HAL-Université de Bretagne Occidentale
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Dating of Quaternary deposits on the Coast of Brittany (W France) by Optically Stimulated Luminescence and Terrestrial Cosmogenic Nuclides: Preliminary results of the cronBRET Project
No full textNational audienceThe Quaternary record along the Coast of Brittany (W France) is well represented, offering important information about the geomorphological processes that have shaped this coast during this period. However, chronological data using numerical dating methods are very scarce leading to uncertain hypotheses put forward on the basis of correlations and extrapolations. Thanks to the cronBRET Project (MSCA-Bienvenüe Bretagne COFUND 2023) from the Geo-Ocean Lab of the Université de Bretagne Sud and the RenDaL laboratory of Géosciences-Rennes (Univ. Renes), in collaboration with the Cosmogenic Laboratory of the Institute of Geology and Mineralogy of the University of Cologne (Germany) and the Institute of Geology of the University of Coruña (Spain), numerous sedimentary outcrops along the Bretagne Coast are currently dated. For the burial age calculation, the optically stimulated luminescence (OSL) signal of quartz sands included in the sedimentary matrix is analyzed, as well as the concentration of 10Be and 26Al produced in situ, as a consequence of cosmic-ray interaction with quartzite cobbles, by using the isochron method. The first results include those obtained in the Falaisse de La Mine D'Or at Pénestin (SE Brittany), with a lower unit dated at 2.7 My (Plio-Quaternary boundary). The upper unit has been dated by OSL between 410 and 260 ky (Middle Pleistocene). As for the coastal deposits dated in Morbihan (ie, Betahon, Rhuys, Ploemeur), ages between 265 and 125 ky have been obtained. These data will be complemented with the dating of several sedimentary deposits from Brittany's West Coast (Finisterre) and North Coast (Côtes d´Armor) to achieve a comprehensive analysis at regional scale. This study highlights the importance of numerical dating as an essential tool to constrain the formation of coastal sediments within a more accurate paleoclimatic framework and integrate them in the glacioeustatic and neotectonic processes linked to the Glacial-Interglacial cycles of the Quaternary, and more specifically during the last 500,000 years
La correspondance "exceptionnelle/normale" du marin J. E. Odend’halet de son épouse M. Bigot (1914) : une fenêtre sur les normes de féminité du début du XXe siècle
No full textInternational audienc
AntFlie: Frugal Visual Teach and Repeat on Narrow FoV Micro-Drones
No full textWe present AntFlie, an ant-inspired Visual Teachand-Repeat (VT&R) framework demonstrated on a 33-gram, 9-cm MAV equipped with an ultra-low-resolution (24×24 px) camera and narrow 87°field of view (FoV). During a oneshot teach flight along an outbound route, the MAV performs periodic physical scans and uses a local compass based on inertial and optic flow cues to categorize views as left or right relative to the path, storing compact, lateralized visual memories in a Mushroom Body (MB) neural network with a footprint under 4 kB. In the repeat phase, the MAV flies the inbound route by retracing the outbound path, and autonomously lands at its home location using only visual familiarity through direct sensorimotor coupling, rather than map-based reasoning. Offline simulations show that the Route Lateralized (RoLa) algorithm in AntFlie matches the accuracy of a state-of-the-art insect visual compass (ViCo) while running up to 20× faster and supporting narrow FoVs. Real-world indoor experiments further demonstrate 24 autonomous inbound repeats totaling 110 meters of flight, with a 13-cm median lateral error and 34-cm landing precision on average. These results highlight the feasibility of frugal, bio-inspired, vision-only navigation for MAVs operating under strict size, weight, power, and cost (SWaP-C) constraints, inspired by the navigation of Cataglyphis and Melophorus ants
On the risk of fatigue failure of structural elements exposed to bottom wave slamming – Impulse response regime
No full textInternational audienceThis study aims to investigate whether fatigue damage induced by bottom wave slamming can be a failure mode, important to consider when sizing a marine structural element. The body exposed to wave impacts is assumed to have a shape and structural arrangement such that the duration of wave-impact loads is short relative to the structure's vibratory response time. In this dynamical regime, fatigue is found to be a potentially important failure mechanism: accounting for the risk of failure due to fatigue damage may result in design constraints that are significantly more conservative than those based on the risk of ultimate strength exceedance. The role of fatigue damage depends on the elevation of the body. It is predominant for low elevations, for which slamming events are frequent. Since this study aims to provide general insight, the specific details of the body, such as its shape and structural arrangement, are not specified. Instead, a general framework is used for the analysis. The way forward to address a specific case study, possibly including the effects of forward and seakeeping motions, is briefly explained
In situ measurement of trace sulfide concentrations in marine coastal waters using diffusive gradient in thin film passive samplers
No full textInternational audienceThe diffusive gradient in thin film technique (DGT) represents an in situ passive sampling method designed to preconcentrate various compounds, including sulfides, for detection at low concentrations. While DGT applications for sulfides have been studied in freshwater, this research extends its use to marine environments. A detailed methodology is presented for synthesizing, assembling, calibrating, and field-deploying DGT samplers to measure sulfides in the low micromolar range in marine waters. The in-house DGT samplers developed in this study demonstrated improved performance, with more homogeneous binding gels and smaller silver iodide particles (0.51 ± 0.34 µm) compared to commercial alternatives. Grayscale imaging enabled accurate quantification of sulfide accumulation in the gels, confirming the method's reliability for detecting trace-level sulfides in marine environments. Comparative analysis showed in-house and commercial samplers performed similarly in estimating sulfide concentrations. Field deployments along the Peruvian coast revealed significant vertical and spatial sulfide gradients. In the Callao coastal area (July-August 2022), concentrations ranged from 0.03 to 0.45 µM across a 35 m depth profile. In Paracas (March-April 2023), a shallower coastal station, concentrations ranged from 1.17 to 6.46 µM, reflecting increased benthic production. These results highlight the utility of DGT samplers as cost-effective tools for biogeochemical monitoring, enabling studies of the ocean sulfur cycle. The findings emphasize the growing application of DGTs in marine and coastal water column research
Enquête sur les immersions à l’université. Analyse d’un échec et des écueils méthodologiques
No full textInternational audienceCette communication présente un travail d’enquête mené entre septembre 2024 et aout 2025 dans le cadre du PIA Réussite, Information et Orientation (BRIO) lauréat en 2019 de l’appel à projets Dispositifs territoriaux pour l’orientation vers les études supérieures. L'enquête entend saisir l’engagement des lycées dans l’orientation (Draelants, 2012) et l’expérience des élèves (Dubet et Martuccelli, 1996 ; Geuring, 2024) avant, pendant et après les immersions
Influence of light intensity on the toxicity of herbicides, alone or in mixture, to freshwater phytoplankton
No full textInternational audienceLight intensity directly affects phytoplankton and can alter the toxicity of phytotoxic pollutants present in natural water bodies. Light fluctuation in aquatic ecosystems often occurs as a function of water turbidity, water movement, cloud cover, and seasonality. Atrazine and simazine are commonly used herbicides that inhibit photosynthesis, posing significant risks to aquatic primary producers, and may be found simultaneously in aquatic ecosystems. The interactions between light and herbicide mixtures on phytoplankton growth and physiological state are poorly understood. Therefore, we addressed the toxicity of the herbicides, atrazine and simazine (individually and mixed), on the growth and photosynthetic activity of three freshwater phytoplankton under three light intensities. We found that the toxic effects of single and mixed herbicides are species-specific and significantly modulated by light intensity, with synergistic effects observed for herbicide mixtures under high light conditions. Atrazine and simazine (individually and mixed) toxicities on photosynthesis were greater for the three species grown under low light than under very low light. However, high-light adapted strains of M. aeruginosa were less sensitive to single and mixed herbicides than those adapted to low-and very low-light conditions. Under low-and high-light conditions, the photoprotective ability was extremely sensitive to the inhibitory effects of atrazine and simazine, individually and when mixed. Understanding these interactions is important because microalgae form the base of aquatic food webs and their impairment can have cascading effects on ecosystems. These findings underscore the importance of considering multiple environmental stressors in assessing the ecological risks of herbicides, highlighting potential impacts on aquatic primary productivity
Preserved phonological but impaired semantic processing in Williams syndrome: Evidence from a word association judgment task
No full textInternational audienceWilliams syndrome (WS) is a genetic neurodevelopmental disorder affecting intellectual, cognitive, and language development. We re-examined the phonological-semantic imbalance hypothesis by probing phonological and semantic processing abilities within the same task context, in 19 children with WS and 57 typically developing (TD) children. Participants saw pictures pairs, heard their names, and indicated whether the words were related; the words, if related, shared either phonological or semantic features. Using a generalized linear mixed model, results showed that WS children exhibited a stronger preference for phonological associations over semantic associations, compared to TD children, after controlling for general verbal or non-verbal abilities. Both groups showed similar sensitivity to phonological relations, but WS children showed reduced sensitivity to semantic ones. This pattern suggests that WS individuals have a less developed or an atypical semantic network, emphasizing the need for language intervention to focus on semantic levels of processing
HG-TBI (Heat Generation in Traumatic Brain Injury). Association entre génération de chaleur et pronostic neurologique chez les patients cérébrolésés recevant un contrôle ciblé de température : une étude de cohorte rétro et prospective observationnelle
No full textLa thermorégulation est un processus complexe qui implique plusieurs acteurs centraux et périphériques afin d’assurer le maintien de la température interne. L’hypothalamus, après réception d’un signal par voie nerveuse ou humorale, entraîne une cascade de réponse au niveau nerveux, somatique et hormonal entraînant soit la thermogénèse, soit la thermolyse. Observée dans des études animales, l’hypothermie thérapeutique aurait un intérêt physiopathologique de protection neuronale au cours d’une agression cérébrale. Ces résultats restent controversés chez l’Homme, mais bien que des études récentes n’aient pas observé de bénéfice sur le devenir neurologique, elle reste utilisée au cours de le prise en charge de l’arrêt cardiorespiratoire et des traumatisés crâniens. La relation entre production de chaleur et devenir neurologique au cours de l’hypothermie thérapeutique après un arrêt cardiorespiratoire a été étudiée : la plupart des études animales ont observé que plus le délai pour atteindre l’hypothermie était court, meilleur était le devenir neurologique. Chez l’Homme, il a été constaté des résultats plus controversés, voire opposés aux études animales. Les patients qui généraient plus de chaleur, et donc avec un temps plus long de refroidissement, étaient statistiquement associés à un meilleur devenir neurologique. Cette association n’ayant pas été étudiée chez les cérébrolésés (HSA, AVC hémorragique et traumatisés crâniens), l’objectif de cette étude était donc de déterminer si la génération de chaleur au cours de l’hypothermie thérapeutique chez les patients en HTIC réfractaire était associée à un meilleur devenir neurologique. Il s’agit d’une étude monocentrique observationnelle rétro et prospective réalisée au CHU de Brest entre août 2023 et février 2025. Au total, 14 patients ont été inclus dans l’étude. Le critère de jugement principal était le devenir neurologique (GOSE) à 3 mois. Cette étude n’a pas objectivé d’association entre devenir neurologique et génération de chaleur
The Paclitaxel Biosynthesis Pathway Unlocked
No full textInternational audiencePaclitaxel, a natural product produced by yew trees, has become an important drug in the fight against cancer. Although more than 4 decades of research have identified numerous enzymes involved in paclitaxel synthesis, our understanding of this pathway’s architecture remains incomplete, and a few enzymes have yet to be identified. In a new article published in Nature , McClune and colleagues have developed a pipeline of multi-omics approaches to unravel the remaining enzymes performing key steps in the paclitaxel biosynthetic pathway. These findings open up new possibilities for producing this major anticancer drug using innovative biotechnological processes