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A Prototype Hybrid Mode Cavity for Heterodyne Axion Detection
No full textInternational audienceIn the heterodyne approach to axion detection, axion dark matter induces transitions between two modes of a microwave cavity, resulting in a parametrically enhanced signal power. We describe the fabrication and characterization of a prototype normal conducting cavity specifically optimized for heterodyne detection. Corrugations on the cavity walls support linearly polarized hybrid modes which maximize the signal power while strongly suppressing noise. We demonstrate tuning mechanisms which allow one mode's frequency to be scanned across a 4 MHz range, while suppressing cross-coupling noise by at least 80 dB. A future superconducting cavity with identical geometry to our prototype would have the potential to probe orders of magnitude beyond astrophysical bounds
Ancestral [Fe-S] biogenesis system SMS has a unique mechanism of cluster assembly and sulfur utilization
No full textInternational audience[Fe-S] clusters are ancient and ubiquitous protein co-factors, which contributed to the emergence of life in an anoxic planet. We have recently identified two minimal [Fe-S] biogenesis systems, MIS and SMS, inferred to be ancestral systems dating back to the Last Universal Common Ancestor and which gave rise to the well-studied modern Iron-Sulfur Cluster (ISC), Nitrogen Fixation (NIF), and Sulfur Mobilization (SUF) machineries. The present study focuses on the ancestor SMS from the hyperthermophilic archaeon Methanocaldococcus jannaschii. Biochemical and structural studies showed that SMS is made of a SmsC2B2 heterotetratmer wherein the SmsC subunit hosts both ATP and [Fe-S] cluster binding sites. Binding of ATP and assembly of [Fe-S] were found to be mutually exclusive allowing for a regulatory coupling between binding of both substrates. Mutagenesis and in vitro transfer experiments revealed the key role of SmsC-contained Cys residues in cluster assembly. Strikingly, the SMS system rescued a non-viable Escherichia coli strain lacking endogenous ISC and SUF systems grown under anoxic conditions, in the presence of Na2S, indicating that sulfide is a source of sulfur for SMS. In addition, we predict that most archaea SmsC proteins hold a similar C-terminal [Fe-S] cluster assembly site. Taking into account those unique structural and functional features, we propose a mechanistic model describing how SmsC2B2 assembles and distributes [4Fe-4S] clusters. Altogether this study established SMS as a new bona fide [Fe-S] biogenesis system that operated in anaerobic prokaryotes prior to evolve to SUF after the Great Oxydation Event
Exploring intellectual history with dynamic word embeddings: semantic change in 18th-century France
No full textInternational audienceThis study leverages dynamic contextual embeddings to analyze conceptual evolution in 18th-century French texts. Employing fine-tuned BERT and CamemBERT models, we identify diachronic semantic shifts across historical subcorpora. Quantitative metrics and qualitative assessments reveal nuanced changes in key concepts land concept clusters, advancing methods in computational intellectual history
Hyperelastic nature of Hoek-Brown criterion
No full textWe propose a nonlinear elasto-plastic model, for which a specific class of hyperbolic elasticity arises as a straight consequence of the yield criterion invariance on the plasticity level. We superimpose this nonlinear elastic (or hyperelastic) behavior with plasticity obeying the associated flow rule. Interestingly, we find that a linear yield criterion on the thermodynamical force associated with plasticity results in a quadratic yield criterion in the stress space. This suggests a specific hyperelastic connection between Mohr–Coulomb and Hoek–Brown (or alternatively between Drucker–Prager and Pan–Hudson) yield criteria. We compare the elasto-plastic responses of standard tests for the Drucker–Prager yield criterion using either linear or the suggested hyperbolic elasticity. Notably, the nonlinear case stands out due to dilatancy saturation observed during cyclic loading in the triaxial compression test. We conclude this study with structural finite element simulations that clearly demonstrate the numerical applicability of the proposed model
Elaboration de ferrites spinelles par impression 3D pour applications à haute fréquence
No full text(Mn,Zn)Fe2O4 and (Ni,Zn,Cu)Fe2O4 ferrites are widely used as soft magnetic materials for passive components (transformers, inductors) operating up to several MHz in power electronics applications, such as power converters. However, reducing the size of these components, which occupy about 40% of the volume of converters, could be facilitated by the design of complex-shaped cores potentially including property gradients.In this context, additive manufacturing techniques applied to ferrite magnetic cores present an interesting opportunity to improve core integration, particularly by enabling the realization of innovative architectures.The objective of this thesis is to study the potential of 3D printing magnetic cores based on MnZn and NiZnCu ferrites through paste extrusion and to demonstrate that the components produced using this shaping method can achieve magnetic performance comparable to, or even superior to, those obtained by the conventional die pressing process. Work on the formulation of the pastes has led to the optimization of the mass loading rate (82 wt% for MnZn ferrite and 84 wt% for NiZnCu ferrite), as well as an investigation into the influence of particle size and shape on viscosity. A degassing step for the paste was added to limit air inclusions and improve the green density of the printed parts.Process parameters, particularly printing speed and printing bed temperature, were adjusted based on systematic characterizations of the rheological behavior of the pastes. This approach enabled the printing of components with geometries corresponding to CAD models, in particular because of very good resistance to sagging during extrusion. The debinding and sintering cycles were defined to ensure effective densification while avoiding cracking of the components and ensuring the formation of the desired ferrimagnetic spinel phase for both MnZn and NiZnCu ferrites. Printed parts made with degassed pastes achieved a relative density greater than 90%, and their microstructure (grain size, residual porosity) could be correlated with powder characteristics and sintering parameters.In some cases, samples produced from uniaxial compaction exhibited higher losses than those printed, measuring 448 mW/cm³ compared to 363 mW/cm³ (for MnZn ferrite: at 1 MHz and under 50 mT). The study showed that the geometry of the components significantly influences eddy current losses and can induce dimensional resonance. We demonstrated that permeability is primarily related to porosity, whether macro or micro, and that grain size plays a key role in optimizing the magnetic performance of NiZnCu ferrites. We overcame the issue of low green density in printed parts by using a paste composed of two different particle sizes.Les ferrites (Mn,Zn)Fe2O4 et (Ni,Zn,Cu)Fe2O4 sont largement utilisés comme matériaux magnétiques doux pour les composants passifs (transformateurs, inducteurs) fonctionnant jusqu'à plusieurs MHz dans les applications d'électronique de puissance, telles que les convertisseurs de puissance. Toutefois, une réduction de la taille de ces composants, qui occupent environ 40 % du volume des convertisseurs, pourrait être facilitée par la conception de noyaux de forme complexe comprenant éventuellement des gradients de propriétés.Dans ce contexte, les techniques de fabrication additive appliquées aux noyaux magnétiques de ferrite constituent une opportunité intéressante pour améliorer l’intégration des noyaux, en accédant notamment à la réalisation d’architectures innovantes.L’objectif de cette thèse est d’étudier de potentiel de l’impression 3D de noyaux magnétiques à base de ferrites MnZn et NiZnCu par extrusion de pâte et de démontrer que les pièces élaborées avec cette méthode de mise en forme peuvent atteindre des performances magnétiques comparables, voire supérieures, à celles obtenues par le procédé conventionnel de pressage en matrice. Le travail sur la formulation des pâtes a permis l’optimisation du taux de charge massique (82 wt% pour ferrite MnZn et 84 wt% pour ferrite NiZnCu), ainsi que l’étude de l’influence de la granulométrie et de la forme des particules sur la viscosité. Une étape de dégazage de la pâte a été ajoutée pour limiter les inclusions d’air et améliorer la densité crue des pièces imprimées.Les paramètres de procédé, en particulier la vitesse d’impression et la température de support d’impression, ont été ajustés sur la base de caractérisations systématiques du comportement rhéologique des pâtes. Cette approche a permis d’imprimer des pièces avec des géométries correspondant aux modèles de CAO, notamment grâce à une très bonne résistance aux affaissements durant l’extrusion. Les cycles de déliantage et de frittage ont été définis pour garantir une densification efficace en évitant la fissuration des pièces et pour assurer la formation de la phase spinelle ferrimagnétique souhaitée pour les ferrites MnZn et les ferrites NiZnCu. Les pièces imprimées avec des pâtes dégazées ont atteint une densité relative supérieure à 90 % et leur microstructure (taille de grain, porosité résiduelle) a pu être reliée aux caractéristiques des poudres et des paramètres de frittage.Dans certains cas, les échantillons issus de la compaction uni-axiale présentent des pertes plus élevées que ceux imprimées 448 mW/cm³ contre 363 mW/cm³ (pour le ferrite MnZn : à 1 MHz et sous 50 mT). L’étude a montré que la géométrie des pièces influence significativement les pertes par courants de Foucault et peut induire une résonance dimensionnelle. Nous avons démontré que la perméabilité est principalement liée à la porosité, qu'elle soit macro ou micro et que la taille des grains joue un rôle clé dans l’optimisation des performances magnétiques des ferrites NiZnCu. Nous avons surmonté le problème de la faible densité à cru dans les pièces imprimées, par l’emploi d’une pâte composée de deux granulométries différentes
Cation–Cation Interactions in Neptunium(V,VI)-diglycolamide System
No full textInternational audienceThe SC-XRD structure and Raman spectra of two new mixed-valence Np(V)–Np(VI) compounds with cation–cation interactions (CCIs) using TEDGA (tetraethyldiglycolamide, belonging to the diglycolamide family) as a ligand are reported: a trimeric species, [NpVO2(TEDGA)2]2[NpVIO2(NO3)2](NO3)2 (1), which is the first neptunium representative of a linear actinide trimer with CCIs, and a dimeric species, [NpVO2(TEDGA)2][NpVIO2(NO3)3]·CH3CN (2). These two structures were prepared thanks to controlled and reproducible syntheses, based on the mixing of the two monomer solutions in an inert solvent: a Np(V)-TEDGA monomer solution mixed with a dinitrate or trinitrate Np(VI) solution. To better understand the impact of the CCIs on the actinyl cation electronic properties, these structures were compared to the constituent monomers, [NpVO2(TEDGA)2]+ (3), which was also synthesized, and NpVIO2(NO3)2(H2O)2. To complete the series, the [NpVIO2(TEDGA)2]2+ (4) monomer is also reported. In addition, DFT calculations were performed to aid in interpreting the Raman experimental data, to characterize the bonding in such polynuclear species, and to identify the main parameters influencing the stability of cation–cation structures, such as the nature of counterions, the influence of alkyl chains and the presence of weak intra- or intermolecular interactions
The in crystallo optical spectroscopy toolbox
No full textInternational audienceOver the past ten years, there has been a surge in the demand for in crystallo optical spectroscopy ( ic OS), since optical spectroscopy is one of the few biophysical characterization methods applicable to both protein solutions and crystals. Historically, ic OS has been used to compare the state of proteins in crystals and in solution, and to assess their functionality by determining the redox state of metal ions, cofactors or chromophores. The recent rejuvenation of time-resolved crystallography experiments has sparked a renewed interest in optical spectroscopy as a bridge between kinetic studies in solution and in the crystalline state. The method of ic OS can be defined as the ensemble of spectroscopic techniques in the UV–visible–infrared range that can be applied to crystals. It has also been instrumental in understanding specific X-ray radiation damage to redox-sensitive parts of proteins. Spectra recorded from crystals are affected by crystal orientation, shape or position due to various optical phenomena. Fortunately, these can be modelled and their effect can be corrected. The ic OS laboratory at the European Synchrotron Radiation Facility (ESRF) specializes in recording UV–Vis absorption, fluorescence emission and Raman spectra from protein crystals. Here, we present a suite of utilities that streamline the analysis and correction of UV–Vis absorption ic OS data, encased in a graphical interface. This was originally developed for the ic OS laboratory at ESRF but is available as a standalone package, with the aim of making ic OS more accessible
Growth orientation and magnetic properties of GdVO 3 tailored by epitaxial strain engineering
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Euclid: An emulator for baryonic effects on the matter bispectrum
No full textInternational audienceThe Euclid mission and other next-generation large-scale structure surveys will enable high-precision measurements of the cosmic matter distribution. Understanding the impact of baryonic processes such as star formation and AGN feedback on matter clustering is crucial to ensure precise and unbiased cosmological inference. Most theoretical models of baryonic effects to date focus on two-point statistics, neglecting higher-order contributions. This work develops a fast and accurate emulator for baryonic effects on the matter bispectrum, a key non-Gaussian statistic in the nonlinear regime. We employ high-resolution -body simulations from the BACCO suite and apply a combination of cutting-edge techniques such as cosmology scaling and baryonification to efficiently span a large cosmological and astrophysical parameter space. A deep neural network is trained to emulate baryonic effects on the matter bispectrum measured in simulations, capturing modifications across various scales and redshifts relevant to Euclid. We validate the emulator accuracy and robustness using an analysis of \Euclid mock data, employing predictions from the state-of-the-art FLAMINGO hydrodynamical simulations. The emulator reproduces baryonic suppression in the bispectrum to better than 2 for the percentile across most triangle configurations for and ensures consistency between cosmological posteriors inferred from second- and third-order weak lensing statistics
Le nettoyage à l'eau atténue-t-il la dégradation atmosphérique des verres instables du patrimoine ? Une étude expérimentale sur des verres modèles
No full textInternational audienceGlass curators often question how their treatments affect the long-term stability of historical glass. While damp cotton swabs are commonly used to remove surface salts and dust, the use of water remains controversial, particularly for heavily altered glass, due to concerns about worsening hydration. This study investigates the effect of water rinsing on an unstable soda-lime glass altered for six months (monoliths) and fifteen months (powders) at 35 °C and 85% relative humidity. Samples were then rinsed with Milli-Q water at 20 °C or 50 °C, and the monolithic glass was subsequently subjected to an additional 15 months of alteration under the same conditions. The glass surface was characterized by optical and scanning electron microscopy (SEM) as well as Raman spectroscopy to identify the nature of the salts. The evolution of the hydrated layer was assessed using transmission FTIR, Raman and solid-state NMR spectroscopies, ToF-SIMS, and thermogravimetric analysis (TGA). The results show that rinsing effectively removes surface salts—primarily sodium carbonate—and induces structural changes in the hydrated layer, promoting silicate network polymerization. Upon resuming alteration, rinsed monolithic samples exhibit no further degradation after the additional 15 months of alteration. These findings offer promising insights for conservation practices and may help curators refining their treatment strategies for altered glass.Les conservateurs de musée ayant en charge des objets en verre s'interrogent souvent sur l'impact de leurs traitements sur la stabilité à long terme de ces objets du patrimoine. Alors que des cotons-tiges humides sont couramment utilisés pour éliminer les sels présents en surface et la poussière, l'utilisation de l'eau reste controversée, en particulier pour les verres fortement altérés, en raison des craintes d'aggravation de l'hydratation. Cette étude examine l'effet du rinçage à l'eau sur un verre sodocalcique instable altéré pendant six mois (monolithes) et quinze mois (poudres) à 35 °C et 85 % d'humidité relative. Les échantillons ont ensuite été rincés avec de l'eau Milli-Q à 20 °C ou 50 °C, et le verre monolithique a ensuite été soumis à une altération supplémentaire de 15 mois dans les mêmes conditions. La surface du verre a été caractérisée par microscopie optique et électronique à balayage (MEB) ainsi que par spectroscopie Raman pour identifier la nature des sels. L'évolution de la couche hydratée a été évaluée à l'aide des spectroscopies FTIR en transmission, Raman et RMN à l'état solide, ToF-SIMS et analyse thermogravimétrique (TGA). Les résultats montrent que le rinçage élimine efficacement les sels de surface - principalement le carbonate de sodium - et induit des changements structuraux dans la couche hydratée, favorisant la polymérisation du réseau silicaté. Lors de la reprise de l'altération, les échantillons monolithiques rincés ne présentent plus de dégradation après 15 mois supplémentaires d'altération. Ces résultats offrent des perspectives prometteuses pour les pratiques de conservation et peuvent aider les conservateurs à affiner leurs stratégies de traitement du verre altéré