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On the damping and coupling impacts of DC fault-limiting reactors in multi-terminal DC grids
No full textInternational audienceThis paper investigates the impact of DC fault-limiting reactors (DCRs) on the dynamics of Modular Multilevel converter-based multi-terminal DC (MTDC) grids, with a particular focus on their damping and coupling characteristics. The first part examines the instability introduced by large DCR values using a simplified low-frequency model and a comprehensive small-signal analysis of a four-terminal meshed DC grid. A dedicated controller is proposed to stabilize the system and is compared with other mitigation measures, such as modifying the control mode and changing the power flow direction. The second part investigates the coupling effects of DCRs in DC grids, showing that the commonly assumed equivalent DC grid capacitance becomes invalid in the presence of DCRs. This leads to different conclusions regarding DC voltage support between stations, particularly during fast transient responses. All findings are validated through time-domain simulations of a four-terminal DC grid
The Global Spectra-Trait Initiative: A database of paired leaf spectroscopy and functional traits associated with leaf photosynthetic capacity
No full textInternational audienceAccurate assessment of leaf functional traits is crucial for a diverse range of applications from crop phenotyping to parameterizing global climate models. Leaf reflectance spectroscopy offers a promising avenue to advance ecological and agricultural research by complementing traditional, time-consuming gas exchange measurements. However, the development of robust hyperspectral models for predicting leaf photosynthetic capacity and associated traits from reflectance data has been hindered by limited data availability across species and environments. Here we introduce the Global Spectra-Trait Initiative (GSTI), a collaborative repository of paired leaf hyperspectral and gas exchange measurements from diverse ecosystems. The GSTI repository currently encompasses over 7500 observations from 397 species and 41 sites gathered from 36 published and unpublished studies, thereby offering a key resource for developing and validating hyperspectral models of leaf photosynthetic capacity. The GSTI database is developed on GitHub (https://github.com/plantphys/gsti, last access: 4 January 2026) and published to ESS-DIVE https://doi.org/10.15485/2530733, Lamour et al., 2025). It includes gas exchange data, derived photosynthetic parameters, and key leaf traits often associated with traditional gas exchange measurements such as leaf mass per area and leaf elemental composition. By providing a standardized repository for data sharing and analysis, we present a critical step towards creating hyperspectral models for predicting photosynthetic traits and associated leaf traits for terrestrial plants
The microbiota affects energy production, nitrogen excretion and sterol metabolism in mosquito larvae
No full textPosted December 18, 2025 on bioRxiv.Mosquito larvae rely on a living microbiota for normal development because the microbiota supplies essential nutrients, particularly vitamins. Beyond vitamin provision, transcriptomic data suggest that the microbiota also supports other key nutritional processes. Here, we explored these roles by conducting a metabolomics analysis on Aedes aegypti third instar larvae following microbiota depletion. We sampled larvae and dissected guts 12- and 20-hours post-decolonization and analysed methanol-soluble metabolites using untargeted gas chromatography–mass spectrometry. Our findings reveal a pronounced impact of gut microbial presence on several metabolites involved in the tricarboxylic acid cycle and the uricolytic pathway. Germ-free larvae also had a lower quantity of cholesterol in guts and their long-chain fatty acid profile was altered in guts and whole larvae. Sterols, including cholesterol, are essential precursors for the production of the moulting hormone 20-hydroxyecdysone. We therefore tested how supplementing exogenous cholesterol affects the development of germ-free larvae. The effects proved to be highly concentration-dependent, ranging from a marginally significant increase in successful development to adulthood at low concentrations to a pronounced developmental impairment at higher concentrations. Moreover, bacteria deficient in fatty acids beta-oxidation had a significantly lower ability to support larval development. Together, the observed alterations suggest that microbiota-deprived larvae exhibit a downregulation of metabolic processes related to energy production, nitrogen excretion and sterol metabolism, likely due to the absence of microbiota-derived vitamins essential for these central metabolic functions.ImportanceMosquito larvae depend on gut microbiota for normal growth because microbes supply essential nutrients, particularly B vitamins. To explore microbial roles beyond vitamin provision, we analysed metabolic changes in Aedes aegypti larvae after microbiota removal using gas chromatography-mass spectrometry. Germ-free larvae exhibited decreased metabolites associated with the tricarboxylic acid cycle and uricolytic pathway, indicating a general slowdown in metabolic activity and nitrogen waste processing. Additionally, the absence of a microbiota affected cholesterol and fatty acid metabolism. To validate these findings, we found that supplementing germ-free larvae with low levels of cholesterol modestly improved their development. In contrast, larvae colonized with bacteria deficient in fatty acid metabolism exhibited significantly reduced developmental success. Overall, the findings show that removing the microbiota downregulates key metabolic pathways related to energy production, nitrogen excretion, and sterol metabolism, highlighting that bacterial vitamins and fatty acid degradation are vital for mosquito larval development and successful transformation into adults
Improving visibility for knowledge holders in ethnobiological and ethnopharmacological publications
No full textInternational audienceEthnopharmacological relevance: Ethnopharmacology and ethnobiology largely focus on the study of traditional knowledge related to medicinal and other uses of plants, animals or minerals. Despite decades of political advocacy, ethnopharmacological and ethnobiological information is still sometimes published without proper attribution of the cultural identities and affiliations of the communities that shared it.Aim of the study: Identify key guidelines to ensure the proper attribution of ethnobiological and ethnopharmacological knowledge recorded in scientific publications to the communities who provided it.Material and methods: This article is based on extensive group discussions that started at a workshop entitled “A worldwide database of local uses of biodiversity: Why? For whom? And how?” (18th Congress of the International Society of Ethnobiology in Marrakech, Morocco, May 15–19, 2024), and was attended by around 50 participants. The guidelines were developed through an iterative revision process.Results: We propose practical guidelines to improve the attribution and thus, visibility, of communities whose knowledge contributes to ethnobiological and ethnopharmacological publications. Recognising individual knowledge holders remains a critical topic on its own right.Conclusion: Transparent and consistent reporting of the provenance of place-based ancestral knowledge from communities is essential for advancing the objectives of the Nagoya Protocol, the Treaty on Intellectual Property, Genetic Resources and Associated Traditional Knowledge, and for strengthening academic inquir
Rapport sur les services climatiques réussis dans le monde et leurs critères de succès: Livrable commun au Projet ciblé TRACCS-PC1-DIALOG (D5.3) et au Projet Ciblé TRACCS-PC3-DEMOCLIMA (D1)
No full textLes enjeux socio-économiques liés aux effets du réchauffement climatique sont tels qu’une demande croissante d’informations climatiques adaptées pour la mise en place de stratégies d’atténuation et/ou d’adaptation est clairement exprimée par les secteurs économiques (e.g. agriculture, énergie, tourisme, infrastructures terrestres ou maritimes, etc…) et par les territoires/régions qui mesurent pleinement leursvulnérabilités. En réponse à ces demandes, de nombreux projets de recherche nationaux (e.g., la "Convention relative à l’attribution d’un appui financier au bénéfice des services climatiques", signée entre le Ministère de la Transition Écologique et Solidaire (MTES) et le CNRS en mars 2017, ou le développement du portail DRIAS), européens (e.g., le programme ERA4CS « European Research Area for Climate Services » du JPI Climate, ou encore Copernicus) ou internationaux (e.g., les outils développés par la NASA, le GIEC…) ont permis le financement de « services climatiques ». Plusieurs acteurs opérationnels nationaux et européens développent et mettent à disposition des « services climatiques » via des plateformes souvent libres d’accès et enfin, apparaissent sur le marché des bureaux d’études dont l’activité commerciale vise le développement de « services climatiques » à la carte et adaptés aux demandes des clients.L’offre pour les « services climatiques » est donc aujourd’hui multiforme par l’information fournie (données climatiques « simples », indicateurs, outils d’aide à la décision) et par son mode de développement. Face à cette diversité, les enjeux sont de documenter et comprendre le paysage des services climatiques actuels, de faire ressortir les besoins, et de se munir de moyens pour caractériser la réussite des services climatiques, pour évaluer l'existant et guider le développement de nouveaux projets. Menée conjointement par les projets ciblés DIALOG (PC1) et DEMOCLIMA (PC3) du PEPR TRACCS, cette étude vise quatre objectifs :i) Documenter le paysage actuel des services climatiques (section 2) en France et dans le monde (identifiés par la communauté TRACCS) en les présentant par usages et cibles ;ii) Identifier des besoins non satisfaits vis-à-vis des services climatiques (section 4) ;iii) Identifier un ensemble de critères de réussite d'un service climatique pour les évaluer (section 5) ;iv) Proposer des bonnes pratiques pour atteindre ces critères de réussite (section 6); ces éléments guideront les choix des futurs démonstrateurs qui seront conçus et développés au sein de DEMOCLIMA.Notre travail repose en grande partie sur le recueil de dires d'acteurs des "services climatiques", dans une approche "bottom-up"
Monitoring tropical forests with light drones: ensuring spatial and temporal consistency in stereophotogrammetric products
No full textInternational audienceThis study benefited from an "Investissement d'Avenir" grant managed by the Agence Nationale de la Recherche (CEBA, ref. ANR-10-LABX-25-01), via project PHENOBS. We also acknowledge the support of the UE Biodiversa+ BiodivMon program (Project Coforfunc). We are thankful to Ilona Clocher, Jean-Louis Smock, Jean-Yves Goret, Florian Jeanne and Julien Engel for their help with drone data acquisition and/or processing. Access to the Paracou site and infrastructure (https://paracou.cirad.fr) was granted by CIRAD/Ecofog, and we thank Géraldine Derroire and all Phenobs project participants. We are grateful to Raphaël Pélissier for helping in the initial shaping of the Phenobs project and for his continued support
Dynamics and environmental drivers of methane and nitrous oxide fluxes at the soil and ecosystem levels in a wet tropical forest
No full textInternational audienceTropical forests are critical for maintaining the global carbon balance and mitigating climate change, yet their exchange of greenhouse gases with the atmosphere remains understudied, particularly for methane (CH 4 ) and nitrous oxide (N 2 O). This study reports on continuous measurements of CH 4 and N 2 O fluxes at the ecosystem and soil levels, respectively through eddy covariance and an automated chamber technique, in a wet tropical forest in French Guiana over a period of 26 months. We studied the magnitude of CH 4 and N 2 O fluxes and their drivers (climatic variables) during the driest and wettest seasons. Seasonal ecosystem fluxes showed near-zero net CH 4 uptake during the driest season and emissions during the wettest season that were larger in magnitude than the uptake. Meanwhile, N 2 O emissions were of similar magnitudes in both seasons. Upland soils within the footprint of the eddy covariance tower emitted N 2 O in both seasons, although these fluxes were particularly small. In contrast, upland soils were characterised by CH 4 uptake. Overall, seasonal ecosystem and soil CH 4 and N 2 O fluxes were partially explained by seasonal variations in soil water content, soil temperature and global radiation. The magnitude and sign of the net ecosystem fluxes of CH 4 and N 2 O were likely due to outgassing from aboveground biomass and the presence of seasonally flooded areas within the footprint of the eddy covariance system. Further studies of other ecosystem compartments in different forest habitats are needed to better understand the temporal variations in CH 4 and N 2 O fluxes in wet tropical forests
Les risques naturels à Mayotte dans le contexte du réchauffement climatique.
No full textPrésentation dans le cadre du COMEX « Gestion de crise et risque naturel » de l’association Mlézi Maore, Cavani, Mayotte
Bridging Knowledge: Transdisciplinary Approaches to Climate Adaptation in the Pacific
No full textInternational audienceThis panel posed the following guiding question: how can we conduct research that is truly relevant to the countries in which we work? What factors enabled us to formulate useful questions for populations and decision-makers in the context of climate change? What difficulties did researchers and institutional staff encounter when conducting such demanding research? Finally, what results were expected and discussed during the project's development?The panel proposed exploring these issues based on five years of transdisciplinary and applied research on climate change and adaptation conducted in the Pacific Islands. These islands, which are highly exposed to hazards, have also served as testing grounds. Since 2022, the CLIPSSA (Pacific Climate, Local Knowledge and Adaptation Strategies) project has been bringing together climatologists and social scientists with institutional and political actors in Vanuatu, New Caledonia, French Polynesia and Wallis and Futuna to co-develop a programme aligned with the priorities of local authorities. After a year of consultation with governments, the food-water-agriculture nexus was selected as a common focus, with family farming — central to food security — being chosen more specifically. A crucial component focused on linking indigenous and local knowledge, climate science and public decision-making more effectively to accelerate adaptation.The consortium's researchers presented three contributions: (1) producing future atmospheric projections at a Pacific scale (20 km grid) and at a very high resolution on the islands (2.5 km); (2) analysing future climate impacts on agriculture in Melanesian and Polynesian contexts; and (3) studying the ways in which family farmers combine knowledge, experience and know-how today. Beyond the methods and initial results, the panel examined the constraints and opportunities of such approaches, fuelling a debate on their expected effects
Prognosis of Hepatocellular carcinoma in the French Overseas Territories and Comparison with a Tertiary Center in Mainland France.
No full textInternational audienceIntroduction and objectives: Limited data are available on the prognosis of hepatocellular carcinoma (HCC) in the French overseas territories (FOT). This study aimed to describe the characteristics and outcomes of patients diagnosed with HCC in FOT, comparing them to those from a tertiary center located in Île-de-France (IDF).Materials and methods: We retrospectively included all patients with HCC diagnosis between 2013 and 2023 in the FOT and IDF. Socio-demographic and medical data were collected, with the first treatment performed and survival data. Overall survival was analyzed using Kaplan- Meier methods and Cox proportional hazards models.Results: A total of 1114 patients were included (FOT 11%, IDF 89%). FOT patients had higher rates of hepatitis B (36% vs. 16%, p<0.001) and worse liver function (defined by higher MELD scores and fewer Child A cases) at HCC diagnosis. In contrast, IDF patients had a higher prevalence of MASLD (29% vs. 16%, p=0.004). HCC was diagnosed at more advanced stages in FOT compared to IDF, with 71% vs. 49% (p<0.001) of cases outside Milan criteria and 29% vs. 5% (p<0.001) in BCLC-D, leading to a significantly lower survival in FOT (median 9 vs. 23 months, p=0.02).Conclusions: HCC patients in FOT have a poorer prognosis compared to IDF, with diagnoses at more advanced stages, limiting curative treatment options. These findings highlight the need for improved access to care and screening strategies for earlier diagnosis of HCC in FOT