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Contributions to the development and simulations of generic, modular and multiphysics greenhouses dynamic models, evaluated with a whole year study case dataset
No full textAlso known as : A greenhouse dynamic model to assess sustainable solutions Contributions to the development and simulations of generic, modular and multiphysics greenhouses dynamic models, evaluated with a whole year study case datasetInternational audienceNorth-Western Europe heated greenhouses need to address their high fossil energy dependency while they start to face with climate change. In this context, physics-based greenhouses dynamic models can be used for prospective assessments of innovative shapes, equipment, control, etc. A prerequisite for such model-based evaluation is a review of existing implementations, the improvement and development of suitable sub-models in a generic and modular approach that do not require calibration, and the evaluation of a use case global model with a solid experimental dataset. First, this paper details contributions to existing models regarding several aspects: solar gain, boundaries effects, airflows and leakages, heat and mass transfer. The second part is dedicated to the evaluation of an experimental tomato greenhouse global model for an 11-month period. Its assessment is multiphysics: indoor climate, utilities consumptions, yield and Leaf Area Index. The resulting 5 min sampling indoor air climate Root Mean Square Error is 1.3 °C (temperature) and 8.1%RH (relative humidity). The tomato yield Mean Absolute Error is 1.1 kg m-2. Mass balances also quantify the losses and potentials for water and CO2. The global model outputs are compared with literature, and it is demonstrated that assessing the accuracy of models based only on statistical indicators is questionable. This approach is compatible with assessments of prospective solutions, it increases the confidence for scaling results from small to large commercial greenhouses, and it constitutes a base from which simpler and black box models can be derived for other applications such as predictive control
The Big Short ! Comprendre par la fiction les décisions à contre-courant en trading
No full textInternational audienceThis paper uses a fictional detour through cinema to explore organizational behavior in crisis situations. The film The Big Short—an adaptation of Michael Lewis' book The Big Short: Inside the Doomsday Machine—revisits the subprime mortgage crisis that began in 2007. To what extent do this narrative and its protagonists illuminate the conceptual framework of decision-making in management studies? This analysis unfolds in three acts, each offering a distinct perspective on the film: the first act examines the structure of the narrative; the second focuses on the financial ecosystem and the practices of the protagonists; and the third investigates the artifacts employed by the key actors in their organizations to support their roles and intuitions in the decision-making process
Using historical samples to re-construct the predatory diet of carabid beetles through time
No full textInternational audienc
Vorticity-dependent and symmetry-preserving LES models
No full textInternational audienceWithin the Large Eddy Simulation framework, we propose a methodology based on the Lie theory to derive symmetry-preserving turbulence models. We apply this methodology to the incompressible Navier–Stokes equations. These models explicitly depend on both the filtered strain-rate tensor and the filtered vorticity tensor. Particular emphasis is placed on models that additionally ensure stability
"Moi, Arcade Hoang, Interprète chinois du Roi-Soleil" (法国太阳王的中文翻译 - 黄嘉略)
No full textISBN 2-7003-0474-8Danielle ElisseeffMoi, Arcade Hoang, Interprète chinois du Roi-Soleil"L'interprète chinois du Roi Soleil - Arcade Huang" est une autobiographie présentant un pionnier des premiers échanges culturels entre la Chine et la France. Le livre présente principalement la vie de Huang Jialiu, le premier Chinois à s'installer à Paris, et ses contributions à la diffusion de la culture chinoise et chinoise dans les premiers échanges entre la Chine et la France
L’avenir de la ressource en eau face aux changements climatiques dans les Pays de la Loire: Rapport spécial Eau
No full textEn Pays de la Loire, les évolutions climatiques transforment profondément le cycle de l’eau. La hausse des températures, l’augmentation de l’évapotranspiration et la modification du régime des précipitations accentuent les déficits estivaux, fragilisent la recharge des nappes et renforcent les tensions sur les cours d’eau. Dans le même temps, les risques d’inondation et de submersion demeurent, tandis que la qualité de l’eau reste un défi majeur pour les milieux et l’alimentation en eau potable.Ces effets ne s’expriment pas de manière homogène sur le territoire régional. Selon les bassins versants, les caractéristiques géologiques, l’occupation des sols et l’intensité des usages, la disponibilité de la ressource et les marges d’adaptation varient fortement. Derrière une apparente abondance, des déséquilibres structurels s’installent, rendant certains territoires plus exposés aux pénuries, aux conflits d’usages et aux dégradations écologiques. Une question centrale s’impose alors : comment adapter la gestion de l’eau sans aggraver les vulnérabilités existantes ?Ce rapport du GIEC des Pays de la Loire propose une analyse scientifique de l’avenir de la ressource en eau dans la région. Il éclaire les mécanismes à l’oeuvre, documente les vulnérabilités territoriales et identifie les leviers d’action mobilisables. Il rappelle que l’adaptation ne peut se limiter à des réponses ponctuelles, mais qu’elle suppose une transformation durable des pratiques, fondée sur la sobriété, la protection des milieux et une gouvernance capable d’anticiper les évolutions à venir
First evidence of deleterious effect of pesticide mixture on health status in semi-captive grey partridges
No full textInternational audiencePesticides are mainly used in agroecosystems to control pests. Due to their limited specificity, the resulting widespread contamination may cause unintended effects on non-target organisms that use these habitats. While increasing attention is paid to the relationship between single substances and phenotype on non-target species, their combined impacts are still largely unknown. Since interactions between pesticides may also impact organisms' health, studying them as complex mixtures is the more realistic approach. Here, we present the first experimental study testing the relationship between an environmentally relevant pesticide mixture and health biomarkers on a farmland avian non-target model. To do so, we used 40 semi-captive grey partridges (Perdix perdix) fed for five months with conventional grains. Their plant protection product (PPP) load (i.e., the number of PPPs, the total sum of scaled pesticide concentrations and the total toxicity index) in blood and proxies of health status (evaluated using behavioral and physiological features) were monitored at the end of the exposure period. We demonstrated, for the first time, concerning correlations between PPP load indexes and bird healthrelated features (physical activity, flight initiation distance, eye ring redness and acetylcholinesterase activity). Overall, we highlighted the urgent need to consider environmentally-relevant PPP mixture when biomonitoring non-target vertebrates in ecotoxicological studies.</div
Sulfur Isotopes Reveal Spatial Variation in Waterbird Trace Element Contamination from Tropical Estuaries to the Open Ocean
No full textInternational audienceMarine and freshwater pollution is a major environmental concern, yet the spatial extent of estuarine contamination in marine food webs remains poorly understood. In this study, we sampled blood from piscivorous waterbirds (15 species, 316 individuals) along a gradient from estuaries in southeastern Brazil to the nearshore and offshore southwestern Atlantic Ocean to assess trace element concentrations and the influence of habitat and trophic position on the basis of stable isotopes of carbon, nitrogen, and sulfur. All non-essential trace elements (arsenic, cadmium, lead, and mercury) were inversely related to sulfur isotope values (δ34S) and decreased along the estuarine−open ocean gradient. Conversely, most essential elements (chromium, copper, and manganese) were positively correlated with δ34S, suggesting an increase from estuarine to oceanic waters. Non-essential trace elements in estuarine birds were above the benchmarks of toxicity established for bird species, suggesting potential health impairment due to trace element contamination associated with freshwater inputs. In addition, the lower concentrations of essential elements in estuarine birds may suggest interference in metal homeostasis caused by high concentrations of non-essential elements. Assessments combining multiple trace elements and stable isotopes, particularly sulfur, remain rare over large spatial scales. Across this broad environmental gradient, stable sulfur isotopes proved to be efficient markers of bird habitats for assessing spatial patterns in trace element contamination in aquatic food webs
Energetics link long‐term environmental variations to breeding success in a wild penguin population
No full textInternational audienceEnvironmental variability shapes species' population dynamics. Yet, the mechanisms linking environmental changes to individual‐level metrics (e.g. foraging behaviour, body condition) and reproductive outcomes in the wild remain poorly understood. Energetics play a central role in mediating trade‐offs between self‐maintenance and reproduction under fluctuating environmental conditions. As such, it provides a powerful framework for identifying how individual responses to environmental variation scale up to influence population dynamics. Using a unique long‐term monitoring and bio‐logging dataset spanning over 25 years providing continuous measures of diving behaviour, feeding activity and daily energy expenditure, this study investigates how individual responses to environmental variation affect population dynamics. Focusing on Adélie penguins ( Pygoscelis adeliae ) during the energetically demanding chick‐rearing phase, we integrated individual‐level foraging and energetics data with colony‐wide reproductive metrics to elucidate how environmental cues lead to life‐history trade‐offs. Winter sea‐ice conditions exhibited a quadratic relationship with key individual behavioural and energetic parameters. Specifically, increased sea‐ice concentration and delayed ice retreat led to longer foraging trips, reduced time spent diving and poorer body condition. At the population level, while energy expenditure was not associated with changes in reproductive outcome, increased foraging effort (time spent feeding per day) led to enhanced fledging success. Adverse on‐land conditions, such as higher snowfall, had negative impacts on reproductive outcomes. These findings support the central role of energy as a common currency of maintenance and reproduction. By linking individual energetics to demographic performance, our work advances our understanding of how energy allocation strategies in response to environmental stressors shape population dynamics. These insights are crucial for improving predictive models of population trajectories and offer valuable guidance for conservation strategies aimed at mitigating the impacts of global change on ecosystems
Inundation flow velocities generated by tropical cyclones across atoll islands, derived from two centuries of megaclast deposits in French Polynesia
No full textInternational audienceUnderstanding potential flow velocities during high-energy marine inundation events is crucial for coastal risk assessment. However, modelling struggles to simulate wave energy dissipation across atoll island coastlines. Here, we examined coral reefblocks transported by past tropical cyclones to calculate the minimum flow velocities (MFVs) responsible. Fieldwork on 6 atolls in the Tuamotu archipelago (South Pacific) examined 196 reefblocks, some megaclasts exceeding 300 cubic metres in size. These blocks are scattered between the oceanside reef edge and the atoll lagoon over several hundred metres and suggest flow velocities much higher than those modelled in an assumed ‘extreme reference scenario’ (HS = 12 m). Through U/Th dating and by studying archives and historical aerial photos, the cyclones that moved these reefblocks were identified. Inundation flows generated by two recent cyclones (March and April 1983), two historical cyclones (1903 AD and 1906 AD) and one prehistorical cyclone (54–80 AD) were calculated (storms with swells 10–18.5 m in height). Calculations reveal that previous modelling underestimates flow velocities across atoll islands (inhabited areas) for two reasons: the underestimation of extreme swell heights and the unaccounted-for degradation of shoreline rubble ramparts. During a supercyclone (HS > 15 m), flows can exceed 3 m/s at 350 m from the reef edge and are capable of transporting 20-ton coral blocks. Findings have a wider significance to tropical coral reef coastlines beyond these atolls studied, where the presence of reefblocks can allow hindcasting of the characteristics of prehistorical cyclone inundations