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Closed-form estimators for multivariate regressions models -a single categorical variable approach
No full textInternational audienceThe maximum likelihood estimator (MLE) remains the most frequently used method to estimate the parameters of generalized linear models. But even for distributions within the exponential family, MLEs are not always tractable and need to be computed with time consuming numerical methods like the Iterative Weighted Least Square algorithm. In order to improve the computation time, closed-form estimators have been found in case of categorical explanatory variables for univariate random variables of one-parameter exponential type. In the context of multivariate generalized linear models (MGLM), we propose a new way to look at the score in case of single categorical variables for any distribution in the exponential family. Firstly, we derive closed-form MLE for MGLM assuming multinomial and negative multinomial distributions. Secondly, we deduce similar results for the multivariate normal distributions. For the Dirichlet distribution, we propose a closed-form estimator, yet not MLE, for which we prove the consistency. We illustrate the computation time gains on simulated datasets: closed-form estimators are about 1000 times faster, especially for high dimension. Closed-form estimators are computed in constant times.. Finally, we show the relevancy of the proposed estimator on real-world datasets by modeling cause-of-death mortality in US. We are able to catch the first-order effects of covid between 2019 and 2021
Critique écosystémique des droits humains
No full textInternational audienceL'urgence écologique exige la mise en place de contraintes sur le système productif, et donc sur les modes de consommation qui en découlent. Mais celles-ci sont bien souvent repoussées comme autant d'atteintes aux libertés fondamentales. Semble ainsi s'opérer une confusion entre liberté individuelle et mode de vie non soutenable, qui façonne les représentations individuelles, sociétales, médiatiques, politiques, jusqu'à rejaillir dans la sphère juridique où se manifestent les tensions entre protection de l'environnement et préservation des libertés fondamentales. Cet amalgame court-circuite la réflexion sur les changements sociétaux à conduire pour faire face à l'urgence écologique via le spectre de l'« écologie punitive » ou de la « dictature verte ». Le projet de recherche CritÉcoDhu -Critique écosystémique des droits humains : repenser les « droits de l'Homme » à l'aune des limites planétaires -vise à repenser la fondamentalité des droits dans le cadre d'un nouveau contrat social lié à l'urgence écologique. Ce premier ouvrage collectif, issu d'un séminaire de cadrage entre juristes, philosophes, politistes, anthropologues et climatopaléontologue, réunit tout à la fois des études de cas, des analyses inédites et des relectures critiques de textes fondamentaux qui confrontent libertés individuelles, urgence environnementale et démocratie
Diversité dans les systèmes pastoraux : perceptions et pratiques de gestion d’éleveurs ovins du sud de France
No full textInternational audienceContext: In a context of global change and increasing pressure on pastoral livestock systems, managing animal diversity is a central challenge for the sustainability of small-population flocks. The three local sheep breeds studied here, all endangered, represent an essential genetic and cultural heritage in Southern France. Objective: This article aims to analyse how breeders perceive, define, and manage diversity within their flocks, by examining the interplay between selection criteria, herd management practices, and conceptions of rusticity and animal behaviour. Methods: The study draws on an ethnographic approach combining 17 semi-structured interviews, and field observations with breeders involved in the conservation and valorisation of these local breeds. Qualitative analysis was used to identify the criteria mobilised in diversity management and to explore their articulation with breeders’ trajectories and farming conditions. Results: The selection of breeding animals is based on a combination of zootechnical criteria (conformation, breed standard), ecological criteria (adaptation to the environment, behaviour, rusticity), and personal criteria (attachments, individual preferences). The relative importance of these criteria varies according to breeders’ professional trajectories, environmental contexts, and socio-economic constraints. The analysis also highlights the central role of rusticity, understood as a dynamic quality shaped by management practices. Furthermore, day-to-day management practices (lambing periods, feeding strategies, mobility, flock organisation) also contribute to structuring diversity. Conclusions: The study offers an integrated interpretation of animal diversity that links local ecological knowledge, perceptions of animals, and herd management practices. It shows that diversity results from a co-construction between breeders, animals, and their environment, and underscores the importance of recognising these knowledge systems and practices in policies aimed at conserving local breeds.Contexto: En un contexto de cambios globales y presión creciente sobre la ganadería pastoral, la gestión de la diversidad animal representa un reto central para la sostenibilidad de los sistemas con pocos efectivos. Las tres razas ovinas locales estudiadas, todas ellas amenazadas, constituyen un patrimonio genético y cultural esencial en el sur de Francia. Objetivo: Este artículo tiene el objetivo de analizar cómo los ganaderos perciben, definen y gestionan la diversidad de sus rebaños, combinando criterios de selección, prácticas de manejo y concepciones de la rusticidad y del comportamiento animal. Métodos: El estudio se basa en un enfoque etnográfico que combina observaciones de terreno con 17 entrevistas semidirectivas a ganaderos comprometidos en la conservación y la valoración de estas razas locales. Los datos fueron analizados cualitativamente para identificar los criterios adoptados en la gestión de la diversidad y su articulación con las trayectorias de los ganaderos y las condiciones de cría. Resultados: La selección de los reproductores se basa en una combinación de criterios zootécnicos (conformación, estándar de la raza), ecológicos (adaptación al medio, comportamiento, rusticidad) y personales (vínculos, preferencias individuales). Estos criterios se jerarquizan según la historia profesional, el contexto medioambiental y las limitaciones socioeconómicas de los ganaderos. El análisis pone también en evidencia el rol central de la rusticidad, considerada como un constructo dinámico moldeado por las prácticas de conducción. Finalmente, las prácticas de gestión cotidianas (estacionalidad de las pariciones, alimentación, movilidad, organización del rebaño) también contribuyen a estructurar la diversidad. Conclusiones: El estudio propone una lectura integrada de la diversidad animal que combina saberes ecológicos locales, percepciones de los animales y prácticas de manejo. Muestra que la diversidad resulta de una construcción conjunta entre los ganaderos, los animales y el entorno, y destaca la importancia de reconocer estos saberes y prácticas en las políticas de conservación de las razas locales.Contexte : Dans un contexte de changements globaux et de pressions croissantes sur l’élevage pastoral, la gestion de la diversité animale représente un enjeu central pour la durabilité des systèmes à petits effectifs. Les trois races ovines locales étudiées, toutes menacées, constituent un patrimoine génétique et culturel essentiel dans le sud de la France. Objectif : Cet article vise à analyser comment les éleveurs perçoivent, définissent et gèrent la diversité au sein de leurs troupeaux, en articulant critères de sélection, pratiques de conduite et conceptions de la rusticité et des comportements animaux. Méthodes : L’étude repose sur une approche ethnographique combinant 17 entretiens semi-directifs et des observations de terrain auprès d’éleveurs engagés dans la conservation et la valorisation de ces races locales. Les données ont été analysées qualitativement afin d’identifier les critères mobilisés dans la gestion de la diversité et leur articulation aux trajectoires des éleveurs et aux conditions d’élevage. Résultats : La sélection des reproducteurs repose sur une combinaison de critères zootechniques (conformation, standard de la race), écologiques (adaptation au milieu, comportements, rusticité) et personnels (attachements, préférences individuelles). Ces critères se hiérarchisent selon l’histoire professionnelle, le contexte environnemental et les contraintes socio-économiques des éleveurs. L’analyse met également en évidence le rôle central de la rusticité, considérée comme un construit dynamique façonné par les pratiques de conduite. Enfin, les pratiques de gestion (agnelages, alimentation, mobilité, organisation du troupeau) contribuent elles aussi à structurer la diversité au quotidien. Conclusions : L’étude propose une lecture intégrée de la diversité animale articulant savoirs écologiques locaux, perceptions des animaux et pratiques de conduite. Elle montre que la diversité résulte d’une co-construction entre les éleveurs, les animaux et le milieu, et souligne l’importance de reconnaître ces savoirs et pratiques dans les politiques de conservation des races locales
Modelling of solar plant operating loss for preventive maintenance scheduling optimization
No full textInternational audienceModelling of solar plant operating loss for preventive maintenance scheduling optimizatio
Euclid preparation. Impact of galaxy intrinsic alignment modelling choices on Euclid 3x2pt cosmology
No full textInternational audienceThe Euclid galaxy survey will provide unprecedented constraints on cosmology, but achieving unbiased results will require an optimal characterisation and mitigation of systematic effects. Among these, the intrinsic alignments (IA) of galaxies are one of the dominant contaminants of the weak lensing (WL) and galaxy-galaxy lensing (GGL) probes. In this work, we assess IA modelling choices for Euclid DR1 3x2pt analyses by comparing the performance of the two most commonly used IA models, nonlinear alignment (NLA) and tidal alignment tidal torquing (TATT), along with several variations. Our analyses combine three perspectives: i) the constraining power on the IA and cosmological parameters for each IA model, ii) the bias that results when the IA analysis model differs from the model used to generate the synthetic data vector, and iii) the degeneracies between IA and photometric redshift (photo-z) nuisance parameters. Among the IA models analysed, the redshift-dependent TATT model (zTATT) provides the most flexible description of IA, with a similar constraining power compared to simpler IA models, making it a well-motivated choice for Euclid DR1 3x2pt analyses
Political attitudes differ but share a common low-dimensional structure across social media and survey data
No full textDoes polarization online reflect the state of polarization in society? We study ideological positions and attitudes on several issues in France, a country with documented issue nonalignment. We compare distributions on X/Twitter with a nationally representative sample, focusing on two key properties: ideological polarization and issue alignment. Despite significant issue-wise divergences, positions of both the X population and the nationally representative sample present a similar bi-dimensional structure along two dominant bundles of aligned issues: a Left-Right divide, and a Global-Local divide. We then study how our results vary when accounting for key structural parameters of the online public sphere: activity, popularity, and visibility. We find that the dimensionality of attitude distributions shrinks as ideological polarization increases when selecting more active users. The divergence between political attitudes on social media and in survey data is greatly mediated by the combination of activity and popularity of social media users: users benefiting from the most exposure are also the most representative of the general public. Together, our results shed light on the structural similarities and differences between political attitudes from social media users and the general public
TRAKNN: Efficient Trajectory Aware Spatiotemporal kNN for Rare Meteorological Trajectory Detection
No full textExtreme weather events, such as windstorms and heatwaves, are driven by persistent atmospheric circulation patterns that evolve over several consecutive days. While traditional circulation-based studies often focus on instantaneous atmospheric states, capturing the temporal evolution, or trajectory, of these spatial fields is essential for characterizing rare and potentially impactful atmospheric behavior. However, performing an exhaustive similarity search on multi-decadal, continental-scale gridded datasets presents significant computational and memory challenges. In this paper, we propose TRAKNN (TRajectory Aware KNN), a fully unsupervised and data-agnostic framework for detecting geometrically rare short trajectories in spatio-temporal data with an exact kNN approach. TRAKNN leverages a recurrence-based algorithm that decouples computational complexity from trajectory length and efficient batch operations, maximizing computational intensity. These optimizations enable exhaustive analysis on standard workstations, either on CPU or on GPU.We evaluate our approach on 75 years of daily European sea-level pressure data. Our results illustrate that rare trajectories identified by TRAKNN correspond to physically coherent atmospheric anomalies and align with independent extreme-event databases
Impacts of epistasis, recombination, and genome architecture on population recovery following radical habitat change
No full textInternational audienceUnder radical environmental change, populations may need to adapt quickly to avoid substantial declines in abundance and threats to their persistence. The outcome of this race between evolution and demography depends on the genetic architecture of adaptation, which determines how fast evolution can proceed. In particular, adaptation may require coordinated evolution at multiple loci (e.g., cooperating ion transporters for ion uptake), with single-locus changes being deleterious. Such selection on coadapted genes leads to a fitness landscape with a valley, which can in turn favor the evolution of structural variants that link beneficial alleles at different loci. Here, we investigate how epistasis and recombination jointly affect population dynamics under such a fitness valley. We assume that adaptation occurs from standing genetic variation and model the eco-evolutionary dynamics deterministically. We show that recombination has strong impacts on population decline and recovery in this context. Higher recombination rates cause evolutionary trajectories to be pulled toward unfit states, leading to prolonged evolutionary plateaus, during which the population can decline precipitously. In highly detrimental cases where coadapted mutations are located on different chromosomes, chromosomal fusions that are preexisting at low frequency can lead to faster population recovery by allowing the genetic system to escape the attraction to unfit intermediate states. Our results provide insights into eco-evolutionary dynamics in systems where chromosome number varies drastically among sibling species, such as the copepod Eurytemora affinis species complex, and offer new perspectives on the impacts of genome architecture on population dynamics in stressful environments
Les prescriptions auctoriales comme guide pour l'activation esthétique
No full textInternational audienc