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Asynchronous Traces and Open Petri Nets
No full textInternational audienceThe relation between process calculi and Petri nets, two fundamental models of concurrency, has been widely investigated. Many proposals exist for encoding process calculi into Petri nets while preserving some behavioural features of interest. We recently introduced a framework where a net encoding can be defined uniformly for calculi with different communication patterns, including synchronous two-party, multi-party, and asynchronous communication. The encoding preserves and reflects several behavioural semantics, notably bisimulation equivalence. The situation is less immediate for asynchronous calculi and trace semantics: considering traces that arise when viewing asynchronous calculi as a fragment of the synchronous ones, trace equivalence is not reflected by the encoding. Focusing on CCS, we argue that this phenomenon is related to the imperfect match between trace inclusion and may testing preorder. We consider an alternative labelled transition systems where the latter issue is solved, and we show that, indeed, the corresponding trace semantics is preserved and reflected by the net encoding
Dynamic stability of a bar under high loading rate: Response to local perturbations
No full textInternational audienceOf interest here is the influence of loading rate on the stability of structures where inertia is taken intoaccount. The approach currently used in the literature to analyze these stability problems, is the methodof modal analysis that determines the structure’s fastest growing wavelength, which is meaningful onlyfor cases where the velocity of the perfect structure is significantly lower than the associated characteristicwave propagation speeds. The novel idea here is to analyze the time-dependent response to perturbationsof the transient (high strain rates) states of these structures, in order to understand the initiationof the corresponding failure mechanisms.We are motivated by the recent experimental studies of Zhang and Ravi-Chandar (2006) on the highstrain rate extension of thin rings that show no evidence of a dominant wavelength in their failure modeand no influence of strain-rate sensitivity on the necking strains. In the interest of analytical tractability,we study the extension of an incompressible, nonlinearly elastic bar at different strain rates. The dynamicstability of these bars is studied by following the evolution of localized small perturbations introduced atdifferent times. It is shown that these structures are stable until the static necking strain is reached atsome point. Moreover their failure pattern is dictated by the distribution of defects, the minimum distancebetween necks diminishes with increasing strain rate and there is no dominant wavelength mode,exactly as observed experimentally in Zhang and Ravi-Chandar (2006)
A New Rate-Optimal Series Expansion of Fractional Brownian Motion
No full textIn this paper, we give a new series expansion to simulate B an fBm based on harmonic analysis of the auto-covariance function. We prove that the convergence holds in and uniformly, with a rate-optimal decay of the norm of the rest of the series in both senses. We also give a general framework of rate-optimal series expansion for a class of Gaussian processes. Finally we apply this expansion to functional quantization
Impact of rare earth element clusters on the excited state lifetime evolution under irradiation in oxide glasses
No full textInternational audienceRare earth doped active glasses and fibers can be exposed to ionizing radiations in space and nuclear applications. In this work, we analyze the evolution of 2 F 5/2 excited state lifetime in Yb 3+ ions in irradiated aluminosilicate glasses by electrons and γ rays. It is found that the variation of lifetimes depends on the Yb 3+ clusters content of the glasses for irradiation doses in the 10 2 – 1.5·10 9 Gy range. In particular, glasses with high clustering show a smaller decrease in lifetime with increasing radiation dose. This behavior is well correlated to the variation in paramagnetic defects concentration determined by electron paramagnetic resonance. This effect is also observed in Yb 3+ doped phosphate and Er 3+ doped aluminosilicate glasses, inferring that clustering plays an important role in irradiation induced quenching
First in vivo results of an innovative sensor to detect stent-related complications
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DNA Replication Restart in Archaea
No full textInternational audienceOne fundamental challenge of cells is to accurately copy their genetic material for cell prolif‐eration. This task is performed by core machineries considered conserved in all three domainsof life: bacteria, archaea and eukaryotes..
Phases Topologiques Fortement Corrélées
No full textThis thesis is dedicated largely to the study of theoretical models describinginteracting fermions with a spin-orbit coupling. These models (i) can describe a class of 2Diridate materials on the honeycomb lattice or (ii) could be realized artificially in ultra-coldgases in optical lattices. We have studied, in the first part, the half-filled honeycomb latticemodel with on-site Hubbard interaction and anisotropic spin-orbit coupling. We find sev-eral different phases: the topological insulator phase at weak coupling, and two frustratedmagnetic phases, the Néel order and spiral order, in the limit of strong correlations. Thetransition between the weak and strong correlation regimes is a Mott transition, throughwhich electrons are fractionalized into spins and charges. Charges are localized by the in-teractions. The spin sector exhibits strong fluctuations which are modeled by an instantongas. Then, we have explored a system described by the Kitaev-Heisenberg spin Hamil-tonian at half-filling, which exhibits a zig-zag magnetic order. While doping the systemaround the quarter filling, the band structure presents novel symmetry centers apart fromthe inversion symmetry point. The Kitaev-Heisenberg coupling favors the formation oftriplet Cooper pairs around these new symmetry centers. The condensation of these pairsaround these non-trivial wave vectors is manifested by the spatial modulation of the super-conducting order parameter, by analogy to the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO)superconductivity. The last part of the thesis is dedicated to an implementation of theHaldane and Kane-Mele topological phases in a system composed of two fermionic specieson the honeycomb lattice. The driving mechanism is the RKKY interaction induced bythe fast fermion species on the slower one.Cette thèse porte principalement sur l'étude de modèles de fermions en interactions contenant un couplage spin-orbite. Ces modèles (i) peuvent décrire une classe de matériaux composés d'iridates sur le réseau en nid d'abeille ou (ii) pourraient être réalisés artificiellement dans des systèmes d’atomes froids. Nous avons étudié, dans un premier temps, le système à demi-remplissage avec l'interaction de Hubbard et un couplage spin-orbite anisotrope. Nous avons trouvé plusieurs phases: la phase isolant topologique pour de faibles corrélations, et deux phases avec des ordres magnétiques frustrés, l'ordre de Néel et l'ordre spiral, dans la limite de très fortes corrélations. La transition entre les régimes de faibles et de fortes corrélations est une transition de Mott dans laquelle les excitations électroniques se fractionnent en excitations de charge et de spin. Les charges sont localisées par l'interaction. Le secteur de spin présente de fortes fluctuations qui sont modélisées par un gaz d’instantons. Nous avons ensuite exploré la physique d'un système régi au demi-remplissage par le modèle de Kitaev-Heisenberg, qui présente une phase magnétique de type zig-zag. En dopant le système, autour du quart remplissage, la structure de bande présente de nouveaux centres de symétrie en plus de la symétrie d'inversion. Le couplage de spin de Kitaev-Heisenberg favorise alors la formation de paires de Cooper dans un état triplet autour de ces centres de symétrie. La condensation de ces paires de Cooper autour de ces vecteurs d'onde non triviaux se manifeste par une modulation spatiale du paramètre d'ordre supraconducteur, comme dans la supraconductivité de Fulde–Ferrell–Larkin–Ovchinnikov (FFLO). La dernière partie de la thèse propose et étudie une implémentation des phases topologiques dite de Haldane et de Kane-Mele dans un système avec deux espèces de fermions sur le réseau en nid d'abeille, stabilisée grâce à l’interaction RKKY médiée par l’espèce rapide et qui agit sur l’espèce lente
Markov State Models Reveal a Two-Step Mechanism of miRNA Loading into the Human Argonaute Protein: Selective Binding followed by Structural Re-arrangement.
No full textInternational audienceArgonaute (Ago) proteins and microRNAs (miRNAs) are central components in RNA interference, which is a key cellular mechanism for sequence-specific gene silencing. Despite intensive studies, molecular mechanisms of how Ago recognizes miRNA remain largely elusive. In this study, we propose a two-step mechanism for this molecular recognition: selective binding followed by structural re-arrangement. Our model is based on the results of a combination of Markov State Models (MSMs), large-scale protein-RNA docking, and molecular dynamics (MD) simulations. Using MSMs, we identify an open state of apo human Ago-2 in fast equilibrium with partially open and closed states. Conformations in this open state are distinguished by their largely exposed binding grooves that can geometrically accommodate miRNA as indicated in our protein-RNA docking studies. miRNA may then selectively bind to these open conformations. Upon the initial binding, the complex may perform further structural re-arrangement as shown in our MD simulations and eventually reach the stable binary complex structure. Our results provide novel insights in Ago-miRNA recognition mechanisms and our methodology holds great potential to be widely applied in the studies of other important molecular recognition systems
Recherche du boson de Higgs se désintégrant en pair de taus avec la méthode de l’élément de matrice et optimisation des déclenchements pour les taus dans l’expérience CMS auprès du LHC
No full textI performed my thesis work in Particle Physics at the Laboratoire Leprince-Ringuet of the Ecole Polytechnique. I have participated to the analysis of the 8 TeV proton-proton collisions produced by the Large Hadron Collider (LHC) and collected by the CMS experiment. The discovery of the Higgs boson has been a major breakthrough in particle physics as the mass of the vector bosons are explained through their interactions with the Higgs field. I worked on the newly discovered Higgs boson analysis. As its direct coupling to fermions remained to be exhibited, I focused on the search for the Higgs boson decaying in tau lepton pairs. The Higgs decay into a tau pair is the only channel allowing the couplings between the Higgs boson and the leptons to be measured. This is due to the large event rate expected in the Standard Model compared to the other leptonic decay modes. The Higgs boson decaying to tau lepton analysis is particularly challenging at the trigger level because the large background imposes high thresholds. I worked on a trigger that ran at the end of the data-taking using the missing transverse energy to lower the threshold on the single lepton. This approach allows the recovery of 41% of the signal events. Events with missing transverse momentum were selected in order to control the trigger rate. My personal contribution consisted in a thorough characterization of this trigger, including the measure of the associated uncertainty. The results of this approach led to an amelioration of 2% in the exclusion limits computed in the Higgs to taus semileptonic channel.For the Run 2, the center-of-mass energy of the LHC collisions has been increased to 13 TeV and the instantaneous luminosity will reach 2E34/cm2/s. To guarantee a successful and ambitious physics program under this intense environment, the CMS Trigger and Data acquisition system has been consolidated. In particular the Level 1 (L1, hardware based first level of the CMS trigger system) benefited from the recent microTCA technology allowing the calorimeter granularity to be better exploited with more advanced algorithms. Thanks to the enhanced granularity provided by the new system, an innovative dynamic clustering technique has been developed to obtain an optimized tau selection algorithm. I took the responsibility of developing a complete new tau trigger algorithm at L1 and measuring its performance. This original approach resulted in the first hardware tau lepton trigger efficient at a hadron collider with a sustainable rate. I had the opportunity to present a poster showing my work at the ICHEP-2014 conference, in Valencia and the proceedings were published in Nuclear Physics B afterwards. During my last year of PhD I focused on the Higgs decays into di-taus analysis, initiating the very first matrix element (ME) approach in this channel, starting with the most sensitive final state: the semileptonic decay mode. The aim is to increase the sensitivity of the analysis to the SM Higgs boson, with respect to the traditional methods. No ME-based analysis using tau leptons has ever been published. The novelty of my work is the treatment of the tau decay. In addition, I have derived a parameterization of the detector response through transfer functions. Finally, the numerical aspects related of multidimensional integrals computations have been tackled. I have fully characterized the method using simulated samples before applying it to the 8 TeV data. The performance in the context of the CMS Higgs into di-taus of this pioneering method are very promising, with a S/B ratio improved by a factor 3, and constitute a baseline for the analysis of the upcoming Run 2 data of the LHC.J’ai effectué ma thèse en physique des particules au laboratoire Leprince-Ringuet à l’École Polytechnique. J’ai participé à l’analyse des collisions proton-proton à 8 TeV produites par le Large Hadron Collider (LHC) et collectées par le détecteur CMS. La découverte du boson de Higgs a été un événement majeur pour la physique des hautes énergies car la masse des bosons vecteurs provient de leur interaction avec le champ de Higgs. Le couplage du boson de Higgs avec les leptons n’ayant pas encore été découvert, mon travail de thèse s’est articulé autour du canal de désintégration en pair de tau, car c’est le seul qui permet de mettre ce couplage en évidence. En effet, le boson de Higgs se désintègre beaucoup plus souvent en taus qu’en muons ou électrons.Cette analyse est difficile au niveau du déclenchement. En effet, l’important bruit de fond impose d’appliquer des seuils en énergie élevés. Un critère de déclenchement utilisant l’énergie transverse manquante pour abaisser le seuil sur les leptons a été introduit à la fin de la prise de données. Cette approche permet de récupérer 41% d’événements en plus. J’ai effectué une caractérisation exhaustive de ce déclenchement, et en particulier étudié les erreurs systématiques associées au niveau de l’analyse. Ce déclenchement a permis d’améliorer de 2% la limite d’exclusion dans le canal Higgs en tau-tau semi-leptonique.Au Run 2, l’énergie des collisions a été portée à 13 TeV et la luminosité va augmenter. Pour garantir un déclenchement efficace pour la physique, le premier niveau du système de déclenchement (L1) a été remplacé en se basant sur la technologie microTCA. Ce nouveau système permet un accès à des informations plus détaillées en provenance du détecteur. J’ai développé, pour ce nouveau système, un algorithme de sélection des taus basé sur un algorithme d’agrégation dynamique exploitant au maximum la granularité du calorimètre. J’ai mesuré ses performances en terme d’efficacité et de taux de déclenchement, et pour la première fois auprès d’un collisionneur hadronique, CMS disposera en 2016 d’un déclenchement efficace sur les taus au L1 avec un taux raisonnable. J’ai présenté ce travail sous forme de poster à la conférence ICHEP 2014. Dans la dernière partie de ma thèse, je me concentre sur la recherche du boson de Higgs se désintégrant en une paire de taus, en me concentrant sur le canal semi-leptonique et en introduisant pour la première fois la méthode des éléments de matrice (MEM) qui permet d’améliorer la sensibilité par rapport aux méthodes traditionnelles. Aucune analyse utilisant la MEM avec des taus n’a jamais été publiée. L’innovation dans ce travail consiste notamment dans le traitement de la désintégration des taus. La réponse du détecteur est quant-à-elle modélisée par des fonctions de transfert. Puis, j’ai du tenir compte des limitations numériques intervenants dans l’évaluation des intégrales multidimensionnelles à la base de cette méthode. Enfin, j’ai mesuré le gain en sensibilité apporté par la méthode sur les données à 8 TeV. Les performances dans le cadre de la recherche du boson de Higgs se désintégrant en une paire de tau de cette méthode pionnière sont très prometteuses, avec un rapport S/B amélioré d’un facteur 3, et constituent une référence pour l’analyse des futures données du Run 2 du LHC
Opinions and Beliefs as constraint system operators
No full textAppears as Abstract Paper at the Technical Communications of the 31st International Conference on Logic Programming (ICLP 2015)International audienceThe growing presence of digital distributed systems in social life is exemplified by many particular instances, including opinion forums, social networks, dating sites and photo sharing portals. The increased usage in the last decade of these systems brings various risks and behaviors, inherent from the social interaction therein. An epistemic aspect is singled out as a common feature shared between these systems and the behaviors carried within them. Designing, constructing and verifying formalisms to represent information that is epistemic in nature can help develop a sound theory to analyze the scenarios mentioned before and at the same time bridge the concepts involved to a logical and mathematical domain. Regarding this, a specific concept of declarative and logic programming, that of a constraint system, deals with information represented by constraints (a constraint c could be a logical proposition partially describing a bigger system, e.g. temperature > 20). Constraint systems capable of incorporating the concept of spatiality such as user-spaces or message walls already exist (i.e. [c]_i , could read as " data/belief/constraint c belongs to agent i "). However, the movement of information between spaces is still not designed nor included in said constraint systems. Some process algebras do possess a concept of space mobility, notwithstanding, it is from an operational point of view, specifying only its behavior. Therefore it remains to mathematically define it along with all its properties. The proposed project intends to provide constraint systems with an algebraic operator that correspond to moving information in-between spaces as to mimic the mobility of data of distributed systems such as posting opinions/lies to other spaces or publicly disclosing data (i.e. ↑_i c reads as " extruding data/belief/constraint c from the space of agent i). Also, this extrusion operator should have a direct relationship with the spatiality operator, meaning that it should be modeled in constraint systems that also posses the concept of space (i.e. [c u ↑_i d] i = [c]_i u d reads " information d is extruded from the space of agent i " , it can be alternatively interpreted as agent i posting an opinion d). The authors developed a constraint system implementing the concepts of space and extrusion. The interaction between these conceptos account for mobility with no side effects , it is modeled as extrusion being the right inverse of space (i.e. [↑_i c]_i = c for any agent i). Additionally, given an already defined concept of space in a constraint system, the authors described different constructive ways of defining its extrusion and their mathematical properties. As a practical example, by means of a constraint system with space and extrusion, the authors gave semantic meaning to a logic with modalities of belief Bi and utterance Ui where BiUiφ ⇔ φ for any formula φ of the logic