Portail HAL Nantes Université
Not a member yet
120169 research outputs found
Sort by
Protection du littoral et droit au respect des biens. Quid de l'atteinte à la « substance » du droit de propriété ?
No full textInternational audienceCour européenne des droits de l'homme, 7 octobre 2025, no 29061/21, Hastaoğlu c/ Turquie, D. act., 23 oct. 2025, note M. de Ravel d'Esclapo
Diffusion radar d'une coque de bateau calculée avec l'optique physique itérée
No full textInternational audienceComputing the electromagnetic signature of a boat at sea is very useful for interpreting or simulating SAR images in a maritime environment. However, interactions between the boat and sea are impossible to obtain with a full-wave approach such as the Method of Moments (MoM). A precise mesh of the moving sea would be too difficult to manage because of the size of the 3D-scene. Asymptotic methods offer a good compromise between the computation time and the results accuracy. In this article, the scattered field of a tilted plate above the sea is calculated using the physical optics approximation. This allows an analytical computation of the coherent component. This approach is compared to the MoM thanks to a Monte Carlo process. First results for the incoherent component are also shown.Afin d'interpréter ou de modéliser des images SAR observant un environnement maritime, le calcul de la signature électromagnétique d'un objet situé sur la mer, tel qu'une coque de bateau, s'avère très utile. La modélisation de ces interactions par une approche "full wave", comme la méthode des moments (MdM), s'avère impossible en 3D compte tenu de la taille de la scène à mailler. Les méthodes asymptotiques sont alors un bon compromis entre temps de calcul et précision des résultats. Dans cet article, nous proposons de calculer le champ diffracté par une plaque inclinée au voisinage de la surface de mer en appliquant l'approximation de l'optique physique. De plus, la formulation obtenue permettra de calculer la composante cohérente analytiquement et elle sera validée par comparaison avec la MdM en 2D par un processus de Monte Carlo. Des premiers résultats de la composante incohérente sont également montrés
Chimeric virus-like particles carrying the CLEC17A carbohydrate-recognition domain significantly reduce Macrobrachium rosenbergii nodavirus infection in Sf9 cells
No full textInternational audienceOur previous studies demonstrated that Macrobrachium rosenbergii nodavirus (MrNV) infects and replicates in Sf9 insect cells, where fucosylated N-and O-glycans (HexNAc (Fuc)HexNAc-R or Fuc-LacdiNAc) serve as essential binding molecules for viral attachment. Additionally, we showed that the virus-like particles of the virus itself (MrNV-VLPs) were able to bind to the white-tail disease (WTD)associated tissues and infect Sf9 cells; and these processes were significantly reduced by removing 27 amino acids from the C-terminus of the protruding (P) domain. In this study, we demonstrated that icosahedral particles could still form following the truncation of the P-domain at sites adjacent to known calcium-binding domains (CBDs) present in the S-shell domain in the MrNV capsid protein. We further showed that icosahedral particles could still form after truncation of the P-domain near calcium-binding sites in the S-domain. This generated smaller but intact particles lacking protrusions, designated V250-MrNV-VLPs. The particles with their intact S-shells enabled our complete replacement of the original MrNV capsid protein P-domains with the fucose-binding carbohydraterecognition domain (CRD) of CLEC17A lectin (Prolectin), successfully creating CLEC17A/CRD-MrNV-VLPs. The chimeric CLEC17A/CRD-MrNV-VLPs were stable icosahedral particles with P-domains structurally distinct from both the smooth V250-MrNV-VLPs and the blade-like domains of wild-type MrNV-VLPs. Furthermore, the chimeric VLPs presented specific binding activities towards immobilized fucosylated glycoconjugates and Sf9 cell protein lysates. Notably, CLEC17A/CRD-MrNV-VLPs were able to reduce MrNV binding and infection in Sf9 cells. Therefore, this study demonstrated the potential for CLEC17A/CRD-MrNV-VLPs as particles that can effectively bind to fucosylated glycans, and their potential development as nanoparticles that can significantly reduce the level of infection by MrNV in susceptible cells
(Ne pas) hériter du métier ? Des parcours d’entrée aux inégalités professionnelles entre agriculteur·ices
No full textInternational audienc
A Rendez-Vous in Time: Frequency-Domain Precoding for LoS Alignment in Distributed MISO
No full textNational audienceThis paper investigates the impact of Line-of-Sight (LoS) path misalignment in distributed Multiple-Input Single-Output (MISO) systems, particularly in millimeter-wave (mmWave) bands where phase synchronization and timing precision are critical. The goal is to validate a bit error rate model under practical OFDM transmission scenarios involving multiple access points communicating with user equipment. We highlight how time misalignment between LoS paths can degrade system performance and evaluate the effectiveness of various compensation strategies under such conditions. A key contribution of this work is the proposed compensation technique for LoS path misalignment. By applying a frequency-dependent linear phase shift to each subcarrier—an operation that is both low in complexity and easy to implement—we induce a circular rotation of the OFDM time-domain symbol. This rotation effectively aligns the various LoS contributions in time, as long as the path delays remain within the cyclic prefix duration. Notably, the method is fully compatible with analog beamforming architectures, which are essential in mmWave systems to reduce the number of costly RF chains. As a result, the proposed strategy enables efficient time compensation with minimal computational and hardware overhead, making it particularly attractive for distributed Multiple-Input Multiple-Output (MIMO) deployments at mmWave frequencies
Sorption efficiency of radioactive iodine compounds by nuclear-grade activated carbon - a review and processing of literature data
No full textInternational audienceThe sorption properties of I2 and CH3I on activated carbon were reviewed. The dependence of the sorption capacity on activated carbon of iodine and methyl iodide in air or effluent gas on the sampling operating conditions (temperature, relative humidity, linear velocity and bed length) was investigated. A compilation of experimental data on the sorption efficiency, penetration or decontamination factor of gaseous radioactive iodine species was carried out for nuclear-grade activated carbon. Non-linear surface fitting of experimental data of I2 and CH3I sorption efficiencies by activated carbon at different values of temperature and relative humidity shows that there are ranges of variation in both parameters where the removal capacity remains relatively constant. The values and associated uncertainties of the sorption efficiencies of I2 and CH3I by activated carbon cartridges with bed lengths of 25 and 50 mm were determined for different specified ranges of temperature, relative humidity and linear gas flow velocity. The Sorption Efficiency (SE) values can be used to determine the concentration of iodine radioisotopes in the gaseous effluent or ambient air in Bq/m3 from the results of radionuclide activity in the cartridge measured by gamma spectrometry .</jats:p
Cloroplast sequestration by benthic foraminifers in deep-shelf sediments of the High Arctic
No full textInternational audienceWhile foraminiferan protists (single-celled eukaryotes) inhabit a wide variety of habitats and have been doing so for hundreds of millions of years, we still do not fully understand their physiological capabilities. One rather unusual attribute is the ability of certain benthic foraminifera to sequester chloroplasts, which are the photosynthetic organelle of (other) eukaryotes. Such "kleptoplasty" has been documented in approximately 20 foraminifera species, mostly from shallow-water habitats such as mudflats where sunlight is readily available. Kleptoplasty in deeper-water benthic foraminifers is less commonly documented. Sediment cores collected via ROV in 2018 from a ~380-m deep area off southern Svalbard were sourced for living benthic foraminifera. Foraminifera were identified using DNA barcoding. Using Transmission Electron Microscopy (TEM) and subsequent cellular ultrastructural analysis, we established specimen viability and the presence of sequestered chloroplasts. Eukaryotic microbiomes of these four taxa were also sequenced to investigate the identity of the putative kleptoplast donors. The common benthic foraminifera Buccella sp., Elphidium clavatum (Phylotype Elphidium S4), Nonionellina labradorica, and Robertina arctica contained abundant structurally intact chloroplasts that appear to be of diatom origin based on morphology. While it is known that N. labradorica and some Elphidium species are kleptoplastidic, this is the first report of kleptoplasty for Buccella and Robertina, primary documentation of kleptoplastidic Elphidium living at >375-m water depth, and the first time kleptoplastidic N. labradorica has been noted in a microbial mat of a deep-water hydrocarbon seep. We believe R. arctica represents an unprecedented case of kleptoplasty in an aragonitic benthic foraminifera
Cluster Overlap as Objective Function
No full textInternational audienceK-means uses the sum-of-squared error as the objective function to minimize within-cluster distances. We show that, as a consequence, it also maximizes between-cluster variances. This means that the two measures do not provide complementary information and that using only one is enough. Based on this property, we propose a new objective function called cluster overlap, which is measured intuitively as the proportion of points shared between the clusters. We adopt the new function within k-means and present an algorithm called overlap k-means. It is an alternative way to design a k-means algorithm. A localized variant is also provided by limiting the overlap calculation to the neighboring points
