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Évaluation de la limite de fatigue des Composites à Matrice Organique CMO : Vers des nouvelles approches en auto-échauffement
No full textInternational audienceIn addition to the stabilized temperature, classically used in self-heating, this innovative study proposes to estimate thefatigue limit of monolithic polymer-matrix composites (PMC) using other physical magnitudes: the electrical response ofthe embedded piezoelectric transducer and the piezoresistive response of carbon-based PMC. Similarly, the studystipulates a new automatic approach (based on the concept of distance calculation) and objective (no need for visualizationof the experimental curve in order to adjust the two linear regimes), called the Knee method, in order to automate thedetermination of the fatigue limit. The obtained values were compared with those evaluated in classical fatigue, the resultsare in good agreement.En plus de la température stabilisée, classiquement utilisée en auto-échauffement, cette étude novatrice propose d’estimerla limite de fatigue de composites à matrice organique (CMO) monolithiques grâce à d’autres grandeurs physiques : laréponse électrique du transducteur piézoélectrique embarqué à cœur et la réponse piézorésistive de CMO à base decarbone. De même, l’étude stipule une nouvelle approche automatique (basée sur le concept de calcul des distances) etobjective (pas besoin d’une visualisation de la courbe expérimentale afin d’ajuster les deux régimes linéaires), nomméeméthode de coude (Knee method), afin d’automatiser la détermination de la limite de fatigue. Les valeurs obtenues ontété confrontées à celles évaluées en fatigue classique, les résultats sont en bonne adéquation
Utilisation de Statistiques paramétriques avec la méthodologie Best-Worst Scaling pour l'Analyse de Test Perceptif
No full textPerception sonore : session générale ; GPS - Perception SonoreNational audienceLa réalisation d'une expérience perceptive en audition est soumise à de nombreuses contraintes méthodologiques comme le nombre de stimuli ou le nombre de participants. La méthodologie d'évaluation par Best-Worst Scaling (BWS) ; qui consiste à présenter des séries de N stimuli, souvent quatre, parmi lesquels un participant doit choisir le meilleur et le pire ; a récemment prouvé qu'elle offrait de nombreux avantages. Principalement, la BWS facilite le traitement d'un large corpus de sons. L'implémentation de fonctions de "tournament scoring" sur les données obtenues permet d'obtenir des valeurs numériques fortement corrélées à celles obtenues par une évaluation plus classique comme l'évaluation directe sur une échelle, bien que la BWS ne demande pas aux participants de fournir eux-mêmes des valeurs numériques (Rosi, Ravillion, Houix & Susini, 2022). De plus, la BWS est une procédure expérimentale qui prend moins de temps, et qui est préférée par les participants. Un inconvénient important de la BWS est cependant que les données récoltées ne permettent pas de conduire des analyses statistiques inférentielles, puisque les données individuelles ne sont pas numériques et consistent en des classements de préférences. Il n'existe donc pas de métrique indiquant la confiance que l'on peut accorder aux résultats, et, par extension, sur le nombre de participants à inclure dans une étude suivant cette méthodologie. L'étude présentée ici propose d'explorer la possibilité de construire un estimateur statistique, permettant de réaliser des tests statistiques à partir des données BWS. Cet estimateur, fondé sur les fonctions de scores utilisées, est introduit théoriquement afin de vérifier les propriétés nécessaires à l'application de tests statistiques de type t-test et ANOVA, puis comparé numériquement, à partir de données d'expériences simulées, aux méthodes d'évaluation directes. La BWS combinée aux analyses statistiques usuelles est très prometteuse pour mener des expériences paramétriques générant un nombre important de stimuli audio
Reduction in Brake Wear Emissions with Cr2O3 and WC-CoCr Coatings for Cast Iron Discs
No full textInternational audienceThe present contribution showcases the potential brake emission reduction with Cr2O3 (chromium oxide) and WC-CoCr (tungsten carbide–chromium–cobalt) rotor coatings, as realized in our joint public–private research consortium. Particulate matter (PM) emissions from automotive braking systems have been characterized using a pin-on-disc tribometer equipped with particle measurement devices: a CPC (Condensation Particle Counter), an APS (Aerodynamic Particle Sizer), an SMPS (Scanning Mobility Particle Sizer), and a PM2.5 sampling unit. Brake pad samples made from the same low-steel friction material were tested against a grey flake cast iron disc and two types of custom coated discs: a Cr2O3-coated disc and a WC-CoCr-coated disc. The friction pairs were investigated at a constant contact pressure of 1.2 MPa while the sliding velocity varied during the test, starting with 25 sequences at 3.6 m/s, followed by 19 sequences at 6.1 m/s, and finishing with 6 sequences at 11.2 m/s. The test results show encouraging 64% to 84% reductions in particle number (PN) emissions between 4 nm and 3 µm and 84% to 95% reductions in mass emissions (PM2.5) thanks to the respective coated discs. SEM-EDXS (Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy) analyses show that the hardness and roughness of the discs, the chemical reactivity (oxidation), and the abrasiveness of the three friction pairs are parameters that might explain this reduction in emission
On the value of varied evidence for imprecise probabilities
No full textInternational audienceIt has long been considered a truism that we can learn more from a variety of sources than from highly correlated sources. This truism is captured by the Variety of Evidence Thesis. To the surprise of many, this thesis turned out to fail in a number of Bayesian settings. In other words, replication can trump variation. Translating the thesis into IP we obtain two distinct, a priori plausible formulations in terms of 'increased confirmation' and 'uncertainty reduction', respectively. We investigate both formulations, which both fail for different parameters and different reasons, that cannot be predicted prior to formal analysis. The emergence of two distinct formulations distinguishing confirmation increase from uncertainty reduction, which are conflated in the Bayesian picture, highlights fundamental differences between IP and Bayesian reasoning
Prolonged heat stress in Brassica napus during flowering negatively impacts yield and alters glucosinolate and sugars metabolism
No full textThe datasets presented in this study can be found in onlinerepositories. The names of the repository/repositories and accessionnumber(s) can be found below: https://www.ncbi.nlm.nih.gov/SUB14296957.International audienceOilseed rape ( Brassica napus ), one of the most important sources of vegetable oil worldwide, is adversely impacted by heatwave-induced temperature stress especially during its yield-determining reproductive stages. However, the underlying molecular and biochemical mechanisms are still poorly understood. In this study, we investigated the transcriptomic and metabolomic responses to heat stress in B. napus plants exposed to a gradual increase in temperature reaching 30°C in the day and 24°C at night for a period of 6 days. High-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC-MS) was used to quantify the content of carbohydrates and glucosinolates, respectively. Results showed that heat stress reduced yield and altered oil composition. Heat stress also increased the content of carbohydrate (glucose, fructose, and sucrose) and aliphatic glucosinolates (gluconapin and progoitrin) in the leaves but decreased the content of the indolic glucosinolate (glucobrassicin). RNA-Seq analysis of flower buds showed a total of 1,892, 3,253, and 4,553 differentially expressed genes at 0, 1, and 2 days after treatment (DAT) and 4,165 and 1,713 at 1 and 7 days of recovery (DOR), respectively. Heat treatment resulted in downregulation of genes involved in respiratory metabolism, namely, glycolysis, pentose phosphate pathway, citrate cycle, and oxidative phosphorylation especially after 48 h of heat stress. Other downregulated genes mapped to sugar transporters, nitrogen transport and storage, cell wall modification, and methylation. In contrast, upregulated genes mapped to small heat shock proteins (sHSP20) and other heat shock factors that play important roles in thermotolerance. Furthermore, two genes were chosen from the pathways involved in the heat stress response to further examine their expression using real-time RT-qPCR. The global transcriptome profiling, integrated with the metabolic analysis in the study, shed the light on key genes and metabolic pathways impacted and responded to abiotic stresses exhibited as a result of exposure to heat waves during flowering. DEGs and metabolites identified through this study could serve as important biomarkers for breeding programs to select cultivars with stronger resistance to heat. In particular, these biomarkers can form targets for various crop breeding and improvement techniques such as marker-assisted selection
Photodynamic Therapy Using Pulsed-Laser Irradiation of Gold Nanoparticles for the Treatment of Cancers with High Basal Oxidative Stress
No full textInternational audienceFor over 20 years, considerable research has been carried out on the use of nanotechnologies in cancer treatment. Beyond the photothermal effect of irradiating gold nanoparticles, the photodynamic effect with reactive oxygen species (ROS) production at the tissue level is poorly known. We showed that renal cancers had high basal ROS levels. We engineered different gold nanoparticles and optimized the irradiation parameters. Then, we intravenously injected several patient-derived xenografts with tailored gold nanorods that we irradiated using a pulsed laser. We optimized irradiation parameters to decrease toxic effects on normal tissue and showed that the local monitoring of skin temperature was an accurate marker for predicting histological toxicity. We demonstrated a significant additional effect of irradiating gold nanoparticles, with the increased activation of the autophagy pathway following irradiation, associated with the disappearance of renal cancer cells. Our study highlights the elevated ROS levels in cancers as a potential therapeutic target for ROS-mediated cytotoxicity therapies
How flagella glycosylation of the phytopathogenic bacteria Pseudomonas amygdali pv. tabaci 6605 affect transport and deposition in saturated sandy porous media
No full textInternational audienceAbstract To mitigate bacterial contamination in underground farmland, a comprehensive understanding of the transport and adhesion mechanisms of phytopathogenic bacteria in porous media is crucial for safeguarding soil and groundwater. This study aims to elucidate the effects of Pseudomonas amygdali pv. tabaci 6605 flagella (Wild type, Δ fliC strain) and its glycosylation (Δ fgt1 and Δ fgt2 strains) on bacterial transport and deposition in sandy porous media through a combination of experimental observations and numerical simulations. Flagella play a key role in bacterial transport and deposition dynamics through its surface properties. Its intrinsic hydrophobicity enhances bacterial adhesion and promotes deposition onto sandy grains, while simultaneously limiting transport through the porous medium. However, glycosylation of flagellin introduces hydrophilic glycans, which counteract this effect by increasing the overall hydrophilicity of the bacterial surface. As a result, glycosylated flagella facilitate bacterial mobility and improves recovery in the effluent, while reducing retention within the sand matrix. These findings highlight the critical influence of flagella’s biochemical modifications on bacterial behavior in porous environments. They provide valuable insights for understanding and managing microbial contamination in subsurface systems. Importance This work, conducted using homogeneous laboratory sand, could be extended to other types of abiotic media found in natural environments, such as clay, heterogeneous sands, and soils. Our study highlights the impact of flagellar glycosylation on bacterial behavior, an essential factor for assessing the risk posed by phytopathogenic bacteria in agricultural settings and for developing effective soil bioremediation strategies. Moreover, this study provided valuable insights into the mechanisms governing bacterial transport and deposition at the macroscopic (column) scale under dynamic flow conditions. Investigating unsaturated flow conditions, which better approximate real field scenarios, may further our understanding of bacterial interactions at air/solid/water interfaces. Future research should explore bacterial movement across different spatial scales. In particular, pore-scale experiments can provide direct evidence of processes such as attachment and motility. This could significantly enhance our understanding of microbial dynamics in complex environments
Fusion vs. Isolation: Evaluating the Performance of Multi-Sensor Integration for Meat Spoilage Prediction
No full textInternational audienceHigh-throughput and portable sensor technologies are increasingly used in food production/distribution tasks as rapid and non-invasive platforms offering real-time or near real-time monitoring of quality and safety. These are often coupled with analytical techniques, including machine learning, for the estimation of sample quality and safety through monitoring of key physical attributes. However, the developed predictive models often show varying degrees of accuracy, depending on food type, storage conditions, sensor platform, and sample sizes. This work explores various fusion approaches for potential predictive enhancement, through the summation of information gathered from different observational spaces: infrared spectroscopy is supplemented with multispectral imaging for the prediction of chicken and beef spoilage through the estimation of bacterial counts in differing environmental conditions. For most circumstances, at least one of the fusion methodologies outperformed single-sensor models in prediction accuracy. Improvement in aerobic, vacuum, and mixed aerobic/vacuum chicken spoilage scenarios was observed, with performance enhanced by up to 15%. The improved cross-batch performance of these models proves an enhanced model robustness using the presented multi-sensor fusion approach. The batch-based results were corroborated with a repeated nested cross-validation approach, to give an out-of-sample generalised view of model performance across the whole dataset. Overall, this work suggests potential avenues for performance improvements in real-world, minimally invasive food monitoring scenarios
Microstructural and Mechanical Properties of AFSDed Materials
No full textAdditive Friction Stir Deposition (AFSD) is a solid-state metal additive manufacturing technique that enables the production of dense, high-quality metallic components without melting. This report presents a comprehensive overview of the microstructural characteristics and mechanical performance of AFSDed materials across different alloy systems, including aluminium, magnesium, stainless steels, duplex stainless steels, inconel 625, and copper. The studies reviewed highlight the ability of AFSD to refine grains through dynamic recrystallization, improve mechanical strength and ductility, and minimize solidification-related defects typical of fusion-based additive processes
Cybersecurity Standards Across Industries: A Critical Analysis of Current Practices and Future Directions in the Railway Sector
No full textInternational audienceThe increasing digitalization of railway systems has significantly expanded their cyber-physical attack surface, raising critical concerns about the adequacy of current cybersecurity governance, particularly in safety-critical environments. Although cybersecurity standards provide structured approaches to risk management, their integration into railway-specific system lifecycles remains fragmented, and their practical implementation is still underexplored in both academic and industrial domains. This paper presents a comprehensive and methodologically grounded study addressing these limitations through two main contributions. First, it provides a detailed analysis of the primary cybersecurity standards applicable to the railway domain, with a particular focus on the risk assessment frameworks defined in CENELEC TS 50701 and IEC 62443. Second, it offers a comparative analysis of selected standards, identifying complementarities and opportunities for cross-domain synergies with other safety-critical sectors, supported by illustrative examples of practical applications. Additionally, the paper delivers a critical review of existing literature on railway cybersecurity, revealing persistent gaps in lifecycle integration, interdisciplinary alignment, and the contextual adaptation of cybersecurity measures to the specific operational and safety constraints of the railway sector. By synthesizing these findings, the study contributes a coherent foundation for aligning cybersecurity governance with the unique demands of railway systems, offering actionable insights for researchers, practitioners, and regulatory bodies working to secure next-generation railway infrastructures