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Connecting the Atlantic Meridional Overturning Circulation to the Southern Ocean Following the Closure of Equatorial Seaways During the Cenozoic
No full textInternational audienceAbstract Global ocean circulation regulates climate and has undergone significant changes over the Cenozoic. Today, the Atlantic Meridional Overturning Circulation (AMOC) is driven by North Atlantic Deep Water (NADW) formation and Southern Ocean upwelling. By contrast, during the middle Eocene to early Oligocene (48–28 Ma), a restricted Drake Passage was limiting the northern Ekman transport, while a circum‐equatorial current sustained by trade winds promoted low‐latitude upwelling. Our set of simulations with the IPSL‐CM5A2 model reveals that this paleogeographic setting favored proto‐NADW upwelling at low latitudes, confining the AMOC to the Northern Hemisphere. Consequently, the role of southern westerly winds was limited, and the northward heat transport was weaker than in the modern ocean
Relativistic Feedback Discharges in Dielectric Solids
No full textInternational audienceThe photoelectric feedback processes leading to growth of relativistic runaway electron avalanches are believed to be responsible for extreme uxes of gamma rays produced from very compact regions of space with dimensions on the order of hundred meters in association with lightning activity in the Earths natural environment (Pasko et al., 2025, https://doi.org/10.1029/2025JD043897). Here we demonstrate for the rst time that the same photoelectric feedback discharges can be realized on centimeter scales in common solid state dielectric materials, like quartz, acrylic and bismuth germanate. These discharge can serve as new sources of high energy X-ray radiation
From Molecule to Material: How Support Changes Heterobimetallic Catalysts in Lactide Polymerization
No full textInternational audienceSustainable production of polylactide demands catalysts that are both recoverable and capable of delivering precise molar mass and stereocontrol. A series of heterobimetallic complexes [(THF)NaFe(OtBu)3]2 , [(THF)2KFe(OtBu)3]2, [KZn(OtBu)3]2, [(THF)KCu(OtBu)3]∞ and [(THF)KCo(OtBu)3]2 was evaluated as precursors for heterogeneous catalysts by grafting onto dehydroxylated silica. All complexes demonstrated activity in the ring‐opening polymerization of lactide. Notably, the silica‐supported [(THF)KFe(OtBu)2]/SiO2‐700 and [(THF)NaFe(OtBu)2]/SiO2‐700 systems exhibited high efficiency, promising recyclability, and afforded predictable molar masses (Mn,exp close to Mn,th) with narrow dispersities. These findings highlight new opportunities for designing recyclable catalysts for sustainable PLA synthesis
Les disques de théâtre pour l’enfance et pour la jeunesse (France, 1930-1970)Écoutons-les pour les raisons qui les avaient fait oublier
No full textdirection du dossier: Florence Baillet, Marie SorelInternational audienceLong overlooked by theatre studies and ignored by childhood and youth specialists, theatre recordings aimed at young listeners are the subject of a first historical study that captures them at two key moments: their emergence in the 1930s (the era of 78 rpm records) and their heyday in the 1950s (the golden age of the vinyl record), before analyzing them as archives of a vanished “theatrical civilization” where the audible and the imaginary took precedence over the image, multimedia devices ahead of their time, organized around listening, potentially inspiring for contemporary pedagogy and creation.Longtemps oubliés par les études théâtrales, ignorés par les spécialistes de l’enfance et de la jeunesse, les disques de théâtre destinés aux jeunes auditeurs font l’objet d’une première étude historique qui les saisit à deux moments clés : leur émergence dans les années 1930 (l’ère du 78 tours), leur épanouissement dans les années 1950 (l’âge d’or du microsillon), avant de les analyser comme étant eux-mêmes les archives d'une « civilisation théâtrale » disparue où l'audible et l'imaginaire primaient sur l'image, des dispositifs multimédia avant l’heure, organisés autour de l’écoute, et potentiellement inspirants pour la pédagogie et la création contemporaines
Adoption des programmes d'agriculture carbone : les risques comptent
No full textInternational audienceEnsuring that carbon farming credits accurately reflect actual carbon sequestration is a major challenge. Although activity-based schemes are the most common design in voluntary carbon farming schemes, the economic literature has shown that result-based schemes are more cost-effective. However, the risk induced by result-based schemes when carbon sequestration is not known with certainty ex ante is often overlooked. We propose a stylized economic framework that integrates soil science data and models to investigate how carbon accrual uncertainty affects farmers' adoption of carbon farming schemes. This framework is illustrated with a data set combining observations from a long-term experimental site (Ultuna, Sweden), multi-model ensemble simulations of soil organic carbon dynamics, and a wide range of economic assumptions. We investigate both analytically and quantitatively the conditions under which a farmer chooses to participate in a voluntary carbon farming scheme when the quantity of carbon eventually stored is uncertain. Various carbon are explored, farming schemes differing inmonitoring costs and accuracy, with contrasting risk implications for the farmer. In particular, hybrid schemes that are based on the expected SOC accrual, but include an uncertainty discount are examined. It is shown that the incentives to participate in a result-based scheme may decrease with increasing carbon prices, and that hybrid schemes may foster adoption by farmers.Veiller à ce que les crédits de carbone agricole reflètent fidèlement la séquestration réelle du carbone représente un défi majeur. Bien que les programmes basés sur les activités soient les plus courants dans les programmes volontaires de carbone agricole, la littérature économique a montré que les programmes basés sur les résultats sont plus rentables. Cependant, le risque induit par les programmes basés sur les résultats lorsque la séquestration du carbone n'est pas connue avec certitude ex ante est souvent négligé. Nous proposons un cadre économique stylisé qui intègre des données et des modèles de science du sol afin d'étudier comment l'incertitude liée à l'accumulation de carbone affecte l'adoption des programmes de culture carbone par les agriculteurs. Ce cadre est illustré à l'aide d'un ensemble de données combinant des observations provenant d'un site expérimental à long terme (Ultuna, Suède), des simulations multi-modèles de la dynamique du carbone organique du sol et un large éventail d'hypothèses économiques. Nous étudions de manière analytique et quantitative les conditions dans lesquelles un agriculteur choisit de participer à un programme volontaire de culture carbone lorsque la quantité de carbone finalement stockée est incertaine. Divers programmes de carbone sont explorés, avec des coûts de surveillance et des niveaux de précision variables, et des implications contrastées en termes de risque pour l'agriculteur. En particulier, les programmes hybrides basés sur l'accumulation prévue de carbone organique dans le sol, mais incluant une décote pour incertitude, sont examinés. Il est démontré que les incitations à participer à un programme basé sur les résultats peuvent diminuer avec l'augmentation des prix du carbone, et que les programmes hybrides peuvent favoriser l'adoption par les agriculteur
Circular Belief Propagation for Approximate Probabilistic Inference
No full textBelief Propagation (BP) is a simple probabilistic inference algorithm, consisting of passing messages between nodes of a graph representing a probability distribution. Its analogy with a neural network suggests that it could have far-ranging applications for neuroscience and artificial intelligence. Unfortunately, it is only exact when applied to cycle-free graphs, which restricts the potential of the algorithm. In this paper, we propose Circular Belief Propagation (CBP), an extension of BP which limits the detrimental effects of message reverberation caused by cycles by learning to detect and cancel spurious correlations and belief amplifications. We show in numerical experiments involving binary probabilistic graphs that CBP far outperforms BP and reaches good performance compared to that of previously proposed algorithms
A precessing jet from a supermassive black hole: multi-wavelength observations of S5 1044+71
No full textInternational audienceThe bright gamma-ray blazar S5 1044+71 has been identified as showing very significant quasi-periodic oscillations in the Fermi-LAT data in recent studies, with a periodicity of about 3 years. With the completion of a new gamma-ray cycle, we aim to revisit the periodicity in Fermi-LAT data, and analyze all available multi-wavelength (MWL) data to search for possible correlations and time-lags. These observations will be used to test for the compatibility of the observed periodicity with a precessing jet from the supermassive black hole. We analyze data from Fermi-LAT, NuSTAR, Swift, AstroSat, ASAS-SN, ZTF, Pan-STARRS, and NEOWISE. In addition we present an analysis from historical observations from Palomar and Pulkovo. Single-band spectral variability, MWL correlations, and cross-correlations are computed. We then model the Fermi-LAT light curve with a precessing jet model, providing constraints on the geometry of the system and providing the evolution of the Doppler factor with time. The latter is used as input for MWL fitting of the spectral energy distribution. We confirm previous claims on the existence of a periodic gamma-ray signal. We detect significant spectral variability in gamma-ray, X-rays, and optical/UV data. We detect significant correlation between low-energy (infrared/optical/ultraviolet) data and gamma-rays, with a correlation index of about 1; the correlation between X-rays and gamma-ray is milder, with a correlation index of about 0.3. We do not detect any significant time-lag between bands. The Fermi-LAT light curve is successfully fit by a precessing jet model. The fit to the spectral energy distributions indicate that S5 1044+71 is a typical blazar, in which the gamma-ray emission is located beyond the broad-line region. All MWL observations we present in this work are consistent with the existence of a precessing relativistic jet from the supermassive black hole
Geographic variation in floral scent reinforces local pollinator attraction in the fig–fig wasp mutualism
No full textInternational audienceBackgroundVolatile organic compounds (VOCs) emitted during floral receptivity are crucial for attracting pollinators, especially in brood-site pollination systems. Geographic variation in floral scent can alter host recognition cues, potentially shaping pollinator behavior in obligate mutualisms such as the fig–fig wasp system. Understanding whether and how such variation affects pollinator responses is essential for assessing the stability of these interactions. Here, we investigated geographic variation in floral scent and pollinator responses in Ficus hispida, a dioecious species widely distributed in tropical Asia.Using dynamic headspace sampling and GC-MS, we characterized receptive fig VOCs from populations in South China, Southwest China, and South Thailand. Behavioral assays tested the responses of Ceratosolen marchali wasps from the South China Botanical Garden (SCBG) and Xishuangbanna Tropical Botanical Garden (XTBG) to local versus non-local fig odors.ResultsScent profiles differed significantly among regions, forming three distinct clusters. Although C. marchali was present at both sites, Y-tube experiments revealed that wasps responded only to odors from their local population.ConclusionsThis local scent specificity may reinforce population-level mutualisms and restrict long-distance pollinator movement. While such divergence could promote reproductive isolation among closely related wasp lineages, the mechanisms allowing cryptic species to coexist on the same host remain unclear. Overall, our results highlight the key role of chemical cues in shaping plant–pollinator interactions across different populations
Coastal occupation and relative sea-level changes during Martinique's Early Ceramic Period: Reassessment of the impact of Holocene marine transgression in a supposed tectonically stable zone
No full textInternational audienceWhile the uniformity of settlement dynamics at Martinique's Early Ceramic sites is beyond dispute, it must be acknowledged that today's North Atlantic coastlines of the island, characterized by subvertical cliffs and pebble beaches, are poorly suited for canoe landing and other coastal activities. Yet, from both cultural and economic perspectives, these inherently maritime populations remain intrinsically connected to the coast and the sea. Thus, on an island offering many other types of environments, the choice of these early agro-ceramicist groups raises questions. This article aims to challenge this perception, based on the current morphology of the coastline, by reconstructing the evolution of the coastline over the last two millennia, particularly in regard to reassessing the impact of Holocene marine transgression. This is also an opportunity to examine the archaeological potential of the intertidal zone of Martinique