HAL Université de Toulouse, et Toulouse INP
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Oscillatory Brain Activity in the Canonical Alpha-Band Conceals Distinct Mechanisms in Attention
No full textInternational audienceBrain oscillations in the alpha-band (8-14 Hz) have been linked to specific processes in attention and perception. In particular, decreases in posterior alpha-amplitude are thought to reflect activation of perceptually relevant brain areas for target engagement, while alpha-amplitude increases have been associated with inhibition for distractor suppression. Traditionally, these alpha-changes have been viewed as two facets of the same process. However, recent evidence calls for revisiting this interpretation. Here, we recorded MEG/EEG in 32 participants (19 females) during covert visuospatial attention shifts (spatial cues) and two control conditions (neutral cue, no-attention cue), while tracking fixational eye movements. In disagreement with a single, perceptually relevant alpha-process, we found the typical alpha-modulations contra- and ipsilateral to the attention focus to be triple dissociated in their timing, topography, and spectral features: Ipsilateral alpha-increases occurred early, over occipital sensors, at a high alpha-frequency (10-14 Hz) and were expressed during spatial attention (alpha spatial cue > neutral cue). In contrast, contralateral alpha-decreases occurred later, over parietal sensors, at a lower alpha-frequency (7-10 Hz) and were associated with attention deployment in general (alpha spatial and neutral cue < no-attention cue). Additionally, the lateralized early alpha-increases but not alpha-decreases during spatial attention coincided in time with directionally biased microsaccades. Overall, this suggests that the attention-related early alpha-increases and late alpha-decreases reflect distinct, likely reflexive versus endogenously controlled attention mechanisms. We conclude that there is more than one perceptually relevant posterior alpha-oscillation, which need to be dissociated for a detailed account of their roles in perception and attention
Cross-regulation of (p)ppGpp and c-di-GMP pathways controls a cell-cycle transition
No full textAbstract Bacteria must adapt their physiology to changing environments, a process often orchestrated by nucleotide messengers such as (p)ppGpp and cyclic di-GMP (c-di-GMP). While (p)ppGpp promotes survival under nutrient stress by suppressing growth, c-di-GMP supports sessile lifestyles and cell differentiation. In the α-proteobacterium Caulobacter crescentus , these messengers have opposite effects on the cell cycle, suggesting potential cross-regulations. Here, we uncover direct molecular cross-talk between (p)ppGpp and c-di-GMP signaling pathways. Using biochemical, structural and genetic approaches, we show that (p)ppGpp binds to the diguanylate cyclase PleD and inhibits c-di-GMP synthesis by competing with GTP at the active site. This interaction prevents c-di-GMP accumulation under nutrient-limiting conditions, linking metabolic stress to inhibition of developmental progression. Our findings reveal a new paradigm for second messenger interplay, in which one messenger directly suppresses synthesis of another. This work provides insight into how bacteria integrate metabolic and developmental cues through small-molecule cross-talk to guide adaptive behavior
Légitimations et subversions de l'Open : pour une analyse de l'openwashing dans la publication scientifique
No full textThis article presents a novel state of the art on the notion of openwashing in scholarly publishing. Tackling phenomena of washing, it deals with various forms of misappropriations of Open Access in scholarly publications. Based on an interdisciplinary literature review on 50 publications and blog entries (2014-2025), we acknowledge a relative “silence” on openwashing about scientific publications, compared to the uses of the term in articles and essays to describe, and often denounce, open data public policies and “open AI”. These publications show layers of discourse and semantic circulation in the 2010s and early 2020s, based on which we acknowledge the relevance and the limits of a conceptual analogy (with other forms of washing and of openwashing) for scientific openwashing in terms of publicness, proprietary practices and relations to professional norms. The discussion proceeds with the discussion of four broad examples of practices of openwashing. The article brings a better understanding of openwashing, both as a critical concept, tied to scientific publications as a cultural industry, and as an object of discourse about scientific deviance and its evolutions. Finally, it allows implementing a definition grounded in the evolving field of Open Access, as well as justifying its uses to understand its diverse mechanisms at work.Ce texte propose un état de l'art inédit sur la notion d'openwashing dans l'espace des publications scientifiques. En s'appuyant sur les phénomènes de washing, il aborde une variété de formes de détournement des principes de l'ouverture scientifique. À partir d'une analyse critique d'une littérature interdisciplinaire, le concept sténographique élaboré est appliqué aux plateformes numériques pour analyser de la déviance à bas bruit et à faible concernement. L'article apporte une meilleure compréhension de la genèse de l'openwashing à la fois comme concept critique et vecteur de discours de dénonciation de la déviance et de ses évolutions. Enfin, il permet de forger une définition ancrée dans le champ de la communication scientifique ouverte, autant que de légitimer son usage pour appréhender les mécanismes complexes de ses transformations
The DeepSea' Nnovation Project: Innovative Sensing and Sampling for Breakthrough Deep-Sea Marine Sciences
No full textInternational audienceThe France 2030 DeepSea'Nnovation project (ANR-21-ESRE-0042, 2021–2029) is dedicated to the development and scientific use of 15 innovative devices for the deep-sea vehicles of the French Oceanographic Fleet operated by Ifremer (IR* FOF). These devices enable in-situ multidisciplinary investigation and exploration of the marine realm from sea-surface to oceanic seafloor. Here, we present the scientific approaches for selecting these new developments which improve the perception and spatial analysis of the environment, increase measurement precision and performance and extend in-situ sampling capacity from metric to micro metric spatial scale. The methodology section provides a detailed overview of the technological approaches required to carry out system integration and scientific validation at sea. Then we describe the 15 instruments developed and integrated on the deepsea underwater vehicles. At last, we provide an overview of scientific outcomes that can be achieved by association of multi-disciplinary devices, thus delivering breakthrough and innovative scientific datasets
Measuring the magnetic fields in the chromospheres of low-mass stars
No full textInternational audienceMagnetic fields in the upper atmospheres of solar-like stars are believed to provide an enormous amount of energy to power the hot coronae and drive large-scale eruptions that could impact the habitability of planetary systems around these stars. However, these magnetic fields have never been routinely measured on stars beyond the solar system. Through decade-long spectropolarimetric observations, we have now achieved the measurements of magnetic fields in the lower and middle chromospheres of three M-dwarfs. Our results indicate that the line-of-sight component of the chromospheric magnetic fields can reach up to hundreds of Gauss, whose sign frequently opposes that of the photospheric field. The measurements highlight the magnetic field complexity and the variation with height close to the surface of these M-dwarfs. They provide critical constraints on the energy budget responsible for heating and eruptions of stellar upper atmospheres, and enable assessments of how stellar magnetic activity may affect exoplanet environments
Comparing the motion of dark matter and standard model particles on cosmological scales
No full textInternational audienceSince dark matter particles have never been directly detected, we do not know how they move, and in particular we do not know how they fall inside gravitational potential wells. Usually it is assumed that dark matter only interacts gravitationally with itself and with particles of the standard model, and therefore that its motion is governed by Euler’s equation. In this paper, we do test this assumption directly at cosmological scales, by combining measurements of galaxy velocities with measurements of gravitational potential wells, encoded in the Weyl potential. We find that current data are consistent with Euler’s equation at redshifts z ∈ [0.3, 0.8], and we place constraints on the strength of a potential fifth force, which would alter the way dark matter particles fall. We find that a positive fifth force cannot exceed 7% of the gravitational interaction strength, while a negative fifth force is limited to 21%. The coming generation of surveys, including the Legacy Survey of Space and Time of the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument will drastically improve the constraints, allowing to constrain a departure from pure gravitational interaction at the level of 2%
Introduction to Hall thrusters: concept & last results in research
No full textGuest Lecture - LTU Kiruna - Swede
The zircon record of Carboniferous partial melting in Silurian mafic rocks from the Lyonnais metamorphic complex (French Massif Central)
No full textNational audienceWe report the petrological and zircon U-Pb and trace element study of metamafic rocks from the Saint-Joseph massif in the Lyonnais metamorphic complex. The samples are ultrabasic and predominantly composed of garnet–amphibole (up to 75–85%), with plagioclase–quartz (10–15%), titaniferous minerals (5–10%), and clinopyroxene relics (>5%). Some samples show a layering marked by garnet abundance ranging from 0 to 40 %. Plagioclase coats the grain boundaries of garnet and amphibole porphyroblasts, resembling a melt pseudomorph. Thermodynamic modelling of a selected sample indicates that fluid-fluxed melting at 10–12 kbar and 800–900 °C, followed by cooling to ~700 °C, can explain the assemblage garnet–amphibole–plagioclase–quartz–titanite. Separated zircon crystals commonly display a core with oscillatory, or sector zoning, rimmed by domains with complex convolute zoning. This pattern suggests polyphase zircon coupled dissolution-reprecipitation. The analyses of zircon rims show either a flat or a positive slope in the heavy REE pattern, irrespective of the date or intra-grain location. This feature is tentatively attributed to the variable garnet content in the rock layering. Zircon core and rim yield an equivalent smear of apparent ages between c. 360–320 Ma, interpreted as a result of melt-mediated dissolution-reprecipitation. One sample contains an additional zircon zone found as CL-dark cores with oscillatory or featureless zoning, and characterised by an exceptionally high trace-element content, e.g. up to 2000 ppm of U. These cores also yield a smear of apparent, on average, older ages, between c. 425–320 Ma. Nine-spots yield a concordia date of 423.8 ± 4.8 Ma with a MSWD of 0.99 regarded as the age of the magmatic protolith. The occurrence of a Silurian mafic magmatism may be related to mantle melting at the northern Gondwana margin, possibly in a suprasubduction setting. The sample records predominantly a Carboniferous fluid-fluxed partial melting event
Magnetic imaging under high pressure with a spin-based quantum sensor integrated in a van der Waals heterostructure
No full textInternational audiencePressure is a powerful tool for tuning the magnetic properties of van der Waals magnets owing to their weak interlayer bonding. However, local magnetometry measurements under high pressure still remain elusive for this important class of emerging materials. Here we demonstrate magnetic imaging of a van der Waals magnet under high pressure with sub-micron spatial resolution, using a two-dimensional (2D) quantum sensing platform based on boron-vacancy () centers in hexagonal boron nitride (hBN). We first analyze the performances of centers in hBN for magnetic imaging under pressures up to few GPa, and we then use this 2D sensing platform to investigate the pressure-dependent magnetization in micrometer-sized flakes of 1T-CrTe2. Besides providing a new path for studying pressure-induced phase transitions in van der Waals magnets, this work also opens up interesting perspectives for exploring the physics of 2D superconductors under pressure via local measurements of the Meissner effect
Développement d'un moyen d'essai expérimental pour l'étude du comportement des stratifiés composites en environnement cryogénique
No full textInternational audienceDéveloppement d'un moyen d'essai expérimental pour l'étude du comportement des stratifiés composites en environnement cryogéniqu