HAL Portal IOGS (nstitut d'Optique Graduate School)
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Laser-induced transformation mechanisms of plasmonic Ag nanoparticles in TiO2 and applications
No full textInternational audienceLaser processing provides significant advantages in manipulating the colors of plasmonic metasurfaces over large areas. This adaptable and cost-effective method enables the production of high-resolution color images that are visible to the naked eye. Despite inhomogeneity in the size and organization of the metallic nano-objects created through laser processing, the resulting colors are reproducible. This presentation explores the diverse physical and chemical mechanisms induced by lasers on plasmonic metasurfaces composed of silver nanoparticles embedded in a TiO2 thin film. Under continuous wave (cw)1, nanosecond, or femtosecond2 laser exposure, silver nanoparticles undergo reshaping, shrinking, or growth, and self-organize along subwavelength gratings. Various laser-induced self-organized nanostructures are identified and their origins are elucidated through multi-physical models. Once formed, these self-organized nanostructures exhibit intriguing dichroic optical properties, whose origin, elucidated through electromagnetic modeling, lies in the hybridization of resonant modes.3 These singular optical properties present opportunities for innovation, particularly in high-end anti-counterfeiting applications.4 Laser-induced printed image multiplexing emerges as a recently developed inkless technique, providing high flexibility to print multiplexed colored images observable independently under natural light by altering the viewing angle
Chapter 7: Advances in Ultrafast Laser Structuring of Materials at the Nanoscale
No full textInternational audienceThe capability of ultrashort laser pulses to deliver high precision and high yield processing in laser material micro-structuring is already on the verge of industrial uptake. Whether on surfaces or in the bulk, sub-micron processing capabilities are equally approaching a significant level of process maturity, qualifying laser technology for advanced applications in micro- and nano-fabrication. Applications in optics, energy, biology, electronics, and mechanics depend on the accessible fabrication scale. A question about the resolution limits of an ultrafast laser manufacturing process can thus be posed. What are the physical phenomena that enable confinement of light to the smallest scales? New strategies of ultrafast laser structuring are emerging nowadays that go well beyond the current optical resolutions. Harnessing the ensemble of properties of light, shaping phase and amplitude, manipulating polarization, synthesizing complex spectral fields, and mixing far and near-field components, with strategies for flexible geometries in 2D and 3D, current ultrafast laser processing techniques can reach resolutions below 100 nm, paving the way toward super-resolved laser processing, well into the nanoscale. The chapter will review several relevant tendencies in extreme laser nanostructuring on surfaces and in the bulk underlining physical mechanisms and pointing out promising emerging applications
AGMA-PESS: a deep learning-based infant pose estimator and sequence selector software for general movement assessment
No full textL'article est en open access.International audienceThe General Movement Assessment (GMA) is a validated evaluation of brain maturation essential to shaping early individual developmental trajectories of preterm infants. To ensure a reliable GMA, preterm infants should be recorded for 30 to 60 min before manually selecting at least three sequences with general movements. This time-consuming task of manually selecting short video sequences from lengthy recordings impedes its implementation within the Neonatal Unit. Moreover, an accurate pose estimation tool for preterm infants is paramount to developing the field of GMA automation. We introduce the AGMA Pose Estimator and Sequence Selector (AGMA-PESS) software, based on the state-of-the-art deep learning infant pose estimation network, to automatically select the video sequences for GMA at preterm and writhing ages and estimate the pose of infants in 2D. Its simplicity and efficiency make AGMA-PESS a valuable tool to promote GMA use within the Neonatal Unit, both for clinical practice and research purposes
Retraction notice to "Bridging the shocked monazite gap- Deformation microstructures in natural and laser shock-loaded samples" [Earth and Planetary Science Letters 595 (2022) 117727]
No full textInternational audienceThis article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal).This article has been retracted at the request of Publisher/Editor for the below details: Authors submitted a revised paper due to some errors appearing in the paper. Rather than a corrigendum being posted for this original paper, a second version was published: Earth Planet. Sci. Lett. 628 (2024) 118587, https://doi.org/10.1016/j.epsl.2024.118587. We need to retract at least one version of this paper
Modélisation des transferts radiatifs avec fluorescence pour la quantification de biomarqueurs en neurochirurgie
No full textInternational audienceUn modèle de propagation du rayonnement avec fluorescence pour la quantification de biomarqueurs en neurochirurgie est proposé dans cette étude et simulé avec la méthode de Monte-Carlo. Ce modèle s'appuie sur l'équation de transfert radiatif dans laquelle est ajouté un terme source tenant compte de l'émission par fluorescence, et qui va impliquer un couplage entre les équations définies à la longueur d'onde d'absorption par le fluorophore, et aux longueurs d'onde d'émission fluorescente. Des mesures de spectroscopie de fluorescence sur fantômes optiques ont permis de valider expérimentalement l'approche proposée.</div
Détection de fraude à l'assurance maladie à l'aide de modèles d'apprentissage automatique et de fouille de données explicables et interprétables.
No full textThis thesis addresses the detection of fraud in health insurance reimbursement claims using attributed graphs. The objective is to develop effective methods to identify anomalies, even in contexts where data is limited or contains errors. The Suspicious model, based on Graph Auto-Encoders (GAE), was designed to detect anomalies while being robust to poorly labelled samples. Additionally, a specific explanation method for GAEs was developed to better understand why an element is identified as abnormal. By leveraging reconstruction errors, this method highlights the most important attributes or connections in anomaly detection. These contributions were tested on various datasets, both synthetic and real, and successfully applied to detecting new cases of fraud in the French healthcare system, demonstrating their relevance for practical applications.Cette thèse traite de la détection de fraudes dans les demandes de remboursement à l’assurance maladie en utilisant des graphes attribués. L’objectif est de développer des méthodes efficaces pour identifier des anomalies, même dans des contextes où les données sont limitées ou incluent des erreurs. Le modèle Suspicious, basé sur les Graph Auto-Encoders (GAE), a été conçu pour détecter des anomalies tout en étant robuste aux échantillons mal étiquetés. Par ailleurs, une méthode d’explication spécifique aux GAE a été développée pour mieux comprendre pourquoi un élément est identifié comme anormal. En utilisant les erreurs de reconstruction, cette méthode met en évidence les attributs ou connexions les plus importants dans la détection des anomalies. Ces contributions ont été testées sur divers jeux de données, synthétiques et réels, et appliquées avec succès à la détection de nouvelles fraudes dans le système de santé français, soulignant leur pertinence pour des applications pratiques
Differential polarizability of the strontium intercombination transition at 1064.7 nm
No full textInternational audienceWe measure the scalar, vector, and tensor components of the differential dynamic polarizability of the strontium intercombination transition at 1064.7nm. We compare the experimental values with the theoretical prediction based on the most recently published spectroscopic data, and find a very good agreement. We also identify a close-to-circular “magic” polarization where the differential polarizability strictly vanishes, and precisely determine its ellipticity. Our work opens new perspectives for laser cooling optically trapped strontium atoms and provides a benchmark for atomic models in the near-infrared spectral range
A novel in vitro tubular model to recapitulate features of distal airways: The bronchioid
No full textInternational audienceBackground Airflow limitation is the hallmark of obstructive pulmonary diseases, with the distal airways representing a major site of obstruction. Although numerous in vitro models of bronchi already exist, there is currently no culture system for obstructive diseases that reproduces the architecture and function of small airways. Here, we aimed to engineer a model of distal airways to overcome the limitations of current culture systems. Methods We developed a so-called bronchioid model by encapsulating human bronchial adult stem cells derived from clinical samples in a tubular scaffold made of alginate gel. Results This template drives the spontaneous self-organisation of epithelial cells into a tubular structure. Fine control of the level of contraction is required to establish a model of the bronchiole, which has a physiologically relevant shape and size. 3D imaging, gene expression and single-cell RNA-seq analysis of bronchioids made of bronchial epithelial cells revealed tubular organisation, epithelial junction formation and differentiation into ciliated and goblet cells. Ciliary beating is observed, at a decreased frequency in bronchioids made of cells from COPD patients. The bronchioid can be infected by rhinovirus. An air-liquid interface is introduced that modulates gene expression. Conclusion Here, we provide a proof of concept of a perfusable bronchioid with proper mucociliary and contractile functions. The key advantages of our approach, such as the air‒liquid interface, lumen accessibility, recapitulation of pathological features and possible assessment of clinically relevant endpoints, will make our pulmonary organoid-like model a powerful tool for preclinical studies