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Drivers of contaminated sediment dynamics over 80 years at a basin scale (Loire river basin, France): a multifactorial approach
No full textInternational audienceUnderstanding the long-term dynamics of sediment contamination requires integrating multiple drivers, including anthropogenic activities, river management and sediment transport processes. This study investigates legacy trace element (TE) contamination (Ag, Bi, Cd, Cu, Hg, Pb, Sb, Sn, Zn) in sediments from the Loire river and its main tributaries, highlighting contamination hot periods and hotspots over eight decades. Prior to the 1950s, sediment composition was stable but limited localized contamination was already identified. During the 1950s–1970s, TE enrichments spread basin-wide, driven by industrial and mining activities plus active sediment transport. River modifications such as dam construction and intensive sand mining started to intensify in the 1970s. From the 1980s onward, TE concentrations globally declined due to regulatory measures, industrial closures and sediment connectivity disruptions caused by sand mining, dams and weirs, confining contamination hotspots mostly within sub-basins. Since the 2000s, sediment quality has significantly improved. However, legacy contaminants can still be remobilized during specific events (major flood events and/or river management operations). A conceptual proxy, the Dynamic of the Recovery Period index, expressed as a percentage of remaining contamination over the period 1970s–2010s, enables comparative analysis of recovery trends, independently of the time frame, the river station or maximum of contamination. It emphasizes the influence of spatially heterogeneous legacy contamination and river management practices on sediment quality. Despite overall recovery, some areas remain impacted, notably by mercury. These findings highlight the importance of integrating riverbed and bank sediment quality and dynamics monitoring into river management to support the resilience of fluvial ecosystems
Set to Be Fair: Demographic Parity Constraints for Set-Valued Classification
No full textSet-valued classification is used in multiclass settings where confusion between classes can occur and lead to misleading predictions. However, its application may amplify discriminatory bias motivating the development of set-valued approaches under fairness constraints. In this paper, we address the problem of set-valued classification under demographic parity and expected size constraints. We propose two complementary strategies: an oracle-based method that minimizes classification risk while satisfying both constraints, and a computationally efficient proxy that prioritizes constraint satisfaction. For both strategies, we derive closed-form expressions for the (optimal) fair set-valued classifiers and use these to build plug-in, data-driven procedures for empirical predictions. We establish distribution-free convergence rates for violations of the size and fairness constraints for both methods, and under mild assumptions we also provide excess-risk bounds for the oracle-based approach. Empirical results demonstrate the effectiveness of both strategies and highlight the efficiency of our proxy method.</div
Investigating the accuracy of road surface reflection characterisation based on round-robin measurements
No full textInternational audienceKnowing the reflection properties of road surfaces is necessary for road lighting design. Road surface reflection is commonly specified by a set of luminance coefficients q. However, measured data q are limited and a fortiori, little is systematically known about the accuracy of measurements. To address this, a comparison based on the recommendations of standard ISO 5725 was organized among three laboratories. Seven samples were measured (six different road surfaces and one near diffuse reflective material). The calculations include trueness and precision. While trueness was checked for a suitable geometry (as we lack reference road surface reflection data) and was found to be quite good, the precision proved to be quite variable, e.g. for characteristic values versus those of single q-values. Precision was not closely related to the values of q, but rather to the geometrical conditions of the measurement
Influence of Visual-Inertial Sensor-To-Segment Calibration on Upper Limb Joint Angles Estimation from Multiple Inverse Kinematics Methods
No full textInternational audienceThis study aims to explore the potential for accurately estimating joint angles during upper limb rehabilitation tasks with different calibration procedures, inverse kinematics methods and measurement modalities. Affordable embedded visual-inertial measurement units offer a promising alternative to the costly and cumbersome gold standard marker-based stereophotogrammetric systems. However, affordability comes with inherent sensors inaccuracies. Hence, prior to their application in a real clinical setting, it is important to demonstrate their ability for accurate joint angle estimation. Discrepancies in joint angles arise due to the inaccuracies of different sensing modalities but also to sensor-to-segment calibration procedures that significantly alter the joint offsets. Therefore, in this paper, the impact of functional and anatomical calibration procedures on joint angle estimation was compared among seven healthy young volunteers. When the same calibration procedures were applied with visual-inertial measurement units and stereophotogrammetric systems data, a relatively small root mean square error of 7.9deg and correlation coefficients exceeding 0.86 were observed. When different calibration procedures were applied with visual-inertial measurement units and stereophotogrammetric systems data, higher root mean square superior to 10deg were observed, highlighting the importance of consistency with the reference set when assessing accuracy. Furthermore, our analysis shows the benefit of using multi-body inverse kinematics procedure over treating inverse kinematics separately for each segment when dealing with inaccurate visual-inertial measurement units data
Multitwists in big mapping class groups
No full text7 pages, 1 figureInternational audienceWe show that the closure of the compactly supported mapping class group of an infinite-type surface is not generated by the collection of multitwists (i.e. products of powers of twists about disjoint non-accumulating curves)
Combinatorics of the Quantum Symmetric Simple Exclusion Process, associahedra and free cumulants
No full textInternational audienceThe quantum symmetric simple exclusion process (QSSEP) is a model of quantum particles hopping on a finite interval and satisfying the exclusion principle. Recently, Bernard and Jin have studied the fluctuations of the invariant measure for this process, when the number of sites goes to infinity. These fluctuations are encoded into polynomials, for which they have given equations and proved that these equations determine the polynomials completely. In this paper, we give an explicit combinatorial formula for these polynomials, in terms of Schröder trees. We also show that, quite surprisingly, these polynomials can be interpreted as free cumulants of a family of commuting random variables
Data paper en humanités numériques : Adressbuch 1854
No full textInternational audienceThis chapter presents a data paper on the datasets related to the project "Adressbuch der Deutschen in Paris von 1854", a project on German immigration to Paris in the 19th century carried out at the German Historical Institute in Paris. During the research project, a database was built with over 4700 addresses of German individuals and companies who settled in Paris and its suburbs in 1854. The information is derived from a historical document, a kind of business directory or yellow pages of Germans in Paris established in 1854.In addition to the description of the data collection methods, this data paper presents the way in which the datasets are enriched, valorised, presented and visualised on historic city maps. Particular attention is paid to the respect of standards and values of digital humanities and open science alike, in coherence with the specific needs of the main users of the database (historians and genealogists).Ce chapitre présente un data paper qui porte sur les jeux de données liés au projet « Adressbuch der Deutschen in Paris von 1854 » au long cours d’histoire sur l’immigration des Allemands à Paris au XIXe siècle réalisé à l’Institut historique allemand de Paris. Le projet a pour objectif de mettre à la disposition des chercheuses et chercheurs et généalogistes, dans une interface, les informations sur les individus et entreprises allemands installés à Paris en 1854. Ces informations sont issues d’un document historique, une sorte de bottin de commerce ou pages jaunes des Allemands à Paris.Outre la description de méthodes de collecte des données, ce data paper présente la manière dont les jeux de données sont enrichis et valorisés dans le dispositif de consultation. Nous portons une attention particulière sur le respect des valeurs des humanités numériques et de la science ouverte, en cohérence avec les spécificités des historiennes et historiens, ainsi que les généalogistes amenés à le consulter
What is alternative finance? (Re)defining the French equity crowdfunding organizational field
No full textInternational audienc
A statistical approach to unveil phytoplankton adaptation to ocean fronts
No full textFine-scale oceanic fronts are ubiquitous and ephemeral physical features that separate contrasting water masses, creating significant heterogeneity in the physical seascape and plankton distributions. Because phytoplankton community composition (PCC) is a key driver of marine ecosystem functioning, understanding the extent to which fine-scale fronts influence PCC remains a critical challenge. However, studying PCC across and within fronts is particularly difficult due to data scarcity and high biophysical variability. We developed a tailored statistical model to characterize PCC within oceanic fronts in the Mediterranean Sea. We modeled the frontal community as a finite mixture model with three components: two communities of adjacent water masses and a potential front-adapted community. Each component was further considered as a discrete mixture of an unknown number of multivariate Gaussian sub-components. First, we used an Expectation-Maximization algorithm to estimate the Gaussian parameters and determine the optimal number of sub-components based on in situ datasets of the PCC within a frontal zone and its adjacent water masses. Second, a hierarchical Bayesian approach was applied to estimate the weight of all components within the frontal dataset. Our results show that within the front a new community component, distinct from those in adjacent water masses, accounts for 70% of the frontal community, indicating that a specific phytoplankton community can emerge in fine-scale oceanic fronts. Despite the limited number of frontal observations, our Bayesian modelling approach provides statistical evidence of the front's influence on phytoplankton community composition, effectively overcoming data scarcity and high variability
Rapport de Terrain - Le village de ma petite-fille: penser l'avenir du territoire indigène du Xingu
No full textLe rapport sur l’**atelier de co-anticipation « A Aldeia da Minha Neta »**, mené dans le territoire du Xingu en avril 2024, retrace une expérimentation pédagogique et scientifique interdisciplinaire qui a réuni des chercheurs brésiliens, français et portugais et des représentant·es autochtones dans une démarche de co-construction de futurs. Organisé en partenariat entre l’**AEI International School – UPEC**, Nova Medical School, Fiocruz et l’**Associação Terra Indígena Xingu** (ATIX), cet atelier a mobilisé la méthodologie des **Futures Literacy Labs**, adaptée au contexte des savoirs ancestraux. À partir de la question imagée « À quoi ressemblera l’aldeia de ma petite-fille dans 30 ? », les participant·es ont produit des visions contrastées du futur, révélant à la fois les menaces perçues (climatiques, culturelles, territoriales) et les espoirs de continuité. L’expérience a permis d’explorer comment les savoirs autochtones peuvent enrichir les démarches anticipatoires, tout en affirmant le droit à l’autodétermination des peuples dans la production de leurs futurs. L’atelier a également renforcé les ponts entre science, pédagogie et action territoriale dans une perspective de recherche engagée