Portail HAL de l'Université du Littoral Côte d'Opale
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Small in the heat, transparent in the bloom : copepod morphological responses in the California upwelling ecosystem
No full textInternational audienceCopepods are central to marine food webs as they link primary producers to higher trophic levels. This study used in situ images collected with an Underwater Vision Profiler during four cruises (2008, 2012, 2014 and 2016) in the California Current Ecosystem to investigate how copepod morphologies relate to environmental conditions. Consistent with Bergmann’s rule, our results indicate that smaller copepods were associated with warmer environments. Copepods with more complex body shapes, owing to extended appendages, were observed in waters with higher fluorescence and diatom concentrations. Finally, more transparent copepods were found in shallower waters with higher fluorescence, potentially suggesting predatory avoidance of darker copepods found deeper in the water column. These findings support the power of imaging-based functional trait-based approaches to link zooplankton morphological variability with environmental gradients, enhancing our understanding of zooplankton dynamics in productive upwelling systems
Enseigner l'entreprenariat à l'université: Liberté d'entreprendre, interdictions professionnelles et fonds de commerce
No full textInternational audienceL’ouvrage comprend essentiellement quatre chapitres. Le premier s’intéresse à l’accès et au maintien dans le monde des affaires. Il y est à la fois question de la liberté du commerce et de l’industrie, pour presque tous, ainsi que de la fermeture du monde des affaires à quelques personnes. Le deuxième chapitre constate la recherche d’une atténuation de son risque financier par l’entrepreneur. Cela se traduit en général par la dilution du risque entrepreneurial dans une structure commune. Du reste, il lui est possible d’envisager l’échappement à la ruine même seul dans une entreprise. Le troisième chapitre traite du domicile de l’entreprise, c’est-à-dire de son siège social. Quoique obligatoire, la domiciliation pourrait se faire à l’étranger. Mais si le choix s’est porté sur la France, il faut alors se préoccuper du titre (payant ou gratuit) de l’obtention des locaux en cause. Enfin, le quatrième chapitre est relatif au fonds de commerce. Dans ce cadre, des précisions sont données sur la protection dont bénéficie le professionnel grâce à la fiction juridique dénommée propriété commerciale. Une protection toutefois moindre lorsque l’installation du professionnel s’est faite à titre précaire et révocable ; par exemple sur le domaine public
Bialgebraic structures on boolean functions
No full textWe study several bialgebraic structures on boolean functions, that is to say maps defined on the set of subsets of a finite set , taking the value on . Examples of boolean functions are given by the indicator function of the hyperedges of a given hypergraph, or the rank function of a matroid. We give the species of boolean functions a two-parameters family of products and a coproduct, and this defines a two-parameters family of twisted bialgebras. We then try to define a second coproduct on boolean functions, based on contractions, in order to obtain a double bialgebra. We show that this is not possible on the whole species of boolean functions, but that there exists a maximal subspecies where this is possible.This subspecies being rather mysterious, we introduce rigid boolean functions and show that this subspecies has indeed a second coproduct, as wished, and that it contains rank functions of matroids and indicator functions associated to hypergraphs.As a consequence, we obtain a unique polynomial invariant on rigid boolean functions, which is a generalization of the chromatic polynomial of graphs
Hyperspectral space transformations for texture classification
No full textInternational audience3D color space transformations are widely used in color imaging to enhance the results of various tasks, including image segmentation, object recognition, and texture classification. However, such useful transformations are much more limited in hyperspectral imaging, where images contain hundreds to thousands of spectral bands. To improve the performance of hyperspectral image analysis, we introduce four new hyperspectral space transformations in this paper: the Hyper-Chrominance-Luminance (H-CL), the Hyper-Hue-Chroma-Luminance (H-HCL), the Hyper-Hue-Saturation-Intensity (H-HSI), and the Hyper-Hue-Saturation-Value (H-HSV). These transformations extend the corresponding CL, HCL, HSI, and HSV 3D color spaces to multiple dimensions. To investigate their suitability in the context of texture classification, several well-known texture descriptors, including both theory-driven (handcrafted) and data-driven (deep learning) methods, are used in the experiments. Ten hyperspectral datasets are considered: HyTexila, SpecTex, HyperPlastic, and seven datasets extracted from the Timbers database. Among these datasets, six new ones are introduced in this paper. The proposed H-CL, H-HCL, H-HSI, and H-HSV transformations are also compared with state-of-the-art transformation strategies. The experiments conducted in this paper demonstrate the efficacy of the proposed space transformations with an accuracy improvement that can reach +43.47 %
SVH-BD : Synthetic Vegetation Hyperspectral Benchmark Dataset for Emulation of Remote Sensing Images
No full textThis dataset provides a large collection of 10,915 synthetic hyperspectral image cubes paired with pixel-level vegetation trait maps, designed to support research in radiative transfer emulation, vegetation trait retrieval, and uncertainty quantification. Each hyperspectral cube contains 211 bands spanning 400--2500 nm at 10 nm resolution and a fixed spatial layout of 64 \times 64 pixels, offering continuous simulated surface reflectance spectra suitable for emulator development and machine-learning tasks requiring high spectral detail. Vegetation traits were derived by inverting Sentinel-2 Level-2A surface reflectance using a PROSAIL-based lookup-table approach, followed by forward PROSAIL simulations to generate hyperspectral reflectance under physically consistent canopy and illumination conditions. The dataset covers four ecologically diverse regions -- East Africa, Northern France, Eastern India, and Southern Spain -- and includes 5th and 95th percentile uncertainty maps as well as Sentinel-2 scene classification layers. This resource enables benchmarking of inversion methods, development of fast radiative transfer emulators, and studies of spectral--biophysical relationships under controlled yet realistic environmental variability
Ferroelectric and dielectric studies of a ferroelectric liquid crystal (FLC) dispersed ferroelectric nanoparticles (NPs) : Impact of NP dispersions on the rotational viscoelastic properties of the FLC
No full textInternational audienceThis study focuses on the effects of dispersing tin thiohypodiphosphate ferroelectric nanoparticles (Sn2P2S6) on the structural, ferroelectric, and dielectric properties of a ferroelectric liquid crystal (SmC*) phase. Our findings show that nanoparticle dispersion leads to modifications in phase transition temperatures, spontaneous polarization, and dielectric relaxation modes associated with ferroelectricity. These effects are attributed to changes in the viscoelastic parameters of the SmC* phase. Two concentration regimes were identified: at low concentrations, nanoparticles are well-dispersed, introducing local defects in the smectic layers and distortions in the helical structure, thereby enhancing the viscoelastic properties of the FLC. At higher concentrations, aggregation of nanoparticles reduces the dispersion effects, and the nanocomposite behavior tends to resemble that of the pure liquid crystal
Unraveling how mycorrhizal inoculation shapes the wheat foliar transcriptome and enhances resistance to septoria tritici blotch
No full textInternational audienceArbuscular mycorrhizal fungi (AMF), known to form mutualistic associations with most terrestrial plant species, could represent promising ecological alternatives to agrochemicals, which are harmful to both human health and environment. Although most studies investigate the effectiveness of mycorrhizal symbiosis in controlling root diseases, its influence on foliar diseases is still poorly explored, particularly in wheat. A prior investigation conducted under controlled conditions revealed that inoculation with the AMF species Funneliformis mosseae (Fm) protects wheat leaves from both pathogenic fungi, the biotrophic Blumeria graminis f. sp. tritici, responsible for powdery mildew (Mustafa et al, 2016, 2017), and the hemibiotrophic Zymoseptoria tritici (Zt), causing septoria tritici blotch (STB). This protection seems to be linked to the activation of "Mycorrhiza-Induced Resistance" (MIR), facilitating the systemic induction of plant defenses mediated by AMF (Allario et al., 2025). Nonetheless, the metabolic alterations that contribute to this resistance are poorly understood. In this study, we performed transcriptomic analyses to investigate how mycorrhizal symbiosis impacts gene expression in wheat leaves, resulting in plant protection against STB. Leaves from 6-week-old seedlings, inoculated or not with Fm and/or Zt, were sampled to study gene expression, 48 hours after Zt spores inoculation. Transcriptomic data showed a systemic induction of numerous genes in leaves of mycorrhizal plants under non-infectious conditions, many of which were common to those induced by Zt inoculation in non-mycorrhizal plants. These genes were involved in proteolysis, antioxidant mechanisms and plant immune response, particularly linked to jasmonic acid and ethylene signalling pathways. This induction of specific defense mechanisms by Fm before Zt inoculation (cell wall thickening, stomatal closure, defense proteins, maintenance of homeostasis and cellular function) was later completed by a downregulation of genes participating in photosynthesis and chloroplastic functions in mycorrhizal plants under infectious conditions. Together, these findings highlight AMF potential to induce MIR in wheat through systemic and coordinated metabolic reprogramming, leading to STB symptom reduction.Keywords : Wheat, septoria tritici blotch, arbuscular mycorrhizal fungi, Mycorrhiza-Induced Resistance, transcriptomic analysis
Pellet combustion: strategies for the reduction of pollutant emissions
No full textInternational audienc
Ordonnancement prédictif/réactif des parcours patients aux urgences
No full textInternational audienceOrdonnancement prédictif/réactif des parcours patients aux urgence
Caractérisation de la dynamique à sous-mésoéchelle dans les régions côtières du Viêt Nam par courantographie radar HF et modélisation numérique
No full textThe coastal regions of Vietnam, part of the Vietnam East Sea, are socio-economically vital. However, they still lack a comprehensive understanding of their dynamics, which limits effective and sustainable coastal management. In this PhD work, coastal circulation at the submesoscale and tracer dispersion are investigated in two contrasting regions : a deep-water region along the Vietnam mid-southern coast (VMSC) and the shallow-water Red River (RR) plume region in the Gulf of Tonkin. For the first time, datasets of high spatio-temporal resolution surface currents covering large domains (with widths of approximately 60-80 km from the shore) were obtained, enabling new insights into the submesoscale dynamics of the surface circulation in these regions. In the VMSC region, coastal dynamics during the monsoon transition (April-May, 2019) is controlled by winds and large-scale circulation resulting in a large variability in surface flow fields. Two winf-forcing optimization methods, Ensemble Perturbation Smoother (EnPS) and wind-driven surface current correction (EkW), are introduced to improve the model simulation for the VMSC and resulted in a significant error reduction (~40% in v-component) compared to observations. The performance of both methods was limited under calm winds, as the coastal dynamics of the VMSC region is largely governed by ocean intrinsic variability and external large-scale circulations. Open boundary conditions together with wind forcing optimization, is therefore necessary to enhance the accuracy and the realism of model simulations. In the RR plume regions, coastal dynamics showed strong seasonal variability as observed by HF radars : in summer, prevailing southwesterly winds allowed the plume to extend more than 30 km offshore, whereas in winter, northeasterly winds confined it to approximately 10 km from the coast. Particle tracking approach was used to investigate the Lagrangian dispersion. The Richardson super-diffusive regime of dispersion dominated the plume area in both winter and summer, with higher spreading rates in summer attributable to high river discharge and submesoscale eddies. The thesis also provided the first analysis of coastal dynamics and dispersion under an extreme event, typhoon Yagi (September 2024). Tracers were spread more than ten times faster as the flow rapidly adjusted to strong winds, while relative dispersion of particles in clusters exhibited a lower rate than under normal conditions, following a ballistic dispersion regime. The effectiveness of HF radars for monitoring surface currents has been demonstrated in the VMSC and RR plume regions of Vietnam, two coastal systems with contrasting dynamics, thereby advancing understanding of coastal ocean circulation variability and submesoscale processes.Les régions côtières du Vietnam, qui font partie de la mer de l'Est du Vietnam, sont d'une importance socio-économique vitale. Cependant, elles ne bénéficient toujours pas d'une compréhension globale de leur dynamique, ce qui limite la gestion efficace et durable du littoral. Dans le cadre de cette thèse de doctorat, la circulation côtière à sous-mésoéchelle et la dispersion des traceurs sont étudiées dans deux régions contrastées : une région en eaux profondes le long de la côte du centre-sud du Vietnam (VMSC) et la région du panache du fleuve Rouge en eaux peu profondes dans le golfe du Tonkin. Pour la première fois, des mesures de courants de surface à haute résolution spatio-temporelle couvrant de vastes domaines (sur une distance d'environ 60 à 80 km à partir de la côte) ont été obtenues, permettant de nouvelles perspectives d'investigation de la circulation à sous- mésoéchelle dans ces régions. Dans la région VMSC, la dynamique côtière pendant la transition de la mousson (avril-mai 2019) est contrôlée par les vents et la circulation à grande échelle, ce qui entraîne une grande variabilité des courants de surface. Deux méthodes d'optimisation du forçage éolien lisseur du filtre de Kalman (Ensemble Perturbation Smoother, EnPS) et correction des courants induits par le vent (EkW), ont été mises en oeuvre afin d'améliorer les performances du modèle de circulation SYMPHONIE pour le VMSC. L'optimisation a permis de réduire considérablement les erreurs (~40% dans la composante v) par rapport aux observations. Cependant, les performances des deux méthodes ont été réduites en conditions des vents faibles, car la dynamique côtière de la région VMSC est largement régie par la variabilité intrinsèque de l'océan et le forçage à plus grande échelle. L'optimisation des conditions aux limites ouvertes du modèle, en complément du forçage par le vent est donc nécessaire pour améliorer davantage la précision et le réalisme des simulations numériques. Dans la région du panache du fleuve Rouge, la dynamique côtière a été caractérisée par une forte variabilité saisonnière, comme l'ont observé les radars HF : en été, les vents dominants du sud-ouest permettent au panache de s'étendre à plus de 30 km au large tandis qu'en hiver, les vents du nord-est le confinent à environ 10 km de la côte. Le suivi des particules a permis de quantifier la dispersion lagrangienne. Le régime de dispersion superdiffusif de Richardson domine la zone du panache en hiver comme en été, avec l'intensité plus élevée en été attribuable à un fort débit fluvial et à des tourbillons de sous-mésoéchelle. La thèse a également fourni la première analyse de la dynamique côtière et de la dispersion lors d'un évènement extrême, le typhon Yagi (septembre 2024). La dispersion absolue des traceurs a été plus de dix fois supérieure tandis que la dispersion relative a été plus faible qu'en conditions normales. Cette dernière a été caractérisée par le régime balistique. Le potentiel des radars HF pour la surveillance des courants de surface a été évalué dans les régions VMSC et du panache du fleuve Rouge du Vietnam, deux systèmes côtiers présentant des dynamiques contrastées, permettant de mieux comprendre la variabilité à sous-mésoéchelle de la circulation côtière et les processus qui la gouvernent