HAL Université de Toulouse, et Toulouse INP
Not a member yet
159308 research outputs found
Sort by
COUPURES D'UN GROUPE ABELIEN TOTALEMENT ORDONNE
No full textIn this article, we study the cuts of a totally ordered abelian group Γ. We begin by recalling some results on ordered sets I and on the associated sets IS(I) and FS(I) of initial and final segments of I.For a totally ordered set I we review the notion of an I-structure defined on a module over a ring R, and the definition of the Hahn product of a family of R-modules indexed by I.The set Cv(Γ)of convex subgroups of a totally ordered group Γ is also a totally ordered set, canonically isomorphic to the set of cuts of the subset Pr(Γ)of principal convex subgroups. One of the first results is then to equip the group Γ with an I-structure where I is the set Pr(Γ) endowed with the opposite order.We associate a convex subgroup with every cut of the group Γ, and conversely, we can associate a family of cuts with every convex subgroup of Γ. It is by looking at these subgroups, and the I-structure of Γ that we can obtain a classification of the different types of cuts.</div
Euclid: From Galaxies to Gravitational Waves – Forecasting Stochastic Gravitational Wave Background Anisotropies and Their Cross-Correlation
No full textInternational audienceWe estimate the amplitude and spatial anisotropy in the stochastic gravitational wave background (SGWB) energy density due to compact binary coalescence (CBC) events: binary black holes (BBH), binary neutron stars (BNS), and black hole-neutron star (BHNS) mergers. Our starting point is the Flagship Simulation Galaxy Catalogue developed by the Euclid Consortium. For each galaxy in the Catalogue, we use the simulated mass and starformation to constrain the galaxy's star-formation history, and predict its contribution to the gravitational-wave energy density through CBC mergers. Combining such contributions from all galaxies in the Catalogue results in a prediction for the frequency spectrum and spatial anisotropy of the CBC SGWB. We also compare this prediction to semi-analytical models of SGWB generated by compact binaries. We identify a set of effective parameters that capture the key features of these models, and we apply a Bayesian framework to infer these parameters assuming an ideal scenario of cosmic variance-limited search. This represents the first step toward developing a comprehensive framework that will eventually enable the correlation of SGWB anisotropy and \textit{Euclid} galaxy data, potentially allowing us to extract valuable astrophysical information from this new observable
Optimizing eel passage at large hydroelectric facilities: the contribution of multiple eel ramps
No full textInternational audienceIn a context of climate change, hydropower can produce renewable energy with a limited carbon footprint. However, dams and weirs built for this purpose form barriers that are detrimental for ecological connectivity. This can be particularly damaging for migratory fish species such as the European eel (Anguilla Anguilla). European eel is a threatened diadromous fish that needs freshwater habitats to grow before its reproductive migration, and impaired ecological connectivity can affect the amount of available habitats or completely impair the migration. To mitigate the effect of obstacles, eel ramps can be installed but to be effective, such devices must be attractive. This attractiveness depends on the location of the ramps, the configuration and potential management operations of the facility (e.g. discharge repartition in different turbines) and, more generally, on the hydrodynamic conditions at different scales. In order to improve the passage of eels upstream of a large hydroelectric dam on the Dordogne River (France), one permanent ramp was added in 2010 and two additional ramps have been installed over a three-years period. A mark-recapture experiment was carried out: some eels were captured after climbing the ramps, marked with PIT-tags, and released downstream. The marked individuals could then be detected at each ramp during their second passage by antenna. With these data, we developed a hierarchical, mechanistic Bayesian model. The aims were 1) to disentangle the different drivers involved, i.e. the decision to migrate as a function of environmental conditions and the attractiveness of ramps as a function of dam management, and 2) to find out whether 3 ramps were more effective (number of succeeding individuals, delays) than a single one. This study provides recommendations on the location and number of ramps to be installed at large hydroelectric facilities to maximise the passage of eels in a minimum time
The Mediator complex subunit Med19 extends healthy lifespan in Drosophila by preventing cellular and organismal frailty
No full textAging involves a progressive decline in physiological functions, often marked by the onset of a “frailty point” just before survival rates decrease rapidly. Here, we investigate how the Mediator subunit Med19 modulates this transition in Drosophila . We find that upregulating Med19 extends the median lifespan by nearly 90% and postpones the onset of accelerated mortality, suggesting that Med19 helps preserve the resilience phase of aging. In contrast, Med19 downregulation sharply reduces both median and maximum lifespan, advancing the frailty threshold. We show that Med19 knockdown increases fly vulnerability to environmental insults such as oxidative and genotoxic challenges whereas Med19 upregulation helps them resist these stresses, underscoring Med19’s protective role in maintaining genomic integrity. We link these phenotypes to altered stress-response pathways at the cellular level: Med19-depleted cells show a compensatory upregulation of genes involved in iron–sulfur cluster biogenesis, glutathione metabolism, and DNA damage repair. At the cellular level, Med19 depletion triggers a “loser” phenotype in cell competition assays, activating the JNK pathway and undergoing apoptosis, highlighting a form of “cellular frailty” that parallels organismal frailty. Finally, we found that the Med19 protein level naturally decreases with age and showed that restoring Med19 expression in aged flies increases fitness and delays the onset of frailty even in older, “frail” individuals, underscoring its significance as an aging regulator. Altogether, our findings establish Med19 as a crucial mediator of lifespan and stress resilience, suggesting it acts as a rheostat that modulates the transition from healthy aging to frailty in Drosophila . GRAPHICAL ABSTRACT Highlights - At the organismal level, Med19 upregulation extends Drosophila lifespan by 90%, delays the onset of frailty and enhances oxidative and DNA damage stress resistance, while its depletion has the opposite effect. - Med19 depletion alters the expression of stress response genes and induces a loser-cell phenotype in cell competition assays revealing its crucial function in controlling cellular fitness. - Med19 protein levels naturally decline with age, and its restoration in aged flies improves both healthspan and lifespan
ANNUAL FRENCH WORKSHOP ON WELL-BEING IN ASTROPHYSICS : CREATING A POSITIVE AND INCLUSIVE WORK ENVIRONMENT
No full textInternational audienceDiversity is very important within an organisation because it fosters creativity and innovation, but it can occasionally lead to difficulties in understanding others, bias towards colleagues or even discrimination. Here we provide a summary of the ideas discussed during the 2025 French Well-being in Astrophysics workshop held at the French National astronomy meeting, which can help promote a positive and inclusive working environment, regardless of age, experience, origin, religion, gender, sexual orientation or disability. These included better understanding colleagues and current problems through a national survey, methods and feedback from mentoring programmes and ideas for preventing conflict
The Djourdé-Sinassi magmatic-migmatitic complex, Northern Cameroon: a record of vertical extrusion of the Pan-African partially molten orogenic root
No full textInternational audienceThe Djourdé-Sinassi magmatic-migmatitic complex is part of the juvenile Neoproterozoic Garoua Domain located in Northern Cameroon. It is surrounded by the Zalbi, Poli and Rey-Bouba greenstone belts, limited to the east by the sinistral Tcholliré-Banyo Shear zone and to the south by the Poli Thrust System. The Djourdé-Sinassi magmatic-migmatitic complex is subdivided into a western magmatic domain made of diorite, tonalite, granodiorite, with numerous enclaves of mafic and ultramafic rocks, and an eastern domain dominated by metatexite migmatites enclosing ubiquitous mafic to ultramafic rafts. The plutonic rocks of the western domain display a gently dipping to vertical magmatic fabric with variable trends. Locally, trains of hornblendite enclaves with lobate boundaries and dismembered into a network of felsic veins points to injection of mafic magma that mingled with a host magmatic mush and/or partially molten rocks. The migmatites display a foliation delineated by the alternation of leucosome and mesosome layers, that are mainly subvertical and wrapped around the metric to kilometric size rafts of mafic and ultramafic rocks. A texturally continuous network of leucosome veins concordant to discordant relative to the syn-migmatitic foliation and the mineral assemblage attests for syntectonic melt segregation under granulite facies conditions (Hbl + Pl ± Bt ± Grt±Opx±Cpx ; peak: ≥800 °C/8–10 kbar). The magmatic fabric of plutonic rocks and the syn-migmatitic foliation are locally transposed into subvertical shear zones with a steeply plunging mineral and stretching lineation. Kinematic criteria are identified in the subhorizontal plane perpendicular to the lineation, which indicates that deformation was not plane strain and occurred in 3D. N-S to NE-SW striking shear zones are sinistral whereas E-W to WNW-ESE trending ones are dextral. These shear zones first developed in the presence of melt but then under solid-state during progressive retrogression from amphibolite to greenschist facies (Ab+Qtz + Ep ± Op ± Chl+Ser+Ep). These data suggest that the Djourdé-Sinassi magmatic-migmatitic complex corresponds to the former root of the Central African Orogenic Belt originating from partial melting of a juvenile mafic crust. This root has been vertically extruded under a pure-shear dominated constrictional regime with vertical stretching in the presence of melt coeval with the injection of mantle-derived mafic magmas and was then progressively exhumed towards the surface. This deformation pattern is consistent with the position of the Sinassi complex surrounded by greenstone belts and on a larger scale, confined in between the West African − Congo cratons and Saharan metacraton.Le complexe magmatique-migmatitique de Djourdé-Sinassi fait partie du domaine Néoproterozoïque juvénile de Garoua, situé dans le Nord du Cameroun, entouré par les ceintures de roches vertes de Zalbi, Poli et Rey-Bouba, limité à l’est par la zone de cisaillement senestre de Tcholliré-Banyo et au sud par le système de faille de Poli. Le complexe magmatique-migmatitique de Djourdé-Sinassi est subdivisé en un domaine magmatique à l’ouest composée de diorite, tonalite, granodiorite et granite avec de nombreuses enclaves de roches mafiques et ultramafiques, et une partie à l’est dominée par des migmatites métatexitiques contenant des enclaves mafiques à ultramafiques omniprésentes. Les roches plutoniques à l’est présentent une fabrique magmatique légèrement pentée à verticale à orientation variable. Localement, des trains d’enclaves de hornblendite aux contours lobés et disloqués par un réseau de veines felsiques indiquent l’injection de magma mafique qui s’est mélangé avec une masse magmatique hôte et/ou des roches partiellement fondues. Les migmatites affichent une foliation définie par l’alternance de niveaux de leucosome et de mésosome, principalement subverticale suivant une direction parallèle à l’alignement des enclaves de roches mafiques et ultramafiques de taille métrique à kilométrique. Un réseau continu de veines de leucosome, concordant et discordant par rapport à la foliation syn-migmatitique, atteste d’une ségrégation syntectonique du magma sous des conditions de faciès granulite (pic : ≥800 °C/8–10 kbar). La texture magmatique des roches plutoniques et la foliation syn-migmatitique sont localement transposées en zones de cisaillement subverticales avec une linéation minérale et d’étirement à plongement fort. Des critères cinématiques sont identifiés dans le plan subhorizontal perpendiculaire à la linéation, ce qui indique que la déformation n’était pas plane et s’est produite en 3D. Les zones de cisaillement orientées N-S à NE-SW affichent des critères cinématiques senestres, tandis que celles orientées E-W à WNW-ESE sont dextres. Ces zones de cisaillement se sont d’abord développées en présence de magma, puis à l’état solide lors de la rétrogression progressive du faciès amphibolite au faciès schiste vert (Ab+Qtz + Ep ± Op ± Chl+Ser+Ep). Ces données suggèrent que le complexe magmatique-migmatitique de Djourdé-Sinassi représente un témoin de la racine de la Ceinture Orogénique d’Afrique Centrale, issue de la fusion partielle d’une croûte mafique juvénile. Cette racine a ensuite été extrudée verticalement sous un régime dominé par le cisaillement pur avec un étirement vertical en présence de magma, coïncidant avec l’injection de magmas mafiques dérivés du manteau, et a été progressivement exhumée vers la surface. Ce schéma de déformation est cohérent avec la position du complexe de Sinassi, entouré de ceintures de roches vertes et, à une échelle plus large, confiné entre les cratons Ouest-Africain − Congo et le métacraton du Sahara
Modelling the ion behaviour in polyethylene containing by-products and submitted to high DC field stress
No full textInternational audienceHigh voltage direct current links increasingly use polyethylene (PE) based materials as insulation, due to their outstanding electrical and thermal properties. However, it is known for long that ions, present in the crosslinked PE material, play a major role in the space charge behaviour, and hence in the ageing of the material. Crosslinking by-products seem to be related to the activity of ionic processes. However, it is a real challenge to identify the kind of ions and to determine its amount. In this context, simulation tools related to charge transport are of interest to apprehend the impact of the presence of ions, their transport and accumulation, on the overall macroscopic behaviour. The goal of the present paper is to propose a new model related to ion generation and transport, either accounting for dissociation of molecules or to their ionization. The simulations results, consisting in space charge density profiles and currents, are compared to experimental observations available in the literature to conclude on the possible mechanism of ion generation in PE materials containing by-products
Thermal Hall conductivity in the strongest cuprate superconductor: Estimate of the mean free path in the trilayer cuprate HgBa 2 Ca 2 Cu 3 O 8 + δ
No full textInternational audienceThe thermal Hall conductivity of the trilayer cuprate HgBaCaCuO (Hg1223) - the superconductor with the highest critical temperature at ambient pressure - was measured at temperatures down to 2 K for three dopings in the underdoped regime ( = 0.09, 0.10, 0.11). By combining a previously introduced simple model and prior theoretical results, we derive a formula for the inverse mean free path, , which allows us to estimate the mean free path of -wave quasiparticles in Hg1223 below . We find that grows as , in agreement with the theoretical expectation for a clean -wave superconductor. Measurements were also conducted on the single layer mercury-based cuprate HgBaCuO (Hg1201), revealing that the mean free path in this compound is roughly half that of its three-layered counterpart at the same doping ( = 0.10). This observation is be attributed to the protective role of the outer planes in Hg1223, which results in a more pristine inner plane. We also report data in an ultraclean crystal of YBaCuO (YBCO) with full oxygen content = 0.18, believed to be the cleanest of any cuprate, and find that is not longer than in Hg1223
Evaluation des émissions de gaz à effet de serre (CO2 et CH4) par le barrage subtropical Nam Theun 2
No full textHydroelectric reservoirs are categorized as a renewable energy production but emit significant GHGs, especially in tropical regions. It raises a need of understanding the biogeochemical cycles underlying the greenhouse gas production and emissions. Therefore, the goals of the thesis are to quantifying the long term GHG emissions from a subtropical reservoir, to assess the dynamics (seasonality, spatial-temporal variabilities) of GHG emissions, and contribute to the development of water quality modelling approach to quantify GHG emissions. This thesis presented a 14-year (2009-2022) assessment of water quality and GHG (CH4 and CO2) emissions, one of the longest continuous high frequency monitoring datasets, from the NT2 reservoir (Lao PDR), combining discrete sampling, high-frequency bubbling trap and EC measurements (included a comparison between quantifying methodology), and modelling attempts. Emission pathways (diffusion, degassing, and ebullition) were quantified using a multi-method approach. Spatial, seasonal, and long-term trends were evaluated. A comparison between EC-derived fluxes and fluxes calculated from discrete sampling revealed that each method has advantages and limitations: EC provided continuous, high-frequency measurements, while discrete sampling offered broader spatial coverage and was more cost-effective. This thesis quantified GHG emissions based on water measurements due to the availability and consistency of the dataset, but highlighted the importance of using complementary techniques to better capture spatial and temporal variability, particularly diurnal patterns. Total emissions reached 10736 Gg CO2eq, with CH4 and CO2 contributing 51% and 49%, respectively. Emissions peaked in 2010 (1276 Gg CO2eq) and declined 70% by 2021 due to reservoir aging and reduced organic matter. Seasonal shares were WD (35.5%), CD (35.8%), and WW (28.7%). CH4 peaked in WD seasons via enhanced ebullition under stratified, anoxic conditions, while CO2 peaked during CD seasons, associated with overturn. Ebullition dominated CH4 (77%) and remained stable; diffusive CH4 dropped 97%. CO2 was mainly diffusive (96%) and declined 87% over time. Especially, the long-term bubbling remained as significant sources of total emissions, suggesting the sustainability of soil organic matter pool. A DELFT3D-based modelling framework was developed for the study period. The FLOW module, driven by ERA5 meteorology and in-situ data, accurately simulated water levels and temperature profiles with <1 °C absolute average error at key stations (RES1, RES4) and correct simulation of the seasonality of the reservoir water column. Comprehensive set of sensitivity tests identified Ozmidov length, Secchi depth, and Dalton and Stanton numbers as key drivers of stratification and heat exchange model.[...]Les réservoirs hydroélectriques sont considérés comme des sources d'énergie renouvelable, mais peuvent émettre des quantités importantes de GES, surtout dans les régions tropicales. Cela soulève la nécessité d'une meilleure compréhension des cycles biogéochimiques contrôlant la production et l'émission de ces gaz. Cette thèse a pour objectifs de quantifier les émissions de GES à long terme d'un réservoir subtropical, d'analyser leur dynamique saisonnière et spatio-temporelle, et de contribuer au développement de la modélisation de la qualité de l'eau pour estimer ces émissions de manière plus précise. L'étude repose sur 14 années de données continues (2009-2022) issues du réservoir NT2, et combine différentes méthodes de mesure : échantillonnage discret classique, pièges à bulles à haute fréquence, et mesures par EC. La comparaison entre les flux mesurés par EC et ceux dérivés des échantillons discrets a montré que chaque approche présente des avantages méthodologiques spécifiques : EC permet une couverture temporelle fine, notamment sur les cycles diurnes, tandis que les échantillons discrets assurent une bonne couverture spatiale avec un coût opérationnel réduit. Le calcul final des émissions a été réalisé à partir des mesures de l'eau, en raison de leur représentativité à long terme, mais l'importance d'utiliser des approches complémentaires est clairement mise en avant. Les émissions cumulées atteignent 10736 Gg CO2eq, réparties entre CH4 (51 %) et CO2 (49 %). Le pic des émissions a été observé en 2010 (1276 Gg CO2eq), suivi d'une décroissance progressive de 70 % jusqu'en 2021. Cette diminution est attribuée au vieillissement du réservoir et à la réduction des apports de matière organique labile. Les parts saisonnières se répartissent en saison WD (35,5 %), CD (35,8%) et WW (28,7 %). CH4 atteint un maximum en saison WD, en lien avec une ébullition favorisée par une stratification thermique stable et des conditions anoxiques accrues, tandis que CO2 culmine en saison CD lors du brassage vertical de la colonne d'eau, révélant l'importance de la minéralisation microbienne. L'ébullition représente 77 % des émissions de CH4 et reste relativement constante dans le temps ; en revanche, les flux diffusifs chutent de 97%. CO2, majoritairement diffusif (96 %), diminue de 87 % sur la période étudiée. La persistance des émissions par ébullition suggère la durabilité d'un stock actif de matière organique dans les sédiments. Un cadre de modélisation fondé sur la suite DELFT3D a été mis en place pour simuler l'évolution hydrothermique du réservoir. Le module FLOW a reproduit fidèlement les variations du niveau d'eau et les profils de température, avec une erreur absolue moyenne < 1°C aux stations RES1 et RES4. Des tests de sensibilité approfondis ont identifié plusieurs paramètres physiques critiques pour la dynamique de stratification.[...
