Portail "HAL-Francophonie Afrique et Océan Indien"
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De la mesure a la construction de carte de qualité de l'air par la modélisation a base d'agents: l'exemple de Cotonou
No full textInternational audiencePollution is a major global public health issue. According to WHO estimates, more than 8 million premature deaths are attributable to air pollution, representing 10% of all deaths worldwide. However, there are significant spatial disparities. By 2030, Africa could account for half of global emissions of gaseous and particulate pollutants. Furthermore, there are very few devices for monitoring air quality on this continent, leaving public authorities blind to the health risks associated with air pollution. Using a network of microsensors deployed across the city of Cotonou, this project aims to produce dynamic maps of fine particulate pollution in the city. By combining these maps with a multi-agent model, the objective is also to simulate the exposure to pollution of children traveling to school. Although the model designed requires improvements in terms of the validity of the data produced, it demonstrates its potential to provide advice on urban planning and public health.La pollution est un problème majeur de santé publique au niveau mondial. D'après une estimation de l'OMS, plus de 8 millions de décès prématurés seraient attribuables à la pollution de l'air, soit 10% de l'ensemble des décès mondiaux. Les disparités spatiales sont cependant importantes. A l'horizon 2030, l'Afrique pourrait être à l'origine de la moitié des émissions mondiales des polluants gazeux et particulaires. De plus, très peu de dispositifs permettent de surveiller la qualité de l'air sur ce continent, rendant ainsi les pouvoirs publics aveugles sur les risques sanitaires liés à la pollution de l'air. En s'appuyant sur un réseau de micro-capteurs déployé sur la ville de Cotonou, ce travail vise à produire des cartes dynamiques de la pollution aux particules fines dans la ville. En couplant ces cartes à un modèle multi-agent, l'objectif est également de simuler l'exposition à la pollution d'enfants se rendant à l'école. Le modèle conçu, bien que nécessitant des améliorations sur la validité des données produites, montre un aperçu de sa capacité à conseiller en termes d'aménagement urbain et de santé publique
Short alternating light/dark periods priming improves tobacco (Nicotiana tabacum L.) tolerance to clomazone herbicide: growth, chlorophyll a fluorescence transient and photosynthesis rate
No full textInternational audienceNicotiana tabacum L. cv. Virginie vk51 seedlings at the three-leaf stage were grown in a hydroponic culture system. Those seedlings were subjected to a photoperiod priming treatment with alternating light/dark periods (AL) (16 min light/8 min dark cycles and a photosynthetic photon flux density (PPFD) of 50 μmol photons m−2 s−1) for 3 days. After 2 weeks, the plantlets were transferred to two soil types with 0 (control) or 100 µM clomazone. Compared with the non-primed plants, the AL-primed plants exhibited greater clomazone tolerance with respect to all of the growth parameters and during all of the growth stages. This AL priming effect was demonstrated by increases in plant leaf area and dry and fresh plant weights, which might have been related to increases in the CO2 assimilation rate (Pn and Pmax). Furthermore, the reduced photon absorption (ABS/RC) and heat dissipation (DI0/RC) rates as well as the observed increase in photosystem II (PSII) efficiency (the maximum quantum yield of PSII (Fv/Fm), photochemical quenching (qP), actual PSII efficiency (ФPSII)) and electron transport (the light-saturated electron transport rate (ETR) and electron flux beyond the first quinone electron acceptor of PSII (QA) evaluated as (1–VJ)) provide strong evidence of a higher tolerance to clomazone. Collectively, these results suggest that AL priming treatment could potentially improve the protection or production of other transplanted species
Improvement and Stabilization of Output Voltages in a Vertical Tidal Turbine Using Intelligent Control Strategies
No full textInternational audienceThis article investigates on the improvement and stabilization of alternating current (AC) and direct current (DC) output voltages in a Permanent Magnet Synchronous Generator (PMSG) driven by a vertical-axis tidal turbine using advanced control strategies. The research integrates artificial intelligence (AI)-based techniques to enhance voltage stability and efficiency. Initially, the Maximum Power Point Tracking (MPPT) approach based on Tip Speed Ratio (TSR) and Artificial Neural Network (ANN) Fuzzy logic controllers is explored. To further optimize the performance, Particle Swarm Optimization (PSO) and a hybrid ANN-PSO methodology are implemented. These strategies aim to refine the reference rotational speed of the turbine while minimizing deviations from optimal power extraction conditions. The simulation results of a tidal turbine operating at a water flow velocity of 1.5 m/s demonstrate that the PSO-based control approach significantly enhances the voltage stability compared to conventional MPPT-TSR and ANN-Fuzzy controllers. The hybrid ANN-PSO technique improves the voltage regulation by dynamically adapting to system variations and providing real-time reference speed adjustments. This research highlights the AI-based hybrid optimization benefit to stabilize the output voltage of tidal energy systems, thereby increasing reliability and efficiency in renewable energy applications
Kinematics of mountain-building of the Central Andes, from structural geology to analogue modeling
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The Combination of Motor Imagery and Breathing Optimizes the Performance of the Serve in Skilled Tennis Players
No full textInternational audienceBackground: Tennis players frequently use motor imagery (MI) to improve serve accuracy and efficiency. Moreover, breathing, such as forced expiration, can improve serving speed. Hypothesis: A combination of MI before action and breathing during movement would increase serve performance in skilled tennis players. Study Design: Nonrandomized, repeated-measures design. Level of Evidence: Level 3. Methods: A total of 20 tennis players (mean age, 24.2 years; SD = 5.9), with between 9 and 18 years of regular practice, completed 4 experimental counterbalanced sessions: Control (no instruction), Breathing (inhalation while throwing the ball and forced expiration while hitting), Imagery (external visual mental simulation before serving), and Imagery + Breathing (combination of both). Each session included the completion of 10 first-serves in an actual match condition. The speed, percentage of success, accuracy, and efficiency scores served as performance indicators and dependent variables. Results: Compared with the Control condition, Imagery significantly improved accuracy and percentage of success, and Breathing increased speed of the serves. Participants had significantly better performances in the Imagery + Breathing condition than in the Control condition; better serving speed than in the Imagery condition; and higher accuracy, efficiency, and percentage of success than in the Breathing condition. Conclusion: The combination of MI plus breathing resulted in an overall improvement in serve performance. Clinical Relevance: Tennis coaches and practitioners should integrate MI interventions and breathing practice during training and matches
Euclid Quick Data Release (Q1). Quenching precedes bulge formation in dense environments but follows it in the field
No full textInternational audience(Abridged) The bimodality between star-forming discs and quiescent spheroids requires the existence of two main processes: the galaxy quenching and the morphological transformation. In this paper, we aim to understand the link between these processes and their relation with the stellar mass of galaxies and their local environment. Taking advantage of the first data released by the Euclid Collaboration, covering more than 60 deg2 with space-based imaging and photometry, we analyse a mass-complete sample of nearly one million galaxies in the range 0.2510^{9.5} M_\odot$. We divide the sample into four sub-populations of galaxies, based on their star-formation activity and morphology. We then analyse the physical properties of these populations and their relative abundances in the stellar mass vs. local density plane. Together with confirming the passivity-density relation and the morphology-density relation, we find that quiescent discy galaxies are more abundant in the low-mass regime of high-density environment. At the same time, star-forming bulge-dominated galaxies are more common in field regions, preferentially at high masses. Building on these results and interpreting them through comparison with simulations, we propose a scenario where the evolution of galaxies in the field significantly differs from that in higher-density environments. The morphological transformation in the majority of field galaxies takes place before the onset of quenching and is mainly driven by secular processes taking place within the main sequence, leading to the formation of star-forming bulge-dominated galaxies as intermediate-stage galaxies. Conversely, quenching of star formation precedes morphological transformation for most galaxies in higher-density environments. This causes the formation of quiescent disc-dominated galaxies before their transition into bulge-dominated ones
Advanced Analytical Approach for Characterizing Uranium-Organic Matter Interactions
No full textInternational audienceUranium plays a major role in both natural and anthropogenic environments, where its speciation influences its mobility and ecological impact. Natural organic matter (NOM) is ubiquitous in natural aqueous systems, and forms highly mobile nanoscale colloids that are able to increase the transport of pollutants. Thus, understanding the interactions between uranyl ions (UO22+) and NOM nano-colloids is essential for predicting its behavior in natural subsurface systems.In order to explore uranium speciation in presence of NOM colloids in a soil interstitial water, we employed an advanced analytical approach to examine quantitatively the distribution of uranium between the dissolved and colloidal phases in the presence of NOM.Asymmetric flow field-flow fractionation (AF4) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was used to characterize the size distribution of the colloidal fractions and qualify uranium association within each fraction. An insight in the calibration procedure of AF4/ICP-MS coupling allows determining the quantitative distribution of U(VI) along the colloidal size continuum.This procedure is applied to determine uranium speciation in a suspension of in-field sampled NOM colloids through experimental isotherms. We show that uranium distributes equally between the dissolved and the colloidal phases, with the balance influenced by soil lixiviation conditions. However, this distribution remains principally related to the NOM compounds and relatively stable across the dissolved uranium concentration range considered (1 μg/L – 1 mg/L).Additionally, ultra-high-resolution mass spectrometry (Orbitrap) was used to determine the detailed composition of NOM and identify the families of organic compounds likely involved in uranium complexation. Orbitrap analysis reveals that uranyl interacts with a wide range of organic compounds but shows a particular affinity for a specific sub-fraction of NOM.These results will be used to feed a modeling approach of U(VI)-NOM interactions by integrating experimental data with thermodynamic simulations. Complexation constants for U(VI)- NOM association in both colloidal and dissolved fractions are evaluated from experimental isotherms, helping to predict their impact on uranium mobility in natural environments
Safety in the shallows: nearshore coastal habitats can provide physical and thermal features that optimize escape performance in newborn blacktip reef sharks ( Carcharhinus melanopterus )
No full textInternational audienceThe prevailing shark nursery paradigm suggests that high survival in these habitats is primarily driven by reduced predator encounters: so-called pre-encounter risk. In this study, we propose an alternative or complementary mechanism: that some nurseries may lower post-encounter risk by providing environmental conditions that maximize escape performance. To test this hypothesis, we examined how temperature, depth and habitat complexity influence the escape performance of newborn blacktip reef sharks (Carcharhinus melanopterus) in Mo′orea, French Polynesia. In a controlled setting, we exposed 48 newborn sharks to four temperature treatments (25, 27, 29 and 31°C) and measured fast-start acceleration, turning rate and latency to respond to a stimulus. We also calculated aerobic scope at 27, 29 and 31°C, as greater aerobic scope is associated with faster recovery from burst swimming. Our results show that warmer temperatures improve escape performance, with 29% higher acceleration, 9% faster turning rates and 48% shorter reaction times at elevated temperatures. Furthermore, aerobic scope remained ≥80% of its maximum capacity between 27.5 and 30.8°C, suggesting that newborn sharks can sustain high metabolic performance within this thermal window. Field measurements at nursery habitats revealed that daily thermal fluctuations generally remained within this optimal aerobic scope range, meaning that newborns can maintain high escape performance for most of the day. Additionally, high-resolution mapping confirmed that previously reported home ranges were associated with shallow (median depth = 0.74 m), structurally complex reef flats dominated by coral substrate. The combination of reduced hydrodynamic drag in shallow water and increased manoeuvrability in complex habitats likely enhances predator evasion. However, extreme warming events that exceed critical thermal limits may trigger behavioural trade-offs that compromise escape performance and elevate predation risk. Our findings suggest that these nurseries provide habitat-specific advantages for predator evasion, reinforcing their critical role in the survival of newborn sharks
Dual role of plasmablasts as immune regulators or amplifiers in COVID-19.
No full textInternational audienceCOVID-19 induces a marked plasmablast (PB) expansion, whose functional role remains unclear. We performed B-cell immunophenotyping and multiplex cytokine analysis in a prospective cohort of 50 COVID-19 patients. PB expansion occurred early and correlated with both maximal disease severity and inflammatory markers. A retrospective cohort of 282 steroid-naïve patients was used to validate PB dynamics, model trajectories, and perform transcriptomic profiling. Two PB trajectories emerged: a transient one and a persistent, amplified one, the latter associated with a sixfold increase in 30-day mortality (p < 0.001). In severe cases, PB upregulated purine metabolism genes; in non-severe cases, they expressed interferon and CIITA-mediated MHC-II programs. BAFF levels at day 7 correlated with severity suggesting a role in sustaining PB expansion. PB exhibit functional duality in COVID-19—acting as immune regulators in non-severe cases and as inflammation amplifiers in severe disease. BAFF emerges as a potential therapeutic target in PB-driven immune dysregulation
Que faire des appartenances religieuses ? Une déclinaison réunionnaise du modèle français d’éducation à la citoyenneté
No full textInternational audienceThe article aims to examine the way in which religious diversity is categorized, problematized and pedagogically treated as part of the current citizenship education curriculum in France, and the way in which its deployment is declined in La Réunion. To achieve this, the sociological analysis is based, on the one hand, on the moral and civic education curricula for school, middle school and high school (2015, 2018) as well as the framing texts relating to the implementation of the citizenship program and, on the other hand, on the results of an empirical inquiry into 78 work situations related to moral and civic education (EMC), secularism and religion in public middle schools and high schools (conducted between 2021 and 2024 among 24 teachers and school life staff). The purpose is to identify the extent to which the implementation of EMC in La Reunion has led to the emergence of a model of citizenship that distances itself from the Jacobin model or could even be described as multiculturalist.L’article propose d’examiner la manière dont la diversité religieuse est catégorisée, problématisée et traitée pédagogiquement dans le cadre de l’actuel curriculum d’éducation à la citoyenneté en France, et la façon dont sa mise en oeuvre est déclinée à La Réunion. Pour ce faire, l’analyse s’appuie d’une part sur les programmes d’enseignement moral et civique de l’école, du collège et du lycée (2015, 2018) ainsi que sur les textes de cadrage relatifs à la mise en oeuvre du parcours citoyen, et d’autre part, sur les résultats d’une enquête empirique réalisée entre 2021 et 2024 auprès de 24 professionnels de l’éducation nationale (professeurs et personnel de la vie scolaire). Ont été recueillies 78 situations de travail rattachées à l’EMC, à la laïcité et au religieux dans des collèges et des lycées publics de La Réunion. L’objectif est d’identifier dans quelle mesure la mise en oeuvre de l’enseignement moral et civique (EMC) à La Réunion fait apparaître un modèle de citoyenneté distant du modèle jacobin, voire multiculturaliste