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Advanced insights into biomass burning aerosols during the 2023 Canadian wildfires from dual-site Raman and fluorescence lidar observations
No full textInternational audienceThis study presents lidar observations of long-range transported biomass burning aerosol (BBA) plumes from the exceptional 2023 Canadian wildfire season, recorded between May and September at the ATOLL observatory (France) and the GPI site (Russia). ATOLL operates a multi-wavelength Raman lidar with 3 polarization channels (355, 532 and 1064 nm) and a single fluorescence channel at 466 nm. GPI uses a fluorescence lidar with 5 broadband fluorescence channels excited by 355 nm. The dual-site dataset combines multi-wavelength elastic scattering and depolarization measurements with fluorescence observations, enabling a comprehensive characterization of BBA properties in the free troposphere (FT) and upper troposphere–lower stratosphere (UTLS). UTLS layers exhibit higher particle depolarization ratios, slightly lower lidar ratios, lower extinction- and backscatter-related Angström exponents, and a redshift in fluorescence spectral peaks. Cross-site comparisons show consistent fluorescence magnitudes and spectral shapes, highlighting the potential of coordinated multi-lidar fluorescence observations. Correlation analysis indicates that depolarization ratio, extinction-related Angström exponent, and fluorescence color ratio are moderately (r2 ≈ 0.61–0.68) correlated with layer altitude, however, this correlation is not sufficient to confirm a solid altitude dependence. It is likely that altitude is an intermediate variable linked to other controlling factors such as injection height of the plume, in-layer temperature and the plume origin. In addition, we observed BBAs showing no clear hygroscopic growth at RH of 90 %–100 % and statistically low RH values in the detected nearly 100 layers, suggesting aged BBAs, which were typically considered as hygroscopic, may have limited water uptake capability
Characterization of the submarine disposal of a Bayer effluent (Gardanne alumina plant, southern France) IV: Consequences of the change in the effluent composition following modifications in the production process from 2016 to 2024
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Probing the Distance Duality Relation with Machine Learning and Recent Data
No full textInternational audienceThe distance duality relation (DDR) relates two independent ways of measuring cosmological distances, namely the angular diameter distance and the luminosity distance. These can be measured with baryon acoustic oscillations (BAO) and Type Ia supernovae (SNe Ia), respectively. Here, we use recent DESI DR1, Pantheon+, SH0ES and DES-SN5YR data to test this fundamental relation. We employ a parametrised approach and also use model-independent Generic Algorithms (GA), which are a machine learning method where functions evolve loosely based on biological evolution. When we use DESI and Pantheon+ data without Cepheid calibration or big bang nucleosynthesis (BBN), there is a violation of the DDR in the parametrised approach. Then, we add high-redshift BBN data and the low-redshift SH0ES Cepheid calibration. This reflects the Hubble tension since both data sets are in tension in the standard cosmological model CDM. In this case, we find a significant violation of the DDR in the parametrised case at . Replacing the Pantheon+ SNe Ia data by DES-SN5YR, we find similar results. For the model-independent approach, we find no deviation in the uncalibrated case and a small deviation with BBN and Cepheids which remains at 1. This shows the importance of considering model-independent approaches for the DDR
Opportunities from energy-loss near-edge fine structure analysis to track chemical and structural damage in zircon
No full textInternational audienceZircon (ZrSiO4) is the oldest-known mineral of Earth and an ubiquitous silicate in geochronology. More specifically, the accumulation of alpha decay damage in zircon over time significantly affects its physical and chemical properties, and can lead to a disturbance of the ages measured in this mineral. Therefore, analytical tools that enable comprehensive structural and chemical information at the nanoscale in this compound are highly sought after. In this context, we explore the electron energy-loss fine structures resulting from the excitation of O1s and Si2p core electrons in zircon, which are interpreted from ab initio calculations in a single-particle framework. An excellent agreement is obtained between the experimental and calculated fine structures, emphasizing the large distortion of the final electronic states induced by the core-hole potential. The O-K edge is particularly rich in information, with intense peaks dominated by O2p - Zr4d and O2p - Si3sp hybrids. This work suggests that the near-edge structures from the O1s and Si2p excitations accessible from electron energy-loss spectroscopy or X-ray absorption spectroscopy could be used as tools to follow, interpret and understand structural and chemical modifications in zircon subject to natural radiation damage. We illustrate the potential of this approach through the evolution of near-edge fine structures in a zircon sample that exhibits a locally amorphized zone formed by ultrafast laser excitation
“From blue to red: first evidence of heat treatment in the production of Minoan serpentinite vases through non-invasive study and experimental petrology”
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HALO I: Photometric continuum reverberation mapping of Fairall 9
No full textInternational audienceWe investigate the origin of inter-band continuum time delays in active galactic nuclei (AGNs) to study the structure and properties of their accretion disks. We aim to measure the inter-band continuum time delays through photometric monitoring of Seyfert galaxy Fairall 9 to construct the lag-spectrum. Additionally, we explain the observed features in the Fairall 9 lag-spectrum and discuss the potential drivers behind them, based on our newly collected data from the Obserwatorium Cerro Murphy (OCM) telescope. We initiated a long-term, continuous AGN photometric monitoring program in 2024, titled 'Hubble constant constraints through AGN Light curve Observations' (HALO) using intermediate and broad band filters. Here, we present the first results from HALO, focusing on photometric light curves and continuum time-delay measurements for Fairall 9. To complement these observations and extend the wavelength coverage of the lag-spectrum, we also reanalyzed archival Swift light curves and spectroscopic data available in the literature. Using HALO and Swift light curves, we measured inter-band continuum delays to construct the lag-spectrum of Fairall 9. Excess lags appear in the and bands (Balmer continuum contamination) and in the band (Paschen jump/dust emission from the torus). Overall, the lag-spectrum deviates significantly from standard disk model predictions. We find that inter-band delays deviate from the power-law, due to BLR scattering, reprocessing, and dust contributions at longer wavelengths. Power-law fits are therefore not well suited for characterizing the nature of the time delays
Search for Magnetic Monopoles with the Complete ANTARES Dataset
No full textInternational audienceThis study presents a novel search for magnetic monopoles using data collected over a 14 year period (2008-2022) by the ANTARES neutrino telescope. The interaction of magnetic monopoles with matter was modeled according to Kazama, Yang, and Goldhaber cross-section. Upper limits on the flux of magnetic monopoles are obtained for velocities both above and below the Cherenkov threshold. No events consistent with the passage of magnetic monopoles were detected, enabling the setting of an upper flux limit for relativistic magnetic monopoles of the order of
Discrete numerical analysis of cohesive granular flow in a thin rotating drum: Flow regimes and cohesion estimation
No full textInternational audienceIn this study, we investigate the rheological behavior of cohesive granular flows within a rotating drum geometry using discrete element method (DEM) simulations. By systematically varying particle size, cohesion, and stiffness, we identify the emergence of distinct flow regimes-consistent with prior experimental observations. While the transitions between these regimes are primarily governed by cohesion, particle stiffness is also shown to significantly influence flow dynamics.To interpret the numerical results, we employ a dimensional analysis rooted in the physics of adhesive particle collisions. This analysis provides a conceptual framework for the remainder of the paper, which explores how "upscaled" discrete simulations can replicate experimental findings and help infer interparticle contact properties such as the adhesive surface energy. Notably, we use it to examine rotating drum experiments involving a unique class of granular materials, ice powders, which holds particular relevance in planetary science applications, and which flowability was shown to be strongly temperature-dependent
Spatiotemporal changes and drivers of net greenhouse gas emissions from major cropping systems in China during 1984–2018
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Exner diagnosis method for two-fluid morphodynamics simulations
No full textInternational audienceMass balance in sediment transport is often associated with single-phase flow model through the resolution of the Exner equation. In this contribution, the mass balance is derived from the two-phase flow, two-fluid, model equations and compared with the conventional single-phase flow approach. Five terms are identified from the two-phase flow formulation: the bed evolution, the storage evolution, the lateral flux, the bed flux and the top flux. Three different flow configurations with increasing complexity are tested, namely a one dimensional pure sedimentation, a two dimensional scour downstream an apron and a three dimensional scour around a vertical square cylinder. The mass balance formulation identifies the driving process of an erosion or a deposition process in each case. This approach can be applied on other configurations related with sediment flux and morphology bed evolution such as scour process