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Architecture structurale et dynamique quaternaire de l'avant-arc terre-mer des Andes du Nord (Bassins de Guayaquil, Tumbes et Talara)
No full textThe Northern Andes forearc zone has historically been regarded as a region characterised by low tectonic activity, predominantly due to the presence of weak interseismic coupling along the subduction interface. However, the structural architecture and tectonic regime of this forearc remain debated, with some arguing for a regime dominated by normal faulting indicative of tectonic erosion, and others favoring a thrust-fault-dominated regime suggesting an accretionary process. This thesis aims to define the structural architecture, recent tectonic activity and kinematics, of the northern Peruvian forearc, while exploring the broader implications for Quaternary geodynamics. Onshore and offshore structural and morpho-tectonic analyses of the North Peruvian forearc, integrating surface and subsurface data and dating of Quaternary morpho-tectonic markers, revealed large-scale active deformation across the entire forearc. The results of this thesis work demonstrate that active deformation extends across the entire North Peruvian forearc basin. This deformation is expressed by large-scale gravity tectonics in the Gulf of Guayaquil, situated off the South Ecuadorian and North Peruvian coasts during the Quaternary period. Indeed, the Tumbes-Guayaquil basin was predominantly characterized by four tectono-stratigraphic features throughout the Quaternary period. These include a transtensional tectonic regime associated with a major active dextral strike-slip system, driven by oblique convergence; progressive trenchward tilting of the margin, induced by coastal uplift; exceptionally high sedimentation rates; and the presence of overpressured shales that facilitate seaward sliding of the sedimentary sequence along décollement faults. Onshore, Quaternary tectonic activity resulted in active shortening of the forearc prism, as evidenced by the presence of an active thrust fault reaching the surface approximately 200 km from the trench. This deformation also includes differential coastal uplift, manifested by tectonic tilting of the Tablazos, likely related to antiform structures resulting from forearc prism shortening.La zone d'avant-arc des Andes du Nord a longtemps été perçue comme une région à faible activité tectonique, principalement en raison d'un faible couplage intersismique au niveau de l'interface de subduction. Par ailleurs, l'architecture structurale et le régime tectonique de cet avant-arc demeurent néanmoins sujets à débat. Ce débat oppose un régime dominé par des failles normales, indiquant une érosion tectonique, à un régime dominé par des chevauchements, suggérant un processus d'accrétion. Les principaux objectifs de cette thèse visent à déterminer l'architecture structurale et l'activité tectonique récente et sa cinématique, tout en considérant les implications à grande échelle pour la géodynamique du Quaternaire de l'avant-arc nord-péruvien. Les analyses structurales et morpho-tectoniques onshore et offshore de l'avant-arc nord-péruvien, en intégrant des données de surface et de subsurface et la datation de marqueurs morpho-tectoniques quaternaires, ont révélé une déformation active à grande échelle de l'ensemble de l'avant-arc. Les résultats de ce travail de thèse montrent en effet une déformation active qui s'étend à travers l'ensemble du bassin d'avant-arc terre-mer nord-péruvien. Cette déformation s'exprime par une tectonique gravitaire à grande échelle dans le Golfe de Guayaquil, au large des côtes sud-équatorienne et nord-péruvienne pendant le Quaternaire. En effet, le bassin de Tumbes-Guayaquil est principalement dominé par quatre caractéristiques tectono-stratigraphiques au cours du Quaternaire, à savoir un régime tectonique transtensif le long d'un grand système crustal décrochant dextre actif, lié à l'obliquité de la convergence ; un basculement progressif de la marge vers la fosse, induit par le soulèvement côtier ; un taux de sédimentation exceptionnellement élevé et la présence d'argiles en surpression de fluides, favorisant le glissement de la pile sédimentaire depuis la côte vers la fosse, le long de décollements. À terre, l'activité tectonique durant le Quaternaire se traduit par un raccourcissement actif du prisme d'avant-arc, matérialisé par un chevauchement actif atteignant la surface à environ 200 km de la fosse. Cette déformation du prisme d'avant-arc inclut également un soulèvement côtier différentiel majeur, marqué par le basculement tectonique des Tablazos, probablement associé à des antiformes causées par ce raccourcissement
Keck and Gemini Characterization of Hayabusa2# Rendezvous Target 1998 KY<sub>26</sub>
No full textInternational audienceNear-Earth object (NEO) 1998 KY26 is a target of the Hayabusa2# spacecraft, which it will rendezvous with in 2031 July. The asteroid has been noted to rotate rapidly and has a large out-of-plane nongravitational acceleration. We present observations consisting of deep-g- and R-band imaging obtained with the Keck I/Low Resolution Imaging Spectrometer (LRIS) and visible spectroscopy from Gemini North/Gemini Multi-Object Spectrograph (GMOS) taken of 1998 KY26 on 2024 June 8–9 when the asteroid was ∼0.037 au from the Earth. The asteroid does not show evidence of a dust coma and has a surface brightness profile similar to nearby background stars in the deep images. The spectrum of 1998 KY26 from the combined LRIS and GMOS observations most closely resembles Xe-type asteroids, possessing a spectral slope of 6.71% ± 0.43% 100 nm‑1, and color indices g – r = 0.63 ± 0.03, r – i = 0.15 ± 0.03, i – z = 0.05 ± 0.04, and implies a diameter of ∼10 m. From our deep image stacks, we compute a 3σ upper limit on the dust production of 1998 KY26 of <10‑5 kg s‑1, <10‑2 kg s‑1, and <10‑1 kg s‑1 assuming μm, mm, and cm size dust particles. In addition, we compare the orbit of 1998 KY26 and other known asteroids with large nongravitational parameters to NEO population models and find that the majority, including 1998 KY26, likely originated from the inner Main Belt, while the second most numerous group originates from the outer main belt, followed by a third group possibly originating from the Jupiter Family Comet population. Given its inner Main Belt origin, its Xe-type spectrum, and rapid rotation, we hypothesize that the nongravitational acceleration of 1998 KY26 may be caused by the shedding of large dust grains from its surface due to its rotation rather than H2O vapor outgassing
Spirals, rings, and vortices shaped by shadows in protoplanetary discs: from radiative hydrodynamical simulations to observable signatures
No full textInternational audienceNumerous protoplanetary discs exhibit shadows in scattered light observations. These shadows are typically cast by misaligned inner discs and are associated with observable structures in the outer disc, such as bright arcs and spirals. Investigating the dynamics of the shadowed outer disc is therefore essential in understanding the formation and evolution of these structures. We carry out two-dimensional radiation hydrodynamics simulations that include radiative diffusion and dust–gas dynamics to study the formation of substructure in shadowed discs. We find that spiral arms are launched at shadow edges, permeating the entire disc. The local dissipation of these spirals results in an angular momentum flux, opening multiple gaps, and leading to a series of concentric, regularly spaced rings. We find that ring formation is favoured in weakly turbulent discs where dust growth is taking place. These conditions are met for typical Class II discs, in which bright rings should form well within a fraction of their lifetime (0.1–0.2 Myr). For hotter discs, gap opening is more efficient, such that the gap edges quickly collapse into vortices that can appear as bright arcs in continuum emission before decaying into rings or merging into massive, long-lived structures. Synthetic observations show that these structures should be observable in scattered light and millimetre continuum emission, providing a new way to probe the presence of substructure in protoplanetary discs. Our results suggest that the formation of rings and gaps is a common process in shadowed discs and can explain the rich radial substructure observed in several protoplanetary discs
exoALMA. V. Gaseous Emission Surfaces and Temperature Structures
No full textInternational audienceAn analysis of the gaseous component in protoplanetary disks can inform us about their thermal and physical structure, chemical composition, and kinematic properties, all of which are crucial for understanding various processes within the disks. By exploiting the asymmetry of the line emission, or via line profile analysis, we can locate the emitting surfaces. Here, we present the emission surfaces of the exoALMA sources in 12CO J = 3–2, 13CO J = 3–2, and CS J = 7–6. We find that 12CO traces the upper disk atmosphere, with mean values of ≈0.28, while 13CO and CS trace lower regions of the disk with mean values of ≈0.16 and ≈0.18, respectively. We find that 12CO and the disk mass are positively correlated with each other; this relationship offers a straightforward way to infer the disk mass. We derive 2D r – z temperature distributions of the disks. Additionally, we search for substructure in the surfaces and radial intensity profiles; we find evidence of localized substructure in the emission surfaces and peak intensity profiles of nearly every disk, with this substructure often being coincident between molecular tracers, intensity profiles, and kinematic perturbations. Four disks display evidence of potential photodesorption, implying that this effect may be common even in low far-ultraviolet star-forming regions. For most disks, we find that the physical and thermal structure is more complex than analytical models can account for, highlighting a need for more theoretical work and a better understanding of the role of projection effects on our observations
Averaged models for compressible two-phase stratified flows on thin domains
No full textThis paper deals with the derivation of compressible two-phase flow models. We use a thin domain approximation of a two-layer configuration governed by the Navier-Stokes equations, following the works [H. B. Stewart and B. Wendroff, J. Comp. Phys., 56 (1984)] and [V. H. Ransom and D. L. Hicks, J. Comput. Phys., 75 (1988)]. In order to recover source terms and two-velocity models directly from this asymptotic analysis, we remove the continuity of the tangential component of the velocity at the interface, and properly scale friction and viscosity coefficients. We are then able to derive two-velocity one-pressure models, first in the barotropic case and then in the full Navier-Stokes-Fourier case
Supports anticipés, contextuels et communicationnels pour l'enseignement des mathématiques en UPE2A primaire
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Non‐homogeneous distribution of inhibitory inputs among motor units in response to nociceptive stimulation at moderate contraction intensity
No full textInternational audienceAbstract Pain significantly influences movement, yet the neural mechanisms underlying the range of observed motor adaptations remain unclear. This study combined experimental data and in silico models to investigate the contribution of inhibitory and neuromodulatory inputs to motor unit behaviour in response to nociceptive stimulation during contractions at 30% of maximal torque. Specifically, we aimed to unravel the distribution pattern of inhibitory inputs to the motor unit pool. Seventeen participants performed isometric knee extension tasks under three conditions: Control, Pain (induced by injecting hypertonic saline into the infra‐patellar fat pad) and Washout. We identified large samples of motor units in the vastus lateralis (up to 53/participant) from high‐density electromyographic signals, leading to three key observations. First, while motor unit discharge rates significantly decreased during Pain, a substantial proportion of motor units (14.8–24.8%) did not show this decrease and, in some cases, even exhibited an increase. Second, using complementary approaches, we found that pain did not significantly affect neuromodulation, making it unlikely to be a major contributor to the observed changes in motor unit behaviour. Third, we observed a significant reduction in the proportion of common inputs to motor units during Pain. To explore potential neurophysiological mechanisms underlying these results, we simulated the behaviour of motor unit pools with varying distribution patterns of inhibitory inputs. Our simulations support the hypothesis that a non‐homogeneous distribution of inhibitory inputs, not strictly organised according to motor unit size, is a key mechanism underlying the motor response to nociceptive stimulation during moderate contraction intensity. image Key points Pain affects movement, but the neural mechanisms underlying these motor adaptations are not well defined. The traditional view is that pain causes uniform (homogeneous) inhibition among motor units. Recent research has observed differential motor unit responses to experimental pain – some with decreased discharge rates and others with increased discharge rates. Combining experimental data with modelling, we provide compelling evidence of increased inhibition that is non‐uniformly distributed across motor units, regardless of their size
Telomeric antisense oligonucleotides reduce premature aging phenotypes in telomerase mutant zebrafish
No full textTelomerase activity is restricted in somatic cells, resulting in progressive telomere shortening. Telomere erosion eventually activates the DNA damage response (DDR), inducing cell-cycle arrest and cellular senescence or apoptosis. We previously reported that telomere dysfunction induces the transcription of telomeric non-coding RNAs (tncRNAs) which are critical mediators of DDR activation. Blocking tncRNAs with telomeric antisense oligonucleotides (tASOs) suppresses in vivo DDR signaling and its downstream effects. Here, we show that tASO-mediated inhibition of telomeric DDR in second-generation tert−/− zebrafish embryos with critically short telomeres leads to improved developmental outcomes and rescues premature aging phenotypes, including enhanced survival. Notably, a single tASO treatment administered at the one-cell stage of first-generation tert −/− embryos leads to enhanced fertility observed in 6-month-old adults. Overall, these findings demonstrate that tASO-based inhibition of telomeric DDR is sufficient to effectively rescue premature aging phenotypes in zebrafish
Vers un renforcement des prérogatives judiciaires des polices municipales ?
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Management of invasive candidiasis in French ICUs: insights from a 2024 nationwide survey
No full textInternational audiencePurpose: Invasive candidiasis (IC) is a major challenge in intensive care units (ICUs) given its high prevalence, mortality rate, and diagnostic complexity. This national survey aimed to evaluate the knowledge of French intensive care specialists, assess the available resources for IC management, and analyze current bedside practices in ICUs. Methods:A cross-sectional survey was conducted among senior ICU physicians from 221 French ICUs. A structured questionnaire addressing organizational, diagnostic, and therapeutic approaches to IC management, including clinical cases, was distributed, achieving a participation rate of 54.7%.Results: Of the 121 respondents, 75 provided complete data. Most respondents were experienced intensivists working in public centers and managing hematological oncology patients. Although 65 (74%) respondents reported organizing multidisciplinary staff meeting, mycologists were rarely involved. Despite the availability of rapid diagnostic tools such as serum (1,3)-β-D-glucan (BDG), which was accessible to 63 (75%) respondents, integrating them into patient management at the bedside remains challenging. Additionally, 55 (67%) respondents had access to antifungal therapeutic drug monitoring (TDM), with voriconazole being the most frequently monitored antifungal drug. However, only 5 (9.1%) respondents had access to TDM every day of the week. Conclusion:This survey highlights the strengths of multidisciplinary teams, TDM and rapid diagnostic tools for managing IC. However, significant gaps remain in their practical application, particularly the integration of diagnostic tools into clinical algorithms to guide bedside decision-making. Optimizing antifungal stewardship through coordinated interventions is essential for accelerating the diagnosis of IC, improving clinical outcomes, reducing resistance and adverse events.</div