Portail HAL de l'Université du Littoral Côte d'Opale
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Extending the unconditional support in an Iwaniec-Luo-Sarnak family
No full text12 pagesInternational audienceWe study the harmonically weighted one-level density of low-lying zeros of -functions in the family of holomorpic newforms of fixed even weight and prime level tending to infinity. For this family, Iwaniec, Luo and Sarnak proved that the Katz--Sarnak prediction for the one-level density holds unconditionally when the support of the Fourier transform of the implied test function is contained in . In this paper, we extend this admissible support to , where and tends monotonically to as tends to infinity. This is asymptotically as good as the best known GRH result. The main novelty in our analysis is the use of zero-density estimates for Dirichlet -functions
Atmospheric fate of prenol, a second-generation biofuel, in simulation chambers : Insights into kinetics and gaseous / particulate oxidation products formation
No full textInternational audienc
Numerical control of a semilinear wave equation on an interval
No full textInternational audienceWe are concerned with the numerical exact controllability of the semilinear wave equa-tion on the interval (0, 1). We introduce a Picard iterative scheme yielding a sequence ofapproximated solutions which converges towards a solution of the null controllability prob-lem, provided that the initial data are small enough. The boundary control, which is appliedat the endpoint x = 1, is taken in the space H^1_0(0, T ) for T = 2. For the linear part, thecontrol input is obtained by imposing a transparent boundary condition at x = 1. Next, weprovide several simulations to show the efficiency of the algorithm, using collocation pseu-dospectral methods on Chebychev grids to discretize the second order derivative in space inthe wave equation
Fraudes aux virements : beaucoup de bruit pour rien: commentaire de Cass. com., 12 juin 2025 (3 arrêts)
No full textInternational audienceSolution. - Ne commet pas de négligence grave au sens des articles L. 133-18 et suivants du Code monétaire et financier l'utilisateur de services de paiement victime de spoofing dans une hypothèse dans laquelle tout concourait à lui faire croire qu'il était en lien avec un technicien de sa banque et qu'un incident informatique était bien survenu (Cass. com., 12 juin 2025, n° 24-13.777).Les articles L. 133-18 et suivants du Code monétaire et financier ne sont pas applicables lorsqu'une contestation concerne une opération de paiement autorisée. Le payeur peut seulement demander la mise en jeu de la responsabilité civile de sa banque pour manquement à son devoir de vigilance (Cass. com., 12 juin 2025, n° 24-13.697), ce qui suppose que les opérations présentent des anomalies suffisamment apparentes pour alerter la banque (Cass. com., 12 juin 2025, n° 24-10.168).Lorsque, tel est le cas, la banque doit demander une confirmation des ordres suspects auprès d'une personne habilitée à émettre des ordres de paiement (Cass. com., 12 juin 2025, n° 24-13.697)
Aerosol dry deposition fluxes on snow during the ALPACA campaign in Fairbanks, Alaska
No full textInternational audienceA comprehensive study of aerosol exchange surface fluxes was conducted at a suburban site in Fairbanks (Alaska) during the Arctic winter as part of the ALPACA experiment. Aerosol fluxes were measured by an eddy covariance system on a snow-covered field located at the University of Alaska Fairbanks (UAF) Farm site from January 26 th to February 17 th , 2022. In general, bidirectional (emission and deposition) fluxes were measured at the site. Median deposition velocities were 0.61, 0.04, and 8.73 mm s⁻¹ for ultrafine (< 50 nm), accumulation (0.25 -0.8 µm), and quasi-coarse (0.8 -3 µm) particles, respectively. Anticyclonic synoptic meteorological conditions enhanced atmospheric stagnation and favoured pollutant accumulation near the surface, whereas cyclonic conditions increased aerosol dispersion, thus reducing deposition rates.Despite the frequent conditions of atmospheric stability and pronounced temperature inversions resulting from the strong surface radiative cooling, turbulence was generated mechanically by wind friction, leading to particle deposition. Our findings provide quantitative evidence that wintertime aerosol dry deposition in Arctic urban areas contributes significantly to pollutant accumulation in the snowpack, potentially enhancing contaminant remobilization during snowmelt. Finally, this study provides data for improving aerosol transport models and understanding pollutant-snow interactions in cold urban regions.</p
Lagrangian Survey in the Southern Ocean : CARIOCA Time Series Statistics
No full textInternational audienceThe Southern Ocean, as a net annual CO2 sink, plays a fundamental role in the global carbon cycle. According to estimates from global models, it could account for 40 % of the oceanic CO2 uptake, corresponding to 10 % of annual human emissions (DeVries, 2014; Friedlingstein et al., 2025). Between 2001 and 2012, researchers from the LOCEAN laboratory in Paris sampled the dynamics of several scalar variables using 15 CARIOCA drifting buoys (Boutin et al., 2008): temperature, salinity, CO2 fugacity (fCO2), and fluorescence. The hourly data collected by these buoys proved to be highly informative, shedding new light on carbon dynamics in the Southern Ocean, a region still poorly understood due to sampling challenges. In this study, we focused on the temporal dynamics of these time series, which constitute the largest Lagrangian dataset within the SOCAT (https://socat.info/) database. Based on Lagrangian turbulence theory (Landau & Lifshitz, 1944), we identified the existence of two distinct spectral regimes, separated by a characteristic timescale of 10 days, corresponding to the synoptic scale in the Southern Ocean. At smaller scales, the results for temperature and salinity align with expectations for homogeneous and isotropic Lagrangian turbulence, whereas it was still scaling with different slopes for fluorescence and fCO2. We also examined the intermittency properties of these time series and found that intermittency is pronounced at small scales (below 10 days) across all variables. Finally, we investigated the scale-dependent relationships between fCO2 increments (i.e., temporal fluctuations) and those of other scalar variables. We found increased dependence on temperature and salinity at very fine scales, while an asymmetric dependence on fluorescence emerged at timescales greater than 10 days. Overall, these results highlight the temporal dynamics of fCO2 variability in the Southern Ocean and emphasize its scale-dependent behavior, shaped by both physical and biological influences. In this study, we adopted a Lagrangian framework for our analyses, which is particularly well-suited for tracking the movement of planktonic organisms and the dispersion of pollutants, as it follows the motion of water parcels. Such analyses have not yet been conducted using data from Lagrangian drifting buoys: this study therefore represents a first attempt to investigate Lagrangian dynamics using float-based observations. This work is presently submitted to JGR: Oceans, and the preprint is available online at: https://doi.org/10.22541/essoar.175138833.30131599/v1Boutin, J. et al. (2008). Air-sea CO2 flux variability in frontal regions of the Southern Ocean from CARbon Interface Ocean Atmosphere drifters. Limnology and Oceanography, 53 (5part2), 2062–2079. doi: 10602.4319/lo.2008.53.5 part 2.2062DeVries, T. (2014). The oceanic anthropogenic CO2 sink: Storage, air-sea fluxes, and transports over the industrial era. Global Biogeochemical Cycles, 28 (7), 631–647. doi: 10.1002/2013GB004739Friedlingstein, P., et al. (2025). Global Carbon Budget 2024. Earth System Science Data, 17 (3), 965–1039. doi: 10.5194/essd-17-965-2025Landau, L. D., & Lifshitz, E. M. (1944). Fluid mechanics, 1st Russian edition. USSR Academy of Sciences Publishing House, Moscow
¿Cómo digitalizar la agricultura familiar ?
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/615900/) * Autres projets (id;sigle;titre): ;;(FRA) Projet Fracture Numérique// ;ACOTAF;(FRA) Renforcer le conseil agricole pour accompagner les transitions agroécologiques de l’agriculture familiale en Afrique subsaharienne// ;Compairs;(FRA) Certification par les pairs pour une qualité éco-solidaire : co-construction d’un commun intellectuel// ;DigiCLA;(BEN) Le digital pour lutter contre la Chenille Légionnaire d'Automne//International audienceLa digitalización del sector agrícola en África Occidental promete numerosos beneficios para los actores de las cadenas agrícolas y del sector tecnológico. Estas promesas se basan en la apropiación voluntaria y masiva por parte de los productores agrícolas de herramientas telefónicas conectadas a la red de internet. El uso del teléfono celular y de sus aplicaciones podría favorecer la creación de redes autónomas entre los productores, estructurar mejor las cadenas de valor y aumentar el valor económico del sector. Los productores agrícolas son ahora el objetivo de un número creciente de proveedores de “servicios digitales”, desarrollados en forma de aplicaciones por empresas emergentes de tecnología y agrotecnología. Sin embargo, el éxito de las aplicaciones desarrolladas para los productores agrícolas ha sido desigual. ¿Qué lecciones podemos aprender de este éxito parcial y qué medidas deben tomarse para que los servicios digitales estén plenamente a disposición de los agricultores y facilitar una transición hacia prácticas sostenibles en lo social, económico y ambiental
Substantially underestimated winter CO 2 sources of the Southern Ocean
No full textInternational audienceThe size and control mechanism of the Southern Ocean’s carbon fluxes remain highly uncertain due to sparse winter observations. Here, we integrate satellite light detection and ranging (LIDAR) measurements with machine learning to assess the Southern Ocean air-sea CO2 fluxes between 2007 and 2020. We reveal that CO2 outgassing south of 50°S was underestimated by up to 40% in previous studies. While the midlatitude Southern Ocean (30° to 50°S) strengthens as a carbon sink, the high-latitude region (50° to 90°S) shows Southern Annular Mode (SAM)–modulated alternation between uptake and outgassing. The air-sea CO2 partial pressure difference (ΔpCO2) increasingly dominates flux variability over wind-driven transfer velocity. We propose a framework involving three latitudinal loops with differing pCO2 controls: (i) Antarctic (salinity/sea ice), (ii) polar front (atmospheric CO2/chlorophyll), and (iii) subpolar (sea surface temperature/CO2). The findings underscore the winter processes’ critical role and necessitate year-round observations to understand Southern Ocean’s global carbon cycle impact
Overview of BLOOFINZ/INDITUN investigations of the southern bluefin spawning region off northwest Australia, January-March 2022
No full textInternational audienceSouthern Bluefin Tuna (SBT, Thunnus maccoyii) range broadly in rich feeding grounds of the Southern Hemisphere but spawn only in a small tropical region off northwestern Australia directly downstream of the Indonesian Throughflow. Here, we describe goals, physical context, design and major findings of an end-to-end process study conducted during the peak SBT spawning season (January–March 2022) to understand nutrient sources, productivity, pelagic food web structure and their relationships to larval SBT feeding, growth and survival. Mesoscale variability was investigated by continuous underway measurements of surface waters and station sampling along the cruise track. Biogeochemical and community relationships, process rates, and trophic interactions were determined in four multi-day Lagrangian experiments in the southern Argo Basin. The study revealed strong system balances among nitrogen fluxes, phytoplankton production, grazing processes, and export. Highly selective feeding on appendicularians allows efficient trophic transfer from picophytoplankton-dominated production to SBT larvae. Plankton productivity, phytoplankton carbon and zooplankton biomass were proportionately elevated compared to similar measurements from the Atlantic bluefin larval habitat in the Gulf of Mexico, but with less advective input from the coastal margins. Individual-based otolith and stable isotope analyses identify larvae of low trophic position, narrow diet, and narrow maternal diet as the fastest growers most likely to contribute to stock recruitment. Our study highlights the importance of system-level studies to document and understand the subtleties of how food webs of oligotrophic regions respond to climate change, which may not be predictable from the acquired knowledge of historical studies