226280 research outputs found
Sort by
Hydration mechanisms in Roman seawater concrete: Archaeological analogue for validation of long-term ageing reactive transport model
No full textInternational audienceCement-based materials are considered for sealing plugs in deep geological disposal of radioactive waste. Ensuring their long-term durability is critical for safety over millennia. The Roman Concrete (RoC) project uses ancient Roman underwater concretes as analogues to validate reactive transport models for long-term ageing.This study focuses on hydration mechanisms in Roman concrete made with Phlegrean pozzolan, slaked lime, and seawater. Various techniques (XRD, SEM-EDS, NMR, nanoindentation, microtomography, ICP-OES, ion chromatography) were used to characterize hydration products. Casting underwater led to aragonite and brucite layers with a 60 GPa Young's modulus, protecting the concrete from further degradation. In the core, pozzolanicreactions produce C-(A)-S-H phases (Ca/Si = 1.2; Al/Si = 0.2) with a modulus of 12 GPa. HYTEC modeling confirmed the mechanism: incongruent pozzolan dissolution releases ions (K+, SiO₄ 4− , Al3+, Na+), promoting C-(A)-S-H formation and portlandite consumption
Décolonisation et nickel en Nouvelle-Calédonie. Nationaliser plutôt qu’écologiser durant les Accords de 1988 et 1998
No full textInternational audienc
From Compassionate Use Toward High-Level Evidence for Radiopharmaceutical Therapy in Recurrent Meningioma: The LUMEN-1 and MOMENTUM-1 Trials
No full textInternational audienc
Conserving and regenerating the High Atlas cultural landscapes: gendered perspectives from the local Amazigh communities
No full textInternational audienceLocal communities play a vital role in conserving biocultural diversity; yet their priorities are seldom considered when designing sustainable measures and actions, particularly in remote areas. These processes are frequently developed from urban perspectives, focusing on regional or national scales, and local social dynamics are often overlooked. In this paper, we explore community-based conservation recommendations to develop a strategy for the cultural landscapes of the High Atlas, integrating insights from both local Amazigh voices and academic perspectives. We conducted focus groups with three representative communities in the High Atlas, involving 92 participants. We first documented the environmental changes that both women and men perceived separately. Next, community members provided recommendations for biocultural diversity conservation, which were further discussed among all participants. The participants' perceived changes and the proposed recommendations varied significantly between villages, even over short distances. These variations emerged from each village's primary livelihood and the types of ecosystems on which they depend. Both men and women noted numerous changes in agriculture, pastoralism, and the economy, and suggested actions to address the negative impacts. Women highlighted positive developments in medicinal practices; however, they also pointed out infrastructural deficiencies that hinder human well-being. These discussions served as the grounds for preparing community action plans that guided biocultural conservation action with these populations. Grounding rural development planning, programming, and monitoring in gendered local perceptions and aspirations is crucial for the resilience and adaptation of these landscapes, the people and other non-human living beings inhabiting them
Dust deposition on plasma-facing substrates extracted from the WEST Tokamak
No full textInternational audienceDust particles deposited during the first phase of operation of the WEST tokamak were collected and analyzed from substrates positioned at four distinct poloidal locations along the inner wall. Among various particle types composed of materials present in the vacuum vessel, previously unreported tungsten molten splashes exhibiting highly distinctive "stethoscope-like" morphologies were discovered. These unusual tungsten particles were found in large numbers exclusively on substrates located closest to the lower divertor. They display a well-defined log-normal size distribution, with average lengths ranging from 0.75 to 1.5 µm, and a clear angular alignment pointing predominantly away from the divertor. This directional distribution provides compelling evidence that they were ejected from the lower divertor region. Additionally, more conventional tungsten spheroidal particles were identified across all four poloidal positions. These spheroids were most abundant near the divertor and exhibited progressively more elongated shapes and less distinct alignment patterns with increasing distance, suggesting a common origin but different transport histories. Their size distributions are also lognormal, with average diameters between 100 and 200 nm. The characteristics of both particle types (distribution, size scaling, and directionality) suggest a common origin in molten tungsten droplets expelled from the lower divertor, most likely as a result of arcing events.</div
Coarse-grained physics-based modelling for tape casting of fuel-electrode supports in Solid Oxide Cells
No full textInternational audienceOptimising the tape casting process for fabricating NiO/YSZ cermet-based fuel-electrode supports in Solid Oxide Cells remains a resource-intensive challenge. Improving the green tape properties are often reliant on trial-and-error procedures or proprietary knowledge that is inaccessible to the broader scientific community. In this work, we use computational simulations as a powerful tool to link the manufacturing process to the final microstructure of the tape. A novel three-dimensional physics-based model is presented to simulate the slip preparation and the homogeneous drying process of the tape casting producing the fuel electrode support in Solid Oxide Cells. Our model is well-calibrated to experimental data, and we investigate the dried microstructure of the simulated support
Understory plant indicator values poorly perform at monitoring temporal changes in French forest soil chemical properties
No full textInternational audienceUnderstory plant communities are widely used to infer soil conditions through species indicator values (IVs), scores reflecting species’ ecological preferences for factors such as soil acidity, moisture, or nutrient levels. While their reliability to describe soil conditions along spatial gradients is well established, their ability to capture temporal changes in soil chemistry remains largely untested at both temporal and geographical scales. We combined 26 years of vegetation monitoring with two French national soil surveys (1993–1997; 2007–2012) across 102 permanent forest plots to assess the reliability of community soil indices (CSIs) as bioindicators of soil pH, carbon-to-nitrogen ratio (C/N), and extractable phosphorus. CSIs were computed by averaging species IVs for each plot and survey. Temporal dynamics of measured soil properties and CSIs were analyzed using mixed-effects models at the national scale, while local trends were estimated separately for each plot to directly compare measured and vegetation-inferred changes. CSIs showed strong spatial correlations with measured pH and C/N, but weaker relationships for phosphorus. In contrast, no significant coupling was found between temporal changes in CSIs and measured soil parameters, with frequent mismatches in both direction and magnitude at the plot level. Measured soil dynamics were mainly driven by initial edaphic conditions and stand age, whereas CSI dynamics responded primarily to canopy openness and anthropogenic disturbances such tree harvesting. These findings confirm the value of IVs for spatial bioindication but highlight their limited sensitivity for detecting long-term soil changes, especially where soil changes remain modest
Detecting the signature of helium reionization through 3HeII 3.46cm line-intensity mapping
No full textInternational audienceHelium reionization is the most recent phase change of the intergalactic medium, yet its timing and main drivers remain uncertain. Among the probes to trace its unfolding, the 3.46 cm hyperfine line of singly-ionized helium opens the study of helium reionization to upcoming radio surveys. We aim to evaluate the detectability of the 3.46,cm signal with radio surveys and the possible constraints it can place on helium reionization, in particular whether it can distinguish between early and late helium reionization scenarios. Moreover, we perform a comprehensive study of the advantages of single-dish vs. interferometric setup. Using hydrodynamical simulations post-processed with radiative transfer, we construct mock data cubes for two models of helium reionization. We compute the power spectrum of the signal and forecast the signal-to-noise ratio for SKA-1 MID, DSA-2000, and a PUMA-like survey, in both observational setups. The two scenarios produce distinct power spectra, but the faintness of the signal, largely caused by weak coupling between the spin temperature and the kinetic temperature in low-density regions of the IGM, combined with high instrumental noise, makes detection very difficult within realistic integration times for current surveys. A PUMA-like survey operating in single-dish mode could, however, detect the 3.46 cm signal with an integrated signal-to-noise ratio of a few in < 1000 h in both scenarios. Distinguishing helium reionization scenarios with 3.46 cm line-intensity mapping therefore remains challenging for current facilities. Our results, however, indicate that next-generation, high-sensitivity surveys with optimized observing strategies, especially when combined with complementary probes of the IGM, could begin to place meaningful constraints on the timing and morphology of helium reionization
Parametric strong lensing model of the galaxy cluster Abell 2390 from Euclid and MUSE observations
No full textInternational audienceWe present a new high precision parametric strong lensing total mass reconstruction of the Euclid Early Release Observations (ERO) galaxy cluster Abell 2390, at redshift z = 0.231. We include in this analysis 35 multiple images from 13 background sources, of which 25 are spectroscopically confirmed thanks to observations from the MUSE, spanning a redshift range from z = 0.535 to z = 4.877. After fully reanalysing the MUSE spectroscopy, we combine it with archival spectroscopic catalogues allowing us to select 65 secure cluster members. This sample is further complemented with 114 photometric member galaxies, identified within the Euclid VIS and NISP imaging down to magnitude H = 23. We also measure the stellar velocity dispersions for 22 cluster members, in order to calibrate the Faber-Jackson relation and hence the scaling relations for the subhalo mass components. We test and compare 11 total mass parametrisations of the galaxy cluster with increasing complexity. To do so, we employ the new parametric strong lensing modelling code Gravity.jl. Our best fit total mass parametrisation is characterised by a single large scale halo, 179 subhalo components, and an external shear term. The reference model yields a mean scatter between the model predicted and observed positions of the multiple images of 0.32 arcseconds. We are able to quantify the systematics arising from our modelling choices by taking advantage of all the different explored total mass parametrisations. When our results are compared with those from other lensing studies, we notice an overall agreement in the reconstructed cluster total mass profile in the outermost strong lensing regime: the discrepancy in the innermost region of the cluster (few kiloparsec from the brightest cluster galaxy, where few or no strong lensing features are observed) could possibly be ascribed to the different data and modelling choices