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Calculated and structural analyses of self-assembly formed by [7]thiaheterohelicene-2,13-carboxaldehyde molecules on Au(111)
No full textInternational audienceRecently, the electronic and structural properties of large self-assembled domains of [7]thiahetero- helicene-2,13-carboxaldehyde helicene ([7]TH-dial) molecules on Au(111), Cu(001), and NiAl(110) metal surfaces have been characterized by scanning tunneling microscopy (STM). Several distinct areas of the self-assembled structures can be observed. To describe and explore the morphology of and the interactions in these distinct self-assembled nanostructures, we combine the results obtained through calculations in a semi-empirical framework and calculated STM images. It is revealed that these supramolecular nanostructures, on metallic substrates, originate from the two orientations P and M of the [7]TH-dial molecules linked in different orientations (head-to-tail, sideways, head-on, and tail-on) through van der Waals interactions. The results presented here provide valuable insights for understanding the intermolecular and substrate–molecule interactions within the self-assembled nanostructures of [7]TH-dial molecules on metallic surfaces
Analyse des Systèmes Interconnectés avec Dynamiques Nonlinéaires et Hybrides
No full textNational audienceThe complexity of modern control systems can often be attributed to two elements: firstly, such systems involve logic-based decision making which results in dynamics at different time scales, and secondly, these systems comprise several subsystems which play an important role in shaping the properties of the integrated system. Following this viewpoint, the thesis addresses the analysis techniques for interconnection of systems described by switching, nonsmooth, or more generally, hybrid dynamics in both deterministic and stochastic framework.Starting from some earlier work, we first present the classical cascade configuration for time-dependent switched systems where the stability conditions are formulated for a certain class of switching signals using multiple Lyapunov functions, and the notion of input-to-state stability. As a generalization, and using the tools from nonsmoth analysis, we study the feedback interconnections of Filippov differential inclusions (for state-dependent switched systems) with application to observer-based control, and anti-maximal monotone differential inclusions (for projected systems, complementarity systems, and sweeping processes) with application to analyzing certain optimization algorithms. Moving forward, and in the spirit of studying a broader class of interconnections, we study graph-coupled nonlinear systems where the exchange of information between agents is described by switching, but jointly-connected, graphs. The analysis of such systems is carried out by developing singular perturbation theory for hybrid systems, where we propose a novel decomposition of hybrid systems resulting in a continuous-time quasi-steady-state system and a purely discrete-time boundary layer system with constrained switching. We provide conditions for asymptotic practical stability, which in the setting of graph-based interconnections, translate to checking some properties of the graphs and the stability of reduced-order subsystems.In the final part of the thesis, we step away from the deterministic framework and study interconnections in stochastic setting that appear in the design of certain filtering algorithms. The first such class of interconnections is seen in ensemble filters (for systems described by stochastic differential equations and discrete observations) where we propose algorithms for computing the approximation of the posterior distribution of the state conditioned upon the measurements by simulating particles resulting from continuous-discrete McKean-Vlasov type differential equations. We then develop appropriate tools for analyzing the interconnection of particles coupled to each other via the empirical mean and empirical covariance. Another class of interconnections is seen in studying filtering algorithms with unknown parameters (such as noise covariances), where we use Bayesian inference algorithms and the optimal estimate is described by a probabilisitic weighted sum of the conditional posteriors. Under certain assumptions on system dynamics, we study asymptotic convergence for such algorithms towards the optimal solution determined by complete information of the parameters
Exploring 5-hydroxymethylfurfural hydrogenation pathways using NHC-stabilized water-soluble nanoparticles of various metals and alloys
No full textInternational audienceThe catalytic valorization of 5-hydroxymethylfurfural (5-HMF), a key bio-based platform molecule, is central for sustainable chemical production. In this work, we report the aqueous-phase hydrogenation of 5-HMF using a family of water-soluble nanoparticles stabilized by an N-heterocyclic carbene (IMesPrSO3) ligand. The nanoparticles were comprehensively characterized by BF-TEM, DLS, TGA, ICP-OES, and pair distribution function (PDF) analysis from wide-angle X-ray scattering (WAXS). By only varying the metal core (Ru, Pd, Ir, RuIr2), and slightly modifying the reaction conditions, we accessed a diverse array of high-value products, including 2,5-bis(hydroxymethyl)furan (2,5-BHMF), 2,5-bis(hydroxymethyl)tetrahydrofuran (2,5-BHMTHF), oxidized cyclopentenones, and 1-hydroxyhexane-2,5-dione (HHD), all under environmentally friendly conditions (30–140 °C, 5 bar H2, in water). Specifically, the Ru-based nanoparticles showed high selectivity to 2,5-BHMF (90%) at very mild conditions (30 °C), along with a promising recyclability. Reaction products were identified and quantified through extensive NMR spectroscopy, including 1H, 13C, COSY, HSQC, and HMBC experiments. Our findings demonstrate that these truly colloidal catalytic systems can represent a tuneable and robust platform for green and sustainable biomass transformations
Bath parameterization in multi-band cluster Dynamical Mean-Field Theory
No full textInternational audienceAccurate and reliable algorithms to solve complex impurity problems are instrumental to a routine use of quantum embedding methods for material discovery. In this context, we employ an efficient selected configuration interaction impurity solver to investigate the role of bath discretizationspecifically, bath size and parameterization-in Hamiltonian-based cluster dynamical mean field theory (CDMFT) for the one-and two-orbital Hubbard models. We consider two-and four-site lattices for the single-orbital model and a two-site cluster for the two-orbital model. Our results demonstrate that, for small bath sizes, the choice of parameterization can significantly influence the solution, highlighting the importance of systematic convergence checks. Comparing different bath parameterizations not only reveals the robustness of a given solution but can also provide insights into the nature of different solutions and potential instabilities of the paramagnetic state. We present an extensive analysis of the zero-temperature Mott transition of the paramagnetic half-filled single-band Hubbard model, where we can benchmark with previous literature, and for multi-band models, overcoming limitations of traditional methods and opening the door to systematic studies of multi-orbital systems with the inclusion of non-local effects. Our results show that the dependence on parameterization is strongly reduced for feasible bath sizes in the case of the single-orbital model, while some dependence is still observed for the two-orbital model.</div
From beams to plates: a new Macro-Element for the simplified analysis of bonded joints
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Caractérisation de structures composites thermoplastiques à renforts en fibres de carbone, verre, et biosourcés mises en forme par pultrusion
No full textInternational audienceSolutions adapted for light railway infrastructures made with composite materials are studied with reducing environmental costs in mind in the transport sector. The design of composite rails requires consideration of dimensioning, in particular mechanical and structural strength. To this end, an experimental study is carried out to determine the orthotropic properties of pultruded composite materials with thermoplastic (ex. Elium®) matrix and glass / or carbon / or bio-sourced (basalt and flax) reinforcement fibers. Tensile and compressive characterization tests are carried out in the longitudinal, transverse and off-axis directions of the composite according to ISO 527-4, ASTM 3410 and NF EN 2563 standards. A total of 100 samples were tested. The tests show that the mechanical properties of the thermoplastic matrices are substantially equivalent. Better properties are obtained with carbon fibers compared to glass or vegetable fibers. However, glass fibers would seem to be preferred due to their lower cost and more favorable end of life compared to carbon fibers. Similarly, bio-sourced fibers, with inferior properties of around 25%, still have an interesting and rewardable life cycle.Les solutions adaptées aux infrastructures ferroviaires légères réalisées en matériaux composites sont étudiées dans une optique de réduction des coûts environnementaux dans le secteur des transports. La conception de rails composite exige une réflexion sur le dimensionnement, notamment sur la tenue mécanique et structurelle. A cet effet, une étude expérimentale est réalisée pour déterminer les propriétés orthotropes de matériaux composites pultrudés à matrices thermoplastiques (ex. Elium ® ) et renforts en fibres de verre / ou carbone / ou bio-sourcés (basalte et lin). Des essais de caractérisation en traction et en compression sont effectués dans les directions longitudinale, transversale et hors-axe du composite selon les normes ISO 527-4, ASTM 3410 et NF EN 2563. Un total de 100 échantillons a été testé. Les essais montrent que les propriétés mécaniques des matrices thermoplastiques sont sensiblement équivalentes. De meilleures propriétés sont obtenues avec des fibres de carbone comparées aux fibres de verre ou végétales. Toutefois, les fibres de verre sembleraient être privilégiées en raison de leur coût plus faible et de leur fin de vie plus favorable par rapport aux fibres de carbone. De même, les fibres bio-sourcées, aux propriétés inférieures de l'ordre de 25%, présentent cependant un cycle de vie intéressant et valorisable
The affine geometry of meromorphic connections with irregular singularities
No full textA meromorphic connection on the tangent bundle of a Riemann surface induces a complex affine structure on the complement of the poles. Local models for Fuchsian singularities are already known. In this paper, we introduce a complete set of local invariants for a meromorphic connection and provide local models for a complex affine structure in a punctured neighborhood of an irregular singularity. Generalizing a construction attributed to Veech, we introduce the Delaunay decomposition of a compact Riemann surface endowed with a meromorphic connection with irregular singularities. In particular, we give upper bounds on the complexity of the decomposition
Brown adipose tissue activity impacts systemic lactate clearance in male mice
No full textInternational audienceNon-shivering thermogenesis in brown adipose tissue (BAT) is linked to metabolic health. Yet, how its activity states impact on systemic metabolism and in particular on lactate, a highly abundant metabolite increasingly recognized as a critical player in energy metabolism, remains unresolved. The goal of this study was to investigate the impact of BAT activity on lactate metabolism at the whole organism level. To activate or inactivate non-shivering thermogenesis in BAT, we housed C57Bl6/J male mice at 4, 21 and 30°C and then conducted lactate tolerance tests. In mice exposed to cold exposure (4°C), systemic lactate clearance was elevated. In contrast, clearance of systemic lactate was poor in mice housed under thermoneutral conditions (30°C) that inactivate BAT thermogenesis, as well as in mice deficient for the mitochondrial uncoupling protein-1. To better understand lactate metabolic fate during the clearance phase, in vivo stable isotope tracing experiments with labelled 13C-lactate and analyses by mass spectrometry were performed. These experiments revealed that lactate contribution to gluconeogenesis was increased under cold exposure while its contribution to the tricarboxylic acid cycle was reduced in BAT under thermoneutrality. Remarkably, we also identified that lactate entered a pyruvate cycling process that was highly active in BAT, and repressed at thermoneutrality. Our study shows that inactivation of non-shivering thermogenesis decreased systemic lactate clearance, concomitantly with changes in metabolic fate of lactate in BAT and in gluconeogenic organs, in male mice
Climate impact accounting of biogenic CO2: An open framework towards ALIGNED practices for a diversity of bioeconomy stakeholders
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Multifunctional Diffractive Optical Element for Microcavity Mode Control
No full textInternational audienceThe work introduces a multifunctional diffractive optical element (DOE) designed to achieve precise mode control in photonic microcavities, specifically Cavity Resonator Integrated Grating Filters (CRIGFs). Traditional mode-selective excitation often relies on bulky, costly phase-only spatial light modulators (SLMs), which hinder integration into compact systems.The proposed DOE is a binary phase mask that simultaneously handles phase modulation, effective amplitude shaping (via duty-cycle), and focusing within a single compact device. Its design combines gradient-based numerical optimization with physics-based rules, balancing mode selectivity against scattering losses. Fabricated through standard single-level photolithography, the DOE is compatible with established semiconductor manufacturing. Experimental results demonstrate selective excitation of higher-order CRIGF modes, confirmed by transmission spectra with clear resonance dips. Compared with SLM-based systems, the DOE reduces complexity, size, and cost while retaining flexibility. Future applications include few-mode fiber systems for data multiplexing and integration into collimators or coupling optics, paving the way for highly compact, multifunctional photonic devices.Ce travail présente un élément optique diffractif multifonctionnel (DOE) conçu pour assurer un contrôle précis des modes dans des microcavités photoniques, en particulier les filtres à réseau intégrés résonants de cavité (CRIGF). Les méthodes classiques d’excitation sélective de modes reposent souvent sur des modulateurs spatiaux de phase (SLM) encombrants et coûteux, qui limitent leur intégration dans des systèmes compacts.Le DOE proposé est un masque binaire de phase qui assure simultanément la modulation de phase, le façonnage effectif de l’amplitude (via le rapport cyclique) et la focalisation dans un composant unique et compact. Sa conception combine une optimisation numérique par gradient avec des règles physiques, conciliant sélectivité des modes et pertes par diffusion. Fabriqué par photolithographie standard à un seul niveau, le DOE est compatible avec les procédés de fabrication semi-conducteurs établis.Les résultats expérimentaux démontrent l’excitation sélective de modes d’ordre supérieur dans le CRIGF, confirmée par des spectres de transmission présentant des résonances marquées. Comparé aux systèmes basés sur SLM, le DOE réduit la complexité, la taille et le coût tout en conservant une grande flexibilité. Parmi les perspectives d’application figurent les systèmes à fibres à quelques modes pour le multiplexage de données et l’intégration dans des collimateurs ou des optiques de couplage, ouvrant la voie à des dispositifs photoniques multifonctionnels et très compacts