HAL Université de Toulouse, et Toulouse INP
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Sulfides as environmental stressors in Paracas Bay, Peru
No full textInternational audienceParacas Bay, located in the Humboldt Current system, is a highly variable coastal environment where hypoxia (dissolved oxygen concentrations <2 mg L-1) has been reported as a persistent feature of bottom conditions. In addition to hypoxia, milky water events have been reported in the bay, most likely associated with the presence of sulfides (i.e. sulfidic events), including toxic hydrogen sulfide (H2S). This study is the first report of sulfide concentrations in the water column of Paracas Bay, with concentrations up to 6.79 mu mol L-1 measured in the bottom water layer using Diffusive Gradient in Thin film (DGT) passive samplers. Sulfides showed a marked seasonal pattern, while ENSO phases did not seem to affect their occurrence. The presence of sulfides in the water column is closely linked to hypoxic conditions. Indeed, the analysis of the relationship between the duration of severe bottom hypoxia (dissolved oxygen <= 0.15 mg L-1) and sulfides concentrations revealed a threshold of 18 h for sulfides accumulation in the overlying waters. Also, a gradient in sulfides concentration was observed from the sediment to the upper water layer. This gradient coupled with the variability of environmental variables (temperature, dissolved oxygen and currents velocity) highlights the complexity of this system, and suggests that a combination of advective and local physical and biogeochemical processes are responsible for the sulfidic events to occur in Paracas Bay. This study provides a baseline for assessing the potential toxicity of sulfides to cultured Peruvian scallops in upwelling bays
Optimal Thermal Management Using the Taguchi Method for LED Lighting Squared Heat Sink, Including Statistical Approaches
No full textInternational audienceThe global development of LED lighting in all applications for both public and indoor lighting establishes a very important lever for reducing the carbon impact by significantly reducing energy consumption. Smart lighting will therefore constitute an essential lever in the smart city of tomorrow. The latter is more sustainable and less energy-intensive than other light sources, contributing towards the Sustainable Development Goals set forth by the United Nations (SDGs 7 and 11). With its ease of integration, ergonomics, lightness, and high quality of light, this innovative light source has two major qualities: its energy efficiency and its long service life. However, poor thermal management has catastrophic effects on these two essential criteria. This necessarily requires optimizing thermal management and heat sinks. In some cases, thermal models and simulations can lead to considerable calculation times because they implement many parameters. This work therefore aims to reduce the number of these simulations by applying the method of experimental designs (Taguchi) and analysis of variance (ANOVA) to simulations intended to optimize the dissipation of LED luminaires. We applied the method to a simple finned heat sink model for a unit input power and then to a concrete case of a high-power LED. The control parameters and their respective contributions in the proposed model were studied. The ANOVA results corroborated the conclusions of the Taguchi method, demonstrating a strong agreement between these analytical methods, in which the temperature was adjusted by identifying optimal combinations of parameters. The fields of application relevant to this study include both indoor lighting (false ceiling) and confined spaces with severe sealing constraints such as car headlights or the optical blocks of urban luminaires
A Comprehensive Database of Leaf Temperature, Water, and CO 2 Fluxes in Young Oil Palm Plants Across Diverse Climate Scenarios
No full textData and code availability: The raw data and scripts used to generate the final database are detailed and accessible on Zenodo (Vezy et al., 2025), the code is also accessible via a Github repository (https://github.com/PalmStudio/Biophysics_database_palm), and we also provide a companion website (https://palmstudio.github.io/Biophysics_database_palm) showing how computations were made and the main results. The code to trigger the FLIR camera and for logging the precision scale data is also available on dedicated Zenodo repositories (Vezy, 2025a, 2025b).Functional-structural plant models (FSPM) aim to replicate the intricate ecophysiological and developmental responses of plants to their environment. These models are valuable for projecting plant behaviour in a changing climate but rely heavily on detailed measurements of structural and ecophysiological traits for their parameterization. However, collecting these measurements simultaneously and consistently at multiple scales remains a challenge, often limiting model parameterization and thorough evaluation, and thereby reducing confidence in model predictions. Here, we propose a comprehensive dataset of biophysical measurements from four oil palm plants grown (Elaeis guinnensis) in controlled environments. The dataset includes detailed reconstructions of the three-dimensional plant structures derived from terrestrial LiDAR point clouds and leaf-scale gas exchange measurements for parameterising leaf physiology. We also provide plant-scale gas exchange measurements (CO 2 and H 2 0) and leaf temperature data under multiple controlled environmental scenarios, including varying CO 2 concentrations, light, temperature and humidity conditions. Our aim is to create a digital twin of the four plants to facilitate FSPM robust evaluation, and help identify sources of model uncertainty
A vacuolar invertase gene SlVI modulates sugar metabolism and postharvest fruit quality and stress resistance in tomato
No full textInternational audienceAbstract Sugars act as signaling molecules to modulate various growth processes and enhance plant tolerance to various abiotic and biotic stresses. Moreover, sugars contribute to the postharvest flavor in fleshy fruit crops. To date, the regulation of sugar metabolism and its effect in plant growth, fruit ripening, postharvest quality, and stress resistance remains not fully understood. In this study, we investigated the role of tomato gene encoding a vacuolar invertase, hydrolyzing sucrose to glucose and fructose. SlVI is specifically expressed during the tomato fruit ripening process. We found that overexpression of SlVI resulted in increased leaf size and early flowering, while knockout of SlVI led to increased fruit sucrose content, enhanced fruit firmness, and elevated resistance of postharvest fruit to Botrytis cinerea. Moreover, the content of naringenin and total soluble solids was significantly increased in SlVI knockout fruit at postharvest stage. Transcriptome analysis showed a negative feedback regulation triggered by sucrose accumulation in SlVI knockout fruit resulting in a downregulation of BAM3 and AMY2, which are critical for starch degradation. Moreover, genes associated with cell wall, cutin, wax, and flavonoid biosynthesis and pathogen resistance were upregulated in SlVI knockout fruit. Conversely, the expression levels of genes involved in cell wall degradation were decreased in knockout fruit. These results are consistent with the enhanced postharvest quality and resistance. Our findings not only provide new insights into the relationship between tomato fruit sucrose content and postharvest fruit quality, but also suggest new strategies to enhance fruit quality and extend postharvest shelf life
Découverte fortuite d'outils paléolithiques ancien et néolithique à Ayguesvives en Haute-Garonne
No full textDes découvertes archéologiques significatives ont été réalisées dans la commune d'Ayguesvives mettant en lumière des vestiges de l'époque romaine et du néolithique. Cependant, une découverte plus ancienne a récemment été mise en avant, révélant des outils datant du paléolithique ancien. Neuf outils taillés ainsi qu'une hache polie ont été découverts par Alexandre et Sébastien. Ces artefacts témoignent d'une occupation humaine dans la région il y a environ 450 000 ans. L'authenticité et l'importance de ces objets ont été confirmées par Frédéric Maksud, archéologue responsable du Département de l'Ariège, soulignant ainsi la richesse historique de la commune.Les galets aménagés, également appelés choppers, sont des outils préhistoriques façonnés par percussion. Neuf de ces galets ont été identifiés, chacun présentant un bord tranchant à deux faces. Les dimensions de ces artefacts varient considérablement, allant de 10 cm à 23 cm de longueur, avec une largeur de 5 cm à 15 cm et une épaisseur comprise entre 1,5 cm et 5 cm. Ces outils sont typiques de la culture du galet, qui se caractérisent par l'utilisation comme matière première pour la fabrication d'outils. Les campements associés à cette culture sont souvent situés à proximité de cours d'eau, ce qui suggère une dépendance à l'eau pour les activités quotidiennes. La découverte de ces galets a eu lieu sur le plateau de la Saurine-Beauregard, un site géographique favorable avec un accès à un ruisseau qui était crucial pour les populations préhistoriques.Ces découvertes situées sur cette colline caractérisée par un sommet aplani, situé sur un versant bien exposé au soleil du Midi. Ce site présente un sol léger, composé de terre blanche, et se trouve à proximité d'un petit ruisseau ainsi que d'un point d'eau, désigné par le terme "pesquié". De plus, il est mentionné que cet emplacement n'est pas très éloigné de la Route de Saint Léon. Ces éléments soulignent l'importance</div
Some flocking properties for a model of collective dynamics with topological interactions
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L'impact des spires rapprochées sur la raideur du ressort hélicoïdal
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Mental practice improves pass accuracy in elite rugby players
No full textMental practice has been shown to improve motor performance; however, its effects in elite sports, particularly under constraints, remains underexplored. In this study, we examine the impact of mental practice, preceded by imagined or virtual game scenarios, on pass accuracy in elite rugby players. Seventy-five players from national and regional talent development teams participated in this study. They were divided into three groups: control (CTRL), motor imagery (MI), and virtual reality and motor imagery (VRMI) groups. All players completed pre- and post-tests assessing pass accuracy at three distances (10, 15 and 20 meters) under two conditions (with and without time constraints). Between the tests, the MI and VRMI groups performed three mental practice sessions over three different days. Each session consisted of two blocks of imagined (MI) or virtually observed (VRMI) stressful game scenarios (yellow card or try conceded) followed by imagined passes at each distance. The CTRL group did not engage in any practice during this period. Our results showed that mental practice improved pass accuracy under no constraints, with both MI and VRMI greater than CTRL (p<0.03 in all). Vividness of motor imagery improved over training sessions for MI and VRMI (p=0.01), but VRMI did not further enhance imagery vividness compared to MI alone. Under time constraints, pass accuracy at 20m declined during the pre-test for all groups (p=0.003). However, both mental practice groups failed to counteract this decrease at post-test. In conclusion, three mental practice sessions effectively enhanced pass accuracy under no constraints but did not mitigate the negative effects of time constraints on accuracy. Coaches and practitioners might consider implementing mental practice to further improve motor accuracy and reduce physical workload
