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Reconstruction Acoustique de la Puissance des Eclairs et de la Structure de Charge des Nuages d'Orage
No full textBasses fréquences et infrasons : émission, propagation, instrumentation et perception; GABE - Acoustique du Bâtiment et de l'Environnement: GPS - Perception Sonore: GAHA - Aéro et Hydro-AcoustiqueNational audienceLes méthodes de localisation de sources acoustiques basse fréquence ou infrasonores sont appliquées depuis plusieurs années aux éclairs d’orage sur une gamme de fréquence allant typiquement de 1 à 100 Hz. Elles permettent de reconstruire la géométrie complexe des décharges, incluant à la fois les arcs électriques entre le nuage et le sol, souvent multiples, et les décharges intra- nuages. Cette méthodologie a été récemment étendue à l’estimation de la puissance acoustique des sources, en rétro-propageant également l’amplitude du signal mesuré au sol par un réseau de capteurs et en compensant la réflexion au sol, l’atténuation géométrique, l’absorption et la stratification en densité. Cette méthode offre une unique visualisation de la répartition géométrique de l’énergie au sein d’une décharge donnée. Elle a été appliquée à de nombreux éclairs mesurés lors de deux campagnes de mesure réalisées dans les Cévennes en 2012 et en Corse en 2018 dans le cadre du programme HyMeX d’étude du climat méditerranéen. La présente étude se concentre notamment sur la structure verticale de la répartition de la puissance acoustique. Elle montre que les mesures sonores permettent de localiser les différentes couches de charges à l’intérieur d’un cumulonimbus. Ce résultat est notamment validé par comparaison avec des mesures électromagnétiques à très haute fréquence (60-66 MHz). Dans le cas des décharges nuage-sol à polarité négative (CG-, 90% des cas environ), on observe toutefois que l’essentiel de la puissance acoustique est émise dans les arcs nuage-sol, à une altitude moyenne d’un kilomètre. Cette observation permet de proposer une classification acoustique simple des évènements de type CG-, comme des évènements acoustiques de puissance totale moyenne (autour du MW) émise à basse altitude sous le nuage. (Etude entreprise dans le cadre du laboratoire commun LETMA CEA/CNRS/Ecole Centrale de Lyon/Sorbonne Université
Determination of X- and gamma-ray emission intensities in the decay of I and Lu
No full textInternational audienceDetermination of X-and gamma-ray emission intensities in the decay of 123 I and 177 LuIodine-123 and lutetium-177 are both radionuclides for radiopharmaceutical use. Their short half-lives make them convenient for diagnosis and they are also used for therapy.To contribute to a better characterisation of these radionuclides,. two experiments were conducted to determine the photon emission intensities of both radionuclides by gamma-and X-ray spectrometry.</p
A multiwavelength study of the new Galactic center black hole candidate MAXI J1744-294
No full textInternational audienceFor the first time in nearly a decade, a new, bright transient was detected in the central parsec (pc) of the Galaxy. MAXI J1744-294 was never observed in outburst prior to January 2025. We present the results of a broadband, multi-wavelength study of this enigmatic source, including data from the NuSTAR, Chandra, XMM-Newton, Swift, and NICER X-ray telescopes, as well as complementary radio and near-infrared observations. We find that MAXI J1744-294 remained in the bright/soft state throughout the first months of 2025. Spectral hardening was observed in April 2025, followed by a decline in flux. Based on the spectral and temporal characteristics of the source, we identify MAXI J1744-294 as a candidate black hole (BH) low-mass X-ray binary (LMXB) the fourth candidate BH transient discovered within a (projected) distance of one pc from the Galactic supermassive black hole Sgr A*. This discovery provides further evidence for a cusp of BH-LMXBs in the central pc of our Galaxy, as argued for in previous observational work and suggested by analytical and theoretical work. Our multi wavelength study, involving a complementary range of observatories and spanning different outburst states, can serve as a model for future time domain astrophysics research
Polyanion-mixed off-stoichiometric alluaudites Na3−δFe2±β(PO4)y(SO4)3–y as sustainable positive electrode materials for Na-Ion batteries
No full text"ADC - Accord Couperin / American Chemical Society (2024-2026)"International audienceThe transition to renewable energy sources requires cost-effective and scalable energy storage solutions based on abundant elements, such as Na-ion batteries with sustainable positive electrode materials, based on Na, Fe, and S. The sulfate-based alluaudite Na2+2δFe2−δ(SO4)3 that exhibits excellent cycling performance inspired the investigation of mixed PO43–/SO42– polyanion-based compounds with a view to increase the phase stability of sulfates. Herein, we report on various synthesis methods, such as solid-state, mechanochemical, and ionothermal treatments, to obtain nonreported until now compositions in the mixed phosphate-sulfate iron sodium alluaudite system, using the cost-effective precursors, Na3PO4 and FeSO4. Quite surprisingly, solid-state synthesis followed in situ using the synchrotron X-ray powder diffraction technique revealed the presence of an intermediate phase closely resembling the NaSICON phase Na2.65Fe2PO4(SO4)2 along with Na6Fe(SO4)4, prior to alluaudite formation. Physicochemical investigations of the alluaudite Na2.65Fe1.9(PO4)y(SO4)3–y phase, obtained via solid-state synthesis at 450 °C, confirm that the phosphate incorporation enhanced the thermal stability while preserving promising electrochemical properties, i.e., rate capability and long-term stability with no capacity loss after 50 cycles: a reversible capacity of ≈90 mAh/g is obtained at an average discharge voltage of 3.32 V vs Na+/Na and for an electrode mass loading of 16 mg/cm2. This study proposes easy and effective synthesis approaches to obtain series of compounds and opens the perspective to explore conditions of transitions between NaSICON and alluaudite structural types
Bipolar Batteries in the SOLGAIN® technology for Lithium ion batteries
No full textInternational audienc
p-GaN source integrated GaN/AlGaN/GaN double heterojunction field-effect transistor (FET) for next-generation electronic applications
No full textInternational audienceThe continuous evolution of high-power and high-frequency electronic devices demands advanced semiconductor technologies. The proposed GaN p-FET device architecture incorporates a p-GaN source region that enables the simultaneous formation of two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) channels. This dual-channel mechanism enhances carrier confinement and mobility, offering a pivotal pathway toward high-performance GaN-based electronics. This simulation study systematically examines key parameters to optimize device configurations: Mg2+ doping (0.05 to 50 × 1019 cm− 3), contact metal work function (4.0 to 6.3 eV), AlGaN layer thickness (4 to 25 nm), and Al mole fraction (0.1 to 0.45) in relation to the performance of p-GaN source layer n-GaN/AlGaN/GaN double heterostructure FETs. Extensive analyses reveal that a GaN pFET with a 5 nm p-GaN layer doped with 1 × 10 cm Mg and a 10 nm AlGaN layer with an Al mole fraction of 0.2, demonstrates superior performance metrics. Compared to state-of-the-art technologies, this specific device configuration achieves optimal threshold voltage (~ |4| V) control, high ION/IOFF ratios (0.39 × 10), and minimized leakage current, essential for reliable high-performance operations. Additionally, the study highlights the critical impact of the contact metal work function, with a work function of 5.15 eV significantly reducing contact resistivity and minimizing leakage current, enhancing device efficiency. These findings highlight that precise control over doping, material thickness, and composition is essential for optimizing GaN pFET performance and reliability for next-generation electronic applications
Towards second-order FE2 multiscale solutions for quasi-stationary thermal problems with a heterogeneous heat source
No full textInternational audienc
Upstream open reading frame translation enhances immunogenic peptide presentation in mitotically arrested cancer cells
No full textInternational audienceMitosis is a critical phase of the cell cycle and a vulnerable point where cancer cells can be disrupted, causing cell death and inhibiting tumor growth. Challenges such as drug resistance persist in clinical applications. During mitosis, mRNA translation is generally downregulated, while non-canonical translation of specific transcripts continues. Here, we show that mitotic cancer cells redistribute ribosomes toward the 5′ untranslated region (5′ UTR) and beginning of the coding sequence (CDS), enhancing translation of thousands of upstream open reading frames (uORFs) and upstream overlapping open reading frames (uoORFs). This mitotic induction of uORF/uoORF enriches human leukocyte antigen (HLA) presentation of non-canonical peptides on the surface of cancer cells after mitotic inhibitor treatment. Functional assays indicate these epitopes provoke cancer-cell killing by T cells. Our findings highlight the therapeutic potential of targeting uORF/uoORF-derived epitopes with mitotic inhibitors to enhance immune recognition and tumor cell elimination
Toward Real‐Time Assessment of Infrasound Event Detection Capability Using Deep Learning‐Based Transmission Loss Estimation
No full textInternational audienceAccurate modeling of infrasound transmission loss is crucial for assessing the performance of the International Monitoring System, which monitors compliance with the Comprehensive Nuclear-Test-Ban Treaty by detecting atmospheric explosions. This modeling supports the design and maintenance of the operating monitoring network. State-of-the-art propagation modeling tools enable transmission loss to be finely simulated using atmospheric models. However, the computational cost prohibits the exploration of a large parameter space in operational monitoring applications. To address this, recent studies made use of a deep learning algorithm capable of making transmission loss predictions almost instantaneously. However, the use of nudged atmospheric models leads to an incomplete representation of the medium, and the absence of temperature as an input makes the algorithm incompatible with long-range propagation. In this study, we address these limitations by using both wind and temperature fields as inputs to a neural network, simulated up to 130 km altitude and 4,000 km distance. We exploit convolutional and recurrent layers to capture spatially and range-dependent features embedded in realistic atmospheric models, improving the overall performance. The neural network reaches an average error of 4 dB compared to full parabolic equation simulations and provides epistemic and data-related uncertainty estimates. Its evaluation on the 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption demonstrates its prediction capability using atmospheric conditions and frequencies not included in the training. This represents a significant step toward near real-time assessment of International Monitoring System detection thresholds of explosive sources
Laser-induced breakdown spectroscopy (LIBS) imaging for carbon quantification in archaeological ferrous alloys
No full textInternational audienceThis study demonstrates that μ-LIBS imaging provides high-resolution, quantitative carbon distribution in archaeological ferrous alloys. Ancient ferrous alloys are characterized by a heterogeneous distribution of carbon and other elements within their metallic matrix. This study uses micro-Laser Induced Breakdown Spectroscopy (μ-LIBS) to analyze the characteristic elements in archaeological ferrous alloys, complementing classical metallographic methods. Typically, this latter approach relies on image analysis following optical microscopy observations, which has limitations in accurately quantifying carbon concentrations. The analytical approach using μ-LIBS imaging not only enhances carbon localization but also facilitates the study of other elements present in ferrous alloys, such as phosphorus and manganese. This article shows the potential of μ-LIBS imaging for future archaeometallurgical research