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International audience; It was proved that Euler-Maxwell systems converge globally-in-time to driftdiffusion systems in a slow time scaling, as the relaxation time goes to zero. The convergence was established to the Cauchy problem with smooth periodic initial data sufficiently close to constant equilibrium states. In this paper, we establish error estimates between smooth periodic solutions of Euler-Maxwell systems and those of drift-diffusion systems. Similar error estimates are also obtained for Euler-Poisson systems in place of Euler-Maxwell systems. The proof of these results uses stream function techniques together with energy estimates. Résumé. Il a été prouvé que des systèmes d'Euler-Maxwell convergent globalement en temps vers des systèmes de dérive-diffusion dans une échelle de temps lent, lorsque le temps de relaxation tend vers zéro. La convergence a éte établie au problème de Cauchy avec données initiales régulières périodiques suffisamment proches d'états d'équilibres constants. Dans cet article, nous établissons des estimations d'erreur entre les solutions régulières périodiques des systèmes d'Euler-Maxwell et celles des systèmes de dérivediffusion. Des estimations d'erreur similaires sont aussi obtenues pour des systèmes d'Euler-Poisson au lieu des systèmes d'Euler-Maxwell. Nous utilisons des techniques de fonctions de courant et des estimations d'energies pour la démonstration de ces résultats.

International audience

Hybridization may help drive biological invasions by reducing Allee effects, increasing genetic variation, and generating novel adaptive genotypes/phenotypes. Social insects (ants, bees, wasps, and termites) are among the world's worst invasive species. In this review, we study the relationship between hybridization and invasiveness in social insects. We examine three types of hybridization based on the reproductive characteristics of first-generation hybrids. We discuss several examples of the association between hybridization and invasiveness, which are predominantly found in bees and termites. However, hybridization also occurs in several non-invasive species, and highly invasive species are not consistently associated with hybridization events, indicating that hybridization is not a main driver of invasiveness in social insects. We discuss why hybridization is not more commonly seen in invasive social insects., info:eu-repo/semantics/published

Conformal geodesics are distinguished curves on a conformal manifold, loosely analogous to geodesics of Riemannian geometry. One definition of them is as solutions to a third order differential equation determined by the conformal structure. There is an alternative description via the tractor calculus. In this article we give a third description using ideas from holography. A conformal $n$-manifold $X$ can be seen (formally at least) as the asymptotic boundary of a Poincar\'e--Einstein $(n+1)$-manifold $M$. We show that any curve $\gamma$ in $X$ has a uniquely determined extension to a surface $\Sigma_\gamma$ in $M$, which which we call the \emph{ambient surface of $\gamma$}. This surface meets the boundary $X$ in right angles along $\gamma$ and is singled out by the requirement that it it be a critical point of renormalised area. The conformal geometry of $\gamma$ is encoded in the Riemannian geometry of $\Sigma_\gamma$. In particular, $\gamma$ is a conformal geodesic precisely when $\Sigma_\gamma$ is asymptotically totally geodesic, i.e. its second fundamental form vanishes to one order higher than expected. We also relate this construction to tractors and the ambient metric construction of Fefferman and Graham. In the $(n+2)$-dimensional ambient manifold, the ambient surface is a graph over the bundle of scales. The tractor calculus then identifies with the usual tensor calculus along this surface. This gives an alternative compact proof of our holographic characterisation of conformal geodesics., Comment: 23 pages, 3 figures. v2 acknowledgements added, v3 figures added, minor adjustments to the text to improve exposition, version accepted for publication in Communications in Contemporary Mathematics

This article is a brief presentation of results surrounding the fundamental gap. We begin by recalling Bakry-Emery geometry and demonstrate connections between eigenvalues of the Laplacian with the Dirichlet and Neumann boundary conditions. We then show a connection between the fundamental gap and Bakry-Emery geometry, concluding with a presentation of the key ideas in Andrews's and Clutterbuck's proof of the fundamental gap conjecture. We conclude with a presentation of results for the fundamental gap of triangles and simplices., Comment: in French. This is a preliminary version of the published article of the same title, freely available online!

The asymptotic structure of the Pauli-Fierz theory at spatial infinity is investigated in four spacetime dimensions. Boundary conditions on the massless spin-$2$ field that are invariant under an infinite-dimensional group of non-trivial ``improper'' gauge symmetries are given. The compatibility of these boundary conditions with invariance of the theory under Lorentz boosts is a subtle issue which is investigated in depth and leads to the identification of the improper gauge symmetries with the pure BMS supertranslations. It is also shown how rigid Poincar\'e transformations and improper gauge symmetries of the free Pauli-Fierz theory merge into the full BMS group as one switches on the gravitational coupling. Contrary to the massless spin-$1$ case, where invariance under boosts is implemented differently and where important differences between the free and the interacting cases have been exhibited recently, the free Pauli-Fierz theory and general relativity show very similar behaviours at spatial infinity., Comment: 36 pages

« I was fortunate to be born in a community where the art of story-telling had been practised for many generations. All islands from the beginning of time are natural breeding-grounds for story and legend. » C’est donc en se reclamant d’une tradition ancestrale qui apparente naturellement histoires et legendes que George Mackay Brown definit d’emblee sa position de « raconteur ». Celui-ci, heritier de ses predecesseurs, n’est plus que le porte-parole d’une voix narrative (« many voices speak ...

The Many-Worlds Interpretation (MWI) of quantum mechanics, the rendition of quantum mechanics discovered by theoretical physicist, Hugh Everett III, postulates a radical rendition of reality. MWI is an austere, unequivocal reading of the Schrodinger equation DeWitt calls “schizophrenia with a vengeance.”1 It starts from the premise “all physical processes whatsoever are governed by the Schrodinger equation,”2 then purposefully executes the formalism to let it freely say from itself what the universe is doing, which is: constantly splitting into a stupendous number of branches, all resulting from the measurement like interactions between its myriads of components. Moreover, every quantum transition, in every galaxy, in every star, in every remote corner of the universe is splitting our local world on earth into myriads of copies of itself.3 “Interpretation is an essential part of MWI.”4 The theory contains a discrete hermeneutical point of departure. It begins from a unified conception of reality that contrasts the apparently dualistic perspective assumed by the Copenhagen interpretation of quantum mechanics, and stays the course of thinking it projects-open initially. The Copenhagen interpretation is considered the standard interpretation of quantum mechanics. “Many standard textbooks about quantum mechanics, and probably all popular-scientific treatments of the philosophy of quantum physics,” as Friebe notes, “come to stop at the Copenhagen interpretation.”5 MWI’s answer to

A plasma-enhanced atomic layer deposition (PE-ALD) process to deposit metallic gold is reported, using the previously reported Me3Au(PMe3) precursor with H-2 plasma as the reactant. The process has a deposition window from 50 to 120 degrees C with a growth rate of 0.030 +/- 0.002 nm per cycle on gold seed layers, and it shows saturating behavior for both the precursor and reactant exposure. X-ray photoelectron spectroscopy measurements show that the gold films deposited at 120 degrees C are of higher purity than the previously reported ones (

Nanophotonic waveguide enhanced Raman spectroscopy (NWERS) is a sensing technique that uses a highly confined waveguide mode to excite and collect the Raman scattered signal from molecules in close vicinity of the waveguide. The most important parameters defining the figure of merit of an NWERS sensor include its ability to collect the Raman signal from an analyte, i.e. ANDx201C;the Raman conversion efficiencyANDx201D; and the amount of ANDx201C;Raman backgroundANDx201D; generated from the guiding material. Here, we compare different photonic integrated circuit (PIC) platforms capable of on-chip Raman sensing in terms of the aforementioned parameters. Among the four photonic platforms under study, tantalum oxide and silicon nitride waveguides exhibit high signal collection efficiency and low Raman background. In contrast, the performance of titania and alumina waveguides suffers from a strong Raman background and a weak signal collection efficiency, respectively., info:eu-repo/semantics/published

Along its lowest rotational band, the antiprotonic helium atom undergoes several changes of structure. It evolves from an hydrogenlike atom with broader and broader resonant states, to a quasistable molecularlike structure with narrow resonances, and then to a quasistable Rydberg pseudoatom. The antiprotonic helium atom is studied with high accuracy as a nonrelativistic three-body Coulomb system in the framework of the Lagrange-mesh method. Its metastable states are first determined from L=0 to L=80 by searching conditions of calculation for which energies are stationary. Mean values of distances between the particles are then easily deduced. They show the evolution of the structure of the system. Broad resonances are also analyzed with the complex scaling method. Physical interpretations are provided., SCOPUS: ar.j, info:eu-repo/semantics/published

Let $F$ be a family of graphs. Then for every graph $G$ the maximum number of disjoint subgraphs of $G$, each isomorphic to a member of $F$, is at most the minimum size of a set of vertices that intersects every subgraph of $G$ isomorphic to a member of $F$. We say that $F$ packs if equality holds for every graph $G$. Only very few families pack. As the next best weakening we say that $F$ has the Erdős-Posa property if there exists a function $f$ such that for every graph $G$ and integer $k>0$ the graph $G$ has either $k$ disjoint subgraphs each isomorphic to a member of $F$ or a set of at most $f(k)$ vertices that intersects every subgraph of $G$ isomorphic to a member of $F$. The name is motivated by a [classical 1965 result of Erdős and Posa](https://en.wikipedia.org/wiki/Erd%C5%91s%E2%80%93P%C3%B3sa_theorem) stating that for every graph $G$ and integer $k>0$ the graph $G$ has either $k$ disjoint cycles or a set of $O(k\log k)$ vertices that intersects every cycle. Thus the family of all cycles has the Erdős-Posa property with $f(k)=O(k\log k)$. In contrast, the family of odd cycles fails to have the Erdős-Posa property. For every integer $\ell$, a sufficiently large Escher Wall is a non-bipartite graph that has an embedding in the projective plane such that every face is even and every homotopically non-trivial closed curve intersects the graph at least $\ell$ times. In particular, it contains no set of strictly less than $\ell$ vertices such that each odd cycle contains at least one them, yet it has no two disjoint odd cycles. By now there is a large body of literature proving that various families $F$ have the Erdős-Posa property. A very general theorem of Robertson and Seymour says that for every planar graph $H$ the family $F(H)$ of all graphs with a minor isomorphic to $H$ has the Erdős-Posa property. (When $H$ is non-planar, $F(H)$ does not have the Erdős-Posa property.) The present paper proves that for every planar graph $H$ the family $F(H)$ has the Erdős-Posa property with $f(k)=O(k\log k)$, which is asymptotically best possible for every graph $H$ with at least one cycle.

Banana Pseudo stem (BPS) is an annual renewable agricultural by product with a potential for valorization in the production of paper, textile fibre or new bio–based materials. A gradual deconstruction process was implemented to determine BPS chemical composition and isolate sub–components that may be valorized in the formulation of bio–based polymer composites. At each step, the residues were analyzed by FTIR, X–ray diffraction and TGA–DTG. The chemical composition of the starting material (% of dry weight) was evaluated as:13.4% total extractives, 6% pectins, 14.7% lignins, 28% hemicelluloses and 38% cellulose. The deconstruction process for BPS was efficient but led to mercerized cellulose (cellulose II) as a final residue, as assessed by the intense X–ray scattering peaks centered at 20.5° and 21.5°. Cellulose II formation was induced by the high concentration of the alkaline KOH solution used to dissolve hemicelluloses in holocellulose. The step–wise removal of non cellulosic sub–components led to a more thermally stable residue. Long fibres were also obtained from BPS at a yield of 60%. These fibres display cellulose I structure and a thermal stability similar to the extracted cellulose. SEM analyses of long fibres showed transversal and lateral defects, the presence of surface hairiness and an almost cylindrical morphology. Uniaxial tensile tests were carried out at room temperature on 150 specimens randomly chosen among the less hairy fibres, with diameters ranging from 40 to 140μm.Mechanical investigations (Young modulus: 6.3–26 GPa; nominal stress at break: 140–768 Pa; nominal strain at break:∼3%) reveal a significant disparity strongly influenced by fibre diameter, except for the nominal strain at break which remains fairly constant around 3%. These results are comparable to the upper range of the values reported for fibres extracted from BPS through alternative chemical routes or for fibres obtained from other annual plants such as jute and hemp; La pseudo-tige de banane (BPS) est un produit agricole annuel renouvelable avec un potentiel de valorisation dans la production de papier, de fibre textile ou de nouveaux matériaux biosourcés. Un processus de déconstruction progressive a été mis en œuvre pour déterminer la composition chimique du BPS et isoler les sous – composants susceptibles d'être valorisés dans la formulation de composites polymères biosourcés. À chaque étape, les résidus ont été analysés par FTIR, diffraction des rayons X et TGA – DTG. La composition chimique de la matière de départ (% du poids sec) a été évaluée comme suit:13,4% d'extraits, 6% de pectines, 14,7% de lignines, 28% d'hémicelluloses et 38% de cellulose. Le processus de déconstruction du BPS a été efficace, mais a conduit à la cellulose mercerisée (cellulose II) en tant que résidu final, comme l'indiquent les pics de diffusion des rayons X intenses centrés à 20,5 ° et à 21,5 °. La formation de cellulose II a été induite par la concentration élevée de la solution alcaline de KOH utilisée pour dissoudre les hémicelluloses dans l'holocellulose. L'élimination progressive des sous-composants non cellulosiques a permis d'obtenir un résidu plus stable thermiquement. Des fibres longues ont également été obtenues à partir de BPS avec un rendement de 60%. Ces fibres présentent une structure en cellulose I et une stabilité thermique similaire à celle de la cellulose extraite. Les analyses au MEB de fibres longues ont montré des défauts transversaux et latéraux, la présence de pilosité en surface et une morphologie presque cylindrique. Des tests de traction uniaxiale ont été effectués à température ambiante sur 150 échantillons choisis au hasard parmi les fibres les moins poilues, avec des diamètres allant de 40 à 140 µm.Les investigations mécaniques (module d'Young: 6,3–26 GPa; contrainte nominale à la rupture: 140–768 Pa; contrainte nominale à la rupture: 3%) révèlent une disparité significative fortement influencée par le diamètre de la fibre, à l'exception de la contrainte nominale à la rupture qui reste assez stable constante autour de 3%. Ces résultats sont comparables à la fourchette supérieure des valeurs rapportées pour les fibres extraites du BPS par d'autres voies chimiques ou pour les fibres obtenues d'autres plantes annuelles telles que le jute et le chanvre.

According to a general probabilistic principle, the natural divisors of friable integers (i.e.~free of large prime factors) should normally present a Gaussian distribution. We show that this indeed is the case with conditional density tending to 1 as soon as the standard necessary conditions are met. Furthermore, we provide explicit, essentially optimal estimates for the decay of the involved error terms. The size of the exceptional set is sufficiently small to enable recovery of the average behaviour in the same optimal range. Our argument combines the saddle-point method with new large deviations estimates for the distribution of certain additive functions., Comment: In French, English abstract

The paper studies compactness properties of the affine Sobolev inequality of Lutwak et al. (J Differ Geom 62:17–38, 2002) and Zhang (J Differ Geom 53:183–202, 1999) in the case $$p=2$$ , and existence and regularity of related minimizers, in particular, solutions to the nonlocal Dirichlet problems $$\begin{aligned} -\sum _{i,j=1}^{N}(A^{-1}[u])_{ij}\frac{\partial ^2u}{\partial x_i\partial x_j}=f \text{ in } \Omega \subset {\mathbb {R}}^N, \end{aligned}$$ and $$\begin{aligned} -\sum _{i,j=1}^{N}(A^{-1}[u])_{ij}\frac{\partial ^2u}{\partial x_i\partial x_j}=u^{q-1},\quad u>0, \text{ in } \Omega \subset {\mathbb {R}}^N, \end{aligned}$$ where $$A_{ij}[u]=\int _\Omega \frac{\partial u}{\partial x_i}\frac{\partial u}{\partial x_j}{\mathrm {d}}{x}$$ and $$q\in (2,\frac{2N}{N-2})$$ .

When count data exhibit excess zero, that is more zero counts than a simpler parametric distribution can model, the zero-inflated Poisson (ZIP) or zero-inflated negative binomial (ZINB) models are often used. Variable selection for these models is even more challenging than for other regression situations because the availability of p covariates implies 4 p possible models. We adapt to zero-inflated models an approach for variable selection that avoids the screening of all possible models. This approach is based on a stochastic search through the space of all possible models, which generates a chain of interesting models. As an additional novelty, we propose three ways of extracting information from this rich chain and we compare them in two simulation studies, where we also contrast our approach with regularization (penalized) techniques available in the literature. The analysis of a typical dataset that has motivated our research is also presented, before concluding with some recommendations.

Hyperspectral unmixing is a blind source separation problem which consists in estimating the reference spectral signatures contained in a hyperspectral image, as well as their relative contribution to each pixel according to a given mixture model. In practice, the process is further complexified by the inherent spectral variability of the observed scene and the possible presence of outliers. More specifically, multi-temporal hyperspectral images, i.e., sequences of hyperspectral images acquired over the same area at different time instants, are likely to simultaneously exhibit moderate endmember variability and abrupt spectral changes either due to outliers or to significant time intervals between consecutive acquisitions. Unless properly accounted for, these two perturbations can significantly affect the unmixing process. In this context, we propose a new unmixing model for multitemporal hyperspectral images accounting for smooth temporal variations, construed as spectral variability, and abrupt spectral changes interpreted as outliers. The proposed hierarchical Bayesian model is inferred using a Markov chain Monte-Carlo (MCMC) method allowing the posterior of interest to be sampled and Bayesian estimators to be approximated. A comparison with unmixing techniques from the literature on synthetic and real data allows the interest of the proposed approach to be appreciated., Comment: 14 pages, 13 figures, accepted for publication in IEEE Trans. Comput. Imag., 2017

In this paper we prove a convexity property of the relative entropy along entropic interpolations (solutions of the Schrödinger problem), and a regularity property of the entropic cost along the heat flow. Then we derive a dimensional EVI inequality and a contraction property for the entropic cost along the heat flow. As a consequence, we recover the equivalent results in the Wasserstein space, proved by Erbar, Kuwada and Sturm Résumé Dans cet article nous démontrons une propriété de convexité de l'entropie relative le long des interpolations entropiques (solutions duprobì eme de Schrödinger), et une propriété de régularité du coût entropique le long du flot de la chaleur. Ensuite, nous en déduisons une inégalité EVI dimensionnelle et une propriété de contraction pour le coût entropique le long du flot de la chaleur. En conséquence, nous retrouvons les résultatsrésultatséquivalents dans l'espace de Wasserstein, démontrés par Erbar, Kuwada et Sturm.

Micromachined Joule–Thomson (JT) coolers are of interest for cooling small electronic devices. The long-term performance of JT microcoolers is limited by the clogging phenomenon caused by the deposition of water molecules present as impurity in the working fluid. This work investigates the clogging dynamics in a JT microcooler operating with nitrogen gas. A numerical model is developed to calculate the temperature profile and the deposition rate of water molecules along the counter flow heat exchanger and the restriction of a microcooler. The deposition process is modeled by considering the diffusion of water molecules in nitrogen gas and the kinetic process of water molecules on wall surface, which are both temperature dependent. Numerical results show that the clogging rate during cool down is influenced by gas impurity and gas pressure. The effects of gas purity, gas pressure and cold-end temperature on the continuous operating time of the microcooler are also investigated.

International audience; The advent of next generation sequencing (NGS) technologies is so scale-changing that it modifies molecular diagnostics indications and induces laboratories to rethink their diagnostic strategies, until now based on the Sanger sequencing routine. Several high-throughput approaches are available from the sequencing of a gene panel, to an exome, or even a genome. In all cases, a tremendous amount of data is generated, which has to be filtered, interpreted and analyzed using powerful bioinformatics tools. In parallel, ethical considerations are raised to avoid the potential drifts of these powerful approaches. In all medical fields, and particularly in pediatrics, this new strategy offers better efficacy and faster mutation identification, allowing better support and care for patients and their families and even improving genetic counseling. In the present paper, we discuss the different NGS-based approaches and strategies as well as the issues involved in these new technologies applied to molecular diagnosis of rare diseases. Altogether, rare diseases affect more than 3 million people in France and are responsible for about one-third of childhood deaths.

Still nowadays, no one algebraic definition of heat is taught. Although anybody can easily make is own idea about heat, this non-regular lack, from the point of view of theoretical physics, can be explained by an historical consideration on the creation by Clausius of internal energy. In 1850, Clausius publishes On the Moving Force of Heat in which internal energy and entropy are created in order to make thermodynamics an entirely mathematical science. At the beginning, Clausius deny to Carnot that heat could be a conserved quantity, then, considering an ideal gas in a thermodynamical cycle, he shows that the conserved quantity cannot be heat, but another one, made by Clausius and called later "internal energy" by himself too. The main point of his demonstration is that the elementary quantity δQ cannot be an exact differential. Of course, a so important conclusion has several great consequences about thermodynamics in general. Firstly, internal energy becomes the new main quantity in thermodynamics, secondly, heat can be defined as the internal energy variation not due to mechanical work. Moreover, what is called "first principle of thermodynamics" can be seen as a simple consequence of this heat definition.

In earlier work we studied features of non-holomorphic modular functions associated with Feynman graphs for a conformal scalar field theory on a two-dimensional torus with zero external momenta at all vertices. Such functions, which we will refer to as modular graph functions, arise, for example, in the low energy expansion of genus-one Type II superstring amplitudes. We here introduce a class of single-valued elliptic multiple polylogarithms, which are defined as elliptic functions associated with Feynman graphs with vanishing external momenta at all but two vertices. These functions depend on a coordinate, $\zeta$, on the elliptic curve and reduce to modular graph functions when $\zeta$ is set equal to $1$. We demonstrate that these single-valued elliptic multiple polylogarithms are linear combinations of multiple polylogarithms, and that modular graph functions are sums of single-valued elliptic multiple polylogarithms evaluated at the identity of the elliptic curve, in both cases with rational coefficients. This insight suggests the many interrelations between modular graph functions (a few of which were established in earlier papers) may be obtained as a consequence of identities involving multiple polylogarithms, and explains an earlier observation that the coefficients of the Laurent polynomial at the cusp are given by rational numbers times single-valued multiple zeta values., Comment: 42 pages, significant clarifications added in section 5, minor typos corrected, and references added in version 2

In this paper, we develop new estimation results for functional regressions where both the regressor Z ( t ) and the response Y ( t ) are functions of Hilbert spaces, indexed by the time or a spatial location. The model can be thought as a generalization of the multivariate regression where the regression coefficient is now an unknown operator Π . We propose to estimate the operator Π by Tikhonov regularization, which amounts to apply a penalty on the L 2 norm of Π . We derive the rate of convergence of the mean-square error, the asymptotic distribution of the estimator, and develop tests on Π . As trajectories are often not fully observed, we consider the scenario where the data become more and more frequent (infill asymptotics). We also address the case where Z is endogenous and instrumental variables are used to estimate Π . An application to the electricity consumption completes the paper.

International audience; We have studied by means of Brownian dynamics simulations the dynamics of small ions in model charged porous media. We have focused on the influence on this dynamics of short polyelectrolytes with the same charge sign as the solid phase. We have compared the self-diffusion coefficients of counterions of four families of systems with different compositions (presence or not of charged obstacles and of polyelectrolytes). Our main result is that the presence of polyelectrolytes only modulates a behavior we had already observed before: In the domain where the porosity is relatively high compared to the Debye length, diffusion coefficients of counterions increase when the porosity decreases. Moreover, we have shown that, in the systems investigated here without charges on obstacles, the self-diffusion of counterions is mostly affected by the presence of polyelectrolytes and not by concentration effects, contrarily to co-ions. Also, we have seen that even if the density of the probability of presence of counterions in the vicinity of polyelectrolytes is much higher than that on obstacles, the residence time of ions around polyelectrolytes is shorter than around charged obstacles.

We calculate a wall crossing formula for 4-dimensional Poincare-Einstein metrics, through a wall made of orbifold Poincare-Einstein metrics with A1 singularities. This is based on a formalism which enables to deal with higher order terms of the Einstein equation in this setting. Some other consequences are deduced., 28 pages, in French

There is an increasing need for localized cooling in integrated circuit/microfluidic chips, where cooling is currently achieved by relatively large and bulky cooling systems. Joule–Thomson (JT) cryocoolers are suitable to address these size limitations because they have no cold moving parts and, therefore, can be easily miniaturized. We present a JT microcooler with parallel two-stage expansion that cools down to a no-load temperature of 83 K with an ambient temperature of 295 K, whereas a single-stage microcooler typically cools to about 100 K. In addition, this microcooler has the attractive feature of providing cooling powers at two temperature levels without additional manufacturing or processing steps. In changing the temperature at the first expansion position, the cooling power can be exchanged between the two expansion stages. A dynamic model was developed to predict the actual performance of the microcooler. The accuracy of this model was verified through the comparison between experimental and simulation results.

We prove the quasiinvariance of Gaussian measures (supported by functions of increasing Sobolev regularity) under the flow of one-dimensional Hamiltonian partial differential equations such as the regularized long wave, also known as the Benjamin–Bona–Mahony (BBM) equation.

Given the proposed changes to nutrition labelling in Canada and the dearth of research examining comprehension and use of nutrition facts tables (NFts) by adolescents and young adults, our objective was to experimentally test the efficacy of modifications to NFts on young Canadians' ability to interpret, compare and mathematically manipulate nutrition information in NFts on prepackaged food.An online survey was conducted among 2010 Canadians aged 16 to 24 years drawn from a consumer sample. Participants were randomized to view two NFts according to one of six experimental conditions, using a between-groups 2 x 3 factorial design: serving size (current NFt vs. standardized serving-sizes across similar products) x percent daily value (% DV) (current NFt vs. "low/med/high" descriptors vs. colour coding). The survey included seven performance tasks requiring participants to interpret, compare and mathematically manipulate nutrition information on NFts. Separate modified Poisson regression models were conducted for each of the three outcomes.The ability to compare two similar products was significantly enhanced in NFt conditions that included standardized serving-sizes (p ≤ .001 for all). Adding descriptors or colour coding of % DV next to calories and nutrients on NFts significantly improved participants' ability to correctly interpret % DV information (p ≤ .001 for all). Providing both standardized serving-sizes and descriptors of % DV had a modest effect on participants' ability to mathematically manipulate nutrition information to calculate the nutrient content of multiple servings of a product (relative ratio = 1.19; 95% confidence limit: 1.04-1.37).Standardizing serving-sizes and adding interpretive % DV information on NFts improved young Canadians' comprehension and use of nutrition information. Some caution should be exercised in generalizing these findings to all Canadian youth due to the sampling issues associated with the study population. Further research is needed to replicate this study in a more heterogeneous sample in Canada and across a range of food products and categories.Essai randomisé mesurant l’efficacité des modifications apportées au tableau de la valeur nutritive sur la compréhension et l’utilisation de l'information nutritionnelle par les adolescents et les jeunes adultes au Canada.Compte tenu des changements proposés à l’étiquetage nutritionnel au Canada et de la rareté des travaux de recherche portant sur la compréhension et l’utilisation des tableaux de la valeur nutritive (tVN) chez les adolescents et les jeunes adultes, notre objectif consistait à réaliser un essai expérimental pour déterminer si les modifications apportées au tVN permettaient d’améliorer efficacement la façon dont les jeunes Canadiens interprètent, comparent et manipulent, sur le plan mathématique, l’information nutritionnelle figurant dans le tVN de denrées préemballées.Une enquête en ligne a été menée auprès d’un échantillon de consommateurs composé de 2 010 Canadiens âgés de 16 à 24 ans. Nous avons réparti les participants de façon aléatoire en six groupes d’étude, et nous avons présenté à chacun des groupes deux des six tVN définis comme conditions expérimentales, selon un plan factoriel 2 x 3 : portion de référence (tVN actuel et portions de référence normalisées pour tous les produits similaires) x pourcentage de la valeur quotidienne (% VQ) (tVN actuel, ajout des descripteurs « faible/moyen/élevé » et ajout d’un code de couleurs). L’enquête comprenait sept tâches consistant à interpréter, comparer et manipuler, sur le plan mathématique, l’information nutritionnelle figurant dans les tVN. Des modèles de régression de Poisson modifiés ont été élaborés pour chacun des trois résultats.La capacité à comparer deux produits similaires s’est révélée significativement meilleure quand le tVN incluait une portion de référence normalisée (p ≤ 0,001 dans tous les cas). L’ajout de descripteurs ou d’un code de couleurs indiquant, sur le tVN, le % VQ pour les calories et les nutriments a amélioré de façon significative la capacité des participants à interpréter correctement l’information à propos de ce % VQ (p ≤ 0,001 dans tous les cas). Le fait de présenter aux participants des portions de référence normalisées et des descripteurs du % VQ a eu un effet modeste sur leur capacité à manipuler, sur le plan mathématique, l’information nutritionnelle pour calculer la valeur nutritive de plusieurs portions d’un produit (ratio relatif = 1,19; intervalle de confiance à 95 % : 1,04 à 1,37).La normalisation des portions de référence et l’ajout d’information sur l’interprétation du % VQ dans le tVN ont permis aux jeunes Canadiens de mieux comprendre et utiliser l’information nutritionnelle. Il faut néanmoins faire preuve de prudence avant de généraliser les résultats de l’enquête à l’ensemble des jeunes Canadiens en raison de l’échantillonnage de la population à l’étude. D’autres travaux de recherche sont nécessaires afin de reproduire cette étude au Canada avec un échantillon plus hétérogène, et en utilisant un éventail de produits alimentaires et de catégories d’aliments.

Four-graviton couplings in the low energy effective action of type II string vacua compactified on tori are strongly constrained by supersymmetry and U-duality. While the $R^4$ and $D^4 R^4$ couplings are known exactly in terms of Langlands-Eisenstein series of the U-duality group, the $D^6 R^4$ couplings are not nearly as well understood. Exploiting the coincidence of the U-duality group in $D=6$ with the T-duality group in $D=5$, we propose an exact formula for the $D^6 R^4$ couplings in type II string theory compactified on $T^4$, in terms of a genus-two modular integral plus a suitable Eisenstein series. The same modular integral computes the two-loop correction to $D^6 R^4$ in 5 dimensions, but here provides the non-perturbative completion of the known perturbative terms in $D=6$. This proposal hinges on a systematic re-analysis of the weak coupling and large radius of the $D^6 R^4$ in all dimensions $D\geq 3$, which fills in some gaps and resolves some inconsistencies in earlier studies., 18 pages (+ 26 page appendix), three Mathematica files included with submission; v2: minor corrections, version to appear in JHEP

The present paper describes the energy analysis of a regenerative vapour power system. The regenerative steam turbines based on the Rankine cycle and comprised of vapour extractions have been used industrially since the beginning of the 20th century, particularly regarding the processes of electrical production. After having performed worked in the first stages of the turbine, part of the vapour is directed toward a regenerative exchanger and heats feedwater coming from the condenser. This process is known as regeneration, and the heat exchanger where the heat is transferred from steam is called a regenerator (or a feedwater heater). The profit in the output brought by regenerative rakings is primarily enabled by the lack of exchange of the tapped vapour reheating water with the low-temperature reservoir. The economic optimum is often fixed at seven extractions. One knows the Carnot relation, which is the best possible theoretical yield of a dual-temperature cycle; in a Carnot cycle, one makes the assumption that both compressions and expansions are isentropic. This article studies an ideal theoretical machine comprised of vapour extractions in which each cycle partial of tapped vapour obeys these same compressions and isentropic expansions., Les turbines à vapeur basées sur les cycles de Hirn et de Rankine comportant des soutirages de vapeur sont utilisées industriellement depuis le début du XX siècle. C’est notamment le cas des process de production d’électricité.Après avoir travaillé dans les premiers étages de la turbine, une partie de la vapeur est dirigée vers un échangeur et réchauffe l’eau provenant du condenseur.Le gain en rendement apporté par les soutirages régénératifs est essentiellement du au fait que la vapeur soutirée réchauffe l’eau et n‘échange pas en pure perte avec la source froide. L’optimum économique est souvent fixé à 7 soutirages.On connaît la relation de Carnot qui est le meilleur rendement théorique possible d’un cycle bitherme dans lequel on fait l’hypothèse que les compressions et les détentes sont isentropiques.Cet article étudie une machine théorique idéale comportant des soutirages de vapeur dans laquelle chaque cycle partiel de vapeur soutirée obéit à ces mêmes hypothèses de compressions et détentes isentropiques.

International audience; We provide, in a wide range of the parameters, an estimate for the mean-value over sifted integers of certain arithmetic functions with Dirichlet series analytically close to $1/\zeta_{\mathbb{K}}(s)$, where $\mathbb{K}$ is a number field and $\zeta_{\mathbb{K}}$ its Dedekind zeta function.

International audience; The 1896-1901 Milanese period is a key one to understand Einstein’s training background. When he was a student at the ETH in Zürich (the Swiss Federal Polytechnic in Zürich) from 1896 to 1900, he would make regular trips back to Milan to stay with his family who was involved in the development of the electricity industry in northern Italy. Between 1899 and 1901, he would meet his faithful friend and collaborator, Michele Besso in Milan on a regular basis. Given their relationship, the 1899-1901 Milanese period therefore foreshadowed the Bern period. In order to specify the circumstances under which Einstein and Besso got the chance to meet, we will show that their respective families did have interconnected social networks, especially through the electricity sector and the polytechnic engineering Universities of Zürich and Milan. The branch of the Cantoni family, on Michele’s mother’s side, rather ignored by now, played a crucial role: with Vittorio Cantoni, a renowned electrical engineer who had not been previously identified as being Michele’s uncle, and Giuseppe Jung, professor at the Milan Politecnico. We will also show that when staying in Milan, Einstein, who lived in a well-known Milanese palace in the heart of the city, worked in the nearby rich library of the Istituto Lombardo, Accademia di Scienze e Lettere in Brera. The linkage between the scientific observations which can be found in Einstein’s correspondence and this library collection sheds new light on his scientific work, in particular on his original thesis.; La période milanaise 1896-1901 est une période clé pour comprendre les années de formation d'Albert Einstein. Alors étudiant à l'ETH de Zurich entre 1896 et 1900, il rejoint régulièrement sa famille, installée à Milan, et impliquée de longue date dans le développement de l'électricité en l'Italie du nord. Entre 1899 et 1901, il y retrouve son ami et collaborateur, Michele Besso, qu'il avait connu à Zurich. Du point de vue de la relation Einstein-Besso, la période milanaise 1899-1901 préfigure celle de Berne à partir de 1904, où les deux amis se retrouvent au Bureau des Brevets. Afin de préciser le cadre de leur rencontre, nous mettrons en évidence les liens de leurs familles respectives avec le milieu de l'électricité et des écoles polytechniques de Zurich, Milan. La branche maternelle de la famille de Michele, relativement ignorée jusqu'à présent, tient un rôle important, avec Vittorio Cantoni, ingénieur en chef de la première ligne de transport de courant alternatif en Italie entre Tivoli et Rome, qui n'avait pas été identifié auparavant comme étant un oncle de Michele, et Giuseppe Jung, professeur de mathématiques au Politecnico de Milan, avec lequel Einstein est resté en contact plusieurs années. Nous montrerons aussi qu'Einstein, qui habite un célèbre palais milanais au coeur de la ville, travaille à la riche bibliothèque scientifique de l'Istituto Lombardo, Accademia di Scienze e Lettere située au palais Brera, à 500 mètres de son domicile. La mise en rapport des remarques scientifiques qui apparaissent dans la correspondance d'Albert Einstein avec le fonds de cette bibliothèque apporte un éclairage nouveau sur son travail, en particulier sur sa thèse originale.

Beta-thalassemia is one of most common autosomal recessive disorders worldwide. In France, 5 to 10 new major or intermedia forms are diagnosed annually and the global prevalence is about 500 cases. Since 20 years and thanks to the generalization of iron chelator treatments, the life expectancy has dramatically increased. Nearly 90% of the β-thalassemic alleles are point mutations easily identified by Sanger sequencing or dedicated methods. The remaining 10% are deletions detectable by MLPA or CGH Array. The alpha-globin genotype is also essential in the exploration of beta-thalassemia because an alpha-thalassemia improves the clinical state whereas an alpha triplication worsens it. The additional genotyping of a few HbF inducer polymorphisms allows to predict the age of the first transfusion, thanks to a recent dedicated algorithm, making beta-thalassemia one of the first potential application of predictive medicine. Gene therapy, pre-implantatory diagnosis and new drugs (Sotatercept®, hepcidin-like molecules) have also recently contributed to make beta-thalassemia a main scientific topic again.

cote interne IRCAM: Chardon14a; None / None; National audience; This paper presents a method for designing a robust open spherical microphone array that overcomes the typical problems of open sphere geometries at frequencies related to the zeros of the spherical Bessel functions. The proposed array structure uses only a few additional sampling points inside the spherical volume whose optimal positions are determined by the eigenmodes of the sphere for a given wave number interval. This novel approach minimizes the interpolation error inside the sphere. We illustrate this approach with the design of a 10-th order array using 130 microphones and discuss the simulation results with regard to commonly used error measures (white noise gain, condition number, and interpolation error), and show that the proposed array design compares favorably to previously suggested array designs.

LGEP 2014 ID = 1381; International audience; Semiconducting amorphous YBa2Cu3O6 + x (x < 0.5, a-YBCO) films of 140 nm to 880 nm thickness were deposited by direct current (DC) hollow cathode sputtering at low temperature (≈ 150 °C). The film microstructure was typically granular. Dielectric measurements from 100 Hz to 2 MHz were performed in the 300-430 K range to characterize the charge transport behavior. Alternating current conductivity values were extracted and the frequency dependence revealed a relaxation mechanism, which strength increased with temperature according to an Arrhenius law. The activation energy values matched those deduced from the temperature dependence of DC conductivity. The observed relaxation was in line with the hopping charge transport mechanism. A tri-layer device (metal/a-YBCO/metal on Si/SiO2 substrate) was processed using standard lithography. DC electrical tests confirmed the Schottky nature of the metal/a-YBCO contact. The optical response at 850 nm wavelength exhibited a high-pass behavior (maximum response at 100 kHz/1.6 μs time constant). The device current noise spectrum - of "blue" character - was investigated and discussed, in line with the frequency behavior of a-YBCO conductivity. A large signal/noise ratio was obtained, resulting in detectivity D* > 109 cm*Hz1/2*W− 1 in the 7 kHz to 100 kHz frequency range. These results are testifying for the very good performance of a-YBCO as room temperature pyroelectric sensing material.

Interpolation methods circumvent poor time resolution of breath-by-breath oxygen uptake ( $$\dot{V}{\text{O}}_{2}$$ ) kinetics at exercise onset. We report an interpolation-free approach to the improvement of poor time resolution in the analysis of $$\dot{V}{\text{O}}_{2}$$ kinetics. Noiseless and noisy (10 % Gaussian noise) synthetic data were generated by Monte Carlo method from pre-selected parameters (Exact Parameters). Each data set comprised 10 ( $$\dot{V}{\text{O}}_{2}$$ )-on transitions with noisy breath distribution within a physiological range. Transitions were superposed (no interpolation, None), then analysed by bi-exponential model. Fitted model parameters were compared with those from interpolation methods (average transition after Linear or Step 1-s interpolations), applied on the same data. Experimental data during cycling were also analysed. The 95 % confidence interval around a line of parameters’ equality was computed to analyse agreement between exact parameters and corresponding parameters of fitted functions. The line of parameters’ equality stayed within confidence intervals for noiseless synthetic parameters with None, unlike Step and Linear, indicating that None reproduced Exact Parameters. Noise addition reduced differences among pre-treatment procedures. Experimental data provided lower phase I time constants with None than with Step. In conclusion, None revealed better precision and accuracy than Step and Linear, especially when phenomena characterized by time constants of

Micron-scale characterization of mechanical stress is essential for physic failure studies in power devices. We report the use of Raman spectroscopy to measure mechanical stress in silicon power devices with spatial resolutions down to 500 nm. μ-Raman measurements were realized on diode and Insulated Gate Bipolar Transistor (IGBT) cross sections unbiased and forward biased in order to map internal stress distributions. Temperature and stress contributions on Raman diffusion were deconvoluted fitting Full Width at Half Maximum (FWHM) and position of the stokes peak. For the first time, it was possible to quantify experimentally mechanical stress evolution during operation. These results give experimental data on thermo-mechanical coupling in power devices and could be able to support numerical models.

National audience; This paper deals with the integrated facility location and supplier selection decisions for the design of supply chain network with reliable and unreliable suppliers. Two problems are addressed: (1) facility location/supplier selection; and (2) facility location/supplier reliability. We first consider the facility location and supplier selections problem where all the suppliers are reliable. The decisions concern the selection of suppliers, the location of distribution centres (DCs), the allocation of suppliers to DCs and the allocation of retailers to DCs. The objective is to minimise fixed DCs location costs, inventory and safety stock costs at the DCs and ordering costs and transportation costs across the network. The introduction of inventory costs and safety stock costs leads to a non-linear NP-hard optimisation problem. To solve this problem, a Lagrangian relaxation-based approach is developed. For the second problem, a two-period decision model is proposed in which selected suppliers are reliable in the first period and can fail in the second period. The corresponding facility location/supplier reliability problem is formulated as a non-linear stochastic programming problem. A Monte Carlo optimisation approach combining the sample average approximation scheme and the Lagrangian relaxation-based approach is proposed. Computational results are presented to evaluate the efficiency of the proposed approaches.

We give a proof and extension of two formulas of Frobenius and Stickelberger of Differential Calculus that they used in a fundamental paper concerning elliptic functions theory. Our main ingredient is the introduction of a bilinear form which is a vast generalization of Leibniz formula. This bilinear form is also connected to the Lagrange product formula. As a corollary, we give a different proof of a theorem of P.J. Olver., 26 pages, in French

Dans un r\'ecent article, Lagarias et Soundararajan \'etudient les solutions friables \`a l'\'equation a+b=c. Sous l'hypoth\`ese de Riemann g\'en\'eralis\'ees aux fonctions L de Dirichlet, ils obtiennent une estimation pour le nombre de solutions pond\'er\'ees par un poids lisse et une minoration pour le nombre de solutions non pond\'er\'ees. Le but de cet article est de pr\'esenter des arguments qui permettent d'une part de pr\'eciser les termes d'erreur et d'\'etendre les domaines de validit\'e de ces estimations afin de faire le lien avec un travail de la Bret\`eche et Granville, d'autre part d'obtenir le comportement asymptotique exact du nombre de solutions non pond\'er\'ees. In a recent paper, Lagarias and Soundararajan study the y-smooth solutions to the equation a+b=c. Under the Generalised Riemann Hypothesis, they obtain an estimate for the number of those solutions weighted by a compactly supported smooth function, as well as a lower bound for the number of bounded unweighted solutions. In this paper, we aim to prove a more precise estimate for the number of weighted solutions that is valid when y is relatively large with respect to x, so as to connect our estimate with the one obtained by La Bret\`eche and Granville in a recent work. We also prove the conjectured upper bound for the number of bounded unweighted solutions, thus obtaining its exact asymptotic behaviour., Comment: 20 pages

International audience; In this paper we are looking for quantitative estimates for the convergene to equilibrium of non reversible Markov processes, especialy in short times. The models studied are simple enough to get an explicit expression of the L2 distance betweeen the semigroup and the invariant measure throught time and to compare it with the corresponding reversible cases.

Phase noise plays an important role in the performances of electronic oscillators. Traditional approaches describe the phase noise problem as a purely diffusive process. In this paper we develop a novel phase model reduction technique for phase noise analysis of nonlinear oscillators subject to stochastic inputs. We obtain analytical equations for both the phase deviation and the probability density function of the phase deviation. We show that, in general, the phase reduced models include non Markovian terms. Under the Markovian assumption, we demonstrate that the effect of white noise is to generate both phase diffusion and a frequency shift, i.e. phase noise is best described as a convection-diffusion process. The analysis of a solvable model shows the accuracy of our theory, and that it gives better predictions than traditional phase models.

Cet ouvrage est issu d'un cours de Master 2 enseigne a l'UPMC entre 2004 et 2007. Nous y presentons une selection de techniques mathematiques orientees vers la resolution des equations aux derivees partielles elliptiques semi-lineaires et quasi-lineaires. Apres un vade-mecum d'analyse reelle et d'analyse fonctionnelle de base pour les EDP, sans demonstrations pour les points les plus connus, nous parcourons ainsi les theoremes de point fixe classiques, les operateurs de superposition dans les espaces de Lebesgue et de Sobolev, la methode de Galerkin, les principes du maximum et la regularite elliptique, nous faisons une excursion assez longue dans divers aspects du calcul des variations puis terminons par les operateurs monotones et pseudo-monotones. Tout ceci est agremente d'exemples et chaque chapitre est complete d'un nombre d'exercices qui croit essentiellement avec le numero du chapitre, au fur et a mesure que de nouveaux materiaux sont presentes.This book stems from lectures notes of a Master 2 class held at UPMC between 2004 and 2007. A selection of mathematical techniques geared towards the resolution of semilinear and quasilinear elliptic partial differential equations is presented. After a short survival guide in basic real and functional analysis for PDEs, without proofs for the most well-known results, we walk through the classical fixed point theorems, the superposition operators in Lebesgue and Sobolev spaces, the Galerkin method, the maximum principles and elliptic regularity, we make a rather long foray into various aspects of the calculus of variations, and conclude with monotone and pseudo-monotone operators, by way of numerous examples. Each chapter is complemented by a number of exercises that grows with the chapter number as more and more material is made available.

A numerical model coupling the three-dimensional oceanic circulation, thanks to the MARS3D model, and the sea state computed by the WAVEWATCH III model, is developed in order to study the hydrodynamic of the nearshore zone. The main principle of the coupled model based on the coupler PALM and the necessary modifications made for the coupling procedure to both numerical codes are described. First tests in horizontal two-dimension are made and they allowed us to develop a primary version. For three-dimensional flow, we show that the coupled model must solve the quasi-Eulerian velocity. In fact, a coherent analytical form of the wave forcing for the Lagrangian velocity does not exist. This point is illustrated by one example with large errors in comparison with the analytical solution when solving for the Lagrangian mean flow., Un modèle numérique couplant la circulation tridimensionnelle, résolue par le code MARS3D, et l'état de la mer, calculé par le code WAVEWATCH III, est développé pour étudier l'hydrodynamique des zones côtières et littorales. Le principe général du modèle, faisant appel au coupleur PALM est décrit, ainsi que les aménagements apportés aux deux codes existants afin de rendre le couplage possible. Des premiers tests en deux dimensions horizontales ont permis de développer une première version. En trois dimensions, nous montrons que le modèle doit calculer la vitesse quasi-eulérienne, car il n'existe pas de forme analytique cohérente du forçage par les vagues pour la vitesse lagrangienne. Cet aspect est illustré par un résultat comportant de très fortes erreurs par rapport à la solution analytique, obtenu avec une formulation en vitesse lagrangienne.

During fifty years Einstein’s theory of gravitation was limited to a backward neo-newtonian interpretation. Nevertheless it was sufficient to as­sure its predominance in regard to Newton’s theory. In the late sixties the studies on the structure of spacetime around a star as well as that concerning the cosmological field were essential for general relativity to get a coherent interpretation. What were the difficulties which explain such a delay to re­consider its interpretation? What were the elements, the concepts that will permit the experts the renewal of the sixties? Cosmology, cosmologists are at the very centre of this revolution. Durant cinquante ans, la théorie de la gravitation d’Einstein se limitera à une interprétation néo-newtonienne peu innovante qui suffira pourtant à assurer sa prééminence face à la théorie de Newton. Les études sur la structure de l’espace-temps autour d’une étoile aussi bien que celles qui concernent les solutions cosmologiques ont été essentielles pour que la relativité générale trouve, au tournant des années soixante, une interprétation cohérente. Quelles sont les difficultés qui justifient un tel retard à (bien) penser la théorie ? Quels sont les éléments, les concepts, les spécialistes qui permettront le renouveau des années soixante ? La cosmologie est au centre de cette révolution.

We give an alternative proof, based on the Monge-Ampere equation, of Dacorogna and Moser's result (Dacorogna and Moser. 1990) [4] on the solvability with optimal regularity of the Dirichlet problem for the prescribed Jacobian equation. (C) 2012 Academie des sciences. Publie par Elsevier Masson SAS. Tons droits reserves.

We consider the relationship between derivations $d$ and $g$ of a Banach algebra $B$ that satisfy $\s(g(x)) \subseteq \s(d(x))$ for every $x\in B$, where $\s(\, . \,)$ stands for the spectrum. It turns out that in some basic situations, say if $B=B(X)$, the only possibilities are that $g=d$, $g=0$, and, if $d$ is an inner derivation implemented by an algebraic element of degree 2, also $g=-d$. The conclusions in more complex classes of algebras are not so simple, but are of a similar spirit. A rather definitive result is obtained for von Neumann algebras. In general $C^*$-algebras we have to make some adjustments, in particular we restrict our attention to inner derivations implemented by selfadjoint elements. We also consider a related condition $\|[b,x]\|\leq M\|[a,x]\|$ for all selfadjoint elements $x$ from a $C^*$-algebra $B$, where $a,b\in B$ and $a$ is normal., 12 pages

The chick embryo was the first animal model used to study the extraordinarily complex process of embryonic development. The chick model led to the discovery of cell lineages involved in the constitution of the digestive muscle wall and of the molecular mechanisms underlying the development of structures and patterning of the digestive wall. First we describe the breakthrough achieved in the 1970s with the construction of quail-chick chimeras, which led to the identification of the embryonic origin of enteric neurons and interstitial cells of Cajal. Functional studies are now possible based on gene transfer technics and transcriptomic analysis. Gain and loss of function approaches are used to target the visceral mesoderm, involved in the constitution of the muscle layer of the digestive tract. This model still holds many promises for the future !, Le poulet a été le premier modèle animal utilisé pour comprendre le processus extraordinairement complexe du développement embryonnaire. Ce modèle a permis, en particulier, la découverte des lignages cellulaires impliqués dans la constitution de la paroi musculaire digestive et des mécanismes moléculaires à l’origine de la structuration et de la régionalisation de la paroi digestive. On rappelle d’abord l’avancée réalisée, dès les années 1970, par la construction de chimères caille-poulet, qui ont permis l’identification de l’origine embryologique des neurones entériques et des cellules interstitielles de Cajal. Des études fonctionnelles sont désormais possibles chez le poulet grâce aux techniques de transfert de gènes et à l’analyse transcriptomique. Par des approches de perte ou de gain de fonction, on peut cibler le mésoderme viscéral qui participe à la constitution de la couche musculaire du tube digestif. Ainsi, ce modèle est encore promis à un bel avenir !, Bernex Florence, De Santa Barbara Pascal. L'embryon de poulet, modèle d'étude du développement du tube digestif. In: Bulletin de l'Académie Vétérinaire de France tome 165 n°1, 2012. pp. 67-72.

In a famous experiment, Stanley Milgram showed in 1969 that, on the average, 6 links (therefore passing through 5 intermediates) were sufficient to connect two strangers in the United States. These six degrees of separation have been observed by other studies but also carrying on small samples. The advent of social networks on the Internet has recently allowed checks on a massive scale. Studies of the Microsoft instant messaging, Twitter or Facebook confirmed and even amplified the small world hypothesis. Thus, by analyzing the 69 billion relationships between the 721 million people having logged into Facebook in May 2011, it appears that the average distance (or number of degrees) between two randomly selected users on the planet is 4.7. Various explanations of the small world are discussed in this article (weak ties between clusters, the presence of hubs in a scale-free structure) and appear in the end rather complementary. JEL classification : Z1, Z19

International audience; We study some properties of Lipschitz exact Lagrangian manifolds isotopic to the zero section. We prove that if such a manifold is invariant under an optical Hamiltonian, then it must be a Lipschitz graph. This extends a recent result of Marie–Claude Arnaud. We also obtain a new geometric description of the Mañé–Mather invariant set. Résumé On etudie quelques propriétés des variétés exactes Lagrangiennes Lipschitz isotopes a la section nulle. On montre qu'une telle variété est un graphe Lipschitz si elle est invariante par un Hamiltonian optique, ce quí etend un résultat récent de Marie–Claude Arnaud. On obtient aussi une nouvelle description géométrique de l'ensemble invariant de Mañé–Mather. Resumo Estudamos algumas propriedades das variedades Lagrangianas exactas Lipschitz isotópicas a secç ao nula. Mostramos que uma tal variedade, se for invariante por um Hamiltonianó optico, ´ e um gráfico Lipschitz, o que generaliza um resultado recente de Marie–Claude Arnaud. Obtemos também uma nova descriç ao geométrica do conjunto invariante de Mañé–Mather.