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Les Alpes, Elisée Reclus : la vie morale à l'épreuve du climat
No full textInternational audienceCommunication dans le cadre du séminaire "Géophilosophie" organisé par l'association Présence philosophique au Puy, le 05 janvier 2026 au Puy en Velay
Limitations of Disease X vaccine efficacy and safety clinical trials
No full textAbstract Background In a vaccine clinical trial, the candidate is typically accepted or rejected based on predefined efficacy and safety thresholds. An efficacy threshold is the minimum measured treatment effect deemed statistically significant and clinically relevant. A safety threshold is the maximum number of adverse events deemed acceptable in the vaccine arm of the trial. However, the uncertainties and changing conditions met during the emergence of an unknown infectious disease (Disease X) may hinder such simple approaches. Methods We model the emergence of a Disease X with an SIR (susceptible-infectious-recovered) transmission model. A vaccine is available and the objective is to minimize the total cost over the course of the epidemic, which includes infection, vaccination, and adverse event costs. Uncertainties regarding transmission, vaccine, and cost parameters are represented by prior distributions. We simulate placebo-controlled efficacy and safety trials, and different vaccination policies. Under policies using trial results, the susceptible population is vaccinated if and only if the vaccine candidate passes both the efficacy and safety tests. Results In our baseline scenario and on average over uncertain parameters, using clinical trial outcomes to decide whether to vaccinate the population yields a lower expected total cost compared to indiscriminate emergency vaccination and to no intervention. However, testing both efficacy and safety yields a higher cost compared to testing safety alone. The difference counts in billions of dollars for a population of 10 8 individuals. In our scenario, there is an optimal intermediate safety threshold value that best discriminates vaccine candidates. By contrast, there is no optimal intermediate efficacy threshold value. The incidence difference between the treated and control arms is even a misleading measure of vaccine performance. Conclusions We show with an example that simple threshold-based decision rules may not be appropriate to discriminate candidates in a Disease X vaccine clinical trial. Uncertainties and the disease dynamics need to be fully taken into account, which may require more advanced pattern recognition methods
Les contraintes internes contrôlent la dynamique d’enroulement des vrilles chez les plantes grimpantes
No full textInternational audiencePlant tendrils are mechanosensitive and highly motile organs known for touch-induced differential growth. The resulting coiling dynamics under external traction reveal that non-homogeneous internal stress over the tendril cross-section is fundamental to understanding the system. External loading inhibits curvature generation and can fully suppress it above a threshold force. Remarkably, however, the internal differential stress onset persists even under the highest applied traction forces.We develop an autotropic morphoelastic growth (AMG) model, grounded in a bi-strip geometry and Kirchhoff rod theory, which capture these main features. In particular, the AMG model reproduces the observed 1/4 ratio between the generated intrinsic curvature at high force and that at zero force. According to the AMG model, this ratio depends solely on the twist-to-bend ratio, which is a parameter determined by the plant species.Les vrilles des plantes sont des organes mécanosensibles et hautement mobiles, connus pour leur croissance différentielle induite par le contact. La dynamique d’enroulement sous traction externe montre que la présence de contraintes internes non homogènes à travers la section de la vrille est essentielle pour comprendre le système. La charge externe inhibe la génération de courbure et peut même la supprimer complètement au-delà d’une force seuil. Il est toutefois remarquable que l’apparition de contraintes différentielles internes persiste, même sous les forces de traction les plus élevées appliquées.Nous développons un modèle de croissance morphoélastique autotropique (AMG), fondé sur une géométrie de type bi-lame et sur la théorie des tiges de Kirchhoff, qui rend compte de ces caractéristiques principales. En particulier, le modèle AMG reproduit le rapport expérimental de 1/4 entre la courbure intrinsèque générée sous forte traction et celle observée en l’absence de force. Selon le modèle AMG, ce rapport dépend uniquement du rapport torsion–flexion, un paramètre déterminé par l’espèce végétale
Patellofemoral alignment safe zones in robotic‐assisted TKA do not affect outcomes but do influence patellar resurfacing rates
No full textInternational audienceAbstract Purpose Anterior compartment management remains a challenging aspect of total knee arthroplasty (TKA), particularly in personalised alignment strategies. This study aimed to assess whether restoring patellofemoral alignment parameters within predefined safe zones—specifically patellar tilt (PTi), patellar translation (PTr) and patellar offset (PO)—is associated with improved clinical outcomes following robotic‐assisted TKA (rTKA). Methods This retrospective study included 283 patients who underwent primary rTKA between March 2021 and January 2023 using functional alignment (FA) or functional knee positioning (FKP) principles. All surgeries were performed using a CT‐based robotic system (Mako, Stryker). Patients were stratified into groups based on radiographic values of PTi, PTr and ΔPO, using thresholds derived from prior robotic studies to define safe zones. Clinical outcomes at a mean follow‐up of 2.8 ± 0.8 years included Knee Society Score (KSS), Forgotten Joint Score‐12 (FJS‐12) and Kujala Anterior Knee Pain Scale (AKPS). Results There were no statistically significant differences in final KSS, FJS‐12 or AKPS between groups within or outside the safe zones for PTi, PTr or ΔPO. However, patients with PTi < 0°, ΔPO > 0 mm (overstuffing) or PTr within ±2 mm showed significantly higher rates of patellar resurfacing ( p < 0.001). No group demonstrated superior clinical outcomes across the three parameters studied. Conclusion Restoring patellofemoral alignment parameters within predefined safe zones was not associated with improved short‐term clinical outcomes in rTKA. Robotic‐assisted FA provides accurate restoration of the anterior compartment, reducing reliance on patellar resurfacing in eligible patients. Our data suggest that target biomechanical parameters can potentially be achieved without resurfacing in cases where it is not indicated. Our hypothesis that patients within the proposed safe zones would demonstrate improved clinical outcomes was not supported by the current results. Further prospective studies are needed to determine whether femoral safe zones can predict long‐term benefit. Level of Evidence Level II
The EU borders and their procedures. Considerations relative to the fictions of non-entrée
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Stiffness-sensitive gene regulation in human mesenchymal stem cells: Modelling mechanotransduction to predict mineralization and bone protein expression
No full textInternational audienceThe goal of our study was to establish how a specific part of the bone Gene Regulatory Network (GRN) controls mineralization in response to stiffness. We hypothesized that a system of differential equations model stiffness-sensitive gene regulation in human mesenchymal stem cells through the epistatic genetic interactions between stiffness (e.g. WNT-β catenin pathway) and five of the main transcription factors and bone proteins (e.g. RUNX2, BSP, OSX, OC, and OPN). To test this hypothesis, we (i) performed in-vitro experiments culturing bone cells on different stiffness, (i) adapted our previously published model from being continuously time-dependent to continuously stiffness-sensitive, and (iii) simulated protein production in function of stiffness and other protein production from the best estimate of parameters coming from the experimental work. Our experimental findings reveal a non-parametric relationship between stiffness and RUNX2 production, with no discernible linear trends for other proteins. Modeling results demonstrate that continuous variations in stiffness enable simulation of bone GRN gene expression, fitting our novel experimental dataset. Specifically, our computational results indicate that OPN production peaks at low stiffness (8 kPa), while RUNX2, OSX, and OC achieve maximum production at higher stiffness levels (64 kPa). This alignment underscores the model's capacity to replicate experimental data accurately. Additionally, our approach predicts that WNT-β-catenin activation serves as an enhancer for OPN and BSP production. The model also highlights a negative feedback-like interaction between OC and BSP production. Stiffness variations were shown to have a significant impact on OC and BSP production and a moderate effect on OPN production. By employing a stiffness-sensitive gene regulation model, we provide insights into one of the mineralization patterns through the prediction of bone protein expression dynamics
Contrastive learning and physics oriented evaluation for advanced segmentation in electron tomography
No full textInternational audienceDeep learning methods are now achieving strong results for segmentation tasks, and the standard metric for evaluating methods is the Intersection over Union (IOU). However, we show in this paper that IOU is not efficient in evaluating the quality of segmentation for electron tomography (ET) images of zeolites. We perform a physics-oriented evaluation to ensure that the segmentation results yield coherent physical measures. We also formalize Mixed Supervised / Self-Supervised Contrastive Learning Segmentation (M3S-CLS), a semi-supervised approach using a contrastive learning approach that uses expert annotations to train the neural network model. A detailed comparison of this method with a standard cross-entropy-based model is provided. In addition, we publish a database of five fully segmented ET volumes along with corresponding baseline results. The code and the database is available at http://gitlab.univ-st-etienne.fr/labhc-iscv/M3S-CLS
Studying interspecific population synchrony: current status and future perspectives
No full textInternational audienceInterspecific population synchrony, or co‐fluctuations in the population dynamics and demographic parameters of different species, is an important ecological phenomenon with major implications for the stability of communities and ecosystems. It is also central in the context of biodiversity loss, as interspecific synchrony can influence how ecological communities are affected by anthropogenic stressors. Studies of interspecific synchrony are therefore important for understanding fundamental mechanisms underlying the biodiversity changes occurring worldwide. Interspecific synchrony has received increased interest in recent years, and studies have focused on synchrony in abundances, growth rates and vital rates at species, community and metacommunity levels. However, there is little cohesiveness in the literature, as studies focused on different levels of biological organization are largely separate from each other. Still, synchrony at these levels of biological organization is likely interconnected in nature. Understanding these connections would greatly benefit our understanding of interspecific synchrony and its implications for populations and communities. Here, we provide an overview of the current status and future perspectives of interspecific synchrony research, highlighting major knowledge gaps. We show how interspecific synchrony at different levels of biological organization is conceptually linked and present an accessible overview of the terminology and methods used to study it. By providing a common understanding of the meaning and applicability of terms and an overview of commonly used methods, this overview will serve as a point of departure for integrating research on interspecific synchrony. Such integration is important to fully understand the impacts of environmental change on species and ecological communities
Resonant attenuation of surface acoustic waves by a weakly bonded layer
No full textWe investigate the propagation of surface acoustic waves (SAWs) in a layered half-space system comprising a continuous, sub-wavelength-thick layer weakly adhering to a substrate. Using finite element simulations, we demonstrate that this configuration - without requiring surface structuration - gives rise to frequency ranges bounded in k-space and characterized by strong SAW attenuation, which we term adhesion-induced resonant attenuation zones. We show that these attenuation zones closely mimic the resonant behavior typically observed in locally resonant metamaterials and can be understood through a mass-spring analogy, where the adhesion between the layer and substrate governs the frequency and width of the attenuation zones. As a practical demonstration, we propose a bilayer configuration as a practical route to experimentally realize adhesion-induced resonant attenuation of SAWs, where a soft and thin interfacial film serves as an intermediate adhesive bonding between the layer and substrate, providing a realistic and tunable interfacial stiffness. Our findings offer a simplified route to achieving SAW manipulation through continuous layered media with tunable adhesion, providing a practical alternative to complex structural designs in SAW-based devices across a broad frequency range
Eco-friendly Insulating Materials for Transformers in MVDC and HVDC Power Networks
No full textInternational audienceThis work investigates the viability of natural and synthetic ester liquids as potential alternatives to mineral oil in MVDC and HVDC transformer insulation systems. Finite Element Method simulations (FEM) were performed using the measured dielectric properties of the oils and their impregnated pressboards as input parameters to evaluate their influence on steady state electric field distribution. A comparison on the field distribution under AC and DC condition is performed for the different materials, identifying regions of maximum stress around the corona head and high voltage electrode. The temperature dependence of electrical conductivity values of the materials and their effect on the steady state DC electric field distribution is explored. The higher conductivity of ester liquids when compared to mineral oil provides a more uniform field redistribution between the oil and pressboard, also facilitating the shift of maximum electrical stress from the oil to pressboard. The results support the technical merits of using ester-based insulation material for field stress equalization in HVDC networks