Archives ouvertes de Paris-Saclay
Not a member yet
272730 research outputs found
Sort by
Dynamic damage evolution and fracture initiation in finite deformation ductile materials
No full textInternational audienceThis paper presents a semi-explicit algorithm for modeling dynamic damage and fracture in ductile materials under finite deformation. The algorithm combines the efficiency of explicit methods with the stability of implicit schemes, enabling robust simulations in large deformation and contact scenarios. To further enhance numerical stability, a rotational stress update scheme based on Kirchhoff stress is implemented, which effectively handles rigid-body rotations and mitigates artificial stress artifacts. Frictional contact is addressed using an implicit algorithm based on the bi-potential method, ensuring stable and efficient contact resolution. The damage model is formulated within the continuum damage mechanics (CDM) framework, following the damage evolution theory of Chaboche and Lemaitre. Material nonlinearity is captured using an isotropic von Mises yield criterion. The proposed method is implemented in the plastic finite element program CCMPF and verified through a series of numerical examples. Two quasi-static simulations are first conducted to evaluate the mesh sensitivity of the local damage model and to verify the accuracy of the constitutive integration scheme. A dynamic Taylor impact, including both 2D and 3D cases, is performed to validate the algorithm under high strain-rate conditions. The results demonstrate the method’s accuracy, efficiency, and robustness in simulating dynamic failure in ductile materials
Bulletin de veille du réseau d'écotoxicologie terrestre et aquatique N°81
No full textINRAE, réseau ECOTOX → A paraîtreBulletin de veill
Specific killing and resensitization of pathogenic Escherichia coli strains carrying bla CTX-M-15 β-lactamase using targeted-antibacterial-plasmids (TAPs)
No full textInternational audienceAbstract Targeted-Antibacterial-Plasmids (TAPs) offer a precise approach to combat multidrug-resistant bacteria by selectively removing resistant strains while preserving commensals. Here, we assess TAPs that deliver CRISPR/Cas systems via conjugation to kill or resensitize extended-spectrum β-lactamase (ESBL)-producing Escherichia coli carrying the blaCTX-M-15 gene. We systematically tested multiple variables in the TAP approach, including two commensal E. coli donors, three distinct helper plasmids encoding the transfer machineries, and six recipient strains harbouring the resistance gene either chromosomally or on a plasmid. Cas9-based TAPs induced double-stranded breaks in chromosomal blaCTX-M-15 genes, resulting in immediate bacterial death. When the target gene was plasmid-borne, Cas9 cleavage triggered plasmid loss and partial toxin-antitoxin-mediated killing. In contrast, dCas9-based TAPs inhibited blaCTX-M-15 expression without affecting cell viability, thereby restoring third-generation cephalosporin susceptibility. In mixed-culture experiments, TAPs specifically eliminated only blaCTX-M-15-carrying E. coli while sparing other non-targeted bacterial species. Conjugation assays in human faeces demonstrated substantial suppression of cefotaxime-resistant (CtxR) E. coli by both Cas9- and dCas9-based TAPs, underscoring their efficacy in complex microbial environments. These findings highlight TAPs’ decolonization promise, paving the way for future microbiome-editing interventions against multidrug-resistant carriage or infection
Pneumococcus uses COMMD2 to alter host cellular immunity
No full textNF-κB driven cellular immunity is essential for both pro- and anti-inflammatory responses to microbes, which makes it one of the most frequently targeted pathways by bacteria during pathogenesis. How NF-κB tunes the epithelial response to Streptococcus pneumoniae across the spectrum of commensal to pathogenic outcomes is not fully understood. In this study, we compare a commensal-like 6B ST90 strain to an invasive TIGR4 isolate and demonstrate, through comparative mass spectrometry of the p65 interactome, TIGR4 challenge triggers a novel interaction of COMMD2 with p65 and p62. Mechanistically, we show this complex mediates export of p65 for degradation and COMMD2 is necessary for altering host cellular immunity. With these results, we reveal for the first time a new bacterial pathogenesis mechanism to repress host inflammatory response though COMMD2 and p65 degradation while presenting a paradigm for diverging NF-κB responses to pneumococcus
State and Unknown Input Estimation using a Left-Invertibility Constrained NeuralEstimator in Delayed Autonomic Cardiac Dynamics
No full textInternational audienceUnderstanding brain–heart interaction (BHI) requires models that capture how thecentral nervous and cardiovascular systems co-regulate under stressors to preserve homeostasis and generate macroscopic states such as sleep, arousal, or vigilance. At the core of this loop are interoceptive variables, latent autonomic control signals that drive cardiac adjustments; however, these variables are not directly measurable. Recovering these hidden drives from peripheral cardiac recordings is confounded by nonlinear dynamics, physiological delays, and limited measurement data. This work proposes a physics-informed neural estimator for joint state estimation and unknown autonomic input reconstruction in a delayed nonlinear model of autonomic cardiac regulation. The framework derives left-invertibility conditions from the delay-free system and determines a system-intrinsic bound on physiological delay driven only by heart-rate dynamics, preserving constraint validity for the delayed system within that bound.Validation on stress-evoked cardiac recordings shows accurate recovery of heart rate, blood pressure state estimation, and input reconstruction (the blood-pressure setpoint), enabling identifiable, physiology-consistent inference of interoceptive autonomic control dynamics
Radio-PPG: photoplethysmogram digital twin synthesis using deep neural representation of 6G/WiFi ISAC signals
No full textDigital twins for 1D bio-signals enable real-time monitoring of physiological processes of a person, which enables early disease diagnosis and personalized treatment. This work introduces a novel non-contact method for digital twin (DT) photoplethysmogram (PPG) signal synthesis under the umbrella of 6G/WiFi integrated sensing and communication (ISAC) systems. We employ a software-defined radio (SDR) operating at 5.23 GHz that illuminates the chest of a nearby person with a wideband 6G/WiFi signal and collects the reflected signals. This allows us to acquire Radio-PPG dataset that consists of 300 minutes worth of near synchronous 64-channel radio data, PPG data, along with the labels (three body vitals) of 30 healthy subjects. With this, we test two artificial intelligence (AI) models for DT-PPG signal synthesis: i) discrete cosine transform followed by a multi-layer perceptron, ii) two U-NET models (Approximation network, Refinement network) in cascade, along with a custom loss function. Experimental results indicate that U-NET model achieves an impressive relative mean absolute error of 0.194 with a small ISAC sensing overhead of 15.62%, for DT-PPG synthesis. Furthermore, we performed quality assessment of the synthetic DT-PPG by computing the accuracy of DT-PPG-based vitals estimation and feature extraction, which turned out to be at par with that of reference PPG-based vitals estimation and feature extraction. This work highlights the potential of generative AI and 6G/WiFi ISAC technologies and serves as a foundational step towards the development of non-contact screening tools for covid-19, cardiovascular diseases and well-being assessment of people with special needs
Technical report on direct geolocalization from remote sensing S1 images
No full textThis small technical report highlights that coarse direct position prediction from image is somehow possible given current deep network efficiency. 80% localisation bin accuracy is achieved accross a 400km x 300km corridor quantified on a 10km x 10km grid
Unearthing facets of sustainability initiatives reporting and legitimacy: a knowledge management perspective
No full textFNEGE 2, ABS 2International audiencePurpose - The purpose of this study is to investigate the sustainability disclosure framework surrounding India’s tourism firms and to analyze the Environmental Initiatives (EI), Social Initiatives (SI) and Governance Initiatives (GI) of these firms, which constitute their intellectual capital (IC) and establish their legitimacy. Design/methodology/approach - This inductive approach–based study investigates the sustainability reports of listed tourism firms. It analyzes the extent and variance of sustainability disclosures concerning environmental (E), social (S) and governance (G) aspects through a combination of qualitative content analysis and quantitative methods. Findings - Based on a sample of 30 listed tourism companies that are publishing business responsibility and sustainability reports (BRSR), the results of these reports, based on content and quantitative analysis, indicate the extent and variance of environmental, societal and governance (ESG) initiatives reported by the tourism firms that help legitimize their activities and contribute to intellectual capital formation. Research limitations/implications - This study sought to analyze the sustainability reports as per the BRSR 2021 framework, which is so far applicable to the top 1,000 listed companies of India; however, not many tourism firms fall into this category. As a result, the number of firms that published sustainability reports in 2021–2022 is small. Future studies can extend this research in tourism with a more extensive data set for qualitative and quantitative analysis. Moreover, there is no limitation to applying this methodology in other industry sectors with a larger sample size. Practical implications - ESG disclosures by these firms contribute to Sustainable Development Goals (SDGs) through their business operations and initiatives’ ESG impact. Policymakers and managers, both at national and global levels, can push ahead the agenda of sustainable tourism through the interaction of firms and stakeholders within the national policy preview, such as BRSR reporting, and international policy purview, such as SDG mapping of ESG initiatives as a part of larger sustainability goals where tourism firms are one of the key contributors to them. Social implications - The quality and extent of ESG initiatives and their variance in tourism firms affect how diverse stakeholders gauge and assess the business and social responsibility discharged by the listed entities in this sector. Originality/value - Most disclosure-based studies focus on aggregate disclosures; however, this study aims to examine the extent and variance of sustainability disclosures related to environment (E), social (S) and governance (G) in a disaggregated manner within the tourism sector. Such ESG initiative-based disclosures are then mapped to SDGs to find that ESG initiatives are in tandem with the SDG goals. This study found that the listed tourism firms in India are passably reporting on sustainability to establish legitimacy, and the extent of associated initiative disclosures varies significantly within the groups contributing primarily toward green intellectual capital formation due to overarching EI. In addition, the knowledge management–enabled ESG disclosures collectively contribute toward enhancing human, structural and relational capital to legitimize their initiatives
L’escalade en salle : d’un « sport d’action » à une industrie
No full textInternational audienceIntegrated to the action sports category (Wheaton & Thorpe, 2016), sport climbing is currently developping at an international scale. The market of climbing gyms has an important growth in France and abroad (Aubel & Lefèvre, 2022), leading to transform the organisation and the practise of the sport. Using oral (N=28) and written sources (N=447), including interviews with climbing gym owners, this paper aims to contribute the understanding of industrial stakes of climbing. The analysis focus on the developpement of the climbing gym sector in France, in order to explain the « intensive marketization » (Callon, 2015) of this market, throught sociotechnical innovations (Akrich, 1989) such as route setting. This case study enlighten about organisational changes of sport climbing, formerly known as an alternative sport and now in a marketization process (Rogeaux, 2023). In the end, we question the place of sport climbing in the action sports category, and more widely the limits of this categorization. While climbing is a singular activity, its congruence with different categories (such as extreme, alternative, lifestyle or action sports) doesn’t always enable to explain the full complexity of the sport. It shows the limits, recognized in the litterature, of classification processes such as action sports.Intégré à la catégorie des action sports (Wheaton & Thorpe, 2016), l’escalade est une activité sportive qui connaît un développement récent important. En effet, le marché des salles commerciales est en pleine croissance en France et dans le monde (Aubel & Lefèvre, 2022), conduisant à transformer l’organisation du sport et les modalités de pratique. En s’appuyant sur des sources orales (N=28) et écrites (N=447), dont des entretiens avec des dirigeants de salles privées, cet article se propose de contribuer à comprendre les enjeux industriels que connaît l’activité. L’analyse porte sur le développement du secteur des salles marchandes d’escalade en France, afin de montrer comment ce marché a connu un processus de « marketization intensive » (Callon, 2015), porté par plusieurs innovations sociotechniques (Arkich, 1989), comme l’évolution de l’ouverture des passages d’escalade. Cette étude de cas permet d’éclairer les mutations organisationnelles de l’escalade, considéré jadis comme un sport alternatif et désormais en proie à une mise en économie (Rogeaux, 2023). En conclusion, nous questionnerons la présence de l’escalade parmi les action sports, et plus globalement, les limites d’une telle catégorisation. Alors que l’escalade est une activité singulière, la congruence avec les différentes catégories dans laquelle celle-ci est parfois présentée (telles que sports libres, alternatifs, lifestyle, extrêmes) ne permet pas toujours d’appréhender la complexité du sport. Cela montre les limites, bien comprises par les différents auteurs, d’une classification des différentes activités sportives telle que le propose la notion de action sports
Divergence-Free Diffusion Models for Incompressible Fluid Flows
No full textGenerative diffusion models are extensively used in unsupervised and self-supervised machine learning with the aim to generate new samples from a probability distribution estimated with a set of known samples. They have demonstrated impressive results in replicating dense, real-world contents such as images, musical pieces, or human languages. This work investigates their application to the numerical simulation of incompressible fluid flows, with a view toward incorporating physical constraints such as incompressibility in the probabilistic forecasting framework enabled by generative networks. For that purpose, we explore different conditional, score-based diffusion models where the divergence-free constraint is imposed by the Leray spectral projector, and autoregressive conditioning is aimed at stabilizing the forecasted flow snapshots at distant time horizons. The proposed models are run on a benchmark turbulence problem, namely a Kolmogorov flow, which allows for a fairly detailed analytical and numerical treatment and thus simplifies the evaluation of the numerical methods used to simulate it. Numerical experiments of increasing complexity are performed in order to compare the advantages and limitations of the diffusion models we have implemented and appraise their performances, including: (i) in-distribution assessment over the same time horizons and for similar physical conditions as the ones seen during training; (ii) rollout predictions over time horizons unseen during training; and (iii) out-of-distribution tests for forecasting flows markedly different from those seen during training. In particular, these results illustrate the ability of diffusion models to reproduce the main statistical characteristics of Kolmogorov turbulence in scenarios departing from the ones they were trained on