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The effects of local vibration inducing a tonic vibration reflex or movement illusion on acute modulations of corticospinal excitability
No full textInternational audienceStimulation of muscle afferents by local vibration (LV) can lead to two distinct perceptual and motor responses: the tonic vibration reflex (TVR) or the movement illusion. This study aimed to evaluate the effect of TVR and movement illusion on corticospinal excitability. In two experiments, EMG activity of the vibrated flexor carpi radialis (FCR) muscle (80 Hz, 6 min) and the extensor carpi radialis (ECR) muscle were recorded. Illusion was assessed using questionnaires. LV conditions were adjusted to favour either TVR (visual attention focused on the vibrating wrist) or ILLUSION (hidden hand, visual attention focused on the EMG of the FCR muscle). Motor‐evoked potential (MEP) and cervicomedullary motor‐evoked potential (CMEP) were recorded at rest for both muscles before (10 and 0 min) and after (0 and 30 min) each LV condition. Only the TVR condition increased EMG of the FCR muscle (+490% compared to resting, P = 0.005), while movement illusion was greater in the ILLUSION condition ( P < 0.001). Concerning the vibrated muscle at P0, TVR reduced the amplitude of CMEP (−13.8 ± 15.8%, P = 0.011) without altering MEP (0.3 ± 27.9%, P = 1), whereas the opposite occurred with movement illusion (i.e. CMEP: −4.5 ± 13.7%, P = 0.891; MEP: −25.1 ± 17.2%, P = 0.002). Cortical excitability (MEP/CMEP ratio) of the vibrated muscle was reduced by 24 ± 13.3% on average compared to values obtained before LV, only in the ILLUSION condition. In conclusion, this study highlights the relevance of measuring and reporting the perceptual and motor responses induced during LV, demonstrating that TVR and movement illusion partly determine the acute effects on the neural network. image Key points Tonic vibration reflex and movement illusion are rarely controlled and measured in studies investigating the effect of LV on corticospinal excitability. The application of LV with visual attention focused on the vibrated muscle promotes the presence of a tonic vibration reflex (TVR). The absence of visual feedback on the latter promotes the presence of an illusion of movement. The cortical excitability of the vibrated muscle is influenced differently according to the perceptual and motor responses induced during LV, with an opposite effect on the cortical excitability of the antagonist muscle. Improved control of LV application conditions, quantification of perceptual and motor responses, and reporting of results (e.g. EMG activity of the vibrated muscle or illusion of movement during the protocol) are required to enhance our understanding of the physiological mechanisms associated with LV use and, consequently, the effectiveness of LV as a therapeutic modality
Search for the Higgs boson decay to a boson and a photon in collisions at TeV and TeV with the ATLAS detector
No full textInternational audienceA search for the Higgs boson decay to a boson and a photon in the () final state is performed using collisions at TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022-2024, corresponding to an integrated luminosity of 165 fb. The signal yield, normalised to the Standard Model prediction, is measured to be , compared to an expected value of . This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations for the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb of TeV collisions to provide the most stringent expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of (), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation
Exploring small-angle emissions in charm quark jets in proton-proton collisions at = 5.02 TeV
No full textInternational audienceA measurement of the angular structure of jets containing a prompt D meson and of inclusive jets in proton-proton collisions at the LHC at a center-of-mass energy of 5.02 TeV is presented. The data corresponding to an integrated luminosity of 301 pb were collected by the CMS experiment in 2017. Two jet grooming algorithms, late- and soft drop, are used to study the intrajet radiation pattern using iterative CambridgeAachen declustering. The splitting-angle distributions of jets with transverse momentum () of around 100 GeV, obtained with these two algorithms, show that there is a shift of the distribution for jets containing a prompt D meson with respect to inclusive jets. The shift observed in the late- grooming approach is consistent with the dead-cone effect, whereas the shift for splittings selected with the soft-drop algorithm appears to be dominated by gluon splitting to charm quark-antiquark pairs. The measured distributions are corrected to the particle level and can be used to constrain model predictions for the substructure of high- charm quark jets
Probing Strain in Individual Palladium Nanocrystals during Electrochemically Induced Phase Transitions
No full textInternational audienceThe palladium-hydrogen system plays a crucial role in catalysis, hydrogen production and storage, hydrogen embrittlement, and sensing technologies. Understanding the transition of palladium nanocrystals from the hydrogen-poor (α) phase to the hydrogen-rich (β) phase is crucial for elucidating hydrogen absorption/desorption mechanisms, as well as related phenomena such as hydrogen trapping. In this study, we carefully minimised undesired beam effects and used in situ Bragg Coherent Diffraction Imaging under electrochemical control to map the strain and lattice parameter distribution within individual palladium nanocrystals across electrochemical potentials relevant to hydrogen absorption and desorption. Lattice parameter changes in both α and β phases are tracked and reversible strain inversion during the α-to-β phase transition is observed. Through strain and reciprocal space analysis, and molecular simulations, a model for the α-to-β phase transition is proposed which includes a hydrogen-saturated subsurface shell, hydrogen depletion from the α phase during β phase nucleation, and propagation of the β phase in a spherical-cap fashion
An experimental test of cyanotoxins as a potential driver of microbial community structure
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Etude et modélisation des phénomènes à l'interface entre une électrode en lithium métal et un électrolyte
No full textLithium metal electrodes are good candidates for the next generation of all-solid-state batteries. However, lithium dendrite formation remains a major problem hampering the commercialization of this new technology. Dendritic growth remains a poorly understood phenomenon and appears to be linked to poor local current density distribution due to inhomogeneities in the lithium/electrolyte interface. The formation of a heterogeneous passivation layer, called Solid Electrolyte Interphase (SEI), on the surface of lithium metal electrodes favors the appearance of dendritic structures. A better understanding of the relationship between SEI heterogeneity and dendrite nucleation and growth phenomena remains a key to finding solutions to this problem. Several multi-scale numerical approaches have been proposed to study the mechanisms of dendritic growth. The complexity of the lithium/SEI system remains a major modelling challenge that numerical approaches overlook.The aim of this thesis is to propose, for the first time, an approach based on the multi-phase field formalism, from which it is possible to account for the heterogeneity of the SEI at the surface of the lithium metal electrode. Assumptions have been made on the basis of a literature review of the elements required for the construction of a numerical model.Multi-phase field models are based on the definition of model regions with identical physical, chemical and mechanical properties, known as phases. System dynamic is then driven by minimizing the phases interfaces. With the construction of a model SEI, it was possible to identify four characteristic interface behaviors during a plating cycle. In particular, at low deposition speed (less than ten μA/cm²), homogeneous electrode growth is obtained. At typical regimes (of the order of mA/cm²), three SEI responses were characterized, giving rise to fractures between or within SEI domains. It has been shown that the nature of these responses is strongly coupled to the deposition regime and to the geometric and physical properties of the SEI. Work has been carried out to make the physics and geometry of the SEI more complex, in order to identify ways of improving the model towards a more realistic interface. Preliminary experimental studies have also been carried out to propose a quantitative coupling between the numerical results obtained from the model and the experimental characterizations carried out by XPS, AES and NI-AFM.Les électrodes en lithium métal sont des candidates de choix pour la prochaine génération de batterie tout-solide. Cependant, la formation de dendrite de lithium reste un problème majeur qui entrave la commercialisation de cette nouvelle technologie. La croissance dendritique reste un phénomène mal compris et semble liée à une mauvaise distribution de la densité de courant locale du fait des inhomogénéités de l'interface lithium/électrolyte. La formation d'une couche de passivation hétérogène, appelée Solid Electrolyte Interphase (SEI), en surface des électrodes en lithium métal favorise l'apparition de structure dendritique. Une meilleure compréhension de la relation entre hétérogénéité de la SEI et phénomènes de nucléation et de croissance des dendrites reste un verrou pour apporter des solutions à ce problème. Plusieurs approches numériques multi-échelles ont été proposées pour étudier les mécanismes de croissance dendritique. La complexité du système lithium/SEI reste un dé majeur pour la modélisation que les approches numériques négligent.L'objectif de cette thèse est de proposer, pour la première fois, une approche basée sur le formalisme multi-champs de phase, à partir duquel il est possible de rendre compte de l'hétérogénéité de la SEI à la surface de l'électrode en lithium métal. Des hypothèses ont été effectuées sur la base d'une étude bibliographique des éléments nécessaires pour la construction d'un modèle numérique.Les modèles multi-champs de phase reposent sur la définition de régions modèles avec des propriétés physiques, chimiques et mécaniques identiques appelées phases. La dynamique du système est alors pilotée par la minimisation de leurs interfaces. Avec la construction d'une SEI modèle, il a été possible d'identifier quatre comportements caractéristiques de l'interface pendant un cycle de plating. En particulier, à faible régime (inférieur à la dizaine de μA/cm²), une croissance homogène de l'électrode est obtenue. A des régimes usuels (de l'ordre du mA/cm²), trois réponses de la SEI ont été caractérisées, donnant lieu à des fractures entre les domaines de SEI ou au sein des domaines. Il a été montré que la nature de ces réponses est fortement couplée au régime de déposition et aux propriétés géométriques et physiques de la SEI. Des travaux visant à complexifier la physique et la géométrie de la SEI ont été réalisés an d'identifier les axes d'améliorations du modèle pour tendre vers une interface plus réaliste. Egalement, des études expérimentales préliminaires ont été effectuées afin de proposer un couplage quantitatif entre les résultats numériques issus du modèle et les caractérisations expérimentales effectuées par spectroscopie XPS, AES et par NI-AFM
A Self-Powered Parallel SSHI Interface for Vibration Energy Harvesting
No full textInternational audienceThis paper proposes an original implementation of a self-powered parallel synchronized switch harvesting on inductor interface. Compared to state-of-the-art interfaces, its originality lies in the novel method of detecting switching instants, the use of low-power off-the-shelf logic gates, and the absence of diodes in the switching path. Experimental tests conducted on a custom-designed bistable piezoelectric energy harvester show a power gain of up to 10.2 and a bandwidth gain of about 3 compared to a fully passive interface such as the standard energy harvesting interface. In addition, the proposed interface achieves a smaller phase shift, a wider harvesting frequency range and starts operating at a lower voltage compared to state-of-the-art discrete components interfaces
Cerium occurs as cerium-phosphate clusters around bioapatite nanocrystals in deep-sea sediments
No full textInternational audienceDeep-sea mud is rich in rare-earth elements, primarily found in fluorapatite, a mineral deposit that forms over hundreds of thousands to millions of years through the accumulation of fish remains. After fish die, biogenic apatite captures rare earth elements from seawater on the seafloor and from pore waters during the diagenesis process. The conventional model for rare earth element enrichment suggests that they are incorporated into the bioapatite crystal structure through solid-state diffusion. However, our data reveal that cerium atoms are instead precipitated within an amorphous layer surrounding bioapatite nanocrystals, as shown by high-energy-resolution X-ray absorption spectroscopy and transmission electron microscopy. Computational simulations further support this finding, predicting that cerium atoms cluster on the surface of fluorapatite. These results suggest that the fluorapatite-water interface plays a crucial role in the enrichment of cerium, as well as other rare earth elements, in marine sediments
