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The potential of Employee Ownership in LATAM: The case of Colombia and Argentina.
No full textInternational audienc
Isometric path complexity of graphs
No full textInternational audienceA set of isometric paths of a graph is "-rooted", where is a vertex of , if is one of the end-vertices of all the isometric paths in . The isometric path complexity of a graph , denoted by , is the minimum integer such that there exists a vertex satisfying the following property: the vertices of any isometric path of can be covered by many -rooted isometric paths. First, we provide an -time algorithm to compute the isometric path complexity of a graph with vertices and edges. Then we show that the isometric path complexity remains bounded for graphs in three seemingly unrelated graph classes, namely, hyperbolic graphs, (theta, prism, pyramid)-free graphs, and outerstring graphs. Hyperbolic graphs are extensively studied in Metric Graph Theory. The class of (theta, prism, pyramid)-free graphs are extensively studied in Structural Graph Theory, e.g. in the context of the Strong Perfect Graph Theorem. The class of outerstring graphs is studied in Geometric Graph Theory and Computational Geometry. Our results also show that the distance functions of these (structurally) different graph classes are more similar than previously thought. There is a direct algorithmic consequence of having small isometric path complexity. Specifically, we show that if the isometric path complexity of a graph is bounded by a constant, then there exists a polynomial-time constant-factor approximation algorithm for ISOMETRIC PATH COVER, whose objective is to cover all vertices of a graph with a minimum number of isometric paths. This applies to all the above graph classes
Altermagnétisme : la face cachée du monde magnétique
No full textInternational audienceQuand nous pensons à un matériau magnétique, nous imaginons instinctivement un aimant et le champ magnétique qu’il produit de lui-même. C’est en effet cette propriété qui est exploitée dans de nombreuses applications de la vie courante : transformateurs électriques, moteurs, générateurs, capteurs, appareils médicaux, électroménagers, stockage de données... Cependant, il existe de nombreux matériaux qui ne sont pas spontanément aimantés et qui, pourtant, possèdent microscopiquement un ordre magnétique bien déterminé. Cet article met en lumière une famille de matériaux de ce genre, découverte récemment : les altermagnétiques. Leurs propriétés, supérieures par bien des aspects à celles des aimants usuels, élargissent le spectre des applications des matériaux magnétiques, notamment dans le domaine de l’électronique de spin
MALDI-TOF mass spectrometry coupled with machine learning: an accurate tool to detect toxigenic Clostridioides difficile strains
No full textInternational audienc
Chamber implant for chronic optical recordings from the cerebral cortex of marmosets
No full textInternational audienceBackground: Marmosets are becoming an increasingly important animal model in Neuroscience and optical approaches such as two-photon microscopy are expected to provide data significantly contributing to our understanding of the brain, especially when performed chronically. New method: We describe a novel imaging chamber that provides an optical window onto the marmoset cerebral cortex over several months, together with the surgery needed for its implantation and that of an associated headpost. MRI data allow optimal positioning on the skull. The chamber is tightly inserted into a craniotomy and its sealing system combines a thread with a silicone elastomer minimizing infection risk and CSF leakage. Continuous contact between the window and the cortex delays tissue regrowth. Opening and sterile re-sealing are easy to perform whenever access to the cortex is needed. Results: Functional data from longitudinal two-photon imaging using genetically encoded fluorescent calcium sensors reveal high optical quality over months. We also demonstrate the feasibility of two-photon imaging of genetically encoded voltage sensors in the marmoset cortex in-vivo.Comparison with existing methods: The chamber provides a field of view twice as large as current designs yet can be machined with standard equipment. Using a curved rather than flat glass window together with easy adjustment of the window's distance with respect to the underlying cortex allows achieving gentle but continuous contact with the underlying cortex. Conclusions: Currently, our chamber already provides a durable solution for long-term imaging in marmosets. Yet, we discuss a few straightforward modifications that may improve its performance even further.</div
De la tendance technique dans l’aide à la conception industrielle
No full textInternational audienceMaintaining that technology shapes the organization of activity exposes us to the qualification of technological determinism. This position, quite widespread in social sciences concerned with economic organizations, favors a strong notion of managerial autonomy. It is common to consider that the social consequences of technology depend more on its social significance than on its material properties. Our study of the development of computer-aided design over the period 1950-2024 tends to demonstrate the persistence of a structuring technical trend. The analysis is based on the concept of technical tendency developed by Leroi-Gourhan. The empirical study concerns the functional logic of design in major industries and at leading simulation software publishers. We propose to place technical mediations in the elaboration of socio-technical systems at the heart of the analysis.Soutenir que la technique forme l’organisation de l’activité expose à la qualification de déterminisme technologique. Cette position, assez répandue au sein des sciences sociales s’intéressant aux organisations économiques, privilégie une notion d’autonomie de gestion forte. Il est alors courant de considérer que les conséquences sociales de la technologie dépendent plus de ses significations sociales que de ses propriétés matérielles. Notre étude du développement de la conception industrielle assistée par l’informatique durant la période 1950-2024 tend à démontrer la persistance d’une tendance technique structurante. L’analyse s’appuie sur le concept de tendance technique développé par Leroi-Gourhan. L’étude empirique concerne la logique fonctionnelle du dessin au sein de grandes industries et chez les principaux éditeurs de logiciels de simulation. Nous proposons de replacer au centre de l’analyse les médiations techniques dans l’élaboration des systèmes sociotechniques
Local cubic spline interpolation for Vlasov-type equations on a multi-patch geometry
No full textInternational audienceWe present a semi-Lagrangian method for the numerical resolution of Vlasov-type equations on multi-patch meshes. Following N. Crouseilles et al. [A parallel Vlasov solver based on local cubic spline interpolation on patches. Journal of Computational Physics (2009)], we employ a local cubic spline interpolation with Hermite boundary conditions between the patches. The derivative reconstruction is adapted to cope with non-uniform meshes as well as non-conforming situations. In the conforming case, there are no longer any constraints on the number of points for each patch; however, a small global system must now be solved. In that case, the local spline representations coincide with the corresponding global spline reconstruction. Alternatively, we can choose not to apply the global system and the derivatives can be approximated. The influence of the most distant points diminishes as the number of points per patch increases. For uniform per patch configurations, a study of the explicit and asymptotic behavior of this influence has been led. The method is validated using a two-dimensional guiding-center model with an O-point. All the numerical results are carried out in the Gyselalib++ library
Keplerian shear for Chacon Transformations
No full textThe concept of keplerian shear was introduced by Damien Thomine recently. It is useful for non ergodic systems, and can be seen as strong mixing conditionally on invariant fibers. The notion is particularly interesting when a.e. fiber is not strongly mixing.We develop here an approach appropriate for systems such that a.e. fiber is weakly mixing, and apply it to a family of rank one transformations. Each transformation is a kind of Chacon map, built with a random number of spacers at each step of the Rochklin tower. We prove that this new dynamical system exhibits keplerian shear. The method relies on a version of a local limit theorem for time dependent Birkhoff sums along the fullshift.</div
Nondiffusive transport of inertial heavy impurities in drift-wave turbulence
No full textInternational audienceWe investigate the transport behavior of tungsten impurities with finite inertia in drift-wave turbulence using the Hasegawa-Wakatani model. Unlike previous tracer-based models, our simulations reveal a transition to nondiffusive dynamics for a range of charge states. This mechanism offers a turbulence-driven route to core impurity accumulation. This finding underscores the nontrivial role of particle inertia in impurity dynamics and has strong implications for impurity control in future fusion devices such as ITER
Deciphering the anti-Mycobacterium tuberculosis activity of bioinspired lipidic alkynylcarbinols
No full textInternational audienceThis article reports the first in-depth structure-activity relationship investigation of the anti-Mycobacterium tuberculosis (Mtb) potential of falcarindiol, a representative natural acetylenic lipid found in medicinal herbs of various traditional pharmacopeias. Prompted by our previous work on bioinspired anticancer lipidic alkynylcarbinols, we implemented a chemistry-driven deconstruction-reconstruction approach. This led to a detailed analysis of the key structural elements required for an optimized balance between potent anti-mycobacterial activity and low cytotoxicity against mammalian cells. More than 40 synthetic falcarindiol analogues were prepared and evaluated, including individual stereoisomers thanks to a combined chromatographic and chemoenzymatic resolution strategy. Structural evolution guidelines for decoupling of the cytotoxic and anti-Mtb activities of falcarindiol were thus defined. This allowed to increase the level of activity and selectivity by one order of magnitude as compared to the parent natural product falcarindiol with an anti-Mtb minimum inhibitory concentration down to 0.3 μM and a selectivity index up to 242. Overall, this study identifies a new anti-Mtb pharmacophore and opens up prospects for the development of first-in-class anti-Mtb chemical series through the design of novel bio-inspired chemotypes that could fuel the anti-tuberculosis drug discovery and development pipelines