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La genèse des septarias
No full texthttps://planet-terre.ens-lyon.fr/ressource/septaria-formation.xmlThe relationships between the planet's great reservoirs sometimes have unexpected consequences. In the depths of the oceans, gases rise from the underlying Earth's crust. Among them, on the ocean floor, methane reacts with sulfates via bacteria in what is called the Sulfate Methane Transition Zone (SMTZ). These reactions cause carbonate accretions in the form of nodules. These nodules then align themselves with diagenetic horizons, marking a stable SMTZ for a sufficient time for these nodules to grow. The early diagenesis of these nodules will transform them into geodes filled with partitions, called septaria1. These septaria will then fracture under the weight of the sediments. Then the migrations of hydrothermal fluids will cause varied crystallizations within them. These crystals bear witnesses to the geological history of these paleo-horizons of septaria.Les relations entre les grands réservoirs de la planète ont parfois des conséquences inattendues. Dans les bassins marins profonds, généralement des bassins épicontinentaux sur croute continentale amincie, des gaz remontent issus de la croute terrestre sous-jacente le plus souvent issus de phénomènes diagénétiques et/ou bactériens.Parmi eux, sur les fonds sédimentaires, le méthane entre en réaction avec les sulfates via des bactéries dans ce qu'on appelle la Sulfate Methane Transition Zone (SMTZ). Ces réactions provoquent des accrétions carbonatées sous forme de nodules. Ces nodules s'alignent alors sur des horizons diagénétiques marquant une SMTZ stable pendant un temps suffisant pour que ces nodules croissent. La diagenèse précoce de ces nodules va les transformer en géodes emplies de cloisons, appelées septarias – du latin sæptum (septum) : clôture, barrière, enceinte. Ces septarias vont ensuite se fracturer sous le poids des sédiments. Alors les migrations de fluides hydrothermaux vont provoquer en leur sein des cristallisations variées. Ces cristaux sont les témoins de l'histoire géologique de ces paléo-horizons à septarias
: ISBN 978-2-35755-039-1
No full text978-2-35755-039-1Carlo Gozzi, Memorie inutili, Venise, ed. Palese, 1797Traduction française collective fondée sur la princeps de 1797: Carlo Gozzi, Memorie inutili, Venise, ed. Palese, 179
kAOV : kernel hypothesis testing on general designs
No full textA Python library for kernel hypothesis testing on general design
Young domination on Hamming rectangles
No full textIn the neighborhood growth dynamics on a Hamming rectangle , the decision to add a point is made by counting the currently occupied points on the horizontal and the vertical line through it, and checking whether the pair of counts lies outside a fixed Young diagram. After the initially occupied set is chosen, the synchronous rule is iterated. The Young domination number with a fixed latency is the smallest cardinality of an initial set that covers the rectangle by steps, for We compute this number for some special cases, including -domination for any when , and devise approximation algorithms in the general case. These results have implications in extremal graph theory, via an equivalence between the case and bipartite Tur\'an numbers for families of double stars. Our approach is based on a variety of techniques including duality, algebraic formulations, explicit constructions, and dynamic programming
New constraints on mechanisms driving Valanginian marl-limestone alternations in the Vocontian Basin (SE France) using 3HeET
No full textInternational audienceMarl-limestone alternations are remarkable binary interbedded deposits mostly observed in pelagic to hemi-pelagic environments. These rhythmical patterns result from Milankovitch cycles and their influences on climate. However, previous studies have not reached any consensus regarding the sedimentological mechanisms driving them. Resolution in most previous approaches only reached the timescale of a precession cycle (ca. 20 ka). Thus, these works were unable to document absolute variations in silico-clastic and carbonate net depositional fluxes.To untangle the mechanisms driving marl-limestone alternations (variable dilution of CaCO3 by detrital fluxes or varying CaCO3 production), extra-terrestrial 3He (3HeET) might be a valuable asset. Since this isotope is brought by interplanetary dust particles at a rather constant flux at the orbital timescales, it makes it possible to reconstruct near-instantaneous terrigenous and carbonate sedimentation rates. Here, we sampled every 15 cm of three highly studied, reference Valanginian sections: Angles, La Charce, Vergol in the Vocontian Basin (SE France). Preliminary 3HeET results from the La Charce site indicate consistent sedimentation rates compared to astrochronology showing 3HeET can complement and refine astronomical time scale of Pre-Quaternary series. In agreement with recent 3HeET observations from the nearby Barles-Digne region, our results indicate the generation of marl-limestone alternations as being primarily controlled by variations in CaCO3 productivity at precession time scales. This suggests that the detrital flux is probably too inertial to generate visually clear hemipelagic marl-limestone alternations. Hence, their formations require more dynamical processes, such as sustained productivity and export from the carbonate platforms
Hepatitis E Virus-induced antiviral response by plasmacytoid dendritic cells is modulated by the ORF2 protein
No full textInternational audienceType I and III interferons (IFN-I/III) are critical to protect the host during viral infection. IFN-mediated antiviral responses against hepatitis E virus (HEV) are suppressed and defeated by viral escape mechanisms at play in infected hepatocytes. Here, we studied the anti-HEV function of IFN secreted by plasmacytoid dendritic cells (pDCs), which are specialized producers of IFNs. We showed that pDCs co-cultured with HEV-infected cells secreted IFN in a cell-to-cell contact-dependent manner. Pharmacological inhibitor and antibodies targeting contact proteins revealed that pDC response against HEV required the endosomal nucleic-acid sensor TLR7 and adhesion molecules, such as ICAM-I and α L β 2 -integrin. IFNs secreted by pDCs reduced viral spread. Intriguingly, ORF2, the capsid protein of HEV, can be produced in various forms by the infected cells. During infection, a fraction of the intracellular ORF2 protein localizes into the nucleus while another ORF2 fraction packages viral genomes to produce infectious virions. In parallel, glycosylated forms of ORF2 are also massively secreted by infected cells. Using viral genome expressing ORF2 mutants, we showed that glycosylated ORF2 forms contribute to better recognition of infected cells by pDCs by regulating contacts between infected cells and pDCs. ORF2 forms may thus modulate pDC-mediated anti-HEV response. Together, our results suggest that liver-resident pDCs, which exhibit comparable IFN-producing ability as blood-derived pDCs, may be essential to control HEV replication
Limite semi-classique de l'équation de Bogoliubov–de Gennes
No full textInternational audienceIn this paper, we rewrite the time-dependent Bogoliubov\unicode{x2013}de Gennes equation in an appropriate semiclassical form and establish its semiclassical limit to a two-particle kinetic transport equation with an effective mean-field background potential satisfying the one-particle Vlasov equation. Moreover, for some semiclassical regimes, we obtain a higher-order correction to the two-particle kinetic transport equation, capturing a nontrivial two-body interaction effect. The convergence is proven for interaction potentials in terms of a semiclassical optimal transport pseudo-metric. Furthermore, combining our current results with the results of Marcantoni et al. [arXiv:2310.15280], we establish a joint semiclassical and mean-field approximation of the dynamics of a system of spin- Fermions by the Vlasov equation in some negative order Sobolev topology
Annotation et dossier critique de l'article ACIER (Diderot, Encyclopédie, 1751, t. I, p. 100a–108a)
No full textInternational audienceL’enjeu principal de l’article ACIER semble être la démonstration de la nature moyenne de l’acier entre le fer de fonte et le fer forgé ; autrement dit, une réfutation de l’opinion communément admise d’un acier qui serait fer pur. Toutefois, la thèse s’efface au fil du texte de Diderot. Deux aciers sont en effet à distinguer : l’« artificiel » à partir de fer forgé traité par cémentation, dont Réaumur a donné en 1722 un procédé, et le « naturel » à partir simplement de l’affinage et de la trempe de la fonte d’un fer brut naturellement disposé à se transformer en acier. Inutile donc de supposer quelque secret pour obtenir de l’acier ; dans un cas, il n’y a qu’à suivre Réaumur (ou même un autre ; Geoffroy par exemple), et dans l’autre, partir d’un fer que la nature a formé pour cela. Reste que les aciers les plus excellents nous viennent de l’étranger. Après tout le discours des savants de l’Académie Royale des Sciences et autres auteurs d’ouvrages sur le sujet, Diderot laisse alors le soin à un ouvrier, le maître coutelier Foucou, de poser un constat général quant à la piètre qualité de l’acier français, malgré la richesse en habiles ouvriers du royaume et en fer de son sous-sol, puis glisse une explication : le défaut d’intelligence des entrepreneurs. Pour y remédier, des chimistes « surtout en petit, des contemplatifs systématiques ne suffisent pas : il faut des ouvriers » expérimentés dont on ne fait pas assez cas ; « ce sont peut-être les seuls dont on puisse attendre quelque découverte solide ». Le problème est important puisque la France importe pour trois millions par an d’acier. Aussi faut-il, pour Diderot, se libérer de notre dépendance de l’étranger en considérant avec plus de soin le travail de notre fer, que ce soit en produisant de l’acier artificiel ou de l’acier naturel. Dans ACIER, la question d’ordre scientifique de départ n’avait finalement pour but que de conduire le lecteur aux 31 lignes, six paragraphes avant la fin, qui forment la raison même de l’article sur près de dix-sept colonnes de texte : démontrer que la France, à l’instar de l’Angleterre et de l’Allemagne, dispose de tous les moyens pour produire du bon acier. La raison est doublée d’une morale : dans ces affaires-là, on doit davantage attendre de l’ouvrier que du savant
A mathematical model to the melanoma dynamics involving CAR T-cells
No full textInternational audienc
Iron shackles from the Ptolemaic gold mines of Ghozza (Egypt, Eastern desert)
No full textInternational audienceSince 1994, the French Archaeological Mission at the Eastern Desert has excavated more than 20 sites, initially focusing on Roman forts and now on Hellenistic mining sites. Rich in natural resources, especially gold, the region was heavily exploited by the Ptolemies. Recent excavations at Ghozza reveal the miners’ harsh conditions