HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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High Kinetic Inductance in Platinum‐Coated Aluminum Nanobridge Interferometers
No full textInternational audienceThe transport properties of a nanobridge superconducting quantum interference device made of Al/Pt bilayer have been studied. Measurement and approximation of the voltage-field dependencies allow to estimate the inductance of the structure. It is found that this value significantly exceeds the expected geometric inductance and exhibits an atypical temperature dependence. To explain this effect, a microscopic model of electron transport in SN bilayers is developed, considering the proximity effect, and the available regimes of the current distribution are described. The measured properties may be indicative of the formation of high-resistance aluminum with high values of kinetic inductance during the fabrication of Al/Pt bilayers
All-Josephson junction logic cells and bio-inspired neuron based on 0−0−π junction inductorless blocks
No full textInternational audienceRepresenting information as magnetic flux in superconducting circuits has enabled the development of fast and energy-efficient post-Moore digital circuits. Similar Josephson schemes have also been used to implement promising spiking neural networks. The primary limitation to the practical use of such devices is the relatively low integration density, mainly due to the presence of inductive elements in the circuit. Recently, a solution has been proposed to overcome this problem in circuits by completely removing the inductances and replacing them with conventional Josephson junctions and junctions with π-shifted current-phase relation (π-junctions). In this article, we consider the origin of the required bistability in circuits containing 0-and π-junctions. Furthermore, we extend the application of the all-Josephson junction (all-JJ) circuit approach to the realization of bio-inspired neuromorphic cells, using a superconducting neuron as an example. We claim that the 0-0-π inductorless block of Josephson junctions is a fundamental element for all-JJ logic and neuromorphic cells
Hybrid CIGS‐Cobalt Quaterpyridine Photocathode with Backside Illumination: a New Paradigm for Solar Fuel Production
No full textInternational audienceChalcogenide‐based thin‐film solar cell optimized for rear illumination and used for CO2 reduction is presented. Central to this innovation is a thinner, Cu(In,Ga)S2 chalcopyrite absorber coated with a robust metallic top layer, which potentially surpasses the performance of conventional front‐illuminated designs. Using cobalt quaterpyridine molecular catalyst, photocurrent densities for CO2 reduction exceeding 10 mA/cm2 at 0.0 V vs. RHE under 1 Sun illumination, and ca. 16 mA/cm2 at ‐0.25 V vs. RHE were achieved in voltammetry experiments. Controlled potential electrolysis showed catalytic activity over 20 h with selectivity for CO ranging from > 92% (first 4 hours) to 86% at the end of the experiment. This approach opens limitless possibilities for employing various reduction catalysts, extending far beyond CO2 reduction. It imposes minimal constraints on absorption properties, immobilization methods, and catalyst nature, setting the stage for high‐performance, adaptable PEC devices
The Ascent of Supramolecular Polymers and Gels in Asymmetric Catalysis
No full textInternational audienceSupramolecular polymers (SPs) and gels, formed by the spontaneous assembly of small molecules through various types of noncovalent interactions, are attractive materials for many applications. Their modularity also offers many opportunities in asymmetric catalysis that have been tackled in the last two decades and more intensively in the last one. In this review, strategies adopted to develop efficient asymmetric catalysts supported on SPs and gels are first categorized according to the chiral or achiral nature of the monomers used for their construction and second to their ability to be commuted into different states. Catalytic SPs have been described for which enantioselectivity stems mostly from the molecular chirality located next to the reactive group, or at opposite ends of the spectrum, exclusively from the chiral environment provided by the supramolecular helices. New paradigms revealed by these systems include (i) the organization of catalytic sites at the periphery of modular and well-structured 1D assemblies, (ii) the possibility to conduct asymmetric reactions with a sub-catalytic amount of chiral inducers and even in the absence of chiral monomers, and (iii) the development of a new class of switchable asymmetric catalysts
Démonstration in vivo d'un ophtalmoscope par illumination structurée corrigé par optique adaptative sur rétine humaine
No full textInternational audienceStructured illumination microscopy (SIM) is one of the most versatile super-resolution techniques. Yet, its application to high-resolution live imaging has been mainly limited to fluorescent and stationary specimens. Here, we present advancements in SIM to jointly tackle all the challenges of imaging living samples, i.e. , obtaining super-resolution over an undistorted wide-field while dealing with sample motion, multiple scattering, sample-induced optical aberrations, and low signal-to-noise ratio. By using adaptive optics to compensate for optical aberrations and a reconstruction algorithm tailored for moving and thick tissue, we successfully apply SIM to in vivo retinal imaging and demonstrate structured illumination ophthalmoscopy with optical sectioning and resolution improvement for in vivo imaging of the human retina
Développement d'une architecture analogique symétrique pour le retournement temporel de signaux RF large bande à l'aide de cristaux dopés aux ions de terre rare
No full textThis thesis focuses on the development of an innovative optical analog architecture for the time-reversal of radiofrequency signals, leveraging the unique properties of a crystal doped with rare-earth ions. The proposed architecture is based on a three-pulse photon echo sequence and enables the time-reversal of signals modulated in both amplitude and phase.The implementation of this architecture for wideband signals required the development of an agile laser source capable of performing frequency sweeps that are both extremely fast and highly precise. Starting with a commercially available laser source that was agile but lacked precision, we designed a method to effectively correct frequency excursions. This method is compatible with both rapid frequency sweeps and fixed-frequency operation. We demonstrated arbitrary frequency sweeps (up to 300 MHz in 330 ns) with a relative error on the order of MHz, while maintaining excellent stability in fixed-frequency mode with a 30 kHz linewidth.However, an in-depth analysis of the photon echo formation process revealed fundamental scaling laws that limit the echo amplitude during the time-reversal of broadband signals. Additionally, we identified Instantaneous Spectral Diffusion (ISD)—a decoherence mechanism associated with the massive excitation of rare-earth ions—as a major factor limiting the performance of time-reversal. Despite these constraints, we successfully achieved the time-reversal of an amplitude-modulated signal with a record time-bandwidth product of P = 280. The duration of the processed signals reached several microseconds, but the obtained bandwidth remains modest at 32.5 MHz, due to the echo degradation caused by scaling laws and ISD. Nevertheless, the demonstrated phase stability paves the way for the time-reversal of phase-modulated signals, a critical requirement for refocusing applications in complex media.Cette thèse porte sur le développement d’une architecture analogique optique innovante pour le retournement temporel de signaux radiofréquence, exploitant les propriétés uniques d'un cristal dopé aux ions de terre rare. L'architecture étudiée est dérivée d'une séquence d’écho de photons à trois impulsions, et offre la capacité de retourner des signaux modulés en amplitude et en phase.La mise en oeuvre de cette architecture pour des signaux large bande a nécessité le développement d'une source laser agile, capable de réaliser des balayages en fréquence à la fois très rapides et précis. A partir d'une source laser commerciale agile mais peu précise, nous avons conçu une méthode permettant de corriger efficacement les excursions en fréquence. Cette méthode est compatible avec des balayages rapides mais aussi avec un fonctionnement à fréquence fixe. Nous avons ainsi démontré des balayages arbitraires (jusqu'à 300 MHz en 330 ns) avec une erreur relative de l'ordre du MHz tout en conservant une excellente stabilité à fréquence fixe avec une largeur de raie de 30 kHz.Cependant, une analyse approfondie du processus de formation des échos de photon a mis en évidence des lois d’échelle fondamentales limitant l'amplitude des échos lors du retournement temporel de signaux à large bande. De plus, nous avons identifié la diffusion spectrale instantanée (ISD), un mécanisme de décohérence lié à l'excitation massive des ions de terre rare, comme un facteur majeur de limitation des performances du retournement temporel. Malgré ces contraintes, nous avons réussi à retourner un signal modulé en amplitude atteignant un produit temps-bande passante record de P = 280. La durée des signaux traités a été portée à plusieurs microsecondes, mais la bande passante obtenue reste modeste avec 32.5 MHz en raison de la dégradation des échos provoquée par les lois d'échelle et l'ISD. Néanmoins, la stabilité en phase démontrée ouvre la voie au retournement de signaux modulés en phase, un critère essentiel pour des applications de refocalisation en milieu complexe
Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures
No full textInternational audienceAs winds blow over sand, grains are mobilized and reorganized into bedforms such as ripples and dunes. In turn, sand transport and bedforms affect the winds themselves. These complex interactions between winds and sediment render modeling of windswept landscapes challenging. A critical parameter in such models is the aerodynamic roughness length, z 0 , defined as the height above the bed at which wind velocity predicted from the log law drops to zero. In aeolian environments, z 0 can variably be controlled by the laminar viscous sublayer, grain roughness, form drag from bedforms, or the saltation layer. Estimates of z 0 are used on Mars, notably, to predict wind speeds, sand fluxes, and global circulation patterns; yet, no robust measurements of z 0 have been performed over rippled sand on Mars to date. Here, we measure z 0 over equilibrated rippled sand beds with active saltation under atmospheric pressures intermediate between those of Earth and Mars. Extrapolated to Mars, our results suggest that z 0 over rippled beds and under active saltation may be dominated by form drag across a plausible range of wind velocities, reaching values up to 1 cm -- two orders of magnitude larger than typically assumed for flat beds under similar sediment transport conditions.</div
Droplet-on-demand using a positive pressure pulse
No full textInternational audienceDroplet generation under steady conditions is a common microfluidic method for producing biphasic systems. However, this process works only over a limited range of imposed pressure: beyond a critical value, a stable liquid jet can instead form. Furthermore, for a given geometry the pressure conditions set both the generation rate of droplets and their volume. Here, we report on-demand droplet production using a positive pressure pulse to the dispersed-phase inlet of a flow-focusing geometry. This strategy enables confined droplet generation within and beyond the pressure range observed under steady conditions, and decouples volume and production rate. In particular, elongated plugs not possible under steady conditions may be formed when the maximal pressure during the pulse reaches the jet regime. The measured volume of droplets-on-demand, as well as the onset of droplet generation are both captured with a simple model that considers hydraulic resistances. This work provides a strategy and design rules for processes that require individual droplets or elongated plugs in a simple microfluidic chip design
Empathi: Embedding-based Phage Protein Annotation Tool by Hierarchical Assignment
No full textBacteriophages, viruses infecting bacteria, are estimated to outnumber their cellular hosts by 10-fold, acting as key players in all microbial ecosystems. Under evolutionary pressure by their host, they evolve rapidly and encode a large diversity of protein sequences. Consequently, the majority of functions carried by phage proteins remain elusive. Current tools to comprehensively identify phage protein functions from their sequence either lack sensitivity (those relying on homology for instance) or specificity (assigning a single coarse grain function to a protein). Here, we introduce Empathi, a protein-embedding-based classifier that assigns functions in a hierarchical manner – from general functional categories such as “structural” and “DNA-associated” proteins to more specific ones including “nucleases”, “tail appendages” and “endolysins” to name only a few. These categories were specifically tailored for phage protein functions and organized such that molecular-level functions are respected in each category, making it well suited for training machine learning classifiers based on protein embeddings. We show on a dataset of cultured phage genomes that Empathi significantly outperforms homology-based methods, tripling the number of annotated homologous groups. On the EnVhog database, the most recent and extensive database of metagenomically-sourced phage proteins, Empathi doubled the annotated fraction of protein families from 16% to 33%. On complete genomes taken from new viromes, almost twice as many proteins are annotated using our method, predictions are consistent when compared to existing tools and Empathi predictions are highly colocalized. In addition, by leveraging Empathi’s ability to assign multiple labels to the same protein, it is possible to identify multifunctional proteins such as virion-associated lysins. Having a more global view of the repertoire of functions a phage possesses will assuredly help to understand them and their interactions with bacteria better
Chemical dissection of selective myeloid leukemia-1 inhibitors: How they were found and evolved
No full textInternational audienceMyeloid cell leukemia-1 (MCL-1), a key anti-apoptotic protein within the BCL-2 family, is essential in regulating cell survival, particularly in cancer, where its overexpression is often linked to therapeutic resistance. This review begins with an overview of BCL-2-mediated apoptosis, highlighting the pivotal role of MCL-1 in cellular homeostasis. We then focus on the structure and function of MCL-1, elucidating how its unique structural features contribute to its function and interaction with pro-apoptotic proteins. The core of this review is a detailed structural analysis of selective MCL-1 inhibitors, tracing their development from initial discovery to stepwise optimization.We explore various classes of inhibitors, including those with distinct core structures, covalent inhibitors that reversibly/irreversibly bind to MCL-1, and innovative approaches such as metal-based inhibitors and proteolysis-targeting chimeras (PROTACs). The structural evolution of these inhibitors is discussed, with particular emphasis on the modifications that have enhanced their selectivity, potency, and pharmacokinetic profiles. Additionally, we summarize the synergistic potential of MCL-1 inhibitors when used in combination with other therapeutic agents, emphasizing their role in overcoming drug resistance. The review concludes with a discussion of current challenges in MCL-1 modulation and future perspectives, proposing alternative strategies for targeting this critical protein for cancer therapy.</p