Cocons skyrmioniques : nouvelles textures magnétiques 3D dans des multicouches magnétiques apériodiques

The field of 3D nanomagnetism is rapidly expanding within spintronics, encompassing magnetic nanostructures and intricate spin textures that extend beyond two effective dimensions and vary along the third dimension, normal to the film's plane. Magnetic multilayers, composed of repetitions of a ferromagnetic element encapsulated between metals, enable excellent control over magnetic properties and the stabilization of various spin textures, making them excellent platforms for developing 3D nanomagnetism.This thesis explores the tunability of magnetic multilayers to stabilize novel 3D magnetic textures, that we have baptized "skyrmionic cocoons". These are ellipsoidal objects which occupy only a fraction of the multilayer thickness. Two distinct multilayer structures have been thoroughly studied with varying ferromagnet thickness. The first allows for the stabilization of cocoons whose extension can be controlled with an external magnetic field or structural adjustments. The second multilayer utilizes ferromagnetic layers with strong perpendicular magnetic anisotropy to modulate magnetic textures along the thickness. This results in the coexistence of two types of spin textures: the more common 2D columnar skyrmion alongside the 3D skyrmionic cocoon. This cohabitation is important for developing future spintronics devices, for example to encode several memory states.However, observing and measuring magnetization in 3D remains a challenge, often relying on techniques involving synchrotron light. During this thesis, various experimental approaches have been employed to confirm the 3D nature of skyrmionic cocoons, including magnetic force microscopy and magnetotransport measurements as well as advanced X-rays techniques like holography and laminography. Micromagnetic simulations were also conducted, supporting the existence of 3D spin textures and corroborating the experimental findings. This research paves the way for further exploiting multilayer tunability to harness the third dimension of magnetization, representing a significant step towards the development of 3D skyrmionic devices.Le domaine du nanomagnétisme tri-dimensionnel (3D) connaît une expansion rapide au sein de la spintronique, englobant des nanostructures magnétiques et des textures de spin complexes qui s'étendent au-delà de deux dimensions effectives et varient selon la troisième, le long de la normale du film magnétique. Les multicouches magnétiques, composées de répétitions d'un élément ferromagnétique encapsulé entre des métaux, permettent un excellent contrôle des propriétés magnétiques et la stabilisation de différentes textures de spin, ce qui en fait d'excellentes plateformes pour le développement du nanomagnétisme 3D.Cette thèse exploite le potentiel des multicouches magnétiques pour stabiliser de nouvelles textures magnétiques 3D, que nous avons dénommées cocons skyrmioniques. Ce sont des objets ellipsoïdaux occupant une fraction de l'épaisseur totale de la multicouche magnétique. Deux structures de multicouches distinctes ont été minutieusement étudiées qui sont caractérisées par une épaisseur variable de l'épaisseur de l'élément ferromagnétique. La première permet de stabiliser les cocons skyrmioniques dont l'extension peut être contrôlée à l'aide d'un champ magnétique externe ou d'ajustements structurels. La deuxième multicouche utilise des couches ferromagnétiques présentant une forte anisotropie magnétique perpendiculaire pour moduler les textures magnétiques le long de l'épaisseur. Il en résulte la coexistence de deux types de textures de spin : le skyrmion colonnaire 2D aux côtés du cocon skyrmionique 3D. Cette cohabitation est importante pour le développement de futurs dispositifs de spintronique, par exemple pour encoder plusieurs états de mémoire.Cependant, l'observation et la mesure de l'aimantation en 3D continue d'\^etre un défi, reposant souvent sur des techniques impliquant la lumière synchrotron. Au cours de cette thèse, diverses approches expérimentales ont été utilisées pour confirmer la nature en 3D des cocons skyrmioniques, notamment la microscopie à force magnétique et les mesures de magnétotransport, ainsi que des techniques avancées utilisant des rayons X comme l'holographie et la laminographie. Des simulations micromagnétiques ont également été réalisées, soutenant l'existence de textures de spin 3D et corroborant les résultats expérimentaux. Cette recherche ouvre la voie à une maîtrise plus poussée des multicouches pour exploiter la troisième dimension de l'aimantation, représentant ainsi une étape significative vers le développement de dispositifs skyrmioniques 3D

Grégoire de Nysse : la Bible dans la construction de son discours. Actes du colloque de Paris, 9-10 février 2007

Le colloque international consacré à Grégoire de Nysse qui s'est tenu à Paris en février 2008 a porté sur les rapports de cet auteur à l'Écriture. Après de nombreuses études sur l'exégèse de l'évêque de Nysse, il a paru fructueux de s'intéresser à la manière dont le texte biblique intervient dans l'organisation et la composition de ses œuvres. Quelques communications portent, de manière transversale, sur la place de la Bible dans l'élaboration de la théologie de Grégoire (théologie trinitaire, infinité divine, etc.) ; la plupart concernent les fonctions du matériau biblique dans une œuvre ou un groupe d'œuvres données. L'ensemble de ces études a permis de préciser le contexte d'écriture et les visées propres des œuvres, mais surtout de dégager quelques constantes dans l'emploi et le rôle des textes bibliques, en fonction des genres littéraires, du contexte doctrinal et des destinataires visés. Les rapports à la pratique liturgique ainsi qu'à la définition d'une tradition ecclésiale ont également été envisagés

Three-dimensional skyrmionic cocoons in magnetic multilayers

Three-dimensional (3D) topological spin textures emerge as promising quasi-particles for encoding information in future spintronic devices. The third dimension provides more malleability regarding their magnetic properties as well as more flexibility for potential applications. However, the stabilization and characterization of such quasi-particles in easily implementable systems remain a work in progress. Here we observe a new type of 3D magnetic textures that we called skyrmionic cocoons that sits in the interior of magnetic thin films multilayers and possesses a characteristic ellipsoidal shape. Interestingly, these cocoons can coexist with more standard `tubular' skyrmions going through all the multilayer as evidenced by the existence of two very different contrasts in the MFM images recorded at room temperature. The presence of these novel skyrmionic textures as well as the understanding of their layer resolved chiral and topological properties have been investigated by micromagnetic simulations. In order to experimentally stabilize the combination of 3D skyrmion tubes and cocoons, we have elaborated metallic multilayers in which the magnetic properties, notably the anisotropy, of the magnetic films in the stacks is varied depending on their vertical position. Finally, in complement to the magnetic imaging, we also measure the magneto-resistive response of the multilayers as a function of the magnetic field, and succeed to fit its evolution using the 3D micromagnetic simulations as inputs for the magnetic configuration. The excellent agreement that is reached brings additional evidence of the presence of skyrmionic cocoons that hence can be electrically detected.Comment: 13 pages, 4 figure

Integrated chain for the hydrometeorological forecasting of low flows and droughts in France. The CIPRHES project

International audienceThere has been a growing interest in extending forecast lead times to facilitate water resources planning and management during droughts and low-flow events. This can be partly achieved by improving integrated hydrometeorological forecasting systems, which offer forecasts of future meteorological and hydrological conditions over continuous space and time scales. Several initiatives have been recently carried out at continental or global scales, in Europe and worldwide, to set up forecasting chains that run with numerical weather and climate model predictions as input to distributed hydrological models. Overall, these systems have been developed in response to a call for seamless forecasts in time (from short to medium and long-ranges) and space (at well-monitored and partially-monitored or ungauged catchments). These systems usually have to deal with limited calibration and evaluation against local data.In France, the CIPRHES project (2021-2025) aims at building an efficient and integrated methodology and an online operational service for a country-wide hydrological drought and low-flow forecasting system, based on the proof-of-concept PREMHYCE platform. The first step focuses on producing seamless atmospheric forecasts, combining information from climatology, weather predictions and seasonal forecasts. Then forecasts are post-processed and tailored for hydrological purposes of drought and low-flow forecasting.The first outcomes of the project will be presented, towards providing short- to long-term seamless hydrological forecasts. The outputs of a workshop organized with end-users to improve a forecasting prototype will be discussed.The CIPRHES project is funded by the French National Research Agency (grant ANR-20-CE04-0009-03)

Chaine intégrée pour la prévision hydrométéorologique des étiages et des sécheresses (CIPRHES) en France

National audienc

Chaine intégrée pour la prévision hydrométéorologique des étiages et des sécheresses (CIPRHES) en France

National audienc

Rilpivirine in HIV-1-positive women initiating pregnancy: to switch or not to switch?

International audienceBackgroundSafety data about rilpivirine use during pregnancy remain scarce, and rilpivirine plasma concentrations are reduced during second/third trimesters, with a potential risk of viral breakthroughs. Thus, French guidelines recommend switching to rilpivirine-free combinations (RFCs) during pregnancy.ObjectivesTo describe the characteristics of women initiating pregnancy while on rilpivirine and to compare the outcomes for virologically suppressed subjects continuing rilpivirine until delivery versus switching to an RFC.MethodsIn the ANRS-EPF French Perinatal cohort, we included women on rilpivirine at conception in 2010–18. Pregnancy outcomes were compared between patients continuing versus interrupting rilpivirine. In women with documented viral suppression (<50 copies/mL) before 14 weeks of gestation (WG) while on rilpivirine, we compared the probability of viral rebound (≥50 copies/mL) during pregnancy between subjects continuing rilpivirine versus those switching to RFC.ResultsAmong 247 women included, 88.7% had viral suppression at the beginning of pregnancy. Overall, 184 women (74.5%) switched to an RFC (mostly PI/ritonavir-based regimens) at a median gestational age of 8.0 WG. Plasma HIV-1 RNA nearest delivery was <50 copies/mL in 95.6% of women. Among 69 women with documented viral suppression before 14 WG, the risk of viral rebound was higher when switching to RFCs than when continuing rilpivirine (20.0% versus 0.0%, P = 0.046). Delivery outcomes were similar between groups (overall birth defects, 3.8/100 live births; pregnancy losses, 2.0%; preterm deliveries, 10.6%). No HIV transmission occurred.ConclusionsIn virologically suppressed women initiating pregnancy, continuing rilpivirine was associated with better virological outcome than changing regimen. We did not observe a higher risk of adverse pregnancy outcomes