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Patterning and micromanipulation of miscible fluids using vortex-based single-beam acoustic tweezers
No full textInternational audienceVortex-based single-beam tweezers have the ability to precisely and selectively move a wide range of objects, including particles, bubbles, droplets, and cells with sizes ranging from the millimeter to micrometer scale. In 2017, Karlsen and Bruus [Phys. Rev. Appl. 7, 034017 (2017)] theoretically suggested that these tweezers could also address one of the most challenging issues: the patterning and manipulation of miscible fluids. In this paper, we experimentally demonstrate this ability using acoustic vortex beams generated by interdigital transducer-based active holograms. The experimental results are supported by a numerical model based on acoustic body force simulations. This work paves the way for the precise shaping of chemical concentration fields, a crucial factor in numerous chemical and biological processes
Thermal properties of nano-objects by means of scanning thermal microscopy
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Advancing RF GaN HEMT Technology: Innovations in Buffer Engineering for Enhanced Performance and Robustness
No full textInternational audienceAdvancing RF GaN HEMT technology is essential to meet the growing demands of next-generation RF power devices, particularly in the mm-wave spectrum, where high efficiency, robustness, and superior output power density are critical. Highly scaled GaN transistors, however, face significant challenges that limit their performance. Efficiency in state-of-the-art GaN HEMTs is typically constrained to 50% or below in the millimeter-wave range, especially at power densities exceeding 3 W/mm. These limitations stem from reduced power gain, increased trapping effects, and diminished electron confinement as device dimensions are scaled down. Furthermore, reliability remains a concern for sub-150 nm GaN devices, hindering their widespread adoption in demanding applications. This talk highlights innovative approaches to overcoming these challenges through advanced buffer and epilayer engineering. By leveraging highly scaled epitaxial heterostructures, the proposed solutions aim to enhance electron confinement, mitigate trapping effects, and improve thermal management, thereby boosting device performance and robustness. These advancements are poised to enable GaN HEMTs to achieve unprecedented efficiency and power density in the mm-wave regime. The integration of these cutting-edge epitaxial designs not only addresses current limitations but also paves the way for the development of reliable, high-performance GaN-based transistors, essential for next-generation communication systems, radar, and other RF power applications. This work underscores the critical role of material and structural innovations in pushing the boundaries of GaN HEMT technology
Achieving Avalanche in GaN-on-silicon Diodes
No full textInternational audienceAlthough qualified up to 650 V voltage operation, lateral GaN devices are subject to severe limitations for higher voltage applications such as a large device size, surface trap related reliability concerns or the absence of avalanche breakdown due to the peak electric field at the gate vicinity. This led to vertical GaN development, which is under extensive investigations worldwide as all the above-mentioned issues could be cured. State-of-the-art vertical GaN devices are fabricated on bulk GaN substrates, thanks to the high quality of the substrates in terms of low dislocation density and low impurity concentrations. However, they are prohibitively expensive, and only rather small area substrates are available.In this talk, we will describe the current status of GaN-based fully vertical devices grown on large diameter silicon substrate with a particular focus on ongoing efforts in this domain, which are part of the EU-funded YESvGaN project. Despite the common belief about the limited drift layer thickness or wafer diameter due to the large mismatch in coefficient of thermal expansion (CTE) between Si and GaN, we will show that a local substrate removal with suitable related growth and process optimization enabled outstanding initial achievements such as extremely low on-resistance in 1200 V-class fully vertical pn diodes with avalanche breakdown capability. Furthermore, the enhancement of the mechanical robustness of the resulting membranes during the fabrication process enables the implementation of a heat sink based on thick Copper and consequently high on-state current spreading well-above 10 A
Cancer Classification through Gene Selection Using the Social Spider Optimization Algorithm
No full textInternational audienceCancer is a leading cause of global mortality, underscoring the need for advanced diagnostic tools to enable early and accurate detection. Microarray technology allows for the simultaneous analysis of thousands of genes, offering valuable insights into cancer biology. However, the high dimensionality of microarray data presents significant challenges for classification tasks. In this study, we propose a novel approach that integrates the Social Spider Optimization (SSO) algorithm with mutual information-based feature selection to identify the most discriminative genes for cancer classification. We evaluate the performance of four machine learning classifiers-Decision Tree (DT), K-Nearest Neighbors (K-NN), Neural Networks (NN), and Support Vector Machines (SVM)-with and without feature selection. Our results demonstrate that the SSO algorithm significantly enhances classification accuracy, with SVM achieving near-perfect performance on leukemia and lymphoma datasets when combined with Max-Relevance Min-Redundancy (MRMR) feature selection. This hybrid approach provides a robust solution for cancer diagnosis by addressing key challenges such as data redundancy and computational complexity
White paper: Introducing Lprobes® and XLprobes® technology for Atomic Force Microscopy
No full textWhite paperWe present a new MEMS (MicroElectroMechanical Systems) fabrication process enabling batch production of in-plane Atomic Force Microscopy (AFM) probes with very high lengths and high aspect ratios. This process enables to introduce two probe series: Lprobe® featuring 30 to 40 µm tip lengths, and XLprobe® with tip lengths above 100 µm. These long, high-aspect-ratio probes are fully compatible with standard AFM systems and offer prospects for enhanced imaging range and spatial resolution in topography. We also discuss about benefits that long tips should bring regarding Electrostatic Force Microscopy (EFM), Kelvin Probe Force Microscopy (KPFM), and Piezoresponse Force Microscopy (PFM). Finally, we describe the advantages expected in infrared nanospectroscopy (AFM-IR) and scattering-type Scanning Near-Field Optical Microscopy (s-SNOM)
Evaluating the Impact of Playing Video Games on Baseline Technical Aptitude in Pre‐Clinical Dental Students
No full textInternational audienceAimResearch on video games is growing, with literature indicating a link between psychomotor and cognitive faculties and playing video games. Their benefits have been observed in various fields, including medical training; however, no study has evaluated the beneficial effects on the technical skills of dental students. The main objective of our study was to determine whether students without any dental practice experience who play action video games perform better than those who do not play video games in three psychomotor skills: (1) Ability to represent a volume in three dimensions, (2) manual precision and dexterity, and (3) speed of execution of a technical dental gesture.MethodologyThe study was observational, monocentric, blind, controlled, and cross-sectional. Video game players and non-video game players were identified through a preliminary questionnaire. The psychomotor skills were assessed respectively by (1) Vandenberg & Kusel Mental Rotation test, (2) modified Precision Manual Dexterity test (mPMD test), and (3) pulpotomy test.ResultsEighty-five students were included, 22 were video game players, and 63 were non-players. The video game players showed a better ability to represent a volume in three dimensions (p = 0 .031) than the non-players. For the mPMD test (p = 0.83) and pulpotomy test (p = 0.077), there was a tendency for the video game players to perform better than the non-video game players but these differences did not reach statistical significance.ConclusionThe study seems to demonstrate a beneficial impact of playing video games on pre-clinical dental students in their ability to represent a volume in three dimensions
A robust sliding mode controller for nonlinear systems with mismatched perturbations
No full textInternational audienceFor many control systems the presence of perturbations may decrease performance, so that their rejection has been an area of active research for the last decades. Roughly speaking, there are two kind of perturbations, those which are matched, i.e. the control input can act directly on them, and those which are mismatched, i.e. the control input cannot act directly on them. While there are many solutions for the first case, the second one remains a challenge. This note improves a former result by the authors to avoid singularities in a Sliding Mode Control (SMC) approach which provides ultimate boundedness of the desired output with an ultimate bound that can be made arbitrarily small. Simulation results are provided to validate the introduced theory.</div
Le 'modèle parlementaire écossais': réflexions à partir du vote annuel du projet de loi de finances (1999-2024)
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Breaking through Microbial Defenses─Organic Acid-Based Deep Eutectic Solvents as a Neoteric Strategy in Bacterial Biofilms, Persister, and Fungal Control
No full textInternational audienceThis study explores the adaptation of organic acid-based deep eutectic solvents (OA-DESs) as effective antimicrobial agents. Having already demonstrated their efficacy against planktonic bacteria in our previous research, herein we investigate their impact on more complex microbial forms, including biofilms, persister cells, and fungi (both human pathogenic and phytopathogenic). Our experiments revealed that OA-DESs effectively eradicated methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli in the biofilms, inducing significant morphological changes. A three-log-unit reduction was observed for most OA-DESs at concentrations below 1% (v/v), a remarkable achievement for this class of materials. Additionally, with only one exception, OA-DESs did not promote persister cells formation, underscoring their potential for complete eradication of biofilm-enveloped bacteria. In another part of our study, OA-DESs were compared to conventional DESs against Candida albicans, Candida auris, and Aspergillus fumigatus. Results showed that while individual DES components exhibited minimal activity, their combination effectively inhibited fungal growth and induced substantial morphological changes. Lastly, OA-DESs were tested against the phytopathogens Zymoseptoria tritici and Venturia inaequalis. Though their activity was less pronounced compared to pathogenic strains, most OA-DESs inhibited the growth of both fungi at the highest tested concentrations. Despite the broad scope of this investigation, we believe this work provides valuable insights into the potential of DESs as antimicrobial agents, offering a strong foundation for future research and innovation in this field