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Floods and Large Wood in Rivers: Exploring Their Dynamic Interactions Through Numerical Modelling and Field Data on the Allier River
No full textInternational audienceFlood events are among the most devastating natural hazards, presenting multi-risks to infrastructure, ecosystems, and communities. Beyond the immediate impact of inundation, the entrainment and transport of large wood (LW) during these events amplify their destructive potential. Mobilized LW can obstruct critical infrastructure such as bridges, leading to increased backwater effects, exacerbating flooding, and causing structural damage. However, LW also plays a vital ecological role, contributing to habitat formation, nutrient cycling, and riverine biodiversity. As such, it cannot simply be removed without ecological consequences. Understanding the dynamics of LW entrainment, transport, and deposition is crucial for balancing flood risk reduction with the preservation of ecosystem functions.This study addresses the challenge of modeling LW dynamics in rivers, with a specific focus on the Allier River in France. For this purpose, the study utilizes the ORSA2D_WT model, an Eulerian-Lagrangian two-way coupled approach, which integrates the two-dimensional Shallow Water Equations (SWE) with the Discrete Element Method (DEM). This hybrid model allows for a representation of entrainment thresholds, transport pathways, and inelastic collisions between LW elements and obstacles such as riverbanks and infrastructure.This research integrates extensive field data, numerical simulations, and experimental findings to enhance predictions of wood mobilization during flood events. Field data collected from the Allier River, France (2020–2024), provides a robust basis for model improvement. This dataset includes Radio Frequency Identification (RFID)-tracked LW positions over multiple years, high-resolution Digital Terrain Models, granulometric sediment analyses and LW characteristics such as size, shape, density and burial conditions.By combining numerical simulations with extensive field data, this study aims to refine the model’s ability to predict LW mobilization and transport across different flood scenarios, from moderate flows to extreme flood events. Furthermore, the study seeks to enhance the understanding of how environmental factors, such as LW properties and sediment dynamics, influence LW behavior during floods. The outcomes of this research will contribute to the development of a more accurate and reliable hydrodynamic model coupled with a LW transport model, offering insights into how the dynamics of LW affect riverine systems during flood events
Une contribution à la connaissance des professionnel·les de l’APA et des dynamiques du secteur
No full textInternational audienceLes politiques publiques de santé, depuis 2001, ont largement façonné l’organisation de l’APA. Celle-ci est également traversée de logiques marchandes complexes (Belorgey, 2010 ; Collinet, Delalandre, 2016) ; au point que cette activité peut être appréhendée comme un quasi-marché (Nyssens, 2015). Cette configuration se traduit notamment par une séparation entre le financement et la régulation menés par l’État d’une part, et d’autre part, la prestation des services assurée par d’autres acteurs publics et privés - à but lucratif ou non (Prescapp, 2023). Les enjeux de définition et de délimitation de l’AP à des fins de santé (dont l’APA), de formation, de qualification et de légitimation des professionnel·les (Perrin, 2016) témoignent de la difficulté à saisir cette sphère d’activité (Brier, 2021). Alors que le référentiel professionnel des enseignants en APA (Barbin et al., 2016), issue d’une enquête sociologique, considère uniquement les secteurs sanitaire, médico-social et social, nous avons fait le choix, dans une enquête mixte menée en France entière, d’intégrer également le secteur sportif (Handisport, Sport adapté, fédérations sportives et affinitaires), et de considérer la diversité des professionnel·les susceptibles de s’identifier au secteur de l’APA, incluant formé·es en STAPS et ailleurs.Les résultats présentés sont principalement issus du traitement des réponses à un questionnaire auto-administré à destination des professionnel·les de l’activité physique à des fins de santé [N=930 questionnaires complétés] diffusé entre juin et décembre 2024, complétés par des éléments d’analyse d’entretiens (enquête en cours) conduits avec des professionnel·les de l’APA. Après avoir présenté les modes de diffusion du questionnaire, nous souhaitons soumettre à la discussion la représentation de la structure de l’espace des professionnel·les issue de ce travail, et les premiers résultats quant aux effets, sur les conditions d’emploi et les pratiques des professionnel·les de l’APA, de leur inscription dans des domaines d’activité distincts. Si les résultats font apparaître un espace dans lequel les EAPA sont majoritaires, l’acception volontairement élargie de l’APA permet de saisir un centre (bénéficiant certainement du travail de légitimation de la filière universitaire et de certains effets des politiques publiques de santé) sans invisibiliser pour autant d’autres profils professionnels situés en périphérie et dans les segments limitrophes (déclarant par exemple exercer dans le domaine du sport-santé et effectuer quelques heures d’APA) dont les situations illustrent le caractère flou et mouvant du secteur de l’APA en même temps qu’ils participent à la diffusion et la légitimation de ce principe d’intervention
Syntactic study of self-repair and self-reformulation in French and Spanish: Effects of utterance length
No full textInternational audienceIn this article we propose a study of self-repair and self-reformulation based on the analysis of a corpus of nearly 19,000 tokens, fully segmented into utterances. This corpus includes two languages, French and Spanish, which are equally represented, and five different communicative contexts (sociolinguistic interview, public interview, work meeting, meeting between friends and service interaction) for each of these two languages. This corpus architecture, as well as the segmentation of the entire corpus into utterances, allows us to point out some general trends, not previously described, regarding the effect of unit length on self-repair. Indeed, the average length in tokens of the utterance not only predicts the proportion of units with at least one self-repair, but also models the site of initiation of self-repair and type: if less than 10 % of utterances with 5 tokens or less have self-repair, almost 40 % of utterances with between 11 and 20 tokens have self-repair, and about 70 % of utterances with more than 31 tokens have self-repair. Moreover, in utterances with 5 tokens or less, self-repair is most likely to be without reformulation and to occur in a unit without a predicate, whereas in utterances with more than 11 tokens self-repair is likely to be with or without reformulation and to be initiated after the predicate, towards the middle of the unit
A la poursuite de radiotočka: Une enquête ethnoradiophonique en six épisodes par Olivier Givre et Raphaël Cordray
No full text"Un ethnologue français part en Bulgarie sur la piste d'une radio communiste disparue..."A partir de 1947, la Bulgarie s’équipe massivement en matériel de diffusion radiophonique, sous l’influence de l’Union Soviétique : apparait alors un récepteur câblé monocanal, appelé radiotočka (радиоточка). Présent dans les maisons privées, l’espace public et différents bâtiments institutionnels, ce “point radio” diffusait les émissions nationales et des programmes locaux, entre information et propagande.Que reste-t-il de radiotočka ? Quelle était sa portée auprès des gens ? De quoi est faite la mémoire sonore du communisme en Bulgarie ? Quelles en sont les voix, les musiques, les ambiances, les textures ? Entre réalité et fiction, documentaire et imaginaire, recherche et création, cette série embarque l’auditeur dans une enquête ethnographique aussi originale que surprenante.Olivier Givre : recherche – prise de son – écriture – traduction – voix.Raphaël Cordray : réalisation – prise de son – montage – mixage – musique – voix."Un ethnologue français part en Bulgarie sur la piste d'une radio communiste disparue..."A partir de 1947, la Bulgarie s’équipe massivement en matériel de diffusion radiophonique, sous l’influence de l’Union Soviétique : apparait alors un récepteur câblé monocanal, appelé radiotočka (радиоточка). Présent dans les maisons privées, l’espace public et différents bâtiments institutionnels, ce “point radio” diffusait les émissions nationales et des programmes locaux, entre information et propagande.Que reste-t-il de radiotočka ? Quelle était sa portée auprès des gens ? De quoi est faite la mémoire sonore du communisme en Bulgarie ? Quelles en sont les voix, les musiques, les ambiances, les textures ? Entre réalité et fiction, documentaire et imaginaire, recherche et création, cette série embarque l’auditeur dans une enquête ethnographique aussi originale que surprenante.Olivier Givre : recherche – prise de son – écriture – traduction – voix.Raphaël Cordray : réalisation – prise de son – montage – mixage – musique – voix
Compétences sociolinguistiques des grands modèles de langage: représentations sociales et considérations épistémologiques
No full textInternational audienceLes sciences humaines et sociales (SHS) reconnaissent que toute production de savoir est socialement située. La rigueur épistémologique exige donc l’explicitation des points de vue, des valeurs et des implicites sous-jacents aux discours analysés ou produits. Dès lors que les modèles de langage (LLM) sont mobilisés en SHS, leurs productions doivent être traitées comme des discours porteurs de représentations sociales. Cette présentation explore cette hypothèse en évaluant les compétences sociolinguistiques de plusieurs LLMs à travers une tâche d’inférence du genre d’auteurs de tweets. Les modèles doivent également justifier leurs réponses, permettant d’interroger non seulement la nature des représentations activées, mais aussi la manière dont elles sont formulées. L’originalité de l’approche tient à la modulation du positionnement social du modèle lui-même, via des prompts qui simulent différents profils sociaux. L’analyse des prédictions et des justifications permet ainsi d’évaluer comment les cadres énonciatifs influencent les discours générés et les implicites qu’ils véhiculent
The juxtamembrane domain of StkP is phosphorylated and influences cell division in Streptococcus pneumoniae
No full textInternational audienceABSTRACT Eukaryotic-like membrane Ser/Thr protein kinases play a pivotal role in different aspects of bacterial physiology. In contrast to the diversity of their extracellular domains, their cytoplasmic catalytic domains are highly conserved. However, the function of a long juxtamembrane domain (JMD), which connects the catalytic domain to the transmembrane helix, remains elusive. In this study, we investigated the function of the JMD of the Ser/Thr protein kinase StkP in the cell division of Streptococcus pneumoniae . We observed that the deletion of the JMD affected the ability of StkP to phosphorylate some of its endogenous substrates, thereby resulting in significant cell morphogenesis defects. Furthermore, multiple threonine residues were identified as being phosphorylated in the JMD. To investigate the functional significance of these phosphorylation sites, we conducted an integrative analysis, combining structural biology, proteomics, and bacterial cell imaging. Our results revealed that the phosphorylation of the JMD did not perturb the phosphorylation of StkP substrates. However, we observed that it modulated the timing of StkP localization to the division septum and the dynamics of cell constriction. We further demonstrated that phosphorylation of the JMD facilitated the recruitment of several cell division proteins, suggesting that it is required to assemble the division machinery at the division septum. In conclusion, this study demonstrates that the function of the JMD of StkP is modulated by phosphorylation and is critical for the cell division of S. pneumoniae . These observations may serve as a model for understanding the regulatory function of other bacterial Ser/Thr protein kinases. IMPORTANCE How bacterial serine/threonine protein kinases are activated remains highly debated. In particular, models rely on the observations made with their eukaryotic counterparts, and only a few studies have investigated the molecular activation mechanism of bacterial serine/threonine protein kinases. This is particularly the case with regard to the juxtamembrane domain (JMD), which is proposed to contribute to kinase activation in numerous eukaryotic kinases. This study demonstrates that the juxtamembrane domain is likely not essential for the activation of the serine/threonine protein kinase StkP of S. pneumoniae . Rather, our findings reveal that it is required for cell division, where its phosphorylation affects the assembly of the division machinery at the division septum. These observations allow us to assign a function to the JMD in StkP-mediated regulation of pneumococcal cell division, thereby providing a new avenue for understanding the contribution of membrane serine/threonine protein kinases in the physiology of other bacteria
A Dual Inhibition-Stimulation Mechanism at the Basis of Phyllotaxis?
No full textInternational audiencePhyllotaxis, the arrangement of plant leaves around stems, demonstrates strikingly regular patterns. For the last decades, researchers have sought to uncover the molecular actors regulating the positioning of organs, called primordia, at the tip of the stem in the shoot apical meristem (SAM). The local accumulation of the phytohormone auxin initiates primordia. A main regulator of auxin distribution is the PIN proteins, which are polar auxin exporters. Numerical simulations modeling auxin transport by PIN polarities were able to produce phyllotactic patterns due to a lateral inhibition mechanism, in which emergent convergences of PIN polarities were thought to drain auxin from primordia surroundings, making it impossible for new organs to initiate nearby. However, recent 3D live quantifications of auxin and PIN polarities challenge the realism of these models. In particular, no convergent sites of PIN polarities are observed. We analyze the quantified PIN distributions and show that the changes of intensity of PIN polarities, which were overlooked so far, constitute the main component of the convergence of PIN polarities. Together with the directions of PIN polarities, they create an evolving pattern which depletes auxin nearby the primordia, but also promotes its accumulation further away. This dual inhibition-stimulation mechanism promotes a new interpretation for phyllotaxis
Spontaneous stochasticity in the Armstrong-Vicol passive scalar
No full textSpontaneous stochasticity refers to the emergence of intrinsic randomness in deterministic systems under singular limits, a phenomenon conjectured to be fundamental in turbulence. Armstrong and Vicol [5] recently constructed a deterministic, divergence-free multiscale vector field arbitrarily close to a weak Euler solution, proving that a passive scalar transported by this field exhibits anomalous dissipation and lacks a selection principle in the vanishing-diffusivity limit. We show that this advection-diffusion PDE also selects a non-Dirac measure in the space of weak solutions in the inviscid limit, thereby exhibiting Eulerian spontaneous stochasticity. We further provide numerical evidence of Lagrangian spontaneous stochasticity, together with a numerical illustration of the Obukhov-Corrsin conjecture for this system. We formulate a general framework for spontaneous stochasticity in arbitrary finite-dimensional systems under arbitrary regularizations, distinguishing two regimes: weak, where different probability measures may arise along subsequences of inviscid limits, and strong, where the limit measure is unique. The advectiondiffusion system of [5] lies in the strong regime. We prove that the set of selected measures is compact and equals the closed convex hull of Dirac measures. Moreover, for any non-Dirac measure supported on the set of nonunique solutions of the inviscid system, there exists a regularization that produces strong spontaneous stochasticity. Finally, we relate this framework to renormalization-group methods à la Feigenbaum and examine how the underlying dynamical system influences the inviscid limit. The discussion is complemented by elementary finite-dimensional examples illustrating a variety of cases
Pushing Vertices to Make Graphs Irregular
No full textInternational audienceIn connection with the so-called 1-2-3 Conjecture, we introduce and study a new problem related to proper labellings. In the regular problem, proper labellings of graphs are designed by assigning strictly positive labels to the edges so that any two adjacent vertices get incident to distinct sums of labels, and the main goal, for a given graph, is to minimise the value of the largest label assigned. In the new problem we introduce, we construct proper labellings through pushing vertices, where pushing a vertex means increasing by the labels assigned to all edges incident to that vertex. We focus on the study of two related metrics of interest, being the total number of times vertices have been pushed, and the maximum number of times a vertex has been pushed, which we aim at minimising, for given graphs. As a contribution, we establish bounds, some of which are tight, on these two parameters, in general and for particular graph classes. We also prove that minimising any of the two parameters is an \textsf{NP}-hard problem. Finally, we also compare our new problem with the original one, and raise directions and questions for further work on the topic