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Measuring unit relevance and stability in hierarchical spatio-temporal clustering
No full textInternational audienceUnderstanding the significance of individual data points within clustering structures is critical to effective data analysis. Traditional stability methods, while valuable, often overlook the nuanced impact of individual units, particularly in spatial contexts. In this paper, we explore the concept of unit relevance in clustering analysis, emphasizing its importance in capturing the spatio-temporal nature of the clustering problem. We propose a simple measure of unit relevance, the Unit Relevance Index (URI), and define an overall measure of clustering stability based on the aggregation of computed URIs. Considering two experiments on real datasets with geo-referenced time series, we find that the use of spatial constraints in the clustering task yields more stable results. Therefore, the inclusion of the spatial dimension can be seen as a way to stabilize the clustering
Recurrence rates of explosive volcanism in paleo-equatorial Pangaea, and implications for climate near the peak late Paleozoic ice age
No full textInternational audienceThe continental Brousse-Broqui and egrave;s basin (Massif Central, France) preserves a well-exposed section of upper Carboniferous pyroclastic-volcaniclastic lacustrine strata. We present high-precision geochronology and detailed sedimentology that together define a Kasimovian (305.77-306.10 Ma) volcanic recurrence interval of < 10 ky. This is the first quantification of volcanic recurrence from deep (pre-Mesozoic) time, and importantly, represents an unique opportunity to gain insight into the nature of frequent and highly explosive silicic volcanism occurring across eastern equatorial Pangaea during the peak of the late Paleozoic ice age (LPIA). These data emanate from a single, unusually well-exposed and well-constrained site. However, this site is representative of many documented but poorly preserved volcanic centers of coeval or similar ages across west-central Europe. The concentration in both time and space of such highly explosive volcanism in paleoequatorial Pangaea has large implications for the climate system during Earth's penultimate icehouse. The recurrence rates established here support ongoing climate modeling efforts to test the hypothesis that this volcanism imposed a significant cooling effect near and during peak LPIA conditions prior to Permian icehouse collapse. In the wake of enhanced precision in geochronological tools, the integrated approach we apply for quantifying volcanic recurrence rates has broad utility in Earth's deep-time record
Deep learning model applied to real-time delineation of colorectal polyps
No full textInternational audienceBACKGROUND: Deep learning models have shown considerable potential to improve diagnostic accuracy across medical fields. Although YOLACT has demonstrated real-time detection and segmentation in non-medical datasets, its application in medical settings remains underexplored. This study evaluated the performance of a YOLACT-derived Real-time Polyp Delineation Model (RTPoDeMo) for real-time use on prospectively recorded colonoscopy videos. METHODS: Twelve combinations of architectures, including Mask-RCNN, YOLACT, and YOLACT++, paired with backbones such as ResNet50, ResNet101, and DarkNet53, were tested on 2,188 colonoscopy images with three image resolution sizes. Dataset preparation involved pre-processing and segmentation annotation, with optimized image augmentation. RESULTS: RTPoDeMo, using YOLACT-ResNet50, achieved 72.3 mAP and 32.8 FPS for real-time instance segmentation based on COCO annotations. The model performed with a per-image accuracy of 99.59% (95% CI: [99.45 - 99.71%]), sensitivity of 90.63% (95% CI: [78.95 - 93.64%]), specificity of 99.95% (95% CI: [99.93 - 99.97%]) and a F1-score of 0.94 (95% CI: [0.87-0.98]). In validation, out of 36 polyps detected by experts, RTPoDeMo missed only one polyp, compared to six missed by senior endoscopists. The model demonstrated good agreement with experts, reflected by a Cohen’s Kappa coefficient of 0.72 (95% CI: [0.54-1.00], p < 0.0001). CONCLUSIONS: Our model provides new perspectives in the adaptation of YOLACT to the real-time delineation of colorectal polyps. In the future, it could improve the characterization of polyps to be resected during colonoscopy
Anticoagulant drugs targeting Factor XI/XIa and coagulation tests: we urgently need reliable pharmacodynamic data
No full textInternational audienceAntifactor (F)XI/FXIa anticoagulants under development include antisense oligonucleotides, monoclonal antibodies, and small molecules. They do not require routine monitoring, but knowledge of their impact on coagulation tests is essential in view of their expected widespread use. A concentration-dependent prolongation of activated partial thromboplastin time has been shown but varies according to reagents, and the lack of comprehensive data makes interpretation of this test difficult. Measurement of FXI clotting activity is relevant only in case of treatment with antisense oligonucleotides. Measurement of contact pathway factors, if required, should be performed after multiple dilutions of the plasma sample to overcome any inhibitory effect of the anticoagulant. All other tests used in clinical trials (FXIa, FXI antigenic method, and specific thrombin generation assay) are not implemented in clinical laboratories. More comprehensive information on the effect of anti-FXI/FXIa anticoagulants on coagulation tests is urgently needed to anticipate the use of these drugs once they are approved
The Timing and Origin of Lobate Ejecta Forms at Craters in Mercury's South Polar Region
No full textInternational audienceWe present six newly identified examples of lobate ejecta in Mercury's south polar quadrangle (H15), providing the first evidence of syn-impact formation through our observation of perched impact melt at Nairne and Magritte craters. This finding challenges the idea that lobate forms could have developed post-impact via mass wasting or landslide processes, suggesting instead that many, if not all, lobate ejecta deposits formed contemporaneously with the impact event. We present detailed morphostratigraphic maps of two exemplary case studies: Nairne and Magritte, for which we used shadow measurements to better constrain the morphology of their lobes. Many examples globally, including Nairne, have been formed by deposition of the lobe material into a topographically lower antecedent crater. While we confirm that topography plays a significant role in the formation of lobate ejecta, it cannot be the sole factor, as similar impacts onto pre-existing craters do not always produce these features and not all lobate ejecta exhibit evidence for a topographic control. Our study also highlights the frequent association between lobate ejecta and characteristics of oblique impacts. Considering analogous features at Mars and the Moon in particular, lobate ejecta on Mercury is likely the result of either fluidized or dry granular flows, with minimal delay between impact and emplacement. Our findings suggest that lobate ejecta are more widespread on Mercury than previously recognized, and future studies and missions, such as a comprehensive global survey with higher resolution data from BepiColombo, will continue to constrain their formation mechanisms and prevalence
Comprendre et gérer les dynamiques de foule dans le football : approches théoriques et stratégies d’atténuation des risques de violence
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Nécessité écologique de changements transformateurs en aménagement et essai de croisements disciplinaires
No full textInternational audienceLe colloque Contre Nature s’est tenu à Paris en janvier 2025. Il a exploré les tensions entre aménagement du territoire et conservation de la nature, face à l’urgence écologique et environnementale globale. Centré sur les modèles de land sparing (séparation stricte des espaces naturels et anthropisés) et land sharing (intégration de la nature dans les espaces aménagés), il a interrogé leur pertinence dans des configurations et des contextes spatiaux variés. Cinq sessions ont croisé sciences sociales et sciences de la nature, analysant les politiques publiques, les dynamiques paysagères, les conflits d’usages et les récits d’une transition écologique qui pourrait advenir. L’événement a aussi mis en débat les défis de traduction et d’adaptation de ces concepts pour repenser l’aménagement à l’ère des changements globaux
Early-Life Exposure to Organophosphate Esters and Child Neurodevelopment in the French National Birth Cohort
No full textInternational audienceOrganophosphorus esters (OPEs) are ubiquitous flame retardants and/or plasticizers, raising concerns regarding their possible neurodevelopmental toxicity.We aimed exploring association between pre- and post-natal exposure to OPEs and cognitive abilities among 3.5-year-old children.We included 381 mother-child pairs from the French ELFE national birth cohort. Pre- and post-natal exposures were estimated using concentrations of 9 OPEs measured in the hair of mothers collected at birth and children at age 3.5. Children’s cognitive development was evaluated using the Picture Similarities Test (PST) from the British Ability Scale. Analyses were weighted in order to transpose results to French births in 2011. For each OPE, the association with PST scores was assessed by linear regression accounting for DAG-selected adjustment covariables.The only observed association between prenatal exposure to OPEs and PST score was a decrease of 4.5 points (95%CI: -8.8, -0.3) among the 25% of mothers having the highest hair-concentrations of tri-n-butyl phosphate (TBP) versus the 25% having the lowestones. Regarding childhood exposure, we observed a decrease (-1.9 points, 95%CI: -3.0, -0.8) in PST score per twofold increase in children’s hair-concentrations of ethylhexyl diphenyl phosphate (EHDPP). Decreased scores were also observed for higher childhood exposure levels for triphenyl phosphate (TPHP). An increase in the PST score was observed for intermediate childhood exposure levels for tris(2-chloropropyl) phosphate (TCPP).Due to the ubiquitous exposure of the general population, however, further studies are urgently required to assess various subdomains of cognition before any robust conclusions on the neurodevelopmental risks of these compounds can be drawn
Unpacking retailers’ practices towards more sustainability: a Marketing-as-practice approach adapted to retailing: Working Paper
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Qualification des modèles de microclimat et des outils de simulation : une intercomparaison académique
No full textInternational audienceIn recent decades, numerous urban microclimate models have been developed to address various applications, such as diagnosing urban overheating and evaluating heat mitigation strategies using green or grey solutions. These models account for complex physical interactions; however, their qualification and validation remain significant challenges due to their complexity and the lack of a standardized framework and comprehensive reference datasets.This paper presents the first step of a comprehensive qualification and validation methodology through the definition of an academic benchmark and its application to four urban microclimate models. The proposed methodology follows an incremental phenomenological approach, systematically analysing heat transfer processes within an idealized street canyon with well-defined conditions across four cases: shortwave radiation, longwave radiation, aeraulics, and their coupling with heat conduction and storage in walls and ground. The benchmark aims to analyse the behaviour of different microclimate models, quantify deviations between simulation results, and identify their underlying sources within the physical models. This is achieved through the intercomparison of simulation results, incorporating reference data with a known standard deviation where available.The results show good agreement between models for solar radiation, infrared radiation, and heat conduction but reveal significant deviations in surface convection, stressing the need for further research into convection modelling and its influence on coupled processes. Additionally, the results confirm the suitability of the proposed methodology in identifying the sources of deviations between models. This benchmark provides a robust framework for model qualification and is expected to be widely adopted in future studies.Au cours des dernières décennies, plusieurs modèles de microclimat urbain ont été développés et utilisés pour diverses applications. Ces modèles permettent de diagnostiquer les surchauffes urbaines ou d'évaluer différentes stratégies d'atténuation de la chaleur, basées par exemple sur des solutions vertes ou grises, en tenant compte de toutes les interactions physiques. Cependant, leur validation reste un défi pour la recherche, en raison de leur complexité et de l'absence d'un cadre de qualification commun. Cet article propose et met en œuvre la première étape d'une méthodologie de qualification commune progressive par le biais d'un benchmark sur une étude de cas académique idéale, correspondant à un canyon de rue. La méthodologie proposée vise à analyser d'abord, de manière aussi indépendante que possible, les différents phénomènes physiques simulés, tels que le rayonnement solaire, le rayonnement infrarouge, l'aéraulique et la conduction thermique, puis leur couplage. Cette méthodologie a été appliquée à quatre modèles de microclimat urbain : MATHIS, SOLENE-Microclimat, SOLENE-SUSHI et TRABOULE-ProLB, mettant en évidence leurs capacités respectives, leurs similitudes et leurs différences. Dans l'ensemble, les résultats montrent une bonne correspondance pour le rayonnement solaire, le rayonnement infrarouge et la conduction thermique, mais des écarts significatifs pour la convection à la surface. Ces résultats soulignent l'importance de poursuivre les travaux de recherche sur la modélisation de la convection. Ils montrent également la pertinence de la méthodologie développée afin d'évaluer l'origine des divergences entre les modèles. Par conséquent, cette méthodologie devrait être appliquée plus largement à l'avenir