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Freed from Iron easy release of a stable ketene from the reaction of CO with di-iron bis-μ2-alkylidenes.
No full textInternational audienceIron bis-μ2-alkylidene complexes were shown to perform CO/alkylidene coupling and liberate a stable ketene derivative. The easy release of the ketene formed from CO incorporation is usually the prerogative of terminal iron carbene complexes, while dimetallic, bridging carbenes tend to retain bridging acyl ligands after 1,1 migratory insertion of CO. Observations at -40 °C showed that an acyl intermediate could evolve into a ketene and form a stable μ2-alkylidene di-iron hexacarbonyl complex. Ketene release was shown to depend on the redox state of the iron byproducts. The CC bond formation is reversible, with instant hydration-decarboxylation upon water addition at room temperature
Détection multidomaine d'anomalies dans un réseau 5G
No full textNational audienceWith the advent of 5G, mobile networks are becoming more dynamic and will therefore present a wider attack surface. To secure these new systems, we propose a multi-domain anomaly detection method that is distinguished by the study of traffic correlation on three dimensions: temporal by analyzing message sequences, semantic by abstracting the parameters these messages contain, and topological by linking them in the form of a graph. Unlike traditional approaches, which are limited to considering these domains independently, our method studies their correlations to obtain a global, coherent and explainable view of anomalies.Avec l'avènement de la 5G, les réseaux mobiles se dynamisent et vont donc présenter une plus large surface d'attaque. Pour sécuriser ces nouveaux systèmes, nous proposons une méthode de détection d'anomalies multidomaine qui se distingue par l'étude de la corrélation du trafic sur trois dimensions : temporel en analysant les séquences de messages, sémantique en abstrayant les paramètres que ces messages contiennent et topologique en les reliant sous forme de graphe. Contrairement aux approches traditionnelles qui se limitent à considérer ces domaines indépendamment, notre méthode étudie leurs corrélations pour obtenir une vision globale, cohérente et explicable des anomalies
Lanthanide(III)-dependent hydration of the methanol dehydrogenase cofactor, pyrroloquinoline quinone
No full textInternational audienceThe mechanism by which pyrroloquinoline quinone (PQQ)-dependent methanol dehydrogenases (MDH), bearing either a Ca2+ or a lanthanide (Ln3+) ion in their active site, oxidize methanol has been intensely debated. In particular, the Ln3+-dependent activity of Ln-MDH remains poorly understood. The lack of experimental evidence represents a significant limitation to improve our understanding of these enzymes. In this work, we propose that insights on Ca- and Ln-MDH reactivity can be gained by examining a model reaction, the hydration of PQQ. Indeed, this reaction is similar to the first step of the putative methanol addition-elimination mechanism and is expected to be similarly influenced by the metal ion. The apparent affinity constants of PQQ for Ca2+ and Ln3+ were determined by UVvis absorption spectroscopy. Ln-PQQ complexes in aqueous solution were analyzed by steady-state and time-resolved fluorescence spectroscopy. The thermodynamic and kinetic parameters describing the equilibrium were obtained by variable-temperature and proton exchange spectroscopy (EXSY) NMR, as well as DFT calculations. Results demonstrated a Ln-dependent exchange rate for PQQ hydration equilibrium, the late and more Lewis acidic Ln3+ having the stronger impact
Solving unbounded optimal control problems with the moment-SOS hierarchy *
No full textInternational audienceThe behaviour of the moment-sums-of-squares (moment-SOS) hierarchy for polynomial optimal control problems on compact sets has been explored to a large extent. Our contribution focuses on the case of non-compact control sets. We describe a new approach to optimal control problems with unbounded controls, using compactification by partial homogenization, leading to an equivalent infinite dimensional linear program with compactly supported measures. Our results are closely related to the results of a previous approach using DiPerna-Majda measures. However, our work provides a sound proof of the absence of relaxation gap, which was conjectured in the previous work, and thereby enables the design of a moment-sum-of-squares relaxation with guaranteed convergence
Learning with Differentially Private (Sliced) Wasserstein Gradients
No full textIn this work, we introduce a novel framework for privately optimizing objectives that rely on Wasserstein distances between data-dependent empirical measures. Our main theoretical contribution is, based on an explicit formulation of the Wasserstein gradient in a fully discrete setting, a control on the sensitivity of this gradient to individual data points, allowing strong privacy guarantees at minimal utility cost. Building on these insights, we develop a deep learning approach that incorporates gradient and activations clipping, originally designed for DP training of problems with a finite-sum structure. We further demonstrate that privacy accounting methods extend to Wasserstein-based objectives, facilitating large-scale private training. Empirical results confirm that our framework effectively balances accuracy and privacy, offering a theoretically sound solution for privacy-preserving machine learning tasks relying on optimal transport distances such as Wasserstein distance or sliced-Wasserstein distance
Design of crystalline layered coordination polymers that respond to light and heat stimuli
No full textInternational audienceLayered coordination polymers have attracted significant attention as a class of crystsalline materials characterized by the layer-by-layer stacking of rigid two-dimensional (2D) coordination networks. One of their remarkable features is the flexibility of their crystal structures, which allows for interlayer displacement, swelling, and exfoliation. Incorporating stimuli-responsive moieties into their structures is a promising strategy for the rational design of layered coordination polymers with targeted flexible properties and functions. Despite the challenges associated with crystal design, a variety of stimuli-responsive layered coordination polymers have been developed over the past two decades. This article provides an overview of representative examples of layered coordination polymers whose properties and functions can be modulated by photo- and thermal stimuli
Solution methods for a class of finite-horizon vector-valued Markov decision processes
No full textInternational audienceThis paper investigates and develops solution methods for a class of finite-horizon Markov decision processes characterized by additive or multiplicative vector rewards. Two concepts of optimality are treated: (1) optimality in the space of return vectors, whereby a policy is optimal if it delivers a maximal total reward from any initial state; and (2) optimality in the space of return functions, whereby a policy is optimal if its total reward function is maximal among all total reward functions. The paper elucidates the relation between the two concepts, proposes a procedure for utilizing this relation to determine the set of optimal policies under concept (1), and formulates a dynamic programming approach to calculating optimal policies under concept (2). The paper demonstrates that dynamic programming yields all optimal policies under concept (2). The paper's results are illustrated with numerical experiments and a multi-objective stochastic inventory control problem
Integrated Co-extraction Protocol for Transcriptomic and 1H NMR Metabolomic Analysis of Multi-species Biofilms
No full textInternational audienceCapturing produced, consumed, or exchanged metabolites (metabolomics) and the result of gene expression (transcriptomics) require the extraction of metabolites and RNA. Multi-omics approaches and, notably, the combination of metabolomics and transcriptomic analyses are required for understanding the functional changes and adaptation of microorganisms to different physico-chemical and environmental conditions. A protocol was developed to extract total RNA and metabolites from less than 6 mg of a kind of phototrophic biofilm: oxygenic photogranules. These granules are aggregates of several hundred micrometers up to several millimeters. They harbor heterotrophic bacteria and phototrophs. After a common step for cell disruption by bead-beating, a part of the volume was recovered for RNA extraction, and the other half was used for the methanol- and dichloromethane-based extraction of metabolites. The solvents enabled the separation of two phases (aqueous and lipid) containing hydrophilic and lipophilic metabolites, respectively. The 1H nuclear magnetic resonance (NMR) analysis of these extracts produced spectra that contained over a hundred signals with a signal-to-noise ratio higher than 10. The quality of the spectra enabled the identification of dozens of metabolites per sample. Total RNA was purified using a commercially available kit, yielding sufficient concentration and quality for metatranscriptomic analysis. This novel method enables the co-extraction of RNA and metabolites from the same sample, as opposed to the parallel extraction from two samples. Using the same sample for both extractions is particularly advantageous when working with inherently heterogeneous complex biofilm. In heterogeneous systems, differences between samples may be substantial. The co-extraction will enable a holistic analysis of the metabolomics and metatranscriptomics data generated, minimizing experimental biases, including technical variations and, notably, biological variability. As a result, it will ensure more robust multi-omics analyses, particularly by improving the correlation between metabolic changes and transcript modifications
Design of Multimode Hybrid Plasmonic waveguide for Refractometry
No full textWe investigate a multimode Si 3 N 4 -based hybrid plasmonic waveguide measuring less than 2 µm in length. Increasing Au slot thickness enhances sensitivity, achieving 780 nm/RIU in water medium, enabling high-sensitivity optical biosensing in integrated plasmonic sensors
Global optimization of low-rank polynomials
No full textThis work considers polynomial optimization problems where the objective admits a lowrank canonical polyadic tensor decomposition. We introduce LRPOP (low-rank polynomial optimization), a new hierarchy of semidefinite programming relaxations for which the size of the semidefinite blocks is determined by the canonical polyadic rank rather than the number of variables. As a result, LRPOP can solve low-rank polynomial optimization problems that are far beyond the reach of existing sparse hierarchies. In particular, we solve problems with up to thousands of variables with total degree in the thousands. Numerical conditioning for problems of this size is improved by using the Bernstein basis. The LRPOP hierarchy converges from below to the global minimum of the polynomial under standard assumptions.</div