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Development of a Generic Bio-Interface for Immuno-Biodetection on an Oxide Surface Targeting Pathogen Bacteria
No full textInternational audienceWith the increase in contamination by microbial agents (bacteria, viruses, etc.) in the fields of agri-food, healthcare, and environment, it is necessary to detect and quantify these biological elements present in complex fluids in a short time with high selectivity, high sensitivity, and, if possible, moderate cost. Acoustic wave biosensors, based on immuno-detection, appear to meet a certain number of these criteria. In this context, we are developing a generic antibody-based biointerface that can detect a wide range of pathogenic bacterial agents using a specific bioreceptor. Based on the silane–oxide chemistry, the process is transferable to any kind of surface that can be either oxidized in surface or activated with O2-plasma, for instance. For this proof of concept, we have chosen to develop our biointerface on titanium and lithium niobate surfaces. The development of the biointerface consists of grafting antibodies via a self-assembled monolayer (SAM) composed of an aminopropyltriethoxysilane (APTES) and a linker (phenylene diisothiocyanate, PDITC). Two functionalization routes were tested for grafting APTES: in anhydrous toluene followed by a heating step at 110 °C or in chloroform at room temperature. The results obtained on titanium show comparable grafting efficiency between these two routes, allowing us to consider the transposition of the route at room temperature on lithium niobate. The latest route was chosen for fragile materials that do not require the heating steps necessary when using toluene for grafting aminopropyltriethoxysilane. Different surface characterization techniques were used, such as IR spectroscopy (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), and contact angle (WCA), to verify the successful grafting of each layer. Biodetection experiments in static conditions were also carried out to demonstrate the specificity of pathogenic detection, testing an ideal medium with solely bacteria, with no other food sampling nutrients. This paper demonstrates the successful elaboration of a biointerface using APTES as the first anchoring layer, with chloroform as a mild solvent. The process is easily transferable to any kind of fragile surface. Moreover, following anti-L. monocytogenes antibodies, our biointerface shows a specificity of capture in static mode (at a concentration of 107 CFU/mL for an incubation time of 4 h at 37 °C) of up to 98% compared to a species negative control (E. coli) and up to 85% in terms of strain specificity (L. innocua)
Controlling the group velocity of a Bessel Beam
No full textInternational audienceBessel beams are a family of beams resulting from interference between plane waves propagating at an angle θ in a conical geometry. The result is a needle-like intense central spot along the optical axis. In some applications, such as terahertz generation [1], controlling the group velocity of the Bessel beam is fundamental. It is well known that the group velocity of the Bessel beam is influenced by its spatio-temporal profile [2]. Two examples are the Bessel X-pulse and the pulsed Bessel beam with a velocity of c cos(θ) and c cos(θ) respectively [3]. However, Bessel pulses can have an infinite number of spatio-temporal profiles, and simulating their profile could give us the velocity of the Bessel beam. Although some existing programs can simulate spatio-temporal coupling in a setup [4], they are computationally intensive. Here, we present a program that simulates the spatio-temporal profile of any Bessel beam in an arbitrary optical setup. Using a Zemax ray-tracing simulation of the optical setup, the program retrieves the optical path length, the incidence angle, and the transverse position x of each ray for a fixed longitudinal position z. We then compute the integral of the cw-contributions to the total pulse amplitude in space and time, as shown in Fig.1We first validated our program with axicons and spatial light modulators to generate Bessel X-pulses and pulsed Bessel beams respectively. Figure 1 shows a more sophisticated setup, composed of a reflective axicon, a lens, and a half-ball lens, generating a high-angle Bessel beam [5]. In the top and bottom rows, the relative distances between optics are modified and we see, on the right side, the upper-half of the pulse just before the interference field. We see that the design overall has a strong impact on the spatio-temporal shape. We could compute the respective group velocities, which are respectively 2.3c and 1.6c. This shows that the group velocity of a Bessel beam can be quasi-arbitrarily changed without changing any of the components in the optical setup. In conclusion, we have developed a program to simulate the spatio-temporal shape of pulses in complex optical setup and demonstrate it is particularly useful to evaluate the effective group velocity of the Bessel beam. Our effective approach will impact on future design of of ultrafast Bessel beam shaper for a wide field of applications
Compressor Power and Efficiency Optimization: A Finite-Time Thermodynamics Approach
No full textInternational audienceThis paper presents a theoretical optimization of an endoreversiblecompressor under steady-state conditions. A parametric study usingfinite-time thermodynamic principles highlights the effect ofexternal irreversibilities on compressor performance. A compressorefficiency metric is established based on heat pump theory’sanalogous performance coefficient concept. The externalirreversibilities are characterized as functions of the conductancecoefficients between the compressor and the low- and high-pressurereservoirs. In particular, the influence of suction and dischargetube diameters and gas pressures is investigated to determine theoptimum compressor operating performance for a given gas mass flowrate. The results highlight the importance of selecting optimalsuction and discharge tube diameters to improve compressor powerefficiency and minimize energy consumption during gas compression
Comparative study of pNaSS and pVBP on titanium: Protein adsorption, cell adhesion, and bacterial colonization
No full textInternational audienceIn biomaterials, surface science encompasses the characterization of surfaces’ physicochemical properties, mechanical behavior and the development of surface modification strategies, all aimed at understanding and controlling biological interactions. This study examines how grafted polymers on titanium surfaces drive biological processes, focusing on the role of pre-adsorbed proteins in modulating cell and bacterial behavior. Here, pre-adsorbed proteins are used to mimic the initial physiological response post-implantation, not as a pre-coating strategy. Previous studies have shown that grafted poly(styrene sodium sulfonate) (pNaSS) enhances fibroblast (L929) adhesion, while poly(vinylbenzyl phosphonic acid) (pVBP) improves MC3T3 pre-osteoblast cells’ osseointegration. Enhanced adhesion of fibronectin and fibrinogen on grafted surfaces, attributed to increased wettability, provides an organic matrix that promotes cell adhesion and favorable morphology. Bacterial adhesion of S. aureus was significantly reduced on pNaSS and pVBP-grafted surfaces (by 70 % and 80 %, respectively), as quantified by CFU assays. These results highlight the specificity of biological responses based on surface modifications, protein type and bacterial strain. The findings deepen understanding of how polymer grafting influences titanium’s biological performance and guide its applications. They help address responses to questions like: Which cells should be targeted? Which proteins are key to these interactions? These insights enable tailoring biomaterial surfaces to specific clinical needs
Apport de l'apprentissage non supervisé à l'analyse des résultats de nanoindentation : Identification de l'interphase fibre/matrice dans un matériau composite à partir des valeurs de module élastique
No full textInternational audienceLes approches par partitionnement de données, ou clustering, telles que la méthode des k-means, constituent des outils d’aide à l’analyse des résultats obtenus lors d’essais de nanoindentation. Elles permettent, dans cette étude purement numérique, d’identifier convenablement l’interphase fibre/matrice dans un matériau composite
« Claudel et la constellation des langues bibliques. Latin, grec, hébreu, araméen »
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Training of Physical Neural Networks
No full text29 pages, 4 figuresInternational audiencePhysical neural networks (PNNs) are a class of neural-like networks that leverage the properties of physical systems to perform computation. While PNNs are so far a niche research area with small-scale laboratory demonstrations, they are arguably one of the most underappreciated important opportunities in modern AI. Could we train AI models 1000x larger than current ones? Could we do this and also have them perform inference locally and privately on edge devices, such as smartphones or sensors? Research over the past few years has shown that the answer to all these questions is likely "yes, with enough research": PNNs could one day radically change what is possible and practical for AI systems. To do this will however require rethinking both how AI models work, and how they are trained - primarily by considering the problems through the constraints of the underlying hardware physics. To train PNNs at large scale, many methods including backpropagation-based and backpropagation-free approaches are now being explored. These methods have various trade-offs, and so far no method has been shown to scale to the same scale and performance as the backpropagation algorithm widely used in deep learning today. However, this is rapidly changing, and a diverse ecosystem of training techniques provides clues for how PNNs may one day be utilized to create both more efficient realizations of current-scale AI models, and to enable unprecedented-scale models
Estimation of subcritical Galton Watson processes with correlated immigration
No full textWe consider an observed subcritical Galton Watson process with correlated stationary immigration process . Two situations are presented. The first one is when \mbox{Cov}(\epsilon_0,\epsilon_k)=0 for larger than some : a consistent estimator for the reproduction and mean immigration rates is given, and a central limit theorem is proved. The second one is when has general correlation structure: under mixing assumptions, we exhibit an estimator for the the logarithm of the reproduction rate and we prove that it converges in quadratic mean with explicit speed. In addition, when the mixing coefficients decrease fast enough, we provide and prove a two terms expansion for the estimator. Numerical illustrations are provided.Nous considérons un processus observé de Galton Watson avec immigration modélisé par un processus corrélé . Nous présentons des résultats d’estimation du taux de reproduction et l’espérance de l’immigration dans deux situations. La première est lorsque \mbox{Cov}(\epsilon_0,\epsilon_k)=0 pour supérieur à un certain : nous fournissons un estimateur et prouvons un résultat de normalité asymptotique. Dans un deuxième temps, nous considérons le cas où a une structure de corrélation générale. Sous des hypothèses de mélange, nous déterminons un estimateur pour le taux de reproduction et nous montrons sa convergence en moyenne quadratique avec vitesse explicite. Lorsque le coefficient de mélange décroit suffisamment vite, un développement d’ordre 2 pour cet estimateur est établi
Advancing Alzheimer's disease pharmacotherapy: efficacy of glucocorticoid modulation with dazucorilant (CORT113176) in preclinical mouse models
No full textInternational audienceBackground and Purpose: Exposure to chronic stress and high levels of glucocorticoid hormones in adulthood has been associated with cognitive deficits and increased risk of Alzheimer's disease (AD). Dazucorilant has recently emerged as a selective glucocorticoid receptor (NR3C1) modulator, exhibiting efficacy in counteracting amyloid‐ β toxicity in an acute model of AD. We aim to assess the therapeutic potential of dazucorilant in reversing amyloid and tau pathologies through the inhibition of glucocorticoid receptor pathological activity, and providing additional evidence for its consideration in AD treatment.Experimental Approach: The efficacy of dazucorilant was evaluated in two transgenic mouse models of amyloid pathology. The slowly progressing J20 and the aggressively pathological 5xFAD mice. Behavioural analysis was conducted to evaluate welfare, cognitive performances and anxiety levels. The activity of the glucocorticoid receptor system, neuroinflammation, amyloid burden and tau phosphorylation were examined in hippocampi. Key Results: In both AD models, chronic treatment with dazucorilant improved working and long‐term spatial memories along with the inhibition of glucocorticoid receptor‐dependent pathogenic processes and the normalization of plasma glucocorticoid levels. Dazucorilant treatment also resulted in a reduction in tau hyperphosphorylation and amyloid production and aggregation. Additionally, dazucorilant seemed to mediate a specific re‐localization of activated glial cells onto amyloid plaques in J20 mice, suggesting a restoration of physiological neuroinflammatory processes.Conclusion and Implications Dazucorilant exhibited sustained disease‐modifying effects in two AD models. Given that this compound has demonstrated safety and tolerability in human subjects, our results provide pre‐clinical support for conducting clinical trials to evaluate its potential in AD
Copula methods for modeling pair densities in density functional theory
No full textInternational audienceWe propose a new approach towards approximating the density-to-pair-density map based on copula theory from statistics. We extend the copula theory to multi-dimensional marginals, and deduce that one can describe any (exact or approximate) pair density by the single-particle density and a copula. We present analytical formulas for the exact copula in scaling limits, numerically compute the copula for dissociating systems with two to four particles in one dimension, and propose accurate approximations of the copula between equilibrium and dissociation for two-particle systems