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203706 research outputs found
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Radio Morphing: Fast computation of inclined air shower radio emission
No full textInternational audienceThe preparation of next-generation large-scale radio experiments requires running a fast and efficient number of simulations to explore multiple detector configurations over vast areas and develop novel methods for the reconstruction of air shower parameters. While Monte Carlo simulations are accurate and reliable tools, they are too computationally expensive to explore the full parameter space of these new detectors within a reasonable timescale. We introduce a new version of Radio Morphing, a semi-analytical tool designed to simulate the radio emission of any cosmic-ray induced air shower with zenith angle , at any desired antenna position, from the simulation data of a few reference showers at given positions. We present the latest performances of Radio Morphing which now provides simulation of air shower radio signals with average relative differences on the peak amplitude below on raw traces, below with a trigger threshold, below in the band, and even below in the band. These results are combined with a computation time reduced by more than four orders of magnitude, compared to standard Monte Carlo simulations
Decoupling surface stiffness from surface chemistry: Impact on bacterial adhesion and retention under shear conditions
No full textInternational audienceUnderstanding how substrate mechanics influence bacterial adhesion and retention is essential for controlling biofilm formation on synthetic materials. Studies on soft polymers such as PDMS are often confounded by uncontrolled variations in surface chemistry and topography. In this work, a PS-PIB bilayer system was designed to decouple surface chemistry from mechanics, enabling independent control of stiffness while maintaining constant surface properties. Static adhesion assays with Pseudomonas aeruginosa PAO1 showed that initial attachment was insensitive to substrate modulus when surface chemistry and roughness were held constant. In contrast, retention under shear flow decreased with increasing stiffness and correlated more closely with the work of separation obtained from nanoindentation experiments. This parameter, which integrates both adhesive and dissipative contributions, is introduced as an empirical descriptor of interfacial mechanical resistance. Retention data were described by a power-law model consistent with stochastic frameworks of multivalent adhesion, reflecting population heterogeneity in the number and strength of adhesive contacts. Altogether, these findings suggest that viscoelastic dissipation is a key factor influencing P. aeruginosa PAO1 detachment under flow and highlight the need for future studies using bacterial mutants and diverse species to assess the generality of this correlation across different adhesion strategies
Evaluation of annual maximum snow depth data estimation from the European-wide reanalysis C3S MTMSI (Copernicus Climate Change Service – Mountain Tourism Meteorological and Snow Indicators) against in-situ observations
No full textInternational audienceAbstract. Large snow load events are a major hazard for both human societies, in particular buildings and transport safety, and natural ecosystems. National and European frameworks provide guidelines and standards in order to take into account extreme snow load hazard in infrastructure design. However, there is a lack of reference data for their implementation. This is even more challenging in the context of climate change, which modifies the frequency and intensity of major snow load events. In the context of the Framework Partnership Agreement on Copernicus User Uptake, we have developed a pan-European extreme value analysis of annual snow load maxima based on the Mountain Tourism Meteorological and Snow Indicators (MTMSI) dataset available from the Copernicus Climate Change Service. This dataset includes reanalysis data for the period 1962–2015, based on the UERRA (Uncertainties in Ensembles of Regional Reanalyses) reanalysis and snow cover simulations, and past and future climate projections based on regional climate simulations for the period 1951–2100. Here, we describe the evaluation of the MTMSI reanalysis component in terms of annual snow depth maxima against multiple in-situ observation datasets. Results are provided at the NUTS-3 (Nomenclature des unités territoriales statistiques) scale used in MTMSI, for multiple elevations over a large area stretching from the European Alps to the Scandinavian countries. For 75 % of the comparisons between observed and simulated snow depth maxima, we report absolute bias scores between −0.23 and 0.15 m, correlations above 0.59, and a Kling–Gupta Efficiency metric above 0.29. We identify some areas where MTMSI does not adequately portray in-situ observations of snow depth maxima, located in the Alps and coastal areas of the Netherlands, Norway, Sweden, and Croatia. This study thus provides background information for assessing the relevance of this pan-European dataset in terms of annual snow depth maxima, relevant for annual snow mass and snow load maxima based on complementary information derived from snow cover model output. The MTMSI annual maximum snow depth reanalysis dataset is available through the following link: https://doi.org/10.5281/zenodo.15181401 (Kamir et al., 2025)
Du serment doctoral d'intégrité scientifique à un serment personnel : un atelier d'écriture et de réflexion sur la responsabilité et le rôle des scientifiques dans la société
No full textNous présentons un atelier de réflexion sur le serment doctoral d’intégrité scientifique et d’écriture d’un serment personnel, destiné aux doctorantes et doctorants, et plus généralement au personnel de la recherche. L’atelier est proposé depuis 2025 comme formation à l’éthique de la recherche dans quelques écoles doctorales en France. Avec un dispositif original, il permet d’examiner plusieurs aspects de la pratique et des enjeux sociaux-environnementaux de le Recherche : la responsabilité des scientifiques, l’engagement, le rôle des sciences dans l’anthropocène, la place de l’éthique et de l’intégrité dans la pratique du doctorat et des sciences en général
A comprehensive study of Surface Water and Ocean Topography (SWOT) Pixel Cloud data for flood extent extraction
No full textInternational audienceCurrent disaster and emergency management services produce flood maps within hours using satellite data. To handle large-scale events efficiently, a reliable automated method is needed to generate an initial flood extent map, which can then be refined manually.Launched in December 2022, the Surface Water and Ocean Topography (SWOT) satellite, equipped with the Ka-band Radar Interferometer (KaRIn), provides high-resolution radar observations used here for flood detection. While not initially designed for detailed flood mapping in vegetated or urban regions, the performance of SWOT’s Pixel Cloud products was assessed during four major flood events in Greece, France, Brazil, and the USA. Each event is paired with Sentinel-1 or Sentinel-2 imagery within a 3-hour time frame, providing a valuable opportunity to compare and evaluate SWOT’s flood detection capabilities.Three radar variables of the Pixel Cloud products are studied for extracting flood extents: , coherent power, and interferometric coherence — which is computed from the two complex interferograms. They are compared to the built-in classification and flood masks computed from Sentinel-1/2. The study demonstrates the capabilities of the SWOT satellite in detecting flooded vegetation, flooded urban areas, and even regions with high snow cover. However, limitations are observed: (1) when high soil moisture is observed, causing signal saturation, (2) SWOT can be sensitive to the incidence angle, both of which lead to less reliable flood extent estimation. These findings highlight the potential of SWOT satellite for improving global flood mapping, as well as the need for further exploration to address current limitations and enhance flood monitoring capabilities in the near future
Electromagnetic phenomena associated with dust particle dynamics in a simulated Martian atmosphere: an experimental study
No full textInternational audienceElectromagnetic phenomena associated with dust particle collisions contribute to the local electrostatic processes within Martian dust storms, impacting surface interactions and posing potential risks to spacecraft and instruments. This study investigates the generation and characteristics of electromagnetic discharges under controlled laboratory conditions designed to approximate key aspects of the Martian atmosphere. Experiments were conducted in a vacuum chamber, replicating Martian atmospheric conditions with CO2 at low pressure. A 3D-printed dust chamber was used to create dust vortices with several materials including sand particles, and Martian regolith analogs of varying particle sizes. Electromagnetic signals generated during dust collisions were measured using the Dust Complex module developed for the ExoMars-2022 landing mission. Results of the laboratory experiments demonstrate distinct discharge characteristics across different materials, influenced by particle size, composition, and morphology. Signals exhibited variations in amplitude, frequency, and waveform, reflecting the complex interactions between dust particles in a CO2 environment under low-pressure conditions. Comparative analysis with prior studies under earth conditions highlights the role of the Martian atmosphere in enhancing charge transfer processes. These findings provide new insights into the electrostatic environment of Martian dust storms and contribute to understanding electromagnetic interference risks for future exploration missions
Mercury concentrations, habitat and trophic position of Antimora rostrata and Macrourus holotrachys from South Georgia (Southern Ocean)
No full textInternational audienceMercury (Hg) is a neurotoxic element that can harm marine wildlife. Hg can reach the Southern Ocean through atmospheric and oceanic currents. However, data on Hg in Southern Ocean deep-sea fishes remain scarce. Our study assessed the influence of biological and ecological factors on Hg bioaccumulation in two deep-sea species, blue antimora (Antimora rostrata) and bigeye grenadier (Macrourus holotrachys), inhabiting the South Georgia region. Specifically, we aimed to: 1) analyse the habitat and trophic position of both species; 2) understand how Hg concentrations vary between tissues (muscle, brain, liver and gills); 3) evaluate how biological (length and weight) and ecological characteristics (trophic position (δ15N) and habitat (δ13C)) influence Hg concentrations. Muscle tissue had the highest Hg concentrations in both species, while the liver in A. rostrata and gills in M. holotrachys had the lowest. Overall, A. rostrata exhibited lower Hg concentrations (51.0 ± 9.0) than M. holotrachys (62.0 ± 11.0). No significant relationships were found between Hg concentrations and length, weight nor trophic position of A. rostrata. In contrast, M. holotrachys showed a positive relationship between Hg concentrations and habitat in all tissues, whereas for length and weight this positive relationship was observed in most tissues except the brain. A. rostrata is a pelagic feeder, whereas M. holotrachys mostly feeds near the sea bottom, highlighting how feeding strategy and habitat influence Hg bioaccumulation. It also reveals unexpectedpatterns of Hg distribution among tissues, particularly in the brain, where M. holotrachys exhibited one of thehighest Hg concentrations
Short note: on the determination of the relaxation time distributions using Bézier curves
No full textInternational audienceFor the interpretation of spectral induced polarization spectra, the determination of the relaxation time distributions (RTD) can be useful, for instance to extract the grain size distribution. However, this is an ill-posed problem, and retrieving the RTD often requires regularization during the inversion process. In this note, we use Bézier curves and simulated annealing to determine the RTD. The procedure that does not require any regularization nor smoothing, by reducing the number of parameters thanks to Bézier curves which are intrinsically continuous and infinitely derivable. We successfully applied our methodology to three examples (Cole–Cole model, Davidson–Cole model, and an experimental spectrum), demonstrating its interest and efficiency
A Framework for Minimizing the Impact of Wet Antenna Attenuation on Rainfall Estimates Provided by Commercial Microwave Links
No full textInternational audienceThe compensation of the extra attenuation introduced by wet antennas is crucial to get reliable rainfall intensity estimates from the data collected by commercial microwave links (CMLs). This study reviews the available wet antenna attenuation (WAA) models and proposes a new framework for calibrating WAA model parameters, based on rain gauge measurements (assumed as ground truth). The framework has been applied to the data measured by 86 CMLs located in the Seveso River basin (Northern Italy) during 44 rainy days in 2019-2020. As most WAA models are basically equivalent in spite of different formulations, we selected only a subset, including the Schleiss-Rieckerman-Berne model (SRB) and the Valtr-Fencl-Bareš (VFB) model, the latter in the versions with the original parameter values and with the parameters calibrated over our CML data (VFBm). We found that WAA increases with rainfall intensity, as predicted by the VFB model, and it is weakly dependent on link frequency. We derived two sets of optimum WAA model parameters for the Ka-band (17-23 GHz) and the Q-band (37-43 GHz), respectively. WAA values are up to 4 dB at heavy rainfall intensities (50 mm/h) in the Q-band. The VFBm model performs better than VFB and outperforms SRB, when assessed over the entire set of CML data and over different classes of CMLs (based on distance to the neighbor rain gauge, frequency, and path length) or, again, over different classes of rainfall intensity.</div
