HAL Université des Antilles
Not a member yet
25497 research outputs found
Sort by
Des plaques résistantes aux frontières mécaniquement faibles : localisation de la déformation dans le manteau lithosphérique par fluage-dislocation basse et haute températures.
No full textPlate-like behavior may be reproduced in numerical experiments of mantle convection if rheology combines a temperature-dependent viscosity capped with a low yield stress. Other processes limiting the mantle ductile strength have been proposed, among which low-temperature plasticity. We propose to investigate how such a rheology can promote deformation localization at the lithospheric scale. We design a 2-D thermo-mechanical model of plate extension to compare the modes of strain localization as a function of the rheological parameterization. Various experimental flow laws for olivine (diffusion creep and dislocation creep at low-and/or high-temperature) are tested, sometimes combined with a yield-stress formulation.We quantify the evolution of the deformation pattern throughout the lithosphere, and define new diagnostics to assess whether the decrease in plate viscosity is due to an increase in strain rate ('mechanical weakening') and/or in temperature ('thermal weakening'). Deformation localization leads to a new extensional plate boundary in two successive stages: (i) narrowing of the deforming zone, (ii) rapid thinning of the highly deformed lithosphere. Here, a rheology combining diffusion creep and yield stress results in a mantle weakening that is either fully mechanical, respectively fully thermal, for temperatures lower, respectively higher, than ∼1300 K. Accounting for dislocation creep enables additional feedbacks between mechanical and thermal weakening within the deforming plate, thereby enhancing the efficiency of strain localization. We demonstrate the consistency of using a yield-stress approximation to cap the mantle strength for temperature below ∼1000 K. We also show that dislocation creep and yield-stress are not interchangeable for most of the lithospheric mantle (1000-1500 K), and using only the latter may overestimate the duration of plate break-up. Finally, we discuss how our results compare to natural continental rifting cases.</div
Healthy forests safeguard traditional wild meat food systems in Amazonia
No full textInternational audienceAmazonia is the largest and the most species-rich tropical forest region on Earth , where hundreds of Indigenous cultures and thousands of animal species have interacted over millennia. Although Amazonia offers a unique context to appraise the value of wildlife as a source of food to millions of rural inhabitants, the diversity, geographic extent, volumes and nutritional value of harvested wild meat are unknown. Here, leveraging a dataset comprising 447,438 animals hunted across 625 rural localities, we estimate an annual extraction of 0.57 Mt of undressed animal biomass across Amazonia, equivalent to 0.34 Mt of edible wild meat. Just 20 out of 174 taxa account for 72% of all animals hunted and 84% of the overall biomass extracted. We show that this amount of wild meat can meet nearly half of protein and iron dietary requirements for rural peoples, along with a substantial portion of their needs for B vitamins (18–126%) and zinc (23%). However, wild meat productivity is likely to have decreased by 67% in nearly 500,000 km² of highly deforested areas of Amazonia. Furthermore, the availability of wild meat per capita decreases significantly in areas with higher human population, greater proximity to cities, and more extensive deforestation. These findings highlight the urgent need to preserve the forest to safeguard biodiversity and traditional wild meat food systems, which will be essential for ensuring Amazonian peoples’ well-being and achieving several of the United Nations Sustainable Development Goals
Épidémiologie descriptive des maladies inflammatoires primaires pédiatriques du système nerveux central dans la population afro-descendante de l'île de la Martinique, Antilles françaises
No full textIntroduction: The epidemiology of Primary inflammatory diseases of the central nervous system (CNS) is poorly described, in Caribbean and Afro-descendant children. There is only one paediatric tertiary centre dedicated to treating these diseases in Martinique, which has a predominantly Afro-descendant population. We studied the incidence, clinical and biological characteristics, immunological profiles and prognosis of primary inflammatory diseases of the pediatric CNS treated in Martinique. Methods: We conducted a descriptive, retrospective, multicenter study from 01.01.2010 to 01.07.2024 including all children aged 0 to 17 years hospitalized for autoimmune encephalitis, multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD) or myelin oligodendrocyte glycoprotein associated disease (MOGAD) in the pediatric and intensive care units of the Martinique university hospital in Fort de France and the Trinité hospital. The diagnosis of primary CNS inflammatory disease was made according to the latest international recommendations specific to each pathology. The sequelae of these pathologies were assessed using an EDDS score. Results: 25 children were hospitalized for primary neuroinflammatory disease of the CNS in Martinique between 2010 and 2024 and 16% were admitted to intensive care. The median age was 14 years (2-17). The incidence rates found were 0,44/100.000 children per year for NMOSD and 0,66/100.000 children per year for MOGAD, the incidence rate of MS was 0.6/100,000 children per year. The immunological profile of NMOSD/MOGAD was 70% seropositive (4 AQP4 and 3 MOG). First-line treatment was high-dose corticosteroid therapy in most cases (88%). Sequelae were rare for MOGAD and NMOSD, and similar to international studies in MS and encephalitis. Mortality was null. Conclusions: Our study showed an increase in the incidence of NMSOD disease compared to international studies and no significant difference in the incidence rates of the other neuroinflammatory disorders of the central nervous system in children. Outcomes were comparable to European and North American countries in our population. The immunological profile showed a high proportion of anti-AQP4 antibodies compared to the literature.Introduction : L’épidémiologie des maladies inflammatoires primitives du système nerveux central est peu documentée chez l’enfant dans les populations Caribéennes et Afro-descendantes. La Martinique, avec sa population majoritairement Afro-descendante et son unique centre tertiaire pédiatrique capable de gérer ces pathologies, permet une étude exhaustive de ces pathologies. Notre objectif était d’étudier l’incidence, les caractéristiques cliniques et biologiques, les profils immunologiques et le pronostic des maladies inflammatoires primitives du SNC de l’enfant prises en charge en Martinique. Méthode : Étude épidémiologique descriptive, rétrospective et multicentrique du 01/01/2010 au 01/07/2024 avec inclusion de tous les enfants de 0 à 17 ans hospitalisés pour une encéphalite auto immune, une sclérose en plaque (SEP), un Neuromyelitis optica spectrum disorder (NMOSD) ou une myelin oligodendrocyte glycoprotein associated disease (MOGAD) dans les services de pédiatrie et de réanimation de la Maison de la femme et de l’enfant CHU de Fort de France et de l’hôpital de Trinité. Le diagnostic de maladie inflammatoire primitive du SNC était posé selon les dernières recommandations internationales spécifiques à chaque pathologie. Les séquelles de ces pathologies ont été évaluées par un score score EDDS. Résultats : 25 enfants ont été hospitalisés pour une maladie neuro inflammatoire primitive du SNC en Martinique entre 2010 et 2024 dont 16% en réanimation. L’âge médian était de 14 ans (2 ans -17 ans). Les taux d’incidence retrouvés étaient de 0,44/100.000 enfant par an pour NMOSD et 0,66/100.000 pour MOGAD, le taux d’incidence de la SEP était de 0.6/100.000 enfant par an. Le profil immunologique NMOsd/MOGAD était 70% séropositif dans 70 % des cas (4 AQP4 et 3 MOG). Le traitement de première intention était la corticothérapie à forte dose dans la majorité des cas (88%). Les séquelles étaient rares pour les MOGAD et NMOSD, et similaires aux études internationales dans le cadre des SEP et encéphalites. La mortalité était nulle. Conclusion : Dans la population pédiatrique Afro-descendante en Martinique, notre étude retrouve une incidence des NMOSD supérieure à celle rapportée dans la littérature, sans différence significative pour les autres pathologies étudiées. Le taux et le type de séquelles étaient comparables dans notre population avec celle rapportée dans les dernières études internationales. L’étude des profils immunologiques a révélé une proportion importante d'anticorps anti-AQP4 par rapport aux données de la littérature
Lorsque les enfants d'Océanie dessinent la mer et la pêche : inclure les enfants dans la recherche en sciences sociales marines
No full textLe projet « SOCPacific » (A Sea of Connections: Contextualizing Fisheries in the South Pacific Region, 2018-2022, financement ANR-DFG) visait à explorer « l'océan de connexions » au sein duquel les pratiques de pêche etde gestion des pêcheries se déploient dans le Pacifique Sud. Impliquer les enfants était essentiel pour engager uneapproche de la durabilité marine reconnaissant les enjeux de justice intergénérationnelle et les droits de l'enfant.En effet, les enfants de cette région participent activement à la pêche et au maintien des relations entre les humains, lamer et la vie marine. Comme les adultes, ils peuvent ainsi exercer leur droits et leurs responsabilités envers l'Océan.Des ateliers de dessin ont ainsi permis leur participation à la co-construction de nos axes de recherche
Analysis of the interaction of cannabinoids with their human CNR1 and CNR2 receptors.
No full textInternational audienceThe field of hemp-derived compounds has been experiencing exponential growth, raising significant scientific, economic, and therapeutic challenges. Cannabinoids are classified into phytocannabinoids, endocannabinoids, and synthetic cannabinoids, all of which interact with various cellular targets, including the human cannabinoid receptors CNR1 and CNR2, members of the GPCR family. Among them, cannabidiol (CBD) has gained attention due to its potential effects on anxiety, pain, and inflammation. However, its interactions with these receptors remain poorly understood.In this study, we used molecular modeling approaches to explore the interaction dynamics of CBD, Δ9-tetrahydrocannabinol (THC), and tetrahydrocannabiorcol (THC7) with both CNR1 and CNR2. After completing structural data through homology modeling and energy minimization, we performed molecular docking followed by molecular dynamics simulations in a neuronal membrane environment over multiple microseconds. Several activation markers were analyzed, including ionic lock disruption, toggle switch movement, and intracellular loop (ICL3) involvement.Our results reveal complex activation dynamics. An active-like conformation of CNR1 was identified, characterized by a displacement of helix TM6 and a role of the ICL3 loop in receptor activation. Interestingly, CBD appears to facilitate access to these active states, despite its lack of classical agonist activity, suggesting a possible influence on the basal activity of CNR1. THC and THC7 exhibited distinct stabilization patterns, highlighting potential pharmacological differences. A comparative analysis of CNR2 revealed notable structural divergences in its activation pathway.These findings provide new insights into CNR1 and CNR2 activation mechanisms and may contribute to a better understanding of phytocannabinoid pharmacology, with potential therapeutic implications
Genome-wide screen for deficiencies modifying Cyclin G-induced developmental instability in Drosophila melanogaster
No full textDespite long-lasting interest and research efforts, the genetic bases of developmental stability the robustness to developmental noise and its most commonly used estimator, fluctuating asymmetry (FA), remain poorly understood. The Drosophila melanogaster Cyclin G gene ( CycG ) encodes a transcriptional cyclin that regulates growth and the cell cycle. Over-expression of a potentially more stable isoform of the protein (deleted of a PEST-rich domain, hereafter called CycG P ) induces extreme wing size and shape FA ( i.e. high developmental noise), indicating a major disruption of developmental stability. Previous attempts to identify the genetic bases of FA have been impeded by the constitutively low level of developmental noise, strongly limiting the power to detect any effect. Here, we leverage the extreme developmental instability induced by overexpression of CycG P to explore the genetic bases of FA: we perform a genome-wide screen for deficiencies that enhance or reduce CycG P -induced wing FA. 499 deficiencies uncovering 90% of the euchromatic genome were combined with a recombinant chromosome expressing CycG P . We identified 13 and 16 deficiencies that enhance and decrease FA, respectively. Analysis of mutants for some genes located in these deficiencies shows that Cyclin G ensures homogeneous growth of organs in synergy with the major morphogens of the wing, Dpp and Wg, as well as the Hippo and InR/TOR pathways. They also reveal that CycG P -induced FA involves Larp, a potential direct interactor of Cyclin G, that regulates translation at the mitochondrial membrane. This opens up new research perspectives for understanding developmental stability, suggesting a significant role for mitochondrial activity
ClimBurst: A Novel Method to Detect Climatological Anomalies Over Time and Space
No full textInternational audienceDetecting abnormal climate events is crucial for understanding, predicting, and managing climate risks. However, most existing methods require prior knowledge about when and where to search for these events, limiting their effectiveness. In this study, we introduce ClimBurst, a new method to identify climate-related anomalies that does not require any prior information about their duration or spatial extent. We propose computing climate bursts to detect abnormal seasonal activity. The ClimBurst approach can detect anomalies at any time scale. The approach also compares anomalies at neighboring locations enabling the tracking of events across time and space. We apply our method on sea surface temperature data from the Mediterranean Sea between 1960 and 2021, where we detect particularly strong warm anomalies that can last from a few days to a few months over a few kilometers to hundreds, such as the 2015 marine heatwave. Our results reveal a noticeable increase in the frequency, magnitude and the spatial extent of these hot anomalies over time. Researchers and practitioners can use ClimBurst to detect and study climate anomalies, providing a basis for event attribution and long-term trend analysis
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
Carleman Estimates and Exact Controllability Results for a Transmission System of two Nonconservative wave Equations
No full textInternational audienceWe consider a transmission system of two nonconservative wave equations with nonconstant coefficients in the one-dimensional setting. We investigate the exact (boundary and internal) controllability of this system using a single control. To solvethese exact controllability problems, we rely on the duality approach which consists in proving inverse or observability inequality for the corresponding adjoint system. To prove these observability inequalities, we establish new Carleman estimates for the corresponding uncontrolled transmission system. These Carleman estimates require the introduction of new weight functions adapted to the coefficients of the principal operators. In particular, our Carleman estimates with internal observation are new in the framework of transmission systems
Combining population genomics with ancient DNA to understand island colonization history of the Madagascar turtle dove
No full textAbstract The Mascarene archipelago (Mauritius, Reunion and Rodrigues), characterized by first human arrival being recent, offers a unique setting to study species colonization. Here we use a combination of modern and ancient DNA data as a case study to investigate the recent colonization history of a species of concern in relation to conservation programs – the Madagascar turtle dove ( Nesoenas picturata ) on Mauritius and Reunion. We generated a reference genome and re-sequenced genomes from contemporary N. picturata populations, as well as genome-wide data from relevant subfossils. A combination of model-free inferences, site frequency spectrum (SFS) based demographic modelling, and analyses of population structure including that of subfossils indicate that N. picturata colonized both islands independently and naturally from Madagascar, long before human arrival. Summary statistics and SFS-based modeling reveal large effective population sizes ( Ne ) and high genetic diversity in island populations, conflicting with historical accounts of human-induced demographic collapse. Based on goodness-of-fit, genetic structure and diversity indices do not discriminate between two solutions, one of which posits large recent Ne and negligible translocation rates, while the other supports recent severe bottlenecks followed by high post-human translocation from Madagascar. Nonetheless, linkage disequilibrium provides stronger evidence for the latter scenario, which may also explain high genetic diversity. Both modern and ancient DNA data sources independently support the classification of N. picturata as native to both islands. Our findings highlight the importance of validating demographic models with multiple summary statistics, and potential of using a combination of different data sources to resolve colonization history in recent time