l’unification monétaire canadienne (1841-1867) afin de souligner les caractéristiques clés del’unification monétaire européenne et pour juger de la pertinence de notre concept. Les négociations intergouvernementales de 1989 à 1992 correspondent à un point temporel qui met en évidence les logiques de pouvoir entre les exécutifs français et allemand. Ces logiques ont déterminé la mobilité des biens, des services, des personnes et des capitaux (interne et externe), le régime de change (interne et externe), les objectifs et les missions de la banque centrale, l’existence ou non d’un Etat central, ses modalités d’endettement et la présence de transferts fiscaux qui se sont stabilisés dans un compromis socio-politique. Il en a découlé un cadre de politique budgétaire qui, par son interaction avec les caractéristiques précédentes, oblige les Etats membres à mettre en place des politiques économiques spécifiques. La désinflation compétitive et les politiques procycliques questionnent la reproduction de l’ordre économique, c’est-à-dire l’accumulation du capital qui permet une reconnaissance des dettes émises à la période précédente. Cette insoutenabilité du régime politique de la monnaie européenne a provoqué une crise, qui se résoudra selon le contexte institutionnel mis en place lors du compromis socio-politique. En raison de l’absence d’un Etat européen, il est impossible de modifier les caractéristiques de ce compromis, compromettant ce régime politique de la monnaie