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Coupler les données satellitaires aux données de terrain pour comprendre les dynamiques des socio-hydrosystèmes à différents niveaux d'organisation
No full textNote scientifique du PEPR OneWate
Latitude affects continental acidity in the Smithian–Spathian boundary biotic crisis
No full textInternational audienceThe extent to which continental acidity during the Early Triassic varied with latitude remains insufficiently constrained, despite its relevance for understanding environmental stress and biotic recovery patterns across the Smithian–Spathian boundary (SSB). We examined the abundance, textures and compositions of strontium-rich hydrated aluminium phosphate–sulphate (APS) minerals in 179 continental samples spanning tropical to high paleolatitudes in both hemispheres. APS minerals display broadly comparable early-diagenetic features across sections, indicating formation shortly after deposition under acidic meteoric conditions. Their distribution suggests a latitudinal trend: APS contents commonly exceed 0.1 vol.% in equatorial western peri-Tethyan basins, where faunal and floral records are sparse during the SSB, whereas concentrations decrease towards higher latitudes and are rare beyond ∼40° in both hemispheres. This pattern does not appear to correlate with lithological or textural variability and may reflect spatial differences in the intensity or duration of acidification linked to Siberian Traps volcanism. Equatorial basins thus likely experienced more prolonged or recurrent acidic episodes, whereas higher-latitude areas may have been subject to comparatively attenuated effects, potentially contributing to earlier ecological recovery. These results provide a useful framework for evaluating continental acidification and its environmental implications during the interval following the end-Permian mass extinction (EPME)
Evidence for subglacial flooding in labyrinthine channels on Devon Island, Nunavut, Canada
No full textAbstract. Subglacial drainage systems route glacial meltwater to the ice margin either via efficient, channelized systems or inefficient, distributed systems. The interplay between channelized and distributed drainage systems varies spatially and temporally, governed by meltwater supply and abundance, bed roughness and topography, ice sliding velocity, and ice driving stress. Subglacial channel formation and evolution are therefore affected by variability in meltwater supply to subglacial conduits, and these changes may be recorded in the geomorphology of these channels. The formation of subglacial bedrock channels is attributed to higher energy and/or higher magnitude discharge events, such as the episodic release of meltwater in the form of either subglacial or proglacial floods, in comparison to the energy or discharge required to excavate channels in soft sediment. Common features of landscapes modified by meltwater floods include anastomosing channels and multiple erosive surfaces, wherein the pre-existing drainage system is inundated, resulting in the incision of new channels that reconnect downstream. Devon Island in the Canadian Arctic Archipelago was covered by the thin (<1000 m), cold-to-polythermal based Innuitian Ice Sheet over the course of at least three glacial expansions during the last glacial cycle. Despite this, there is a conspicuous lack of typical glacial landforms, and instead, the inland plateau region of the island is incised by ubiquitous subglacial and lateral meltwater channels. Some sets of bedrock subglacial channels on Devon Island bear a striking resemblance to the morphology of The Labyrinth in Antarctica, which formed by the episodic drainage of a subglacial lake. The characteristics, topology, and morphology of these channels, referred to as 'Labyrinthine channels' hereafter, together with two subglacial channel networks make the focus of this study. We argue that, within both labyrinthine and other subglacial channel networks on Devon Island, the presence of distinct erosional surfaces, anastomosing channels, and profile slope breaks imply formation by short-lived locally intense episodes of erosion. The presence of well-defined erosional surfaces suggests floods progressively incised into lower elevations where meltwater was captured by pre-existing or incipient channels. Moreover, steep contacts between erosional surfaces, termed here as "slope breaks", are similar to fluvial knickpoints and hanging valleys found in other notable landscapes caused by flooding, such as the Channeled Scablands, possibly indicating channel headward erosion in response to pulses of intense erosion. Overall, we suggest that the presence of discrete erosional surfaces implies multiple flooding events, and that changing flow conditions during these events are evidenced by slope breaks. Multiple erosional surfaces, scabland-type landscapes, anastomosing bedrock channels, and hanging valleys with steep slope breaks are not consistent with ice marginal melt, demanding large discharge conditions and pulses of activity, and pointing at subglacial rather than marginal or proglacial environments of formation. This work aids in enhancing the current understanding of the role and dynamics of meltwater drainage systems operating under the cold-to-polythermal based Innuitian Ice Sheet, perhaps shedding light into its retreat dynamics, and bolstering the interpretation of glacial dynamics on Devon Island
LivingBench: an IoT/Edge Platform Benchmark Based on an Environmental Observation Use-Case
No full textInternational audienceIn recent years, a number of edge computing platforms have been proposed to process data produced by IoT sensors. Performing computation close to the sources of data allows faster insight and greater reliability at a lower cost compared to traditional cloud-based deployments. However, designers of IoT/edge platforms face difficult issues. In particular, exercising and testing a new platform in conditions that approach a real deployment requires a sufficient number of standard benchmarking systems capable of generating realistic workloads. In this paper, we propose LivingBench, a benchmarking tool with the capability of incorporating real or synthetic workload injection, developed to exercise edge computing systems. LivingBench integrates a real-world data trace captured in an environmental observatory, together with a collection of actual applications designed for processing these data, and a load injector tool capable of replaying a (possibly pre-processed) trace to benchmark an MQTT-based edge system. We describe the architecture of LivingBench and show how it may be used to evaluate the maximum data processing capacity of an edge system under test
Extremely UV-bright starbursts at the end of cosmic reionization
No full textInternational audienceWe present a study of 27 very UV-bright (-22.010, suggesting a shared evolutionary pathway.[Abridged
Uncovering the population of compact binary mergers and their formation pathways with gravitational waves through the Einstein Telescope
No full textInternational audienceGround-based gravitational-wave (GW) observatories have transformed our view of compact-object mergers, yet their reach still limits a comprehensive reconstruction of the processes that generate these systems. Only next-generation observatories, with order-of-magnitude improvements in sensitivity and access to lower frequencies, will be capable of radically extending this detection horizon. GW observations will make it possible to detect the complete population of binary black hole (BBH) mergers out to redshifts of . This capability will deliver an unprecedented map of merger events across cosmic time and enable precise reconstruction of their mass and spin distributions, while for several thousand events the signal-to-noise ratio will surpass 100, enabling precision physics of BHs and neutron stars (NSs). The access to lower frequencies will also open the intermediate-mass window, detecting systems of order , potentially in coordination with multi-band observations from LISA. At higher redshifts, where Population III stars have so far remained beyond reach - even for the James Webb Space Telescope - GW observations by next-generation detectors will routinely provide observations of BH mergers thought to originate from these primordial stellar populations. Such measurements are expected to play a central role in clarifying the early assembly of supermassive black holes. A single detection of a binary BH system at , or of a compact object with sub-solar mass and no tidal deformability, would constitute strong evidence for the existence of primordial black holes. Such a discovery would have profound consequences for our understanding of dark matter and the early Universe. Ultimately, the GW observations will become revolutionary for identifying the physical channels responsible for compact binary formation
Experimental and numerical investigation of the impact force generated by cylindrical ice water pellets
No full textInternational audienceThis study focuses on the force-time response of cylindrical water ice specimens subjected to impact loadings. Spherical specimens are traditionally used to characterize the impact behavior of water ice. However, they cannot be used to study the geometric effects induced by a cylindrical shape. Impact tests were carried out on a Hopkinson bar at 30 m.s -1 . These tests have demonstrated the importance of the impact angle in terms of both the increase in the load and the peak force at impact. Contrarily to what was observed for tensile spalling test, porosity has no noticeable impact on the maximum peak force measured here. The importance of the impact angle is illustrated by comparing the mechanical response of ice spheres with pellet cylinders for equivalent kinetic energies and temperatures
“No land’s land? ” Squatting informality and governing the ungoverned in Beirut’s southern peripheries
No full textInternational audienceIn a neighborhood where property titles are as absent as garbage collection and stormwater drains, squatting isn't resistance—it’s the default condition of urban life. This communication examines Hay el Sellom, an informal settlement on the southern edge of Beirut, where occupation is not a political choice but a socio-urban outcome of decades of systemic neglect. Built on squatted agricultural land since the 1970s, the district embodies a striking paradox: a vacuum of state services coexists with dense informal governance by politico-sectarian networks. Institutions are largely absent—except during elections. In the meantime, the garbage piles up, the floodwaters rise, and residents adapt. And adapt. And adapt again.Drawing on ethnographic fieldwork conducted between 2021 and 2024—including semi-structured interviews, transect walks, participatory mapping, and direct observation—this communication explores how residents navigate chronic flood risk in a context where legal status, infrastructure, and authority are all in flux. These “squatters” may not claim political intent, but their daily improvisations—homemade drains, ad-hoc sandbag systems, negotiated access to aid—constitute micro-political acts that shape space, survival, and power.Rather than distinguish “squats of necessity” from “political squats,” I argue for recognizing the infrapolitical practices (Scott, 1985; Simone, 2008) that structure everyday life in such environments. In Hay el Sellom, agency is not heroic, but partial, situated, and tactical. It both sustains informality and unsettles dominant narratives of urban order. The selective formalization of neighboring zones, often in exchange for political loyalty, further reveals how the state governs by fragmentation—tolerating or repressing occupation along sectarian and electoral lines (Fawaz, 2016; Roy, 2011).In this “unplanned city within the planned,” squatting is not a temporary act—it is a temporal strategy, sustained through continuous adaptation, negotiation, and endurance. This case invites us to rethink squatting beyond legal frameworks and militant postures. It calls for an expanded, decolonized vocabulary of urban practice—one that accounts for the blurred lines between survival and politics, and recognizes occupation not just as protest, but as the infrastructure of everyday life. And if the state won’t provide drainage, planning, or recognition, then people build their own kind of infrastructure—both material and social. It may not be legal, but it holds up better than most official plans. At least until the next flood
The BIOMASP+ project on biosphere-atmosphere exchanges and their role in air pollution in the subtropical megacity of São Paulo: motivations, methods and preliminary observations
No full textInternational audienceAir pollution, especially in urban areas, is the result of a complex mixture of natural and anthropogenic emissions and their atmospheric processing. It causes millions of premature deaths worldwide and affects plant metabolism, which in turn alters the emissions of Biogenic Volatile Organic Compound (BVOCs) by plants. By taking the subtropical Metropolitan Area of São Paulo (MASP) as a natural laboratory, the BIOMASP+ project (BIOsphere-atmosphere interactions in the Metropolitan Area of São Paulo - plus) a ims to evaluate the interplay between the biosphere and secondary pollution (ozone and SOA formation and aging). The Brazilian Atlantic Forest (Mata Atlântica) is the target ecosystem as the fifth biodiversity hotspot in the world. Here we present the scientific motivations of the project, its methodology and the preliminary observations from the Special Observation Periods of year 2023 (SOP1, 2, 3 and 4). BIOMASP+ is (i) integrative, by combining in-situ/remote/laboratory observations andmodeling, (ii) multidisciplinary, addressing micrometeorology, urban climate, atmospheric chemistry and biology. The project involves multiple nested scales: from leaf to above-canopy levels, from very short time (microseconds) to multi-year scale, from few millimeters (turbulence scale) to synoptic scale. In particular, the experimental effort relies on the implementation of two contrasting supersites (primary forest and urban forest) with a 30-m and 20-m flux towers, respectively, and a variety of state-of-the-art instruments. Ambient observations and the quantification of BVOC emissions have highlighted the complex interactions between meteorology, atmospheric composition of pollution, biogenic emissions of representative remnants of the Atlantic Forest and anthropogenic emissions
Beyond single nanomaterial exposure: investigating the fate of a TiO 2 and CeO 2 nanomaterial mixture in freshwater mesocosms
No full textInternational audienceAssessing the environmental risks of emerging contaminants related to new technologies remains a major challenge due to the diversity of pollutants, their complex interactions, and the limitations of conventional testing frameworks. Among these contaminants, engineered nanomaterials (ENMs) stand out for their unique surface reactivities and transformation pathways, which can significantly alter their behavior and that of co-occurring pollutants. Although many studies have addressed the toxicity and fate of individual ENMs, real-world scenarios often involve complex mixtures, whose combined effects are less investigated. This study addresses this gap by investigating the fate, behavior, and ecological impacts of a mixture of two representative metal oxide ENMs i.e. an industrial TiO2 and a combustion-derived CeO2. This study shows that under environmentally relevant conditions using freshwater mesocosms, these two ENMs undergo primary hetero-aggregation. Co-exposure of the freshwater snail Planorbarius corneus revealed that ENM aggregates (homo- or primary hetero-aggregates) interact with egg layings, potentially affecting early developmental stages, while slight but measurable uptakes were also observed in co-exposed adult snails. Importantly, no quenching of reactive oxygen species generated by the photocatalytic TiO2 was detected in the presence of CeO2, suggesting that the combusted CeO2 does not mitigate potentially TiO2-induced phototoxicity. These findings underscore the importance of considering ENM mixtures in environmental risk assessments and the relevance of mesocosm experiments to capture realistic exposure scenarios. Future studies should prioritize investigating how unique surface reactivities and transformation mechanisms of ENM mixtures shape their ecological impacts throughout their life cycles