HAL - La Rochelle Université, Archives Ouvertes
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Du "navire de Libourne" à la "nef de Bordeaux" : Louis XII, les villes et la marine du Ponant (1508-1513)
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Mercury levels in chicks of a long-lived seabird – parental effects and links with growth and survival
No full textInternational audienceEnvironmental mercury levels continue to rise, leading to increased exposure, especially in long-lived species at high trophic positions, such as many seabirds. During breeding, female seabirds can transfer mercury to their eggs, exposing their offspring to its harmful effects. After hatching, dietary exposure may further compound the risk, although excretion pathways exist as well. Despite extensive research, the relative contributions of maternal transfer, dietary exposure, and excretion to mercury dynamics in chicks, as well as its impacts on growth and survival, remain poorly understood. As such, across seven years, we artificially incubated 578 common tern (Sterna hirundo) eggs, and monitored the resulting chicks from hatching to fledging. We assessed total mercury levels in the eggshells, in chick blood and feathers, as well as in the blood of the parents. Chicks found dead were used to study mercury concentrations in brain, gut, kidney, liver and muscle. Mercury levels in organs were highest among chicks that died young, then lower among chicks that died by approximately day 24, suggesting growth dilution and excretion through feather growth, before being higher again among fully-grown chicks that died around fledging. Chick blood mercury levels predicted brain and feather mercury concentrations, but only showed marginal associations with those in other tissues. Maternal mercury levels were a key predictor of chick levels early in development, whereas paternal mercury levels were less consistently linked with those in chicks. Higher mercury levels in eggshells and chick blood were associated with reduced growth, and, in turn, survival. These findings demonstrate that early-life mercury exposure, shaped partly by maternal transfer, varies with chick development and survival. Future research should clarify the causalities linking mercury to chick growth, survival, recruitment and adult fitness to better understand its population-level consequences
Au milieu du réseau, les corps des techniciens
No full textInternational audienceOù installer un instrument de mesure ? C’est à partir de cette question, posée aux experts en charge de surveiller la qualité de l’air que la communication propose de retracer la genèse d’une enquête ethnographique qui s’est déroulée entre 2022 et 2024 en Auvergne Rhône-Alpes et en Martinique. Durant l’équivalent de six mois, j’ai accompagné les experts relevant des différents métiers – techniciens, prévisionnistes, modélisateurs, inventoristes, correspondants territoriaux, etc. – que regroupent les AASQA, dans l’objectif de comprendre les prises dont ils disposent pour décrire les milieux de vie. La communication propose de revenir sur une énigme partagée entre lesexperts et l’ethnographe qui a émergé au grès de conversations, où chacun essayait de comprendre les méthodes de son interlocuteur et d’en tisser des analogies sur les pratiques de l’observation empirique. De ces échanges ressort l’usage par les experts de la notion de représentativité spatiale, à partir de laquelle ils déploient, réorganisent et optimisent les réseaux de stations de mesure depuis les années 1980. La représentativité spatiale est une des réponses apportées par les sciences modernes au principe de réalité auquel est confrontée toute observation empirique : l’agencement dans l’espace et le temps de ce qui est observé et de ce qui observe. Durant les journées d’études, il s’agira de retracer les détours pris par l’enquête et de montrer en quoi la description de ces agencements est une entrée pour rendre compte de modalités du sensible et du travail des techniciens qui régissent le dispositif national de surveillance de la qualité de l’air
A novel parametric spectral technique to solve inverse heat problems for the estimation of wall thermophysical properties
No full textInternational audienceThis study proposes reducing the computational cost of gradient-based method for solving inverse heat conduction problem of the thermal diffusivity estimation. It relies on using a spectral parametric reduced order model to build a solution dependent on spatial and temporal coordinates, as well as on an extra-parameter of the problem, such as the thermal diffusivity. This parametric solution of the direct problem and its sensitivity function is computed off-line significantly lowering the computational cost of the iterative inverse problem algorithm. Synthetic data are used to verify the reliability of the method. Results show its potential for building diagnostics and energy efficiency, offering a reliable tool for characterizing building wall thermal properties
Le Marin, la Carte et l'Ingénieur. La carte nautique et ses usages (1830-1880)
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IDTrust: Deep Identity Document Quality Detection with Bandpass Filtering
No full textInternational audienceThe increasing use of digital technologies and mobile-based registration procedures highlights the vital role of personal identity documents (IDs) in verifying users and safeguarding sensitive information. However, the rise in counterfeit ID production poses a significant challenge, necessitating the development of reliable and efficient automated verification methods. This paper introduces IDTrust, a deep-learning framework for assessing the quality of IDs. IDTrust is a system that enhances the quality of identification documents by using a deep learning-based approach. This method eliminates the need for relying on original document patterns for quality checks and pre-processing steps for alignment. As a result, it offers significant improvements in terms of dataset applicability. By utilizing a bandpass filtering-based method, the system aims to effectively detect and differentiate ID quality. Comprehensive experiments on the MIDV-2020 and L3i-ID datasets identify optimal parameters, significantly improving discrimination performance and effectively distinguishing between original and scanned ID documents
Malcolm Gaskill, The Ruin of All Witches. Life and Death in the New World , Londres, Penguin/Random House, 2022, xxv + 309 p., ISBN 978-0-141-99148-1
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Eco-friendly corrosion inhibition and antioxidant potential of Ficus elastica leaf extract for C1020 carbon steel in acidic medium
No full textInternational audienceEco-friendly corrosion inhibitors provide sustainable, biodegradable, and non-toxic alternatives to synthetic inhibitors, minimizing environmental impact. This study investigates the corrosion inhibition potential of Ficus elastica extract (FEE) for C1020 mild steel in 1M HCl. Antioxidant activity was assessed using ferric reducing antioxidant power (FRAP) and free radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, while phytochemical screening identified key metabolites such as flavonoids, alkaloids, tannins, steroids, terpenes, glycosides, and anthocyanins. Electrochemical techniques, including OCP, potentiodynamic polarization, and EIS, evaluated inhibition efficiency, while FT-IR, UV-Vis spectroscopy, SEM-EDS, optical microscopy, and non-contact white-light optical profilometry (WLI) analyzed the inhibition mechanism. The results show that FEE exhibits strong antioxidant properties (DPPH IC₅₀ = 23.99 μg/mL, FRAP EC₅₀ = 25.67 μg/mL) and achieves 82% inhibition at just 300 ppm, indicating high efficiency at low concentrations. Tafel polarization curves confirm FEE acts as a mixed-type inhibitor, following Langmuir monolayer adsorption. Microstructural analysis further validates its protective barrier effect against corrosion.</div
Human contributions to global soundscapes are less predictable than the acoustic rhythms of wildlife
No full textInternational audienceAcross the world, human (anthropophonic) sounds add to sounds of biological (biophonic) and geophysical (geophonic) origin, with human contributions including both speech and technophony (sounds of technological devices). To characterize society’s contribution to the global soundscapes, we used passive acoustic recorders at 139 sites across 6 continents, sampling both urban green spaces and nearby pristine sites continuously for 3 years in a paired design. Recordings were characterized by bird species richness and by 14 complementary acoustic indices. By relating each index to seasonal, diurnal, climatic and anthropogenic factors, we show here that latitude, time of day and day of year each predict a substantial proportion of variation in key metrics of biophony—whereas anthropophony (speech and traffic) show less predictable patterns. Compared to pristine sites, the soundscape of urban green spaces is more dominated by technophony and less diverse in terms of acoustic energy across frequencies and time steps, with less instances of quiet. We conclude that the global soundscape is formed from a highly predictable rhythm in biophony, with added noise from geophony and anthropophony. At urban sites, animals experience an increasingly noisy background of sound, which poses challenges to efficient communication
